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Sample records for multislice helical computed

  1. Pitch dependence of longitudinal sampling and aliasing effects in multi-slice helical computed tomography (CT)

    International Nuclear Information System (INIS)

    La Riviere, Patrick J.; Pan Xiaochuan

    2002-01-01

    In this work, we investigate longitudinal sampling and aliasing effects in multi-slice helical CT. We demonstrate that longitudinal aliasing can be a significant, complicated, and potentially detrimental effect in multi-slice helical CT reconstructions. Multi-slice helical CT scans are generally undersampled longitudinally for all pitches of clinical interest, and the resulting aliasing effects are spatially variant. As in the single-slice case, aliasing is shown to be negligible at the isocentre for circularly symmetric objects due to a fortuitous aliasing cancellation phenomenon. However, away from the isocentre, aliasing effects can be significant, spatially variant, and highly pitch dependent. This implies that measures more sophisticated than isocentre slice sensitivity profiles are needed to characterize longitudinal properties of multi-slice helical CT systems. Such measures are particularly important in assessing the question of whether there are preferred pitches in helical CT. Previous analyses have generally focused only on isocentre sampling patterns, and our more global analysis leads to somewhat different conclusions than have been reached before, suggesting that pitches 3, 4, 5, and 6 are favourable, and that half-integer pitches are somewhat suboptimal. (author)

  2. The effect of pitch in multislice spiral/helical CT

    International Nuclear Information System (INIS)

    Wang, G.; Vannier, M.W.

    2000-01-01

    The purpose of this study is to understand the effect of pitch on raw data interpolation in multislice spiral/helical computed tomography (CT) and provide guidelines for scanner design and protocol optimization. Multislice spiral CT is mainly characterized by the three parameters: the number of detector arrays, the detector collimation, and the table increment per x-ray source rotation. The pitch in multislice spiral CT is defined as the ratio of the table increment over the detector collimation in this study. In parallel to the current framework for studying longitudinal image resolution, the central fan-beam rays of direct and opposite directions are considered, assuming a narrow cone-beam angle. Generally speaking, sampling in the Radon domain by the direct and opposite central rays is nonuniform along the longitudinal axis. Using a recently developed methodology for quantifying the sensibility of signal reconstruction from non-uniformly sampled finite points, the effect of pitch on raw data interpolation is analyzed in multislice spiral CT. Unlike single-slice spiral CT, in which image quality decreases monotonically as the pitch increases, the sensibility of raw data interpolation in multislice spiral CT increases, suggesting that image quality does not decrease monotonically in this case. The most favorable pitch can be found from the sensitivity-slice spiral CT is provided. The study on the effect of pitch using the sensitivity analysis approach reveals the fundamental characteristics of raw data interpolation in multislice spiral CT, and gives insights into interaction between pitch and image quality. These results may be valuable for design of multislice spiral CT scanners and imaging protocol optimization in clinical applications. (authors)

  3. Multislice helical computed tomography in the evaluation of lumbar spine diseases

    International Nuclear Information System (INIS)

    Rosemberg, Laercio Alberto; Rios, Adriana Martins; Almeida, Milena Oliveira; Garbaccio, Viviane Ladeira; Kim, Nelson Ji Tae; Daniel, Mauro Miguel; Funari, Marcelo Buarque de Gusmao

    2003-01-01

    Multislice computed tomography has advantages in comparison to conventional computer tomography such as reduction in study time, lower radiation dose, fewer metal artifacts and high quality multiplanar reformatting and three-dimensional reconstructions. We reviewed approximately 300 lumbar spine examinations and selected the most illustrative cases including congenital anomalies, degenerative lesions, spinal infections, neoplasms traumatic injuries, spondylolysis and postoperative changes. In the majority of the cases the high quality multiplanar reformatted and volume reconstructions of multislice computed tomography allowed better evaluation of the lesions, particularly in the cases of complex anatomy (author)

  4. SU-E-I-93: Improved Imaging Quality for Multislice Helical CT Via Sparsity Regularized Iterative Image Reconstruction Method Based On Tensor Framelet

    International Nuclear Information System (INIS)

    Nam, H; Guo, M; Lee, K; Li, R; Xing, L; Gao, H

    2014-01-01

    Purpose: Inspired by compressive sensing, sparsity regularized iterative reconstruction method has been extensively studied. However, its utility pertinent to multislice helical 4D CT for radiotherapy with respect to imaging quality, dose, and time has not been thoroughly addressed. As the beginning of such an investigation, this work carries out the initial comparison of reconstructed imaging quality between sparsity regularized iterative method and analytic method through static phantom studies using a state-of-art 128-channel multi-slice Siemens helical CT scanner. Methods: In our iterative method, tensor framelet (TF) is chosen as the regularization method for its superior performance from total variation regularization in terms of reduced piecewise-constant artifacts and improved imaging quality that has been demonstrated in our prior work. On the other hand, X-ray transforms and its adjoints are computed on-the-fly through GPU implementation using our previous developed fast parallel algorithms with O(1) complexity per computing thread. For comparison, both FDK (approximate analytic method) and Katsevich algorithm (exact analytic method) are used for multislice helical CT image reconstruction. Results: The phantom experimental data with different imaging doses were acquired using a state-of-art 128-channel multi-slice Siemens helical CT scanner. The reconstructed image quality was compared between TF-based iterative method, FDK and Katsevich algorithm with the quantitative analysis for characterizing signal-to-noise ratio, image contrast, and spatial resolution of high-contrast and low-contrast objects. Conclusion: The experimental results suggest that our tensor framelet regularized iterative reconstruction algorithm improves the helical CT imaging quality from FDK and Katsevich algorithm for static experimental phantom studies that have been performed

  5. Suitability of helical multislice acquisition technique for routine unenhanced brain CT: an image quality study using a 16-row detector configuration

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    Hernalsteen, Danielle; Cosnard, Guy; Grandin, Cecile; Duprez, Thierry [Universite Catholique de Louvain, Cliniques Universitaires Saint-Luc, Department of Radiology and Medical Imaging, Brussels (Belgium); Robert, Annie [Public Health School, Universite Catholique de Louvain, Department of Epidemiologics and Medical Statistics, Brussels (Belgium); Vlassenbroek, Alain [CT Clinical Science, Philips Medical Systems, Cleveland, OH (United States)

    2007-04-15

    Subjective and objective image quality (IQ) criteria, radiation doses, and acquisition times were compared using incremental monoslice, incremental multislice, and helical multislice acquisition techniques for routine unenhanced brain computed tomography (CT). Twenty-four patients were examined by two techniques in the same imaging session using a 16-row CT system equipped with 0.75-width detectors. Contiguous ''native'' 3-mm-thick slices were reconstructed for all acquisitions from four detectors for each slice (4 x 0.75 mm), with one channel available per detector. Two protocols were tailored to compare: (1) one-slice vs four-slice incremental images; (2) incremental vs helical four-slice images. Two trained observers independently scored 12 subjective items of IQ. Preference for the technique was assessed by one-tailed t test and the interobserver variation by two-tailed t test. The two observers gave very close IQ scores for the three techniques without significant interobserver variations. Measured IQ parameters failed to reveal any difference between techniques, and an approximate half radiation dose reduction was obtained by using the full 16-row configuration. Acquisition times were cumulatively shortened by using the multislice and the helical modality. (orig.)

  6. Suitability of helical multislice acquisition technique for routine unenhanced brain CT: an image quality study using a 16-row detector configuration

    International Nuclear Information System (INIS)

    Hernalsteen, Danielle; Cosnard, Guy; Grandin, Cecile; Duprez, Thierry; Robert, Annie; Vlassenbroek, Alain

    2007-01-01

    Subjective and objective image quality (IQ) criteria, radiation doses, and acquisition times were compared using incremental monoslice, incremental multislice, and helical multislice acquisition techniques for routine unenhanced brain computed tomography (CT). Twenty-four patients were examined by two techniques in the same imaging session using a 16-row CT system equipped with 0.75-width detectors. Contiguous ''native'' 3-mm-thick slices were reconstructed for all acquisitions from four detectors for each slice (4 x 0.75 mm), with one channel available per detector. Two protocols were tailored to compare: (1) one-slice vs four-slice incremental images; (2) incremental vs helical four-slice images. Two trained observers independently scored 12 subjective items of IQ. Preference for the technique was assessed by one-tailed t test and the interobserver variation by two-tailed t test. The two observers gave very close IQ scores for the three techniques without significant interobserver variations. Measured IQ parameters failed to reveal any difference between techniques, and an approximate half radiation dose reduction was obtained by using the full 16-row configuration. Acquisition times were cumulatively shortened by using the multislice and the helical modality. (orig.)

  7. Multislice helical computed tomography in the evaluation of lumbar spine diseases; Tomografia computadorizada 'multislice' no diagnostico das afeccoes da coluna lombar

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    Rosemberg, Laercio Alberto; Rios, Adriana Martins; Almeida, Milena Oliveira [Hospital Israelita Albert Einstein, Sao Paulo, SP (Brazil)]. E-mail: laercio@einstein.br; Garbaccio, Viviane Ladeira; Kim, Nelson Ji Tae; Daniel, Mauro Miguel; Funari, Marcelo Buarque de Gusmao [Hospital Israelita Albert Einstein, Sao Paulo, SP (Brazil). Dept. de Imagem

    2003-06-01

    Multislice computed tomography has advantages in comparison to conventional computer tomography such as reduction in study time, lower radiation dose, fewer metal artifacts and high quality multiplanar reformatting and three-dimensional reconstructions. We reviewed approximately 300 lumbar spine examinations and selected the most illustrative cases including congenital anomalies, degenerative lesions, spinal infections, neoplasms traumatic injuries, spondylolysis and postoperative changes. In the majority of the cases the high quality multiplanar reformatted and volume reconstructions of multislice computed tomography allowed better evaluation of the lesions, particularly in the cases of complex anatomy (author)

  8. Volumetric analysis of maxillary sinuses of Zulu and European crania by helical, multislice computed tomography.

    Science.gov (United States)

    Fernandes, C L

    2004-11-01

    The volumes of the maxillary sinuses are of interest to surgeons operating endoscopically as variation in maxillary sinus volume may mean variation in anatomical landmarks. Other surgical disciplines, such as dentistry, maxillo-facial surgery and plastic surgery, may benefit from this information. To compare the maxillary sinus volumes of dried crania from cadavers of European and Zulu descent, with respect to ethnic group and gender. Helical, multislice computed tomography (CT) was performed using 1-mm coronal slices. The area for each slice was obtained by tracing the outline of each slice. The CT machine calculated a volume by totalling the slices for each sinus. Ethnic and gender variations were found in the different groups. It was found that European crania had significantly larger antral volumes than Zulu crania and men had larger volumes than women. Race and gender interaction was also assessed, as was maxillary sinus side. A variation in maxillary sinus volume between different ethnic groups and genders exists, and surgeons operating in this region should be aware of this.

  9. The accuracy of ventricular volume measurement and the optimal slice thickness by using multislice helical computed tomography

    International Nuclear Information System (INIS)

    Cui Wei; Guo Yuyin

    2005-01-01

    Objective: To determine the optimal slice thickness for ventricular volume measurement by tomographic multislice Simpson's method and to evaluate the accuracy of ventricular volume measured by multislice helical computed tomography (MSCT) in human ventricular casts. Methods: Fourteen human left ventricular (LV) and 15 right ventricular (RV) casts were scanned with MSCT scanner by using a scanning protocol similar to clinical practice. A series of LV and RV short-axis images were reconstructed with slice thickness of 2 mm, 3.5 mm, 5 mm, 7 mm, and 10 mm, respectively. Multislice Simpson's method was used to calculate LV and RV volumes and true cast volume was determined by water displacement. Results: The true LV and RV volumes were (55.57 ± 28.91) ml, and (64.23 ± 24.51) ml, respectively. The calculated volumes from different slice thickness ranged from (58.78 ± 28.93) ml to (68.15 ± 32.57) ml for LV casts, and (74.45 ± 27.81) ml to (88.14 ± 32.91) ml for RV casts, respectively. Both the calculated LV and RV volumes correlated closely with the corresponding true volumes (all r > 0.95, P<0.001), but overestimated the corresponding true volume by (3.21 ± 5.95) to (12.58 ± 8.56) ml for LV and (10.22 ± 8.45) to (23.91 ± 12.24) ml for RV (all P<0.01). There was a close correlation between the overestimation and the selected slice thickness for both LV and RV volume measurements (r=0.998 and 0.996, P<0.001). However, when slice thickness was reduced to 5.0 mm, the overestimation became nonsignificant for slice thickness through 2.0 mm to 5.0 mm, and also for both LV and RV volume measurements. Conclusion: Both LV and RV volumes can be accurately calculated with MSCT. A 5 mm slice thickness is enough and most efficient for accurate measurement of LV and RV volume. (authors)

  10. Multislice helical CT in the diagnosis of hilar cholangiocarcinoma

    International Nuclear Information System (INIS)

    Yang Li; Zhao Shaohong; Nie Yongkang; Zhao Hong; Fang Jie; Cai Zulong; Yang Zhou; Ying Yifeng

    2005-01-01

    Objective: To investigate the value ofMSCT in observing the direct findings of hilar cholangiocarcinoma1Methods Multislice helical CT studies were performed on the upper abdomen in 19 consecutive patientswith painless jaundice1 Precontrast and dynamic contrast enhanced (25 s phase and 60 s phase) scanswere conducted, and 3D imageswere reconstructed using enhanced raw data in 15 cases1 The direct CT findings of hilar cholangiocarcinoma were studied by three radiologists respectively in a 32scale strategy1 The morphological features and extension of bile duct involvement by hilar cholangiocarcinoma were analyzed1 All the 19 caseswere pathologically p roved as hilar cholangiocarcinoma by surgery (15 cases) and ERCP ( 4 cases) 1 Results The direct findings and extension of hilar cholangiocarcinoma could be demonstrated in 14 out of 15 3D reconstruction images, 8 out of 19 in 25 s phase, and 7 out of 19 in 60 s phase of contrast enhancement scans, respectively ( P < 0105 ) 1 The tumor involving the bile duct was enhanced most remarkablely on 25 s phase, and the bile duct wall thickening, bile duct narrowing or occlusion were demonstrated as the p rimary findings of hilar cholangiocarcinoma1 The intraductal sp read of tumor could be demonstrated as small nodules on the bile duct wall p roximal or distal to the tumor1 Conclusion. The tumor involving the bile duct can be enhanced most remarkablely on 25 s phase after contrast injection1 Multislice helical CT, especially 3D reconstructed images, can be used to detect the direct findings of hilar cholangiocarcinomas and the extension of tumor involving the bile duct. (authors)

  11. Acquiring 4D thoracic CT scans using a multislice helical method

    International Nuclear Information System (INIS)

    Keall, P J; Starkschall, G; Shukla, H; Forster, K M; Ortiz, V; Stevens, C W; Vedam, S S; George, R; Guerrero, T; Mohan, R

    2004-01-01

    Respiratory motion degrades anatomic position reproducibility during imaging, necessitates larger margins during radiotherapy planning and causes errors during radiation delivery. Computed tomography (CT) scans acquired synchronously with the respiratory signal can be used to reconstruct 4D CT scans, which can be employed for 4D treatment planning to explicitly account for respiratory motion. The aim of this research was to develop, test and clinically implement a method to acquire 4D thoracic CT scans using a multislice helical method. A commercial position-monitoring system used for respiratory-gated radiotherapy was interfaced with a third generation multislice scanner. 4D cardiac reconstruction methods were modified to allow 4D thoracic CT acquisition. The technique was tested on a phantom under different conditions: stationary, periodic motion and non-periodic motion. 4D CT was also implemented for a lung cancer patient with audio-visual breathing coaching. For all cases, 4D CT images were successfully acquired from eight discrete breathing phases, however, some limitations of the system in terms of respiration reproducibility and breathing period relative to scanner settings were evident. Lung mass for the 4D CT patient scan was reproducible to within 2.1% over the eight phases, though the lung volume changed by 20% between end inspiration and end expiration (870 cm 3 ). 4D CT can be used for 4D radiotherapy, respiration-gated radiotherapy, 'slow' CT acquisition and tumour motion studies

  12. Multislice computed tomographic coronary angiography: experience in a UK centre

    International Nuclear Information System (INIS)

    Morgan-Hughes, G.J.; Marshall, A.J.; Roobottom, C.A.

    2003-01-01

    AIM: To evaluate the technique of coronary angiography with retrospectively electrocardiogram (ECG)-gated four-slice helical computed tomography (CT). MATERIALS AND METHODS: Within 1 month of undergoing routine day-case diagnostic coronary angiography, 30 consecutive patients also underwent retrospectively ECG-gated multislice CT coronary angiography. This enabled direct comparison of seven segments of proximal and mid-coronary artery for each patient by two blinded assessors. Each segment of coronary artery from the multislice CT image was evaluated initially for 'assessability' and those segments deemed assessable were subsequently investigated for the presence or absence of a significantly (n=70%) stenotic lesion. RESULTS: Overall 68% of proximal and mid-coronary artery segments were assessable. The sensitivity and specificity of four-slice CT coronary angiography in assessable segments for detecting the presence or absence (n=70%) of stenoses were 72 and 86%, respectively. These results correspond to a positive predictive value of 53% and a 93% negative predictive value. If the 32% of non-assessable segments are added into the calculation then the sensitivity and specificity fall to 49 and 66%, respectively. CONCLUSION: Although multislice CT coronary angiography is a promising technique, the overall assessability and diagnostic accuracy of four-slice CT acquisition is not sufficient to justify routine clinical use. Further, evaluation should investigate the benefit of the reduction in temporal and spatial resolution offered by 16 and 32 slice acquisition

  13. Dynamic multislice helical CT of maxillomandibular lesions. Distinction of ameloblastomas from other cystic lesions

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    Tozaki, Mitsuhiro; Hayashi, Katsuhiko; Fukuda, Kunihiko [Jikei Univ., Tokyo (Japan). School of Medicine

    2001-10-01

    The purpose of this study was to evaluate the clinical usefulness of dynamic multislice helical CT in differentiating ameloblastoma from other cystic lesions in cases of maxillomandibular cystic lesions. The study included 32 patients with maxillomandibular cystic lesions (ameloblastoma [n=6], myxofibroma [n=1], odontogenic keratocyst [n=3], dentigerous cyst [n=11], radicular cyst [n=11], and paradental cyst [n=2]). Dynamic study was performed before and 30 sec, and 90 sec after intravenous contrast medium administration. CT density values and percentage of density increase were calculated at 30 and 90 sec. In five cases of ameloblastoma, a rapidly enhancing area was detected within the cystic lesions at 30 sec, while no apparent rapid enhancement was seen in the other cystic lesions. Three cysts showed gradual enhancement in the marginal area at 90 sec. Comparing ameloblastoma and other kinds of cysts, we found significant differences in the percentage of density increase at 30 sec (p<0.01) and 90 sec (p<0.05). Dynamic multislice helical CT is useful in the diagnosis of cystic lesions of the maxillomandibular region, especially in the detection of neovascularities in ameloblastoma. (author)

  14. Dynamic multislice helical CT of maxillomandibular lesions. Distinction of ameloblastomas from other cystic lesions

    International Nuclear Information System (INIS)

    Tozaki, Mitsuhiro; Hayashi, Katsuhiko; Fukuda, Kunihiko

    2001-01-01

    The purpose of this study was to evaluate the clinical usefulness of dynamic multislice helical CT in differentiating ameloblastoma from other cystic lesions in cases of maxillomandibular cystic lesions. The study included 32 patients with maxillomandibular cystic lesions (ameloblastoma [n=6], myxofibroma [n=1], odontogenic keratocyst [n=3], dentigerous cyst [n=11], radicular cyst [n=11], and paradental cyst [n=2]). Dynamic study was performed before and 30 sec, and 90 sec after intravenous contrast medium administration. CT density values and percentage of density increase were calculated at 30 and 90 sec. In five cases of ameloblastoma, a rapidly enhancing area was detected within the cystic lesions at 30 sec, while no apparent rapid enhancement was seen in the other cystic lesions. Three cysts showed gradual enhancement in the marginal area at 90 sec. Comparing ameloblastoma and other kinds of cysts, we found significant differences in the percentage of density increase at 30 sec (p<0.01) and 90 sec (p<0.05). Dynamic multislice helical CT is useful in the diagnosis of cystic lesions of the maxillomandibular region, especially in the detection of neovascularities in ameloblastoma. (author)

  15. Organ and effective doses in newborn patients during helical multislice computed tomography examination

    Science.gov (United States)

    Staton, Robert J.; Lee, Choonik; Lee, Choonsik; Williams, Matt D.; Hintenlang, David E.; Arreola, Manuel M.; Williams, Jonathon L.; Bolch, Wesley E.

    2006-10-01

    In this study, two computational phantoms of the newborn patient were used to assess individual organ doses and effective doses delivered during head, chest, abdomen, pelvis, and torso examinations using the Siemens SOMATOM Sensation 16 helical multi-slice computed tomography (MSCT) scanner. The stylized phantom used to model the patient anatomy was the revised ORNL newborn phantom by Han et al (2006 Health Phys.90 337). The tomographic phantom used in the study was that developed by Nipper et al (2002 Phys. Med. Biol. 47 3143) as recently revised by Staton et al (2006 Med. Phys. 33 3283). The stylized model was implemented within the MCNP5 radiation transport code, while the tomographic phantom was incorporated within the EGSnrc code. In both codes, the x-ray source was modelled as a fan beam originating from the focal spot at a fan angle of 52° and a focal-spot-to-axis distance of 57 cm. The helical path of the source was explicitly modelled based on variations in collimator setting (12 mm or 24 mm), detector pitch and scan length. Tube potentials of 80, 100 and 120 kVp were considered in this study. Beam profile data were acquired using radiological film measurements on a 16 cm PMMA phantom, which yielded effective beam widths of 14.7 mm and 26.8 mm for collimator settings of 12 mm and 24 mm, respectively. Values of absolute organ absorbed dose were determined via the use of normalization factors defined as the ratio of the CTDI100 measured in-phantom and that determined by Monte Carlo simulation of the PMMA phantom and ion chamber. Across various technique factors, effective dose differences between the stylized and tomographic phantoms ranged from +2% to +9% for head exams, -4% to -2% for chest exams, +8% to +24% for abdominal exams, -16% to -12% for pelvic exams and -7% to 0% for chest-abdomen-pelvis (CAP) exams. In many cases, however, relatively close agreement in effective dose was accomplished at the expense of compensating errors in individual organ

  16. Organ and effective doses in newborn patients during helical multislice computed tomography examination

    International Nuclear Information System (INIS)

    Staton, Robert J; Lee, Choonik; Lee, Choonsik; Williams, Matt D; Hintenlang, David E; Arreola, Manuel M; Williams, Jonathon L; Bolch, Wesley E

    2006-01-01

    In this study, two computational phantoms of the newborn patient were used to assess individual organ doses and effective doses delivered during head, chest, abdomen, pelvis, and torso examinations using the Siemens SOMATOM Sensation 16 helical multi-slice computed tomography (MSCT) scanner. The stylized phantom used to model the patient anatomy was the revised ORNL newborn phantom by Han et al (2006 Health Phys.90 337). The tomographic phantom used in the study was that developed by Nipper et al (2002 Phys. Med. Biol. 47 3143) as recently revised by Staton et al (2006 Med. Phys. 33 3283). The stylized model was implemented within the MCNP5 radiation transport code, while the tomographic phantom was incorporated within the EGSnrc code. In both codes, the x-ray source was modelled as a fan beam originating from the focal spot at a fan angle of 52 0 and a focal-spot-to-axis distance of 57 cm. The helical path of the source was explicitly modelled based on variations in collimator setting (12 mm or 24 mm), detector pitch and scan length. Tube potentials of 80, 100 and 120 kVp were considered in this study. Beam profile data were acquired using radiological film measurements on a 16 cm PMMA phantom, which yielded effective beam widths of 14.7 mm and 26.8 mm for collimator settings of 12 mm and 24 mm, respectively. Values of absolute organ absorbed dose were determined via the use of normalization factors defined as the ratio of the CTDI 100 measured in-phantom and that determined by Monte Carlo simulation of the PMMA phantom and ion chamber. Across various technique factors, effective dose differences between the stylized and tomographic phantoms ranged from +2% to +9% for head exams, -4% to -2% for chest exams, +8% to +24% for abdominal exams, -16% to -12% for pelvic exams and -7% to 0% for chest-abdomen-pelvis (CAP) exams. In many cases, however, relatively close agreement in effective dose was accomplished at the expense of compensating errors in individual organ

  17. Diagnostic accuracy of multi-slice computed tomographic angiography in the detection of cerebral aneurysms

    International Nuclear Information System (INIS)

    Haghighatkhah, H. R.; Sabouri, S.; Borzouyeh, F.; Bagherzadeh, M. H.; Bakhshandeh, H.; Jalali, A. H.

    2008-01-01

    Multislice computed tomographic angiography is a rapid and minimally invasive method for the detection of intracranial aneurysms. The purpose of this study was to compare Multislice computed tomographic angiography with digital subtraction angiography In the diagnosis of cerebral aneurysms. Patients and Methods: In this cross sectional study we evaluated 111 consecutive patients [42(37.8%) male and 69(62.2%) female], who were admitted under clinical symptoms and signs. suggestive of harboring an intracranial aneurysm by using a four detector Multislice computed tomographic angiography. Then we compared results of Multislice computed tomographic angiography with digital subtraction angiography results as a gold standard method. Digital subtraction angiography was performed by bilateral selective common carotid artery injections and either unilateral or bilateral vertebral artery injections, as necessary. Multislice computed tomographic angiography images were interpreted by one radiologist and digital subtraction angiography was performed by another radiologist who was blinded to the interpretation of the Multislice computed tomographic angiograms. Results: The mean ±S D age of the patients was 49.1±13.6 years (range: 12-84 years). We performed Multislice computed tomographic in 111 and digital subtraction angiography in 85 patients. The sensitivity, specificity, positive predictive value, negative predictive value, positive and negative likelihood ratio of Multislice computed tomographic angiography, when compared with digital subtraction angiography as the gold standard, were 100%, 90%, 87.5%, 100%, 10 and 0, respectively. Conclusion: Multislice computed tomographic angiography seems to be an accurate and noninvasive imaging modality in the diagnosis of intracranial aneurysms

  18. Evaluation of the retrospective ECG-gated helical scan using half-second multi-slice CT. Motion phantom study for volumetry

    International Nuclear Information System (INIS)

    Yamamoto, Shuji; Matsumoto, Takashi; Nakanishi, Shohzoh; Hamada, Seiki; Takahei, Kazunari; Naito, Hiroaki; Ogata, Yuji

    2002-01-01

    ECG synchronized technique on multi-slice CT provide the thinner (less 2 mm slice thickness) and faster (0.5 sec/rotation) scan than that of the single detector CT and can acquire the coverage of the entire heart volume within one breath-hold. However, temporal resolution of multi-slice CT is insufficient on practical range of heart rate. The purpose of this study was to evaluate the accuracy of volumetry on cardiac function measurement in retrospective ECG-gated helical scan. We discussed the influence of the degradation of image quality and limitation of the heart rate in cardiac function measurement (volumetry) using motion phantom. (author)

  19. Optimization of multi-slice helical respiration-correlated CT: the effects of table speed and rotation time

    International Nuclear Information System (INIS)

    Wink, Nicole M; McNitt-Gray, Michael F; Solberg, Timothy D

    2005-01-01

    While respiration-correlated CT is gaining acceptance in clinical radiotherapy, the effect of scanning parameters on the image quality has yet to be addressed. The intent of this study was to characterize the effects of gantry rotation and table speed on various image quality characteristics in multi-slice, helical, retrospectively-gated CT images. Images of stationary and moving phantoms were obtained in helical mode on a 20-slice CT scanner. Motion was generated by a computer-controlled platform capable of moving simultaneously in two dimensions. Motion was monitored using a pressure gauge inserted inside an adjustable belt. Selected scans were retrospectively gated into ten phases based on the monitored motion. Gantry rotation speeds of 0.5 s and 1.0 s were evaluated with pitches ranging from 0.1 to 0.45. Several parameters, including calculated object volumes, trajectory (movement from peak to trough), deformation (actual volume divided by volume created with the maximum diameter of contoured object) and z-axis resolution, were used to characterize image quality. These studies indicate that for objects in the peak phase of a movement pattern that simulates breathing, retrospectively gated scans using fast gantry rotation speeds produce volume, trajectory, deformation and z-axis resolution results comparable with those of a stationary object

  20. Scanning and contrast enhancement protocols for multi-slice CT in evaluation of the upper abdomen

    International Nuclear Information System (INIS)

    Awai, Kazuo; Onishi, Hiromitsu; Takada, Koichi; Yamaguchi, Yasuo; Eguchi, Nobuko; Hiraishi, Kumiko; Hori, Shinichi

    2000-01-01

    The advent of multi-slice CT is one of the quantum leaps in computed tomography since the introduction of helical CT. Multi-slice CT can rapidly scan a large longitudinal (z-axis) volume with high longitudinal resolution and low image artifacts. The rapid volume coverage speed of multi-slice CT can increase the difficulty in optimizing the delay time between the beginning of contrast material injection and the acquisition of images and we need accurate knowledge about optimal temporal window for adequate contrast enhancement. High z-axis resolution of multi-slice can improve the quality of three-dimensional images and MPR images and we must select adequate slice thickness and slice intervals in each case. We discuss basic considerations for adequate contrast enhancement and scanning protocols by multi-slice CT scanner in the upper abdomen. (author)

  1. Our experience in the diagnosis of aortic dissection by multislice computed tomography

    International Nuclear Information System (INIS)

    Llerena Rojas, Luis R; Mendoza Rodriguez, Vladimir; Olivares Aquiles, Eddy

    2011-01-01

    Aortic dissection (AD) is the most frequent and life-threatening acute aortic syndrome. Currently the more used method for the aortic study is the multislice computed tomography. The purpose of this paper is to expose the more relevant features in 22 patients with AD consecutively studied by multislice computed tomography

  2. Experimental study of quantity to be taken as patient dose in helical multi-slice CT scan

    International Nuclear Information System (INIS)

    Liu Lantao; Wei Kedao; Yue Brorong; Wang Jianchao

    2009-01-01

    Objective: To bring forward a novel quantity which is used to be taken as effective dose in helical multi - slice CT scan and to validate it by experiment. Methods: Dot chamber and pencil-chamber were used to measure the doses which were performed under axial mode and helical multi-slice mode. Then the readings of doses were compared and analyzed. Results: The dose reading from dot chamber was close to the one from pencil - chamber under axial mode. The ratio is 1.14 for the readings from dot chamber under two scan modes and is 2.88 for the readings from pencil-chamber under two scan modes. Conclusions: The dose measured from dot chamber is an effective quantity to be taken as effective dose. However it is insufficient that the CTDI and DLP be used to be taken as effective dose as the limitation of pencil-chamber in length. (authors)

  3. Approximations of noise covariance in multi-slice helical CT scans: impact on lung nodule size estimation.

    Science.gov (United States)

    Zeng, Rongping; Petrick, Nicholas; Gavrielides, Marios A; Myers, Kyle J

    2011-10-07

    Multi-slice computed tomography (MSCT) scanners have become popular volumetric imaging tools. Deterministic and random properties of the resulting CT scans have been studied in the literature. Due to the large number of voxels in the three-dimensional (3D) volumetric dataset, full characterization of the noise covariance in MSCT scans is difficult to tackle. However, as usage of such datasets for quantitative disease diagnosis grows, so does the importance of understanding the noise properties because of their effect on the accuracy of the clinical outcome. The goal of this work is to study noise covariance in the helical MSCT volumetric dataset. We explore possible approximations to the noise covariance matrix with reduced degrees of freedom, including voxel-based variance, one-dimensional (1D) correlation, two-dimensional (2D) in-plane correlation and the noise power spectrum (NPS). We further examine the effect of various noise covariance models on the accuracy of a prewhitening matched filter nodule size estimation strategy. Our simulation results suggest that the 1D longitudinal, 2D in-plane and NPS prewhitening approaches can improve the performance of nodule size estimation algorithms. When taking into account computational costs in determining noise characterizations, the NPS model may be the most efficient approximation to the MSCT noise covariance matrix.

  4. The significance of multi-slice helical CT multiplanar reconstruction in the diagnoses of laryngeal carcinoma

    International Nuclear Information System (INIS)

    Li Lin; Luo Dehong; Zhou Chunwu; Zhao Xinming; Jiang Liming; Huang Yao; Jiang Lingxia; Li Jing; Wu Ning

    2006-01-01

    Objective: To evaluate the significance of multi-slice helical CT with multiplanar reconstruction in laryngeal carcinoma. Methods: Thirty-five patients with laryngeal carcinoma were studied by helical CT, MPR were subsequently done. The lesion extent of the axial image findings, MPR findings and the combined image findings were compared with the pathological results respectively. The data were statistically analyzed. Results: In the evaluation of the anterior commissure, the axial image findings, MPR findings and the combined image findings were 82.9%, 68.6% and 91.4% in accuracy respectively, the results were statistically different (P 0.05). The combined images were superior to the axial images and the MPR images in sensitivity, specificity and accuracy of the lesion extent. Conclusion: The axial images could show the shape, size, extension of the tumor and the lymphadenopathy, MPR images displayed the shape, size and extension roundly and directly, they were the supplement for the axial images. Axial images combined with MPR could improve the accuracy in the diagnoses of laryngeal carcinoma. (authors)

  5. Intraoperative cone-beam computed tomography and multi-slice computed tomography in temporal bone imaging for surgical treatment.

    Science.gov (United States)

    Erovic, Boban M; Chan, Harley H L; Daly, Michael J; Pothier, David D; Yu, Eugene; Coulson, Chris; Lai, Philip; Irish, Jonathan C

    2014-01-01

    Conventional computed tomography (CT) imaging is the standard imaging technique for temporal bone diseases, whereas cone-beam CT (CBCT) imaging is a very fast imaging tool with a significant less radiation dose compared with conventional CT. We hypothesize that a system for intraoperative cone-beam CT provides comparable image quality to diagnostic CT for identifying temporal bone anatomical landmarks in cadaveric specimens. Cross-sectional study. University tertiary care facility. Twenty cadaveric temporal bones were affixed into a head phantom and scanned with both a prototype cone-beam CT C-arm and multislice helical CT. Imaging performance was evaluated by 3 otologic surgeons and 1 head and neck radiologist. Participants were presented images in a randomized order and completed landmark identification questionnaires covering 21 structures. CBCT and multislice CT have comparable performance in identifying temporal structures. Three otologic surgeons indicated that CBCT provided statistically equivalent performance for 19 of 21 landmarks, with CBCT superior to CT for the chorda tympani and inferior for the crura of the stapes. Subgroup analysis showed that CBCT performed superiorly for temporal bone structures compared with CT. The radiologist rated CBCT and CT as statistically equivalent for 18 of 21 landmarks, with CT superior to CBCT for the crura of stapes, chorda tympani, and sigmoid sinus. CBCT provides comparable image quality to conventional CT for temporal bone anatomical sites in cadaveric specimens. Clinical applications of low-dose CBCT imaging in surgical planning, intraoperative guidance, and postoperative assessment are promising but require further investigation.

  6. General surface reconstruction for cone-beam multislice spiral computed tomography

    International Nuclear Information System (INIS)

    Chen Laigao; Liang Yun; Heuscher, Dominic J.

    2003-01-01

    A new family of cone-beam reconstruction algorithm, the General Surface Reconstruction (GSR), is proposed and formulated in this paper for multislice spiral computed tomography (CT) reconstructions. It provides a general framework to allow the reconstruction of planar or nonplanar surfaces on a set of rebinned short-scan parallel beam projection data. An iterative surface formation method is proposed as an example to show the possibility to form nonplanar reconstruction surfaces to minimize the adverse effect between the collected cone-beam projection data and the reconstruction surfaces. The improvement in accuracy of the nonplanar surfaces over planar surfaces in the two-dimensional approximate cone-beam reconstructions is mathematically proved and demonstrated using numerical simulations. The proposed GSR algorithm is evaluated by the computer simulation of cone-beam spiral scanning geometry and various mathematical phantoms. The results demonstrate that the GSR algorithm generates much better image quality compared to conventional multislice reconstruction algorithms. For a table speed up to 100 mm per rotation, GSR demonstrates good image quality for both the low-contrast ball phantom and thorax phantom. All other performance parameters are comparable to the single-slice 180 deg. LI (linear interpolation) algorithm, which is considered the 'gold standard'. GSR also achieves high computing efficiency and good temporal resolution, making it an attractive alternative for the reconstruction of next generation multislice spiral CT data

  7. Ground-glass opacity: High-resolution computed tomography and 64-multi-slice computed tomography findings comparison

    International Nuclear Information System (INIS)

    Sergiacomi, Gianluigi; Ciccio, Carmelo; Boi, Luca; Velari, Luca; Crusco, Sonia; Orlacchio, Antonio; Simonetti, Giovanni

    2010-01-01

    Objective: Comparative evaluation of ground-glass opacity using conventional high-resolution computed tomography technique and volumetric computed tomography by 64-row multi-slice scanner, verifying advantage of volumetric acquisition and post-processing technique allowed by 64-row CT scanner. Methods: Thirty-four patients, in which was assessed ground-glass opacity pattern by previous high-resolution computed tomography during a clinical-radiological follow-up for their lung disease, were studied by means of 64-row multi-slice computed tomography. Comparative evaluation of image quality was done by both CT modalities. Results: It was reported good inter-observer agreement (k value 0.78-0.90) in detection of ground-glass opacity with high-resolution computed tomography technique and volumetric Computed Tomography acquisition with moderate increasing of intra-observer agreement (k value 0.46) using volumetric computed tomography than high-resolution computed tomography. Conclusions: In our experience, volumetric computed tomography with 64-row scanner shows good accuracy in detection of ground-glass opacity, providing a better spatial and temporal resolution and advanced post-processing technique than high-resolution computed tomography.

  8. Three-dimensional multislice CT imaging of otitis media

    International Nuclear Information System (INIS)

    Suzuki, Miyako; Yoshikawa, Hiroshi; Hosokawa, Akira; Furukawa, Tomoyasu; Ichikawa, Ginichiro; Wada, Akihiro; Ando, Ichiro

    2002-01-01

    In recent years, the multislice CT system has come into practical use that enables table movement of half mm, resulting in a significant improvement in resolution. The use of this CT system enables to depict the entire auditory ossicles, including the stapes. 3D reconstruction was performed using helical CT data in 5 patients with chronic otitis media and 5 patients with cholesteatoma. An Aquilion Multi (Toshiba) multislice helical CT scanner and a Xtension (Toshiba) image workstation were used in this study. We demonstrated the 3D display with axial, coronal and sagittal images. Compared with the normal ears, it was necessary to set a higher threshold for the affected ears. It is important to select suitable threshold for demonstration of 3D images optimally. Bone destruction of the stapes was confirmed at surgery in 2 ears. The stapes was observed at 3D-CT imaging in other 18 ears. It was found that the 3D images of the ossicular destruction in ears with cholesteatoma were consistent with surgical findings. It is therefore concluded that 3D imaging of the middle ear using a multislice CT scanner is clinically useful. (author)

  9. Three-dimensional multislice CT imaging of otitis media

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Miyako [Yanagibasi Hospital, Tokyo (Japan); Yoshikawa, Hiroshi; Hosokawa, Akira; Furukawa, Tomoyasu; Ichikawa, Ginichiro [Juntendo Univ., Tokyo (Japan). School of Medicine; Wada, Akihiro; Ando, Ichiro [Juntendo Univ., Chiba (Japan). Urayasu Hospital

    2002-07-01

    In recent years, the multislice CT system has come into practical use that enables table movement of half mm, resulting in a significant improvement in resolution. The use of this CT system enables to depict the entire auditory ossicles, including the stapes. 3D reconstruction was performed using helical CT data in 5 patients with chronic otitis media and 5 patients with cholesteatoma. An Aquilion Multi (Toshiba) multislice helical CT scanner and a Xtension (Toshiba) image workstation were used in this study. We demonstrated the 3D display with axial, coronal and sagittal images. Compared with the normal ears, it was necessary to set a higher threshold for the affected ears. It is important to select suitable threshold for demonstration of 3D images optimally. Bone destruction of the stapes was confirmed at surgery in 2 ears. The stapes was observed at 3D-CT imaging in other 18 ears. It was found that the 3D images of the ossicular destruction in ears with cholesteatoma were consistent with surgical findings. It is therefore concluded that 3D imaging of the middle ear using a multislice CT scanner is clinically useful. (author)

  10. Investigation of the slice sensitivity profile for step-and-shoot mode multi-slice computed tomography

    International Nuclear Information System (INIS)

    Hsieh Jiang

    2001-01-01

    Multislice computed tomography (MCT) is one of the recent technology advancements in CT. Compared to single slice CT, MCT significantly improves examination time, x-ray tube efficiency, and contrast material utilization. Although the scan mode of MCT is predominately helical, step-and-shoot (axial) scans continue to be an important part of routine clinical protocols. In this paper, we present a detailed investigation on the slice sensitivity profile (SSP) of MCT in the step-and-shoot mode. Our investigation shows that, unlike single slice CT, the SSP for MCT exhibits multiple peaks and valleys resulting from intercell gaps between detector rows. To fully understand the characteristics of the SSP, we developed an analytical model to predict the behavior of MCT. We propose a simple experimental technique that can quickly and accurately measure SSP. The impact of the SSP on image artifacts and low contrast detectability is also investigated

  11. Optimization of pediatric examinations in a multislice helical CT

    International Nuclear Information System (INIS)

    Ombada, T. H. A.

    2010-12-01

    Radiological protection of pediatric patients undergoing medical imaging procedures involving ionizing radiation has always received special attention. This is due to the fact that children have higher radiation sensitivity and increased likelihood for radiation-induced cancer manifesting in many more years of their life than adults. In computed tomography (CT), such attention is more important because of the potential of relatively higher radiation doses during these procedures. Such high doses are possible with technological developments where volume scanning using faster multi-slice CT systems is now preferred to conventional CT equipment. The task of this study is to assess the optimization of paediatric doses in multi-slice CT examinations. It was carried out in Alrebat University Hospital for 31 pediatric patients, 43 examinations (27 head examination and 16 body (chest, abdomen and pelvis) examinations). Data were collected for scan parameters (kV, m As, pitch, scan length, number of slices and slice thickness) and doses displayed in monitor (CTDI v ol and DLP) for head examinations and body (chest, abdomen and pelvis) examinations. For head CT, displayed CTDI v ol ranged from 1.56 to 69.12 mGy, calculated value from 2.10 to 70.93 mGy. Displayed DLP ranged from 53 to 1817 mGy.cm, calculated from 95.30 to 1532.16 mGy. cm. For body examination, the range of displayed CTDI from 1.63 to 3.92 mGy, calculated value from 2.22 to 5.34 mGy. Displayed DLP ranged from 34 to 194 mGy.cm, for calculated from 45.89 to 161.98 mGy. cm. The calculated values are in agreement with reference study dose values although there are some high values in this study for some examinations, this variation or difference may attribute to variation in pediatric ages (9 days- 15 years), scan length and m As values. There is variation between calculated and displayed values. more optimization for CT doses is needed. (Author)

  12. Optimization of pediatric examinations in a multislice helical CT

    Energy Technology Data Exchange (ETDEWEB)

    Ombada, T H. A. [Atomic Energy Council, Sudan Academy of Sciences (SAS), Khartoum (Sudan)

    2010-12-15

    Radiological protection of pediatric patients undergoing medical imaging procedures involving ionizing radiation has always received special attention. This is due to the fact that children have higher radiation sensitivity and increased likelihood for radiation-induced cancer manifesting in many more years of their life than adults. In computed tomography (CT), such attention is more important because of the potential of relatively higher radiation doses during these procedures. Such high doses are possible with technological developments where volume scanning using faster multi-slice CT systems is now preferred to conventional CT equipment. The task of this study is to assess the optimization of paediatric doses in multi-slice CT examinations. It was carried out in Alrebat University Hospital for 31 pediatric patients, 43 examinations (27 head examination and 16 body (chest, abdomen and pelvis) examinations). Data were collected for scan parameters (kV, m As, pitch, scan length, number of slices and slice thickness) and doses displayed in monitor (CTDI{sub v}ol and DLP) for head examinations and body (chest, abdomen and pelvis) examinations. For head CT, displayed CTDI{sub v}ol ranged from 1.56 to 69.12 mGy, calculated value from 2.10 to 70.93 mGy. Displayed DLP ranged from 53 to 1817 mGy.cm, calculated from 95.30 to 1532.16 mGy. cm. For body examination, the range of displayed CTDI from 1.63 to 3.92 mGy, calculated value from 2.22 to 5.34 mGy. Displayed DLP ranged from 34 to 194 mGy.cm, for calculated from 45.89 to 161.98 mGy. cm. The calculated values are in agreement with reference study dose values although there are some high values in this study for some examinations, this variation or difference may attribute to variation in pediatric ages (9 days- 15 years), scan length and m As values. There is variation between calculated and displayed values. more optimization for CT doses is needed. (Author)

  13. 64 multislice computed tomography imaging of coronary artery origin anomalies in adults

    International Nuclear Information System (INIS)

    Dai Qinyi; Lv Biao; Zhang Zhaoqi

    2006-01-01

    Objective: To assess the value of 64 multislice computed tomography (64 MSCT) in the evaluation of coronary artery origin anomalies in adults. Methods: Nine hundred and seventy eight Chinese adult patients undergone coronary artery CT angiography (CTA) between March and July 2005 at Anzhen hospital were reviewed for this study. Results: In consecutive 978 patients, 64 MSCT identified (3.07%) with an anomalous origin of the coronary artery, in 30 patients including anomalous origin of the right coronary artery (RCA) in 9 patients, the left coronary artery (LCA)in 7 patients, both RCA and LCA in 2 patients, the absence of the left circumflex artery (LCX) in 1 patient and anomalous origin of the branch of coronary artery in 11 patients. Conclusion: Noninvasive 64 multislice computed tomography can detect the anomalous origin of the coronary artery with high resolution. (authors)

  14. Evaluation of gastrointestinal stromal tumors by multislice computed tomography and magnetic resonance imaging

    International Nuclear Information System (INIS)

    Porto, Fabiano Elias; Baroni, Ronaldo Hueb; Rocha, Manoel de Souza; Funari, Marcelo Buarque de Gusmao; Macedo, Antonio Luiz de Vasconcellos; Pelizon, Christina Helena de Toledo

    2005-01-01

    This article presents three cases of gastrointestinal stromal tumors with clinical manifestations and pathological features, along with differential diagnoses, with special emphasis on multislice computed tomography and magnetic resonance imaging findings. (author)

  15. Evaluation of radiation exposure with singleslice- and a multislice-spiral CT system (a phantom study)

    International Nuclear Information System (INIS)

    Giacomuzzi, S.M.; Rieger, M.; Lottersberger, C.; Peer, S.; Peer, R.; Buchberger, W.; Bale, R.; Mallouhi, A.; Jaschke, W.; Torbica, P.; Perkmann, R.

    2001-01-01

    The purpose of study was to compare patient dose applying singleslice- and multislice-spiral CT. Methods: The examinations were performed with a singleslice-spiral CT (Highspeed Advantage; GE Medical Systems; Milwaukee, USA) and with a multislice CT systems (LightSpeed QX/i GE Medical Systems; Milwaukee, USA). For the determination of the radiation exposure (absorbed dose) a selection of most executed protocols (thorax-helical, abdomen-helical, petrous bone-axial, head-axial) were simulated using an Alderson Rando Phantom. The dose was determined by means of lithiumfluorid-thermoluminescence dosimeters (TLD-GR 200). Results: For thorax and abdomen protocols higher energy dose values could be found using a multislice CT. On the average the energy dose values were increased by 2.6 on an average in relation to single slice spiral CT. The energy dose values of the multisclice CT using head protocols could be reduced by 30% in relation to single slice spiral CT due to suitable parameter selections. The energy dose applying a petrous bone protocol resulted in an average increase by a factor 1.5 using a multislice CT. Conclusion: Using the new multislice CT technique protocol strategies must be optimized regarding the patient doses. Users can operate critically in the sense of the radiation protection only if they are aware of the occurring dose amounts to the patient. (orig.) [de

  16. Diagnostic value of 64 multislice computed tomography in the assessment of the coronary graft patency

    International Nuclear Information System (INIS)

    Llerena Rojas, Luis R; Mendoza Rodriguez, Vladimir; Olivares Aquiles, Eddy

    2011-01-01

    Symptoms recurrence after surgical coronary artery revascularization requires the assessment of graft patency. At the moment, promissory results have been reported using the multislice computed tomography

  17. Role of Multislice Computed Tomography and Local Contrast in the Diagnosis and Characterization of Choanal Atresia

    Directory of Open Access Journals (Sweden)

    Khaled Al-Noury

    2011-01-01

    Full Text Available Objective. To illustrate the role of multislice computed tomography and local contrast instillation in the diagnosis and characterization of choanal atresia. To review the common associated radiological findings. Methods. We analyzed 9 pediatric patients (5 males and 4 females with suspected choanal atresia by multislice computed tomography. We recorded the type of atresia plate and other congenital malformations of the skull. Results. Multislice computed tomography with local contrast installed delineated the posterior choanae. Three patients had unilateral mixed membranous and bony atresia. Three patients had unilateral pure bony atresia. Only 1 of 7 patients have bilateral bony atresia. It also showed other congenital anomalies in the head region. One patient is with an ear abnormality. One patient had congenital nasal pyriform aperture stenosis. One of these patients had several congenital abnormalities, including cardiac and renal deformities and a hypoplastic lateral semicircular canal. Of the 6 patients diagnosed to have choanal atresia, 1 patient had esophageal atresia and a tracheoesophageal fistula. The remaining patients had no other CHARGE syndrome lesions. Conclusions. Local Contrast medium with the application of the low-dose technique helps to delineate the cause of the nasal obstruction avoiding a high radiation dose to the child.

  18. Multi-slice Computed Tomography Appearance of Abscess of Cavum Septum Pellucidum: A Case Report and Review of the Literature

    Energy Technology Data Exchange (ETDEWEB)

    Vasudev, M.K.; Chavan, R.G.; Nagarajan, K.; Shukla, D.; Devi, B.I. [National Inst. of Mental Health and Neurosciences, Bangalore (India). Depts. of Neuroimaging and Interventional Radiology and of Neurosurgery

    2006-04-15

    Abscesses involving the cavum septum pellucidum are rare and, owing to their location, detection may be difficult with routine conventional computed tomography (CT). Only a few isolated cases have been reported and mostly in children. We report a case of abscess involving the cavum septum pellucidum in an adult and its appearance on multi-slice spiral CT Abscess, cavum septum pellucidum, multi-slice CT, surgery.

  19. Multidetector-row helical computed tomography in the evaluation of cervical spine disorders; Tomografia computadorizada multislice no diagnostico das afeccoes da coluna cervical

    Energy Technology Data Exchange (ETDEWEB)

    Rosemberg, Laercio Alberto; Almeida, Milena Oliveira; Rios, Adriana Martins; Garbaccio, Viviane Ladeira; Kim, Nelson Ji Tae; Daniel, Mauro Miguel; Funari, Marcelo Buarque de Gusmao [Hospital Israelita Albert Einstein, Sao Paulo, SP (Brazil). Dept. de Imagem]. E-mail: laercio@einstein.br

    2003-07-01

    Multidetector-row computed tomography (MRCT) has advantages in comparison to conventional helical computed tomography, such as reduction of study time, lower radiation doses, fewer metallic artifacts and high quality multiplanar reformatting and three dimensional reconstructions. We reviewed 150 cervical spine examinations and selected the most illustrative cases including congenital anomalies, degenerative lesions, spinal infections, neoplasms, traumatic injuries and postoperative abnormalities. The quality of multiplanar reformatting and volume reconstructions of the MRCT made the detection and evaluation of most of cases with complex anatomy easier and more precise. (author)

  20. Role of Postmortem Multislice Computed Tomography Scan in Close Blunt Head Injury

    Directory of Open Access Journals (Sweden)

    Prijo Sidipratomo

    2014-08-01

    Full Text Available BACKGROUND: Conventional autopsy in Indonesia is not well accepted as it is contrary to religion and culture. New radiological imaging method such as multislice computed tomography (MSCT scan has potential to be a diagnostic tool in forensic pathology. The purpose of this study is to determine the ability of MSCT scan in finding abnormalities in close blunt head injury compared with autopsy. METHODS: This study used descriptive qualitative method. Postmortem cases in Department of Forensic Medicine and Radiology of Dr. Cipto Mangunkusumo Hospital were selected based on inclusion criteria. Then MSCT scan and autopsy were conducted. MSCT scan and autopsy results were compared and analyzed. RESULTS: There were 491 postmortem cases of blunt head injury. However, only 10 cases fulfilled inclusion criteria. Subarachnoid haemorrhages were identified 100% with MSCT scan and 80% with autopsy. Cerebral oedemas were identified 100% either with MSCT scan and autopsy. Subdural haemorrhages were identified 100% with MSCT scan, while 50% with autopsy. Multiple fractures were identified 80% with MSCT scan, while 40% with auto. CONCLUSIONS: MSCT scan showed a sensitive detection in finding abnormalities in close blunt head injury. Therefore it could be as an alternative choice of examination in close blunt head injury cases. KEYWORDS: multislice computed tomography scan, postmortem, blunt head injury, autopsy.

  1. Multislice helical CT (MSCT) for mid-facial trauma: optimization of parameters for scanning and reconstruction

    International Nuclear Information System (INIS)

    Dammert, S.; Funke, M.; Obernauer, S.; Grabbe, E.; Merten, H.A.

    2002-01-01

    Purpose: To determine the optimal scan parameters in multislice helical CT (MSCT) of the facial bone complex for both axial scanning and multiplanar reconstructions. Material and Methods: An anthropomorphic skull phantom was examined with a MSCT. Axial scans were performed with continuously increasing collimations (4 x 1.25 - 4 x 2.5 mm), tube current (20 - 200 mA) and table speeds (3.75 mm/rot. and 7.5 mm/rot.). Multiplanar reconstructions in coronal and parasagittal planes with different reconstruction increment and slice thickness were evaluated in terms of image noise, contour artifacts and visualisation of anatomical structures. Results: The best image quality was obtained with a collimation of 4 x 1.25 mm and a - table speed of 3.75 mm/rot. A reconstruction increment of 0.6 mm achieved the best time to image quality relation. With these parameters the bone structures were depicted in an optimal way without artifacts. The tube current could be reduced to 50 mA without significant loss of image quality. The optimized protocol was used for regular routine examinations in patients with facial trauma (n = 66). Conclusions: Low-dose MSCT using thin collimation, low table speed and small reconstruction increments provides excellent data for both axial images and multiplanar reconstructions in patients with facial trauma. An additional examination in coronal orientation is therefore no longer necessary. (orig.) [de

  2. Diagnostic accuracy of coronary angiography with multislice computed tomography applied to 'the Real World'

    International Nuclear Information System (INIS)

    Rodriguez Granillo, Gaston A.; Rosales, Miguel A.; Llaurado, Claudio; Fernandez Pereira, Carlos; Garcia Carcia, Hector M.

    2006-01-01

    Objective: To assess the diagnostic accuracy of Coronary Angiography with Multislice Computed Tomography (MSCT) for the detection of significant coronary artery stenoses. Material and methods: Patients studied had an indication for diagnostic coronary angiography and no history of contrast allergies, renal failure or arrhythmias. A multislice tomography equipment (Brilliance 40, Philips, The Netherlands) with ECG gating was used for image acquisition. A total of 90-125 mI of iodinated contrast was administered by IV route. Obesity, diabetes, diffusely calcified segments with a diameter < 2.0 mm, and segments treated with stents were not considered exclusion criteria. Lesions were defined as significant when the decrease in Iumen was ≥ 50% by MSCT and quantitative coronary angiography (QCA). Results: A total of 38 patients were scanned before the intervention. Of them, one (3%) was excluded because of inadequate image quality. The remaining 37 patients (444 segments), with an adequate quality image, were included in the study (81% men, mean age 62.43 ± 12.5 years, 13.5% diabetics). Mean scan time was 15.12 ± 2.6 seconds, and 444 segments were assessed with both techniques. The number of lesions deemed significant by QCA and MSCT were 88 (17%) and 93 (18%), respectively. Sensitivity, specificity, positive and negative predictive values of MSCT to detect significant stenoses were 82%, 93%, 72% and 96%, respectively. Conclusion: In non-selected patients, coronary angiography by multislice computed tomography exhibits a high negative predictive value for the detection of obstructive coronary disease. (author)

  3. Role of Postmortem Multislice Computed Tomography Scan in Close Blunt Head Injury

    OpenAIRE

    Sidipratomo, Prijo; Prija, Trijono Karmawan Sukana; Murtala, Bachtiar; Purwadianto, Agus; Lawrence, Gatot Susilo

    2014-01-01

    BACKGROUND: Conventional autopsy in Indonesia is not well accepted as it is contrary to religion and culture. New radiological imaging method such as multislice computed tomography (MSCT) scan has potential to be a diagnostic tool in forensic pathology. The purpose of this study is to determine the ability of MSCT scan in finding abnormalities in close blunt head injury compared with autopsy. METHODS: This study used descriptive qualitative method. Postmortem cases in Department of Forensic M...

  4. Multislice spiral computed tomography imaging in congenital inner ear malformations.

    Science.gov (United States)

    Ma, Hui; Han, Ping; Liang, Bo; Tian, Zhi-liang; Lei, Zi-qiao; Kong, Wei-jia; Feng, Gan-sheng

    2008-01-01

    The purpose of this study is to evaluate the usefulness of multislice spiral computed tomography (CT) in the diagnosis of congenital inner ear malformations. Forty-four patients with sensorineural hearing loss were examined on a Somatom Sensation 16 (Siemens) CT scanner. The 3-dimensional reconstructions and multiplanar reformation (MPR) were performed using the volume-rendering technique (VRT) on the workstation. Of the 44 patients examined for this study, 25 patients were found to be normal and 19 patients (36 ears) were diagnosed with congenital inner ear malformations. Of the malformations, the axial, MPR, and VRT images can all display the site and degree in 33 of the ears. Volume-rendering technique images were superior to the axial images in displaying the malformations in 3 ears with small lateral semicircular canal malformations. The common malformations were Michel deformity (1 ear), common cavity deformity (3 ears), incomplete partition I (3 ears), incomplete partition II (Mondini deformity) (5 ears), vestibular and semicircular canal malformations (14 ears), enlarged vestibular aqueduct (16 ears, 6 of which had other malformations), and internal auditory canal malformation (8 ears, all accompanied by other malformations). Multislice spiral CT allows a comprehensively assessment of various congenital inner ear malformations through high-quality MPR and VRT reconstructions. Volume-rendering technique images can display the site and degree of the malformation 3-dimensionally and intuitionisticly. This is very useful to the cochlear implantation.

  5. Anatomical variations of paranasal sinuses at multislice computed tomography: what to look for

    International Nuclear Information System (INIS)

    Miranda, Christiana Maia Nobre Rocha de; Maranhao, Carol Pontes de Miranda; Padilha, Igor Gomes; Farias, Lucas de Padua Gomes de; Jatoba, Mayara Stephanie de Araujo; Andrade, Anna Carolina Mendonca de; Padilha, Bruno Gomes

    2011-01-01

    Multislice computed tomography is currently the imaging modality of choice for evaluating paranasal sinuses and adjacent structures. Such a method has been increasingly utilized in the assessment of anatomical variations, allowing their accurate identification with high anatomical details. Some anatomical variations may predispose to sinusal diseases, constituting areas of high risk for injuries and complications during surgical procedures. Therefore, the recognition of such variations is critical in the preoperative evaluation for endoscopic surgery. (author)

  6. Anatomical variations of paranasal sinuses at multislice computed tomography: what to look for

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, Christiana Maia Nobre Rocha de; Maranhao, Carol Pontes de Miranda [Clinica de Medicina Nuclear e Radiologia de Maceio (Medradius), Maceio, AL (Brazil). Setor de Tomografia Computadorizada; Arraes, Fabiana Maia Nobre Rocha [Clinica Sinus, Maceio, AL (Brazil); Padilha, Igor Gomes; Farias, Lucas de Padua Gomes de; Jatoba, Mayara Stephanie de Araujo; Andrade, Anna Carolina Mendonca de; Padilha, Bruno Gomes [Universidade Federal de Alagoas (UFAL), Maceio, AL (Brazil)

    2011-07-15

    Multislice computed tomography is currently the imaging modality of choice for evaluating paranasal sinuses and adjacent structures. Such a method has been increasingly utilized in the assessment of anatomical variations, allowing their accurate identification with high anatomical details. Some anatomical variations may predispose to sinusal diseases, constituting areas of high risk for injuries and complications during surgical procedures. Therefore, the recognition of such variations is critical in the preoperative evaluation for endoscopic surgery. (author)

  7. Optimized control of X-ray exposure and image noise using a particular multislice CT scanner

    International Nuclear Information System (INIS)

    Yamamoto, Shuji; Suzuki, Masahiro; Kakinuma, Ryutaro; Moriyama, Noriyuki; Koyama, Yoshihiro; Nagasawa, Hirofumi

    2008-01-01

    Patient dose reduction in computed tomography (CT) always results in a trade off between radiation exposure and image quality. There are few reports that estimate the relationship between image quality and X-ray exposure in CT examinations as one optimal index. The purpose of this study was to determine the optimal parameter settings enabling a low radiation exposure without compromising image quality using a particular 4-row multislice CT (MSCT) scanner (Aquilion VZ 4-slice CT scanner, Toshiba Medical Systems Corporation, Otawara, Tochigi, Japan). Normalized dose divided by image noise for helical pitches (nDNR: normalized dose to noise ratio) were calculated in consideration of beam collimation and tube current-time product. Optimal tube current-time product was calculated using the nDNR for the helical pitches based on user-defined standards of quality of the CT image. As a result, the nDNR proved to be well-supported to decrease the patient exposure in various exposure conditions of MSCT scans; however, the dose and image noise did not show a linear relation to the helical pitch. In conclusion, nDNR can be applied to patient dose reduction while keeping an acceptable image quality using a particular 4-row MSCT scanner. (author)

  8. Cardiac motion extraction and characterization in multislice computed tomography

    International Nuclear Information System (INIS)

    Simon, A.

    2005-12-01

    Cardiac kinetics analysis is of a great diagnostic interest in the fight against cardiovascular pathologies. Two methods are proposed in order to estimate cardiac motion from dynamic sequences of three-dimensional volumes acquired in multislice computed tomography. These methods both lie on a feature matching process, carried out within a Markovian framework and according to a multi-resolution scheme. The first method, estimating the correspondences between pre-segmented surfaces, is dependent on the temporal coherence of this segmentation. The second method estimates the correspondences between, on the one hand, a segmented surface and, on the other hand, the original data volume corresponding to the next moment. The motion estimation and the segmentation are then carried out, on the whole sequence, during a single process. Both methods are validated on simulated and real data. (author)

  9. Three-dimensional multislice spiral computed tomographic angiography: a potentially useful tool for safer free tissue transfer to complicated regions

    DEFF Research Database (Denmark)

    Demirtas, Yener; Cifci, Mehmet; Kelahmetoglu, Osman

    2009-01-01

    Three-dimensional multislice spiral computed tomographic angiography (3D-MSCTA) is a minimally invasive method of vascular mapping. The aim of this study was to evaluate the clinical usefulness of this imaging technique in delineating the recipient vessels for safer free tissue transfer to compli......Three-dimensional multislice spiral computed tomographic angiography (3D-MSCTA) is a minimally invasive method of vascular mapping. The aim of this study was to evaluate the clinical usefulness of this imaging technique in delineating the recipient vessels for safer free tissue transfer...... be kept in mind, especially inthe patients with peripheral vascular disease. 3D-MSCTA has the potential to replace digital subtraction angiography for planning of microvascular reconstructions and newer devices with higher resolutions will probably increase the reliability of this technique. (c) 2009...

  10. Demonstration of the right inferior phrenic artery by using multislice helical CT

    International Nuclear Information System (INIS)

    Zhao Shaohong; Liu Xin; Cai Zulong; Zhao Hong; Yang Li

    2006-01-01

    Objective: To demonstrate the origin of the right inferior phrenic artery (RIPA) in normal and hepatocellular carcinoma (HCC) patients and provide valuable anatomical information for angiographers before and after transcatheter arterial chemoembolization (TACE). Methods: Four hundred and forty consecutive patients including 133 HCC cases who had biphase abdominal CT were assessed in this study. The routine abdominal enhanced CT scan (GE, LightSpeed16) was performed with 120 kV, 200-240 mAs, 10 mm collimation, 1.375 pitch, and 10 mm reconstruction interval at 22-25 seconds for arterial phase triggered by timing bolus, 60 seconds for portal venous phase after injection of 100 ml contrast material (300 mg I/ml) at a rate of 3.5 ml/s. Multiplanar reconstruction (MPR) and maximum intensity projection (MIP) images were generated using 1.25 mm images reconstructed with 1 mm interval in arterial phase and reviewed by two radiologists. An enhanced artery medial-posterior to the IVC, originated from aorta or its branches to the diaphragmatic dome was interpreted as the RIPA. Results: The RIPA was showed in all 440 patients (100%). Among 218 (49.5%) RIPAs originated from the aorta, 140 were from the fight side of the aorta, 22 from the left side of the aorta, 56 from the anterior wall of the aorta, 36 RIPAs had the same origin with the left inferior phrenic artery. Among 138 (31.4%) RIPAs from the celiac artery, 10 RIPAs had the same origin with the left gastric artery, and 33 RIPAs had the same origin with the left inferior phrenic artery. 78 (17.7%) were from the fight renal artery, 6 (1.4%) were from the left gastric artery (the left gastric artery from aorta). The dilatation of the RIPA was demonstrated in 16 of 133 hepatocellular carcinoma patients. Conclusion: Multislice helical CT could demonstrate the origin of the RIPA in arterial phase and provide useful anatomical information for angiographer before and after TACE. (authors)

  11. Five-year clinical and functional multislice computed tomography angiographic results after coronary implantation of the fully resorbable polymeric everolimus-eluting scaffold in patients with de novo coronary artery disease

    DEFF Research Database (Denmark)

    Onuma, Yoshinobu; Dudek, Dariusz; Thuesen, Leif

    2013-01-01

    This study sought to demonstrate the 5-year clinical and functional multislice computed tomography angiographic results after implantation of the fully resorbable everolimus-eluting scaffold (Absorb BVS, Abbott Vascular, Santa Clara, California).......This study sought to demonstrate the 5-year clinical and functional multislice computed tomography angiographic results after implantation of the fully resorbable everolimus-eluting scaffold (Absorb BVS, Abbott Vascular, Santa Clara, California)....

  12. Pulmonary artery aneurysm in Bechcet's disease: helical computed tomography study

    International Nuclear Information System (INIS)

    Munoz, J.; Caballero, P.; Olivera, M. J.; Cajal, M. L.; Caniego, J. L.

    2000-01-01

    Behcet's disease is a vasculitis of unknown etiology that affects arteries and veins of different sizes and can be associated with pulmonary artery aneurysms. We report the case of a patient with Behcet's disease and a pulmonary artery aneurysm who was studied by means of plain chest X ray, helical computed tomography and pulmonary arteriography. Helical computed tomography is a reliable technique for the diagnosis and follow-up of these patients. (Author) 9 refs

  13. Concept and development of measurement method of time sensitivity profile (TSP) in X-ray CT. Comparison of non-helical, single-slice helical, and multi-slice helical scans

    International Nuclear Information System (INIS)

    Tsujioka, Katsumi; Ida, Yoshihiro; Ohtsubo, Hironori; Takahashi, Yasukata; Niwa, Masayoshi

    2000-01-01

    We focused on the time element contained in a single CT image, and devised the concept of a time-sensitivity profile (TSP) describing how the time element is translated into an image. We calculated the data collection time range when the helical pitch is changed in non helical scans, single slice helical scans, and multi slice helical scans. We then calculated the time sensitivity profile (TSP) from the weighting applied when the data collection time range is translated into an image. TSP was also measured for each scanning method using our self-made moving phantom. TSPs obtained from the calculation and the experiments were very close. TSP showed interesting characteristics with each scanning method, especially in the case of multi slice helical scanning, in which TSP became shorter as helical pitch increased. We referred to the TSP's FWHM as the effective scanning time. When we conducted multi slice helical scanning at helical pitch 3, the effective scanning time increased to about 24% longer than that of a non helical scan. When we conducted multi slice helical scanning at helical pitch 5 or 6, the effective scanning time was about half that of a non helical scan. The time sensitivity profile (TSP) is a totally new concept that we consider an important element in discussing the time resolution of a CT scanner. The results of this review will provide significant data in determining the scanning parameters when scanning a moving object. (author)

  14. Analysis of intensity variability in multislice and cone beam computed tomography.

    Science.gov (United States)

    Nackaerts, Olivia; Maes, Frederik; Yan, Hua; Couto Souza, Paulo; Pauwels, Ruben; Jacobs, Reinhilde

    2011-08-01

    The aim of this study was to evaluate the variability of intensity values in cone beam computed tomography (CBCT) imaging compared with multislice computed tomography Hounsfield units (MSCT HU) in order to assess the reliability of density assessments using CBCT images. A quality control phantom was scanned with an MSCT scanner and five CBCT scanners. In one CBCT scanner, the phantom was scanned repeatedly in the same and in different positions. Images were analyzed using registration to a mathematical model. MSCT images were used as a reference. Density profiles of MSCT showed stable HU values, whereas in CBCT imaging the intensity values were variable over the profile. Repositioning of the phantom resulted in large fluctuations in intensity values. The use of intensity values in CBCT images is not reliable, because the values are influenced by device, imaging parameters and positioning. © 2011 John Wiley & Sons A/S.

  15. Budd-Chiari syndrome: dynamic enhancement findings with multi-slice helical CT and CT angiography analysis

    International Nuclear Information System (INIS)

    Meng Xiaochun; Shan Hong; Zhu Kangshun; Xu Chuan; Zhang Jiansheng; Liu Lingyun; Ye Binbin

    2005-01-01

    Objective: To investigate the dynamic enhancement regulations of liver and their mechanism in Budd-Chiari syndrome (BCS) by using multi-slice CT and evaluate the value of CT angiography in the diagnosis of BCS. Methods: 28 cases with BCS confirmed by digital subtraction angiography (DSA) were retrospectively analyzed. All patients underwent dynamic enhancement examinations with multi-slice CT within 1 week before DSA. The relevant vessels were reconstructed respectively with MIP, VR and MPR. Compared with the results of DSA, we analyzed the dynamic enhancement regulations of liver in BCS, estimated the value of dynamic enhancement CT exams and CTA techniques in judging the obstruction level and showing collateral vessels. Results: Of all 28 cases, CT correctly showed the obstruction level in 26 cases, and 2 had incorrect results which proved to be membranous obstruction of the inferior vena cava superior to diaphragm. In 22 cases with hepatic vein obstructions, hepatic parenchyma displayed typical patchy enhancement in 19, atypical patchy enhancement in 3.8 cases among these showed benign nodules. Simultaneously, CT showed stenosis and rigidity of portal vein branches in 20, enlargement of hepatic artery in 14, hepatic collateral vessels in 20 out of 22 cases. In 6 cases with simple obstruction of inferior vena cava, hepatic changes were not found. Collateral circulations in or out of liver corresponded to the obstruction level. Conclusion: Dynamic enhancement examinations with multi-slice CT can correctly reflect the hepatic hemodynamic changes. Transverse images, combined with CTA, can explicitly display the obstruction level of vascular lesions and collateral circulations in BCS. (authors)

  16. Computed gray levels in multislice and cone-beam computed tomography.

    Science.gov (United States)

    Azeredo, Fabiane; de Menezes, Luciane Macedo; Enciso, Reyes; Weissheimer, Andre; de Oliveira, Rogério Belle

    2013-07-01

    Gray level is the range of shades of gray in the pixels, representing the x-ray attenuation coefficient that allows for tissue density assessments in computed tomography (CT). An in-vitro study was performed to investigate the relationship between computed gray levels in 3 cone-beam CT (CBCT) scanners and 1 multislice spiral CT device using 5 software programs. Six materials (air, water, wax, acrylic, plaster, and gutta-percha) were scanned with the CBCT and CT scanners, and the computed gray levels for each material at predetermined points were measured with OsiriX Medical Imaging software (Geneva, Switzerland), OnDemand3D (CyberMed International, Seoul, Korea), E-Film (Merge Healthcare, Milwaukee, Wis), Dolphin Imaging (Dolphin Imaging & Management Solutions, Chatsworth, Calif), and InVivo Dental Software (Anatomage, San Jose, Calif). The repeatability of these measurements was calculated with intraclass correlation coefficients, and the gray levels were averaged to represent each material. Repeated analysis of variance tests were used to assess the differences in gray levels among scanners and materials. There were no differences in mean gray levels with the different software programs. There were significant differences in gray levels between scanners for each material evaluated (P <0.001). The software programs were reliable and had no influence on the CT and CBCT gray level measurements. However, the gray levels might have discrepancies when different CT and CBCT scanners are used. Therefore, caution is essential when interpreting or evaluating CBCT images because of the significant differences in gray levels between different CBCT scanners, and between CBCT and CT values. Copyright © 2013 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

  17. Application of low dose multi-slice helical CT in orbital trauma patients

    International Nuclear Information System (INIS)

    Yang Rui; Dai Limei; Li Jianying; Wang Fengyan; Du Guoquan

    2010-01-01

    Objective: To investigate the most appropriate low radiation dose in multi-slice CT (MSCT) scans for orbital trauma patients. Methods: Thirty trauma patients with suspected orbital fractures who underwent helical CT scans with a 64-MSCT using regular dose were selected. Noise was artificially introduced to the axial images using an image space noise addition tool to simulate 6 sets of lower dose scans with tube current of 30, 70, 100, 140, 170 and 200 mA, respectively. The lowest tube current with adequate image quality for confident diagnosis was determined based on the evaluation of the overall image quality and fracture detection on images at different dose levels. The determined lowest tube current was then validated using clinical scans. Radiation dose related parameters CTDIvol, DLP, ED were also recorded. Image quality was evaluated according to its low-density resolution, noise and structure clarity and characterized into 5-grades of excellent, good, fair, worse and worst. Rank sum test and χ 2 test were used for statistics. Results: In 30 trauma patients with regular dose of 300 mA, there were 30 cases of orbital fracture, 19 cases of intraorbital emphysema, 12 cases of ocular muscle injury and 1 case of intraorbital foreign body. These changes could still be clearly observed and correctly diagnosed when the tube current was reduced to as low as 70 mA. However, the overall image quality was mostly fair. At the simulated dose of 100 mA, the majority of images were characterized as excellent or good, and there was no statistical difference compared with that of regular dose scans (P>0.05). In the clinical evaluation for 20 orbital trauma patients with the reduced tube current of 100 m A , the majority of images were judged to be excellent (9 cases) or good (17 cases) and fair (4 cases). The radiation dose (0.29 mSv) was reduced by 70% compared with that of regular tube current of 300 mA (0.86 mSv). Conclusion: The tube current of MSCT may be used as low as

  18. Care-bolus tracking systems in multislice-helical computed tomography - a new method in the screening of cardiovascular failure?

    International Nuclear Information System (INIS)

    Stueckle, C.A.; Kickuth, R.; Kirchner, E.M.; Liermann, D.; Kirchner, J.

    2002-01-01

    Purpose. Recently bolus tracking systems were developed to improve the timing of intravenous contrast media application in helical computed tomography. We investigated the benefit of this new method as a parameter of the cardiac function.Material and methods. Retrospective analysis of 64 patients which incidentally underwent bolus triggered contrast enhanced helical CT and invasive investigation of the heart within one week. All examinations were performed on the CT scanner Somatom Plus 4 Volume Zoom (Siemens Corp., Forchheim, Germany) using the C.A.R.E. trademark Bolus software. This performs repetitive low- dose test scans (e.g. for the abdomen: 140 kV, 20 mA, TI 0,5 s) and measures the Hounsfield attenuation (increase over the baseline) in a preselected region of interest. The displayed increase of vascular density over the time after peripheral contrast media injection (75 ml Iopromid (300 mg/ml), 2 ml/s) was categorised to three types: (a) rapid increase, (b) deceleration before a 100 HE threshold was reached and (c) one or more peaks. The findings of the invasive investigation of the heart were correlated to the findings of the bolus-tracking measurements.Results. The examinations were categorized as follows: 19 type A, 34 type B, 11 type C. We found a high significant correlation between the type of the Hounsfield attenuation and systolic pressure in the left ventricle. There was no correlation between the type of the Hounsfield attenuation and the diastolic pressure in the left ventricle, the pressures related to the right ventricle or the ejection fraction. The bolus- tacking system showed a sensitivity of 53, a specificity of 82, an accuracy of 70%, a positive predictive value of 70% and a negative predictive value of 70% in detection of left heart failure.Conclusion. The bolus tracking system C.A.R.E.-bolus copyright often shows atypical Hounsfield attenuation in cases of cardiac failure but is not suitable as a screening method of the cardiopulmonary

  19. Differences in atherosclerotic plaque burden and morphology between type 1 and 2 diabetes as assessed by multislice computed tomography

    NARCIS (Netherlands)

    Djaberi, Roxana; Schuijf, Joanne D.; Boersma, Eric; Kroft, Lucia J. M.; Pereira, Alberto M.; Romijn, Johannes A.; Scholte, Arthur J.; Jukema, J. Wouter; Bax, Jeroen J.

    2009-01-01

    OBJECTIVE It is unclear whether the coronary atherosclerotic plaque burden is similar in patients with type 1 and type 2 diabetes. By using multislice computed tomography (MSCT), the presence, degree, and morphology of coronary artery disease (CAD) in patients with type 1 and type 2 diabetes were

  20. Whole-body multislice computed tomography as the primary and sole diagnostic tool in patients with blunt trauma: searching for its appropriate indication.

    Science.gov (United States)

    Wurmb, Thomas Erik; Frühwald, Peter; Hopfner, Wittiko; Roewer, Norbert; Brederlau, Jörg

    2007-11-01

    In our hospital, whole-body multislice computed tomography is used as the primary diagnostic tool in patients with suspected multiple trauma. A triage rule is used for its indication. We have retrospectively analyzed data of sedated, intubated and ventilated patients consecutively admitted to our trauma center to assess whether the triage rule can help identify patients with severe trauma (injury severity score > or = 16). We have found that overtriage (injury severity score < 16) occurs in 30%, and undertriage occurs in 6% of patients. Although we have found the triage rule to be highly sensitive, this results in a high rate of overtriage. Until we know more about the most relevant and independent predictive factors, sole reliance upon multislice computed tomography in triaging suspected polytrauma victims will imply the risk to overscan many patients.

  1. Multislice Spiral Computed Tomography of the Heart: Technique, Current Applications, and Perspective

    International Nuclear Information System (INIS)

    Mahnken, Andreas H.; Wildberger, Joachim E.; Koos, Ralf; Guenther, Rolf W.

    2005-01-01

    Multislice spiral computed tomography (MSCT) is a rapidly evolving, noninvasive technique for cardiac imaging. Knowledge of the principle of electrocardiogram-gated MSCT and its limitations in clinical routine are needed to optimize image quality. Therefore, the basic technical principle including essentials of image postprocessing is described. Cardiac MSCT imaging was initially focused on coronary calcium scoring, MSCT coronary angiography, and analysis of left ventricular function. Recent studies also evaluated the ability of cardiac MSCT to visualize myocardial infarction and assess valvular morphology. In combination with experimental approaches toward the assessment of aortic valve function and myocardial viability, cardiac MSCT holds the potential for a comprehensive examination of the heart using one single examination technique

  2. Collateral abdominal circulation in patient with Leriche's syndrome diagnosed with 64-row multislice computed tomography (MSCT)

    International Nuclear Information System (INIS)

    Staskiewicz, G.; Drop, A.

    2008-01-01

    Leriche's syndrome results from slowly developing occlusion of the abdominal aorta. It affects mainly middle-aged males. The blood flow distal to the occlusion site is secured by collateral circulation. Signs of Leriche's syndrome include claudication, gluteal pain and impotence. The paper presents a patient with Leriche's syndrome, in whom a detailed visualization of collateral circulation was obtained with multislice computed tomography angiography. Patient underwent surgical recanalization of the aorta with an excellent result. To our knowledge, the presented case is the first description of collateral circulation in Leriche's syndrome obtained with 64-row computed tomography. (author)

  3. Retrospective analysis of whole-body multislice computed tomography findings taken in trauma patients

    Directory of Open Access Journals (Sweden)

    Ozlem Bingol

    2015-09-01

    Full Text Available Objectives: Using whole-body multislice computed tomography (MSCT excessively or with irrelevant indications can be seen in many centers. The aim of this study was to analyze retrospectively the MSCT findings in trauma patients admitted to the emergency department. Methods: Records of the patients who have applied to the emergency department due to blunt trauma in a 12 month period and whose whole body MSCT images have been taken, were evaluated using the “Nucleus Medical Information System”. Results: The most frequent type of trauma was traffic accidents in 61.4%, falling down from the height in 22.4%, and motorcycle accidents in 11.4% of patients. Of the patients, 25.2% were discharged from the emergency, while 73.8% were hospitalized. At least one CT findings associated with trauma was present in 61.4% of our patients. Pathological findings in MSCT were most frequently detected in the head and face (35.3% and thoracic (28.6% regions, respectively. The most common finding in the head and face region was fractures. The most common pathological findings in the thoracic region were pulmonary contusion and rib fractures. A significant relationship was detected between trauma type and spinal MSCT result (p < 0.001. In a large percentage of the patients, MSCT findings were normal in the abdominal region and genitourinary system. Vertebral fractures were most frequently detected in the thoracolumbar region. Conclusions: In our study, our rate of negative CT was found to be 38.6%, which is a higher ratio compared to other studies conducte on this topic. Keywords: Emergency, Trauma, Whole-body multislice computed tomography

  4. Multislice helical CT analysis of small-sized airway wall thickness in smokers and patients with bronchial asthma

    International Nuclear Information System (INIS)

    Sekimura, Kenshi; Ito, Harumasa; Nakamura, Yutaka; Kobayashi, Hitoshi; Oikawa, Hirobumi; Inoue, Hiroshi; Ehara, Shigeru; Yamauchi, Kohei

    2010-01-01

    There is accumulating evidence that airway remodeling, which contributes to airway narrowing, plays a role in the pathogenesis of bronchial asthma (BA) and chronic obstructive pulmonary disease (COPD). Development of the multislice helical CT (MSCT) with improved spatial resolution has made it possible to obtain more precise imaging of small-sized airways. Small-sized airway wall-thickness was measured using the MSCT scan to analyze small-sized airways of smokers and BA patients, and examine the effects of a β 2 agonists on small-sized airway wall-thickness of BA patients. Thirty-six non-asthmatics who participated in the Health Check Program of Iwate Medical University and 25 patients with asthma were recruited. Amongst the 36 non-asthmatics were 20 healthy never-smokers and 15 smokers. The other 25 asthmatics were recruited from the outpatient clinic at Iwate Medical University. MSCT was performed and the right B10 bronchus was chosen for dimensional analysis. Airway wall thickness was expressed as a percentage of wall area (WA%). WA% of the 7 asthmatics before and 30 mim after procaterol (20μg) inspiration were compared. Small-sized airway wall thickness was significantly increased in smokers and patients with asthma compared to healthy never-smokers, when determined by MSCT. Both %V 50 and %V 25 had significant negative correlations with WA% among the healthy never-smokers and smoker population. Procaterol inspiration reduced WA% in the small airway of patients with asthma. Increase of small-sized airway thickness measured by MSCT scan may reflect peripheral obstructive lesions of smokers and BA patients. (author)

  5. Multi-slice computed tomography-assisted endoscopic transsphenoidal surgery for pituitary macroadenoma: a comparison with conventional microscopic transsphenoidal surgery.

    Science.gov (United States)

    Tosaka, Masahiko; Nagaki, Tomohito; Honda, Fumiaki; Takahashi, Katsumasa; Yoshimoto, Yuhei

    2015-11-01

    Intraoperative computed tomography (iCT) is a reliable method for the detection of residual tumour, but previous single-slice low-resolution computed tomography (CT) without coronal or sagittal reconstructions was not of adequate quality for clinical use. The present study evaluated the results of multi-slice iCT-assisted endoscopic transsphenoidal surgery for pituitary macroadenoma. This retrospective study included 30 consecutive patients with newly diagnosed or recurrent pituitary macroadenoma with supradiaphragmatic extension who underwent endoscopic transsphenoidal surgery using iCT (eTSS+iCT group), and control 30 consecutive patients who underwent conventional endoscope-assisted transsphenoidal surgery (cTSS group). The tumour volume was calculated by multiplying the tumour area by the slice thickness. Visual acuity and visual field were estimated by the visual impairment score (VIS). The resection extent, (preoperative tumour volume - postoperative residual tumour volume)/preoperative tumour volume, was 98.9% (median) in the eTSS+iCT group and 91.7% in the cTSS group, and had significant difference between the groups (P = 0.04). Greater than 95 and >90% removal rates were significantly higher in the eTSS+iCT group than in the cTSS group (P = 0.02 and P = 0.001, respectively). However, improvement in VIS showed no significant difference between the groups. The rate of complications also showed no significant difference. Multi-slice iCT-assisted endoscopic transsphenoidal surgery may improve the resection extent of pituitary macroadenoma. Multi-slice iCT may have advantages over intraoperative magnetic resonance imaging in less expensive, short acquisition time, and that special protection against magnetic fields is not needed.

  6. The development of remote teaching laboratory access software for multi-slice computed optical tomography for use in undergraduate nuclear education

    International Nuclear Information System (INIS)

    Price, T.J.; Nichita, E.

    2013-01-01

    Internet-based laboratory exercises were developed for a course on biomedical imaging at the University of Ontario Institute of Technology. These exercises used a multi-slice computed optical tomography machine named DeskCAT to instruct students on the principals of computed tomography. User management software was developed which enabled course instructors to quickly set up a computer to accept a series of scheduled remote user connections for a classroom. Laboratory exercises using the DeskCAT machine were developed to be conducted remotely. (author)

  7. The development of remote teaching laboratory access software for multi-slice computed optical tomography for use in undergraduate nuclear education

    Energy Technology Data Exchange (ETDEWEB)

    Price, T.J.; Nichita, E., E-mail: Terry.Price@gmail.com [Univ. of Ontario Inst. of Technology, Oshawa, Ontario (Canada)

    2013-07-01

    Internet-based laboratory exercises were developed for a course on biomedical imaging at the University of Ontario Institute of Technology. These exercises used a multi-slice computed optical tomography machine named DeskCAT to instruct students on the principals of computed tomography. User management software was developed which enabled course instructors to quickly set up a computer to accept a series of scheduled remote user connections for a classroom. Laboratory exercises using the DeskCAT machine were developed to be conducted remotely. (author)

  8. Multi-slice computed tomography assessment of bronchial compression with absent pulmonary valve

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Yu-Min; Sun, Ai-Min; Wang, Qian; Zhu, Ming; Qiu, Hai-Sheng [Shanghai Children' s Medical Center and Shanghai Jiao Tong University Medical School, Department of Radiology, Shanghai (China); Jaffe, Richard B. [Primary Children' s Medical Center, Department of Medical Imaging, Salt Lake City, UT (United States); Liu, Jin-Fen [Shanghai Children' s Medical Center, Department of Cardiothoracic Surgery, Shanghai (China); Gao, Wei [Shanghai Children' s Medical Center and Shanghai Jiao Tong University Medical School, Department of Cardiology, Shanghai (China); Berdon, Walter E. [Children' s Hospital of New York, Department of Radiology, New York, NY (United States)

    2014-07-15

    Absent pulmonary valve is a rare cardiovascular anomaly that can result in profound tracheobronchial compression. To demonstrate the advantage of multi-slice CT in diagnosing tracheobronchial compression, its severity as related to the adjacent dilated pulmonary arteries, and associated lung and cardiac lesions. We included children with absent pulmonary valve who were reviewed by multi-slice CT during a 17-year period. The number and locations of stenoses and lung lesions were noted and the severity of stenosis was categorized. The diameter of the pulmonary artery was measured and associated cardiac defects were demonstrated. Thirty-one children (14 girls and 17 boys) were included. Of these, 29 had ventricular septal defect and 2 had an intact ventricular septum. Twenty-nine children (94%) had tracheobronchial compression, judged to be mild in nine children (31%), moderate in 10 (34%) and severe in 10 (34%). The different locations of the stenosis (carina, main bronchi, lobar and segmental bronchi) were observed. And the number and location of lung lesions demonstrated that the right middle and left upper and lower lobes were often affected. The diameter of the pulmonary artery in these children was well above normal published values, and Spearman rank correlation analysis showed a correlation between the size of the pulmonary artery and the severity of the tracheobronchial stenosis. Nineteen children (61%) underwent surgery and 4 of these children had a multi-slice CT post-operative follow-up study. Absent pulmonary valve can cause significant morbidity and mortality in children. Multi-slice CT can accurately depict areas of tracheobronchial compression, associated lung lesions and cardiac defects, helping to direct the surgeon. (orig.)

  9. Single-slice rebinning method for helical cone-beam CT

    International Nuclear Information System (INIS)

    Noo, F.; Defrise, M.; Clackdoyle, R.

    1999-01-01

    In this paper, we present reconstruction results from helical cone-beam CT data, obtained using a simple and fast algorithm, which we call the CB-SSRB algorithm. This algorithm combines the single-slice rebinning method of PET imaging with the weighting schemes of spiral CT algorithms. The reconstruction is approximate but can be performed using 2D multislice fan-beam filtered backprojection. The quality of the results is surprisingly good, and far exceeds what one might expect, even when the pitch of the helix is large. In particular, with this algorithm comparable quality is obtained using helical cone-beam data with a normalized pitch of 10 to that obtained using standard spiral CT reconstruction with a normalized pitch of 2. (author)

  10. Comparison of effects of ProTaper, HeroShaper, and Gates Glidden Burs on cervical dentin thickness and root canal volume by using multislice computed tomography.

    Science.gov (United States)

    Mahran, Abeer H; AboEl-Fotouh, Mona M

    2008-10-01

    The purpose of this study was to compare the effects of 3 different instruments used to prepare curved root canals on the remaining cervical dentin thickness and total amount of dentin removed from root canals during instrumentation by using multislice computed tomography. Mesiobuccal canals of 45 mandibular first molars with curvature between 30-40 degrees were divided into 3 equal groups: ProTaper, Hero Shaper, and Gates Glidden Bur with Flex-R hand file. Cervical dentin thickness and canal volume were measured before and after instrumentation by using multislice computed tomography and image analysis software. The results indicated that ProTaper removed significantly less cervical dentin from distal wall of the root (dangerous zone) than HeroShaper and Gates Glidden Bur (P ProTaper system (P < .05).

  11. Computer-aided diagnosis workstation and network system for chest diagnosis based on multislice CT images

    Science.gov (United States)

    Satoh, Hitoshi; Niki, Noboru; Eguchi, Kenji; Moriyama, Noriyuki; Ohmatsu, Hironobu; Masuda, Hideo; Machida, Suguru

    2008-03-01

    Mass screening based on multi-helical CT images requires a considerable number of images to be read. It is this time-consuming step that makes the use of helical CT for mass screening impractical at present. To overcome this problem, we have provided diagnostic assistance methods to medical screening specialists by developing a lung cancer screening algorithm that automatically detects suspected lung cancers in helical CT images, a coronary artery calcification screening algorithm that automatically detects suspected coronary artery calcification and a vertebra body analysis algorithm for quantitative evaluation of osteoporosis likelihood by using helical CT scanner for the lung cancer mass screening. The function to observe suspicious shadow in detail are provided in computer-aided diagnosis workstation with these screening algorithms. We also have developed the telemedicine network by using Web medical image conference system with the security improvement of images transmission, Biometric fingerprint authentication system and Biometric face authentication system. Biometric face authentication used on site of telemedicine makes "Encryption of file" and Success in login" effective. As a result, patients' private information is protected. Based on these diagnostic assistance methods, we have developed a new computer-aided workstation and a new telemedicine network that can display suspected lesions three-dimensionally in a short time. The results of this study indicate that our radiological information system without film by using computer-aided diagnosis workstation and our telemedicine network system can increase diagnostic speed, diagnostic accuracy and security improvement of medical information.

  12. Acute myocardial ischemia after aortic valve replacement: A comprehensive diagnostic evaluation using dynamic multislice spiral computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Lembcke, Alexander [Department of Radiology, Charite-Universitaetsmedizin Berlin, Freie Universitaet Berlin and Humboldt-Universitaet zu Berlin, Berlin (Germany)]. E-mail: alexander.lembcke@gmx.de; Hein, Patrick A. [Department of Radiology, Charite-Universitaetsmedizin Berlin, Freie Universitaet Berlin and Humboldt-Universitaet zu Berlin, Berlin (Germany); Enzweiler, Christian N.H. [Department of Radiology, Charite-Universitaetsmedizin Berlin, Freie Universitaet Berlin and Humboldt-Universitaet zu Berlin, Berlin (Germany); Hoffmann, Udo [Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA (United States); Klessen, Christian [Department of Radiology, Charite-Universitaetsmedizin Berlin, Freie Universitaet Berlin and Humboldt-Universitaet zu Berlin, Berlin (Germany); Dohmen, Pascal M. [Department of Cardiovascular Surgery, Charite-Universitaetsmedizin Berlin, Freie Universitaet Berlin and Humboldt-Universitaet zu Berlin, Berlin (Germany)

    2006-03-15

    We describe the case of a 72-year-old man presenting with endocarditis and clinical signs of acute myocardial ischemia after biological aortic valve replacement. A comprehensive cardiac dynamic multislice spiral computed tomography demonstrated: (1) an endocarditic vegetation of the aortic valve; (2) a subvalvular leakage feeding a paravalvular pseudoaneurysm based on an aortic root abscess with subsequent compromise of the systolic blood flow in the left main coronary artery and the resulting myocardial perfusion deficit.

  13. Acute myocardial ischemia after aortic valve replacement: A comprehensive diagnostic evaluation using dynamic multislice spiral computed tomography

    International Nuclear Information System (INIS)

    Lembcke, Alexander; Hein, Patrick A.; Enzweiler, Christian N.H.; Hoffmann, Udo; Klessen, Christian; Dohmen, Pascal M.

    2006-01-01

    We describe the case of a 72-year-old man presenting with endocarditis and clinical signs of acute myocardial ischemia after biological aortic valve replacement. A comprehensive cardiac dynamic multislice spiral computed tomography demonstrated: (1) an endocarditic vegetation of the aortic valve; (2) a subvalvular leakage feeding a paravalvular pseudoaneurysm based on an aortic root abscess with subsequent compromise of the systolic blood flow in the left main coronary artery and the resulting myocardial perfusion deficit

  14. Bicuspid aortic valve demonstrated with multislice computed tomography - a case report

    International Nuclear Information System (INIS)

    Marzec, M.; Lasek, W.; Serafin, Z.; Laskowska, K.; Swiatkiewicz, I.; Kubica, J.

    2004-01-01

    Bicuspid aortic valve (BAV) is one of the most common congenital heart defects and often coexists with other congenital abnormalities of the heart and great vessels. A standard diagnostic technique for valve imaging is echocardiography. However, suboptimal images may cause a diagnostic problem, especially in obese patients, women and in case of significant valve calcifications. The paper reports a case of a 27-year-old male patient with recurrent chest pain, appearing regardless of exertion. Routine physical examination, laboratory tests and echocardiography were negative. Multislice computed tomography (MSCT) showed normal coronary arteries and bicuspid aortic valve. The diagnostics of bicuspid aortic valve and the diagnostic value of MSCT are discussed. MSCT seems to be an important point in cardiac diagnostic algorithms, being an alternative modality for MR in BAV imaging. The presented case emphasizes the potential of MSCT for the diagnostics of cardiac valve congenital diseases. (author)

  15. Multislice Helical CT Angiography in Diagnostic of Intracranial and Extracranial Arterial Dissection

    International Nuclear Information System (INIS)

    Radzina, M.; Krumina, G.; Pupols, J.

    2007-01-01

    Arterial dissection is detachment of inner layer of the vessel wall. Head-neck trauma, congenital connectives tissue disorders like fibromuscular dysplasia, infectious diseases, hypertension, migraine, alcohol abuse and oral contraception are the typical causes. Urgent, complete, detailed verification is essential for successful treatment decision. Purpose. Aim of the study was to develop new appropriate CTA (angiography) protocols for patients with intracranial and extracranial arterial dissections using high speed multislice CT; to evaluate its clinical value in different locations and stages of disease, perspectives, advantages and disadvantages of new method. Materials and methods. 30 adult patients with suspected intra- or extracranial arterial blood vessels dissections were investigated in the clinical hospital 'Gailezers' using following algorithm: native CT; contrast CTA with post processing on the workstation. 80 ml iodine contrast media was administered intravenously, line speed 3-4 ml/sec, delay 10-15 seconds. For detection of maximum contrast intensity in the vessel the test contrast injection was performed before. Primary scan series were post processed in different kind of reconstructions - MPR (Multiplanar Reconstructions), MIP (Maximal Intensity Projection), VR (Volume Rendering), CR (Curved Reformat) and vessel analysis. Two different types of protocols were used - for intracranial and brachiocefalic arteries examinations. Results and Discussion. Following CTA symptoms of dissection were verified: 1) irregular vessel contour changes - narrowing, 'string' sign above dissection level; 2) tapered stenosis and/or distal occlusion; 3) double contour and/or double lumen sign; 4) fusiform aneurysmal dilatation. Clinical cases of different arterial dissection localization will be demonstrated during the presentation Advantages and disadvantages of CTA will be presented and disputed. Conclusions. CTA is non-invasive radiologic diagnostic method that yields

  16. Incorporating multislice imaging into x-ray CT polymer gel dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, H., E-mail: holly.johnston@utsw.edu [Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8W 2Y2 (Canada); Hilts, M. [Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada and Medical Physics, BC Cancer Agency, Vancouver Island Centre, Victoria, British Columbia V8R 6V5 (Canada); Jirasek, A. [Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada and Department of Physics, University of British Columbia—Okanagan Campus, Kelowna, British Columbia V1V 1V7 (Canada)

    2015-04-15

    Purpose: To evaluate multislice computed tomography (CT) scanning for fast and reliable readout of radiation therapy (RT) dose distributions using CT polymer gel dosimetry (PGD) and to establish a baseline assessment of image noise and uniformity in an unirradiated gel dosimeter. Methods: A 16-slice CT scanner was used to acquire images through a 1 L cylinder filled with water. Additional images were collected using a single slice machine. The variability in CT number (N{sub CT}) associated with the anode heel effect was evaluated and used to define a new slice-by-slice background subtraction artifact removal technique for CT PGD. Image quality was assessed for the multislice system by evaluating image noise and uniformity. The agreement in N{sub CT} for slices acquired simultaneously using the multislice detector array was also examined. Further study was performed to assess the effects of increasing x-ray tube load on the constancy of measured N{sub CT} and overall scan time. In all cases, results were compared to the single slice machine. Finally, images were collected throughout the volume of an unirradiated gel dosimeter to quantify image noise and uniformity before radiation is delivered. Results: Slice-by-slice background subtraction effectively removes the variability in N{sub CT} observed across images acquired simultaneously using the multislice scanner and is the recommended background subtraction method when using a multislice CT system. Image noise was higher for the multislice system compared to the single slice scanner, but overall image quality was comparable between the two systems. Further study showed N{sub CT} was consistent across image slices acquired simultaneously using the multislice detector array for each detector configuration of the slice thicknesses examined. In addition, the multislice system was found to eliminate variations in N{sub CT} due to increasing x-ray tube load and reduce scanning time by a factor of 4 when compared to

  17. Comparative study of single and multislice computed tomography for assessment of the mandibular canal

    Directory of Open Access Journals (Sweden)

    Adriana da Silva Ferreira Paes

    2007-06-01

    Full Text Available OBJECTIVE: The purpose of this study was to evaluate the accuracy of relative measurements from the roof of the mandibular canal to the alveolar crest in multislice (multidetector computed tomography (MDCT and single-slice computed tomography (SSCT. MATERIAL AND METHODS: The sample consisted of 26 printed CT films (7 SSCT and 19 MDCT from the files of the LABI-3D (3D Imaging Laboratory of the School of Dentistry of the University of São Paulo (FOUSP, which had been acquired using different protocols. Two observers analyzed in a randomized and independent order a series of 22 oblique CT reconstructions of each patient. Each observer analyzed the CT scans twice. The length of the mandibular canal and the distance between the mandibular canal roof and the crest of the alveolar ridge were obtained. Dahlberg test was used for statistical analysis. RESULTS: The mean error found for the mandibular canal length measurements obtained from SSCT was 0.53 mm in the interobserver analysis, and 0.38 mm for both observers. On MDCT images, the mean error was 0.0 mm in the interobserver analysis, and 0.0 and 0.23 mm in the intraobserver analysis. Regarding the distance between the mandibular canal roof and the alveolar bone crest, the SSCT images showed a mean error of 1.16 mm in the interobserver analysis and 0.66 and 0.59 mm in the intraobserver analysis. In the MDCT images, the mean error was 0.72 mm in the interobserver analysis and 0.50 and 0.54 mm in the intraobserver analysis. CONCLUSION: Multislice CT was demonstrated a more accurate method and demonstrated high reproducibility in the analysis of important anatomical landmarks for planning of mandibular dental implants, namely the mandibular canal pathway and alveolar crest height.

  18. Imaging skeletal anatomy of injured cervical spine specimens: comparison of single-slice vs multi-slice helical CT

    Energy Technology Data Exchange (ETDEWEB)

    Obenauer, S.; Alamo, L.; Herold, T.; Funke, M.; Kopka, L.; Grabbe, E. [Department of Radiology, Georg August-University Goettingen, Robert-Koch-Strasse 40, 37075 Goettingen (Germany)

    2002-08-01

    Our objective was to compare a single-slice CT (SS-CT) scanner with a multi-slice CT (MS-CT) scanner in the depiction of osseous anatomic structures and fractures of the upper cervical spine. Two cervical spine specimens with artificial trauma were scanned with a SS-CT scanner (HighSpeed, CT/i, GE, Milwaukee, Wis.) by using various collimations (1, 3, 5 mm) and pitch factors (1, 1.5, 2, 3) and a four-slice helical CT scanner (LightSpeed, QX/i, GE, Milwaukee, Wis.) by using various table speeds ranging from 3.75 to 15 mm/rotation for a pitch of 0.75 and from 7.5 to 30 mm/rotation for a pitch of 1.5. Images were reconstructed with an interval of 1 mm. Sagittal and coronal multiplanar reconstructions of the primary and reconstructed data set were performed. For MS-CT a tube current resulting in equivalent image noise as with SS-CT was used. All images were judged by two observers using a 4-point scale. The best image quality for SS-CT was achieved with the smallest slice thickness (1 mm) and a pitch smaller than 2 resulting in a table speed of up to 2 mm per gantry rotation (4 points). A reduction of the slice thickness rather than of the table speed proved to be beneficial at MS-CT. Therefore, the optimal scan protocol in MS-CT included a slice thickness of 1.25 mm with a table speed of 7.5 mm/360 using a pitch of 1.5 (4 points), resulting in a faster scan time than when a pitch of 0.75 (4 points) was used. This study indicates that MS-CT could provide equivalent image quality at approximately four times the volume coverage speed of SS-CT. (orig.)

  19. Impact of polychromatic x-ray sources on helical, cone-beam computed tomography and dual-energy methods

    International Nuclear Information System (INIS)

    Sidky, Emil Y; Zou Yu; Pan Xiaochuan

    2004-01-01

    Recently, there has been much work devoted to developing accurate and efficient algorithms for image reconstruction in helical, cone-beam computed tomography (CT). Little attention, however, has been directed to the effect of physical factors on helical, cone-beam CT image reconstruction. This work investigates the effect of polychromatic x-rays on image reconstruction in helical, cone-beam computed tomography. A pre-reconstruction dual-energy technique is developed to reduce beam-hardening artefacts and enhance contrast in soft tissue

  20. Cerebral blood volume imaging by flat detector computed tomography in comparison to conventional multislice perfusion CT

    International Nuclear Information System (INIS)

    Struffert, Tobias; Kloska, Stephan; Engelhorn, Tobias; Doerfler, Arnd; Deuerling-Zheng, Yu; Boese, Jan; Zellerhoff, Michael; Schwab, Stefan

    2011-01-01

    We tested the hypothesis that Flat Detector computed tomography (FD-CT) with intravenous contrast medium would allow the calculation of whole brain cerebral blood volume (CBV) mapping (FD-CBV) and would correlate with multislice Perfusion CT (PCT). Twenty five patients were investigated with FD-CBV and PCT. Correlation of the CBV maps of both techniques was carried out with measurements from six anatomical regions from both sides of the brain. Mean values of each region and the correlation coefficient were calculated. Bland-Altman analysis was performed to compare the two different imaging techniques. The image and data quality of both PCT and FD-CBV were suitable for evaluation in all patients. The mean CBV values of FD-CBV and PCT showed only minimal differences with overlapping standard deviation. The correlation coefficient was 0.79 (p < 0.01). Bland-Altman analysis showed a mean difference of -0.077 ± 0.48 ml/100 g between FD-CBV and PCT CBV measurements, indicating that FD-CBV values were only slightly lower than those of PCT. CBV mapping with intravenous contrast medium using Flat Detector CT compared favourably with multislice PCT. The ability to assess cerebral perfusion within the angiographic suite may improve the management of ischaemic stroke and evaluation of the efficacy of dedicated therapies. (orig.)

  1. Clinical application of multi-slice helical CT volumetric scanning in lumber spine

    International Nuclear Information System (INIS)

    Wang Ling; Ge Yinghui; Zhu Shaocheng; Zhang Ming; Cheng Tianming; Lei Zhidan; Lv Chuanjian; Sun Xiaoping; Wu Minghui; Guo Ying; Ma Qianli; Wen Zeying

    2008-01-01

    Objective: To evaluate the clinical application value of multi-slice helical CT volumetric (VH) scanning in lumber spine. Methods: One thousand of patients with back and leg pain who underwent CT examinations were selected as subjects. We simulated the traditional protocol of single-slice(SS) discrete scanning for L3/4, L4/5, and L5/S1 intervertebral discs. The VH scanning mode was performed with 120 kV, 210 mAs, pitch of 1.5 and coverage of 97.5 mm. The simulated SS scanning mode was performed with 120 kV, 240 mAs and coverage of 45.0 mm. The diagnostic outcomes and the radiation doses were compared between the two scanning modes. Two groups doctors observed ten terms, including the osseous spinal stenosis, narrowed intervertebral space and so on in two scanning modes respectively. Then consistency analysis of the data was carded out. Results: The VH scanning mode showed far more features than the SS mode. The detection rates of the VH mode in the osseous spinal stenosis, narrowed intervertebral space, herniated nucleus pulposus, narrowed lateral recess, vertebral lesion, hypertrophy of L5 transverse process, abnormal direction of facet, facet degeneration, lumbar spondyloschisis, and paraspinal soft tissue were 11.8% (n=118), 38.5% (n=385), 9.3% (n=93), 46.8% (n=468), 31.4% (n=314), 5.7% (n= 57), 25.4% (n=254), 49.7% (n=497), 9.9% (n=99), and 0.6% (n=6) respectively, while the detection rates of the SS mode in ten terms were 5.6% (n=56), 0, 0.6% (n=6), 27.9% (n=279), 22.4% (n=224), 1.2% (n=12), 16.7% (n=167), 37.2% (n=372), 0.5% (n=5), and 0.2% (n=2) respectively. The difference between the two groups had statistically significance (average P 0.05). The detection rates of the VH mode were higher than the SS mode in the osseous spinal stenosis, narrowed intervertebral space, herniated nucleus pulposus, lumbar spondyloschisis, being 6.2% (n=62), 38.5% (n=385), 8.7% (n=87), and 9.4% (n=94), respectively. In addition, VH mode only partially showed the articular

  2. The pattern of renal vessels in live related potential donors pool. A multislice computed tomography angiography review

    International Nuclear Information System (INIS)

    Mishra, A.; Ehtuish, Ehtuish F.

    2006-01-01

    To assess the renal vessel anatomy, compare the findings with the perioperative findings, to determine the sensitivity of multislice computed tomography (CT) angiography in the work-up of live potential donors and to discuss and compare the results of the present study with the reported results using single slice CT, magnetic resonance (MRI) and conventional angiography (CA).Retrospective analysis of the angiographic data of 118 of prospective live related kidney donors was carried out from October 2004 to August 2005 at the National Organ Transplant Centre, Tripoli Central Hospital, Libya. All donors underwent renal angiography on multislice (16-slice) CT scan using 80 cc intravenous contrast with 1.25 mm slice thickness followed by maximum intensity projection (MIP) and volume rendering techniques (VRT) post-processing algorithms. The number of vessels, vessel bifurcation, vessel morphology and venous anatomy were analyzed and the findings were compared with the surgical findings. Multislice spiral CT angiography (MSCTA) showed clear delineation of the main renal arteries in all donors with detailed vessel morphology. The study revealed 100% sensitivity in detection of accessory renal vessels, with an overall incidence of 26.7%, which is the most common distribution in the parahilar region. The present study showed 100% sensitivity in the visualization and detection of main and accessory renal vessels. These results were comparable with conventional angiography which has so far been considered as the gold standard and were found superior in specificity and accuracy to the use of single slice CT (SSCT) and MR in the angiographic work-up of live renal donors. Due to improved detection of accessory vessels less than 2 mm in diameter, a higher incidence of aberrant vessels was seen on the right side as has been suggested so far. (author)

  3. Comparison of aortic root dimensions and geometries before and after transcatheter aortic valve implantation by 2- and 3-dimensional transesophageal echocardiography and multislice computed tomography.

    NARCIS (Netherlands)

    Ng, A.C.; Delgado, V.; Kley, F. van der; Shanks, M.; Veire, N.R. van de; Bertini, M.; Nucifora, G.; Bommel, R.J. van; Tops, L.F.; Weger, A. de; Tavilla, G.; Roos, A. de; Kroft, L.J.; Leung, D.Y.; Schuijf, J.; Schalij, M.J.; Bax, J.J.

    2010-01-01

    BACKGROUND: 3D transesophageal echocardiography (TEE) may provide more accurate aortic annular and left ventricular outflow tract (LVOT) dimensions and geometries compared with 2D TEE. We assessed agreements between 2D and 3D TEE measurements with multislice computed tomography (MSCT) and changes in

  4. Multislice Computed Tomography Coronary Angiography at a Local Hospital: Pitfalls and Potential

    Energy Technology Data Exchange (ETDEWEB)

    Kolnes, K.; Velle, Ose H.; Hareide, S.; Hegbom, K.; Wiseth, R. [Volda Hospital (Norway). Depts. of Radiology and Internal Medicine

    2006-09-15

    Purpose: To evaluate whether the favorable results achieved with multislice computed tomography (MSCT) of coronary arteries at larger centers could be paralleled at a local hospital. Material and Methods: Fifty consecutive patients with suspected coronary artery disease scheduled for invasive investigation with quantitative coronary angiography (QCA) at a university hospital underwent MSCT with a 16-slice scanner at a local hospital. Diagnostic accuracy of MSCT for coronary artery disease was assessed using a 16-segment coronary artery model with QCA as the gold standard. Results: Segments with diameter 50% stenosis for the 416 assessable segments were 92%, 82%, 53%, and 98%, respectively. Conclusion: Our beginners' experience demonstrated favorable results regarding sensitivity and negative predictive value. The positive predictive value, however, was unsatisfactory. Calcifications were identified as the most important factor for false-positive results with MSCT. With widespread use of MSCT coronary angiography, there is a risk of recruiting patients without significant coronary artery disease to unnecessary and potentially harmful invasive procedures.

  5. Pictorial review: Electron beam computed tomography and multislice spiral computed tomography for cardiac imaging

    International Nuclear Information System (INIS)

    Lembcke, Alexander; Hein, Patrick A.; Dohmen, Pascal M.; Klessen, Christian; Wiese, Till H.; Hoffmann, Udo; Hamm, Bernd; Enzweiler, Christian N.H.

    2006-01-01

    Electron beam computed tomography (EBCT) revolutionized cardiac imaging by combining a constant high temporal resolution with prospective ECG triggering. For years, EBCT was the primary technique for some non-invasive diagnostic cardiac procedures such as calcium scoring and non-invasive angiography of the coronary arteries. Multislice spiral computed tomography (MSCT) on the other hand significantly advanced cardiac imaging through high volume coverage, improved spatial resolution and retrospective ECG gating. This pictorial review will illustrate the basic differences between both modalities with special emphasis to their image quality. Several experimental and clinical examples demonstrate the strengths and limitations of both imaging modalities in an intraindividual comparison for a broad range of diagnostic applications such as coronary artery calcium scoring, coronary angiography including stent visualization as well as functional assessment of the cardiac ventricles and valves. In general, our examples indicate that EBCT suffers from a number of shortcomings such as limited spatial resolution and a low contrast-to-noise ratio. Thus, EBCT should now only be used in selected cases where a constant high temporal resolution is a crucial issue, such as dynamic (cine) imaging. Due to isotropic submillimeter spatial resolution and retrospective data selection MSCT seems to be the non-invasive method of choice for cardiac imaging in general, and for assessment of the coronary arteries in particular. However, technical developments are still needed to further improve the temporal resolution in MSCT and to reduce the substantial radiation exposure

  6. A methodology for direct quantification of over-ranging length in helical computed tomography with real-time dosimetry.

    Science.gov (United States)

    Tien, Christopher J; Winslow, James F; Hintenlang, David E

    2011-01-31

    In helical computed tomography (CT), reconstruction information from volumes adjacent to the clinical volume of interest (VOI) is required for proper reconstruction. Previous studies have relied upon either operator console readings or indirect extrapolation of measurements in order to determine the over-ranging length of a scan. This paper presents a methodology for the direct quantification of over-ranging dose contributions using real-time dosimetry. A Siemens SOMATOM Sensation 16 multislice helical CT scanner is used with a novel real-time "point" fiber-optic dosimeter system with 10 ms temporal resolution to measure over-ranging length, which is also expressed in dose-length-product (DLP). Film was used to benchmark the exact length of over-ranging. Over-ranging length varied from 4.38 cm at pitch of 0.5 to 6.72 cm at a pitch of 1.5, which corresponds to DLP of 131 to 202 mGy-cm. The dose-extrapolation method of Van der Molen et al. yielded results within 3%, while the console reading method of Tzedakis et al. yielded consistently larger over-ranging lengths. From film measurements, it was determined that Tzedakis et al. overestimated over-ranging lengths by one-half of beam collimation width. Over-ranging length measured as a function of reconstruction slice thicknesses produced two linear regions similar to previous publications. Over-ranging is quantified with both absolute length and DLP, which contributes about 60 mGy-cm or about 10% of DLP for a routine abdominal scan. This paper presents a direct physical measurement of over-ranging length within 10% of previous methodologies. Current uncertainties are less than 1%, in comparison with 5% in other methodologies. Clinical implantation can be increased by using only one dosimeter if codependence with console readings is acceptable, with an uncertainty of 1.1% This methodology will be applied to different vendors, models, and postprocessing methods--which have been shown to produce over-ranging lengths

  7. Detection of hepatocellular carcinoma with multi-slice spiral CT by ...

    African Journals Online (AJOL)

    STORAGESEVER

    2010-06-07

    Jun 7, 2010 ... The purpose of the study is to evaluate the effect of iodine concentration of contrast material on detection of hepatocellular carcinoma with multi-slice spiral computed tomography (CT) by using double-arterial phase and portal venous phase enhanced scanning. Ninety-four (94) patients with hepatocellular ...

  8. Establishment of multi-slice computed tomography (MSCT) reference level in Johor, Malaysia

    Science.gov (United States)

    Karim, M. K. A.; Hashim, S.; Bakar, K. A.; Muhammad, H.; Sabarudin, A.; Ang, W. C.; Bahruddin, N. A.

    2016-03-01

    Radiation doses from computed tomography (CT) are the highest and most hazardous compared to other imaging modalities. This study aimed to evaluate radiation dose in Johor, Malaysia to patients during computed tomography examinations of the brain, chest and abdomen and to establish the local diagnostic reference levels (DRLs) as are present with the current, state- of-art, multi-slice CT scanners. Survey forms were sent to five centres performing CT to obtain data regarding acquisition parameters as well as the dose information from CT consoles. CT- EXPO (Version 2.3.1, Germany) was used to validate the dose information. The proposed DRLs were indicated by rounding the third quartiles of whole dose distributions where mean values of CTDIw (mGy), CTDIvol (mGy) and DLP (mGy.cm) were comparable with other reference levels; 63, 63, and 1015 respectively for CT Brain; 15, 14, and 450 respectively for CT thorax and 16, 17, and 590 respectively for CT abdomen. The study revealed that the CT practice and dose output were revolutionised, and must keep up with the pace of introductory technology. We suggest that CTDIvol should be included in current national DRLs, as modern CTs are configured with a higher number of detectors and are independent of pitch factors.

  9. Establishment of multi-slice computed tomography (MSCT) reference level in Johor, Malaysia

    International Nuclear Information System (INIS)

    Karim, M K A; Hashim, S; Ang, W C; Bahruddin, N A; Bakar, K A; Muhammad, H; Sabarudin, A

    2016-01-01

    Radiation doses from computed tomography (CT) are the highest and most hazardous compared to other imaging modalities. This study aimed to evaluate radiation dose in Johor, Malaysia to patients during computed tomography examinations of the brain, chest and abdomen and to establish the local diagnostic reference levels (DRLs) as are present with the current, state- of-art, multi-slice CT scanners. Survey forms were sent to five centres performing CT to obtain data regarding acquisition parameters as well as the dose information from CT consoles. CT- EXPO (Version 2.3.1, Germany) was used to validate the dose information. The proposed DRLs were indicated by rounding the third quartiles of whole dose distributions where mean values of CTDI w (mGy), CTDI vol (mGy) and DLP (mGy.cm) were comparable with other reference levels; 63, 63, and 1015 respectively for CT Brain; 15, 14, and 450 respectively for CT thorax and 16, 17, and 590 respectively for CT abdomen. The study revealed that the CT practice and dose output were revolutionised, and must keep up with the pace of introductory technology. We suggest that CTDI vol should be included in current national DRLs, as modern CTs are configured with a higher number of detectors and are independent of pitch factors. (paper)

  10. Computer-aided diagnosis workstation and telemedicine network system for chest diagnosis based on multislice CT images

    Science.gov (United States)

    Satoh, Hitoshi; Niki, Noboru; Eguchi, Kenji; Ohmatsu, Hironobu; Kakinuma, Ryutaru; Moriyama, Noriyuki

    2009-02-01

    Mass screening based on multi-helical CT images requires a considerable number of images to be read. It is this time-consuming step that makes the use of helical CT for mass screening impractical at present. Moreover, the doctor who diagnoses a medical image is insufficient in Japan. To overcome these problems, we have provided diagnostic assistance methods to medical screening specialists by developing a lung cancer screening algorithm that automatically detects suspected lung cancers in helical CT images, a coronary artery calcification screening algorithm that automatically detects suspected coronary artery calcification and a vertebra body analysis algorithm for quantitative evaluation of osteoporosis likelihood by using helical CT scanner for the lung cancer mass screening. The functions to observe suspicious shadow in detail are provided in computer-aided diagnosis workstation with these screening algorithms. We also have developed the telemedicine network by using Web medical image conference system with the security improvement of images transmission, Biometric fingerprint authentication system and Biometric face authentication system. Biometric face authentication used on site of telemedicine makes "Encryption of file" and "Success in login" effective. As a result, patients' private information is protected. We can share the screen of Web medical image conference system from two or more web conference terminals at the same time. An opinion can be exchanged mutually by using a camera and a microphone that are connected with workstation. Based on these diagnostic assistance methods, we have developed a new computer-aided workstation and a new telemedicine network that can display suspected lesions three-dimensionally in a short time. The results of this study indicate that our radiological information system without film by using computer-aided diagnosis workstation and our telemedicine network system can increase diagnostic speed, diagnostic accuracy and

  11. SU-E-T-70: Commissioning a Multislice CT Scanner for X-Ray CT Polymer Gel Dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, H [University of Victoria, Victoria, BC (Australia); UT Southwestern Medical Center, Dallas, TX (United States); Hilts, M [University of Victoria, Victoria, BC (Australia); BC Cancer Agency, Kelowna, BC (Australia); Jirasek, A [University of Victoria, Victoria, BC (Australia)

    2014-06-01

    Purpose: To commission a multislice computed tomography (CT) scanner for fast and reliable readout of radiation therapy (RT) dose distributions using CT polymer gel dosimetry (PGD). Methods: Commissioning was performed for a 16-slice CT scanner using images acquired through a 1L cylinder filled with water. Additional images were collected using a single slice machine for comparison purposes. The variability in CT number associated with the anode heel effect was evaluated and used to define a new slice-by-slice background image subtraction technique. Image quality was assessed for the multislice system by comparing image noise and uniformity to that of the single slice machine. The consistency in CT number across slices acquired simultaneously using the multislice detector array was also evaluated. Finally, the variability in CT number due to increasing x-ray tube load was measured for the multislice scanner and compared to the tube load effects observed on the single slice machine. Results: Slice-by-slice background subtraction effectively removes the variability in CT number across images acquired simultaneously using the multislice scanner and is the recommended background subtraction method when using a multislice CT system. Image quality for the multislice machine was found to be comparable to that of the single slice scanner. Further study showed CT number was consistent across image slices acquired simultaneously using the multislice detector array for each detector configuration of the slice thickness examined. In addition, the multislice system was found to eliminate variations in CT number due to increasing x-ray tube load and reduce scanning time by a factor of 4 when compared to imaging a large volume using a single slice scanner. Conclusion: A multislice CT scanner has been commissioning for CT PGD, allowing images of an entire dose distribution to be acquired in a matter of minutes. Funding support provided by the Natural Sciences and Engineering

  12. ALOHA: Automatic libraries of helicity amplitudes for Feynman diagram computations

    Science.gov (United States)

    de Aquino, Priscila; Link, William; Maltoni, Fabio; Mattelaer, Olivier; Stelzer, Tim

    2012-10-01

    We present an application that automatically writes the HELAS (HELicity Amplitude Subroutines) library corresponding to the Feynman rules of any quantum field theory Lagrangian. The code is written in Python and takes the Universal FeynRules Output (UFO) as an input. From this input it produces the complete set of routines, wave-functions and amplitudes, that are needed for the computation of Feynman diagrams at leading as well as at higher orders. The representation is language independent and currently it can output routines in Fortran, C++, and Python. A few sample applications implemented in the MADGRAPH 5 framework are presented. Program summary Program title: ALOHA Catalogue identifier: AEMS_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEMS_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: http://www.opensource.org/licenses/UoI-NCSA.php No. of lines in distributed program, including test data, etc.: 6094320 No. of bytes in distributed program, including test data, etc.: 7479819 Distribution format: tar.gz Programming language: Python2.6 Computer: 32/64 bit Operating system: Linux/Mac/Windows RAM: 512 Mbytes Classification: 4.4, 11.6 Nature of problem: An effcient numerical evaluation of a squared matrix element can be done with the help of the helicity routines implemented in the HELAS library [1]. This static library contains a limited number of helicity functions and is therefore not always able to provide the needed routine in the presence of an arbitrary interaction. This program provides a way to automatically create the corresponding routines for any given model. Solution method: ALOHA takes the Feynman rules associated to the vertex obtained from the model information (in the UFO format [2]), and multiplies it by the different wavefunctions or propagators. As a result the analytical expression of the helicity routines is obtained. Subsequently, this expression is

  13. Evaluation of effective regurgitant orifice area of mitral valvular regurgitation by multislice cardiac computed tomography

    International Nuclear Information System (INIS)

    Vural, M.; Ucar, O.; Celebi, O.O.; Cicekcioglu, H.; Durmaz, H.A.; Selvi, N.A.; Koparal, S.; Aydogdu, S.

    2010-01-01

    The purpose of our study was to assess the diagnostic accuracy of multislice computed tomography (MSCT) for the identification and quantification of mitral valve regurgitation in comparison with transthoracic echocardiography (TTE). Twenty-six patients (15 females, 11 males with a mean age of 44.6±14.1 years) who were in follow-up with the diagnosis of mitral regurgitation and those who were referred for MSCT were enrolled. MSCT results were compared with TTE measurements. The mean effective mitral regurgitant orifice area at MSCT was 23.1±13.0 mm 2 and at echocardiography was 24.4±16.0mm 2 . Bland-Altman analysis showed good agreement between the two imaging methods. MSCT provides reliable and good results for the evaluation of mitral regurgitation. (author)

  14. Intravenous digital subtraction angiography and helical computed tomography in evaluation of living renal donors

    International Nuclear Information System (INIS)

    Watarai, Yoshihiko; Usuki, Tomoaki; Takeuchi, Ichiro; Nonomura, Katsuya; Koyanagi, Tomohiko; Kubo, Kozo; Hirano, Tetsuo; Togashi, Masaki; Ohashi, Nobuo

    2001-01-01

    The present study was carried out to evaluate the accuracy of helical computed tomography (CT) and intravenous digital subtraction angiography (IV-DSA) on anatomical assessment of renal vasculature for living renal donors. Forty-two healthy potential renal donors were prospectively evaluated and 35 subsequently underwent donor nephrectomy after helical CT and IV-DSA evaluation. The vascular and non-vascular findings were compared between the findings on helical CT, IV-DSA and surgery. Ten prehilar branches and five accessory renal arteries were found at nephrectomy. Overall, operative findings agreed with the findings by IV-DSA in 89% and by helical CT in 83%. In delineating accessory arteries, IV-DSA had a sensitivity of 60% and specificity of 97%, whereas helical CT had a sensitivity of 40% and specificity of 100%. In delineating prehilar branches, IV-DSA had a sensitivity of 90% and specificity of 100%, whereas helical CT had a sensitivity of 70% and specificity of 100%. Accessory arteries and prehilar branches that were not detected by helical CT or IV-DSA, were less than 2 mm in diameter and did not require vascular reconstruction. Renal veins were delineated in 63% by IV-DSA, whereas they were clearly imaged by helical CT in all cases, including a case with a circumaortic renal vein. Non-vascular findings were obtained in 64% by helical CT, including two renal tumors. None of these findings were obtained by IV-DSA. Helical CT and IV-DSA provide comparably sufficient information on renal artery vasculature. However, helical CT provides significantly more information on venous and non-vascular findings as a single-imaging modality. (author)

  15. Helical computed tomography and the workstation: introduction to a symbiosis

    International Nuclear Information System (INIS)

    Garcia-Santos, J.M.

    1997-01-01

    We do a brief introduction to the possibilities of an helical computed tomography system when it is associated with a powerful workstation. The fast and volumetric way of acquisition constitutes, basically, the main advantage of this sort of computed tomography. The anatomical and radio pathological study, in a workstation, of the acquired information (thanks to multiplanar and 3D reconstruction), increases significantly our capacity of analysis in each patient. Only the clinical and radiological experience will tell us which is the right place that this symbiosis occupies within our diagnosis tools. (Author) 11 refs

  16. Accuracy of 16-detector Multislice Spiral Computed Tomography in the initial evaluation of dilated cardiomyopathy

    International Nuclear Information System (INIS)

    Cornily, Jean-Christophe; Gilard, Martine; Le Gal, Gregoire; Pennec, Pierre-Yves; Vinsonneau, Ulric; Blanc, Jean-Jacques; Mansourati, Jacques; Boschat, Jacques

    2007-01-01

    Background: Multislice Computed Tomography (MSCT) recently proved its accuracy in the detection of coronary artery disease (CAD). It can also give information about left ventricular function and venous network anatomy. We here sought to validate a MSCT-based strategy in the initial evaluation of patients with dilated cardiomyopathy (DCM). Methods: 36 patients with DCM underwent cardiac MSCT before conventional coronary angiography with ventriculography. We analysed arterial calcium score (Agatston score equivalent: ASE), coronary stenosis, left ventricular parameters and venous network. Results: The sensitivity of a MSCT-based strategy in detecting significant CAD was 100% and the specificity 80%. The positive and negative predictive values were respectively 67% and 100%. For ASE 1.000, conventional coronary angiography is mandatory due to MSCT's poor interest in such cases; when ASE <1.000, a contrast-enhanced MSCT may, when normal, replace coronary angiography

  17. Myocardial bridging: evaluation with multislice computed tomography coronary angiography

    Energy Technology Data Exchange (ETDEWEB)

    Barros, M.V.L. de; Rabelo, D.R.; Nunes, M.C.P.; Siqueira, M.H.A. [Mater Dei Hospital, Belo Horizonte, MG (Brazil)

    2012-04-15

    Myocardial bridging (MB) is defined as a segment of a major epicardial coronary artery that proceeds intramurally through the myocardium beneath the muscle bridge. Although MB is clinically silent in most cases, it has been associated with myocardial ischemia, myocardial infarction, arrhythmia, and sudden death. Conventional coronary angiography (CCA) is the gold standard for detection, but it is invasive and may not be sensitive enough to detect a thin bridge. Recently, multislice computed tomography coronary angiography (MCTCA) have made possible the clear detection of the entire running courses of coronary arteries and the MB itself. Objective: To evaluate the prevalence MB in patients suspect to coronary artery disease submitted to MCTCA and assessing the predictive value of this method in the midterm. Methods: 498 consecutive patients were examined by MCTCA for the diagnosis of coronary artery disease and followed for a mean follow-up of 17 months for the occurrence of cardiovascular events (death, hospitalization and / or revascularization myocardial). Results: The mean age of patients was 58.4 ± 12.5 years old, 74.3% male. Among the patients, 6,02% (30 patients) showed MB. The major indications were angina pectoris in 45,8% and positive stress testing in 33,3%. 62,5% showed absent atherosclerotic disease and only 1 patient showed moderade descending anterior stenosis. During the follow-up none patient showed hard events. Conclusion: Patients with MB could present with angina pectoris and positive stress testing and showed midterm excellent prognosis. MCTCA is an alternative noninvasive imaging tool that allows for easy and accurate evaluation of MB.

  18. Do we still need autopsy in times of modern multislice computed tomography?-Missed diagnoses in the emergency room.

    Science.gov (United States)

    Euler, S A; Kastenberger, T; Attal, R; Rieger, M; Blauth, M; Petri, M

    2017-01-01

    In spite of increasing quality of emergency room (ER) assessment in trauma patients and improved accuracy of modern multislice computed tomography (MSCT), the number of potentially missed diagnoses is still controversial. The aim of this study was to compare the initial findings of ER assessment and MSCT to the findings during autopsy in trauma patients not surviving the first 48 h after admission. We hypothesized that autopsy was more accurate than MSCT in diagnosing potentially fatal diagnoses. Between January 2004 and September 2007, all trauma patients undergoing ER treatment in our institution who deceased within 48 h after admission were analyzed regarding diagnoses from initial ER assessment, including MSCT, and diagnoses from autopsy. Data were prospectively collected and retrospectively analyzed. Autopsy reports were compared to diagnoses of ER assessment and MSCT. Missed diagnoses (MD) and missed potentially fatal diagnoses (MPFD) were analyzed. Seventy-three patients with a mean age of 53.2 years were included into the study. Sixty-three percent were male. Autopsy revealed at least one missed diagnosis in 25% of the patients, with the thoracic area accounting for 67% of these. At least one MPFD was found in 4.1% of the patients, all of them being located in the thorax. Total numbers of MD and MPFD were significantly lower for the newer CT generation (64 MSCT, N = 11), compared to older one (4 MSCT, N = 26). As determined by autopsy, modern multislice computed tomography is an accurate method to diagnose injuries. However, 25% of all diagnoses, and 4.1% of potentially fatal diagnoses are still missed in trauma patients, who deceased within the first 48 h after admission. Therefore, autopsy seems to be necessary to determine potentially missed diagnoses for both academic and medicolegal reasons as well as for quality control.

  19. Multislice CT angiography

    Energy Technology Data Exchange (ETDEWEB)

    Prokop, Mathias E-mail: mathias.prokop@univie.ac.at

    2000-11-01

    Multislice CT has overcome past limitations of CT angiography (CTA): Scan length and spatial resolution can be simultaneously optimized with multislice CTA, contrast medium can be saved, and the evaluation of large anatomic areas and vessels smaller than 1 mm become possible. This article describes how to optimize scanning protocols and contrast injection, and discusses the main clinical applications of this new technique. Only three main scanning protocolssuffice for all indications. A high speed / high-volume protocol (using 4*2mm or 4*2.5mm collimation) can be employed to scan the chest or abdomen in 8-10s, or to cover the whole abdominal aorta and the peripheral runoff including the feet within 40-65s. A high resolution protocol (using 4*1mm or 4*1.25mm) can be employed for the aorta and most regional vascular beds. It allows for near isotrophic imaging and depicts fine vascular structures with excellent detail. Ultra-high resolution protocols (using 2*0.5mm or 4*0.5mm collimation) yield totally isotropic data sets, and are mainly reserved for cerebrovascular imaging. Image processing techniques, and, in particular, volume rendering have made image presentation faster and easier. Multislice CTA exceeds MRA in spatial resolution and is now able to display even small vascular side branches. Its main indications will be aortic diseases, suspected pulmonary embolism but also renal artery stenoses, preoperative workup of abdominal or cerebral vessels, and acute vascular diseases. Multisplice CTA will become a strong competitor of other minimally invasive vascular imaging techniques.

  20. The bases for the use of interpolation in helical computed tomography: an explanation for radiologists

    International Nuclear Information System (INIS)

    Garcia-Santos, J. M.; Cejudo, J.

    2002-01-01

    In contrast to conventional computed tomography (CT), helical CT requires the application of interpolators to achieve image reconstruction. This is because the projections processed by the computer are not situated in the same plane. Since the introduction of helical CT. a number of interpolators have been designed in the attempt to maintain the thickness of the reconstructed section as close as possible to the thickness of the X-ray beam. The purpose of this article is to discuss the function of these interpolators, stressing the advantages and considering the possible inconveniences of high-grade curved interpolators with respect to standard linear interpolators. (Author) 7 refs

  1. Comparison of helical computed tomography and ultrasonography in diagnosis of acute appendicitis

    International Nuclear Information System (INIS)

    Nafees, M.; Abbas, G.; Sarwar, S.

    2010-01-01

    The objective of study is to compare the diagnostic accuracy of helical computed tomography and ultrasonography in acute appendicitis using histopathology as gold standard. Thirty cases of clinically suspected acute appendicitis were included in the study selected on non probability convenience sampling technique. Computed tomography and graded compression ultrasonography of right lower quadrant of abdomen were conducted and results compared with histopathological findings. Amongst 30 patients who underwent computed tomography and graded compression ultrasonography examinations of right lower quadrant for diagnosis of acute appendicitis, on computed tomography 19 were diagnosed with acute appendicitis, 10 were diagnosed as not having the disease and 01 patient diagnosed as not having appendicitis on computed tomography did not improve clinically, was operated upon and histopathology proved it as acute appendicitis. While on graded compression ultrasonography 15 were diagnosed with acute appendicitis, 11 were diagnosed as not having the disease and 04 patients diagnosed as not having appendicitis on ultrasonography, did not improve clinically, were operated upon and histopathology proved it as acute appendicitis. This showed that CT scan has sensitivity of 95%, specificity 100%, positive predictive value 100%, negative predictive value 90.91% and overall accuracy of 96.67% while ultrasonography has sensitivity of 78.9%, specificity 100%, positive predictive value 100%, negative predictive value 73.33% and overall accuracy of 86.67%. We concluded that Helical computed tomography is highly accurate in diagnosing acute appendicitis as compared to ultrasonography and it helps to reduce negative appendectomy rate. (author)

  2. Apneic oxygenation for elimination of respiratory motion artefact in an intubated patient undergoing helical chest computed tomography angiography.

    Directory of Open Access Journals (Sweden)

    Ioannis Pneumatikos

    2008-10-01

    Full Text Available Respiratory motion artifact in intubated and mechanically ventilated patients often reduces the quality of helical computed tomography pulmonary angiography (CTPA. Apneic oxygenation is a well established intra-operative technique that allows adequate oxygenation for short periods (up to 10 min in sedated and paralyzed patients. We describe the use of the apneic oxygenation for elimination of respiratory motion artefact in an intubated patient undergoing helical chest computed tomography angiography.

  3. Value of multislice computed tomography angiography of the thorax in preparation for catheter ablation for the treatment of atrial fibrillation: The impact of unexpected cardiac and extracardiac findings on patient care

    Energy Technology Data Exchange (ETDEWEB)

    Wissner, Erik; Wellnitz, Clinton V.; Srivathsan, Komandoor; Scott, Luis R. [Mayo Clinic Arizona - Mayo Clinic Hospital, Cardiovascular Diseases, 5777 East Mayo Boulevard, Phoenix, AZ 85054 (United States); Altemose, Gregory T. [Mayo Clinic Arizona - Mayo Clinic Hospital, Cardiovascular Diseases, 5777 East Mayo Boulevard, Phoenix, AZ 85054 (United States)], E-mail: altemose.gregory@mayo.edu

    2009-11-15

    Objective: In patients referred for catheter ablation for the treatment of atrial fibrillation, multislice computed tomography angiography of the thorax is routinely performed to assess pulmonary vein anatomy. We sought to investigate the incidence of unexpected cardiac and extracardiac findings in this select patient population and to establish how these findings influence subsequent patient care. Methods: Ninety-five patients (mean age 62 {+-} 10 years, 35% female) referred to our institution for ablation therapy for atrial fibrillation between July 2003 and October 2007 underwent multislice computed tomography angiography of the thorax. Radiologists interpreted all images. Need for additional testing, consultation and eventual diagnosis were assessed by electronic record review. Results: A total of 83 (5 cardiac, 78 extracardiac) unexpected findings were observed in 50/95 (53%) of patients. The findings prompted 23 additional tests (5 cardiac, 18 noncardiac) in 15/95 (16%) of patients and 8 subsequent referrals in 7/95 (7%) patients. In 6 patients the findings significantly altered future patient care and resulted in postponement of ablation therapy in 4 patients. In 2 patients, extracardiac findings (pulmonary emboli and adenocarcinoma of the lung) were of potentially life-saving consequence. Conclusions: In patients undergoing multislice computed tomography angiography of the thorax in anticipation of planned catheter ablation therapy for the treatment of atrial fibrillation, unexpected findings are common and of potentially significant value. In comparison, there is a higher prevalence of unexpected extracardiac, rather than cardiac findings. Further investigation of these findings may lead to postponement of ablation therapy, but may also be of potentially lifesaving consequence.

  4. Value of multislice computed tomography angiography of the thorax in preparation for catheter ablation for the treatment of atrial fibrillation: The impact of unexpected cardiac and extracardiac findings on patient care

    International Nuclear Information System (INIS)

    Wissner, Erik; Wellnitz, Clinton V.; Srivathsan, Komandoor; Scott, Luis R.; Altemose, Gregory T.

    2009-01-01

    Objective: In patients referred for catheter ablation for the treatment of atrial fibrillation, multislice computed tomography angiography of the thorax is routinely performed to assess pulmonary vein anatomy. We sought to investigate the incidence of unexpected cardiac and extracardiac findings in this select patient population and to establish how these findings influence subsequent patient care. Methods: Ninety-five patients (mean age 62 ± 10 years, 35% female) referred to our institution for ablation therapy for atrial fibrillation between July 2003 and October 2007 underwent multislice computed tomography angiography of the thorax. Radiologists interpreted all images. Need for additional testing, consultation and eventual diagnosis were assessed by electronic record review. Results: A total of 83 (5 cardiac, 78 extracardiac) unexpected findings were observed in 50/95 (53%) of patients. The findings prompted 23 additional tests (5 cardiac, 18 noncardiac) in 15/95 (16%) of patients and 8 subsequent referrals in 7/95 (7%) patients. In 6 patients the findings significantly altered future patient care and resulted in postponement of ablation therapy in 4 patients. In 2 patients, extracardiac findings (pulmonary emboli and adenocarcinoma of the lung) were of potentially life-saving consequence. Conclusions: In patients undergoing multislice computed tomography angiography of the thorax in anticipation of planned catheter ablation therapy for the treatment of atrial fibrillation, unexpected findings are common and of potentially significant value. In comparison, there is a higher prevalence of unexpected extracardiac, rather than cardiac findings. Further investigation of these findings may lead to postponement of ablation therapy, but may also be of potentially lifesaving consequence.

  5. Fourier-based approach to interpolation in single-slice helical computed tomography

    International Nuclear Information System (INIS)

    La Riviere, Patrick J.; Pan Xiaochuan

    2001-01-01

    It has recently been shown that longitudinal aliasing can be a significant and detrimental presence in reconstructed single-slice helical computed tomography (CT) volumes. This aliasing arises because the directly measured data in helical CT are generally undersampled by a factor of at least 2 in the longitudinal direction and because the exploitation of the redundancy of fanbeam data acquired over 360 degree sign to generate additional longitudinal samples does not automatically eliminate the aliasing. In this paper we demonstrate that for pitches near 1 or lower, the redundant fanbeam data, when used properly, can provide sufficient information to satisfy a generalized sampling theorem and thus to eliminate aliasing. We develop and evaluate a Fourier-based algorithm, called 180FT, that accomplishes this. As background we present a second Fourier-based approach, called 360FT, that makes use only of the directly measured data. Both Fourier-based approaches exploit the fast Fourier transform and the Fourier shift theorem to generate from the helical projection data a set of fanbeam sinograms corresponding to equispaced transverse slices. Slice-by-slice reconstruction is then performed by use of two-dimensional fanbeam algorithms. The proposed approaches are compared to their counterparts based on the use of linear interpolation - the 360LI and 180LI approaches. The aliasing suppression property of the 180FT approach is a clear advantage of the approach and represents a step toward the desirable goal of achieving uniform longitudinal resolution properties in reconstructed helical CT volumes

  6. Multislice computed tomography: angiographic emulation versus standard assessment for detection of coronary stenoses

    Energy Technology Data Exchange (ETDEWEB)

    Schnapauff, Dirk; Hamm, Bernd; Dewey, Marc [Humboldt-Universitaet zu Berlin, Department of Radiology, Charite - Universitaetsmedizin Berlin, Chariteplatz 1, P.O. Box 10098, Berlin (Germany); Duebel, Hans-Peter; Baumann, Gert [Charite - Universitaetsmedizin Berlin, Department of Cardiology, Berlin (Germany); Scholze, Juergen [Charite - Universitaetsmedizin Berlin, Charite Outpatient Centre, Berlin (Germany)

    2007-07-15

    The present study investigated angiographic emulation of multislice computed tomography (MSCT) (catheter-like visualization) as an alternative approach of analyzing and visualizing findings in comparison with standard assessment. Thirty patients (120 coronary arteries) were randomly selected from 90 prospectively investigated patients with suspected coronary artery disease who underwent MSCT (16-slice scanner, 0.5 mm collimation, 400 ms rotation time) prior to conventional coronary angiography for comparison of both approaches. Sensitivity and specificity of angiographic emulation [81% (26/32) and 93% (82/88)] were not significantly different from those of standard assessment [88% (28/32) and 99% (87/88)], while the per-case analysis time was significantly shorter for angiographic emulation than for standard assessment (3.4 {+-} 1.5 vs 7.0 {+-} 2.5 min, P < 0.001). Both interventional and referring cardiologists preferred angiographic emulation over standard curved multiplanar reformations of MSCT coronary angiography for illustration, mainly because of improved overall lucidity and depiction of sidebranches (P < 0.001). In conclusion, angiographic emulation of MSCT reduces analysis time, yields a diagnostic accuracy comparable to that of standard assessment, and is preferred by cardiologists for visualization of results. (orig.)

  7. Early clinical phase of patient's management after polytrauma using 1- and 4-slice helical CT

    International Nuclear Information System (INIS)

    Kloeppel, R.; Kahn, T.; Schreiter, D.; Dietrich, J.; Josten, C.

    2002-01-01

    In the early clinical phase the comprehensive imaging of patients with multiple trauma using helical CT is already established. Aim of this study was to assess whether MSCT may improve the patient management and the diagnostic results.The procedure is designed as follows: after life-thretening treatment x-ray of chest and ultrasound are carried out in the emergency room. Then the patient is moved to CT. From 1998 to december 2000 241 patients were examined using a single slice helical CT (Somatom plus 4), in 2001 79 patients using a 4-slice helical CT (Somatom VZ, Siemens Med.Sol.). After CT selected radiograms of the extremities were taken.359 of 360 procedures were carried out successfully. Excluding 1 case (death during 1-sl. h CT) all relevant lesions of head, neck, and body were diagnosed. Although the patients had an injury severity score of ∼30. The change from 1slice-helical CT to 4 slice-helical CT allowed us to reduce the stay in the CT room from 28 to 16 min. The total lethality decreased by ∼4%.Advantages for the patient arose from the standardized examination protocol using multislice CT. If integrated in an interdisciplinary management concept, it is a good compromise between examination time, comprehensive diagnostic imaging, life-saving therapeutic procedures, and therapy planning. (orig.) [de

  8. Computer-aided diagnosis workstation and database system for chest diagnosis based on multi-helical CT images

    Science.gov (United States)

    Satoh, Hitoshi; Niki, Noboru; Mori, Kiyoshi; Eguchi, Kenji; Kaneko, Masahiro; Kakinuma, Ryutarou; Moriyama, Noriyuki; Ohmatsu, Hironobu; Masuda, Hideo; Machida, Suguru; Sasagawa, Michizou

    2006-03-01

    Multi-helical CT scanner advanced remarkably at the speed at which the chest CT images were acquired for mass screening. Mass screening based on multi-helical CT images requires a considerable number of images to be read. It is this time-consuming step that makes the use of helical CT for mass screening impractical at present. To overcome this problem, we have provided diagnostic assistance methods to medical screening specialists by developing a lung cancer screening algorithm that automatically detects suspected lung cancers in helical CT images and a coronary artery calcification screening algorithm that automatically detects suspected coronary artery calcification. We also have developed electronic medical recording system and prototype internet system for the community health in two or more regions by using the Virtual Private Network router and Biometric fingerprint authentication system and Biometric face authentication system for safety of medical information. Based on these diagnostic assistance methods, we have now developed a new computer-aided workstation and database that can display suspected lesions three-dimensionally in a short time. This paper describes basic studies that have been conducted to evaluate this new system. The results of this study indicate that our computer-aided diagnosis workstation and network system can increase diagnostic speed, diagnostic accuracy and safety of medical information.

  9. Computational Prediction of Atomic Structures of Helical Membrane Proteins Aided by EM Maps

    Science.gov (United States)

    Kovacs, Julio A.; Yeager, Mark; Abagyan, Ruben

    2007-01-01

    Integral membrane proteins pose a major challenge for protein-structure prediction because only ≈100 high-resolution structures are available currently, thereby impeding the development of rules or empirical potentials to predict the packing of transmembrane α-helices. However, when an intermediate-resolution electron microscopy (EM) map is available, it can be used to provide restraints which, in combination with a suitable computational protocol, make structure prediction feasible. In this work we present such a protocol, which proceeds in three stages: 1), generation of an ensemble of α-helices by flexible fitting into each of the density rods in the low-resolution EM map, spanning a range of rotational angles around the main helical axes and translational shifts along the density rods; 2), fast optimization of side chains and scoring of the resulting conformations; and 3), refinement of the lowest-scoring conformations with internal coordinate mechanics, by optimizing the van der Waals, electrostatics, hydrogen bonding, torsional, and solvation energy contributions. In addition, our method implements a penalty term through a so-called tethering map, derived from the EM map, which restrains the positions of the α-helices. The protocol was validated on three test cases: GpA, KcsA, and MscL. PMID:17496035

  10. Computer-assisted diagnostic procedure for multislice computed tomography for assessment of the pulmonary arterial circulation. Clinical relevance

    International Nuclear Information System (INIS)

    Malich, A.; Hentrich, D.; Hansch, A.; Teichgraeber, U.; Boettcher, J.

    2012-01-01

    A recently developed CAD software which highlights intravascular thrombotic structures from multislice computed tomography (MSCT) data was tested regarding feasibility, interobserver reliability and effect on radiology reports. The CAD system ImageChecker registered CT-Lung was tested in a randomized double-blinded study on 160 MSCT datasets (standardized technical conditions) performed for suspected pulmonary embolism (PE). The CAD data and images were analyzed by three radiologists in an independent and blinded fashion. The data from all 160 cases could be analyzed and 604 CAD prompts were set. Using the CAD analysis significantly more PEs were found in the peripheral pulmonary arterial circulation than described in the initial report. In 38 cases the 3 radiologists in consensus scored the images with the CAD adjunct as PE positive in peripheral vessels, which were initially reported as negative. Despite differences in the evaluation between two radiologists the amended assessment of the imaging data using the CAD softwear was reliable. There was a significant correlation between D-dimer values and the number of embolic structures detected by the CAD analysis. The recently developed CAD system is a useful adjunct as second reader to detect subtle emboli in peripheral vessels of MSCT datasets. (orig.) [de

  11. Trabecular bone structure parameters from 3D image processing of clinical multi-slice and cone-beam computed tomography data

    Energy Technology Data Exchange (ETDEWEB)

    Klintstroem, Eva; Smedby, Oerjan [Linkoeping University, Center for Medical Image Science and Visualization (CMIV), Linkoeping (Sweden); UHL County Council of Oestergoetland, Department of Radiology, Linkoeping (Sweden); Linkoeping University, Department of Medical and Health Sciences (IMH)/Radiology, Linkoeping (Sweden); Moreno, Rodrigo [Linkoeping University, Center for Medical Image Science and Visualization (CMIV), Linkoeping (Sweden); Linkoeping University, Department of Medical and Health Sciences (IMH)/Radiology, Linkoeping (Sweden); Brismar, Torkel B. [KUS Huddinge, Department of Clinical Science, Intervention and Technology at Karolinska Institutet and Department of Radiology, Stockholm (Sweden)

    2014-02-15

    Bone strength depends on both mineral content and bone structure. The aim of this in vitro study was to develop a method of quantitatively assessing trabecular bone structure by applying three-dimensional image processing to data acquired with multi-slice and cone-beam computed tomography using micro-computed tomography as a reference. Fifteen bone samples from the radius were examined. After segmentation, quantitative measures of bone volume, trabecular thickness, trabecular separation, trabecular number, trabecular nodes, and trabecular termini were obtained. The clinical machines overestimated bone volume and trabecular thickness and underestimated trabecular nodes and number, but cone-beam CT to a lesser extent. Parameters obtained from cone beam CT were strongly correlated with μCT, with correlation coefficients between 0.93 and 0.98 for all parameters except trabecular termini. The high correlation between cone-beam CT and micro-CT suggest the possibility of quantifying and monitoring changes of trabecular bone microarchitecture in vivo using cone beam CT. (orig.)

  12. Multislice CT imaging of pulmonary embolism

    International Nuclear Information System (INIS)

    Schoepf, J.U.; Kessler, M.A.; Rieger, C.T.; Herzog, P.; Wiesgigl, S.; Becker, C.R.; Exarhos, D.N.; Reiser, M.F.

    2001-01-01

    In recent years CT has been established as the method of choice for the diagnosis of central pulmonary embolism (PE) to the level of the segmental arteries. The key advantage of CT over competing modalities is the reliable detection of relevant alternative or additional disease causing the patient's symptoms. Although the clinical relevance of isolated peripheral emboli remains unclear, the alleged poor sensitivity of CT for the detection of such small clots has to date prevented the acceptance of CT as the gold standard for diagnosing PE. With the advent of multislice CT we can now cover the entire chest of a patient with 1-mm slices within one breath-hold. In comparison with thicker sections, the detection rate of subsegmental emboli can be significantly increased with 1-mm slices. In addition, the interobserver correlation which can be achieved with 1-mm sections by far exceeds the reproducibility of competing modalities. Meanwhile use of multislice CT for a combined diagnosis of PE and deep venous thrombosis with the same modality appears to be clinically accepted. In the vast majority of patients who receive a combined thoracic and venous multislice CT examination the scan either confirms the suspected diagnosis or reveals relevant alternative or additional disease. The therapeutic regimen is usually chosen based on the functional effect of embolic vascular occlusion. With the advent of fast CT scanning techniques, also functional parameters of lung perfusion can be non-invasively assessed by CT imaging. These advantages let multislice CT appear as an attractive modality for a non-invasive, fast, accurate, and comprehensive diagnosis of PE, its causes, effects, and differential diagnoses. (orig.)

  13. Imaging Features of Helical Computed Tomography Suggesting Advanced Urothelial Carcinoma Arising from the Pelvocalyceal System

    International Nuclear Information System (INIS)

    Kwak, Kyung Won; Park, Byung Kwan; Kim, Chan Kyo; Lee, Hyun Moo; Choi, Han Y ong

    2008-01-01

    Background: Urothelial carcinoma is the most common malignant tumor arising from the pelvocalyceal system. Helical computed tomography (CT) is probably the best preoperative-stage modality for the determination of treatment plan and prognosis. Purpose: To obtain helical CT imaging features suggesting advanced pelvocalyceal urothelial carcinoma. Material and Methods: Preoperative CT images in 44 patients with pelvocalyceal urothelial carcinoma were retrospectively reviewed and correlated with the pathological examination to determine imaging features suggesting stage III or IV of the disease. Results: Pathological stages revealed stage I in 16, stage II in three, stage III in 17, and stage IV in eight patients. Seven patients had metastatic lymph nodes. CT imaging showed that renal parenchymal invasion, sinus fat invasion, and lymph node metastasis were highly suggestive of advanced urothelial cell carcinoma (P<0.05). Helical CT sensitivity, specificity, and accuracy for advanced pelvocalyceal urothelial carcinoma were 76% (19/25), 84% (16/19), and 80% (35/44), respectively. Conclusion: Preoperative helical CT may suggest imaging features of advanced urothelial carcinoma, influencing treatment plan and patient prognosis, even though its accuracy is not so high

  14. Unsupervised motion-compensation of multi-slice cardiac perfusion MRI

    DEFF Research Database (Denmark)

    Stegmann, Mikkel Bille; Ólafsdóttir, Hildur; Larsson, Henrik B. W.

    2005-01-01

    This paper presents a novel method for registration of single and multi-slice cardiac perfusion MRI. Utilising computer intensive analyses of variance and clustering in an annotated training set off-line, the presented method is capable of providing registration without any manual interaction...... in less than a second per frame. Changes in image intensity during the bolus passage are modelled by a slice-coupled active appearance model, which is augmented with a cluster analysis of the training set. Landmark correspondences are optimised using the MDL framework due to Davies et al. Image search...

  15. Bone quality evaluation at dental implant site using multislice CT, micro-CT, and cone beam CT

    NARCIS (Netherlands)

    Parsa, A.; Ibrahim, N.; Hassan, B.; van der Stelt, P.; Wismeijer, D.

    2015-01-01

    Objectives The first purpose of this study was to analyze the correlation between bone volume fraction (BV/TV) and calibrated radiographic bone density Hounsfield units (HU) in human jaws, derived from micro-CT and multislice computed tomography (MSCT), respectively. The second aim was to assess the

  16. A multislice theory of electron scattering in crystals including backscattering and inelastic effects.

    Science.gov (United States)

    Spiegelberg, Jakob; Rusz, Ján

    2015-12-01

    In the framework of the slice transition operator technique, a general multislice theory for electron scattering in crystals is developed. To achieve this generalization, we combine the approaches for inelastic scattering derived by Yoshioka [J. Phys. Soc. Jpn. 12, 6 (1957)] and backscattering based on the formalism of Chen and Van Dyck [Ultramicroscopy 70, 29-44 (1997)]. A computational realization of the obtained equations is suggested. The proposed computational scheme is tested on elastic backscattering of electrons, where we consider single backscattering in analogy to the computational scheme proposed by Chen and Van Dyck. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Cardiac motion extraction and characterization in multislice computed tomography; Extraction et caracterisation du mouvement cardiaque en imagerie scanner multibarrette

    Energy Technology Data Exchange (ETDEWEB)

    Simon, A

    2005-12-15

    Cardiac kinetics analysis is of a great diagnostic interest in the fight against cardiovascular pathologies. Two methods are proposed in order to estimate cardiac motion from dynamic sequences of three-dimensional volumes acquired in multislice computed tomography. These methods both lie on a feature matching process, carried out within a Markovian framework and according to a multi-resolution scheme. The first method, estimating the correspondences between pre-segmented surfaces, is dependent on the temporal coherence of this segmentation. The second method estimates the correspondences between, on the one hand, a segmented surface and, on the other hand, the original data volume corresponding to the next moment. The motion estimation and the segmentation are then carried out, on the whole sequence, during a single process. Both methods are validated on simulated and real data. (author)

  18. Dose optimization for multislice computed tomography protocols of the midface

    International Nuclear Information System (INIS)

    Lorenzen, M.; Wedegaertner, U.; Weber, C.; Adam, G.; Lorenzen, J.; Lockemann, U.

    2005-01-01

    Purpose: to optimize multislice computed tomography (MSCT) protocols of the midface for dose reduction and adequate image quality. Materials and methods: MSCT (somatom volume zoom, siemens) of the midface was performed on 3 cadavers within 24 hours of death with successive reduction of the tube current, applying 150, 100, 70 and 30 mAs at 120 kV as well as 40 and 21 mAs at 80 kV. At 120 kV, a pitch of 0.875 and collimation of 4 x 1 mm were used, and at 80 kV, a pitch of 0.7 and collimation of 2 x 0.5 mm. Images were reconstructed in transverse and coronal orientation. Qualitative image analysis was separately performed by two radiologists using a five-point scale (1 = excellent; 5 = poor) applying the following parameters: image quality, demarcation and sharpness of lamellar bone, overall image quality, and image noise (1 = minor; 5 = strong). The effective body dose [mSv] and organ dose [mSv] of the ocular lens (using the dosimetry system ''WINdose'') were calculated, and the interobserver agreement (kappa coefficient) was determined. Results: for the evaluation of the lamellar bone, adequate sharpness, demarcation and image quality was demonstrated at 120 kV/30 mAs, and for the overall image quality and noise, 120 kV/40 mAs was acceptable. With regard to image quality, the effective body dose could be reduced from 1.89 mSv to 0.34 mSv and the organ dose of the ocular lens from 27.2 mSv to 4.8 mSv. Interobserver agreement was moderate (kappa = 0.39). Conclusion: adequate image quality was achieved for MSCT protocols of the midface with 30 mAs at 120 kV, resulting in a dose reduction of 70% in comparison to standard protocols. (orig.)

  19. Lung scintigraphy and helical computed tomography for the diagnosis of pulmonary embolism : A meta-analysis

    NARCIS (Netherlands)

    van Beek, EJR; Brouwers, Elise M J; Song, B; Bongaerts, AHH; Oudkerk, M

    To assess the diagnostic value of lung scintigraphy and helical computed tomography (hCT) in patients with suspected pulmonary embolism (PE), all English-language articles that described lung scintigraphy and hCT in patients with suspected PE were retrieved. Articles were assessed for strength of

  20. The cause of the artifact in 4-slice helical computed tomography

    International Nuclear Information System (INIS)

    Taguchi, Katsuyuki; Aradate, Hiroshi; Saito, Yasuo; Zmora, Ilan; Han, Kyung S.; Silver, Michael D.

    2004-01-01

    The causes of the image artifacts in a 4-slice helical computed tomography have been discussed as follows: (1) changeover in pairs of data used in z interpolation, (2) sampling interval in z, and (3) the cone angle. This study analyzes the first two causes of the artifact and describes how the current algorithm [K. Taguchi and H. Aradate, Radiology 205P, 390 (1997); 205P, 618 (1997); Med. Phys. 25, 550-561 (1998); H. Hu, ibid. 26, 5-18 (1999); S. Schaller et al., IEEE Trans. Med. Imaging 19, 822-834 (2000); K. Taguchi, Ph.D. thesis, University of Tsukuba, 2002] solves the problem. An interpolated sinogram for a slice at the edge of a ball phantom shows discontinuity caused by the changeover. If we extend the streak artifact in the reconstructed image, it crosses the focus orbit at the corresponding projection angle. Applying z filtering can reduce such causes by its feathering effect and mixing data obtained by different cone angles; the best results are provided when z filtering is applied to densely sampled helical data

  1. Evaluation of the accuracy of linear measurements on multi-slice and cone beam computed tomography scans to detect the mandibular canal during bilateral sagittal split osteotomy of the mandible.

    Science.gov (United States)

    Freire-Maia, B; Machado, V deC; Valerio, C S; Custódio, A L N; Manzi, F R; Junqueira, J L C

    2017-03-01

    The aim of this study was to compare the accuracy of linear measurements of the distance between the mandibular cortical bone and the mandibular canal using 64-detector multi-slice computed tomography (MSCT) and cone beam computed tomography (CBCT). It was sought to evaluate the reliability of these examinations in detecting the mandibular canal for use in bilateral sagittal split osteotomy (BSSO) planning. Eight dry human mandibles were studied. Three sites, corresponding to the lingula, the angle, and the body of the mandible, were selected. After the CT scans had been obtained, the mandibles were sectioned and the bone segments measured to obtain the actual measurements. On analysis, no statistically significant difference was found between the measurements obtained through MSCT and CBCT, or when comparing the measurements from these scans with the actual measurements. It is concluded that the images obtained by CT scan, both 64-detector multi-slice and cone beam, can be used to obtain accurate linear measurements to locate the mandibular canal for preoperative planning of BSSO. The ability to correctly locate the mandibular canal during BSSO will reduce the occurrence of neurosensory disturbances in the postoperative period. Copyright © 2016 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

  2. Multi-slice computed tomography urography after diuretic injection in children with urinary tract dilatation

    Energy Technology Data Exchange (ETDEWEB)

    Kosucu, P.; Ahmetoglu, A.; Imamoglu, M.; Cay, A.; Ozdemir, O.; Dinc, H.; Kosucu, M.; Sari, A.; Saruhan, H.; Gumele, H.R. [Farabi Hospital, Trabzon (Turkey). Dept. of Radiology

    2004-02-01

    To evaluate the potential use of multi-slice computed tomography urography (MSCTU) after diuretic injection in children with urinary tract dilatation. MSCTU was performed in 19 patients (11 boys, 8 girls, mean age 5.4 years) with suspicion of urinary tract obstruction and dilatation. Furosemide, 1 mg/kg, was injected 3 min before contrast material administration and followed by a bolus of 30 ml of physiologic saline solution immediately after application of contrast material. Excretory-phase images were obtained through the abdomen and pelvis beginning 10 min after initiation of the injection of contrast material. Maximum intensity projection (MIP) and volume rendering (VR) images were post-processed to obtain urographic views. MSCTU revealed pathology in 16 of 19 patients, while 3 patients had normal findings. Ureteropelvic obstruction was found in 4 patients, obstructive megaureter in 8. Both ureteropelvic obstruction and obstructive megaureter were disclosed in 1 patient, partial ureteral duplication in 1 patient, and both complete ureteral duplication and ureterocele in 2 patients. In all patients, MIP and VR images could satisfactorily show the pathologies of the urinary tract. The estimated effective average doses of MSCTU were higher than IVU. Preliminary results of furosemide-enhanced MSCTU demonstrated consistently dilated urinary tracts, obstruction levels, and underlying pathologies better than US and IVU.

  3. Spin versus helicity in processes involving transversity

    CERN Document Server

    Mekhfi, Mustapha

    2011-01-01

    We construct the spin formalism in order to deal in a direct and natural way with processes involving transversity which are now of increasing popularity. The helicity formalism which is more appropriate for collision processes of definite helicity has been so far used also to manage processes with transversity, but at the price of computing numerous helicity amplitudes generally involving unnecessary kinematical variables.In a second step we work out the correspondence between both formalisms and retrieve in another way all results of the helicity formalism but in simpler forms.We then compute certain processes for comparison.A special process:the quark dipole magnetic moment is shown to be exclusively treated within the spin formalism as it is directly related to the transverse spin of the quark inside the baryon.

  4. Mapping the extent of disease by multislice computed tomography, magnetic resonance imaging and sentinel node evaluation in stage I and II cervical carcinoma

    Directory of Open Access Journals (Sweden)

    Rajaram S

    2010-01-01

    Full Text Available Aims: (1 To map the extent of disease in women with stage I and II carcinoma cervix by multislice spiral computed tomography (CT, magnetic resonance imaging (MRI and sentinel nodes. (2 To assess accuracy of each modality individually and in conjunction with FIGO clinical staging. Design and Setting: Prospective, single-blind study. Departments of Obstetrics and Gynaecology, Radiodiagnosis, and Pathology, UCMS and GTBH and Division of Radiological Imaging and Bioinformatics, INMAS, Delhi. Material and Method: The study was conducted on 25 women with cervical cancer FIGO stage I and II. Each woman underwent clinical staging, multislice spiral CT and MRI which was compared to the gold-standard histopathology/cytology. The overall accuracy of each modality and improvement of clinical staging by CT/MRI were noted. Sentinel nodes were evaluated by intracervical Patent Blue V dye injection. Statistical Analysis: Sensitivity, specificity, positive and negative predictive values were calculated by 2Χ2 contingency tables. Results: The accuracy of staging by FIGO, CT and MRI was 68%, 52% and 80%, respectively. MRI and CT improved the overall accuracy of FIGO staging to 96% and 80%, respectively. Sentinel nodes were identified in 89% of patients with 91% accuracy. Conclusion: MRI emerges as the most valuable stand-alone modality improving accuracy of FIGO staging to 96%. Sentinel lymph-node evaluation appears promising in evaluating spread beyond cervix.

  5. Association between epicardial fat volume and coronary plaques diagnosed by multislice computed tomography

    Directory of Open Access Journals (Sweden)

    José A. Morán Quijada

    2016-01-01

    Full Text Available Introduction: Coronary atherosclerotic disease is a major cause of death in Cuba and elsewhere. The volume of epicardial fat is considered a new cardiovascular risk factor because of its association with coronary atherogenesis.Objective: To determine, by multislice computed tomography, the association between epicardial fat volume and the presence of coronary atherosclerotic plaques.Method: A descriptive study was conducted with a universe of 130 patients with chest pain suggestive of ischemic heart disease, of which 117 were selected by opinion sampling. These patients underwent a calcium score study, a coronary angiography and a measurement of the epicardial fat volume.Results: Male patients predominated (54.7% and those aged 60-69 years (32.5%. A high volume of epicardial fat was found in 51.3% of patients, affecting 52.8% of women; 78.9% of patients with a calcium score between 100 and 399 UH had a high volume of epicardial fat, just as 71.2% of those with plaques and 100% of those with 4 or 5 plaques; 41% of patients had various types of plaque, which were mainly located in the anterior descending artery (88.1%.Conclusions: The measurement of the volume of epicardial fat is a useful tool to estimate the presence of coronary disease. When it was high, it was associated with older age, female gender and the presence of a higher calcium score, more plaques, more injuries and a greater involvement of the anterior descending artery.

  6. Impact of glucose intolerance on coronary calcified lesions evaluated using multislice computed tomography

    International Nuclear Information System (INIS)

    Nomura, Kyoko; Ohwaki, Kazuhiro; Yano, Eiji; Yamanouchi, Toshikazu; Kim, Gwang U.

    2007-01-01

    Metabolic syndrome has the unique concept that the common occurrence of individual disease components increases the risk of coronary artery disease (CAD). However, some studies suggest that the burden of different CAD risk factors is not equal, and focusing on the whole set of risk factors might neglect the impact of individual factors that could be useful targets for prophylactic therapies. The purpose of this study was to investigate the effect of glucose intolerance on CAD using multislice computed tomography (MSCT). Ninety-eight consecutive patients with at least one traditional CAD risk factor who visited a municipal hospital were enrolled in this study. The risk factors were impaired glucose tolerance (fasting glucose≥110 mg/dl or patients with diabetes), low high-density lipoprotein cholesterol (HDL-C, 25 kg/m 2 for men and >23 kg/m 2 for women). CAD was determined by the presence of either stenoses, non-calcified plaques or calcified lesions. The following risk factors were significantly related in univariate logistic models: glucose intolerance and coronary calcified lesions (p=0.001), and hypertriglycemia and non-calcified plaque lesions (p=0.048). Multivariate models showed that glucose intolerance was significantly associated with calcified lesions, even after adjustment for gender, age, low HDL-C, hypertriglycemia, hypertension, and obesity (p=0.018). Our results suggest that glucose intolerance might be closely related to the presence of coronary calcified lesions among traditional CAD risk factors. (author)

  7. Chronic thromboembolic pulmonary hypertension: diagnostic impact of multislice-CT and selective pulmonary-DSA

    International Nuclear Information System (INIS)

    Pitton, M.B.; Kemmerich, G.; Herber, S.; Schweden, F.; Thelen, M.; Mayer, E.

    2002-01-01

    Purpose: To evaluate the diagnostic impact of multislice-CT and selective pulmonary DSA in chronic thromboembolic pulmonary hypertension (CTEPH). Methods: 994 vessel segments of 14 consecutive patients with CTEPH were investigated with multislice-CT (slice thickness 3 mm, collimation 2.5 mm, reconstruction intervall 2 mm) and selective pulmonary DSA posterior-anterior, 45 oblique, and lateral projection. Analysis was performed by 2 investigators independently for CT and DSA. Diagnostic criteria were occlusions and non-occlusive changes like webs and bands, irregularities of the vessel wall, diameter reduction and thromboembolic depositions at different levels from central pulmonary arteries to subsegmental arteries. Reference diagnosis was made by synopsis of CT and DSA by consensus. Results: Concerning patency CT and DSA showed concordant findings overall in 88.9%, 92.9% for segmental arteries and 85.4% for subsegmental arteries. Concerning any thromboembolic changes, multislice-CT was significantly inferior to selective DSA (concordance 67.0% overall, 70.4% for segments and 63.6% for subsegments). Non-occlusive changes of the vessels were significantly underdiagnosed by CT (concordance of CT versus DSA: 23.1%). Conclusion: Multislice-CT and selective pulmonary DSA are equivalent for diagnosis of vessel occlusions at the level of segmental and subsegmental arteries. However, for visualisation of the non-occlusive thromboembolic changes of the vessel wall selective pulmonary DSA is still superior compared to multislice-CT. Multislice-CT and selective pulmonary DSA are complementary tools for diagnosis and treatment planning of chronic thromboembolic pulmonary hypertension (CTEPH). (orig.) [de

  8. Comparison between helical computed tomography angiography and intraoperative findings

    Directory of Open Access Journals (Sweden)

    Abijit Shetty

    2014-01-01

    Conclusions: Helical CT is important in delineating the arterial, venous, and ureteral anatomy and can show the important incidental findings. Left renal donors and males have more variations in their renal anatomy. Technically challenging laparoscopic nephrectomy on the multiple-vessel-side donor is possible with the aid of helical CT. The importance of the CT in evaluating donor renal anatomy for a technically challenging laparoscopic donor nephrectomy is commendable.

  9. IMAGING DIAGNOSIS-ECTOPIC SPLEEN MIMICKING HEPATIC TUMOR WITH INTRA-ABDOMINAL METASTASES INVESTIGATED VIA TRIPLE-PHASE HELICAL COMPUTED TOMOGRAPHY IN A DOG.

    Science.gov (United States)

    Kutara, Kenji; Konno, Toshiaki; Kondo, Hirotaka; Aoki, Kotoyo; Yamazoe, Hinako; Matsunaga, Satoru

    2017-05-01

    A 10-year-old castrated male miniature dachshund was presented with an abdominal mass. The dog had a history of splenectomy. Triple-phase helical computed tomography was utilized, revealing a hepatic mass and multiple intra-abdominal solid masses. In triple-phase helical computed tomography the images, hepatic mass and two of four intra-abdominal masses were heterogenous in all phases. Therefore, we diagnosed a malignant hepatic tumor and presumed intra-abdominal metastases. The masses were surgically removed and were histologically composed of normal spleen tissues, findings which were consistent with ectopic spleen. © 2016 American College of Veterinary Radiology.

  10. Selection of multislice in nuclear magnetic resonance tomography. Selecao de multiplos planos em tomografia por ressonancia magnetica nuclear

    Energy Technology Data Exchange (ETDEWEB)

    Frare, Junior, P L

    1990-01-01

    The study and the implementation of three techniques for the selection of multislice, aiming the optimization of the NMR tomography is presented. The first technique uses the simultaneous excitation of multiple slices, being each plane encoded with a pre determined phase for a latter decodification of the information by the linear combination of n experiments. The second one makes use of the multislice simultaneous excitation, like the first one, but the slices are acquired in the presence of an oblique reading gradient, which provides us the multi slices signal without any further computer processing. The third technique uses frequency multiplexed excitation, that is, different slices are successively excited during the repetition time of an acquisition, making possible multislice acquisition at the same time of a single slice. The construction and the use of a phantom for the equipment characterization are discussed too. Many technical aspects necessary for an improvement of the tomography performance, like reception circuits and resonators, are discussed. A brief introduction to the gradient modulated adiabatic excitation (GMAX) technique and the first results ever obtained with it, using surface coils, is presented. (author).

  11. Non-invasive coronary angiography with multislice computed tomography. Technology, methods, preliminary experience and prospects.

    Science.gov (United States)

    Traversi, Egidio; Bertoli, Giuseppe; Barazzoni, Giancarlo; Baldi, Maurizia; Tramarin, Roberto

    2004-02-01

    The recent technical developments in multislice computed tomography (MSCT), with ECG retro-gated image reconstruction, have elicited great interest in the possibility of accurate non-invasive imaging of the coronary arteries. The latest generation of MSCT systems with 8-16 rows of detectors permits acquisition of the whole cardiac volume during a single 15-20 s breath-hold with a submillimetric definition of the images and an outstanding signal-to-noise ratio. Thus the race which, between MSCT, electron beam computed tomography and cardiac magnetic resonance imaging, can best provide routine and reliable imaging of the coronary arteries in clinical practice has recommenced. Currently available MSCT systems offer different options for both cardiac image acquisition and reconstruction, including multiplanar and curved multiplanar reconstruction, three-dimensional volume rendering, maximum intensity projection, and virtual angioscopy. In our preliminary experience including 176 patients suffering from known or suspected coronary artery disease, MSCT was feasible in 161 (91.5%) and showed a sensitivity of 80.4% and a specificity of 80.3%, with respect to standard coronary angiography, in detecting critical stenosis in coronary arteries and artery or venous bypass grafts. These results correspond to a positive predictive value of 58.6% and a negative predictive value of 92.2%. The true role that MSCT is likely to play in the future in non-invasive coronary imaging is still to be defined. Nevertheless, the huge amount of data obtainable by MSCT along with the rapid technological advances, shorter acquisition times and reconstruction algorithm developments will make the technique stronger, and possible applications are expected not only for non-invasive coronary angiography, but also for cardiac function and myocardial perfusion evaluation, as an all-in-one examination.

  12. Magnetic Helicities and Dynamo Action in Magneto-rotational Turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Bodo, G.; Rossi, P. [INAF/Osservatorio Astrofisico di Torino, Strada Osservatorio 20, I-10025 Pino Torinese (Italy); Cattaneo, F. [Department of Astronomy and Astrophysics, The University of Chicago, 5640 S. Ellis Avenue, Chicago IL 60637 (United States); Mignone, A., E-mail: bodo@oato.inaf.it [Dipartimento di Fisica, Università degli Studi di Torino, Via Pietro Giuria 1, 10125 Torino (Italy)

    2017-07-10

    We examine the relationship between magnetic flux generation, taken as an indicator of large-scale dynamo action, and magnetic helicity, computed as an integral over the dynamo volume, in a simple dynamo. We consider dynamo action driven by magneto-rotational turbulence (MRT) within the shearing-box approximation. We consider magnetically open boundary conditions that allow a flux of helicity in or out of the computational domain. We circumvent the problem of the lack of gauge invariance in open domains by choosing a particular gauge—the winding gauge—that provides a natural interpretation in terms of the average winding number of pairwise field lines. We use this gauge precisely to define and measure the helicity and the helicity flux for several realizations of dynamo action. We find in these cases that the system as a whole does not break reflectional symmetry and that the total helicity remains small even in cases when substantial magnetic flux is generated. We find no particular connection between the generation of magnetic flux and the helicity or the helicity flux through the boundaries. We suggest that this result may be due to the essentially nonlinear nature of the dynamo processes in MRT.

  13. Four-dimensional measurement of the displacement of internal fiducial and skin markers during 320-multislice computed tomography scanning of breast cancer.

    Science.gov (United States)

    Yamashita, Hideomi; Okuma, Kae; Tada, Keiichiro; Shiraishi, Kenshiro; Takahashi, Wataru; Shibata-Mobayashi, Shino; Sakumi, Akira; Saotome, Naoya; Haga, Akihiro; Onoe, Tsuyoshi; Ino, Kenji; Akahane, Masaaki; Ohtomo, Kuni; Nakagawa, Keiichi

    2012-10-01

    To study the three-dimensional movement of internal tumor bed fiducial and breast skin markers, using 320-multislice computed tomography (CT); and to analyze intrafractional errors for breast cancer patients undergoing breast irradiation. This study examined 280 markers on the skin of the breast (200 markers) and on the primary tumor bed (80 markers) of 20 patients treated by external-beam photon radiotherapy. Motion assessment was analyzed in 41 respiratory phases during 20 s of cine CT in the radiotherapy position. To assess intrafractional errors resulting from respiratory motion, four-dimensional CT scans were acquired for 20 patients. Motion in the anterior-posterior (A/P) and superior-inferior (S/I) directions showed a strong correlation (|r| > 0.7) with the respiratory curve for most markers (79% and 70%, respectively). The average marker displacements between maximum and minimum value during 20 s for the 200 breast skin metal markers were 1.1 ± 0.3 mm, 2.1 ± 0.6 mm, and 1.6 ± 0.4 mm in the left-right, A/P, and S/I directions, respectively. For the 80 tumor bed clips, displacements were 0.9 ± 0.2 mm in left-right, 1.7 ± 0.5 mm in A/P, and 1.1 ± 0.3 mm in S/I. There was no significant difference in the motion between breast quadrant regions or between the primary site and the other regions. Motion in primary breast tumors was evaluated with 320-multislice CT. Very little change was detected during individual radiation treatment fractions. Copyright © 2012 Elsevier Inc. All rights reserved.

  14. [Virtual bronchoscopy in the child using multi-slice CT: initial clinical experiences].

    Science.gov (United States)

    Kirchner, J; Laufer, U; Jendreck, M; Kickuth, R; Schilling, E M; Liermann, D

    2000-01-01

    Virtual bronchoscopy of the pediatric patient has been reported to be more difficult because of artifacts due to breathing or motion. We demonstrate the benefit of the accelerated examination based on multislice spiral CT (MSCT) in the pediatric patient which has not been reported so far. MSCT (tube voltage 120 kV, tube current 110 mA, 4 x 1 mm Slice thickness, 500 ms rotation time, Pitch 6) was performed on a CT scanner of the latest generation (Volume Zoom, Siemens Corp. Forchheim, Germany). In totally we examined 11 patients (median age 48 months, range 2-122 months) suspected of having tracheoesophageal fistula (n = 2), tracheobronchial narrowing (n = 8) due to intrinsic or extrinsic factors or injury of the bronchial system (n = 1). In all patients we obtained sufficient data for 3D reconstruction avoiding general anesthesia. 6/11 examinations were described to be without pathological finding. A definite diagnosis was obtained in 10 patients. Virtual bronchoscopy could avoid other invasive diagnostic examination in 8/11 patients (73%). Helical CT provides 3D-reconstruction and virtual bronchoscopy in the newborn as well as the infant. It avoids additional diagnostic bronchoscopy in a high percentage of all cases.

  15. Validities of three multislice algorithms for quantitative low-energy transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ming, W.Q.; Chen, J.H., E-mail: jhchen123@hnu.edu.cn

    2013-11-15

    Three different types of multislice algorithms, namely the conventional multislice (CMS) algorithm, the propagator-corrected multislice (PCMS) algorithm and the fully-corrected multislice (FCMS) algorithm, have been evaluated in comparison with respect to the accelerating voltages in transmission electron microscopy. Detailed numerical calculations have been performed to test their validities. The results show that the three algorithms are equivalent for accelerating voltage above 100 kV. However, below 100 kV, the CMS algorithm will introduce significant errors, not only for higher-order Laue zone (HOLZ) reflections but also for zero-order Laue zone (ZOLZ) reflections. The differences between the PCMS and FCMS algorithms are negligible and mainly appear in HOLZ reflections. Nonetheless, when the accelerating voltage is further lowered to 20 kV or below, the PCMS algorithm will also yield results deviating from the FCMS results. The present study demonstrates that the propagation of the electron wave from one slice to the next slice is actually cross-correlated with the crystal potential in a complex manner, such that when the accelerating voltage is lowered to 10 kV, the accuracy of the algorithms is dependent of the scattering power of the specimen. - Highlights: • Three multislice algorithms for low-energy transmission electron microscopy are evaluated. • The propagator-corrected algorithm is a good alternative for voltages down to 20 kV. • Below 20 kV, a fully-corrected algorithm has to be employed for quantitative simulations.

  16. Validities of three multislice algorithms for quantitative low-energy transmission electron microscopy

    International Nuclear Information System (INIS)

    Ming, W.Q.; Chen, J.H.

    2013-01-01

    Three different types of multislice algorithms, namely the conventional multislice (CMS) algorithm, the propagator-corrected multislice (PCMS) algorithm and the fully-corrected multislice (FCMS) algorithm, have been evaluated in comparison with respect to the accelerating voltages in transmission electron microscopy. Detailed numerical calculations have been performed to test their validities. The results show that the three algorithms are equivalent for accelerating voltage above 100 kV. However, below 100 kV, the CMS algorithm will introduce significant errors, not only for higher-order Laue zone (HOLZ) reflections but also for zero-order Laue zone (ZOLZ) reflections. The differences between the PCMS and FCMS algorithms are negligible and mainly appear in HOLZ reflections. Nonetheless, when the accelerating voltage is further lowered to 20 kV or below, the PCMS algorithm will also yield results deviating from the FCMS results. The present study demonstrates that the propagation of the electron wave from one slice to the next slice is actually cross-correlated with the crystal potential in a complex manner, such that when the accelerating voltage is lowered to 10 kV, the accuracy of the algorithms is dependent of the scattering power of the specimen. - Highlights: • Three multislice algorithms for low-energy transmission electron microscopy are evaluated. • The propagator-corrected algorithm is a good alternative for voltages down to 20 kV. • Below 20 kV, a fully-corrected algorithm has to be employed for quantitative simulations

  17. Multislice computed tomography coronary angiography

    NARCIS (Netherlands)

    F. Cademartiri (Filippo)

    2005-01-01

    markdownabstract__Abstract__ Computed Tomography (CT) imaging is also known as "CAT scanning" (Computed Axial Tomography). Tomography is from the Greek word "tomos" meaning "slice" or "section" and "graphia" meaning "describing". CT was invented in 1972 by British engineer Godfrey Hounsfield

  18. Assessment of coronary arteries in infants by 64-detector-row multislice spiral computed tomography

    International Nuclear Information System (INIS)

    Tahara, Masahiro; Waki, Chiaki; Komatsu, Hiroaki; Hayashi, Tomohiro; Sato, Tomoyasu

    2008-01-01

    Heart rate is one of the most important factors for optimal visualization of cardiac CT. We investigated the relation between heart rate and visibility of the coronary arteries with 64-detector row multislice spiral computed tomography (MSCT). Three simulated coronary artery stenosis models (3, 4, and 5 mm) were attached to a moving heart phantom and scanned using 64-detector row MSCT. The heart rate of the phantom was varied between 60 and 150 beats per minutes (bpm). The visibility of simulated coronary arteries was assessed in comparison between cardiac half reconstruction (CHR) and multi-sector reconstruction (MSR). Then contrast-enhanced 64-detector row MSCT was performed in 16 patients under 3 years of age with congenital heart disease and Kawasaki disease without heart rate control. The visibility of coronary artery segments was graded on a three-point scale. The simulated coronary artery patency was detected in the moving phantom at maximum heart rate (150 bpm) with MSR. Minimum lumen diameter was 0.75 mm. Electrocardiogram (ECG)-gated cardiac CT was performed in 9 patients, and non-ECG-gated cardiac CT was performed in 7 patients. The origin and proximal course of coronary arteries in all 9 patients with ECG-gated acquisition were visually evaluated. 64-detector row MSCT with ECG-gated acquisition is able to visualize the origin and proximal course of coronary arteries in infants under 3 years of age. (author)

  19. Slice sensitivity profiles and pixel noise of multi-slice CT in comparison with single-slice CT

    International Nuclear Information System (INIS)

    Schorn, C.; Obenauer, S.; Funke, M.; Hermann, K.P.; Kopka, L.; Grabbe, E.

    1999-01-01

    Purpose: Presentation and evaluation of slice sensitivity profile and pixel noise of multi-slice CT in comparison to single-slice CT. Methods: Slice sensitivity profiles and pixel noise of a multi-slice CT equiped with a 2D matrix detector array and of a single-slice CT were evaluated in phantom studies. Results: For the single-slice CT the width of the slice sensitivity profiles increased with increasing pitch. In spite of a much higher table speed the slice sensitivity profiles of multi-slice CT were narrower and did not increase with higher pitch. Noise in single-slice CT was independent of pitch. For multi-slice CT noise increased with higher pitch and for the higher pitch decreased slightly with higher detector row collimation. Conclusions: Multi-slice CT provides superior z-resolution and higher volume coverage speed. These qualities fulfill one of the prerequisites for improvement of 3D postprocessing. (orig.) [de

  20. A theoretically exact reconstruction algorithm for helical cone-beam differential phase-contrast computed tomography

    International Nuclear Information System (INIS)

    Li Jing; Sun Yi; Zhu Peiping

    2013-01-01

    Differential phase-contrast computed tomography (DPC-CT) reconstruction problems are usually solved by using parallel-, fan- or cone-beam algorithms. For rod-shaped objects, the x-ray beams cannot recover all the slices of the sample at the same time. Thus, if a rod-shaped sample is required to be reconstructed by the above algorithms, one should alternately perform translation and rotation on this sample, which leads to lower efficiency. The helical cone-beam CT may significantly improve scanning efficiency for rod-shaped objects over other algorithms. In this paper, we propose a theoretically exact filter-backprojection algorithm for helical cone-beam DPC-CT, which can be applied to reconstruct the refractive index decrement distribution of the samples directly from two-dimensional differential phase-contrast images. Numerical simulations are conducted to verify the proposed algorithm. Our work provides a potential solution for inspecting the rod-shaped samples using DPC-CT, which may be applicable with the evolution of DPC-CT equipments. (paper)

  1. The relationship between the peripheral lung cancer and the bronchi, pulmonary artery and vein: a multislice helical CT observation

    International Nuclear Information System (INIS)

    Liu Xueguo; Liang Mingzhu; Chen Cuifen; Qin Peixin; Zhong Guomei; He Yanguo; Liu Xiaobing; Han Mingqun; Yi Xianping; Wang Yong; Zhang Hao

    2008-01-01

    Objective: To investigate the relationships between the peripheral lung cancer and pulmonary vessels or bronchi by 16-row multislice computed tomography (MSCT) and analyze the related factors. Methods: Fifty-four patients with peripheral lung cancer confirmed pathologically underwent contrast-enhanced MSCT. Multiplanar reformation (MPR) and maximum intensity projection (MIP) in all patients were used to demonstrate the relationships between the peripheral lung cancer and pulmonary vessels, bronchi. The relationships were categorized five types: Type 1, erupted at the edge of nodule. Type 2, erupted at the center of nodule. Type 3, penetrated through the nodule. Type 4, contacting the nodule but stretched or encased. Type 5, contacting the nodule but smoothly compressed. The pathology type, stage, size, density and location of the peripheral lung cancer were recorded and the relationships with five types were evaluated by using Chi-square test and correlation analysis. Results: (1) Tumor-bronchi relationship: type 1 (33,61.1%) was more often seen in ≥2.0 cm and solid lesions with stage II-IV, while Type 2(14,25.9%) was often seen in < 2.0 cm and part-solid or non-solid lesions with stage I. (2) Tumor-PA relationship: Type 1 was more often seen in ≥2.0 cm and solid lesions with stage II-IV, while Type 2 was often seen in part-solid or non-solid lesions with stage I. (3) Tumor-PV relationship: type 4 was the most common type (29, 53.7%). Type 2 (13, 24.1%) was more often seen in part-solid or non-solid lesions. (4) Tumor-bronchi relationship and tumor-PA relationship had a positive correlation (r0.5265, P<0.01). Conclusions: MSCT can demonstrate the relations between the peripheral lung cancer and bronchi, PA and PV. It is useful for the differential diagnosis and prognosis evaluation of the lung cancer. (authors)

  2. Application of the FDK algorithm for multi-slice tomographic image reconstruction; Aplicacao do algoritmo FDK para a reconstrucao de imagens tomograficas multicortes

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Paulo Roberto, E-mail: pcosta@if.usp.b [Universidade de Sao Paulo (IFUSP), SP (Brazil). Inst. de Fisica. Dept. de Fisica Nuclear; Araujo, Ericky Caldas de Almeida [Fine Image Technology, Sao Paulo, SP (Brazil)

    2010-08-15

    This work consisted on the study and application of the FDK (Feldkamp- Davis-Kress) algorithm for tomographic image reconstruction using cone-beam geometry, resulting on the implementation of an adapted multi-slice computed tomography system. For the acquisition of the projections, a rotating platform coupled to a goniometer, an X-ray equipment and a digital image detector charge-coupled device type were used. The FDK algorithm was implemented on a computer with a Pentium{sup R} XEON{sup TM} 3.0 processor, which was used for the reconstruction process. Initially, the original FDK algorithm was applied considering only the ideal physical conditions in the measurement process. Then some artifacts corrections related to the projections measurement process were incorporated. The implemented MSCT system was calibrated. A specially designed and manufactured object with a known linear attenuation coefficient distribution ({mu}(r)) was used for this purpose. Finally, the implemented MSCT system was used for multi-slice tomographic reconstruction of an inhomogeneous object, whose distribution {mu}(r) was unknown. Some aspects of the reconstructed images were analyzed to assess the robustness and reproducibility of the system. During the system calibration, a linear relationship between CT number and linear attenuation coefficients of materials was verified, which validate the application of the implemented multi-slice tomographic system for the characterization of linear attenuation coefficients of distinct several objects. (author)

  3. Mid-term results of off-pump coronary artery bypass grafting assessed by multi-slice computed tomography

    International Nuclear Information System (INIS)

    Yoshida, Seijiro; Nitta, Yoshio; Oda, Katsuhiko

    2004-01-01

    Off-pump coronary artery bypass (OPCAB) has recently increased in popularity, but the long-term results are still unknown. We evaluated the mid-term results of OPCAB surgery using multi-slice computed tomography (MSCT), which is a non-invasive postoperative evaluation method. Thirty-one consecutive patients who underwent OPCAB surgery at least 2 years prior to the study were selected. The age was 50 to 79 years (66.9±6.5) and the ratio of men to women was 26:5. Coronary angiography was performed in all patients at 2 weeks postoperatively. The follow-up was complete, and mean follow-up was 30.9 months. There were no hospital deaths and 1 non-cardiac late death. The graft patency rate in coronary angiography was left internal thoracic artery (LITA) 30/30 (100%), right internal thoracic artery (RITA) 2/2 (100%), radial artery (RA) 14/15 (93%), saphenous vein graft (SVG) 15/17 (88%). No graft became occluded on MSCT study and all patients have been angina-free during the follow-up period. We suggest that OPCAB is feasible in most patients with good patency and low mortality. MSCT is an effective follow up method for the morphological findings and noninvasive quantitative evaluation of the bypass grafts. (author)

  4. Magnetic helicity and active filament configuration

    Science.gov (United States)

    Romano, P.; Zuccarello, F.; Poedts, S.; Soenen, A.; Zuccarello, F. P.

    2009-11-01

    Context: The role of magnetic helicity in active filament formation and destabilization is still under debate. Aims: Although active filaments usually show a sigmoid shape and a twisted configuration before and during their eruption, it is unclear which mechanism leads to these topologies. In order to provide an observational contribution to clarify these issues, we describe a filament evolution whose characteristics seem to be directly linked to the magnetic helicity transport in corona. Methods: We applied different methods to determine the helicity sign and the chirality of the filament magnetic field. We also computed the magnetic helicity transport rate at the filament footpoints. Results: All the observational signatures provided information on the positive helicity and sinistral chirality of the flux rope containing the filament material: its forward S shape, the orientation of its barbs, the bright and dark threads at 195 Å. Moreover, the magnetic helicity transport rate at the filament footpoints showed a clear accumulation of positive helicity. Conclusions: The study of this event showed a correspondence between several signatures of the sinistral chirality of the filament and several evidences of the positive magnetic helicity of the filament magnetic field. We also found that the magnetic helicity transported along the filament footpoints showed an increase just before the change of the filament shape observed in Hα images. We argued that the photospheric regions where the filament was rooted might be the preferential ways where the magnetic helicity was injected along the filament itself and where the conditions to trigger the eruption were yielded.

  5. Helicity conservation under quantum reconnection of vortex rings.

    Science.gov (United States)

    Zuccher, Simone; Ricca, Renzo L

    2015-12-01

    Here we show that under quantum reconnection, simulated by using the three-dimensional Gross-Pitaevskii equation, self-helicity of a system of two interacting vortex rings remains conserved. By resolving the fine structure of the vortex cores, we demonstrate that the total length of the vortex system reaches a maximum at the reconnection time, while both writhe helicity and twist helicity remain separately unchanged throughout the process. Self-helicity is computed by two independent methods, and topological information is based on the extraction and analysis of geometric quantities such as writhe, total torsion, and intrinsic twist of the reconnecting vortex rings.

  6. [Diagnostic significance of multi-slice computed tomography imaging in congenital inner ear malformations].

    Science.gov (United States)

    Ma, Hui; Han, Ping; Liang, Bo; Liu, Fang; Tian, Zhi-Liang; Lei, Zi-Qiao; Li, You-Lin; Kong, Wei-Jia

    2005-04-01

    To evaluate the feasibility and usability of multi-slice computed tomography (MSCT) in congenital inner ear malformations. Fourty-four patients with sensorineural hearing loss (SNHL) were examined by a Somatom Sensation 16 (siemens, Germany) CT scanner with following parameters: 120 kV, 100 mAs, 0.75 mm collimation, 1 mm reconstruction increment, a pitch factor of 1 and a field of view of 100 mm. The axial images of interested ears were reconstructed with 0.1 mm reconstruction increment, and a field of view of 50 mm. The 3D reconstructions were done with volume rendering technique (VRT) on the workstation (3D Virtuoso and Wizard,siemens). Twenty-five patients were normal and 19 patients (36 ears) were congenital inner ear malformations among 44 patients scanned with MSCT. Of the malformations, all the axial, MPR and VRT images can display the site and degree in 33 ears. VRT images were superior to the axial images in displaying the malformations in 3 ears with the small lateral semicircular canal malformations. The malformations were Michel deformity (1 ear), common cavity deformity (3 ears), incomplete partition I (3 ears), incomplete partition II (Mondini deformity, 5 ears), vestibular and semicircular canal malformations( 14 ears), vestibular aqueduct dilate( 16 ears, of which 6 ears accompanied by other malformations), the internal auditory canal malformation(8 ears, all accompanied by other malformations). MSCT allows a comprehensively assessing various congenital ear malformations through high quality MPR and VRT reconstructions. VRT images can display the site and degree of the malformations three-dimensionally and intuitionisticly. It is very useful to the cochlear implantation.

  7. Multi-slice and dual-source CT in cardiac imaging. Principles - protocols - indications - outlook. 2. ed.

    International Nuclear Information System (INIS)

    Ohnesorge, B.M.; Flohr, T.G.; Becker, C.R.; Reiser, M.F.; Knez, A

    2007-01-01

    Cardiac diseases, and in particular coronary artery disease, are the leading cause of death and morbidity in industrialized countries. The development of non-invasive imaging techniques for the heart and the coronary arteries has been considered a key element in improving patient care. A breakthrough in cardiac imaging using CT occurred in 1998, with the introduction of multi-slice computed tomography (CT). Since then, amazing advances in performance have taken place with scanners that acquire up to 64 slices per rotation. This book discusses the state-of-the-art developments in multi-slice CT for cardiac imaging as well as those that can be anticipated in the future. It serves as a comprehensive work that covers all aspects of this technology, from the technical fundamentals and image evaluation all the way to clinical indications and protocol recommendations. This fully reworked second edition draws on the most recent clinical experience obtained with 16- and 64-slice CT scanners by world-leading experts from Europe and the United States. It also includes ''hands-on'' experience in the form of 10 representative clinical case studies, which are included on the accompanying CD. As a further highlight, the latest results of the very recently introduced dual-source CT, which may soon represent the CT technology of choice for cardiac applications, are presented. This book will not only convince the reader that multi-slice cardiac CT has arrived in clinical practice, it will also make a significant contribution to the education of radiologists, cardiologists, technologists, and physicists-whether newcomers, experienced users, or researchers. (orig.)

  8. Geometry Dynamics of α-Helices in Different Class I Major Histocompatibility Complexes

    Directory of Open Access Journals (Sweden)

    Reiner Ribarics

    2015-01-01

    Full Text Available MHC α-helices form the antigen-binding cleft and are of particular interest for immunological reactions. To monitor these helices in molecular dynamics simulations, we applied a parsimonious fragment-fitting method to trace the axes of the α-helices. Each resulting axis was fitted by polynomials in a least-squares sense and the curvature integral was computed. To find the appropriate polynomial degree, the method was tested on two artificially modelled helices, one performing a bending movement and another a hinge movement. We found that second-order polynomials retrieve predefined parameters of helical motion with minimal relative error. From MD simulations we selected those parts of α-helices that were stable and also close to the TCR/MHC interface. We monitored the curvature integral, generated a ruled surface between the two MHC α-helices, and computed interhelical area and surface torsion, as they changed over time. We found that MHC α-helices undergo rapid but small changes in conformation. The curvature integral of helices proved to be a sensitive measure, which was closely related to changes in shape over time as confirmed by RMSD analysis. We speculate that small changes in the conformation of individual MHC α-helices are part of the intrinsic dynamics induced by engagement with the TCR.

  9. Physics properties of non-helical scan using 320-row multi detector computed tomography

    International Nuclear Information System (INIS)

    Urikura, Atsushi; Nakaya, Yoshihiro; Kawatani, Keisuke; Kawashima, Ippei; Goto, Hironori; Ichikawa, Katsuhiro

    2012-01-01

    Recently, clinical applications utilizing 320-row multi detector computed tomography (320MDCT) have increased, and the physical image properties of 320MDCT have been more concerned. We evaluated the spatial resolution in scan plane and z-direction, image noise and low-contrast sensitivity of non-helical mode (320NH), 640 slices mode by a double slice reconstruction technology (640DS), and 64-row helical mode (64HE) by using a 320MDCT. The spatial resolution in z-direction was evaluated by the section sensitivity profile (SSP) measurement with the micro coin phantom and the contrast transfer ratio (CTR) with the 0.5-mm comb phantom. The in-plane spatial resolution of 320NH was uniform over all the slice positions. The spatial resolution in z-direction decreased from the cathode side toward the anode side. The image noise of the anode side was higher than that of the cathode side. The contrast to noise ratio as index of the low contrast sensitivity was uniform over all the slice position. The CTR of 320NH fluctuated in the z-position, and the fluctuation was improved by 640DS except for the center of rotation. (author)

  10. A comparative evaluation of Cone Beam Computed Tomography (CBCT) and Multi-Slice CT (MSCT)

    Energy Technology Data Exchange (ETDEWEB)

    Liang Xin, E-mail: Xin.Liang@med.kuleuven.b [Oral Imaging Centre, School of Dentistry, Oral Pathology and Maxillofacial Surgery, Faculty of Medicine, Catholic University of Leuven (Belgium); College of Stomatology, Dalian Medical University (China); Jacobs, Reinhilde, E-mail: Reinhilde.Jacobs@uz.kuleuven.b [Oral Imaging Centre, School of Dentistry, Oral Pathology and Maxillofacial Surgery, Faculty of Medicine, Catholic University of Leuven (Belgium); Hassan, Bassam, E-mail: b.hassan@acta.n [Department of Oral Radiology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam (Netherlands); Li Limin, E-mail: Limin.Li@uz.kuleuven.b [Department of Paediatric Dentistry and Special Dental Care, School of Dentistry, Oral Pathology and Maxillofacial Surgery, Faculty of Medicine, Catholic University of Leuven (Belgium); Pauwels, Ruben, E-mail: Ruben.Pauwels@med.kuleuven.b [Oral Imaging Centre, School of Dentistry, Oral Pathology and Maxillofacial Surgery, Faculty of Medicine, Catholic University of Leuven (Belgium); Corpas, Livia, E-mail: LiviaCorpas@gmail.co [Oral Imaging Centre, School of Dentistry, Oral Pathology and Maxillofacial Surgery, Faculty of Medicine, Catholic University of Leuven (Belgium); Souza, Paulo Couto, E-mail: Paulo.CoutoSouza@med.kuleuven.b [Oral Imaging Centre, School of Dentistry, Oral Pathology and Maxillofacial Surgery, Faculty of Medicine, Catholic University of Leuven (Belgium); Martens, Wendy, E-mail: wendy.martens@uhasselt.b [Department of Basic Medical Sciences, Faculty of Medicine, University of Hasselt, Diepenbeek (Belgium); Shahbazian, Maryam, E-mail: Maryam.Shahbazian@student.kuleuven.b [Oral Imaging Centre, School of Dentistry, Oral Pathology and Maxillofacial Surgery, Faculty of Medicine, Catholic University of Leuven (Belgium); Alonso, Arie, E-mail: ariel.alonso@uhasselt.b [Department of Biostatistics and Statistical Bioinformatics, Universiteit Hasselt (Belgium)

    2010-08-15

    Aims: To compare image quality and visibility of anatomical structures in the mandible between five Cone Beam Computed Tomography (CBCT) scanners and one Multi-Slice CT (MSCT) system. Materials and methods: One dry mandible was scanned with five CBCT scanners (Accuitomo 3D, i-CAT, NewTom 3G, Galileos, Scanora 3D) and one MSCT system (Somatom Sensation 16) using 13 different scan protocols. Visibility of 11 anatomical structures and overall image noise were compared between CBCT and MSCT. Five independent observers reviewed the CBCT and the MSCT images in the three orthographic planes (axial, sagittal and coronal) and assessed image quality on a five-point scale. Results: Significant differences were found in the visibility of the different anatomical structures and image noise level between MSCT and CBCT and among the five CBCT systems (p = 0.0001). Delicate structures such as trabecular bone and periodontal ligament were significantly less visible and more variable among the systems in comparison with other anatomical structures (p = 0.0001). Visibility of relatively large structures such as mandibular canal and mental foramen was satisfactory for all devices. The Accuitomo system was superior to MSCT and all other CBCT systems in depicting anatomical structures while MSCT was superior to all other CBCT systems in terms of reduced image noise. Conclusions: CBCT image quality is comparable or even superior to MSCT even though some variability exists among the different CBCT systems in depicting delicate structures. Considering the low radiation dose and high-resolution imaging, CBCT could be beneficial for dentomaxillofacial radiology.

  11. A comparative evaluation of Cone Beam Computed Tomography (CBCT) and Multi-Slice CT (MSCT)

    International Nuclear Information System (INIS)

    Liang Xin; Jacobs, Reinhilde; Hassan, Bassam; Li Limin; Pauwels, Ruben; Corpas, Livia; Souza, Paulo Couto; Martens, Wendy; Shahbazian, Maryam; Alonso, Arie

    2010-01-01

    Aims: To compare image quality and visibility of anatomical structures in the mandible between five Cone Beam Computed Tomography (CBCT) scanners and one Multi-Slice CT (MSCT) system. Materials and methods: One dry mandible was scanned with five CBCT scanners (Accuitomo 3D, i-CAT, NewTom 3G, Galileos, Scanora 3D) and one MSCT system (Somatom Sensation 16) using 13 different scan protocols. Visibility of 11 anatomical structures and overall image noise were compared between CBCT and MSCT. Five independent observers reviewed the CBCT and the MSCT images in the three orthographic planes (axial, sagittal and coronal) and assessed image quality on a five-point scale. Results: Significant differences were found in the visibility of the different anatomical structures and image noise level between MSCT and CBCT and among the five CBCT systems (p = 0.0001). Delicate structures such as trabecular bone and periodontal ligament were significantly less visible and more variable among the systems in comparison with other anatomical structures (p = 0.0001). Visibility of relatively large structures such as mandibular canal and mental foramen was satisfactory for all devices. The Accuitomo system was superior to MSCT and all other CBCT systems in depicting anatomical structures while MSCT was superior to all other CBCT systems in terms of reduced image noise. Conclusions: CBCT image quality is comparable or even superior to MSCT even though some variability exists among the different CBCT systems in depicting delicate structures. Considering the low radiation dose and high-resolution imaging, CBCT could be beneficial for dentomaxillofacial radiology.

  12. The relationship between image quality and CT dose index of multi-slice low-dose chest CT

    International Nuclear Information System (INIS)

    Zhu Xiaohua; Shao Jiang; Shi Jingyun; You Zhengqian; Li Shijun; Xue Yongming

    2003-01-01

    Objective: To explore the rationality and possibility of multi-slice low-dose CT scan in the examination of the chest. Methods: (1) X-ray dose index measurement: 120 kV tube voltage, 0.75 s rotation, 8 mm and 3 mm slice thickness, and the tube current setting of 115.0, 40.0, 25.0, and 7.5 mAs were employed in every section. The X-ray radiation dose was measured and compared statistically. (2) phantom measurement of homogeneity and noise: The technical parameters were 120 kV, 0.75 s, 8 mm and 3 mm sections, and every slice was scanned using tube current of 115.0, 40.0, 25.0, and 7.5 mAs. Five same regions of interest were measured on every image. The homogeneity and noise level of CT were appraised. (3) The multi-slice low-dose CT in patients: 30 patients with mass and 30 with patch shadow in the lung were selected randomly. The technical parameters were 120 kV, 0.75 s, 8 mm and 3 mm slice thickness. 115.0, 40.0, 25.0, 15.0, and 7.5 mAs tube current were employed in each same slice. Otherwise, 15 cases with helical scan were examined using 190, 150, 40, 25, and 15 mAs tube current. The reconstruction images of MIP, MPR, CVR, HRCT, 3D, CT virtual endoscopy, and variety of interval reconstruction were compared. (4) Evaluation of image quality: CT images were evaluated by four doctors using single-blind method, and 3 degrees including normal image, image with few artifact, and image with excessive artifact, were employed and analyzed statistically. Results: (1) The CT dose index with 115.0 mAs tube current exceeded those of 40.0, 25.0, and 7.5 mAs by about 60%, 70%, and 85%, respectively. (2) The phantom measurement showed that the lower of CT dose the lower of homogeneity, the lower of CT dose the higher of noise level. (3) Result of image quality evaluation: The percentage of the normal image had no significant difference between 8 and 3 mm in 115, 40, and 25 mAs (P>0.05). Conclusion: Multi-slice low-dose chest CT technology may protect the patients and guarantee the

  13. Computed tomography of the vesicular glands: anatomical animal model (Oryctolagus cuniculus)

    International Nuclear Information System (INIS)

    Dimitrov, R.; Stamatova-Yovcheva, K.; Hamza, S.; Toneva, Y.

    2014-01-01

    Spiral CT is a non-invasive imaging method of choice for animal anatomical studies. The aim of the study was to establish the imaging anatomical features of the vesicular glands in the rabbit. Eight sexually mature healthy clinically male New Zealand rabbits of 18 months of age with body weight from 2.8 kg to 3.2 kg were used. The animals were anesthetized. As contrast medium Opti-ray350 was administrated. The computed tomography scan was complied with certain bone and soft tissue markers. For this purpose, a whole body multi-slice spiral computed tomography scanner was used. The both soft tissue glands were heterogeneous and relatively hyperdense structures, and defined in detail from the adjacent soft tissues. The urinary bladder neck was ventrally to the glands. Both vesicular glands were better differentiated each other when the rabbit is examined in abdominal recumbence. In dorsal recumbence the shape of the transversal image of the glandular finding was oval. In abdominal recumbence both the left and right soft tissue vesicular gland were defined. Transversal anatomical computed tomographic investigation of the rabbit vesicular gland is a detailed and definitive method, to study the normal morphology of these glands. Key words: Vesicular Gland. Helical Computed Tomography. Anatomy. Rabbit

  14. Pulmonary artery aneurysm in Bechcet's disease: helical computed tomography study; Aneurisma de la arteria pulmonar en la enfermedad de Behcet. Estudio con tomografia computarizada helicoidal

    Energy Technology Data Exchange (ETDEWEB)

    Munoz, J.; Caballero, P.; Olivera, M. J.; Cajal, M. L.; Caniego, J. L. [Hospital de la Princesa. Iniversidad Autonoma. Madrid (Spain)

    2000-07-01

    Behcet's disease is a vasculitis of unknown etiology that affects arteries and veins of different sizes and can be associated with pulmonary artery aneurysms. We report the case of a patient with Behcet's disease and a pulmonary artery aneurysm who was studied by means of plain chest X ray, helical computed tomography and pulmonary arteriography. Helical computed tomography is a reliable technique for the diagnosis and follow-up of these patients. (Author) 9 refs.

  15. Optimization of helical acquisition parameters to preserve uniformity of mouse whole body using multipinhole collimator in single-photon emission computed tomography

    Directory of Open Access Journals (Sweden)

    Naoyuki Ukon

    Full Text Available Focusing on whole-body uniformity in small-animal single-photon emission computed tomography (SPECT, we examined the optimal helical acquisition parameters using five-pinhole collimators for mouse imaging. SPECT images of an 80-mm-long cylindrical phantom with 99mTc solution were acquired using an Inveon multimodality imaging platform. The bed travels used in this study were 0, 30, 60, 90 and 120 mm, and the numbers of revolutions traversed during the SPECT scan were 1.0, 2.0, 3.0, 4.0, 5.0 and 7.0, respectively. Artifacts that degrade uniformity in reconstructed images were conspicuous when the bed travel was smaller than the object length. Regarding the distal-to-center ratio (DCR of SPECT values in the object’s axial direction, the DCR nearest to the ideal ratio of 1.00 was 1.02 in the optimal uniformity with 4.0 revolutions and a bed travel of 120 mm. Moreover, the helical acquisition using these parameters suppressed the formation of artifacts. We proposed the optimal parameters in whole-body helical SPECT; the bed travel was sufficiently larger than the object length; the 4.0 or more revolutions were required for a pitch of approximately 30 mm/revolution. The optimal acquisition parameters in SPECT to preserve uniformity would contribute to the accurate quantification of whole-body biodistribution. Keywords: Helical acquisition, Multipinhole collimator, Computed tomography, SPECT

  16. Favorable noise uniformity properties of Fourier-based interpolation and reconstruction approaches in single-slice helical computed tomography

    International Nuclear Information System (INIS)

    La Riviere, Patrick J.; Pan Xiaochuan

    2002-01-01

    Volumes reconstructed by standard methods from single-slice helical computed tomography (CT) data have been shown to have noise levels that are highly nonuniform relative to those in conventional CT. These noise nonuniformities can affect low-contrast object detectability and have also been identified as the cause of the zebra artifacts that plague maximum intensity projection (MIP) images of such volumes. While these spatially variant noise levels have their root in the peculiarities of the helical scan geometry, there is also a strong dependence on the interpolation and reconstruction algorithms employed. In this paper, we seek to develop image reconstruction strategies that eliminate or reduce, at its source, the nonuniformity of noise levels in helical CT relative to that in conventional CT. We pursue two approaches, independently and in concert. We argue, and verify, that Fourier-based longitudinal interpolation approaches lead to more uniform noise ratios than do the standard 360LI and 180LI approaches. We also demonstrate that a Fourier-based fan-to-parallel rebinning algorithm, used as an alternative to fanbeam filtered backprojection for slice reconstruction, also leads to more uniform noise ratios, even when making use of the 180LI and 360LI interpolation approaches

  17. Evaluation of coronary artery remodeling in patients with acute coronary syndrome and stable angina by multislice computed tomography

    International Nuclear Information System (INIS)

    Imazeki, Takako; Sato, Yuichi; Inoue, Fumio; Anazawa, Takeo; Tani, Shigemasa; Matsumoto, Naoya; Takayama, Tadateru; Uchiyama, Takahisa; Saito, Satoshi

    2004-01-01

    Multislice computed tomography (MSCT) was used to evaluate coronary artery remodeling in patients with acute coronary syndrome (ACS) and stable angina (SA). MSCT was performed in 31 patients with ACS and 26 patients with SA and intravascular ultrasound (IVUS) was performed in 28 of these 57 patients. In both the MSCT and IVUS analyses, coronary artery remodeling was assessed by the remodeling index (RI): RI>1.10 was defined as positive coronary artery remodeling (PCAR) and RI<0.95 was defined as negative coronary artery remodeling (NCAR). The RI assessed by MSCT closely correlated with that of IVUS (r=0.86, n=28). The vessel area at the region of maximum luminal narrowing was also comparable between the MSCT and IVUS measurements (r=0.92). PCAR was present in 19 patients (61.3%) with ACS, but in none of the patients with SA (p<0.0001). However, NCAR was present in only 1 patient with ACS (3.2%), but was present in 18 patients (62.9%) with SA. The RI was significantly larger in patients with ACS (1.19±0.18) than in those with SA (0.89±0.10, p<0.0001). MSCT accurately assesses coronary artery remodeling. (author)

  18. Diagnostic efficacy and pitfalls of a 64-raw multislice computed tomography scan for mild head injuries in children

    International Nuclear Information System (INIS)

    Matsumoto, Yoshihisa; Nawashiro, Hiroshi; Uozumi, Youichi

    2010-01-01

    The aim of this study is to analyze the usefulness of 64-raw multislice computed tomography (CT) scans and bone images of three-dimensional CT (3D-CT) scans for evaluation of mild head injuries in children. Thirteen children (9 boys and 4 girls, less than or equal to 15 years old) with mild head injury were included in the study. Head CT scans obtained within 24 hours after injury. All children had no episodes of loss of consciousness, amnesia, epilepsy, vomiting, and no neurological abnormality on arrival at hospital. We detected 9 positive findings on CT scans, which looked like fracture lines at the frontal bone in 7 cases. The bone images of CT axial views revealed a true fracture in one case in which a skull X-ray could not demonstrate a fracture line, but, other positive findings turned out to be a diploic vein surrounded by a thin bone cortex. All false positive findings were detected in the patients under the age of 6. By the 3D-reconstructive CT scan, it is easier to detect not only the intracranial lesions but also the cranial fracture. But, the diploic vein is apt to be misdiagnosed as the fracture line, especially in patients under the age of 6. (author)

  19. Helicity content and tokamak applications of helicity

    International Nuclear Information System (INIS)

    Boozer, A.H.

    1986-05-01

    Magnetic helicity is approximately conserved by the turbulence associated with resistive instabilities of plasmas. To generalize the application of the concept of helicity, the helicity content of an arbitrary bounded region of space will be defined. The definition has the virtues that both the helicity content and its time derivative have simple expressions in terms of the poloidal and toroidal magnetic fluxes, the average toroidal loop voltage and the electric potential on the bounding surface, and the volume integral of E-B. The application of the helicity concept to tokamak plasmas is illustrated by a discussion of so-called MHD current drive, an example of a stable tokamak q profile with q less than one in the center, and a discussion of the possibility of a natural steady-state tokamak due to the bootstrap current coupling to tearing instabilities

  20. Evaluation by multislice computed tomography of atherosclerotic coronary artery plaques in non-culprit, remote coronary arteries of patients with acute coronary syndrome

    International Nuclear Information System (INIS)

    Kunimasa, Taeko; Sugi, Kaoru; Moroi, Masao; Sato, Yuichi

    2005-01-01

    Patients with acute coronary syndrome (ACS) frequently have vulnerable plaques in the remote coronary arteries, suggesting that ACS is part of the pan-coronary process. In the present study the computed tomography (CT) plaque density in non-culprit atherosclerotic coronary artery lesions was evaluated by multi-slice computed tomography (MSCT) in patients with ACS and non-ACS. MSCT was performed in 21 patients with ACS and 53 patients with non-ACS: 16 of the 21 ACS patients (76%) and 30 of the non-ACS 53 patients (57%) had non-calcified plaques in the non-culprit coronary arteries (p=0.18). CT-low-density plaques (CT density <68 Hounsfield units (HU)) were more frequent in the ACS group (13/16 patients, 81%) than in the non-ACS group (13/30 patients, 43%, p=0.03). In addition, the CT density of the non-culprit lesion was significantly lower in patients with ACS than in those with non-ACS (44.1±22.9 and 77.3±33.7 HU, respectively). Patients with ACS more frequently had CT-low-density plaques in the non-culprit, remote arteries than those with non-ACS, which suggests that ACS treatment should focus not only on stabilizing the culprit lesion but also on systemic stabilization of non-culprit lesions. (author)

  1. Hydrogen bonds and heat diffusion in α-helices: a computational study.

    Science.gov (United States)

    Miño, German; Barriga, Raul; Gutierrez, Gonzalo

    2014-08-28

    Recent evidence has shown a correlation between the heat diffusion pathways and the known allosteric communication pathways in proteins. Allosteric communication in proteins is a central, yet unsolved, problem in biochemistry, and the study and characterization of the structural determinants that mediate energy transfer among different parts of proteins is of major importance. In this work, we characterized the role of hydrogen bonds in diffusivity of thermal energy for two sets of α-helices with different abilities to form hydrogen bonds. These hydrogen bonds can be a constitutive part of the α-helices or can arise from the lateral chains. In our in vacuo simulations, it was observed that α-helices with a higher possibility of forming hydrogen bonds also had higher rates of thermalization. Our simulations also revealed that heat readily flowed through atoms involved in hydrogen bonds. As a general conclusion, according to our simulations, hydrogen bonds fulfilled an important role in heat diffusion in structural patters of proteins.

  2. A comparative evaluation of Cone Beam Computed Tomography (CBCT) and Multi-Slice CT (MSCT). Part II: On 3D model accuracy

    International Nuclear Information System (INIS)

    Liang Xin; Lambrichts, Ivo; Sun Yi; Denis, Kathleen; Hassan, Bassam; Li Limin; Pauwels, Ruben; Jacobs, Reinhilde

    2010-01-01

    Aim: The study aim was to compare the geometric accuracy of three-dimensional (3D) surface model reconstructions between five Cone Beam Computed Tomography (CBCT) scanners and one Multi-Slice CT (MSCT) system. Materials and methods: A dry human mandible was scanned with five CBCT systems (NewTom 3G, Accuitomo 3D, i-CAT, Galileos, Scanora 3D) and one MSCT scanner (Somatom Sensation 16). A 3D surface bone model was created from the six systems. The reference (gold standard) 3D model was obtained with a high resolution laser surface scanner. The 3D models from the five systems were compared with the gold standard using a point-based rigid registration algorithm. Results: The mean deviation from the gold standard for MSCT was 0.137 mm and for CBCT were 0.282, 0.225, 0.165, 0.386 and 0.206 mm for the i-CAT, Accuitomo, NewTom, Scanora and Galileos, respectively. Conclusion: The results show that the accuracy of CBCT 3D surface model reconstructions is somewhat lower but acceptable comparing to MSCT from the gold standard.

  3. Multislice CT of the auditory ossicles and ossicular ligaments. Delineation of normal anatomy and diagnosis of congenital anomaly

    International Nuclear Information System (INIS)

    Matsumoto, Shigeru; Tozaki, Hiromitu; Miyazaki, Hidemi

    2001-01-01

    By using four detector rows with 0.5 mm collimation, high resolution isotropic voxel data throughout the middle ear can be obtained with Multislice Helical CT (MSCT). The purpose of this study is to evaluate the usefulness of MSCT in demonstrating the auditory ossicles and ossicular ligaments and in the diagnosis of congenital ossicular anomalies. Thirty normal middle ears and 23 ear of 20 patients with suspicious congenital ossicular anomalies were examined. Axial images and multiplanar images were reconstructed. In the normal group, the images were evaluated based on scores for the visualization of the anatomical structure of the auditory ossicles and ossicular ligaments. In the group with anomalies, the findings suggesting ossicular anomalies were referenced and the prevalence was conjectured. Visualization of the auditory ossicles and ossicular ligaments was 98.3%-100% and 78.3%-100%, respectively. Congenital ossicular anomalies were detected in 20 ears (87.0%). MSCT is an accurate method for demonstrating minute and complicated 3D structures of the middle ear, and is found to be a technique of choice for diagnosis of ossicular anomalies. (author)

  4. Modelling the Siemens SOMATOM Sensation 64 Multi-Slice CT (MSCT) Scanner

    International Nuclear Information System (INIS)

    Amin, A T Mohd; Rahni, A A Abd

    2017-01-01

    Reconstructing large volumetric 3D images with minimal radiation dosage exposure with reduced scanning time has been one of the main objectives in the advancement of CT development. One of its advancement is the introduction of multi-slice arc detector geometry from a cone-beam source in third generation scanners. In solving this complex geometry, apart from the known vast computations in CT image reconstruction due to large CT images, iterative reconstruction methods are preferred compared to analytic methods due to its flexibility in image reconstruction. A scanner of interest that has this type of geometry is the Siemens SOMATOM Sensation 64 Multi-Slice CT (MSCT) Scanner , which has a total of 32 slices with 672 detector elements on each slice. In this paper, the scanner projection is modelled via the intersecting lengths between each ray (exhibited from the source to the detector elements) with the scanned image voxels, which are evaluated using the classical Siddon’s algorithm to generate the system matrix, H . This is a prerequisite to perform various iterative reconstruction methods, which involves solving the inverse problem arising from the linear equation: S = H· I; where S is the projections produced from the image, I. Due to the ‘cone-beam geometry’ along the z -axis, the effective field-of-view (FOV) with voxel dimensions (0.4×0.4×0.4) mm 3 is 512×512×32 voxels. The scanner model is demonstrated by reconstructing an image from simulated projections using the analytic Feldkamp-Davis-Kress (FDK) method against basic iterative image reconstruction methods. (paper)

  5. Finite element analysis of helical flows in human aortic arch: A novel index

    OpenAIRE

    Lee, Cheng-Hung; Liu, Kuo-Sheng; Jhong, Guan-Heng; Liu, Shih-Jung; Hsu, Ming-Yi; Wang, Chao-Jan; Hung, Kuo-Chun

    2014-01-01

    This study investigates the helical secondary flows in the aortic arch using finite element analysis. The relationship between helical flow and the configuration of the aorta in patients of whose three-dimensional images constructed from computed tomography scans was examined. A finite element model of the pressurized root, arch, and supra-aortic vessels was developed to simulate the pattern of helical secondary flows. Calculations indicate that most of the helical secondary flow was formed i...

  6. Clinical application of three-dimensional imaging with multislice CT for laparoscopic colorectal surgery

    Energy Technology Data Exchange (ETDEWEB)

    Matsuki, Mitsuru; Okuda, Jyunji; Yoshikawa, Syushi [Osaka Medical Coll., Takatsuki (Japan)] (and others)

    2003-03-01

    Laparoscopic colorectal surgery, while minimally invasive, is a complicated technique. Therefore, prior to this surgery, it is important to determine the anatomical information of colorectal cancer. Fifty-eight cases of patients with a confirmed diagnosis of colon cancer [caecal (n=4), ascending colon (n=6), transverse colon (n=7), descending colon (n=2), sigmoid colon (n=22), and rectal (n=17) cancer] were evaluated using multislice CT before laparoscopic surgery. CT examination was performed in an air-filled colorectum by colon fiberscopy. Contrast-enhanced images on multislice CT were obtained at arterial and venous phases. All images were reviewed on a workstation, and three-dimensional (3D) images of vessels, colorectum, cancer, and swollen lymph nodes were reconstructed by volume rendering and fused (integrated 3D imaging). We evaluated the usefulness of integrated 3D imaging with multislice CT for laparoscopic colorectal surgery. Integrated 3D imaging demonstrated clearly the distribution of arteries feeding the colorectal cancer and the anatomical location of colorectal cancer and arterial and venous systems. Moreover, measurement of the distance between the aortic bifurcation and the origin of the inferior mesenteric artery and that between the base of the inferior mesenteric artery and the origin of the left colic artery on integrated 3D imaging contributed to safe, prompt ligation of the vessels and excision of lymph nodes. Integrated 3D imaging with multislice CT was useful for simulation of laparoscopic colorectal surgery. (author)

  7. Clinical application of three-dimensional imaging with multislice CT for laparoscopic colorectal surgery

    International Nuclear Information System (INIS)

    Matsuki, Mitsuru; Okuda, Jyunji; Yoshikawa, Syushi

    2003-01-01

    Laparoscopic colorectal surgery, while minimally invasive, is a complicated technique. Therefore, prior to this surgery, it is important to determine the anatomical information of colorectal cancer. Fifty-eight cases of patients with a confirmed diagnosis of colon cancer [caecal (n=4), ascending colon (n=6), transverse colon (n=7), descending colon (n=2), sigmoid colon (n=22), and rectal (n=17) cancer] were evaluated using multislice CT before laparoscopic surgery. CT examination was performed in an air-filled colorectum by colon fiberscopy. Contrast-enhanced images on multislice CT were obtained at arterial and venous phases. All images were reviewed on a workstation, and three-dimensional (3D) images of vessels, colorectum, cancer, and swollen lymph nodes were reconstructed by volume rendering and fused (integrated 3D imaging). We evaluated the usefulness of integrated 3D imaging with multislice CT for laparoscopic colorectal surgery. Integrated 3D imaging demonstrated clearly the distribution of arteries feeding the colorectal cancer and the anatomical location of colorectal cancer and arterial and venous systems. Moreover, measurement of the distance between the aortic bifurcation and the origin of the inferior mesenteric artery and that between the base of the inferior mesenteric artery and the origin of the left colic artery on integrated 3D imaging contributed to safe, prompt ligation of the vessels and excision of lymph nodes. Integrated 3D imaging with multislice CT was useful for simulation of laparoscopic colorectal surgery. (author)

  8. Refined staging in hilar bronchial neoplasms with ECG-gated multislice-CT. Case report

    International Nuclear Information System (INIS)

    Ohlmann, S.; Daliri, A.; Froelich, J.J.; Nowak, R.; Michulla, R.

    2008-01-01

    Equivocal initial CT-based staging in 2 patients with hilar bronchial neoplasms was reassessed with retrospective ECG-gated Multislice-CT and optimized examination parameters prior to definition of treatment. An initially suspected irresectable T 4 tumor with mediastinal infiltration was downstaged to T 2 in one case, while tumor infiltration into the left atrium could be confirmed in the other case. In doubtful conditions, ECG-gated multislice CT with optimized examination parameters may be helpful for refined staging in patients with hilar bronchial neoplasma, thus possibly influencing treatment strategies. (orig.)

  9. Low-dose multislice CT in febrile neutropenic patients

    International Nuclear Information System (INIS)

    Wendel, F.; Jenett, M.; Hahn, D.; Sandstede, J.; Geib, A.

    2005-01-01

    Purpose: to define the value of low-dose multislice CT in a clinical setting for early detection of pneumonia in neutropenic patients with fever of unknown origin. Materials and methods: thirty-five neutropenic patients suffering from fever of unknown origin with normal chest X-ray underwent unenhanced low-dose CT of the chest (120 kV, 10 eff. mAs, collimation 4 x 1 mm) using a multislice CT scanner. Axial und frontal slices with a thickness of 5 mm were calculated. If no pneumonia was found, standard antibiotics were given and a repeated examination was performed if fever continued. In case of pneumonia, antimycotic therapy was added and a follow-up CT was performed within one week. Regression or progression of pneumonia at follow-up served as evidence of pneumonia; lowering of fever within 48 h or inconspicuous follow-up CT was regarded as absence of pneumonia. Results: ten of 35 patients had pneumonic infiltration, which decreased or increased on follow-up CT in 3 and 6 patients, respectively. One patient revealed leucemic infiltration by bronchoalveolar lavage. Twenty-five of 35 patients had no evidence of pneumonia. Twenty of these patients were free of fever within 48 h under antibiotics; one patient died due to his basic illness. Out of 4 patients with persisting fever, 3 patients had no pneumonia on repeated examination; one patient showed disseminated micronodular infiltration. Frontal reconstructions helped to differentiate infiltration from atelectasis in 4 patients. Sensitivity and specificity for the detection of pneumonia at the first examination were 90% and 96%, negative predictive value was 96%. Conclusion: low-dose multislice CT should be performed in neutropenic patients having a fever of unknown origin and normal chest X-ray. (orig.)

  10. Reduced bispectrum seeded by helical primordial magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Hortúa, Héctor Javier [Universidad Nacional de Colombia-Bogotá, Facultad de Ciencias, Departamento de Física, Carrera 30 Calle 45-03, C.P. 111321 Bogotá (Colombia); Castañeda, Leonardo, E-mail: hjhortuao@unal.edu.co, E-mail: lcastanedac@unal.edu.co [Grupo de Gravitación y Cosmología, Observatorio Astronómico Nacional, Universidad Nacional de Colombia, cra 45 No 26-85, Edificio Uriel Gutierréz, Bogotá, D.C. (Colombia)

    2017-06-01

    In this paper, we investigate the effects of helical primordial magnetic fields (PMFs) on the cosmic microwave background (CMB) reduced bispectrum. We derive the full three-point statistics of helical magnetic fields and numerically calculate the even contribution in the collinear configuration. We then numerically compute the CMB reduced bispectrum induced by passive and compensated PMF modes on large angular scales. There is a negative signal on the bispectrum due to the helical terms of the fields and we also observe that the biggest contribution to the bispectrum comes from the non-zero IR cut-off for causal fields, unlike the two-point correlation case. For negative spectral indices, the reduced bispectrum is enhanced by the passive modes. This gives a lower value of the upper limit for the mean amplitude of the magnetic field on a given characteristic scale. However, high values of IR cut-off in the bispectrum, and the helical terms of the magnetic field relaxes this bound. This demonstrates the importance of the IR cut-off and helicity in the study of the nature of PMFs from CMB observations.

  11. Godbillon Vey Helicity and Magnetic Helicity in Magnetohydrodynamics

    Science.gov (United States)

    Webb, G. M.; Hu, Q.; Anco, S.; Zank, G. P.

    2017-12-01

    The Godbillon-Vey invariant arises in homology theory, and algebraic topology, where conditions for a layered family of 2D surfaces forms a 3D manifold were elucidated. The magnetic Godbillon-Vey helicity invariant in magnetohydrodynamics (MHD) is a helicity invariant that occurs for flows, in which the magnetic helicity density hm= A\\cdotB=0 where A is the magnetic vector potential and B is the magnetic induction. Our purpose is to elucidate the evolution of the magnetic Godbillon-Vey field η =A×B/|A|2 and the Godbillon-Vey helicity hgv}= η \\cdot∇ × η in general MHD flows in which the magnetic helicity hm≠q 0. It is shown that hm acts as a source term in the Godbillon-Vey helicity transport equation, in which hm is coupled to hgv via the shear tensor of the background flow. The transport equation for hgv depends on the electric field potential ψ , which is related to the gauge for A, which takes its simplest form for the advected A gauge in which ψ =A\\cdot u where u is the fluid velocity.

  12. COMPUTED TOMOGRAPHY DOSE INDEX MEASUREMENT FOR Hi-ART MEGAVOLTAGE HELICAL CT.

    Science.gov (United States)

    Liu, Minglu; Wang, Yunlai; Liao, Xiongfei

    2016-11-01

    On-line megavoltage computed tomography (MVCT) images are used to verify patient daily set-up in Hi-ART helical TomoTherapy unit. To evaluate the patient dose from MVCT scanning in image guidance, weighted computed tomography (CT) dose index (CTDI w ) was measured with PTW TM30009 CT pencil chamber in head and body phantoms for slice thicknesses of 2, 4 and 6 mm with different scan lengths. Dose length products (DLPs) were subsequently calculated. The CTDI w and DLP were compared with XVI kV CBCT and Brilliance simulator CT for routine clinical protocols. It was shown that CTDI and DLP had close relationship with the slice thickness and the scan length. The dose distribution in the transversal plane was very inhomogeneous due to the attenuation of the couch. Patient dose from MVCT was lower than XVI CBCT for the head scan, while larger for body scan. CTDI w , which is measured easily and reproducibly, can be used to assess the patient dose in MVCT. Regular measurement should be performed in QA & QC programmes. Appropriate slice thickness and scan range should be chosen to reduce the patient dose. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  13. Association of achondroplasia with Down syndrome: difficulty in prenatal diagnosis by sonographic and 3-D helical computed tomographic analyses.

    Science.gov (United States)

    Kaga, Akimune; Murotsuki, Jun; Kamimura, Miki; Kimura, Masato; Saito-Hakoda, Akiko; Kanno, Junko; Hoshi, Kazuhiko; Kure, Shigeo; Fujiwara, Ikuma

    2015-05-01

    Achondroplasia and Down syndrome are relatively common conditions individually. But co-occurrence of both conditions in the same patient is rare and there have been no reports of fetal analysis of this condition by prenatal sonographic and three-dimensional (3-D) helical computed tomography (CT). Prenatal sonographic findings seen in persons with Down syndrome, such as a thickened nuchal fold, cardiac defects, and echogenic bowel were not found in the patient. A prenatal 3-D helical CT revealed a large head with frontal bossing, metaphyseal flaring of the long bones, and small iliac wings, which suggested achondroplasia. In a case with combination of achondroplasia and Down syndrome, it may be difficult to diagnose the co-occurrence prenatally without typical markers of Down syndrome. © 2014 Japanese Teratology Society.

  14. High-resolution multi-slice PET

    International Nuclear Information System (INIS)

    Yasillo, N.J.; Chintu Chen; Ordonez, C.E.; Kapp, O.H.; Sosnowski, J.; Beck, R.N.

    1992-01-01

    This report evaluates the progress to test the feasibility and to initiate the design of a high resolution multi-slice PET system. The following specific areas were evaluated: detector development and testing; electronics configuration and design; mechanical design; and system simulation. The design and construction of a multiple-slice, high-resolution positron tomograph will provide substantial improvements in the accuracy and reproducibility of measurements of the distribution of activity concentrations in the brain. The range of functional brain research and our understanding of local brain function will be greatly extended when the development of this instrumentation is completed

  15. Peripheral pulmonary arteries: identification at multi-slice spiral CT with 3D reconstruction

    International Nuclear Information System (INIS)

    Coche, Emmanuel; Pawlak, Sebastien; Dechambre, Stephane; Maldague, Baudouin

    2003-01-01

    Our objective was to analyze the peripheral pulmonary arteries using thin-collimation multi-slice spiral CT. Twenty consecutive patients underwent enhanced-spiral multi-slice CT using 1-mm collimation. Two observers analyzed the pulmonary arteries by consensus on a workstation. Each artery was identified on axial and 3D shaded-surface display reconstruction images. Each subsegmental artery was measured at a mediastinal window setting and compared with anatomical classifications. The location and branching of every subsegmental artery was recorded. The number of well-visualized sub-subsegmental arteries at a mediastinal window setting was compared with those visualized at a lung window setting. Of 800 subsegmental arteries, 769 (96%) were correctly visualized and 123 accessory subsegmental arteries were identified using the mediastinal window setting. One thousand ninety-two of 2019 sub-subsegmental arteries (54%) identified using the lung window setting were correctly visualized using the mediastinal window setting. Enhanced multi-slice spiral CT with thin collimation can be used to analyze precisely the subsegmental pulmonary arteries and may identify even more distal pulmonary arteries. (orig.)

  16. Conventional multi-slice computed tomography (CT) and cone-beam CT (CBCT) for computer-aided implant placement. Part II: reliability of mucosa-supported stereolithographic guides.

    Science.gov (United States)

    Arisan, Volkan; Karabuda, Zihni Cüneyt; Pişkin, Bülent; Özdemir, Tayfun

    2013-12-01

    Deviations of implants that were placed by conventional computed tomography (CT)- or cone beam CT (CBCT)-derived mucosa-supported stereolithographic (SLA) surgical guides were analyzed in this study. Eleven patients were randomly scanned by a multi-slice CT (CT group) or a CBCT scanner (CBCT group). A total of 108 implants were planned on the software and placed using SLA guides. A new CT or CBCT scan was obtained and merged with the planning data to identify the deviations between the planned and placed implants. Results were analyzed by Mann-Whitney U test and multiple regressions (p < .05). Mean angular and linear deviations in the CT group were 3.30° (SD 0.36), and 0.75 (SD 0.32) and 0.80 mm (SD 0.35) at the implant shoulder and tip, respectively. In the CBCT group, mean angular and linear deviations were 3.47° (SD 0.37), and 0.81 (SD 0.32) and 0.87 mm (SD 0.32) at the implant shoulder and tip, respectively. No statistically significant differences were detected between the CT and CBCT groups (p = .169 and p = .551, p = .113 for angular and linear deviations, respectively). Implant placement via CT- or CBCT-derived mucosa-supported SLA guides yielded similar deviation values. Results should be confirmed on alternative CBCT scanners. © 2012 Wiley Periodicals, Inc.

  17. Computational Fluid Dynamics Model for Solar Thermal Storage Tanks with Helical Jacket Heater and Upper Spiral Coil Heater

    Energy Technology Data Exchange (ETDEWEB)

    Baek, Seung Man [Seoul Nat' l Univ., Seoul (Korea, Republic of); Zhong, Yiming; Nam, Jin Hyun [Daegu Univ., Daegu (Korea, Republic of); Chung, Jae Dong [Sejong Univ., Seoul (Korea, Republic of); Hong, Hiki [Kyung Hee Univ., Seoul (Korea, Republic of)

    2013-04-15

    In a solar domestic hot water (Shadow) system, solar energy is collected using collector panels, transferred to a circulating heat transfer fluid (brine), and eventually stored in a thermal storage tank (Test) as hot water. In this study, a computational fluid dynamics (CAD) model was developed to predict the solar thermal energy storage in a hybrid type Test equipped with a helical jacket heater (mantle heat exchanger) and an immersed spiral coil heater. The helical jacket heater, which is the brine flow path attached to the side wall of a Test, has advantages including simple system design, low brine flow rate, and enhanced thermal stratification. In addition, the spiral coil heater further enhances the thermal performance and thermal stratification of the Test. The developed model was validated by the good agreement between the CAD results and the experimental results performed with the hybrid-type Test in Shadow settings.

  18. Computational Fluid Dynamics Model for Solar Thermal Storage Tanks with Helical Jacket Heater and Upper Spiral Coil Heater

    International Nuclear Information System (INIS)

    Baek, Seung Man; Zhong, Yiming; Nam, Jin Hyun; Chung, Jae Dong; Hong, Hiki

    2013-01-01

    In a solar domestic hot water (Shadow) system, solar energy is collected using collector panels, transferred to a circulating heat transfer fluid (brine), and eventually stored in a thermal storage tank (Test) as hot water. In this study, a computational fluid dynamics (CAD) model was developed to predict the solar thermal energy storage in a hybrid type Test equipped with a helical jacket heater (mantle heat exchanger) and an immersed spiral coil heater. The helical jacket heater, which is the brine flow path attached to the side wall of a Test, has advantages including simple system design, low brine flow rate, and enhanced thermal stratification. In addition, the spiral coil heater further enhances the thermal performance and thermal stratification of the Test. The developed model was validated by the good agreement between the CAD results and the experimental results performed with the hybrid-type Test in Shadow settings

  19. Impact of intravascular enhancement, heart rate, and calcium score on diagnostic accuracy in multislice Computed Tomography coronary angiography

    International Nuclear Information System (INIS)

    Cademartiri, Filippo; Mollet, Nico R.; Kriestin, Gabriel P.; Runza, Giuseppe; Bartolotta, Tommaso Vincenzo; Galia, Massimo; Midiri, Massimo; Belgrano, Manuel; Pozzi Mucelli, Roberto

    2005-01-01

    Purpose. To assess the effect of intravascular enhancement, heart rate, and calcium score on diagnostic accuracy in the detection of significant coronary artery stenosis using 16-row multislice computed tomography (MSCT). Materials and methods. One hundred patients (88 males; 59±11 years) with suspected coronary artery disease who had undergone conventional coronary angiography (CA) and MSCT-CA were retrospectively enrolled for the study. Patients underwent a MSCT-CA, with the following protocol: collimation 16x0.75 mm, gantry rotation time 420 ms, feed/rotation 2.8 mm, kV 120, mAs 400-500. The protocol for contrast material administration was 100 ml of Iodixanol 320 mgI/nl at 4 ml/s and the scan delay was defined with a bolus tracking technique. In all patients vascular enhancement was measured in the aortic root, and the left and the right coronary arteries. The average enhancement was used to divide the population in two groups of 50 patients each, one with lower enhancement (Low), and one with higher enhancement (High). In the two groups diagnostic accuracy (per coronary segment) for the detection of significant stenosis (≥50% lumen reduction) was evaluated in vessels ≥2mm in diameter using quantitative CA as the reference standard. The differences in diagnostic accuracy were compared with a Chi-square test and a p [it

  20. Dynamic helical CT mammography of breast cancer

    International Nuclear Information System (INIS)

    Yamamoto, Akira; Fukushima, Hitoshi; Okamura, Ryuji; Nakamura, Yoshiaki; Morimoto, Taisuke; Urata, Yoji; Mukaihara, Sumio; Hayakawa, Katsumi

    2006-01-01

    The purpose of this study was to determine whether dynamic helical computed tomography (CT)-mammography could assist in selecting the most appropriate surgical method in women with breast cancer. Preoperative contrast-enhanced helical CT scanning of the breast was performed on 133 female patients with suspicion of breast cancer at the same time as clinical, mammographic, and/or ultrasonographic examinations. The patients were scanned in the prone position with a specially designed CT-compatible device. A helical scan was made with rapid intravenous bolus injection (3 ml/s) of 100 ml of iodine contrast material. Three-dimensional maximum intensity projection (MIP) images were reconstructed, and CT findings were correlated with surgical and histopathological findings. Histopathological analysis revealed 84 malignant lesions and seven benign lesions. The sensitivity, specificity, and accuracy levels of the CT scanning were 94.6%, 58.6%, and 78.9%. Helical scanning alone revealed additional contralateral carcinomas in three of four patients and additional ipsilateral carcinomas in three of five patients. However, the technique gave false-positive readings in 24 patients. The preoperative CT-mammogram altered the surgical method in six patients. Dynamic helical CT-mammography in the prone position may be one of the choices of adjunct imaging in patients with suspected breast cancer scheduled for surgery. (author)

  1. A comparative study for image quality and radiation dose of a cone beam computed tomography scanner and a multislice computed tomography scanner for paranasal sinus imaging.

    Science.gov (United States)

    De Cock, Jens; Zanca, Federica; Canning, John; Pauwels, Ruben; Hermans, Robert

    2015-07-01

    To evaluate image quality and radiation dose of a state of the art cone beam computed tomography (CBCT) system and a multislice computed tomography (MSCT) system in patients with sinonasal poliposis. In this retrospective study two radiologists evaluated 57 patients with sinonasal poliposis who underwent a CBCT or MSCT sinus examination, along with a control group of 90 patients with normal radiological findings. Tissue doses were measured using a phantom model with thermoluminescent dosimeters (TLD). Overall image quality in CBCT was scored significantly higher than in MSCT in patients with normal radiologic findings (p-value: 0.00001). In patients with sinonasal poliposis, MSCT scored significantly higher than CBCT (p-value: 0.00001). The average effective dose for MSCT was 42% higher compared to CBCT (108 μSv vs 63 μSv). CBCT and MSCT are both suited for the evaluation of sinonasal poliposis. In patients with sinonasal poliposis, clinically important structures of the paranasal sinuses can be better delineated with MSCT, whereas in patients without sinonasal poliposis, CBCT turns out to define the important structures of the sinonasal region better. However, given the lower radiation dose, CBCT can be considered for the evaluation of the sinonasal structures in patients with sinonasal poliposis. • CBCT and MSCT are both suited for evaluation of sinonasal poliposis. • Effective dose for MSCT was 42% higher compared to CBCT. • In patients with sinonasal poliposis, clinically important anatomical structures are better delineated with MSCT. • In patients with normal radiological findings, clinically important anatomical structures are better delineated with CBCT.

  2. Congenital abnormalities of aortic artery. Assessment in neonates and early childhood with multislice tomography

    International Nuclear Information System (INIS)

    Haberman, D.; Gurfinkel, E.; Beresnak, A.; Martinez, A.; Emsani, R.; Toledo, R.

    2009-01-01

    In the evaluation of aortic artery congenital abnormalities, the echocardiography and the plain X ray are the traditionally used imaging methods. Multislice angiotomography appears as an important method in diagnosis of these different diseases allowing evaluate these entities in a non invasive, fast and accurate form, giving to cardiovascular surgeons very important information to delineate the surgical strategy. In this article, we review the applications of multislice angiotomography in the evaluation of most frequent congenital anomalies of aorta artery, performed in neonates and early childhood. (authors) [es

  3. Assessment of temporal resolution of multi-detector row computed tomography in helical acquisition mode using the impulse method.

    Science.gov (United States)

    Ichikawa, Katsuhiro; Hara, Takanori; Urikura, Atsushi; Takata, Tadanori; Ohashi, Kazuya

    2015-06-01

    The purpose of this study was to propose a method for assessing the temporal resolution (TR) of multi-detector row computed tomography (CT) (MDCT) in the helical acquisition mode using temporal impulse signals generated by a metal ball passing through the acquisition plane. An 11-mm diameter metal ball was shot along the central axis at approximately 5 m/s during a helical acquisition, and the temporal sensitivity profile (TSP) was measured from the streak image intensities in the reconstructed helical CT images. To assess the validity, we compared the measured and theoretical TSPs for the 4-channel modes of two MDCT systems. A 64-channel MDCT system was used to compare TSPs and image quality of a motion phantom for the pitch factors P of 0.6, 0.8, 1.0 and 1.2 with a rotation time R of 0.5 s, and for two R/P combinations of 0.5/1.2 and 0.33/0.8. Moreover, the temporal transfer functions (TFs) were calculated from the obtained TSPs. The measured and theoretical TSPs showed perfect agreement. The TSP narrowed with an increase in the pitch factor. The image sharpness of the 0.33/0.8 combination was inferior to that of the 0.5/1.2 combination, despite their almost identical full width at tenth maximum values. The temporal TFs quantitatively confirmed these differences. The TSP results demonstrated that the TR in the helical acquisition mode significantly depended on the pitch factor as well as the rotation time, and the pitch factor and reconstruction algorithm affected the TSP shape. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  4. Influence of intracoronary attenuation on coronary plaque measurements using multislice computed tomography: observations in an ex vivo model of coronary computed tomography angiography

    International Nuclear Information System (INIS)

    Cademartiri, Filippo; Krestin, Gabriel P.; Mollet, Nico R.; Feyter, Pim J. de; Runza, Giuseppe; Midiri, Massimo; Bruining, Nico; Hamers, Ronald; Somers, Pamela; Knaapen, Michiel; Verheye, Stefan

    2005-01-01

    Assessment of attenuation (measured in Hounsfield units, HU) of human coronary plaques was performed using multislice computed tomography (MSCT) in an ex vivo model. In three ex vivo specimens of left coronary arteries in oil, MSCT was performed after intracoronary injection of four solutions of contrast material (400 mgI/ml iomeprol). The four solutions were diluted as follows: 1/∞, 1/200, 1/80, and 1/20. All scans were performed with the following parameters: slices/collimation 16/0.75 mm, rotation time 375 ms. Each specimen was scored for the presence of atherosclerotic plaques. In each plaque the attenuation was measured in four regions of interest for lumen, plaque (non-calcified thickening of the vessel wall), calcium, and surrounding (oil surrounding the vessel). The results were compared with a one-way analysis of variance test and were correlated with Pearson's test. There were no significant differences in the attenuation of calcium and oil in the four solutions. The mean attenuation in the four solutions for lumen (35±10, 91±7, 246±18, 511±89 HU) and plaque (22±22, 50±26, 107±36, 152±67 HU) was significantly different between each decreasing dilution (p<0.001). The mean attenuation of lumen and plaque of coronary plaques showed high correlation, while the values were significantly different (r=0.73; p<0.001). Intracoronary attenuation modifies significantly the attenuation of plaques assessed with MSCT. (orig.)

  5. Helicity amplitudes and electromagnetic decays of hyperon resonances

    International Nuclear Information System (INIS)

    Cauteren, T. van; Ryckebusch, J.; Metsch, B.; Petry, H.R.

    2005-01-01

    We present results for the helicity amplitudes of the lowest-lying hyperon resonances Y * , computed within the framework of the Bonn Constituent-Quark model, which is based on the Bethe-Salpeter approach. The seven parameters entering the model were fitted to the best-known baryon masses. Accordingly, the results for the helicity amplitudes are genuine predictions. Some hyperon resonances are seen to couple more strongly to a virtual photon with finite Q 2 than to a real photon. Other Y * 's, such as the S 01 (1670) Λ-resonance or the S 11 (1620) Σ-resonance, couple very strongly to real photons. We present a qualitative argument for predicting the behaviour of the helicity asymmetries of baryon resonances at high Q 2 . (orig.)

  6. Congenital intrahepatic arterioportal and portosystemic venous fistulae with jejunal arteriovenous malformation depicted on multislice spiral CT

    International Nuclear Information System (INIS)

    Chae, Eun Jin; Goo, Hyun Woo; Yoon, Chong Hyun; Kim, Seong-Chul

    2004-01-01

    We report a symptomatic infant with very rare congenital arterioportal and portosystemic venous fistulae in the liver. Multislice CT after partial transcatheter embolisation revealed not only the complicated vascular architecture of the lesion, but also an incidental jejunal arteriovenous malformation which explained the patient's melena. The patient underwent ligation of the hepatic artery and resection of the jejunal arteriovenous malformation. Postoperative multislice CT clearly demonstrated the success of the treatment. (orig.)

  7. Multislice theory of fast electron scattering incorporating atomic inner-shell ionization

    International Nuclear Information System (INIS)

    Dwyer, C.

    2005-01-01

    It is demonstrated how atomic inner-shell ionization can be incorporated into a multislice theory of fast electron scattering. The resulting theory therefore accounts for both inelastic scattering due to inner-shell ionization and dynamical elastic scattering. The theory uses a description of the ionization process based on the angular momentum representation for both the initial and final states of the atomic electron. For energy losses near threshold, only a small number of independent states of the ejected atomic electron need to be considered, reducing demands on computing time, and eliminating the need for tabulated inelastic scattering factors. The theory is used to investigate the influence of the collection aperture size on the spatial origin of the silicon K-shell EELS signal generated by a STEM probe. The validity of a so-called local approximation is also considered

  8. A Prospective Evaluation of Helical Tomotherapy

    International Nuclear Information System (INIS)

    Bauman, Glenn; Yartsev, Slav; Rodrigues, George; Lewis, Craig; Venkatesan, Varagur M.; Yu, Edward; Hammond, Alex; Perera, Francisco; Ash, Robert; Dar, A. Rashid; Lock, Michael; Baily, Laura; Coad, Terry C; Trenka, Kris C.; Warr, Barbara; Kron, Tomas; Battista, Jerry; Van Dyk, Jake

    2007-01-01

    Purpose: To report results from two clinical trials evaluating helical tomotherapy (HT). Methods and Materials: Patients were enrolled in one of two prospective trials of HT (one for palliative and one for radical treatment). Both an HT plan and a companion three-dimensional conformal radiotherapy (3D-CRT) plan were generated. Pretreatment megavoltage computed tomography was used for daily image guidance. Results: From September 2004 to January 2006, a total of 61 sites in 60 patients were treated. In all but one case, a clinically acceptable tomotherapy plan for treatment was generated. Helical tomotherapy plans were subjectively equivalent or superior to 3D-CRT in 95% of plans. Helical tomotherapy was deemed equivalent or superior in two thirds of dose-volume point comparisons. In cases of inferiority, differences were either clinically insignificant and/or reflected deliberate tradeoffs to optimize the HT plan. Overall imaging and treatment time (median) was 27 min (range, 16-91 min). According to a patient questionnaire, 78% of patients were satisfied to very satisfied with the treatment process. Conclusions: Helical tomotherapy demonstrated clear advantages over conventional 3D-CRT in this diverse patient group. The prospective trials were helpful in deploying this technology in a busy clinical setting

  9. Evaluation of spinal cord vessels using multi-slice CT angiography

    International Nuclear Information System (INIS)

    Chen Shuang; Zhu Ruijiang; Feng Xiaoyuan

    2006-01-01

    Objective: To evaluate the value of Multi-slice spiral CT angiography for spinal cord vessels. Methods: 11 adult subjects with suspected of myelopathy were performed with Multi-slice spiral CT angiography, An iodine contrast agent was injected at 3.5 ml/s, for total 100 ml. The parameters were axial 16 slice mode, 0.625 mm slice thickness, 0.8 s rotation, delay time depending on smartprep(15-25 s), multi-phase scan. The coronal and sagittal MPR and SSD were generated on a workstation compared with spinal digital subtraction angiography (DSA) to analyze normal or abnormal spinal cord vessels. Results: Normal findings at spinal CTA and digital subtraction angiography in six adult normal subjects and spinal cord vascular malformations (1 intradural extramedullary AVF, 4 dural AVFs) in five cases, Recognizable intradural vessels corresponding to anterior median (midline) veins and/or anterior spinal arteries were show in six adult normal subjects. Abnormal intradural vessels were detected in all five spinal cord vascular malformation with CT angiography, in comparison with digital subtraction angiography these vessels were primarily enlarged veins of the coronal venous plexus on the cord surface, radiculomedullary-dural arteries could not be clearly shown in four dural AVF, only one anterior spinal artery was detected in one patient with intradural medullary AVF, which direct shunt between anterior spinal artery and perimedullary vein with tortuous draining vessel. Conclusion: Multi-slice CT angiography is able to visualize the normal or abnormal spinal cord vessels. It could be used as a noninvasive method to screen the spinal cord vascular disease. (authors)

  10. Can multi-slice or navigator-gated R2* MRI replace single-slice breath-hold acquisition for hepatic iron quantification?

    International Nuclear Information System (INIS)

    Loeffler, Ralf B.; McCarville, M.B.; Song, Ruitian; Hillenbrand, Claudia M.; Wagstaff, Anne W.; Smeltzer, Matthew P.; Krafft, Axel J.; Hankins, Jane S.

    2017-01-01

    Liver R2* values calculated from multi-gradient echo (mGRE) magnetic resonance images (MRI) are strongly correlated with hepatic iron concentration (HIC) as shown in several independently derived biopsy calibration studies. These calibrations were established for axial single-slice breath-hold imaging at the location of the portal vein. Scanning in multi-slice mode makes the exam more efficient, since whole-liver coverage can be achieved with two breath-holds and the optimal slice can be selected afterward. Navigator echoes remove the need for breath-holds and allow use in sedated patients. To evaluate if the existing biopsy calibrations can be applied to multi-slice and navigator-controlled mGRE imaging in children with hepatic iron overload, by testing if there is a bias-free correlation between single-slice R2* and multi-slice or multi-slice navigator controlled R2*. This study included MRI data from 71 patients with transfusional iron overload, who received an MRI exam to estimate HIC using gradient echo sequences. Patient scans contained 2 or 3 of the following imaging methods used for analysis: single-slice images (n = 71), multi-slice images (n = 69) and navigator-controlled images (n = 17). Small and large blood corrected region of interests were selected on axial images of the liver to obtain R2* values for all data sets. Bland-Altman and linear regression analysis were used to compare R2* values from single-slice images to those of multi-slice images and navigator-controlled images. Bland-Altman analysis showed that all imaging method comparisons were strongly associated with each other and had high correlation coefficients (0.98 ≤ r ≤ 1.00) with P-values ≤0.0001. Linear regression yielded slopes that were close to 1. We found that navigator-gated or breath-held multi-slice R2* MRI for HIC determination measures R2* values comparable to the biopsy-validated single-slice, single breath-hold scan. We conclude that these three R2* methods can be

  11. Can multi-slice or navigator-gated R2* MRI replace single-slice breath-hold acquisition for hepatic iron quantification?

    Energy Technology Data Exchange (ETDEWEB)

    Loeffler, Ralf B.; McCarville, M.B.; Song, Ruitian; Hillenbrand, Claudia M. [St. Jude Children' s Research Hospital, Diagnostic Imaging, Memphis, TN (United States); Wagstaff, Anne W. [St. Jude Children' s Research Hospital, Diagnostic Imaging, Memphis, TN (United States); Rhodes College, Memphis, TN (United States); University of Alabama at Birmingham School of Medicine, Birmingham, AL (United States); Smeltzer, Matthew P. [St. Jude Children' s Research Hospital, Department of Biostatistics, Memphis, TN (United States); University of Memphis, Division of Epidemiology, Biostatistics, and Environmental Health, School of Public Health, Memphis, TN (United States); Krafft, Axel J. [St. Jude Children' s Research Hospital, Diagnostic Imaging, Memphis, TN (United States); University Hospital Center Freiburg, Department of Radiology, Freiburg (Germany); Hankins, Jane S. [St. Jude Children' s Research Hospital, Department of Hematology, Memphis, TN (United States)

    2017-01-15

    Liver R2* values calculated from multi-gradient echo (mGRE) magnetic resonance images (MRI) are strongly correlated with hepatic iron concentration (HIC) as shown in several independently derived biopsy calibration studies. These calibrations were established for axial single-slice breath-hold imaging at the location of the portal vein. Scanning in multi-slice mode makes the exam more efficient, since whole-liver coverage can be achieved with two breath-holds and the optimal slice can be selected afterward. Navigator echoes remove the need for breath-holds and allow use in sedated patients. To evaluate if the existing biopsy calibrations can be applied to multi-slice and navigator-controlled mGRE imaging in children with hepatic iron overload, by testing if there is a bias-free correlation between single-slice R2* and multi-slice or multi-slice navigator controlled R2*. This study included MRI data from 71 patients with transfusional iron overload, who received an MRI exam to estimate HIC using gradient echo sequences. Patient scans contained 2 or 3 of the following imaging methods used for analysis: single-slice images (n = 71), multi-slice images (n = 69) and navigator-controlled images (n = 17). Small and large blood corrected region of interests were selected on axial images of the liver to obtain R2* values for all data sets. Bland-Altman and linear regression analysis were used to compare R2* values from single-slice images to those of multi-slice images and navigator-controlled images. Bland-Altman analysis showed that all imaging method comparisons were strongly associated with each other and had high correlation coefficients (0.98 ≤ r ≤ 1.00) with P-values ≤0.0001. Linear regression yielded slopes that were close to 1. We found that navigator-gated or breath-held multi-slice R2* MRI for HIC determination measures R2* values comparable to the biopsy-validated single-slice, single breath-hold scan. We conclude that these three R2* methods can be

  12. Energy and helicity of magnetic torus knots and braids

    Science.gov (United States)

    Oberti, Chiara; Ricca, Renzo L.

    2018-02-01

    By considering steady magnetic fields in the shape of torus knots and unknots in ideal magnetohydrodynamics, we compute some fundamental geometric and physical properties to provide estimates for magnetic energy and helicity. By making use of an appropriate parametrization, we show that knots with dominant toroidal coils that are a good model for solar coronal loops have negligible total torsion contribution to magnetic helicity while writhing number provides a good proxy. Hence, by the algebraic definition of writhe based on crossing numbers, we show that the estimated values of writhe based on image analysis provide reliable information for the exact values of helicity. We also show that magnetic energy is linearly related to helicity, and the effect of the confinement of magnetic field can be expressed in terms of geometric information. These results can find useful application in solar and plasma physics, where braided structures are often present.

  13. Respiratory-Gated Helical Computed Tomography of Lung: Reproducibility of Small Volumes in an Ex Vivo Model

    International Nuclear Information System (INIS)

    Biederer, Juergen; Dinkel, Julien; Bolte, Hendrik; Welzel, Thomas; Hoffmann, Beata M.Sc.; Thierfelder, Carsten; Mende, Ulrich; Debus, Juergen; Heller, Martin; Kauczor, Hans-Ulrich

    2007-01-01

    Purpose: Motion-adapted radiotherapy with gated irradiation or tracking of tumor positions requires dedicated imaging techniques such as four-dimensional (4D) helical computed tomography (CT) for patient selection and treatment planning. The objective was to evaluate the reproducibility of spatial information for small objects on respiratory-gated 4D helical CT using computer-assisted volumetry of lung nodules in a ventilated ex vivo system. Methods and Materials: Five porcine lungs were inflated inside a chest phantom and prepared with 55 artificial nodules (mean diameter, 8.4 mm ± 1.8). The lungs were respirated by a flexible diaphragm and scanned with 40-row detector CT (collimation, 24 x 1.2 mm; pitch, 0.1; rotation time, 1 s; slice thickness, 1.5 mm; increment, 0.8 mm). The 4D-CT scans acquired during respiration (eight per minute) and reconstructed at 0-100% inspiration and equivalent static scans were scored for motion-related artifacts (0 or absent to 3 or relevant). The reproducibility of nodule volumetry (three readers) was assessed using the variation coefficient (VC). Results: The mean volumes from the static and dynamic inspiratory scans were equal (364.9 and 360.8 mm 3 , respectively, p = 0.24). The static and dynamic end-expiratory volumes were slightly greater (371.9 and 369.7 mm 3 , respectively, p = 0.019). The VC for volumetry (static) was 3.1%, with no significant difference between 20 apical and 20 caudal nodules (2.6% and 3.5%, p = 0.25). In dynamic scans, the VC was greater (3.9%, p = 0.004; apical and caudal, 2.6% and 4.9%; p = 0.004), with a significant difference between static and dynamic in the 20 caudal nodules (3.5% and 4.9%, p = 0.015). This was consistent with greater motion-related artifacts and image noise at the diaphragm (p <0.05). The VC for interobserver variability was 0.6%. Conclusion: Residual motion-related artifacts had only minimal influence on volumetry of small solid lesions. This indicates a high reproducibility of

  14. Three-phase CT examination of the pancreatobiliary region using multislice CT with 1-mm collimation

    International Nuclear Information System (INIS)

    Itoh, Shigeki; Ikeda, Mitsuru; Suzuki, Koujiro; Iwano, Shingo; Satake, Hiroko; Ota, Toyohiro; Ishigaki, Takeo

    2005-01-01

    The purpose of this study was to evaluate the degree of contrast enhancement and accuracy of imaging of the circulatory phase in the first-pass, second-pass, and third-pass acquisitions in the pancreato-biliary region with 1-mm collimation obtained by multislice computed tomography (CT). In 53 patients, two sequential acquisitions from the porta hepatis to the pancreas were performed during a single breath-hold, followed by a third-pass acquisition including the liver beginning 15 sec after the second-pass acquisition. Contrast enhancement in each acquisition was measured in the aorta, portal vein and its branches, and pancreas. Four experienced radiologists graded using four-point scoring whether or not each acquisition was appropriate for imaging of the arterial phase, pancreatic phase, and portal venous phase. Aortic enhancement was highest at the beginning of the second-pass acquisition. The portal and splenic veins and pancreas showed maximum enhancement in the second-pass acquisition, while the superior mesenteric vein showed maximum enhancement in the third-pass acquisition. In the visual assessment, significantly higher grades were achieved in the first-pass, second-pass, and third-pass acquisitions with regard to imaging of the arterial phase, pancreatic phase, and portal venous phase, respectively. Multislice CT permits the acquisition of three distinct circulatory phases (arterial, pancreatic, and portal venous phases) in the pancreatobiliary region with 1-mm collimation. (author)

  15. Correlation between a 2D channelized Hotelling observer and human observers in a low-contrast detection task with multislice reading in CT.

    Science.gov (United States)

    Yu, Lifeng; Chen, Baiyu; Kofler, James M; Favazza, Christopher P; Leng, Shuai; Kupinski, Matthew A; McCollough, Cynthia H

    2017-08-01

    Model observers have been successfully developed and used to assess the quality of static 2D CT images. However, radiologists typically read images by paging through multiple 2D slices (i.e., multislice reading). The purpose of this study was to correlate human and model observer performance in a low-contrast detection task performed using both 2D and multislice reading, and to determine if the 2D model observer still correlate well with human observer performance in multislice reading. A phantom containing 18 low-contrast spheres (6 sizes × 3 contrast levels) was scanned on a 192-slice CT scanner at five dose levels (CTDI vol = 27, 13.5, 6.8, 3.4, and 1.7 mGy), each repeated 100 times. Images were reconstructed using both filtered-backprojection (FBP) and an iterative reconstruction (IR) method (ADMIRE, Siemens). A 3D volume of interest (VOI) around each sphere was extracted and placed side-by-side with a signal-absent VOI to create a 2-alternative forced choice (2AFC) trial. Sixteen 2AFC studies were generated, each with 100 trials, to evaluate the impact of radiation dose, lesion size and contrast, and reconstruction methods on object detection. In total, 1600 trials were presented to both model and human observers. Three medical physicists acted as human observers and were allowed to page through the 3D volumes to make a decision for each 2AFC trial. The human observer performance was compared with the performance of a multislice channelized Hotelling observer (CHO_MS), which integrates multislice image data, and with the performance of previously validated CHO, which operates on static 2D images (CHO_2D). For comparison, the same 16 2AFC studies were also performed in a 2D viewing mode by the human observers and compared with the multislice viewing performance and the two CHO models. Human observer performance was well correlated with the CHO_2D performance in the 2D viewing mode [Pearson product-moment correlation coefficient R = 0.972, 95% confidence

  16. Conversion from mutual helicity to self-helicity observed with IRIS

    Science.gov (United States)

    Li, L. P.; Peter, H.; Chen, F.; Zhang, J.

    2014-10-01

    Context. In the upper atmosphere of the Sun observations show convincing evidence for crossing and twisted structures, which are interpreted as mutual helicity and self-helicity. Aims: We use observations with the new Interface Region Imaging Spectrograph (IRIS) to show the conversion of mutual helicity into self-helicity in coronal structures on the Sun. Methods: Using far UV spectra and slit-jaw images from IRIS and coronal images and magnetograms from SDO, we investigated the evolution of two crossing loops in an active region, in particular, the properties of the Si IV line profile in cool loops. Results: In the early stage two cool loops cross each other and accordingly have mutual helicity. The Doppler shifts in the loops indicate that they wind around each other. As a consequence, near the crossing point of the loops (interchange) reconnection sets in, which heats the plasma. This is consistent with the observed increase of the line width and of the appearance of the loops at higher temperatures. After this interaction, the two new loops run in parallel, and in one of them shows a clear spectral tilt of the Si IV line profile. This is indicative of a helical (twisting) motion, which is the same as to say that the loop has self-helicity. Conclusions: The high spatial and spectral resolution of IRIS allowed us to see the conversion of mutual helicity to self-helicity in the (interchange) reconnection of two loops. This is observational evidence for earlier theoretical speculations. Movie associated with Fig. 1 and Appendix A are available in electronic form at http://www.aanda.org

  17. Preliminary feasibility assessment on the investigation of bronchogenic adenocarcinoma angiogenesis with dynamic multi-slice spiral computed tomography

    International Nuclear Information System (INIS)

    Li Shenjiang; Xiao Xiangsheng; Li Huimin; Liu Shiyuan; Li Chengzhou; Zhang Chenshi; Tao Zhiwei

    2003-01-01

    Objective: To evaluate the feasibility on the investigation of bronchogenic adenocarcinoma angiogenesis with dynamic multi-slice spiral computed tomography (MSCT) . Methods: 27 patients with bronchogenic adenocarcinomas (diameter ≤4 cm) underwent multi-location dynamic contrast material-enhanced (90 ml, 4 ml/s) serial CT. These dynamic images were processed with the 'time lapse' software and the 'functional CT' software. Peak heights of bronchogenic adenocarcinoma and the aorta, perfusion and mean transit time (MTT) were measured. Ratio of peak height of the bronchogenic adenocarcinoma to that of the aorta was calculated. Perfusion and mean transit time images were obtained. Results: Peak height of bronchogenic adenocarcinoma was (36.66 ± 13.53) HU. No statistically significant difference in the peak height was found between our results and the results of Ukihide et al (mean peak height 34.1 HU) (t =0.981, P = 0.335). Bronchogenic adenocarcinoma-to-aorta ratio was (15.72±4.66 )%. The difference in bronchogenic adenocarcinoma -to-aorta ratio between our results and the results of Zhang and Kono (mean malignant SPN-to-aorta ratio 14.6%) did not reach statistical significance (t=1.244, P=0.225). The mean perfusion value (3.278 ml·min - · kg -1 ) was in the range of that (1.36-2.98 ml·min -1 ·kg -1 ) measured with a single photon emission CT (SPECT). Mean transit time was (17.60 ± 4.52) s. Conclusion: It is feasible to investigate bronchogenic adenocarcinoma angiogenesis with dynamic MSCT

  18. Unenhanced helical computed tomography in the evaluation of acute flank pain

    International Nuclear Information System (INIS)

    Ahmad, N.A.; Ather, M.H.; Rees, J.

    2003-01-01

    The purpose of this study was to determine the value of unenhanced helical computed tomography (UHCT) in the diagnosis of acute flank pain at our institution. Two hundred and thirty-three consecutive UHCT examinations, performed for suspected renal/ureteral colic between July 2000 and August 2001 were reviewed, along with pertinent medical records. Ureteral calculi were identified in 148 (64%) examinations, evidence of recent passage of calculi was found in 10 (4%) and no calculi were found in 75 (32%). Thirty-two of the conservatively managed patients were excluded for inadequate follow-up. In the remaining 201 patients, sensitivity of UHCT in diagnosing calculi was 99% and specificity was 98%, while the positive predictive value was 99% and negative positive predictive value was 98%. Overall, an alternative or additional diagnosis was established in 28 (12%) patients. Upon diagnosis of ureterolithiasis on UHCT, none of the patients required additional imaging studies for confirmation. UHCT is a highly sensitive imaging modality for the detection of urinary tract calculi and obstruction. (author)

  19. Investigation of relation between visceral and subcutaneous abdominal fat volumes and calcified aortic plaques via multislice computed tomography.

    Science.gov (United States)

    Efe, Duran; Aygün, Fatih; Acar, Türker; Yildiz, Melda; Gemici, Kazım

    2015-08-01

    The present study investigated effect of subcutaneous fat volume and abdominal visceral fat volume on aortic atherosclerosis via multislice computed tomography. The present study comprised 424 subjects who underwent non-contrast-enhanced abdominal CT in our clinic between June 2012 and June 2013. Using dedicated software visceral fat volume was calculated for each individual and then subcutaneous fat volume was calculated by subtracting visceral fat volume from total fat volume. By dividing visceral fat volume/subcutaneous fat volume participants were assigned to three groups according to their mean visceral fat volume/subcutaneous fat volume: Group 1 consisted of subjects with visceral fat volume/subcutaneous fat volume lower than 0.48 (Group 1 fat volume/subcutaneous fat volume equal to or higher than 0.48 and lower than 0.69 (0.48 ≤ Group 2 fat volume/subcutaneous fat volume equal to or higher than 0.69 (Group 3 ≥ 0.69). The mean abdominal aortic calcium scores according to Agatston scoring (au) were 136.8 ± 418.7 au in Group 1, 179.9 ± 463 au in Group 2 and 212.2 ± 486.9 in Group 3, respectively. We have demonstrated a significant correlation between visceral fat volume and abdominal aorta atherosclerosis, while there was absence of significant correlation between subcutaneous fat volume and abdominal atherosclerosis. © The Author(s) 2014.

  20. Helicity, Reconnection, and Dynamo Effects

    International Nuclear Information System (INIS)

    Ji, Hantao

    1998-01-01

    The inter-relationships between magnetic helicity, magnetic reconnection, and dynamo effects are discussed. In laboratory experiments, where two plasmas are driven to merge, the helicity content of each plasma strongly affects the reconnection rate, as well as the shape of the diffusion region. Conversely, magnetic reconnection events also strongly affect the global helicity, resulting in efficient helicity cancellation (but not dissipation) during counter-helicity reconnection and a finite helicity increase or decrease (but less efficiently than dissipation of magnetic energy) during co-helicity reconnection. Close relationships also exist between magnetic helicity and dynamo effects. The turbulent electromotive force along the mean magnetic field (alpha-effect), due to either electrostatic turbulence or the electron diamagnetic effect, transports mean-field helicity across space without dissipation. This has been supported by direct measurements of helicity flux in a laboratory plasma. When the dynamo effect is driven by electromagnetic turbulence, helicity in the turbulent field is converted to mean-field helicity. In all cases, however, dynamo processes conserve total helicity except for a small battery effect, consistent with the observation that the helicity is approximately conserved during magnetic relaxation

  1. Imaging of coronary artery stents using multislice computed tomography: in vitro evaluation

    International Nuclear Information System (INIS)

    Maintz, David; Juergens, Kai-Uwe; Heindel, Walter; Fischbach, Roman; Wichter, Thomas; Grude, Matthias

    2003-01-01

    The aim of this study was to evaluate imaging features of different coronary artery stents during multislice CT Angiography (MSCTA). Nineteen stents made of varying material (steel, nitinol, tantalum) and of varying stent design were implanted in plastic tubes with an inner diameter of 3 mm to simulate a coronary artery. The tubes were filled with iodinated contrast material diluted to 200 Hounsfield units (HU), closed at both ends and positioned in a plastic container filled with oil (-70 HU). The MSCT scans were obtained perpendicular to the stent axes (detector collimation 4 x 1 mm, table feed 2 mm/rotation, 300 mAs, 120 kV). Axial images and multiplanar reformations were evaluated regarding artifact size, lumen visibility, and intraluminal attenuation values. Artifacts characterized by artifactual thickening of the stent struts leading to apparent reduction in the lumen diameter and increased intraluminal attenuation values were observed in all cases. The stent lumen was totally obscured in the Wiktor stent, the Wallgraft stent, and the Nir Royal stent. Partial residual of the stent lumen could be visualized in all other utilized stent products (artificial lumen reductions ranged from 62% in the V-Flex stent to 94% in the Bx Velocity stent). Parts of the stent lumen can be visualized in most coronary artery stents; however, detectability of in-stent stenoses remains to be evaluated for each stent type. (orig.)

  2. Multislice CT imaging of anomalous coronary arteries

    International Nuclear Information System (INIS)

    Shi Heshui; Aschoff, Andrik J.; Brambs, Hans-Juergen; Hoffmann, Martin H.K.

    2004-01-01

    The purpose of the present study was to evaluate the role of 16 multislice computed tomography (MSCT) to identify the origin of anomalous coronary arteries and to confirm their anatomic course in relation to the great vessels. Accuracy of coronary artery disease (CAD) detection was a secondary aim and was tested with conventional angiograms (CA) serving as standard of reference. Two hundred and forty-two consecutive patients referred for noninvasive coronary CT imaging were reviewed for the study. Sixteen patients (6.6%) with anomalous coronary arteries were detected and included as the study group. MSCT and CA images were analyzed in a blinded fashion for accuracy of anomalous artery origin and path detection. Results were compared in a secondary consensus evaluation. Accuracy ratios to detect CAD with MSCT in all vessels were calculated. Coronary anomalies for all 16 patients were correctly displayed on MSCT. CA alone achieved correct identification of the abnormality in only 53% (P=0.016). Sensitivity and specificity of MSCT to detect significantly stenosed vessels was 90 and 92%. 16-MSCT is accurate to delineate abnormally branching coronary arteries and allows sufficiently accurate detection of obstructive coronary artery disease in distal branches. It should therefore be considered as a prime non-invasive imaging tool for suspected coronary anomalies. (orig.)

  3. Optimization of a stellarator design including modulation of the helical winding geometry

    International Nuclear Information System (INIS)

    Sharp, L.E.; Petersen, L.F.; Blamey, J.W.

    1979-06-01

    The optimization of the helical winding geometry of the next generation of high performance stellarators is of critical importance as the current in the helical conductors must be kept to a minimum to reduce the very large electromechanical forces on the conductors. Using a modified version of the Culham computer code MAGBAT, steps towards optimization are described

  4. A rigid motion correction method for helical computed tomography (CT)

    International Nuclear Information System (INIS)

    Kim, J-H; Kyme, A; Fulton, R; Nuyts, J; Kuncic, Z

    2015-01-01

    We propose a method to compensate for six degree-of-freedom rigid motion in helical CT of the head. The method is demonstrated in simulations and in helical scans performed on a 16-slice CT scanner. Scans of a Hoffman brain phantom were acquired while an optical motion tracking system recorded the motion of the bed and the phantom. Motion correction was performed by restoring projection consistency using data from the motion tracking system, and reconstructing with an iterative fully 3D algorithm. Motion correction accuracy was evaluated by comparing reconstructed images with a stationary reference scan. We also investigated the effects on accuracy of tracker sampling rate, measurement jitter, interpolation of tracker measurements, and the synchronization of motion data and CT projections. After optimization of these aspects, motion corrected images corresponded remarkably closely to images of the stationary phantom with correlation and similarity coefficients both above 0.9. We performed a simulation study using volunteer head motion and found similarly that our method is capable of compensating effectively for realistic human head movements. To the best of our knowledge, this is the first practical demonstration of generalized rigid motion correction in helical CT. Its clinical value, which we have yet to explore, may be significant. For example it could reduce the necessity for repeat scans and resource-intensive anesthetic and sedation procedures in patient groups prone to motion, such as young children. It is not only applicable to dedicated CT imaging, but also to hybrid PET/CT and SPECT/CT, where it could also ensure an accurate CT image for lesion localization and attenuation correction of the functional image data. (paper)

  5. Comparison of excretory phase, helical computed tomography with intravenous urography in patients with painless haematuria

    International Nuclear Information System (INIS)

    O'Malley, M.E.; Hahn, P.F.; Yoder, I.C.; Gazelle, G.S.; McGovern, F.J.; Mueller, P.R.

    2003-01-01

    AIM: To compare excretory phase, helical computed tomography (CT) with intravenous (IV) urography for evaluation of the urinary tract in patients with painless haematuria. MATERIALS AND METHODS: Ninety-one out-patients had IV urography followed by helical CT limited to the urinary tract. Both IV urograms and CT images were evaluated for abnormalities of the urinary tract in a blinded, prospective manner. The clinical significance of abnormalities was scored subjectively and receiver operator characteristic curve analysis was performed. RESULTS: In 69 of 91 patients (76%), no cause of haematuria was identified. In 22 of 91 patients (24%), the cause of haematuria was identified as follows: transitional cell cancer of the bladder (n=15), urinary tract stones (n=3), cystitis (n=2), haemorrhagic pyelitis (n=1) and benign ureteral stricture (n=1). With IV urography, there were 15 true-positive, seven false-negative and three false-positive interpretations. With CT, there were 18 true-positive, four false-negative and two false-positive interpretations. There was no significant difference between IV and CT urography for the significance of the positive interpretations (n=0.47). CONCLUSION: Excretory phase CT urography was comparable with IV urography for evaluation of the urinary tract in patients with painless haematuria. However, the study population did not include any upper tract cancers. O'Malley M. E. et al. (2003). Clinical Radiology 58, 294-300

  6. Imaging of peripheral arteries by 16-slice computed tomography angiography: a valuable tool

    International Nuclear Information System (INIS)

    Mishra, A.; Ehtuish, Ehtuish F.

    2007-01-01

    To evaluate the efficacy of multidetector (16-row) computed tomography (MDCT) in imaging the upper and lower limb arterial tree in trauma and peripheral vascular disease. Thirty three patients underwent multislice computed tomography angiography (MSCTA) of the upper or the lower limb on multislice (16-slice) CT scanner between November 2004 and July 2005 in the Department of Radiology, National Organ Transplant Center, Tripoli, Libya. The findings were retrospectively compared with the surgical outcome in cases of trauma with suspected arterial injuries; or color Doppler correlation was obtained, for patients of peripheral vascular disease. Multislice computed tomography angiography allows a comprehensive diagnostic work-up in all trauma cases with suspected arterial injuries. In 23 cases of peripheral vascular diseases, MSCTA adequately demonstrated the presence of any stenosis or occlusion, its degree and extent, the presence of collaterals and distal reformation if any; the presence of plaques. Our experience of computed tomography angiography with 16-row MDCT scanner has clearly demonstrated its efficacy as a promising, new, fast, accurate, safe and non-invasive imaging modality of choice in cases of trauma with suspected arterial injuries; and as a useful screening modality in cases of peripheral vascular disease for diagnosis and for grading. (author)

  7. Helical type vacuum container

    International Nuclear Information System (INIS)

    Owada, Kimio.

    1989-01-01

    Helical type vacuum containers in the prior art lack in considerations for thermal expansion stresses to helical coils, and there is a possibility of coil ruptures. The object of the present invention is to avoid the rupture of helical coils wound around the outer surface of a vacuum container against heat expansion if any. That is, bellows or heat expansion absorbing means are disposed to a cross section of a helical type vacuum container. With such a constitution, thermal expansion of helical coils per se due to temperature elevation of the coils during electric supply can be absorbed by expansion of the bellows or absorption of the heat expansion absorbing means. Further, this can be attained by arranging shear pins in the direction perpendicular to the bellows axis so that the bellows are not distorted when the helical coils are wound around the helical type vacuum container. (I.S.)

  8. Correlation between a 2D Channelized Hotelling Observer and Human Observers in a Low-contrast Detection Task with Multi-slice Reading in CT

    Science.gov (United States)

    Yu, Lifeng; Chen, Baiyu; Kofler, James M.; Favazza, Christopher P.; Leng, Shuai; Kupinski, Matthew A.; McCollough, Cynthia H.

    2017-01-01

    Purpose Model observers have been successfully developed and used to assess the quality of static 2D CT images. However, radiologists typically read images by paging through multiple 2D slices (i.e. multi-slice reading). The purpose of this study was to correlate human and model observer performance in a low-contrast detection task performed using both 2D and multi-slice reading, and to determine if the 2D model observer still correlate well with human observer performance in multi-slice reading. Methods A phantom containing 18 low-contrast spheres (6 sizes × 3 contrast levels) was scanned on a 192-slice CT scanner at 5 dose levels (CTDIvol = 27, 13.5, 6.8, 3.4, and 1.7 mGy), each repeated 100 times. Images were reconstructed using both filtered-backprojection (FBP) and an iterative reconstruction (IR) method (ADMIRE, Siemens). A 3D volume of interest (VOI) around each sphere was extracted and placed side-by-side with a signal-absent VOI to create a 2-alternative forced choice (2AFC) trial. Sixteen 2AFC studies were generated, each with 100 trials, to evaluate the impact of radiation dose, lesion size and contrast, and reconstruction methods on object detection. In total, 1600 trials were presented to both model and human observers. Three medical physicists acted as human observers and were allowed to page through the 3D volumes to make a decision for each 2AFC trial. The human observer performance was compared with the performance of a multi-slice channelized Hotelling observer (CHO_MS), which integrates multi-slice image data, and with the performance of previously validated CHO, which operates on static 2D images (CHO_2D). For comparison, the same 16 2AFC studies were also performed in a 2D viewing mode by the human observers and compared with the multi-slice viewing performance and the two CHO models. Results Human observer performance was well correlated with the CHO_2D performance in the 2D viewing mode (Pearson product-moment correlation coefficient R=0

  9. Computed tomography with multidetectors in the diagnosis of coronary stenosis

    International Nuclear Information System (INIS)

    Lombo, Bernardo; Carvajal, Codos A; Tafur, Monica; Gomez, Rafael

    2007-01-01

    Coronary angiography that uses multislice spiral computed tomography is a noninvasive technique for the detection of coronary stenosis that has had significant improvements in recent years. The introduction of 16 and 64 row scanners, the development of synchronized scanning electrocardiogram and better reconstruction techniques permit higher spatial and temporal resolution that allows better identification of coronary plaques and significant obstructive coronary lesions. In the next years Multislice spiral computed tomography will continue maturing and it will become a useful non invasive diagnostic imaging tool for the diagnosis of coronary disease and will be integrated to the cardiologic management protocols. Our next review will be focused on the basic and technical aspects of the scanner, diagnostic performance and clinical applications of this new technology

  10. Impact of sirolimus-eluting stent fractures without early cardiac events on long-term clinical outcomes: A multislice computed tomography study

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Tsuyoshi [Toyohashi Heart Center, Oyama-cho, Toyohashi (Japan); Nagoya City University Graduate School of Medical Sciences, Department of Cardio-Renal Medicine and Hypertension, Nagoya (Japan); Kimura, Masashi; Ehara, Mariko; Terashima, Mitsuyasu; Nasu, Kenya; Kinoshita, Yoshihisa; Habara, Maoto; Tsuchikane, Etsuo; Suzuki, Takahiko [Toyohashi Heart Center, Oyama-cho, Toyohashi (Japan)

    2014-05-15

    This study sought to evaluate the impact of sirolimus-eluting stent (SES) fractures on long-term clinical outcomes using multislice computed tomography (MSCT). In this study, 528 patients undergoing 6- to 18-month follow-up 64-slice MSCT after SES implantation without early clinical events were followed clinically (the median follow-up interval was 4.6 years). A CT-detected stent fracture was defined as a complete gap with Hounsfield units (HU) <300 at the site of separation. The major adverse cardiac events (MACEs), including cardiac death, stent thrombosis, and target lesion revascularisation, were compared according to the presence of stent fracture. Stent fractures were observed in 39 patients (7.4 %). MACEs were more common in patients with CT-detected stent fractures than in those without (46 % vs. 7 %, p < 0.01). Univariate Cox regression analysis indicated a significant relationship between MACE and stent fracture [hazard ratio (HR) 7.65; p < 0.01], age (HR 1.03; p = 0.04), stent length (HR 1.03; p < 0.01), diabetes mellitus (HR 1.77; p = 0.04), and chronic total occlusion (HR 2.54; p = 0.01). In the multivariate model, stent fracture (HR 5.36; p < 0.01) and age (HR 1.03; p = 0.04) remained significant predictors of MACE. An SES fracture detected by MSCT without early clinical events was associated with long-term clinical adverse events. (orig.)

  11. Topology of modified helical gears and Tooth Contact Analysis (TCA) program

    Science.gov (United States)

    Litvin, Faydor L.; Zhang, Jiao

    1989-01-01

    The contents of this report covers: (1) development of optimal geometries for crowned helical gears; (2) a method for their generation; (3) tooth contact analysis (TCA) computer programs for the analysis of meshing and bearing contact of the crowned helical gears; and (4) modelling and simulation of gear shaft deflection. The developed method for synthesis was used to determine the optimal geometry for a crowned helical pinion surface and was directed to localize the bearing contact and guarantee favorable shape and a low level of transmission errors. Two new methods for generation of the crowned helical pinion surface are proposed. One is based on the application of a tool with a surface of revolution that slightly deviates from a regular cone surface. The tool can be used as a grinding wheel or as a shaver. The other is based on a crowning pinion tooth surface with predesigned transmission errors. The pinion tooth surface can be generated by a computer-controlled automatic grinding machine. The TCA program simulates the meshing and bearing contact of the misaligned gears. The transmission errors are also determined. The gear shaft deformation was modelled and investigated. It was found that the deflection of gear shafts has the same effect as gear misalignment.

  12. Four-Dimensional Measurement of the Displacement of Internal Fiducial Markers During 320-Multislice Computed Tomography Scanning of Thoracic Esophageal Cancer

    International Nuclear Information System (INIS)

    Yamashita, Hideomi; Kida, Satoshi; Sakumi, Akira; Haga, Akihiro; Ito, Saori; Onoe, Tsuyoshi; Okuma, Kae; Ino, Kenji; Akahane, Masaaki; Ohtomo, Kuni; Nakagawa, Keiichi

    2011-01-01

    Purpose: To investigate the three-dimensional movement of internal fiducial markers placed near esophageal cancers using 320-multislice CT. Methods and Materials: This study examined 22 metal markers in the esophageal wall near the primary tumors of 12 patients treated with external-beam photon radiotherapy. Motion assessment was analyzed in 41 respiratory phases during 20 s of cine CT in the radiotherapy position. Results: Motion in the cranial-caudal (CC) direction showed a strong correlation (R 2 > 0.4) with the respiratory curve in most markers (73%). The average absolute amplitude of the marker movement was 1.5 ± 1.6 mm, 1.6 ± 1.7 mm, and 3.3 ± 3.3 mm in the left-right (LR), anterior-posterior (AP), and CC directions, respectively. The average marker displacements in the CC direction between peak exhalation and inhalation for the 22 clips were 1.1 mm (maximum, 5.5 mm), 3.0 mm (14.5 mm), and 5.1 mm (16.3 mm) for the upper, middle, and lower thoracic esophagus, respectively. Conclusions: Motion in primary esophagus tumor was evaluated with 320-multislice CT. According to this study, 4.3 mm CC, 1.5 mm AP, and 2.0 mm LR in the upper, 7.4 mm CC, 3.0 mm AP, and 2.4 mm LR in the middle, and 13.8 mm CC, 6.6 mm AP, and 6.8 mm LR in the lower thoracic esophagus provided coverage of tumor motion in 95% of the cases in our study population.

  13. Visualization of brain surface structures by weighted summation technique using multislice MR images

    International Nuclear Information System (INIS)

    Machida, Yoshio; Hatanaka, Masahiko; Hagiwara, Masayuki; Sugimoto, Hiroshi; Yoshida, Tadatoki; Katada, Kazuhiro.

    1991-01-01

    Surface anatomy scanning (SAS) technique which visualizes brain surface structures has been developed since 1987. In this paper, we propose a modified method called 'multislice SAS', which also generates such surface structure images, and has several advantages compared with conventional SAS technique. The conventional SAS technique uses a very long echo time sequence (e.g. SE(3000, 250)) with a thick slice and a surface coil to enhance CSF on the brain surface. Our modified technique also uses a long echo time sequence. But, added multislice images, each appropriately weighted, are used in stead of a thick slice and a surface coil. Our basic studies have shown that this modified method has the following advantage: Several surface images with slightly different summation directions are obtained, and they are used for stereographic display and cine display. This is very useful for visualizing the spatial relationship of brain surface structures. By choosing appropriate weighting, we can obtain clinically legible surface images. This technique dose not require a surface coil. It means that flexibility of selecting imaging direction is high. We can make a lot of modifications, because the original multislice images of weighted summation are arbitrary. And we also clarify some limitation or disadvantage of this modified method. In conclusion, we think that this technique is one of the practical approaches for surface anatomy imaging. (author)

  14. Distributed Computing on Gadgetron: A new paradigm for MRI reconstruction

    DEFF Research Database (Denmark)

    Xue, Hui; Kelmann, Peter; Inati, Souheil

    cloud computing. With this extension (named GT-Plus), any number of Gadgetron processes can run cooperatively across multiple computers. GT-Plus framework was deployed on Amazon EC2 cloud and NIH’s Biowulf system. We demonstrate that with the GT-Plus cloud, a multi-slice free-breathing myocardial cine...

  15. Helicity formalism and spin effects

    International Nuclear Information System (INIS)

    Anselmino, M.; Caruso, F.; Piovano, U.

    1990-01-01

    The helicity formalism and the technique to compute amplitudes for interaction processes involving leptons, quarks, photons and gluons are reviewed. Explicit calculations and examples of exploitation of symmetry properties are shown. The formalism is then applied to the discussion of several hadronic processes and spin effects: the experimental data, when related to the properties of the elementary constituent interactions, show many not understood features. Also the nucleon spin problem is briefly reviewed. (author)

  16. Temporal resolution measurement of 128-slice dual source and 320-row area detector computed tomography scanners in helical acquisition mode using the impulse method.

    Science.gov (United States)

    Hara, Takanori; Urikura, Atsushi; Ichikawa, Katsuhiro; Hoshino, Takashi; Nishimaru, Eiji; Niwa, Shinji

    2016-04-01

    To analyse the temporal resolution (TR) of modern computed tomography (CT) scanners using the impulse method, and assess the actual maximum TR at respective helical acquisition modes. To assess the actual TR of helical acquisition modes of a 128-slice dual source CT (DSCT) scanner and a 320-row area detector CT (ADCT) scanner, we assessed the TRs of various acquisition combinations of a pitch factor (P) and gantry rotation time (R). The TR of the helical acquisition modes for the 128-slice DSCT scanner continuously improved with a shorter gantry rotation time and greater pitch factor. However, for the 320-row ADCT scanner, the TR with a pitch factor of pitch factor of >1.0, it was approximately one half of the gantry rotation time. The maximum TR values of single- and dual-source helical acquisition modes for the 128-slice DSCT scanner were 0.138 (R/P=0.285/1.5) and 0.074s (R/P=0.285/3.2), and the maximum TR values of the 64×0.5- and 160×0.5-mm detector configurations of the helical acquisition modes for the 320-row ADCT scanner were 0.120 (R/P=0.275/1.375) and 0.195s (R/P=0.3/0.6), respectively. Because the TR of a CT scanner is not accurately depicted in the specifications of the individual scanner, appropriate acquisition conditions should be determined based on the actual TR measurement. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  17. Partial volume and aliasing artefacts in helical cone-beam CT

    International Nuclear Information System (INIS)

    Zou Yu; Sidky, Emil Y; Pan, Xiaochuan

    2004-01-01

    A generalization of the quasi-exact algorithms of Kudo et al (2000 IEEE Trans. Med. Imaging 19 902-21) is developed that allows for data acquisition in a 'practical' frame for clinical diagnostic helical, cone-beam computed tomography (CT). The algorithm is investigated using data that model nonlinear partial volume averaging. This investigation leads to an understanding of aliasing artefacts in helical, cone-beam CT image reconstruction. An ad hoc scheme is proposed to mitigate artefacts due to the nonlinear partial volume and aliasing artefacts

  18. Three-dimensional helical CT for treatment planning of breast cancer

    Energy Technology Data Exchange (ETDEWEB)

    Hiramatsu, Hideko; Enomoto, Kohji; Ikeda, Tadashi [Keio Univ., Tokyo (Japan). School of Medicine] [and others

    1999-01-01

    The role of three-dimensional (3D) helical CT in the treatment planning of breast cancer was evaluated. Of 36 patients examined, 30 had invasive ductal carcinoma, three had invasive lobular carcinoma, one had DCIS, one had DCIS with minimal invasion, and 1 had Paget`s disease. Patients were examined in the supine position. The whole breast was scanned under about 25 seconds of breath-holding using helical CT (Proceed, Yokogawa Medical Systems, or High-speed Advantage, GE Medical Systems). 3D imaging was obtained with computer assistance (Advantage Windows, GE Medical Systems). Linear and/or spotty enhancement on helical CT was considered to suggest DCIS or intraductal spread in the area surrounding the invasive cancer. Of 36 patients, 24 showed linear and/or spotty enhancement on helical CT, and 22 of those 24 patients had DCIS or intraductal spread. In contrast, 12 of 36 patients were considered to have little or no intraductal spread on helical CT, and eight of the 12 patients had little or no intraductal spread on pathological examination. The sensitivity, specificity, and accuracy rates for detecting intraductal spread on MRI were 85%, 80%, and 83%, respectively. 3D helical CT was considered useful in detecting intraductal spread and planning surgery, however, a larger study using a precise correlation with pathology is necessary. (author)

  19. Magnetic Helicity Estimations in Models and Observations of the Solar Magnetic Field. III. Twist Number Method

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Y. [School of Astronomy and Space Science and Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, Nanjing University, Nanjing 210023 (China); Pariat, E.; Moraitis, K. [LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, F-92190 Meudon (France); Valori, G. [University College London, Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey, RH5 6NT (United Kingdom); Anfinogentov, S. [Institute of Solar-Terrestrial Physics SB RAS 664033, Irkutsk, P.O. box 291, Lermontov Street, 126a (Russian Federation); Chen, F. [Max-Plank-Institut für Sonnensystemforschung, D-37077 Göttingen (Germany); Georgoulis, M. K. [Research Center for Astronomy and Applied Mathematics of the Academy of Athens, 4 Soranou Efesiou Street, 11527 Athens (Greece); Liu, Y. [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States); Thalmann, J. K. [Institute of Physics, Univeristy of Graz, Universitätsplatz 5/II, A-8010 Graz (Austria); Yang, S., E-mail: guoyang@nju.edu.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2017-05-01

    We study the writhe, twist, and magnetic helicity of different magnetic flux ropes, based on models of the solar coronal magnetic field structure. These include an analytical force-free Titov–Démoulin equilibrium solution, non-force-free magnetohydrodynamic simulations, and nonlinear force-free magnetic field models. The geometrical boundary of the magnetic flux rope is determined by the quasi-separatrix layer and the bottom surface, and the axis curve of the flux rope is determined by its overall orientation. The twist is computed by the Berger–Prior formula, which is suitable for arbitrary geometry and both force-free and non-force-free models. The magnetic helicity is estimated by the twist multiplied by the square of the axial magnetic flux. We compare the obtained values with those derived by a finite volume helicity estimation method. We find that the magnetic helicity obtained with the twist method agrees with the helicity carried by the purely current-carrying part of the field within uncertainties for most test cases. It is also found that the current-carrying part of the model field is relatively significant at the very location of the magnetic flux rope. This qualitatively explains the agreement between the magnetic helicity computed by the twist method and the helicity contributed purely by the current-carrying magnetic field.

  20. Biot-Savart helicity versus physical helicity: A topological description of ideal flows

    Science.gov (United States)

    Sahihi, Taliya; Eshraghi, Homayoon

    2014-08-01

    For an isentropic (thus compressible) flow, fluid trajectories are considered as orbits of a family of one parameter, smooth, orientation-preserving, and nonsingular diffeomorphisms on a compact and smooth-boundary domain in the Euclidian 3-space which necessarily preserve a finite measure, later interpreted as the fluid mass. Under such diffeomorphisms the Biot-Savart helicity of the pushforward of a divergence-free and tangent to the boundary vector field is proved to be conserved and since these circumstances present an isentropic flow, the conservation of the "Biot-Savart helicity" is established for such flows. On the other hand, the well known helicity conservation in ideal flows which here we call it "physical helicity" is found to be an independent constant with respect to the Biot-Savart helicity. The difference between these two helicities reflects some topological features of the domain as well as the velocity and vorticity fields which is discussed and is shown for simply connected domains the two helicities coincide. The energy variation of the vorticity field is shown to be formally the same as for the incompressible flow obtained before. For fluid domains consisting of several disjoint solid tori, at each time, the harmonic knot subspace of smooth vector fields on the fluid domain is found to have two independent base sets with a special type of orthogonality between these two bases by which a topological description of the vortex and velocity fields depending on the helicity difference is achieved since this difference is shown to depend only on the harmonic knot parts of velocity, vorticity, and its Biot-Savart vector field. For an ideal magnetohydrodynamics (MHD) flow three independent constant helicities are reviewed while the helicity of magnetic potential is generalized for non-simply connected domains by inserting a special harmonic knot field in the dynamics of the magnetic potential. It is proved that the harmonic knot part of the vorticity

  1. Performance characterization of megavoltage computed tomography imaging on a helical tomotherapy unit

    International Nuclear Information System (INIS)

    Meeks, Sanford L.; Harmon, Joseph F. Jr.; Langen, Katja M.; Willoughby, Twyla R.; Wagner, Thomas H.; Kupelian, Patrick A.

    2005-01-01

    Helical tomotherapy is an innovative means of delivering IGRT and IMRT using a device that combines features of a linear accelerator and a helical computed tomography (CT) scanner. The HI-ART II can generate CT images from the same megavoltage x-ray beam it uses for treatment. These megavoltage CT (MVCT) images offer verification of the patient position prior to and potentially during radiation therapy. Since the unit uses the actual treatment beam as the x-ray source for image acquisition, no surrogate telemetry systems are required to register image space to treatment space. The disadvantage to using the treatment beam for imaging, however, is that the physics of radiation interactions in the megavoltage energy range may force compromises between the dose delivered and the image quality in comparison to diagnostic CT scanners. The performance of the system is therefore characterized in terms of objective measures of noise, uniformity, contrast, and spatial resolution as a function of the dose delivered by the MVCT beam. The uniformity and spatial resolutions of MVCT images generated by the HI-ART II are comparable to that of diagnostic CT images. Furthermore, the MVCT scan contrast is linear with respect to the electron density of material imaged. MVCT images do not have the same performance characteristics as state-of-the art diagnostic CT scanners when one objectively examines noise and low-contrast resolution. These inferior results may be explained, at least partially, by the low doses delivered by our unit; the dose is 1.1 cGy in a 20 cm diameter cylindrical phantom. In spite of the poorer low-contrast resolution, these relatively low-dose MVCT scans provide sufficient contrast to delineate many soft-tissue structures. Hence, these images are useful not only for verifying the patient's position at the time of therapy, but they are also sufficient for delineating many anatomic structures. In conjunction with the ability to recalculate radiotherapy doses on

  2. Can 16-detector multislice CT exclude skeletal lesions during tumour staging? Implications for the cancer patient

    International Nuclear Information System (INIS)

    Groves, Ashley M.; Beadsmoore, Clare J.; Courtney, Helen M.; Harish, Srinivasan; Bearcroft, Philip W.P.; Dixon, Adrian K.; Cheow, Heok K.; Balan, Kottekkattu K.; Kaptoge, Stephen; Win, Thida

    2006-01-01

    Current imaging guidelines recommend that many cancer patients undergo soft-tissue staging by computed tomography (CT) whilst the bones are imaged by skeletal scintigraphy (bone scan). New CT technology has now made it feasible, for the first time, to perform a detailed whole-body skeletal CT. This advancement could save patients from having to undergo duplicate investigations. Forty-three patients with known malignancy were investigated for bone metastasis using skeletal scintigraphy and 16-detector multislice CT. Both studies were performed within six weeks of each other. Whole-body images were taken 4 h after injection of 500 Mbq 99m Tc-MDP using a gamma camera. CT was performed on a 16-detector multislice CT machine from the vertex to the knee. The examinations were reported independently and discordant results were compared at follow-up. Statistical equivalence between the two techniques was tested using the Newcombe-Wilson method within the pre-specified equivalence limits of ±20%. Scintigraphy detected bone metastases in 14/43 and CT in 13/43 patients. There were seven discordances; four cases were positive on scintigraphy, but negative on CT; three cases were positive on CT and negative on scintigraphy. There was equivalence between scintigraphy and CT in detecting bone metastases within ±19% equivalence limits. Patients who have undergone full whole-body staging on 16-detector CT may not need additional skeletal scintigraphy. This should shorten the cancer patient's diagnostic pathway. (orig.)

  3. STEMsalabim: A high-performance computing cluster friendly code for scanning transmission electron microscopy image simulations of thin specimens

    International Nuclear Information System (INIS)

    Oelerich, Jan Oliver; Duschek, Lennart; Belz, Jürgen; Beyer, Andreas; Baranovskii, Sergei D.; Volz, Kerstin

    2017-01-01

    Highlights: • We present STEMsalabim, a modern implementation of the multislice algorithm for simulation of STEM images. • Our package is highly parallelizable on high-performance computing clusters, combining shared and distributed memory architectures. • With STEMsalabim, computationally and memory expensive STEM image simulations can be carried out within reasonable time. - Abstract: We present a new multislice code for the computer simulation of scanning transmission electron microscope (STEM) images based on the frozen lattice approximation. Unlike existing software packages, the code is optimized to perform well on highly parallelized computing clusters, combining distributed and shared memory architectures. This enables efficient calculation of large lateral scanning areas of the specimen within the frozen lattice approximation and fine-grained sweeps of parameter space.

  4. STEMsalabim: A high-performance computing cluster friendly code for scanning transmission electron microscopy image simulations of thin specimens

    Energy Technology Data Exchange (ETDEWEB)

    Oelerich, Jan Oliver, E-mail: jan.oliver.oelerich@physik.uni-marburg.de; Duschek, Lennart; Belz, Jürgen; Beyer, Andreas; Baranovskii, Sergei D.; Volz, Kerstin

    2017-06-15

    Highlights: • We present STEMsalabim, a modern implementation of the multislice algorithm for simulation of STEM images. • Our package is highly parallelizable on high-performance computing clusters, combining shared and distributed memory architectures. • With STEMsalabim, computationally and memory expensive STEM image simulations can be carried out within reasonable time. - Abstract: We present a new multislice code for the computer simulation of scanning transmission electron microscope (STEM) images based on the frozen lattice approximation. Unlike existing software packages, the code is optimized to perform well on highly parallelized computing clusters, combining distributed and shared memory architectures. This enables efficient calculation of large lateral scanning areas of the specimen within the frozen lattice approximation and fine-grained sweeps of parameter space.

  5. Multislice helical CT (MSCT) for mid-facial trauma: optimization of parameters for scanning and reconstruction; Mehrschicht-Spiral-CT (MSCT) beim Mittelgesichtstrauma: Optimierung der Aufnahme- und Rekonstruktionsparameter

    Energy Technology Data Exchange (ETDEWEB)

    Dammert, S.; Funke, M.; Obernauer, S.; Grabbe, E. [Abt. Roentgendiagnostik I, Georg-August-Univ. Goettingen (Germany); Merten, H.A. [Abt. fuer Mund-, Kiefer- und Gesichtschirurgie, Georg-August-Univ. Goettingen (Germany)

    2002-07-01

    Purpose: To determine the optimal scan parameters in multislice helical CT (MSCT) of the facial bone complex for both axial scanning and multiplanar reconstructions. Material and Methods: An anthropomorphic skull phantom was examined with a MSCT. Axial scans were performed with continuously increasing collimations (4 x 1.25 - 4 x 2.5 mm), tube current (20 - 200 mA) and table speeds (3.75 mm/rot. and 7.5 mm/rot.). Multiplanar reconstructions in coronal and parasagittal planes with different reconstruction increment and slice thickness were evaluated in terms of image noise, contour artifacts and visualisation of anatomical structures. Results: The best image quality was obtained with a collimation of 4 x 1.25 mm and a - table speed of 3.75 mm/rot. A reconstruction increment of 0.6 mm achieved the best time to image quality relation. With these parameters the bone structures were depicted in an optimal way without artifacts. The tube current could be reduced to 50 mA without significant loss of image quality. The optimized protocol was used for regular routine examinations in patients with facial trauma (n = 66). Conclusions: Low-dose MSCT using thin collimation, low table speed and small reconstruction increments provides excellent data for both axial images and multiplanar reconstructions in patients with facial trauma. An additional examination in coronal orientation is therefore no longer necessary. (orig.) [German] Zielsetzung: Verbesserung der Aufnahme- und Rekonstruktionsparameter in der Mehrschicht Spiral-CT (MSCT) zur Untersuchung des knoechernen Mittelgesichtes in verschiedenen Ebenen. Material und Methode: Ein anthropomorphes Schaedel-Phantom wurde in axialer Schichtfuehrung mit einem MSCT untersucht, wobei die Kollimation (1,25 - 2,5 mm), der Tischvorschubfaktor (Pitch 3 - 6) und der Roehrenstrom (20 - 200 mA) systematisch variiert wurden. Aus den Volumendatensaetzen wurden jeweils koronare und parasagittale Sekundaerreformationen mit unterschiedlichen

  6. The impact of different cone beam computed tomography and multi-slice computed tomography scan parameters on virtual three-dimensional model accuracy using a highly precise ex vivo evaluation method.

    Science.gov (United States)

    Matta, Ragai-Edward; von Wilmowsky, Cornelius; Neuhuber, Winfried; Lell, Michael; Neukam, Friedrich W; Adler, Werner; Wichmann, Manfred; Bergauer, Bastian

    2016-05-01

    Multi-slice computed tomography (MSCT) and cone beam computed tomography (CBCT) are indispensable imaging techniques in advanced medicine. The possibility of creating virtual and corporal three-dimensional (3D) models enables detailed planning in craniofacial and oral surgery. The objective of this study was to evaluate the impact of different scan protocols for CBCT and MSCT on virtual 3D model accuracy using a software-based evaluation method that excludes human measurement errors. MSCT and CBCT scans with different manufacturers' predefined scan protocols were obtained from a human lower jaw and were superimposed with a master model generated by an optical scan of an industrial noncontact scanner. To determine the accuracy, the mean and standard deviations were calculated, and t-tests were used for comparisons between the different settings. Averaged over 10 repeated X-ray scans per method and 19 measurement points per scan (n = 190), it was found that the MSCT scan protocol 140 kV delivered the most accurate virtual 3D model, with a mean deviation of 0.106 mm compared to the master model. Only the CBCT scans with 0.2-voxel resolution delivered a similar accurate 3D model (mean deviation 0.119 mm). Within the limitations of this study, it was demonstrated that the accuracy of a 3D model of the lower jaw depends on the protocol used for MSCT and CBCT scans. Copyright © 2016 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

  7. Multislice CT cholangiography without biliary contrast agent: technique and initial clinical results in the assessment of patients with biliary obstruction

    Energy Technology Data Exchange (ETDEWEB)

    Zandrino, F.; Benzi, L.; Ferretti, M.L.; Ferrando, R.; Reggiani, G.; Musante, F. [Department of Radiology, Azienda Ospedaliera ' ' SS Antonio e Biagio e C. Arrigo' ' , Alessandria (Italy)

    2002-05-01

    Our objective was to describe our technique for multislice CT cholangiography without cholangiographic contrast agent, and to present our preliminary clinical results. Thirty-seven patients with suspected biliary obstruction were studied. A multislice CT unit was used with the following technical parameters: 2.5-mm collimation; 7.5-mm/s table speed; pitch 6; 0.8-s rotation time; 300 mA; 120 kVp; 18- to 24-s scan time; scan volume ranging from the hepatic dome to below the pancreatic head; 70-s delay after injection of 150 ml of iodinated contrast agent at 4 ml/s. No biliary contrast material was given; oral iodinated contrast agent was administered to opacify bowel loops. Axial, multiplanar reformatted, and minimum intensity projection images were evaluated. The CT findings were compared with the gold standard techniques: endoscopic retrograde cholangiography (ERCP) in 30 patients, percutaneous transhepatic cholangiography in 5, and intraoperative cholangiography in 2. In 5 patients with ampullary lesions biopsy was made during ERCP, 9 underwent surgery, and 11 US-guided fine-needle aspiration. Bile ducts appeared hypodense within the surrounding enhanced structures. Regarding the site of obstruction, agreement between multislice CT and conventional cholangiography was observed in all cases. One patient presented negative findings on both CT and ERCP. In 31 of 36 (86%) patients, multislice CT cholangiography without cholangiographic contrast agent correctly assessed the cause of bile duct obstruction. Multislice CT cholangiography without cholangiographic contrast agent seems to be a promising diagnostic tool in the assessment of patients with bile duct obstruction. (orig.)

  8. Multislice CT cholangiography without biliary contrast agent: technique and initial clinical results in the assessment of patients with biliary obstruction

    International Nuclear Information System (INIS)

    Zandrino, F.; Benzi, L.; Ferretti, M.L.; Ferrando, R.; Reggiani, G.; Musante, F.

    2002-01-01

    Our objective was to describe our technique for multislice CT cholangiography without cholangiographic contrast agent, and to present our preliminary clinical results. Thirty-seven patients with suspected biliary obstruction were studied. A multislice CT unit was used with the following technical parameters: 2.5-mm collimation; 7.5-mm/s table speed; pitch 6; 0.8-s rotation time; 300 mA; 120 kVp; 18- to 24-s scan time; scan volume ranging from the hepatic dome to below the pancreatic head; 70-s delay after injection of 150 ml of iodinated contrast agent at 4 ml/s. No biliary contrast material was given; oral iodinated contrast agent was administered to opacify bowel loops. Axial, multiplanar reformatted, and minimum intensity projection images were evaluated. The CT findings were compared with the gold standard techniques: endoscopic retrograde cholangiography (ERCP) in 30 patients, percutaneous transhepatic cholangiography in 5, and intraoperative cholangiography in 2. In 5 patients with ampullary lesions biopsy was made during ERCP, 9 underwent surgery, and 11 US-guided fine-needle aspiration. Bile ducts appeared hypodense within the surrounding enhanced structures. Regarding the site of obstruction, agreement between multislice CT and conventional cholangiography was observed in all cases. One patient presented negative findings on both CT and ERCP. In 31 of 36 (86%) patients, multislice CT cholangiography without cholangiographic contrast agent correctly assessed the cause of bile duct obstruction. Multislice CT cholangiography without cholangiographic contrast agent seems to be a promising diagnostic tool in the assessment of patients with bile duct obstruction. (orig.)

  9. Substantial dose reduction in modern multi-slice spiral computed tomography (MSCT)-guided craniofacial and skull base surgery

    International Nuclear Information System (INIS)

    Widmann, G.; Fasser, M.; Jaschke, W.; Bale, R.; Schullian, P.; Zangerl, A.; Puelacher, W.; Kral, F.; Riechelmann, H.

    2012-01-01

    Purpose: Reduction of the radiation exposure involved in image-guided craniofacial and skull base surgery is an important goal. The purpose was to evaluate the influence of low-dose protocols in modern multi-slice spiral computed tomography (MSCT) on target registration errors (TREs). Materials and Methods: An anthropomorphic skull phantom with target markers at the craniofacial bone and the anterior skull base was scanned in Sensation Open (40-slice), LightSpeed VCT (64-slice) and Definition Flash (128-slice). Identical baseline protocols (BP) at 120 kV/100 mAs were compared to the following low-dose protocols (LD) in care dose/dose modulation: (LD-I) 100 kV/35ref. mAs, (LD-II) 80 kV/40 - 41ref. mAs, and (LD-III) 80 kV/15 - 17ref. mAs. CTDIvol and DLP were obtained. TREs using an optical navigation system were calculated for all scanners and protocols. Results were statistically analyzed in SPSS and compared for significant differences (p ≤ 0.05). Results: CTDIvol for the Sensation Open/LightSpeed VCT/Definition Flash showed: (BP) 22.24 /32.48 /14.32 mGy; (LD-I) 4.61 /3.52 /1,62 mGy; (LD-II) 3.15 /2.01 /0.87 mGy; and (LD-III) na/0.76 /0.76 mGy. Differences between the BfS (Bundesamt fuer Strahlenschutz) reference CTDIvol of 9 mGy and the lowest CTDIvol were approximately 3-fold for Sensation Open, and 12-fold for the LightSpeed VCT and Definition Flash. A total of 33 registrations and 297 TRE measurements were performed. In all MSCT scanners, the TREs did not significantly differ between the low-dose and the baseline protocols. Conclusion: Low-dose protocols in modern MSCT provided substantial dose reductions without significant influence on TRE and should be strongly considered in image-guided surgery. (orig.)

  10. Deceleration of arginine kinase refolding by induced helical structures.

    Science.gov (United States)

    Li, Hai-Long; Zhou, Sheng-Mei; Park, Daeui; Jeong, Hyoung Oh; Chung, Hae Young; Yang, Jun-Mo; Meng, Fan-Guo; Hu, Wei-Jiang

    2012-04-01

    Arginine kinase (AK) is a key metabolic enzyme for keeping energy balance in invertebrates. Therefore, regulation of the enzymatic activity and the folding studies of AK from the various invertebrates have been the focus of investigation. We studied the effects of helical structures by using hexafluoroisopropanol (HFIP) on AK folding. Folding kinetic studies showed that the folding rates of the urea-denatured AKs were significantly decelerated after being induced in various concentrations of HFIP. AK lost its activity completely at concentrations greater than 60%. The results indicated that the HFIP-induced helical structures in the denatured state play a negative role in protein folding, and the helical structures induced in 5% (v/v) HFIP act as the most effective barrier against AK taking its native structure. The computational docking simulations (binding energies for -2.19 kcal/mol for AutoDock4.2 and -20.47 kcal/mol for Dock6.3) suggested that HFIP interacts with the several important residues that are predicted by both programs. The excessively pre-organized helical structures not only hampered the folding process, but also ultimately brought about changes in the three-dimensional conformation and biological function of AK.

  11. Sixteen-row multislice computed tomography in the assessment of pulmonary veins prior to ablative treatment: validation vs conventional pulmonary venography and study of reproducibility

    Energy Technology Data Exchange (ETDEWEB)

    Maksimovic, R.; Cademartiri, F.; Pattynama, P.M.T. [Erasmus Medical Center, Rotterdam (Netherlands). Dept. of Radiology; Scholten, M; Jordaens, L.J. [Erasmus Medical Center, Rotterdam (Netherlands). Dept. of Cardiology

    2004-03-01

    The aim of this study was to validate multislice computed tomography (MSCT) venography measurements of pulmonary vein (PV) diameters vs conventional pulmonary venography (CPV), and to assess the reproducibility of MSCT data. The study included 21 consecutive patients with atrial fibrillation who were planned for cryothermal ablation of PVs. One day before ablation, all patients underwent CPV and contrast-enhanced non-gated MSCT venography. The MSCT was repeated 3 months after ablation. The CPV images of the treated PVs (n=40) were analyzed and compared with the results of MSCT measurements. Reproducibility of MSCT venography-based data was assessed by interobserver (n=84 PVs) and interexamination (n=44 PVs) variability. Pre-treatment PV diameters on MSCT and CPV showed good correlation (r=0.87, p<0.01; 18.9{+-}2.3 mm, 188.5{+-}2.4 mm, respectively). Interobserver agreement and interexamination reproducibility were good (r=0.91, r=0.82, respectively, p<0.01), with narrow limits of agreement (Bland and Altman method). The MSCT venography allows accurate and reproducible assessment of PVs. It can be used both in non-invasive planning of treatment for ablative therapy and in the follow-up of patients.

  12. Magnetic field generation by pointwise zero-helicity three-dimensional steady flow of an incompressible electrically conducting fluid

    Science.gov (United States)

    Rasskazov, Andrey; Chertovskih, Roman; Zheligovsky, Vladislav

    2018-04-01

    We introduce six families of three-dimensional space-periodic steady solenoidal flows, whose kinetic helicity density is zero at any point. Four families are analytically defined. Flows in four families have zero helicity spectrum. Sample flows from five families are used to demonstrate numerically that neither zero kinetic helicity density nor zero helicity spectrum prohibit generation of large-scale magnetic field by the two most prominent dynamo mechanisms: the magnetic α -effect and negative eddy diffusivity. Our computations also attest that such flows often generate small-scale field for sufficiently small magnetic molecular diffusivity. These findings indicate that kinetic helicity and helicity spectrum are not the quantities controlling the dynamo properties of a flow regardless of whether scale separation is present or not.

  13. Bearing capacity of helical pile foundation in peat soil from different, diameter and spacing of helical plates

    Science.gov (United States)

    Fatnanta, F.; Satibi, S.; Muhardi

    2018-03-01

    In an area dominated by thick peat soil layers, driven piles foundation is often used. These piles are generally skin friction piles where the pile tips do not reach hard stratum. Since the bearing capacity of the piles rely on the resistance of their smooth skin, the bearing capacity of the piles are generally low. One way to increase the bearing capacity of the piles is by installing helical plates around the pile tips. Many research has been performed on helical pile foundation. However, literature on the use of helical pile foundation on peat soil is still hardly found. This research focus on the study of axial bearing capacity of helical pile foundation in peat soil, especially in Riau Province. These full-scale tests on helical pile foundation were performed in a rectangular box partially embedded into the ground. The box is filled with peat soil, which was taken from Rimbo Panjang area in the district of Kampar, Riau Province. Several helical piles with different number, diameter and spacing of the helical plates have been tested and analysed. The tests result show that helical pile with three helical plates of uniform diameter has better bearing capacity compared to other helical piles with varying diameter and different number of helical plates. The bearing capacity of helical pile foundation is affected by the spacing between helical plates. It is found that the effective helical plates spacing for helical pile foundation with diameter of 15cm to 35cm is between 20cm to 30cm. This behaviour may be considered to apply to other type of helical pile foundations in peat soil.

  14. Global and regional left ventricular function: a comparison between gated SPECT, 2D echocardiography and multi-slice computed tomography

    International Nuclear Information System (INIS)

    Henneman, Maureen M.; Bax, Jeroen J.; Holman, Eduard R.; Schuijf, Joanne D.; Jukema, J.W.; Wall, Ernst E. van der; Stokkel, Marcel P.M.; Lamb, Hildo J.; Roos, Albert de

    2006-01-01

    Global and regional left ventricular (LV) function are important indicators of the cardiac status in patients with coronary artery disease (CAD). Therapy and prognosis are to a large extent dependent on LV function. Multi-slice computed tomography (MSCT) has already earned its place as an imaging modality for non-invasive assessment of the coronary arteries, but since retrospective gating to the patient's ECG is performed, information on LV function can be derived. In 49 patients with known or suspected CAD, coronary angiography with MSCT imaging was performed, in addition to gated SPECT and 2D echocardiography. LV end-diastolic and LV end-systolic volumes and LV ejection fraction were analysed with dedicated software (CMR Analytical Software System, Medis, Leiden, The Netherlands for MSCT; gated SPECT by QGS, Cedars-Sinai Medical Center, Los Angeles, CA, USA), and by the biplane Simpson's rule for 2D echocardiography. Regional wall motion was evaluated according to a 17-segment model and a three-point score system. Correlations were fairly good between gated SPECT and MSCT (LVEDV: r=0.65; LVESV: r=0.63; LVEF: r=0.60), and excellent between 2D echocardiography and MSCT (LVEDV: r=0.92; LVESV: r=0.93; LVEF: r=0.80). Agreement for regional wall motion was 95% (κ=0.66) between gated SPECT and MSCT, and 96% (κ=0.73) between 2D echocardiography and MSCT. Global and regional LV function and LV volumes can be adequately assessed with MSCT. Correlations with 2D echocardiography are stronger than with gated SPECT. (orig.)

  15. Comparison of multislice computed tomography with intravascular ultrasound for detection and characterization of coronary artery plaques: A systematic review

    Energy Technology Data Exchange (ETDEWEB)

    Springer, Ivonne [Department of Radiology, Charite, Medical School, Humboldt-Universitaet zu Berlin (Germany); Dewey, Marc [Department of Radiology, Charite, Medical School, Humboldt-Universitaet zu Berlin (Germany)], E-mail: marc.dewey@charite.de

    2009-08-15

    Purpose: Multislice computed tomography (MSCT) is a novel non-invasive test for detection and analysis of coronary artery plaques. A systematic review was conducted of the literature to compare MSCT with IVUS as the reference standard for assessing coronary artery plaques. Materials and methods: We performed a literature search in the online database MEDLINE, which was accessed at (http://www.pubmed.gov) on 9th April 2008. Results: The search identified 14 studies with 340 patients (mean age 59 {+-} 5 years). The systematic review revealed a sensitivity of MSCT on the lesion level (n = 1779 coronary plaques) on the order of 90% (range from 87 to 92%) in comparison to IVUS. Per-segment analysis (n = 356) yielded a lower sensitivity of 81-86%. In the per-vessel analysis (n = 90), MSCT had a better sensitivity and specificity for the RCA (83-89% and 92-100%) and the LAD (83-87% and 93%) than for the LCX (71-85% and 77-89%), and on the vessel level and the cross-section analysis MSCT was more sensitive for calcified plaques than for non-calcified plaque. It is noteworthy that most studies provide only incomplete data on technical and methodological parameters such as radiation exposure and patient characteristics. Conclusion: MSCT is an accurate and reliable test for detection of coronary artery plaques in comparison to IVUS with limitations in regards to the LCX and non-calcified plaques. Studies published thus far are limited by the sample sizes and methodological quality issues.

  16. Imaging of Composites by Helical X-Ray Computed Tomography

    DEFF Research Database (Denmark)

    Wang, Ying; Pyka, Grzegorz; Jespersen, Kristine Munk

    Understanding the fatigue damage mechanisms of composite materials used in wind turbine rotor blades could potentially enhance the reliability and energy efficiency of wind turbines by improving the structure design. In this paper, the fatigue damage propagating mechanisms of unidirectional glass...... fibre composites was characterised by helical X-ray CT. The staining approach was used and it was effective to enhance the visibility of thin matrix cracks and partly closed fibre breaks instead of widely opened cracks. Fibre breaks in the centre UD bundle were found to occur locally, instead of being...

  17. Reliability of voxel gray values in cone beam computed tomography for preoperative implant planning assessment

    NARCIS (Netherlands)

    Parsa, A.; Ibrahim, N.; Hassan, B.; Motroni, A.; van der Stelt, P.; Wismeijer, D.

    2012-01-01

    Purpose: To assess the reliability of cone beam computed tomography (CBCT) voxel gray value measurements using Hounsfield units (HU) derived from multislice computed tomography (MSCT) as a clinical reference (gold standard). Materials and Methods: Ten partially edentulous human mandibular cadavers

  18. Helical CT defecography

    International Nuclear Information System (INIS)

    Ferrando, R.; Fiorini, G.; Beghello, A.; Cicio, G.R.; Derchi, L.E.; Consigliere, M.; Resasco, M.; Tornago, S.

    1999-01-01

    The purpose of this work is to investigate the possible role of Helical CT defecography in pelvic floor disorders by comparing the results of the investigations with those of conventional defecography. The series analyzed consisted of 90 patients, namely 62 women and 28 men, ranging in age 24-82 years. They were all submitted to conventional defecography, and 18 questionable cases were also studied with Helical CT defecography. The conventional examination was performed during the 4 standard phases of resting, squeezing, Valsalva and straining; it is used a remote-control unit. The parameters for Helical CT defecography were: 5 mm beam collimation, pitch 2, 120 KV, 250 m As and 18-20 degrees gantry inclination to acquire coronal images of the pelvic floor. The rectal ampulla was distended with a bolus of 300 mL nonionic iodinated contrast agent (dilution: 3g/cc). The patient wore a napkin and was seated on the table, except for those who could not hold the position and were thus examined supine. Twenty-second helical scans were performed at rest and during evacuation; multiplanar reconstructions were obtained especially on the sagittal plane for comparison with conventional defecographic images. Coronal Helical CT defecography images permitted to map the perineal floor muscles, while sagittal reconstructions provided information on the ampulla and the levator ani. To conclude, Helical CT defecography performed well in study of pelvic floor disorders and can follow conventional defecography especially in questionable cases [it

  19. One-loop QCD and Higgs bosons to partons processes using six-dimensional helicity and generalized unitarity

    International Nuclear Information System (INIS)

    Davies, Scott

    2011-01-01

    We combine the six-dimensional helicity formalism of Cheung and O'Connell with D-dimensional generalized unitarity to obtain a new formalism for computing one-loop amplitudes in dimensionally regularized QCD. With this procedure, we simultaneously obtain the pieces that are constructible from four-dimensional unitarity cuts and the rational pieces that are missed by them, while retaining a helicity formalism. We illustrate the procedure using four- and five-point one-loop amplitudes in QCD, including examples with external fermions. We also demonstrate the technique's effectiveness in next-to-leading order QCD corrections to Higgs processes by computing the next-to-leading order correction to the Higgs plus three positive-helicity gluons amplitude in the large top-quark mass limit.

  20. Demonstration of a helical armature for a superconducting generator

    International Nuclear Information System (INIS)

    Conley, P.L.; Kirtley, J.L. Jr.; Hagman, W.H.; Ula, A.H.M.S.

    1979-01-01

    This is a report on the design, construction and testing of an experimental helical armature for a superconducting geneator. Rated at 60 kVA, this armature was built to be operated in conjunction with the rotor of the first experimental superconducting machine built at MIT. It incorporates, in addition to the helical winding form, a high density edge-brazed end turn geometry, molded bar groups, and silicone fluid coolant and insulation impregnant. Tests showed that the thermal performance of the armature was within reasonable limits, magnetic analyses leading to the computation of reactance and voltage geneation were approximately correct. No abnormal cheating was observed. 9 refs

  1. Weyl-van-der-Waerden formalism for helicity amplitudes of massive particles

    CERN Document Server

    Dittmaier, Stefan

    1999-01-01

    The Weyl-van-der-Waerden spinor technique for calculating helicity amplitudes of massive and massless particles is presented in a form that is particularly well suited to a direct implementation in computer algebra. Moreover, we explain how to exploit discrete symmetries and how to avoid unphysical poles in amplitudes in practice. The efficiency of the formalism is demonstrated by giving explicit compact results for the helicity amplitudes of the processes gamma gamma -> f fbar, f fbar -> gamma gamma gamma, mu^- mu^+ -> f fbar gamma.

  2. Conventional multi-slice computed tomography (CT) and cone-beam CT (CBCT) for computer-assisted implant placement. Part I: relationship of radiographic gray density and implant stability.

    Science.gov (United States)

    Arisan, Volkan; Karabuda, Zihni Cüneyt; Avsever, Hakan; Özdemir, Tayfun

    2013-12-01

    The relationship of conventional multi-slice computed tomography (CT)- and cone beam CT (CBCT)-based gray density values and the primary stability parameters of implants that were placed by stereolithographic surgical guides were analyzed in this study. Eighteen edentulous jaws were randomly scanned by a CT (CT group) or a CBCT scanner (CBCT group) and radiographic gray density was measured from the planned implants. A total of 108 implants were placed, and primary stability parameters were measured by insertion torque value (ITV) and resonance frequency analysis (RFA). Radiographic and subjective bone quality classification (BQC) was also classified. Results were analyzed by correlation tests and multiple regressions (p < .05). CBCT-based gray density values (765 ± 97.32 voxel value) outside the implants were significantly higher than those of CT-based values (668.4 ± 110 Hounsfield unit, p < .001). Significant relations were found among the gray density values outside the implants, ITV (adjusted r(2)  = 0.6142, p = .001 and adjusted r(2)  = 0.5166, p = .0021), and RFA (adjusted r(2)  = 0.5642, p = .0017 and adjusted r(2)  = 0.5423, p = .0031 for CT and CBCT groups, respectively). Data from radiographic and subjective BQC were also in agreement. Similar to the gray density values of CT, that of CBCT could also be predictive for the subjective BQC and primary implant stability. Results should be confirmed on different CBCT scanners. © 2012 Wiley Periodicals, Inc.

  3. Multi-slice ultrasound image calibration of an intelligent skin-marker for soft tissue artefact compensation.

    Science.gov (United States)

    Masum, M A; Pickering, M R; Lambert, A J; Scarvell, J M; Smith, P N

    2017-09-06

    In this paper, a novel multi-slice ultrasound (US) image calibration of an intelligent skin-marker used for soft tissue artefact compensation is proposed to align and orient image slices in an exact H-shaped pattern. Multi-slice calibration is complex, however, in the proposed method, a phantom based visual alignment followed by transform parameters estimation greatly reduces the complexity and provides sufficient accuracy. In this approach, the Hough Transform (HT) is used to further enhance the image features which originate from the image feature enhancing elements integrated into the physical phantom model, thus reducing feature detection uncertainty. In this framework, slice by slice image alignment and calibration are carried out and this provides manual ease and convenience. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Peculiarities of dynamic evaluation of globular formation outlines of the lungs with multislice computed tomography

    Directory of Open Access Journals (Sweden)

    Vladimir G. Kolmogorov

    2017-01-01

    Full Text Available Background. Visualization of infiltration in lung tissue surrounding the globular formation of the lungs (GFL determined by X-ray is one of the important points in the differential diagnosis of primary lung cancer, specific and non-specific inflammatory processes. At CT gauge body phantoms test facilities are widely used for evaluating the performance of scanners that allow the evaluation of scanner characteristics : noise, contrast sensitivity, positioning accuracy, stiffness of the radiation beam, the layer thickness, spatial resolution, etc.Aim. To develop a methodology for assessing the GFL outlines of the dynamics of multislice computed tomography (MSCT by selecting the optimal image processing algorithms.Materials and methods. The visual analysis of two- component physical model images of the electronic window level (WL and electronic window width (WW was installed on the basis of the best conditions for studying a specific group of tissues. In the case of indistinct, poorly defined outlines of globular formations, visual assessment is operator-dependent and requires development and application of quantitative methods of analysis. For a quantitative description of the outlines of the image of the GFL model, a vector in a polar coordinate system coming from the center of the figure mass bounded by the outline was used. The following outline complexity measures were adopted: modified Shannon information entropy H(S(k for k harmonics of the normalized spectral power density S(k of the length of oscillation of loop radius vector R(n; the number of local maxima L of signature radius vector R(n; the maximum value of the normalized power spectral density S(k; product (multiplicity of the entropy H(S and the number of local maxima L.Results. “Multiplicity”, “the number of local maxima” of the outline depend on the GFL geometric dimensions and cannot be used for diagnosis without first normalizing for GFL outline length. The parameters

  5. Pulling Helices inside Bacteria: Imperfect Helices and Rings

    Science.gov (United States)

    Allard, Jun F.; Rutenberg, Andrew D.

    2009-04-01

    We study steady-state configurations of intrinsically-straight elastic filaments constrained within rod-shaped bacteria that have applied forces distributed along their length. Perfect steady-state helices result from axial or azimuthal forces applied at filament ends, however azimuthal forces are required for the small pitches observed for MreB filaments within bacteria. Helix-like configurations can result from distributed forces, including coexistence between rings and imperfect helices. Levels of expression and/or bundling of the polymeric protein could mediate this coexistence.

  6. Multislice CT enteroclysis in the diagnosis of bowel endometriosis

    International Nuclear Information System (INIS)

    Biscaldi, Ennio; Rollandi, Gian A.; Ferrero, Simone; Ragni, Nicola; Remorgida, Valentino; Fulcheri, Ezio

    2007-01-01

    This prospective study aims to evaluate the efficacy of multislice computed tomography combined with colon distension by water enteroclysis (MSCTe) in determining the presence and depth of bowel endometriotic lesions. Ninety-eight women with symptoms suggestive of colorectal endometriosis underwent MSCTe; locations, number of nodule/s, size of the nodule/s and depth of bowel wall infiltration were determined. Independently from the findings of MSCTe, all women underwent laparoscopy. MSCTe findings were compared with surgical and histological results. Abnormal findings suggestive of bowel endometriotic nodules were detected by MSCTe in 75 of the 76 patients with bowel endometriosis. MSCTe identified 110 (94.8%) of the 116 bowel endometriotic nodules removed at surgery; 6 nodules missed at MSCTe were located on the rectum. MSCTe correctly determined the degree of infiltration of the bowel wall in all of the 34 serosal bowel nodules identified at MSCTe. In six nodules reaching the submucosa, the depth of infiltration was underestimated by MSCTe. MSCTe had a sensitivity of 98.7%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 95.7% in identifying women with bowel endometriosis. MSCTe is effective in determining the presence and depth of bowel endometriotic lesions. (orig.)

  7. Multislice CT enteroclysis in the diagnosis of bowel endometriosis

    Energy Technology Data Exchange (ETDEWEB)

    Biscaldi, Ennio; Rollandi, Gian A. [' ' Duchesse of Galliera' ' -Hospital, Genoa (Italy). Dept. of Radiology; Ferrero, Simone; Ragni, Nicola; Remorgida, Valentino [San Martino Hospital and Genoa Univ. (Italy). Dept. of Obstretics and Gynaecology; Fulcheri, Ezio [San Martino Hospital and Genoa Univ. (Italy). Unit of Anatomy and Histopathology

    2007-01-15

    This prospective study aims to evaluate the efficacy of multislice computed tomography combined with colon distension by water enteroclysis (MSCTe) in determining the presence and depth of bowel endometriotic lesions. Ninety-eight women with symptoms suggestive of colorectal endometriosis underwent MSCTe; locations, number of nodule/s, size of the nodule/s and depth of bowel wall infiltration were determined. Independently from the findings of MSCTe, all women underwent laparoscopy. MSCTe findings were compared with surgical and histological results. Abnormal findings suggestive of bowel endometriotic nodules were detected by MSCTe in 75 of the 76 patients with bowel endometriosis. MSCTe identified 110 (94.8%) of the 116 bowel endometriotic nodules removed at surgery; 6 nodules missed at MSCTe were located on the rectum. MSCTe correctly determined the degree of infiltration of the bowel wall in all of the 34 serosal bowel nodules identified at MSCTe. In six nodules reaching the submucosa, the depth of infiltration was underestimated by MSCTe. MSCTe had a sensitivity of 98.7%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 95.7% in identifying women with bowel endometriosis. MSCTe is effective in determining the presence and depth of bowel endometriotic lesions. (orig.)

  8. Weaving Knotted Vector Fields with Tunable Helicity.

    Science.gov (United States)

    Kedia, Hridesh; Foster, David; Dennis, Mark R; Irvine, William T M

    2016-12-30

    We present a general construction of divergence-free knotted vector fields from complex scalar fields, whose closed field lines encode many kinds of knots and links, including torus knots, their cables, the figure-8 knot, and its generalizations. As finite-energy physical fields, they represent initial states for fields such as the magnetic field in a plasma, or the vorticity field in a fluid. We give a systematic procedure for calculating the vector potential, starting from complex scalar functions with knotted zero filaments, thus enabling an explicit computation of the helicity of these knotted fields. The construction can be used to generate isolated knotted flux tubes, filled by knots encoded in the lines of the vector field. Lastly, we give examples of manifestly knotted vector fields with vanishing helicity. Our results provide building blocks for analytical models and simulations alike.

  9. New generation methods for spur, helical, and spiral-bevel gears

    Science.gov (United States)

    Litvin, F. L.; Tsung, W.-J.; Coy, J. J.; Handschuh, R. F.; Tsay, C.-B. P.

    1987-01-01

    New methods for generating spur, helical, and spiral-bevel gears are proposed. These methods provide the gears with conjugate gear tooth surfaces, localized bearing contact, and reduced sensitivity to gear misalignment. Computer programs have been developed for simulating gear meshing and bearing contact.

  10. Robust integer and fractional helical modes in the quantum Hall effect

    Science.gov (United States)

    Ronen, Yuval; Cohen, Yonatan; Banitt, Daniel; Heiblum, Moty; Umansky, Vladimir

    2018-04-01

    Electronic systems harboring one-dimensional helical modes, where spin and momentum are locked, have lately become an important field of their own. When coupled to a conventional superconductor, such systems are expected to manifest topological superconductivity; a unique phase hosting exotic Majorana zero modes. Even more interesting are fractional helical modes, yet to be observed, which open the route for realizing generalized parafermions. Possessing non-Abelian exchange statistics, these quasiparticles may serve as building blocks in topological quantum computing. Here, we present a new approach to form protected one-dimensional helical edge modes in the quantum Hall regime. The novel platform is based on a carefully designed double-quantum-well structure in a GaAs-based system hosting two electronic sub-bands; each tuned to the quantum Hall effect regime. By electrostatic gating of different areas of the structure, counter-propagating integer, as well as fractional, edge modes with opposite spins are formed. We demonstrate that, due to spin protection, these helical modes remain ballistic over large distances. In addition to the formation of helical modes, this platform can serve as a rich playground for artificial induction of compounded fractional edge modes, and for construction of edge-mode-based interferometers.

  11. Multislice ct in gut related pathologies

    International Nuclear Information System (INIS)

    Nadeem, A.; Shaukat, A.; Ahmad, M.W.; Amin, Y.

    2007-01-01

    The objective of this study is to evaluate the effectiveness of Multislice CT in Gut related pathologies. 50 consecutive patients, referred from surgical and medical departments, with gut pathology suspicion were scanned in this respect on Toshiba MSCT 4 slice Aquilion. Patients were. 100 ml iodinated non ionic IV contrast was given. Preferably water was used as oral contrast and oral iodinated contrast was used only in selective cases. As a result, 33 patients showed positive response and 17 were normal; 23 were females and 10 were males. We found following pathologies Acute Appendicitis 10, Diverticulitis 02, Inflammatory Bowel Disease 03, Small Bowel Obstruction 04, Malignant Gut masses 08, Omental Implants 05, Perforation (Duodenal) 01. It is thus concluded that MDCT has a definite role in gut pathologies especially when the ultrasound is negative. (author)

  12. Helical system. History and current state of helical research

    International Nuclear Information System (INIS)

    Yokoyama, Masayuki

    2017-01-01

    This paper described the following: (1) history of nuclear fusion research of Japan's original heliotron method, (2) worldwide development of nuclear fusion research based on helical system such as stellarator, and (3) worldwide meaning of large helical device (LHD) aiming to demonstrate the steady-state performance of heliotron type in the parameter area extrapolable to the core plasma, and research results of LHD. LHD demonstrated that the helical system is excellent in steady operation performance at the world's most advanced level. In an experiment using deuterium gas in 2017, LHD achieved to reach 120 million degrees of ion temperature, which is one index of nuclear fusion condition, demonstrated the realization of high-performance plasma capable of extrapolating to future nuclear fusion reactors, and established the foundation for full-scale research toward the realization of nuclear fusion reactor. Besides experimental research, this paper also described the helical-type stationary nuclear fusion prototype reactor, FFHR-d1, which was based on progress of large-scale simulation at the world's most advanced level. A large-scale superconducting stellarator experimental device, W7-X, with the same scale as LHD, started experiment in December 2015, whose current state is also touched on here. (A.O.)

  13. Review of the helicity formalism

    International Nuclear Information System (INIS)

    Barreiro, F.; Cerrada, M.; Fernandez, E.

    1972-01-01

    Our purpose in these notes has been to present a brief and general review of the helicity formalism. We begin by discussing Lorentz invariance, spin and helicity ideas, in section 1 . In section 2 we deal with the construction of relativistic states and scattering amplitudes in the helicity basis and we study their transformation properties under discrete symmetries. Finally we present some more sophisticated topics like kinematical singularities of helicity amplitudes, kinematical constraints and crossing relations 3, 4, 5 respectively. (Author) 8 refs

  14. Multislice CT coronary angiography: how to do it and what is the current clinical performance?

    International Nuclear Information System (INIS)

    Cademartiri, Filippo; Runza, Giuseppe; Schuijf, Joanne D.; Mollet, Nico R.; Feyter, Pim J. de; Malagutti, Patrizia; Bax, Jeroen J.

    2005-01-01

    The introduction of multislice computed tomography (MSCT) has allowed non-invasive coronary angiography. Although widely applied, extensive information on technical details of the technique is lacking. This survey offers detailed information on patient preparation, data acquisition, reconstruction and interpretation. In addition, a summary of the available studies using MSCT for non-invasive angiography is provided. Based on pooled analysis of direct comparisons between MSCT and invasive angiography, the weighted mean sensitivity and specificity of current 16-slice MSCT for the detection of coronary artery disease are 88% and 96%, respectively. At present, the technique is particularly well suited for reliable exclusion of coronary artery disease. It is important to emphasise that MSCT only provides anatomical images, visualising the presence of atherosclerosis; information on the haemodynamic significance of these lesions (i.e. ischaemia) cannot be derived. (orig.)

  15. Measurement of modulation transfer function in z-axis for multi-slice spiral CT using the micro-disk method. Comparison with the bead method and examination of geometric influence

    International Nuclear Information System (INIS)

    Hara, Takanori

    2003-01-01

    Many methods of measuring the section-sensitive profile (SSP) of computed tomography (CT) by the input of a delta function have been reported. In Japan, the bead method is used as a common measurement because of the high flexibility of the multi-purpose method. However, the intensity of the response of the bead method tends to decline, creating a relatively large error in the base of SSPs. A problem is considered to be the accuracy of measurement in evaluating spatial resolution along the z-axis in multi-slice spiral/helical CT (MSCT). We therefore evaluated the modulation transfer function (MTF) by conducting research with the micro-disk method (100 μm thickness and 1.0 mmφ diameter) and the bead method (1.0 mmφ diameter) for the same input width. Moreover, in the micro-disk method, we also examined alignment, circular region of interest (ROI), and the energy characteristic. Our comparison of MTFs obtained by the micro-disk method and the bead method showed that the former resulted in a higher value and lower standard deviation. The difference was significant at p<0.01. Measurement using the micro-disk method did not show significant differences in terms of alignment and ROIs. Moreover, the energy characteristic was not indicated. This research demonstrated that the accuracy of MTF measurement with the micro-disk method was greater than that with the bead method, and it was found that there was no influence on the actual measurement level of the geometric structure with the micro-disk method. (author)

  16. [Myocardial infarction as cause of an accident. The role of multislice CT in polytrauma management, differential diagnosis and insurance aspects].

    Science.gov (United States)

    Kleber, C; Oswald, B; Bail, H J; Haas, N P; Kandziora, F

    2008-12-01

    We present for the first time the use of contrast-enhanced multislice computed tomography in trauma care to detect acute myocardial infarction and verify it as the cause of a traffic accident. In addition to the case report, cardiac contusion, coronary dissection, and facets of insurance law are discussed. The determination of acute myocardial infarction, cardiac contusion, and coronary dissection can be challenging, but answers can be found in the medical history and accident details. The trauma surgeon in the emergency department must always be interested in clarifying the cause of trauma and keeping a secondary diagnosis in mind to strive for the goal of optimal and complete polytrauma care.

  17. Multislice CT as a Primary Screening Tool for the Prediction of an Involved Mesorectal Fascia and Distant Metastases in Primary Rectal Cancer : A Multicenter Study

    NARCIS (Netherlands)

    Wolberink, Steven V. R. C.; Beets-Tan, Regina G. H.; de Haas-Kock, Danielle F. M.; van de Jagt, Eric J.; Span, Mark M.; Wiggers, Theo

    PURPOSE: The purposes of this study were to assess whether multislice CT can identify tumors having a free or involved circumferential margin, to investigate the additional role of multislice CT as a "one-stop shopping'' staging tool for staging nodal and distant metastases. METHODS: A total of 250

  18. A note on helicity

    International Nuclear Information System (INIS)

    Bialynicki-Birula, I.; Newmann, E.T.; Porter, J.; Winicour, J.; Lukacs, B.; Perjes, Z.; Sebestyen, A.

    1981-03-01

    The authors give a formal definition of the helicity operator for integral spin fields, which does not involve their momentum-space decomposition. The discussion is based upon a representation of the Pauli-Lubanski operator in terms of the action on tensor fields by the Killing vectors associated with the generators of the Poincare group. This leads to an identification of the helicity operator with the duality operator defined by the space-time alternating tensor. Helicity eigenstates then correspond to self-dual or anti-self-dual fields, in agreement with usage implicit in the literature. In addiition, the relationship between helicity eigenstates which are intrinsically non-classical, and states of right or left circular polarization in classical electrodynamics are discussed. (author)

  19. Usefulness of helical computed tomography in the acute diverticulitis

    International Nuclear Information System (INIS)

    Rossini, S.A.; Gonzalez Villaveiran, R.F.; Merola, S.

    2009-01-01

    Objective: The evaluation of the usefulness of helical computed tomography (HCT) in the diagnosis and therapeutic management of the acute diverticulitis. Materials and methods: Six months retrospective cohort study of 100 patient population clinically suspected of diverticulitis was carried out. The exams were made with oral and intravenous contrast unless the patient presented contraindications. A correlation of these studies with the therapeutic response and clinical follow up was done with surgery and histopathology. Results: From a total of 100 patients studied, 62 presented tomographic diagnosis of diverticulitis, 41 were classified as simple diverticulitis and 21 were complicated cases (abscess, phlegmon, plastron, free perforation, vesicocolonic fistula and intestinal obstruction). In 24 patients an alternative diagnosis was made (appendicitis, appendagitis, urethral litiasis, colitis, salpingitis, pancreatitis, uraco cyst complication, colonic mechanical obstruction, colonic perforation with foreign body): 14 patients did not present tomographic findings to support the clinical symptoms, two of them were false-negative by the clinic and by the response to treatment. These data represented a sensibility of 96,87%, specificity of 100%, PPV of 100% and NPV of 94,7% and a certainty of 98 for the tomography diagnosis of acute diverticulitis. Of the 41 patients with tomographic diagnostic of not complicated diverticulitis, 37 received medical outpatient treatment and only 4 medical treatment with placement; of the 21 patients diagnosed with complicated diverticulitis, 18 were hospitalised with medical treatment and the other 3 patients needed surgery; of the 14 patients without tomographic findings of diverticulitis, in 12 outpatients an expectant conduct was followed and the other 2 received medical outpatient treatment. Conclusion: HCT is very useful and effective in diagnosis, evaluation and management of patients with clinical suspicion of diverticulitis

  20. Validation of a computational method for assessing the impact of intra-fraction motion on helical tomotherapy plans

    Energy Technology Data Exchange (ETDEWEB)

    Ngwa, Wilfred; Meeks, Sanford L; Kupelian, Patrick A; Langen, Katja M [Department of Radiation Oncology, M D Anderson Cancer Center Orlando, 1400 South Orange Avenue, Orlando, FL 32806 (United States); Schnarr, Eric [TomoTherapy, Inc., 1240 Deming Way, Madison, WI 53717 (United States)], E-mail: wilfred.ngwa@orlandohealth.com

    2009-11-07

    In this work, a method for direct incorporation of patient motion into tomotherapy dose calculations is developed and validated. This computational method accounts for all treatment dynamics and can incorporate random as well as cyclical motion data. Hence, interplay effects between treatment dynamics and patient motion are taken into account during dose calculation. This allows for a realistic assessment of intra-fraction motion on the dose distribution. The specific approach entails modifying the position and velocity events in the tomotherapy delivery plan to accommodate any known motion. The computational method is verified through phantom and film measurements. Here, measured prostate motion and simulated respiratory motion tracks were incorporated in the dose calculation. The calculated motion-encoded dose profiles showed excellent agreement with the measurements. Gamma analysis using 3 mm and 3% tolerance criteria showed over 97% and 96% average of points passing for the prostate and breathing motion tracks, respectively. The profile and gamma analysis results validate the accuracy of this method for incorporating intra-fraction motion into the dose calculation engine for assessment of dosimetric effects on helical tomotherapy dose deliveries.

  1. Aquilion ONE / ViSION Edition CT scanner realizing 3D dynamic observation with low-dose scanning

    International Nuclear Information System (INIS)

    Kazama, Masahiro; Saito, Yasuo

    2015-01-01

    Computed tomography (CT) scanners have been continuously advancing as essential diagnostic imaging equipment for the diagnosis and treatment of a variety of diseases, including the three major disease classes of cerebrovascular disease, cardiovascular disease, and cancer. Through the development of helical CT scanners and multislice CT scanners, Toshiba Medical Systems Corporation has developed the Aquilion ONE, a CT scanner with a scanning range of up to 160 mm per rotation that can obtain three-dimensional (3D) images of the brain, heart, and other organs in a single rotation. We have now developed the Aquilion ONE / ViSION Edition, a next-generation 320-row multislice CT scanner incorporating the latest technologies that achieves a shorter scanning time and significant reduction in dose compared with conventional products. This product with its low-dose scanning technology will contribute to the practical realization of new diagnosis and treatment modalities employing four-dimensional (4D) data based on 3D dynamic observations through continuous rotations. (author)

  2. Generalized helicity and its time derivative

    International Nuclear Information System (INIS)

    Jarboe, T.R.; Marklin, G.J.

    1985-01-01

    Spheromaks can be sustained against resistive decay by helicity injection because they tend to obey the minimum energy principle. This principle states that a plasma-laden magnetic configuration will relax to a state of minimum energy subject to the constraint that the magnetic helicity is conserved. Use of helicity as a constraint on the minimization of energy was first proposed by Woltjer in connection with astrophysical phenomena. Helicity does decay on the resistive diffusion time. However, if helicity is created and made to flow continuoiusly into a confinement geometry, these additional linked fluxes can relax and sustain the configuration indefinitely against the resistive decay. In this paper we will present an extension of the definition of helicity to include systems where B vector can penetrate the boundary and the penetration can be varying in time. We then discuss the sustainment of RFPs and spheromaks in terms of helicity injection

  3. Evaluation of early coronary graft patency after coronary artery bypass graft surgery using multislice computed tomography angiography

    Directory of Open Access Journals (Sweden)

    Raissi Kamal

    2009-12-01

    Full Text Available Abstract Background Coronary artery bypass graft (CABG surgery is the standard of care in the treatment of advanced coronary artery disease, and its long-term results are affected by the failure of bypass grafts. The aim of the present study was to evaluate the early patency rate in coronary bypass grafts. Methods A total of 107 consecutive patients who underwent CABG were included in this study. Early graft patency was evaluated via computed tomography (CT angiography in the first week after surgery. Results There were a total of 366 grafts, comprised of 250 venous grafts and 116 arterial grafts. Multi-slice CT detected acute graft occlusions in 32 (8.7% of all the grafts, including 26 (10% of the 250 venous grafts and 6 (5% of the 116 arterial grafts. The patency rates obtained were 97.3% for the left internal mammary (IMA grafts, 50% for the radial artery grafts, and 50% for the right IMA grafts. Additionally, 107 (96.4% grafts to the left anterior descending artery (LAD were classified as patent, whereas 1 (30% of the 3 grafts in the left circumflex (LCX region and 1 (50% of the 2 grafts in the right coronary artery (RCA territory were found to be occluded. In the venous category, 8 (13.7% of the 58 grafts to LAD were found to be occluded. In the LCX region, 9 (8.5% of the 106 grafts were classified as occluded, while the remaining 97 (91.5% grafts were patent. The venous grafts to RCA were occluded in 9 (10.4% of the 86 grafts. Amongst the multiple preoperative, intraoperative, and postoperative factors, pump time was significantly longer in the patients with occluded grafts than in those with patent grafts (P = 0.04. Conclusion The IMA grafts had the highest early patency rate amongst the coronary bypass grafts. However, the other arterial grafts were associated with a high rate of acute occlusions.

  4. Standard and Nonstandard Craniospinal Radiotherapy Using Helical TomoTherapy

    International Nuclear Information System (INIS)

    Parker, William; Brodeur, Marylene; Roberge, David; Freeman, Carolyn

    2010-01-01

    Purpose: To show the advantages of planning and delivering craniospinal radiotherapy with helical TomoTherapy (TomoTherapy Inc., Madison, WI) by presenting 4 cases treated at our institution. Methods and Materials: We first present a standard case of craniospinal irradiation in a patient with recurrent myxopapillary ependymoma (MPE) and follow this with 2 cases requiring differential dosing to multiple target volumes. One of these, a patient with recurrent medulloblastoma, required a lower dose to be delivered to the posterior fossa because the patient had been previously irradiated to the full dose, and the other required concurrent boosts to leptomeningeal metastases as part of his treatment for newly diagnosed MPE. The final case presented is a patient with pronounced scoliosis who required spinal irradiation for recurrent MPE. Results: The four cases presented were planned and treated successfully with Helical Tomotherapy. Conclusions: Helical TomoTherapy delivers continuous arc-based intensity-modulated radiotherapy that gives high conformality and excellent dose homogeneity for the target volumes. Increased healthy tissue sparing is achieved at higher doses albeit at the expense of larger volumes of tissue receiving lower doses. Helical TomoTherapy allows for differential dosing of multiple targets, resulting in very elegant dose distributions. Daily megavoltage computed tomography imaging allows for precision of patient positioning, permitting a reduction in planning margins and increased healthy tissue sparing in comparison with standard techniques.

  5. Total scalp irradiation using helical tomotherapy

    International Nuclear Information System (INIS)

    Orton, Nigel; Jaradat, Hazim; Welsh, James; Tome, Wolfgang

    2005-01-01

    Homogeneous irradiation of the scalp poses technical and dosimetric challenges due to the extensive, superficial, curved treatment volume. Conventional treatments on a linear accelerator use multiple matched electron fields or a combination of electron and photon fields. Problems with these techniques include dose heterogeneity in the target due to varying source-to-skin distance (SSD) and angle of beam incidence, significant dose to the brain, and the potential for overdose or underdose at match lines between the fields. Linac-based intensity-modulated radiation therapy (IMRT) plans have similar problems. This work presents treatment plans for total scalp irradiation on a helical tomotherapy machine. Helical tomotherapy is well-suited for scalp irradiation because it has the ability to deliver beamlets that are tangential to the scalp at all points. Helical tomotherapy also avoids problems associated with field matching and use of more than one modality. Tomotherapy treatment plans were generated and are compared to plans for treatment of the same patient on a linac. The resulting tomotherapy plans show more homogeneous target dose and improved critical structure dose when compared to state-of-the-art linac techniques. Target equivalent uniform dose (EUD) for the best tomotherapy plan was slightly higher than for the linac plan, while the volume of brain tissue receiving over 30 Gy was reduced by two thirds. Furthermore, the tomotherapy plan can be more reliably delivered than linac treatments, because the patient is aligned prior to each treatment based on megavoltage computed tomography (MVCT)

  6. A comparative study of accuracy of linear measurements using cone beam and multi-slice computed tomographies for evaluation of mandibular canal location in dry mandibles.

    Science.gov (United States)

    Naser, Asieh Zamani; Mehr, Bahar Behdad

    2013-01-01

    Cross- sectional tomograms have been used for optimal pre-operative planning of dental implant placement. The aim of the present study was to assess the accuracy of Cone Beam Computed Tomography (CBCT) measurements of specific distances around the mandibular canal by comparing them to those obtained from Multi-Slice Computed Tomography (MSCT) images. Ten hemi-mandible specimens were examined using CBCT and MSCT. Before imaging, wires were placed at 7 locations between the anterior margin of the third molar and the anterior margin of the second premolar as reference points. Following distances were measured by two observers on each cross-sectional CBCT and MSCT image: Mandibular Width (W), Length (L), Upper Distance (UD), Lower Distance (LD), Buccal Distance (BD), and Lingual Distance (LID). The obtained data were evaluated using SPSS software, applying paired t-test and intra-class correlation coefficient (ICC). There was a significant difference between the values obtained by MSCT and CBCT measurement for all areas such as H, W, UD, LD, BD, and LID, (P < 0.001), with a difference less than 1 mm. The ICC for all distances by both techniques, measured by a single observer with a one week interval and between 2 observers was 99% and 98%, respectively. Comparing the obtained data of both techniques indicates that the difference between two techniques is 2.17% relative to MSCT. The results of this study showed that there is significant difference between measurements obtained by CBCT and MSCT. However, the difference is not clinically significant.

  7. Perfusion abnormalities in congenital and neoplastic pulmonary disease: comparison of MR perfusion and multislice CT imaging

    International Nuclear Information System (INIS)

    Boll, Daniel T.; Lewin, Jonathan S.; Young, Philip; Gilkeson, Robert C.; Siwik, Ernest S.

    2005-01-01

    The aim of this work was to assess magnetic resonance (MR) perfusion patterns of chronic, nonembolic pulmonary diseases of congenital and neoplastic origin and to compare the findings with results obtained with pulmonary, contrast-enhanced multislice computed tomography (CT) imaging to prove that congenital and neoplastic pulmonary conditions require MR imaging over the pulmonary perfusion cycle to successfully and directly detect changes in lung perfusion patterns. Twenty-five patients underwent concurrent CT and MR evaluation of chronic pulmonary diseases of congenital (n=15) or neoplastic (n=10) origin. Analysis of MR perfusion and contrast-enhanced CT datasets was realized by defining pulmonary and vascular regions of interest in corresponding positions. MR perfusion calculated time-to-peak enhancement, maximal enhancement and the area under the perfusion curve. CT datasets provided pulmonary signal-to-noise ratio measurements. Vessel centerlines of bronchial arteries were determined. Underlying perfusion type, such as pulmonary arterial or systemic arterial supply, as well as regions with significant variations in perfusion were determined statistically. Analysis of the pulmonary perfusion pattern detected pulmonary arterial supply in 19 patients; six patients showed systemic arterial supply. In pulmonary arterial perfusion, MR and multislice CT imaging consistently detected the perfusion type and regions with altered perfusion patterns. In bronchial arterial supply, MR perfusion and CT imaging showed significant perfusion differences. Patients with bronchial arterial supply had bronchial arteries ranging from 2.0 to 3.6 mm compared with submillimeter diameters in pulmonary arterial perfusion. Dynamic MR imaging of congenital and neoplastic pulmonary conditions allowed characterization of the pulmonary perfusion type. CT imaging suggested the presence of systemic arterial perfusion by visualizing hypertrophied bronchial arteries. (orig.)

  8. The value of three-dimensional helical computed tomography for the retrograde flexible ureteronephroscopy in the treatment of lower pole calyx stones

    Directory of Open Access Journals (Sweden)

    Yan Xu

    2016-03-01

    Full Text Available Objective: The aim of our study was to determine if there is any advantage of three-dimensional helical computed tomography (3D-HCT over intravenous urogram (IVU for the retrograde flexible ureteronephroscopy in the treatment of lower pole calyx stones. Methods: From June 2012 to January 2014, a total of 52 cases of lower pole renal stones underwent retrograde intrarenal surgery (RIRS in our center. All patients underwent a preoperative IVU and three-dimensional helical computed tomography urography (3D-CTU program to define the collecting system anatomy, manly concerning the following lower pole features; infundibu-lopelvic angle (IPA, infundibular length (IL, and infundibular width (IW. The examinations were performed in the same center of reference with a standardized method and with 3D-HCT Siemens Somaton Plus equipment. The measurements were performed by the same researcher, using a ruler and a square. Results: Based on clinical threshold difference of the anatomic factors on an IVU image to compare the difference between an IVU image and a 3D-CT image of 52 patients, the IPA was <30° when measured on intravenous pyelography (IVP for 21 patients. We found that with the IPA of <30° measured with IVP only 19% (4/21 were correctly classified in the same size category using 3D-HCT, whereas 81% (17/21 were upgraded to 40–50° on 3D-CT. This difference was significant between IVP and 3D-HCT. Conclusions: 3D-HCT has advantages over IVU when analyzing the morphometric and the morphological features of kidney lower pole spatial anatomy for the retrograde flexible ureteronephroscopy in the treatment of lower pole calyx stones. Keywords: Intravenous urogram, Computed tomography urography, Flexible ureterorenoscopy, Lower pole, Renal stones

  9. Diagnostic value of multislice computed tomography angiography in coronary artery disease: A meta-analysis

    International Nuclear Information System (INIS)

    Sun Zhonghua; Jiang Wen

    2006-01-01

    Purpose: To perform a meta-analysis of the diagnostic value of multislice CT (MSCT) angiography in the detection of coronary artery disease (CAD) when compared to conventional coronary angiography. Materials and methods: A search of PubMed and MEDLINE databases for English literature was performed. Only studies with at least 10 patients comparing MSCT angiography with conventional coronary angiography in the detection of CAD were included. Diagnostic value of MSCT angiography compared to coronary angiography was compared and analyzed at segment-, vessel- and patient-based assessment. Results: 47 studies (67 comparisons) met the criteria and were included in our study. Pooled overall sensitivity, specificity and 95% confidence interval for MSCT angiography in the detection of CAD were 83% (79%, 89%), 93% (91%, 96%) at segment-based analysis; 90% (87%, 94%), 87% (80%, 93%) at vessel-based analysis; and 91% (88%, 95%), 86% (81%, 92%) at patient-based analysis, respectively. Diagnostic accuracy of MSCT angiography in evaluating assessable segments was significantly improved with 64-slice scanners when compared to that with 4- and 16-slice scanners (p < 0.05). Conclusion: Our meta-analysis showed that MSCT angiography has potential diagnostic accuracy in the detection of CAD. Diagnostic performance of MSCT angiography has been significantly improved with the latest 64-slice CT, with resultant high qualitative and quantitative diagnostic accuracy. 16-slice CT was limited in spatial resolution which makes it difficult to perform quantitative assessment of coronary artery stenoses

  10. Comparative study of multi-slice spiral CT angiography and color doppler ultrasound in diagnosis of arteriosclerotic occlusive disease of lower extremity

    International Nuclear Information System (INIS)

    Li Wanjun; Lai Zhenhui; Cui Dong; Lin Xiupeng; Du Muxuan

    2010-01-01

    Objective: To compare the difference between multi-slice spiral CT angiography (MSCTA) and color doppler ultrasound in diagnosis of arteriosclerotic occlusive disease of lower extremity. Methods: Patients with arteriosclerosis occlusion were assessed by color doppler ultrasound, multi-slice spiral CT angiography and digital subtraction angiography (DSA). The image information of color doppler ultrasound and MSCTA were compared with that of DSA. Results: Color doppler ultrasound showed the anatomical shape and hemodynamics of the arteries of lower extremity. The sensitivity, specificity, and accuracy for diagnosis arteriosclerotic occlusive disease of lower extremity were 88.04%, 90.69% and 88.77% respectively. MSCTA showed the three dimensional structure of the arteries of lower extremity as well as the collateral arteries and the distal arterials. The sensitivity, specificity and accuracy of MSCTA were 97.69%, 96.90% and 97.66%, respectively. Conclusion: Multi-slice spiral CT angiography is an ideal imaging method for the diagnosis of arteriosclerotic occlusive disease of lower extremity. (authors)

  11. Helical CT of traumatic injuries of the thoracic aorta

    International Nuclear Information System (INIS)

    Mengozzi, E.; Burzi, M.; Miceli, M.; Lipparini, M.; Sartoni Galloni, S.

    2000-01-01

    Acute thoracic aortic injuries account for up to 10-20% of fatalities in high-speed deceleration road accidents and have an estimated immediate fatality rate of 80-90%. Untreated survivors to acute trauma (10-20%) have a dismal prognosis: 30% of them die within 6 hours, 40-50% die within 24 hours, and 90% within 4 months. It was investigated the diagnostic accuracy of Helical Computed Tomography (Helical CT) in acute traumatic injuries of the thoracic aorta, and the role of this technique in the diagnostic management of trauma patients with a strong suspicion of aortic rupture. It was compared retrospectively the chest Helical CT findings of 256 trauma patients examined June 1995 through August 1999. Chest Helical CT examinations were performed according to trauma score, to associated traumatic lesions and to plain chest radiographic findings. All the examinations were performed with no intravenous contrast agent administration and the pitch 2 technique. After a previous baseline study, contrast-enhanced scans were acquired with pitch 1 in 87 patients. Helical CT showed aortic lesions in 9 of 256 patients examined. In all the 9 cases it was found a mediastinal hematoma and all of them had positive plain chest radiographic findings of mediastinal enlargement. Moreover, in 6 cases aortic knob blurring was also evident on plain chest film and in 5 cases depressed left mainstem bronchus and trachea deviation rightwards were observed. All aortic lesions were identified on axial scans and located at the isthmus of level. Aortic rupture was always depicted as pseudo diverticulum of the proximal descending tract and intimal flap. It was also found that periaortic hematoma in 6 cases and intramural hematoma in 1 case. There were non false positive results in the series: 7 patients with Helical CT diagnosis of aortic rupture were submitted to conventional aortography that confirmed both type and extension of the lesions as detected by Helical CT, and all findings were

  12. Evaluation of endometrial carcinoma by multislice dynamic MR imaging with Turbo FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Asakawa, Mari [Okayama Univ. (Japan). School of Medicine

    1995-04-01

    The purpose of this study was to investigate the usefulness of multislice dynamic MR imaging with Turbo FLASH in assessing myometrial invasion by endometrial carcinoma. Dynamic MR imaging was performed with bolus injection of Gd-DTPA and with 1.5-T Siemens Magnetom imager using Turbo FLASH. Thirty-six endometrial carcinomas were evaluated with pathologic correlation. Junctional zone showed more rapid contrast enhancement effects than myometrium even after menopause. Contrast to noise ratio between junctional zone and endometrial carcinoma was the highest about fifty seconds after bolus injection. Only at that time could the degree of invasion to junctional zone in post-menopausal women whose junctional zones could not be seen on T{sub 2}-weighted images or contrast-enhanced T{sub 1}-weighted images be evaluated correctly. The accuracy in assessing myometrial invasion with T{sub 2}-weighted images, postcontrast T{sub 1}-weighted images, and dynamic MR imaging was 75%, 81% and 89% respectively. Though there was no statistically significant difference, multislice dynamic imaging with Turbo FLASH technique is considered to be a useful imaging method for the pre-operative assessment of myometrial invasion by endometrial carcinoma. (author).

  13. The utility of helical CT in assessing the frequency of ureterolithiasis in Saudi patients

    International Nuclear Information System (INIS)

    Al-Nakshabandi, Nizar A.; Zayed, Mohamed A.; Elsharkaway, Mohamed S.; Al-Boukai, Ahmad S.; Al-Omar, M.

    2008-01-01

    Objective was to identify 650 patients who underwent Ct for renal colic and review them for age and gender in Saudi Arabia. Scans were performed on a 16 multislice scanner. A total of 650 patients with the clinical suspicion of ureteric colic were reviewed; 220 females (33.8%) and 430 males (66.2%), with a female to male ratio of 1:2. Examinations were carried out from January 2005 to November 2006, at King Khalid University Hospital, Riyadh, Kingdom of Saudi Arabia. Three hundred and ninety five patients out of 650 had stones; 2 of 395 (0.5%) had stones in the 5-15 years age group, 28 (7.%) in the 16-25 years age group, 99 (25.1%) in the 26-35 years, 106 (26.8%) in the 36-45 age group, 84 (21.9%) in the 46-55 age group, 51 (12.9%) in the 56-65 age group, and 25 (6.3%) in the above 66 years age group. The most significant finding in our study is that as the patients age increases so does the percentage of stones up to the age of 56, with a peak at age group of 26-35 where stone percentage reaches 26.8%. Unenhanced helical CT is useful for the diagnosis of ureterolithiasis. (author)

  14. Implementation of virtual simulation with a wide-bore multislice helcalct scanner

    International Nuclear Information System (INIS)

    Greer, P.; Kenny, J.

    2004-01-01

    Full text: Multislice large-bore CT scanners specifically designed for radiotherapy have very recently become available. The issues relating to these type of scanners in radiotherapy and the implementation of virtual simulation are therefore of much current interest. A GE LightSpeed RT 4-slice helical CT scanner with a 80 cm bore size was installed in the radiation oncology department of the Newcastle Mater Hospital. This replaced our only simulator, a conventional unit. Specific issues relating to the imaging performance, and virtual simulation process with the large-bore multislice scanner were studied to ensure an accurate radiotherapy process. The detector array fully samples a 50 cm diameter scan circle. The reconstructed diameter can be increased to 65 cm with partial sampling of the extra volume. The GE Advantage Sim (ASim) virtual simulation software was commissioned, with transfer of CT images and DICOM RT plans to the Pinnacle radiotherapy planning system (RTPS) for dose calculation. Some specific issues investigated were: 1) The image quality performance for image reconstruction with the 65 cm area compared to 50 cm was measured with a line-pair phantom. 2) The accuracy of CT numbers with lateral position was assessed with a commercial electron density phantom. 3) Couch lateral movement and sag during acquisition were measured with the couch weighted with 86 kg. 4) The accuracy of the transfer of plans from ASim to Pinnacle was verified with known plan geometries. Image resolution throughout the entire CT image was found to be significantly lower when scan reconstruction was performed with 65 cm scan circle compared to 50 cm. The 0.3, 0.38 and 0.5 1p/mm bars were clearly distinguishable with the 50 cm reconstruction compared to only the 0.3 1p/mm bars in the 65 cm reconstruction. 2) CT numbers varied significantly outside the 50 cm reconstructed area. 3) Couch lateral movement during scanning was within 1 mm. Couch sag was 4 mm at the imaging plane

  15. Simulation of multi-pulse coaxial helicity injection in the Sustained Spheromak Physics Experiment

    Science.gov (United States)

    O'Bryan, J. B.; Romero-Talamás, C. A.; Woodruff, S.

    2018-03-01

    Nonlinear, numerical computation with the NIMROD code is used to explore magnetic self-organization during multi-pulse coaxial helicity injection in the Sustained Spheromak Physics eXperiment. We describe multiple distinct phases of spheromak evolution, starting from vacuum magnetic fields and the formation of the initial magnetic flux bubble through multiple refluxing pulses and the eventual onset of the column mode instability. Experimental and computational magnetic diagnostics agree on the onset of the column mode instability, which first occurs during the second refluxing pulse of the simulated discharge. Our computations also reproduce the injector voltage traces, despite only specifying the injector current and not explicitly modeling the external capacitor bank circuit. The computations demonstrate that global magnetic evolution is fairly robust to different transport models and, therefore, that a single fluid-temperature model is sufficient for a broader, qualitative assessment of spheromak performance. Although discharges with similar traces of normalized injector current produce similar global spheromak evolution, details of the current distribution during the column mode instability impact the relative degree of poloidal flux amplification and magnetic helicity content.

  16. Prospective versus retrospective ECG-gated multislice CT coronary angiography: A systematic review of radiation dose and diagnostic accuracy

    International Nuclear Information System (INIS)

    Sun Zhonghua; Ng, Kwan-Hoong

    2012-01-01

    Purpose: To perform a systematic review of the radiation dose and diagnostic accuracy of prospective versus retrospective ECG-gated multislice CT coronary angiography. Materials and methods: A search of Pubmed/Medline and Sciencedirect databases for English literature was performed to identify studies comparing prospective and retrospective ECG-gated multislice CT angiography in the diagnosis of coronary artery disease. Effective dose, dose length product, image quality and diagnostic value were compared between two groups of studies. Results: 22 studies were included for analysis. The mean effective dose of prospective ECG-gated scans was 4.5 mSv (95% CI: 3.6, 5.3 mSv), which is significantly lower than that of retrospective scans, which is 13.8 mSv (95% CI: 11.5, 16.0 mSv) (p < 0.001). The mean dose length product was 225 mGy cm (95% CI: 188, 262 mGy cm) and 822 mGy cm (95% CI: 630, 1013 mGy cm) for the prospective and retrospective ECG-gated scans, respectively, indicating a statistically significant difference between these two protocols (p < 0.0001). The mean sensitivity and specificity of multislice CT angiography in the diagnosis of coronary artery disease was 97.7% (95% CI: 93.7%, 100%) and 92.1% (95% CI: 87.2%, 97%) for prospective ECG-gated scans; 95.2% (95% CI: 91%, 99.5%) and 94.4% (95% CI: 88.5%, 100%) for retrospective ECG-gated scans, respectively, with no significant difference for sensitivity but significant difference for specificity (p = 0.047). Conclusion: Multislice CT coronary angiography with prospective ECG-gating leads to a significant reduction of radiation dose when compared to that of retrospective ECG-gating, while offering comparable image quality and diagnostic value.

  17. Handling data redundancy in helical cone beam reconstruction with a cone-angle-based window function and its asymptotic approximation

    International Nuclear Information System (INIS)

    Tang Xiangyang; Hsieh Jiang

    2007-01-01

    A cone-angle-based window function is defined in this manuscript for image reconstruction using helical cone beam filtered backprojection (CB-FBP) algorithms. Rather than defining the window boundaries in a two-dimensional detector acquiring projection data for computed tomographic imaging, the cone-angle-based window function deals with data redundancy by selecting rays with the smallest cone angle relative to the reconstruction plane. To be computationally efficient, an asymptotic approximation of the cone-angle-based window function is also given and analyzed in this paper. The benefit of using such an asymptotic approximation also includes the avoidance of functional discontinuities that cause artifacts in reconstructed tomographic images. The cone-angle-based window function and its asymptotic approximation provide a way, equivalent to the Tam-Danielsson-window, for helical CB-FBP reconstruction algorithms to deal with data redundancy, regardless of where the helical pitch is constant or dynamically variable during a scan. By taking the cone-parallel geometry as an example, a computer simulation study is conducted to evaluate the proposed window function and its asymptotic approximation for helical CB-FBP reconstruction algorithm to handle data redundancy. The computer simulated Forbild head and thorax phantoms are utilized in the performance evaluation, showing that the proposed cone-angle-based window function and its asymptotic approximation can deal with data redundancy very well in cone beam image reconstruction from projection data acquired along helical source trajectories. Moreover, a numerical study carried out in this paper reveals that the proposed cone-angle-based window function is actually equivalent to the Tam-Danielsson-window, and rigorous mathematical proofs are being investigated

  18. EVOLUTION OF SPINNING AND BRAIDING HELICITY FLUXES IN SOLAR ACTIVE REGION NOAA 10930

    Energy Technology Data Exchange (ETDEWEB)

    Ravindra, B. [Indian Institute of Astrophysics, Koramangala, Bangalore 560 034 (India); Yoshimura, Keiji [Department of Physics, Montana State University Bozeman, MT 59717 (United States); Dasso, Sergio, E-mail: ravindra@iiap.res.in, E-mail: yosimura@solar.physics.montana.edu, E-mail: dasso@df.uba.ar [Instituto de Astronomia y Fisica del Espacio (CONICET-UBA), 1428 Buenos Aires (Argentina)

    2011-12-10

    The line-of-sight magnetograms from Solar Optical Telescope Narrowband Filter Imager observations of NOAA Active Region 10930 have been used to study the evolution of spinning and braiding helicities over a period of five days starting from 2006 December 9. The north (N) polarity sunspot was the follower and the south (S) polarity sunspot was the leader. The N-polarity sunspot in the active region was rotating in the counterclockwise direction. The rate of rotation was small during the first two days of observations and it increased up to 8 Degree-Sign hr{sup -1} on the third day of the observations. On the fourth and fifth days it remained at 4 Degree-Sign hr{sup -1} with small undulations in its magnitude. The sunspot rotated about 260 Degree-Sign in the last three days. The S-polarity sunspot did not complete more than 20 Degree-Sign in five days. However, it changed its direction of rotation five times over a period of five days and injected both the positive and negative type of spin helicity fluxes into the corona. Through the five days, both the positive and negative sunspot regions injected equal amounts of spin helicity. The total injected helicity is predominantly negative in sign. However, the sign of the spin and braiding helicity fluxes computed over all the regions were reversed from negative to positive five times during the five-day period of observations. The reversal in spinning helicity flux was found before the onset of the X3.4-class flare, too. Though, the rotating sunspot has been observed in this active region, the braiding helicity has contributed more to the total accumulated helicity than the spinning helicity. The accumulated helicity is in excess of -7 Multiplication-Sign 10{sup 43} Mx{sup 2} over a period of five days. Before the X3.4-class flare that occurred on 2006 December 13, the rotation speed and spin helicity flux increased in the S-polarity sunspot. Before the flare, the total injected helicity was larger than -6

  19. Pyrolysis of Helical Coordination Polymers for Metal-Sulfide-Based Helices with Broadband Chiroptical Activity.

    Science.gov (United States)

    Hirai, Kenji; Yeom, Bongjun; Sada, Kazuki

    2017-06-27

    Fabrication of chiroptical materials with broadband response in the visible light region is vital to fully realize their potential applications. One way to achieve broadband chiroptical activity is to fabricate chiral nanostructures from materials that exhibit broadband absorption in the visible light region. However, the compounds used for chiroptical materials have predominantly been limited to materials with narrowband spectral response. Here, we synthesize Ag 2 S-based nanohelices derived from helical coordination polymers. The right- and left-handed coordination helices used as precursors are prepared from l- and d-glutathione with Ag + and a small amount of Cu 2+ . The pyrolysis of the coordination helices yields right- and left-handed helices of Cu 0.12 Ag 1.94 S/C, which exhibit chiroptical activity spanning the entire visible light region. Finite element method simulations substantiate that the broadband chiroptical activity is attributed to synergistic broadband light absorption and light scattering. Furthermore, another series of Cu 0.10 Ag 1.90 S/C nanohelices are synthesized by choosing the l- or d-Glu-Cys as starting materials. The pitch length of nanohelicies is controlled by changing the peptides, which alters their chiroptical properties. The pyrolysis of coordination helices enables one to fabricate helical Ag 2 S-based materials that enable broadband chiroptical activity but have not been explored owing to the lack of synthetic routes.

  20. The comparative study between multi-slice spiral CT angiography and color flow ultrasonography in hepatic and splenic trauma

    International Nuclear Information System (INIS)

    Yan Youxia; Zhang Jin'e; Chen Xiaocong; Cai Shufang

    2007-01-01

    Objective: To investigate the clinical value of multi-slice spiral CT angiography and color flow ultra- sonography in hepatic and splenic trauma. Methods Thirty-six cases of hepatic and splenic trauma were collected, the MSCT were analyzed and compared with that of color flow ultrasonography. Results: Seventeen cases were Hepatic trauma including nine cases of hepatic contusion, six cases of sub-envelope hematoma, two cases of both sub-envelope hematoma and hepatic contusion. Nineteen cases were splenic trauma including nine cases of splenic contusion, ten cases of sub-envelope hematoma. Conclusion: Multi-slice spiral CT angiography show hepatic and splenic trauma clearer than that of color flow ultrasonography, and can provide reliable basis for clinic diagnosis and therapy. (authors)

  1. Employing helicity amplitudes for resummation

    International Nuclear Information System (INIS)

    Moult, Ian; Stewart, Iain W.; Tackmann, Frank J.; Waalewijn, Wouter J.; Amsterdam Univ.

    2015-08-01

    Many state-of-the-art QCD calculations for multileg processes use helicity amplitudes as their fundamental ingredients. We construct a simple and easy-to-use helicity operator basis in soft-collinear effective theory (SCET), for which the hard Wilson coefficients from matching QCD onto SCET are directly given in terms of color-ordered helicity amplitudes. Using this basis allows one to seamlessly combine fixed-order helicity amplitudes at any order they are known with a resummation of higher-order logarithmic corrections. In particular, the virtual loop amplitudes can be employed in factorization theorems to make predictions for exclusive jet cross sections without the use of numerical subtraction schemes to handle real-virtual infrared cancellations. We also discuss matching onto SCET in renormalization schemes with helicities in 4- and d-dimensions. To demonstrate that our helicity operator basis is easy to use, we provide an explicit construction of the operator basis, as well as results for the hard matching coefficients, for pp → H+0,1,2 jets, pp → W/Z/γ+0,1,2 jets, and pp → 2,3 jets. These operator bases are completely crossing symmetric, so the results can easily be applied to processes with e + e - and e - p collisions.

  2. Multi-slice spiral CT detects spread of small laryngeal tumors

    International Nuclear Information System (INIS)

    Bruening, R.; Schoepf, U.; Becker, C.; Reiser, M.; Hong, C.; Sturm, C.; Wollenberg, B.

    1999-01-01

    The purpose of the study was to preoperatively investigate small laryngeal carcinomas using multi-slice spiral CT (MSCT) and subsequent multiplanar reconstructions (MPR) and to compare the results to the detailed spread found a surgery and histology. Nine patients with small (T1, T2) laryngeal cancer were investigated on a MSCT scanner (Siemens plus 4 Volume Zoom, Siemens). A 4x1 mm collimation, 120 kV, 200 mAs and a 0.5 seconds rotation time were used, allowing a coverage of the entire larynx in approximately 10 seconds within a single breathhold. Multiplanar reconstruction's (MPR) in sagittal and coronal plane were reconstructed in all patients and rated in consensus reading. In 8 of nine patients, the glottic spread was detected by MSCT, in one case of a supraglottic tumor a glottic invasion was excluded. The infiltration of the anterior commissure, the infiltration into the subglottic space and the extension into the hypo-pharynx was correctly assessed in all patients. MSCT was not able to predict infiltration of the arythnoids in two patients. The use of multi-slice CT for the preoperative assessment of small laryngeal tumors shows great promise. The detection or exclusion of subtle spread of these tumors into the supra- or subglottic space and along the glottic level was possible with high accuracy. As the examination time is short, artifacts are rare and multiplanar reconstructions gain in clinical importance. (orig.) [de

  3. Magnetic Energy and Helicity in Two Emerging Active Regions in the Sun

    Science.gov (United States)

    Liu, Y.; Schuck, P. W.

    2012-01-01

    The magnetic energy and relative magnetic helicity in two emerging solar active regions, AR 11072 and AR 11158,are studied. They are computed by integrating over time the energy and relative helicity fluxes across the photosphere. The fluxes consist of two components: one from photospheric tangential flows that shear and braid field lines (shear term), the other from normal flows that advect magnetic flux into the corona (emergence term). For these active regions: (1) relative magnetic helicity in the active-region corona is mainly contributed by the shear term,(2) helicity fluxes from the emergence and the shear terms have the same sign, (3) magnetic energy in the corona (including both potential energy and free energy) is mainly contributed by the emergence term, and(4) energy fluxes from the emergence term and the shear term evolved consistently in phase during the entire flux emergence course.We also examine the apparent tangential velocity derived by tracking field-line footpoints using a simple tracking method. It is found that this velocity is more consistent with tangential plasma velocity than with the flux transport velocity, which agrees with the conclusion by Schuck.

  4. Radiation safety concerns and diagnostic reference levels for computed tomography scanners in Tamil Nadu

    International Nuclear Information System (INIS)

    Livingstone, Roshan S.; Dinakaran, Paul M.

    2011-01-01

    Radiation safety in computed tomography (CT) scanners is of concern due its widespread use in the field of radiological imaging. This study intends to evaluate radiation doses imparted to patients undergoing thorax, abdomen and pelvic CT examinations and formulate regional diagnostic reference levels (DRL) in Tamil Nadu, South India. In-site CT dose measurement was performed in 127 CT scanners in Tamil Nadu for a period of 2 years as a part of the Atomic Energy Regulatory Board (AERB)-funded project. Out of the 127 CT scanners,13 were conventional; 53 single-slice helical scanners (SSHS); 44 multislice CT (MSCT) scanners; and 17 refurbished scanners. CT dose index (CTDI) was measured using a 32-cm polymethyl methacrylate (PMMA)-body phantom in each CT scanner. Dose length product (DLP) for different anatomical regions was generated using CTDI values. The regional DRLs for thorax, abdomen and pelvis examinations were 557, 521 and 294 mGy cm, respectively. The mean effective dose was estimated using the DLP values and was found to be 8.04, 6.69 and 4.79 mSv for thorax, abdomen and pelvic CT examinations, respectively. The establishment of DRLs in this study is the first step towards optimization of CT doses in the Indian context. (author)

  5. Left atrial accessory appendages, diverticula, and left-sided septal pouch in multi-slice computed tomography. Association with atrial fibrillation and cerebrovascular accidents.

    Science.gov (United States)

    Hołda, Mateusz K; Koziej, Mateusz; Wszołek, Karolina; Pawlik, Wiesław; Krawczyk-Ożóg, Agata; Sorysz, Danuta; Łoboda, Piotr; Kuźma, Katarzyna; Kuniewicz, Marcin; Lelakowski, Jacek; Dudek, Dariusz; Klimek-Piotrowska, Wiesława

    2017-10-01

    The aim of this study is to provide a morphometric description of the left-sided septal pouch (LSSP), left atrial accessory appendages, and diverticula using cardiac multi-slice computed tomography (MSCT) and to compare results between patient subgroups. Two hundred and ninety four patients (42.9% females) with a mean of 69.4±13.1years of age were investigated using MSCT. The presence of the LSSP, left atrial accessory appendages, and diverticula was evaluated. Multiple logistic regression analysis was performed to check whether the presence of additional left atrial structures is associated with increased risk of atrial fibrillation and cerebrovascular accidents. At least one additional left atrial structure was present in 51.7% of patients. A single LSSP, left atrial diverticulum, and accessory appendage were present in 35.7%, 16.0%, and 4.1% of patients, respectively. After adjusting for other risk factors via multiple logistic regression, patients with LSSP are more likely to have atrial fibrillation (OR=2.00, 95% CI=1.14-3.48, p=0.01). The presence of a LSSP was found to be associated with an increased risk of transient ischemic attack using multiple logistic regression analysis after adjustment for other risk factors (OR=3.88, 95% CI=1.10-13.69, p=0.03). In conclusion LSSPs, accessory appendages, and diverticula are highly prevalent anatomic structures within the left atrium, which could be easily identified by MSCT. The presence of LSSP is associated with increased risk for atrial fibrillation and transient ischemic attack. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Three-dimensional quantification of vorticity and helicity from 3D cine PC-MRI using finite-element interpolations.

    Science.gov (United States)

    Sotelo, Julio; Urbina, Jesús; Valverde, Israel; Mura, Joaquín; Tejos, Cristián; Irarrazaval, Pablo; Andia, Marcelo E; Hurtado, Daniel E; Uribe, Sergio

    2018-01-01

    We propose a 3D finite-element method for the quantification of vorticity and helicity density from 3D cine phase-contrast (PC) MRI. By using a 3D finite-element method, we seamlessly estimate velocity gradients in 3D. The robustness and convergence were analyzed using a combined Poiseuille and Lamb-Ossen equation. A computational fluid dynamics simulation was used to compared our method with others available in the literature. Additionally, we computed 3D maps for different 3D cine PC-MRI data sets: phantom without and with coarctation (18 healthy volunteers and 3 patients). We found a good agreement between our method and both the analytical solution of the combined Poiseuille and Lamb-Ossen. The computational fluid dynamics results showed that our method outperforms current approaches to estimate vorticity and helicity values. In the in silico model, we observed that for a tetrahedral element of 2 mm of characteristic length, we underestimated the vorticity in less than 5% with respect to the analytical solution. In patients, we found higher values of helicity density in comparison to healthy volunteers, associated with vortices in the lumen of the vessels. We proposed a novel method that provides entire 3D vorticity and helicity density maps, avoiding the used of reformatted 2D planes from 3D cine PC-MRI. Magn Reson Med 79:541-553, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  7. 3D CT versus axial helical CT versus conventional tomography in the classification of acetabular fractures: A ROC analysis

    International Nuclear Information System (INIS)

    Kickuth, Ralph; Laufer, Ulf; Hartung, Guido; Gruening, Christian; Stueckle, Christoph; Kirchner, Johannes

    2002-01-01

    AIM: To assess the diagnostic power of three-dimensional computed tomography (3D CT), axial helical computed tomography (CT) and conventional tomography in the classification of acetabular fractures by interdisciplinary review. MATERIALS AND METHODS: Receiver operating characteristics (ROCs) were assessed for two radiologists and two surgeons blinded to the presence of acetabular fractures in an animal model (a total of 62 porcine hips, 40 of them with artificial acetabular fractures). Main target parameter was the diagnostic accuracy in the classification of the artificial fractures following Judet et al. RESULTS: ROC analysis for radiologists showed A z values of 0·83 for 3D CT, 0·81 for axial helical CT, and 0·78 for conventional tomography; differences between the three techniques were not significant (P = 0·46-0·73). A z values for the surgeons were 0·87 for 3D CT, 0·68 for axial helical CT, and 0·60 for conventional tomography; 3D CT was significantly better than axial helical CT (P = 0·01) and conventional tomography (P = 0·001). The differences between axial helical CT and conventional tomography were not significant (P = 0·37). CONCLUSION: Acetabular fractures are best classified by 3D CT, followed by axial helical CT and conventional tomography when assessed by surgeons. 3D CT did not provide any additional significant benefit in the classification performed by radiologists. Kickuth, R. et al. (2002)

  8. Magnetic helicity balance in the Sustained Spheromak Plasma Experiment

    International Nuclear Information System (INIS)

    Stallard, B.W.; Hooper, E.B.; Woodruff, S.; Bulmer, R.H.; Hill, D.N.; McLean, H.S.; Wood, R.D.

    2003-01-01

    The magnetic helicity balance between the helicity input injected by a magnetized coaxial gun, the rate-of-change in plasma helicity content, and helicity dissipation in electrode sheaths and Ohmic losses have been examined in the Sustained Spheromak Plasma Experiment (SSPX) [E. B. Hooper, L. D. Pearlstein, and R. H. Bulmer, Nucl. Fusion 39, 863 (1999)]. Helicity is treated as a flux function in the mean-field approximation, allowing separation of helicity drive and losses between closed and open field volumes. For nearly sustained spheromak plasmas with low fluctuations, helicity balance analysis implies a decreasing transport of helicity from the gun input into the spheromak core at higher spheromak electron temperature. Long pulse discharges with continuously increasing helicity and larger fluctuations show higher helicity coupling from the edge to the spheromak core. The magnitude of the sheath voltage drop, inferred from cathode heating and a current threshold dependence of the gun voltage, shows that sheath losses are important and reduce the helicity injection efficiency in SSPX

  9. Diffusion in a tokamak with helical magnetic cells

    International Nuclear Information System (INIS)

    Wakatani, Masahiro

    1975-05-01

    In a tokamak with helical magnetic cells produced by a resonant helical magnetic field, diffusion in the collisional regime is studied. The diffusion coefficient is greatly enhanced near the resonant surface even for a weak helical magnetic field. A theoretical model for disruptive instabilities based on the enhanced transport due to helical magnetic cells is discussed. This may explain experiments of the tokamak with resonant helical fields qualitatively. (author)

  10. Measurement of multi-slice computed tomography dose profile with the Dose Magnifying Glass and the MOSkin radiation dosimeter

    International Nuclear Information System (INIS)

    Lian, C.P.L.; Wong, J.H.D.; Young, A.; Cutajar, D.; Petasecca, M.; Lerch, M.L.F.; Rosenfeld, A.B.

    2013-01-01

    This study describes the application of two in-house developed dosimeters, the Dose Magnifying Glass (DMG) and the MOSkin dosimeter at the Centre for Medical Radiation Physics, University of Wollongong, Australia, for the measurement of CT dose profiles for a clinical diagnostic 16-slice MSCT scanner. Two scanner modes were used; axial mode and helical mode, and the effect of varying beam collimation and pitch was studied. With an increase in beam collimation in axial mode and an increase of CT pitch in helical mode, cumulative point dose at scanner isocentre decreased while FWHM increased. There was generally good agreement to within 3% between the acquired dose profiles obtained by the DMG and the film except at dose profile tails, where film over-responded by up to 30% due to its intrinsic depth dose dependence at low doses. -- Highlights: ► This study shows the CT beam profiles acquired with our institution's detectors. ► The DMG is a relative dosimeter calibrated to absolute MOSkin readings. ► There was good agreement between dose profiles acquired by the DMG and the film

  11. Helical tomotherapy as a new treatment technique for whole abdominal irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Rochet, N.; Sterzing, F.; Jensen, A.; Herfarth, K.; Schubert, K.; Debus, J.; Harms, W. [Heidelberg Univ. (Germany). Dept. of Radiation Oncology; Dinkel, J. [German Cancer Research Center (dkfz), Heidelberg (Germany). Dept. of Radiology; Eichbaum, M.; Schneeweiss, A.; Sohn, C. [Heidelberg Univ. (Germany). Dept. of Gynecology and Obstetrics

    2008-03-15

    Purpose: To describe a new intensity-modulated radiotherapy (IMRT) technique using helical tomotherapy for whole abdominal irradiation (WAI) in patients with advanced ovarian cancer. Material and Methods: A patient with radically operated ovarian cancer FIGO stage IIIc was treated in a prospective clinical trial with WAI to a total dose of 30 Gy in 1.5-Gy fractions as an additional therapy after adjuvant platinum-based chemotherapy. The planning target volume (PTV) included the entire peritoneal cavity. PTV was adapted according to breathing motion as detected in a four-dimensional respiratory-triggered computed tomography (4D-CT). Inverse treatment planning was done with the Hi-Art tomotherapy planning station. Organs at risk (OARs) were kidneys, liver, bone marrow, spinal cord, thoracic and lumbosacral vertebral bodies, and pelvic bones. Daily control of positioning accuracy was performed with megavoltage computed tomography (MV-CT). Results: Helical tomotherapy enabled a very homogeneous dose distribution with excellent sparing of OARs and coverage of the PTV (V90 of 93.1%, V95 of 86.9%, V105 of 1.9%, and V110 of 0.01%). Mean liver dose was 21.57 Gy and mean kidney doses were 9.75 Gy and 9.14 Gy, respectively. Treatment could be performed in 18.1 min daily and no severe side effects occurred. Conclusion: Helical tomotherapy is feasible and fast for WAI. Tomotherapy enabled excellent coverage of the PTV and effective sparing of liver, kidneys and bone marrow. (orig.)

  12. Helical tomotherapy as a new treatment technique for whole abdominal irradiation

    International Nuclear Information System (INIS)

    Rochet, N.; Sterzing, F.; Jensen, A.; Herfarth, K.; Schubert, K.; Debus, J.; Harms, W.; Dinkel, J.; Eichbaum, M.; Schneeweiss, A.; Sohn, C.

    2008-01-01

    Purpose: To describe a new intensity-modulated radiotherapy (IMRT) technique using helical tomotherapy for whole abdominal irradiation (WAI) in patients with advanced ovarian cancer. Material and Methods: A patient with radically operated ovarian cancer FIGO stage IIIc was treated in a prospective clinical trial with WAI to a total dose of 30 Gy in 1.5-Gy fractions as an additional therapy after adjuvant platinum-based chemotherapy. The planning target volume (PTV) included the entire peritoneal cavity. PTV was adapted according to breathing motion as detected in a four-dimensional respiratory-triggered computed tomography (4D-CT). Inverse treatment planning was done with the Hi-Art tomotherapy planning station. Organs at risk (OARs) were kidneys, liver, bone marrow, spinal cord, thoracic and lumbosacral vertebral bodies, and pelvic bones. Daily control of positioning accuracy was performed with megavoltage computed tomography (MV-CT). Results: Helical tomotherapy enabled a very homogeneous dose distribution with excellent sparing of OARs and coverage of the PTV (V90 of 93.1%, V95 of 86.9%, V105 of 1.9%, and V110 of 0.01%). Mean liver dose was 21.57 Gy and mean kidney doses were 9.75 Gy and 9.14 Gy, respectively. Treatment could be performed in 18.1 min daily and no severe side effects occurred. Conclusion: Helical tomotherapy is feasible and fast for WAI. Tomotherapy enabled excellent coverage of the PTV and effective sparing of liver, kidneys and bone marrow. (orig.)

  13. Dynamics of zonal flows in helical systems.

    Science.gov (United States)

    Sugama, H; Watanabe, T-H

    2005-03-25

    A theory for describing collisionless long-time behavior of zonal flows in helical systems is presented and its validity is verified by gyrokinetic-Vlasov simulation. It is shown that, under the influence of particles trapped in helical ripples, the response of zonal flows to a given source becomes weaker for lower radial wave numbers and deeper helical ripples while a high-level zonal-flow response, which is not affected by helical-ripple-trapped particles, can be maintained for a longer time by reducing their bounce-averaged radial drift velocity. This implies a possibility that helical configurations optimized for reducing neoclassical ripple transport can simultaneously enhance zonal flows which lower anomalous transport.

  14. Parameterization and measurements of helical magnetic fields

    International Nuclear Information System (INIS)

    Fischer, W.; Okamura, M.

    1997-01-01

    Magnetic fields with helical symmetry can be parameterized using multipole coefficients (a n , b n ). We present a parameterization that gives the familiar multipole coefficients (a n , b n ) for straight magnets when the helical wavelength tends to infinity. To measure helical fields all methods used for straight magnets can be employed. We show how to convert the results of those measurements to obtain the desired helical multipole coefficients (a n , b n )

  15. Imaging of head and neck tumors -- methods: CT, spiral-CT, multislice-spiral-CT

    International Nuclear Information System (INIS)

    Baum, Ulrich; Greess, Holger; Lell, Michael; Noemayr, Anton; Lenz, Martin

    2000-01-01

    Spiral-CT is standard for imaging neck tumors. In correspondence with other groups we routinely use spiral-CT with thin slices (3 mm), a pitch of 1.3-1.5 and an overlapping reconstruction increment (2-3 mm). In patients with dental fillings a short additional spiral parallel to the corpus of the mandible reduces artifacts behind the dental arches and improves the diagnostic value of CT. For the assessment of the base of the skull, the orbital floor, the palate and paranasal sinuses an additional examination in the coronal plane is helpful. Secondary coronal reconstructions of axial scans are helpful in the evaluation of the crossing of the midline by small tumors of the tongue base or palate. For an optimal vascular or tissue contrast a sufficient volume of contrast medium and a start delay greater than 70-80 s are necessary. In our opinion the best results can be achieved with a volume of 150 ml, a flow of 2.5 ml/s and a start delay of 80 s. Dynamic enhanced CT is only necessary in some special cases. There is clear indication for dynamic enhanced CT where a glomus tumor is suspected. Additional functional CT imaging during i-phonation and/or Valsalva's maneuver are of great importance to prove vocal cords mobility. Therefore, imaging during i-phonation is an elemental part of every thorough examination of the hypopharynx and larynx region. Multislice-spiral-CT allows almost isotropic imaging of the head and neck region and improves the assessment of tumor spread and lymph node metastases in arbitrary oblique planes. Thin structures (the base of the skull, the orbital floor, the hard palate) as well as the floor of the mouth can be evaluated sufficiently with multiplanar reformations. Usually, additional coronal scanning is not necessary with multislice-spiral-CT. Multislice-spiral-CT is especially advantageous in defining the critical relationships of tumor and lymph node metastases and for functional imaging of the hypopharynx and larynx not only in the

  16. Is correction necessary when clinically determining quantitative cerebral perfusion parameters from multi-slice dynamic susceptibility contrast MR studies?

    International Nuclear Information System (INIS)

    Salluzzi, M; Frayne, R; Smith, M R

    2006-01-01

    Several groups have modified the standard singular value decomposition (SVD) algorithm to produce delay-insensitive cerebral blood flow (CBF) estimates from dynamic susceptibility contrast (DSC) perfusion studies. However, new dependences of CBF estimates on bolus arrival times and slice position in multi-slice studies have been recently recognized. These conflicting findings can be reconciled by accounting for several experimental and algorithmic factors. Using simulation and clinical studies, the non-simultaneous measurement of arterial and tissue concentration curves (relative slice position) in a multi-slice study is shown to affect time-related perfusion parameters, e.g. arterial-tissue-delay measurements. However, the current clinical impact of relative slice position on amplitude-related perfusion parameters, e.g. CBF, can be expected to be small unless any of the following conditions are present individually or in combination: (a) high concentration curve signal-to-noise ratios, (b) small tissue mean transit times, (c) narrow arterial input functions or (d) low temporal resolution of the DSC image sequence. Recent improvements in magnetic resonance (MR) technology can easily be expected to lead to scenarios where these effects become increasingly important sources of inaccuracy for all perfusion parameter estimates. We show that using Fourier interpolated (high temporal resolution) residue functions reduces the systematic error of the perfusion parameters obtained from multi-slice studies

  17. Pumping Characteristics of a Helical Screw Agitator with a Draught Tube

    Science.gov (United States)

    Hwang, Jung-Hoon; Kim, Youn-Jea

    In the use of helical type agitator, the mixing process is usually restricted to the laminar flow regime. Common examples of laminar mixing are found where the fluid has a very high viscosity, i.e., pseudoplastic fluids. It can be indicated that a helical type agitator is sufficiently suited to the creeping flow mixing. The pumping characteristic of a Helical Screw Agitator with a draught tube (HSA) is required to evaluate its capacity for the optimal configuration of the mixing chamber. It could be executed by changing some parameters such as the number of helix, the angular velocity and the rotating direction and so on. In this study, the numerical simulation was carried out with the Eulerian multiphase mixture model and the moving mesh approximation. Some of the optimum design parameters have been developed with the aid of numerical data from the Computational Fluid Dynamics (CFD) analysis. Using the commercial code, Fluent, the pumping characteristics in the HSA are investigated from the rheological properties, and the results are graphically depicted.

  18. Follow-up after stent insertion in the tracheobronchial tree: role of helical computed tomography in comparison with fiberoptic bronchoscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ferretti, G.R.; Kocier, M.; Calaque, O.; Coulomb, M. [Service Central de Radiologie et Imagerie Medicale, INSERM EMI 9924, CHU, BP 217, 38043, Grenoble Cedex 9 (France); Arbib, F.; Pison, C. [Departement de Medecine Aigue Specialisee (DMAS), CHU Grenoble, CHU, BP 217, 38043, Grenoble Cedex 9 (France); Righini, C. [Service d' Oto Rhino Laryngologie, CHU Grenoble, BP 217, 38043, Grenoble Cedex 9 (France)

    2003-05-01

    The aim of this study was to compare helical CT with fiberoptic bronchoscopy findings to appraise the medium-term results of proximal-airways stenting. Twenty-five patients with 28 endobronchial metallic stents inserted for local advanced malignancy (n=13) or benign diseases (n=12) underwent follow-up CT from 3 days to 50 months (mean 8 months). All studies were obtained using helical CT with subsequent multiplanar reformation and three-dimensional reconstruction including virtual bronchoscopy. The location, shape, and patency of stents and adjacent airway were assessed. The results of CT were compared with the results of fiberoptic bronchoscopy obtained with a mean delay of 2.5 days (SD 9 days) after CT scan. Twelve stents (43%) remained in their original position, patent and without deformity. Sixteen stents were associated with local complications: migration (n=6); external compression with persistent stenosis (n=4); local recurrence of malignancy (n=4); fracture (n=1); and non-congruence between the airway and the stent (n=1). The CT demonstrated all the significant abnormalities demonstrated at fiberoptic bronchoscopy except two moderate stenoses (20%) related to granulomata at the origin of the stent. Ten of 14 stents inserted for benign conditions were without complications as compared with 2 of 14 in malignant conditions (p=0.008). Computed tomography is an accurate noninvasive method for evaluating endobronchial stents. The CT is a useful technique for follow-up of patients who have undergone endobronchial stenting. (orig.)

  19. Follow-up after stent insertion in the tracheobronchial tree: role of helical computed tomography in comparison with fiberoptic bronchoscopy

    International Nuclear Information System (INIS)

    Ferretti, G.R.; Kocier, M.; Calaque, O.; Coulomb, M.; Arbib, F.; Pison, C.; Righini, C.

    2003-01-01

    The aim of this study was to compare helical CT with fiberoptic bronchoscopy findings to appraise the medium-term results of proximal-airways stenting. Twenty-five patients with 28 endobronchial metallic stents inserted for local advanced malignancy (n=13) or benign diseases (n=12) underwent follow-up CT from 3 days to 50 months (mean 8 months). All studies were obtained using helical CT with subsequent multiplanar reformation and three-dimensional reconstruction including virtual bronchoscopy. The location, shape, and patency of stents and adjacent airway were assessed. The results of CT were compared with the results of fiberoptic bronchoscopy obtained with a mean delay of 2.5 days (SD 9 days) after CT scan. Twelve stents (43%) remained in their original position, patent and without deformity. Sixteen stents were associated with local complications: migration (n=6); external compression with persistent stenosis (n=4); local recurrence of malignancy (n=4); fracture (n=1); and non-congruence between the airway and the stent (n=1). The CT demonstrated all the significant abnormalities demonstrated at fiberoptic bronchoscopy except two moderate stenoses (20%) related to granulomata at the origin of the stent. Ten of 14 stents inserted for benign conditions were without complications as compared with 2 of 14 in malignant conditions (p=0.008). Computed tomography is an accurate noninvasive method for evaluating endobronchial stents. The CT is a useful technique for follow-up of patients who have undergone endobronchial stenting. (orig.)

  20. Anomalous origin of coronary artery: the role of multislice CT Angiography: a case report and literature review

    Energy Technology Data Exchange (ETDEWEB)

    Rabelo, Daniel Rocha; Barros, Marcio Vinicius Lins; Nunes, Maria do Carmo Pereira; Siqueira, Maria Helena Albernaz, E-mail: marciovlbarros@uol.com.br [Hospital Mater Dei, Belo Horizonte, MG (Brazil)

    2012-07-15

    Anomalous origin of coronary arteries is a relatively rare entity and can present different clinical forms. Recently, CT angiography of the coronary arteries have demonstrated an important role in the diagnosis and management of these anomalies. We present the case of a young female without significant comorbidities who presented with cardiopulmonary arrest, being revived by a team of customer service mobile emergency. After completion of multislice CT angiography of the coronary arteries was observed anomalous origin of left main coronary artery in the right coronary artery, no signs of extrinsic compression. Patient received a defibrillator and had an uneventful follow-up performed. Multislice CT angiography is minimally invasive diagnostic methods to detect the origin and trajectory of the coronary arteries, allowing an alternative to cardiac catheterization for evaluation of patients with anomalous origin of coronary arteries. (author)

  1. Dynamics and deformability of α-, 310- and π-helices

    Directory of Open Access Journals (Sweden)

    Narwani Tarun Jairaj

    2018-01-01

    Full Text Available Protein structures are often represented as seen in crystals as (i rigid macromolecules (ii with helices, sheets and coils. However, both definitions are partial because (i proteins are highly dynamic macromolecules and (ii the description of protein structures could be more precise. With regard to these two points, we analyzed and quantified the stability of helices by considering α-helices as well as 310- and π-helices. Molecular dynamic (MD simulations were performed on a large set of 169 representative protein domains. The local protein conformations were followed during each simulation and analyzed. The classical flexibility index (B-factor was confronted with the MD root mean square flexibility (RMSF index. Helical regions were classified according to their level of helicity from high to none. For the first time, a precise quantification showed the percentage of rigid and flexible helices that underlie unexpected behaviors. Only 76.4% of the residues associated with α-helices retain the conformation, while this tendency drops to 40.5% for 310-helices and is never observed for π-helices. α-helix residues that do not remain as an α-helix have a higher tendency to assume β-turn conformations than 310- or π-helices. The 310-helices that switch to the α-helix conformation have a higher B-factor and RMSF values than the average 310-helix but are associated with a lower accessibility. Rare π-helices assume a β-turn, bend and coil conformations, but not α- or 310-helices. The view on π-helices drastically changes with the new DSSP (Dictionary of Secondary Structure of Proteins assignment approach, leading to behavior similar to 310-helices, thus underlining the importance of secondary structure assignment methods.

  2. A multislice theory of electron inelastic scattering in a solid

    International Nuclear Information System (INIS)

    Wang, Z.L.

    1989-01-01

    A multislice theory is proposed to solve Yoshioka's coupling equations for elastic and inelastic scattered high-energy electrons in a solid. This method is capable, in principle, of including the non-periodic crystal structures and the electron multiple scattering among all the excited states in the calculations. It is proved that the proposed theory for calculating the energy-filtered inelastic images, based on the physical optics approach, is equivalent to the quantum-mechanical theory under some approximations. The basic theory of simulating the energy-filtered inelastic image of core-shell losses and thermal diffuse scattering is outlined. (orig.)

  3. Helical Confinement Concepts

    Energy Technology Data Exchange (ETDEWEB)

    Beidler, C; Brakel, R; Burhenn, R; Dinklage, A; Erckmann, V; Feng, Y; Geiger, J; Hartmann, D; Hirsch, M; Jaenicke, R; Koenig, R; Laqua, H P; Maassberg, H; Wagner, F; Weller, A; Wobig, H [Max-Planck Institut fuer Plasmaphysik, EURATOM Association, Greifswald (Germany)

    2012-09-15

    Stellarators, conceived 1951 by Lyman Spitzer in Princeton, are toroidal devices that confine a plasma in a magnetic field which originates from currents in coils outside the plasma. A plasma current driven by external means, for example by an ohmic transformer, is not required for confinement. Supplying the desired poloidal field component by external coils leads to a helically structured plasma topology. Thus stellarators - or helical confinement devices - are fully three-dimensional in contrast to the toroidal (rotational) symmetry of tokamaks. As stellarators can be free of an inductive current, whose radial distribution depends on the plasma parameters, their equilibrium must not be established via the evolving plasma itself, but to a first order already given by the vacuum magnetic field. They do not need an active control (like positional feedback) and therefore cannot suffer from its failure. The outstanding conceptual advantage of stellarators is the potential of steady state plasma operation without current drive. As there is no need for current drive, the recirculating power is expected to be smaller than in equivalent tokamaks. The lack of a net current avoids current driven instabilities; specifically, no disruptions, no resistive wall modes and no conventional or neoclassical tearing modes appear. Second order pressure-driven currents (Pfirsch-Schlueter, bootstrap) exist but they can be modified and even minimized by the magnetic design. The magnetic configuration of helical devices naturally possesses a separatrix, which allows the implementation of a helically structured divertor for exhaust and impurity control. (author)

  4. A three-dimensional-weighted cone beam filtered backprojection (CB-FBP) algorithm for image reconstruction in volumetric CT-helical scanning

    International Nuclear Information System (INIS)

    Tang Xiangyang; Hsieh Jiang; Nilsen, Roy A; Dutta, Sandeep; Samsonov, Dmitry; Hagiwara, Akira

    2006-01-01

    Based on the structure of the original helical FDK algorithm, a three-dimensional (3D)-weighted cone beam filtered backprojection (CB-FBP) algorithm is proposed for image reconstruction in volumetric CT under helical source trajectory. In addition to its dependence on view and fan angles, the 3D weighting utilizes the cone angle dependency of a ray to improve reconstruction accuracy. The 3D weighting is ray-dependent and the underlying mechanism is to give a favourable weight to the ray with the smaller cone angle out of a pair of conjugate rays but an unfavourable weight to the ray with the larger cone angle out of the conjugate ray pair. The proposed 3D-weighted helical CB-FBP reconstruction algorithm is implemented in the cone-parallel geometry that can improve noise uniformity and image generation speed significantly. Under the cone-parallel geometry, the filtering is naturally carried out along the tangential direction of the helical source trajectory. By exploring the 3D weighting's dependence on cone angle, the proposed helical 3D-weighted CB-FBP reconstruction algorithm can provide significantly improved reconstruction accuracy at moderate cone angle and high helical pitches. The 3D-weighted CB-FBP algorithm is experimentally evaluated by computer-simulated phantoms and phantoms scanned by a diagnostic volumetric CT system with a detector dimension of 64 x 0.625 mm over various helical pitches. The computer simulation study shows that the 3D weighting enables the proposed algorithm to reach reconstruction accuracy comparable to that of exact CB reconstruction algorithms, such as the Katsevich algorithm, under a moderate cone angle (4 deg.) and various helical pitches. Meanwhile, the experimental evaluation using the phantoms scanned by a volumetric CT system shows that the spatial resolution along the z-direction and noise characteristics of the proposed 3D-weighted helical CB-FBP reconstruction algorithm are maintained very well in comparison to the FDK

  5. Multislice spiral computed tomography to determine the effects of a recruitment maneuver in experimental lung injury

    Energy Technology Data Exchange (ETDEWEB)

    Henzler, Dietrich; Rossaint, Rolf [University Hospital, RWTH Aachen, Anesthesiology Department, Aachen (Germany); Mahnken, Andreas H.; Wildberger, Joachim E.; Guenther, Rolf W. [University Hospital of the RWTH Aachen, Clinic of Diagnostic Radiology, Aachen (Germany); Kuhlen, Ralf [University Hospital of the RWTH Aachen, Operative Intensive Care Department, Aachen (Germany)

    2006-06-15

    Although recruitment of atelectatic lung is a common aim in acute respiratory distress syndrome (ARDS), the effects of a recruitment maneuver have not been assessed quantitatively. By multislice spiral CT (MSCT), we analyzed the changes in lung volumes calculated from the changes in the CT values of hyperinflated (V{sub HYP}), normally (V{sub NORM}), poorly (V{sub POOR}) and nonaerated (V{sub NON}) lung in eight mechanically ventilated pigs with saline lavage-induced acute lung injury before and after a recruitment maneuver. This was compared to single slice analysis near the diaphragm. The increase in aerated lung was mainly for V{sub POOR} and the less in V{sub NORM}. Total lung volume and intrathoracic gas increased. No differences were found for tidal volumes measured by spirometry or determined by CT. The inspiratory-expiratory volume differences were not different after the recruitment maneuver in V{sub NON} (from 62{+-}18 ml to 43{+-}26 ml, P=0.114), and in V{sub NORM} (from 216{+-}51 ml to 251{+-}37 ml, P=0.102). Single slice analysis significantly underestimated the increase in normally and poorly aerated lung. Quantitative analysis of lung volumes by whole lung MSCT revealed the increase of poorly aerated lung as the main mechanism of a standard recruitment maneuver. MSCT can provide additional information as compared to single slice CT. (orig.)

  6. Multislice spiral computed tomography to determine the effects of a recruitment maneuver in experimental lung injury

    International Nuclear Information System (INIS)

    Henzler, Dietrich; Rossaint, Rolf; Mahnken, Andreas H.; Wildberger, Joachim E.; Guenther, Rolf W.; Kuhlen, Ralf

    2006-01-01

    Although recruitment of atelectatic lung is a common aim in acute respiratory distress syndrome (ARDS), the effects of a recruitment maneuver have not been assessed quantitatively. By multislice spiral CT (MSCT), we analyzed the changes in lung volumes calculated from the changes in the CT values of hyperinflated (V HYP ), normally (V NORM ), poorly (V POOR ) and nonaerated (V NON ) lung in eight mechanically ventilated pigs with saline lavage-induced acute lung injury before and after a recruitment maneuver. This was compared to single slice analysis near the diaphragm. The increase in aerated lung was mainly for V POOR and the less in V NORM . Total lung volume and intrathoracic gas increased. No differences were found for tidal volumes measured by spirometry or determined by CT. The inspiratory-expiratory volume differences were not different after the recruitment maneuver in V NON (from 62±18 ml to 43±26 ml, P=0.114), and in V NORM (from 216±51 ml to 251±37 ml, P=0.102). Single slice analysis significantly underestimated the increase in normally and poorly aerated lung. Quantitative analysis of lung volumes by whole lung MSCT revealed the increase of poorly aerated lung as the main mechanism of a standard recruitment maneuver. MSCT can provide additional information as compared to single slice CT. (orig.)

  7. General architecture of the alpha-helical globule.

    Science.gov (United States)

    Murzin, A G; Finkelstein, A V

    1988-12-05

    A model is presented for the arrangement of alpha-helices in globular proteins. In the model, helices are placed on certain ribs of "quasi-spherical" polyhedra. The polyhedra are chosen so as to allow the close packing of helices around a hydrophobic core and to stress the collective interactions of the individual helices. The model predicts a small set of stable architectures for alpha-helices in globular proteins and describes the geometries of the helix packings. Some of the predicted helix arrangements have already been observed in known protein structures; others are new. An analysis of the three-dimensional structures of all proteins for which co-ordinates are available shows that the model closely approximates the arrangements and packing of helices actually observed. The average deviations of the real helix axes from those in the model polyhedra is +/- 20 degrees in orientation and +/- 2 A in position (1 A = 0.1 nm). We also show that for proteins that are not homologous, but whose helix arrangements are described by the same polyhedron, the root-mean-square difference in the position of the C alpha atoms in the helices is 1.6 to 3.0 A.

  8. Evidence for Mixed Helicity in Erupting Filaments

    Science.gov (United States)

    Muglach, K.; Wang, Y.-M.; Kliem, B.

    2009-09-01

    Erupting filaments are sometimes observed to undergo a rotation about the vertical direction as they rise. This rotation of the filament axis is generally interpreted as a conversion of twist into writhe in a kink-unstable magnetic flux rope. Consistent with this interpretation, the rotation is usually found to be clockwise (as viewed from above) if the post-eruption arcade has right-handed helicity, but counterclockwise if it has left-handed helicity. Here, we describe two non-active-region filament events recorded with the Extreme-Ultraviolet Imaging Telescope on the Solar and Heliospheric Observatory in which the sense of rotation appears to be opposite to that expected from the helicity of the post-event arcade. Based on these observations, we suggest that the rotation of the filament axis is, in general, determined by the net helicity of the erupting system, and that the axially aligned core of the filament can have the opposite helicity sign to the surrounding field. In most cases, the surrounding field provides the main contribution to the net helicity. In the events reported here, however, the helicity associated with the filament "barbs" is opposite in sign to and dominates that of the overlying arcade.

  9. Applications of 2D helical vortex dynamics

    DEFF Research Database (Denmark)

    Okulov, Valery; Sørensen, Jens Nørkær

    2010-01-01

    In the paper, we show how the assumption of helical symmetry in the context of 2D helical vortices can be exploited to analyse and to model various cases of rotating flows. From theory, examples of three basic applications of 2D dynamics of helical vortices embedded in flows with helical symmetry...... of the vorticity field are addressed. These included some of the problems related to vortex breakdown, instability of far wakes behind rotors and vortex theory of ideal rotors....

  10. Electronic Band Structure of Helical Polyisocyanides.

    Science.gov (United States)

    Champagne, Benoît; Liégeois, Vincent; Fripiat, Joseph G; Harris, Frank E

    2017-10-19

    Restricted Hartree-Fock computations are reported for a methyl isocyanide polymer (repeating unit -C═N-CH 3 ), whose most stable conformation is expected to be a helical chain. The computations used a standard contracted Gaussian orbital set at the computational levels STO-3G, 3-21G, 6-31G, and 6-31G**, and studies were made for two line-group configurations motivated by earlier work and by studies of space-filling molecular models: (1) A structure of line-group symmetry L9 5 , containing a 9-fold screw axis with atoms displaced in the axial direction by 5/9 times the lattice constant, and (2) a structure of symmetry L4 1 that had been proposed, containing a 4-fold screw axis with translation by 1/4 of the lattice constant. Full use of the line-group symmetry was employed to cause most of the computational complexity to depend only on the size of the asymmetric repeating unit. Data reported include computed bond properties, atomic charge distribution, longitudinal polarizability, band structure, and the convoluted density of states. Most features of the description were found to be insensitive to the level of computational approximation. The work also illustrates the importance of exploiting line-group symmetry to extend the range of polymer structural problems that can be treated computationally.

  11. Theoretical aspects of magnetic helicity

    International Nuclear Information System (INIS)

    Hammer, J.H.

    1985-01-01

    The magnetic helicity, usually defined as K=integralA.Bdv, where A is the vector potential and B the magnetic field, measures the topological linkage of magnetic fluxes. Helicity manifests itself in the twistedness and knottedness of flux tubes. Its significance is that it is an ideal MHD invariant. While the helicity formalism has proven very useful in understanding reversed field pinch and spheromak behavior, some problems exist in applying the method consistently for complex (e.g., toroidal) conductor geometries or in situations where magnetic flux penetrates conducting walls. Recent work has attempted to generalize K to allow for all possible geometries

  12. MH2c: Characterization of major histocompatibility α-helices - an information criterion approach.

    Science.gov (United States)

    Hischenhuber, B; Frommlet, F; Schreiner, W; Knapp, B

    2012-07-01

    Major histocompatibility proteins share a common overall structure or peptide binding groove. Two binding groove domains, on the same chain for major histocompatibility class I or on two different chains for major histocompatibility class II, contribute to that structure that consists of two α -helices ("wall") and a sheet of eight anti-parallel beta strands ("floor"). Apart from the peptide presented in the groove, the major histocompatibility α -helices play a central role for the interaction with the T cell receptor. This study presents a generalized mathematical approach for the characterization of these helices. We employed polynomials of degree 1 to 7 and splines with 1 to 2 nodes based on polynomials of degree 1 to 7 on the α -helices projected on their principal components. We evaluated all models with a corrected Akaike Information Criterion to determine which model represents the α -helices in the best way without overfitting the data. This method is applicable for both the stationary and the dynamic characterization of α -helices. By deriving differential geometric parameters from these models one obtains a reliable method to characterize and compare α -helices for a broad range of applications. Program title: MH 2 c (MH helix curves) Catalogue identifier: AELX_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AELX_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 327 565 No. of bytes in distributed program, including test data, etc.: 17 433 656 Distribution format: tar.gz Programming language: Matlab Computer: Personal computer architectures Operating system: Windows, Linux, Mac (all systems on which Matlab can be installed) RAM: Depends on the trajectory size, min. 1 GB (Matlab) Classification: 2.1, 4.9, 4.14 External routines: Curve

  13. Effects of Magnetic and Kinetic Helicities on the Growth of Magnetic Fields in Laminar and Turbulent Flows by Helical Fourier Decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Linkmann, Moritz; Sahoo, Ganapati; Biferale, Luca [Department of Physics and INFN, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Rome (Italy); McKay, Mairi; Berera, Arjun [School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, EH9 3FD, Edinburgh (United Kingdom)

    2017-02-10

    We present a numerical and analytical study of incompressible homogeneous conducting fluids using a helical Fourier representation. We analytically study both small- and large-scale dynamo properties, as well as the inverse cascade of magnetic helicity, in the most general minimal subset of interacting velocity and magnetic fields on a closed Fourier triad. We mainly focus on the dependency of magnetic field growth as a function of the distribution of kinetic and magnetic helicities among the three interacting wavenumbers. By combining direct numerical simulations of the full magnetohydrodynamics equations with the helical Fourier decomposition, we numerically confirm that in the kinematic dynamo regime the system develops a large-scale magnetic helicity with opposite sign compared to the small-scale kinetic helicity, a sort of triad-by-triad α -effect in Fourier space. Concerning the small-scale perturbations, we predict theoretically and confirm numerically that the largest instability is achived for the magnetic component with the same helicity of the flow, in agreement with the Stretch–Twist–Fold mechanism. Vice versa, in the presence of Lorentz feedback on the velocity, we find that the inverse cascade of magnetic helicity is mostly local if magnetic and kinetic helicities have opposite signs, while it is more nonlocal and more intense if they have the same sign, as predicted by the analytical approach. Our analytical and numerical results further demonstrate the potential of the helical Fourier decomposition to elucidate the entangled dynamics of magnetic and kinetic helicities both in fully developed turbulence and in laminar flows.

  14. Introduction of helical computed tomography affects patient selection for V/Q lung scan

    International Nuclear Information System (INIS)

    Zettinig, G.; Baudrexel, S.; Leitha, Th.

    2002-01-01

    Aim: Retrospective analysis for determination of the effect of helical computed tomography (HCT) on utilization of V/Q lung scanning to diagnose pulmonary embolism (PE) in a large general hospital. Methods: A total number of 2676 V/Q scans of in- and out-patients referred to our department between March 1992 and December 1998 and between April 1997 and December 1998 were analyzed by an identical group of nuclear physicians. Results: Neither the total number of annually performed V/Q scans (446 ± 135) nor the mean age of patients (56 years ± 17) changed significantly since the introduction of HCT. However, the referral pattern was different. The percentage of patients with high and intermediate probability for PE decreased significantly from 15.2% to 9.4% (p <0.01) and from 10.2% to 7.3% (p <0.05), respectively. Low probability scans significantly increased from 37.8% to 42.7% (p <0.05). The percentage of normal scans did not change significantly, however, there was a highly significant increase summarizing patients with normal and low probability scans (74.6% to 83.3%; p <0.01). Conclusion: The introduction of HCT affected the selection of patients referred for V/Q lung scanning since V/Q scanning was primarily used to exclude rather to confirm PE. (orig.)

  15. Electronic transport in single-helical protein molecules: Effects of multiple charge conduction pathways and helical symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Kundu, Sourav, E-mail: sourav.kunduphy@gmail.com; Karmakar, S.N.

    2016-07-15

    We propose a tight-binding model to investigate electronic transport properties of single helical protein molecules incorporating both the helical symmetry and the possibility of multiple charge transfer pathways. Our study reveals that due to existence of both the multiple charge transfer pathways and helical symmetry, the transport properties are quite rigid under influence of environmental fluctuations which indicates that these biomolecules can serve as better alternatives in nanoelectronic devices than its other biological counterparts e.g., single-stranded DNA.

  16. High-n helicity-induced shear Alfven eigenmodes

    International Nuclear Information System (INIS)

    Nakajima, N.; Cheng, C.Z.; Okamoto, M.

    1992-05-01

    The high-n Helicity-induced shear Alfven Eigenmodes (HAE) are considered both analytically and numerically for the straight helical magnetic system, where n is the toroidal mode number. The eigenmode equation for the high-n HAE modes is derived along the field line and with the aid of the averaging method is shown to reduce to the Mathieu equation asymptotically. The discrete HAE modes are shown to exist inside the continuum spectrum gaps. The continuous spectrum gaps appear around ω 2 = ω A 2 [N(lι-m)/2] 2 for N = 1,2,.., where ω A is the toroidal Alfven transit frequency, and l, m, and ι are the polarity of helical coils, the toroidal pitch number of helical coils, and the rotational transform, respectively. For the same ω A and ι, the frequency of the helical continuum gap is larger than that of the continuum gap in tokamak plasmas by |l-ι -1 m|. The polarity of helical coils l plays a crucial role in determining the spectrum gaps and the properties of the high-n HAE modes. The spectrum gaps near the magnetic axis are created by the helical ripple with circular flux surfaces for l = 1, and ≥ 3 helicals. For l = 2 helical systems, the spectrum gaps are created by the ellipticity of the flux surfaces. These analytical results for the continuum gaps and the existence of the high-n HAE modes in the continuum gaps are confirmed numerically for the l = 2 case, and we find that the HAE modes exist for mode structures with the even and the odd parities. (author)

  17. Employing Helicity Amplitudes for Resummation

    NARCIS (Netherlands)

    Moult, I.; Stewart, I.W.; Tackmann, F.J.; Waalewijn, W.J.

    2015-01-01

    Many state-of-the-art QCD calculations for multileg processes use helicity amplitudes as their fundamental ingredients. We construct a simple and easy-to-use helicity operator basis in soft-collinear effective theory (SCET), for which the hard Wilson coefficients from matching QCD onto SCET are

  18. The evaluation of anti-angiogenic treatment effects for implanted rabbit VX2 breast tumors using functional multi-slice spiral computed tomography (f-MSCT)

    International Nuclear Information System (INIS)

    Lei Zhen; Ma Heji; Xu Na; Xi Huanjiu

    2011-01-01

    Objective: Investigate the benefit of functional multi-slice spiral computed tomography (f-MSCT) perfusion imaging in the non-invasive assessment of targeted anti-angiogenesis therapy on an implanted rabbit VX2 breast tumor model. Method: 69 female pure New Zealand white rabbits were randomly assigned to one of the 4 groups and received treatment accordingly: control (saline), Endostar, neoadjuvant chemotherapy (Cyclophosphamide, Epirubicin and 5-Fluorouracil, CEF), combination therapy (Endostar and CEF). After 2 weeks of treatment, f-MSCT perfusion scannings were performed for all rabbits and information about blood flow (BF), blood volume (BV), mean transit time (MTT) and surface permeability (SP) was collected. After perfusion imaging, tumor tissues were sampled for immunohistochemistry and the Western blot test of VEGF protein expression. Results: (1) The VEGF expression level, measured by immunohistochemistry and Western blot, decreased by treatment group (control > Endostar > CEF > combination therapy). The same was true for the mean BF, BV, MTT and PS, which decreased from the control group to the combination therapy group gradually. The mean MTT level increased in reverse order from the control to the combination therapy group. The difference between any 2 groups on these measures was statistically significant (P < 0.05). (2) There was moderate positive correlation between VEGF expression and BE, BV, or PS level (P < 0.05) and a negative correlation between VEGF expression and MTT level for all 4 groups (P < 0.05). Conclusion: Therefore, f-MSCT can be used as a non-invasive approach to evaluate the effect of anti-angiogenic therapy for implanted rabbit VX2 breast tumors.

  19. The evaluation of anti-angiogenic treatment effects for implanted rabbit VX2 breast tumors using functional multi-slice spiral computed tomography (f-MSCT)

    Energy Technology Data Exchange (ETDEWEB)

    Lei Zhen, E-mail: leizhen2004@163.com [Department of Anatomy, Chinese Medical University, No. 92, Beiermalu Road, Heping District, Shenyang, 110001 (China) and Department of Radiology, The First Hospital of Liaoning Medical College, No. 2, Wuduan, Renmin Street, Jinzhou, 121001 (China); Ma Heji, E-mail: maheji9831@sina.com [Department of Radiology, The First Hospital of Liaoning Medical College, No. 2, Wuduan, Renmin Street, Jinzhou, 121001 (China); Xu Na, E-mail: xuna821230@sohu.com [Department of Radiology, The First Hospital of Liaoning Medical College, No. 2, Wuduan, Renmin Street, Jinzhou, 121001 (China); Xi Huanjiu, E-mail: xihuanjiu2004@yahoo.cn [Anthropology Institute, Liaoning Medical College, No. 40, Sanduan, Songpo Rd, Jinzhou, 121001 (China)

    2011-05-15

    Objective: Investigate the benefit of functional multi-slice spiral computed tomography (f-MSCT) perfusion imaging in the non-invasive assessment of targeted anti-angiogenesis therapy on an implanted rabbit VX2 breast tumor model. Method: 69 female pure New Zealand white rabbits were randomly assigned to one of the 4 groups and received treatment accordingly: control (saline), Endostar, neoadjuvant chemotherapy (Cyclophosphamide, Epirubicin and 5-Fluorouracil, CEF), combination therapy (Endostar and CEF). After 2 weeks of treatment, f-MSCT perfusion scannings were performed for all rabbits and information about blood flow (BF), blood volume (BV), mean transit time (MTT) and surface permeability (SP) was collected. After perfusion imaging, tumor tissues were sampled for immunohistochemistry and the Western blot test of VEGF protein expression. Results: (1) The VEGF expression level, measured by immunohistochemistry and Western blot, decreased by treatment group (control > Endostar > CEF > combination therapy). The same was true for the mean BF, BV, MTT and PS, which decreased from the control group to the combination therapy group gradually. The mean MTT level increased in reverse order from the control to the combination therapy group. The difference between any 2 groups on these measures was statistically significant (P < 0.05). (2) There was moderate positive correlation between VEGF expression and BE, BV, or PS level (P < 0.05) and a negative correlation between VEGF expression and MTT level for all 4 groups (P < 0.05). Conclusion: Therefore, f-MSCT can be used as a non-invasive approach to evaluate the effect of anti-angiogenic therapy for implanted rabbit VX2 breast tumors.

  20. Self-assembly of a double-helical complex of sodium.

    Science.gov (United States)

    Bell, T W; Jousselin, H

    1994-02-03

    Spontaneous self-organization of helical and multiple-helical molecular structures occurs on several levels in living organisms. Key examples are alpha-helical polypeptides, double-helical nucleic acids and helical protein structures, including F-actin, microtubules and the protein sheath of the tobacco mosaic virus. Although the self-assembly of double-helical transition-metal complexes bears some resemblance to the molecular organization of double-stranded DNA, selection between monohelical, double-helical and triple-helical structures is determined largely by the size and geometrical preference of the tightly bound metal. Here we present an example of double-helical assembly induced by the weaker and non-directional interactions of an alkali-metal ion with an organic ligand that is pre-organized into a coil. We have characterized the resulting complex by two-dimensional NMR and fast-atom-bombardment mass spectrometry. These results provide a step toward the creation of molecular tubes or ion channels consisting of intertwined coils.

  1. Helicity multiplexed broadband metasurface holograms.

    Science.gov (United States)

    Wen, Dandan; Yue, Fuyong; Li, Guixin; Zheng, Guoxing; Chan, Kinlong; Chen, Shumei; Chen, Ming; Li, King Fai; Wong, Polis Wing Han; Cheah, Kok Wai; Pun, Edwin Yue Bun; Zhang, Shuang; Chen, Xianzhong

    2015-09-10

    Metasurfaces are engineered interfaces that contain a thin layer of plasmonic or dielectric nanostructures capable of manipulating light in a desirable manner. Advances in metasurfaces have led to various practical applications ranging from lensing to holography. Metasurface holograms that can be switched by the polarization state of incident light have been demonstrated for achieving polarization multiplexed functionalities. However, practical application of these devices has been limited by their capability for achieving high efficiency and high image quality. Here we experimentally demonstrate a helicity multiplexed metasurface hologram with high efficiency and good image fidelity over a broad range of frequencies. The metasurface hologram features the combination of two sets of hologram patterns operating with opposite incident helicities. Two symmetrically distributed off-axis images are interchangeable by controlling the helicity of the input light. The demonstrated helicity multiplexed metasurface hologram with its high performance opens avenues for future applications with functionality switchable optical devices.

  2. Diagnosis of pelvic wall tumor on multislice CT

    International Nuclear Information System (INIS)

    Zhang Keyun; Deng Lequn; Lei Hongwei

    2011-01-01

    Objective: To evaluate the value of multi-slice CT (MSCT) in diagnosing pelvic wall tumors. Methods: MSCT of 21 cases of pelvic wall tumors including metastasis (10), neurogenic tumor (5), chondrosarcoma (2), chordoma (1), aneurysmal bone cyst (1), giant cell tumor (1), and osteochondroma (1) was retrospectively analyzed. Results: CT appearances of pelvic wall tumors include bony destruction and soft tissue masses. Common features were bone destruction in metastasis, expansion of the neuroforamen in neurogenic tumor, pleomorphic calcification in chondrosarcoma, lower sacral vertebral location of chordoma, iliac crest bone destruction in giant cell tumor, cauliflower-like nodules in osteochondroma. Conclusion: MSCT with three-dimensional volume rendering demonstrates well the tumor shape, size, extent, internal structure and relationship with the surrounding organs to aid diagnosis of pelvic wall tumors. (authors)

  3. Coronary artery bypass graft imaging using ECG-gated multislice computed tomography: Comparison with catheter angiography

    International Nuclear Information System (INIS)

    Moore, R.K.G.; Sampson, C.; MacDonald, S.; Moynahan, C.; Groves, D.; Chester, M.R.

    2005-01-01

    AIM: To compare the value of multislice computerized tomography (MSCT) in imaging coronary artery bypass grafts (CABGs) by direct quantitative comparison with standard invasive angiography. METHODS: Using MSCT, 50 consecutive patients who had previously undergone CABG surgery and had recently undergone invasive angiography for recurrent angina pectoris, were studied further using MSCT after intravenous injection of non-ionic contrast agent; cardiac imaging was performed during a single breath-hold. Graft anatomy was quantified, using both quantitative coronary angiography (QCA) and MSCT, by different investigators blinded to each other. Reproducibility was quantified using the standard error of the measurement expressed as a percentage in log-transformed values (CV%) and intraclass correlation (ICC). RESULTS: All 150 grafts were imaged using MSCT; only 4 patent grafts were not imaged using selective angiography. Good agreement was achieved between MSCT and QCA on assessment of proximal anastomoses (CV% 25.2, ICC 0.84), mid-vessel luminal diameter (CV% 15.5, ICC 0.91) and aneurysmal dilations (CV% 14.3). Reasonable agreement was reached on assessment of distal anastomoses (CV% 26.7, ICC 0.66) and categorization of distal run-off (ICC 0.73). Good agreement was observed for stenoses of over 50% luminal loss (CV% 8.7, ICC 0.97) but agreement on assessment of less severe lesions was poor (CV% 208.7, ICC 0.51). CONCLUSION: This study demonstrates that CABGs can be quantitatively evaluated using MSCT, and that significant lesions present in all CABG segments can be reliably identified. Agreement between MSCT and QCA for lesions of less than 50% luminal loss was poor

  4. Coronary artery bypass graft imaging using ECG-gated multislice computed tomography: Comparison with catheter angiography

    Energy Technology Data Exchange (ETDEWEB)

    Moore, R.K.G. [Cardiothoracic Centre, Liverpool (United Kingdom)]. E-mail: moore@roger.go-legend.net; Sampson, C. [Cardiothoracic Centre, Liverpool (United Kingdom); MacDonald, S. [Cardiothoracic Centre, Liverpool (United Kingdom); Moynahan, C. [Cardiothoracic Centre, Liverpool (United Kingdom); Groves, D. [National Refractory Angina Centre, Liverpool (United Kingdom); Chester, M.R. [National Refractory Angina Centre, Liverpool (United Kingdom)

    2005-09-01

    AIM: To compare the value of multislice computerized tomography (MSCT) in imaging coronary artery bypass grafts (CABGs) by direct quantitative comparison with standard invasive angiography. METHODS: Using MSCT, 50 consecutive patients who had previously undergone CABG surgery and had recently undergone invasive angiography for recurrent angina pectoris, were studied further using MSCT after intravenous injection of non-ionic contrast agent; cardiac imaging was performed during a single breath-hold. Graft anatomy was quantified, using both quantitative coronary angiography (QCA) and MSCT, by different investigators blinded to each other. Reproducibility was quantified using the standard error of the measurement expressed as a percentage in log-transformed values (CV%) and intraclass correlation (ICC). RESULTS: All 150 grafts were imaged using MSCT; only 4 patent grafts were not imaged using selective angiography. Good agreement was achieved between MSCT and QCA on assessment of proximal anastomoses (CV% 25.2, ICC 0.84), mid-vessel luminal diameter (CV% 15.5, ICC 0.91) and aneurysmal dilations (CV% 14.3). Reasonable agreement was reached on assessment of distal anastomoses (CV% 26.7, ICC 0.66) and categorization of distal run-off (ICC 0.73). Good agreement was observed for stenoses of over 50% luminal loss (CV% 8.7, ICC 0.97) but agreement on assessment of less severe lesions was poor (CV% 208.7, ICC 0.51). CONCLUSION: This study demonstrates that CABGs can be quantitatively evaluated using MSCT, and that significant lesions present in all CABG segments can be reliably identified. Agreement between MSCT and QCA for lesions of less than 50% luminal loss was poor.

  5. Beta-helical polymers from isocyanopeptides

    NARCIS (Netherlands)

    Cornelissen, J.J.L.M.; Donners, J.J.J.M.; Gelder, de R.; Graswinckel, W.S.; Metselaar, G.A.; Rowan, A.E.; Sommerdijk, N.A.J.M.; Nolte, R.J.M.

    2001-01-01

    Polymerization of isocyanopeptides results in the formation of high molecular mass polymers that fold in a proteinlike fashion to give helical strands in which the peptide chains are arranged in ß-sheets. The ß-helical polymers retain their structure in water and unfold in a cooperative process at

  6. Influence of convolution filtering on coronary plaque attenuation values: observations in an ex vivo model of multislice computed tomography coronary angiography

    International Nuclear Information System (INIS)

    Cademartiri, Filippo; Palumbo, Alessandro; La Grutta, Ludovico; Runza, Giuseppe; Maffei, Erica; Mollet, Nico R.; Hamers, Ronald; Bruining, Nico; Bartolotta, Tommaso V.; Midiri, Massimo; Somers, Pamela; Knaapen, Michiel; Verheye, Stefan

    2007-01-01

    Attenuation variability (measured in Hounsfield Units, HU) of human coronary plaques using multislice computed tomography (MSCT) was evaluated in an ex vivo model with increasing convolution kernels. MSCT was performed in seven ex vivo left coronary arteries sunk into oil followingthe instillation of saline (1/∞) and a 1/50 solution of contrast material (400 mgI/ml iomeprol). Scan parameters were: slices/collimation, 16/0.75 mm; rotation time, 375 ms. Four convolution kernels were used: b30f-smooth, b36f-medium smooth, b46f-medium and b60f-sharp. An experienced radiologist scored for the presence of plaques and measured the attenuation in lumen, calcified and noncalcified plaques and the surrounding oil. The results were compared by the ANOVA test and correlated with Pearson's test. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The mean attenuation values were significantly different between the four filters (p < 0.0001) in each structure with both solutions. After clustering for the filter, all of the noncalcified plaque values (20.8 ± 39.1, 14.2 ± 35.8, 14.0 ± 32.0, 3.2 ± 32.4 HU with saline; 74.7 ± 66.6, 68.2 ± 63.3, 66.3 ± 66.5, 48.5 ± 60.0 HU in contrast solution) were significantly different, with the exception of the pair b36f-b46f, for which a moderate-high correlation was generally found. Improved SNRs and CNRs were achieved by b30f and b46f. The use of different convolution filters significantly modified the attenuation values, while sharper filtering increased the calcified plaque attenuation and reduced the noncalcified plaque attenuation. (orig.)

  7. A morphological study of the mandibular molar region using reconstructed helical computed tomographic images

    International Nuclear Information System (INIS)

    Tsuno, Hiroaki; Noguchi, Makoto; Noguchi, Akira; Yoshida, Keiko; Tachinami, Yasuharu

    2010-01-01

    This study investigated the morphological variance in the mandibular molar region using reconstructed helical computed tomographic (CT) images. In addition, we discuss the necessity of CT scanning as part of the preoperative assessment process for dental implantation, by comparing the results with the findings of panoramic radiography. Sixty patients examined using CT as part of the preoperative assessment for dental implantation were analyzed. Reconstructed CT images were used to evaluate the bone quality and cross-sectional bone morphology of the mandibular molar region. The mandibular cortical index (MCI) and X-ray density ratio of this region were assessed using panoramic radiography in order to analyze the correlation between the findings of the CT images and panoramic radiography. CT images showed that there was a decrease in bone quality in cases with high MCI. Cross-sectional CT images revealed that the undercuts on the lingual side in the highly radiolucent areas in the basal portion were more frequent than those in the alveolar portion. This study showed that three-dimensional reconstructed CT images can help to detect variances in mandibular morphology that might be missed by panoramic radiography. In conclusion, it is suggested that CT should be included as an important examination tool before dental implantation. (author)

  8. Reducing task-based fMRI scanning time using simultaneous multislice echo planar imaging

    Energy Technology Data Exchange (ETDEWEB)

    Kiss, Mate [Hungarian Academy of Sciences, Brain Imaging Centre, Research Centre for Natural Sciences, Budapest (Hungary); Janos Szentagothai PhD School, MR Research Centre, Budapest (Hungary); National Institute of Clinical Neuroscience, Department of Neuroradiology, Budapest (Hungary); Hermann, Petra; Vidnyanszky, Zoltan; Gal, Viktor [Hungarian Academy of Sciences, Brain Imaging Centre, Research Centre for Natural Sciences, Budapest (Hungary)

    2018-03-15

    To maintain alertness and to remain motionless during scanning represent a substantial challenge for patients/subjects involved in both clinical and research functional magnetic resonance imaging (fMRI) examinations. Therefore, availability and application of new data acquisition protocols allowing the shortening of scan time without compromising the data quality and statistical power are of major importance. Higher order category-selective visual cortical areas were identified individually, and rapid event-related fMRI design was used to compare three different sampling rates (TR = 2000, 1000, and 410 ms, using state-of-the-art simultaneous multislice imaging) and four different scanning lengths to match the statistical power of the traditional scanning methods to high sampling-rate design. The results revealed that ∝ 4 min of the scan time with 1 Hz (TR = 1000 ms) sampling rate and ∝ 2 min scanning at ∝ 2.5 Hz (TR = 410 ms) sampling rate provide similar localization sensitivity and selectivity to that obtained with 11-min session at conventional, 0.5 Hz (TR = 2000 ms) sampling rate. Our findings suggest that task-based fMRI examination of clinical population prone to distress such as presurgical mapping experiments might substantially benefit from the reduced (20-40%) scanning time that can be achieved by the application of simultaneous multislice sequences. (orig.)

  9. Diagnosis of temporal bone diseases using three-dimensional images with multislice CT

    Energy Technology Data Exchange (ETDEWEB)

    Toyama, Yoshihiro; Togami, Taro; Murota, Makiko; Fukunaga, Kotaro; Hino, Ichiro; Sato, Katashi; Ohkawa, Motoomi [Kagawa Medical Univ., Miki (Japan)

    2001-08-01

    We evaluated the usefulness of three-dimensional images with multislice CT in the temporal bone diseases. Fifty-nine cases (26 with medial otitis, 8 choresteatoma, 10 congenital malformation, 3 high jugular bulb, 2 otosclerosis, and 10 others) were included in this study. In the ossicular and inner ear lesions, oblique multiplanar images of the long axis of each ossicle was useful the detection of abnormality. Structural deformity of ossicles and bony labyrinth were clearly delineated by surface rendering images. (author)

  10. Single-superfield helical-phase inflation

    Energy Technology Data Exchange (ETDEWEB)

    Ketov, Sergei V., E-mail: ketov@tmu.ac.jp [Department of Physics, Tokyo Metropolitan University, Minami-ohsawa 1-1, Hachioji-shi, Tokyo 192-0397 (Japan); Kavli Institute for the Physics and Mathematics of the Universe (IPMU), The University of Tokyo, Chiba 277-8568 (Japan); Institute of Physics and Technology, Tomsk Polytechnic University, 30 Lenin Ave., Tomsk 634050 (Russian Federation); Terada, Takahiro, E-mail: takahiro@hep-th.phys.s.u-tokyo.ac.jp [Department of Physics, The University of Tokyo, Tokyo 113-0033 (Japan); Deutsches Elektronen-Synchrotron (DESY), 22607 Hamburg (Germany)

    2016-01-10

    Large-field inflation in supergravity requires the approximate global symmetry needed to protect flatness of the scalar potential. In helical-phase inflation, the U(1) symmetry of the Kähler potential is assumed, the phase part of the complex scalar of a chiral superfield plays the role of inflaton, and the radial part is strongly stabilized. The original model of helical phase inflation, proposed by Li, Li and Nanopoulos (LLN), employs an extra (stabilizer) superfield. We propose a more economical new class of the helical phase inflationary models without a stabilizer superfield. As the specific examples, the quadratic, the natural, and the Starobinsky-type inflationary models are studied in our approach.

  11. An experimental study for qualitatively diagnosing stapes lesions by helical 3-dimensional CT

    International Nuclear Information System (INIS)

    Kawaue, Akifumi; Kuki, Kiyonori; Yamanaka, Noboru; Nishimura, Michihiko

    2001-01-01

    To evaluate qualitative diagnosis of stapes lesions by 3-dimensional computed tomography (3D-CT) combined with superselective image processing (3D-SS) of stapes, we studied helical 3D-CT on a phantom model of the temporal bone. Two stapes models were used-1 made from the bone filler, Celatite, consistent in bone density but changing in cross sectional area, and the other made from an apacerum rod used in quantitative computed tomography (QCT), consistent in cross sectional area but changing in bone density. These stapes models were put into a skull phantom and analyzed by helical 3D-CT. The influence of the tympanic cavity conditions on CT images of stapes was evaluated by filling the phantom model with Vaseline following 3D selective reconstruction. In all stapes models, lowering the lower CT window width threshold resulted in an enlarged cross-sectional area of the model. The higher the bone density, the lower the increase in cross-sectional area in the image. The stapes model with lower density had greater influence on the imaging by tympanic cavity conditions and was likely to be misdiagnosed as showing higher bone density. Based on the experimental study, 3D-SS by helical 3D-CT appears to be a useful measure for qualitatively diagnosing stapes lesions. (author)

  12. A real-scale helical coil winding trial of the Large Helical Device

    International Nuclear Information System (INIS)

    Senba, T.; Yamamoto, T.; Tamaki, T.; Asano, K.; Suzuki, S.; Yamauchi, T.; Uchida, K.; Nakanishi, K.; Yamagiwa, T.; Suzuki, S.; Miyoshi, R.; Sasa, H.; Watanabe, S.; Tatemura, M.; Hatada, N.; Yamaguchi, S.; Imagawa, S.; Yanagi, N.; Satow, T.; Yamamoto, J.; Motojima, O.

    1995-01-01

    A real-scale helical coil winding trial of the Large Helical Device (LHD) has been conducted for a study of coil winding configuration and winding methods and for exhibiting the state of the art. It includes construction and test run of a specifically designed winding machine and development of various manufacturing methods for accurate coil winding. It has been carried out in Hitachi Works before in situ winding, and has provided much needed engineering data for construction of the LHD. (orig.)

  13. On the helicity of open magnetic fields

    International Nuclear Information System (INIS)

    Prior, C.; Yeates, A. R.

    2014-01-01

    We reconsider the topological interpretation of magnetic helicity for magnetic fields in open domains, and relate this to the relative helicity. Specifically, our domains stretch between two parallel planes, and each of these ends may be magnetically open. It is demonstrated that, while the magnetic helicity is gauge-dependent, its value in any gauge may be physically interpreted as the average winding number among all pairs of field lines with respect to some orthonormal frame field. In fact, the choice of gauge is equivalent to the choice of reference field in the relative helicity, meaning that the magnetic helicity is no less physically meaningful. We prove that a particular gauge always measures the winding with respect to a fixed frame, and propose that this is normally the best choice. For periodic fields, this choice is equivalent to measuring relative helicity with respect to a potential reference field. However, for aperiodic fields, we show that the potential field can be twisted. We prove by construction that there always exists a possible untwisted reference field.

  14. Dosimetry in computed tomography

    International Nuclear Information System (INIS)

    Andisco, D.; Blanco, S.; Buzzia, A.E.

    2014-01-01

    Objective: The amount of computed tomography (CT) studies that are performed each year in the world is growing exponentially mainly due to the incorporation of multislice CT that allows studies in a few seconds. But, despite the benefit received by patients with the diagnosis, radiation dose is a concern in the professional community and it has be reduced as much as reasonably possible. This article describes the main dosimetric CT units used in order to work with this practice easily, using the values that provide modern equipment and internationally known reference levels. (authors) [es

  15. Acute pulmonary embolism in helical computed tomography

    International Nuclear Information System (INIS)

    Paslawski, M.

    2005-01-01

    Pulmonary embolism is a common condition in which diagnostic and therapeutic delays contribute to substantial morbidity and mortality. Clinical diagnosis is difficult because the signs and symptoms re unspecific, and a differential diagnosis is extensive, including pneumonia or bronchitis, asthma, myocardial infraction, pulmonary edema, anxiety, dissection of the aorta, pericardial tamponade, lung cancer, primary pulmonary hypertension, rib fracture, and pneumothorax. The purpose of the study was to present the use of CT in diagnosing acute pulmonary embolism. A group of 23 patients with clinically suspected pulmonary embolism underwent CT examination with a helical CT scanner (Somatom Emotion, Siemens) before and after administration of 150 ml of Ultravist. Pulmonary embolism was found in the CT examinations of 13 patients. In two of these it was a central filling defect. Amputation of the artery was found in one. Parietal filling defect in three patients formed an acute angle with the vessel walls. Saddle emboli appearing as filling defects in the contrast column that hung over vessel bifurcations was found in two patients. In five patients,emboli were found in small segmental arteries. CT provides information not only on the pulmonary arteries, but also on the lung parenchyma, hila, mediastinum, and the heart. Alternative findings may be identified by CT chest examination, stablishing alternative diagnoses, including pulmonary disorders (such as pneumonia or fibrosis), pleural abnormalities, and cardiovascular disease (such as aortic dissection or pericardial tamponade). Another advantage of the CT is its widespread availability.(author)

  16. Helicity-flip in particle production on nuclei

    International Nuclear Information System (INIS)

    Faeldt, G.

    1977-01-01

    Coherent nuclear production processes are generally analyzed assuming helicity conserving production amplitudes. In view of the uncertainties of the actual helicity structure this could be a dangerous assumption. It is shown that helicity-flip contributions might be part of the explanation of the small effective (pππ)-nucleon cross sections observed in coherent production. (Auth.)

  17. Effective dose estimation in whole-body multislice CT in paediatric trauma patients

    Energy Technology Data Exchange (ETDEWEB)

    Munk, Robin D.; Saueressig, Ulrich; Kotter, Elmar; Langer, Mathias; Bley, Thorsten A. [University Hospital, Department of Radiology, Freiburg im Breisgau (Germany); Strohm, Peter C.; Zwingmann, Joern; Suedkamp, Norbert P. [University Hospital, Department of Orthopaedic and Trauma Surgery, Freiburg im Breisgau (Germany); Uhl, Markus [University Hospital, Department of Radiology, Section of Paediatric Radiology, Freiburg im Breisgau (Germany)

    2009-03-15

    The number of multislice CT (MSCT) scans performed in polytraumatized children has increased rapidly. There is growing concern regarding the radiation dose in MSCT and its long-term consequences, especially in children. To determine the effective dose to polytraumatized children who undergo whole-body MSCT. A total of 51 traumatized children aged 0-16 years underwent a polytrauma protocol CT scan between November 2004 and August 2006 at our institution. The effective dose was calculated retrospectively by a computer program (CT-Expo 1.5, Hannover, Germany). The mean effective dose was 20.8 mSv (range 8.6-48.9 mSv, SD{+-}7.9 mSv). There was no statistically significant difference in the effective dose between male and female patients. Whole-body MSCT is a superior diagnostic tool in polytraumatized children with 20.8 mSv per patient being a justified mean effective dose. In a potentially life-threatening situation whole-body MSCT provides the clinicians with relevant information to initiate life-saving therapy. Radiologists should use special paediatric protocols that include dose-saving mechanisms to keep the effective dose as low as possible. Further studies are needed to examine and advance dose-saving strategies in MSCT, especially in children. (orig.)

  18. the complementary roles of radiology and nuclear medicine

    African Journals Online (AJOL)

    blood-brain barrier and liver masses has been replaced by ultrasound, computerised ... Radiology has experienced exponential growth with regard to helical multi-slice CT ... allows mapping of cerebral cortical function by utilising blood oxygen ..... A patient who required open reduction and internal fixation of a fractured left.

  19. Multislice imaging of integrated circuits by precession X-ray ptychography.

    Science.gov (United States)

    Shimomura, Kei; Hirose, Makoto; Takahashi, Yukio

    2018-01-01

    A method for nondestructively visualizing multisection nanostructures of integrated circuits by X-ray ptychography with a multislice approach is proposed. In this study, tilt-series ptychographic diffraction data sets of a two-layered circuit with a ∼1.4 µm gap at nine incident angles are collected in a wide Q range and then artifact-reduced phase images of each layer are successfully reconstructed at ∼10 nm resolution. The present method has great potential for the three-dimensional observation of flat specimens with thickness on the order of 100 µm, such as three-dimensional stacked integrated circuits based on through-silicon vias, without laborious sample preparation.

  20. Cryo-EM Structure Determination Using Segmented Helical Image Reconstruction.

    Science.gov (United States)

    Fromm, S A; Sachse, C

    2016-01-01

    Treating helices as single-particle-like segments followed by helical image reconstruction has become the method of choice for high-resolution structure determination of well-ordered helical viruses as well as flexible filaments. In this review, we will illustrate how the combination of latest hardware developments with optimized image processing routines have led to a series of near-atomic resolution structures of helical assemblies. Originally, the treatment of helices as a sequence of segments followed by Fourier-Bessel reconstruction revealed the potential to determine near-atomic resolution structures from helical specimens. In the meantime, real-space image processing of helices in a stack of single particles was developed and enabled the structure determination of specimens that resisted classical Fourier helical reconstruction and also facilitated high-resolution structure determination. Despite the progress in real-space analysis, the combination of Fourier and real-space processing is still commonly used to better estimate the symmetry parameters as the imposition of the correct helical symmetry is essential for high-resolution structure determination. Recent hardware advancement by the introduction of direct electron detectors has significantly enhanced the image quality and together with improved image processing procedures has made segmented helical reconstruction a very productive cryo-EM structure determination method. © 2016 Elsevier Inc. All rights reserved.

  1. Modern diagnostic assessment of the upper urinary tract using multislice CT urography; Moderne Diagnostik des oberen Harntraktes mittels Mehrschicht-CT-Urographie

    Energy Technology Data Exchange (ETDEWEB)

    Kemper, J.; Adam, G.; Nolte-Ernsting, C. [Klinik und Poliklinik fuer Diagnostische und Interventionelle Radiologie, Universitaetsklinikum Hamburg-Eppendorf (Germany)

    2006-11-15

    The advent of Multislice Computed Tomography (MSCT) has made evaluation of the entire urinary tract with high-resolution sections during a single breath-hold a reality. Acquisition of multiple thin overlapping slices provides excellent two-dimensional (2D) and three-dimensional (3D) reformations of the urinary tract. The concept of 'Multislice CT Urography (MSCTU)' has emerged from this technical improvement. As a result, a wide range of pathologies inside and outside the urinary tract can be identified. During the last several years, MSCTU has challenged intravenous urography (IVU) in the evaluation of urinary tract abnormalities. Compared with IVU, MSCT(U) is more sensitive and specific in the detection and characterization of a variety of urinary tract disorders, including renal masses and urolithiasis. The main advantage of IVU has been its ability to offer excellent delineation of kidney basin cup system and ureteral anatomy and to depict subtle uroepithelial abnormalities. MSCTU has already shown promising results for overcoming this challenge. Optimal opacification and distension appear to be an essential requirement for a thorough evaluation of the collecting system. Dedicated preparation strategies have been developed to meet these technical difficulties. The biggest disadvantage of MSCTU is the significant radiation exposure. For broad routine clinical application, there is still a need for dose reduction protocols despite the ongoing technical developments in MSCTU. In this article, we outline the different concepts of technical processing for MSCTU and summarize the current role of MSCTU in the evaluation of the upper urinary tract. (orig.)

  2. HEMISPHERIC HELICITY TREND FOR SOLAR CYCLE 24

    International Nuclear Information System (INIS)

    Hao Juan; Zhang Mei

    2011-01-01

    Using vector magnetograms obtained with the Spectro-polarimeter (SP) on board Hinode satellite, we studied two helicity parameters (local twist and current helicity) of 64 active regions that occurred in the descending phase of solar cycle 23 and the ascending phase of solar cycle 24. Our analysis gives the following results. (1) The 34 active regions of the solar cycle 24 follow the so-called hemispheric helicity rule, whereas the 30 active regions of the solar cycle 23 do not. (2) When combining all 64 active regions as one sample, they follow the hemispheric helicity sign rule as in most other observations. (3) Despite the so-far most accurate measurement of vector magnetic field given by SP/Hinode, the rule is still weak with large scatters. (4) The data show evidence of different helicity signs between strong and weak fields, confirming previous result from a large sample of ground-based observations. (5) With two example sunspots we show that the helicity parameters change sign from the inner umbra to the outer penumbra, where the sign of penumbra agrees with the sign of the active region as a whole. From these results, we speculate that both the Σ-effect (turbulent convection) and the dynamo have contributed in the generation of helicity, whereas in both cases turbulence in the convection zone has played a significant role.

  3. Ion temperature gradient modes in toroidal helical systems

    Energy Technology Data Exchange (ETDEWEB)

    Kuroda, T. [Graduate University for Advanced Studies, Toki, Gifu (Japan); Sugama, H.; Kanno, R.; Okamoto, M.

    2000-04-01

    Linear properties of ion temperature gradient (ITG) modes in helical systems are studied. The real frequency, growth rate, and eigenfunction are obtained for both stable and unstable cases by solving a kinetic integral equation with proper analytic continuation performed in the complex frequency plane. Based on the model magnetic configuration for toroidal helical systems like the Large Helical Device (LHD), dependences of the ITG mode properties on various plasma equilibrium parameters are investigated. Particularly, relative effects of {nabla}B-curvature drifts driven by the toroidicity and by the helical ripples are examined in order to compare the ITG modes in helical systems with those in tokamaks. (author)

  4. Ion temperature gradient modes in toroidal helical systems

    International Nuclear Information System (INIS)

    Kuroda, T.; Sugama, H.; Kanno, R.; Okamoto, M.

    2000-04-01

    Linear properties of ion temperature gradient (ITG) modes in helical systems are studied. The real frequency, growth rate, and eigenfunction are obtained for both stable and unstable cases by solving a kinetic integral equation with proper analytic continuation performed in the complex frequency plane. Based on the model magnetic configuration for toroidal helical systems like the Large Helical Device (LHD), dependences of the ITG mode properties on various plasma equilibrium parameters are investigated. Particularly, relative effects of ∇B-curvature drifts driven by the toroidicity and by the helical ripples are examined in order to compare the ITG modes in helical systems with those in tokamaks. (author)

  5. Rapid fusion of 2D X-ray fluoroscopy with 3D multislice CT for image-guided electrophysiology procedures

    Science.gov (United States)

    Zagorchev, Lyubomir; Manzke, Robert; Cury, Ricardo; Reddy, Vivek Y.; Chan, Raymond C.

    2007-03-01

    Interventional cardiac electrophysiology (EP) procedures are typically performed under X-ray fluoroscopy for visualizing catheters and EP devices relative to other highly-attenuating structures such as the thoracic spine and ribs. These projections do not however contain information about soft-tissue anatomy and there is a recognized need for fusion of conventional fluoroscopy with pre-operatively acquired cardiac multislice computed tomography (MSCT) volumes. Rapid 2D-3D integration in this application would allow for real-time visualization of all catheters present within the thorax in relation to the cardiovascular anatomy visible in MSCT. We present a method for rapid fusion of 2D X-ray fluoroscopy with 3DMSCT that can facilitate EP mapping and interventional procedures by reducing the need for intra-operative contrast injections to visualize heart chambers and specialized systems to track catheters within the cardiovascular anatomy. We use hardware-accelerated ray-casting to compute digitally reconstructed radiographs (DRRs) from the MSCT volume and iteratively optimize the rigid-body pose of the volumetric data to maximize the similarity between the MSCT-derived DRR and the intra-operative X-ray projection data.

  6. ICRF heating on helical devices

    International Nuclear Information System (INIS)

    Rasmussen, D.A.; Lyon, J.F.; Hoffman, D.J.; Murakami, M.; England, A.C.; Wilgen, J.B.; Jaeger, E.F.; Wang, C.; Batchelor, D.B.

    1995-01-01

    Ion cyclotron range of frequency (ICRF) heating is currently in use on CHS and W7-AS and is a major element of the heating planned for steady state helical devices. In helical devices, the lack of a toroidal current eliminates both disruptions and the need for ICRF current drive, simplifying the design of antenna structures as compared to tokamak applications. However the survivability of plasma facing components and steady state cooling issues are directly applicable to tokamak devices. Results from LHD steady state experiments should be available on a time scale to strongly influence the next generation of steady state tokamak experiments. The helical plasma geometry provides challenges not faced with tokamak ICRF heating, including the potential for enhanced fast ion losses, impurity accumulation, limited access for antenna structures, and open magnetic field lines in the plasma edge. The present results and near term plans provide the basis for steady state ICRF heating of larger helical devices. An approach which includes direct electron, mode conversion, ion minority and ion Bernstein wave heating addresses these issues

  7. ICRF heating on helical devices

    International Nuclear Information System (INIS)

    Rasmussen, D.A.; Lyon, J.F.; Hoffman, D.J.

    1995-01-01

    Ion cyclotron range of frequency (ICRF) heating is currently in use on CHS and W7AS and is a major element of the heating planned for steady state helical devices. In helical devices, the lack of a toroidal current eliminates both disruptions and the need for ICRF current drive, simplifying the design of antenna structures as compared to tokamak applications. However the survivability of plasma facing components and steady state cooling issues are directly applicable to tokamak devices. Results from LHD steady state experiments should be available on a time scale to strongly influence the next generation of steady state tokamak experiments. The helical plasma geometry provides challenges not faced with tokamak ICRF heating, including the potential for enhanced fast ion losses, impurity accumulation, limited access for antenna structures, and open magnetic field lines in the plasma edge. The present results and near term plans provide the basis for steady state ICRF heating of larger helical devices. An approach which includes direct electron, mode conversion, ion minority and ion Bernstein wave heating addresses these issues

  8. Generalized helicity and Beltrami fields

    International Nuclear Information System (INIS)

    Buniy, Roman V.; Kephart, Thomas W.

    2014-01-01

    We propose covariant and non-abelian generalizations of the magnetic helicity and Beltrami equation. The gauge invariance, variational principle, conserved current, energy–momentum tensor and choice of boundary conditions elucidate the subject. In particular, we prove that any extremal of the Yang–Mills action functional 1/4 ∫ Ω trF μν F μν d 4 x subject to the local constraint ε μναβ trF μν F αβ =0 satisfies the covariant non-abelian Beltrami equation. -- Highlights: •We introduce the covariant non-abelian helicity and Beltrami equation. •The Yang–Mills action and instanton term constraint lead to the Beltrami equation. •Solutions of the Beltrami equation conserve helicity

  9. Helical-D pinch

    International Nuclear Information System (INIS)

    Schaffer, M.J.

    1997-08-01

    A stabilized pinch configuration is described, consisting of a D-shaped plasma cross section wrapped tightly around a guiding axis. The open-quotes helical-Dclose quotes geometry produces a very large axial (toroidal) transform of magnetic line direction that reverses the pitch of the magnetic lines without the need of azimuthal (poloidal) plasma current. Thus, there is no need of a open-quotes dynamoclose quotes process and its associated fluctuations. The resulting configuration has the high magnetic shear and pitch reversal of the reversed field pinch (RFP). (Pitch = P = qR, where R = major radius). A helical-D pinch might demonstrate good confinement at q << 1

  10. Development of Integrated Simulation System for Helical Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Y.; Yokoyama, M.; Nakajima, N.; Fukuyama, A.; Watanabe, K. Y.; Funaba, H.; Suzuki, Y.; Murakami, S.; Ida, K.; Sakakibara, S.; Yamada, H.

    2005-07-01

    Recent progress of computers (parallel/vector-parallel computers, PC clusters, for example) and numerical codes for helical plasmas like three-dimensional MHD equilibrium codes, combined with the development of the plasma diagnostics technique, enable us to do the detailed theoretical analyses of the individual experimental observations. Now, it is pointed out that the experimental data analysis from the viewpoints of integrated physics is an important issue to understand the confinement physics globally. In addition to that, there are international movements towards the integrated numerical simulation study. One is several proposals of integrated modeling of burning tokamak plasmas, motivated by the ITER activity. The integrated numerical simulation will be a good help to draw up new experimental plans especially for burning plasma experiments. Another movement is international collaborations on the confinement database and neoclassical transport in helical plasmas/stellarators. These backgrounds motivate us to start the development of the integrated simulation system which has a modular structure and user-friendly interfaces. The integrated simulation system, which is based on the hierarchical and multi-scale (time and space) modeling, will also be a platform for theoreticians to test their own model such as turbulent transport model. In this paper, we will show the strategy of developing the integrated simulation system and present status of the development. Especially, we discuss the modeling of the time evolution of the plasma net current profile, which is equivalent to the time evolution of the rotational transform profile, in the resistive time scale. (Author)

  11. Determination of vitality in myocardial infarction. Comparison of single- and multi-slice MRI techniques with TurboFlash and TrueFISP sequences

    International Nuclear Information System (INIS)

    Huber, A.; Schoenberg, S.O.; Spannagl, B.; Rieber, J.; Klauss, V.; Reiser, M.F.

    2004-01-01

    The aim of the study was to compare the diagnostic accuracy in imaging viability of the myocardium with a multislice inversions recovery 2D single shot TrueFISP sequence and an established inversion recovery TurboFlash sequence. Twelve patients with myocardial infarction were examined at a 1.5 tesla MR system (Sonata, Siemens, Medical Systems) 10 min after application of a single dose multihance (0,1 mmol/kg body weight) with a 2D multislice technique (inversion recovery single shot TrueFISP), that allows to image the entire short axis during one breathhold and a 2D single slice technique (inversion recovery TurboFlash), that requires one breathhold per slice. Signal intensity was determined in normal myocardium, in the infarcted myocardium and in the left ventricle. The contrast/noise ratio of normal and infarcted myocardium was determined. The areas of hyperintense infarction were compared for both sequence techniques. The multislice single shot 2D IR-TrueFisp sequence has a lower contrast/noise ratio than the IR-TurboFlash sequence (mean values 6.9 vs. 12.5) for viable and non viable myocardium. The assessment of the volume of the infarction is possible with excellent correlation of both techniques (r=0.97, p [de

  12. Employing helicity amplitudes for resummation in SCET

    International Nuclear Information System (INIS)

    Moult, Ian; Stewart, Iain W.; Tackmann, Frank J.; Waalewijn, Wouter J.; Nikhef, Amsterdam

    2016-05-01

    Helicity amplitudes are the fundamental ingredients of many QCD calculations for multi-leg processes. We describe how these can seamlessly be combined with resummation in Soft-Collinear Effective Theory (SCET), by constructing a helicity operator basis for which the Wilson coefficients are directly given in terms of color-ordered helicity amplitudes. This basis is crossing symmetric and has simple transformation properties under discrete symmetries.

  13. MHD stability analysis of helical system plasmas

    International Nuclear Information System (INIS)

    Nakamura, Yuji

    2000-01-01

    Several topics of the MHD stability studies in helical system plasmas are reviewed with respect to the linear and ideal modes mainly. Difference of the method of the MHD stability analysis in helical system plasmas from that in tokamak plasmas is emphasized. Lack of the cyclic (symmetric) coordinate makes an analysis more difficult. Recent topic about TAE modes in a helical system is also described briefly. (author)

  14. Theoretical and experimental study on the magnetomechanical behavior of superconducting helical coils for a fusion reactor

    International Nuclear Information System (INIS)

    Takaghi, T.; Miya, K.; Yamada, H.; Takagi, T.

    1984-01-01

    The magnetomechanical behavior of superconducting helical coils for a magnetic fusion reactor was investigated experimentally and theoretically. Deformations of straight and torus type helical coils were caused due to static electromagnetic forces in the liquid helium cryostat and were analysed with the finite element computer code made here. Despite of a large scatter of experimental data due to a non-uniform friction force between the helical coil and the torus of stainless steel, the numerical results are very close to the mean value of the data. Numerical analysis of the force distribution acting on the helical coils was also performed for a Heliotron's coil system to characterize its nature. The force could be categorized conveniently as an extensional force, a tangential force and a toroidal force which correspond respectively to the kind of forces acting on toroidal field coils. Additionally, the effect of mechanical constraint on the magnetomechanical behavior is discussed and shows that the location of the constraint significantly affects the stress distributions in the coils. (orig.)

  15. Two-dimensional speckle-tracking strain echocardiography in long-term heart transplant patients: a study comparing deformation parameters and ejection fraction derived from echocardiography and multislice computed tomography.

    Science.gov (United States)

    Syeda, Bonni; Höfer, Peter; Pichler, Philipp; Vertesich, Markus; Bergler-Klein, Jutta; Roedler, Susanne; Mahr, Stephane; Goliasch, Georg; Zuckermann, Andreas; Binder, Thomas

    2011-07-01

    Longitudinal strain determined by speckle tracking is a sensitive parameter to detect systolic left ventricular dysfunction. In this study, we assessed regional and global longitudinal strain values in long-term heart transplants and compared deformation indices with ejection fraction as determined by transthoracic echocardiography (TTE) and multislice computed tomographic coronary angiography (MSCTA). TTE and MSCTA were prospectively performed in 31 transplant patients (10.6 years post-transplantation) and in 42 control subjects. Grey-scale apical views were recorded for speckle tracking (EchoPAC 7.0, GE) of the 16 segments of the left ventricle. The presence of coronary artery disease (CAD) was assessed by MSCTA. Strain analysis was performed in 1168 segments [496 in transplant patients (42.5%), 672 in control subjects (57.7%)]. Global longitudinal peak systolic strain was significantly lower in the transplant recipients than in the healthy population (-13.9 ± 4.2 vs. -17.4 ± 5.8%, PSimpsons method) was 60.7 ± 10.1%/60.2 ± 6.7% in transplant recipients vs. 64.7 ± 6.4%/63.0 ± 6.2% in the healthy population, P=ns. Even though 'healthy' heart transplants without CAD exhibit normal ejection fraction, deformation indices are reduced in this population when compared with control subjects. Our findings suggests that strain analysis is more sensitive than assessment of ejection fraction for the detection of abnormalities of systolic function.

  16. Generalized helicity and Beltrami fields

    Energy Technology Data Exchange (ETDEWEB)

    Buniy, Roman V., E-mail: roman.buniy@gmail.com [Schmid College of Science, Chapman University, Orange, CA 92866 (United States); Isaac Newton Institute, University of Cambridge, Cambridge, CB3 0EH (United Kingdom); Kephart, Thomas W., E-mail: tom.kephart@gmail.com [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Isaac Newton Institute, University of Cambridge, Cambridge, CB3 0EH (United Kingdom)

    2014-05-15

    We propose covariant and non-abelian generalizations of the magnetic helicity and Beltrami equation. The gauge invariance, variational principle, conserved current, energy–momentum tensor and choice of boundary conditions elucidate the subject. In particular, we prove that any extremal of the Yang–Mills action functional 1/4 ∫{sub Ω}trF{sub μν}F{sup μν}d{sup 4}x subject to the local constraint ε{sup μναβ}trF{sub μν}F{sub αβ}=0 satisfies the covariant non-abelian Beltrami equation. -- Highlights: •We introduce the covariant non-abelian helicity and Beltrami equation. •The Yang–Mills action and instanton term constraint lead to the Beltrami equation. •Solutions of the Beltrami equation conserve helicity.

  17. Acute and chronic myocardial infarction in a pig model: Utility of multi-slice cardiac computed tomography in assessing myocardial viability and infarct parameters

    International Nuclear Information System (INIS)

    Qu Xinkai; Fang Weiyi; Ye Jianding; Koh, Angela S.; Xu Yingjia; Guan Shaofeng; Li Ruogu; Shen Yan

    2012-01-01

    Objectives: The aim of this study was to determine the feasibility of multi-slice computed tomography (MSCT) biphasic imaging in assessing myocardial viability and infarct parameters in both acutely and chronically infarcted pig models. Materials and methods: Seven pigs underwent ligation of the distal left anterior descending artery. Imaging was performed on the day of infarction and 3 months post-infarct, with contrast infusion followed by MSCT scan acquisition at different time-points. Left ventricular ejection fractions (LVEFs) were obtained by left ventriculography (LVG) after 3 months. Infarcted locations found using MSCT were compared with those obtained using SPECT. Infarcted areas were also analysed histopathologically and compared with the findings from MSCT. Results: Chronic phase images had perfusion defects with lower CT values relative to normal myocardium (43 ± 10 HU vs. 156 ± 13 HU, p = 0.001) on the early images but no residual defects on delayed images. However, we found hyperenhancing regions on delayed images (244 ± 20 HU vs. 121 ± 25 HU, p = 0.001), and good correlation between MSCT- and LVG-derived LVEFs (60.56 ± 7.56%). The areas identified by MSCT corresponded to the location of 201 Tl SPECT-/pathologic staining-derived regions in all models. Infarct size was in good agreement with MSCT and pathological analyses of chronic phase models. Conclusions: Necrotic myocardium in different stages after infarction could be qualitatively and quantitatively assessed using MSCT biphasic imaging, as could the status of microcirculation formation. MSCT-measured LVEFs matched well with other modalities, and hence MSCT is a useful tool in assessing post-infarct cardiac function.

  18. NUMERICAL INVESTIGATION OF CURVATURE AND TORSION EFFECTS ON WATER FLOW FIELD IN HELICAL RECTANGULAR CHANNELS

    Directory of Open Access Journals (Sweden)

    A. H. ELBATRAN

    2015-07-01

    Full Text Available Helical channels have a wide range of applications in petroleum engineering, nuclear, heat exchanger, chemical, mineral and polymer industries. They are used in the separation processes for fluids of different densities. The centrifugal force, free surface and geometrical effects of the helical channel make the flow pattern more complicated; hence it is very difficult to perform physical experiment to predict channel performance. Computational Fluid Dynamics (CFD can be suitable alternative for studying the flow pattern characteristics in helical channels. The different ranges of dimensional parameters, such as curvature and torsion, often cause various flow regimes in the helical channels. In this study, the effects of physical parameters such as curvature, torsion, Reynolds number, Froude number and Dean Number on the characteristics of the turbulent flow in helical rectangular channels have been investigated numerically, using a finite volume RANSE code Fluent of Ansys workbench 10.1 UTM licensed. The physical parameters were reported for range of curvature (δ of 0.16 to 0.51 and torsion (λ of 0.032 to 0.1 .The numerical results of this study showed that the decrease in the channel curvature and the increase in the channel torsion numbers led to the increase of the flow velocity inside the channel and the change in the shape of water free surface at given Dean, Reynolds and Froude numbers.

  19. Multiphasic helical Computed Tomography of hepatocellular carcinoma. Evaluation after various percutaneous ablation procedures

    International Nuclear Information System (INIS)

    Catalano, O.; Esposito, M.; Lobianco, R.; Cusati, B.; Altei, F.; Siani, A.

    1999-01-01

    The purpose of this paper is to report the personal experience with helical CT evaluation of hepatocellular carcinoma treated with various percutaneous interventional procedures. From December 1996 to September 1998 it were examined with helical CT 41 patients (73 nodules in all) with hepatocellular carcinoma treated with percutaneous ablation therapies: conventional ethanol injection in 18 subjects (31 nodules), one-shot ethanol injection 3 (8 nodules), radiofrequency thermal ablation in 16 (25 nodules), and combined chemo embolization and ethanol injection in 4 (9 nodules). CT performed was 4-27 days after the last session, acquiring biphasic volumetric images in 14 patients and triphasic volumetric images in 27. A second treatment with subsequent CT study was performed for 28 lesions; 15 underwent 3 serial studies and 6 underwent 4 studies. Compared with pretreatment findings, the diameter was unchanged in 62% of the nodules and increased in 38%. Morphology was unchanged in 63% of the lesions while in 37% a mild deformation toward the needle path or a more regular and round shape was evident. Borders were unchanged in 37% of the cases and modified in 63%, appearing well-defined in 73% and ill-defined in 27%. The necrotic portion had a low attenuation with a nodule-to-parenchyma gradient more evident on delayed than on venous and finally arterial acquisitions; 8% of the lesions were not recognizable on unenhanced scans. During the arterial phase the residual tumor appeared hyperdense in 97% of the nodules and isodense in 3%, while during the portal phase it was hyperdense in 22%, isodense in 28% and hypodense in 50%, and during the delayed phase hypodense in 100%. Residual viable tissue was identified in 44% of the nodules and quantified as 100% in 1% of all lesions, > 75% in 3%, > 50% in 4%, > 25% in 23%. In conclusion, multiple-phase helical CT allows optimal depiction of primitive liver nodules treated with percutaneous interventional procedures and has a

  20. CURRENT AND KINETIC HELICITY OF LONG-LIVED ACTIVITY COMPLEXES

    International Nuclear Information System (INIS)

    Komm, Rudolf; Gosain, Sanjay

    2015-01-01

    We study long-lived activity complexes and their current helicity at the solar surface and their kinetic helicity below the surface. The current helicity has been determined from synoptic vector magnetograms from the NSO/SOLIS facility, and the kinetic helicity of subsurface flows has been determined with ring-diagram analysis applied to full-disk Dopplergrams from NSO/GONG and SDO/HMI. Current and kinetic helicity of activity complexes follow the hemispheric helicity rule with mainly positive values (78%; 78%, respectively, with a 95% confidence level of 31%) in the southern hemisphere and negative ones (80%; 93%, respectively, with a 95% confidence level of 22% and 14%, respectively) in the northern hemisphere. The locations with the dominant sign of kinetic helicity derived from Global Oscillation Network Group (GONG) and SDO/HMI data are more organized than those of the secondary sign even if they are not part of an activity complex, while locations with the secondary sign are more fragmented. This is the case for both hemispheres even for the northern one where it is not as obvious visually due to the large amount of magnetic activity present as compared to the southern hemisphere. The current helicity shows a similar behavior. The dominant sign of current helicity is the same as that of kinetic helicity for the majority of the activity complexes (83% with a 95% confidence level of 15%). During the 24 Carrington rotations analyzed here, there is at least one longitude in each hemisphere where activity complexes occur repeatedly throughout the epoch. These ''active'' longitudes are identifiable as locations of strong current and kinetic helicity of the same sign

  1. Diagnostic Value of Multislice Computed Tomography and Magnetic Resonance Imaging in the Diagnosis of Retroperitoneal Spread of Testicular Cancer: A Literature Review

    International Nuclear Information System (INIS)

    Hansen, J.; Jurik, A.G.

    2009-01-01

    Testicular cancer is the most frequent malignant disorder in men aged 15-35 years. Generally, diagnosing and follow-up include computer tomography (CT) examinations to detect possible retroperitoneal spread (abdomen and pelvis), resulting in at least eight CT examinations. This patient group is thereby exposed to a non-neglectable radiation dose, increasing the risk of future radiation-induced secondary cancer. This is especially problematic in potentially surgically cured patients with stage 1 testicular cancer. Thus, it can be beneficial to substitute CT with magnetic resonance imaging (MRI), provided there is valid evidence that the diagnostic value of MRI is at least comparable to current multislice CT (MSCT). The purpose of this study was to analyze whether there is evidence to recommend a substitution of MSCT with MRI in the diagnosis of retroperitoneal spread of testicular cancer. A literature search on the diagnostic accuracy, specificity, and sensitivity of MSCT and MRI in the diagnosis of retroperitoneal spread of testicular cancer was performed in the following databases: PubMed, EmBase, and ISI Web of Science. The search was limited to include the period from 2000 to September 2008, and to human and English-language publications. Forty-four publications were obtained for formal review (27 from PubMed, 15 from EmBase, two from ISI Web of Science). None of the publications reviewed encompassed diagnostic specificity and sensitivity of MSCT, and they lacked systematic comparison of MSCT and MRI. Only one study included sensitivity and specificity of MRI compared to single-slice CT. Both methods had a sensitivity and a specificity of approximately 70%. The literature review did not reveal valid data regarding diagnostic accuracy of MRI compared with MSCT for diagnosing retroperitoneal spread of testicular cancer. A prospective blinded comparative study is needed to provide valid evidence

  2. Multislice quantitative computed tomography allows early detection of bone mineral density alterations induced by atherogenic diet in a growing rat experimental model

    International Nuclear Information System (INIS)

    Gubert, M.J.; Monforte, F.; Calo, C.; Lylyk, P.; Friedman, M.F.; Gamba, C.A.

    2012-01-01

    Purpose. To demonstrate the utility of Multislice Quantitative Computed Tomography (MS-QCT) in the early detection of mandibular bone mineral density (BMD) alterations induced by an atherogenic diet in a growing rat experimental model. Materials and Methods. Male weanling Wistar rats (n =16) were divided by body weight (Wt) into 2 groups: control (C) and experimental (E), with no significant differences in the mean initial Wt (p>0.05). C was fed rodent stock diet ad libitum, and E an atherogenic diet for 3 weeks (3w). Zoometry (body weight and length) and diet intake (g/100g rat/day) were monitored. At 3 w in serum (mg/dL) lipidlipoprotein profile was studied: total cholesterol (t-C), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), non-HDL cholesterol (non-HDL-C) and MSQCT (Philips 64 CT, quantified with the eFilm Workstation 2.1) in seven mandibular areas (MA): n. 1 to 4: from chin to mandibular foramen, n. 5: coronoid process, n. 6: condylar process, n. 7: angular process. Statistics: Pearson's correlation between BMD in each MA and serum t-C. p 0.05). Correlation coefficients (r) and their significance levels (p) were relevant in 5/7 MA. MA1:-0.580 (p=0.019), MA2:-0.709 (p=0.002), MA3:-0.635 (p=0.008), MA5:-0.674 (p=0.004), MA6:-0.564 (p=0.023). Conclusions. These results suggest that MS-QCT is an imaging diagnostic method that allows the early detection of mandible bone architecture alterations induced by an atherogenic diet. Inverse correlation between BMD and t-C would indicate an association between an atherogenic diet intake and potential temporomandibular disorders. (authors)

  3. Diagnostic Value of Multislice Computed Tomography and Magnetic Resonance Imaging in the Diagnosis of Retroperitoneal Spread of Testicular Cancer: A Literature Review

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, J. (Dept. of Medical Physics, Aarhus Univ. Hospital, Aarhus Sygehus, Aarhus (Denmark)); Jurik, A.G. (Dept. of Radiology, Aarhus Univ. Hospital, Aarhus Sygehus, Aarhus (Denmark))

    2009-11-15

    Testicular cancer is the most frequent malignant disorder in men aged 15-35 years. Generally, diagnosing and follow-up include computer tomography (CT) examinations to detect possible retroperitoneal spread (abdomen and pelvis), resulting in at least eight CT examinations. This patient group is thereby exposed to a non-neglectable radiation dose, increasing the risk of future radiation-induced secondary cancer. This is especially problematic in potentially surgically cured patients with stage 1 testicular cancer. Thus, it can be beneficial to substitute CT with magnetic resonance imaging (MRI), provided there is valid evidence that the diagnostic value of MRI is at least comparable to current multislice CT (MSCT). The purpose of this study was to analyze whether there is evidence to recommend a substitution of MSCT with MRI in the diagnosis of retroperitoneal spread of testicular cancer. A literature search on the diagnostic accuracy, specificity, and sensitivity of MSCT and MRI in the diagnosis of retroperitoneal spread of testicular cancer was performed in the following databases: PubMed, EmBase, and ISI Web of Science. The search was limited to include the period from 2000 to September 2008, and to human and English-language publications. Forty-four publications were obtained for formal review (27 from PubMed, 15 from EmBase, two from ISI Web of Science). None of the publications reviewed encompassed diagnostic specificity and sensitivity of MSCT, and they lacked systematic comparison of MSCT and MRI. Only one study included sensitivity and specificity of MRI compared to single-slice CT. Both methods had a sensitivity and a specificity of approximately 70%. The literature review did not reveal valid data regarding diagnostic accuracy of MRI compared with MSCT for diagnosing retroperitoneal spread of testicular cancer. A prospective blinded comparative study is needed to provide valid evidence

  4. Spatial variation of the section sensitivity profile in helical CT

    International Nuclear Information System (INIS)

    Katsuta, Shoichi; Hanai, Kouzou; Kunii, Takeo; Kimura, Haruki; Imabayashi, Wataru; Muramatsu, Yoshihisa

    1999-01-01

    The section sensitivity profile (SSP) is adequate to express the properties of helical CT images. Although SSP measurement has been performed only at the center of the imaging field, we applied it to off-center positions using a metal bead and controlled tracking technique. The experimental results indicated that SSP curves vary in the imaging field according to the relative position of the x-ray focus. The results were in agreement with computer simulations. (author)

  5. Modelling simple helically delivered dose distributions

    International Nuclear Information System (INIS)

    Fenwick, John D; Tome, Wolfgang A; Kissick, Michael W; Mackie, T Rock

    2005-01-01

    In a previous paper, we described quality assurance procedures for Hi-Art helical tomotherapy machines. Here, we develop further some ideas discussed briefly in that paper. Simple helically generated dose distributions are modelled, and relationships between these dose distributions and underlying characteristics of Hi-Art treatment systems are elucidated. In particular, we describe the dependence of dose levels along the central axis of a cylinder aligned coaxially with a Hi-Art machine on fan beam width, couch velocity and helical delivery lengths. The impact on these dose levels of angular variations in gantry speed or output per linear accelerator pulse is also explored

  6. Helical modes generate antimagnetic rotational spectra in nuclei

    Science.gov (United States)

    Malik, Sham S.

    2018-03-01

    A systematic analysis of the antimagnetic rotation band using r -helicity formalism is carried out for the first time. The observed octupole correlation in a nucleus is likely to play a role in establishing the antimagnetic spectrum. Such octupole correlations are explained within the helical orbits. In a rotating field, two identical fermions (generally protons) with paired spins generate these helical orbits in such a way that its positive (i.e., up) spin along the axis of quantization refers to one helicity (right-handedness) while negative (down) spin along the same quantization-axis decides another helicity (left-handedness). Since the helicity remains invariant under rotation, therefore, the quantum state of a fermion is represented by definite angular momentum and helicity. These helicity represented states support a pear-shaped structure of a rotating system having z axis as the symmetry axis. A combined operation of parity, time-reversal, and signature symmetries ensures an absence of one of the signature partner band from the observed antimagnetic spectrum. This formalism has also been tested for the recently observed negative parity Δ I =2 antimagnetic spectrum in odd-A 101Pd nucleus and explains nicely its energy spectrum as well as the B (E 2 ) values. Further, this formalism is found to be fully consistent with twin-shears mechanism popularly known for such type of rotational bands. It also provides significant clue for extending these experiments in various mass regions spread over the nuclear chart.

  7. On the validity of the use of a localized approximation for helical beams. I. Formal aspects

    Science.gov (United States)

    Gouesbet, Gérard; André Ambrosio, Leonardo

    2018-03-01

    The description of an electromagnetic beam for use in light scattering theories may be carried out by using an expansion over vector spherical wave functions with expansion coefficients expressed in terms of Beam Shape Coefficients (BSCs). A celebrated method to evaluate these BSCs has been the use of localized approximations (with several existing variants). We recently established that the use of any existing localized approximation is of limited validity in the case of Bessel and Mathieu beams. In the present paper, we address a warning against the use of any existing localized approximation in the case of helical beams. More specifically, we demonstrate that a procedure used to validate any existing localized approximation fails in the case of helical beams. Numerical computations in a companion paper will confirm that existing localized approximations are of limited validity in the case of helical beams.

  8. INTERPRETING ERUPTIVE BEHAVIOR IN NOAA AR 11158 VIA THE REGION'S MAGNETIC ENERGY AND RELATIVE-HELICITY BUDGETS

    International Nuclear Information System (INIS)

    Tziotziou, Kostas; Georgoulis, Manolis K.; Liu Yang

    2013-01-01

    In previous works, we introduced a nonlinear force-free method that self-consistently calculates the instantaneous budgets of free magnetic energy and relative magnetic helicity in solar active regions (ARs). Calculation is expedient and practical, using only a single vector magnetogram per computation. We apply this method to a time series of 600 high-cadence vector magnetograms of the eruptive NOAA AR 11158 acquired by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory over a five-day observing interval. Besides testing our method extensively, we use it to interpret the dynamical evolution in the AR, including eruptions. We find that the AR builds large budgets of both free magnetic energy and relative magnetic helicity, sufficient to power many more eruptions than the ones it gave within the interval of interest. For each of these major eruptions, we find eruption-related decreases and subsequent free-energy and helicity budgets that are consistent with the observed eruption (flare and coronal mass ejection (CME)) sizes. In addition, we find that (1) evolution in the AR is consistent with the recently proposed (free) energy-(relative) helicity diagram of solar ARs, (2) eruption-related decreases occur before the flare and the projected CME-launch times, suggesting that CME progenitors precede flares, and (3) self terms of free energy and relative helicity most likely originate from respective mutual terms, following a progressive mutual-to-self conversion pattern that most likely stems from magnetic reconnection. This results in the non-ideal formation of increasingly helical pre-eruption structures and instigates further research on the triggering of solar eruptions with magnetic helicity firmly placed in the eruption cadre

  9. MAGNETIC HELICITY FLUX IN THE PRESENCE OF SHEAR

    International Nuclear Information System (INIS)

    Hubbard, Alexander; Brandenburg, Axel

    2011-01-01

    Magnetic helicity has risen to be a major player in dynamo theory, with the helicity of the small-scale field being linked to the dynamo saturation process for the large-scale field. It is a nearly conserved quantity, which allows its evolution equation to be written in terms of production and flux terms. The flux term can be decomposed in a variety of fashions. One particular contribution that has been expected to play a significant role in dynamos in the presence of mean shear was isolated by Vishniac and Cho. Magnetic helicity fluxes are explicitly gauge dependent however, and the correlations that have come to be called the Vishniac-Cho flux were determined in the Coulomb gauge, which turns out to be fraught with complications in shearing systems. While the fluxes of small-scale helicity are explicitly gauge dependent, their divergences can be gauge independent. We use this property to investigate magnetic helicity fluxes of the small-scale field through direct numerical simulations in a shearing-box system and find that in a numerically usable gauge the divergence of the small-scale helicity flux vanishes, while the divergence of the Vishniac-Cho flux remains finite. We attribute this seeming contradiction to the existence of horizontal fluxes of small-scale magnetic helicity with finite divergences.

  10. Magnetic Helicity Flux in the Presence of Shear

    Science.gov (United States)

    Hubbard, Alexander; Brandenburg, Axel

    2011-01-01

    Magnetic helicity has risen to be a major player in dynamo theory, with the helicity of the small-scale field being linked to the dynamo saturation process for the large-scale field. It is a nearly conserved quantity, which allows its evolution equation to be written in terms of production and flux terms. The flux term can be decomposed in a variety of fashions. One particular contribution that has been expected to play a significant role in dynamos in the presence of mean shear was isolated by Vishniac & Cho. Magnetic helicity fluxes are explicitly gauge dependent however, and the correlations that have come to be called the Vishniac-Cho flux were determined in the Coulomb gauge, which turns out to be fraught with complications in shearing systems. While the fluxes of small-scale helicity are explicitly gauge dependent, their divergences can be gauge independent. We use this property to investigate magnetic helicity fluxes of the small-scale field through direct numerical simulations in a shearing-box system and find that in a numerically usable gauge the divergence of the small-scale helicity flux vanishes, while the divergence of the Vishniac-Cho flux remains finite. We attribute this seeming contradiction to the existence of horizontal fluxes of small-scale magnetic helicity with finite divergences.

  11. Multislice CT Angiography in Renal Artery Stent Evaluation: Prospective Comparison with Intra-Arterial Digital Subtraction Angiography

    International Nuclear Information System (INIS)

    Raza, Syed A.; Chughtai, Aamer R.; Wahba, Mona; Cowling, Mark G.; Taube, David; Wright, Andrew R.

    2004-01-01

    Purpose: To assess the role of multislice computed tomography angiography (MCTA) in the evaluation of renal artery stents, using intra-arterial digital subtraction angiography (DSA) as the gold standard. Methods: Twenty consecutive patients (15 men, 5 women) with 23 renal artery stents prospectively underwent both MCTA and DSA. Axial images, multiplanar reconstructions and maximum intensity projection images were used for diagnosis. The MCTA and DSA images were each interpreted without reference to the result of the other investigation. Results:The three cases of restenosis on DSA were detected correctly by MCTA; in 19 cases where MCTA showed a fully patent stent, the DSA was also negative. Sensitivity and negative predictive value (NPV) of MCTA were therefore 100%. In four cases, MCTA showed apparently minimal disease which was not shown on DSA. These cases are taken as false positive giving a specificity of 80% and a positive predictive value of 43%. Conclusion: The high sensitivity and NPV suggest MCTA may be useful as a noninvasive screen for renal artery stentrestenosis. MCTA detected mild disease in a few patients which was not confirmed on angiography

  12. Transport barrier in Helical system

    International Nuclear Information System (INIS)

    Ida, Katsumi

    1998-01-01

    Experiments on the transport barrier in Helical plasmas are reviewed. There are two mechanisms of transport improvement, that results in the formation of the transport barrier. One is the improvement of neoclassical transport by reducing the ripple loss with radial electric field, which exist only in helical plasma. The other is the improvement of anomalous transport due to the suppression of fluctuations associated with a radial electric field shear both in tokamak and helical plasma. The formation of the transport barrier can be triggered by the radial electric field shear associated with the transition of the radial electric field (L/H transition or ion-electron root transition) or the peaked density or the optimization of magnetic field shear. The mechanisms of transport barrier formation are also discussed. (author). 60 refs

  13. Toroidal helical quartz forming machine

    International Nuclear Information System (INIS)

    Hanks, K.W.; Cole, T.R.

    1977-01-01

    The Scyllac fusion experimental machine used 10 cm diameter smooth bore discharge tubes formed into a simple toroidal shape prior to 1974. At about that time, it was discovered that a discharge tube was required to follow the convoluted shape of the load coil. A machine was designed and built to form a fused quartz tube with a toroidal shape. The machine will accommodate quartz tubes from 5 cm to 20 cm diameter forming it into a 4 m toroidal radius with a 1 to 5 cm helical displacement. The machine will also generate a helical shape on a linear tube. Two sets of tubes with different helical radii and wavelengths have been successfully fabricated. The problems encountered with the design and fabrication of this machine are discussed

  14. Impact of lesion morphology on angiographic and clinical outcomes in patients with chronic total occlusion after recanalization with drug-eluting stents: a multislice computed tomography study

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Tsuyoshi [Toyohashi Heart Center, Toyohashi (Japan); Nagoya City University Graduate School of Medical Sciences, Department of Cardio-Renal Medicine and Hypertension, Nagoya (Japan); Tsuchikane, Etsuo; Nasu, Kenya; Kimura, Masashi; Terashima, Mitsuyasu; Kinoshita, Yoshihisa; Habara, Maoto; Suzuki, Takahiko [Toyohashi Heart Center, Toyohashi (Japan); Suzuki, Yoriyasu; Ehara, Mariko [Nagoya Heart Center, Nagoya (Japan); Ohte, Nobuyuki [Nagoya City University Graduate School of Medical Sciences, Department of Cardio-Renal Medicine and Hypertension, Nagoya (Japan)

    2015-10-15

    The aim of this study was to investigate the multislice computed tomography (MSCT) parameters associated with adverse outcomes after chronic total occlusion percutaneous coronary intervention (CTO-PCI) with drug-eluting stents. A total of 285 patients who underwent MSCT before CTO-PCI were analyzed. Lesion morphology was assessed with MSCT. Angiographic restenosis, reocclusion, and MACE (a composite of cardiac death, myocardial infarction, stent thrombosis, and target lesion revascularization) were analyzed. MACE was observed in 36 patients (13.6 %). Occlusion length was greater (39.5 ± 19.9 mm vs. 22.3 ± 13.7 mm, p < 0.01), minimal vessel area smaller (11.2 ± 5.7 mm{sup 2} vs. 14.5 ± 5.6 mm{sup 2}, p < 0.01), and severe calcification more common (36 % vs. 12 %, p < 0.01) in the MACE group compared to the non-MACE group. We defined occluded length >25.4 mm, minimal vessel area <11.9 mm{sup 2}, which were identified by receiver operating characteristic analysis, and severe calcification as CT-derived risk factors. Angiographic restenosis (60 % vs. 12 % vs. 7 %, p < 0.01), reocclusion (29 % vs. 2 % vs. 2 %, p < 0.01), and MACE (43 % vs. 6 % vs. 3 %, p < 0.01) were more common in patients with 2 or more risk factors than in those with 1 or 0. MSCT characteristics associated with adverse outcomes after CTO-PCI were occlusion length, minimal vessel area, and severe calcification. (orig.)

  15. Comparison of endoscopic ultrasonography and multislice spiral computed tomography for the preoperative staging of gastric cancer - results of a single institution study of 610 Chinese patients.

    Directory of Open Access Journals (Sweden)

    Xing-Yu Feng

    Full Text Available BACKGROUND: This study compared the performance of endoscopic ultrasonography (EUS and multislice spiral computed tomography (MSCT in the preoperative staging of gastric cancer. METHODOLOGY/PRINCIPAL FINDINGS: A total of 610 patients participated in this study, all of whom had undergone surgical resection, had confirmed gastric cancer and were evaluated with EUS and MSCT. Tumor staging was evaluated using the Tumor-Node-Metastasis (TNM staging and Japanese classification. The results from the imaging modalities were compared with the postoperative histopathological outcomes. The overall accuracies of EUS and MSCT for the T staging category were 76.7% and 78.2% (P=0.537, respectively. Stratified analysis revealed that the accuracy of EUS for T1 and T2 staging was significantly higher than that of MSCT (P<0.001 for both and that the accuracy of MSCT in T3 and T4 staging was significantly higher than that of EUS (P<0.001 and 0.037, respectively. The overall accuracy of MSCT was 67.2% when using the 13th edition Japanese classification, and this percentage was significantly higher than the accuracy of EUS (49.3% and MSCT (44.6% when using the 6th edition UICC classification (P<0.001 for both values. CONCLUSIONS/SIGNIFICANCE: Our results demonstrated that the overall accuracies of EUS and MSCT for preoperative staging were not significantly different. We suggest that a combination of EUS and MSCT is required for preoperative evaluation of TNM staging.

  16. Stimuli-Directed Helical Chirality Inversion and Bio-Applications

    Directory of Open Access Journals (Sweden)

    Ziyu Lv

    2016-08-01

    Full Text Available Helical structure is a sophisticated ubiquitous motif found in nature, in artificial polymers, and in supramolecular assemblies from microscopic to macroscopic points of view. Significant progress has been made in the synthesis and structural elucidation of helical polymers, nevertheless, a new direction for helical polymeric materials, is how to design smart systems with controllable helical chirality, and further use them to develop chiral functional materials and promote their applications in biology, biochemistry, medicine, and nanotechnology fields. This review summarizes the recent progress in the development of high-performance systems with tunable helical chirality on receiving external stimuli and discusses advances in their applications as drug delivery vesicles, sensors, molecular switches, and liquid crystals. Challenges and opportunities in this emerging area are also presented in the conclusion.

  17. Simulation Study of the Helical Superconducting Undulator Installation at the Advanced Photon Source

    Energy Technology Data Exchange (ETDEWEB)

    Sajaev, V.; Borland, M.; Sun, Y.; Xiao, A.

    2017-06-25

    A helical superconducting undulator is planned for installation at the APS. Such an installation would be first of its kind – helical devices were never installed in synchrotron light sources before. Due to its reduced horizontal aperture, a lattice modification is required to accommodate for large horizontal oscillations during injection. We describe the lattice change details and show the new lattice experimental test results. To understand the effect of the undulator on single-particle dynamics, first, its kick maps were computed using different methods. We have found that often-used Elleaume formula* for kick maps gives wrong results for this undulator. We then used the kick maps obtained by other methods to simulate the effect of the undulator on injection and lifetime.

  18. System assessment of helical reactors in comparison with tokamaks

    International Nuclear Information System (INIS)

    Yamazaki, K.; Imagawa, S.; Muroga, T.; Sagara, A.; Okamura, S.

    2002-10-01

    A comparative assessment of tokamak and helical reactors has been performed using equivalent physics/engineering model and common costing model. Higher-temperature plasma operation is required in tokamak reactors to increase bootstrap current fraction and to reduce current-drive (CD) power. In helical systems, lower-temperature operation is feasible and desirable to reduce helical ripple transport. The capital cost of helical reactor is rather high, however, the cost of electricity (COE) is almost same as that of tokamak reactor because of smaller re-circulation power (no CD power) and less-frequent blanket replacement (lower neutron wall loading). The standard LHD-type helical reactor with 5% beta value is economically equivalent to the standard tokamak with 3% beta. The COE of lower-aspect ratio helical reactor is on the same level of high-β N tokamak reactors. (author)

  19. THE EFFECTS OF SPATIAL SMOOTHING ON SOLAR MAGNETIC HELICITY PARAMETERS AND THE HEMISPHERIC HELICITY SIGN RULE

    Energy Technology Data Exchange (ETDEWEB)

    Ocker, Stella Koch [Department of Physics, Oberlin College, Oberlin, OH 44074 (United States); Petrie, Gordon, E-mail: socker@oberlin.edu, E-mail: gpetrie@nso.edu [National Solar Observatory, Boulder, CO 80303 (United States)

    2016-12-01

    The hemispheric preference for negative/positive helicity to occur in the northern/southern solar hemisphere provides clues to the causes of twisted, flaring magnetic fields. Previous studies on the hemisphere rule may have been affected by seeing from atmospheric turbulence. Using Hinode /SOT-SP data spanning 2006–2013, we studied the effects of two spatial smoothing tests that imitate atmospheric seeing: noise reduction by ignoring pixel values weaker than the estimated noise threshold, and Gaussian spatial smoothing. We studied in detail the effects of atmospheric seeing on the helicity distributions across various field strengths for active regions (ARs) NOAA 11158 and NOAA 11243, in addition to studying the average helicities of 179 ARs with and without smoothing. We found that, rather than changing trends in the helicity distributions, spatial smoothing modified existing trends by reducing random noise and by regressing outliers toward the mean, or removing them altogether. Furthermore, the average helicity parameter values of the 179 ARs did not conform to the hemisphere rule: independent of smoothing, the weak-vertical-field values tended to be negative in both hemispheres, and the strong-vertical-field values tended to be positive, especially in the south. We conclude that spatial smoothing does not significantly affect the overall statistics for space-based data, and thus seeing from atmospheric turbulence seems not to have significantly affected previous studies’ ground-based results on the hemisphere rule.

  20. Prostate contouring uncertainty in megavoltage computed tomography images acquired with a helical tomotherapy unit during image-guided radiation therapy

    International Nuclear Information System (INIS)

    Song, William Y.; Chiu, Bernard; Bauman, Glenn S.; Lock, Michael; Rodrigues, George; Ash, Robert; Lewis, Craig; Fenster, Aaron; Battista, Jerry J.; Van Dyk, Jake

    2006-01-01

    Purpose: To evaluate the image-guidance capabilities of megavoltage computed tomography (MVCT), this article compares the interobserver and intraobserver contouring uncertainty in kilovoltage computed tomography (KVCT) used for radiotherapy planning with MVCT acquired with helical tomotherapy. Methods and Materials: Five prostate-cancer patients were evaluated. Each patient underwent a KVCT and an MVCT study, a total of 10 CT studies. For interobserver variability analysis, four radiation oncologists, one physicist, and two radiation therapists (seven observers in total) contoured the prostate and seminal vesicles (SV) in the 10 studies. The intraobserver variability was assessed by asking all observers to repeat the contouring of 1 patient's KVCT and MVCT studies. Quantitative analysis of contour variations was performed by use of volumes and radial distances. Results: The interobserver and intraobserver contouring uncertainty was larger in MVCT compared with KVCT. Observers consistently segmented larger volumes on MVCT where the ratio of average prostate and SV volumes was 1.1 and 1.2, respectively. On average (interobserver and intraobserver), the local delineation variability, in terms of standard deviations [Δσ = √(σ 2 MVCT - σ 2 KVCT )], increased by 0.32 cm from KVCT to MVCT. Conclusions: Although MVCT was inferior to KVCT for prostate delineation, the application of MVCT in prostate radiotherapy remains useful

  1. Evaluation of TSE- and T1-3D-GRE-sequences for focal cartilage lesions in vitro in comparison to ultrahigh resolution multi-slice CT

    International Nuclear Information System (INIS)

    Stork, A.; Schulze, D.; Koops, A.; Kemper, J.; Adam, G.

    2002-01-01

    Purpose: Evaluation of TSE- and T 1 -3D-GRE-sequences for focal cartilage lesions in vitro in comparison to ultrahigh resolution multi-slice CT. Materials and methods: Forty artificial cartilage lesions in ten bovine patellae were immersed in a solution of iodinated contrast medium and assessed with ultrahigh resolution multi-slice CT. Fat-suppressed TSE images with intermediate- and T 2 -weighting at a slice thickness of 2, 3 and 4 mm as well as fat-suppressed T 1 -weighted 3D-FLASH images with an effective slice thickness of 1, 2 and 3 mm were acquired at 1.5 T. After adding Gd-DTPA to the saline solution containing the patellae, the T 1 -weighted 3D-FLASH imaging was repeated. Results: All cartilage lesions were visualised and graded with ultrahigh resolution multi-slice CT. The TSE images had a higher sensitivity and a higher inter- and intraobserver kappa compared to the FLASH-sequences (TSE: 70-95%; 0.82-0.83; 0.85-0.9; FLASH: 57.5-85%; 0.53-0.72; 0.73-0.82, respectively). An increase in slice thickness decreased the sensitivity, whereby deep lesions were even reliably depicted on TSE images at a slice thickness of 3 and 4 mm. Adding Gd-DTPA to the saline solution increased the sensitivity by 10% with no detectable advantage over the T 2 -weighted TSE images. Conclusion: TSE sequences and application of Gd-DTPA seemed to be superior to T 1 -weighted 3D-FLASH sequences without Gd-DTPA in the detection of focal cartilage lesions. The ultrahigh resolution multi-slice CT can serve as in vitro reference standard for focal cartilage lesions. (orig.) [de

  2. Early clinical phase of patient's management after polytrauma using 1- and 4-slice helical CT; Fruehes klinisches Management nach Polytrauma mit 1- und 4-Schicht-Spiral-CT

    Energy Technology Data Exchange (ETDEWEB)

    Kloeppel, R.; Kahn, T. [Klinik und Poliklinik fuer Diagnostische Radiologie, Universitaetsklinikum Leipzig (Germany); Schreiter, D. [Chirurgische Intensivtherapieabteilung, Zentrum fuer Chirurgie, Universitaetsklinikum Leipzig (Germany); Dietrich, J. [Abt. Neuroradiologie der Klinik und Poliklinik fuer Diagnostische Radiologie, Universitaetsklinikum Leipzig (Germany); Josten, C. [Klinik und Poliklinik fuer Unfall- und Wiederherstellungschirurgie, Zentrum fuer Chirurgie, Universitaetsklinikum Leipzig (Germany)

    2002-07-01

    In the early clinical phase the comprehensive imaging of patients with multiple trauma using helical CT is already established. Aim of this study was to assess whether MSCT may improve the patient management and the diagnostic results.The procedure is designed as follows: after life-thretening treatment x-ray of chest and ultrasound are carried out in the emergency room. Then the patient is moved to CT. From 1998 to december 2000 241 patients were examined using a single slice helical CT (Somatom plus 4), in 2001 79 patients using a 4-slice helical CT (Somatom VZ, Siemens Med.Sol.). After CT selected radiograms of the extremities were taken.359 of 360 procedures were carried out successfully. Excluding 1 case (death during 1-sl. h CT) all relevant lesions of head, neck, and body were diagnosed. Although the patients had an injury severity score of {approx}30. The change from 1slice-helical CT to 4 slice-helical CT allowed us to reduce the stay in the CT room from 28 to 16 min. The total lethality decreased by {approx}4%.Advantages for the patient arose from the standardized examination protocol using multislice CT. If integrated in an interdisciplinary management concept, it is a good compromise between examination time, comprehensive diagnostic imaging, life-saving therapeutic procedures, and therapy planning. (orig.) [German] Die klinische Erstversorgung Polytraumatisierter schliesst inzwischen in vielen Unfallkliniken den fruehzeitigen Einsatz der Spiral-CT ein. Kann die neuerlich eingefuehrte Mehrschicht-Spiral-CT Ergebnisse und Patientenmanagement weiter verbessern?Nach lebensrettenden Sofortmassnahmen, Thoraxroentgen und Notsonographie im Schockraum erfolgte die CT: Von 1998-2000 wurden 241 Patienten mit einem 1-Schicht-Spiral-CT (Somatom plus 4) und in 2001 79 Patienten mit einem 4-Schicht-Spiral-CT (Somatom VZ, beide Siemens Med. Sol.) untersucht. Klinisch ausgewaehlte Extremitaetenaufnahmen wurden ergaenzt.359 von 360 Untersuchungen verliefen erfolgreich

  3. New formulae for magnetic relative helicity and field line helicity

    Science.gov (United States)

    Aly, Jean-Jacques

    2018-01-01

    We consider a magnetic field {B} occupying the simply connected domain D and having all its field lines tied to the boundary S of D. We assume here that {B} has a simple topology, i.e., the mapping {M} from positive to negative polarity areas of S associating to each other the two footpoints of any magnetic line, is continuous. We first present new formulae for the helicity H of {B} relative to a reference field {{B}}r having the same normal component {B}n on S, and for its field line helicity h relative to a reference vector potential {{C}}r of {{B}}r. These formulae make immediately apparent the well known invariance of these quantities under all the ideal MHD deformations that preserve the positions of the footpoints on S. They express indeed h and H either in terms of {M} and {B}n, or in terms of the values on S of a pair of Euler potentials of {B}. We next show that, for a specific choice of {{C}}r, the field line helicity h of {B} fully characterizes the magnetic mapping {M} and then the topology of the lines. Finally, we give a formula that describes the rate of change of h in a situation where the plasma moves on the perfectly conducting boundary S without changing {B}n and/or non-ideal processes, described by an unspecified term {N} in Ohm’s law, are at work in some parts of D.

  4. Diagnostic value of electron-beam computed tomography (EBT). I. cardiac applications

    International Nuclear Information System (INIS)

    Enzweiler, C.N.H.; Lembcke, A.; Rogalla, P.; Taupitz, M.; Wiese, T.H.; Hammm, B.; Becker, C.R.; Reiser, M.F.; Felix, R.; Knollmann, F.D.; Georgi, M.; Weisser, G.; Lehmann, K.J.

    2004-01-01

    Electron beam tomography (EBT) directly competes with other non-invasive imaging modalities, such as multislice computed tomography, magnetic resonance imaging, and echocardiography, in the diagnostic assessment of cardiac diseases. EBT is the gold standard for the detection and quantification of coronary calcium as a preclinical sign of coronary artery disease (CAD). Its standardized examination protocols and the broad experience with this method favor EBT. First results with multislice CT indicate that this new technology may be equivalent to EBT for coronary calcium studies. The principal value of CT-based coronary calcium measurements continues to be an issue of controversy amongst radiologists and cardiologists due to lack of prospective randomized trials. Coronary angiography with EBT is characterized by a high negative predictive value and, in addition, may be indicated in some patients with manifest CAD. It remains to be shown whether coronary angiography with multislice CT is reliable and accurate enough to be introduced into the routine work-up, to replace some of the many strictly diagnostic coronary catheterizations in Germany and elsewhere. Assessment of coronary stent patency with EBT is associated with several problems and in our opinion cannot be advocated as a routine procedure. EBT may be recommended for the evaluation of coronary bypasses to look for bypass occlusions and significant stenoses, which, however, can be equally well achieved with multislice CT. Quantification of myocardial perfusion with EBT could not replace MRI or other modalities in this field. EBT has proven to be accurate, reliable and in some instances equivalent to MRI, which is the gold standard for the quantitative and qualitative evaluation of cardiac function. Some disadvantages not the least of which is the limited distribution of electron beam scanners, favor MRI for functional assessment of the heart. (orig.) [de

  5. ADDITIVE SELF-HELICITY AS A KINK MODE THRESHOLD

    International Nuclear Information System (INIS)

    Malanushenko, A.; Longcope, D. W.; Fan, Y.; Gibson, S. E.

    2009-01-01

    In this paper, we propose that additive self-helicity, introduced by Longcope and Malanushenko, plays a role in the kink instability for complex equilibria, similar to twist helicity for thin flux tubes. We support this hypothesis by a calculation of additive self-helicity of a twisted flux tube from the simulation of Fan and Gibson. As more twist gets introduced, the additive self-helicity increases, and the kink instability of the tube coincides with the drop of additive self-helicity, after the latter reaches the value of H A /Φ 2 ∼ 1.5 (where Φ is the flux of the tube and H A is the additive self-helicity). We compare the additive self-helicity to twist for a thin subportion of the tube to illustrate that H A /Φ 2 is equal to the twist number, studied by Berger and Field, when the thin flux tube approximation is applicable. We suggest that the quantity H A /Φ 2 could be treated as a generalization of a twist number, when the thin flux tube approximation is not applicable. A threshold on a generalized twist number might prove extremely useful studying complex equilibria, just as the twist number itself has proven useful studying idealized thin flux tubes. We explicitly describe a numerical method for calculating additive self-helicity, which includes an algorithm for identifying a domain occupied by a flux bundle and a method of calculating potential magnetic field confined to this domain. We also describe a numerical method to calculate twist of a thin flux tube, using a frame parallelly transported along the axis of the tube.

  6. Assessment of global and regional left ventricular function using 64-slice multislice computed tomography and 2D echocardiography: A comparison with cardiac magnetic resonance

    International Nuclear Information System (INIS)

    Annuar, Bin Rapaee; Liew, Chee Khoon; Chin, Sze Piaw; Ong, Tiong Kiam; Seyfarth, M. Tobias; Chan, Wei Ling; Fong, Yean Yip; Ang, Choon Kiat; Lin, Naing; Liew, Houng Bang; Sim, Kui Hian

    2008-01-01

    Objectives: To compare the assessment of global and regional left ventricular (LV) function using 64-slice multislice computed tomography (MSCT), 2D echocardiography (2DE) and cardiac magnetic resonance (CMR). Methods: Thirty-two consecutive patients (mean age, 56.5 ± 9.7 years) referred for evaluation of coronary artery using 64-slice MSCT also underwent 2DE and CMR within 48 h. The global left ventricular function which include left ventricular ejection fraction (LVEF), left ventricular end diastolic volume (LVdV) and left ventricular end systolic volume (LVsV) were determine using the three modalities. Regional wall motion (RWM) was assessed visually in all three modalities. The CMR served as the gold standard for the comparison between 64-slice MSCT with CMR and 2DE with CMR. Statistical analysis included Pearson correlation coefficient, Bland-Altman plots and κ-statistics. Results: The 64-slice MSCT agreed well with CMR for assessment of LVEF (r = 0.92; p < 0.0001), LVdV (r = 0.98; p < 0.0001) and LVsV (r = 0.98; p < 0.0001). In comparison with 64-slice MSCT, 2DE showed moderate correlation with CMR for the assessment of LVEF (r = 0.84; p < 0.0001), LVdV (r = 0.83; p < 0.0001) and LVsV (r = 0.80; p < 0.0001). However in RWM analysis, 2DE showed better accuracy than 64-slice MSCT (94.3% versus 82.4%) and closer agreement (κ = 0.89 versus 0.63) with CMR. Conclusion: 64-Slice MSCT correlates strongly with CMR in global LV function however in regional LV function 2DE showed better agreement with CMR than 64-slice MSCT

  7. Assessment of global and regional left ventricular function using 64-slice multislice computed tomography and 2D echocardiography: A comparison with cardiac magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Annuar, Bin Rapaee [Faculty of Medicine, University Malaysia Sarawak (Malaysia); Department of Cardiology, Sarawak General Hospital (Malaysia)], E-mail: rannuar@fmhs.unimas.my; Liew, Chee Khoon; Chin, Sze Piaw; Ong, Tiong Kiam [Department of Cardiology, Sarawak General Hospital (Malaysia); Seyfarth, M. Tobias [Sieman Medical Solution (Germany); Chan, Wei Ling; Fong, Yean Yip; Ang, Choon Kiat [Department of Cardiology, Sarawak General Hospital (Malaysia); Lin, Naing [Universiti Sains Malaysia (Malaysia); Liew, Houng Bang; Sim, Kui Hian [Department of Cardiology, Sarawak General Hospital (Malaysia)

    2008-01-15

    Objectives: To compare the assessment of global and regional left ventricular (LV) function using 64-slice multislice computed tomography (MSCT), 2D echocardiography (2DE) and cardiac magnetic resonance (CMR). Methods: Thirty-two consecutive patients (mean age, 56.5 {+-} 9.7 years) referred for evaluation of coronary artery using 64-slice MSCT also underwent 2DE and CMR within 48 h. The global left ventricular function which include left ventricular ejection fraction (LVEF), left ventricular end diastolic volume (LVdV) and left ventricular end systolic volume (LVsV) were determine using the three modalities. Regional wall motion (RWM) was assessed visually in all three modalities. The CMR served as the gold standard for the comparison between 64-slice MSCT with CMR and 2DE with CMR. Statistical analysis included Pearson correlation coefficient, Bland-Altman plots and {kappa}-statistics. Results: The 64-slice MSCT agreed well with CMR for assessment of LVEF (r = 0.92; p < 0.0001), LVdV (r = 0.98; p < 0.0001) and LVsV (r = 0.98; p < 0.0001). In comparison with 64-slice MSCT, 2DE showed moderate correlation with CMR for the assessment of LVEF (r = 0.84; p < 0.0001), LVdV (r = 0.83; p < 0.0001) and LVsV (r = 0.80; p < 0.0001). However in RWM analysis, 2DE showed better accuracy than 64-slice MSCT (94.3% versus 82.4%) and closer agreement ({kappa} = 0.89 versus 0.63) with CMR. Conclusion: 64-Slice MSCT correlates strongly with CMR in global LV function however in regional LV function 2DE showed better agreement with CMR than 64-slice MSCT.

  8. Assessment of global and regional left ventricular function using 64-slice multislice computed tomography and 2D echocardiography: a comparison with cardiac magnetic resonance.

    Science.gov (United States)

    Annuar, Bin Rapaee; Liew, Chee Khoon; Chin, Sze Piaw; Ong, Tiong Kiam; Seyfarth, M Tobias; Chan, Wei Ling; Fong, Yean Yip; Ang, Choon Kiat; Lin, Naing; Liew, Houng Bang; Sim, Kui Hian

    2008-01-01

    To compare the assessment of global and regional left ventricular (LV) function using 64-slice multislice computed tomography (MSCT), 2D echocardiography (2DE) and cardiac magnetic resonance (CMR). Thirty-two consecutive patients (mean age, 56.5+/-9.7 years) referred for evaluation of coronary artery using 64-slice MSCT also underwent 2DE and CMR within 48h. The global left ventricular function which include left ventricular ejection fraction (LVEF), left ventricular end diastolic volume (LVdV) and left ventricular end systolic volume (LVsV) were determine using the three modalities. Regional wall motion (RWM) was assessed visually in all three modalities. The CMR served as the gold standard for the comparison between 64-slice MSCT with CMR and 2DE with CMR. Statistical analysis included Pearson correlation coefficient, Bland-Altman plots and kappa-statistics. The 64-slice MSCT agreed well with CMR for assessment of LVEF (r=0.92; p<0.0001), LVdV (r=0.98; p<0.0001) and LVsV (r=0.98; p<0.0001). In comparison with 64-slice MSCT, 2DE showed moderate correlation with CMR for the assessment of LVEF (r=0.84; p<0.0001), LVdV (r=0.83; p<0.0001) and LVsV (r=0.80; p<0.0001). However in RWM analysis, 2DE showed better accuracy than 64-slice MSCT (94.3% versus 82.4%) and closer agreement (kappa=0.89 versus 0.63) with CMR. 64-Slice MSCT correlates strongly with CMR in global LV function however in regional LV function 2DE showed better agreement with CMR than 64-slice MSCT.

  9. Clinical application of helical CT colonography

    International Nuclear Information System (INIS)

    Zeng Huiliang; Zhu Xinjin; Liang Rujian; Liang Jianhao; Ou Weiqian; Wen Haomao

    2009-01-01

    Objective: To investigate the clinical value of 16-slice helical CT colonography in the diagnosis of colon tumor and polypus. Methods: 16-slice helical CT volumetric scanning was performed in 18 patients with colonic disease, including colonic tumor (n=16) and colonic polypus (n=2). 3D images, virtual endoscopy and multiplanar reformation were obtained in the AW4.1 workstation. CT appearances were compared with operation and fiberoptic colonoscopy. Results: Satisfied results were achieved from 18 patients, no difference found in results between CT colonography and operation in 16 patients with colonic tumor. Conclusion: 16-slice helical CT colonography is of great value in preoperative staging of colonic tumor and have a high value in clinical application. (authors)

  10. Neutrino's helicity in a gravitational field

    International Nuclear Information System (INIS)

    Pansart, J.P.

    1996-01-01

    By using approximated solutions of Dirac's equation, we show that there is no helicity reversal for light neutrinos in the Schwarzschild metric nor in an expanding universe. The actual coupling between a particle spin and the angular momentum of a heavy rotating body induces a possible helicity reversal but with an unobservable probability proportional to m 2 p / E 2 , where m p is the particle mass and E its energy. In these calculations, the helicity is defined through the spin orientation with respect to the current and not with respect to the linear momentum. This definition gives simple expressions and is equal to the usual definition in the case of a flat space. (N.T.)

  11. Multislice CT for preoperative diagnosis of pancreatic cancer

    International Nuclear Information System (INIS)

    Horiguchi, Akihiko; Ishihara, Shin; Ito, Masahiro

    2007-01-01

    We investigated the ability of multislice (MS) CT to visualize and diagnose the progression of pancreatic cancer. With regard to local progression, good diagnosis was possible for detecting the invasion of the intrapancreatic bile duct, duodenum, portal vein, arteries and other organs, and liver metastasis. Sensitivity was high but specificity was not good for detecting the invasion of the anterior and posterior pancreatic tissue. This is thought to be because of the positive diagnosis with pancreatitis that accompanies cancer. Pancreatic plexus invasion was also thought to be a cause of the lipid elevation of the nerve plexus and decreased sensitivity accompanying pancreatitis. Identification of cancer invasion and tumor periphery changes based on concomitant pancreatitis also depends on the amount of fibrous stroma, but this will require further investigation. Factors other than the size of lymph node metastases also need to be investigated. MS-CT can provide detailed volume data in a short time and making it an essential test in diagnosing the stage of pancreatic cancer. (author)

  12. Introduction to the m = 1 helicity source

    International Nuclear Information System (INIS)

    Platts, D.A.; Jarboe, T.R.; Wright, B.L.

    1985-01-01

    The m = 1 Helicity Source, formerly called the Kinked Z-pinch, was developed as part of the Electrode Studies program at Los Alamos. The Electrode Studies program was initiated to study the control of electrode erosion in long discharge duration spheromak sources. Erosion control is necessary to reduce plasma impurities and to obtain adequate electrode lifetimes. The first task of the Electrode Studies program is to determine, from among a variety of configurations including the coaxial one, a helicity source geometry with good prospects for erosion control. The more efficient the helicity source the easier it will be to control erosion, but the source most also be easy to diagnose and modify if it is to be a useful test bed. The various erosion control techniques which have been proposed will require extensive experimentation to evaluate and optimize. Proposed techniques include, using refractory metals, profiling of the electrodes and magnetic fields, and various gas injection schemes including porous electrodes. It is considered necessary to do these experiments on an optimized helicity source so that the electrode geometries and plasma properties will be relevant. Therefore the present Electrode Studies program is aimed at developing an improved helicity source design

  13. Five-year clinical and functional multislice computed tomography angiographic results after coronary implantation of the fully resorbable polymeric everolimus-eluting scaffold in patients with de novo coronary artery disease: the ABSORB cohort A trial.

    Science.gov (United States)

    Onuma, Yoshinobu; Dudek, Dariusz; Thuesen, Leif; Webster, Mark; Nieman, Koen; Garcia-Garcia, Hector M; Ormiston, John A; Serruys, Patrick W

    2013-10-01

    This study sought to demonstrate the 5-year clinical and functional multislice computed tomography angiographic results after implantation of the fully resorbable everolimus-eluting scaffold (Absorb BVS, Abbott Vascular, Santa Clara, California). Multimodality imaging of the first-in-humans trial using a ABSORB BVS scaffold demonstrated at 2 years the bioresorption of the device while preventing restenosis. However, the long-term safety and efficacy of this therapy remain to be documented. In the ABSORB cohort A trial (ABSORB Clinical Investigation, Cohort A [ABSORB A] Everolimus-Eluting Coronary Stent System Clinical Investigation), 30 patients with a single de novo coronary artery lesion were treated with the fully resorbable everolimus-eluting Absorb scaffold at 4 centers. As an optional investigation in 3 of the 4 centers, the patients underwent multislice computed tomography (MSCT) angiography at 18 months and 5 years. Acquired MSCT data were analyzed at an independent core laboratory (Cardialysis, Rotterdam, the Netherlands) for quantitative analysis of lumen dimensions and was further processed for calculation of fractional flow reserve (FFR) at another independent core laboratory (Heart Flow, Redwood City, California). Five-year clinical follow-up is available for 29 patients. One patient withdrew consent after 6 months, but the vital status of this patient remains available. At 46 days, 1 patient experienced a single episode of chest pain and underwent a target lesion revascularization with a slight troponin increase after the procedure. At 5 years, the ischemia-driven major adverse cardiac event rate of 3.4% remained unchanged. Clopidogrel was discontinued in all but 1 patient. Scaffold thrombosis was not observed in any patient. Two noncardiac deaths were reported, 1 caused by duodenal perforation and the other from Hodgkin's disease. At 5 years, 18 patients underwent MSCT angiography. All scaffolds were patent, with a median minimal lumen area of 3

  14. Genetic association of glutathione peroxidase-1 with coronary artery calcification in type 2 diabetes: a case control study with multi-slice computed tomography

    Directory of Open Access Journals (Sweden)

    Fujimoto Kei

    2007-09-01

    Full Text Available Abstract Background Although oxidative stress by accumulation of reactive oxygen species (ROS in diabetes has become evident, it remains unclear what genes, involved in redox balance, would determine susceptibility for development of atherosclerosis in diabetes. This study evaluated the effect of genetic polymorphism of enzymes producing or responsible for reducing ROS on coronary artery calcification in type 2 diabetes (T2D. Methods An index for coronary-arteriosclerosis, coronary artery calcium score (CACS was evaluated in 91 T2D patients using a multi-slice computed tomography. Patients were genotyped for ROS-scavenging enzymes, Glutathione peroxidase-1 (GPx-1, Catalase, Mn-SOD, Cu/Zn-SOD, as well as SNPs of NADPH oxidase as ROS-promoting elements, genes related to onset of T2D (CAPN10, ADRB3, PPAR gamma, FATP4. Age, blood pressure, BMI, HbA1c, lipid and duration of diabetes were evaluated for a multivariate regression analysis. Results CACS with Pro/Leu genotype of the GPx-1 gene was significantly higher than in those with Pro/Pro (744 ± 1,291 vs. 245 ± 399, respectively, p = 0.006. In addition, genotype frequency of Pro/Leu in those with CACS ≥ 1000 was significantly higher than in those with CACS OR = 3.61, CI = 0.97–13.42; p = 0.045 when tested for deviation from Hardy-Weinberg's equilibrium. Multivariate regression analyses revealed that CACS significantly correlated with GPx-1 genotypes and age. Conclusion The presence of Pro197Leu substitution of the GPx-1 gene may play a crucial role in determining genetic susceptibility to coronary-arteriosclerosis in T2D. The mechanism may be associated with a decreased ability to scavenge ROS with the variant GPx-1.

  15. A z-gradient array for simultaneous multi-slice excitation with a single-band RF pulse.

    Science.gov (United States)

    Ertan, Koray; Taraghinia, Soheil; Sadeghi, Alireza; Atalar, Ergin

    2018-07-01

    Multi-slice radiofrequency (RF) pulses have higher specific absorption rates, more peak RF power, and longer pulse durations than single-slice RF pulses. Gradient field design techniques using a z-gradient array are investigated for exciting multiple slices with a single-band RF pulse. Two different field design methods are formulated to solve for the required current values of the gradient array elements for the given slice locations. The method requirements are specified, optimization problems are formulated for the minimum current norm and an analytical solution is provided. A 9-channel z-gradient coil array driven by independent, custom-designed gradient amplifiers is used to validate the theory. Performance measures such as normalized slice thickness error, gradient strength per unit norm current, power dissipation, and maximum amplitude of the magnetic field are provided for various slice locations and numbers of slices. Two and 3 slices are excited by a single-band RF pulse in simulations and phantom experiments. The possibility of multi-slice excitation with a single-band RF pulse using a z-gradient array is validated in simulations and phantom experiments. Magn Reson Med 80:400-412, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  16. Helicity amplitudes for matter-coupled gravity

    International Nuclear Information System (INIS)

    Aldrovandi, R.; Novaes, S.F.; Spehler, D.

    1992-07-01

    The Weyl-van der Waerden spinor formalism is applied to the evaluation of helicity invariant amplitudes in the framework of linearized gravitation. The graviton couplings to spin-0, 1 - 2 , 1, and 3 - 2 particles are given, and, to exhibit the reach of this method, the helicity amplitudes for the process electron + positron → photon + graviton are obtained. (author)

  17. Hydrodynamic studies of CNT nanofluids in helical coil heat exchanger

    Science.gov (United States)

    Babita; Sharma, S. K.; Mital Gupta, Shipra; Kumar, Arinjay

    2017-12-01

    Helical coils are extensively used in several industrial processes such as refrigeration systems, chemical reactors, recovery processes etc to accommodate a large heat transfer area within a smaller space. Nanofluids are getting great attention due to their enhanced heat transfer capability. In heat transfer equipments, pressure drop is one of the major factors of consideration for pumping power calculations. So, the present work is aimed to study hydrodynamics of CNT nanofluids in helical coils. In this study, pressure drop characteristics of CNT nanofluid flowing inside horizontal helical coils are investigated experimentally. The helical coil to tube diameter was varied from 11.71 to 27.34 keeping pitch of the helical coil constant. Double distilled water was used as basefluid. SDBS and GA surfactants were added to stablilize CNT nanofluids. The volumetric fraction of CNT nanofluid was varied from 0.003 vol% to 0.051 vol%. From the experimental data, it was analyzed that the friction factor in helical coils is greater than that of straight tubes. Concentration of CNT in nanofluids also has a significant influence on the pressure drop/friction factor of helical coils. At a constant concentration of CNT, decreasing helical coil to tube diameter from 27.24 to 11.71, fanning friction factor of helical coil; f c increases for a constant value of p/d t. This increase in the value of fanning friction factor can be attributed to the secondary flow of CNT nanofluid in helical coils.

  18. Progressive and resonant wave helices application to electron paramagnetic resonance; Helices a ondes progressives et resonnantes application a la resonance paramagnetique electronique

    Energy Technology Data Exchange (ETDEWEB)

    Volino, F [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1969-07-01

    We show that helices can be used as resonant systems. Their properties are theoretically and experimentally studied. We describe resonant helices for electron paramagnetic resonance in X-band and develop a comparison between their sensitivity and the sensitivity of a normal resonant cavity. For cylindrical samples less than 3 mm diameter, the helix is more sensitive and can produce more intense microwave magnetic fields. (author) [French] Il est montre que les helices peuvent etre utilisees comme systeme resonnant. Leurs proprietes sont discutees theoriquement et experimentalement. Des helices resonnantes en bande X pour la resonance paramagnetique electronique sont decrites et leur sensibilite est comparee a celle des cavites resonnantes. Pour des echantillons cylindriques de moins de 3 mm de diametre, l'helice est plus sensible et peut produire des champs magnetiques hyper fins plus intenses. (auteur)

  19. Design windows and cost analysis on helical reactors

    International Nuclear Information System (INIS)

    Kozaki, Y.; Imagawa, S.; Sagara, A.

    2007-01-01

    The LHD type helical reactors are characterized by a large major radius but slender helical coil, which give us different approaches for power plants from tokamak reactors. For searching design windows of helical reactors and discussing their potential as power plants, we have developed a mass-cost estimating model linked with system design code (HeliCos), thorough studying the relationships between major plasma parameters and reactor parameters, and weight of major components. In regard to cost data we have much experience through preparing ITER construction. To compare the weight and cost of magnet systems between tokamak and helical reactors, we broke down magnet systems and cost factors, such as weights of super conducting strands, conduits, support structures, and winding unit costs, through estimating ITER cost data basis. Based on FFHR2m1 deign we considered a typical 3 GWth helical plant (LHD type) with the same magnet size, coil major radius Rc 14 m, magnetic energy 120 GJ, but increasing plasma densities. We evaluated the weight and cost of magnet systems of 3 GWth helical plant, the total magnet weights of 16,000ton and costs of 210 BYen, which are similar values of tokamak reactors (10,200 ton, 110 BYen in ITER 2002 report, and 21,900 ton, 275 BYen in ITER FDR1999). The costs of strands and winding occupy 70% of total magnet costs, and influence entire power plants economics. The design windows analysis and comparative economics studies to optimize the main reactor parameters have been carried out. Economics studies show that it is misunderstanding to consider helical coils are too large and too expensive to achieve power plants. But we should notice that the helical reactor design windows and economics are very sensitive to allowable blanket space (depend on ergodic layer conditions) and diverter configuration for decreasing heat loads. (orig.)

  20. Stabilized helical peptides: overview of the technologies and its impact on drug discovery.

    Science.gov (United States)

    Klein, Mark

    2017-11-01

    Protein-protein interactions are predominant in the workings of all cells. Until now, there have been a few successes in targeting protein-protein interactions with small molecules. Peptides may overcome some of the challenges of small molecules in disrupting protein-protein interactions. However, peptides present a new set of challenges in drug discovery. Thus, the study of the stabilization of helical peptides has been extensive. Areas covered: Several technological approaches to helical peptide stabilization have been studied. In this review, stapled peptides, foldamers, and hydrogen bond surrogates are discussed. Issues regarding design principles are also discussed. Furthermore, this review introduces select computational techniques used to aid peptide design and discusses clinical trials of peptides in a more advanced stage of development. Expert opinion: Stabilized helical peptides hold great promise in a wide array of diseases. However, the field is still relatively new and new design principles are emerging. The possibilities of peptide modification are quite extensive and expanding, so the design of stabilized peptides requires great attention to detail in order to avoid a large number of failed lead peptides. The start of clinical trials with stapled peptides is a promising sign for the future.

  1. Particle orbit analysis for LHD helical axis configurations

    International Nuclear Information System (INIS)

    Guasp, J.; Yamazaki, K.; Motojima, O.

    1993-04-01

    Fast ion orbits for helical magnetic axis configurations in LHD (Large Helical Device) are analyzed and compared with the standard circular axis case. Boundaries between passing and helically trapped particle regions show clear differences: in the non-planar axis case the helically trapped region spreads, near the magnetic axis, over a much wider band across the 90deg pitch angle value and shows a very marked asymmetry. The locally trapped particle region is also wider than in the standard case. The differences in the loss cone boundaries of the two cases are rather small, however, the effects of re-entering criteria are very important in both cases. On the contrary, effects of finite coil size are not significant. (author)

  2. Helically linked mirror arrangement

    International Nuclear Information System (INIS)

    Ranjan, P.

    1986-08-01

    A scheme is described for helical linking of mirror sections, which endeavors to combine the better features of toroidal and mirror devices by eliminating the longitudinal loss of mirror machines, having moderately high average β and steady state operation. This scheme is aimed at a device, with closed magnetic surfaces having rotational transform for equilibrium, one or more axisymmetric straight sections for reduced radial loss, a simple geometrical axis for the links and an overall positive magnetic well depth for stability. We start by describing several other attempts at linking of mirror sections, made both in the past and the present. Then a description of our helically linked mirror scheme is given. This example has three identical straight sections connected by three sections having helical geometric axes. A theoretical analysis of the magnetic field and single-particle orbits in them leads to the conclusion that most of the passing particles would be confined in the device and they would have orbits independent of pitch angle under certain conditions. Numerical results are presented, which agree well with the theoretical results as far as passing particle orbits are concerned

  3. Helicity and evanescent waves. [Energy transport velocity, helicity, Lorentz transformation

    Energy Technology Data Exchange (ETDEWEB)

    Agudin, J L; Platzeck, A M [La Plata Univ. Nacional (Argentina); Albano, J R [Instituto de Astronomia y Fisica del Espacio, Buenos Aires, Argentina

    1978-02-20

    It is shown that the projection of the angular momentum of a circularly polarized electromagnetic evanescent wave along the mean velocity of energy transport (=helicity) can be reverted by a Lorentz transformation, in spite of the fact that this velocity is c.

  4. Magnetic islands created by resonant helical windings

    International Nuclear Information System (INIS)

    Fernandes, A.S.; Heller, M.V.; Caldas, I.L.

    1986-01-01

    The triggering of disruptive instabilities by resonant helical windings in large aspect-ratio tokamaks is associated to destruction of magnetic surfaces. The Chirikov condition is applied to estimate analytically the helical winding current thresholds for ergodization of the magnetic field lines. (Autor) [pt

  5. Progressive and resonant wave helices application to electron paramagnetic resonance; Helices a ondes progressives et resonnantes application a la resonance paramagnetique electronique

    Energy Technology Data Exchange (ETDEWEB)

    Volino, F. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1969-07-01

    We show that helices can be used as resonant systems. Their properties are theoretically and experimentally studied. We describe resonant helices for electron paramagnetic resonance in X-band and develop a comparison between their sensitivity and the sensitivity of a normal resonant cavity. For cylindrical samples less than 3 mm diameter, the helix is more sensitive and can produce more intense microwave magnetic fields. (author) [French] Il est montre que les helices peuvent etre utilisees comme systeme resonnant. Leurs proprietes sont discutees theoriquement et experimentalement. Des helices resonnantes en bande X pour la resonance paramagnetique electronique sont decrites et leur sensibilite est comparee a celle des cavites resonnantes. Pour des echantillons cylindriques de moins de 3 mm de diametre, l'helice est plus sensible et peut produire des champs magnetiques hyper fins plus intenses. (auteur)

  6. Superposition of helical beams by using a Michelson interferometer.

    Science.gov (United States)

    Gao, Chunqing; Qi, Xiaoqing; Liu, Yidong; Weber, Horst

    2010-01-04

    Orbital angular momentum (OAM) of a helical beam is of great interests in the high density optical communication due to its infinite number of eigen-states. In this paper, an experimental setup is realized to the information encoding and decoding on the OAM eigen-states. A hologram designed by the iterative method is used to generate the helical beams, and a Michelson interferometer with two Porro prisms is used for the superposition of two helical beams. The experimental results of the collinear superposition of helical beams and their OAM eigen-states detection are presented.

  7. Turbulent Helicity in the Atmospheric Boundary Layer

    Science.gov (United States)

    Chkhetiani, Otto G.; Kurgansky, Michael V.; Vazaeva, Natalia V.

    2018-05-01

    We consider the assumption postulated by Deusebio and Lindborg (J Fluid Mech 755:654-671, 2014) that the helicity injected into the Ekman boundary layer undergoes a cascade, with preservation of its sign (right- or alternatively left-handedness), which is a signature of the system rotation, from large to small scales, down to the Kolmogorov microscale of turbulence. At the same time, recent direct field measurements of turbulent helicity in the steppe region of southern Russia near Tsimlyansk Reservoir show the opposite sign of helicity from that expected. A possible explanation for this phenomenon may be the joint action of different scales of atmospheric flows within the boundary layer, including the sea-breeze circulation over the test site. In this regard, we consider a superposition of the classic Ekman spiral solution and Prandtl's jet-like slope-wind profile to describe the planetary boundary-layer wind structure. The latter solution mimics a hydrostatic shallow breeze circulation over a non-uniformly heated surface. A 180°-wide sector on the hodograph plane exists, within which the relative orientation of the Ekman and Prandtl velocity profiles favours the left rotation with height of the resulting wind velocity vector in the lowermost part of the boundary layer. This explains the negative (left-handed) helicity cascade toward small-scale turbulent motions, which agrees with the direct field measurements of turbulent helicity in Tsimlyansk. A simple turbulent relaxation model is proposed that explains the measured positive values of the relatively minor contribution to turbulent helicity from the vertical components of velocity and vorticity.

  8. Helical Antimicrobial Sulfono- {gamma} -AApeptides

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yaqiong; Wu, Haifan; Teng, Peng; Bai, Ge; Lin, Xiaoyang; Zuo, Xiaobing; Cao, Chuanhai; Cai, Jianfeng

    2015-06-11

    Host-defense peptides (HDPs) such as magainin 2 have emerged as potential therapeutic agents combating antibiotic resistance. Inspired by their structures and mechanism of action, herein we report the fi rst example of antimicrobial helical sulfono- γ - AApeptide foldamers. The lead molecule displays broad-spectrum and potent antimicrobial activity against multi-drug-resistant Gram- positive and Gram-negative bacterial pathogens. Time-kill studies and fl uorescence microscopy suggest that sulfono- γ -AApeptides eradicate bacteria by taking a mode of action analogous to that of HDPs. Clear structure - function relationships exist in the studied sequences. Longer sequences, presumably adopting more-de fi ned helical structures, are more potent than shorter ones. Interestingly, the sequence with less helical propensity in solution could be more selective than the stronger helix-forming sequences. Moreover, this class of antimicrobial agents are resistant to proteolytic degradation. These results may lead to the development of a new class of antimicrobial foldamers combating emerging antibiotic-resistant pathogens.

  9. Stiffness versus architecture of single helical polyisocyanopeptides

    NARCIS (Netherlands)

    Buul, van A.M.; Schwartz, E.; Brocorens, P.; Koepf, M.; Beljonne, D.; Maan, J.C.; Christianen, P.C.M.; Kouwer, P.H.J.; Nolte, R.J.M.; Engelkamp, H.; Blank, K.; Rowan, A.E.

    2013-01-01

    Helical structures play a vital role in nature, offering mechanical rigidity, chirality and structural definition to biological systems. Little is known about the influence of the helical architecture on the intrinsic properties of polymers. Here, we offer an insight into the nano architecture of

  10. Polymorphic transformation of helical flagella of bacteria

    Science.gov (United States)

    Lim, Sookkyung; Howard Berg Collaboration; William Ko Collaboration; Yongsam Kim Collaboration; Wanho Lee Collaboration; Charles Peskin Collaboration

    2016-11-01

    Bacteria such as E. coli swim in an aqueous environment by utilizing the rotation of flagellar motors and alternate two modes of motility, runs and tumbles. Runs are steady forward swimming driven by bundles of flagellar filaments whose motors are turning CCW; tumbles involve a reorientation of the direction of swimming triggered by motor reversals. During tumbling, the helical flagellum undergoes polymorphic transformations, which is a local change in helical pitch, helical radius, and handedness. In this work, we investigate the underlying mechanism of structural conformation and how this polymorphic transition plays a role in bacterial swimming. National Science Foundation.

  11. Three-dimensional printing of freeform helical microstructures: a review.

    Science.gov (United States)

    Farahani, R D; Chizari, K; Therriault, D

    2014-09-21

    Three-dimensional (3D) printing is a fabrication method that enables creation of structures from digital models. Among the different structures fabricated by 3D printing methods, helical microstructures attracted the attention of the researchers due to their potential in different fields such as MEMS, lab-on-a-chip systems, microelectronics and telecommunications. Here we review different types of 3D printing methods capable of fabricating 3D freeform helical microstructures. The techniques including two more common microfabrication methods (i.e., focused ion beam chemical vapour deposition and microstereolithography) and also five methods based on computer-controlled robotic direct deposition of ink filament (i.e., fused deposition modeling, meniscus-confined electrodeposition, conformal printing on a rotating mandrel, UV-assisted and solvent-cast 3D printings) and their advantages and disadvantages regarding their utilization for the fabrication of helical microstructures are discussed. Focused ion beam chemical vapour deposition and microstereolithography techniques enable the fabrication of very precise shapes with a resolution down to ∼100 nm. However, these techniques may have material constraints (e.g., low viscosity) and/or may need special process conditions (e.g., vacuum chamber) and expensive equipment. The five other techniques based on robotic extrusion of materials through a nozzle are relatively cost-effective, however show lower resolution and less precise features. The popular fused deposition modeling method offers a wide variety of printable materials but the helical microstructures manufactured featured a less precise geometry compared to the other printing methods discussed in this review. The UV-assisted and the solvent-cast 3D printing methods both demonstrated high performance for the printing of 3D freeform structures such as the helix shape. However, the compatible materials used in these methods were limited to UV-curable polymers and

  12. Quality assurance of a helical tomotherapy machine

    International Nuclear Information System (INIS)

    Fenwick, J D; Tome, W A; Jaradat, H A; Hui, S K; James, J A; Balog, J P; DeSouza, C N; Lucas, D B; Olivera, G H; Mackie, T R; Paliwal, B R

    2004-01-01

    Helical tomotherapy has been developed at the University of Wisconsin, and 'Hi-Art II' clinical machines are now commercially manufactured. At the core of each machine lies a ring-gantry-mounted short linear accelerator which generates x-rays that are collimated into a fan beam of intensity-modulated radiation by a binary multileaf, the modulation being variable with gantry angle. Patients are treated lying on a couch which is translated continuously through the bore of the machine as the gantry rotates. Highly conformal dose-distributions can be delivered using this technique, which is the therapy equivalent of spiral computed tomography. The approach requires synchrony of gantry rotation, couch translation, accelerator pulsing and the opening and closing of the leaves of the binary multileaf collimator used to modulate the radiation beam. In the course of clinically implementing helical tomotherapy, we have developed a quality assurance (QA) system for our machine. The system is analogous to that recommended for conventional clinical linear accelerator QA by AAPM Task Group 40 but contains some novel components, reflecting differences between the Hi-Art devices and conventional clinical accelerators. Here the design and dosimetric characteristics of Hi-Art machines are summarized and the QA system is set out along with experimental details of its implementation. Connections between this machine-based QA work, pre-treatment patient-specific delivery QA and fraction-by-fraction dose verification are discussed

  13. A small-animal imaging system capable of multipinhole circular/helical SPECT and parallel-hole SPECT

    International Nuclear Information System (INIS)

    Qian Jianguo; Bradley, Eric L.; Majewski, Stan; Popov, Vladimir; Saha, Margaret S.; Smith, Mark F.; Weisenberger, Andrew G.; Welsh, Robert E.

    2008-01-01

    We have designed and built a small-animal single-photon emission computed tomography (SPECT) imaging system equipped with parallel-hole and multipinhole collimators and capable of circular or helical SPECT. Copper-beryllium parallel-hole collimators suitable for imaging the ∼35 keV photons from the decay of 125 I have been built and installed to achieve useful spatial resolution over a range of object-detector distances and to reduce imaging time on our dual-detector array. To address the resolution limitations in the parallel-hole SPECT and the sensitivity and limited field of view of single-pinhole SPECT, we have incorporated multipinhole circular and helical SPECT in addition to expanding the parallel-hole SPECT capabilities. The pinhole SPECT system is based on a 110 mm diameter circular detector equipped with a pixellated NaI(Tl) scintillator array (1x1x5 mm 3 /pixel). The helical trajectory is accomplished by two stepping motors controlling the rotation of the detector-support gantry and displacement of the animal bed along the axis of rotation of the gantry. Results obtained in SPECT studies of various phantoms show an enlarged field of view, very good resolution and improved sensitivity using multipinhole circular or helical SPECT. Collimators with one, three and five, 1-mm-diameter pinholes have been implemented and compared in these tests. Our objective is to develop a system on which one may readily select a suitable mode of either parallel-hole SPECT or pinhole circular or helical SPECT for a variety of small animal imaging applications

  14. Resonant helical fields in tokamaks

    International Nuclear Information System (INIS)

    Okano, V.

    1990-01-01

    Poincare maps of magnetic field lines of a toroidal helical system were made. The magnetic field is a linear superposition of the magnetic fields produced by a toroidal plasma in equilibrium and by external helical currents. Analytical expression for the Poincare maps was no obtained since the magnetic field do not have symmetry. In order to obtain the maps, the equation minus derivative of l vector times B vector = 0 was numerically integrated. In the Poincare maps, the principal and the secondary magnetic island were observed. (author)

  15. Helicity and Filament Channels? The Straight Twist!

    Science.gov (United States)

    Antiochos, Spiro K.

    2010-01-01

    One of the most important and most puzzling features of the coronal magnetic field is that it appears to have smooth magnetic structure with little evidence for non-potentiality except at special locations, photospheric polarity inversions lines where the non-potentiality is observed as a filament channel. This characteristic feature of the closed-field corona is highly unexpected given that photospheric motions continuously tangle its magnetic field. Although reconnection can eliminate some of the injected structure, it cannot destroy the helicity, which should build up to produce observable complexity. We propose that an inverse cascade process transports the injected helicity from the interior of closed flux regions to their boundaries, polarity inversion lines, creating filament channels. We describe how the helicity is injected and transported and calculate the relevant rates. We argue that one process, helicity transport, can explain both the observed lack and presence of structure in the coronal magnetic field.

  16. Helical magnetized wiggler for synchrotron radiation laser

    International Nuclear Information System (INIS)

    Wang Mei; Park, S.Y.; Hirshfield, J.L.

    1999-01-01

    A helical magnetized iron wiggler has been built for a novel infrared synchrotron radiation laser (SRL) experiment. The wiggler consists of four periods of helical iron structure immersed in a solenoid field. This wiggler is to impart transverse velocity to a prebunched 6 MeV electron beam, and thus to obtain a desired high orbit pitch ratio for the SRL. Field tapering at beam entrance is considered and tested on a similar wiggler. Analytic and simulated characteristics of wigglers of this type are discussed and the performance of the fabricated wigglers is demonstrated experimentally. A 4.7 kG peak field was measured for a 6.4 mm air gap and a 5.4 cm wiggler period at a 20 kG solenoid field. The measured helical fields compare favorably with the analytical solution. This type of helical iron wigglers has the potential to be scaled to small periods with strong field amplitude

  17. Using helical compressors for coke gas condensation

    Energy Technology Data Exchange (ETDEWEB)

    Privalov, V E; Rezunenko, Yu I; Lelyanov, N V; Zarnitzkii, G Eh; Gordienko, A A; Derebenko, I F; Venzhega, A G; Leonov, N P; Gorokhov, N N

    1982-08-01

    Coke oven gas compression is discussed. Presently used multilevel piston compressors are criticized. The paper recommends using helical machines which combine advantages of using volume condensing compressors and compact high-efficiency centrifugal machines. Two kinds of helical compressors are evaluated: dry and oil-filled; their productivities and coke oven gas chemical composition are analyzed. Experiments using helical compressors were undertaken at the Yasinovskii plant. Flowsheet of the installation is shown. Performance results are given in a table. For all operating conditions content of insolubles in oil compounds is found to be lower than the acceptable value (0.08%). Compressor productivity measurements with variable manifold pressure are evaluated. Figures obtained show that efficient condensation of raw coke oven gas is possible. Increasing oil-filled compressor productivity is recommended by decreasing amount of oil injected and simultaneously increasing rotation speed. The dry helical compressor with water seal is found to be most promising for raw coke oven gas condensation. (10 refs.)

  18. Helical magnetized wiggler for synchrotron radiation laser

    CERN Document Server

    Wang Mei; Hirshfield, J L

    1999-01-01

    A helical magnetized iron wiggler has been built for a novel infrared synchrotron radiation laser (SRL) experiment. The wiggler consists of four periods of helical iron structure immersed in a solenoid field. This wiggler is to impart transverse velocity to a prebunched 6 MeV electron beam, and thus to obtain a desired high orbit pitch ratio for the SRL. Field tapering at beam entrance is considered and tested on a similar wiggler. Analytic and simulated characteristics of wigglers of this type are discussed and the performance of the fabricated wigglers is demonstrated experimentally. A 4.7 kG peak field was measured for a 6.4 mm air gap and a 5.4 cm wiggler period at a 20 kG solenoid field. The measured helical fields compare favorably with the analytical solution. This type of helical iron wigglers has the potential to be scaled to small periods with strong field amplitude.

  19. Detection of common bile duct stones: comparison between endoscopic ultrasonography, magnetic resonance cholangiography, and helical-computed-tomographic cholangiography

    International Nuclear Information System (INIS)

    Kondo, Shintaro; Isayama, Hiroyuki; Akahane, Masaaki; Toda, Nobuo; Sasahira, Naoki; Nakai, Yosuke; Yamamoto, Natsuyo; Hirano, Kenji; Komatsu, Yutaka; Tada, Minoru; Yoshida, Haruhiko; Kawabe, Takao; Ohtomo, Kuni; Omata, Masao

    2005-01-01

    Objectives: New modalities, namely, endoscopic ultrasonography (EUS), magnetic resonance cholangiopancreatography (MRCP), and helical computed-tomographic cholangiography (HCT-C), have been introduced recently for the detection of common bile duct (CBD) stones and shown improved detectability compared to conventional ultrasound or computed tomography. We conducted this study to compare the diagnostic ability of EUS, MRCP, and HCT-C in patients with suspected choledocholithiasis. Methods: Twenty-eight patients clinically suspected of having CBD stones were enrolled, excluding those with cholangitis or a definite history of choledocholithiasis. Each patient underwent EUS, MRCP, and HCT-C prior to endoscopic retrograde cholangio-pancreatography (ERCP), the result of which served as the diagnostic gold standard. Results: CBD stones were detected in 24 (86%) of 28 patients by ERCP/IDUS. The sensitivity of EUS, MRCP, and HCT-C was 100%, 88%, and 88%, respectively. False negative cases for MRCP and HCT-C had a CBD stone smaller than 5 mm in diameter. No serious complications occurred while one patient complained of itching in the eyelids after the infusion of contrast agent on HCT-C. Conclusions: When examination can be scheduled, MRCP or HCT-C will be the first choice because they were less invasive than EUS. MRCP and HCT-C had similar detectability but the former may be preferable considering the possibility of allergic reaction in the latter. When MRCP is negative, EUS is recommended to check for small CBD stones

  20. Relativistic helicity and link in Minkowski space-time

    International Nuclear Information System (INIS)

    Yoshida, Z.; Kawazura, Y.; Yokoyama, T.

    2014-01-01

    A relativistic helicity has been formulated in the four-dimensional Minkowski space-time. Whereas the relativistic distortion of space-time violates the conservation of the conventional helicity, the newly defined relativistic helicity conserves in a barotropic fluid or plasma, dictating a fundamental topological constraint. The relation between the helicity and the vortex-line topology has been delineated by analyzing the linking number of vortex filaments which are singular differential forms representing the pure states of Banach algebra. While the dimension of space-time is four, vortex filaments link, because vorticities are primarily 2-forms and the corresponding 2-chains link in four dimension; the relativistic helicity measures the linking number of vortex filaments that are proper-time cross-sections of the vorticity 2-chains. A thermodynamic force yields an additional term in the vorticity, by which the vortex filaments on a reference-time plane are no longer pure states. However, the vortex filaments on a proper-time plane remain to be pure states, if the thermodynamic force is exact (barotropic), thus, the linking number of vortex filaments conserves

  1. Role of multislice CT and magnetic resonance cholangiography in preoperative evaluation of potential donor in living related liver transplantation

    Directory of Open Access Journals (Sweden)

    Hossam M. Abdel-Rahman

    2016-03-01

    Conclusion: Multislice CT is a valuable tool in the evaluation of potential living liver donors that provides complete information on the hepatic vascular anatomy, the liver parenchyma, and volumetric measurements. MRC with a 3.0-T MR system demonstrates the preoperative biliary evaluation very well with a high accuracy rate.

  2. Helicity antenna showers for hadron colliders

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Nadine; Skands, Peter [Monash University, School of Physics and Astronomy, Clayton, VIC (Australia); Lifson, Andrew [Monash University, School of Physics and Astronomy, Clayton, VIC (Australia); ETH Zuerich, Zurich (Switzerland)

    2017-10-15

    We present a complete set of helicity-dependent 2 → 3 antenna functions for QCD initial- and final-state radiation. The functions are implemented in the Vincia shower Monte Carlo framework and are used to generate showers for hadron-collider processes in which helicities are explicitly sampled (and conserved) at each step of the evolution. Although not capturing the full effects of spin correlations, the explicit helicity sampling does permit a significantly faster evaluation of fixed-order matrix-element corrections. A further speed increase is achieved via the implementation of a new fast library of analytical MHV amplitudes, while matrix elements from Madgraph are used for non-MHV configurations. A few examples of applications to QCD 2 → 2 processes are given, comparing the newly released Vincia 2.200 to Pythia 8.226. (orig.)

  3. Helicity antenna showers for hadron colliders

    Science.gov (United States)

    Fischer, Nadine; Lifson, Andrew; Skands, Peter

    2017-10-01

    We present a complete set of helicity-dependent 2→ 3 antenna functions for QCD initial- and final-state radiation. The functions are implemented in the Vincia shower Monte Carlo framework and are used to generate showers for hadron-collider processes in which helicities are explicitly sampled (and conserved) at each step of the evolution. Although not capturing the full effects of spin correlations, the explicit helicity sampling does permit a significantly faster evaluation of fixed-order matrix-element corrections. A further speed increase is achieved via the implementation of a new fast library of analytical MHV amplitudes, while matrix elements from Madgraph are used for non-MHV configurations. A few examples of applications to QCD 2→ 2 processes are given, comparing the newly released Vincia 2.200 to Pythia 8.226.

  4. Influence of gantry angle in helical computed tomography. Usefullness of 1-dimension sharpness filter

    Energy Technology Data Exchange (ETDEWEB)

    Kawano, Hirofumi; Suzuki, Toru; Matsuura, Shigeru; Kai, Tsuyoshi; Shimizu, Toshiyuki [Hyuga Hospital of Saiseikai Foundation, Kadogawa, Miyazaki (Japan)

    2001-05-01

    When we let gantry tilt and do scan in helical CT, vertical sharpness deteriorates. We were able to revise it with 1-dimensional sharpness filter which the square sum of difference of MTF was compared, and was designed this time. And the unsharpness was in proportion to sin of gantry angle. As a result, we led several sets of frequency emphasis degree. There is a model to built 1-dimension sharpness filter in a scan plan. It is useful for clinical diagnoses. (author)

  5. Influence of gantry angle in helical computed tomography. Usefullness of 1-dimension sharpness filter

    International Nuclear Information System (INIS)

    Kawano, Hirofumi; Suzuki, Toru; Matsuura, Shigeru; Kai, Tsuyoshi; Shimizu, Toshiyuki

    2001-01-01

    When we let gantry tilt and do scan in helical CT, vertical sharpness deteriorates. We were able to revise it with 1-dimensional sharpness filter which the square sum of difference of MTF was compared, and was designed this time. And the unsharpness was in proportion to sin of gantry angle. As a result, we led several sets of frequency emphasis degree. There is a model to built 1-dimension sharpness filter in a scan plan. It is useful for clinical diagnoses. (author)

  6. The helical tomotherapy thread effect

    International Nuclear Information System (INIS)

    Kissick, M.W.; Fenwick, J.; James, J.A.; Jeraj, R.; Kapatoes, J.M.; Keller, H.; Mackie, T.R.; Olivera, G.; Soisson, E.T.

    2005-01-01

    Inherent to helical tomotherapy is a dose variation pattern that manifests as a 'ripple' (peak-to-trough relative to the average). This ripple is the result of helical beam junctioning, completely unique to helical tomotherapy. Pitch is defined as in helical CT, the couch travel distance for a complete gantry rotation relative to the axial beam width at the axis of rotation. Without scattering or beam divergence, an analytical posing of the problem as a simple integral predicts minima near a pitch of 1/n where n is an integer. A convolution-superposition dose calculator (TomoTherapy, Inc.) included all the physics needed to explore the ripple magnitude versus pitch and beam width. The results of the dose calculator and some benchmark measurements demonstrate that the ripple has sharp minima near p=0.86(1/n). The 0.86 factor is empirical and caused by a beam junctioning of the off-axis dose profiles which differ from the axial profiles as well as a long scatter tail of the profiles at depth. For very strong intensity modulation, the 0.86 factor may vary. The authors propose choosing particular minima pitches or using a second delivery that starts 180 deg off-phase from the first to reduce these ripples: 'Double threading'. For current typical pitches and beam widths, however, this effect is small and not clinically important for most situations. Certain extremely large field or high pitch cases, however, may benefit from mitigation of this effect

  7. The generic geometry of helices and their close-packed structures

    DEFF Research Database (Denmark)

    Olsen, Kasper; Bohr, Jakob

    2010-01-01

    The formation of helices is an ubiquitous phenomenon for molecular structures whether they are biological, organic, or inorganic, in nature. Helical structures have geometrical constraints analogous to close packing of three-dimensional crystal structures. For helical packing the geometrical cons...

  8. Computational study of the fibril organization of polyglutamine repeats reveals a common motif identified in beta-helices.

    Science.gov (United States)

    Zanuy, David; Gunasekaran, Kannan; Lesk, Arthur M; Nussinov, Ruth

    2006-04-21

    The formation of fibril aggregates by long polyglutamine sequences is assumed to play a major role in neurodegenerative diseases such as Huntington. Here, we model peptides rich in glutamine, through a series of molecular dynamics simulations. Starting from a rigid nanotube-like conformation, we have obtained a new conformational template that shares structural features of a tubular helix and of a beta-helix conformational organization. Our new model can be described as a super-helical arrangement of flat beta-sheet segments linked by planar turns or bends. Interestingly, our comprehensive analysis of the Protein Data Bank reveals that this is a common motif in beta-helices (termed beta-bend), although it has not been identified so far. The motif is based on the alternation of beta-sheet and helical conformation as the protein sequence is followed from the N to the C termini (beta-alpha(R)-beta-polyPro-beta). We further identify this motif in the ssNMR structure of the protofibril of the amyloidogenic peptide Abeta(1-40). The recurrence of the beta-bend suggests a general mode of connecting long parallel beta-sheet segments that would allow the growth of partially ordered fibril structures. The design allows the peptide backbone to change direction with a minimal loss of main chain hydrogen bonds. The identification of a coherent organization beyond that of the beta-sheet segments in different folds rich in parallel beta-sheets suggests a higher degree of ordered structure in protein fibrils, in agreement with their low solubility and dense molecular packing.

  9. Coulomb double helical structure

    Science.gov (United States)

    Kamimura, Tetsuo; Ishihara, Osamu

    2012-01-01

    Structures of Coulomb clusters formed by dust particles in a plasma are studied by numerical simulation. Our study reveals the presence of various types of self-organized structures of a cluster confined in a prolate spheroidal electrostatic potential. The stable configurations depend on a prolateness parameter for the confining potential as well as on the number of dust particles in a cluster. One-dimensional string, two-dimensional zigzag structure and three-dimensional double helical structure are found as a result of the transition controlled by the prolateness parameter. The formation of stable double helical structures resulted from the transition associated with the instability of angular perturbations on double strings. Analytical perturbation study supports the findings of numerical simulations.

  10. Stable single helical C- and I-chains inside single-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Yao Z; Li Y; Jing X D; Meng F S; Zhao X; Li J H; Qiu Z Y; Yuan Q; Wang W X; Bi L; Liu H; Zhang Y P; Liu C J; Zheng S P; Liu B B

    2016-01-01

    The helicity of stable single helical carbon chains and iodine chains inside single-walled carbon nanotubes (SWCNTs) is studied by calculating the systematic van der Waals interaction energy. The results show that the optimal helical radius increases linearly with increasing tube radius, which produces a constant separation between the chain structure and the tube wall. The helical angle exhibits a ladder-like decrease with increasing tube radius, indicating that a large tube can produce a small helicity in the helical structures. (paper)

  11. Noninvasive assessment of coronary artery disease by multislice spiral computed tomography using a new retrospectively ECG-gated image reconstruction technique. Comparison with angiographic results

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Yuichi; Matsumoto, Naoya; Kato, Masahiko [Nihon Univ., Tokyo (Japan). Surugadai Hospital] [and others

    2003-04-01

    The present study was designed to investigate the accuracy of multislice spiral computed tomography (MSCT) in detecting coronary artery disease, compared with coronary angiography (CAG), using a new retrospectively ECG-gated reconstruction method that reduced cardiac motion artifact. The study group comprised 54 consecutive patients undergoing MSCT and CAG. MSCT was performed using a SOMATOM Volume Zoom (4-detector-row, Siemens, Germany) with slice thickness 1.0 mm, pitch 1.5 (table feed: 1.5 mm per rotation) and gantry rotation time 500 ms. Metoprolol (20-60 mg) was administered orally prior to MSCT imaging. ECG-gated image reconstruction was performed with the reconstruction window (250 ms) positioned immediately before atrial contraction in order to reduce the cardiac motion artifact caused by the abrupt diastolic ventricular movement occurring during the rapid filling and atrial contraction periods. Following inspection of the volume rendering images, multiplanar reconstruction images and axial images of the left main coronary artery (LMCA), left anterior descending artery (LAD), left circumflex artery (LCx) and right coronary artery (RCA) were obtained and evaluated for luminal narrowing. The results were compared with those obtained by CAG. Of 216 coronary arteries, 206 (95.4%) were assessable; 10 arteries were excluded from the analysis because of severe calcification (n=4), stents (n=3) or insufficient contrast enhancement (n=3). The sensitivity to detect coronary stenoses {>=}50% was 93.5% and the specificity to define luminal narrowing <50% was 97.2%. The positive predictive value and the negative predictive value were 93.5% and 97.2%, respectively. The sensitivity was still satisfactory (80.6%) even when non-assessable arteries were included in the analysis. The new retrospectively ECG-gated reconstruction method for MSCT has excellent diagnostic accuracy in detecting significant coronary artery stenoses. (author)

  12. Motion-induced dose artifacts in helical tomotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Bryan; Chen, Jeff; Battista, Jerry [London Regional Cancer Program, London Health Sciences Centre, London, ON (Canada); Kron, Tomas [Peter MacCallum Cancer Center, Melbourne (Australia)], E-mail: bryan.kim@lhsc.on.ca

    2009-10-07

    Tumor motion is a particular concern for a complex treatment modality such as helical tomotherapy, where couch position, gantry rotation and MLC leaf opening all change with time. In the present study, we have investigated the impact of tumor motion for helical tomotherapy, which could result in three distinct motion-induced dose artifacts, namely (1) dose rounding, (2) dose rippling and (3) IMRT leaf opening asynchronization effect. Dose rounding and dose rippling effects have been previously described, while the IMRT leaf opening asynchronization effect is a newly discovered motion-induced dose artifact. Dose rounding is the penumbral widening of a delivered dose distribution near the edges of a target volume along the direction of tumor motion. Dose rippling is a series of periodic dose peaks and valleys observed within the target region along the direction of couch motion, due to an asynchronous interplay between the couch motion and the longitudinal component of tumor motion. The IMRT leaf opening asynchronization effect is caused by an asynchronous interplay between the temporal patterns of leaf openings and tumor motion. The characteristics of each dose artifact were investigated individually as functions of target motion amplitude and period for both non-IMRT and IMRT helical tomotherapy cases, through computer simulation modeling and experimental verification. The longitudinal dose profiles generated by the simulation program agreed with the experimental data within {+-}0.5% and {+-}1.5% inside the PTV region for the non-IMRT and IMRT cases, respectively. The dose rounding effect produced a penumbral increase up to 20.5 mm for peak-to-peak target motion amplitudes ranging from 1.0 cm to 5.0 cm. Maximum dose rippling magnitude of 25% was calculated, when the target motion period approached an unusually high value of 10 s. The IMRT leaf opening asynchronization effect produced dose differences ranging from -29% to 7% inside the PTV region. This information

  13. Use of pattern recognition for unaliasing simultaneously acquired slices in simultaneous multislice MR fingerprinting.

    Science.gov (United States)

    Jiang, Yun; Ma, Dan; Bhat, Himanshu; Ye, Huihui; Cauley, Stephen F; Wald, Lawrence L; Setsompop, Kawin; Griswold, Mark A

    2017-11-01

    The purpose of this study is to accelerate an MR fingerprinting (MRF) acquisition by using a simultaneous multislice method. A multiband radiofrequency (RF) pulse was designed to excite two slices with different flip angles and phases. The signals of two slices were driven to be as orthogonal as possible. The mixed and undersampled MRF signal was matched to two dictionaries to retrieve T 1 and T 2 maps of each slice. Quantitative results from the proposed method were validated with the gold-standard spin echo methods in a phantom. T 1 and T 2 maps of in vivo human brain from two simultaneously acquired slices were also compared to the results of fast imaging with steady-state precession based MRF method (MRF-FISP) with a single-band RF excitation. The phantom results showed that the simultaneous multislice imaging MRF-FISP method quantified the relaxation properties accurately compared to the gold-standard spin echo methods. T 1 and T 2 values of in vivo brain from the proposed method also matched the results from the normal MRF-FISP acquisition. T 1 and T 2 values can be quantified at a multiband acceleration factor of two using our proposed acquisition even in a single-channel receive coil. Further acceleration could be achieved by combining this method with parallel imaging or iterative reconstruction. Magn Reson Med 78:1870-1876, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  14. Effective dose to patient measurements in flat-detector and multislice computed tomography: a comparison of applications in neuroradiology

    Energy Technology Data Exchange (ETDEWEB)

    Struffert, Tobias; Hauer, Michael; Doerfler, Arnd [University of Erlangen-Nuremberg, Department of Neuroradiology, Erlangen (Germany); Banckwitz, Rosemarie; Koehler, Christoph [Siemens AG, Healthcare Sector, Forchheim (Germany); Royalty, Kevin [Siemens Medical Solutions, USA, Inc, Hoffman Estates, IL (United States); University of Wisconsin, Department of Biomedical Engineering and School of Medicine and Public Health, Madison, WI (United States)

    2014-06-15

    Flat-detector CT (FD-CT) is used for a variety of applications. Additionally, 3D rotational angiography (3D DSA) is used to supplement digital subtraction angiography (DSA) studies. The aim was to measure and compare the dose of (1) standard DSA and 3D DSA and (2) analogous FD-CT and multislice CT (MSCT) protocols. Using an anthropomorphic phantom, the effective dose to patients (according to ICRP 103) was measured on an MSCT and a flat-detector angiographic system using standard protocols as recommended by the manufacturer. (1) Evaluation of DSA and 3D DSA angiography protocols: ap.-lat. Standard/low-dose series 1/0.8 mSv, enlarged oblique projection 0.3 mSv, 3D DSA 0.9 mSv (limited coverage length 0.3 mSv). (2) Comparison of FD-CT and MSCT: brain parenchyma imaging 2.9 /1.4 mSv, perfusion imaging 2.3/4.2 mSv, temporal bone 0.2 /0.2 mSv, angiography 2.9/3.3 mSv, limited to the head using collimation 0.5/0.5 mSv. The effective dose for an FD-CT application depends on the application used. Using collimation for FD-CT applications, the dose may be reduced considerably. Due to the low dose of 3D DSA, we recommend using this technique to reduce the number of DSA series needed to identify working projections. (orig.)

  15. Effective dose to patient measurements in flat-detector and multislice computed tomography: a comparison of applications in neuroradiology

    International Nuclear Information System (INIS)

    Struffert, Tobias; Hauer, Michael; Doerfler, Arnd; Banckwitz, Rosemarie; Koehler, Christoph; Royalty, Kevin

    2014-01-01

    Flat-detector CT (FD-CT) is used for a variety of applications. Additionally, 3D rotational angiography (3D DSA) is used to supplement digital subtraction angiography (DSA) studies. The aim was to measure and compare the dose of (1) standard DSA and 3D DSA and (2) analogous FD-CT and multislice CT (MSCT) protocols. Using an anthropomorphic phantom, the effective dose to patients (according to ICRP 103) was measured on an MSCT and a flat-detector angiographic system using standard protocols as recommended by the manufacturer. (1) Evaluation of DSA and 3D DSA angiography protocols: ap.-lat. Standard/low-dose series 1/0.8 mSv, enlarged oblique projection 0.3 mSv, 3D DSA 0.9 mSv (limited coverage length 0.3 mSv). (2) Comparison of FD-CT and MSCT: brain parenchyma imaging 2.9 /1.4 mSv, perfusion imaging 2.3/4.2 mSv, temporal bone 0.2 /0.2 mSv, angiography 2.9/3.3 mSv, limited to the head using collimation 0.5/0.5 mSv. The effective dose for an FD-CT application depends on the application used. Using collimation for FD-CT applications, the dose may be reduced considerably. Due to the low dose of 3D DSA, we recommend using this technique to reduce the number of DSA series needed to identify working projections. (orig.)

  16. High performance operational limits of tokamak and helical systems

    International Nuclear Information System (INIS)

    Yamazaki, Kozo; Kikuchi, Mitsuru

    2003-01-01

    The plasma operational boundaries of tokamak and helical systems are surveyed and compared with each other. Global confinement scaling laws are similar and gyro-Bohm like, however, local transport process is different due to sawtooth oscillations in tokamaks and ripple transport loss in helical systems. As for stability limits, achievable tokamak beta is explained by ideal or resistive MHD theories. On the other hand, beta values obtained so far in helical system are beyond ideal Mercier mode limits. Density limits in tokamak are often related to the coupling between radiation collapse and disruptive MHD instabilities, but the slow radiation collapse is dominant in the helical system. The pulse length of both tokamak and helical systems is on the order of hours in small machines, and the longer-pulsed good-confinement plasma operations compatible with radiative divertors are anticipated in both systems in the future. (author)

  17. An adaptive approach to metal artifact reduction in helical computed tomography for radiation therapy treatment planning: Experimental and clinical studies

    International Nuclear Information System (INIS)

    Yazdia, Mehran; Gingras, Luc; Beaulieu, Luc

    2005-01-01

    Purpose: In this article, an approach to metal artifact reduction is proposed that is practical for clinical use in radiation therapy. It is based on a new interpolation scheme of the projections associated with metal implants in helical computed tomography (CT) scanners. Methods and Materials: A three-step approach was developed consisting of an automatic algorithm for metal implant detection, a correction algorithm for helical projections, and a new, efficient algorithm for projection interpolation. The modified raw projection data are transferred back to the CT scanner device where CT slices are regenerated using the built-in reconstruction operator. The algorithm was tested on a CT calibration phantom in which the density of inserted objects are known and on clinical prostate cases with two hip prostheses. The results are evaluated using the CT number and shape of the objects. Results: The validations on a CT calibration phantom with various inserts of known densities show that the algorithm improved the overall image quality by restoring the shape and the representative CT number of the objects in the image. For the clinical hip replacement cases, a large fraction of the bladder, rectum, and prostate that were not visible on the original CT slices were recovered using the algorithm. Precise contouring of the target volume was thus feasible. Without this enhancement, physicians would have drawn bigger margins to be sure to include the target and, at the same time, could have prescribed a lower dose to keep the same level of normal tissue toxicity. Conclusions: In both phantom experiment and patient studies, the algorithm resulted in significant artifact reduction with increases in the reliability of planning procedure for the case of metallic hip prostheses. This algorithm is now clinically used as a preprocessing before treatment planning for metal artifact reduction

  18. Review of the helicity formalism; Revision del formalismo de helicidad

    Energy Technology Data Exchange (ETDEWEB)

    Barreiro, F; Cerrada, M; Fernandez, E

    1972-07-01

    Our purpose in these notes has been to present a brief and general review of the helicity formalism. We begin by discussing Lorentz invariance, spin and helicity ideas, in section 1 . In section 2 we deal with the construction of relativistic states and scattering amplitudes in the helicity basis and we study their transformation properties under discrete symmetries. Finally we present some more sophisticated topics like kinematical singularities of helicity amplitudes, kinematical constraints and crossing relations 3, 4, 5 respectively. (Author) 8 refs.

  19. Multiple helical modes of vortex breakdown

    DEFF Research Database (Denmark)

    Sørensen, Jens Nørkær; Naumov, I. V.; Okulov, Valery

    2011-01-01

    Experimental observations of vortex breakdown in a rotating lid-driven cavity are presented. The results show that vortex breakdown for cavities with high aspect ratios is associated with the appearance of stable helical vortex multiplets. By using results from stability theory generalizing Kelvi......’s problem on vortex polygon stability, and systematically exploring the cavity flow, we succeeded in identifying two new stable vortex breakdown states consisting of triple and quadruple helical multiplets....

  20. Maximum-intensity-projection CT angiography for evaluating head and neck tumors. Usefulness of helical CT and auto bone masking method

    International Nuclear Information System (INIS)

    Sakai, Osamu; Nakashima, Noriko; Ogawa, Chiaki; Shen, Yun; Takata, Yasunori; Azemoto, Shougo.

    1994-01-01

    Angiographic images of 10 adult patients with head and neck tumors were obtained by helical computed tomography (CT) using maximum intensity projection (MIP). In all cases, the vasculature of the head and neck region was directly demonstrated. In the head and neck, bone masking is a more important problem than in other regions. We developed an effective automatic bone masking method (ABM) using 2D/3D connectivity. Helical CT angiography with MIP and ABM provided accurate anatomic depiction, and was considered to be helpful in preoperative evaluation of head and neck tumors. (author)

  1. Experimental Evidence of Helical Flow in Porous Media

    DEFF Research Database (Denmark)

    Ye, Yu; Chiogna, Gabriele; Cirpka, Olaf A.

    2015-01-01

    Helical flow leads to deformation of solute plumes and enhances transverse mixing in porous media. We present experiments in which macroscopic helical flow is created by arranging different materials to obtain an anisotropic macroscopic permeability tensor with spatially variable orientation....... The resulting helical flow entails twisting streamlines which cause a significant increase in lateral mass exchange and thus a large enhancement of plume dilution (up to 235%) compared to transport in homogenous media. The setup may be used to effectively mix solutes in parallel streams similarly to static...... mixers, but in porous media....

  2. Radiation Field of a Square, Helical Beam Antenna

    DEFF Research Database (Denmark)

    Knudsen, Hans Lottrup

    1952-01-01

    square helices are used. Further, in connection with corresponding rigorous formulas for the field from a circular, helical antenna with a uniformly progressing current wave of constant amplitude the present formulas may be used for an investigation of the magnitude of the error introduced in Kraus......' approximate calculation of the field from a circular, helical antenna by replacing this antenna with an ``equivalent'' square helix. This investigation is carried out by means of a numerical example. The investigation shows that Kraus' approximate method of calculation yields results in fair agreement...

  3. Geometric analysis of alloreactive HLA α-helices.

    Science.gov (United States)

    Ribarics, Reiner; Karch, Rudolf; Ilieva, Nevena; Schreiner, Wolfgang

    2014-01-01

    Molecular dynamics (MD) is a valuable tool for the investigation of functional elements in biomolecules, providing information on dynamic properties and processes. Previous work by our group has characterized static geometric properties of the two MHC α-helices comprising the peptide binding region recognized by T cells. We build upon this work and used several spline models to approximate the overall shape of MHC α-helices. We applied this technique to a series of MD simulations of alloreactive MHC molecules that allowed us to capture the dynamics of MHC α-helices' steric configurations. Here, we discuss the variability of spline models underlying the geometric analysis with varying polynomial degrees of the splines.

  4. Elbow helical axes of motion are not the same in physiologic and kinetic joint simulators.

    Science.gov (United States)

    Muriuki, Muturi G; Mohagheh-Motlagh, Amin; Smolinski, Patrick J; Miller, Mark Carl

    2012-08-31

    Physiologic and kinetic joint simulators have been widely used for investigations of joint mechanics. The two types of simulator differ in the way joint motion is achieved; through prescribed motions and/or forces in kinetic joint simulators and by tendon loads in physiologic joint simulators. These two testing modalities have produced important insights, as in elucidating the importance of soft tissue structures to joint stability. However, the equivalence of the modalities has not been tested. This study sequentially tested five cadaveric elbows using both a physiologic simulator and a robot/6DOF system. Using position data from markers on the humerus and ulna, we calculated and compared the helical axes of motion of the specimens as the elbows were flexed from full extension. Six step size increments were used in the helical axis calculation. Marker position data at each test's full extension and full flexion point were also used to calculate a datum (overall) helical axis. The angles between the datum axis and step-wise movements were computed and stored. Increasing step size monotonically decreased the variability and the average conical angle encompassing the helical axes; a repeated measures ANOVA using test type (robot or physiologic simulator) and step size found that both type and step caused statistically significant differences (p<0.001). The large changes in helical axis angle observed for small changes in elbow flexion angle, especially in the robot tests, are a caveat for investigators using similar control algorithms. Controllers may need to include increased joint compliance and/or C(1) continuity to reduce variability. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. Helicity conservation and twisted Seifert surfaces for superfluid vortices.

    Science.gov (United States)

    Salman, Hayder

    2017-04-01

    Starting from the continuum definition of helicity, we derive from first principles its different contributions for superfluid vortices. Our analysis shows that an internal twist contribution emerges naturally from the mathematical derivation. This reveals that the spanwise vector that is used to characterize the twist contribution must point in the direction of a surface of constant velocity potential. An immediate consequence of the Seifert framing is that the continuum definition of helicity for a superfluid is trivially zero at all times. It follows that the Gauss-linking number is a more appropriate definition of helicity for superfluids. Despite this, we explain how a quasi-classical limit can arise in a superfluid in which the continuum definition for helicity can be used. This provides a clear connection between a microscopic and a macroscopic description of a superfluid as provided by the Hall-Vinen-Bekarevich-Khalatnikov equations. This leads to consistency with the definition of helicity used for classical vortices.

  6. On Helical Projection and Its Application in Screw Modeling

    Directory of Open Access Journals (Sweden)

    Riliang Liu

    2014-04-01

    Full Text Available As helical surfaces, in their many and varied forms, are finding more and more applications in engineering, new approaches to their efficient design and manufacture are desired. To that end, the helical projection method that uses curvilinear projection lines to map a space object to a plane is examined in this paper, focusing on its mathematical model and characteristics in terms of graphical representation of helical objects. A number of interesting projective properties are identified in regard to straight lines, curves, and planes, and then the method is further investigated with respect to screws. The result shows that the helical projection of a cylindrical screw turns out to be a Jordan curve, which is determined by the screw's axial profile and number of flights. Based on the projection theory, a practical approach to the modeling of screws and helical surfaces is proposed and illustrated with examples, and its possible application in screw manufacturing is discussed.

  7. The role of multislice spiral computed tomography in the diagnosis and management of acute facial trauma in patients with multiple injuries.

    Science.gov (United States)

    Nemsadze, G; Urushadze, O

    2011-11-01

    Using of mutislice spiral CT as first line examination for the diagnosis of Acute Facial trauma in the setting of Polytrauma reduces both: valuable time and cost of patient treatment. After a brief clinical examination, MDCT was performed depending on the area of injury, using a slice thickness of 0.65 mm. The obtained data were analyzed using 3D, MIP and Standard axial with Bone reconstruction protocols. 64 polytrauma patients were evaluated with both Anterior and Lateral craniography (plain skull X ray: AP and Lateral) and Multi Slice CT. Craniography detected only 18 cases of traumatic injuries of facial bones, but exact range of dislocation and accurate management plan could not be established. In the same 64 cases, Multislice CT revealed localization of all existed fractures, range of fragment dislocation, soft tissue damage and status of Paranasal sinus in 62 cases (96.8%). In two cases MS CT missed the facial fracture, in one case the examination was complicated because of bone thinness and numerous fracture fragments, in another multiple foreign body artifacts complicated the investigation. The study results show that, CT investigation based on our MDCT polytrauma protocol, detects all more or less serious facial bone injuries.

  8. Scale Dependence of Magnetic Helicity in the Solar Wind

    Science.gov (United States)

    Brandenburg, Axel; Subramanian, Kandaswamy; Balogh, Andre; Goldstein, Melvyn L.

    2011-01-01

    We determine the magnetic helicity, along with the magnetic energy, at high latitudes using data from the Ulysses mission. The data set spans the time period from 1993 to 1996. The basic assumption of the analysis is that the solar wind is homogeneous. Because the solar wind speed is high, we follow the approach first pioneered by Matthaeus et al. by which, under the assumption of spatial homogeneity, one can use Fourier transforms of the magnetic field time series to construct one-dimensional spectra of the magnetic energy and magnetic helicity under the assumption that the Taylor frozen-in-flow hypothesis is valid. That is a well-satisfied assumption for the data used in this study. The magnetic helicity derives from the skew-symmetric terms of the three-dimensional magnetic correlation tensor, while the symmetric terms of the tensor are used to determine the magnetic energy spectrum. Our results show a sign change of magnetic helicity at wavenumber k approximately equal to 2AU(sup -1) (or frequency nu approximately equal to 2 microHz) at distances below 2.8AU and at k approximately equal to 30AU(sup -1) (or nu approximately equal to 25 microHz) at larger distances. At small scales the magnetic helicity is positive at northern heliographic latitudes and negative at southern latitudes. The positive magnetic helicity at small scales is argued to be the result of turbulent diffusion reversing the sign relative to what is seen at small scales at the solar surface. Furthermore, the magnetic helicity declines toward solar minimum in 1996. The magnetic helicity flux integrated separately over one hemisphere amounts to about 10(sup 45) Mx(sup 2) cycle(sup -1) at large scales and to a three times lower value at smaller scales.

  9. Three-dimensional-CT imaging of colorectal disease with thin collimation helical CT scanning

    International Nuclear Information System (INIS)

    Ogura, Toshihiro; Koizumi, Koichi; Sakai, Tatsuya; Kai, Shunkichi; Takatsu, Kazuaki; Maruyama, Masakazu

    1998-01-01

    We have conducted research on three-dimensional (3D)-CT-colonoscopy with thin collimation helical CT scanning over the past three years. This has lately become a subject of special interest. 3D-CT-colonoscopy has three kinds of visualizing methods depending on the threshold setting of CT values. The first one is the virtual endoscopy method which is displayed in a similar fashion to colonoscopic images. The second one is the air image method using the air in the digestive tract as a contrast medium. The third one is the pseudo-tract method which has characteristics of both virtual endoscopy and the air image method and visualizes in a shape of the digestive tract. The image visualized by 3D-CT-colonoscopy is similar to that of conventional colonoscopy and barium enema study, which is obtained with minimal invasion to patients. Obvious advanced carcinomas were easily visualized, and even a small flat polyp measuring 5 mm in size, was able to be observed retrospectively. The characteristics of our method are that we can easily make an examination in a short time and with little dependence on expert technique. Also patients have little discomfort compared to that experienced during colonoscopy and barium enema study. Important features are as follows; long calculation time, insufficient air insufflation, fecal material in the patient''s bowel, whole abdominal scan, and spatial resolution. In the near future, a multislice CT scanner system will have ability to overcome these problems. Therefore, 3D-CT-colonoscopy might be applied in the future for first line examination as a mass screening for colorectal carcinoma. (author)

  10. Helical axis stellarator equilibrium model

    International Nuclear Information System (INIS)

    Koniges, A.E.; Johnson, J.L.

    1985-02-01

    An asymptotic model is developed to study MHD equilibria in toroidal systems with a helical magnetic axis. Using a characteristic coordinate system based on the vacuum field lines, the equilibrium problem is reduced to a two-dimensional generalized partial differential equation of the Grad-Shafranov type. A stellarator-expansion free-boundary equilibrium code is modified to solve the helical-axis equations. The expansion model is used to predict the equilibrium properties of Asperators NP-3 and NP-4. Numerically determined flux surfaces, magnetic well, transform, and shear are presented. The equilibria show a toroidal Shafranov shift

  11. Assessment of multislice CT to quantify pulmonary emphysema function and physiology in a rat model

    Science.gov (United States)

    Cao, Minsong; Stantz, Keith M.; Liang, Yun; Krishnamurthi, Ganapathy; Presson, Robert G., Jr.

    2005-04-01

    Purpose: The purpose of this study is to evaluate multi-slice computed tomography technology to quantify functional and physiologic changes in rats with pulmonary emphysema. Method: Seven rats were scanned using a 16-slice CT (Philips MX8000 IDT) before and after artificial inducement of emphysema. Functional parameters i.e. lung volumes were measured by non-contrast spiral scan during forced breath-hold at inspiration and expiration followed by image segmentation based on attenuation threshold. Dynamic CT imaging was performed immediately following the contrast injection to estimate physiology changes. Pulmonary perfusion, fractional blood volume, and mean transit times (MTTs) were estimated by fitting the time-density curves of contrast material using a compartmental model. Results: The preliminary results indicated that the lung volumes of emphysema rats increased by 3.52+/-1.70mL (pemphysema rats decreased by 91.76+/-68.11HU (pemphysema rats were 0.25+/-0.04ml/s/ml and 0.32+/-0.09ml/s/ml respectively. The fractional blood volumes for normal and emphysema rats were 0.21+/-0.04 and 0.15+/-0.02. There was a trend toward faster MTTs for emphysema rats (0.42+/-0.08s) than normal rats (0.89+/-0.19s) with ppulmonary emphysema appears promising for small animals.

  12. PRODUCTIVITY OF SOLAR FLARES AND MAGNETIC HELICITY INJECTION IN ACTIVE REGIONS

    International Nuclear Information System (INIS)

    Park, Sung-hong; Wang Haimin; Chae, Jongchul

    2010-01-01

    The main objective of this study is to better understand how magnetic helicity injection in an active region (AR) is related to the occurrence and intensity of solar flares. We therefore investigate the magnetic helicity injection rate and unsigned magnetic flux, as a reference. In total, 378 ARs are analyzed using SOHO/MDI magnetograms. The 24 hr averaged helicity injection rate and unsigned magnetic flux are compared with the flare index and the flare-productive probability in the next 24 hr following a measurement. In addition, we study the variation of helicity over a span of several days around the times of the 19 flares above M5.0 which occurred in selected strong flare-productive ARs. The major findings of this study are as follows: (1) for a sub-sample of 91 large ARs with unsigned magnetic fluxes in the range from (3-5) x 10 22 Mx, there is a difference in the magnetic helicity injection rate between flaring ARs and non-flaring ARs by a factor of 2; (2) the GOES C-flare-productive probability as a function of helicity injection displays a sharp boundary between flare-productive ARs and flare-quiet ones; (3) the history of helicity injection before all the 19 major flares displayed a common characteristic: a significant helicity accumulation of (3-45) x 10 42 Mx 2 during a phase of monotonically increasing helicity over 0.5-2 days. Our results support the notion that helicity injection is important in flares, but it is not effective to use it alone for the purpose of flare forecast. It is necessary to find a way to better characterize the time history of helicity injection as well as its spatial distribution inside ARs.

  13. Metallic and 3D-printed dielectric helical terahertz waveguides.

    Science.gov (United States)

    Vogt, Dominik Walter; Anthony, Jessienta; Leonhardt, Rainer

    2015-12-28

    We investigate guidance of Terahertz (THz) radiation in metallic and 3D-printed dielectric helical waveguides in the frequency range from 0.2 to 1 THz. Our experimental results obtained from THz time-domain spectroscopy (THz-TDS) measurements are in very good agreement with finite-difference time-domain (FDTD) simulations. We observe single-mode, low loss and low dispersive propagation of THz radiation in metallic helical waveguides over a broad bandwidth. The 3D-printed dielectric helical waveguides have substantially extended the bandwidth of a low loss dielectric tube waveguide as observed from the experimental and simulation results. The high flexibility of the helical design allows an easy incorporation into bench top THz devices.

  14. Alteration of helical vortex core without change in flow topology

    DEFF Research Database (Denmark)

    Velte, Clara Marika; Okulov, Valery; Hansen, Martin Otto Laver

    2011-01-01

    topology. The helical symmetry as such is preserved, although the characteristic parameters of helical symmetry of the vortex core transfer from a smooth linear variation to a different trend under the influence of a non-uniform pressure gradient, causing an increase in helical pitch without changing its......The abrupt expansion of the slender vortex core with changes in flow topology is commonly known as vortex breakdown. We present new experimental observations of an alteration of the helical vortex core in wall bounded turbulent flow with abrupt growth in core size, but without change in flow...

  15. Evaluation of classification method of lung lobe for multi-slice CT images

    International Nuclear Information System (INIS)

    Sakurai, Kousuke; Matsuhiro, Mikio; Saita, Shinsuke

    2010-01-01

    Recently, due to the introduction of multi-slice CT, to obtain a high resolution 3D CT image is possible in a short time. The temporal and spatial resolutions are high, so a highly accurate 3D image analysis is possible. To develop a structure analysis of the lung is needed and to be used as a fundamental technology for early detection of the disease. By separating the lung into lung lobes may provide important information for analysis, diagnosis and treatment of lung diseases. Therefore in this report, we adapt to abnormality example with the classification algorithms using the anatomical information of the bronchus, the pulmonary vein and interlobar fissure information, we evaluate the classification. (author)

  16. Patient Dose From Megavoltage Computed Tomography Imaging

    International Nuclear Information System (INIS)

    Shah, Amish P.; Langen, Katja M.; Ruchala, Kenneth J.; Cox, Andrea; Kupelian, Patrick A.; Meeks, Sanford L.

    2008-01-01

    Purpose: Megavoltage computed tomography (MVCT) can be used daily for imaging with a helical tomotherapy unit for patient alignment before treatment delivery. The purpose of this investigation was to show that the MVCT dose can be computed in phantoms, and further, that the dose can be reported for actual patients from MVCT on a helical tomotherapy unit. Methods and Materials: An MVCT beam model was commissioned and verified through a series of absorbed dose measurements in phantoms. This model was then used to retrospectively calculate the imaging doses to the patients. The MVCT dose was computed for five clinical cases: prostate, breast, head/neck, lung, and craniospinal axis. Results: Validation measurements in phantoms verified that the computed dose can be reported to within 5% of the measured dose delivered at the helical tomotherapy unit. The imaging dose scaled inversely with changes to the CT pitch. Relative to a normal pitch of 2.0, the organ dose can be scaled by 0.67 and 2.0 for scans done with a pitch of 3.0 and 1.0, respectively. Typical doses were in the range of 1.0-2.0 cGy, if imaged with a normal pitch. The maximal organ dose calculated was 3.6 cGy in the neck region of the craniospinal patient, if imaged with a pitch of 1.0. Conclusion: Calculation of the MVCT dose has shown that the typical imaging dose is approximately 1.5 cGy per image. The uniform MVCT dose delivered using helical tomotherapy is greatest when the anatomic thickness is the smallest and the pitch is set to the lowest value

  17. Helical Polyacetylenes Induced via Noncovalent Chiral Interactions and Their Applications as Chiral Materials.

    Science.gov (United States)

    Maeda, Katsuhiro; Yashima, Eiji

    2017-08-01

    Construction of predominantly one-handed helical polyacetylenes with a desired helix sense utilizing noncovalent chiral interactions with nonracemic chiral guest compounds based on a supramolecular approach is described. As with the conventional dynamic helical polymers possessing optically active pendant groups covalently bonded to the polymer chains, this noncovalent helicity induction system can show significant chiral amplification phenomena, in which the chiral information of the nonracemic guests can transfer with high cooperativity through noncovalent bonding interactions to induce an almost single-handed helical conformation in the polymer backbone. An intriguing "memory effect" of the induced macromolecular helicity is observed for some polyacetylenes, which means that the helical conformations induced in dynamic helical polyacetylene can be transformed into metastable static ones by tuning their helix-inversion barriers. Potential applications of helical polyacetylenes with controlled helix sense constructed by the "noncovalent helicity induction and/or memory effect" as chiral materials are also described.

  18. Variation in the helical structure of native collagen.

    Directory of Open Access Journals (Sweden)

    Joseph P R O Orgel

    Full Text Available The structure of collagen has been a matter of curiosity, investigation, and debate for the better part of a century. There has been a particularly productive period recently, during which much progress has been made in better describing all aspects of collagen structure. However, there remain some questions regarding its helical symmetry and its persistence within the triple-helix. Previous considerations of this symmetry have sometimes confused the picture by not fully recognizing that collagen structure is a highly complex and large hierarchical entity, and this affects and is effected by the super-coiled molecules that make it. Nevertheless, the symmetry question is not trite, but of some significance as it relates to extracellular matrix organization and cellular integration. The correlation between helical structure in the context of the molecular packing arrangement determines which parts of the amino acid sequence of the collagen fibril are buried or accessible to the extracellular matrix or the cell. In this study, we concentrate primarily on the triple-helical structure of fibrillar collagens I and II, the two most predominant types. By comparing X-ray diffraction data collected from type I and type II containing tissues, we point to evidence for a range of triple-helical symmetries being extant in the molecules native environment. The possible significance of helical instability, local helix dissociation and molecular packing of the triple-helices is discussed in the context of collagen's supramolecular organization, all of which must affect the symmetry of the collagen triple-helix.

  19. Coronary artery anomalies and clinically important anatomy in patients with congenital heart disease: multislice CT findings

    International Nuclear Information System (INIS)

    Goo, Hyun Woo; Seo, Dong-Man; Yun, Tae-Jin; Park, Jeong-Jun; Park, In-Sook; Ko, Jae Kon; Kim, Young Hwee

    2009-01-01

    In patients with congenital heart disease, coronary artery anomalies are common and have different clinical importance from individuals with structurally normal hearts. Visibility of the coronary arteries by CT has markedly improved due to high temporal resolution and ECG-synchronized data acquisition. In this article we describe current multislice CT techniques for coronary artery imaging and illustrate coronary artery anomalies and clinically important coronary artery anatomy from the point of view of congenital heart disease. (orig.)

  20. Coronary artery anomalies and clinically important anatomy in patients with congenital heart disease: multislice CT findings

    Energy Technology Data Exchange (ETDEWEB)

    Goo, Hyun Woo [University of Ulsan College of Medicine, Department of Radiology and Research Institute of Radiology, Asan Medical Center, Seoul (Korea); Seo, Dong-Man; Yun, Tae-Jin; Park, Jeong-Jun [University of Ulsan College of Medicine, Department of Pediatric Cardiac Surgery, Asan Medical Center, Seoul (Korea); Park, In-Sook; Ko, Jae Kon; Kim, Young Hwee [University of Ulsan College of Medicine, Department of Pediatric Cardiology, Asan Medical Center, Seoul (Korea)

    2009-03-15

    In patients with congenital heart disease, coronary artery anomalies are common and have different clinical importance from individuals with structurally normal hearts. Visibility of the coronary arteries by CT has markedly improved due to high temporal resolution and ECG-synchronized data acquisition. In this article we describe current multislice CT techniques for coronary artery imaging and illustrate coronary artery anomalies and clinically important coronary artery anatomy from the point of view of congenital heart disease. (orig.)

  1. EVOLUTION OF MAGNETIC HELICITY AND ENERGY SPECTRA OF SOLAR ACTIVE REGIONS

    International Nuclear Information System (INIS)

    Zhang, Hongqi; Brandenburg, Axel; Sokoloff, D. D.

    2016-01-01

    We adopt an isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field to estimate the magnetic energy and helicity spectra as well as current helicity spectra of two individual active regions (NOAA 11158 and NOAA 11515) and the change of the spectral indices during their development as well as during the solar cycle. The departure of the spectral indices of magnetic energy and current helicity from 5/3 are analyzed, and it is found that it is lower than the spectral index of the magnetic energy spectrum. Furthermore, the fractional magnetic helicity tends to increase when the scale of the energy-carrying magnetic structures increases. The magnetic helicity of NOAA 11515 violates the expected hemispheric sign rule, which is interpreted as an effect of enhanced field strengths at scales larger than 30–60 Mm with opposite signs of helicity. This is consistent with the general cycle dependence, which shows that around the solar maximum the magnetic energy and helicity spectra are steeper, emphasizing the large-scale field

  2. EVOLUTION OF MAGNETIC HELICITY AND ENERGY SPECTRA OF SOLAR ACTIVE REGIONS

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hongqi [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Brandenburg, Axel [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden); Sokoloff, D. D., E-mail: hzhang@bao.ac.cn [Department of Physics, Moscow University, 119992 Moscow (Russian Federation)

    2016-03-10

    We adopt an isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field to estimate the magnetic energy and helicity spectra as well as current helicity spectra of two individual active regions (NOAA 11158 and NOAA 11515) and the change of the spectral indices during their development as well as during the solar cycle. The departure of the spectral indices of magnetic energy and current helicity from 5/3 are analyzed, and it is found that it is lower than the spectral index of the magnetic energy spectrum. Furthermore, the fractional magnetic helicity tends to increase when the scale of the energy-carrying magnetic structures increases. The magnetic helicity of NOAA 11515 violates the expected hemispheric sign rule, which is interpreted as an effect of enhanced field strengths at scales larger than 30–60 Mm with opposite signs of helicity. This is consistent with the general cycle dependence, which shows that around the solar maximum the magnetic energy and helicity spectra are steeper, emphasizing the large-scale field.

  3. Low-energy properties of fractional helical Luttinger liquids

    NARCIS (Netherlands)

    Meng, T.; Fritz, L.|info:eu-repo/dai/nl/371569559; Schuricht, D.|info:eu-repo/dai/nl/369284690; Loss, D.

    2014-01-01

    We investigate the low-energy properties of (quasi) helical and fractional helical Luttinger liquids. In particular, we calculate the Drude peak of the optical conductivity, the density of states, as well as charge transport properties of the interacting system with and without attached Fermi liquid

  4. Helical filaments

    Energy Technology Data Exchange (ETDEWEB)

    Barbieri, Nicholas; Lim, Khan; Durand, Magali; Baudelet, Matthieu; Richardson, Martin [Townes Laser Institute, CREOL—The College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816 (United States); Hosseinimakarem, Zahra; Johnson, Eric [Micro-Photonics Laboratory – Center for Optical Material Science, Clemson, Anderson, South Carolina 29634 (United States)

    2014-06-30

    The shaping of laser-induced filamenting plasma channels into helical structures by guiding the process with a non-diffracting beam is demonstrated. This was achieved using a Bessel beam superposition to control the phase of an ultrafast laser beam possessing intensities sufficient to induce Kerr effect driven non-linear self-focusing. Several experimental methods were used to characterize the resulting beams and confirm the observed structures are laser air filaments.

  5. Heat transfer characteristics of a helical heat exchanger

    International Nuclear Information System (INIS)

    San, Jung-Yang; Hsu, Chih-Hsiang; Chen, Shih-Hao

    2012-01-01

    Heat transfer performance of a helical heat exchanger was investigated. The heat exchanger is composed of a helical tube with rectangular cross section and two cover plates. The ε–Ntu relation of the heat exchanger was obtained using a numerical method. In the analysis, the flow in the tube (helical flow) was considered to be mixed and the flow outside the tube (radial flow) was unmixed. In the experiment, the Darcy friction factor (f) and convective heat transfer coefficient (h) of the radial flow were measured. The radial flow was air and the helical flow was water. Four different channel spacing (0.5, 0.8, 1.2 and 1.6 mm) were individually considered. The Reynolds numbers were in the range 307–2547. Two correlations, one for the Darcy friction factor and the other for the Nusselt number, were proposed. - Highlights: ► We analyze the heat transfer characteristics of a helical heat exchanger and examine the effectiveness–Ntu relation. ► Increasing number of turns of the heat exchanger would slightly increase the effectiveness. ► There is an optimum Ntu value corresponding to a maximum effectiveness. ► We measure the Darcy friction factor and Nusselt number of the radial flow and examine the correlations.

  6. Fluid-elastic Instability of Helical Tubes Subjected to Single-Phase External Flow and Two-Phase Internal Flow

    International Nuclear Information System (INIS)

    Jong Chull Jo; Myung Jo Jhung; Woong Sik Kim; Hho Jung Kim

    2004-01-01

    This study investigates the fluid-elastic instability characteristics of steam generator helical type tubes in operating nuclear power plants. The thermal-hydraulic conditions of both tube side and shell side flow fields are predicted by a general purpose computational fluid dynamics code employing the finite volume element modeling. To get the natural frequency, corresponding mode shape and participation factor, modal analyses are performed for helical type tubes with various conditions. Investigated are the effects of the helix angle, the number of supports and the status of the inner fluid on the modal, and fluid-elastic instability characteristics of the tubes, which are expressed in terms of the natural frequency, corresponding mode shape, and stability ratio. (authors)

  7. A multi-slice gradient sequence for contrast enhanced MR diagnosis of intracranial tumours

    International Nuclear Information System (INIS)

    Schoerner, W.; Sander, B.; Kornmesser, W.; Laniado, M.; Nakamura, T.; Felix, R.

    1988-01-01

    A multi-slice gradient echo sequence (FLASH) was compared with a conventional spin-echo (SE) technique with regard to its value for contrast enhanced MR diagnosis. In 28 patients with cerebral tumours, SE images (SE 400/30; four images/3.4 minutes) and FLASH images (FLASH 315/14; 15 images/1.4 minutes) were obtained before and after gadolinium DTPA. After gadolinium-DTPA results were comparable for both techniques with respect to contrast enhancement, tumor contrast and delineation. Because of the higher efficiency of the FLASH 315/14 technique, this sequence is the method of choice for contrast enhanced cerebral MR imaging. (orig.) [de

  8. Manipulation of wavefront using helical metamaterials.

    Science.gov (United States)

    Yang, Zhenyu; Wang, Zhaokun; Tao, Huan; Zhao, Ming

    2016-08-08

    Helical metamaterials, a kind of 3-dimensional structure, has relatively strong coupling effect among the helical nano-wires. Therefore, it is expected to be a good candidate for generating phase shift and controlling wavefront with high efficiency. In this paper, using the finite-difference time-domain (FDTD) method, we studied the phase shift properties in the helical metamaterials. It is found that the phase shift occurs for both transmitted and reflected light waves. And the maximum of reflection coefficients can reach over 60%. In addition, the phase shift (φ) is dispersionless in the range of 600 nm to 860 nm, that is, it is only dominated by the initial angle (θ) of the helix. The relationship between them is φ = ± 2θ. Using Jones calculus we give a further explanation for these properties. Finally, by arranging the helixes in an array with a constant phase gradient, the phenomenon of anomalous refraction was also observed in a broad wavelength range.

  9. Numerical simulation of thermal-dynamic characteristics through a helical coiled tube with annular cross section for laminar flow

    International Nuclear Information System (INIS)

    Wu Shuangying; Chen Sujun; Li Yourong; Li Longjian

    2009-01-01

    A numerical method for simulating three-dimensional laminar forced convective heat transfer in a helical coiled passage with annular cross section under uniform wall temperature condition is presented. The helical coiled passage is fabricated by bending a 0.03 m inner diameter and 0.05 m outer diameter straight tube into a helical-coil of two turns. The results presented in this paper cover a Reynolds number range of 200 ∼ 1000, a pitch range of 0.1 ∼ 0.2 and a curvature ratio range of 0.1 ∼ 0.3. The numerical computations reveal the development and distribution of heat transfer and flow fields in the helical coiled passage when the inner annular wall is heated and the outer annular wall is insulated. In addition, the effects of Reynolds number, curvature ratio, and coil pitch on the average friction factor, average Nusselt number at different axial cross-section have been discussed. The results show that the secondary flow is weak and can be neglected at the entrance region, but the effect of the secondary flow is enhanced, the maximum velocity perpendicular to axial cross section shifts toward the outer side of helical coiled passage. Furthermore, the average Nusselt number and friction factor at every different axial location present different characteristics when the Reynolds number, curvature ratio and pitch change. Compared with the curvature ratio, the pitch has relatively little influence on the heat transfer and flow performance. (authors)

  10. The effects of slice thickness and reconstructive parameters on VR image quality in multi-slice CT

    International Nuclear Information System (INIS)

    Gao Zhenlong; Wang Qiang; Liu Caixia

    2005-01-01

    Objective: To explore the effects of slice thickness, reconstructive thickness and reconstructive interval on VR image quality in multi-slice CT, in order to select the best slice thickness and reconstructive parameters for the imaging. Methods: Multi-slice CT scan was applied on a rubber dinosaur model with different slice thickness. VR images were reconstructed with different reconstructive thickness and reconstructive interval. Five radiologists were invited to evaluate the quality of the images without knowing anything about the parameters. Results: The slice thickness, reconstructive thickness and reconstructive interval did have effects on VR image quality and the effective degree was different. The effective coefficients were V 1 =1413.033, V 2 =563.733, V 3 =390.533, respectively. The parameters interacted with the others (P<0.05). The smaller of those parameters, the better of the image quality. With a small slice thickness and a reconstructive slice equal to slice thickness, the image quality had no obvious difference when the reconstructive interval was 1/2, 1/3, 1/4 of the slice thickness. Conclusion: A relative small scan slice thickness, a reconstructive slice equal to slice thickness and a reconstructive interval 1/2 of the slice thickness should be selected for the best VR image quality. The image quality depends mostly on the slice thickness. (authors)

  11. Multislice simulations for in-situ HRTEM studies of nanostructured magnesium hydride at ambient hydrogen pressure

    International Nuclear Information System (INIS)

    Surrey, Alexander; Schultz, Ludwig; Rellinghaus, Bernd

    2017-01-01

    Highlights: • Multislice HRTEM contrast simulations of a windowed environmental cell. • Study of Mg and MgH2 nanocrystals as model system in hydrogen at ambient pressure. • Investigation of spatial resolution and contrast depending on specimen thickness, defocus, and hydrogen pressure. • Atomic resolution is expected for specimens as thin as 5  nm. - Abstract: The use of transmission electron microscopy (TEM) for the structural characterization of many nanostructured hydrides, which are relevant for solid state hydrogen storage, is hindered due to a rapid decomposition of the specimen upon irradiation with the electron beam. Environmental TEM allows to stabilize the hydrides by applying a hydrogen back pressure of up to 4.5 bar in a windowed environmental cell. The feasibility of high-resolution TEM (HRTEM) investigations of light weight metals and metal hydrides in such a “nanoreactor” is studied theoretically by means of multislice HRTEM contrast simulations using Mg and its hydride phase, MgH_2, as model system. Such a setup provides the general opportunity to study dehydrogenation and hydrogenation reactions at the nanoscale under technological application conditions. We analyze the dependence of both the spatial resolution and the HRTEM image contrast on parameters such as the defocus, the metal/hydride thickness, and the hydrogen pressure in order to explore the possibilities and limitations of in-situ experiments with windowed environmental cells. Such simulations may be highly valuable to pre-evaluate future experimental studies.

  12. Multislice simulations for in-situ HRTEM studies of nanostructured magnesium hydride at ambient hydrogen pressure

    Energy Technology Data Exchange (ETDEWEB)

    Surrey, Alexander, E-mail: a.surrey@ifw-dresden.de [IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden (Germany); Institut für Festkörperphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Schultz, Ludwig [IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden (Germany); Institut für Festkörperphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Rellinghaus, Bernd, E-mail: b.rellinghaus@ifw-dresden.de [IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden (Germany)

    2017-04-15

    Highlights: • Multislice HRTEM contrast simulations of a windowed environmental cell. • Study of Mg and MgH2 nanocrystals as model system in hydrogen at ambient pressure. • Investigation of spatial resolution and contrast depending on specimen thickness, defocus, and hydrogen pressure. • Atomic resolution is expected for specimens as thin as 5  nm. - Abstract: The use of transmission electron microscopy (TEM) for the structural characterization of many nanostructured hydrides, which are relevant for solid state hydrogen storage, is hindered due to a rapid decomposition of the specimen upon irradiation with the electron beam. Environmental TEM allows to stabilize the hydrides by applying a hydrogen back pressure of up to 4.5 bar in a windowed environmental cell. The feasibility of high-resolution TEM (HRTEM) investigations of light weight metals and metal hydrides in such a “nanoreactor” is studied theoretically by means of multislice HRTEM contrast simulations using Mg and its hydride phase, MgH{sub 2}, as model system. Such a setup provides the general opportunity to study dehydrogenation and hydrogenation reactions at the nanoscale under technological application conditions. We analyze the dependence of both the spatial resolution and the HRTEM image contrast on parameters such as the defocus, the metal/hydride thickness, and the hydrogen pressure in order to explore the possibilities and limitations of in-situ experiments with windowed environmental cells. Such simulations may be highly valuable to pre-evaluate future experimental studies.

  13. Basic examination of in-plane spatial resolution in multi-slice CT

    International Nuclear Information System (INIS)

    Hara, Takanori; Kato, Hideki; Akiyama, Mitsutoshi; Murata, Katsutoshi

    2002-01-01

    In computed tomography (single-slice spiral CT, conventional CT), in-plane (x-y plane) spatial resolution is consistently identified as depending on the detector density of the in-plane (x-y plane). However, we considered that the in-plane (x-y plane) spatial resolution of multi-slice CT (MSCT) was influenced by an error in the detector's sensitivity to the Z-axis and by the frequency of use of direct row data and complementary row data when the image of spiral pitches (SP) was reconstructed. Our goal in this experiment was to analyze the relationship of the in-plane (x-y plane) spatial resolution of an asymmetric-type detector in MSCT to SP, tube current, and rotation time. By employing a tungsten wire phantom of 0.2 mm in diameter, we examined modulation transfer functions (MTF) by point-spread functions (PSF) of CT-images. Next, using the mean-square-root bandwidth theory, we analyzed the MTF of wire phantoms. The analysis of in-plane (x-y plane) spatial resolution revealed that various tube currents had no effect on the value of the mean-square-root bandwidth. However, rotation time and high spiral pitch did have an effect on mean-square-root bandwidth. Considering the results mentioned above, spiral pitch (z-axis reconstruction algorithm) had a slight effect on in-plane (x-y plane) spatial resolution of asymmetric-type detectors in MSCT. Accordingly, we proposed a new general view of VDDz (view/mm) in MSCT that considered view data density on the Z-axis according to spiral pitch (mm/rotation), rotation time (view/rotation), and slice collimation. (author)

  14. Prospective study comparing three-dimensional computed tomography and magnetic resonance imaging for evaluating the renal vascular anatomy in potential living renal donors.

    Science.gov (United States)

    Bhatti, Aftab A; Chugtai, Aamir; Haslam, Philip; Talbot, David; Rix, David A; Soomro, Naeem A

    2005-11-01

    To prospectively compare the accuracy of multislice spiral computed tomographic angiography (CTA) and magnetic resonance angiography (MRA) in evaluating the renal vascular anatomy in potential living renal donors. Thirty-one donors underwent multislice spiral CTA and gadolinium-enhanced MRA. In addition to axial images, multiplanar reconstruction and maximum intensity projections were used to display the renal vascular anatomy. Twenty-four donors had a left laparoscopic donor nephrectomy (LDN), whereas seven had right open donor nephrectomy (ODN); LDN was only considered if the renal vascular anatomy was favourable on the left. CTA and MRA images were analysed by two radiologists independently. The radiological and surgical findings were correlated after the surgery. CTA showed 33 arteries and 32 veins (100% sensitivity) whereas MRA showed 32 arteries and 31 veins (97% sensitivity). CTA detected all five accessory renal arteries whereas MRA only detected one. CTA also identified all three accessory renal veins whereas MRA identified two. CTA had a sensitivity of 97% and 47% for left lumbar and left gonadal veins, whereas MRA had a sensitivity of 74% and 46%, respectively. Multislice spiral CTA with three-dimensional reconstruction was more accurate than MRA for both renal arterial and venous anatomy.

  15. Drift mode calculations for the Large Helical Device

    International Nuclear Information System (INIS)

    Rewoldt, G.; Ku, L.-P.; Tang, W.M.; Sugama, H.; Nakajima, N.; Watanabe, K.Y.; Murakami, S.; Yamada, H.; Cooper, W.A.

    2000-01-01

    A fully kinetic assessment of the stability properties of toroidal drift modes has been obtained for a case for the Large Helical Device (LHD) [A.Iiyoshi, et al., Plasma Physics and Controlled Nuclear Fusion Research, 1998, Nucl.Fusion 39, 1245 (1999)]. This calculation retains the important effects in the linearized gyrokinetic equation, using the lowest-order ''ballooning representation'' for high toroidal mode number instabilities in the electrostatic limit. Results for toroidal drift waves destabilized by trapped particle dynamics and ion temperature gradients are presented, using three-dimensional magnetohydrodynamics equilibria reconstructed from experimental measurements. The effects of helically-trapped particles and helical curvature are investigated

  16. Theoretical modeling of transport barriers in helical plasmas

    International Nuclear Information System (INIS)

    Toda, S.; Itoh, K.; Ohyabu, N.

    2008-10-01

    A unified transport modelling to explain electron Internal Transport Barriers (e-ITB) in helical plasmas and Internal Diffusion Barriers (IDB) observed in Large Helical Device (LHD) is proposed. The e-ITB can be predicted with the effect of zonal flows to obtain the e-ITB in the low collisional regime when the radial variation of the particle anomalous diffusivity is included. Transport analysis in this article can newly show that the particle fuelling induces the IDB formation when this unified transport modelling is used in the high collisional regime. The density limit for the IDB in helical plasmas is also examined including the effect of the radiation loss. (author)

  17. TIME EVOLUTION OF CORONAL MAGNETIC HELICITY IN THE FLARING ACTIVE REGION NOAA 10930

    International Nuclear Information System (INIS)

    Park, Sung-Hong; Jing, Ju; Wang Haimin; Chae, Jongchul; Tan, Changyi

    2010-01-01

    To study the three-dimensional (3D) magnetic field topology and its long-term evolution associated with the X3.4 flare of 2006 December 13, we investigate the coronal relative magnetic helicity in the flaring active region (AR) NOAA 10930 during the time period of December 8-14. The coronal helicity is calculated based on the 3D nonlinear force-free magnetic fields reconstructed by the weighted optimization method of Wiegelmann, and is compared with the amount of helicity injected through the photospheric surface of the AR. The helicity injection is determined from the magnetic helicity flux density proposed by Pariat et al. using Solar and Heliospheric Observatory/Michelson Doppler Imager magnetograms. The major findings of this study are the following. (1) The time profile of the coronal helicity shows a good correlation with that of the helicity accumulation by injection through the surface. (2) The coronal helicity of the AR is estimated to be -4.3 x 10 43 Mx 2 just before the X3.4 flare. (3) This flare is preceded not only by a large increase of negative helicity, -3.2 x 10 43 Mx 2 , in the corona over ∼1.5 days but also by noticeable injections of positive helicity through the photospheric surface around the flaring magnetic polarity inversion line during the time period of the channel structure development. We conjecture that the occurrence of the X3.4 flare is involved with the positive helicity injection into an existing system of negative helicity.

  18. Magnetic Helical Micro- and Nanorobots: Toward Their Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Famin Qiu

    2015-03-01

    Full Text Available Magnetic helical micro- and nanorobots can perform 3D navigation in various liquids with a sub-micrometer precision under low-strength rotating magnetic fields (<10 mT. Since magnetic fields with low strengths are harmless to cells and tissues, magnetic helical micro/nanorobots are promising tools for biomedical applications, such as minimally invasive surgery, cell manipulation and analysis, and targeted therapy. This review provides general information on magnetic helical micro/nanorobots, including their fabrication, motion control, and further functionalization for biomedical applications.

  19. Utility of three-dimensional helical CT in the diagnosis of breast cancer

    International Nuclear Information System (INIS)

    Maeda, Yoshiaki; Hata, Yoshinobu; Matsuoka, Shinnichi; Nakajima, Nobuhisa; Ito, Toichi; Osada, Tadahiro; Sano, Fumio

    2004-01-01

    Although utility of three-dimensional (3D) helical CT for preoperative examination of breast cancer has been discussed, the accuracy of the helical CT in diagnosing breast cancer has not been fully evaluated. In this study 56 malignant and 28 benign breast tumors were evaluated preoperatively with 3D-helical CT, and their imaging results were compared with pathological findings of surgical specimens. Helical CT identified the presence of malignancy in 54 out of the 56 cancer cases tested and the sensitivity and specificity in distinguishing between malignant and benign tumors were 82% and 57%, respectively. The sensitivity and specificity in diagnosing the presence of metastatic axillary lymph nodes using helical CT were 70% and 80%, respectively. The sensitivity and specificity in diagnosing the presence of extensive intraductal component (EIC) using helical CT were 71% and 86%, respectively. Helical CT visualized all of the tumors in multifocal breast cancer cases. In conclusion, 3D-helical CT is a useful modality for preoperative examination of breast cancer, especially for assessing axillary lymph node status, and EIC, and will be helpful for conducting sentinel lymph node biopsy (SNLB) and breast-conserving surgery. (author)

  20. Preliminary study on helical CT algorithms for patient motion estimation and compensation

    International Nuclear Information System (INIS)

    Wang, G.; Vannier, M.W.

    1995-01-01

    Helical computed tomography (helical/spiral CT) has replaced conventional CT in many clinical applications. In current helical CT, a patient is assumed to be rigid and motionless during scanning and planar projection sets are produced from raw data via longitudinal interpolation. However, rigid patient motion is a problem in some cases (such as in the skull base and temporal bone imaging). Motion artifacts thus generated in reconstructed images can prevent accurate diagnosis. Modeling a uniform translational movement, the authors address how patient motion is ascertained and how it may be compensated. First, mismatch between adjacent fan-beam projections of the same orientation is determined via classical correlation, which is approximately proportional to the patient displacement projected onto an axis orthogonal to the central ray of the involved fan-beam. Then, the patient motion vector (the patient displacement per gantry rotation) is estimated from its projections using a least-square-root method. To suppress motion artifacts, adaptive interpolation algorithms are developed that synthesize full-scan and half-scan planar projection data sets, respectively. In the adaptive scheme, the interpolation is performed along inclined paths dependent upon the patient motion vector. The simulation results show that the patient motion vector can be accurately and reliably estimated using their correlation and least-square-root algorithm, patient motion artifacts can be effectively suppressed via adaptive interpolation, and adaptive half-scan interpolation is advantageous compared with its full-scale counterpart in terms of high contrast image resolution

  1. Radiation characteristics of helical tomotherapy

    International Nuclear Information System (INIS)

    Jeraj, Robert; Mackie, Thomas R.; Balog, John; Olivera, Gustavo; Pearson, Dave; Kapatoes, Jeff; Ruchala, Ken; Reckwerdt, Paul

    2004-01-01

    Helical tomotherapy is a dedicated intensity modulated radiation therapy (IMRT) system with on-board imaging capability (MVCT) and therefore differs from conventional treatment units. Different design goals resulted in some distinctive radiation field characteristics. The most significant differences in the design are the lack of flattening filter, increased shielding of the collimators, treatment and imaging operation modes and narrow fan beam delivery. Radiation characteristics of the helical tomotherapy system, sensitivity studies of various incident electron beam parameters and radiation safety analyses are presented here. It was determined that the photon beam energy spectrum of helical tomotherapy is similar to that of more conventional radiation treatment units. The two operational modes of the system result in different nominal energies of the incident electron beam with approximately 6 MeV and 3.5 MeV in the treatment and imaging modes, respectively. The off-axis mean energy dependence is much lower than in conventional radiotherapy units with less than 5% variation across the field, which is the consequence of the absent flattening filter. For the same reason the transverse profile exhibits the characteristic conical shape resulting in a 2-fold increase of the beam intensity in the center. The radiation leakage outside the field was found to be negligible at less than 0.05% because of the increased shielding of the collimators. At this level the in-field scattering is a dominant source of the radiation outside the field and thus a narrow field treatment does not result in the increased leakage. The sensitivity studies showed increased sensitivity on the incident electron position because of the narrow fan beam delivery and high sensitivity on the incident electron energy, as common to other treatment systems. All in all, it was determined that helical tomotherapy is a system with some unique radiation characteristics, which have been to a large extent

  2. Prenatal diagnosis of sirenomelia in the late second trimester with three-dimensional helical computed tomography.

    Science.gov (United States)

    Ono, Tetsuo; Katsura, Daisuke; Tsuji, Shunichiro; Yomo, Hiroko; Ishiko, Akiko; Inoue, Takashi; Kita, Nobuyuki; Takahashi, Kentaro; Murakami, Takashi

    2011-10-01

    Sirenomelia is a rare congenital syndrome that is characterized by the anomalous development of the caudal region of the body. The anomalies include bilateral renal agenesis or dysgenesis and the absence of the sacrum and other vertebral defects. Sirenomelia is also known as "mermaid syndrome," because of the one lower extremity. It is usually associated with severe oligohydramnios, and its prognosis is very poor due to pulmonary hypoplasia that is caused by severe oligohydramnios. The patient referred to our hospital at the gestational age of 27 weeks with fetal growth restriction and oligohydramnios. The estimated fetal body weight was 970 g (-4.9 S.D.). We could identify only one-side extremities, and could not identify kidneys by ultrasound examination. Because a single lower extremity and severe oligohydramnios are characteristics of the sirenomelia, we suspected sirenomelia. However, it could not be confirmed by ultrasound examination because of oligohydramnios. Therefore, we performed three-dimensional helical computed tomography (3D-CT), which is more accurate than ultrasound examinations for prenatal diagnosis of skeletal abnormalities. 3D-CT revealed an only one lower extremity. At 36 weeks and 5 days of gestation, the woman went into spontaneous labor and delivered an infant weighing 870 g. The infant has a single upper extremity and a single lower extremity. We provided supportive care for the neonate, who however died 1 hour 36 minutes after birth from severe respiratory distress. In summary, we report the correct diagnosis of sirenomelia with 3D-CT in the late second trimester.

  3. Noninvasive coronary artery imaging by multislice spiral computed tomography. A novel approach for a retrospectively ECG-gated reconstruction technique

    International Nuclear Information System (INIS)

    Sato, Yuichi; Kanmatsuse, Katsuo; Inoue Fumio

    2003-01-01

    Although the excellent spatial resolution of multislice spiral computed tomography (MSCT) enables the coronary arteries to be visualized, its limited temporal resolution results in poor image reproducibility because of cardiac motion artifact (CMA) and hence limits its widespread clinical use. A novel retrospectively electrocardiogram (ECG)-gated reconstruction method has been developed to minimize CMA. In 88 consecutive patients, the scan data were reconstructed using 2 retrospectively ECG-gated reconstruction methods. Method 1: the end of the reconstruction window (250 ms) was positioned at the peak of the P wave on ECG, which corresponded to the end of the slow filling phase during diastole immediately before atrial contraction. Method 2 (conventional method): relative retrospective gating with 50% referred to the R-R interval was performed so that the beginning of the reconstruction window (250 ms) was positioned at the halfway point between the R-R intervals of the heart cycle. The quality of the coronary artery images was evaluated according to the presence or absence of CMA. The assessment was applied to the left main coronary artery (LMCA), the left anterior descending artery (LAD, segments no.6, no.7, and no.8), the left circumflex artery (LCx, segments no.11 and no.13) and the right coronary artery (RCA, segments no.1, no.2 and no.3). The first diagonal artery (no.9-1), the obtuse marginal artery (no.12-1), the posterior descending artery (no.4-PD), the atrioventricular node branch (no.4-AV) and the first right ventricular branch (RV) were also evaluated. Of the 88 patients, 85 were eligible for image evaluation. Method 1 allowed visualization of the major coronary arteries without CMA in the majority of patients. The left coronary artery (LCA) system (segments no.5-7, no.11 and no.13) and the proximal portion of the RCA were visualized in more than 94% of patients. Artifact-free visualization of the distal portion of the LAD (segment no.8) and RCA (no.4

  4. Controllable helical deformations on printed anisotropic composite soft actuators

    Science.gov (United States)

    Wang, Dong; Li, Ling; Serjouei, Ahmad; Dong, Longteng; Weeger, Oliver; Gu, Guoying; Ge, Qi

    2018-04-01

    Helical shapes are ubiquitous in both nature and engineering. However, the development of soft actuators and robots that mimic helical motions has been hindered primarily due to the lack of efficient modeling approaches that take into account the material anisotropy and the directional change of the external loading point. In this work, we present a theoretical framework for modeling controllable helical deformations of cable-driven, anisotropic, soft composite actuators. The framework is based on the minimum potential energy method, and its model predictions are validated by experiments, where the microarchitectures of the soft composite actuators can be precisely defined by 3D printing. We use the developed framework to investigate the effects of material and geometric parameters on helical deformations. The results show that material stiffness, volume fraction, layer thickness, and fiber orientation can be used to control the helical deformation of a soft actuator. In particular, we found that a critical fiber orientation angle exists at which the twist of the actuator changes the direction. Thus, this work can be of great importance for the design and fabrication of soft actuators with tailored deformation behavior.

  5. Numerical analysis of fluid flow and heat transfer in a helical ...

    African Journals Online (AJOL)

    Helical channels are widely applied in different application areas. In a converging diverging nozzle, helical channels are mainly used for cooling of its wall. The characteristics of fluid flow and heat transfer inside helical duct for a converging diverging nozzle is not commonly dealt in present literatures. In this paper CFD ...

  6. Classification of the maxillary sinus according to area of the medial antral wall: a comparison of two ethnic groups.

    Science.gov (United States)

    Lee, Fernandes Carmen; Fernandes, C M C; Murrell, H C

    2009-06-01

    This study is an anatomical study designed to benefit surgeons working in the region of the maxillary sinus. This paper investigates ethnic and gender variations in the shape of the maxillary sinus in dried crania from the Raymond Dart collection of human skeletons. The paper claims that an estimate of the area of the medial antral wall of the maxillary sinus is one of the best ethnic/gender group predictors. Helical, multislice computed tomography was performed using 1mm coronal slices length, depth, width and volume measurements for each sinus were taken. Classification by shape and estimated area of medial wall was attempted. Shape classification was found to be unsuccessful whilst medial wall classification into ethnic/gender groupings gave encouraging results. The area of the medial wall is related to ethnic/gender groups.

  7. Assessment of hemodynamics in a rat model of liver cirrhosis with precancerous lesions using multislice spiral CT perfusion imaging.

    Science.gov (United States)

    Ma, Guolin; Bai, Rongjie; Jiang, Huijie; Hao, Xuejia; Ling, Zaisheng; Li, Kefeng

    2013-01-01

    To develop an optimal scanning protocol for multislice spiral CT perfusion (CTP) imaging to evaluate hemodynamic changes in liver cirrhosis with diethylnitrosamine- (DEN-) induced precancerous lesions. Male Wistar rats were randomly divided into the control group (n = 80) and the precancerous liver cirrhosis group (n = 40). The control group received saline injection and the liver cirrhosis group received 50 mg/kg DEN i.p. twice a week for 12 weeks. All animals underwent plain CT scanning, CTP, and contrast-enhanced CT scanning. Scanning parameters were optimized by adjusting the diatrizoate concentration, the flow rate, and the delivery time. The hemodynamics of both groups was further compared using optimized multislice spiral CTP imaging. High-quality CTP images were obtained with following parameters: 150 kV; 150 mAs; 5 mm thickness, 5 mm interval; pitch, 1; matrix, 512 × 512; and FOV, 9.6 cm. Compared to the control group, the liver cirrhosis group had a significantly increased value of the hepatic arterial fraction and the hepatic artery perfusion (P spiral CTP imaging can be used to evaluate the hemodynamic changes in the rat model of liver cirrhosis with precancerous lesions.

  8. New reconstruction algorithm in helical-volume CT

    International Nuclear Information System (INIS)

    Toki, Y.; Rifu, T.; Aradate, H.; Hirao, Y.; Ohyama, N.

    1990-01-01

    This paper reports on helical scanning that is an application of continuous scanning CT to acquire volume data in a short time for three-dimensional study. In a helical scan, the patient couch sustains movement during continuous-rotation scanning and then the acquired data is processed to synthesize a projection data set of vertical section by interpolation. But the synthesized section is not thin enough; also, the image may have artifacts caused by couch movement. A new reconstruction algorithm that helps resolve such problems has been developed and compared with the ordinary algorithm. The authors constructed a helical scan system based on TCT-900S, which can perform 1-second rotation continuously for 30 seconds. The authors measured section thickness using both algorithms on an AAPM phantom, and we also compared degree of artifacts on clinical data

  9. Resonant helical fields in the TBR tokamak

    International Nuclear Information System (INIS)

    Bender, O.W.

    1986-01-01

    The influence of external resonant helical fields (RHF) in the tokamak TBR plasma discharges was investigated. These fields were created by helical windings wounded on the TBR vessel with the same helicity of rational magnetic surfaces, producing resonant efects on these surfaces. The characteristics of the MHZ activity (amplitude, frequency and poloidal and toroidal wave numbers, m=2,3,4 and n=1, respectively) during the plasma discharges were modified by eletrical winding currents of the order of 2% of the plasma current. These characterisitics were measured for diferent discharges safety factors at the limiter (q) between 3 and 4, with and without the RHF, with the atenuation of the oscillation amplitudes and the increasing of their frequencies. The existente of expontaneous and induced magnetic islands were investigated. The data were compared with results obtained in other tokamaks. (author) [pt

  10. Recent Results of Helical Nonneutral Plasmas on Compact Helical System (CHS)

    International Nuclear Information System (INIS)

    Himura, H.; Yamamoto, Y.; Sanpei, A.; Masamune, S.; Wakabayashi, H.; Isobe, M.

    2006-01-01

    First of all, non-constant space potential φs and electron density ne on magnetic surfaces of helical nonneutral plasmas are verified experimentally. The difference in φs enlarges significantly at the outer region inside the closed magnetic surfaces, and the corresponding equipotential surfaces are inferred to shift upward vertically with respect to magnetic surfaces. Meanwhile, larger value of ne is clearly observed in the downward region (z < 0) of magnetic surfaces, which seems to be consistent with the φs measurement. These results are the first evidence which strongly suggests the equilibrium proposed for nonneutral plasmas confined in closed magnetic surfaces. Secondly, in order to investigate the mechanism of the multiple disruption of helical nonneutral plasmas observed in experiments, space and time evolutions of electron flux are measured carefully inside the magnetic surfaces, when the plasma disruption occurs. Surprisingly, a set of data show that the observed disruption is at first happened at ρ ∼ 0.8, where ρ is the normalized minor radius, and then, it seems to propagate inside magnetic surfaces

  11. Space vehicle electromechanical system and helical antenna winding fixture

    Science.gov (United States)

    Judd, Stephen; Dallmann, Nicholas; Guenther, David; Enemark, Donald; Seitz, Daniel; Martinez, John; Storms, Steven

    2017-12-26

    A space vehicle electromechanical system may employ an architecture that enables convenient and practical testing, reset, and retesting of solar panel and antenna deployment on the ground. A helical antenna winding fixture may facilitate winding and binding of the helical antenna.

  12. Theory of dynamics in long pulse helical plasmas

    International Nuclear Information System (INIS)

    Itoh, K.; Sanuki, H.; Toda, S.; Yokoyama, M.; Itoh, S.-I.; Yagi, M.; Fukuyama, A.

    2001-01-01

    Self-organized dynamics of toroidal helical plasma, which is induced by the nonlinear transport property, is discussed. Neoclassical ripple diffusion is a dominant mechanism that drives the radial electric field. The bifurcation nature of the electric field generation gives rise to the electric field domain interface, across which the electric field changes strongly. This domain interface is an origin of internal transport barrier in helical systems. This nonlinearity gives rise to the self-organized oscillations; the electric field pulsation is one of the examples. Based on the model of density limit, in which the competition between the transport loss and radiation loss is analyzed, dynamics near the density limit of helical systems is also discussed. (author)

  13. Numerical Analysis of Helical Pile-Soil Interaction under Compressive Loads

    Science.gov (United States)

    Polishchuk, A. I.; Maksimov, F. A.

    2017-11-01

    The results of the field tests of full-scale steel helical piles in clay soils intended for prefabricated temporary buildings foundations are presented in this article. The finite element modeling was used for the evaluation of stress distribution of the clay soil around helical piles. An approach of modeling of the screw-pile geometry has been proposed through the Finite Element Analysis. Steel helical piles with a length of 2.0 m, shaft diameter of 0.108 m and a blade diameter of 0.3 m were used in the experiments. The experiments have shown the efficiency of double-bladed helical piles in the clay soils compared to single-bladed piles. It has been experimentally established that the introduction of the second blade into the pile shaft provides an increase of the bearing capacity in clay soil up to 30% compared to a single-bladed helical pile with similar geometrical dimensions. The numerical results are compared with the measurements obtained by a large scale test and the bearing capacity has been estimated. It has been found that the model results fit the field results. For a double-bladed helical pile it was revealed that shear stresses upon pile loading are formed along the lateral surface forming a cylindrical failure surface.

  14. Self-assembly of hard helices: a rich and unconventional polymorphism.

    Science.gov (United States)

    Kolli, Hima Bindu; Frezza, Elisa; Cinacchi, Giorgio; Ferrarini, Alberta; Giacometti, Achille; Hudson, Toby S; De Michele, Cristiano; Sciortino, Francesco

    2014-11-07

    Hard helices can be regarded as a paradigmatic elementary model for a number of natural and synthetic soft matter systems, all featuring the helix as their basic structural unit, from natural polynucleotides and polypeptides to synthetic helical polymers, and from bacterial flagella to colloidal helices. Here we present an extensive investigation of the phase diagram of hard helices using a variety of methods. Isobaric Monte Carlo numerical simulations are used to trace the phase diagram; on going from the low-density isotropic to the high-density compact phases a rich polymorphism is observed, exhibiting a special chiral screw-like nematic phase and a number of chiral and/or polar smectic phases. We present full characterization of the latter, showing that they have unconventional features, ascribable to the helical shape of the constituent particles. Equal area construction is used to locate the isotropic-to-nematic phase transition, and the results are compared with those stemming from an Onsager-like theory. Density functional theory is also used to study the nematic-to-screw-nematic phase transition; within the simplifying assumption of perfectly parallel helices, we compare different levels of approximation, that is second- and third-virial expansions and a Parsons-Lee correction.

  15. Energy fluxes in helical magnetohydrodynamics and dynamo action

    Indian Academy of Sciences (India)

    ... large-scale magnetic field arising due to non-helical interactions and (2) inverse energy flux of magnetic energy caused by helical interactions. Based on our flux results, a primitive model for galactic dynamo has been constructed. Our calculations yield dynamo time-scale for a typical galaxy to be of the order of 108 years.

  16. Roles of effective helical ripple rates in nonlinear stability of externally induced magnetic islands

    Energy Technology Data Exchange (ETDEWEB)

    Nishimura, Seiya, E-mail: n-seiya@kobe-kosen.ac.jp [Kobe City College of Technology, Kobe, Hyogo 651-2194 (Japan)

    2015-02-15

    Magnetic islands are externally produced by resonant magnetic perturbations (RMPs) in toroidal plasmas. Spontaneous annihilation of RMP-induced magnetic islands called self-healing has been observed in helical systems. A possible mechanism of the self-healing is shielding of RMP penetration by helical ripple-induced neoclassical flows, which give rise to neoclassical viscous torques. In this study, effective helical ripple rates in multi-helicity helical systems are revisited, and a multi-helicity effect on the self-healing is investigated, based on a theoretical model of rotating magnetic islands. It is confirmed that effective helical ripple rates are sensitive to magnetic axis positions. It is newly found that self-healing thresholds also strongly depend on magnetic axis positions, which is due to dependence of neoclassical viscous torques on effective helical ripple rates.

  17. Analytic, High-beta Solutions of the Helical Grad-Shafranov Equation

    International Nuclear Information System (INIS)

    Smith, D.R.; Reiman, A.H.

    2004-01-01

    We present analytic, high-beta (β ∼ O(1)), helical equilibrium solutions for a class of helical axis configurations having large helical aspect ratio, with the helix assumed to be tightly wound. The solutions develop a narrow boundary layer of strongly compressed flux, similar to that previously found in high beta tokamak equilibrium solutions. The boundary layer is associated with a strong localized current which prevents the equilibrium from having zero net current

  18. Characteristic features of edge transport barrier formed in helical divertor configuration of the Large Helical Device

    International Nuclear Information System (INIS)

    Toi, K.; Ohdachi, S.; Watanabe, F.

    2006-10-01

    In a helical divertor configuration of the Large Helical Device (LHD), transport barrier was formed through low to high confinement (L-H) transition in the plasma edge region including ergodic field layer of which region is in the magnetic hill. The plasma stored energy or the averaged bulk plasma beta dia > (derived from diamagnetic measurement) starts to increase just after the transition. In the case that both dia > and line-averaged electron density e > at the transition are relatively high as dia >≥1.5% and e >≥2x10 19 m -3 , the increase is hampered by rapid growth of edge MHD modes and/or small ELM like activities just after the transition. On the other hand, the transition at lower e > (≤1.5x10 19 m -3 ) and dia > (<2%) leads to a continuous increase in the stored energy with a time scale longer than the global energy confinement time, without suffering from these MHD activities near the edge. The ETB typically formed in electron density profile extends into ergodic field layer defined in the vacuum field. The width of ETB is almost independent of the toroidal field strength from 0.5T to 1.5T and is much larger than the poloidal ion gyro-radius. When resonant helical field perturbations are applied to expand a magnetic island size at the rational surface of the rotational transform ι/2π=1 near the edge, the L-H transition is triggered at lower electron density compared with the case without the field perturbations. The application of large helical field perturbations also suppresses edge MHD modes and ELM like activities. (author)

  19. Gynecological applications of helical CT using SmartPrep

    Energy Technology Data Exchange (ETDEWEB)

    Sakurada, Akira; Kakizaki, Dai; Abe, Kimihiko [Tokyo Medical Coll. (Japan)

    1999-11-01

    SmartPrep is software program for scanning a given region of interest (ROI) at optimal contrast density. An operator can arbitrarily define ROI and preset the CT value at which scanning should be started. After the injection of a contrast medium, system conducts continuous monitoring of the ROI and the operator starts helical scanning of the planned region when the present CT value has been reached. In comparison with conventional helical CT that requires a period of time from the beginning of contrast medium injection to the beginning of scanning, SmartPrep minimizes personal error and better depicts the artery-predominant phase under optimal conditions. In this study we examine the usefulness of contrast-enhanced helical CT using SmartPrep in the evaluation of gynecological disease. When the contrast medium was injected into the dorsal vein of the hand at a rate of 3 ml/sec, strong staining of pelvic arteries was observed in the CT images started at 17 to 23 sec after injection. The early-phase helical CT obtained under these conditions provided good depiction of lesions in cases of placenta accreta and invasive mole, as well as clear demonstration of tumor angiogenesis and evaluation of laterality in cases of cervical cancer. Comparison of the early and delayed phase also facilitated easier evaluation of lymph nodes than conventional comparison of simple and contrast-enhanced CT. The results thus suggest the usefulness of contrast-enhanced helical CT using SmartPrep in gynecology. (author)

  20. Helical CT in evaluation of the bronchial tree

    International Nuclear Information System (INIS)

    Perhomaa, M.; Laehde, S.; Rossi, O.; Suramo, I.

    1997-01-01

    Purpose: To establish a protocol for and to assess the value of helical CT in the imaging of the bronchial tree. Material and Methods: Noncontrast helical CT was performed in 30 patients undergoing fiberoptic bronchoscopy for different reasons. Different protocols were compared; they included overlapping 10 mm, 5 mm, or 3 mm slices and non-tilted, cephalad or caudal tilted images. Ordinary cross-sectional and multiplanar 2D reformats were applied for visualization of the bronchial branches. The effect of increasing the helical pitch was tested in one patient. Results: A total of 92.1-100% of the segmental bronchi present in the helical acquisitions were identified by the different protocols. The collimation had no significant impact on the identification of the bronchial branches, but utilization of 3-mm overlapping slices made it easier to distinguish the nearby branches and provided better longitudinal visualization of the bronchi in 2D reformats. The tilted scans illustrated the disadvantage of not covering all segmental bronchi in one breath-hold. An increase of the pitch from 1 to 1.5 did not cause noticeable blurring of the images. CT and bronchoscopic findings correlated well in the area accessible to bronchoscopy, but CT detected 5 additional pathological lesions (including 2 cancers) in the peripheral lung. Conclusion: Helical CT supplemented with bronchography-like 2D reformats provides an effective method complementary to bronchoscopy in the examination of the bronchial tree. (orig.)