Validity of the CT to attenuation coefficient map conversion methods

International Nuclear Information System (INIS)

Faghihi, R.; Ahangari Shahdehi, R.; Fazilat Moadeli, M.

2004-01-01

The most important commercialized methods of attenuation correction in SPECT are based on attenuation coefficient map from a transmission imaging method. The transmission imaging system can be the linear source of radioelement or a X-ray CT system. The image of transmission imaging system is not useful unless to replacement of the attenuation coefficient or CT number with the attenuation coefficient in SPECT energy. In this paper we essay to evaluate the validity and estimate the error of the most used method of this transformation. The final result shows that the methods which use a linear or multi-linear curve accept a error in their estimation. The value of mA is not important but the patient thickness is very important and it can introduce a error more than 10 percent in the final result

Temperature Measurements of the Low-Attenuation Radiographic Ice Ball During CT-Guided Renal Cryoablation

International Nuclear Information System (INIS)

Permpongkosol, Sompol; Link, Richard E.; Kavoussi, Louis R.; Solomon, Stephen B.

2008-01-01

During renal cryoablation a low-attenuation area on CT develops around the cryoprobe. Knowledge of the temperature of the growing low-attenuation area can guide therapy and ensure lethal temperatures. Herein, we report thermocouple results and correlating CT images during the development of the low-attenuation 'radiographic ice ball.' Five patients who underwent percutaneous CT-guided renal cryoablation were identified who had thermocouples inserted and serial intraprocedural CT images that included images with thermocouple measurements of 0 o and sub-0 o C. Thermocouples had been percutaneously placed just beyond the edge of the tumors either to ensure adequate cooling or to ensure safety to adjacent critical structures. Renal cryotherapy under CT guidance produced a growing low-attenuation area corresponding to the radiographic ice ball. When the thermocouple measured 0 o C, CT images showed the thermocouple tip at the edge of the low-attenuation ice ball. At lower temperatures the tip was within the low-attenuation ice ball. We conclude that knowledge of the temperature at the ice ball edge during cryoablation can be used to predict the extent of tissue necrosis and thus provide an estimate of cryotherapy effectiveness during the procedure. Further work is necessary to establish a firm relationship between the thermal conditions and the zone of damage

Ultra-low dose CT attenuation correction for PET/CT: analysis of sparse view data acquisition and reconstruction algorithms

Science.gov (United States)

Rui, Xue; Cheng, Lishui; Long, Yong; Fu, Lin; Alessio, Adam M.; Asma, Evren; Kinahan, Paul E.; De Man, Bruno

2015-01-01

For PET/CT systems, PET image reconstruction requires corresponding CT images for anatomical localization and attenuation correction. In the case of PET respiratory gating, multiple gated CT scans can offer phase-matched attenuation and motion correction, at the expense of increased radiation dose. We aim to minimize the dose of the CT scan, while preserving adequate image quality for the purpose of PET attenuation correction by introducing sparse view CT data acquisition. Methods We investigated sparse view CT acquisition protocols resulting in ultra-low dose CT scans designed for PET attenuation correction. We analyzed the tradeoffs between the number of views and the integrated tube current per view for a given dose using CT and PET simulations of a 3D NCAT phantom with lesions inserted into liver and lung. We simulated seven CT acquisition protocols with {984, 328, 123, 41, 24, 12, 8} views per rotation at a gantry speed of 0.35 seconds. One standard dose and four ultra-low dose levels, namely, 0.35 mAs, 0.175 mAs, 0.0875 mAs, and 0.04375 mAs, were investigated. Both the analytical FDK algorithm and the Model Based Iterative Reconstruction (MBIR) algorithm were used for CT image reconstruction. We also evaluated the impact of sinogram interpolation to estimate the missing projection measurements due to sparse view data acquisition. For MBIR, we used a penalized weighted least squares (PWLS) cost function with an approximate total-variation (TV) regularizing penalty function. We compared a tube pulsing mode and a continuous exposure mode for sparse view data acquisition. Global PET ensemble root-mean-squares-error (RMSE) and local ensemble lesion activity error were used as quantitative evaluation metrics for PET image quality. Results With sparse view sampling, it is possible to greatly reduce the CT scan dose when it is primarily used for PET attenuation correction with little or no measureable effect on the PET image. For the four ultra-low dose levels

MRI-guided attenuation correction in whole-body PET/MR. Assessment of the effect of bone attenuation

International Nuclear Information System (INIS)

Akbarzadeh, A.; Ay, M.R.; Ahmadian, A.; Riahi Alam, N.; Zaidi, H.

2013-01-01

Hybrid positron emission tomography (PET)/MRI presents many advantages in comparison with its counterpart PET/CT in terms of improved soft-tissue contrast, decrease in radiation exposure, and truly simultaneous and multi-parametric imaging capabilities. However, the lack of well-established methodology for MR-based attenuation correction is hampering further development and wider acceptance of this technology. We assess the impact of ignoring bone attenuation and using different tissue classes for generation of the attenuation map on the accuracy of attenuation correction of PET data. This work was performed using simulation studies based on the XCAT phantom and clinical input data. For the latter, PET and CT images of patients were used as input for the analytic simulation model using realistic activity distributions where CT-based attenuation correction was utilized as reference for comparison. For both phantom and clinical studies, the reference attenuation map was classified into various numbers of tissue classes to produce three (air, soft tissue and lung), four (air, lungs, soft tissue and cortical bones) and five (air, lungs, soft tissue, cortical bones and spongeous bones) class attenuation maps. The phantom studies demonstrated that ignoring bone increases the relative error by up to 6.8% in the body and up to 31.0% for bony regions. Likewise, the simulated clinical studies showed that the mean relative error reached 15% for lesions located in the body and 30.7% for lesions located in bones, when neglecting bones. These results demonstrate an underestimation of about 30% of tracer uptake when neglecting bone, which in turn imposes substantial loss of quantitative accuracy for PET images produced by hybrid PET/MRI systems. Considering bones in the attenuation map will considerably improve the accuracy of MR-guided attenuation correction in hybrid PET/MR to enable quantitative PET imaging on hybrid PET/MR technologies. (author)

Clinical evaluation of respiration-induced attenuation uncertainties in pulmonary 3D PET/CT.

Science.gov (United States)

Kruis, Matthijs F; van de Kamer, Jeroen B; Vogel, Wouter V; Belderbos, José Sa; Sonke, Jan-Jakob; van Herk, Marcel

2015-12-01

In contemporary positron emission tomography (PET)/computed tomography (CT) scanners, PET attenuation correction is performed by means of a CT-based attenuation map. Respiratory motion can however induce offsets between the PET and CT data. Studies have demonstrated that these offsets can cause errors in quantitative PET measures. The purpose of this study is to quantify the effects of respiration-induced CT differences on the attenuation correction of pulmonary 18-fluordeoxyglucose (FDG) 3D PET/CT in a patient population and to investigate contributing factors. For 32 lung cancer patients, 3D-CT, 4D-PET and 4D-CT data were acquired. The 4D FDG PET data were attenuation corrected (AC) using a free-breathing 3D-CT (3D-AC), the end-inspiration CT (EI-AC), the end-expiration CT (EE-AC) or phase-by-phase (P-AC). After reconstruction and AC, the 4D-PET data were averaged. In the 4Davg data, we measured maximum tumour standardised uptake value (SUV)max in the tumour, SUVmean in a lung volume of interest (VOI) and average SUV (SUVmean) in a muscle VOI. On the 4D-CT, we measured the lung volume differences and CT number changes between inhale and exhale in the lung VOI. Compared to P-AC, we found -2.3% (range -9.7% to 1.2%) lower tumour SUVmax in EI-AC and 2.0% (range -0.9% to 9.5%) higher SUVmax in EE-AC. No differences in the muscle SUV were found. The use of 3D-AC led to respiration-induced SUVmax differences up to 20% compared to the use of P-AC. SUVmean differences in the lung VOI between EI-AC and EE-AC correlated to average CT differences in this region (ρ = 0.83). SUVmax differences in the tumour correlated to the volume changes of the lungs (ρ = -0.55) and the motion amplitude of the tumour (ρ = 0.53), both as measured on the 4D-CT. Respiration-induced CT variations in clinical data can in extreme cases lead to SUV effects larger than 10% on PET attenuation correction. These differences were case specific and correlated to differences in CT number

SU-F-I-59: Quality Assurance Phantom for PET/CT Alignment and Attenuation Correction

International Nuclear Information System (INIS)

Lin, T; Hamacher, K

2016-01-01

Purpose: This study utilizes a commercial PET/CT phantom to investigate two specific properties of a PET/CT system: the alignment accuracy of PET images with those from CT used for attenuation correction and the accuracy of this correction in PET images. Methods: A commercial PET/CT phantom consisting of three aluminum rods, two long central cylinders containing uniform activity, and attenuating materials such as air, water, bone and iodine contrast was scanned using a standard PET/CT protocol. Images reconstructed with 2 mm slice thickness and a 512 by 512 matrix were obtained. The center of each aluminum rod in the PET and CT images was compared to evaluate alignment accuracy. ROIs were drawn on transaxial images of the central rods at each section of attenuating material to determine the corrected activity (in BQML). BQML values were graphed as a function of slice number to provide a visual representation of the attenuation-correction throughout the whole phantom. Results: Alignment accuracy is high between the PET and CT images. The maximum deviation between the two in the axial plane is less than 1.5 mm, which is less than the width of a single pixel. BQML values measured along different sections of the large central rods are similar among the different attenuating materials except iodine contrast. Deviation of BQML values in the air and bone sections from the water section is less than 1%. Conclusion: Accurate alignment of PET and CT images is critical to ensure proper calculation and application of CT-based attenuation correction. This study presents a simple and quick method to evaluate the two with a single acquisition. As the phantom also includes spheres of increasing diameter, this could serve as a straightforward means to annually evaluate the status of a modern PET/CT system.

SU-F-I-59: Quality Assurance Phantom for PET/CT Alignment and Attenuation Correction

Energy Technology Data Exchange (ETDEWEB)

Lin, T; Hamacher, K [Columbia University Medical Center, New York, NY (United States)

2016-06-15

Purpose: This study utilizes a commercial PET/CT phantom to investigate two specific properties of a PET/CT system: the alignment accuracy of PET images with those from CT used for attenuation correction and the accuracy of this correction in PET images. Methods: A commercial PET/CT phantom consisting of three aluminum rods, two long central cylinders containing uniform activity, and attenuating materials such as air, water, bone and iodine contrast was scanned using a standard PET/CT protocol. Images reconstructed with 2 mm slice thickness and a 512 by 512 matrix were obtained. The center of each aluminum rod in the PET and CT images was compared to evaluate alignment accuracy. ROIs were drawn on transaxial images of the central rods at each section of attenuating material to determine the corrected activity (in BQML). BQML values were graphed as a function of slice number to provide a visual representation of the attenuation-correction throughout the whole phantom. Results: Alignment accuracy is high between the PET and CT images. The maximum deviation between the two in the axial plane is less than 1.5 mm, which is less than the width of a single pixel. BQML values measured along different sections of the large central rods are similar among the different attenuating materials except iodine contrast. Deviation of BQML values in the air and bone sections from the water section is less than 1%. Conclusion: Accurate alignment of PET and CT images is critical to ensure proper calculation and application of CT-based attenuation correction. This study presents a simple and quick method to evaluate the two with a single acquisition. As the phantom also includes spheres of increasing diameter, this could serve as a straightforward means to annually evaluate the status of a modern PET/CT system.

MR-based attenuation correction for cardiac FDG PET on a hybrid PET/MRI scanner: comparison with standard CT attenuation correction

Energy Technology Data Exchange (ETDEWEB)

Vontobel, Jan; Liga, Riccardo; Possner, Mathias; Clerc, Olivier F.; Mikulicic, Fran; Veit-Haibach, Patrick; Voert, Edwin E.G.W. ter; Fuchs, Tobias A.; Stehli, Julia; Pazhenkottil, Aju P.; Benz, Dominik C.; Graeni, Christoph; Gaemperli, Oliver; Herzog, Bernhard; Buechel, Ronny R.; Kaufmann, Philipp A. [University Hospital Zurich, Department of Nuclear Medicine, Zurich (Switzerland)

2015-09-15

The aim of this study was to evaluate the feasibility of attenuation correction (AC) for cardiac {sup 18}F-labelled fluorodeoxyglucose (FDG) positron emission tomography (PET) using MR-based attenuation maps. We included 23 patients with no known cardiac history undergoing whole-body FDG PET/CT imaging for oncological indications on a PET/CT scanner using time-of-flight (TOF) and subsequent whole-body PET/MR imaging on an investigational hybrid PET/MRI scanner. Data sets from PET/MRI (with and without TOF) were reconstructed using MR AC and semi-quantitative segmental (20-segment model) myocardial tracer uptake (per cent of maximum) and compared to PET/CT which was reconstructed using CT AC and served as standard of reference. Excellent correlations were found for regional uptake values between PET/CT and PET/MRI with TOF (n = 460 segments in 23 patients; r = 0.913; p < 0.0001) with narrow Bland-Altman limits of agreement (-8.5 to +12.6 %). Correlation coefficients were slightly lower between PET/CT and PET/MRI without TOF (n = 460 segments in 23 patients; r = 0.851; p < 0.0001) with broader Bland-Altman limits of agreement (-12.5 to +15.0 %). PET/MRI with and without TOF showed minimal underestimation of tracer uptake (-2.08 and -1.29 %, respectively), compared to PET/CT. Relative myocardial FDG uptake obtained from MR-based attenuation corrected FDG PET is highly comparable to standard CT-based attenuation corrected FDG PET, suggesting interchangeability of both AC techniques. (orig.)

Multiphase contrast-enhanced CT with highly concentrated contrast agent can be used for PET attenuation correction in integrated PET/CT imaging

International Nuclear Information System (INIS)

Aschoff, Philip; Plathow, Christian; Lichy, Matthias P.; Claussen, Claus D.; Pfannenberg, Christina; Beyer, Thomas; Erb, Gunter; Oeksuez, Mehmet Oe.

2012-01-01

State-of-the-art positron emission tomography/computed tomography (PET/CT) systems incorporate multislice CT technology, thus facilitating the acquisition of multiphase, contrast-enhanced CT data as part of integrated PET/CT imaging protocols. We assess the influence of a highly concentrated iodinated contrast medium (CM) on quantification and image quality following CT-based attenuation correction (CT-AC) in PET/CT. Twenty-eight patients with suspected malignant liver lesions were enrolled prospectively. PET/CT was performed 60 min after injection of 400 MBq of 18 F-fluorodeoxyglucose (FDG) and following the biphasic administration of an intravenous CM (400 mg iodine/ml, Iomeron 400). PET images were reconstructed with CT-AC using any of four acquired CT image sets: non-enhanced, pre-contrast (n-PET), arterial phase (art-PET), portal venous phase (pv-PET) and late phase (late-PET). Normal tissue activity and liver lesions were assessed visually and quantitatively on each PET/CT image set. Visual assessment of PET following CT-AC revealed no noticeable difference in image appearance or quality when using any of the four CT data sets for CT-AC. A total of 44 PET-positive liver lesions was identified in 21 of 28 patients. There were no false-negative or false-positive lesions on PET. Mean standardized uptake values (SUV) in 36 evaluable lesions were: 5.5 (n-PET), 5.8 (art-PET), 5.8 (pv-PET) and 5.8 (late-PET), with the highest mean increase in mean SUV of 6%. Mean SUV changes in liver background increased by up to 10% from n-PET to pv-PET. Multiphase CT data acquired with the use of highly concentrated CM can be used for qualitative assessment of liver lesions in torso FDG PET/CT. The influence on quantification of FDG uptake is small and negligible for most clinical applications. (orig.)

PET/CT with intravenous contrast can be used for PET attenuation correction in cancer patients

DEFF Research Database (Denmark)

Berthelsen, A K; Holm, S; Loft, A

2005-01-01

PURPOSE: If the CT scan of a combined PET/CT study is performed as a full diagnostic quality CT scan including intravenous (IV) contrast agent, the quality of the joint PET/CT procedure is improved and a separate diagnostic CT scan can be avoided. CT with IV contrast can be used for PET attenuation...... correction, but this may result in a bias in the attenuation factors. The clinical significance of this bias has not been established. Our aim was to perform a prospective clinical study where each patient had CT performed with and without IV contrast agent to establish whether PET/CT with IV contrast can...... scans without, and then with contrast agent, followed by an 18F-fluorodeoxyglucose whole-body PET scan. The CT examinations were performed with identical parameters on a GE Discovery LS scanner. The PET data were reconstructed with attenuation correction based on the two CT data sets. A global...

Analysis of the association between periportal low attenuation, as seen on CT, after blunt abdominal trauma, and elevated central venous pressure

International Nuclear Information System (INIS)

Lee, Jae Hung; Lee, Hyeon Kyeong; Lee, Chae Kyeong; Ku, Kwan Min; Lee, Sung Woo; Kim, Miu Woon; Ahn, Woo Sub; Yoon, Ji Young

1999-01-01

To assess the causes of periportal low attenuation, as seen on CT, in patients with blunt abdominal trauma. From among 812 patients who underwent abdominal CT after blunt abdominal trauma, we retrospectively analysed the findings in 124 with evidence of periportal low attenuation. Among these, hepatic injury was noted in only 87. The presence or absence, and extent of hepatic injury, and of periportal low attenuation, as seen on CT, were carefully evaluated. In each case, the ratio of the transverse diameter of the inferior vena cava(IVC) to the aorta at the level of the right adrenal gland provided an indirect measurement of central venous pressure ; for control purposes, the ratio was also obtained in 21 non-traumatic patients with no abnormal abdominal CT findings. Of the 87 patients with hepatic injury, 46 showed no periportal low attenuation, and average value of the ratio between the IVC and aorta was 1.16±0.12, while the remaining 41 patients showed periportal low attenuation with a ratio of 1.51±0.21(p<0.05). In the 37 patients with periportal low attenuation but no evidence of concomitant hepatic injury, the average ratio was 1.52±0.25, while in 21 non-traumatic patients it was 1.15±0.16. For resuscitation, all patients had received 0.5-5.0 litre of IV fluid therapy before CT, and at the time of CT, were normotensive. Rapidly elevated central venous pressure following massive IV infusion therapy in patients with blunt abdominal trauma can be one of the causes of periportal low attenuation, as seen on CT

Analysis of the association between periportal low attenuation, as seen on CT, after blunt abdominal trauma, and elevated central venous pressure

Energy Technology Data Exchange (ETDEWEB)

Lee, Jae Hung; Lee, Hyeon Kyeong; Lee, Chae Kyeong; Ku, Kwan Min; Lee, Sung Woo; Kim, Miu Woon; Ahn, Woo Sub [Dongguk Univ. College of Medicine, Pohang (Korea, Republic of); Yoon, Ji Young [Sungkyunkwan Univ. College of Medicine, Seoul (Korea, Republic of)

1999-01-01

To assess the causes of periportal low attenuation, as seen on CT, in patients with blunt abdominal trauma. From among 812 patients who underwent abdominal CT after blunt abdominal trauma, we retrospectively analysed the findings in 124 with evidence of periportal low attenuation. Among these, hepatic injury was noted in only 87. The presence or absence, and extent of hepatic injury, and of periportal low attenuation, as seen on CT, were carefully evaluated. In each case, the ratio of the transverse diameter of the inferior vena cava(IVC) to the aorta at the level of the right adrenal gland provided an indirect measurement of central venous pressure ; for control purposes, the ratio was also obtained in 21 non-traumatic patients with no abnormal abdominal CT findings. Of the 87 patients with hepatic injury, 46 showed no periportal low attenuation, and average value of the ratio between the IVC and aorta was 1.16{+-}0.12, while the remaining 41 patients showed periportal low attenuation with a ratio of 1.51{+-}0.21(p<0.05). In the 37 patients with periportal low attenuation but no evidence of concomitant hepatic injury, the average ratio was 1.52{+-}0.25, while in 21 non-traumatic patients it was 1.15{+-}0.16. For resuscitation, all patients had received 0.5-5.0 litre of IV fluid therapy before CT, and at the time of CT, were normotensive. Rapidly elevated central venous pressure following massive IV infusion therapy in patients with blunt abdominal trauma can be one of the causes of periportal low attenuation, as seen on CT.

Non-hodgkin lymphoma containing low attenuation area at enhanced CT : correlation with histopathologic typing

Energy Technology Data Exchange (ETDEWEB)

Lee, Kyung Hoon; Kim, Hyung Jin; Ahn, In Oak; Chung, Sung Hoon [College of Medicine, Gyeongsang National University, Jinju (Korea, Republic of); Park, Ji Hyun [Masan Koryo General Hospital, Masan (Korea, Republic of)

1994-12-15

To evaluate the frequently of low attenuation area in enhanced CT scans of non-Hodgkin lymphoma(NHL) and to find out if there is any pertinent relationship between this and the histopathologic classification. The authors reviewed CT scans in the newly-diagnosed 53 patients with NHL. We defined the low attenuation area as the one with CT attenuation value lower than that of the muscle, surrounding lesion, or other lymph nodes after contrast enhancement. NHL with the low attenuation areas were correlated with the histopathologic findings according to the classification based on the Working Formulation and the frequency of the lesion was evaluated. Of the 53 patients, the low attenuation area was found in 13 patients (25%) at CT. The histopathologic classification could be made in 12 patients, among whom one patient was classified as low-grade, six as intermediate-grade, and five as high-grade. Concerning the specific cell typing, the diffuse large cell type was most common in intermediate-grade NHL seen in five patients and the large cell, immunoblastic type was most common in high-grade NHL seen in three patients. The authors concluded that the low attenuation area within lymphoma is not an infrequent finding at CT, and there was no statistically significant correlation between this finding and the prognostic grading of the Working Formulation.

Correction of oral contrast artifacts in CT-based attenuation correction of PET images using an automated segmentation algorithm

International Nuclear Information System (INIS)

Ahmadian, Alireza; Ay, Mohammad R.; Sarkar, Saeed; Bidgoli, Javad H.; Zaidi, Habib

2008-01-01

Oral contrast is usually administered in most X-ray computed tomography (CT) examinations of the abdomen and the pelvis as it allows more accurate identification of the bowel and facilitates the interpretation of abdominal and pelvic CT studies. However, the misclassification of contrast medium with high-density bone in CT-based attenuation correction (CTAC) is known to generate artifacts in the attenuation map (μmap), thus resulting in overcorrection for attenuation of positron emission tomography (PET) images. In this study, we developed an automated algorithm for segmentation and classification of regions containing oral contrast medium to correct for artifacts in CT-attenuation-corrected PET images using the segmented contrast correction (SCC) algorithm. The proposed algorithm consists of two steps: first, high CT number object segmentation using combined region- and boundary-based segmentation and second, object classification to bone and contrast agent using a knowledge-based nonlinear fuzzy classifier. Thereafter, the CT numbers of pixels belonging to the region classified as contrast medium are substituted with their equivalent effective bone CT numbers using the SCC algorithm. The generated CT images are then down-sampled followed by Gaussian smoothing to match the resolution of PET images. A piecewise calibration curve was then used to convert CT pixel values to linear attenuation coefficients at 511 keV. The visual assessment of segmented regions performed by an experienced radiologist confirmed the accuracy of the segmentation and classification algorithms for delineation of contrast-enhanced regions in clinical CT images. The quantitative analysis of generated μmaps of 21 clinical CT colonoscopy datasets showed an overestimation ranging between 24.4% and 37.3% in the 3D-classified regions depending on their volume and the concentration of contrast medium. Two PET/CT studies known to be problematic demonstrated the applicability of the technique in

Motion-compensated PET image reconstruction with respiratory-matched attenuation correction using two low-dose inhale and exhale CT images

International Nuclear Information System (INIS)

Nam, Woo Hyun; Ahn, Il Jun; Ra, Jong Beom; Kim, Kyeong Min; Kim, Byung Il

2013-01-01

Positron emission tomography (PET) is widely used for diagnosis and follow up assessment of radiotherapy. However, thoracic and abdominal PET suffers from false staging and incorrect quantification of the radioactive uptake of lesion(s) due to respiratory motion. Furthermore, respiratory motion-induced mismatch between a computed tomography (CT) attenuation map and PET data often leads to significant artifacts in the reconstructed PET image. To solve these problems, we propose a unified framework for respiratory-matched attenuation correction and motion compensation of respiratory-gated PET. For the attenuation correction, the proposed algorithm manipulates a 4D CT image virtually generated from two low-dose inhale and exhale CT images, rather than a real 4D CT image which significantly increases the radiation burden on a patient. It also utilizes CT-driven motion fields for motion compensation. To realize the proposed algorithm, we propose an improved region-based approach for non-rigid registration between body CT images, and we suggest a selection scheme of 3D CT images that are respiratory-matched to each respiratory-gated sinogram. In this work, the proposed algorithm was evaluated qualitatively and quantitatively by using patient datasets including lung and/or liver lesion(s). Experimental results show that the method can provide much clearer organ boundaries and more accurate lesion information than existing algorithms by utilizing two low-dose CT images. (paper)

One registration multi-atlas-based pseudo-CT generation for attenuation correction in PET/MRI

International Nuclear Information System (INIS)

Arabi, Hossein; Zaidi, Habib

2016-01-01

The outcome of a detailed assessment of various strategies for atlas-based whole-body bone segmentation from magnetic resonance imaging (MRI) was exploited to select the optimal parameters and setting, with the aim of proposing a novel one-registration multi-atlas (ORMA) pseudo-CT generation approach. The proposed approach consists of only one online registration between the target and reference images, regardless of the number of atlas images (N), while for the remaining atlas images, the pre-computed transformation matrices to the reference image are used to align them to the target image. The performance characteristics of the proposed method were evaluated and compared with conventional atlas-based attenuation map generation strategies (direct registration of the entire atlas images followed by voxel-wise weighting (VWW) and arithmetic averaging atlas fusion). To this end, four different positron emission tomography (PET) attenuation maps were generated via arithmetic averaging and VWW scheme using both direct registration and ORMA approaches as well as the 3-class attenuation map obtained from the Philips Ingenuity TF PET/MRI scanner commonly used in the clinical setting. The evaluation was performed based on the accuracy of extracted whole-body bones by the different attenuation maps and by quantitative analysis of resulting PET images compared to CT-based attenuation-corrected PET images serving as reference. The comparison of validation metrics regarding the accuracy of extracted bone using the different techniques demonstrated the superiority of the VWW atlas fusion algorithm achieving a Dice similarity measure of 0.82 ± 0.04 compared to arithmetic averaging atlas fusion (0.60 ± 0.02), which uses conventional direct registration. Application of the ORMA approach modestly compromised the accuracy, yielding a Dice similarity measure of 0.76 ± 0.05 for ORMA-VWW and 0.55 ± 0.03 for ORMA-averaging. The results of quantitative PET analysis followed the same

One registration multi-atlas-based pseudo-CT generation for attenuation correction in PET/MRI

Energy Technology Data Exchange (ETDEWEB)

Arabi, Hossein [Geneva University Hospital, Division of Nuclear Medicine and Molecular Imaging, Geneva 4 (Switzerland); Zaidi, Habib [Geneva University Hospital, Division of Nuclear Medicine and Molecular Imaging, Geneva 4 (Switzerland); Geneva University, Geneva Neuroscience Center, Geneva (Switzerland); University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine and Molecular Imaging, Groningen (Netherlands); University of Southern Denmark, Department of Nuclear Medicine, Odense (Denmark)

2016-10-15

The outcome of a detailed assessment of various strategies for atlas-based whole-body bone segmentation from magnetic resonance imaging (MRI) was exploited to select the optimal parameters and setting, with the aim of proposing a novel one-registration multi-atlas (ORMA) pseudo-CT generation approach. The proposed approach consists of only one online registration between the target and reference images, regardless of the number of atlas images (N), while for the remaining atlas images, the pre-computed transformation matrices to the reference image are used to align them to the target image. The performance characteristics of the proposed method were evaluated and compared with conventional atlas-based attenuation map generation strategies (direct registration of the entire atlas images followed by voxel-wise weighting (VWW) and arithmetic averaging atlas fusion). To this end, four different positron emission tomography (PET) attenuation maps were generated via arithmetic averaging and VWW scheme using both direct registration and ORMA approaches as well as the 3-class attenuation map obtained from the Philips Ingenuity TF PET/MRI scanner commonly used in the clinical setting. The evaluation was performed based on the accuracy of extracted whole-body bones by the different attenuation maps and by quantitative analysis of resulting PET images compared to CT-based attenuation-corrected PET images serving as reference. The comparison of validation metrics regarding the accuracy of extracted bone using the different techniques demonstrated the superiority of the VWW atlas fusion algorithm achieving a Dice similarity measure of 0.82 ± 0.04 compared to arithmetic averaging atlas fusion (0.60 ± 0.02), which uses conventional direct registration. Application of the ORMA approach modestly compromised the accuracy, yielding a Dice similarity measure of 0.76 ± 0.05 for ORMA-VWW and 0.55 ± 0.03 for ORMA-averaging. The results of quantitative PET analysis followed the same

Assessment of pulmonary emphysema on CT teleradiology

International Nuclear Information System (INIS)

Satoh, Katashi; Kato, Koji; Mitani, Masahiro

2003-01-01

The present study assessed the current wave of using CT for the diagnosis of pulmonary emphysema using teleradiology. Thirty patients were examined. CT images were transmitted by Digital Imaging and Communications in Medicine (DICOM) to an image viewer and displayed in 4-image and 1-image arrays for reading. Pulmonary emphysema was found in 7 of the 30 patients. On both displays, the same diagnosis was obtained in 5 cases. In the remaining 2 cases, the low attenuation areas (LAAs) of mild centrilobular emphysema could be recognized only on the 1-image display. The diagnosis of pulmonary emphysema can be made by CT examination using teleradiology even in cases with mild lesions. (author)

Noninvasive physiologic assessment of coronary stenoses using cardiac CT.

Science.gov (United States)

Xu, Lei; Sun, Zhonghua; Fan, Zhanming

2015-01-01

Coronary CT angiography (CCTA) has become an important noninvasive imaging modality in the diagnosis of coronary artery disease (CAD). CCTA enables accurate evaluation of coronary artery stenosis. However, CCTA provides limited information on the physiological significance of stenotic lesions. A noninvasive "one-stop-shop" diagnostic test that can provide both anatomical significance and functional significance of stenotic lesions would be beneficial in the diagnosis and management of CAD. Recently, with the introduction of novel techniques, such as myocardial CT perfusion, CT-derived fractional flow reserve (FFRCT), and transluminal attenuation gradient (TAG), CCTA has emerged as a noninvasive method for the assessment of both anatomy of coronary lesions and its physiological consequences during a single study. This review provides an overview of the current status of new CT techniques for the physiologic assessments of CAD.

Direct Reconstruction of CT-based Attenuation Correction Images for PET with Cluster-Based Penalties

Science.gov (United States)

Kim, Soo Mee; Alessio, Adam M.; De Man, Bruno; Asma, Evren; Kinahan, Paul E.

2015-01-01

Extremely low-dose CT acquisitions for the purpose of PET attenuation correction will have a high level of noise and biasing artifacts due to factors such as photon starvation. This work explores a priori knowledge appropriate for CT iterative image reconstruction for PET attenuation correction. We investigate the maximum a posteriori (MAP) framework with cluster-based, multinomial priors for the direct reconstruction of the PET attenuation map. The objective function for direct iterative attenuation map reconstruction was modeled as a Poisson log-likelihood with prior terms consisting of quadratic (Q) and mixture (M) distributions. The attenuation map is assumed to have values in 4 clusters: air+background, lung, soft tissue, and bone. Under this assumption, the MP was a mixture probability density function consisting of one exponential and three Gaussian distributions. The relative proportion of each cluster was jointly estimated during each voxel update of direct iterative coordinate decent (dICD) method. Noise-free data were generated from NCAT phantom and Poisson noise was added. Reconstruction with FBP (ramp filter) was performed on the noise-free (ground truth) and noisy data. For the noisy data, dICD reconstruction was performed with the combination of different prior strength parameters (β and γ) of Q- and M-penalties. The combined quadratic and mixture penalties reduces the RMSE by 18.7% compared to post-smoothed iterative reconstruction and only 0.7% compared to quadratic alone. For direct PET attenuation map reconstruction from ultra-low dose CT acquisitions, the combination of quadratic and mixture priors offers regularization of both variance and bias and is a potential method to derive attenuation maps with negligible patient dose. However, the small improvement in quantitative accuracy relative to the substantial increase in algorithm complexity does not currently justify the use of mixture-based PET attenuation priors for reconstruction of CT

The effect of metal artefact reduction on CT-based attenuation correction for PET imaging in the vicinity of metallic hip implants: a phantom study.

Science.gov (United States)

Harnish, Roy; Prevrhal, Sven; Alavi, Abass; Zaidi, Habib; Lang, Thomas F

2014-07-01

To determine if metal artefact reduction (MAR) combined with a priori knowledge of prosthesis material composition can be applied to obtain CT-based attenuation maps with sufficient accuracy for quantitative assessment of (18)F-fluorodeoxyglucose uptake in lesions near metallic prostheses. A custom hip prosthesis phantom with a lesion-sized cavity filled with 0.2 ml (18)F-FDG solution having an activity of 3.367 MBq adjacent to a prosthesis bore was imaged twice with a chrome-cobalt steel hip prosthesis and a plastic replica, respectively. Scanning was performed on a clinical hybrid PET/CT system equipped with an additional external (137)Cs transmission source. PET emission images were reconstructed from both phantom configurations with CT-based attenuation correction (CTAC) and with CT-based attenuation correction using MAR (MARCTAC). To compare results with the attenuation-correction method extant prior to the advent of PET/CT, we also carried out attenuation correction with (137)Cs transmission-based attenuation correction (TXAC). CTAC and MARCTAC images were scaled to attenuation coefficients at 511 keV using a trilinear function that mapped the highest CT values to the prosthesis alloy attenuation coefficient. Accuracy and spatial distribution of the lesion activity was compared between the three reconstruction schemes. Compared to the reference activity of 3.37 MBq, the estimated activity quantified from the PET image corrected by TXAC was 3.41 MBq. The activity estimated from PET images corrected by MARCTAC was similar in accuracy at 3.32 MBq. CTAC corrected PET images resulted in nearly 40 % overestimation of lesion activity at 4.70 MBq. Comparison of PET images obtained with the plastic and metal prostheses in place showed that CTAC resulted in a marked distortion of the (18)F-FDG distribution within the lesion, whereas application of MARCTAC and TXAC resulted in lesion distributions similar to those observed with the plastic replica. MAR combined

CT attenuation in normal aging and Alzheimer's disease

International Nuclear Information System (INIS)

Kim, W.S.; Pearlson, G.D.; Goldfinger, A.D.; Tune, L.E.; Heyler, G.

1986-01-01

113 screened normal volunteers aged 18-85 and 50 elderly demented individuals meeting NINCDS/ADRDA criteria for probable senile dementia of the Alzheimer type, (SDAT), received a non-contrast x-CT head scan on a single 512x512 matrix Siemens Somatom DR3 Scanner. Scanning parameters (KV,MA) were kept constant, and the authors used a specially designed head holder to ensure a uniform scanning angle. Standard 8mm thick cuts, at zero degrees to the supra-orbito-meatal line, were taken through the entire brain. A ''phantom'' consisting of plastics of several different attenuation values was scanned before each patient as a reference to correct for any numerical drift in the scanner. Both patients and controls were scanned during the same sessions to eliminate possible systematic bias, and a single CT technologist carried out all scanning. Numerical CT data were collected on magnetic tape for analysis on a specially designed image processing system. Software was used to read CT density data from the 512x512 matrix scanner output tapes and to transfer the resulting image in standardized format to hard disk on the processing system. This system consists of a PDP-11-34 computer, linked to a Gould DeAnza IP-5000 image processors, hard disk system and tape drive. Once transferred to disk, images were rated blindly to subject identity or diagnosis by another 2 separate raters using a computer-linked cursor, and digitizer tablet. These numerical attenuation data from various anatomically defined regions of interest, (ROI's), were then corrected for head size using a regression model

Effect of Attenuation Correction on Regional Quantification Between PET/MR and PET/CT

DEFF Research Database (Denmark)

Teuho, Jarmo; Johansson, Jarkko; Linden, Jani

2016-01-01

UNLABELLED: A spatial bias in brain PET/MR exists compared with PET/CT, because of MR-based attenuation correction. We performed an evaluation among 4 institutions, 3 PET/MR systems, and 4 PET/CT systems using an anthropomorphic brain phantom, hypothesizing that the spatial bias would be minimized....../MR systems, CTAC was applied as the reference method for attenuation correction. RESULTS: With CTAC, visual and quantitative differences between PET/MR and PET/CT systems were minimized. Intersystem variation between institutions was +3.42% to -3.29% in all VOIs for PET/CT and +2.15% to -4.50% in all VOIs...... for PET/MR. PET/MR systems differed by +2.34% to -2.21%, +2.04% to -2.08%, and -1.77% to -5.37% when compared with a PET/CT system at each institution, and these differences were not significant (P ≥ 0.05). CONCLUSION: Visual and quantitative differences between PET/MR and PET/CT systems can be minimized...

PET/CT with intravenous contrast can be used for PET attenuation correction in cancer patients

International Nuclear Information System (INIS)

Berthelsen, A.K.; Holm, S.; Loft, A.; Klausen, T.L.; Andersen, F.; Hoejgaard, L.

2005-01-01

If the CT scan of a combined PET/CT study is performed as a full diagnostic quality CT scan including intravenous (IV) contrast agent, the quality of the joint PET/CT procedure is improved and a separate diagnostic CT scan can be avoided. CT with IV contrast can be used for PET attenuation correction, but this may result in a bias in the attenuation factors. The clinical significance of this bias has not been established. Our aim was to perform a prospective clinical study where each patient had CT performed with and without IV contrast agent to establish whether PET/CT with IV contrast can be used for PET attenuation without reducing the clinical value of the PET scan. A uniform phantom study was used to document that the PET acquisition itself is not significantly influenced by the presence of IV contrast medium. Then, 19 patients referred to PET/CT with IV contrast underwent CT scans without, and then with contrast agent, followed by an 18 F-fluorodeoxyglucose whole-body PET scan. The CT examinations were performed with identical parameters on a GE Discovery LS scanner. The PET data were reconstructed with attenuation correction based on the two CT data sets. A global comparison of standard uptake value (SUV) was performed, and SUVs in tumour, in non-tumour tissue and in the subclavian vein were calculated. Clinical evaluation of the number and location of lesions on all PET/CT scans was performed twice, blinded and in a different random order, by two independent nuclear medicine specialists. In all patients, the measured global SUV of PET images based on CT with IV contrast agent was higher than the global activity using non-contrast correction. The overall increase in the mean SUV (for two different conversion tables tested) was 4.5±2.3% and 1.6±0.5%, respectively. In 11/19 patients, focal uptake was identified corresponding to malignant tumours. Eight out of 11 tumours showed an increased SUV max (2.9±3.1%) on the PET images reconstructed using IV contrast

Noninvasive Physiologic Assessment of Coronary Stenoses Using Cardiac CT

Directory of Open Access Journals (Sweden)

Lei Xu

2015-01-01

Full Text Available Coronary CT angiography (CCTA has become an important noninvasive imaging modality in the diagnosis of coronary artery disease (CAD. CCTA enables accurate evaluation of coronary artery stenosis. However, CCTA provides limited information on the physiological significance of stenotic lesions. A noninvasive “one-stop-shop” diagnostic test that can provide both anatomical significance and functional significance of stenotic lesions would be beneficial in the diagnosis and management of CAD. Recently, with the introduction of novel techniques, such as myocardial CT perfusion, CT-derived fractional flow reserve (FFRCT, and transluminal attenuation gradient (TAG, CCTA has emerged as a noninvasive method for the assessment of both anatomy of coronary lesions and its physiological consequences during a single study. This review provides an overview of the current status of new CT techniques for the physiologic assessments of CAD.

Design of respiration averaged CT for attenuation correction of the PET data from PET/CT

International Nuclear Information System (INIS)

Chi, Pai-Chun Melinda; Mawlawi, Osama; Nehmeh, Sadek A.; Erdi, Yusuf E.; Balter, Peter A.; Luo, Dershan; Mohan, Radhe; Pan Tinsu

2007-01-01

Our previous patient studies have shown that the use of respiration averaged computed tomography (ACT) for attenuation correction of the positron emission tomography (PET) data from PET/CT reduces the potential misalignment in the thorax region by matching the temporal resolution of the CT to that of the PET. In the present work, we investigated other approaches of acquiring ACT in order to reduce the CT dose and to improve the ease of clinical implementation. Four-dimensional CT (4DCT) data sets for ten patients (17 lung/esophageal tumors) were acquired in the thoracic region immediately after the routine PET/CT scan. For each patient, multiple sets of ACTs were generated based on both phase image averaging (phase approach) and fixed cine duration image averaging (cine approach). In the phase approach, the ACTs were calculated from CT images corresponding to the significant phases of the respiratory cycle: ACT 050phs from end-inspiration (0%) and end-expiration (50%), ACT 2070phs from mid-inspiration (20%) and mid-expiration (70%), ACT 4phs from 0%, 20%, 50% and 70%, and ACT 10phs from all ten phases, which was the original approach. In the cine approach, which does not require 4DCT, the ACTs were calculated based on the cine images from cine durations of 1 to 6 s at 1 s increments. PET emission data for each patient were attenuation corrected with each of the above mentioned ACTs and the tumor maximum standard uptake value (SUV max ), average SUV (SUV avg ), and tumor volume measurements were compared. Percent differences were calculated between PET data corrected with various ACTs and that corrected with ACT 10phs . In the phase approach, the ACT 10phs can be approximated by the ACT 4phs to within a mean percent difference of 2% in SUV and tumor volume measurements. In cine approach, ACT 10phs can be approximated to within a mean percent difference of 3% by ACTs computed from cine durations ≥3 s. Acquiring CT images only at the four significant phases for the

A study on CT attenuation and MR signal intensity of protein solution

International Nuclear Information System (INIS)

Kim, Joung Hae; Choi, Dae Seob; Kim, Soon; Lee, Hyeon Kyeong; Oh, Hyeon Hee; Kim, Seung Hyeon; Lee, Sung Woo; Chang, Kee Hyun; Chung, Jun Ho

2001-01-01

To correlate CT attenuation and MR signal intensity with concentration of protein solution. CT and MR examinations of a phantom containing bovine serum albumin solutions of various concentrations ranging from 0 to 55% were performed. CT Hounsfield units(HUs), MR signal intensities, and apparent diffusion coefficients (ADCs) of each albumin solution were measured, and CT HUs and MR signal intensities of the solutions were compared with those of cerebrospinal fluid (CSF), white matter, and cortical gray matter. CT HU increased gradually with increasing albumin concentration. On T1-weighted images(T1WI), signal intensity increased with increasing albumin concentrations of up to 35% but then decreased. On T2-weighted images(T2Wl), gradually decreasing signal intensity and increasing albumin concentration were observed Fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted images (DWls) showed that signal intensity peaked at a concentration of 10% and then gradually decreased. The ADC of the solution gradually decreased as concentration increased. Compared with those of normal brain structures, the CT HUs of solutions at concentrations of over 20% were higher than those of white and gray matter. At T1WI, the signal intensities of 10-45% solutions were similar to or higher than that of the gray matter. At T2Wl, the signal intensities of solutions above 25, 35, and 40% were lower than those of CSF, gray matter, and white matter, respectively. FLAIR images showed that the signal intensities of 5-35% solutions were higher than that of gray matter. The CT attenuation of albumin solution increased gradually with increasing concentration. MR signal intensities peaked at 35% concentration on T1WI and at 10% on FLAIR and DW images, respectively, and then gradually decreased. T2Wl and ADC map images showed gradually decreasing signal intensity and ADC as albumin concentration increased

Prediction of CT Substitutes from MR Images Based on Local Diffeomorphic Mapping for Brain PET Attenuation Correction.

Science.gov (United States)

Wu, Yao; Yang, Wei; Lu, Lijun; Lu, Zhentai; Zhong, Liming; Huang, Meiyan; Feng, Yanqiu; Feng, Qianjin; Chen, Wufan

2016-10-01

Attenuation correction is important for PET reconstruction. In PET/MR, MR intensities are not directly related to attenuation coefficients that are needed in PET imaging. The attenuation coefficient map can be derived from CT images. Therefore, prediction of CT substitutes from MR images is desired for attenuation correction in PET/MR. This study presents a patch-based method for CT prediction from MR images, generating attenuation maps for PET reconstruction. Because no global relation exists between MR and CT intensities, we propose local diffeomorphic mapping (LDM) for CT prediction. In LDM, we assume that MR and CT patches are located on 2 nonlinear manifolds, and the mapping from the MR manifold to the CT manifold approximates a diffeomorphism under a local constraint. Locality is important in LDM and is constrained by the following techniques. The first is local dictionary construction, wherein, for each patch in the testing MR image, a local search window is used to extract patches from training MR/CT pairs to construct MR and CT dictionaries. The k-nearest neighbors and an outlier detection strategy are then used to constrain the locality in MR and CT dictionaries. Second is local linear representation, wherein, local anchor embedding is used to solve MR dictionary coefficients when representing the MR testing sample. Under these local constraints, dictionary coefficients are linearly transferred from the MR manifold to the CT manifold and used to combine CT training samples to generate CT predictions. Our dataset contains 13 healthy subjects, each with T1- and T2-weighted MR and CT brain images. This method provides CT predictions with a mean absolute error of 110.1 Hounsfield units, Pearson linear correlation of 0.82, peak signal-to-noise ratio of 24.81 dB, and Dice in bone regions of 0.84 as compared with real CTs. CT substitute-based PET reconstruction has a regression slope of 1.0084 and R 2 of 0.9903 compared with real CT-based PET. In this method, no

Alveolar architecture of clear cell renal carcinomas (≤5.0 cm) show high attenuation on dynamic CT scanning

International Nuclear Information System (INIS)

Fujimoto, Hiroyuki; Wakao, Fumihiko; Moriyama, Noriyuki; Tobisu, Kenichi; Kakizoe, Tadao; Sakamoto, Michiie

1999-01-01

To establish the correlation between tumor appearance on CT and tumor histology in renal cell carcinomas. The density and attenuation patterns of 96 renal cell carcinomas, each ≤5 cm in greatest diameter, were studied by non-enhanced CT and early and late after bolus injection of contrast medium using dynamic CT. The density and attenuation patterns and pathological maps of each tumor were individually correlated. High attenuated areas were present in 72 of the 96 tumors on early enhanced dynamic CT scanning. All 72 high attenuated areas were of the clear cell renal cell carcinoma and had alveolar architecture. The remaining 24 tumors that did not demonstrate high attenuated foci on early enhanced scanning included three clear cell, nine granular cell, six papillary, five chromophobe and one collecting duct type. With respect to tumor architecture, all clear cell tumors of alveolar architecture demonstrated high attenuation on early enhanced scanning. Clear cell renal cell carcinomas of alveolar architecture show high attenuation on early enhanced dynamic CT scanning. A larger number of patients are indispensable to obtaining clear results. However, these findings seem to be an important clue to the diagnosis of renal cell carcinomas as having an alveolar structure. (author)

Comparison of iodinated contrast media for the assessment of atherosclerotic plaque attenuation values by CT coronary angiography: Observations in an ex vivo model

NARCIS (Netherlands)

L. la Grutta (Ludovico); M. Galia (Massimo); G. Gentile; G. Lo Re (G.); E. Grassedonio (Emanuele); F. Coppolino; E. Maffei (Erica); E. Maresi (E.); A. Lo Casto (A.); F. Cademartiri (Filippo); M. Midiri (Massimo)

2013-01-01

textabstractObjective: To compare the influence of different iodinated contrast media with several dilutions on plaque attenuation in an ex vivo coronary model studied by multislice CT coronary angiography. Methods: In six ex vivo left anterior descending coronary arteries immersed in oil, CT

The effect of metal artefact reduction on CT-based attenuation correction for PET imaging in the vicinity of metallic hip implants. A phantom study

International Nuclear Information System (INIS)

Harnish, R.; Lang, T.F.; Prevrhal, S.; Alavi, A.; Zaidi, H.

2014-01-01

To determine if metal artefact reduction (MAR) combined with a priori knowledge of prosthesis material composition can be applied to obtain CT-based attenuation maps with sufficient accuracy for quantitative assessment of 18 F-fluorodeoxyglucose uptake in lesions near metallic prostheses. A custom hip prosthesis phantom with a lesion-sized cavity filled with 0.2 ml 18 F-FDG solution having an activity of 3.367 MBq adjacent to a prosthesis bore was imaged twice with a chrome-cobalt steel hip prosthesis and a plastic replica, respectively. Scanning was performed on a clinical hybrid PET/CT system equipped with an additional external 137 Cs transmission source. PET emission images were reconstructed from both phantom configurations with CT-based attenuation correction (CTAC) and with CT-based attenuation correction using MAR (MARCTAC). To compare results with the attenuation-correction method extant prior to the advent of PET/CT, we also carried out attenuation correction with 137 Cs transmission-based attenuation correction (TXAC). CTAC and MARCTAC images were scaled to attenuation coefficients at 511 keV using a trilinear function that mapped the highest CT values to the prosthesis alloy attenuation coefficient. Accuracy and spatial distribution of the lesion activity was compared between the three reconstruction schemes. Compared to the reference activity of 3.37 MBq, the estimated activity quantified from the PET image corrected by TXAC was 3.41 MBq. The activity estimated from PET images corrected by MARCTAC was similar in accuracy at 3.32 MBq. CTAC corrected PET images resulted in nearly 40% overestimation of lesion activity at 4.70 MBq. Comparison of PET images obtained with the plastic and metal prostheses in place showed that CTAC resulted in a marked distortion of the 18 F-FDG distribution within the lesion, whereas application of MARCTAC and TXAC resulted in lesion distributions similar to those observed with the plastic replica. (author)

Hyper-attenuating brain lesions on CT after ischemic stroke and thrombectomy are associated with final brain infarction.

Science.gov (United States)

Cabral, F B; Castro-Afonso, L H; Nakiri, G S; Monsignore, L M; Fábio, Src; Dos Santos, A C; Pontes-Neto, O M; Abud, D G

2017-12-01

Purpose Hyper-attenuating lesions, or contrast staining, on a non-contrast brain computed tomography (NCCT) scan have been investigated as a predictor for hemorrhagic transformation after endovascular treatment of acute ischemic stroke (AIS). However, the association of hyper-attenuating lesions and final ischemic areas are poorly investigated in this setting. The aim of the present study was to assess correlations between hyper-attenuating lesions and final brain infarcted areas after thrombectomy for AIS. Methods Data from patients with AIS of the anterior circulation who underwent endovascular treatment were retrospectively assessed. Images of the brain NCCT scans were analyzed in the first hours and late after treatment. The hyper-attenuating areas were compared to the final ischemic areas using the Alberta Stroke Program Early CT Score (ASPECTS). Results Seventy-one of the 123 patients (65.13%) treated were included. The association between the hyper-attenuating region in the post-thrombectomy CT scan and final brain ischemic area were sensitivity (58.3% to 96.9%), specificity (42.9% to 95.6%), positive predictive values (71.4% to 97.7%), negative predictive values (53.8% to 79.5%), and accuracy values (68% to 91%). The highest sensitivity values were found for the lentiform (96.9%) and caudate nuclei (80.4%) and for the internal capsule (87.5%), and the lowest values were found for the M1 (58.3%) and M6 (66.7%) cortices. Conclusions Hyper-attenuating lesions on head NCCT scans performed after endovascular treatment of AIS may predict final brain infarcted areas. The prediction appears to be higher in the deep brain regions compared with the cortical regions.

Zero-Echo-Time and Dixon Deep Pseudo-CT (ZeDD CT): Direct Generation of Pseudo-CT Images for Pelvic PET/MRI Attenuation Correction Using Deep Convolutional Neural Networks with Multiparametric MRI.

Science.gov (United States)

Leynes, Andrew P; Yang, Jaewon; Wiesinger, Florian; Kaushik, Sandeep S; Shanbhag, Dattesh D; Seo, Youngho; Hope, Thomas A; Larson, Peder E Z

2018-05-01

Accurate quantification of uptake on PET images depends on accurate attenuation correction in reconstruction. Current MR-based attenuation correction methods for body PET use a fat and water map derived from a 2-echo Dixon MRI sequence in which bone is neglected. Ultrashort-echo-time or zero-echo-time (ZTE) pulse sequences can capture bone information. We propose the use of patient-specific multiparametric MRI consisting of Dixon MRI and proton-density-weighted ZTE MRI to directly synthesize pseudo-CT images with a deep learning model: we call this method ZTE and Dixon deep pseudo-CT (ZeDD CT). Methods: Twenty-six patients were scanned using an integrated 3-T time-of-flight PET/MRI system. Helical CT images of the patients were acquired separately. A deep convolutional neural network was trained to transform ZTE and Dixon MR images into pseudo-CT images. Ten patients were used for model training, and 16 patients were used for evaluation. Bone and soft-tissue lesions were identified, and the SUV max was measured. The root-mean-squared error (RMSE) was used to compare the MR-based attenuation correction with the ground-truth CT attenuation correction. Results: In total, 30 bone lesions and 60 soft-tissue lesions were evaluated. The RMSE in PET quantification was reduced by a factor of 4 for bone lesions (10.24% for Dixon PET and 2.68% for ZeDD PET) and by a factor of 1.5 for soft-tissue lesions (6.24% for Dixon PET and 4.07% for ZeDD PET). Conclusion: ZeDD CT produces natural-looking and quantitatively accurate pseudo-CT images and reduces error in pelvic PET/MRI attenuation correction compared with standard methods. © 2018 by the Society of Nuclear Medicine and Molecular Imaging.

Improved attenuation correction for respiratory gated PET/CT with extended-duration cine CT: a simulation study

Science.gov (United States)

Zhang, Ruoqiao; Alessio, Adam M.; Pierce, Larry A.; Byrd, Darrin W.; Lee, Tzu-Cheng; De Man, Bruno; Kinahan, Paul E.

2017-03-01

Due to the wide variability of intra-patient respiratory motion patterns, traditional short-duration cine CT used in respiratory gated PET/CT may be insufficient to match the PET scan data, resulting in suboptimal attenuation correction that eventually compromises the PET quantitative accuracy. Thus, extending the duration of cine CT can be beneficial to address this data mismatch issue. In this work, we propose to use a long-duration cine CT for respiratory gated PET/CT, whose cine acquisition time is ten times longer than a traditional short-duration cine CT. We compare the proposed long-duration cine CT with the traditional short-duration cine CT through numerous phantom simulations with 11 respiratory traces measured during patient PET/CT scans. Experimental results show that, the long-duration cine CT reduces the motion mismatch between PET and CT by 41% and improves the overall reconstruction accuracy by 42% on average, as compared to the traditional short-duration cine CT. The long-duration cine CT also reduces artifacts in PET images caused by misalignment and mismatch between adjacent slices in phase-gated CT images. The improvement in motion matching between PET and CT by extending the cine duration depends on the patient, with potentially greater benefits for patients with irregular breathing patterns or larger diaphragm movements.

Pitfalls in urinary stone identification using CT attenuation values: Are we getting the same information on different scanner models?

Energy Technology Data Exchange (ETDEWEB)

Grosjean, Romain, E-mail: r.grosjean@chu-nancy.fr [IADI Laboratory, INSERM-U947, Nancy-University, Allée du Morvan, 54500 Vandoeuvre-les-Nancy (France); Daudon, Michel, E-mail: michel.daudon@tnn.aphp.fr [IADI Laboratory, INSERM-U947, Nancy-University, Allée du Morvan, 54500 Vandoeuvre-les-Nancy (France); Chammas, Mario F., E-mail: mariochammas@usp.br [University of Sao Paulo – Division of Urology, Av. Dr. Enéas de Carvalho Aguiar, 255, 7" o Andar – s. 7123, São Paulo (Brazil); Claudon, Michel, E-mail: m.claudon@chu-nancy.fr [IADI Laboratory, INSERM-U947, Nancy-University, Allée du Morvan, 54500 Vandoeuvre-les-Nancy (France); Eschwege, Pascal, E-mail: peschwege@yahoo.com [Department of Urology, Brabois Hospital, University Hospital of Nancy, Allée du Morvan, 54511 Vandoeuvre-les-Nancy (France); Felblinger, Jacques, E-mail: j.felblinger@chu-nancy.fr [IADI Laboratory, INSERM-U947, Nancy-University, Allée du Morvan, 54500 Vandoeuvre-les-Nancy (France); Hubert, Jacques, E-mail: j.hubert@chu-nancy.fr [Department of Urology, Brabois Hospital, University Hospital of Nancy, Allée du Morvan, 54511 Vandoeuvre-les-Nancy (France)

2013-08-15

Introduction: Evaluate the capability of different Computed Tomography scanners to determine urinary stone compositions based on CT attenuation values and to evaluate potential differences between each model. Methods: 241 human urinary stones were obtained and their biochemical composition determined. Four different CT scanners (Siemens, Philips, GEMS and Toshiba) were evaluated. Mean CT-attenuation values and the standard deviation were recorded separately and compared with a t-paired test. Results: For all tested CT scanners, when the classification of the various types of stones was arranged according to the mean CT-attenuation values and to the confidence interval, large overlappings between stone types were highlighted. The t-paired test showed that most stone types could not be identified. Some types of stones presented mean CT attenuation values significantly different from one CT scanner to another. At 80 kV, the mean CT attenuation values obtained with the Toshiba Aquilion were significantly different from those obtained with the Siemens Sensation. On the other hand, mean values obtained with the Philips Brilliance were all significantly equal to those obtained with the Siemens Sensation and with the Toshiba Aquilion. At 120 kV mean CT attenuation values of uric acid, cystine and struvite stones obtained with the Philips model are significantly different from those obtained with the Siemens and the Toshiba but equal to those obtained with the GE 64. Conclusions: According to our study, there is a great variability when different brands and models of scanners are compared directly. Furthermore, the CT scan analysis and HU evaluation appears to gather insufficient information in order to characterize and identify the composition of renal stones.

Pitfalls in urinary stone identification using CT attenuation values: Are we getting the same information on different scanner models?

International Nuclear Information System (INIS)

Grosjean, Romain; Daudon, Michel; o Andar – s. 7123, São Paulo (Brazil))" data-affiliation=" (University of Sao Paulo – Division of Urology, Av. Dr. Enéas de Carvalho Aguiar, 255, 7o Andar – s. 7123, São Paulo (Brazil))" >Chammas, Mario F.; Claudon, Michel; Eschwege, Pascal; Felblinger, Jacques; Hubert, Jacques

2013-01-01

Introduction: Evaluate the capability of different Computed Tomography scanners to determine urinary stone compositions based on CT attenuation values and to evaluate potential differences between each model. Methods: 241 human urinary stones were obtained and their biochemical composition determined. Four different CT scanners (Siemens, Philips, GEMS and Toshiba) were evaluated. Mean CT-attenuation values and the standard deviation were recorded separately and compared with a t-paired test. Results: For all tested CT scanners, when the classification of the various types of stones was arranged according to the mean CT-attenuation values and to the confidence interval, large overlappings between stone types were highlighted. The t-paired test showed that most stone types could not be identified. Some types of stones presented mean CT attenuation values significantly different from one CT scanner to another. At 80 kV, the mean CT attenuation values obtained with the Toshiba Aquilion were significantly different from those obtained with the Siemens Sensation. On the other hand, mean values obtained with the Philips Brilliance were all significantly equal to those obtained with the Siemens Sensation and with the Toshiba Aquilion. At 120 kV mean CT attenuation values of uric acid, cystine and struvite stones obtained with the Philips model are significantly different from those obtained with the Siemens and the Toshiba but equal to those obtained with the GE 64. Conclusions: According to our study, there is a great variability when different brands and models of scanners are compared directly. Furthermore, the CT scan analysis and HU evaluation appears to gather insufficient information in order to characterize and identify the composition of renal stones

Dual-energy CT in the assessment of mediastinal lymph nodes: Comparative study of virtual non-contrast and true non-contrast images

International Nuclear Information System (INIS)

Yoo, Seon Young; Kim, Yoo Kyung; Cho, Hyun Hae; Choi, Mi Joo; Shim, Sung Shine; Lee, Jeong Kyong; Baek, Seung Yon

2013-01-01

To evaluate the reliability of virtual non-contrast (VNC) images reconstructed from contrast-enhanced, dual-energy scans compared with true non-contrast (TNC) images in the assessment of high CT attenuation or calcification of mediastinal lymph nodes. A total of 112 mediastinal nodes from 45 patients who underwent non-contrast and dual-energy contrast-enhanced scans were analyzed. Node attenuation in TNC and VNC images was compared both objectively, using computed tomography (CT) attenuation, and subjectively, via visual scoring (0, attenuation ≤ the aorta; 1, > the aorta; 2, calcification). The relationship among attenuation difference between TNC and VNC images, CT attenuation in TNC images, and net contrast enhancement (NCE) was analyzed. CT attenuation in TNC and VNC images showed moderate agreement (intraclass correlation coefficient, 0.612). The mean absolute difference was 7.8 ± 7.6 Hounsfield unit (HU) (range, 0-36 HU), and the absolute difference was equal to or less than 10 HU in 65.2% of cases (73/112). Visual scores in TNC and VNC images showed fair agreement (κ value, 0.335). Five of 16 nodes (31.3%) which showed score 1 (n = 15) or 2 (n = 1) in TNC images demonstrated score 1 in VNC images. The TNC-VNC attenuation difference showed a moderate positive correlation with CT attenuation in TNC images (partial correlation coefficient [PCC] adjusted by NCE: 0.455) and a weak negative correlation with NCE (PCC adjusted by CT attenuation in TNC: -0.245). VNC images may be useful in the evaluation of mediastinal lymph nodes by providing additional information of high CT attenuation of nodes, although it is underestimated compared with TNC images.

Dual-energy CT in the assessment of mediastinal lymph nodes: Comparative study of virtual non-contrast and true non-contrast images

Energy Technology Data Exchange (ETDEWEB)

Yoo, Seon Young; Kim, Yoo Kyung; Cho, Hyun Hae; Choi, Mi Joo; Shim, Sung Shine; Lee, Jeong Kyong; Baek, Seung Yon [School of Medicine, Ewha Womans University, Seou (Korea, Republic of)

2013-06-15

To evaluate the reliability of virtual non-contrast (VNC) images reconstructed from contrast-enhanced, dual-energy scans compared with true non-contrast (TNC) images in the assessment of high CT attenuation or calcification of mediastinal lymph nodes. A total of 112 mediastinal nodes from 45 patients who underwent non-contrast and dual-energy contrast-enhanced scans were analyzed. Node attenuation in TNC and VNC images was compared both objectively, using computed tomography (CT) attenuation, and subjectively, via visual scoring (0, attenuation ≤ the aorta; 1, > the aorta; 2, calcification). The relationship among attenuation difference between TNC and VNC images, CT attenuation in TNC images, and net contrast enhancement (NCE) was analyzed. CT attenuation in TNC and VNC images showed moderate agreement (intraclass correlation coefficient, 0.612). The mean absolute difference was 7.8 ± 7.6 Hounsfield unit (HU) (range, 0-36 HU), and the absolute difference was equal to or less than 10 HU in 65.2% of cases (73/112). Visual scores in TNC and VNC images showed fair agreement (κ value, 0.335). Five of 16 nodes (31.3%) which showed score 1 (n = 15) or 2 (n = 1) in TNC images demonstrated score 1 in VNC images. The TNC-VNC attenuation difference showed a moderate positive correlation with CT attenuation in TNC images (partial correlation coefficient [PCC] adjusted by NCE: 0.455) and a weak negative correlation with NCE (PCC adjusted by CT attenuation in TNC: -0.245). VNC images may be useful in the evaluation of mediastinal lymph nodes by providing additional information of high CT attenuation of nodes, although it is underestimated compared with TNC images.

Dual-energy CT in the assessment of mediastinal lymph nodes: comparative study of virtual non-contrast and true non-contrast images.

Science.gov (United States)

Yoo, Seon Young; Kim, Yookyung; Cho, Hyun Hae; Choi, Mi Joo; Shim, Sung Shine; Lee, Jeong Kyong; Baek, Seung Yon

2013-01-01

To evaluate the reliability of virtual non-contrast (VNC) images reconstructed from contrast-enhanced, dual-energy scans compared with true non-contrast (TNC) images in the assessment of high CT attenuation or calcification of mediastinal lymph nodes. A total of 112 mediastinal nodes from 45 patients who underwent non-contrast and dual-energy contrast-enhanced scans were analyzed. Node attenuation in TNC and VNC images was compared both objectively, using computed tomography (CT) attenuation, and subjectively, via visual scoring (0, attenuation ≤ the aorta; 1, > the aorta; 2, calcification). The relationship among attenuation difference between TNC and VNC images, CT attenuation in TNC images, and net contrast enhancement (NCE) was analyzed. CT attenuation in TNC and VNC images showed moderate agreement (intraclass correlation coefficient, 0.612). The mean absolute difference was 7.8 ± 7.6 Hounsfield unit (HU) (range, 0-36 HU), and the absolute difference was equal to or less than 10 HU in 65.2% of cases (73/112). Visual scores in TNC and VNC images showed fair agreement (κ value, 0.335). Five of 16 nodes (31.3%) which showed score 1 (n = 15) or 2 (n = 1) in TNC images demonstrated score 1 in VNC images. The TNC-VNC attenuation difference showed a moderate positive correlation with CT attenuation in TNC images (partial correlation coefficient [PCC] adjusted by NCE: 0.455) and a weak negative correlation with NCE (PCC adjusted by CT attenuation in TNC: -0.245). VNC images may be useful in the evaluation of mediastinal lymph nodes by providing additional information of high CT attenuation of nodes, although it is underestimated compared with TNC images.

CT assessment of progression in pulmonary emphysema

Energy Technology Data Exchange (ETDEWEB)

Satoh, Katashi; Mitani, Masahiro [Kagawa Medical Univ., Miki (Japan); Murota, Makiko (and others)

2002-01-01

The purpose of this study was to assess the progression of pulmonary emphysema (PE) using CT. We reviewed the records of 25 cases (all male smokers and age range of 36-85 years) in whom progression of PE was recognized using CT scanning. PE was diagnosed by the presence of low attenuation areas on CT scan. PE was divided into 2 subtypes: centrilobular emphysema (CLE) and paraseptal emphysema (PSE). There were 8 younger cases less than 50s. With respect to smoking habit, 6 cases had 1 pack per day at maximum whereas the remaining 19 cases had more over than 1.5 packs per day. Interval periods of observation were from 8 months minimum to 10 years maximum. PE, of both CLE and PSE subtype, was recognized even in younger cases less than 40 years of age, and progressed with cigarette consumption even a minimum during 8 months periods of observation. (author)

The linear attenuation coefficients as features of multiple energy CT image classification

International Nuclear Information System (INIS)

Homem, M.R.P.; Mascarenhas, N.D.A.; Cruvinel, P.E.

2000-01-01

We present in this paper an analysis of the linear attenuation coefficients as useful features of single and multiple energy CT images with the use of statistical pattern classification tools. We analyzed four CT images through two pointwise classifiers (the first classifier is based on the maximum-likelihood criterion and the second classifier is based on the k-means clustering algorithm) and one contextual Bayesian classifier (ICM algorithm - Iterated Conditional Modes) using an a priori Potts-Strauss model. A feature extraction procedure using the Jeffries-Matusita (J-M) distance and the Karhunen-Loeve transformation was also performed. Both the classification and the feature selection procedures were found to be in agreement with the predicted discrimination given by the separation of the linear attenuation coefficient curves for different materials

A knowledge-based method for reducing attenuation artefacts caused by cardiac appliances in myocardial PET/CT

International Nuclear Information System (INIS)

Hamill, James J; Brunken, Richard C; Bybel, Bohdan; DiFilippo, Frank P; Faul, David D

2006-01-01

Attenuation artefacts due to implanted cardiac defibrillator leads have previously been shown to adversely impact cardiac PET/CT imaging. In this study, the severity of the problem is characterized, and an image-based method is described which reduces the resulting artefact in PET. Automatic implantable cardioverter defibrillator (AICD) leads cause a moving-metal artefact in the CT sections from which the PET attenuation correction factors (ACFs) are derived. Fluoroscopic cine images were measured to demonstrate that the defibrillator's highly attenuating distal shocking coil moves rhythmically across distances on the order of 1 cm. Rhythmic motion of this magnitude was created in a phantom with a moving defibrillator lead. A CT study of the phantom showed that the artefact contained regions of incorrect, very high CT values and adjacent regions of incorrect, very low CT values. The study also showed that motion made the artefact more severe. A knowledge-based metal artefact reduction method (MAR) is described that reduces the magnitude of the error in the CT images, without use of the corrupted sinograms. The method modifies the corrupted image through a sequence of artefact detection procedures, morphological operations, adjustments of CT values and three-dimensional filtering. The method treats bone the same as metal. The artefact reduction method is shown to run in a few seconds, and is validated by applying it to a series of phantom studies in which reconstructed PET tracer distribution values are wrong by as much as 60% in regions near the CT artefact when MAR is not applied, but the errors are reduced to about 10% of expected values when MAR is applied. MAR changes PET image values by a few per cent in regions not close to the artefact. The changes can be larger in the vicinity of bone. In patient studies, the PET reconstruction without MAR sometimes results in anomalously high values in the infero-septal wall. Clinical performance of MAR is assessed by two

Influence of density and mean atomic number on CT attenuation corrected PET: Phantom studies

International Nuclear Information System (INIS)

Maintas, D.; Houzard, C.; Galy, G.; Maintas, C.; Itti, R.; Cachin, F.; Mognetti, Th.; Slosman

2007-01-01

Aim: the aim of this work is to study the influence of medium density on the CT or external source attenuation corrected images, by simulation on a phantom, with various positron emission tomographs. Material and method: a series of experiments on a cylindrical phantom filled with water marked with [18 F]-FDG, containing six vials filled per pair with mediums of different densities or solutions of KI, CaCl 2 and saccharose with various densities, was carried out under comparable conditions on three different tomographs. In only one of the vials of each pair, an identical radioactivity of [18 F]-FDG was added, three to five fold the surrounding activity. The reconstructions and attenuation corrections suggested by the manufacturers, were carried out under the usual conditions of each site. The activity of each structure was estimated by the methods of profiles and regions of interest, on the non attenuation corrected images (N.A.C.), the images corrected by CT (C.T.A.C.), and/or external source (G.P.A.C.). Results: with all three tomographs, the activities estimated on the N.A.C. images present an inverse correlation to the medium density (important absorption by dense material). On C.T.A.C. images, we observed with only two of the three tomographs, an overestimation of the activity in the 'radioactive' vials, depending on the medium mean Z number and density (over correction), and a artifactual 'activity' in the denser 'cold' vial (incorrect attenuation correction. The dense saccharose solutions, with non elevated Z number, do not affect the CT attenuation correction. (authors)

Regional nodal staging with 18F-FDG PET–CT in non-small cell lung cancer: Additional diagnostic value of CT attenuation and dual-time-point imaging

International Nuclear Information System (INIS)

Li, Meng; Wu, Ning; Liu, Ying; Zheng, Rong; Liang, Ying; Zhang, Wenjie; Zhao, Ping

2012-01-01

Background: [Fluorine-18]-fluorodeoxyglucose positron emission tomography/computed tomography ( 18 F-FDG PET–CT) is widely performed in the regional nodal staging of non-small cell lung cancer (NSCLC). However, the uptake of 18 F-FDG by tubercular granulomatous tissues may lead to false-positive diagnosis. This is of special concern in China, where tubercular granulomatous disease is epidemic. Herein, we evaluated the efficacy of an additional CT attenuation and a dual-time-point scan in determining the status of lymph nodes. Methods: Eighty NSCLC patients underwent curative surgical resection after 18 F-FDG PET–CT and separate breath-hold CT examinations. The initial images were analyzed by two methods. In method 1, nodal status was determined by 18 F-FDG uptake only. In Method 2, nodal status was determined by 18 F-FDG uptake associated with CT attenuation. For dual-time-point imaging, the retention index (RI) of benign and malignant nodal groups with positive uptake in the initial scan was examined. Results: A total of 265 nodal groups were documented. On a per-nodal-group basis, the diagnostic sensitivity, specificity, and accuracy of Method 1 were 66.7%, 89.7%, and 85.3%, respectively, whereas those of Method 2 were 64.7%, 96.7%, and 90.6%, respectively. The improvement in diagnostic specificity and accuracy associated with the addition of CT attenuation in Method 2 as compared to Method 1 was statistically significant (p 0.05). Conclusion: 18 F-FDG PET–CT has high diagnostic value for preoperative lymph-node (N) staging of NSCLC patients. We show that 18 F-FDG uptake combined with CT attenuation improves the diagnostic specificity and accuracy of nodal diagnosis in NSCLC. For the lymph nodes with positive uptake in the initial scan, dual-time-point imaging has limited effect in differentiation.

Standardised uptake values from PET/CT images: comparison with conventional attenuation-corrected PET

International Nuclear Information System (INIS)

Souvatzoglou, M.; Ziegler, S.I.; Martinez, M.J.; Dzewas, G.; Schwaiger, M.; Bengel, F.; Busch, R.

2007-01-01

In PET/CT, CT-derived attenuation factors may influence standardised uptake values (SUVs) in tumour lesions and organs when compared with stand-alone PET. Therefore, we compared PET/CT-derived SUVs intra-individually in various organs and tumour lesions with stand-alone PET-derived SUVs. Thirty-five patients with known or suspected cancer were prospectively included. Sixteen patients underwent FDG PET using an ECAT HR+scanner, and subsequently a second scan using a Biograph Sensation 16PET/CT scanner. Nineteen patients were scanned in the reverse order. All images were reconstructed with an iterative algorithm (OSEM). Suspected lesions were grouped as paradiaphragmatic versus distant from the diaphragm. Mean and maximum SUVs were also calculated for brain, lung, liver, spleen and vertebral bone. The attenuation coefficients (μ values) used for correction of emission data (bone, soft tissue, lung) in the two data sets were determined. A body phantom containing six hot spheres and one cold cylinder was measured using the same protocol as in patients. Forty-six lesions were identified. There was a significant correlation of maximum and mean SUVs derived from PET and PET/CT for 14 paradiaphragmatic lesions (r=0.97 respectively; p<0.001 respectively) and for 32 lesions located distant from the diaphragm (r=0.87 and r=0.89 respectively; p<0.001 respectively). No significant differences were observed in the SUVs calculated with PET and PET/CT in the lesions or in the organs. In the phantom, radioactivity concentration in spheres calculated from PET and from PET/CT correlated significantly (r=0.99; p<0.001). SUVs of cancer lesions and normal organs were comparable between PET and PET/CT, supporting the usefulness of PET/CT-derived SUVs for quantification of tumour metabolism. (orig.)

Respiration-averaged CT for attenuation correction in non-small-cell lung cancer

International Nuclear Information System (INIS)

Cheng, Nai-Ming; Ho, Kung-Chu; Yen, Tzu-Chen; Yu, Chih-Teng; Wu, Yi-Cheng; Liu, Yuan-Chang; Wang, Chih-Wei

2009-01-01

Breathing causes artefacts on PET/CT images. Cine CT has been used to reduce respiratory artefacts by acquiring multiple images during a single breathing cycle. The aim of this prospective study in non-small-cell lung cancer (NSCLC) patients was twofold. Firstly, we sought to compare the motion artefacts in PET/CT images attenuation-corrected with helical CT (HCT) and with averaged CT (ACT), which provides an average of cine CT images. Secondly, we wanted to evaluate the differences in maximum standardized uptake values (SUV max ) between HCT and ACT. Enrolled in the study were 80 patients with NSCLC. PET images attenuation-corrected with HCT (PET/HCT) and with ACT (PET/ACT) were obtained in all patients. Misregistration was evaluated by measurement of the curved photopenic area in the lower thorax of the PET images for all patients and direct measurement of misregistration for selected lesions. SUV max was measured separately at the primary tumours, regional lymph nodes, and background. A total of 80 patients with NSCLC were included. Significantly lower misregistrations were observed in PET/ACT images than in PET/HCT images (below-thoracic misregistration 0.25±0.58 cm vs. 1.17±1.17 cm, p max were noted in PET/ACT images than in PET/HCT images in the primary tumour (p max in PET/ACT images was higher by 0.35 for the main tumours and 0.34 for lymph nodes. Due to its significantly reduced misregistration, PET/ACT provided more reliable SUV max and may be useful in treatment planning and monitoring the therapeutic response in patients with NSCLC. (orig.)

A knowledge-based method for reducing attenuation artefacts caused by cardiac appliances in myocardial PET/CT

Energy Technology Data Exchange (ETDEWEB)

Hamill, James J [Siemens Medical Solutions, Molecular Imaging, 810 Innovation Dr., Knoxville, TN (United States); Brunken, Richard C [Department of Molecular and Functional Imaging, Cleveland Clinic Foundation, 9500 Euclid Ave., Cleveland, OH (United States); Bybel, Bohdan [Department of Molecular and Functional Imaging, Cleveland Clinic Foundation, 9500 Euclid Ave., Cleveland, OH (United States); DiFilippo, Frank P [Department of Molecular and Functional Imaging, Cleveland Clinic Foundation, 9500 Euclid Ave., Cleveland, OH (United States); Faul, David D [Siemens Medical Solutions, Molecular Imaging, 810 Innovation Dr., Knoxville, TN (United States)

2006-06-07

Attenuation artefacts due to implanted cardiac defibrillator leads have previously been shown to adversely impact cardiac PET/CT imaging. In this study, the severity of the problem is characterized, and an image-based method is described which reduces the resulting artefact in PET. Automatic implantable cardioverter defibrillator (AICD) leads cause a moving-metal artefact in the CT sections from which the PET attenuation correction factors (ACFs) are derived. Fluoroscopic cine images were measured to demonstrate that the defibrillator's highly attenuating distal shocking coil moves rhythmically across distances on the order of 1 cm. Rhythmic motion of this magnitude was created in a phantom with a moving defibrillator lead. A CT study of the phantom showed that the artefact contained regions of incorrect, very high CT values and adjacent regions of incorrect, very low CT values. The study also showed that motion made the artefact more severe. A knowledge-based metal artefact reduction method (MAR) is described that reduces the magnitude of the error in the CT images, without use of the corrupted sinograms. The method modifies the corrupted image through a sequence of artefact detection procedures, morphological operations, adjustments of CT values and three-dimensional filtering. The method treats bone the same as metal. The artefact reduction method is shown to run in a few seconds, and is validated by applying it to a series of phantom studies in which reconstructed PET tracer distribution values are wrong by as much as 60% in regions near the CT artefact when MAR is not applied, but the errors are reduced to about 10% of expected values when MAR is applied. MAR changes PET image values by a few per cent in regions not close to the artefact. The changes can be larger in the vicinity of bone. In patient studies, the PET reconstruction without MAR sometimes results in anomalously high values in the infero-septal wall. Clinical performance of MAR is assessed by

Evaluation of delayed contrast-enhanced CT scan in diagnosing hilar cholangiocarcinoma

International Nuclear Information System (INIS)

Li Jianding; Liang Chenyang; Zhang Hua; Zhang Yuezhen; Li Rui

2001-01-01

Objective: To assess the diagnostic value of delayed CT contrast enhancement patterns in hilar cholangiocarcinoma based on two-phased dynamic incremental CT scanning. Methods: Fifty-two patients with suspected hilar tumor and bile duct obstruction underwent spiral CT scan. The scan time for one revolution of the X-ray tube was 1 second. To elucidate the delay time for optimal imaging, all proved cholangiocarcinoma with delayed (6, 8, 10, 15, 20, 30 minutes) post-equilibrium-phase contrast-enhanced CT scans were acquired with unenhanced, dynamic contrast-enhanced, and delayed images. Degree of delayed enhancement was compared with that of surrounding liver parenchyma. Results: (1) 8-15 minutes after IV injection of contrast material was the delay time for optimal imaging. (2) Of 29 cholangiocarcinomas, the early CT showed hypo-attenuating (lower than that of liver parenchyma) in 23 tumors, iso-attenuating (equal to that of the liver) in 4 tumors, and hyper-attenuating (higher than that of liver) in 2 tumors. The delayed CT scan showed iso-attenuating in 8 tumors, hyper-attenuating in 21 tumors, and no hypo-attenuating. Most of delay imaging of hilar cholangiocarcinoma may appear hyper-attenuating (U = -4.3073, P 2 = 9.09, P < 0.01). Conclusion: When assessing hilar tumor, delayed CT contrast enhancement patterns based on two-phase dynamic incremental CT scans is useful in the detection and characterization of hilar cholangiocarcinoma

Description and assessment of a registration-based approach to include bones for attenuation correction of whole-body PET/MRI.

Science.gov (United States)

Marshall, Harry R; Patrick, John; Laidley, David; Prato, Frank S; Butler, John; Théberge, Jean; Thompson, R Terry; Stodilka, Robert Z

2013-08-01

Attenuation correction for whole-body PET/MRI is challenging. Most commercial systems compute the attenuation map from MRI using a four-tissue segmentation approach. Bones, the most electron-dense tissue, are neglected because they are difficult to segment. In this work, the authors build on this segmentation approach by adding bones using a registration technique and assessing its performance on human PET images. Twelve oncology patients were imaged with FDG PET/CT and MRI using a Turbo-FLASH pulse sequence. A database of 121 attenuation correction quality CT scans was also collected. Each patient MRI was compared to the CT database via weighted heuristic measures to find the "most similar" CT in terms of body geometry. The similar CT was aligned to the MRI with a deformable registration method. Two MRI-based attenuation maps were computed. One was a standard four-tissue segmentation (air, lung, fat, and lean tissue) using basic image processing techniques. The other was identical, except the bones from the aligned CT were added. The PET data were reconstructed with the patient's CT-based attenuation map (the silver standard) and both MRI-based attenuation maps. The relative errors of the MRI-based attenuation corrections were computed in 14 standardized volumes of interest, in lesions, and over whole tissues. The squared Pearson correlation coefficient was also calculated over whole tissues. Statistical testing was done with ANOVAs and paired t-tests. The MRI-based attenuation correction ignoring bone had relative errors ranging from -37% to -8% in volumes of interest containing bone. By including bone, the magnitude of the relative error was reduced in all cases (pbone was improved from a mean of -7.5% to 2% (pbone reduced the magnitude of relative error in three cases (pbone slightly increased relative error in lung from 7.7% to 8.0% (p=0.002), in fat from 8.5% to 9.2% (pbone from -14.6% to 1.3% (pbone was included or not. The approach to include bones in MRI

Comparing 511 keV Attenuation Maps Obtained from Different Energy Mapping Methods for CT Based Attenuation Correction of PET Data

Directory of Open Access Journals (Sweden)

Maryam Shirmohammad

2008-06-01

Full Text Available Introduction:  The  advent  of  dual-modality  PET/CT  scanners  has  revolutionized  clinical  oncology  by  improving lesion localization and facilitating treatment planning for radiotherapy. In addition, the use of  CT images for CT-based attenuation correction (CTAC decreases the overall scanning time and creates  a noise-free  attenuation  map  (6map.  CTAC  methods  include  scaling,  segmentation,  hybrid  scaling/segmentation, bilinear and dual energy methods. All CTAC methods require the transformation  of CT Hounsfield units (HU to linear attenuation coefficients (LAC at 511 keV. The aim of this study is  to compare the results of implementing different methods of energy mapping in PET/CT scanners.   Materials and Methods: This study was conducted in 2 phases, the first phase in a phantom and the  second  one  on  patient  data.  To  perform  the  first  phase,  a  cylindrical  phantom  with  different  concentrations of K2HPO4 inserts was CT scanned and energy mapping methods were implemented on  it. For performing the second phase, different energy  mapping  methods  were implemented on several  clinical studies and compared to the transmission (TX image derived using Ga-68 radionuclide source  acquired on the GE Discovery LS PET/CT scanner.   Results: An ROI analysis was performed on different positions of the resultant 6maps and the average  6value of each ROI was compared to the reference value. The results of the 6maps obtained for 511 keV  compared to the theoretical  values showed that in the phantom for low  concentrations  of K 2 HPO 4 all  these  methods  produce  511  keV  attenuation  maps  with  small  relative  difference  compared  to  gold  standard. The relative difference for scaling, segmentation, hybrid, bilinear and dual energy methods was  4.92,  3.21,  4.43,  2.24  and  2.29%,  respectively.  Although  for  high  concentration �

Quantitative assessment of smoking-induced emphysema progression in longitudinal CT screening for lung cancer

Science.gov (United States)

Suzuki, H.; Mizuguchi, R.; Matsuhiro, M.; Kawata, Y.; Niki, N.; Nakano, Y.; Ohmatsu, H.; Kusumoto, M.; Tsuchida, T.; Eguchi, K.; Kaneko, M.; Moriyama, N.

2015-03-01

Computed tomography has been used for assessing structural abnormalities associated with emphysema. It is important to develop a robust CT based imaging biomarker that would allow quantification of emphysema progression in early stage. This paper presents effect of smoking on emphysema progression using annual changes of low attenuation volume (LAV) by each lung lobe acquired from low-dose CT images in longitudinal screening for lung cancer. The percentage of LAV (LAV%) was measured after applying CT value threshold method and small noise reduction. Progression of emphysema was assessed by statistical analysis of the annual changes represented by linear regression of LAV%. This method was applied to 215 participants in lung cancer CT screening for five years (18 nonsmokers, 85 past smokers, and 112 current smokers). The results showed that LAV% is useful to classify current smokers with rapid progression of emphysema (0.2%/year, pemphysema in CT screening for lung cancer.

MR-based attenuation correction for PET/MRI neurological studies with continuous-valued attenuation coefficients for bone through a conversion from R2* to CT-Hounsfield units.

Science.gov (United States)

Juttukonda, Meher R; Mersereau, Bryant G; Chen, Yasheng; Su, Yi; Rubin, Brian G; Benzinger, Tammie L S; Lalush, David S; An, Hongyu

2015-05-15

MR-based correction for photon attenuation in PET/MRI remains challenging, particularly for neurological applications requiring quantitation of data. Existing methods are either not sufficiently accurate or are limited by the computation time required. The goal of this study was to develop an MR-based attenuation correction method that accurately separates bone tissue from air and provides continuous-valued attenuation coefficients for bone. PET/MRI and CT datasets were obtained from 98 subjects (mean age [±SD]: 66yrs [±9.8], 57 females) using an IRB-approved protocol and with informed consent. Subjects were injected with 352±29MBq of (18)F-Florbetapir tracer, and PET acquisitions were begun either immediately or 50min after injection. CT images of the head were acquired separately using a PET/CT system. Dual echo ultrashort echo-time (UTE) images and two-point Dixon images were acquired. Regions of air were segmented via a threshold of the voxel-wise multiplicative inverse of the UTE echo 1 image. Regions of bone were segmented via a threshold of the R2* image computed from the UTE echo 1 and UTE echo 2 images. Regions of fat and soft tissue were segmented using fat and water images decomposed from the Dixon images. Air, fat, and soft tissue were assigned linear attenuation coefficients (LACs) of 0, 0.092, and 0.1cm(-1), respectively. LACs for bone were derived from a regression analysis between corresponding R2* and CT values. PET images were reconstructed using the gold standard CT method and the proposed CAR-RiDR method. The RiDR segmentation method produces mean Dice coefficient±SD across subjects of 0.75±0.05 for bone and 0.60±0.08 for air. The CAR model for bone LACs greatly improves accuracy in estimating CT values (28.2%±3.0 mean error) compared to the use of a constant CT value (46.9%±5.8, punits. From our analysis, we conclude that the proposed method closely approaches (<3% error) the gold standard CT-scaled method in PET reconstruction accuracy

Mosaic pattern of lung attenuation on thin-section CT : review of 31 cases

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Choi, Young Hi; An, Jee Hyun; Lee, Kye Young; Jee, Young Koo; Lee, Young Seok [Dankook Univ. College of Medicine, Choan (Korea, Republic of)

1998-07-01

To correlate radiologic findings with clinical findings in patients with a mosaic pattern of lung attenuation, as seen on thin-section CT. Materials and Methods : Thirty-one cases in which a mosaic pattern of lung attenuation was detected on combined expiratory and inspiratory scans of thin-section CT were retrospectively analyzed. Cases involving infiltrative lung disease were excluded. Both thin-section CT and clinical findings we reanalyzed and the relationship between the extent of the area of hyperlucency -as seen on expiratory scan- and physiologic parameters was evaluated. The subjects were 10 men and 21 women ranged in age from 25 to 76 (mean 50)years. Results : Twenty-nine patients with small airway disease, [chronic bronchitis and/or bronchiolitis(n=11),bronchiectasis(n=8), bronchial asthma(n=8), mycoplasmic pneumonitis(n=1) and hypersensitive pneumonitis(n=1),] and two patients with pulmonary vascular disease, [chronic pulmonary thromboembolism(n=1) and stenosis of the left upper pulmonary artery(n=1)] were included in our study. Commonly associated thin-section CT findings in the cases involving small airway disease(n=29) were bronchial wall thickening(n=25), nodular opacity(n=25), bronchial and bronchiolar dilatation(n=20) and small branching opacity(n=16). These findings were not observed in two patients with pulmonary vascular disease, though bronchial wall thickening was seen in the patient with chronic pulmonary thromboembolism. At expiratory scan level, there was statistical correlation between FEV1/FVC and the number of pulmonary segments(r= 0.982, p<0.05), but no correlation between FEV1/FVC and the percentage area of hyperlucency(r=0.803, p>0.05). Conclusion: The mosaic pattern of lung attenuation seen on thin-section CT is indicative of various diseases, involving small airways such as bronchiolitis, bronchitis, bronchiectasis and bronchial asthma, and vascular lung disease. Bronchial wall thickening and nodular opacity can be associated with

The effect of metal artefact reduction on CT-based attenuation correction for PET imaging in the vicinity of metallic hip implants : a phantom study

NARCIS (Netherlands)

Harnish, Roy; Prevrhal, Sven; Alavi, Abass; Zaidi, Habib; Lang, Thomas F.

To determine if metal artefact reduction (MAR) combined with a priori knowledge of prosthesis material composition can be applied to obtain CT-based attenuation maps with sufficient accuracy for quantitative assessment of F-18-fluorodeoxyglucose uptake in lesions near metallic prostheses. A custom

The role of aortic wall CT attenuation measurements for the diagnosis of acute aortic syndromes

Energy Technology Data Exchange (ETDEWEB)

Knollmann, Friedrich D., E-mail: friedrich.knollmann@ucdmc.ucdavis.edu [Department of Radiology, University of California, Davis, 4860 Y Street, Sacramento, CA 95817 (United States); Departments of Radiology and Cardiothoracic Surgery, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213 (United States); Lacomis, Joan M.; Ocak, Iclal; Gleason, Thomas [Department of Radiology, University of California, Davis, 4860 Y Street, Sacramento, CA 95817 (United States); Departments of Radiology and Cardiothoracic Surgery, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213 (United States)

2013-12-01

Objectives: To determine if measurements of aortic wall attenuation can improve the CT diagnosis of acute aortic syndromes. Methods: CT reports from a ten year period were searched for acute aortic syndromes (AAS). Studies with both an unenhanced and a contrast enhanced (CTA) series that had resulted in the diagnosis of intramural hematoma (IMH) were reviewed. Diagnoses were confirmed by medical records. The attenuation of aortic wall abnormalities was measured. The observed attenuation threshold was validated using studies from 39 new subjects with a variety of aortic conditions. Results: The term “aortic dissection” was identified in 1206, and IMH in 124 patients’ reports. IMH was confirmed in 31 patients, 21 of whom had both unenhanced and contrast enhanced images. All 21 had pathologic CTA findings, and no CTA with IMH was normal. Attenuation of the aortic wall was greater than 45 HUs on the CTA images in all patients with IMH. When this threshold was applied to the new group, sensitivity for diagnosing AAS was 100% (19/19), and specificity 94% (16/17). Addition of unenhanced images did not improve accuracy. Conclusions: Measurements of aortic wall attenuation in CTA have a high negative predictive value for the diagnosis of acute aortic syndromes.

The role of aortic wall CT attenuation measurements for the diagnosis of acute aortic syndromes

International Nuclear Information System (INIS)

Knollmann, Friedrich D.; Lacomis, Joan M.; Ocak, Iclal; Gleason, Thomas

2013-01-01

Objectives: To determine if measurements of aortic wall attenuation can improve the CT diagnosis of acute aortic syndromes. Methods: CT reports from a ten year period were searched for acute aortic syndromes (AAS). Studies with both an unenhanced and a contrast enhanced (CTA) series that had resulted in the diagnosis of intramural hematoma (IMH) were reviewed. Diagnoses were confirmed by medical records. The attenuation of aortic wall abnormalities was measured. The observed attenuation threshold was validated using studies from 39 new subjects with a variety of aortic conditions. Results: The term “aortic dissection” was identified in 1206, and IMH in 124 patients’ reports. IMH was confirmed in 31 patients, 21 of whom had both unenhanced and contrast enhanced images. All 21 had pathologic CTA findings, and no CTA with IMH was normal. Attenuation of the aortic wall was greater than 45 HUs on the CTA images in all patients with IMH. When this threshold was applied to the new group, sensitivity for diagnosing AAS was 100% (19/19), and specificity 94% (16/17). Addition of unenhanced images did not improve accuracy. Conclusions: Measurements of aortic wall attenuation in CTA have a high negative predictive value for the diagnosis of acute aortic syndromes

Discrimination and anatomical mapping of PET-positive lesions: comparison of CT attenuation-corrected PET images with coregistered MR and CT images in the abdomen

Energy Technology Data Exchange (ETDEWEB)

Kuhn, Felix P.; Crook, David W.; Mader, Caecilia E.; Appenzeller, Philippe; Schulthess, G.K. von; Schmid, Daniel T. [University Hospital Zurich, Department of Medical Radiology, Zurich (Switzerland)

2013-01-15

PET/MR has the potential to become a powerful tool in clinical oncological imaging. The purpose of this prospective study was to evaluate the performance of a single T1-weighted (T1w) fat-suppressed unenhanced MR pulse sequence of the abdomen in comparison with unenhanced low-dose CT images to characterize PET-positive lesions. A total of 100 oncological patients underwent sequential whole-body {sup 18}F-FDG PET with CT-based attenuation correction (AC), 40 mAs low-dose CT and two-point Dixon-based T1w 3D MRI of the abdomen in a trimodality PET/CT-MR system. PET-positive lesions were assessed by CT and MRI with regard to their anatomical location, conspicuity and additional relevant information for characterization. From among 66 patients with at least one PET-positive lesion, 147 lesions were evaluated. No significant difference between MRI and CT was found regarding anatomical lesion localization. The MR pulse sequence used performed significantly better than CT regarding conspicuity of liver lesions (p < 0.001, Wilcoxon signed ranks test), whereas no difference was noted for extrahepatic lesions. For overall lesion characterization, MRI was considered superior to CT in 40 % of lesions, equal to CT in 49 %, and inferior to CT in 11 %. Fast Dixon-based T1w MRI outperformed low-dose CT in terms of conspicuity and characterization of PET-positive liver lesions and performed similarly in extrahepatic tumour manifestations. Hence, under the assumption that the technical issue of MR AC for whole-body PET examinations is solved, in abdominal PET/MR imaging the replacement of low-dose CT by a single Dixon-based MR pulse sequence for anatomical lesion correlation appears to be valid and robust. (orig.)

Discrimination and anatomical mapping of PET-positive lesions: comparison of CT attenuation-corrected PET images with coregistered MR and CT images in the abdomen

International Nuclear Information System (INIS)

Kuhn, Felix P.; Crook, David W.; Mader, Caecilia E.; Appenzeller, Philippe; Schulthess, G.K. von; Schmid, Daniel T.

2013-01-01

PET/MR has the potential to become a powerful tool in clinical oncological imaging. The purpose of this prospective study was to evaluate the performance of a single T1-weighted (T1w) fat-suppressed unenhanced MR pulse sequence of the abdomen in comparison with unenhanced low-dose CT images to characterize PET-positive lesions. A total of 100 oncological patients underwent sequential whole-body 18 F-FDG PET with CT-based attenuation correction (AC), 40 mAs low-dose CT and two-point Dixon-based T1w 3D MRI of the abdomen in a trimodality PET/CT-MR system. PET-positive lesions were assessed by CT and MRI with regard to their anatomical location, conspicuity and additional relevant information for characterization. From among 66 patients with at least one PET-positive lesion, 147 lesions were evaluated. No significant difference between MRI and CT was found regarding anatomical lesion localization. The MR pulse sequence used performed significantly better than CT regarding conspicuity of liver lesions (p < 0.001, Wilcoxon signed ranks test), whereas no difference was noted for extrahepatic lesions. For overall lesion characterization, MRI was considered superior to CT in 40 % of lesions, equal to CT in 49 %, and inferior to CT in 11 %. Fast Dixon-based T1w MRI outperformed low-dose CT in terms of conspicuity and characterization of PET-positive liver lesions and performed similarly in extrahepatic tumour manifestations. Hence, under the assumption that the technical issue of MR AC for whole-body PET examinations is solved, in abdominal PET/MR imaging the replacement of low-dose CT by a single Dixon-based MR pulse sequence for anatomical lesion correlation appears to be valid and robust. (orig.)

Emphysema quantification on low-dose CT using percentage of low-attenuation volume and size distribution of low-attenuation lung regions: Effects of adaptive iterative dose reduction using 3D processing

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Nishio, Mizuho, E-mail: nmizuho@med.kobe-u.ac.jp [Advanced Biomedical Imaging Research Center, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017 (Japan); Division of Functional and Diagnostic Imaging Research, Department of Radiology, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017 (Japan); Matsumoto, Sumiaki, E-mail: sumatsu@med.kobe-u.ac.jp [Advanced Biomedical Imaging Research Center, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017 (Japan); Division of Functional and Diagnostic Imaging Research, Department of Radiology, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017 (Japan); Seki, Shinichiro, E-mail: sshin@med.kobe-u.ac.jp [Division of Radiology, Department of Radiology, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017 (Japan); Koyama, Hisanobu, E-mail: hkoyama@med.kobe-u.ac.jp [Division of Radiology, Department of Radiology, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017 (Japan); Ohno, Yoshiharu, E-mail: yosirad@kobe-u.ac.jp [Advanced Biomedical Imaging Research Center, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017 (Japan); Division of Functional and Diagnostic Imaging Research, Department of Radiology, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017 (Japan); Fujisawa, Yasuko, E-mail: yasuko1.fujisawa@toshiba.co.jp [Toshiba Medical Systems Corporation, 1385 Shimoishigami, Otawara, Tochigi 324-8550 (Japan); Sugihara, Naoki, E-mail: naoki.sugihara@toshiba.co.jp [Toshiba Medical Systems Corporation, 1385 Shimoishigami, Otawara, Tochigi 324-8550 (Japan); and others

2014-12-15

Highlights: • Emphysema quantification (LAV% and D) was affected by image noise on low-dose CT. • For LAV% and D, AIDR 3D improved agreement of quantification on low-dose CT. • AIDR 3D has the potential to quantify emphysema accurately on low-dose CT. - Abstract: Purpose: To evaluate the effects of adaptive iterative dose reduction using 3D processing (AIDR 3D) for quantification of two measures of emphysema: percentage of low-attenuation volume (LAV%) and size distribution of low-attenuation lung regions. Method and materials: : Fifty-two patients who underwent standard-dose (SDCT) and low-dose CT (LDCT) were included. SDCT without AIDR 3D, LDCT without AIDR 3D, and LDCT with AIDR 3D were used for emphysema quantification. First, LAV% was computed at 10 thresholds from −990 to −900 HU. Next, at the same thresholds, linear regression on a log–log plot was used to compute the power law exponent (D) for the cumulative frequency-size distribution of low-attenuation lung regions. Bland–Altman analysis was used to assess whether AIDR 3D improved agreement between LDCT and SDCT for emphysema quantification of LAV% and D. Results: The mean relative differences in LAV% between LDCT without AIDR 3D and SDCT were 3.73%–88.18% and between LDCT with AIDR 3D and SDCT were −6.61% to 0.406%. The mean relative differences in D between LDCT without AIDR 3D and SDCT were 8.22%–19.11% and between LDCT with AIDR 3D and SDCT were 1.82%–4.79%. AIDR 3D improved agreement between LDCT and SDCT at thresholds from −930 to −990 HU for LAV% and at all thresholds for D. Conclusion: AIDR 3D improved the consistency between LDCT and SDCT for emphysema quantification of LAV% and D.

Computed-tomography attenuation values of the peritoneum reflect the severity of peritonitis due to upper gastrointestinal perforations

International Nuclear Information System (INIS)

Tsujimoto, Hironori; Yaguchi, Yoshihisa; Hiraki, Shuichi; Kinoshita, Manabu; Yamamoto, Junji; Hase, Kazuo; Ono, Satoshi

2011-01-01

The aim of this study was to evaluate computed tomography (CT) attenuation values of the peritoneum and to relate these values to the severity of peritonitis in patients with upper gastrointestinal tract (UGI) perforations. A total of 27 consecutive patients with UGI perforations who underwent CT and emergency laparotomy in our hospital were enrolled in this study. The CT attenuation values of the peritoneum were measured at a workstation by 2 independent investigators, and these values were analyzed in relation to the severity of illness. There were significant negative correlations between the peritoneal CT attenuation values and the sequential organ failure assessment score, acute physiology and chronic health evaluation II score, and the Mannheim peritonitis index. There was a significant negative correlation between the peritoneal CT attenuation values and the length of stay in the intensive care unit. Furthermore, patients with dysfunctions in ≥3 organs had significantly lower peritoneal CT attenuation values than those with dysfunction in ≤2 organs. In conclusion, evaluation of peritoneal CT attenuation values in peritonitis patients is simple and can be employed for objective assessment of the severity of peritonitis. (author)

Multi-contrast attenuation map synthesis for PET/MR scanners: assessment on FDG and Florbetapir PET tracers

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Burgos, Ninon [University College London, Translational Imaging Group, Centre for Medical Image Computing, London (United Kingdom); Cardoso, M.J.; Modat, Marc; Ourselin, Sebastien [University College London, Translational Imaging Group, Centre for Medical Image Computing, London (United Kingdom); University College London, Dementia Research Centre, Institute of Neurology, London (United Kingdom); Thielemans, Kris; Dickson, John [University College London, Institute of Nuclear Medicine, London (United Kingdom); Schott, Jonathan M. [University College London, Dementia Research Centre, Institute of Neurology, London (United Kingdom); Atkinson, David [University College London, Centre for Medical Imaging, London (United Kingdom); Arridge, Simon R. [University College London, Centre for Medical Image Computing, London (United Kingdom); Hutton, Brian F. [University College London, Institute of Nuclear Medicine, London (United Kingdom); University of Wollongong, Centre for Medical Radiation Physics, Wollongong, NSW (Australia)

2015-08-15

Positron Emission Tomography/Magnetic Resonance Imaging (PET/MR) scanners are expected to offer a new range of clinical applications. Attenuation correction is an essential requirement for quantification of PET data but MRI images do not directly provide a patient-specific attenuation map. Methods We further validate and extend a Computed Tomography (CT) and attenuation map (μ-map) synthesis method based on pre-acquired MRI-CT image pairs. The validation consists of comparing the CT images synthesised with the proposed method to the original CT images. PET images were acquired using two different tracers ({sup 18}F-FDG and {sup 18}F-florbetapir). They were then reconstructed and corrected for attenuation using the synthetic μ-maps and compared to the reference PET images corrected with the CT-based μ-maps. During the validation, we observed that the CT synthesis was inaccurate in areas such as the neck and the cerebellum, and propose a refinement to mitigate these problems, as well as an extension of the method to multi-contrast MRI data. Results With the improvements proposed, a significant enhancement in CT synthesis, which results in a reduced absolute error and a decrease in the bias when reconstructing PET images, was observed. For both tracers, on average, the absolute difference between the reference PET images and the PET images corrected with the proposed method was less than 2%, with a bias inferior to 1%. Conclusion With the proposed method, attenuation information can be accurately derived from MRI images by synthesising CT using routine anatomical sequences. MRI sequences, or combination of sequences, can be used to synthesise CT images, as long as they provide sufficient anatomical information. (orig.)

Computed tomography (CT) of cervical lymph nodes in patients with oral cancer. Comparison of low-attenuation areas in lymph nodes on CT images with pathological findings

International Nuclear Information System (INIS)

Fukunari, Fumiko; Okamura, Kazuhiko; Yuasa, Kenji; Kagawa, Toyohiro; Zeze, Ryousuke

2008-01-01

The objective of this study was to clarify the histopathological features of low-attenuation areas in computed tomography (CT) images of cervical metastatic and benign lymph nodes in patients with oral squamous cell carcinoma (SCC). CT images of 230 lymph nodes from 37 patients with oral SCC were classified into four categories and compared with histopathological findings. Metastatic lymph nodes were evaluated in terms of focal necrosis, keratinization, fibrous tissue, and the proportion of the lymph node showing focal necrosis. Benign lymph nodes were evaluated in terms of adipose tissue, follicular hyperplasia, sinus histiocytosis, hyperemia, focal hemorrhaging, and the amount of adipose tissue. Histopathologically, all 13 metastatic lymph nodes with rim enhancement on CT images included focal necrosis. However, most of the lymph nodes showed no focal necrosis. In addition, tumor cells, keratinization, and fibrous tissue were observed in the lymph nodes. Of the 26 metastatic lymph nodes with a heterogeneous appearance on CT images, four did not show focal necrosis. These lymph nodes showed keratinization or accumulation of lymph fluid. Histopathologically, 20 of 24 benign lymph nodes with a heterogeneous appearance on CT images (83.3%) had accompanying adipose tissue. Focal necrosis was the most important factor contributing to low attenuation in metastatic lymph nodes. However, other factors, such as tumor cells, keratinization, fibrous tissue, and accumulation of lymph fluid, also contributed. In benign lymph nodes, the presence of adipose tissue was a contributing factor in low-attenuation areas, as was focal hemorrhaging. (author)

Influences of reconstruction and attenuation correction in brain SPECT images obtained by the hybrid SPECT/CT device: evaluation with a 3-dimensional brain phantom

International Nuclear Information System (INIS)

Akamatsu, Mana; Yamashita, Yasuo; Akamatsu, Go; Tsutsui, Yuji; Ohya, Nobuyoshi; Nakamura, Yasuhiko; Sasaki, Masayuki

2014-01-01

The aim of this study was to evaluate the influences of reconstruction and attenuation correction on the differences in the radioactivity distributions in 123 I brain SPECT obtained by the hybrid SPECT/CT device. We used the 3-dimensional (3D) brain phantom, which imitates the precise structure of gray matter, white matter and bone regions. It was filled with 123 I solution (20.1 kBq/mL) in the gray matter region and with K 2 HPO 4 in the bone region. The SPECT/CT data were acquired by the hybrid SPECT/CT device. SPECT images were reconstructed by using filtered back projection with uniform attenuation correction (FBP-uAC), 3D ordered-subsets expectation-maximization with uniform AC (3D-OSEM-uAC) and 3D OSEM with CT-based non-uniform AC (3D-OSEM-CTAC). We evaluated the differences in the radioactivity distributions among these reconstruction methods using a 3D digital phantom, which was developed from CT images of the 3D brain phantom, as a reference. The normalized mean square error (NMSE) and regional radioactivity were calculated to evaluate the similarity of SPECT images to the 3D digital phantom. The NMSE values were 0.0811 in FBP-uAC, 0.0914 in 3D-OSEM-uAC and 0.0766 in 3D-OSEM-CTAC. The regional radioactivity of FBP-uAC was 11.5% lower in the middle cerebral artery territory, and that of 3D-OSEM-uAC was 5.8% higher in the anterior cerebral artery territory, compared with the digital phantom. On the other hand, that of 3D-OSEM-CTAC was 1.8% lower in all brain areas. By using the hybrid SPECT/CT device, the brain SPECT reconstructed by 3D-OSEM with CT attenuation correction can provide an accurate assessment of the distribution of brain radioactivity

Sparse signal reconstruction from polychromatic X-ray CT measurements via mass attenuation discretization

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Gu, Renliang; Dogandžić, Aleksandar

2014-01-01

We propose a method for reconstructing sparse images from polychromatic x-ray computed tomography (ct) measurements via mass attenuation coefficient discretization. The material of the inspected object and the incident spectrum are assumed to be unknown. We rewrite the Lambert-Beer’s law in terms of integral expressions of mass attenuation and discretize the resulting integrals. We then present a penalized constrained least-squares optimization approach for reconstructing the underlying object from log-domain measurements, where an active set approach is employed to estimate incident energy density parameters and the nonnegativity and sparsity of the image density map are imposed using negative-energy and smooth ℓ 1 -norm penalty terms. We propose a two-step scheme for refining the mass attenuation discretization grid by using higher sampling rate over the range with higher photon energy, and eliminating the discretization points that have little effect on accuracy of the forward projection model. This refinement allows us to successfully handle the characteristic lines (Dirac impulses) in the incident energy density spectrum. We compare the proposed method with the standard filtered backprojection, which ignores the polychromatic nature of the measurements and sparsity of the image density map. Numerical simulations using both realistic simulated and real x-ray ct data are presented

Dose reduction in CT examination of children by an attenuation-based on-line modulation of tube current (CARE Dose)

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Greess, Holger; Noemayr, Anton; Baum, Ulrich; Lell, Michael; Boewing, Bernhard; Bautz, Werner A.; Wolf, Heiko; Kalender, Willi

2002-01-01

In a controlled patient study we investigated the potential of attenuation-based on-line modulation of the tube current to reduce milliampere values (mAs) in CT examinations of children without loss of image quality. mAs can be reduced for non-circular patient cross sections without an increase in noise if tube current is reduced at those angular positions where the patient diameter and, consequently, attenuation are small. We investigated a technical approach with an attenuation-based on-line control for the tube current realised as a work-in-progress implementation. The CT projection data are analysed in real time to determine optimal mAs values for each projection angle. We evaluated mAs reduction for 100 spiral CT examinations with attenuation-based on-line modulation of the tube current in a group of children. Two radiologists evaluated image quality by visual interpretation in consensus. We compared the mAs values read from the CT scanner with preset mAs of a standard protocol. Four different scan regions were examined in spiral technique (neck, thorax, abdomen, thorax and abdomen). We found the mAs product to be reduced typically by 10-60% depending on patient geometry and anatomical regions. The mean reduction was 22.3% (neck 20%, thorax 23%, abdomen 23%, thorax and abdomen 22%). In general, no deterioration of image quality was observed. There was no correlation between the age and the mean mAs reduction in the different anatomical regions. By classifying the children respectively to their weight, there is a positive trend between increasing weight and mAs reduction. We conclude that mAs in spiral CT examinations of children can be reduced substantially by attenuation-based on-line modulation of the tube current without deterioration of image quality. Attenuation-based on-line modulation of tube current is efficient and practical for reducing dose exposure to children. (orig.)

Disease progression in usual interstitial pneumonia compared with desquamative interstitial pneumonia. Assessment with serial CT

International Nuclear Information System (INIS)

Hartman, T.E.; Primack, S.L.; Kang, E.Y.

1997-01-01

Objective. To determine the outcome of areas of ground-glass attenuation and assess disease progression on serial high-resolution CT (HRCT) scans of patients with biopsy specimen-proved usual interstitial pneumonia (UIP) and desquamative interstitial pneumonia (DIP). Materials and methods. Twelve patients with biopsy specimen-proved UIP and 11 patients with biopsy specimen-proved DIP who had initial and follow-up HRCT scans (median interval, 10 months) were reviewed. Eleven patients with UIP and 11 with DIP received treatment between the initial and follow-up CT scans. The scans were evaluated for the presence and extent of ground-glass attenuation, irregular linear opacities and honeycombing, and overall extent of parenchymal involvement. Results. On initial CT scans, all 12 patients with UIP had areas of ground-glass attenuation (mean±SD extent, 30±16%) and irregular lines (mean±SD extent, 17±7%) and 10 patients had honeycombing (mean±SD extent, 10±6%). All 11 patients with DIP had areas of ground-glass attenuation on initial HRCT scans (mean±SD extent, 51±26%), 5 patients had irregular linear opacities (mean±SD extent, 5±5%), and 1 patient had honeycombing. Nine of the 12 patients with UIP showed increase in the extent of ground-glass attenuation (n=6) or progression to irregular lines (n=2) or honeycombing (n=4) on follow-up as compared with only 2 patients with DIP who showed progression to irregular lines (n=1) or honeycombing (n=1) (p 2 test). Conclusion. In patients with UIP, areas of ground-glass attenuation usually increase in extent or progress to fibrosis despite treatment. Areas of ground-glass attenuation in most patients with DIP remain stable or improve with treatment. (authors)

CT synthesis in the head & neck region for PET/MR attenuation correction: an iterative multi-atlas approach

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Burgos, Ninon [Translational Imaging Group, Centre for Medical Image Computing, University College London, London (United Kingdom); Cardoso, M Jorge; Modat, Marc [Translational Imaging Group, Centre for Medical Image Computing, University College London, London (United Kingdom); Dementia Research Centre, University College London, London (United Kingdom); Punwani, Shonit [Division of Imaging, University College London Hospitals, London (United Kingdom); Centre for Medical Imaging, University College London, London (United Kingdom); Atkinson, David [Centre for Medical Imaging, University College London, London (United Kingdom); Arridge, Simon R [Centre for Medical Image Computing, University College London, London (United Kingdom); Hutton, Brian F [Institute of Nuclear Medicine, University College London Hospitals, London (United Kingdom); Ourselin, Sébastien [Translational Imaging Group, Centre for Medical Image Computing, University College London, London (United Kingdom); Dementia Research Centre, University College London, London (United Kingdom)

2015-05-18

In this work, we propose to tackle the problem of attenuation correction in the head and neck by synthesising CT from MR images using an iterative multi-atlas approach. The proposed method relies on pre-acquired T2-weighted MRI and CT images of the neck. For each subject, the MRI is non-rigidly mapped to the CT. To synthesise a pseudo CT, all the MRIs in the database are first registered to the target MRI. This registration consists of a robust affine followed by a non-rigid registration. The pseudo CT is obtained by fusing the mapped atlases according to their morphological similarity to the target. In contrast to CTs, T2 images do not provide a good estimate of the bone location. Combining multiple modalities at both the registration and image similarity stages is expected to provide more realistic mappings and to reduce the bias. An initial pseudo CT (pCT) is combined with the target MRI to form a MRI-pCT pair. The MRI-pCT pair is registered to all the MRI-CT pairs from the database. An improved pseudo CT is obtained by fusing the mapped MRI-CT pairs according to their morphological similarity to the target MRI-pCT pair. Results showed that the proposed CT synthesis algorithm based on a multi-atlas information propagation scheme and iterative process is able to synthesise pseudo CT images in a region challenging for registration algorithms. The results also demonstrate that the robust affine decreases the absolute error compared to the classic approach and that the bone refinement process reduces the bias in the bone region. The proposed method could be used to correct for attenuation PET/MR data, but also for dosimetry calculations in the context of MR-based radiotherapy treatment planning.

Subject-specific bone attenuation correction for brain PET/MR: can ZTE-MRI substitute CT scan accurately?

Science.gov (United States)

Khalifé, Maya; Fernandez, Brice; Jaubert, Olivier; Soussan, Michael; Brulon, Vincent; Buvat, Irène; Comtat, Claude

2017-10-01

In brain PET/MR applications, accurate attenuation maps are required for accurate PET image quantification. An implemented attenuation correction (AC) method for brain imaging is the single-atlas approach that estimates an AC map from an averaged CT template. As an alternative, we propose to use a zero echo time (ZTE) pulse sequence to segment bone, air and soft tissue. A linear relationship between histogram normalized ZTE intensity and measured CT density in Hounsfield units (HU ) in bone has been established thanks to a CT-MR database of 16 patients. Continuous AC maps were computed based on the segmented ZTE by setting a fixed linear attenuation coefficient (LAC) to air and soft tissue and by using the linear relationship to generate continuous μ values for the bone. Additionally, for the purpose of comparison, four other AC maps were generated: a ZTE derived AC map with a fixed LAC for the bone, an AC map based on the single-atlas approach as provided by the PET/MR manufacturer, a soft-tissue only AC map and, finally, the CT derived attenuation map used as the gold standard (CTAC). All these AC maps were used with different levels of smoothing for PET image reconstruction with and without time-of-flight (TOF). The subject-specific AC map generated by combining ZTE-based segmentation and linear scaling of the normalized ZTE signal into HU was found to be a good substitute for the measured CTAC map in brain PET/MR when used with a Gaussian smoothing kernel of 4~mm corresponding to the PET scanner intrinsic resolution. As expected TOF reduces AC error regardless of the AC method. The continuous ZTE-AC performed better than the other alternative MR derived AC methods, reducing the quantification error between the MRAC corrected PET image and the reference CTAC corrected PET image.

In vivo micro-CT assessment of airway remodeling in a flexible OVA-sensitized murine model of asthma.

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Mathieu Lederlin

Full Text Available Airway remodeling is a major pathological feature of asthma. Up to now, its quantification still requires invasive methods. In this study, we aimed at determining whether in vivo micro-computed tomography (micro-CT is able to demonstrate allergen-induced airway remodeling in a flexible mouse model of asthma. Sixty Balb/c mice were challenged intranasally with ovalbumin or saline at 3 different endpoints (Days 35, 75, and 110. All mice underwent plethysmography at baseline and just prior to respiratory-gated micro-CT. Mice were then sacrificed to assess bronchoalveolar lavage and lung histology. From micro-CT images (voxel size = 46×46×46 µm, the numerical values of total lung attenuation, peribronchial attenuation (PBA, and PBA normalized by total lung attenuation were extracted. Each parameter was compared between OVA and control mice and correlation coefficients were calculated between micro-CT and histological data. As compared to control animals, ovalbumin-sensitized mice exhibited inflammation alone (Day 35, remodeling alone (Day 110 or both inflammation and remodeling (Day 75. Normalized PBA was significantly greater in mice exhibiting bronchial remodeling either alone or in combination with inflammation. Normalized PBA correlated with various remodeling markers such as bronchial smooth muscle size or peribronchial fibrosis. These findings suggest that micro-CT may help monitor remodeling non-invasively in asthmatic mice when testing new drugs targeting airway remodeling in pre-clinical studies.

Characteristics of images of angiographically proven normal coronary arteries acquired by adenosine-stress thallium-201 myocardial perfusion SPECT/CT-IQ[Symbol: see text]SPECT with CT attenuation correction changed stepwise.

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Takahashi, Teruyuki; Tanaka, Haruki; Kozono, Nami; Tanakamaru, Yoshiki; Idei, Naomi; Ohashi, Norihiko; Ohtsubo, Hideki; Okada, Takenori; Yasunobu, Yuji; Kaseda, Shunichi

2015-04-01

Although several studies have shown the diagnostic and prognostic value of CT-based attenuation correction (AC) of single photon emission computed tomography (SPECT) images for diagnosing coronary artery disease (CAD), this issue remains a matter of debate. To clarify the characteristics of CT-AC SPECT images that might potentially improve diagnostic performance, we analyzed images acquired using adenosine-stress thallium-201 myocardial perfusion SPECT/CT equipped with IQ[Symbol: see text]SPECT (SPECT/CT-IQ[Symbol: see text]SPECT) from patients with angiographically proven normal coronary arteries after changing the CT attenuation correction (CT-AC) in a stepwise manner. We enrolled 72 patients (Male 36, Female 36) with normal coronary arteries according to findings of invasive coronary angiography or CT-angiography within three months after a SPECT/CT study. Projection images were reconstructed at CT-AC values of (-), 40, 60, 80 and 100 % using a CT number conversion program according to our definition and analyzed using polar maps according to sex. CT attenuation corrected segments were located from the mid- and apical-inferior spread through the mid- and apical-septal regions and finally to the basal-anterior and basal- and mid-lateral regions in males, and from the mid-inferior region through the mid-septal and mid-anterior, and mid-lateral regions in females as the CT-AC values increased. Segments with maximal mean counts shifted from the apical-anterior to mid-anterolateral region under both stress and rest conditions in males, whereas such segments shifted from the apical-septal to the mid-anteroseptal region under both stress and rest conditions in females. We clarified which part of the myocardium and to which degree CT-AC affects it in adenosine-stress thallium-201 myocardial perfusion SPECT/CT-IQ[Symbol: see text]SPECT images by changing the CT-AC value stepwise. We also identified sex-specific shifts of segments with maximal mean counts that changed as

Reliability of computed tomography measurements in assessment of thigh muscle cross-sectional area and attenuation

International Nuclear Information System (INIS)

Strandberg, Sören; Wretling, Marie-Louise; Wredmark, Torsten; Shalabi, Adel

2010-01-01

Advancement in technology of computer tomography (CT) and introduction of new medical imaging softwares enables easy and rapid assessment of muscle cross-sectional area (CSA) and attenuation. Before using these techniques in clinical studies there is a need for evaluation of the reliability of the measurements. The purpose of the study was to evaluate the inter- and intra-observer reliability of ImageJ in measuring thigh muscles CSA and attenuation in patients with anterior cruciate ligament (ACL) injury by computer tomography. 31 patients from an ongoing study of rehabilitation and muscle atrophy after ACL reconstruction were included in the study. Axial CT images with slice thickness of 10 mm at the level of 150 mm above the knee joint were analyzed by two investigators independently at two times with a minimum of 3 weeks between the two readings using NIH ImageJ. CSA and the mean attenuation of individual thigh muscles were analyzed for both legs. Mean CSA and mean attenuation values were in good agreement both when comparing the two observers and the two replicates. The inter- and intraclass correlation (ICC) was generally very high with values from 0.98 to 1.00 for all comparisons except for the area of semimembranosus. All the ICC values were significant (p < 0,001). Pearson correlation coefficients were also generally very high with values from 0.98 to 1.00 for all comparisons except for the area of semimembranosus (0.95 for intraobserver and 0.92 for interobserver). This study has presented ImageJ as a method to monitor and evaluate CSA and attenuation of different muscles in the thigh using CT-imaging. The method shows an overall excellent reliability with respect to both observer and replicate

Assessment of airway lesion in obstructive lung diseases by CT

International Nuclear Information System (INIS)

Niimi, Akio; Matsumoto, Hisako; Ueda, Tetsuya; Mishima, Michiaki

2002-01-01

Airway lesion in obstructive pulmonary diseases, such as asthma or chronic obstructive pulmonary disease (COPD), has recently been assessed quantitatively. Especially in asthma, wall thickening of central airways, and its relation to the severity of disease or airflow obstruction has been clarified. Pathophysiologic importance of peripheral airway lesion has also been highlighted by pathologic or physiologic studies. However, direct evaluation of peripheral airway lesion is beyond resolutional limitation of CT. To assess airway trapping, an indirect CT finding of peripheral airway disease, by quantitative and semiquantitative measures and compare them with clinical indices such as pulmonary function, airway responsiveness, or airway inflammation. Patients with stable asthma (n=20) were studied. HRCT at 3 levels of both lungs were scanned. Low attenuation area (LAA)% and mean lung density were quantitatively assessed by an automatic method. Distribution of mosaic pattern was visually scored semiquantitatively. LAA% and mean lung density at full expiratory phase correlated with the degree of airflow obstruction. Mosaic score at full inspiratory phase correlated with the severity of disease and airflow obstruction. Expiratory/inspiratory ratio of mean lung density was also associated with airway responsiveness or residual volume/total lung capacity (RV/TLC). These CT findings may be useful as markers of asthma pathophysiology. (author)

Sources of attenuation-correction artefacts in cardiac PET/CT and SPECT/CT.

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McQuaid, Sarah J; Hutton, Brian F

2008-06-01

Respiratory motion during myocardial perfusion imaging can cause artefacts in both positron emission tomography (PET) and single-photon emission computed tomography (SPECT) images when mismatches between emission and transmission datasets arise. In this study, artefacts from different breathing motions were quantified in both modalities to assess key factors in attenuation-correction accuracy. Activity maps were generated using the NURBS-based cardiac-torso phantom for different respiratory cycles, which were projected, attenuation-corrected and reconstructed to form PET and SPECT images. Attenuation-correction was performed with maps at mismatched respiratory phases to observe the effect on the left-ventricular myocardium. Myocardial non-uniformity was assessed in terms of the standard deviation in scores obtained from the 17-segment model and changes in uniformity were compared for each mismatch and modality. Certain types of mismatch led to artefacts and corresponding increases in the myocardial non-uniformity. For each mismatch in PET, the increases in non-uniformity relative to an artefact-free image were as follows: (a) cardiac translation mismatch, 84% +/- 11%; (b) liver mismatch, 59% +/- 10%, (c) lung mismatch from diaphragm contraction, 28% +/- 8%; and (d) lung mismatch from chest-wall motion, 6% +/- 7%. The corresponding factors for SPECT were (a) 61% +/- 8%, (b) 34% +/- 8%, (c) -2% +/- 7)% and (d) -4% +/- 6%. Attenuation-correction artefacts were seen in PET and SPECT images, with PET being more severely affected. The most severe artefacts were produced from mismatches in cardiac and liver position, whereas lung mismatches were less critical. Both cardiac and liver positions must, therefore, be correctly matched during attenuation correction.

Effectiveness of computed tomography attenuation values in characterization of pericardial effusion.

Science.gov (United States)

Çetin, Mehmet Serkan; Özcan Çetin, Elif Hande; Özdemir, Mustafa; Topaloğlu, Serkan; Aras, Dursun; Temizhan, Ahmet; Aydoğdu, Sinan

2017-04-01

The aim of this study was to evaluate the effectiveness of computed tomography (CT) attenuation values in the characterization of pericardial effusion. This study consisted of 96 patients with pericardial effusion who underwent pericardiocentesis. For further diagnostic evaluation of pericardial effusion, all the patients were assessed by thorax CT. CT attenuation values were measured from at least 5 different areas of pericardial fluid by specifying the largest region of interest. The average of these measurements was computed and considered as the CT attenuation value of the patient. The patients were classified into two groups: patients with transudative pericardial effusion and those with exudative pericardial effusion. CT attenuation values were significantly higher in patients with exudative pericardial effusion than in those with transudative pericardial effusion [14.85±10.7 Hounsfield unit (HU) vs. 1.13±4.3 HU, peffusion. In addition, a cut-off value of 6.5 HU had 71.4% sensitivity and 72.3% specificity for the prediction of cardiac tamponade. In patients with pericardial effusion, CT attenuation values seem to be correlated with the characterization parameters of the fluid and may distinguish exudative pericardial effusion from transudative pericardial effusion. This parameter was also found to be a predictor of cardiac tamponade. CT attenuation values can be a useful tool in the clinical evaluation of patients with pericardial effusion.

Adipose tissue and muscle attenuation as novel biomarkers predicting mortality in patients with extremity sarcomas

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Veld, Joyce; Vossen, Josephina A.; Torriani, Martin; Bredella, Miriam A. [Massachusetts General Hospital and Harvard Medical School, Division of Musculoskeletal Imaging and Intervention, Department of Radiology, Boston, MA (United States); De Amorim Bernstein, Karen [Massachusetts General Hospital and Harvard Medical School, Department of Radiation Oncology, Francis H Burr Proton Therapy Center, Boston, MA (United States); Halpern, Elkan F. [Massachusetts General Hospital and Harvard Medical School, Institute of Technology Assessment, Boston, MA (United States)

2016-12-15

To assess CT-attenuation of abdominal adipose tissue and psoas muscle as predictors of mortality in patients with sarcomas of the extremities. Our study was IRB approved and HIPAA compliant. The study group comprised 135 patients with history of extremity sarcoma (mean age: 53 ± 17 years) who underwent whole body PET/CT. Abdominal subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and psoas muscle attenuation (HU) was assessed on non-contrast, attenuation-correction CT. Clinical information including survival, tumour stage, sarcoma type, therapy and pre-existing comorbidities were recorded. Cox proportional hazard models were used to determine longitudinal associations between adipose tissue and muscle attenuation and mortality. There were 47 deaths over a mean follow-up period of 20 ± 17 months. Higher SAT and lower psoas attenuation were associated with increased mortality (p = 0.03 and p = 0.005, respectively), which remained significant after adjustment for age, BMI, sex, tumor stage, therapy, and comorbidities (p = 0.002 and p = 0.02, respectively). VAT attenuation was not associated with mortality. Attenuation of SAT and psoas muscle, assessed on non-contrast CT, are predictors of mortality in patients with extremity sarcomas, independent of other established prognostic factors, suggesting that adipose tissue and muscle attenuation could serve as novel biomarkers for mortality in patients with sarcomas. (orig.)

Adipose tissue and muscle attenuation as novel biomarkers predicting mortality in patients with extremity sarcomas

International Nuclear Information System (INIS)

Veld, Joyce; Vossen, Josephina A.; Torriani, Martin; Bredella, Miriam A.; De Amorim Bernstein, Karen; Halpern, Elkan F.

2016-01-01

To assess CT-attenuation of abdominal adipose tissue and psoas muscle as predictors of mortality in patients with sarcomas of the extremities. Our study was IRB approved and HIPAA compliant. The study group comprised 135 patients with history of extremity sarcoma (mean age: 53 ± 17 years) who underwent whole body PET/CT. Abdominal subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and psoas muscle attenuation (HU) was assessed on non-contrast, attenuation-correction CT. Clinical information including survival, tumour stage, sarcoma type, therapy and pre-existing comorbidities were recorded. Cox proportional hazard models were used to determine longitudinal associations between adipose tissue and muscle attenuation and mortality. There were 47 deaths over a mean follow-up period of 20 ± 17 months. Higher SAT and lower psoas attenuation were associated with increased mortality (p = 0.03 and p = 0.005, respectively), which remained significant after adjustment for age, BMI, sex, tumor stage, therapy, and comorbidities (p = 0.002 and p = 0.02, respectively). VAT attenuation was not associated with mortality. Attenuation of SAT and psoas muscle, assessed on non-contrast CT, are predictors of mortality in patients with extremity sarcomas, independent of other established prognostic factors, suggesting that adipose tissue and muscle attenuation could serve as novel biomarkers for mortality in patients with sarcomas. (orig.)

Sepsis patients' renal manifestation on contrast-enhanced CT

International Nuclear Information System (INIS)

Sasaguri, K.; Yamaguchi, K.; Nakazono, T.; Mizuguchi, M.; Irie, H.

2016-01-01

Aim: To evaluate renal volume and attenuation changes in patients with sepsis on contrast-enhanced computed tomography (CT) with respect to the severity of sepsis. Materials and methods: Forty-four patients with sepsis who underwent CT before and after the onset of sepsis were retrospectively analysed. Renal volume and CT attenuation value of the renal cortex on contrast-enhanced CT were measured for each patient and changes in renal volume and CT attenuation value from before to after the onset of sepsis were calculated. The changes were correlated with the severity of sepsis (Sepsis-related Organ Failure Assessment [SOFA] score). The time course of the renal volume and CT attenuation changes were also evaluated. Results: Renal volume increased by 17.6% and CT attenuation value decreased by 19% after the onset of sepsis with statistically significant differences (p<0.001 for both renal volume and CT attenuation changes). The renal volume and CT attenuation changes had significant correlations with the SOFA score (r=0.36, p=0.018 and −0.43, p=0.005, respectively). The time course of the renal volume and CT attenuation changes seemed to be gradual compared to that of the SOFA score and to lag behind the peak of the SOFA score. Conclusion: In patients with sepsis, the renal volume increases and the CT attenuation value decreases in proportion to the severity of sepsis. The changes may lag behind the peak of severity of sepsis and can be observed for a relatively long time after a patient's recovery from sepsis. - Highlights: • The renal volume increases and the renal enhancement on contrast-enhanced CT decreases in patients with sepsis. • The degrees of these changes are correlated with severity of sepsis. • These changes may lag behind the peak of severity of sepsis and last for a long time after a patient's recovery from sepsis.

Concordance between fine-needle aspiration and core biopsies for osseous lesions by lesion imaging appearance and CT attenuation.

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Li, John; Weissberg, Zoe; Bevilacqua, Thomas A; Yu, Gordon; Weber, Kristy; Sebro, Ronnie

2018-04-01

To compare the concordance between fine-needle aspiration and core biopsies for osseous lesions by lesion imaging appearance and CT attenuation. Retrospective review of 215 FNAs of osseous lesions performed in conjunction with core biopsy at our institution over a 6-year period (2011-2016). FNAs were interpreted independently of core biopsies. We assessed if FNA in conjunction with core biopsy increased diagnostic accuracy compared to core biopsy alone. We also calculated the concordance between FNA and core biopsy by lesion appearance, lesion CT attenuation, lesion histology, lesion location and FNA needle gauge size. Core biopsy alone provided the diagnosis in 207/215 cases (96.3%), however, the FNA provided the diagnosis in the remaining 8/215 cases (3.7%) where the core biopsy was non-diagnostic. There were 154 (71.6%) lytic lesions, 21 (9.8%) blastic lesions, 25 (11.6%) mixed lytic and blastic lesions and 15 (7.0%) lesions that were neither lytic nor blastic. The concordance between FNA and core biopsy for lytic osseous lesions (136/154 cases, 88.3%) was statistically significantly higher than that for blastic osseous lesions (13/21 cases, 61.9%) [P = 4.2 × 10 -3 ; 95% CI (0.02, 0.50)]. The concordance between FNA and core biopsy was higher for low-attenuation- (110/126) than high-attenuation (58/77) lesions (P = 0.028). The concordance between FNA and core biopsy was also higher for metastases (102/119 cases, 85.7%) than non-metastases (78/96, 81.3%) [P = 0.487; 95% CI (- 0.15, 0.065)]. There was no difference in the rate of concordance between FNA and core biopsy by lesion location or FNA needle gauge size (P > 0.05). FNA with core biopsy increases diagnostic rate compared to core biopsy alone or FNA alone. The concordance between FNA and core biopsy is higher for lytic lesions than for blastic lesions; and higher for low-attenuation lesions than for high-attenuation lesions.

An assessment of pulmonary emphysema in smokers using CT scan

International Nuclear Information System (INIS)

Satoh, Katashi; Kobayashi, Takuya; Misao, Takahiko

1999-01-01

We assessed the relationship between PE and smoking in 639 cases (411 males and 228 females with age ranged 21-86 years) who underwent CT scans during the period, from December 1997 to December 1998, under suspicion of respiratory disease on chest radiograph or some respiratory complaints. PE was diagnosed by the existence of low attenuation areas in CT scan and not by pulmonary function tests. CT was performed with 10 mm collimation in a standard algorithm. PE, regardless of the grade, was seen: in 189 out of 348 (54.3%) cases in male smokers and in only 2 out of 63 (3.2%) cases in male non-smokers; and in 5 out of 25 (20.0%) female smokers and in 4 out of 203 (2.0%) female non-smokers. PE was observed in more than half of male smokers. High incidence of PE was also observed in even younger generation, and its severity progresses with advancing age and increasing smoking index. (author)

Lymphoplasmacytic sclerosing cholangitis: assessment of clinical, CT, and pathological findings

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Itoh, S., E-mail: shigekimiyo@luck.ocn.ne.j [Department of Technical Radiology, Nagoya University School of Health Sciences, Nagoya (Japan); Nagasaka, T. [Department of Pathology, Nagoya University Graduate School of Medicine, Nagoya (Japan); Suzuki, K.; Satake, H.; Ota, T.; Naganawa, S. [Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya (Japan)

2009-11-15

Aim: To assess the clinical, computed tomography (CT), and pathological findings in patients with lymphoplasmacytic sclerosing cholangitis. Materials and methods: Fifteen consecutive patients (four women and 11 men, mean age 71 years) with lymphoplasmacytic sclerosing cholangitis and without the characteristic features of underlying disorders causing benign biliary strictures were retrospectively recruited. Two radiologists evaluated multiphase contrast-enhanced CT images acquired with 0.5 or 1-mm collimation. One pathologist performed all histological examinations, including IgG4 immunostaining. Results: The intrahepatic biliary ducts showed dilatation in all 15 patients, but only seven presented with jaundice. Although laboratory data were not available in all patients, serum gammaglobulin and IgG levels were elevated in five of six patients and six of eight patients, respectively. Anti-nuclear antibody was detected in three of six patients. The involved biliary ducts showed the following CT findings: involvement of the hilar biliary duct (14/15), a mean wall thickness of 4.9 mm, a smooth margin (10/15), a narrow but visible lumen (6/15), hyper-attenuation during the late arterial phase (9/15), homogeneous hyper-attenuation during the delayed phase (11/11), and no vascular invasion (14/15). Abnormal findings in the pancreas and urinary tract were detected in eight of 15 patients. In 13 patients with adequate specimens, moderate to severe lymphoplasmacytic infiltration associated with dense fibrosis was observed. Infiltration of IgG4-positive plasma cells was moderate or severe in nine patients and minimal or absent in four patients. Conclusion: Lymphoplasmacytic sclerosing cholangitis exhibits relatively characteristic clinical and CT findings, although they are not sufficiently specific for differentiation from other biliary diseases.

Lymphoplasmacytic sclerosing cholangitis: assessment of clinical, CT, and pathological findings

International Nuclear Information System (INIS)

Itoh, S.; Nagasaka, T.; Suzuki, K.; Satake, H.; Ota, T.; Naganawa, S.

2009-01-01

Aim: To assess the clinical, computed tomography (CT), and pathological findings in patients with lymphoplasmacytic sclerosing cholangitis. Materials and methods: Fifteen consecutive patients (four women and 11 men, mean age 71 years) with lymphoplasmacytic sclerosing cholangitis and without the characteristic features of underlying disorders causing benign biliary strictures were retrospectively recruited. Two radiologists evaluated multiphase contrast-enhanced CT images acquired with 0.5 or 1-mm collimation. One pathologist performed all histological examinations, including IgG4 immunostaining. Results: The intrahepatic biliary ducts showed dilatation in all 15 patients, but only seven presented with jaundice. Although laboratory data were not available in all patients, serum gammaglobulin and IgG levels were elevated in five of six patients and six of eight patients, respectively. Anti-nuclear antibody was detected in three of six patients. The involved biliary ducts showed the following CT findings: involvement of the hilar biliary duct (14/15), a mean wall thickness of 4.9 mm, a smooth margin (10/15), a narrow but visible lumen (6/15), hyper-attenuation during the late arterial phase (9/15), homogeneous hyper-attenuation during the delayed phase (11/11), and no vascular invasion (14/15). Abnormal findings in the pancreas and urinary tract were detected in eight of 15 patients. In 13 patients with adequate specimens, moderate to severe lymphoplasmacytic infiltration associated with dense fibrosis was observed. Infiltration of IgG4-positive plasma cells was moderate or severe in nine patients and minimal or absent in four patients. Conclusion: Lymphoplasmacytic sclerosing cholangitis exhibits relatively characteristic clinical and CT findings, although they are not sufficiently specific for differentiation from other biliary diseases.

Impact of CT attenuation correction method on quantitative respiratory-correlated (4D) PET/CT imaging

Energy Technology Data Exchange (ETDEWEB)

Nyflot, Matthew J., E-mail: nyflot@uw.edu [Department of Radiation Oncology, University of Washington, Seattle, Washington 98195-6043 (United States); Lee, Tzu-Cheng [Department of Bioengineering, University of Washington, Seattle, Washington 98195-6043 (United States); Alessio, Adam M.; Kinahan, Paul E. [Department of Radiology, University of Washington, Seattle, Washington 98195-6043 (United States); Wollenweber, Scott D.; Stearns, Charles W. [GE Healthcare, Waukesha, Wisconsin 53188 (United States); Bowen, Stephen R. [Department of Radiation Oncology, University of Washington, Seattle, Washington 98195-6043 and Department of Radiology, University of Washington, Seattle, Washington 98195-6043 (United States)

2015-01-15

Purpose: Respiratory-correlated positron emission tomography (PET/CT) 4D PET/CT is used to mitigate errors from respiratory motion; however, the optimal CT attenuation correction (CTAC) method for 4D PET/CT is unknown. The authors performed a phantom study to evaluate the quantitative performance of CTAC methods for 4D PET/CT in the ground truth setting. Methods: A programmable respiratory motion phantom with a custom movable insert designed to emulate a lung lesion and lung tissue was used for this study. The insert was driven by one of five waveforms: two sinusoidal waveforms or three patient-specific respiratory waveforms. 3DPET and 4DPET images of the phantom under motion were acquired and reconstructed with six CTAC methods: helical breath-hold (3DHEL), helical free-breathing (3DMOT), 4D phase-averaged (4DAVG), 4D maximum intensity projection (4DMIP), 4D phase-matched (4DMATCH), and 4D end-exhale (4DEXH) CTAC. Recovery of SUV{sub max}, SUV{sub mean}, SUV{sub peak}, and segmented tumor volume was evaluated as RC{sub max}, RC{sub mean}, RC{sub peak}, and RC{sub vol}, representing percent difference relative to the static ground truth case. Paired Wilcoxon tests and Kruskal–Wallis ANOVA were used to test for significant differences. Results: For 4DPET imaging, the maximum intensity projection CTAC produced significantly more accurate recovery coefficients than all other CTAC methods (p < 0.0001 over all metrics). Over all motion waveforms, ratios of 4DMIP CTAC recovery were 0.2 ± 5.4, −1.8 ± 6.5, −3.2 ± 5.0, and 3.0 ± 5.9 for RC{sub max}, RC{sub peak}, RC{sub mean}, and RC{sub vol}. In comparison, recovery coefficients for phase-matched CTAC were −8.4 ± 5.3, −10.5 ± 6.2, −7.6 ± 5.0, and −13.0 ± 7.7 for RC{sub max}, RC{sub peak}, RC{sub mean}, and RC{sub vol}. When testing differences between phases over all CTAC methods and waveforms, end-exhale phases were significantly more accurate (p = 0.005). However, these differences were driven by

Assessment of vertebral artery stents using 16-slice multi-detector row CT angiography in vivo evaluation: Comparison of a medium-smooth kernel and a sharp kernel

International Nuclear Information System (INIS)

Yoo, Won Jong; Lim, Yeon Soo; Ahn, Kook Jin; Choi, Byung Gil; Kim, Ji Young; Kim, Sung Hoon

2009-01-01

Objectives: To assess the lumen visibility of extracranial vertebral artery stents examined with 16-slice multi-detector row computed tomography (MDCT) angiography in vivo using a medium-smooth kernel (B30s) and a sharp kernel (B60s), and to compare these with digital subtraction angiography (DSA) after stent placement. Methods: Twenty stents from 20 patients (14 men, 6 women; mean age, 62.7 ± 10.1 years) who underwent CT angiography (CTA) with 16-slice MDCT were retrospectively analyzed. In CT angiograms using a B30s and a B60s, the lumen diameters and CT attenuations of the stented vessels were measured three times by three observers, and artificial luminal narrowing (ALN) was calculated. To assess measurement reliability on CT angiograms, the intraclass correlation coefficient (ICC) was used. DSA served as the reference standard for the in-stent luminal measurements on CT angiography. The median interval between CT angiography and DSA was 1 day (range 1-10). Results: For interobserver reliability, intraclass correlation coefficients for the lumen diameters on CT angiograms with a B30s and a B60s were 0.90 and 0.96, respectively. The lumen diameters on CT angiograms using a B30s were consistently smaller than that on CT angiograms using a B60s (p < 0.01). The mean ALN was 37 ± 7% on CT angiograms using a B30s and 25 ± 9% on CT angiograms using a B60s. The mean CT attenuation in in-stent lumen was 347 ± 55 HU on CT angiograms using a B30s and 295 ± 46 HU on CT angiograms using a B60s. The ALN and CT attenuation within the stented vessels between CT angiograms using a B30s and a B60s was significant (p < 0.01). Conclusions: 16-slice MDCT using a sharp kernel allows good visualization of the stented vessels and is useful in the assessment of vertebral artery stent patency after stent placement.

CT assessment of subtypes of pulmonary emphysema in females

International Nuclear Information System (INIS)

Togami, Taro; Yamamoto, Yuka; Kameyama, Reiko; Murota, Makiko; Kimura, Naruhide; Nishiyama, Yoshihiro; Satoh, Katashi

2011-01-01

We performed a retrospective study examining the prevalence and subtypes of pulmonary emphysema (PE) identified by computed tomography (CT) in females. We reviewed the records of 1,687 female subjects who had undergone CT. They were divided into the following 2 age groups: group A (<50 years) and group B (≥50 years). PE was diagnosed by the presence of low-attenuation areas using visual assessment (grades 0-3) on CT images. Two subtypes of PE were observed: centrilobular emphysema (CLE) and paraseptal emphysema (PSE). PE was divided into the following 3 categories: I (CLE or CLE-predominant); II (CLE and PSE of equal extent); and III (PSE or PSE-predominant). PE was found in 64 of 274 smokers (23.3%) and 54 of 1,413 non-smokers (3.8%). In smoking subjects, when grades 1 and 2 were grouped together as mild PE, the mean age for CT grade 3 (severe PE) was significantly higher than that for mild PE. In group A, category III predominated, whereas category I was more prevalent in group B, in both smoking and non-smoking subjects. A high incidence of PE was found in smoking subjects as compared with non-smoking subjects. PSE predominated in younger subjects, whereas CLE predominated in older subjects. (author)

Size and attenuation CT (SACT) of residual masses in patients with follicular Non-Hodgkin Lymphoma: More than a status quo?

International Nuclear Information System (INIS)

Spira, Daniel; Vogel, Wichard; Sökler, Martin; Löffler, Sarah; Sauter, Alexander; Schulze, Maximilian; Horger, Marius

2012-01-01

Purpose: To evaluate CT-attenuation ratio of residual masses in patients with follicular Non-Hodgkin lymphoma (FL) at end-treatment compared to baseline mass density and determine its potential prognostic relevance. Materials and methods: 52 consecutive patients with FL presenting with residual masses after chemotherapy receiving whole-body-CECT at baseline, end-treatment, and post-treatment were identified retrospectively by a search of our electronic medical record database from 2002 through 2010. An attenuation ratio (AR), defined as the quotient of CT-attenuation [HU] between tumor and muscle was measured. Size was recorded as the product of long- and short-axis diameter of masses. In 38/52 patients a follow-up period of ≥2 years was available to correlate results with relapse-free survival. Results: AR and tumor size of masses significantly decreased in responders when baseline was compared to end-treatment (n = 70; p 1 at end-control the specificity and sensitivity for relapsing disease within 2 years reached 83% and 75%, respectively. Conclusion: CT-attenuation measurements of residual masses in patients with FL at end-control may aid in the risk stratification of early (≤2 years) relapsing disease.

A new technique to characterize CT scanner bow-tie filter attenuation and applications in human cadaver dosimetry simulations

Science.gov (United States)

Li, Xinhua; Shi, Jim Q.; Zhang, Da; Singh, Sarabjeet; Padole, Atul; Otrakji, Alexi; Kalra, Mannudeep K.; Xu, X. George; Liu, Bob

2015-01-01

Purpose: To present a noninvasive technique for directly measuring the CT bow-tie filter attenuation with a linear array x-ray detector. Methods: A scintillator based x-ray detector of 384 pixels, 307 mm active length, and fast data acquisition (model X-Scan 0.8c4-307, Detection Technology, FI-91100 Ii, Finland) was used to simultaneously detect radiation levels across a scan field-of-view. The sampling time was as short as 0.24 ms. To measure the body bow-tie attenuation on a GE Lightspeed Pro 16 CT scanner, the x-ray tube was parked at the 12 o’clock position, and the detector was centered in the scan field at the isocenter height. Two radiation exposures were made with and without the bow-tie in the beam path. Each readout signal was corrected for the detector background offset and signal-level related nonlinear gain, and the ratio of the two exposures gave the bow-tie attenuation. The results were used in the geant4 based simulations of the point doses measured using six thimble chambers placed in a human cadaver with abdomen/pelvis CT scans at 100 or 120 kV, helical pitch at 1.375, constant or variable tube current, and distinct x-ray tube starting angles. Results: Absolute attenuation was measured with the body bow-tie scanned at 80–140 kV. For 24 doses measured in six organs of the cadaver, the median or maximum difference between the simulation results and the measurements on the CT scanner was 8.9% or 25.9%, respectively. Conclusions: The described method allows fast and accurate bow-tie filter characterization. PMID:26520720

Bias atlases for segmentation-based PET attenuation correction using PET-CT and MR.

Science.gov (United States)

Ouyang, Jinsong; Chun, Se Young; Petibon, Yoann; Bonab, Ali A; Alpert, Nathaniel; Fakhri, Georges El

2013-10-01

This study was to obtain voxel-wise PET accuracy and precision using tissue-segmentation for attenuation correction. We applied multiple thresholds to the CTs of 23 patients to classify tissues. For six of the 23 patients, MR images were also acquired. The MR fat/in-phase ratio images were used for fat segmentation. Segmented tissue classes were used to create attenuation maps, which were used for attenuation correction in PET reconstruction. PET bias images were then computed using the PET reconstructed with the original CT as the reference. We registered the CTs for all the patients and transformed the corresponding bias images accordingly. We then obtained the mean and standard deviation bias atlas using all the registered bias images. Our CT-based study shows that four-class segmentation (air, lungs, fat, other tissues), which is available on most PET-MR scanners, yields 15.1%, 4.1%, 6.6%, and 12.9% RMSE bias in lungs, fat, non-fat soft-tissues, and bones, respectively. An accurate fat identification is achievable using fat/in-phase MR images. Furthermore, we have found that three-class segmentation (air, lungs, other tissues) yields less than 5% standard deviation of bias within the heart, liver, and kidneys. This implies that three-class segmentation can be sufficient to achieve small variation of bias for imaging these three organs. Finally, we have found that inter- and intra-patient lung density variations contribute almost equally to the overall standard deviation of bias within the lungs.

Assessment of lobar perfusion in smokers according to the presence and severity of emphysema: preliminary experience with dual-energy CT angiography

International Nuclear Information System (INIS)

Pansini, Vittorio; Remy-Jardin, Martine; Faivre, Jean-Baptiste; Remy, Jacques; Schmidt, Bernhard; Dejardin-Bothelo, Alexis; Perez, Thierry; Delannoy, Valerie; Duhamel, Alain

2009-01-01

The purpose of the study was to assess pulmonary perfusion on a lobar level in smokers using dual-energy computed tomography (CT). Forty-seven smokers and ten non-smokers underwent a dual-energy multi-detector CT angiogram of the chest that allowed automatic quantification of emphysema and determination of the iodine content at the level of the microcirculation (i.e. ''perfusion imaging''). Emphysema was present in 37 smokers and absent in ten smokers. Smokers with an upper lobe predominance of emphysema (n = 8) had: (1) significantly lower attenuation enhancement values in the upper lobes compared with smokers without emphysema; (2) the lobes with the most severe emphysematous changes had a statistically significantly higher percentage of emphysema (p = 0.0001) and lower mean attenuation enhancement values (p = 0.0001) than the ipsilateral lobes with less severe emphysema, matching parenchymal destruction; (3) a correlation was found between the difference in percentage of emphysema between the upper and lower lobes and the difference in attenuation attenuation enhancement values in the corresponding lobes (p = 0.0355; r = -0.54). Regional alterations of lung perfusion can be depicted by dual-energy CT in smokers with predominant emphysema. (orig.)

Comparison of MR-based attenuation correction and CT-based attenuation correction of whole-body PET/MR imaging

Energy Technology Data Exchange (ETDEWEB)

Izquierdo-Garcia, David [Mount Sinai School of Medicine, Translational and Molecular Imaging Institute, New York, NY (United States); Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA (United States); Sawiak, Stephen J. [University of Cambridge, Wolfson Brain Imaging Centre, Cambridge (United Kingdom); Knesaurek, Karin; Machac, Joseph [Mount Sinai School of Medicine, Division of Nuclear Medicine, Department of Radiology, New York, NY (United States); Narula, Jagat [Mount Sinai School of Medicine, Department of Cardiology, Zena and Michael A. Weiner Cardiovascular Institute and Marie-Josee and Henry R. Kravis Cardiovascular Health Center, New York, NY (United States); Fuster, Valentin [Mount Sinai School of Medicine, Department of Cardiology, Zena and Michael A. Weiner Cardiovascular Institute and Marie-Josee and Henry R. Kravis Cardiovascular Health Center, New York, NY (United States); The Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid (Spain); Fayad, Zahi A. [Mount Sinai School of Medicine, Translational and Molecular Imaging Institute, New York, NY (United States); Mount Sinai School of Medicine, Department of Cardiology, Zena and Michael A. Weiner Cardiovascular Institute and Marie-Josee and Henry R. Kravis Cardiovascular Health Center, New York, NY (United States); Mount Sinai School of Medicine, Department of Radiology, New York, NY (United States)

2014-08-15

The objective of this study was to evaluate the performance of the built-in MR-based attenuation correction (MRAC) included in the combined whole-body Ingenuity TF PET/MR scanner and compare it to the performance of CT-based attenuation correction (CTAC) as the gold standard. Included in the study were 26 patients who underwent clinical whole-body FDG PET/CT imaging and subsequently PET/MR imaging (mean delay 100 min). Patients were separated into two groups: the alpha group (14 patients) without MR coils during PET/MR imaging and the beta group (12 patients) with MR coils present (neurovascular, spine, cardiac and torso coils). All images were coregistered to the same space (PET/MR). The two PET images from PET/MR reconstructed using MRAC and CTAC were compared by voxel-based and region-based methods (with ten regions of interest, ROIs). Lesions were also compared by an experienced clinician. Body mass index and lung density showed significant differences between the alpha and beta groups. Right and left lung densities were also significantly different within each group. The percentage differences in uptake values using MRAC in relation to those using CTAC were greater in the beta group than in the alpha group (alpha group -0.2 ± 33.6 %, R{sup 2} = 0.98, p < 0.001; beta group 10.31 ± 69.86 %, R{sup 2} = 0.97, p < 0.001). In comparison to CTAC, MRAC led to underestimation of the PET values by less than 10 % on average, although some ROIs and lesions did differ by more (including the spine, lung and heart). The beta group (imaged with coils present) showed increased overall PET quantification as well as increased variability compared to the alpha group (imaged without coils). PET data reconstructed with MRAC and CTAC showed some differences, mostly in relation to air pockets, metallic implants and attenuation differences in large bone areas (such as the pelvis and spine) due to the segmentation limitation of the MRAC method. (orig.)

Comparison of MR-based attenuation correction and CT-based attenuation correction of whole-body PET/MR imaging

International Nuclear Information System (INIS)

Izquierdo-Garcia, David; Sawiak, Stephen J.; Knesaurek, Karin; Machac, Joseph; Narula, Jagat; Fuster, Valentin; Fayad, Zahi A.

2014-01-01

The objective of this study was to evaluate the performance of the built-in MR-based attenuation correction (MRAC) included in the combined whole-body Ingenuity TF PET/MR scanner and compare it to the performance of CT-based attenuation correction (CTAC) as the gold standard. Included in the study were 26 patients who underwent clinical whole-body FDG PET/CT imaging and subsequently PET/MR imaging (mean delay 100 min). Patients were separated into two groups: the alpha group (14 patients) without MR coils during PET/MR imaging and the beta group (12 patients) with MR coils present (neurovascular, spine, cardiac and torso coils). All images were coregistered to the same space (PET/MR). The two PET images from PET/MR reconstructed using MRAC and CTAC were compared by voxel-based and region-based methods (with ten regions of interest, ROIs). Lesions were also compared by an experienced clinician. Body mass index and lung density showed significant differences between the alpha and beta groups. Right and left lung densities were also significantly different within each group. The percentage differences in uptake values using MRAC in relation to those using CTAC were greater in the beta group than in the alpha group (alpha group -0.2 ± 33.6 %, R 2 = 0.98, p 2 = 0.97, p < 0.001). In comparison to CTAC, MRAC led to underestimation of the PET values by less than 10 % on average, although some ROIs and lesions did differ by more (including the spine, lung and heart). The beta group (imaged with coils present) showed increased overall PET quantification as well as increased variability compared to the alpha group (imaged without coils). PET data reconstructed with MRAC and CTAC showed some differences, mostly in relation to air pockets, metallic implants and attenuation differences in large bone areas (such as the pelvis and spine) due to the segmentation limitation of the MRAC method. (orig.)

Effects of attenuation map accuracy on attenuation-corrected micro-SPECT images

NARCIS (Netherlands)

Wu, C.; Gratama van Andel, H.A.; Laverman, P.; Boerman, O.C.; Beekman, F.J.

2013-01-01

Background In single-photon emission computed tomography (SPECT), attenuation of photon flux in tissue affects quantitative accuracy of reconstructed images. Attenuation maps derived from X-ray computed tomography (CT) can be employed for attenuation correction. The attenuation coefficients as well

Fat Attenuation at CT in Anorexia Nervosa

Science.gov (United States)

Gill, Corey M.; Torriani, Martin; Murphy, Rachel; Harris, Tamara B.; Miller, Karen K.; Klibanski, Anne

2016-01-01

Purpose To investigate the composition, cross-sectional area (CSA), and hormonal correlates of different fat depots in women with anorexia nervosa (AN) and control subjects with normal weights to find out whether patients with AN have lower fat CSA but higher attenuation than did control subjects and whether these changes may be mediated by gonadal steroids, cortisol, and thyroid hormones. Materials and Methods This study was institutional review board approved and HIPAA compliant. Written informed consent was obtained. Forty premenopausal women with AN and 40 normal-weight women of comparable age (mean age ± standard deviation, 26 years ± 5) were studied. All individuals underwent computed tomography of the abdomen and thigh with a calibration phantom. Abdominal subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), thigh SAT, and thigh intermuscular adipose tissue CSA and attenuation were quantified. Serum estradiol, thyroid hormones, and urinary free cortisol levels were assessed. Variables were compared by using analysis of variance. Associations were examined by using linear regression analysis. Results Women with AN had higher fat attenuation than did control subjects (−100.1 to −46.7 HU vs −117.6 to −61.8 HU, P < .0001), despite lower fat CSA (2.0–62.8 cm2 vs 5.5–185.9 cm2, P < .0001). VAT attenuation but not CSA was inversely associated with lowest prior lifetime body mass index in AN (r = −0.71, P = .006). Serum estradiol levels were inversely associated with fat attenuation (r = −0.34 to −0.61, P = .03 to <.0001) and were positively associated with fat CSA of all compartments (r = 0.42–0.64, P = .007 to <.0001). Thyroxine levels and urinary free cortisol levels were positively associated with thigh SAT attenuation (r = 0.64 [P = .006] and r = 0.68 [P = .0004], respectively) and were inversely associated with abdominal SAT and VAT CSA (r = −0.44 to −0.58, P = .04 to .02). Conclusion Women with AN have differences in fat

Improvement of quantitation in SPECT: Attenuation and scatter correction using non-uniform attenuation data

International Nuclear Information System (INIS)

Mukai, T.; Torizuka, K.; Douglass, K.H.; Wagner, H.N.

1985-01-01

Quantitative assessment of tracer distribution with single photon emission computed tomography (SPECT) is difficult because of attenuation and scattering of gamma rays within the object. A method considering the source geometry was developed, and effects of attenuation and scatter on SPECT quantitation were studied using phantoms with non-uniform attenuation. The distribution of attenuation coefficients (μ) within the source were obtained by transmission CT. The attenuation correction was performed by an iterative reprojection technique. The scatter correction was done by convolution of the attenuation corrected image and an appropriate filter made by line source studies. The filter characteristics depended on μ and SPEC measurement at each pixel. The SPECT obtained by this method showed the most reasonable results than the images reconstructed by other methods. The scatter correction could compensate completely for a 28% scatter components from a long line source, and a 61% component for thick and extended source. Consideration of source geometries was necessary for effective corrections. The present method is expected to be valuable for the quantitative assessment of regional tracer activity

Improved quantitation and reproducibility in multi-PET/CT lung studies by combining CT information.

Science.gov (United States)

Holman, Beverley F; Cuplov, Vesna; Millner, Lynn; Endozo, Raymond; Maher, Toby M; Groves, Ashley M; Hutton, Brian F; Thielemans, Kris

2018-06-05

Matched attenuation maps are vital for obtaining accurate and reproducible kinetic and static parameter estimates from PET data. With increased interest in PET/CT imaging of diffuse lung diseases for assessing disease progression and treatment effectiveness, understanding the extent of the effect of respiratory motion and establishing methods for correction are becoming more important. In a previous study, we have shown that using the wrong attenuation map leads to large errors due to density mismatches in the lung, especially in dynamic PET scans. Here, we extend this work to the case where the study is sub-divided into several scans, e.g. for patient comfort, each with its own CT (cine-CT and 'snap shot' CT). A method to combine multi-CT information into a combined-CT has then been developed, which averages the CT information from each study section to produce composite CT images with the lung density more representative of that in the PET data. This combined-CT was applied to nine patients with idiopathic pulmonary fibrosis, imaged with dynamic 18 F-FDG PET/CT to determine the improvement in the precision of the parameter estimates. Using XCAT simulations, errors in the influx rate constant were found to be as high as 60% in multi-PET/CT studies. Analysis of patient data identified displacements between study sections in the time activity curves, which led to an average standard error in the estimates of the influx rate constant of 53% with conventional methods. This reduced to within 5% after use of combined-CTs for attenuation correction of the study sections. Use of combined-CTs to reconstruct the sections of a multi-PET/CT study, as opposed to using the individually acquired CTs at each study stage, produces more precise parameter estimates and may improve discrimination between diseased and normal lung.

Low-tube-voltage (80 kVp) CT aortography using 320-row volume CT with adaptive iterative reconstruction: lower contrast medium and radiation dose

Energy Technology Data Exchange (ETDEWEB)

Chen, Chien-Ming; Chu, Sung-Yu; Hsu, Ming-Yi [Chang Gung University, Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital Linkou, College of Medicine, Taoyuan (China); Liao, Ying-Lan [National Tsing Hua University, Department of Biomedical Engineering and Environmental Sciences, Hsinchu (China); Tsai, Hui-Yu [Chang Gung University, Department of Medical Imaging and Radiological Sciences, College of Medicine, Taoyuan (China); Chang Gung University, Healthy Aging Research Center, Taoyuan (China); Chang Gung University, Department of Medical Imaging and Radiological Sciences, Taoyuan (China)

2014-02-15

To evaluate CT aortography at reduced tube voltage and contrast medium dose while maintaining image quality through iterative reconstruction (IR). The Institutional Review Board approved a prospective study of 48 patients who underwent follow-up CT aortography. We performed intra-individual comparisons of arterial phase images using 120 kVp (standard tube voltage) and 80 kVp (low tube voltage). Low-tube-voltage imaging was performed on a 320-detector CT with IR following injection of 40 ml of contrast medium. We assessed aortic attenuation, aortic attenuation gradient, image noise, contrast-to-noise ratio (CNR), volume CT dose index (CTDI{sub vol}), and figure of merit (FOM) of image noise and CNR. Two readers assessed images for diagnostic quality, image noise, and artefacts. The low-tube-voltage protocol showed 23-31 % higher mean aortic attenuation and image noise (both P < 0.01) than the standard-tube-voltage protocol, but no significant difference in the CNR and aortic attenuation gradients. The low-tube-voltage protocol showed a 48 % reduction in CTDI{sub vol} and an 80 % increase in FOM of CNR. Subjective diagnostic quality was similar for both protocols, but low-tube-voltage images showed greater image noise (P = 0.01). Application of IR to an 80-kVp CT aortography protocol allows radiation dose and contrast medium reduction without affecting image quality. (orig.)

Assessment of the optimal temporal window for intravenous CT cholangiography

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Schindera, Sebastian T.; Nelson, Rendon C.; Paulson, Erik K.; DeLong, David M.; Merkle, Elmar M. [Duke University Medical Center, Department of Radiology, P.O. Box 3808, Durham, NC (United States)

2007-10-15

The optimal temporal window of intravenous (IV) computed tomography (CT) cholangiography was prospectively determined. Fifteen volunteers (eight women, seven men; mean age, 38 years) underwent dynamic CT cholangiography. Two unenhanced images were acquired at the porta hepatis. Starting 5 min after initiation of IV contrast infusion (20 ml iodipamide meglumine 52%), 15 pairs of images at 5-min intervals were obtained. Attenuation of the extrahepatic bile duct (EBD) and the liver parenchyma was measured. Two readers graded visualization of the higher-order biliary branches. The first biliary opacification in the EBD occurred between 15 and 25 min (mean, 22.3 min {+-} 3.2) after initiation of the contrast agent. Biliary attenuation plateaued between the 35- and the 75-min time points. Maximum hepatic parenchymal enhancement was 18.5 HU {+-} 2.7. Twelve subjects demonstrated poor or non-visualization of higher-order biliary branches; three showed good or excellent visualization. Body weight and both biliary attenuation and visualization of the higher-order biliary branches correlated significantly (P<0.05). For peak enhancement of the biliary tree, CT cholangiography should be performed no earlier than 35 min after initiation of IV infusion. For a fixed contrast dose, superior visualization of the biliary system is achieved in subjects with lower body weight. (orig.)

Attenuation correction in positron emission tomography: Quality control and performance evaluation

International Nuclear Information System (INIS)

Nalis, J.; Courbon, F.; Brillouet, S.; Marre, D.; Serre, D.; Colin, V.; Caselles, O.; Flouzat, G.

2007-01-01

Objective: The aim of this study is to evaluate the performance of the Computed Tomography based Attenuation Correction (CTAC) for Positron Emission Tomography (PET) data. Attenuation maps containing linear attenuation coefficients at 511 keV (LAC 511 keV ) are calculated by trilinear conversion of Hounsfield Units (HU) obtained from CT slices after matrix size-reduction and Gaussian filtering. Our work focusses on this trilinear conversion. Materials and methods: CT slices of an electron density phantom. composed of 17 cylindrical inserts made of different tissue-equivalent materials, were acquired using a Discovery ST4 PET-CT. Data were processed with a customized version of CT quality control software, giving automatically the experimental conversion function: LAC 511 keV =f(HU). Furthermore, data from patient datasets were assessed using both smoothed CT slices and attenuation maps. Results: LAC 511 keV extracted from phantom data are in good correlation with the expected theoretical values, except for the standard 10 mm diameter dense bone insert, where the obtained CTAC values are underestimated, Assuming a sample size issue, similar acquisitions were performed with a special 30 mm-diameter dense bone insert, confirming the underestimation as a consequence of the sample size. (authors)

Fatty liver: prospective comparative study with sonography and CT

International Nuclear Information System (INIS)

Kim, Sung Jin; Kim, Y. M.; Kim, W. S.; Choi, B. I.; Lee, J. S.; Han, C. K.; Kim, C. W.

1990-01-01

To identify the reasonable criteria in detection of the degree of Fatty liver, we prospectively evaluated sonograms and CT scans in 33 Patients With bright liver on sonography. On sonograms, we analyzed the echogenicity of the liver, acoustic attenuation, and visualization of the portal vein and the diaphragm, Each criterion was scored from 0 to 2. CT criterion for fatty liver was assessed by the attenuation difference between the liver and the spleen on nonocontrast CT scans, The average sonographic grade for CT Grade I was 1.3, Grade II was 2.1,and Grade III was 2.8. The accurate detection rate of each sonographic grade was as follows, Grade

Precision and accuracy in CT attenuation measurement of vascular wall using region-of-interest supported by differentiation curve

International Nuclear Information System (INIS)

Suzuki, Shigeru; Kidouchi, Takashi; Kuwahara, Sadatoshi; Vembar, Mani; Takei, Ryoji; Yamamoto, Asako

2012-01-01

Objectives: To evaluate the precision and accuracy in CT attenuation measurement of vascular wall using region-of-interest (ROI) supported by differentiation curves. Study design: We used vascular models (actual attenuation value of the wall: 87 HU) with wall thicknesses of 1.5, 1.0, or 0.5 mm, filled with contrast material of 250, 348, or 436 HU. The nine vascular models were scanned with a 64-detector CT. The wall attenuation values were measured using three sizes (diameter: 0.5, 1.0, and 1.5 mm) of ROIs without differentiation curves. Sixteen measurements were repeated for each vascular model by each of two operators. Measurements supported by differentiation curves were also performed. We used analyses of variance with repeated measures for the measured attenuations for each size of the ROI. Results: Without differentiation curves, there were significant differences in the attenuation values of the wall among the three densities of contrast material, and the attenuation values tended to be overestimated more as the contrast material density increased. Operator dependencies were also found in measurements for 0.5- and 1.5-mm thickness models. With differentiation curves, measurements were not possible for 0.5- and 1.0-mm thickness models. Using differentiation curves for 1.5-mm thickness models with a ROI of 1.0- or 1.5-mm diameter, the wall attenuations were not affected by the contrast material densities and were operator independent, measuring between 75 and 103 HU. Conclusions: The use of differentiation curves can improve the precision and accuracy in wall attenuation measurement using a ROI technique, while measurements for walls of ≤1.0 mm thickness are difficult.

SU-C-9A-06: The Impact of CT Image Used for Attenuation Correction in 4D-PET

International Nuclear Information System (INIS)

Cui, Y; Bowsher, J; Yan, S; Cai, J; Das, S; Yin, F

2014-01-01

Purpose: To evaluate the appropriateness of using 3D non-gated CT image for attenuation correction (AC) in a 4D-PET (gated PET) imaging protocol used in radiotherapy treatment planning simulation. Methods: The 4D-PET imaging protocol in a Siemens PET/CT simulator (Biograph mCT, Siemens Medical Solutions, Hoffman Estates, IL) was evaluated. CIRS Dynamic Thorax Phantom (CIRS Inc., Norfolk, VA) with a moving glass sphere (8 mL) in the middle of its thorax portion was used in the experiments. The glass was filled with 18 F-FDG and was in a longitudinal motion derived from a real patient breathing pattern. Varian RPM system (Varian Medical Systems, Palo Alto, CA) was used for respiratory gating. Both phase-gating and amplitude-gating methods were tested. The clinical imaging protocol was modified to use three different CT images for AC in 4D-PET reconstruction: first is to use a single-phase CT image to mimic actual clinical protocol (single-CT-PET); second is to use the average intensity projection CT (AveIP-CT) derived from 4D-CT scanning (AveIP-CT-PET); third is to use 4D-CT image to do the phase-matched AC (phase-matching- PET). Maximum SUV (SUVmax) and volume of the moving target (glass sphere) with threshold of 40% SUVmax were calculated for comparison between 4D-PET images derived with different AC methods. Results: The SUVmax varied 7.3%±6.9% over the breathing cycle in single-CT-PET, compared to 2.5%±2.8% in AveIP-CT-PET and 1.3%±1.2% in phasematching PET. The SUVmax in single-CT-PET differed by up to 15% from those in phase-matching-PET. The target volumes measured from single- CT-PET images also presented variations up to 10% among different phases of 4D PET in both phase-gating and amplitude-gating experiments. Conclusion: Attenuation correction using non-gated CT in 4D-PET imaging is not optimal process for quantitative analysis. Clinical 4D-PET imaging protocols should consider phase-matched 4D-CT image if available to achieve better accuracy

SU-C-9A-06: The Impact of CT Image Used for Attenuation Correction in 4D-PET

Energy Technology Data Exchange (ETDEWEB)

Cui, Y; Bowsher, J; Yan, S; Cai, J; Das, S; Yin, F [Duke University Medical Center, Durham, NC (United States)

2014-06-01

Purpose: To evaluate the appropriateness of using 3D non-gated CT image for attenuation correction (AC) in a 4D-PET (gated PET) imaging protocol used in radiotherapy treatment planning simulation. Methods: The 4D-PET imaging protocol in a Siemens PET/CT simulator (Biograph mCT, Siemens Medical Solutions, Hoffman Estates, IL) was evaluated. CIRS Dynamic Thorax Phantom (CIRS Inc., Norfolk, VA) with a moving glass sphere (8 mL) in the middle of its thorax portion was used in the experiments. The glass was filled with {sup 18}F-FDG and was in a longitudinal motion derived from a real patient breathing pattern. Varian RPM system (Varian Medical Systems, Palo Alto, CA) was used for respiratory gating. Both phase-gating and amplitude-gating methods were tested. The clinical imaging protocol was modified to use three different CT images for AC in 4D-PET reconstruction: first is to use a single-phase CT image to mimic actual clinical protocol (single-CT-PET); second is to use the average intensity projection CT (AveIP-CT) derived from 4D-CT scanning (AveIP-CT-PET); third is to use 4D-CT image to do the phase-matched AC (phase-matching- PET). Maximum SUV (SUVmax) and volume of the moving target (glass sphere) with threshold of 40% SUVmax were calculated for comparison between 4D-PET images derived with different AC methods. Results: The SUVmax varied 7.3%±6.9% over the breathing cycle in single-CT-PET, compared to 2.5%±2.8% in AveIP-CT-PET and 1.3%±1.2% in phasematching PET. The SUVmax in single-CT-PET differed by up to 15% from those in phase-matching-PET. The target volumes measured from single- CT-PET images also presented variations up to 10% among different phases of 4D PET in both phase-gating and amplitude-gating experiments. Conclusion: Attenuation correction using non-gated CT in 4D-PET imaging is not optimal process for quantitative analysis. Clinical 4D-PET imaging protocols should consider phase-matched 4D-CT image if available to achieve better accuracy.

CT virtual intravascular endoscopy assessment of coronary artery plaques: A preliminary study

International Nuclear Information System (INIS)

Sun Zhonghua; Dimpudus, Franky Jacobus; Nugroho, Johanes; Adipranoto, Jeffrey Daniel

2010-01-01

Purpose: The purpose of this study was to investigate the potential value of CT virtual intravascular endoscopy (VIE) in the visualization and assessment of coronary plaques in patients suspected of coronary artery disease. Materials and methods: 20 (13 men, 7 women, mean age 54 years) consecutive patients with suspected coronary artery disease undergoing 64-slice CT angiography were included in the study. Four main coronary artery branches were assessed with regard to the presence of coronary plaques based on 2D axial, multiplanar reformation, 3D volume rendering and VIE visualizations. The coronary plaques were characterized into calcified, noncalcified and mixed plaques. The intraluminal appearances of these coronary plaques were demonstrated with VIE images and correlated with 2D and 3D images to determine the diagnostic value of VIE for the assessment of the plaques. Results: VIE was able to identify and demonstrate the intraluminal appearances of coronary plaques in 18 patients involving 32 coronary artery branches which were shown as an irregularly intraluminal protruding sign in extensively calcified plaques and smooth protruding appearance in noncalcified or focally calcified plaques. An irregular intraluminal appearance was also noticed in the presence of mixed plaques due to variable components with different CT attenuations contained within the plaques. VIE accurately confirmed the degree of coronary stenosis or occlusion despite the presence of heavy calcification. Conclusion: VIE could be used as a complementary tool to conventional CT visualizations for the analysis of luminal changes and assessment of disease extent caused by the coronary plaques.

CT and MR imaging of the liver. Clinical importance of nutritional status

International Nuclear Information System (INIS)

Leander, P.; Sjoeberg, S.; Hoeglund, P.

2000-01-01

Purpose: In an experimental study in rats a correlation between nutritional status and hepatic attenuation in CT and signal intensities in MR imaging was shown. Is physiological nutritional status of importance in clinical CT and MR imaging? Material and methods: In a cross-over study including 12 healthy volunteers (6 women and 6 men, mean age 34 years), CT and MR imaging of the liver were performed with nutritional status at three different levels, i.e., normal, fasting and after glycogen-rich meals. CT and MR were performed on clinical imaging systems and hepatic attenuation and signal intensity, respectively, were assessed. In MR, T1-weighted, proton density-weighted and T2-weighted pulse-sequences were used. Results: In CT there were significantly (p<0.01) higher liver attenuations in normal nutritional status and after glycogen rich-meals compared to the fasting condition. The difference between fasting and glycogen-rich meals were 10.5 HU for men, 7.4 for women and mean 8.8 HU for all 12 volunteers. In MR imaging the differences were small and non-significant. The results of this study are in accordance with an earlier experimental study in rats. Conclusion: In CT it may be of importance not to have patients in a fasting condition as it lowers the attenuation in normal liver tissue. The findings are important for planning of clinical studies where hepatic attenuation will be assessed and may be of some importance in clinical CT. In MR imaging the results indicate that the nutritional status is of less importance

Development of digital phantoms based on a finite element model to simulate low-attenuation areas in CT imaging for pulmonary emphysema quantification.

Science.gov (United States)

Diciotti, Stefano; Nobis, Alessandro; Ciulli, Stefano; Landini, Nicholas; Mascalchi, Mario; Sverzellati, Nicola; Innocenti, Bernardo

2017-09-01

To develop an innovative finite element (FE) model of lung parenchyma which simulates pulmonary emphysema on CT imaging. The model is aimed to generate a set of digital phantoms of low-attenuation areas (LAA) images with different grades of emphysema severity. Four individual parameter configurations simulating different grades of emphysema severity were utilized to generate 40 FE models using ten randomizations for each setting. We compared two measures of emphysema severity (relative area (RA) and the exponent D of the cumulative distribution function of LAA clusters size) between the simulated LAA images and those computed directly on the models output (considered as reference). The LAA images obtained from our model output can simulate CT-LAA images in subjects with different grades of emphysema severity. Both RA and D computed on simulated LAA images were underestimated as compared to those calculated on the models output, suggesting that measurements in CT imaging may not be accurate in the assessment of real emphysema extent. Our model is able to mimic the cluster size distribution of LAA on CT imaging of subjects with pulmonary emphysema. The model could be useful to generate standard test images and to design physical phantoms of LAA images for the assessment of the accuracy of indexes for the radiologic quantitation of emphysema.

Dual-energy attenuation coefficient decomposition with differential filtration and application to a microCT scanner

International Nuclear Information System (INIS)

Taschereau, R; Silverman, R W; Chatziioannou, A F

2010-01-01

Dual-energy x-ray computed tomography (DECT) has the capability to decompose attenuation coefficients using two basis functions and has proved its potential in reducing beam-hardening artifacts from reconstructed images. The method typically involves two successive scans with different x-ray tube voltage settings. This work proposes an approach to dual-energy imaging through x-ray beam filtration that requires only one scan and a single tube voltage setting. It has been implemented in a preclinical microCT tomograph with minor modifications. Retrofitting of the microCT scanner involved the addition of an automated filter wheel and modifications to the acquisition and reconstruction software. Results show that beam-hardening artifacts are reduced to noise level. Acquisition of a μ-Compton image is well suited for attenuation-correction of PET images while dynamic energy selection (4D viewing) offers flexibility in image viewing by adjusting contrast and noise levels to suit the task at hand. All dual-energy and single energy reference scans were acquired at the same soft tissue dose level of 50 mGy.

Dual-energy attenuation coefficient decomposition with differential filtration and application to a microCT scanner

Energy Technology Data Exchange (ETDEWEB)

Taschereau, R; Silverman, R W; Chatziioannou, A F [Crump Institute for Molecular Imaging, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 (United States)], E-mail: rtaschereau@mednet.ucla.edu

2010-02-21

Dual-energy x-ray computed tomography (DECT) has the capability to decompose attenuation coefficients using two basis functions and has proved its potential in reducing beam-hardening artifacts from reconstructed images. The method typically involves two successive scans with different x-ray tube voltage settings. This work proposes an approach to dual-energy imaging through x-ray beam filtration that requires only one scan and a single tube voltage setting. It has been implemented in a preclinical microCT tomograph with minor modifications. Retrofitting of the microCT scanner involved the addition of an automated filter wheel and modifications to the acquisition and reconstruction software. Results show that beam-hardening artifacts are reduced to noise level. Acquisition of a {mu}-Compton image is well suited for attenuation-correction of PET images while dynamic energy selection (4D viewing) offers flexibility in image viewing by adjusting contrast and noise levels to suit the task at hand. All dual-energy and single energy reference scans were acquired at the same soft tissue dose level of 50 mGy.

Assessment of CT numbers in limited and medium field-of-view scans taken using Accuitomo 170 and Veraviewepocs 3De cone-beam computed tomography scanners

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Matheus L. [Dept. of Oral Diagnosis, Piracicaba Dental School, State University of Campinas, Campinas (Brazil); Tosoni, Guilherme M. [Dept. of Oral Diagnosis and Surgery, Araraquara Dental School, Sao Paulo State University, Araraquara (Brazil); Lindsey, David H.; Mendoza, Kristopher; Tetradis, Sotirios; Mallya, Sanjay M. [Section of Oral and Maxillofacial Radiology, School of Dentistry, University of California, Los Angeles (United States)

2014-12-15

To assess the influence of anatomic location on the relationship between computed tomography (CT) number and X-ray attenuation in limited and medium field-of-view (FOV) scans. Tubes containing solutions with different concentrations of K2HPO4 were placed in the tooth sockets of a human head phantom. Cone-beam computed tomography (CBCT) scans were acquired, and CT numbers of the K{sub 2}HPO{sub 4} solutions were measured. The relationship between CT number and K{sub 2}HPO{sub 4} concentration was examined by linear regression analyses. Then, the variation in CT number according to anatomic location was examined. The relationship between K{sub 2}HPO{sub 4} concentration and CT number was strongly linear. The slopes of the linear regressions for the limited FOVs were almost 2-fold lower than those for the medium FOVs. The absolute CT number differed between imaging protocols and anatomic locations. There is a strong linear relationship between X-ray attenuation and CT number. The specific imaging protocol and anatomic location of the object strongly influence this relationship.

CT findings of pancreatic carcinoma. Evaluation with the combined method of early enhancement CT and high dose enhancement CT

International Nuclear Information System (INIS)

Itoh, Shigeki; Endo, Tokiko; Isomura, Takayuki; Ishigaki, Takeo; Ikeda, Mitsuru; Senda, Kouhei.

1995-01-01

Computed tomographic (CT) findings of pancreatic ductal adenocarcinoma were studied with the combined method of early enhancement CT and high dose enhancement CT in 72 carcinomas. Common Findings were change in pancreatic contour, abnormal attenuation in a tumor and dilatation of the main pancreatic duct. The incidence of abnormal attenuation and dilatation of the main pancreatic duct and bile duct was constant regardless of tumor size. The finding of hypoattenuation at early enhancement CT was most useful for demonstrating a carcinoma. However, this finding was negative in ten cases, five of which showed inhomogenous hyperattenuation at high dose enhancement CT. The detection of change in pancreatic contour and dilatation of the main pancreatic duct was most frequent at high dose enhancement CT. The finding of change in pancreatic contour and/or abnormal attenuation in a tumor could be detected in 47 cases at plain CT, 66 at early enhancement CT and 65 at high dose enhancement CT. Since the four cases in which neither finding was detected by any CT method showed dilatated main pancreatic duct, there was no case without abnormal CT findings. This combined CT method will be a reliable diagnostic technique in the imaging of pancreatic carcinoma. (author)

Simulation evaluation of quantitative myocardial perfusion assessment from cardiac CT

Science.gov (United States)

Bindschadler, Michael; Modgil, Dimple; Branch, Kelley R.; La Riviere, Patrick J.; Alessio, Adam M.

2014-03-01

Contrast enhancement on cardiac CT provides valuable information about myocardial perfusion and methods have been proposed to assess perfusion with static and dynamic acquisitions. There is a lack of knowledge and consensus on the appropriate approach to ensure 1) sufficient diagnostic accuracy for clinical decisions and 2) low radiation doses for patient safety. This work developed a thorough dynamic CT simulation and several accepted blood flow estimation techniques to evaluate the performance of perfusion assessment across a range of acquisition and estimation scenarios. Cardiac CT acquisitions were simulated for a range of flow states (Flow = 0.5, 1, 2, 3 ml/g/min, cardiac output = 3,5,8 L/min). CT acquisitions were simulated with a validated CT simulator incorporating polyenergetic data acquisition and realistic x-ray flux levels for dynamic acquisitions with a range of scenarios including 1, 2, 3 sec sampling for 30 sec with 25, 70, 140 mAs. Images were generated using conventional image reconstruction with additional image-based beam hardening correction to account for iodine content. Time attenuation curves were extracted for multiple regions around the myocardium and used to estimate flow. In total, 2,700 independent realizations of dynamic sequences were generated and multiple MBF estimation methods were applied to each of these. Evaluation of quantitative kinetic modeling yielded blood flow estimates with an root mean square error (RMSE) of ~0.6 ml/g/min averaged across multiple scenarios. Semi-quantitative modeling and qualitative static imaging resulted in significantly more error (RMSE = ~1.2 and ~1.2 ml/min/g respectively). For quantitative methods, dose reduction through reduced temporal sampling or reduced tube current had comparable impact on the MBF estimate fidelity. On average, half dose acquisitions increased the RMSE of estimates by only 18% suggesting that substantial dose reductions can be employed in the context of quantitative myocardial

Clinical Applications of a CT Window Blending Algorithm: RADIO (Relative Attenuation-Dependent Image Overlay).

Science.gov (United States)

Mandell, Jacob C; Khurana, Bharti; Folio, Les R; Hyun, Hyewon; Smith, Stacy E; Dunne, Ruth M; Andriole, Katherine P

2017-06-01

A methodology is described using Adobe Photoshop and Adobe Extendscript to process DICOM images with a Relative Attenuation-Dependent Image Overlay (RADIO) algorithm to visualize the full dynamic range of CT in one view, without requiring a change in window and level settings. The potential clinical uses for such an algorithm are described in a pictorial overview, including applications in emergency radiology, oncologic imaging, and nuclear medicine and molecular imaging.

Measurement of vascular wall attenuation: Comparison of CT angiography using model-based iterative reconstruction with standard filtered back-projection algorithm CT in vitro

International Nuclear Information System (INIS)

Suzuki, Shigeru; Machida, Haruhiko; Tanaka, Isao; Ueno, Eiko

2012-01-01

Objectives: To compare the performance of model-based iterative reconstruction (MBIR) with that of standard filtered back projection (FBP) for measuring vascular wall attenuation. Study design: After subjecting 9 vascular models (actual attenuation value of wall, 89 HU) with wall thickness of 0.5, 1.0, or 1.5 mm that we filled with contrast material of 275, 396, or 542 HU to scanning using 64-detector computed tomography (CT), we reconstructed images using MBIR and FBP (Bone, Detail kernels) and measured wall attenuation at the center of the wall for each model. We performed attenuation measurements for each model and additional supportive measurements by a differentiation curve. We analyzed statistics using analyzes of variance with repeated measures. Results: Using the Bone kernel, standard deviation of the measurement exceeded 30 HU in most conditions. In measurements at the wall center, the attenuation values obtained using MBIR were comparable to or significantly closer to the actual wall attenuation than those acquired using Detail kernel. Using differentiation curves, we could measure attenuation for models with walls of 1.0- or 1.5-mm thickness using MBIR but only those of 1.5-mm thickness using Detail kernel. We detected no significant differences among the attenuation values of the vascular walls of either thickness (MBIR, P = 0.1606) or among the 3 densities of intravascular contrast material (MBIR, P = 0.8185; Detail kernel, P = 0.0802). Conclusions: Compared with FBP, MBIR reduces both reconstruction blur and image noise simultaneously, facilitates recognition of vascular wall boundaries, and can improve accuracy in measuring wall attenuation.

Hyper-attenuating nodules on CT during arterial portography (CTAP). Analysis using single-level dynamic CTAP

International Nuclear Information System (INIS)

Nasu, Akihiro; Kita, Ryuichi; Sakamoto, Yasuaki

2007-01-01

Recently several cases of hyper-attenuating nodules on CT during arterial portography (CTAP) have been reported as the chance of meticulous examination has been increasing. For the study reported here, seven cases of hyper-attenuating nodules on CTAP were analyzed by means of single-level dynamic CTAP (sCTAP). Peak values of the time-density curve from the 7 cases were 110, 106, 71, 75, 65, 45, 246 Hounsfield unit (HU) for the ROIs (regions of interest) placed on the nodule, and 63, 73, 41, 35, 20, 28, 22 HU for those placed on the surrounding liver parenchyma, respectively. Average peak value in another set of 46 cases as a control, including chronic hepatitis, liver cirrhosis and normal liver, was 55.3±17.6 HU. These results seem to indicate that portal flow shows an absolute increase in some cases of hyper-attenuating nodules on CTAP and that a decreased portal flow in the surrounding parencyma may cause the visual effect of hyper-attenuation on CTAP in some cases. (author)

Recurrent pyogenic cholangitis: clinico-pathologic correlation of focal attenuation differences on multi-phasic spiral CT

International Nuclear Information System (INIS)

Jeong, Jun Yong; Han, Joon Koo; Kim, Tae Kyoung; Kim, Seog Joon; Kim, Hyun Bum; Choi, Byung Ihn

2002-01-01

To determine the clinical and the pathologic significance of the focal attenuation differences (FAD) and bile duct wall enhancement occurring in recurrent pyogenic cholangitis (RPC) and seen at multiphasic spiral CT. Among the multiphasic (non-contrast, arterial and portal or delayed phase) spiral CT findings of 60 consecutive patients, two types of FAD were noted during the non-contrast phase. These were Type A (iso) and Type B (low attenuation), and their distribution pattern (lobar versus patchy, multifocal) and the and the presence or absence of bile duct wall enhancement were recorded. The radiologic findings were correlated with the clinical and pathologic findings. Two types of FAD were noted in 40 of the 60 patients. Active in flammation was present in 19 of the 27 with Type-A and in ten of the 15 in whom the presence of RPC was pathologically proven. Ten of the 13 with Type-B FAD were in a subclinical state, and nine of the ten in whom RPC was pathologically proven had chronic inflammation. Among 20 patients who did not have FAD, RPC was subclinical in 18 and dormant in nine of the eleven in whom its presence was pathologically proven (p<0.001). Clinico-pathologic correlation with bile duct wall enhancement and the distribution pattern of FAD showed no statistical significance. The inflammatory activity of RPC can be predicted by analysis of the FAD seen at multiphasic spiral CT

Ultra-low Dose CT for Attenuation Correction of 82Rb Cardiac PET

DEFF Research Database (Denmark)

Sørensen, Maria Balshøj; Bouchelouche, Kirsten; Tolbod, Lars Poulsen

Aim: Myocardial perfusion imaging (MPI) using cardiac PET with tracers like 82Rb and 15O-water is substantially lower in radiation dose than classic MIBI-based SPECT. However, for cardiac PET, the dose contribution of CT for attenuation correction (CTAC) is typically 20-30% of the total dose....... To reduce the total radiation dose of cardiac PET further, we set out to examine if the use of ultra-low dose CTAC (UL-CTAC) would affect the accuracy of the quantitative parameters related to MPI. Furthermore, we examined whether the low quality of the UL-CTAC would affect the technologist’s ability...... to perform manual adjustment for misalignment between PET and CTAC. The CT reconstruction algorithm Q.AC was used to improve quality and consistency of the CTAC. Method: 23 consecutive clinical patients (BMI: 26.9 [range: 15.4-38.8]) referred for 82Rb PET rest and stress imaging were included in the study...

Ultralow dose computed tomography attenuation correction for pediatric PET CT using adaptive statistical iterative reconstruction

International Nuclear Information System (INIS)

Brady, Samuel L.; Shulkin, Barry L.

2015-01-01

Purpose: To develop ultralow dose computed tomography (CT) attenuation correction (CTAC) acquisition protocols for pediatric positron emission tomography CT (PET CT). Methods: A GE Discovery 690 PET CT hybrid scanner was used to investigate the change to quantitative PET and CT measurements when operated at ultralow doses (10–35 mA s). CT quantitation: noise, low-contrast resolution, and CT numbers for 11 tissue substitutes were analyzed in-phantom. CT quantitation was analyzed to a reduction of 90% volume computed tomography dose index (0.39/3.64; mGy) from baseline. To minimize noise infiltration, 100% adaptive statistical iterative reconstruction (ASiR) was used for CT reconstruction. PET images were reconstructed with the lower-dose CTAC iterations and analyzed for: maximum body weight standardized uptake value (SUV bw ) of various diameter targets (range 8–37 mm), background uniformity, and spatial resolution. Radiation dose and CTAC noise magnitude were compared for 140 patient examinations (76 post-ASiR implementation) to determine relative dose reduction and noise control. Results: CT numbers were constant to within 10% from the nondose reduced CTAC image for 90% dose reduction. No change in SUV bw , background percent uniformity, or spatial resolution for PET images reconstructed with CTAC protocols was found down to 90% dose reduction. Patient population effective dose analysis demonstrated relative CTAC dose reductions between 62% and 86% (3.2/8.3–0.9/6.2). Noise magnitude in dose-reduced patient images increased but was not statistically different from predose-reduced patient images. Conclusions: Using ASiR allowed for aggressive reduction in CT dose with no change in PET reconstructed images while maintaining sufficient image quality for colocalization of hybrid CT anatomy and PET radioisotope uptake

Ultralow dose computed tomography attenuation correction for pediatric PET CT using adaptive statistical iterative reconstruction

Energy Technology Data Exchange (ETDEWEB)

Brady, Samuel L., E-mail: samuel.brady@stjude.org [Division of Diagnostic Imaging, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105 (United States); Shulkin, Barry L. [Nuclear Medicine and Department of Radiological Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105 (United States)

2015-02-15

Purpose: To develop ultralow dose computed tomography (CT) attenuation correction (CTAC) acquisition protocols for pediatric positron emission tomography CT (PET CT). Methods: A GE Discovery 690 PET CT hybrid scanner was used to investigate the change to quantitative PET and CT measurements when operated at ultralow doses (10–35 mA s). CT quantitation: noise, low-contrast resolution, and CT numbers for 11 tissue substitutes were analyzed in-phantom. CT quantitation was analyzed to a reduction of 90% volume computed tomography dose index (0.39/3.64; mGy) from baseline. To minimize noise infiltration, 100% adaptive statistical iterative reconstruction (ASiR) was used for CT reconstruction. PET images were reconstructed with the lower-dose CTAC iterations and analyzed for: maximum body weight standardized uptake value (SUV{sub bw}) of various diameter targets (range 8–37 mm), background uniformity, and spatial resolution. Radiation dose and CTAC noise magnitude were compared for 140 patient examinations (76 post-ASiR implementation) to determine relative dose reduction and noise control. Results: CT numbers were constant to within 10% from the nondose reduced CTAC image for 90% dose reduction. No change in SUV{sub bw}, background percent uniformity, or spatial resolution for PET images reconstructed with CTAC protocols was found down to 90% dose reduction. Patient population effective dose analysis demonstrated relative CTAC dose reductions between 62% and 86% (3.2/8.3–0.9/6.2). Noise magnitude in dose-reduced patient images increased but was not statistically different from predose-reduced patient images. Conclusions: Using ASiR allowed for aggressive reduction in CT dose with no change in PET reconstructed images while maintaining sufficient image quality for colocalization of hybrid CT anatomy and PET radioisotope uptake.

Attenuation changes of the normal and ischemic canine kidney. Dynamic CT scanning after intravenous contrast medium bolus

Energy Technology Data Exchange (ETDEWEB)

Jaschke, W.; Lipton, M.J.; Boyd, D.P.; Cann, C.; Strauss, L.; Sievers, R.S.

The potential of CT scanning to explore total and regional renal blood flow was evaluated in a dog model with unilateral renal artery stenosis (n=7, reduction of renal blood flow: 32-75% of base line flow). Attenuation versus time curves were generated for the renal cortex and medulla, as well as for the aorta and renal vein. A fast CT scanner was used which allowed for up to 24 scans/minute at the same level (slice thickness: 10 mm). A total of 10 ml contrast medim was injected into a peripheral vein for each scan series taken. During baseline conditions, the curve of the renal cortex and medulla demonstrated 2 peaks. The first peak was mainly related to early vascular enhancement, whereas the second peak corresponded mainly to the appearance of contrast medium in the distal convolutes and collecting ducts. Ischemia of the kidney resulted in a reduction of the first peak and a flattening of the leading edge slope. Transport of contrast medium through the extravascular compartments of the kidney was delayed during ischemia. Relative renal blood flow was obtained from the CT data by dividing peak enhancement by rise-time as assessed from the cortical curve. All measurements were related to baseline flow and validated by flow measurements using radioactive labeled microspheres (n=5). Correlation was found to be r=0.97. (orig.).

Spiral CT versus conventional CT in the preoperative assessment of metallic intraocular foreign bodies

International Nuclear Information System (INIS)

Prokesch, R.; Bankier, A.; Ba-Ssalamah, A.; Imhof, H.; Lakits, A.; Scholda, C.

1998-01-01

Purpose: To compare the effectiveness of spiral CT versus conventional CT in the preoperative assessment of metallic intraocular foreign bodies. Results: All foreign bodies were detected by each scanning modality on the axial and on the reconstructed planes. The quality of the axial images was similar for spiral and conventional CT. The spiral technique provided high-quality reconstructed images which allowed accurate localization of the foreign bodies in all cases. Reconstructions by conventional technique were inadequate for preoperative assessment. The examination time for the total orbital volume was 18 s for spiral CT and 52 s for conventional CT. Radiation dose delivered to the lens was 35 mGy for spiral CT and 56 mGy for conventional CT axial scanning. Conclusion: Spiral CT multiplanar offers several significant advantages for the preoperative assessment of metallic intraocular foreign bodies compared to the conventional CT technique in clinical practice, including short examination time, minimized motion artifacts, reduced radiation exposure, and accurate localization. (orig.) [de

Measurement of vascular wall attenuation: comparison of CT angiography using model-based iterative reconstruction with standard filtered back-projection algorithm CT in vitro.

Science.gov (United States)

Suzuki, Shigeru; Machida, Haruhiko; Tanaka, Isao; Ueno, Eiko

2012-11-01

To compare the performance of model-based iterative reconstruction (MBIR) with that of standard filtered back projection (FBP) for measuring vascular wall attenuation. After subjecting 9 vascular models (actual attenuation value of wall, 89 HU) with wall thickness of 0.5, 1.0, or 1.5 mm that we filled with contrast material of 275, 396, or 542 HU to scanning using 64-detector computed tomography (CT), we reconstructed images using MBIR and FBP (Bone, Detail kernels) and measured wall attenuation at the center of the wall for each model. We performed attenuation measurements for each model and additional supportive measurements by a differentiation curve. We analyzed statistics using analyzes of variance with repeated measures. Using the Bone kernel, standard deviation of the measurement exceeded 30 HU in most conditions. In measurements at the wall center, the attenuation values obtained using MBIR were comparable to or significantly closer to the actual wall attenuation than those acquired using Detail kernel. Using differentiation curves, we could measure attenuation for models with walls of 1.0- or 1.5-mm thickness using MBIR but only those of 1.5-mm thickness using Detail kernel. We detected no significant differences among the attenuation values of the vascular walls of either thickness (MBIR, P=0.1606) or among the 3 densities of intravascular contrast material (MBIR, P=0.8185; Detail kernel, P=0.0802). Compared with FBP, MBIR reduces both reconstruction blur and image noise simultaneously, facilitates recognition of vascular wall boundaries, and can improve accuracy in measuring wall attenuation. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Whole-body PET/MRI: The effect of bone attenuation during MR-based attenuation correction in oncology imaging

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Aznar, M.C., E-mail: marianne.aznar@regionh.dk [Department of Oncology, Section of Radiotherapy 3994, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen (Denmark); Sersar, R., E-mail: rachidadk@hotmail.com [DTU Informatics, Technical University of Denmark, Kongens Lyngby (Denmark); Saabye, J., E-mail: julie_saa@hotmail.com [DTU Informatics, Technical University of Denmark, Kongens Lyngby (Denmark); Ladefoged, C.N., E-mail: claesnl@gmail.com [Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen (Denmark); Andersen, F.L., E-mail: Flemming.Andersen@regionh.dk [Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen (Denmark); Rasmussen, J.H., E-mail: jacobrasmu@gmail.com [Department of Oncology, Section of Radiotherapy 3994, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen (Denmark); Löfgren, J., E-mail: Johan.Loefgren@regionh.dk [Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen (Denmark); Beyer, T., E-mail: thomas.beyer@meduniwien.ac.at [Centre for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna (Austria)

2014-07-15

Purpose: In combined PET/MRI standard PET attenuation correction (AC) is based on tissue segmentation following dedicated MR sequencing and, typically, bone tissue is not represented. We evaluate PET quantification in whole-body (WB)-PET/MRI following MR-AC without considering bone attenuation and then investigate different strategies to account for bone tissue in clinical PET/MR imaging. To this purpose, bone tissue representation was extracted from separate CT images, and different bone representations were simulated from hypothetically derived MR-based bone classifications. Methods: Twenty oncology patients referred for a PET/CT were injected with either [18F]-FDG or [18F]-NaF and imaged on PET/CT (Biograph TruePoint/mCT, Siemens) and PET/MRI (mMR, Siemens) following a standard single-injection, dual-imaging clinical WB-protocol. Routine MR-AC was based on in-/opposed-phase MR imaging (orgMR-AC). PET(/MRI) images were reconstructed (AW-OSEM, 3 iterations, 21 subsets, 4 mm Gaussian) following routine MR-AC and MR-AC based on four modified attenuation maps. These modified attenuation maps were created for each patient by non-linear co-registration of the CT images to the orgMR-AC images, and adding CT bone mask values representing cortical bone: 1200 HU (cortCT), spongiosa bone: 350 HU (spongCT), average CT value (meanCT) and original CT values (orgCT). Relative difference images of the PET following AC using the modified attenuation maps were compared. SUVmean was calculated in anatomical reference regions and for PET-positive lesions. Results: The relative differences in SUVmean across patients following orgMR-AC and orgCT in soft tissue lesions and in bone lesions were similar (range: 0.0% to −22.5%), with an average underestimation of SUVmean of 7.2% and 10.0%, respectively when using orgMR-AC. In bone lesions, spongCT values were closest to orgCT (median bias of 1.3%, range: –9.0% to 13.5%) while the overestimation of SUVmean with respect to orgCT was

The effect of the cranial bone CT numbers on the brain CT numbers

Energy Technology Data Exchange (ETDEWEB)

Fukuda, Hitoshi; Kobayashi, Shotai; Koide, Hiromi; Yamaguchi, Shuhei; Okada, Kazunori; Shimote, Koichi; Tsunematsu, Tokugoro (Shimane Medical Univ., Izumo (Japan))

1989-06-01

The effects of the cranial size and the computed tomography (CT) numbers of the cranial bone on that of the brain were studied in 70 subjects, aged from 30 to 94 years. The subjects had no histories of cerebrovascular accidents and showed no abnormalities in the central nervous system upon physical examinations and a CT scan. We measured the average attenuation values (CT numbers) of each elliptical region (165 pixels, 0.39 cm{sup 2}) at the bilateral thalamus and at twelve areas of the deep white matter. Multiple regression analysis was used to assess the effects of age, cranial size, and cranial bone CT numbers on the brain CT numbers. The effect of the cranial bone CT numbers on the brain CT numbers was statistically significant. The brain CT numbers increased with the increase in the cranial bone CT numbers. There was, however, no significant correlation between brain CT numbers and cranial size. In measuring the brain CT numbers, it is desirable that consideration be given to the cranial bone CT numbers. (author).

Myocardial perfusion imaging and coronary calcium scoring with a two-slice SPECT/CT system: can the attenuation map be calculated from the calcium scoring CT scan?

Energy Technology Data Exchange (ETDEWEB)

Wenning, Christian; Rahbar, Kambiz; Schober, Otmar; Stegger, Lars [University of Muenster, Department of Nuclear Medicine, Muenster (Germany); Vrachimis, Alexis; Schaefers, Michael [University of Muenster, Department of Nuclear Medicine, Muenster (Germany); University of Muenster, European Institute for Molecular Imaging, Muenster (Germany)

2013-07-15

Coronary artery calcium scoring can complement myocardial perfusion imaging (MPI). The purpose of this study was to evaluate the feasibility and accuracy of using the CalciumScore-CT derived from a combined SPECT/CT device also for SPECT attenuation correction (AC). The study group comprised 99 patients who underwent both post-stress and rest MPI using a two-slice SPECT/CT system. For AC, one of the two scans was accompanied by a CalciumScore-CT scan (CalciumScore-CTAC) and the other by a conventional spiral CT (AttenCorr-CT) scan (AttenCorr-CTAC). In 48 patients the CalciumScore-CT scan was acquired with the post-stress scan and the AttenCorr-CT scan with the rest scan, and in 51 patients the order was reversed. The accuracy of the images based on AC was determined qualitatively by consensus reading with respect to the clinical diagnoses as well as quantitatively by comparing the perfusion summed stress scores (SSS) and the summed rest scores (SRS) between attenuation-corrected and uncorrected images. In comparison to the uncorrected images CalciumScore-CTAC led to regional inaccuracies in 14 of 51 of studies (27.5 %) versus 12 of 48 studies (25 %) with AttenCorr-CTAC for the stress studies and in 5 of 48 (10 %) versus 1 of 51 (2 %) for the rest studies, respectively. This led to intermediate and definite changes in the final diagnosis (ischaemia and/or scarring) in 12 % of the studies (12 of 99) and in 7 % of the studies (7 of 99) with CalciumScore-CTAC and in 9 % of the studies (9 of 99) and 4 % of the studies (4 of 99) with AttenCorr-CTAC. Differences in SSS and SRS with respect to the uncorrected images were greater for the CalciumScore-CTAC images than for the AttenCorr-CTAC images ({Delta}SSS 4.5 {+-} 5.6 and 2.1 {+-} 4.4, p = 0.023; {Delta}SRS 4.2 {+-} 4.9 and 1.6 {+-} 3.2, p = 0.004, respectively). Using the same CT scan for calcium scoring and SPECT AC is feasible. Image interpretation must, however, include uncorrected images since CT-based AC relatively

Multiphase CT scanning and different intravenous contrast media concentrations in combined F-18-FDG PET/CT: Effect on quantitative and clinical assessment

Energy Technology Data Exchange (ETDEWEB)

Rebiere, Marilou, E-mail: Marilou.Rebiere@rwth-aachen.de [Department of Nuclear Medicine, University Hospital RWTH Aachen, Pauwelsstrasse 30, 52057 Aachen (Germany); Verburg, Frederik A., E-mail: fverburg@ukaachen.de [Department of Nuclear Medicine, University Hospital RWTH Aachen, Pauwelsstrasse 30, 52057 Aachen (Germany); Department of Nuclear Medicine, Maastricht University Medical Center, P. Debeylaan 25, 6202 AZ Maastricht (Netherlands); Palmowski, Moritz, E-mail: mpalmowski@ukaachen.de [Department of Nuclear Medicine, University Hospital RWTH Aachen, Pauwelsstrasse 30, 52057 Aachen (Germany); Department of Radiology, University Hospital RWTH Aachen, Pauwelsstrasse 30, 52057 Aachen (Germany); Department of Experimental Molecular Imaging, University Hospital RWTH Aachen, Pauwelsstrasse 30, 52057 Aachen (Germany); Krohn, Thomas, E-mail: tkrohn@ukaachen.de [Department of Nuclear Medicine, University Hospital RWTH Aachen, Pauwelsstrasse 30, 52057 Aachen (Germany); Pietsch, Hubertus, E-mail: hubertus.pietsch@bayer.com [Contrast Media Research, Bayer Pharma AG, Muellerstr. 178, 13353 Berlin (Germany); Kuhl, Christiane K., E-mail: ckuhl@ukaachen.de [Department of Radiology, University Hospital RWTH Aachen, Pauwelsstrasse 30, 52057 Aachen (Germany); Mottaghy, Felix M., E-mail: fmottaghy@ukaachen.de [Department of Nuclear Medicine, University Hospital RWTH Aachen, Pauwelsstrasse 30, 52057 Aachen (Germany); Department of Nuclear Medicine, Maastricht University Medical Center, P. Debeylaan 25, 6202 AZ Maastricht (Netherlands); Behrendt, Florian F., E-mail: fbehrendt@ukaachen.de [Department of Nuclear Medicine, University Hospital RWTH Aachen, Pauwelsstrasse 30, 52057 Aachen (Germany)

2012-08-15

Purpose: To evaluate the influence of multiphase CT scanning and different intravenous contrast media on contrast enhancement, attenuation correction and image quality in combined PET/CT. Material and methods: 140 patients were prospectively enrolled for F-18-FDG-PET/CT including a low-dose unenhanced, arterial and venous contrast enhanced CT. The first (second) 70 patients, received contrast medium with 370 (300) mg iodine/ml. The iodine delivery rate (1.3 mg/s) and total iodine load (44.4 g) were identical for both groups. Contrast enhancement and maximum and mean standardized FDG uptake values (SUVmax and SUVmean) were determined for the un-enhanced, arterial and venous PET/CT at multiple anatomic sites and PET reconstructions were visually evaluated. Results: Arterial contrast enhancement was significantly higher for the 300 mg/ml contrast medium compared to 370 mg I/ml at all anatomic sites. Venous enhancement was not different between the two contrast media. SUVmean and SUVmax were significantly higher for the contrast enhanced compared to the non-enhanced PET/CT at all anatomic sites (all P < 0.001). Tracer uptake was significantly higher in the arterial than in the venous PET/CT in the arteries using both contrast media (all P < 0.001). No differences in tracer uptake were found between the contrast media (all P > 0.05). Visual assessment revealed no relevant differences between the different PET reconstructions. Conclusions: There is no relevant qualitative influence on the PET scan from the use of different intravenous contrast media in its various phases in combined multiphase PET/CT. For quantitative analysis of tracer uptake it is required to use an identical PET/CT protocol.

Coronary stent on coronary CT angiography: Assessment with model-based iterative reconstruction technique

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Lee, Eun Chae; Kim, Yeo Koon; Chun, Eun Ju; Choi, Sang IL [Dept. of of Radiology, Seoul National University Bundang Hospital, Seongnam (Korea, Republic of)

2016-05-15

To assess the performance of model-based iterative reconstruction (MBIR) technique for evaluation of coronary artery stents on coronary CT angiography (CCTA). Twenty-two patients with coronary stent implantation who underwent CCTA were retrospectively enrolled for comparison of image quality between filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR) and MBIR. In each data set, image noise was measured as the standard deviation of the measured attenuation units within circular regions of interest in the ascending aorta (AA) and left main coronary artery (LM). To objectively assess the noise and blooming artifacts in coronary stent, we additionally measured the standard deviation of the measured attenuation and intra-luminal stent diameters of total 35 stents with dedicated software. All image noise measured in the AA (all p < 0.001), LM (p < 0.001, p = 0.001) and coronary stent (all p < 0.001) were significantly lower with MBIR in comparison to those with FBP or ASIR. Intraluminal stent diameter was significantly higher with MBIR, as compared with ASIR or FBP (p < 0.001, p = 0.001). MBIR can reduce image noise and blooming artifact from the stent, leading to better in-stent assessment in patients with coronary artery stent.

Mosaic Pattern of Lung Attenuation on Chest CT in Patients with Pulmonary Hypertension

Directory of Open Access Journals (Sweden)

Kamonpun Ussavarungsi

2015-09-01

Full Text Available A mosaic pattern of lung attenuation on chest computed tomography (CT may be due to various etiologies. There is limited published data on CT results when used to evaluate pulmonary hypertension (PH. We retrospectively studied the frequency of mosaic pattern in patients with PH and the cause of the PH by diagnostic group, as well as the correlation between the mosaic pattern and the following: demographics, severity of the PH, main pulmonary artery (PA size, PA/aorta (PA/Ao ratio, pulmonary function tests (PFT, and ventilation perfusion scan results. Overall, 18% of the cohort had CT mosaic pattern (34/189. Mosaic pattern was present in 17/113 (15% in Group 1 pulmonary arterial hypertension, 5/13 (28% in Group 2 pulmonary venous hypertension and 8/50 (16% in Group 3 PH. Conversely, Group 4 chronic thromboembolic PH was more prevalent in 4/8 (50%. Main PA size, PA/Ao ratio, and segmental perfusion defect were positively associated with mosaic pattern. In contrast, factors such as age, gender, body mass index, functional class, hemodynamic data, and PFT values were not associated with mosaic pattern. Mosaic pattern is not specific as an isolated finding for distinguishing the subtype of PH.

Material Separation Using Dual-Energy CT: Current and Emerging Applications.

Science.gov (United States)

Patino, Manuel; Prochowski, Andrea; Agrawal, Mukta D; Simeone, Frank J; Gupta, Rajiv; Hahn, Peter F; Sahani, Dushyant V

2016-01-01

Dual-energy (DE) computed tomography (CT) offers the opportunity to generate material-specific images on the basis of the atomic number Z and the unique mass attenuation coefficient of a particular material at different x-ray energies. Material-specific images provide qualitative and quantitative information about tissue composition and contrast media distribution. The most significant contribution of DE CT-based material characterization comes from the capability to assess iodine distribution through the creation of an image that exclusively shows iodine. These iodine-specific images increase tissue contrast and amplify subtle differences in attenuation between normal and abnormal tissues, improving lesion detection and characterization in the abdomen. In addition, DE CT enables computational removal of iodine influence from a CT image, generating virtual noncontrast images. Several additional materials, including calcium, fat, and uric acid, can be separated, permitting imaging assessment of metabolic imbalances, elemental deficiencies, and abnormal deposition of materials within tissues. The ability to obtain material-specific images from a single, contrast-enhanced CT acquisition can complement the anatomic knowledge with functional information, and may be used to reduce the radiation dose by decreasing the number of phases in a multiphasic CT examination. DE CT also enables generation of energy-specific and virtual monochromatic images. Clinical applications of DE CT leverage both material-specific images and virtual monochromatic images to expand the current role of CT and overcome several limitations of single-energy CT. (©)RSNA, 2016.

CT Densitometry of the Lung in Healthy Nonsmokers with Normal Pulmonary Function

Energy Technology Data Exchange (ETDEWEB)

Oh, Tack Sun; Chae, Eun Jin; Seo, Joon Beom; Jung, Young Ju; Oh, Yeon Mok; Lee, Sang Do [University of Ulsan College of Medicine, Asan Medical Center, Seoul (Korea, Republic of)

2012-09-15

To investigate the upper normal limit of low attenuation area in healthy nonsmokers. A total of 36 nonsmokers with normal pulmonary function test underwent a CT scan. Six thresholds (-980 --930 HU) on inspiration CT and two thresholds (-950 and -910 HU) on expiration CT were used for obtaining low attenuation area. The mean lung density was obtained on both inspiration CT and expiration CT. Descriptive statistics of low attenuation area and the mean lung density, evaluation of difference of low attenuation area and the mean lung density in both sex and age groups, analysis of the relationship between demographic information and CT parameters were performed. Upper normal limit for low attenuation area was 12.96% on inspiration CT (-950 HU) and 9.48% on expiration CT (-910 HU). Upper normal limit for the mean lung density was -837.58 HU on inspiration CT and 686.82 HU on expiration CT. Low attenuation area and the mean lung density showed no significant differences in both sex and age groups. Body mass index (BMI) was negatively correlated with low attenuation area on inspiration CT (-950 HU, r = -0.398, p = 0.016) and positively correlated with the mean lung density on inspiration CT (r 0.539, p = 0.001) and expiration CT (r = 0.432, p = 0.009). Age and body surface area were not correlated with low attenuation area or the mean lung density. Low attenuation area on CT densitometry of the lung could be found in healthy nonsmokers with normal pulmonary function, and showed negative association with BMI. Reference values, such as range and upper normal limit for low attenuation area in healthy subjects could be helpful in quantitative analysis and follow up of early emphysema, using CT densitometry of the lung.

Clinical assessment of SPECT/CT co-registration image fusion

International Nuclear Information System (INIS)

Zhou Wen; Luan Zhaosheng; Peng Yong

2004-01-01

Objective: Study the methodology of the SPECT/CT co-registration image fusion, and Assessment the Clinical application value. Method: 172 patients who underwent SPECT/CT image fusion during 2001-2003 were studied, 119 men, 53 women. 51 patients underwent 18FDG image +CT, 26 patients underwent 99m Tc-RBC Liver pool image +CT, 43 patients underwent 99mTc-MDP Bone image +CT, 18 patients underwent 99m Tc-MAA Lung perfusion image +CT. The machine is Millium VG SPECT of GE Company. All patients have been taken three steps image: X-ray survey, X-ray transmission and nuclear emission image (Including planer imaging, SPECT or 18 F-FDG of dual head camera) without changing the position of the patients. We reconstruct the emission image with X-ray map and do reconstruction, 18FDG with COSEM and 99mTc with OSEM. Then combine the transmission image and the reconstructed emission image. We use different process parameters in deferent image methods. The accurate rate of SPECT/CT image fusion were statistics, and compare their accurate with that of single nuclear emission image. Results: The nuclear image which have been reconstructed by X-ray attenuation and OSEM are apparent better than pre-reconstructed. The post-reconstructed emission images have no scatter lines around the organs. The outline between different issues is more clear than before. The validity of All post-reconstructed images is better than pre-reconstructed. SPECT/CT image fusion make localization have worthy bases. 138 patients, the accuracy of SPECT/CT image fusion is 91.3% (126/138), whereas 60(88.2%) were found through SPECT/CT image fusion, There are significant difference between them(P 99m Tc- RBC-SPECT +CT image fusion, but 21 of them were inspected by emission image. In BONE 99m Tc -MDP-SPECT +CT image fusion, 4 patients' removed bone(1-6 months after surgery) and their relay with normal bone had activity, their morphologic and density in CT were different from normal bones. 11 of 20 patients who could

Serial micro-CT assessment of the therapeutic effects of rosiglitazone in a bleomycin-induced lung fibrosis mouse model

Energy Technology Data Exchange (ETDEWEB)

Choi, Eun Jung; Jin, Gong Yong; Bok, Se Mi; Han, Young Min; Lee, Young Sun; Jung, Myung Ja; Kwon, Keun Sang [Research Institute of Clinical Medicine of Chonbuk National University, Biomedical Research Institute of Chonbuk National University Hospital, Institute for Medical Sciences, Jeonju (Korea, Republic of)

2014-08-15

The aim of this study was to assess the therapeutic effects of rosiglitazone with serial micro-CT findings before and after rosiglitazone administration in a lung fibrosis mouse model induced with bleomycin. We instilled the bleomycin solution directly into the trachea in twenty mice (female, C57BL/6 mice). After the instillation with bleomycin, mice were closely observed for 3 weeks and then all mice were scanned using micro-CT without sacrifice. At 3 weeks, the mice were treated with rosiglitazone on days 21 to 27 if they had abnormal CT findings (n = 9, 45%). For the mice treated with rosiglitazone, we performed micro-CT with mouse sacrifice 2 weeks after the rosiglitazone treatment completion. We assessed the abnormal CT findings (ground glass attenuation, consolidation, bronchiectasis, reticular opacity, and honeycombing) using a five-point scale at 3 and 6 weeks using Wilcoxon-signed ranked test. The micro-CT findings were correlated with the histopathologic results. One out of nine (11.1%) mice improved completely. In terms of consolidation, all mice (100%) showed marked decrease from 3.1 ± 1.4 at 3 weeks to 0.9 ± 0.9 at 6 weeks (p = 0.006). At 6 weeks, mild bronchiectasis (n = 6, 66.7%), mild reticular opacity (n 7, 77.8%) and mild honeycomb patterns (n = 3, 33.3%) appeared. A serial micro-CT enables the evaluation of drug effects in a lung fibrosis mouse model.

Evaluation of colonic lesions and pitfalls in CT colonography: A systematic approach based on morphology, attenuation and mobility

International Nuclear Information System (INIS)

Mang, Thomas; Gryspeerdt, Stefaan; Schima, Wolfgang; Lefere, Philippe

2013-01-01

Computed tomographic colonography is a reliable technique for the detection and classification of neoplastic and non-neoplastic lesions of the colon. It is based on a thin-section CT dataset of the cleansed and air-distended colon, acquired in prone and supine position. Two-dimensional and 3D projections are used in combination for image interpretation. The evaluation of CT colonography datasets is based on two steps, lesion perception to detect a polyp candidate and image interpretation to correctly characterize colonic filling defects. A thorough knowledge of the morphologic and attenuation characteristics of common colonic lesions and artifacts facilitates characterization of the findings. The purpose of this review article is to give an overview of the key CT colonographic imaging criteria to correctly characterize common colorectal lesions and to identify typical pitfalls and pseudolesions

Extent of emphysema estimated by the three dimensional CT (3D-CT) predicts pulmonary dysfunction in patients with COPD

International Nuclear Information System (INIS)

Fujita, Etsuo; Inoue, Yoshikazu; Tanaka Isao

2003-01-01

We assessed the extent of emphysematous area by the 3D-CT in 35 chronic stable patients (age 66.5±8.9 yrs). And we evaluated the data from the total lung volume estimated by the 3D-CT, % low attenuation area below -950 HU (%LAA) and pulmonary function tests (PFT). Total lung volume estimated by 3D-CT was correlated with total lung capacity (TLC) by PFT (r=0.736, p<0.0005). The % LAA correlated with forced expiratory volume (FEV) 1% (r=-0.716, p<0.001). We concluded that the 3D-CT is the excellent method of evaluating the extent of emphysema without effort. (author)

Reduction of artefacts caused by hip implants in CT-based attenuation-corrected PET images using 2-D interpolation of a virtual sinogram on an irregular grid

NARCIS (Netherlands)

Abdoli, Mehrsima; de Jong, Johan R.; Pruim, Jan; Dierckx, Rudi A. J. O.; Zaidi, Habib

2011-01-01

Purpose Metallic prosthetic replacements, such as hip or knee implants, are known to cause strong streaking artefacts in CT images. These artefacts likely induce over-or underestimation of the activity concentration near the metallic implants when applying CT-based attenuation correction of positron

Follow-up CT and CT angiography after intracranial aneurysm clipping and coiling - improved image quality by iterative metal artifact reduction

Energy Technology Data Exchange (ETDEWEB)

Bier, Georg; Hempel, Johann-Martin; Oergel, Anja; Hauser, Till-Karsten; Ernemann, Ulrike; Hennersdorf, Florian [Eberhard Karls University Tuebingen, Department of Diagnostic and Interventional Neuroradiology, Tuebingen (Germany); Bongers, Malte Niklas [Eberhard Karls University Tuebingen, Department of Diagnostic and Interventional Radiology, Tuebingen (Germany)

2017-07-15

This paper aims to evaluate a new iterative metal artifact reduction algorithm for post-interventional evaluation of brain tissue and intracranial arteries. The data of 20 patients that underwent follow-up cranial CT and cranial CT angiography after clipping or coiling of an intracranial aneurysm was retrospectively analyzed. After the images were processed using a novel iterative metal artifact reduction algorithm, images with and without metal artifact reduction were qualitatively evaluated by two readers, using a five-point Likert scale. Moreover, artifact strength was quantitatively assessed in terms of CT attenuation and standard deviation alterations. The qualitative analysis yielded a significant increase in image quality (p = 0.0057) in iteratively processed images with substantial inter-observer agreement (k = 0.72), while the CTA image quality did not differ (p = 0.864) and even showed vessel contrast reduction in six cases (30%). The mean relative attenuation difference was 27% without metal artifact reduction vs. 11% for iterative metal artifact reduction images (p = 0.0003). The new iterative metal artifact reduction algorithm enhances non-enhanced CT image quality after clipping or coiling, but in CT-angiography images, the contrast of adjacent vessels can be compromised. (orig.)

Follow-up CT and CT angiography after intracranial aneurysm clipping and coiling - improved image quality by iterative metal artifact reduction

International Nuclear Information System (INIS)

Bier, Georg; Hempel, Johann-Martin; Oergel, Anja; Hauser, Till-Karsten; Ernemann, Ulrike; Hennersdorf, Florian; Bongers, Malte Niklas

2017-01-01

This paper aims to evaluate a new iterative metal artifact reduction algorithm for post-interventional evaluation of brain tissue and intracranial arteries. The data of 20 patients that underwent follow-up cranial CT and cranial CT angiography after clipping or coiling of an intracranial aneurysm was retrospectively analyzed. After the images were processed using a novel iterative metal artifact reduction algorithm, images with and without metal artifact reduction were qualitatively evaluated by two readers, using a five-point Likert scale. Moreover, artifact strength was quantitatively assessed in terms of CT attenuation and standard deviation alterations. The qualitative analysis yielded a significant increase in image quality (p = 0.0057) in iteratively processed images with substantial inter-observer agreement (k = 0.72), while the CTA image quality did not differ (p = 0.864) and even showed vessel contrast reduction in six cases (30%). The mean relative attenuation difference was 27% without metal artifact reduction vs. 11% for iterative metal artifact reduction images (p = 0.0003). The new iterative metal artifact reduction algorithm enhances non-enhanced CT image quality after clipping or coiling, but in CT-angiography images, the contrast of adjacent vessels can be compromised. (orig.)

Cone-beam CT image contrast and attenuation-map linearity improvement (CALI) for brain stereotactic radiosurgery procedures

Science.gov (United States)

Hashemi, Sayed Masoud; Lee, Young; Eriksson, Markus; Nordström, Hâkan; Mainprize, James; Grouza, Vladimir; Huynh, Christopher; Sahgal, Arjun; Song, William Y.; Ruschin, Mark

2017-03-01

A Contrast and Attenuation-map (CT-number) Linearity Improvement (CALI) framework is proposed for cone-beam CT (CBCT) images used for brain stereotactic radiosurgery (SRS). The proposed framework is used together with our high spatial resolution iterative reconstruction algorithm and is tailored for the Leksell Gamma Knife ICON (Elekta, Stockholm, Sweden). The incorporated CBCT system in ICON facilitates frameless SRS planning and treatment delivery. The ICON employs a half-cone geometry to accommodate the existing treatment couch. This geometry increases the amount of artifacts and together with other physical imperfections causes image inhomogeneity and contrast reduction. Our proposed framework includes a preprocessing step, involving a shading and beam-hardening artifact correction, and a post-processing step to correct the dome/capping artifact caused by the spatial variations in x-ray energy generated by bowtie-filter. Our shading correction algorithm relies solely on the acquired projection images (i.e. no prior information required) and utilizes filtered-back-projection (FBP) reconstructed images to generate a segmented bone and soft-tissue map. Ideal projections are estimated from the segmented images and a smoothed version of the difference between the ideal and measured projections is used in correction. The proposed beam-hardening and dome artifact corrections are segmentation free. The CALI was tested on CatPhan, as well as patient images acquired on the ICON system. The resulting clinical brain images show substantial improvements in soft contrast visibility, revealing structures such as ventricles and lesions which were otherwise un-detectable in FBP-reconstructed images. The linearity of the reconstructed attenuation-map was also improved, resulting in more accurate CT#.

Emerging role of FDG-PET/CT in assessing atherosclerosis in large arteries

International Nuclear Information System (INIS)

Chen, Wengen; Bural, Gonca G.; Torigian, Drew A.; Alavi, Abass; Rader, Daniel J.

2009-01-01

Atherosclerosis is a dynamic inflammatory disorder. The biological composition and inflammatory state of an atherosclerotic plaque, rather than the degree of stenosis or its size are the major determinants of acute clinical events. A noninvasive technique to detect vulnerable atherosclerotic plaque is critically needed. FDG-PET/CT, a combined functional and structural whole-body imaging modality, holds great potential for this purpose. FDG uptake in large arteries has been frequently observed and is associated with cardiovascular risk factors. FDG accumulates in plaque macrophages and uptake is correlated with macrophage density. It is known that vascular FDG uptake and calcification do not overlap significantly and changes of FDG uptake are common, suggesting that FDG uptake may represent a dynamic inflammatory process. It has been reported that vascular FDG uptake can be attenuated by simvastatin in patients, and by the antiinflammatory drug probucol in rabbits. Vascular FDG uptake has been linked to cardiovascular events in some preliminary studies. Data from basic sciences, and animal and clinical studies support the emerging role of FDG-PET/CT in assessing atherosclerosis in large arteries in humans. (orig.)

Detectability index of differential phase contrast CT compared with conventional CT: a preliminary channelized Hotelling observer study

Science.gov (United States)

Tang, Xiangyang; Yang, Yi; Tang, Shaojie

2013-03-01

Under the framework of model observer with signal and background exactly known (SKE/BKE), we investigate the detectability of differential phase contrast CT compared with that of the conventional attenuation-based CT. Using the channelized Hotelling observer and the radially symmetric difference-of-Gaussians channel template , we investigate the detectability index and its variation over the dimension of object and detector cells. The preliminary data show that the differential phase contrast CT outperforms the conventional attenuation-based CT significantly in the detectability index while both the object to be detected and the cell of detector used for data acquisition are relatively small. However, the differential phase contrast CT's dominance in the detectability index diminishes with increasing dimension of either object or detector cell, and virtually disappears while the dimension of object or detector cell approaches a threshold, respectively. It is hoped that the preliminary data reported in this paper may provide insightful understanding of the differential phase contrast CT's characteristic in the detectability index and its comparison with that of the conventional attenuation-based CT.

Attenuation correction for the NIH ATLAS small animal PET scanner

CERN Document Server

Yao, Rutao; Liow, JeihSan; Seidel, Jurgen

2003-01-01

We evaluated two methods of attenuation correction for the NIH ATLAS small animal PET scanner: 1) a CT-based method that derives 511 keV attenuation coefficients (mu) by extrapolation from spatially registered CT images; and 2) an analytic method based on the body outline of emission images and an empirical mu. A specially fabricated attenuation calibration phantom with cylindrical inserts that mimic different body tissues was used to derive the relationship to convert CT values to (I for PET. The methods were applied to three test data sets: 1) a uniform cylinder phantom, 2) the attenuation calibration phantom, and 3) a mouse injected with left bracket **1**8F right bracket FDG. The CT-based attenuation correction factors were larger in non-uniform regions of the imaging subject, e.g. mouse head, than the analytic method. The two methods had similar correction factors for regions with uniform density and detectable emission source distributions.

Virtual non-contrast in second-generation, dual-energy computed tomography: Reliability of attenuation values

International Nuclear Information System (INIS)

Toepker, Michael; Moritz, Thomas; Krauss, Bernhard; Weber, Michael; Euller, Gordon; Mang, Thomas; Wolf, Florian; Herold, Christian J.; Ringl, Helmut

2012-01-01

Purpose: To evaluate the reliability of attenuation values in virtual non-contrast images (VNC) reconstructed from contrast-enhanced, dual-energy scans performed on a second-generation dual-energy CT scanner, compared to single-energy, non-contrast images (TNC). Materials and methods: Sixteen phantoms containing a mixture of contrast agent and water at different attenuations (0–1400 HU) were investigated on a Definition Flash-CT scanner using a single-energy scan at 120 kV and a DE-CT protocol (100 kV/SN140 kV). For clinical assessment, 86 patients who received a dual-phase CT, containing an unenhanced single-energy scan at 120 kV and a contrast enhanced (110 ml Iomeron 400 mg/ml; 4 ml/s) DE-CT (100 kV/SN140 kV) in an arterial (n = 43) or a venous phase, were retrospectively analyzed. Mean attenuation was measured within regions of interest of the phantoms and in different tissue types of the patients within the corresponding VNC and TNC images. Paired t-tests and Pearson correlation were used for statistical analysis. Results: For all phantoms, mean attenuation in VNC was 5.3 ± 18.4 HU, with respect to water. In 86 patients overall, 2637 regions were measured in TNC and VNC images, with a mean difference between TNC and VNC of −3.6 ± 8.3 HU. In 91.5% (n = 2412) of all cases, absolute differences between TNC and VNC were under 15 HU, and, in 75.3% (n = 1986), differences were under 10 HU. Conclusions: Second-generation dual-energy CT based VNC images provide attenuation values close to those of TNC. To avoid possible outliers multiple measurements are recommended especially for measurements in the spleen, the mesenteric fat, and the aorta.

Virtual non-contrast in second-generation, dual-energy computed tomography: reliability of attenuation values.

Science.gov (United States)

Toepker, Michael; Moritz, Thomas; Krauss, Bernhard; Weber, Michael; Euller, Gordon; Mang, Thomas; Wolf, Florian; Herold, Christian J; Ringl, Helmut

2012-03-01

To evaluate the reliability of attenuation values in virtual non-contrast images (VNC) reconstructed from contrast-enhanced, dual-energy scans performed on a second-generation dual-energy CT scanner, compared to single-energy, non-contrast images (TNC). Sixteen phantoms containing a mixture of contrast agent and water at different attenuations (0-1400 HU) were investigated on a Definition Flash-CT scanner using a single-energy scan at 120 kV and a DE-CT protocol (100 kV/SN140 kV). For clinical assessment, 86 patients who received a dual-phase CT, containing an unenhanced single-energy scan at 120 kV and a contrast enhanced (110 ml Iomeron 400 mg/ml; 4 ml/s) DE-CT (100 kV/SN140 kV) in an arterial (n=43) or a venous phase, were retrospectively analyzed. Mean attenuation was measured within regions of interest of the phantoms and in different tissue types of the patients within the corresponding VNC and TNC images. Paired t-tests and Pearson correlation were used for statistical analysis. For all phantoms, mean attenuation in VNC was 5.3±18.4 HU, with respect to water. In 86 patients overall, 2637 regions were measured in TNC and VNC images, with a mean difference between TNC and VNC of -3.6±8.3 HU. In 91.5% (n=2412) of all cases, absolute differences between TNC and VNC were under 15HU, and, in 75.3% (n=1986), differences were under 10 HU. Second-generation dual-energy CT based VNC images provide attenuation values close to those of TNC. To avoid possible outliers multiple measurements are recommended especially for measurements in the spleen, the mesenteric fat, and the aorta. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Intravenous contrast injection significantly affects bone mineral density measured on CT

Energy Technology Data Exchange (ETDEWEB)

Pompe, Esther; Willemink, Martin J.; Dijkhuis, Gawein R.; Verhaar, Harald J.J.; Hoesein, Firdaus A.A.M.; Jong, Pim A. de [University Medical Center Utrecht, Department of Radiology and Internal Medicine-Geriatrics, Postbus 85500, Postbox: E.03.511, GA, Utrecht (Netherlands)

2014-09-05

The objective is to evaluate the effect of intravenous contrast media on bone mineral density (BMD) assessment by comparing unenhanced and contrast-enhanced computed tomography (CT) examinations performed for other indications. One hundred and fifty-two patients (99 without and 53 with malignant neoplasm) who underwent both unenhanced and two contrast-enhanced (arterial and portal venous phase) abdominal CT examinations in a single session between June 2011 and July 2013 were included. BMD was evaluated on the three examinations as CT-attenuation values in Hounsfield Units (HU) in the first lumbar vertebra (L1). CT-attenuation values were significantly higher in both contrast-enhanced phases, compared to the unenhanced phase (p < 0.01). In patients without malignancies, mean ± standard deviation (SD) HU-values increased from 128.8 ± 48.6 HU for the unenhanced phase to 142.3 ± 47.2 HU for the arterial phase and 147.0 ± 47.4 HU for the portal phase (p < 0.01). In patients with malignancies, HU-values increased from 112.1 ± 38.1 HU to 126.2 ± 38.4 HU and 130.1 ± 37.3 HU (p < 0.02), respectively. With different thresholds to define osteoporosis, measurements in the arterial and portal phase resulted in 7-25 % false negatives. Our study showed that intravenous contrast injection substantially affects BMD-assessment on CT and taking this into account may improve routine assessment of low BMD in nonquantitative CT. (orig.)

Intravenous contrast injection significantly affects bone mineral density measured on CT

International Nuclear Information System (INIS)

Pompe, Esther; Willemink, Martin J.; Dijkhuis, Gawein R.; Verhaar, Harald J.J.; Hoesein, Firdaus A.A.M.; Jong, Pim A. de

2015-01-01

The objective is to evaluate the effect of intravenous contrast media on bone mineral density (BMD) assessment by comparing unenhanced and contrast-enhanced computed tomography (CT) examinations performed for other indications. One hundred and fifty-two patients (99 without and 53 with malignant neoplasm) who underwent both unenhanced and two contrast-enhanced (arterial and portal venous phase) abdominal CT examinations in a single session between June 2011 and July 2013 were included. BMD was evaluated on the three examinations as CT-attenuation values in Hounsfield Units (HU) in the first lumbar vertebra (L1). CT-attenuation values were significantly higher in both contrast-enhanced phases, compared to the unenhanced phase (p < 0.01). In patients without malignancies, mean ± standard deviation (SD) HU-values increased from 128.8 ± 48.6 HU for the unenhanced phase to 142.3 ± 47.2 HU for the arterial phase and 147.0 ± 47.4 HU for the portal phase (p < 0.01). In patients with malignancies, HU-values increased from 112.1 ± 38.1 HU to 126.2 ± 38.4 HU and 130.1 ± 37.3 HU (p < 0.02), respectively. With different thresholds to define osteoporosis, measurements in the arterial and portal phase resulted in 7-25 % false negatives. Our study showed that intravenous contrast injection substantially affects BMD-assessment on CT and taking this into account may improve routine assessment of low BMD in nonquantitative CT. (orig.)

Early small-bowel ischemia: dual-energy CT improves conspicuity compared with conventional CT in a swine model.

Science.gov (United States)

Potretzke, Theodora A; Brace, Christopher L; Lubner, Meghan G; Sampson, Lisa A; Willey, Bridgett J; Lee, Fred T

2015-04-01

To compare dual-energy computed tomography (CT) with conventional CT for the detection of small-bowel ischemia in an experimental animal model. The study was approved by the animal care and use committee and was performed in accordance with the Guide for Care and Use of Laboratory Animals issued by the National Research Council. Ischemic bowel segments (n = 8) were created in swine (n = 4) by means of surgical occlusion of distal mesenteric arteries and veins. Contrast material-enhanced dual-energy CT and conventional single-energy CT (120 kVp) sequences were performed during the portal venous phase with a single-source fast-switching dual-energy CT scanner. Attenuation values and contrast-to-noise ratios of ischemic and perfused segments on iodine material-density, monospectral dual-energy CT (51 keV, 65 keV, and 70 keV), and conventional 120-kVp CT images were compared. Linear mixed-effects models were used for comparisons. The attenuation difference between ischemic and perfused segments was significantly greater on dual-energy 51-keV CT images than on conventional 120-kVp CT images (mean difference, 91.7 HU vs 47.6 HU; P conventional CT by increasing attenuation differences between ischemic and perfused segments on low-kiloelectron volt and iodine material density images. © RSNA, 2014.

Assessment of US score and CT number for diagnosis of fatty liver

International Nuclear Information System (INIS)

Ogasawara, Tetsuo; Tanda, Shigeru; Lim, Insu; Oota, Keisuke; Taima, Tadashi

1987-01-01

The author evaluates US and CT for diagnosis of fatty liver in 70 cases with fatty change of the liver. We tried to score the US findings of the fatty change, i.e., ''bright liver pattern'', ''liver-kidney contrast'', ''vascular blurring'', ''deep attenuation'', and the usefulness of the scoring was examined. Comparing with CT number, US score was more sensitive, but had no significant correlation with the amount of the fat in the liver and with the abnormality of the liver function tests. The results indicate that US should be used as a primary screening examination, and for the further evaluation of the fatty change of the liver, CT should be carried out. (author)

Comparative assessment of image quality for coronary CT angiography with iobitridol and two contrast agents with higher iodine concentrations: iopromide and iomeprol. A multicentre randomized double-blind trial

Energy Technology Data Exchange (ETDEWEB)

Achenbach, Stephan [Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Department of Cardiology, Erlangen (Germany); Paul, Jean-Francois [Centre Chirurgical Marie Lannelongue, Department of Radiology, Le Plessis Robinson (France); Laurent, Francois [University of Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux, U1045, Bordeaux (France); CHU de Bordeaux, Service d' Imagerie Thoracique et Cardiovasculaire, Pessac (France); Becker, Hans-Christoph [University Hospital Grosshadern, Department of Clinical Radiology, Munich (Germany); Rengo, Marco [Sapienza - University of Rome, ICOT Hospital, Department of Radiological Sciences, Oncology and Pathology, Latina (Italy); Caudron, Jerome [University Hospital of Rouen, Department of Radiology, Rouen (France); Leschka, Sebastian [Saint Gallen Hospital, Department of Radiology, Saint Gallen (Switzerland); Vignaux, Olivier [Cochin Hospital, Department of Radiology, Paris (France); Knobloch, Gesine [La Charite, Department of Radiology, Berlin (Germany); Benea, Giorgio [Ospedale del Delta, Ferrara (Italy); Schlosser, Thomas [Elisabeth-Krankenhaus Hospital, Essen (Germany); Andreu, Jordi [Hospital Vall d' Hebron, Barcelona (Spain); Cabeza, Beatriz [Hospital Clinico San Carlos, Madrid (Spain); Jacquier, Alexis [La Timone Adult Hospital, Department of Radiology, Marseille (France); Souto, Miguel [Complejo Hospitalario Universitario, Santiago de Compostela (Spain); Revel, Didier [Louis Pradel Hospital, Department of Radiology, Lyon (France); Qanadli, Salah Dine [University of Lausanne, Department of Radiology, Lausanne (Switzerland); Cademartiri, Filippo [Giovanni XXIII Hospital, Department of Radiology, Monastier di Treviso (Italy); Collaboration: X-ACT Study Group

2017-02-15

To demonstrate non-inferiority of iobitridol 350 for coronary CT angiography (CTA) compared to higher iodine content contrast media regarding rate of patients evaluable for the presence of coronary artery stenoses. In this multicentre trial, 452 patients were randomized to receive iobitridol 350, iopromide 370 or iomeprol 400 and underwent coronary CTA using CT systems with 64-detector rows or more. Two core lab readers assessed 18 coronary segments per patient regarding image quality (score 0 = non diagnostic to 4 = excellent quality), vascular attenuation, signal and contrast to noise ratio (SNR, CNR). Patients were considered evaluable if no segment had a score of 0. Per-patient, the rate of fully evaluable CT scans was 92.1, 95.4 and 94.6 % for iobitridol, iopromide and iomeprol, respectively. Non-inferiority of iobitridol over the best comparator was demonstrated with a 95 % CI of the difference of [-8.8 to 2.1], with a pre-specified non-inferiority margin of -10 %. Although average attenuation increased with higher iodine concentrations, average SNR and CNR did not differ between groups. With current CT technology, iobitridol 350 mg iodine/ml is not inferior to contrast media with higher iodine concentrations in terms of image quality for coronary stenosis assessment. (orig.)

SPECT/CT: main applications in nuclear medicine

International Nuclear Information System (INIS)

Perera Pintado, Alejandro; Torres Aroche, Leonel A.; Vergara Gil, Alex; Batista Cuéllar, Juan F.; Prats Capote, Anaís

2017-01-01

SPECT/CT has represented not only the possibility of acquiring anatomical and functional images in one single study, but also a revolution for the clinical management of several diseases, taking the better of each one of these imaging modalities. The present work is aimed at presenting an overview of the most important applications of the SPECT/CT in the field of oncology, cardiology and neurology. New technological advances in the design of innovative solid state detectors and related equipment have had a positive effect on the performance of this kind of dual modality. This hybrid technique improves the sensitivity and the specificity of gammagraphic studies, as well as shortens the acquisition times and gives attenuation correction of co-registered images, which, in turn, makes their analysis easier. Some of the main applications for the study of oncological diseases are the following: localization and follow-up of different kinds of tumors, their metastasis and relapses, as well as the optimization of radiotherapy doses. This technique has been useful to evaluate the coronary artery disease allowing an adequate attenuation correction of images, the determination of calcium score, and performing angio-CT studies, according to the CT quality. SPECT/CT has also gained ground in the assessment of some neurological diseases. Conclusions: The introduction of new technological advances and radiopharmaceuticals thus predicting a more relevant place for SPECT/CT in clinical practice. (author)

Quantitative and qualitative assessment of Yttrium-90 PET/CT imaging.

Directory of Open Access Journals (Sweden)

Ali Asgar Attarwala

Full Text Available Yttrium-90 is known to have a low positron emission decay of 32 ppm that may allow for personalized dosimetry of liver cancer therapy with (90Y labeled microspheres. The aim of this work was to image and quantify (90Y so that accurate predictions of the absorbed dose can be made. The measurements were performed within the QUEST study (University of Sydney, and Sirtex Medical, Australia. A NEMA IEC body phantom containing 6 fillable spheres (10-37 mm ∅ was used to measure the 90Y distribution with a Biograph mCT PET/CT (Siemens, Erlangen, Germany with time-of-flight (TOF acquisition. A sphere to background ratio of 8:1, with a total (90Y activity of 3 GBq was used. Measurements were performed for one week (0, 3, 5 and 7 d. he acquisition protocol consisted of 30 min-2 bed positions and 120 min-single bed position. Images were reconstructed with 3D ordered subset expectation maximization (OSEM and point spread function (PSF for iteration numbers of 1-12 with 21 (TOF and 24 (non-TOF subsets and CT based attenuation and scatter correction. Convergence of algorithms and activity recovery was assessed based on regions-of-interest (ROI analysis of the background (100 voxels, spheres (4 voxels and the central low density insert (25 voxels. For the largest sphere, the recovery coefficient (RC values for the 30 min -2-bed position, 30 min-single bed and 120 min-single bed were 1.12 ± 0.20, 1.14 ± 0.13, 0.97 ± 0.07 respectively. For the smaller diameter spheres, the PSF algorithm with TOF and single bed acquisition provided a comparatively better activity recovery. Quantification of Y-90 using Biograph mCT PET/CT is possible with a reasonable accuracy, the limitations being the size of the lesion and the activity concentration present. At this stage, based on our study, it seems advantageous to use different protocols depending on the size of the lesion.

Very low-dose (0.15 mGy) chest CT protocols using the COPDGene 2 test object and a third-generation dual-source CT scanner with corresponding third-generation iterative reconstruction software.

Science.gov (United States)

Newell, John D; Fuld, Matthew K; Allmendinger, Thomas; Sieren, Jered P; Chan, Kung-Sik; Guo, Junfeng; Hoffman, Eric A

2015-01-01

The purpose of this study was to evaluate the impact of ultralow radiation dose single-energy computed tomographic (CT) acquisitions with Sn prefiltration and third-generation iterative reconstruction on density-based quantitative measures of growing interest in phenotyping pulmonary disease. The effects of both decreasing dose and different body habitus on the accuracy of the mean CT attenuation measurements and the level of image noise (SD) were evaluated using the COPDGene 2 test object, containing 8 different materials of interest ranging from air to acrylic and including various density foams. A third-generation dual-source multidetector CT scanner (Siemens SOMATOM FORCE; Siemens Healthcare AG, Erlangen, Germany) running advanced modeled iterative reconstruction (ADMIRE) software (Siemens Healthcare AG) was used.We used normal and very large body habitus rings at dose levels varying from 1.5 to 0.15 mGy using a spectral-shaped (0.6-mm Sn) tube output of 100 kV(p). Three CT scans were obtained at each dose level using both rings. Regions of interest for each material in the test object scans were automatically extracted. The Hounsfield unit values of each material using weighted filtered back projection (WFBP) at 1.5 mGy was used as the reference value to evaluate shifts in CT attenuation at lower dose levels using either WFBP or ADMIRE. Statistical analysis included basic statistics, Welch t tests, multivariable covariant model using the F test to assess the significance of the explanatory (independent) variables on the response (dependent) variable, and CT mean attenuation, in the multivariable covariant model including reconstruction method. Multivariable regression analysis of the mean CT attenuation values showed a significant difference with decreasing dose between ADMIRE and WFBP. The ADMIRE has reduced noise and more stable CT attenuation compared with WFBP. There was a strong effect on the mean CT attenuation values of the scanned materials for ring

Diagnosis of Grave's disease with pulmonary hypertension on chest CT.

Science.gov (United States)

Lee, Hwa Yeon; Yoo, Seung Min; Kim, Hye Rin; Chun, Eun Ju; White, Charles S

To evaluate the diagnostic accuracy of chest CT findings to diagnose Grave's disease in pulmonary hypertension. We retrospectively evaluated chest CT and the medical records of 13 patients with Grave's disease with (n=6) or without pulmonary hypertension (n=7) and in 17 control patients. Presence of iso-attenuation of diffusely enlarged thyroid glands compared with adjacent neck muscle on non-enhanced CT as a diagnostic clue of Grave's disease, and assessment of pulmonary hypertension on CT has high diagnostic accuracy. Chest CT has the potential to diagnose Grave's disease with pulmonary hypertension in the absence of other information. Copyright © 2017 Elsevier Inc. All rights reserved.

Specificity of unenhanced CT for non-invasive diagnosis of hepatic steatosis: implications for the investigation of the natural history of incidental steatosis

Energy Technology Data Exchange (ETDEWEB)

Pickhardt, Perry J.; Hahn, Luke [University of Wisconsin School of Medicine and Public Health, Department of Radiology, Madison, WI (United States); Park, Seong Ho [University of Ulsan College of Medicine, Asan Medical Center, Department of Radiology and Research Institute of Radiology, Seoul (Korea, Republic of); Lee, Sung-Gyu [University of Ulsan College of Medicine, Asan Medical Center, Division of Hepatobiliary Surgery and Liver Transplantation, Department of Surgery, Seoul (Korea, Republic of); Bae, Kyongtae T. [University of Pittsburgh, Department of Radiology, Pittsburgh, PA (United States); Yu, Eun Sil [University of Ulsan College of Medicine, Asan Medical Center, Department of Pathology, Seoul (Korea, Republic of)

2012-05-15

To determine a highly specific liver attenuation threshold at unenhanced CT for biopsy-proven moderate to severe hepatic steatosis ({>=}30% at histology). 315 asymptomatic adults (mean age {+-} SD, 31.5 {+-} 10.1 years; 207 men, 108 women) underwent same-day unenhanced liver CT and ultrasound-guided liver biopsy. Blinded to biopsy results, CT liver attenuation was measured using standard region-of-interest methodology. Multiple linear regression analysis was used to assess the relationship of CT liver attenuation with patient age, gender, BMI, CT system, and hepatic fat and iron content. Thirty-nine subjects had moderate to severe steatosis and 276 had mild or no steatosis. A liver attenuation threshold of 48 HU was 100% specific (276/276) for moderate to severe steatosis, with no false-positives. Sensitivity, PPV and NPV at this HU threshold was 53.8%, 100% and 93.9%. Hepatic fat content was the overwhelming determinant of liver attenuation values, but CT system (P < 0.001), and hepatic iron (P = 0.035) also had a statistically significant independent association. Unenhanced CT liver attenuation alone is highly specific for moderate to severe hepatic steatosis, allowing for confident non-invasive identification of large retrospective/prospective cohorts for natural history evaluation of incidental non-alcoholic fatty liver disease. Low sensitivity, however, precludes effective population screening at this threshold. (orig.)

Specificity of unenhanced CT for non-invasive diagnosis of hepatic steatosis: implications for the investigation of the natural history of incidental steatosis

International Nuclear Information System (INIS)

Pickhardt, Perry J.; Hahn, Luke; Park, Seong Ho; Lee, Sung-Gyu; Bae, Kyongtae T.; Yu, Eun Sil

2012-01-01

To determine a highly specific liver attenuation threshold at unenhanced CT for biopsy-proven moderate to severe hepatic steatosis (≥30% at histology). 315 asymptomatic adults (mean age ± SD, 31.5 ± 10.1 years; 207 men, 108 women) underwent same-day unenhanced liver CT and ultrasound-guided liver biopsy. Blinded to biopsy results, CT liver attenuation was measured using standard region-of-interest methodology. Multiple linear regression analysis was used to assess the relationship of CT liver attenuation with patient age, gender, BMI, CT system, and hepatic fat and iron content. Thirty-nine subjects had moderate to severe steatosis and 276 had mild or no steatosis. A liver attenuation threshold of 48 HU was 100% specific (276/276) for moderate to severe steatosis, with no false-positives. Sensitivity, PPV and NPV at this HU threshold was 53.8%, 100% and 93.9%. Hepatic fat content was the overwhelming determinant of liver attenuation values, but CT system (P < 0.001), and hepatic iron (P = 0.035) also had a statistically significant independent association. Unenhanced CT liver attenuation alone is highly specific for moderate to severe hepatic steatosis, allowing for confident non-invasive identification of large retrospective/prospective cohorts for natural history evaluation of incidental non-alcoholic fatty liver disease. Low sensitivity, however, precludes effective population screening at this threshold. (orig.)

Pediatric renal leukemia: spectrum of CT imaging findings

International Nuclear Information System (INIS)

Hilmes, Melissa A.; Dillman, Jonathan R.; Mody, Rajen J.; Strouse, Peter J.

2008-01-01

The kidneys are a site of extramedullary leukemic disease that can be readily detected by CT. To demonstrate the spectrum of CT findings in children with renal leukemic involvement. Twelve children were identified retrospectively as having renal leukemic involvement by contrast-enhanced CT of the abdomen. Contrast-enhanced CT images through the kidneys of each patient were reviewed by two pediatric radiologists. Pertinent imaging findings and renal lengths were documented. The electronic medical record was accessed to obtain relevant clinical and pathologic information. Five patients with renal leukemic involvement presented with multiple bilateral low-attenuation masses, while three patients demonstrated large areas of wedge-shaped and geographic low attenuation. Four other patients presented with unique imaging findings, including a solitary unilateral low-attenuation mass, solitary bilateral low-attenuation masses, multiple bilateral low-attenuation masses including unilateral large conglomerate masses, and bilateral areas of ill-defined parenchymal low attenuation. Two patients showed unilateral nephromegaly, while eight other patients showed bilateral nephromegaly. Two patients had normal size kidneys. Two patients had elevated serum creatinine concentrations at the time of imaging. Renal leukemic involvement in children can present with a variety of CT imaging findings. Focal renal abnormalities as well as nephromegaly are frequently observed. Most commonly, renal leukemic involvement does not appear to impair renal function. (orig.)

Pediatric renal leukemia: spectrum of CT imaging findings

Energy Technology Data Exchange (ETDEWEB)

Hilmes, Melissa A. [University of Michigan Health System, C.S. Mott Children' s Hospital, Section of Pediatric Radiology, Ann Arbor, MI (United States); Vanderbilt University Children' s Hospital, Section of Pediatric Radiology, Nashville, TN (United States); Dillman, Jonathan R. [University of Michigan Health System, C.S. Mott Children' s Hospital, Section of Pediatric Radiology, Ann Arbor, MI (United States); University of Michigan Health System, Department of Radiology, Ann Arbor, MI (United States); Mody, Rajen J. [University of Michigan Health System, C.S. Mott Children' s Hospital, Division of Pediatric Hematology-Oncology and Bone Marrow Transplantation, Ann Arbor, MI (United States); Strouse, Peter J. [University of Michigan Health System, C.S. Mott Children' s Hospital, Section of Pediatric Radiology, Ann Arbor, MI (United States)

2008-04-15

The kidneys are a site of extramedullary leukemic disease that can be readily detected by CT. To demonstrate the spectrum of CT findings in children with renal leukemic involvement. Twelve children were identified retrospectively as having renal leukemic involvement by contrast-enhanced CT of the abdomen. Contrast-enhanced CT images through the kidneys of each patient were reviewed by two pediatric radiologists. Pertinent imaging findings and renal lengths were documented. The electronic medical record was accessed to obtain relevant clinical and pathologic information. Five patients with renal leukemic involvement presented with multiple bilateral low-attenuation masses, while three patients demonstrated large areas of wedge-shaped and geographic low attenuation. Four other patients presented with unique imaging findings, including a solitary unilateral low-attenuation mass, solitary bilateral low-attenuation masses, multiple bilateral low-attenuation masses including unilateral large conglomerate masses, and bilateral areas of ill-defined parenchymal low attenuation. Two patients showed unilateral nephromegaly, while eight other patients showed bilateral nephromegaly. Two patients had normal size kidneys. Two patients had elevated serum creatinine concentrations at the time of imaging. Renal leukemic involvement in children can present with a variety of CT imaging findings. Focal renal abnormalities as well as nephromegaly are frequently observed. Most commonly, renal leukemic involvement does not appear to impair renal function. (orig.)

Localized-low attenuation of the lung on thin-section CT in experimentally induced pulmonary arterial occlusion with balloon catheter in pigs

International Nuclear Information System (INIS)

Lee, Hyun Ju; Goo, Jin Mo; Im, Jung Gi; Kim, Ji Hye

2008-01-01

To determine whether a localized low-attenuation (LLA) is induced on a thin-section CT (TSCT) during an acute pulmonary arterial occlusion in pigs. In eight pigs, 14 sites of the descending pulmonary artery were obstructed using balloon catheters. The lung TSCTs were obtained immediately after pulmonary artery obstruction (n=13), 10 min (n=10), 30 min (n=14) and 60 min (n=14) after pulmonary artery obstruction at the end of expiration. The TSCTs were also obtained after balloon-deflation at the end of expiration (n=11) and with the balloon-reinflation at inspiration (n=6). Of the 14 sites of pulmonary artery obstruction, 11 (79%) showed LLA. However, LLA progressively became fainter or disappeared on a follow-up CT in seven sites. When the balloon was deflated, 10 of the 11 sites measured showed no change in lung attenuation. After full inspiration, LLA disappeared in three of the six sites. The corresponding areas of LLA on the CT showed a statistically significant increase compared to the baseline CT immediately after inflation (ρ =0.021) and 30 minutes after inflation (ρ = 0.041), and after balloon deflation (ρ = 0.036). LLA was induced by acute pulmonary artery obstruction. However, LLA, gradually faded over the 60 minutes following obstruction. LLAs were maintained despite the restoration of pulmonary arterial flow, but disappeared as a result of a full inspiration. Thus, LLA might be caused by air trapping

Basic studies of CT in the maxillofacial areas, 1

International Nuclear Information System (INIS)

Suzuki, Shinichiro; Kaneko, Hiroshi; Higashi, Tomomitsu; Takenaka, Eiichi.

1982-01-01

As CT values of hard tissues would pose problems in the application of CT to the maxillofacial area, attenuation coefficients of each oral hard tissue were examined based on the existing data, and the linearity in the area of high x-ray attenuation was examined. We thought that a new contrast scale suitable for each area should be established for measurements of CT values of tissues of high x-ray attenuation such as teeth. (Chiba, N.)

Fundamental studies for CT in the oral region

International Nuclear Information System (INIS)

Suzuki, Shinichiro

1984-01-01

Fundamental studies were attempted regarding the clinical application of CT (TCT-60A) in the oral region. The investigation assessed the following: 1) calculation of CT-No for oral hard tissues, 2) test for linearity CT-No vs. the linear attenuation coefficient in high X-ray attenuation materials, 3) observation of artifacts caused by dental materials and 4) measurement of patient doses of CT used at the maxillary sinus. The results obtained were as follows. 1) Calculated CT-No (E=70 KeV) values for oral hard tissues were enamel 3.51 x 10 3 , dentine 2.40 x 10 3 , cementum 1.88 x 10 3 , cortical bone 1.48 x 10 3 and mandible 1.01 x 10 3 . 2) Linearity for CT-No vs. the linear attenuation coefficient gave a good relative coefficient between lucite and teflon, but linearity between lucite and aluminum was not good enough. 3) Three different artifacts from the copper rod were observed: (1) connection line artifact, (2) star-burst artifact and (3) figure-eight artifact. 4) Under shot caused by composite resin was observed, and artifact from both the radiopaque composite resin and amalgam were the same kinds as those from the copper rod. 5) Calculated CT-No (E=66 KeV) values for dental materials were copper 5.48 x 10 4 , composite resin 1.24 x 10 3 , radiopaque composite resin 4.65 x 10 3 and amalgam 2.27 x 10 5 . 6) Absorbed doses of lenses and thyroid gland using CT at the mixillary sinus region were 59 mrad (59 x 10 -2 mGy) and 17 mrad (17 x 10 -2 mGy) for a single scanning. 7) The volume dose of the head under a single CT scanning was estimated as 820 g.rad (820 x 10 -5 Kg.Gy) by the TLD method, and 900 g.rad (900 x 10 -5 Kg.Gy) by the film dosimetry method. The difference in these values was considered to be the effect arising from ununiformity of the X-ray beam. (author)

Modified CT imaging by reduction factor transformations

International Nuclear Information System (INIS)

Doehring, W.; Linke, G.

1981-01-01

The possibilities of CT image modification which had existed so far for given matrix of attenuation values (window setting, highlighting, black-and-white or colour reversal and logarithmic distortion of the video signal) are supplemented by the method of attenuation value transformation. As a specific case a linear interval by interval attenuation value transformation is described. First of all, the intirety of the measured CT values is transformed into the corresponding CT quotients (CTQ) and then subdivided into 5 optional intervals. Each one freely selected CTQ value can be allocated to the first and to the last interval; the intermediate 3 intervals can be linearly transformed at random. The article discusses the influence of such a manipulation on CT image reproduction; this is of particular importance for the image visualisation of the results of quantitative organ analyses by means of computed tomography. The presented paper also points to the possibility of effecting further attenuation value transformations. (orig.) [de

Attenuation values of renal parenchyma in virtual noncontrast images acquired from multiphase renal dual-energy CT: Comparison with standard noncontrast CT.

Science.gov (United States)

Lin, Yuan-Mao; Chiou, Yi-You; Wu, Mei-Han; Huang, Shan-Su; Shen, Shu-Huei

2018-04-01

To compare the renal parenchyma attenuation of virtual noncontrast (VNC) images derived from multiphase renal dual-energy computed tomography (DECT) with standard noncontrast (SNC) images, and to determine the optimum phase for VNC images. Twenty-nine men and 16 women (mean age, 61 ± 13 years; range, 37-89 years) underwent dynamic renal DECT (100/Sn140 kVp) were included in this institutional review board-approved retrospective study. There were four phases of the scan, which included noncontrast, corticomedullary (CMP), nephrographic (NP), and excretory phases (EP). The VNC images was generated from CMP, NP and EP. CT numbers of SNC images and VNC images of each phases were measured in the renal cortex and medulla. Mean standard deviation of subcutaneous fat was measured as image noise on SNC and VNC images. Radiation dose was recorded and potential radiation dose reduction was estimated. Results were tested for statistical significance using the unpaired t-test and agreement using Bland-Altman plot analysis. The difference in mean attenuation between SNC and each phase of VNC images were ≤4 HU. The mean attenuation of renal cortex and medulla was 33.2 ± 4.4 HU, and 34.2 ± 4.8 HU in SNC, 33.6 ± 7.6 HU and 31.1 ± 8.3 HU in VNC of CMP, 34.8 ± 8.6 HU and 35.6 ± 8.5 HU in VNC of NP, 31.5 ± 7.6 HU and 32.4 ± 7.5 HU in VNC of EP. In VNC of CMP, the attenuation of the cortex was higher than the medulla (p VNC of NP, the attenuation of renal cortex was higher than SNC (p VNC of EP, the attenuation of cortex and medulla were lower than SNC (p VNC images from multiphase renal DECT were similar to SNC images. Using the nephrographic phase can gives more comparable VNC images to SNC images in renal parenchyma than other phases. Copyright © 2018 Elsevier B.V. All rights reserved.

TU-H-207A-03: CT Hounsfield Unit Accuracy: Effect of Beam Hardening On Phantom and Clinical Whole-Body CT Images

Energy Technology Data Exchange (ETDEWEB)

Ai, H; Wendt, R [The University of Texas MD Anderson Cancer Center, Houston, TX (United States)

2016-06-15

Purpose: To assess the effect of beam hardening on measured CT HU values. Methods: An anthropomorphic knee phantom was scanned with the CT component of a GE Discovery 690 PET/CT scanner (120kVp, 300mAs, 40?0.625mm collimation, pitch=0.984, FOV=500mm, matrix=512?512) with four different scan setups, each of which induces different degrees of beam hardening by introducing additional attenuation media into the field of view. Homogeneous voxels representing “soft tissue” and “bone” were segmented by HU thresholding followed by a 3D morphological erosion operation which removes the non-homogenous voxels located on the interface of thresholded tissue mask. HU values of segmented “soft tissue” and “bone” were compared.Additionally, whole-body CT data with coverage from the skull apex to the end of toes were retrospectively retrieved from seven PET/CT exams to evaluate the effect of beam hardening in vivo. Homogeneous bone voxels were segmented with the same method previously described. Total In-Slice Attenuation (TISA) for each CT slice, defined as the summation of HU values over all voxels within a CT slice, was calculated for all slices of the seven whole-body CT datasets and evaluated against the mean HU values of homogeneous bone voxels within that slice. Results: HU values measured from the phantom showed that while “soft tissue” HU values were unaffected, added attenuation within the FOV caused noticeable decreases in the measured HU values of “bone” voxels. A linear relationship was observed between bone HU and TISA for slices of the torso and legs, but not of the skull. Conclusion: Beam hardening effect is not an issue of concern for voxels with HU in the soft tissue range, but should not be neglected for bone voxels. A linear relationship exists between bone HU and the associated TISA in non-skull CT slices, which can be exploited to develop a correction strategy.

Ct enterography/ct abdomen and pelvis using neutral oral contrast. a new combination of natural products

International Nuclear Information System (INIS)

Aslam, M.O.

2014-01-01

Our purpose was to assess the performance of a new combination of neutral oral contrast for CT abdomen and CT Enterography in comparison with commercially available neutral oral contrast VoLumen. Seventy three consecutive patients were given sorbitol/CMC (Carboxy Methyl Cellulose) solution or VoLumen as oral contrast agent for abdominal computed tomography (CT) scan. 23 patients were male and 37 females. Age range was between 16 and 67 years. Since the use of CT scan for abdominal pathologies, there was need to separate bowel loops to localize the pathology. Three types of oral contrast can be used in CT-Scan abdomen; Positive, Neutral and negative. The above used contrasts are Neutral contrast these refers to agents that have an attenuation value similar to that of water (0-30 H).Our results show this new combination of Cc and Sorbitol to be equally good as VoLumen, for luminal distension and mural details, in duodenum and jejunum. While better than VoLumen for Ileal distension. (author)

Reduction of metal artifacts from hip prostheses on CT images of the pelvis: value of iterative reconstructions.

Science.gov (United States)

Morsbach, Fabian; Bickelhaupt, Sebastian; Wanner, Guido A; Krauss, Andreas; Schmidt, Bernhard; Alkadhi, Hatem

2013-07-01

To assess the value of iterative frequency split-normalized (IFS) metal artifact reduction (MAR) for computed tomography (CT) of hip prostheses. This study had institutional review board and local ethics committee approval. First, a hip phantom with steel and titanium prostheses that had inlays of water, fat, and contrast media in the pelvis was used to optimize the IFS algorithm. Second, 41 consecutive patients with hip prostheses who were undergoing CT were included. Data sets were reconstructed with filtered back projection, the IFS algorithm, and a linear interpolation MAR algorithm. Two blinded, independent readers evaluated axial, coronal, and sagittal CT reformations for overall image quality, image quality of pelvic organs, and assessment of pelvic abnormalities. CT attenuation and image noise were measured. Statistical analysis included the Friedman test, Wilcoxon signed-rank test, and Levene test. Ex vivo experiments demonstrated an optimized IFS algorithm by using a threshold of 2200 HU with four iterations for both steel and titanium prostheses. Measurements of CT attenuation of the inlays were significantly (P algorithm for CT image reconstruction significantly reduces metal artifacts from hip prostheses, improves the reliability of CT number measurements, and improves the confidence for depicting pelvic abnormalities.

The influence of different contrast medium concentrations and injection protocols on quantitative and clinical assessment of FDG–PET/CT in lung cancer

Energy Technology Data Exchange (ETDEWEB)

Verburg, Frederik A., E-mail: fverburg@ukaachen.de [RWTH Aachen University Hospital, Department of Nuclear Medicine, Pauwelsstraße 30, 52074 Aachen (Germany); Maastricht University Medical Center, Department of Nuclear Medicine, P. Debyelaan 25, 6229 HX Maastricht (Netherlands); Kuhl, Christiane K. [RWTH Aachen University Hospital, Department of Diagnostic and Interventional Radiology, Pauwelsstraße 30, 52074 Aachen (Germany); Pietsch, Hubertus [Bayer Pharma AG, Berlin, Müllerstrasse 178, 13353 Berlin (Germany); Palmowski, Moritz [RWTH Aachen University Hospital, Department of Nuclear Medicine, Pauwelsstraße 30, 52074 Aachen (Germany); Mottaghy, Felix M. [RWTH Aachen University Hospital, Department of Nuclear Medicine, Pauwelsstraße 30, 52074 Aachen (Germany); Maastricht University Medical Center, Department of Nuclear Medicine, P. Debyelaan 25, 6229 HX Maastricht (Netherlands); Behrendt, Florian F. [RWTH Aachen University Hospital, Department of Nuclear Medicine, Pauwelsstraße 30, 52074 Aachen (Germany)

2013-10-01

Objectives: To compare the effects of two different contrast medium concentrations for use in computed X-ray tomography (CT) employing two different injection protocols on positron emission tomography (PET) reconstruction in combined 2-{sup 18}F-desoxyglucose (FDG) PET/CT in patients with a suspicion of lung cancer. Methods: 120 patients with a suspicion of lung cancer were enrolled prospectively. PET images were reconstructed with the non-enhanced and venous phase contrast CT obtained after injection of iopromide 300 mg/ml or 370 mg/ml using either a fixed-dose or a body surface area adapted injection protocol. Maximum and mean standardized uptake values (SUVmax and SUVmean) and contrast enhancement (HU) were determined in the subclavian vein, ascending aorta, abdominal aorta, inferior vena cava, portal vein, liver and kidney and in the suspicious lung lesion. PET data were evaluated visually for the presence of malignancy and image quality. Results: At none of the sites a significant difference in the extent of the contrast enhancement between the four different protocols was found. However, the variability of the contrast enhancement at several anatomical sites was significantly greater in the fixed dose groups than in the BSA groups for both contrast medium concentrations. At none of the sites a significant difference was found in the extent of the SUVmax and SUVmean increase as a result of the use of the venous phase contrast enhanced CT for attenuation. Visual clinical evaluation of lesions showed no differences between contrast and non-contrast PET/CT (P = 0.32). Conclusions: Contrast enhanced CT for attenuation correction in combined PET/CT in lung cancer affects neither the clinical assessment nor image quality of the PET-images. A body surface adapted contrast medium protocol reduces the interpatient variability in contrast enhancement.

Generation of a Four-Class Attenuation Map for MRI-Based Attenuation Correction of PET Data in the Head Area Using a Novel Combination of STE/Dixon-MRI and FCM Clustering.

Science.gov (United States)

Khateri, Parisa; Saligheh Rad, Hamidreza; Jafari, Amir Homayoun; Fathi Kazerooni, Anahita; Akbarzadeh, Afshin; Shojae Moghadam, Mohsen; Aryan, Arvin; Ghafarian, Pardis; Ay, Mohammad Reza

2015-12-01

The aim of this study is to generate a four-class magnetic resonance imaging (MRI)-based attenuation map (μ-map) for attenuation correction of positron emission tomography (PET) data of the head area using a novel combination of short echo time (STE)/Dixon-MRI and a dedicated image segmentation method. MR images of the head area were acquired using STE and two-point Dixon sequences. μ-maps were derived from MRI images based on a fuzzy C-means (FCM) clustering method along with morphologic operations. Quantitative assessment was performed to evaluate generated MRI-based μ-maps compared to X-ray computed tomography (CT)-based μ-maps. The voxel-by-voxel comparison of MR-based and CT-based segmentation results yielded an average of more than 95 % for accuracy and specificity in the cortical bone, soft tissue, and air region. MRI-based μ-maps show a high correlation with those derived from CT scans (R (2) > 0.95). Results indicate that STE/Dixon-MRI data in combination with FCM-based segmentation yields precise MR-based μ-maps for PET attenuation correction in hybrid PET/MRI systems.

Bronchus-associated lymphoid tissue (BALT) lymphoma of the lung showing mosaic pattern of inhomogeneous attenuation on thin-section CT: a case report

International Nuclear Information System (INIS)

Lee, In Jae; Kim, Sung Hwan; Koo, Soo Hyun; Kim, Hyun Beom; Hwang, Dae Hyun; Lee, Kwan Seop; Lee, Yul; Jang, Kee Taek; Kim, Duck Hwan

2000-01-01

The authors present a case of histologically proven bronchus-associated lymphoid tissue (BALT) lymphoma of the lung in a patient with primary Sjogren's syndrome that manifested on thin-section CT scan as a mosaic pattern of inhomogeneous attenuation due to mixed small airway and infiltrative abnormalities

The usefulness of the combined PET-CT scanner

International Nuclear Information System (INIS)

Yoshikawa, Kyosan

2003-01-01

Recently, combined PET-CT scanners that simultaneously reveal both anatomical and metabolic images within the body have been developed. The Siemens Biograph was the first PET-CT used in Japan and was installed at National Institute of Radiological Sciences (NIRS) at the end of March 2002. The Biograph system integrates Siemens PET (HR+) and spiral CT (SOMATOM Emotion Duo) technologies with a multimodality computer platform. The CT data obtained with PET-CT is also used for attenuation corrections of the PET images. The advantages of PET-CT for clinical use are much shorter study time for each patient, easy and precise alignment of the patient's lesion within the PET field of view, an increase in PET image quality due to the CT attenuation correction system which gives a higher spatial resolution and produces much less noise in the attenuation correction data, and an improvement in diagnostic accuracy provided by both functional and anatomic imaging. The Japanese government has not yet approved the marketing of PET-CT. We are continuing to investigate its usefulness. We expect that PET-CT will be a major diagnostic tool for oncology imaging in the near future. (authors)

Is metal artefact reduction mandatory in cardiac PET/CT imaging in the presence of pacemaker and implantable cardioverter defibrillator leads?

Energy Technology Data Exchange (ETDEWEB)

Ghafarian, Pardis [Shahid Beheshti University, Department of Radiation Medicine, Tehran (Iran, Islamic Republic of); Geneva University Hospital, Division of Nuclear Medicine, Geneva 4 (Switzerland); Tehran University of Medical Sciences, Research Center for Science and Technology in Medicine, Tehran (Iran, Islamic Republic of); Aghamiri, S.M.R. [Shahid Beheshti University, Department of Radiation Medicine, Tehran (Iran, Islamic Republic of); Ay, Mohammad R. [Tehran University of Medical Sciences, Research Center for Science and Technology in Medicine, Tehran (Iran, Islamic Republic of); Tehran University of Medical Sciences, Department of Medical Physics and Biomedical Engineering, Tehran (Iran, Islamic Republic of); Tehran University of Medical Sciences, Research Institute for Nuclear Medicine, Tehran (Iran, Islamic Republic of); Rahmim, Arman [Johns Hopkins University, Department of Radiology, Baltimore, MD (United States); Schindler, Thomas H. [Geneva University, Cardiovascular Center, Nuclear Cardiology, Geneva (Switzerland); Ratib, Osman [Geneva University Hospital, Division of Nuclear Medicine, Geneva 4 (Switzerland); Zaidi, Habib [Geneva University Hospital, Division of Nuclear Medicine, Geneva 4 (Switzerland); Geneva University, Geneva Neuroscience Center, Geneva (Switzerland)

2011-02-15

Cardiac PET/CT imaging is often performed in patients with pacemakers and implantable cardioverter defibrillator (ICD) leads. However, metallic implants usually produce artefacts on CT images which might propagate to CT-based attenuation-corrected (CTAC) PET images. The impact of metal artefact reduction (MAR) for CTAC of cardiac PET/CT images in the presence of pacemaker, ICD and ECG leads was investigated using both qualitative and quantitative analysis in phantom and clinical studies. The study included 14 patients with various leads undergoing perfusion and viability examinations using dedicated cardiac PET/CT protocols. The PET data were corrected for attenuation using both artefactual CT images and CT images corrected using the MAR algorithm. The severity and magnitude of metallic artefacts arising from these leads were assessed on both linear attenuation coefficient maps ({mu}-maps) and attenuation-corrected PET images. CT and PET emission data were obtained using an anthropomorphic thorax phantom and a dedicated heart phantom made in-house incorporating pacemaker and ICD leads attached at the right ventricle of the heart. Volume of interest-based analysis and regression plots were performed for regions related to the lead locations. Bull's eye view analysis was also performed on PET images corrected for attenuation with and without the MAR algorithm. In clinical studies, the visual assessment of PET images by experienced physicians and quantitative analysis did not reveal erroneous interpretation of the tracer distribution or significant differences when PET images were corrected for attenuation with and without MAR. In phantom studies, the mean differences between tracer uptake obtained without and with MAR were 10.16{+-}2.1% and 6.86{+-}2.1% in the segments of the heart in the vicinity of metallic ICD or pacemaker leads, and were 4.43{+-}0.5% and 2.98{+-}0.5% in segments far from the leads. Although the MAR algorithm was able to effectively improve

Assessment of anatomic relation between pulmonary perfusion and morphology in pulmonary emphysema with breath-hold SPECT-CT fusion images

International Nuclear Information System (INIS)

Suga, Kazuyoshi; Kawakami, Yasuhiko; Iwanaga, Hideyuki; Hayashi, Noriko; Seto, Akiko; Matsunaga, Naofumi

2008-01-01

Anatomic relation between pulmonary perfusion and morphology in pulmonary emphysema was assessed on deep-inspiratory breath-hold (DIBrH) perfusion single-photon emission computed tomography (SPECT)-CT fusion images. Subjects were 38 patients with pulmonary emphysema and 11 non-smoker controls, who successfully underwent DIBrH and non-BrH perfusion SPECT using a dual-headed SPECT system during the period between January 2004 and June 2006. DIBrH SPECT was three-dimensionally co-registered with DIBrH CT to comprehend the relationship between lung perfusion defects and CT low attenuation areas (LAA). By comparing the appearance of lung perfusion on DIBrH with non-BrH SPECT, the correlation with the rate constant for the alveolar-capillary transfer of carbon monoxide (DLCO/VA) was compared between perfusion abnormalities on these SPECTs and LAA on CT. DIBrH SPECT provided fairly uniform perfusion in controls, but significantly enhanced perfusion heterogeneity when compared with non-BrH SPECT in pulmonary emphysema patients (P<0.001). The reliable DIBrH SPECT-CT fusion images confirmed more extended perfusion defects than LAA on CT in majority (73%) of patients. Perfusion abnormalities on DIBrH SPECT were more closely correlated with DLCO/VA than LAA on CT (P<0.05). DIBrH SPECT identifies affected lungs with perfusion abnormality better than does non-BrH SPECT in pulmonary emphysema. DIBrH SPECT-CT fusion images are useful for more accurately localizing affected lungs than morphologic CT alone in this disease. (author)

In vitro CT evaluation of intrahepatic stones: correlation with chemical composition

International Nuclear Information System (INIS)

Kim, Young Jun; Han, Joon Koo; Jeong, Jun Yong; Lee, Kyoung Ho; Kim, Se Hyung; Kim, Young Il; Lee, Jeong Min; Choi, Byung Ihn; Park, Youn-Chan; Kim, Sun-Whe

2005-01-01

Objective: To describe in vitro CT features of intrahepatic stones and to correlate CT attenuation with chemical composition. Materials and methods: Of the patients who underwent choledochoscopic intrahepatic stone removal between 1998 and 2001, 54 patients with stones larger than 3 mm were enrolled in this study. In each case, a chemical compositional analysis was performed to determine calcium, cholesterol, total bilirubin, and inorganic phosphorus compositions. The three largest stones obtained from each patient were imaged by CT. CT attenuation numbers were measured in the center images of each stone by drawing free-hand region of interest (ROI). The measured CT attenuation numbers were correlated with their chemical composition. Also, CT attenuation numbers of stones were compared with that of the liver on non-contrast CT (50-70 HU). Results: Stone size ranged from 3.1 to 10.5 mm (mean ± S.D.: 6.0 ± 1.4). The CT attenuation numbers (HU) of stones ranged from 36.4 to 410.19 (mean ± S.D.: 94.6 ± 49.9). CT numbers of stones were below 70 HU in 11 patients (20.4%), and below 90 HU in 33 patients (59.3%). The chemical analysis data of the stones were as follows: calcium (0.5-6.5 wt.%; mean ± S.D., 2.6 ± 1.4), total bilirubin (0.45-24.4 wt.%; 13.1 ± 6.2), cholesterol (5.4-73.9 wt.%; 29.3 ± 17.4), phosphorus (0.1-1.2 wt.%; 0.6 ± 0.3), and non-soluble residue (17.6-85.4 wt.%; 57.0 ± 22.6). There was a weak but significant correlation between calcium composition and CT attenuation (r = 0.38, P 0.01; total bilirubin, r = 0.05, P > 0.01; phosphorus, r = 0.01, P > 0.01). Conclusion: On non-contrast CT, intrahepatic stones would not be hyperattenuating with respect to liver parenchyma in about one fifth of patients. The CT attenuation of stones correlates with calcium and does not correlate with any other chemical composition

Whole-body bone segmentation from MRI for PET/MRI attenuation correction using shape-based averaging

DEFF Research Database (Denmark)

Arabi, Hossein; Zaidi, H.

2016-01-01

Purpose: The authors evaluate the performance of shape-based averaging (SBA) technique for whole-body bone segmentation from MRI in the context of MRI-guided attenuation correction (MRAC) in hybrid PET/MRI. To enhance the performance of the SBA scheme, the authors propose to combine it with stati......Purpose: The authors evaluate the performance of shape-based averaging (SBA) technique for whole-body bone segmentation from MRI in the context of MRI-guided attenuation correction (MRAC) in hybrid PET/MRI. To enhance the performance of the SBA scheme, the authors propose to combine...... it with statistical atlas fusion techniques. Moreover, a fast and efficient shape comparisonbased atlas selection scheme was developed and incorporated into the SBA method. Methods: Clinical studies consisting of PET/CT and MR images of 21 patients were used to assess the performance of the SBA method. In addition...... voting (MV) atlas fusion scheme was also evaluated as a conventional and commonly used method. MRI-guided attenuation maps were generated using the different segmentation methods. Thereafter, quantitative analysis of PET attenuation correction was performed using CT-based attenuation correction...

Investigation of CT diagnostic imaging of 'Eosinophilic chronic rhinosinusitis'

International Nuclear Information System (INIS)

Ogino, Nobuhiro; Matsuwaki, Yoshinori; Ojiri, Hiroya; Kanou, Asami; Fukuda, Kunihiko

2011-01-01

'Eosinophilic chronic rhinosinusitis (ECRS)' is a newly developed entity of chronic rhinosinusitis, which shows resistance against conventional treatment and poor prognosis. Pathologically, ECRS is manifested by high-degree of eosinophilic infiltration in the paranasal sinus mucosa. We structure the CT diagnostic criteria of ECRS and assess its availability. This diagnostic criteria consists of disease distribution (bilateral and predominant in the ethmoid sinus), existence of nasal polyp (s) and high attenuation which suggestive of allergic mucine. We retrospectively review CT of clinically diagnosed 14 ECRS cases to see if CT features of each case fit the criteria or not. The current CT diagnostic criteria of ECRS were proven to be useful to evaluate cases with clinical suspicion of ECRS. (author)

CT quantification of lung and airways in normal Korean subjects

Energy Technology Data Exchange (ETDEWEB)

Kim, Song Soo; Lee, Jeong Eun; Shin, Hye Soo [Dept. of Radiology, Chungnam National University Hospital, Chungnam National University School of Medicine, Daejeon (Korea, Republic of); Jin, Gong Yong; Li, Yuan Zhe [Dept. of Radiology, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Jeonju (Korea, Republic of)

2017-08-01

To measure and compare the quantitative parameters of the lungs and airways in Korean never-smokers and current or former smokers (“ever-smokers”). Never-smokers (n = 119) and ever-smokers (n = 45) who had normal spirometry and visually normal chest computed tomography (CT) results were retrospectively enrolled in this study. For quantitative CT analyses, the low attenuation area (LAA) of LAA{sub I-950}, LAA{sub E-856}, CT attenuation value at the 15th percentile, mean lung attenuation (MLA), bronchial wall thickness of inner perimeter of a 10 mm diameter airway (Pi10), total lung capacity (TLC{sub CT}), and functional residual capacity (FRC{sub CT}) were calculated based on inspiratory and expiratory CT images. To compare the results between groups according to age, sex, and smoking history, independent t test, one way ANOVA, correlation test, and simple and multiple regression analyses were performed. The values of attenuation parameters and volume on inspiratory and expiratory quantitative computed tomography (QCT) were significantly different between males and females (p < 0.001). The MLA and the 15th percentile value on inspiratory QCT were significantly lower in the ever-smoker group than in the never-smoker group (p < 0.05). On expiratory QCT, all lung attenuation parameters were significantly different according to the age range (p < 0.05). Pi10 in ever-smokers was significantly correlated with forced expiratory volume in 1 second/forced vital capacity (r = −0.455, p = 0.003). In simple and multivariate regression analyses, TLC{sub CT}, FRC{sub CT}, and age showed significant associations with lung attenuation (p < 0.05), and only TLC{sub CT} was significantly associated with inspiratory Pi10. In Korean subjects with normal spirometry and visually normal chest CT, there may be significant differences in QCT parameters according to sex, age, and smoking history.

Semi-quantitative assessment of tricuspid regurgitation on contrast-enhanced multidetector CT

International Nuclear Information System (INIS)

Groves, A.M.; Win, T.; Charman, S.C.; Wisbey, C.; Pepke-Zaba, J.; Coulden, R.A.

2004-01-01

AIM: To assess whether the early regurgitation of intravenous contrast medium into the inferior vena cava (IVC) and/or hepatic veins on computed tomography (CT), indicates tricuspid regurgitation (TR), and if so, whether it be used to grade severity. MATERIALS AND METHODS: We identified 86 consecutive patients that had been investigated for possible pulmonary endarterectomy at Papworth Hospital. From these, 61 patients were selected in whom CT, transthoracic echocardiography, and right heart catheterization (RHC) had been performed within 6 weeks. Using an arbitrary visual scale, the degree of TR assessed by intravenous contrast-enhanced CT was compared with echocardiography. Results were analysed using a kappa weighted statistical test. In addition, CT and echocardiographic assessments of TR severity were correlated with pulmonary artery pressure measurements obtained by RHC (Spearman's rank correlation coefficient). RESULTS: CT assessment of TR had a sensitivity of 90.4% and a specificity of 100% in detecting echocardiographic TR. For TR graded as more than trivial by echocardiography, sensitivity of CT was 100%. With respect to RHC data, the correlation between severity assessment of TR between CT and echocardiography using the Kappa weighted coefficient was 0.56 (moderately good agreement). With respect to RHC data, the correlation between mean pulmonary pressure and TR grading on CT and echocardiography was r=0.685 (p<0.001) and r=0.727 (p<0.001), respectively. CONCLUSION: Early opacification of the IVC or hepatic veins on first-pass contrast-enhanced CT almost invariably indicates TR. There is moderately good agreement between CT and echocardiographic assessment of the severity of TR. Both CT and echocardiographic grading of TR correlate well with RHC measurements of pulmonary artery pressure

Liver tumors, correlation of computed tomography (CT) and pathology

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Okazaki, Atsushi; Niibe, Hideo; Mitsuhashi, Norio

1984-09-01

Computed tomographic and pathologic correlation was studied in 12 autopsied cases with 11 cases of metastatic liver tumors and 1 case of hepatocellular carcinoma. Despite of proliferative patterns of the tumors, nodular low attenuations on CT showed scattered nodular lesions and geographic low attenuations on CT showed groups of multiple small nodular lesions, macroscopically. Abnormal areas of low attenuation were generally diminished by drip infusion contrast enhancement, which was more significant on tumors of infiltrative proliferation. Tumors of infiltrative proliferation revealed little degeneration of surrounding liver cells and abnormal areas of low attenuation were more distinct before contrast enhancement. Tumors of expansive proliferation revealed obvious degeneration of surrounding liver cells and a case having about 200 layers of degenerated liver cells revealed more distinct after contrast enhancement. The central lower density areas in abnormal areas of low attenuation on CT coincided with liquefactive necroses with scanty capillary. vessels and fibrotic changes, histopathologically. But coagulative necroses without decrease of surrouding blood flows were not visualized on CT. CT could not demonstrate the liquefactive necroses in more small nodules than 2 cm in diameter. (J.P.N.).

Bronchus-associated lymphoid tissue (BALT) lymphoma of the lung showing mosaic pattern of inhomogeneous attenuation on thin-section CT: a case report

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Lee, In Jae; Kim, Sung Hwan; Koo, Soo Hyun; Kim, Hyun Beom; Hwang, Dae Hyun; Lee, Kwan Seop; Lee, Yul; Jang, Kee Taek; Kim, Duck Hwan [Hallym University Sacred Heart Hospital, Anyang (Korea, Republic of)

2000-09-01

The authors present a case of histologically proven bronchus-associated lymphoid tissue (BALT) lymphoma of the lung in a patient with primary Sjogren's syndrome that manifested on thin-section CT scan as a mosaic pattern of inhomogeneous attenuation due to mixed small airway and infiltrative abnormalities.

High density renal medulla on unenhanced CT : significance and relation with hydration status

International Nuclear Information System (INIS)

Lee, Eun Jung; Kim, Hyun Suk; Oh, Kyung Seung; Kim, Jong Min; Kim, Sung Min; Jung, Gyoo Sik; Huh, Jin Do; Joh, Young Duk

1999-01-01

To assess the effect of hydration status on renal medullary attenuation and to evaluate the incidence of dense renal medulla, as seen on unenhanced CT. We prospectively studied unenhanced CT scans of 12 healthy volunteers. Obtained done after 10 hours and 15 hours of dehydration and after oral intake of 2L of water. BUN/Cr, urine specific gravity, urine osmole and hematocrit were evaluated after 10 hours of dehydration. CT images were reviewed for the presence of dense renal medulla and differential attenuation of dense renal and isodense medulla and cortex at the same level. The density changes of renal medulla after hydration were evaluated. and CT findings were compared with the results of biochemical studies. In addition, we retrospectively reviewed the CT scans of 200 consecutive patients for evaluation of the incidence of dense renal medulla. In 8 of 12 volunteers, dense renal medulla was seen on CT scan after dehydration. Mean attenuation was 71.3±10.42HU after 10 hours of dehydration, 68.6±13.54HU after 15 hours, and 34.5±11.47HU after hydration. No significant attenuation differences were detected between 10 hours and 15 hours of dehydration, but significantly lower attenuation values were noted after hydration. For isodense medulla, the mean attenuation value was 35.7±7.9HU after 10 hours of dehydration, 39.58±9.66HU after 15 hours, and 36.58±7.77HU after hydration. The mean attenuation values of cortex were 35.9±5.95HU after 10 hours of dehydration. 37.58±5.95HU after 15 hours, and 37.08±9.75HU after hydration. With regard not only to duration of dehydration, but also ti hydration, no differences in attenuation values were noted for renal cortex or isodense renal medulla. However, higher density was noted in dense renal medulla than in isodense medulla or cortex for the same duration of dehydration. After hydration, complete resolution was seen at five of eight sites and incomplete resolution at three of eight sites. There was no correlation

X-ray-based attenuation correction for positron emission tomography/computed tomography scanners.

Science.gov (United States)

Kinahan, Paul E; Hasegawa, Bruce H; Beyer, Thomas

2003-07-01

A synergy of positron emission tomography (PET)/computed tomography (CT) scanners is the use of the CT data for x-ray-based attenuation correction of the PET emission data. Current methods of measuring transmission use positron sources, gamma-ray sources, or x-ray sources. Each of the types of transmission scans involves different trade-offs of noise versus bias, with positron transmission scans having the highest noise but lowest bias, whereas x-ray scans have negligible noise but the potential for increased quantitative errors. The use of x-ray-based attenuation correction, however, has other advantages, including a lack of bias introduced from post-injection transmission scanning, which is an important practical consideration for clinical scanners, as well as reduced scan times. The sensitivity of x-ray-based attenuation correction to artifacts and quantitative errors depends on the method of translating the CT image from the effective x-ray energy of approximately 70 keV to attenuation coefficients at the PET energy of 511 keV. These translation methods are usually based on segmentation and/or scaling techniques. Errors in the PET emission image arise from positional mismatches caused by patient motion or respiration differences between the PET and CT scans; incorrect calculation of attenuation coefficients for CT contrast agents or metallic implants; or keeping the patient's arms in the field of view, which leads to truncation and/or beam-hardening (or x-ray scatter) artifacts. Proper interpretation of PET emission images corrected for attenuation by using the CT image relies on an understanding of the potential artifacts. In cases where an artifact or bias is suspected, careful inspection of all three available images (CT and PET emission with and without attenuation correction) is recommended. Copyright 2003 Elsevier Inc. All rights reserved.

Application of CT texture analysis in predicting histopathological characteristics of gastric cancers

International Nuclear Information System (INIS)

Liu, Shunli; Liu, Song; Ji, Changfeng; Zheng, Huanhuan; Pan, Xia; Zhang, Yujuan; He, Jian; Zhou, Zhengyang; Guan, Wenxian; Chen, Ling; Guan, Yue; Li, Weifeng; Ge, Yun

2017-01-01

To explore the application of computed tomography (CT) texture analysis in predicting histopathological features of gastric cancers. Preoperative contrast-enhanced CT images and postoperative histopathological features of 107 patients (82 men, 25 women) with gastric cancers were retrospectively reviewed. CT texture analysis generated: (1) mean attenuation, (2) standard deviation, (3) max frequency, (4) mode, (5) minimum attenuation, (6) maximum attenuation, (7) the fifth, 10th, 25th, 50th, 75th and 90th percentiles, and (8) entropy. Correlations between CT texture parameters and histopathological features were analysed. Mean attenuation, maximum attenuation, all percentiles and mode derived from portal venous CT images correlated significantly with differentiation degree and Lauren classification of gastric cancers (r, -0.231 ∝-0.324, 0.228 ∝ 0.321, respectively). Standard deviation and entropy derived from arterial CT images also correlated significantly with Lauren classification of gastric cancers (r = -0.265, -0.222, respectively). In arterial phase analysis, standard deviation and entropy were significantly lower in gastric cancers with than those without vascular invasion; however, minimum attenuation was significantly higher in gastric cancers with than those without vascular invasion. CT texture analysis held great potential in predicting differentiation degree, Lauren classification and vascular invasion status of gastric cancers. (orig.)

Application of CT texture analysis in predicting histopathological characteristics of gastric cancers

Energy Technology Data Exchange (ETDEWEB)

Liu, Shunli; Liu, Song; Ji, Changfeng; Zheng, Huanhuan; Pan, Xia; Zhang, Yujuan; He, Jian; Zhou, Zhengyang [The Affiliated Hospital of Nanjing University Medical School, Department of Radiology, Nanjing Drum Tower Hospital, Nanjing, Jiangsu Province (China); Guan, Wenxian [The Affiliated Hospital of Nanjing University Medical School, Department of Gastrointestinal Surgery, Nanjing Drum Tower Hospital, Nanjing (China); Chen, Ling [The Affiliated Hospital of Nanjing University Medical School, Department of Pathology, Nanjing Drum Tower Hospital, Nanjing, Jiangsu Province (China); Guan, Yue; Li, Weifeng; Ge, Yun [Nanjing University, School of Electronic Science and Engineering, Nanjing (China)

2017-12-15

To explore the application of computed tomography (CT) texture analysis in predicting histopathological features of gastric cancers. Preoperative contrast-enhanced CT images and postoperative histopathological features of 107 patients (82 men, 25 women) with gastric cancers were retrospectively reviewed. CT texture analysis generated: (1) mean attenuation, (2) standard deviation, (3) max frequency, (4) mode, (5) minimum attenuation, (6) maximum attenuation, (7) the fifth, 10th, 25th, 50th, 75th and 90th percentiles, and (8) entropy. Correlations between CT texture parameters and histopathological features were analysed. Mean attenuation, maximum attenuation, all percentiles and mode derived from portal venous CT images correlated significantly with differentiation degree and Lauren classification of gastric cancers (r, -0.231 ∝-0.324, 0.228 ∝ 0.321, respectively). Standard deviation and entropy derived from arterial CT images also correlated significantly with Lauren classification of gastric cancers (r = -0.265, -0.222, respectively). In arterial phase analysis, standard deviation and entropy were significantly lower in gastric cancers with than those without vascular invasion; however, minimum attenuation was significantly higher in gastric cancers with than those without vascular invasion. CT texture analysis held great potential in predicting differentiation degree, Lauren classification and vascular invasion status of gastric cancers. (orig.)

Predictive value of low tube voltage and dual-energy CT for successful shock wave lithotripsy: an in vitro study.

Science.gov (United States)

Largo, Remo; Stolzmann, Paul; Fankhauser, Christian D; Poyet, Cédric; Wolfsgruber, Pirmin; Sulser, Tullio; Alkadhi, Hatem; Winklhofer, Sebastian

2016-06-01

This study investigates the capabilities of low tube voltage computed tomography (CT) and dual-energy CT (DECT) for predicting successful shock wave lithotripsy (SWL) of urinary stones in vitro. A total of 33 urinary calculi (six different chemical compositions; mean size 6 ± 3 mm) were scanned using a dual-source CT machine with single- (120 kVp) and dual-energy settings (80/150, 100/150 Sn kVp) resulting in six different datasets. The attenuation (Hounsfield Units) of calculi was measured on single-energy CT images and the dual-energy indices (DEIs) were calculated from DECT acquisitions. Calculi underwent SWL and the number of shock waves for successful disintegration was recorded. The prediction of required shock waves regarding stone attenuation/DEI was calculated using regression analysis (adjusted for stone size and composition) and the correlation between CT attenuation/DEI and the number of shock waves was assessed for all datasets. The median number of shock waves for successful stone disintegration was 72 (interquartile range 30-361). CT attenuation/DEI of stones was a significant, independent predictor (P waves with the best prediction at 80 kVp (β estimate 0.576) (P waves ranged between ρ = 0.31 and 0.68 showing the best correlation at 80 kVp (P < 0.001). The attenuation of urinary stones at low tube voltage CT is the best predictor for successful stone disintegration, being independent of stone composition and size. DECT shows no added value for predicting the success of SWL.

Attenuation-based size metric for estimating organ dose to patients undergoing tube current modulated CT exams

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Bostani, Maryam, E-mail: mbostani@mednet.ucla.edu; McMillan, Kyle; Lu, Peiyun; Kim, Hyun J.; Cagnon, Chris H.; McNitt-Gray, Michael F. [Departments of Biomedical Physics and Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90024 (United States); DeMarco, John J. [Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California 90095 (United States)

2015-02-15

Purpose: Task Group 204 introduced effective diameter (ED) as the patient size metric used to correlate size-specific-dose-estimates. However, this size metric fails to account for patient attenuation properties and has been suggested to be replaced by an attenuation-based size metric, water equivalent diameter (D{sub W}). The purpose of this study is to investigate different size metrics, effective diameter, and water equivalent diameter, in combination with regional descriptions of scanner output to establish the most appropriate size metric to be used as a predictor for organ dose in tube current modulated CT exams. Methods: 101 thoracic and 82 abdomen/pelvis scans from clinically indicated CT exams were collected retrospectively from a multidetector row CT (Sensation 64, Siemens Healthcare) with Institutional Review Board approval to generate voxelized patient models. Fully irradiated organs (lung and breasts in thoracic scans and liver, kidneys, and spleen in abdominal scans) were segmented and used as tally regions in Monte Carlo simulations for reporting organ dose. Along with image data, raw projection data were collected to obtain tube current information for simulating tube current modulation scans using Monte Carlo methods. Additionally, previously described patient size metrics [ED, D{sub W}, and approximated water equivalent diameter (D{sub Wa})] were calculated for each patient and reported in three different ways: a single value averaged over the entire scan, a single value averaged over the region of interest, and a single value from a location in the middle of the scan volume. Organ doses were normalized by an appropriate mAs weighted CTDI{sub vol} to reflect regional variation of tube current. Linear regression analysis was used to evaluate the correlations between normalized organ doses and each size metric. Results: For the abdominal organs, the correlations between normalized organ dose and size metric were overall slightly higher for all three

The effect of intravenous contrast on SUV value in 18F-FDG PET/CT using diagnostic high energy CT

International Nuclear Information System (INIS)

Jeong, Young Jin; Kang, Do Young

2006-01-01

According to the development of CT scanner in PET/CT system, the role of CT unit as a diagnostic tool has been more important. To improve the diagnostic ability of CT scanner, it is a key aspect that CT scanning has to be performed with high dose energy and intravenous (IV) contrast. So we investigated the effect of IV contrast media on the maximum SUV (maxSUV) of normal tissues and pathologic lesions using PET/CT scanner with high dose CT scanning. The study enrolled 13 patients who required PET/CT evaluation. At first, the patients were performed whole body non-contrast CT (NCCT - 120 kVp, 130 mAs) scan. Than contrast enhanced CT (CECT) scan was performed immediately. Finally PET scan was followed. The PET emission data were reconstructed twice, once with the NCCT and again with the CECT. We measured the maxSUV of 10 different body regions that were considered as normal in all patients. Also pathologic lesions were investigated. There were not seen focal artifacts in PET images based on CT with IV contrast agent. Firstly, 130 normal regions in 13 patients were evaluated. The maxSUV was significantly different between two PET images (p < 0.001). The maxSUV was 1.1 ± 0.5 in PET images with CECT-corrected attenuation and 1.0 ± 0.5 in PET images with NCCT-corrected attenuation. The limit of agreement was 0.1 ± 0.3 in Bland-Altman analysis. Especially there were significant differences in 6 of 10 regions, apex and base of the right lung, ascending aorta, segment 6 and segment 8 of the liver and spleen (p <0.05). Secondly, 39 pathologic lesions were evaluated. The maxSUV was significantly different between two PET images (p < 0.001). The maxSUV was 4.7 ± 2.0 in PET images with CECT-corrected attenuation and 4.4 ± 2.0 in PET images with NCCT- corrected attenuation. The limit of agreement was 0.4 ± 0.8 in Bland-Altman analysis. Although there were increases of maxSUVs in the PET images based on CT with IV contrast agent, it was very narrow in the range of limit of

Electrocardiography-triggered high-resolution CT for reducing cardiac motion artifact. Evaluation of the extent of ground-glass attenuation in patients with idiopathic pulmonary fibrosis

International Nuclear Information System (INIS)

Nishiura, Motoko; Johkoh, Takeshi; Yamamoto, Shuji

2007-01-01

The aim of this study was to evaluate the decreasing of cardiac motion artifact and whether the extent of ground-glass attenuation of idiopathic pulmonary fibrosis (IPF) was accurately assessed by electrocardiography (ECG)-triggered high-resolution computed tomography (HRCT) by 0.5-s/rotation multidetector-row CT (MDCT). ECG-triggered HRCT were scanned at the end-diastolic phase by a MDCT scanner with the following scan parameters; axial four-slice mode, 0.5 mm collimation, 0.5-s/rotation, 120 kVp, 200 mA/rotation, high-frequency algorithm, and half reconstruction. In 42 patients with IPF, both conventional HRCT (ECG gating (-), full reconstruction) and ECG-triggered HRCT were performed at the same levels (10-mm intervals) with the above scan parameters. The correlation between percent diffusion of carbon monoxide of the lung (%DLCO) and the mean extent of ground-glass attenuation on both conventional HRCT and ECG-triggered HRCT was evaluated with the Spearman rank correlation coefficient test. The correlation between %DLCO and the mean extent of ground-glass attenuation on ECG-triggered HRCT (observer A: r=-0.790, P<0.0001; observer B: r=-0.710, P<0.0001) was superior to that on conventional HRCT (observer A: r=-0.395, P<0.05; observer B: r=-0.577, P=0.002) for both observers. ECG-triggered HRCT by 0.5 s/rotation MDCT can reduce the cardiac motion artifact and is useful for evaluating the extent of ground-glass attenuation of IPF. (author)

An evaluation of in-plane shields during thoracic CT.

Science.gov (United States)

Foley, S J; McEntee, M F; Rainford, L A

2013-08-01

The object of this study was to compare organ dose and image quality effects of using bismuth and barium vinyl in-plane shields with standard and low tube current thoracic CT protocols. A RANDO phantom was scanned using a 64-slice CT scanner and three different thoracic protocols. Thermoluminescent dosemeters were positioned in six locations to record surface and absorbed breast and lung doses. Image quality was assessed quantitatively using region of interest measurements. Scanning was repeated using bismuth and barium vinyl in-plane shields to cover the breasts and the results were compared with standard and reduced dose protocols. Dose reductions were most evident in the breast, skin and anterior lung when shielding was used, with mean reductions of 34, 33 and 10 % for bismuth and 23, 18 and 11 % for barium, respectively. Bismuth was associated with significant increases in both noise and CT attenuation values for all the three protocols, especially anteriorly and centrally. Barium shielding had a reduced impact on image quality. Reducing the overall tube current reduced doses in all the locations by 20-27 % with similar increases in noise as shielding, without impacting on attenuation values. Reducing the overall tube current best optimises dose with minimal image quality impact. In-plane shields increase noise and attenuation values, while reducing anterior organ doses primarily. Shielding remains a useful optimisation tool in CT and barium is an effective alternative to bismuth especially when image quality is of concern.

Evaluation of the attenuation properties of MR equipment for its use in a whole-body PET/MR scanner

International Nuclear Information System (INIS)

Delso, G; Martinez-Moeller, A; Bundschuh, R A; Ziegler, S I; Ladebeck, R; Candidus, Y; Faul, D

2010-01-01

The combination of magnetic resonance imaging (MR) and positron emission tomography (PET) scanners can provide a powerful tool for clinical diagnosis and investigation. Among the challenges of developing a combined scanner, obtaining attenuation maps for PET reconstruction is of critical importance. This requires accounting for the presence of MR hardware in the field of view. The attenuation introduced by this hardware cannot be obtained from MR data. We propose the creation of attenuation models of MR hardware, to be registered into the MR-based attenuation map prior to PET reconstruction. Two steps were followed to assess the viability of this method. First, transmission and emission measurements were performed on MR components (RF coils and medical probes). The severity of the artifacts in the reconstructed PET images was evaluated. Secondly, a high-exposure computed tomography (CT) scan was used to obtain a model of a head coil. This model was registered into the attenuation map of PET/CT scans of a uniform phantom fitted with the coil. The resulting PET images were compared to the PET/CT reconstruction in the absence of coils. The artifacts introduced by misregistration of the model were studied. The transmission scans revealed 17% count loss due to the presence of head and neck coils in the field of view. Important sources of attenuation were found in the lock, signal cables and connectors. However, the worst source of attenuation was the casing between both coils. None of the measured medical probes introduced a significant amount of attenuation. Concerning the attenuation model of the head coil, reconstructed PET images with model-based correction were comparable to the reference PET/CT reconstruction. However, inaccuracies greater than 1-2 mm in the axial positioning of the model led to important artifacts. In conclusion, the results show that model-based attenuation correction is possible. Using a high-exposure scan to create an attenuation model of the

Xenon-enhanced CT using subtraction CT: Basic and preliminary clinical studies for comparison of its efficacy with that of dual-energy CT and ventilation SPECT/CT to assess regional ventilation and pulmonary functional loss in smokers

International Nuclear Information System (INIS)

Ohno, Yoshiharu; Yoshikawa, Takeshi; Takenaka, Daisuke; Fujisawa, Yasuko; Sugihara, Naoki; Kishida, Yuji; Seki, Shinichiro; Koyama, Hisanobu; Sugimura, Kazuro

2017-01-01

Purpose: To prospectively and directly compare the capability for assessments of regional ventilation and pulmonary functional loss in smokers of xenon-ventilation CT obtained with the dual-energy CT (DE-CT) and subtraction CT (Sub-CT) Materials and methods: Twenty-three consecutive smokers (15 men and 8 women, mean age: 69.7 ± 8.7 years) underwent prospective unenhanced and xenon-enhanced CTs, the latter by Sub-CT and DE-CT methods, ventilation SPECT and pulmonary function tests. Sub-CT was generated from unenhanced and xenon-enhanced CT, and all co-registered SPECT/CT data were produced from SPECT and unenhanced CT data. For each method, regional ventilation was assessed by using a 11-point scoring system on a per-lobe basis. To determine the functional lung volume by each method, it was also calculated for individual sublets with a previously reported method. To determine inter-observer agreement for each method, ventilation defect assessment was evaluated by using the χ2 test with weighted kappa statistics. For evaluation of the efficacy of each method for pulmonary functional loss assessment, functional lung volume was correlated with%FEV 1 . Results: Each inter-observer agreement was rated as substantial (Sub-CT: κ = 0.69, p < 0.0001; DE-CT: κ = 0.64, p < 0.0001; SPECT/CT: κ = 0.64, p < 0.0001). Functional lung volume for each method showed significant to good correlation with%FEV 1 (Sub-CT: r = 0.72, p = 0.0001; DE-CT: r = 0.74, p < 0.0001; SPECT/CT: r = 0.66, p = 0.0006). Conclusion: Xenon-enhanced CT obtained by Sub-CT can be considered at least as efficacious as that obtained by DE-CT and SPECT/CT for assessment of ventilation abnormality and pulmonary functional loss in smokers.

Xenon-enhanced CT using subtraction CT: Basic and preliminary clinical studies for comparison of its efficacy with that of dual-energy CT and ventilation SPECT/CT to assess regional ventilation and pulmonary functional loss in smokers

Energy Technology Data Exchange (ETDEWEB)

Ohno, Yoshiharu, E-mail: yosirad@kobe-u.ac.jp [Division of Functional and Diagnostic Imaging Research, Department of Radiology, Kobe University Graduate School of Medicine, Kobe (Japan); Advanced Biomedical Imaging Research Center, Kobe University Graduate School of Medicine, Kobe (Japan); Yoshikawa, Takeshi [Division of Functional and Diagnostic Imaging Research, Department of Radiology, Kobe University Graduate School of Medicine, Kobe (Japan); Advanced Biomedical Imaging Research Center, Kobe University Graduate School of Medicine, Kobe (Japan); Takenaka, Daisuke [Department of Radiology, Hyogo Cancer Center, Akashi (Japan); Fujisawa, Yasuko; Sugihara, Naoki [Toshiba Medical Systems Corporation, Otawara (Japan); Kishida, Yuji; Seki, Shinichiro; Koyama, Hisanobu; Sugimura, Kazuro [Division of Radiology, Department of Radiology, Kobe University Graduate School of Medicine (Japan)

2017-01-15

Purpose: To prospectively and directly compare the capability for assessments of regional ventilation and pulmonary functional loss in smokers of xenon-ventilation CT obtained with the dual-energy CT (DE-CT) and subtraction CT (Sub-CT) Materials and methods: Twenty-three consecutive smokers (15 men and 8 women, mean age: 69.7 ± 8.7 years) underwent prospective unenhanced and xenon-enhanced CTs, the latter by Sub-CT and DE-CT methods, ventilation SPECT and pulmonary function tests. Sub-CT was generated from unenhanced and xenon-enhanced CT, and all co-registered SPECT/CT data were produced from SPECT and unenhanced CT data. For each method, regional ventilation was assessed by using a 11-point scoring system on a per-lobe basis. To determine the functional lung volume by each method, it was also calculated for individual sublets with a previously reported method. To determine inter-observer agreement for each method, ventilation defect assessment was evaluated by using the χ2 test with weighted kappa statistics. For evaluation of the efficacy of each method for pulmonary functional loss assessment, functional lung volume was correlated with%FEV{sub 1}. Results: Each inter-observer agreement was rated as substantial (Sub-CT: κ = 0.69, p < 0.0001; DE-CT: κ = 0.64, p < 0.0001; SPECT/CT: κ = 0.64, p < 0.0001). Functional lung volume for each method showed significant to good correlation with%FEV{sub 1} (Sub-CT: r = 0.72, p = 0.0001; DE-CT: r = 0.74, p < 0.0001; SPECT/CT: r = 0.66, p = 0.0006). Conclusion: Xenon-enhanced CT obtained by Sub-CT can be considered at least as efficacious as that obtained by DE-CT and SPECT/CT for assessment of ventilation abnormality and pulmonary functional loss in smokers.

Utility and limitations of CT in otitis media

International Nuclear Information System (INIS)

Asensio, J.; Lopez-Rios, J.

1998-01-01

To assess the degree of reliability of computed tomography (CT) and the agreement between the imaging studies and intraoperative findings in chronic otitis media (COM) with cholesteatoma. We studied 51 patients diagnosed clinically as having inflammatory disease of the middle ear. All the patients under-went high-resolution Ct of temporal bone in axial and coronal planes. The imaging studies were retrospectively correlated with the intraoperative findings and the sensitivity of CT in the detection of erosive cholesteatoma was determined. Open radical mastoidectomy is the surgical technique most frequently used to treat cholesteatoma in our center. The greatest radio-surgical correlation was achieved in the detection of masses presenting soft tissue attenuation in air-filled cavities in middle ear (100%) and in bone erosion (87.5%). The 20 patients (39%) who were diagnosed as having COM with cholesteatoma underwent surgical treatment in our center. CT is the technique of choice in the study of COM with cholesteatoma, providing basic and necessary information for the image-based diagnosis of this disease, the detection of masses presenting soft tissue attenuation and bone erosion. We also point out the role of CT as an intraoperative guide and discuss its low sensitivity for the detection of small areas of dura mater exposure, ossicular luxation and facial canal dehiscence. (Author) 8 refs

Gastrointestinal stromal tumor: role of spiral CT in diagnosis and evaluation of treatment with STI571

International Nuclear Information System (INIS)

Hu Jiawang; Zhou Linjiang; Wei Jiangong

2011-01-01

Objective: To investigate the CT appearance of gastrointestinal stromal tumors (GISTs) after oral imatinib mesylate (STI571) treatment. Methods: CT scans of 58 cases of GISTs proven by histology and immunohistochemistry were retrospectively analyzed. Dynamic contrast-enhanced CT of 8 patients after STI571 treatment was also evaluated. Results: The tumors originated from the stomach (n=28), small intestine (n=12), duodenum (n=6), colon (n=5), rectum (n=4), mesentery (n=2), and esophagus (n=2). Small GISTs appeared as round or oval, endo- or exophytic masses with well-defined margins and homogeneous contrast enhancement. Large lesions were often irregular infiltrative exophytic masses with heterogeneous enhancement. Ulceration, fistulization and neovascularity can be seen within the larger tumors. CT scans of 5 patients with good treatment response showed rapid transition form a heterogeneously hyper-attenuating pattern to homogeneously hypo-attenuating pattern with resolution of the enhancing tumor nodules and decreased tumor neovascularity. In 3 poor responders, CT showed enlarging or new enhancing nodules within the treated hypo-attenuating tumor, new lesions or metastasis outside the primary tumor. Conclusion: CT can demonstrate changes resulting from treatment of GISTs. It is valuable for guiding and assessing treatment response to STI571. (authors)

The Value of Attenuation Correction in Hybrid Cardiac SPECT/CT on Inferior Wall According to Body Mass Index

International Nuclear Information System (INIS)

Tamam, Muge; Mulazimoglu, Mehmet; Edis, Nurcan; Ozpacaci, Tevfik

2016-01-01

The purpose of this study was to evaluate the diagnostic value of attenuation-corrected single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) on the inferior wall compared to uncorrected (NC) SPECT MPI between obese and nonobese patients. A total of 157 consecutive patients (122 males and 35 females, with median age: 57.4 ± 11 years) who underwent AC technetium 99m-methoxyisobutylisonitrile (AC Tc99m-sestamibi) SPECT MPI were included to the study. A hybrid SPECT and transmission computed tomography (CT) system was used for the diagnosis with 1-day protocol, and stress imaging was performed first. During attenuation correction (AC) processing on a Xeleris Workstation using Myovation cardiac software with ordered subset expectation maximization (OSEM), iterative reconstruction with attenuation correction (IRAC) and NC images filtered back projection (FBP) were used. For statistical purposes, P < 0.05 was considered significant. This study included 73 patients with body mass index (BMI) <30 and 84 patients with BMI ≥ 30. In patients with higher BMI, increased amount of both visual and semiquantitative attenuation of the inferior wall was detected. IRAC reconstruction corrects the diaphragm attenuation of the inferior wall better than FBP. AC with OSEM iterative reconstruction significantly improves the diagnostic value of stress-only SPECT MPI in patients with normal weight and those who are obese, but the improvements are significantly greater in obese patients. Stress-only SPECT imaging with AC provides shorter and lower radiation exposure

The Effects of Iodine Attenuation on Pulmonary Nodule Volumetry using Novel Dual-Layer Computed Tomography Reconstructions.

Science.gov (United States)

den Harder, A M; Bangert, F; van Hamersvelt, R W; Leiner, T; Milles, Julien; Schilham, A M R; Willemink, M J; de Jong, P A

2017-12-01

To assess the effect of iodine attenuation on pulmonary nodule volumetry using virtual non-contrast (VNC) and mono-energetic reconstructions. A consecutive series of patients who underwent a contrast-enhanced chest CT scan were included. Images were acquired on a novel dual-layer spectral CT system. Conventional reconstructions as well as VNC and mono-energetic images at different keV levels were used for nodule volumetry. Twenty-four patients with a total of 63 nodules were included. Conventional reconstructions showed a median (interquartile range) volume and diameter of 174 (87 - 253) mm 3 and 6.9 (5.4 - 9.9) mm, respectively. VNC reconstructions resulted in a significant volume reduction of 5.5% (2.6 - 11.2%; p<0.001). Mono-energetic reconstructions showed a correlation between nodule attenuation and nodule volume (Spearman correlation 0.77, (0.49 - 0.94)). Lowering the keV resulted in increased volumes while higher keV levels resulted in decreased pulmonary nodule volumes compared to conventional CT. Novel dual-layer spectral CT offers the possibility to reconstruct VNC and mono-energetic images. Those reconstructions show that higher pulmonary nodule attenuation results in larger nodule volumes. This may explain the reported underestimation in nodule volume on non-contrast enhanced compared to contrast-enhanced acquisitions. • Pulmonary nodule volumes were measured on virtual non-contrast and mono-energetic reconstructions • Mono-energetic reconstructions showed that higher attenuation results in larger volumes • This may explain the reported nodule volume underestimation on non-contrast enhanced CT • Mostly metastatic pulmonary nodules were evaluated, results might differ for benign nodules.

Quantitative CT characterization of pediatric lung development using routine clinical imaging

Energy Technology Data Exchange (ETDEWEB)

Stein, Jill M.; Brody, Alan S.; Fleck, Robert J. [Cincinnati Children' s Hospital Medical Center, Department of Radiology, Cincinnati, OH (United States); Walkup, Laura L. [Cincinnati Children' s Hospital Medical Center, Center for Pulmonary Imaging Research, Pulmonary Medicine and Radiology, Cincinnati, OH (United States); Woods, Jason C. [Cincinnati Children' s Hospital Medical Center, Department of Radiology, Cincinnati, OH (United States); Cincinnati Children' s Hospital Medical Center, Center for Pulmonary Imaging Research, Pulmonary Medicine and Radiology, Cincinnati, OH (United States)

2016-12-15

The use of quantitative CT analysis in children is limited by lack of normal values of lung parenchymal attenuation. These characteristics are important because normal lung development yields significant parenchymal attenuation changes as children age. To perform quantitative characterization of normal pediatric lung parenchymal X-ray CT attenuation under routine clinical conditions in order to establish a baseline comparison to that seen in pathological lung conditions. We conducted a retrospective query of normal CT chest examinations in children ages 0-7 years from 2004 to 2014 using standard clinical protocol. During these examinations semi-automated lung parenchymal segmentation was performed to measure lung volume and mean lung attenuation. We analyzed 42 CT examinations in 39 children, ages 3 days to 83 months (mean ± standard deviation [SD] = 42 ± 27 months). Lung volume ranged 0.10-1.72 liters (L). Mean lung attenuation was much higher in children younger than 12 months, with values as high as -380 Hounsfield units (HU) in neonates (lung volume 0.10 L). Lung volume decreased to approximately -650 HU by age 2 years (lung volume 0.47 L), with subsequently slower exponential decrease toward a relatively constant value of -860 HU as age and lung volume increased. Normal lung parenchymal X-ray CT attenuation decreases with increasing lung volume and age; lung attenuation decreases rapidly in the first 2 years of age and more slowly thereafter. This change in normal lung attenuation should be taken into account as quantitative CT methods are translated to pediatric pulmonary imaging. (orig.)

Quantitative CT characterization of pediatric lung development using routine clinical imaging

International Nuclear Information System (INIS)

Stein, Jill M.; Brody, Alan S.; Fleck, Robert J.; Walkup, Laura L.; Woods, Jason C.

2016-01-01

The use of quantitative CT analysis in children is limited by lack of normal values of lung parenchymal attenuation. These characteristics are important because normal lung development yields significant parenchymal attenuation changes as children age. To perform quantitative characterization of normal pediatric lung parenchymal X-ray CT attenuation under routine clinical conditions in order to establish a baseline comparison to that seen in pathological lung conditions. We conducted a retrospective query of normal CT chest examinations in children ages 0-7 years from 2004 to 2014 using standard clinical protocol. During these examinations semi-automated lung parenchymal segmentation was performed to measure lung volume and mean lung attenuation. We analyzed 42 CT examinations in 39 children, ages 3 days to 83 months (mean ± standard deviation [SD] = 42 ± 27 months). Lung volume ranged 0.10-1.72 liters (L). Mean lung attenuation was much higher in children younger than 12 months, with values as high as -380 Hounsfield units (HU) in neonates (lung volume 0.10 L). Lung volume decreased to approximately -650 HU by age 2 years (lung volume 0.47 L), with subsequently slower exponential decrease toward a relatively constant value of -860 HU as age and lung volume increased. Normal lung parenchymal X-ray CT attenuation decreases with increasing lung volume and age; lung attenuation decreases rapidly in the first 2 years of age and more slowly thereafter. This change in normal lung attenuation should be taken into account as quantitative CT methods are translated to pediatric pulmonary imaging. (orig.)

Postoperative assessment of surgical results using three dimensional surface reconstruction CT (3D-CT) in a craniofacial anomaly

International Nuclear Information System (INIS)

Nishimura, Jiro; Sato, Kaoru; Nishimoto, Hiroshi; Tsukiyama, Takashi; Fujioka, Mutsuhisa; Akagawa, Tetsuya.

1988-01-01

In 1983, Michael W. Vannier and Jeffrey L. Marsh developed a computer method that reconstructs three dimensional (3D) born and soft tissue surfaces, given a high resolution CT scan-series of the facial skeleton. This method has been applied to craniofacial anomalies, basal encephaloceles, and musculoskeletal anomalies. In this study, a postoperative assessment of the craniofacial surgical results has been accomplished using this 3D-CT in 2 children with craniofacial dysmorphism. The authors discuss the advantages of this 3D-CT imaging method in the postoperative assessments of craniofacial anomalies. Results are detailed in the following listing : 1) a postoperative 3D-CT reveals the anatomical details corrected by the craniofacial surgery more precisely and stereographically than conventional radiological methods ; 2) secondary changes of the cranium after the surgery, such as bony formation in the area of the osteotomy and postoperative asymmetric deformities, are detected early by the 3D-CT imaging technique, and, 3) 3D-CT mid-sagittal and top axial views of the intracranial skull base are most useful in postoperative assessments of the surgical results. Basesd on our experience, we expect that three dimensional surface reconstructions from CT scans will become to be used widely in the postoperative assessments of the surgical results of craniofacial anomalies. (author)

Hepatic entropy and uniformity: additional parameters that can potentially increase the effectiveness of contrast enhancement during abdominal CT

International Nuclear Information System (INIS)

Ganeshan, B.; Miles, K.A.; Young, R.C.D.; Chatwin, C.R.

2007-01-01

Aim: To determine how hepatic entropy and uniformity of computed tomography (CT) images of the liver change after the administration of contrast material and to assess whether these additional parameters are more sensitive to tumour-related changes in the liver than measurements of hepatic attenuation or perfusion. Materials and methods: Hepatic attenuation, entropy, uniformity, and perfusion were measured using multi-phase CT following resection of colorectal cancer. Based on conventional CT and fluorodeoxyglucose positron emission tomography, 12 patients were classified as having no evidence of malignancy, eight with extra-hepatic tumours only, and eight with metastatic liver disease. Results: Hepatic attenuation and entropy increased after CM administration whereas uniformity decreased. Unlike hepatic attenuation, entropy and uniformity changed maximally in the arterial phase. No significant differences in hepatic perfusion or attenuation were found between patient groups, whereas arterial-phase entropy was lower (p = 0.034) and arterial-phase uniformity was higher (p = 0.034) in apparently disease-free areas of liver in patients with hepatic metastases compared with those with no metastases. Conclusion: Temporal changes in hepatic entropy and uniformity differ from those for hepatic attenuation. By reflecting the distribution of hepatic enhancement, these additional parameters are more sensitive to tumour-related changes in the liver than measurements of hepatic attenuation or perfusion

CT and MRI assessment of symptomatic organized pancreatic fluid collections and pancreatic duct disruption: an interreader variability study using the revised Atlanta classification 2012.

Science.gov (United States)

Kamal, Ayesha; Singh, Vikesh K; Akshintala, Venkata S; Kawamoto, Satomi; Tsai, Salina; Haider, Maera; Fishman, Elliot K; Kamel, Ihab R; Zaheer, Atif

2015-08-01

Compare CT and MRI for fluid/debris component estimate and pancreatic duct (PD) communication with organized pancreatic fluid collections in acute pancreatitis. Evaluate fat density globules on CT as marker for debris. 29 Patients with 46 collections with CECT and MRI performed ≥4 weeks of symptom onset assessed for necrotizing pancreatitis, estimated percentage of fluid volume and PD involvement by two radiologists on separate occasions. T2WI used as standard for estimated percentage of fluid volume. Presence of fat globules and fluid attenuation on CT was recorded. Spearman rank correlation and kappa statistics were used to assess the correlation between imaging techniques and interreader agreement, respectively. Necrotizing pancreatitis seen on CT in 27 (93%, κ 0.119) vs. 20 (69%, κ 0.748) patients on MRI. CT identified 42 WON and 4 pseudocysts vs. 34 WON, and 12 pseudocysts on MRI. Higher interreader agreement for percentage fluid volume on MRI (κ = 0.55) vs. CT (κ = 0.196). Accuracy of CT in evaluation of percentage fluid volume was 65% using T2WI MRI used as standard. Fat globules identified on CT in 13(65%) out of 20 collections containing collections containing >75% fluid (p = 0.0001). PD involvement confidently excluded on CT in 68% collections vs. 93% on MRI. MRI demonstrates higher reproducibility for fluid to debris component estimation. Fat globules on CT were frequently seen in organized pancreatic fluid collections with large amount of debris. PD disruption more confidently excluded on MRI. This information may be helpful for pre-procedure planning.

Usefulness of percentage enhancement washout value calculated on unenhanced, contrast-enhanced, and delayed enhanced CT in adrenal masses: adenoma versus metastasis

International Nuclear Information System (INIS)

Sohn, Kyung Myung; Lee, Sung Yong; Lee, Keun Ho

2003-01-01

To determine the usefulness of percentage enhancement washout value calculated on unenhanced, enhanced and delayed enhanced CT scans for the characterization of adrenal masses. Forty adrenal masses less than 5 cm in size were assessed using a protocol consisting of unenhanced CT, enhanced CT 60 seconds after intravenous administration of contrast material, and delayed enhanced CT at 10 minutes. The CT attenuation value of adrenal tumors was estimated on each scan, and percentage enhancement washout value was calculated as follows:[(attenuation value at enhanced CT-attenuation value at delayed CT)/ (attenuation value at enhanced CT-attenuation value at unenhanced CT)x100]. An adrenal mass was considered benign if its percentage enhancement washout value was at the threshold value, set to 60% and 50%, or higher. The accuracy of the procedure was determined by comparing its findings with the final clinical diagnosis. Twenty-nine massess were benign and 11 were malignant. The mean percentage enhancement washout value of the former was significantly higher than that of the latter (66.7% vs. 21.8%; p<0.01). All adenomas except one had a washout value of more than 50%. With a percentage washout threshold of 60%, 35 of 40 lesions were correctly characterized as benign or malignant [sensitivity 82.7% (24/29), specificity 100% (11/11), accuracy 87.5% (35/40)]; with a threshold of 50%, 39 of 40 lesions were correctly characterized [(sensitivity 96.5% (28/29), specificity 100% (11/11), accuracy 97.5% (39/40)]. Percentage enhancement washout values are useful for characterizing an adrenal mass as benign or malignant. For characterization, a threshold value of 50% was more accurate than one of 60%

Follow-up CT Evaluation of the Mural Changes in Active Takayasu Arteritis

International Nuclear Information System (INIS)

Kim, Sang Young; Park, Jae Hyung; Chung, Jin Wook; Kim, Hyo Cheol; Lee, Whal; So, Young Ho; Jae, Hwan Jun

2007-01-01

We wanted to evaluate the mural changes by CT on the follow-up examination of patients with active Takayasu arteritis. The study included 18 patients, (4 males and 14 females), with active Takayasu arteritis. A total of 44 CT examinations were done during the follow-up period (mean: 55.6 months). At the time of the last follow-up CT, the disease, on the basis of the erythrocyte sedimentation rate (ESR), was found to be inactive in five patients and the disease was active and persistent in 13 patients. The thickness and CT attenuation of the aortic wall on the precontrast, arterial and venous phases were measured on the initial and the follow-up CT examinations. The ratio of the mural attenuation over that of the back muscle on the initial CT was compared with the ratio found on the follow-up CT. The initial CT findings included high density and calcifications of the aortic wall in the precontrast images and a thickened wall with enhancements in the arterial and the venous phases. A low-attenuation ring was demonstrated in the venous phase in 15 patients (83%). On the follow-up evaluation, the mean mural thickness decreased significantly from 4.1 mm to 2.4 mm. The mean mural attenuation ratio in the venous phase decreased significantly from 1.9 to 1.3 (p 0.001). The low attenuation ring was identified in seven patients (39%) who had only with active, persistent Takayasu arteritis. The mural changes demonstrated by the follow-up CT evaluations for the patients with active Takayasu arteritis included a decrease of the mural thickness and enhancement, disappearance of the low-attenuation ring on the venous phase, and an increase of the mural attenuation and calcification on the precontrast phase

Quantification of Emphysema with a Three-Dimensional Chest CT Scan: Correlation with the Visual Emphysema Scoring on Chest CT, Pulmonary Function Tests and Dyspnea Severity

Energy Technology Data Exchange (ETDEWEB)

Park, Hyun Jeong; Hwang, Jung Hwa [Dept. of Radiology, Soonchunhyang University Seoul Hospital, Seoul (Korea, Republic of)

2011-09-15

We wanted to prospectively evaluate the correlation between the quantification of emphysema using 3D CT densitometry with the visual emphysema score, pulmonary function tests (PFT) and the dyspnea score in patients with chronic obstructive pulmonary disease (COPD). Non-enhanced chest CT with 3D reconstruction was performed in 28 men with COPD (age 54-88 years). With histogram analysis, the total lung volume, mean lung density and proportion of low attenuation lung volume below predetermined thresholds were measured. The CT parameters were compared with the visual emphysema score, the PFT and the dyspnea score. A low attenuation lung volume below -950 HU was well correlated with the DLco and FEV{sub 1}/FVC. A Low attenuation lung volume below -950 HU and -930 HU was correlated with visual the emphysema score. A low attenuation lung volume below -950 HU was correlated with the dyspnea score, although the correlations between the other CT parameters and the dyspnea score were not significant. Objective quantification of emphysema using 3D CT densitometry was correlated with the visual emphysema score. A low attenuation lung volume below -950 HU was correlated with the DLco, the FEV{sub 1}/FVC and the dyspnea score.

Quantification of Emphysema with a Three-Dimensional Chest CT Scan: Correlation with the Visual Emphysema Scoring on Chest CT, Pulmonary Function Tests and Dyspnea Severity

International Nuclear Information System (INIS)

Park, Hyun Jeong; Hwang, Jung Hwa

2011-01-01

We wanted to prospectively evaluate the correlation between the quantification of emphysema using 3D CT densitometry with the visual emphysema score, pulmonary function tests (PFT) and the dyspnea score in patients with chronic obstructive pulmonary disease (COPD). Non-enhanced chest CT with 3D reconstruction was performed in 28 men with COPD (age 54-88 years). With histogram analysis, the total lung volume, mean lung density and proportion of low attenuation lung volume below predetermined thresholds were measured. The CT parameters were compared with the visual emphysema score, the PFT and the dyspnea score. A low attenuation lung volume below -950 HU was well correlated with the DLco and FEV 1 /FVC. A Low attenuation lung volume below -950 HU and -930 HU was correlated with visual the emphysema score. A low attenuation lung volume below -950 HU was correlated with the dyspnea score, although the correlations between the other CT parameters and the dyspnea score were not significant. Objective quantification of emphysema using 3D CT densitometry was correlated with the visual emphysema score. A low attenuation lung volume below -950 HU was correlated with the DLco, the FEV 1 /FVC and the dyspnea score.

The role of CT in assessing chest pain

International Nuclear Information System (INIS)

Capsa, R.

2012-01-01

Full text: Objective: Thoracic pain represents the common feature of a wide range of diseases of different causes. Usually, chest pain requires a fast workup, in order to eliminate potentially hazardous underlying conditions. The objective of the paper consists of presenting the role of computerized tomography (CT) in assessing the different causes and conditions related to chest pain. Materials and methods: The educational presentation relies on current literature data and mostly on images obtained from patients admitted in the various clinics and departments of our hospital, suffering from chest pain as admittance condition or as a symptom appeared during the hospital stay. Results: There are various radiological and imaging options for assessing a patient with chest pain, with reference to the underlying condition, type of pain onset (acute or chronic), specific indications and contraindications. From all these, CT is considered one of the most useful imaging options, in terms of diagnosis accuracy, fast workup, cost and availability. This paper focuses on the role of CT, presenting the most important diseases and conditions related to potential occurrence of chest pain and the most specific CT signs and findings usually reported in this setting. Furthermore, the presentation separates acute and chronic conditions, presenting the actual imaging protocols employed in this circumstances. Finally, there are considerations regarding CT rule-out protocols used in patients with acute chest pain in emergency conditions. Conclusions: Fast and accurate diagnosis is crucial for patient outcome, often life-saving, but currently there is no single algorithm in the imaging assessment of chest pain, while choosing the best imaging option relies mainly on history, clinical and laboratory data. CT is one of the most important imaging options available in patients with both acute and chronic chest pain. CT rule-out techniques have still to establish their clear role in a

The effects of iodine attenuation on pulmonary nodule volumetry using novel dual-layer computed tomography reconstructions

Energy Technology Data Exchange (ETDEWEB)

Harder, A.M. den; Hamersvelt, R.W. van; Leiner, T.; Schilham, A.M.R.; Willemink, M.J.; Jong, P.A. de [University Medical Center Utrecht, Department of Radiology, Utrecht (Netherlands); Bangert, F. [Sint Antonius Ziekenhuis, Department of Radiology, Nieuwegein (Netherlands); Milles, Julien [Philips Healthcare, Best (Netherlands)

2017-12-15

To assess the effect of iodine attenuation on pulmonary nodule volumetry using virtual non-contrast (VNC) and mono-energetic reconstructions. A consecutive series of patients who underwent a contrast-enhanced chest CT scan were included. Images were acquired on a novel dual-layer spectral CT system. Conventional reconstructions as well as VNC and mono-energetic images at different keV levels were used for nodule volumetry. Twenty-four patients with a total of 63 nodules were included. Conventional reconstructions showed a median (interquartile range) volume and diameter of 174 (87 - 253) mm{sup 3} and 6.9 (5.4 - 9.9) mm, respectively. VNC reconstructions resulted in a significant volume reduction of 5.5% (2.6 - 11.2%; p<0.001). Mono-energetic reconstructions showed a correlation between nodule attenuation and nodule volume (Spearman correlation 0.77, (0.49 - 0.94)). Lowering the keV resulted in increased volumes while higher keV levels resulted in decreased pulmonary nodule volumes compared to conventional CT. Novel dual-layer spectral CT offers the possibility to reconstruct VNC and mono-energetic images. Those reconstructions show that higher pulmonary nodule attenuation results in larger nodule volumes. This may explain the reported underestimation in nodule volume on non-contrast enhanced compared to contrast-enhanced acquisitions. (orig.)

The effects of iodine attenuation on pulmonary nodule volumetry using novel dual-layer computed tomography reconstructions

International Nuclear Information System (INIS)

Harder, A.M. den; Hamersvelt, R.W. van; Leiner, T.; Schilham, A.M.R.; Willemink, M.J.; Jong, P.A. de; Bangert, F.; Milles, Julien

2017-01-01

To assess the effect of iodine attenuation on pulmonary nodule volumetry using virtual non-contrast (VNC) and mono-energetic reconstructions. A consecutive series of patients who underwent a contrast-enhanced chest CT scan were included. Images were acquired on a novel dual-layer spectral CT system. Conventional reconstructions as well as VNC and mono-energetic images at different keV levels were used for nodule volumetry. Twenty-four patients with a total of 63 nodules were included. Conventional reconstructions showed a median (interquartile range) volume and diameter of 174 (87 - 253) mm 3 and 6.9 (5.4 - 9.9) mm, respectively. VNC reconstructions resulted in a significant volume reduction of 5.5% (2.6 - 11.2%; p<0.001). Mono-energetic reconstructions showed a correlation between nodule attenuation and nodule volume (Spearman correlation 0.77, (0.49 - 0.94)). Lowering the keV resulted in increased volumes while higher keV levels resulted in decreased pulmonary nodule volumes compared to conventional CT. Novel dual-layer spectral CT offers the possibility to reconstruct VNC and mono-energetic images. Those reconstructions show that higher pulmonary nodule attenuation results in larger nodule volumes. This may explain the reported underestimation in nodule volume on non-contrast enhanced compared to contrast-enhanced acquisitions. (orig.)

X-ray CT core imaging of Oman Drilling Project on D/V CHIKYU

Science.gov (United States)

Michibayashi, K.; Okazaki, K.; Leong, J. A. M.; Kelemen, P. B.; Johnson, K. T. M.; Greenberger, R. N.; Manning, C. E.; Harris, M.; de Obeso, J. C.; Abe, N.; Hatakeyama, K.; Ildefonse, B.; Takazawa, E.; Teagle, D. A. H.; Coggon, J. A.

2017-12-01

We obtained X-ray computed tomography (X-ray CT) images for all cores (GT1A, GT2A, GT3A and BT1A) in Oman Drilling Project Phase 1 (OmanDP cores), since X-ray CT scanning is a routine measurement of the IODP measurement plan onboard Chikyu, which enables the non-destructive observation of the internal structure of core samples. X-ray CT images provide information about chemical compositions and densities of the cores and is useful for assessing sample locations and the quality of the whole-round samples. The X-ray CT scanner (Discovery CT 750HD, GE Medical Systems) on Chikyu scans and reconstructs the image of a 1.4 m section in 10 minutes and produces a series of scan images, each 0.625 mm thick. The X-ray tube (as an X-ray source) and the X-ray detector are installed inside of the gantry at an opposing position to each other. The core sample is scanned in the gantry with the scanning rate of 20 mm/sec. The distribution of attenuation values mapped to an individual slice comprises the raw data that are used for subsequent image processing. Successive two-dimensional (2-D) slices of 512 x 512 pixels yield a representation of attenuation values in three-dimensional (3-D) voxels of 512 x 512 by 1600 in length. Data generated for each core consist of core-axis-normal planes (XY planes) of X-ray attenuation values with dimensions of 512 × 512 pixels in 9 cm × 9 cm cross-section, meaning at the dimensions of a core section, the resolution is 0.176 mm/pixel. X-ray intensity varies as a function of X-ray path length and the linear attenuation coefficient (LAC) of the target material is a function of the chemical composition and density of the target material. The basic measure of attenuation, or radiodensity, is the CT number given in Hounsfield units (HU). CT numbers of air and water are -1000 and 0, respectively. Our preliminary results show that CT numbers of OmanDP cores are well correlated to gamma ray attenuation density (GRA density) as a function of chemical

Quality control in PET/CT systems. Experiences and requirements

International Nuclear Information System (INIS)

Geworski, Lilli; Fitz, Eduard; Knoop, Bernd; Karwarth, Cornelia; Plotkin, Michail

2010-01-01

Today, in most cases PET examinations are performed using PET/CT hybrid systems. While acceptance testing and routine control of the basic modalities PET and CT, respectively, are described by appropriate regulations, corresponding instructions with regard to the interface connecting both are still missing. This interface includes the adjustment of gantries and patient bed to each other as well as the energy scaling of attenuation coefficients from CT energy to 511 keV. Measurements checking the mechanical adjustment (determination of off-set parameters) are performed following manufacturer's recommendation, with a typical frequency twice a year. On a Biograph 16 (Siemens, Inc.), these measurements were systematically extended to a weekly frequency over an observation period of 10 months, supplemented by measurements with additional load to the patient bed (up to 135 kg), and different vertical bed positions. The results show, that for the construction tested additional off-set measurements for routine control extending well beyond manufacturer's recommendation are not necessary. The energy scaling of attenuation coefficients is depending on methodological aspects and software implementation, and therefore is not part of routine control. On the contrary, the development of appropriate methods for acceptance testing to assess and to determine the mechanical adjustment in all its degrees of freedom as well as the accuracy of attenuation corrected emission data is urgently needed. (orig.)

Automated image quality assessment for chest CT scans.

Science.gov (United States)

Reeves, Anthony P; Xie, Yiting; Liu, Shuang

2018-02-01

Medical image quality needs to be maintained at standards sufficient for effective clinical reading. Automated computer analytic methods may be applied to medical images for quality assessment. For chest CT scans in a lung cancer screening context, an automated quality assessment method is presented that characterizes image noise and image intensity calibration. This is achieved by image measurements in three automatically segmented homogeneous regions of the scan: external air, trachea lumen air, and descending aorta blood. Profiles of CT scanner behavior are also computed. The method has been evaluated on both phantom and real low-dose chest CT scans and results show that repeatable noise and calibration measures may be realized by automated computer algorithms. Noise and calibration profiles show relevant differences between different scanners and protocols. Automated image quality assessment may be useful for quality control for lung cancer screening and may enable performance improvements to automated computer analysis methods. © 2017 American Association of Physicists in Medicine.

X-ray attenuation of the liver and kidney in cats considered at varying risk of hepatic lipidosis.

Science.gov (United States)

Lam, Richard; Niessen, Stijn J; Lamb, Christopher R

2014-01-01

X-ray attenuation of the liver has been measured using computed tomography (CT) and reported to decrease in cats with experimentally induced hepatic lipidosis. To assess the clinical utility of this technique, medical records and noncontrast CT scans of a series of cats were retrospectively reviewed. A total of 112 cats met inclusion criteria and were stratified into three hepatic lipidosis risk groups. Group 1 cats were considered low-risk based on no history of inappetence or weight loss, and normal serum chemistry values; Group 2 cats were considered intermediate risk based on weight loss, serum hepatic enzymes above normal limits, or reasonably controlled diabetes mellitus; and Group 3 cats were considered high risk based on poorly controlled diabetes mellitus due to hypersomatotropism. Mean CT attenuation values (Hounsfield units, HU) were measured using regions of interest placed within the liver and cranial pole of the right kidney. Hepatic and renal attenuation were weakly positively correlated with each other (r = 0.2, P = 0.03) and weakly negatively correlated with body weight (r = -0.21, P = 0.05, and r = -0.34, P = 0.001, respectively). Mean (SD) hepatic and renal cortical attenuation values were 70.7 (8.7) HU and 49.6 (9.2) HU for Group 1 cats, 71.4 (7.9) HU and 48.6 (9.1) HU for Group 2, and 68.9 (7.6) HU and 47.6 (7.2) HU for Group 3. There were no significant differences in hepatic or renal attenuation among groups. Findings indicated that CT measures of X-ray attenuation in the liver and kidney may not be accurate predictors of naturally occurring hepatic lipidosis in cats. © 2013 American College of Veterinary Radiology.

The Effects of Iodine Attenuation on Pulmonary Nodule Volumetry using Novel Dual-Layer Computed Tomography Reconstructions

NARCIS (Netherlands)

den Harder, A M; Bangert, F; van Hamersvelt, R W; Leiner, T; Milles, Julien; Schilham, A M R; Willemink, M J; de Jong, P A

2017-01-01

OBJECTIVES: To assess the effect of iodine attenuation on pulmonary nodule volumetry using virtual non-contrast (VNC) and mono-energetic reconstructions. METHODS: A consecutive series of patients who underwent a contrast-enhanced chest CT scan were included. Images were acquired on a novel

CT-based attenuation correction and resolution compensation for I-123 IMP brain SPECT normal database: a multicenter phantom study.

Science.gov (United States)

Inui, Yoshitaka; Ichihara, Takashi; Uno, Masaki; Ishiguro, Masanobu; Ito, Kengo; Kato, Katsuhiko; Sakuma, Hajime; Okazawa, Hidehiko; Toyama, Hiroshi

2018-03-19

Statistical image analysis of brain SPECT images has improved diagnostic accuracy for brain disorders. However, the results of statistical analysis vary depending on the institution even when they use a common normal database (NDB), due to different intrinsic spatial resolutions or correction methods. The present study aimed to evaluate the correction of spatial resolution differences between equipment and examine the differences in skull bone attenuation to construct a common NDB for use in multicenter settings. The proposed acquisition and processing protocols were those routinely used at each participating center with additional triple energy window (TEW) scatter correction (SC) and computed tomography (CT) based attenuation correction (CTAC). A multicenter phantom study was conducted on six imaging systems in five centers, with either single photon emission computed tomography (SPECT) or SPECT/CT, and two brain phantoms. The gray/white matter I-123 activity ratio in the brain phantoms was 4, and they were enclosed in either an artificial adult male skull, 1300 Hounsfield units (HU), a female skull, 850 HU, or an acrylic cover. The cut-off frequency of the Butterworth filters was adjusted so that the spatial resolution was unified to a 17.9 mm full width at half maximum (FWHM), that of the lowest resolution system. The gray-to-white matter count ratios were measured from SPECT images and compared with the actual activity ratio. In addition, mean, standard deviation and coefficient of variation images were calculated after normalization and anatomical standardization to evaluate the variability of the NDB. The gray-to-white matter count ratio error without SC and attenuation correction (AC) was significantly larger for higher bone densities (p correction. The proposed protocol showed potential for constructing an appropriate common NDB from SPECT images with SC, AC and spatial resolution compensation.

Calculation of shielding and radiation doses for PET/CT nuclear medicine facility

International Nuclear Information System (INIS)

Mollah, A.S.; Muraduzzaman, S.M.

2011-01-01

Positron emission tomography (PET) is a new modality that is gaining use in nuclear medicine. The use of PET and computed tomography (CT) has grown dramatically. Because of the high energy of the annihilation radiation (511 keV), shielding requirements are an important consideration in the design of a PET or PET/CT imaging facility. The goal of nuclear medicine and PET facility shielding design is to keep doses to workers and the public as low as reasonably achievable (ALARA). Design involves: 1. Calculation of doses to occupants of the facility and adjacent regions based on projected layouts, protocols and workflows, and 2. Reduction of doses to ALARA through adjustment of the aforementioned parameters. The radiological evaluation of a PET/CT facility consists of the assessment of the annual effective dose both to workers occupationally exposed, and to members of the public. This assessment takes into account the radionuclides involved, the facility features, the working procedures, the expected number of patients per year, and so on. The objective of the study was to evaluate shielding requirements for a PET/CT to be installed in the department of nuclear medicine of Bangladesh Atomic Energy Commission (BAEC). Minimizing shielding would result in a possible reduction of structural as well as financial burden. Formulas and attenuation coefficients following the basic AAPM guidelines were used to calculate un-attenuated radiation through shielding materials. Doses to all points on the floor plan are calculated based primarily on the AAPM guidelines and include consideration of broad beam attenuation and radionuclide energy and decay. The analysis presented is useful for both, facility designers and regulators. (author)

CT assessment of muscle hypertrophy utilizing automatic contouring techniques

International Nuclear Information System (INIS)

Steinbach, L.S.; Block, J.; Steiger, P.W.; Ellis, W.; Morris, J.; Genant, H.K.

1986-01-01

Quantitative CT was one method used to assess changes in density and area of thigh muscles in paraplegics before and after aerobic leg training. Muscle density and area were measured from the CT image by an automatic contouring algorithm. In the first three patients, total muscle density increased from 11.5% to 18.3% and area increased from 18.3% to 31.3%. In one patient who did not comply with the exercise regimen, only a 10% increase in muscle density and area was detected. This CT program is valuable in the assessment of composition and alteration of limb musculature in the treatment and follow-up of muscular disorders

Strategies to reduce radiation dose in cardiac PET/CT

Energy Technology Data Exchange (ETDEWEB)

Wu, Tung Hsin; Wu, Nien-Yun [Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan (China); Wang, Shyh-Jen [Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan (China); Department of Nuclear Medicine, Taipei Veterans General Hospital, Taipei, Taiwan (China); Wu, Jay [Institute of Radiological science, Central Taiwan University of Science and Technology, Taichung, Taiwan (China); Mok, Greta S.P. [Department of Electrical and Electronics Engineering, Faculty of Science and Technology, University of Macau, Macau (China); Yang, Ching-Ching, E-mail: g39220003@yahoo.com.tw [Department of Radiological Technology, Tzu Chi College of Technology, 880, Sec.2, Chien-kuo Rd. Hualien 970, Taiwan (China); Huang, Tzung-Chi, E-mail: tzungchi.huang@mail.cmu.edu.tw [Department of Biomedical Imaging and Radiological Science, China Medical University, No.91 Hsueh-Shih Road, Taichung 40402, Taiwan (China)

2011-08-21

Background: Our aim was to investigate CT dose reduction strategies on a hybrid PET/CT scanner for cardiac applications. Materials: Image quality and dose estimation of different CT scanning protocols for CT coronary angiography (CTCA), and CT-based attenuation correction for PET imaging were investigated. Fifteen patients underwent CTCA, perfusion PET imaging at rest and under stress, and FDG PET for myocardial viability. These patients were divided into three groups based on the CTCA technique performed: retrospectively gated helical (RGH), ECG tube current modulation (ETCM), and prospective gated axial (PGA) acquisitions. All emission images were corrected for photon attenuation using CT images obtained by default setting and an ultra-low dose CT (ULDCT) scan. Results: Radiation dose in RGH technique was 22.2{+-}4.0 mSv. It was reduced to 10.95{+-}0.82 and 4.13{+-}0.31 mSv using ETCM and PGA techniques, respectively. Radiation dose in CT transmission scan was reduced by 96.5% (from 4.53{+-}0.5 to 0.16{+-}0.01 mSv) when applying ULDCT as compared to the default CT. No significant difference in terms of image quality was found among various protocols. Conclusion: The proposed CT scanning strategies, i.e. ETCM or PGA for CTCA and ULDCT for PET attenuation correction, could reduce radiation dose up to 47% without degrading imaging quality in an integrated cardiac PET/CT coronary artery examination.

Oral contrast medium in PET/CT: should you or shouldn't you?

International Nuclear Information System (INIS)

Groves, Ashley M.; Kayani, Irfan; Dickson, John C.; Townsend, Caroline; Croasdale, Ian; Syed, Rizwan; Nagabushan, Nagesh; Hain, Sharon F.; Ell, Peter J.; Bomanji, Jamshed B.

2005-01-01

It has been suggested that the use of computed tomography (CT) positive contrast agents has led to attenuation-induced artefacts on 18 F-fluorodeoxyglucose positron emission tomography ( 18 F-FDG PET/CT) systems. Consequently, centres may withhold the use of such agents. Whilst there is theoretical evidence to support the aforementioned claim, the clinical relevance of the induced artefacts has not been widely established. Moreover, the potential benefits of bowel enhancement on PET/CT have yet to be formally evaluated. We therefore prospectively examined PET/CT studies to assess whether the use of oral contrast medium induces clinically relevant artefacts and whether the use of these agents is diagnostically helpful. Over a 2-month period, 18 F-FDG PET/CT images were prospectively reviewed from 200 patients following Gastrografin administration 2 h prior to examination. Both a radiologist and a nuclear medicine physician reviewed the images for contrast medium-mediated clinically relevant artefacts. Artefacts were sought on the CT attenuation-corrected images and were compared with the appearance on non-attenuated-corrected images. The number of examinations in which the oral contrast aided image interpretation was also noted. There were no oral contrast medium-induced clinically significant artefacts. In 38 of the 200 patients, oral contrast aided image interpretation (owing to differentiation of mass/node from bowel, discrimination of intestinal wall from lumen or definition of the anatomy of a relevant site). In 33 of these 38 patients, the anatomical site of interest was the abdomen/pelvis. The use of oral contrast medium in 18 F-FDG PET studies should not be withheld as it improves image interpretation and does not produce clinically significant artefacts. (orig.)

Necrotizing pneumonia: CT findings and its clinical significance

International Nuclear Information System (INIS)

Park, Hong Suk; Im, Jung Gi; Ryoo, Jae Wook; Yeon, Kyung Mo; Han, Man Chung

1995-01-01

To analyze CT and follow-up chest radiographic findings in patients with necrotizing pneumonia and to evaluate clinical significance of the extent of necrosis. We reviewed medical records and retrospectively analysed CT scans and follow-up chest radiographs of 22 patients with necrotizing pneumonia, confirmed by biopsy (n = 7) and culture (n = 15). Inclusion criteria for necrotizing pneumonia was necrotic low attenuation, with or without cavitation on postcontrast enhanced CT scan. The study group included 15 men and seven women, aged 11-66 years (average: 47 years). The pathogens of necrotizing pneumonia were Klebsiella spp (n = 7), Enterobacter spp (n = 5), Actinomyces spp (n = 4), Pseudomonas spp (n = 4), Nocardia spp (n = 4), and others (n = 5). Average duration of pneumonia was 4.1 months. On CT scan, pneumonic consolidations were well-marginated in 14 patients and there were cavities on initial CT scan in 16 cases. Margins of the necrotic portion on CT scan were well-demarcated in majority of the patients (16/22). Low attenuation areas on initial CT scan resulted in cavitation, fibrosis and volume loss as shown on follow-up chest radiographs. The larger the necrotic areas on CT, the more the volume loss was. CT findings of necrotizing pneumonia were well-marginated air-space consolidation with low attenuation area, with or without cavity. The extent of necrotic area was closely related with the degree of fibrotic change later on. CT is important tool for diagnosis and prediction of parenchymal damage in necrotizing pneumonia

CT findings of the patients with bronchial asthma

International Nuclear Information System (INIS)

Katagiri, Shiro; Ohshima, Kazuki; Ohsawa, Takehiko.

1996-01-01

CT scans were obtained in 45 patients with bronchial asthma including 23 patients during asthmatic attack. CT findings were as follows. 1) In all cases, thickening of bronchial wall throughout from central to peripheral bronchi and without tapering and/or slight swelling of bronchovascular bundles were observed. 2) Characteristics findings in 23 patients with asthmatic attack, lobular and multilobular high attenuation area were observed in 17 patients (74%) and nonhomogeneous attenuation in lung fields were noticed in 13 patients (57%). 3) Multiple centrilobular sized high attenuation area were observed in 23 patients, but it was difficult to differenciation whether these findings were due to tiny nodules or to small vessels. In conclusion, further studies are needed to know which pathomorphological and/or pathophysiological conditions are underlying these CT findings. (author)

Attenuation correction method for single photon emission CT

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Morozumi, Tatsuru; Nakajima, Masato [Keio Univ., Yokohama (Japan). Faculty of Science and Technology; Ogawa, Koichi; Yuta, Shinichi

1983-10-01

A correction method (Modified Correction Matrix method) is proposed to implement iterative correction by exactly measuring attenuation constant distribution in a test body, calculating a correction factor for every picture element, then multiply the image by these factors. Computer simulation for the comparison of the results showed that the proposed method was specifically more effective to an application to the test body, in which the rate of attenuation constant change is large, than the conventional correction matrix method. Since the actual measurement data always contain quantum noise, the noise was taken into account in the simulation. However, the correction effect was large even under the noise. For verifying its clinical effectiveness, the experiment using an acrylic phantom was also carried out. As the result, the recovery of image quality in the parts with small attenuation constant was remarkable as compared with the conventional method.

Effect of X-Ray Attenuation of Arterial Obstructions on Intravenous Thrombolysis and Outcome after Ischemic Stroke.

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Grant Mair

Full Text Available To assess whether the x-ray attenuation of intra-arterial obstruction measured on non-contrast CT in ischemic stroke can predict response to thrombolysis and subsequent functional outcome.The Third International Stroke Trial (IST-3 was a multicenter randomized-controlled trial of intravenous thrombolysis (rt-PA given within six hours of ischemic stroke. Ethical approval and informed consent were obtained. In a subgroup of 109 IST-3 patients (38 men, median age 82 years, a single reader, masked to all clinical and other imaging data, manually measured x-ray attenuation (Hounsfield Units, HU on non-contrast CT at the location of angiographically-proven intra-arterial obstructions, pre-randomization and at 24-48 hour follow-up. We calculated change in attenuation between scans. We assessed the impact of pre-randomization arterial obstruction attenuation on six-month functional outcome.Most arterial obstructions (64/109, 59% were hyperattenuating (mean 51.0 HU. Compared with control, treatment with rt-PA was associated with a greater, but non-significant, reduction in obstruction attenuation at follow-up (-8.0 HU versus -1.4 HU in patients allocated control, p = 0.117. In multivariable ordinal regression analysis controlled for patient age, stroke severity, location and extent of obstruction, time from stroke onset to baseline scan and rt-PA treatment allocation, the attenuation of pre-randomization arterial obstruction was not independently associated with six-month outcome (odds ratio = 0.99, 95% confidence interval = 0.94-1.03, p = 0.516.In ischemic stroke, the x-ray attenuation of the arterial obstruction may decline more rapidly from baseline to 24-48 hours following treatment with thrombolysis but we found no evidence that baseline arterial obstruction attenuation predicts six-month outcome.

Evaluation of MLACF based calculated attenuation brain PET imaging for FDG patient studies

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Bal, Harshali; Panin, Vladimir Y.; Platsch, Guenther; Defrise, Michel; Hayden, Charles; Hutton, Chloe; Serrano, Benjamin; Paulmier, Benoit; Casey, Michael E.

2017-04-01

Calculating attenuation correction for brain PET imaging rather than using CT presents opportunities for low radiation dose applications such as pediatric imaging and serial scans to monitor disease progression. Our goal is to evaluate the iterative time-of-flight based maximum-likelihood activity and attenuation correction factors estimation (MLACF) method for clinical FDG brain PET imaging. FDG PET/CT brain studies were performed in 57 patients using the Biograph mCT (Siemens) four-ring scanner. The time-of-flight PET sinograms were acquired using the standard clinical protocol consisting of a CT scan followed by 10 min of single-bed PET acquisition. Images were reconstructed using CT-based attenuation correction (CTAC) and used as a gold standard for comparison. Two methods were compared with respect to CTAC: a calculated brain attenuation correction (CBAC) and MLACF based PET reconstruction. Plane-by-plane scaling was performed for MLACF images in order to fix the variable axial scaling observed. The noise structure of the MLACF images was different compared to those obtained using CTAC and the reconstruction required a higher number of iterations to obtain comparable image quality. To analyze the pooled data, each dataset was registered to a standard template and standard regions of interest were extracted. An SUVr analysis of the brain regions of interest showed that CBAC and MLACF were each well correlated with CTAC SUVrs. A plane-by-plane error analysis indicated that there were local differences for both CBAC and MLACF images with respect to CTAC. Mean relative error in the standard regions of interest was less than 5% for both methods and the mean absolute relative errors for both methods were similar (3.4%  ±  3.1% for CBAC and 3.5%  ±  3.1% for MLACF). However, the MLACF method recovered activity adjoining the frontal sinus regions more accurately than CBAC method. The use of plane-by-plane scaling of MLACF images was found to be a

Differentiation of adrenal adenomas from nonadenomas using CT histogram analysis method: A prospective study

International Nuclear Information System (INIS)

Halefoglu, Ahmet Mesrur; Bas, Nagihan; Yasar, Ahmet; Basak, Muzaffer

2010-01-01

Objective: The objective of our study was to prospectively evaluate the effectiveness of computed tomography (CT) histogram analysis method in the differentiation of benign and malignant adrenal masses. Materials and Methods: Between March 2007 and June 2008, 94 patients (46 males, 48 females, age range: 30-79 years, mean age: 57.7 years) with 113 adrenal masses (mean diameter: 3.03 cm, range: 1.07-8.02 cm) were prospectively evaluated. These included 66 adenomas, 45 metastases and 2 pheochromocytomas. Histogram analysis method was performed using a circular region of interest (ROI) and mean attenuation, total number of pixels, number of negative pixels and subsequent percentage of negative pixels were detected on both unenhanced and delayed contrast-enhanced CT images for each adrenal mass. A mean attenuation threshold of 10 Hounsfield unit (HU) for unenhanced CT and 5% and 10% negative pixel thresholds for both unenhanced and delayed contrast-enhanced CT were calculated by a consensus of at least two reviewers and the correlation between mean attenuation and percentage of negative pixels was determined. Final diagnoses were based on imaging follow-up of minimum 6 months, biopsy, surgery and adrenal washout study. Results: 51 of 66 adenomas (77.3%) showed attenuation values of ≤10 HU and 15 (22.7%) adenomas showed more than 10 HU on unenhanced CT. All of these adenomas contained negative pixels on unenhanced CT. Eight of 66 (12.1%) adenomas showed a mean attenuation value of ≤10 HU on delayed contrast-enhanced scans and 45 adenomas (68.2%) persisted on containing negative pixels. All metastases had an attenuation value of greater than 10 HU on unenhanced CT images. 21 of 45 (46.6%) metastases contained negative pixels on unenhanced images but only seven metastases (15.5%) had negative pixels on delayed contrast-enhanced images. Two pheochromocytomas had negative pixels on both unenhanced and delayed contrast-enhanced CT images. Increase in the percentage of

Muscular involvement by malignant lymphoma: CT and MR findings

International Nuclear Information System (INIS)

Kim, Baek Hyun

2000-01-01

To investigate the CT and MR findings of muscular involvement by malignant lymphoma. Thirteen patients with biopsy-proved muscular involvement by malignant lymphoma were included in this study. Two patients were primary muscle lymphoma and 11 patients were muscle lymphoma by secondary involvement of malignant lymphoma. CT of 10 patients (6 pre-contrast CT and 9 postcontrast CT) and MRI of 6 patients (all with pre a nd post-contrast studies) were retrospectively analyzed. In the majority of patients (84.6%, 11/13), the appearance of muscular involvement was the diffuse enlargement of several muscles as like as a group. The muscles involved by malignant lymphoma showed iso-attenuation (5/6) and homogeneity (6/6) on pre-contrast CT scan, and high attenuation (5/9) or iso-attenuation (4/9) and homogeneity (7/9) on post-contrast CT scan. The signal intensity of involved muscle showed slightly hyper- (4/6) or iso-intense (2/6) and homogeneous (6/6) on T1-weighted images, and hyper-intense (6/6) and homogeneous (4/6) on T2- and Gadolinium-enhanced T1-weighted images. Adjacent bone change was demonstrated in 69.2% (9/13), subcutaneous fat change in 61.5% (8/13), and neurovascular encasement within involved muscle in 53.8% (7/13). The CT and MR findings of muscular involvement by malignant lymphoma were diffuse enlargement of several muscles with homogeneous attenuation or signal intensity, and frequent changes in adjacent bones and subcutaneous fat, or neurovascular encasement. (author)

Head and neck imaging with PET and PET/CT: artefacts from dental metallic implants

International Nuclear Information System (INIS)

Goerres, Gerhard W.; Hany, Thomas F.; Kamel, Ehab; Schulthess von, Gustav K.; Buck, Alfred

2002-01-01

Germanium-68 based attenuation correction (PET Ge68 ) is performed in positron emission tomography (PET) imaging for quantitative measurements. With the recent introduction of combined in-line PET/CT scanners, CT data can be used for attenuation correction. Since dental implants can cause artefacts in CT images, CT-based attenuation correction (PET CT ) may induce artefacts in PET images. The purpose of this study was to evaluate the influence of dental metallic artwork on the quality of PET images by comparing non-corrected images and images attenuation corrected by PET Ge68 and PET CT . Imaging was performed on a novel in-line PET/CT system using a 40-mAs scan for PET CT in 41 consecutive patients with high suspicion of malignant or inflammatory disease. In 17 patients, additional PET Ge68 images were acquired in the same imaging session. Visual analysis of fluorine-18 fluorodeoxyglucose (FDG) distribution in several regions of the head and neck was scored on a 4-point scale in comparison with normal grey matter of the brain in the corresponding PET images. In addition, artefacts adjacent to dental metallic artwork were evaluated. A significant difference in image quality scoring was found only for the lips and the tip of the nose, which appeared darker on non-corrected than on corrected PET images. In 33 patients, artefacts were seen on CT, and in 28 of these patients, artefacts were also seen on PET imaging. In eight patients without implants, artefacts were seen neither on CT nor on PET images. Direct comparison of PET Ge68 and PET CT images showed a different appearance of artefacts in 3 of 17 patients. Malignant lesions were equally well visible using both transmission correction methods. Dental implants, non-removable bridgework etc. can cause artefacts in attenuation-corrected images using either a conventional 68 Ge transmission source or the CT scan obtained with a combined PET/CT camera. We recommend that the non-attenuation-corrected PET images also be

Quantitative Evaluation of Segmentation- and Atlas-Based Attenuation Correction for PET/MR on Pediatric Patients.

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Bezrukov, Ilja; Schmidt, Holger; Gatidis, Sergios; Mantlik, Frédéric; Schäfer, Jürgen F; Schwenzer, Nina; Pichler, Bernd J

2015-07-01

Pediatric imaging is regarded as a key application for combined PET/MR imaging systems. Because existing MR-based attenuation-correction methods were not designed specifically for pediatric patients, we assessed the impact of 2 potentially influential factors: inter- and intrapatient variability of attenuation coefficients and anatomic variability. Furthermore, we evaluated the quantification accuracy of 3 methods for MR-based attenuation correction without (SEGbase) and with bone prediction using an adult and a pediatric atlas (SEGwBONEad and SEGwBONEpe, respectively) on PET data of pediatric patients. The variability of attenuation coefficients between and within pediatric (5-17 y, n = 17) and adult (27-66 y, n = 16) patient collectives was assessed on volumes of interest (VOIs) in CT datasets for different tissue types. Anatomic variability was assessed on SEGwBONEad/pe attenuation maps by computing mean differences to CT-based attenuation maps for regions of bone tissue, lungs, and soft tissue. PET quantification was evaluated on VOIs with physiologic uptake and on 80% isocontour VOIs with elevated uptake in the thorax and abdomen/pelvis. Inter- and intrapatient variability of the bias was assessed for each VOI group and method. Statistically significant differences in mean VOI Hounsfield unit values and linear attenuation coefficients between adult and pediatric collectives were found in the lungs and femur. The prediction of attenuation maps using the pediatric atlas showed a reduced error in bone tissue and better delineation of bone structure. Evaluation of PET quantification accuracy showed statistically significant mean errors in mean standardized uptake values of -14% ± 5% and -23% ± 6% in bone marrow and femur-adjacent VOIs with physiologic uptake for SEGbase, which could be reduced to 0% ± 4% and -1% ± 5% using SEGwBONEpe attenuation maps. Bias in soft-tissue VOIs was less than 5% for all methods. Lung VOIs showed high SDs in the range of 15% for

Capability of abdominal 320-detector row CT for small vasculature assessment compared with that of 64-detector row CT

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Kitajima, Kazuhiro, E-mail: kitajima@med.kobe-u.ac.jp [Department of Radiology, Kobe University Graduate School of Medicine, 7-5-2, Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017 (Japan); Maeda, Tetsuo; Ohno, Yoshiharu [Department of Radiology, Kobe University Graduate School of Medicine, 7-5-2, Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017 (Japan); Division of Radiology, Kobe University Hospital, Kobe (Japan); Yoshikawa, Takeshi [Department of Radiology, Kobe University Graduate School of Medicine, 7-5-2, Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017 (Japan); Konishi, Minoru [Division of Radiology, Kobe University Hospital, Kobe (Japan); Kanda, Tomonori; Onishi, Yumiko; Matsumoto, Keiko; Koyama, Hisanobu; Takenaka, Daisuke; Sugimura, Kazuro [Department of Radiology, Kobe University Graduate School of Medicine, 7-5-2, Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017 (Japan)

2011-11-15

Objective: To compare the capability of 320-detector row CT (area-detector CT: ADCT) with step-and-shoot scan protocol for small abdominal vasculature assessment with that of 64-detector row CT with helical scan protocol. Materials and methods: Total of 60 patients underwent contrast-enhanced abdominal CT for preoperative assessment. Of all, 30 suspected to have lung cancer underwent ADCT using step-and-shoot scan protocol. The other 30 suspected to have renal cell carcinoma underwent 64-MDCT using helical scan protocol. Two experienced radiologists independently assessed inferior epigastric, hepatic subsegmental (in the segment 8), mesenteric marginal (Griffith point) and inferior phrenic arteries by using 5-point visual scoring systems. Kappa analysis was used for evaluation of interobserver agreement. To compare the visualization capability of the two systems, the Mann-Whitney U-test was used to compare the scores for each of the arteries. Results: Overall interobserver agreements for both systems were almost perfect ({kappa} > 0.80). Visualization scores for inferior epigastric and mesenteric arteries were significantly higher for ADCT than for 64-detector row CT (p < 0.05). No significant difference was found for hepatic subsegmental and inferior phrenic arteries. Conclusion: Small abdominal vasculature assessment by ADCT with step-and-shoot scan protocol is potentially equal to or better than that by 64-detector row CT with helical scan protocol.

Capability of abdominal 320-detector row CT for small vasculature assessment compared with that of 64-detector row CT

International Nuclear Information System (INIS)

Kitajima, Kazuhiro; Maeda, Tetsuo; Ohno, Yoshiharu; Yoshikawa, Takeshi; Konishi, Minoru; Kanda, Tomonori; Onishi, Yumiko; Matsumoto, Keiko; Koyama, Hisanobu; Takenaka, Daisuke; Sugimura, Kazuro

2011-01-01

Objective: To compare the capability of 320-detector row CT (area-detector CT: ADCT) with step-and-shoot scan protocol for small abdominal vasculature assessment with that of 64-detector row CT with helical scan protocol. Materials and methods: Total of 60 patients underwent contrast-enhanced abdominal CT for preoperative assessment. Of all, 30 suspected to have lung cancer underwent ADCT using step-and-shoot scan protocol. The other 30 suspected to have renal cell carcinoma underwent 64-MDCT using helical scan protocol. Two experienced radiologists independently assessed inferior epigastric, hepatic subsegmental (in the segment 8), mesenteric marginal (Griffith point) and inferior phrenic arteries by using 5-point visual scoring systems. Kappa analysis was used for evaluation of interobserver agreement. To compare the visualization capability of the two systems, the Mann-Whitney U-test was used to compare the scores for each of the arteries. Results: Overall interobserver agreements for both systems were almost perfect (κ > 0.80). Visualization scores for inferior epigastric and mesenteric arteries were significantly higher for ADCT than for 64-detector row CT (p < 0.05). No significant difference was found for hepatic subsegmental and inferior phrenic arteries. Conclusion: Small abdominal vasculature assessment by ADCT with step-and-shoot scan protocol is potentially equal to or better than that by 64-detector row CT with helical scan protocol.

Initial thoracic involvement in lymphoma. CT assessment

International Nuclear Information System (INIS)

Bustos, A.; Corredoira, J.; Ferreiros, J.; Cabeza, B.; Jorquera, M.; Pedrosa, I.; Martinez, R.; Fernandez, C.

2002-01-01

To analyze the initial thoracic involvement by CT in a consecutive series of patients with lymphoma. A retrospective analysis was made of thoracic CT studies made at the time of diagnosis of 259 patients with lymphoma. Mediastinal pulmonary, pleural, pericardial and chest wall involvement was assessed by CT. Of 259 patients (129 men y 130 women), 56 had Hodgkin's disease (HD) and 203 had non-Hodgkin lymphoma (NHL). Forty-two percent (42.5%, 110/259) of the patients had chest involvement on CT: 33 of 56 patients with HD (58.9%) and 77 of 203 patients with NHL (37.9%). All the patients with thoracic HD) and 71.4% of patients with thoracic NHL, had mediastinal lymph node involvement. of the patients with thoracic involvement 12.1% (4/33) of the patient with HD and 23.3% (18/77) of the patients with NHL had pulmonary involvement. Thoracic involvement on CT was more frequent in HD. Mediastinal lymph node involvement was the most common finding fundamentally in HD. Pulmonary disease always occurred in the presence of mediastinal lymph node involvement in HD but could occur as an isolated finding in NHL. (Author) 24 refs

Optimization of SPECT-CT Hybrid Imaging Using Iterative Image Reconstruction for Low-Dose CT: A Phantom Study.

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Oliver S Grosser

Full Text Available Hybrid imaging combines nuclear medicine imaging such as single photon emission computed tomography (SPECT or positron emission tomography (PET with computed tomography (CT. Through this hybrid design, scanned patients accumulate radiation exposure from both applications. Imaging modalities have been the subject of long-term optimization efforts, focusing on diagnostic applications. It was the aim of this study to investigate the influence of an iterative CT image reconstruction algorithm (ASIR on the image quality of the low-dose CT images.Examinations were performed with a SPECT-CT scanner with standardized CT and SPECT-phantom geometries and CT protocols with systematically reduced X-ray tube currents. Analyses included image quality with respect to photon flux. Results were compared to the standard FBP reconstructed images. The general impact of the CT-based attenuation maps used during SPECT reconstruction was examined for two SPECT phantoms. Using ASIR for image reconstructions, image noise was reduced compared to FBP reconstructions for the same X-ray tube current. The Hounsfield unit (HU values reconstructed by ASIR were correlated to the FBP HU values(R2 ≥ 0.88 and the contrast-to-noise ratio (CNR was improved by ASIR. However, for a phantom with increased attenuation, the HU values shifted for low X-ray tube currents I ≤ 60 mA (p ≤ 0.04. In addition, the shift of the HU values was observed within the attenuation corrected SPECT images for very low X-ray tube currents (I ≤ 20 mA, p ≤ 0.001.In general, the decrease in X-ray tube current up to 30 mA in combination with ASIR led to a reduction of CT-related radiation exposure without a significant decrease in image quality.

Blind CT image quality assessment via deep learning strategy: initial study

Science.gov (United States)

Li, Sui; He, Ji; Wang, Yongbo; Liao, Yuting; Zeng, Dong; Bian, Zhaoying; Ma, Jianhua

2018-03-01

Computed Tomography (CT) is one of the most important medical imaging modality. CT images can be used to assist in the detection and diagnosis of lesions and to facilitate follow-up treatment. However, CT images are vulnerable to noise. Actually, there are two major source intrinsically causing the CT data noise, i.e., the X-ray photo statistics and the electronic noise background. Therefore, it is necessary to doing image quality assessment (IQA) in CT imaging before diagnosis and treatment. Most of existing CT images IQA methods are based on human observer study. However, these methods are impractical in clinical for their complex and time-consuming. In this paper, we presented a blind CT image quality assessment via deep learning strategy. A database of 1500 CT images is constructed, containing 300 high-quality images and 1200 corresponding noisy images. Specifically, the high-quality images were used to simulate the corresponding noisy images at four different doses. Then, the images are scored by the experienced radiologists by the following attributes: image noise, artifacts, edge and structure, overall image quality, and tumor size and boundary estimation with five-point scale. We trained a network for learning the non-liner map from CT images to subjective evaluation scores. Then, we load the pre-trained model to yield predicted score from the test image. To demonstrate the performance of the deep learning network in IQA, correlation coefficients: Pearson Linear Correlation Coefficient (PLCC) and Spearman Rank Order Correlation Coefficient (SROCC) are utilized. And the experimental result demonstrate that the presented deep learning based IQA strategy can be used in the CT image quality assessment.

Chest wall tuberculosis; CT findings in 14 patients

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Han, Young Min; Lee, Sang Yong; Lee, Dong Won; Kim, Chong Soo; Chung, Gyung Ho; Sohn, Myung Hee; Choi, Ki Chul [Chonbuk National Univ. School of Medicine, Chonju (Korea, Republic of); Kim, Dong Woo [Daejoen Eulji Hospital, Daejon (Korea, Republic of); Juhng, Seon Kwan [Wonkwang Univ. Medical School, Iksan (Korea, Republic of)

1996-01-01

To present CT findings of chest wall tuberculosis. CT scans were obtained in 14 patients with proven chest wall tuberculosis. Diagnosis was confirmed by means of right open thoracostomy with abscess evacuation (n=1), excision and curettage (n=11) or excision and curettage along with resection of the involved lung (n=2). The images were assessed with emphasis for the extrapleural, pleural, and pulmonary lesions. All patients showed juxtacostal soft tissue mass with central low attenuation and peripheral rim enhancement. The lesions were located in the left hemithorax in eight patients and in the right in six. Multiple lesions were found in three patients (two in one and three in two). Rib destruction was observed in four patients. Intercostal muscle involvement of thickening and enhancement were shown in all patients. Thirteen patients (93%) had evidence of pulmonary tuberculosis: active pulmonary tuberculosis in nine and stable tuberculosis in four. Pleural lesions, including empyema necessitatis in six, were observed in eleven (79%). On CT scan, chest wall tuberculosis is characterized by juxtacostal soft tissue lesion with central low attenuation and peripheral rim enhancement. Rib destruction may be associated. Additionally, enhancing intercostal muscle suggest direct inflammatory process of tuberculosis and spread channel to the chest wall involvement of pleuropulmonary tuberculosis.

Chest wall tuberculosis; CT findings in 14 patients

International Nuclear Information System (INIS)

Han, Young Min; Lee, Sang Yong; Lee, Dong Won; Kim, Chong Soo; Chung, Gyung Ho; Sohn, Myung Hee; Choi, Ki Chul; Kim, Dong Woo; Juhng, Seon Kwan

1996-01-01

To present CT findings of chest wall tuberculosis. CT scans were obtained in 14 patients with proven chest wall tuberculosis. Diagnosis was confirmed by means of right open thoracostomy with abscess evacuation (n=1), excision and curettage (n=11) or excision and curettage along with resection of the involved lung (n=2). The images were assessed with emphasis for the extrapleural, pleural, and pulmonary lesions. All patients showed juxtacostal soft tissue mass with central low attenuation and peripheral rim enhancement. The lesions were located in the left hemithorax in eight patients and in the right in six. Multiple lesions were found in three patients (two in one and three in two). Rib destruction was observed in four patients. Intercostal muscle involvement of thickening and enhancement were shown in all patients. Thirteen patients (93%) had evidence of pulmonary tuberculosis: active pulmonary tuberculosis in nine and stable tuberculosis in four. Pleural lesions, including empyema necessitatis in six, were observed in eleven (79%). On CT scan, chest wall tuberculosis is characterized by juxtacostal soft tissue lesion with central low attenuation and peripheral rim enhancement. Rib destruction may be associated. Additionally, enhancing intercostal muscle suggest direct inflammatory process of tuberculosis and spread channel to the chest wall involvement of pleuropulmonary tuberculosis

Probabilistic atlas-based segmentation of combined T1-weighted and DUTE MRI for calculation of head attenuation maps in integrated PET/MRI scanners.

Science.gov (United States)

Poynton, Clare B; Chen, Kevin T; Chonde, Daniel B; Izquierdo-Garcia, David; Gollub, Randy L; Gerstner, Elizabeth R; Batchelor, Tracy T; Catana, Ciprian

2014-01-01

We present a new MRI-based attenuation correction (AC) approach for integrated PET/MRI systems that combines both segmentation- and atlas-based methods by incorporating dual-echo ultra-short echo-time (DUTE) and T1-weighted (T1w) MRI data and a probabilistic atlas. Segmented atlases were constructed from CT training data using a leave-one-out framework and combined with T1w, DUTE, and CT data to train a classifier that computes the probability of air/soft tissue/bone at each voxel. This classifier was applied to segment the MRI of the subject of interest and attenuation maps (μ-maps) were generated by assigning specific linear attenuation coefficients (LACs) to each tissue class. The μ-maps generated with this "Atlas-T1w-DUTE" approach were compared to those obtained from DUTE data using a previously proposed method. For validation of the segmentation results, segmented CT μ-maps were considered to the "silver standard"; the segmentation accuracy was assessed qualitatively and quantitatively through calculation of the Dice similarity coefficient (DSC). Relative change (RC) maps between the CT and MRI-based attenuation corrected PET volumes were also calculated for a global voxel-wise assessment of the reconstruction results. The μ-maps obtained using the Atlas-T1w-DUTE classifier agreed well with those derived from CT; the mean DSCs for the Atlas-T1w-DUTE-based μ-maps across all subjects were higher than those for DUTE-based μ-maps; the atlas-based μ-maps also showed a lower percentage of misclassified voxels across all subjects. RC maps from the atlas-based technique also demonstrated improvement in the PET data compared to the DUTE method, both globally as well as regionally.

Automated tube potential selection for standard chest and abdominal CT in follow-up patients with testicular cancer: comparison with fixed tube potential

Energy Technology Data Exchange (ETDEWEB)

Gnannt, Ralph; Winklehner, Anna; Frauenfelder, Thomas; Alkadhi, Hatem [University Hospital Zurich, Institute of Diagnostic and Interventional Radiology, Zurich (Switzerland); Eberli, Daniel [University Hospital Zurich, Clinic for Urology, Zurich (Switzerland); Knuth, Alexander [University Hospital Zurich, Clinic for Oncology, Zurich (Switzerland)

2012-09-15

To evaluate prospectively, in patients with testicular cancer, the radiation dose-saving potential and image quality of contrast-enhanced chest and abdominal CT with automated tube potential selection. Forty consecutive patients with testicular cancer underwent contrast-enhanced arterio-venous chest and portal-venous abdominal CT with automated tube potential selection (protocol B; tube potential 80-140 kVp), which is based on the attenuation of the CT topogram. All had a first CT at 120 kVp (protocol A) using the same 64-section CT machine and similar settings. Image quality was assessed; dose information (CTDI{sub vol}) was noted. Image noise and attenuation in the liver and spleen were significantly higher for protocol B (P < 0.05 each), whereas attenuation in the deltoid and erector spinae muscles was similar. In protocol B, tube potential was reduced to 100 kVp in 18 chest and 33 abdominal examinations, and to 80 kVp in 5 abdominal CT examinations; it increased to 140 kVp in one patient. Image quality of examinations using both CT protocols was rated as diagnostic. CTDI{sub vol} was significantly lower for protocol B compared to protocol A (reduction by 12%, P < 0.01). In patients with testicular cancer, radiation dose of chest and abdominal CT can be reduced with automated tube potential selection, while image quality is preserved. (orig.)

The effectiveness of WebCT as a progress-assessment tool in ...

African Journals Online (AJOL)

Journal for Language Teaching ... In support of this strategy the US has implemented WebCT as an electronic course management system. ... The WebCT assessment function was used as a complement to traditional lectures and traditional end-of-course written assessment to enrich teaching, promote learning and gauge ...

Objective assessment of image quality and dose reduction in CT iterative reconstruction

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Vaishnav, J. Y., E-mail: jay.vaishnav@fda.hhs.gov; Jung, W. C. [Diagnostic X-Ray Systems Branch, Office of In Vitro Diagnostic Devices and Radiological Health, Center for Devices and Radiological Health, United States Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, Maryland 20993 (United States); Popescu, L. M.; Zeng, R.; Myers, K. J. [Division of Imaging and Applied Mathematics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, Maryland 20993 (United States)

2014-07-15

Purpose: Iterative reconstruction (IR) algorithms have the potential to reduce radiation dose in CT diagnostic imaging. As these algorithms become available on the market, a standardizable method of quantifying the dose reduction that a particular IR method can achieve would be valuable. Such a method would assist manufacturers in making promotional claims about dose reduction, buyers in comparing different devices, physicists in independently validating the claims, and the United States Food and Drug Administration in regulating the labeling of CT devices. However, the nonlinear nature of commercially available IR algorithms poses challenges to objectively assessing image quality, a necessary step in establishing the amount of dose reduction that a given IR algorithm can achieve without compromising that image quality. This review paper seeks to consolidate information relevant to objectively assessing the quality of CT IR images, and thereby measuring the level of dose reduction that a given IR algorithm can achieve. Methods: The authors discuss task-based methods for assessing the quality of CT IR images and evaluating dose reduction. Results: The authors explain and review recent literature on signal detection and localization tasks in CT IR image quality assessment, the design of an appropriate phantom for these tasks, possible choices of observers (including human and model observers), and methods of evaluating observer performance. Conclusions: Standardizing the measurement of dose reduction is a problem of broad interest to the CT community and to public health. A necessary step in the process is the objective assessment of CT image quality, for which various task-based methods may be suitable. This paper attempts to consolidate recent literature that is relevant to the development and implementation of task-based methods for the assessment of CT IR image quality.

Objective assessment of image quality and dose reduction in CT iterative reconstruction

International Nuclear Information System (INIS)

Vaishnav, J. Y.; Jung, W. C.; Popescu, L. M.; Zeng, R.; Myers, K. J.

2014-01-01

Purpose: Iterative reconstruction (IR) algorithms have the potential to reduce radiation dose in CT diagnostic imaging. As these algorithms become available on the market, a standardizable method of quantifying the dose reduction that a particular IR method can achieve would be valuable. Such a method would assist manufacturers in making promotional claims about dose reduction, buyers in comparing different devices, physicists in independently validating the claims, and the United States Food and Drug Administration in regulating the labeling of CT devices. However, the nonlinear nature of commercially available IR algorithms poses challenges to objectively assessing image quality, a necessary step in establishing the amount of dose reduction that a given IR algorithm can achieve without compromising that image quality. This review paper seeks to consolidate information relevant to objectively assessing the quality of CT IR images, and thereby measuring the level of dose reduction that a given IR algorithm can achieve. Methods: The authors discuss task-based methods for assessing the quality of CT IR images and evaluating dose reduction. Results: The authors explain and review recent literature on signal detection and localization tasks in CT IR image quality assessment, the design of an appropriate phantom for these tasks, possible choices of observers (including human and model observers), and methods of evaluating observer performance. Conclusions: Standardizing the measurement of dose reduction is a problem of broad interest to the CT community and to public health. A necessary step in the process is the objective assessment of CT image quality, for which various task-based methods may be suitable. This paper attempts to consolidate recent literature that is relevant to the development and implementation of task-based methods for the assessment of CT IR image quality

Evaluation of solitary pulmonary nodules by integrated PET/CT: improved accuracy by FDG uptake pattern and CT findings

International Nuclear Information System (INIS)

Joon Young Choi; Kyung Soo Lee; O Jung Kwon; Young Mog Shim; Kyung-Han Lee; Yong Choi; Yearn Seong Choe; Byung-Tae Kim

2004-01-01

Objective: FDG PET is useful to differentiate malignancy from benign lesions in the evaluation of solitary pulmonary nodules (SPNs). However, FDG PET showed false positive results in benign inflammatory lesions such as tuberculosis and organizing pneumonia. Furthermore, malignant tumors such as adenocarcinoma (AC) with bronchioloalveolar carcinoma (BAC) type had lower FDG uptake than other cell types of non-small cell lung cancer. We investigated whether FDG uptake pattern and image findings of CT for attenuation correction could improve accuracy for evaluating SPNs over SUV in integrated PET/CT imaging using FDG. Methods: Forty patients (M:F = 23:17, mean age 58.2±9.4 yrs) with non-calcified SPNs (diameter on CT 30 mm, no significant mediastinal node enlargement, no atelectasis) were included. All subjects underwent integrated PET/CT imaging using FDG. One nuclear medicine physician and 1 chest radiologist interpreted the PET and non-contrast CT images for attenuation correction, respectively. On PET images, maximum SUV of SPN was acquired, and FDG uptake pattern was categorized as diffusely increased or heterogeneously increased with upper threshold of window setting adjusted to maximum SUV of each nodule. A radiologist interpreted SPNs as benign or malignant based on CT images with lung and mediastinai window settings blinded to PET findings. Results: On pathological exam, 30 SPNs were confirmed to be malignant (11 AC with non-BAC type, 8 AC with BAC type, 8 squamous cell carcinoma, 1 adenosquamous cell carcinoma, 1 neuroendocrine carcinoma, 1 large cell carcinoma), and 10 were benign (4 tuberculosis, 3 organizing pneumonia, 2 sclerosing pneumocytoma, 1 non-specific inflammation). All 5 nodules with max SUV 7.0 except one with tuberculoma had malignancy. When only nodules with diffusely increased uptake were considered malignant in indeterminate group with max SUV of 4.0 to 7.0, PET could diagnose 5 of 9 malignant nodules with one false positive nodule. In 6 of

Multi-atlas attenuation correction supports full quantification of static and dynamic brain PET data in PET-MR

Science.gov (United States)

Mérida, Inés; Reilhac, Anthonin; Redouté, Jérôme; Heckemann, Rolf A.; Costes, Nicolas; Hammers, Alexander

2017-04-01

In simultaneous PET-MR, attenuation maps are not directly available. Essential for absolute radioactivity quantification, they need to be derived from MR or PET data to correct for gamma photon attenuation by the imaged object. We evaluate a multi-atlas attenuation correction method for brain imaging (MaxProb) on static [18F]FDG PET and, for the first time, on dynamic PET, using the serotoninergic tracer [18F]MPPF. A database of 40 MR/CT image pairs (atlases) was used. The MaxProb method synthesises subject-specific pseudo-CTs by registering each atlas to the target subject space. Atlas CT intensities are then fused via label propagation and majority voting. Here, we compared these pseudo-CTs with the real CTs in a leave-one-out design, contrasting the MaxProb approach with a simplified single-atlas method (SingleAtlas). We evaluated the impact of pseudo-CT accuracy on reconstructed PET images, compared to PET data reconstructed with real CT, at the regional and voxel levels for the following: radioactivity images; time-activity curves; and kinetic parameters (non-displaceable binding potential, BPND). On static [18F]FDG, the mean bias for MaxProb ranged between 0 and 1% for 73 out of 84 regions assessed, and exceptionally peaked at 2.5% for only one region. Statistical parametric map analysis of MaxProb-corrected PET data showed significant differences in less than 0.02% of the brain volume, whereas SingleAtlas-corrected data showed significant differences in 20% of the brain volume. On dynamic [18F]MPPF, most regional errors on BPND ranged from -1 to  +3% (maximum bias 5%) for the MaxProb method. With SingleAtlas, errors were larger and had higher variability in most regions. PET quantification bias increased over the duration of the dynamic scan for SingleAtlas, but not for MaxProb. We show that this effect is due to the interaction of the spatial tracer-distribution heterogeneity variation over time with the degree of accuracy of the attenuation maps. This

Effect of hybrid iterative reconstruction technique on quantitative and qualitative image analysis at 256-slice prospective gating cardiac CT

International Nuclear Information System (INIS)

Utsunomiya, Daisuke; Weigold, W. Guy; Weissman, Gaby; Taylor, Allen J.

2012-01-01

To evaluate the effect of hybrid iterative reconstruction on qualitative and quantitative parameters at 256-slice cardiac CT. Prospective cardiac CT images from 20 patients were analysed. Paired image sets were created using 3 reconstructions, i.e. filtered back projection (FBP) and moderate- and high-level iterative reconstructions. Quantitative parameters including CT-attenuation, noise, and contrast-to-noise ratio (CNR) were determined in both proximal- and distal coronary segments. Image quality was graded on a 4-point scale. Coronary CT attenuation values were similar for FBP, moderate- and high-level iterative reconstruction at 293 ± 74-, 290 ± 75-, and 283 ± 78 Hounsfield units (HU), respectively. CNR was significantly higher with moderate- and high-level iterative reconstructions (10.9 ± 3.5 and 18.4 ± 6.2, respectively) than FBP (8.2 ± 2.5) as was the visual grading of proximal vessels. Visualisation of distal vessels was better with high-level iterative reconstruction than FBP. The mean number of assessable segments among 289 segments was 245, 260, and 267 for FBP, moderate- and high-level iterative reconstruction, respectively; the difference between FBP and high-level iterative reconstruction was significant. Interobserver agreement was significantly higher for moderate- and high-level iterative reconstruction than FBP. Cardiac CT using hybrid iterative reconstruction yields higher CNR and better image quality than FBP. circle Cardiac CT helps clinicians to assess patients with coronary artery disease circle Hybrid iterative reconstruction provides improved cardiac CT image quality circle Hybrid iterative reconstruction improves the number of assessable coronary segments circle Hybrid iterative reconstruction improves interobserver agreement on cardiac CT. (orig.)

Diagnostic impact of SPECT-CT in the assessment of endocrine tumors

International Nuclear Information System (INIS)

El Badaoui, A.; Clermont, H. de; Valli, N.; Caignon, J.M.; Fernandez, P.; Allard, M.; Barat, J.L.; Ducassou, D.; Clermont, H. de; Valli, N.; Caignon, J.M.; Fernandez, P.; Allard, M.; Barat, J.L.; Ducassou, D.; Clermont, H. de; Allard, M.

2008-01-01

Image fusion using single photon emission computed tomography - computed tomography (SPECT - CT) associates functional and morphological images. This study evaluates the added value of SPECT- CT, obtained with a hybrid SPECT- CT gamma camera, on anatomic localization and diagnostic impact in assessment of endocrine tumours and pheochromocytomas. Method: Six months prospective study was undertaken including 33 consecutive exams encompassing 20 Somatostatin Receptor Scintigraphies (S.R.S.) and 13 123 I-meta-iodo-benzyl-guanidine (Mibg) scans. Two experienced nuclear medicine physicians independently analysed independently planar and SPECT images in a first time, then, SPECT- CT fused images in a second time. They evaluated two parameters: SPECT- CT impact on anatomic localization (L.A.) and its diagnostic impact (I.D.). Each parameter was scored according three levels of evaluation. Results: An added value of SPECT- CT images was evidenced in 55% of cases on the anatomic localization and in 41% of the patients on the diagnostic impact. Therefore, a more important benefit was noted when SPECT was positive (L.A.: 90%; I.D.: 70%) than when it was negative (L.A.: 15%; I.D.: 8%). Furthermore, the added value proved higher for the S;R.S. compared to Mibg scans. Conclusion: SPECT- CT fusion images obtained by a hybrid system is more relevant to determine anatomic localization and more accurate than SPECT alone, particularly in the assessment of endocrine tumours. The added value of SPECT- CT seems to be lower for Mibg scans in the assessment of pheochromocytomas. (authors)

Metallic artifacts caused by dental metal prostheses on PET images. A PET/CT phantom study using different PET/CT scanners

International Nuclear Information System (INIS)

Shimamoto, Hiroaki; Kakimoto, Naoya; Murakami, Shumei; Furukawa, Souhei; Fujino, Kouichi; Hamada, Seiki; Shimosegawa, Eku; Hatazawa, Jun

2009-01-01

The objective of this study was to investigate the effects of computed tomography (CT) artifacts caused by dental metal prostheses on positron emission tomography (PET) images. A dental arch cast was fixed in a cylindrical water-bath phantom. A spherical phantom positioned in the vicinity of the dental arch cast was used to simulate a tumor. To simulate the tumor imaging, the ratio of the 18 F-fluoro-deoxy-glucose radioactivity concentration of the spherical phantom to that of the water-bath phantom was set at 2.5. A dental bridge composed of a gold-silver-palladium alloy on the right mandibular side was prepared. A spherical phantom was set in the white artifact area on the CT images (site A), in a slightly remote area from the white artifact (site B), and in a black artifact area (site C). A PET/CT scan was performed with and without the metal bridge at each simulated tumor site, and the artifactual influence was evaluated on the axial attenuation-corrected (AC) PET images, in which the simulated tumor produced the strongest accumulation. Measurements were performed using three types of PET/CT scanners (scanners 1 and 2 with CT-based attenuation correction, and 3 with Cesium-137 ( 137 Cs)-based attenuation correction). The influence of the metal bridge was evaluated using the change rate of the SUVmean with and without the metal bridge. At site A, an overestimation was shown (scanner 1: +5.0% and scanner 2: +2.5%), while scanner 3 showed an underestimation of -31.8%. At site B, an overestimation was shown (scanner 1: +2.1% and scanner 2: +2.0%), while scanner 3 showed an underestimation of -2.6%. However, at site C, an underestimation was shown (scanner 1: -25.0%, scanner 2: -32.4%, and scanner 3: -8.4%). When CT is used for attenuation correction in patients with dental metal prostheses, an underestimation of radioactivity of accumulated tracer is anticipated in the dark streak artifact area on the CT images. In this study, the dark streak artifacts of the CT

High resolution micro-CT of low attenuating organic materials using large area photon-counting detector

International Nuclear Information System (INIS)

Kumpová, I.; Jandejsek, I.; Jakůbek, J.; Vopálenský, M.; Vavřík, D.; Fíla, T.; Koudelka, P.; Kytýř, D.; Zlámal, P.; Gantar, A.

2016-01-01

To overcome certain limitations of contemporary materials used for bone tissue engineering, such as inflammatory response after implantation, a whole new class of materials based on polysaccharide compounds is being developed. Here, nanoparticulate bioactive glass reinforced gelan-gum (GG-BAG) has recently been proposed for the production of bone scaffolds. This material offers promising biocompatibility properties, including bioactivity and biodegradability, with the possibility of producing scaffolds with directly controlled microgeometry. However, to utilize such a scaffold with application-optimized properties, large sets of complex numerical simulations using the real microgeometry of the material have to be carried out during the development process. Because the GG-BAG is a material with intrinsically very low attenuation to X-rays, its radiographical imaging, including tomographical scanning and reconstructions, with resolution required by numerical simulations might be a very challenging task. In this paper, we present a study on X-ray imaging of GG-BAG samples. High-resolution volumetric images of investigated specimens were generated on the basis of micro-CT measurements using a large area flat-panel detector and a large area photon-counting detector. The photon-counting detector was composed of a 010× 1 matrix of Timepix edgeless silicon pixelated detectors with tiling based on overlaying rows (i.e. assembled so that no gap is present between individual rows of detectors). We compare the results from both detectors with the scanning electron microscopy on selected slices in transversal plane. It has been shown that the photon counting detector can provide approx. 3× better resolution of the details in low-attenuating materials than the integrating flat panel detectors. We demonstrate that employment of a large area photon counting detector is a good choice for imaging of low attenuating materials with the resolution sufficient for numerical

High resolution micro-CT of low attenuating organic materials using large area photon-counting detector

Science.gov (United States)

Kumpová, I.; Vavřík, D.; Fíla, T.; Koudelka, P.; Jandejsek, I.; Jakůbek, J.; Kytýř, D.; Zlámal, P.; Vopálenský, M.; Gantar, A.

2016-02-01

To overcome certain limitations of contemporary materials used for bone tissue engineering, such as inflammatory response after implantation, a whole new class of materials based on polysaccharide compounds is being developed. Here, nanoparticulate bioactive glass reinforced gelan-gum (GG-BAG) has recently been proposed for the production of bone scaffolds. This material offers promising biocompatibility properties, including bioactivity and biodegradability, with the possibility of producing scaffolds with directly controlled microgeometry. However, to utilize such a scaffold with application-optimized properties, large sets of complex numerical simulations using the real microgeometry of the material have to be carried out during the development process. Because the GG-BAG is a material with intrinsically very low attenuation to X-rays, its radiographical imaging, including tomographical scanning and reconstructions, with resolution required by numerical simulations might be a very challenging task. In this paper, we present a study on X-ray imaging of GG-BAG samples. High-resolution volumetric images of investigated specimens were generated on the basis of micro-CT measurements using a large area flat-panel detector and a large area photon-counting detector. The photon-counting detector was composed of a 010× 1 matrix of Timepix edgeless silicon pixelated detectors with tiling based on overlaying rows (i.e. assembled so that no gap is present between individual rows of detectors). We compare the results from both detectors with the scanning electron microscopy on selected slices in transversal plane. It has been shown that the photon counting detector can provide approx. 3× better resolution of the details in low-attenuating materials than the integrating flat panel detectors. We demonstrate that employment of a large area photon counting detector is a good choice for imaging of low attenuating materials with the resolution sufficient for numerical simulations.

Construction of Realistic Liver Phantoms from Patient Images using 3D Printer and Its Application in CT Image Quality Assessment.

Science.gov (United States)

Leng, Shuai; Yu, Lifeng; Vrieze, Thomas; Kuhlmann, Joel; Chen, Baiyu; McCollough, Cynthia H

2015-01-01

The purpose of this study is to use 3D printing techniques to construct a realistic liver phantom with heterogeneous background and anatomic structures from patient CT images, and to use the phantom to assess image quality with filtered backprojection and iterative reconstruction algorithms. Patient CT images were segmented into liver tissues, contrast-enhanced vessels, and liver lesions using commercial software, based on which stereolithography (STL) files were created and sent to a commercial 3D printer. A 3D liver phantom was printed after assigning different printing materials to each object to simulate appropriate attenuation of each segmented object. As high opacity materials are not available for the printer, we printed hollow vessels and filled them with iodine solutions of adjusted concentration to represent enhance levels in contrast-enhanced liver scans. The printed phantom was then placed in a 35×26 cm oblong-shaped water phantom and scanned repeatedly at 4 dose levels. Images were reconstructed using standard filtered backprojection and an iterative reconstruction algorithm with 3 different strength settings. Heterogeneous liver background were observed from the CT images and the difference in CT numbers between lesions and background were representative for low contrast lesions in liver CT studies. CT numbers in vessels filled with iodine solutions represented the enhancement of liver arteries and veins. Images were run through a Channelized Hotelling model observer with Garbor channels and ROC analysis was performed. The AUC values showed performance improvement using the iterative reconstruction algorithm and the amount of improvement increased with strength setting.

RADIODIAGNOSIS OF PLEURAL LESIONS WITH USG AND CT SCAN

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Bheemashanker

2017-09-01

Full Text Available BACKGROUND Ultrasound is easy available, less expensive study. It differentiates pleural effusion, consolidation and masses. CT scores in diagnosing early pleural lesions and helps in localising lesions differentiating benign and malignant. The aim of the study is to- 1. Assess the value of ultrasonography and computed tomography in evaluation of pleural lesions. 2. Determine the sensitivity and specificity of ultrasound and CT in pleural lesions. MATERIALS AND METHODS The present study was aimed at assessing the value of ultrasonography and CT in evaluating the pleural lesions. In our study, during the period of 12 months, 100 patients with pleural effusions were evaluated. The most common cause was transudate. Exudates consist of malignant and non-malignant causes. RESULTS The study group was defined into two groups- Malignant and non-malignant group based on pleural effusion of transudate and exudate types. CT and ultrasound has success rate of 100% and 85% respectively to identify neoplastic and non-neoplastic disease. Diagnostic accuracy of CT and ultrasound are comparable while CT scores over ultrasound in failed cases. CT has 100% sensitivity and 100% specificity in pleural lesions. CT has more therapeutic value compared to ultrasound. CONCLUSION The role of ultrasound and CT are complimentary, give high yield of positive results for pleural mass differentiation; useful for guided procedures like pleural biopsy and pleural drainage. Combined study not only useful for localisation of lesion, but also gives information about the extent of disease and characterising the tissue density by analysis of attenuation coefficient.

Patent foramen ovale: detection with nongated multidetector CT.

Science.gov (United States)

Revel, Marie-Pierre; Faivre, Jean-Baptiste; Letourneau, Thierry; Henon, Hilde; Leys, Didier; Delannoy-Deken, Valérie; Remy-Jardin, Martine; Remy, Jacques

2008-10-01

To evaluate nongated multidetector computed tomography (CT) in the detection of patent foramen ovale (PFO) and atrial septal aneurysm (ASA) in comparison with transesophageal echocardiography (TEE). The study was approved by the institutional review board, and informed consent was obtained from all patients. One hundred five patients (57 men, 48 women; mean age, 53 years) with a recent stroke underwent TEE and multidetector CT on the same day. After injection of a diluted iodinated contrast material, a series of 2.4-mm-thick transverse images centered on the fossa ovalis were acquired in conjunction with release of the Valsalva maneuver. Two independent radiologists considered PFO present if left atrial enhancement was detected visually before enhancement of the pulmonary veins or if an early peak of left atrial enhancement was found at time-attenuation curve analysis. PFO was detected with 98% specificity (95% confidence interval [CI]: 0.91, 0.99). Overall sensitivity was 55% (95% CI: 0.38, 0.70), ranging from 28% for shunts classified as grade 1 at TEE to 91% for those classified as grade 4 at TEE. Interreader agreement was good (kappa = 0.81). Visual assessment was better than time-attenuation curve analysis, which enabled detection of only 15 of the 40 cases of PFO. Multidetector CT depicted only 22% of cases of ASA. The mean effective radiation dose was 2.3 mSv. Nongated multidetector CT can be used to diagnose high-grade shunts through a PFO, with 91% sensitivity and 98% specificity. Thus, PFO detection, in addition to routine CT evaluation of the lungs, could be indicated in patients with unexplained hypoxemia. (c) RSNA, 2008.

Tuberculous pneumonia and bacteriaI pneumonia in diabetic patients: comparison of CT findings

Energy Technology Data Exchange (ETDEWEB)

Kim, Yoo Kyung; Shim, Sung Shine [College of Medicine, Chungnam Univ., Daejeon (Korea, Republic of); Kim, Jin Hwan [College of Medicine, Ewha Womans Univ., Seoul (Korea, Republic of)

2004-07-01

To compare the CT findings of tuberculous pneumonia (TBPN) with those of bacterial pneumonia (BAPN) in diabetic patients and to evaluate the usefulness of CT in the differential diagnosis of these two diseases. The chest CT scans of 23 diabetic patients with TBPN (M:F=21:2; mean age, 59 yrs.) and of 37 diabetic patients with BAPN (M:F=21:16; mean age, 63 yrs.) were evaluated by two radiologists with regard to low attenuation areas in regions of consolidation, cavities, air bronchogram, volume changes, ground-glass attenuation, findings of bronchogenic spread, and other associated findings. The involvement of each segment was recorded in all patients. The frequencies of multiple small low-attenuation areas in regions of consolidation (52%, 0%), multiple cavities (35%, 3%), loss of volume (70%, 30%) and findings of bronchogenic spread (96%, 30%) were significantly higher in TBPN than in BAPN (p< .05). Low-attenuation masses and bizarre-shaped cavities were noted only in TBPN. Large areas of ground-glass attenuation (4%, 38%) and bilateral pleural effusions (0%, 19%) were more common in BAPN, while air-bronchogram was common in both groups (96%, 86%). The involvement of the superior segment was significantly more common in TBPN (p< .05). In the diabetic patients with pulmonary consolidation, CT findings of multiple small low-attenuation areas, multiple cavities, bizarre-shaped cavities, low attenuation masses in cavities, volume loss, and findings of bronchogenic spread are more suggestive of TBPN, while large areas of ground-glass attenuation and bilateral pleural effusions are more suggestive of BAPN. CT may be useful in the differential diagnosis between TBPN and BAPN.

SU-E-I-86: Ultra-Low Dose Computed Tomography Attenuation Correction for Pediatric PET CT Using Adaptive Statistical Iterative Reconstruction (ASiR™)

Energy Technology Data Exchange (ETDEWEB)

Brady, S; Shulkin, B [St. Jude Children’s Research Hospital, Memphis, TN (United States)

2015-06-15

Purpose: To develop ultra-low dose computed tomography (CT) attenuation correction (CTAC) acquisition protocols for pediatric positron emission tomography CT (PET CT). Methods: A GE Discovery 690 PET CT hybrid scanner was used to investigate the change to quantitative PET and CT measurements when operated at ultra-low doses (10–35 mAs). CT quantitation: noise, low-contrast resolution, and CT numbers for eleven tissue substitutes were analyzed in-phantom. CT quantitation was analyzed to a reduction of 90% CTDIvol (0.39/3.64; mGy) radiation dose from baseline. To minimize noise infiltration, 100% adaptive statistical iterative reconstruction (ASiR) was used for CT reconstruction. PET images were reconstructed with the lower-dose CTAC iterations and analyzed for: maximum body weight standardized uptake value (SUVbw) of various diameter targets (range 8–37 mm), background uniformity, and spatial resolution. Radiation organ dose, as derived from patient exam size specific dose estimate (SSDE), was converted to effective dose using the standard ICRP report 103 method. Effective dose and CTAC noise magnitude were compared for 140 patient examinations (76 post-ASiR implementation) to determine relative patient population dose reduction and noise control. Results: CT numbers were constant to within 10% from the non-dose reduced CTAC image down to 90% dose reduction. No change in SUVbw, background percent uniformity, or spatial resolution for PET images reconstructed with CTAC protocols reconstructed with ASiR and down to 90% dose reduction. Patient population effective dose analysis demonstrated relative CTAC dose reductions between 62%–86% (3.2/8.3−0.9/6.2; mSv). Noise magnitude in dose-reduced patient images increased but was not statistically different from pre dose-reduced patient images. Conclusion: Using ASiR allowed for aggressive reduction in CTAC dose with no change in PET reconstructed images while maintaining sufficient image quality for co

Determining the proportion of coronary segments assessable on 16-slice CT coronary angiography: a brief report

International Nuclear Information System (INIS)

Soon, K. H.; Cox, N.; Eccleston, D.; Lim, Y.; Chaitowitz, I.; Bell, K. W.; Kelly, A-M.

2007-01-01

Computed tomography coronary angiography (CT-CA) is becoming a popular non-invasive coronary imaging method. We aimed to determine the proportion of coronary segments assessable on a 16-slice CT in comparison with conventional selective coronary angiography (SCA). We identified all patients who had both 16-slice CT-CA and recent SCA (less than 12 months) from March 2004 to July 2005. Two CT reporters blinded to SCA independently classified coronary segment assessability on CT-CA. A cardiologist blinded to CT findings classified assess-ability of coronary segments on SCA. Data were analysed using descriptive statistics and proportion of agreement. Ninety-five study pairs were included in the analysis. Of those, 1161 coronary segments were deemed assessable on SCA and 1103 segments (95%) were also assessable on CT-CA. Nonassessable segments on CT-CA were predominantly in the distal segments and branches of coronary arteries. Reasons for nonassessability were small calibre (48.3%), motion artefacts (20.7%) and poorly reconstructed segments (22.4%). The 16-slice CT was able to assess a high proportion of but not all coronary segments. Nonassessable segments were predominantly distal segments or branches of coronary arteries. Motion artefacts due to heart-rate changes, small calibre and poorly reconstructed images were main causes of nonassessability on 16-slice CT-CA

CT quantification of lung and airways in normal Korean subjects

International Nuclear Information System (INIS)

Kim, Song Soo; Lee, Jeong Eun; Shin, Hye Soo; Jin, Gong Yong; Li, Yuan Zhe

2017-01-01

To measure and compare the quantitative parameters of the lungs and airways in Korean never-smokers and current or former smokers (“ever-smokers”). Never-smokers (n = 119) and ever-smokers (n = 45) who had normal spirometry and visually normal chest computed tomography (CT) results were retrospectively enrolled in this study. For quantitative CT analyses, the low attenuation area (LAA) of LAA_I_-_9_5_0, LAA_E_-_8_5_6, CT attenuation value at the 15th percentile, mean lung attenuation (MLA), bronchial wall thickness of inner perimeter of a 10 mm diameter airway (Pi10), total lung capacity (TLC_C_T), and functional residual capacity (FRC_C_T) were calculated based on inspiratory and expiratory CT images. To compare the results between groups according to age, sex, and smoking history, independent t test, one way ANOVA, correlation test, and simple and multiple regression analyses were performed. The values of attenuation parameters and volume on inspiratory and expiratory quantitative computed tomography (QCT) were significantly different between males and females (p < 0.001). The MLA and the 15th percentile value on inspiratory QCT were significantly lower in the ever-smoker group than in the never-smoker group (p < 0.05). On expiratory QCT, all lung attenuation parameters were significantly different according to the age range (p < 0.05). Pi10 in ever-smokers was significantly correlated with forced expiratory volume in 1 second/forced vital capacity (r = −0.455, p = 0.003). In simple and multivariate regression analyses, TLC_C_T, FRC_C_T, and age showed significant associations with lung attenuation (p < 0.05), and only TLC_C_T was significantly associated with inspiratory Pi10. In Korean subjects with normal spirometry and visually normal chest CT, there may be significant differences in QCT parameters according to sex, age, and smoking history

Mycoplasma pneumoniae pneumonia: CT features in 16 patients

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Lee, Inho; Kim, Tae Sung; Yoon, Hye-Kyung [Sungkyunkwan University School of Medicine, Department of Radiology and Center for Imaging Science, Samsung Medical Center, Seoul (Korea)

2006-03-15

The objective of this study was to assess the computed tomography (CT) features of Mycoplasma pneumoniae pneumonia. We retrospectively reviewed CT findings of 16 patients (M:F=9:7, age range 1-74 years, median 9 years) with serologically proven Mycoplasma pneumoniae pneumonia and with chest CT scan available. Two distinctive patterns of CT features of M. pneumoniae pneumonia were noted between the paediatric (age <18 years) and the adult (age {>=}18 years) groups. The pediatric group (n=11) showed lobar or segmental consolidation (100%) with frequent pleural effusion (82%) and regional lymphadenopathy (82%) and mild volume decrease of the involved lobe (73%), while four of the five adult patients showed diffuse and/or multifocal, centrilobular or peribronchovascular areas of ground-glass attenuation (80%) with a lobular distribution, and frequent thickening of interlobular septa (60%) and the bronchial walls (40%) were also detected at high-resolution CT. The CT finding of a lobar or segmental consolidation with a parapneumonic effusion seen in our children with M. pneumoniae pneumonia was similar to that of bacterial lobar pneumonia. In contrast, the CT findings noted in our adult patients consisted of a mixture of a bacterial bronchopneumonia pattern and a viral interstitial pneumonia pattern. (orig.)

Mycoplasma pneumoniae pneumonia: CT features in 16 patients

International Nuclear Information System (INIS)

Lee, Inho; Kim, Tae Sung; Yoon, Hye-Kyung

2006-01-01

The objective of this study was to assess the computed tomography (CT) features of Mycoplasma pneumoniae pneumonia. We retrospectively reviewed CT findings of 16 patients (M:F=9:7, age range 1-74 years, median 9 years) with serologically proven Mycoplasma pneumoniae pneumonia and with chest CT scan available. Two distinctive patterns of CT features of M. pneumoniae pneumonia were noted between the paediatric (age <18 years) and the adult (age ≥18 years) groups. The pediatric group (n=11) showed lobar or segmental consolidation (100%) with frequent pleural effusion (82%) and regional lymphadenopathy (82%) and mild volume decrease of the involved lobe (73%), while four of the five adult patients showed diffuse and/or multifocal, centrilobular or peribronchovascular areas of ground-glass attenuation (80%) with a lobular distribution, and frequent thickening of interlobular septa (60%) and the bronchial walls (40%) were also detected at high-resolution CT. The CT finding of a lobar or segmental consolidation with a parapneumonic effusion seen in our children with M. pneumoniae pneumonia was similar to that of bacterial lobar pneumonia. In contrast, the CT findings noted in our adult patients consisted of a mixture of a bacterial bronchopneumonia pattern and a viral interstitial pneumonia pattern. (orig.)

Crackle analysis for chest auscultation and comparison with high-resolution CT findings.

Science.gov (United States)

Kawamura, Takeo; Matsumoto, Tsuneo; Tanaka, Nobuyuki; Kido, Shoji; Jiang, Zhongwei; Matsunaga, Naofumi

2003-01-01

The purpose of our study was to clarify the correlation between respiratory sounds and the high-resolution CT (HRCT) findings of lung diseases. Respiratory sounds were recorded using a stethoscope in 41 patients with crackles. All had undergone inspiratory and expiratory CT. Subjects included 18 patients with interstitial pneumonia and 23 without interstitial pneumonia. Two parameters, two-cycle duration (2CD) and initial deflection width (IDW) of the "crackle," were induced by time-expanded waveform analysis. Two radiologists independently assessed 11 HRCT findings. An evaluation was carried out to determine whether there was a significant difference in the two parameters between the presence and absence of each HRCT finding. The two parameters of crackles were significantly shorter in the interstitial pneumonia group than the non-interstitial pneumonia group. Ground-glass opacity, honeycombing, lung volume reduction, traction bronchiectasis, centrilobular nodules, emphysematous change, and attenuation and volume change between inspiratory and expiratory CT were correlated with one or two parameters in all patients, whereas the other three findings were not. Among the interstitial pneumonia group, traction bronchiectasis, emphysematous change, and attenuation and volume change between inspiratory and expiratory CT were significantly correlated with one or two parameters. Abnormal respiratory sounds were correlated with some HRCT findings.

Crackle analysis for chest auscultation and comparison with high-resolution CT findings

International Nuclear Information System (INIS)

Kawamura, Takeo; Matsumoto, Tsuneo; Tanaka, Nobuyuki; Matsunaga, Naofumi; Kido, Shoji; Jiang Zhongwei

2003-01-01

The purpose of our study was to clarify the correlation between respiratory sounds and the high-resolution CT (HRCT) findings of lung diseases. Respiratory sounds were recorded using a stethoscope in 41 patients with crackles. All had undergone inspiratory and expiratory CT. Subjects included 18 patients with interstitial pneumonia and 23 without interstitial pneumonia. Two parameters, two-cycle duration (2CD) and initial deflection width (IDW) of the ''crackle,'' were induced by time-expanded waveform analysis. Two radiologists independently assessed 11 HRCT findings. An evaluation was carried out to determine whether there was a significant difference in the two parameters between the presence and absence of each HRCT finding. The two parameters of crackles were significantly shorter in the interstitial pneumonia group than the non-interstitial pneumonia group. Ground-glass opacity, honeycombing, lung volume reduction, traction bronchiectasis, centrilobular nodules, emphysematous change, and attenuation and volume change between inspiratory and expiratory CT were correlated with one or two parameters in all patients, whereas the other three findings were not. Among the interstitial pneumonia group, traction bronchiectasis, emphysematous change, and attenuation and volume change between inspiratory and expiratory CT were significantly correlated with one or two parameters. Abnormal respiratory sounds were correlated with some HRCT findings. (author)

Automated size-specific CT dose monitoring program: Assessing variability in CT dose

International Nuclear Information System (INIS)

Christianson, Olav; Li Xiang; Frush, Donald; Samei, Ehsan

2012-01-01

Purpose: The potential health risks associated with low levels of ionizing radiation have created a movement in the radiology community to optimize computed tomography (CT) imaging protocols to use the lowest radiation dose possible without compromising the diagnostic usefulness of the images. Despite efforts to use appropriate and consistent radiation doses, studies suggest that a great deal of variability in radiation dose exists both within and between institutions for CT imaging. In this context, the authors have developed an automated size-specific radiation dose monitoring program for CT and used this program to assess variability in size-adjusted effective dose from CT imaging. Methods: The authors radiation dose monitoring program operates on an independent health insurance portability and accountability act compliant dosimetry server. Digital imaging and communication in medicine routing software is used to isolate dose report screen captures and scout images for all incoming CT studies. Effective dose conversion factors (k-factors) are determined based on the protocol and optical character recognition is used to extract the CT dose index and dose-length product. The patient's thickness is obtained by applying an adaptive thresholding algorithm to the scout images and is used to calculate the size-adjusted effective dose (ED adj ). The radiation dose monitoring program was used to collect data on 6351 CT studies from three scanner models (GE Lightspeed Pro 16, GE Lightspeed VCT, and GE Definition CT750 HD) and two institutions over a one-month period and to analyze the variability in ED adj between scanner models and across institutions. Results: No significant difference was found between computer measurements of patient thickness and observer measurements (p= 0.17), and the average difference between the two methods was less than 4%. Applying the size correction resulted in ED adj that differed by up to 44% from effective dose estimates that were not

Poster — Thur Eve — 06: Dose assessment of cone beam CT imaging protocols as part of SPECT/CT examinations

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Tonkopi, E; Ross, AA [Department of Diagnostic Imaging, Queen Elizabeth II Health Sciences Centre, CDHA (Canada); Department of Radiology, Dalhousie University (Canada)

2014-08-15

Purpose: To assess radiation dose from the cone beam CT (CBCT) component of SPECT/CT studies and to compare with other CT examinations performed in our institution. Methods: We used an anthropomorphic chest phantom and the 6 cc ion chamber to measure entrance breast dose for several CBCT and diagnostic CT acquisition protocols. The CBCT effective dose was calculated with ImPACT software; the CT effective dose was evaluated from the DLP value and conversion factor, dependent on the anatomic region. The RADAR medical procedure radiation dose calculator was used to assess the nuclear medicine component of exam dose. Results: The entrance dose to the breast measured with the anthropomorphic phantom was 0.48 mGy and 9.41 mGy for cardiac and chest CBCT scans; and 4.59 mGy for diagnostic thoracic CT. The effective doses were 0.2 mSv, 3.2 mSv and 2.8 mSv respectively. For a small patient represented by the anthropomorphic phantom, the dose from the diagnostic CT was lower than from the CBCT scan, as a result of the exposure reduction options available on modern CT scanners. The CBCT protocols used the same fixed scanning techniques. The diagnostic CT dose based on the patient data was 35% higher than the phantom dose. For most SPECT/CT studies the dose from the CBCT component was comparable with the dose from the radiopharmaceutical. Conclusions: The patient radiation dose from the cone beam CT scan can be higher than that from a diagnostic CT and should be taken into consideration in evaluating total SPECT/CT patient dose.

CT findings of orbital langerhans cell histiocytosis

International Nuclear Information System (INIS)

Yi, Gina; Yoon, Hye Kyung; Han, Bokyung Kim; Kim, Kyeong Ah; Choo, In Wook

2000-01-01

To evaluate the CT findings in patients with Langerhans cell histiocytosis (LCH) involving the orbit. Orbital CT scans of six children with pathologically proven LCH were retrospectively analyzed. Follow-up CT (n=3D5) and MR (n=3D1) imaging findings were also reviewed. Initial CT scans revealed varying degree of bone destruction with soft-tissue masses, and on nonenhanced images the mean attenuation value was 44 Hounsfield units (HU). All masses showed mild to moderate enhancement with a mean attenuation value of 74 HU. The bony margins abutting onto soft tissue masses were irregular but clearly demarcated. No evidence of calcification or periosteal reaction was noted. Suprasellar mass and rib involvement was noted in one patient and hepatosplenomegaly in two. Follow-up CT and MR images showed that the soft tissue masses were almost completely resolved, with bone remodeling and reossification. A soft tissue mass with irregular but clearly demarcated bone destruction is thought to be a characteristic finding of LCH involving the orbit. Follow-up images after treatment showed bone remodeling and reossification. (author)

Comprehensive Assessment of Osteoporosis and Bone Fragility with CT Colonography

Science.gov (United States)

Murthy, Naveen S.; Khosla, Sundeep; Clarke, Bart L.; Bruining, David H.; Kopperdahl, David L.; Lee, David C.; Keaveny, Tony M.

2016-01-01

Purpose To evaluate the ability of additional analysis of computed tomographic (CT) colonography images to provide a comprehensive osteoporosis assessment. Materials and Methods This Health Insurance Portability and Accountability Act–compliant study was approved by our institutional review board with a waiver of informed consent. Diagnosis of osteoporosis and assessment of fracture risk were compared between biomechanical CT analysis and dual-energy x-ray absorptiometry (DXA) in 136 women (age range, 43–92 years), each of whom underwent CT colonography and DXA within a 6-month period (between January 2008 and April 2010). Blinded to the DXA data, biomechanical CT analysis was retrospectively applied to CT images by using phantomless calibration and finite element analysis to measure bone mineral density and bone strength at the hip and spine. Regression, Bland-Altman, and reclassification analyses and paired t tests were used to compare results. Results For bone mineral density T scores at the femoral neck, biomechanical CT analysis was highly correlated (R2 = 0.84) with DXA, did not differ from DXA (P = .15, paired t test), and was able to identify osteoporosis (as defined by DXA), with 100% sensitivity in eight of eight patients (95% confidence interval [CI]: 67.6%, 100%) and 98.4% specificity in 126 of 128 patients (95% CI: 94.5%, 99.6%). Considering both the hip and spine, the classification of patients at high risk for fracture by biomechanical CT analysis—those with osteoporosis or “fragile bone strength”—agreed well against classifications for clinical osteoporosis by DXA (T score ≤−2.5 at the hip or spine), with 82.8% sensitivity in 24 of 29 patients (95% CI: 65.4%, 92.4%) and 85.7% specificity in 66 of 77 patients (95% CI: 76.2%, 91.8%). Conclusion Retrospective biomechanical CT analysis of CT colonography for colorectal cancer screening provides a comprehensive osteoporosis assessment without requiring changes in imaging protocols. �

CT and MRI Findings of Soft Tissue Adult Fibrosarcoma in Extremities

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Hexiang Wang

2018-01-01

Full Text Available Objective. To characterize and evaluate CT and MRI features of extremity soft tissue adult fibrosarcoma. Methods. CT and MRI images from 10 adult patients with pathologically proven fibrosarcomas were retrospectively analyzed with regard to tumor location, size, number, shape, margins, attenuation, signal intensity, and enhancement patterns on MR images. Additionally, the relationships between lesions, deep fascia, and change in adjacent bones were also assessed. Results. Nineteen tumor lesions in 10 patients were selected for this study. Eighteen lesions were lobulated and one was oval in shape. Most cases were located under the deep fascia, including seven cases that had a nodular lump adjacent to the deep fascia and one case that had broken lesion through the deep fascia. On CT, the adult fibrosarcomas mostly showed iso-attenuated soft tissue masses (n=6. On MRI, all the cases (n=9 displayed low signal on T1-weighted imaging (T1WI and heterogeneous low and high intensity signals on T2-weighted imaging (T2WI, with band-like areas of low signal on both T1WI and T2WI. On contrast-enhanced MRI images, three cases showed heterogeneous peripheral enhancement and one case demonstrated a spoke-wheel-like enhancement. Eight cases showed muscle edema signals in the peritumoral muscle and one case involved adjacent bone. Conclusion. CT and MR imaging have respective advantages in diagnosing adult fibrosarcoma. Combined application of CT and MR is recommended for patients with suspected adult fibrosarcoma.

Implications of CT noise and artifacts for quantitative 99mTc SPECT/CT imaging

International Nuclear Information System (INIS)

Hulme, K. W.; Kappadath, S. C.

2014-01-01

Purpose: This paper evaluates the effects of computed tomography (CT) image noise and artifacts on quantitative single-photon emission computed-tomography (SPECT) imaging, with the aim of establishing an appropriate range of CT acquisition parameters for low-dose protocols with respect to accurate SPECT attenuation correction (AC). Methods: SPECT images of two geometric and one anthropomorphic phantom were reconstructed iteratively using CT scans acquired at a range of dose levels (CTDI vol = 0.4 to 46 mGy). Resultant SPECT image quality was evaluated by comparing mean signal, background noise, and artifacts to SPECT images reconstructed using the highest dose CT for AC. Noise injection was performed on linear-attenuation (μ) maps to determine the CT noise threshold for accurate AC. Results: High levels of CT noise (σ ∼ 200–400 HU) resulted in low μ-maps noise (σ ∼ 1%–3%). Noise levels greater than ∼10% in 140 keV μ-maps were required to produce visibly perceptible increases of ∼15% in 99m Tc SPECT images. These noise levels would be achieved at low CT dose levels (CTDI vol = 4 μGy) that are over 2 orders of magnitude lower than the minimum dose for diagnostic CT scanners. CT noise could also lower (bias) the expected μ values. The relative error in reconstructed SPECT signal trended linearly with the relative shift in μ. SPECT signal was, on average, underestimated in regions corresponding with beam-hardening artifacts in CT images. Any process that has the potential to change the CT number of a region by ∼100 HU (e.g., misregistration between CT images and SPECT images due to motion, the presence of contrast in CT images) could introduce errors in μ 140 keV on the order of 10%, that in turn, could introduce errors on the order of ∼10% into the reconstructed 99m Tc SPECT image. Conclusions: The impact of CT noise on SPECT noise was demonstrated to be negligible for clinically achievable CT parameters. Because CT dose levels that affect

Abdominal aspergillosis: CT findings

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Yeom, Suk Keu, E-mail: pagoda20@hanmail.net [Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, 388-1, Poongnap2-dong, Songpa-gu, Seoul, 138-736 (Korea, Republic of); Kim, Hye Jin, E-mail: kimhyejin@amc.seoul.kr [Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, 388-1, Poongnap2-dong, Songpa-gu, Seoul, 138-736 (Korea, Republic of); Byun, Jae Ho, E-mail: jhbyun@amc.seoul.kr [Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, 388-1, Poongnap2-dong, Songpa-gu, Seoul, 138-736 (Korea, Republic of); Kim, Ah Young, E-mail: aykim@amc.seoul.kr [Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, 388-1, Poongnap2-dong, Songpa-gu, Seoul, 138-736 (Korea, Republic of); Lee, Moon-Gyu, E-mail: mglee@amc.seoul.kr [Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, 388-1, Poongnap2-dong, Songpa-gu, Seoul, 138-736 (Korea, Republic of); Ha, Hyun Kwon, E-mail: hkha@amc.seoul.kr [Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, 388-1, Poongnap2-dong, Songpa-gu, Seoul, 138-736 (Korea, Republic of)

2011-03-15

Objective: In order to retrospectively evaluate the CT findings of abdominal aspergillosis in immunocompromised patients. Materials and methods: CT scans were reviewed with regard to the sites, number, morphologic appearance, attenuation, and the contrast enhancement patterns of the lesions in six patients (5 women, 1 man; mean age, 43.4 years; range, 23-59 years) with pathologically proved abdominal aspergillosis by two gastrointestinal radiologists in consensus. Medical records were also reviewed to determine each patient's clinical status and outcome. Results: All patients were immunocompromised state: 4 patients received immunosuppressive therapy for solid organ transplantation and 2 patients received chemotherapy for acute myeloid leukemia. Aspergillosis involved blood vessels (n = 3), liver (n = 2), spleen (n = 2), gastrointestinal tract (n = 2), native kidney (n = 1), transplanted kidney (n = 1), peritoneum (n = 1), and retroperitoneum (n = 1). CT demonstrated solid organ or bowel infarction or perforation secondary to vascular thrombosis or pseudoaneurysm, multiple low-attenuating lesions of solid organs presenting as abscesses, concentric bowel wall thickening mimicking typhlitis, or diffuse or nodular infiltration of the peritoneum and retroperitoneum. Conclusion: Familiarity with findings commonly presenting as angioinvasive features or abscesses on CT, may facilitate the diagnosis of rare and fatal abdominal aspergillosis.

Refinements to calandria tube - liquid injection nozzle (CT-LIN) contact assessments

International Nuclear Information System (INIS)

Sedran, P.J.

2012-01-01

In recent years, the issue of CT-LIN contact, which first gained attention in 1989, has been addressed through CT-LIN gap measurements, followed by analytical predictions of time-to-contact. CT-LIN time-to-contact predictions have been preformed independently by CPUS Limited for Point Lepreau and Gentilly-2 and by AECL Sheridan Park (now Candu Energy Inc.) for Bruce Power and Gentilly-2. Both companies used the CDEPTH code in combination with CT-LIN gap measurements. Subsequent to the assessments for Point Lepreau and Gentilly-2, a recommended approach for future assessments was presented at the 2008 CANDU maintenance conference. Since that time, a number of refinements to the overall strategy for predicting CT-LIN time-to-contact have been developed and are outlined in this paper. The refinements include: 1. The use of ultrasonic LIN elevation measurements to confirm LIN creep sag behaviour 2. The development of a non-linear empirical CT Creep Sag Model 3. The development of a rationale for discrepancies observed in repeated optical CT-LIN gap measurements and a discussion of alternative CT-LIN gap measurements With these refinements, more accurate CT-LIN time-to-contact predictions can be obtained. For stations that plan to refurbish by 210,000 EFPH, the improvement in time-to-contact predictions resulting from the fore mentioned refinements will not be of any real benefit.. However, for stations that are planning life extensions in order to operate beyond 210,000 EFPH, CT-LIN contact will be an issue. For these stations, improvements in CT-LIN contact time predictions would be beneficial. This paper presents a summary of the proposed refinements and demonstrates how they would impact CT-LIN time-to-contact predictions. (author)

Current Roles and Future Applications of Cardiac CT: Risk Stratification of Coronary Artery Disease

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Yoon, Yeonyee Elizabeth [Department of Cardiology, Cardiovascular Center, Seoul National University Bundang Hospital, Seongnam 463-707 (Korea, Republic of); Lim, Tae-Hwan [Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736 (Korea, Republic of)

2014-07-01

Cardiac computed tomography (CT) has emerged as a noninvasive modality for the assessment of coronary artery disease (CAD), and has been rapidly integrated into clinical cares. CT has changed the traditional risk stratification based on clinical risk to image-based identification of patient risk. Cardiac CT, including coronary artery calcium score and coronary CT angiography, can provide prognostic information and is expected to improve risk stratification of CAD. Currently used conventional cardiac CT, provides accurate anatomic information but not functional significance of CAD, and it may not be sufficient to guide treatments such as revascularization. Recently, myocardial CT perfusion imaging, intracoronary luminal attenuation gradient, and CT-derived computed fractional flow reserve were developed to combine anatomical and functional data. Although at present, the diagnostic and prognostic value of these novel technologies needs to be evaluated further, it is expected that all-in-one cardiac CT can guide treatment and improve patient outcomes in the near future.

Characterization of Hepatocellular Carcinomas with Triphasic CT and Correlation with Histopathologic Findings

International Nuclear Information System (INIS)

Karahan, O.I.; Yikilmaz, A.; Isin, S.; Orhan, S.

2003-01-01

Purpose: To determine the utility of triphasic CT in the characterization of hepatocellular carcinomas (HCCs) and correlations with histopathologic findings. Material and Methods: Thirty patients with hepatocellular carcinomas were included in the study and triphasic CT examinations were performed. The CT protocol included hepatic arterial, portal venous and late phases. A histopathologic examination was carried out in all but 3 patients, and the diagnosis and degrees of differentiation were determined. Results: Hepatocellular carcinomas were hyper attenuated in 17 (57%) and hypo attenuated in 13 (43%) of the 30 patients in arterial phase images. The lesions were hypo attenuated in 26 (87%) and hyper attenuated in 4 (13%) patients in portal venous phase images. These hyper attenuated tumors were well-differentiated in the histopathologic examinations (P ≤ 0.05). Portal vein invasion was seen in 50% of the patients and this relationship was significant in patients whose lesions was greater than 10 cm (P < 0.05). Capsule formation, abnormal internal vessels and necrosis were detected in 57%, 53% and 40% of the patients, respectively. Conclusion: Triphasic CT can aid in the histopathologic differentiation of HCCs, in addition to their characterization. Hyper attenuation in PVP images was found to be associated with well-differentiated HCCs and portal vein invasion was more frequent in tumors larger than 10 cm

Selecting optimal monochromatic level with spectral CT imaging for improving imaging quality in hepatic venography

International Nuclear Information System (INIS)

Sun Jun; Luo Xianfu; Wang Shou'an; Wang Jun; Sun Jiquan; Wang Zhijun; Wu Jingtao

2013-01-01

Objective: To investigate the effect of spectral CT monochromatic images for improving imaging quality in hepatic venography. Methods: Thirty patients underwent spectral CT examination on a GE Discovery CT 750 HD scanner. During portal phase, 1.25 mm slice thickness polychromatic images and optimal monochromatic images were obtained, and volume rendering and maximum intensity projection were created to show the hepatic veins respectively. The overall imaging quality was evaluated on a five-point scale by two radiologists. Inter-observer agreement in subjective image quality grading was assessed by Kappa statistics. Paired-sample t test were used to compare hepatic vein attenuation, hepatic parenchyma attenuation, CT value difference between the hepatic vein and the liver parenchyma, image noise, vein-to-liver contrast-to-noise ratio (CNR), the image quality score of hepatic venography between the two image data sets. Results: The monochromatic images at 50 keV were found to demonstrate the best CNR for hepatic vein.The hepatic vein attenuation [(329 ± 47) HU], hepatic parenchyma attenuation [(178 ± 33) HU], CT value difference between the hepatic vein and the liver parenchyma [(151 ± 33) HU], image noise (17.33 ± 4.18), CNR (9.13 ± 2.65), the image quality score (4.2 ± 0.6) of optimal monochromatic images were significantly higher than those of polychromatic images [(149 ± 18) HU], [(107 ± 14) HU], [(43 ±11) HU], 12.55 ± 3.02, 3.53 ± 1.03, 3.1 ± 0.8 (t values were 24.79, 13.95, 18.85, 9.07, 13.25 and 12.04, respectively, P < 0.01). In the comparison of image quality, Kappa value was 0.81 with optimal monochromatic images and 0.69 with polychromatic images. Conclusion: Monochromatic images of spectral CT could improve CNR for displaying hepatic vein and improve the image quality compared to the conventional polychromatic images. (authors)

The influence of body mass index and gender on coronary arterial attenuation with fixed iodine load per body weight at dual-source CT coronary angiography

International Nuclear Information System (INIS)

Zhu, Xiaomei; Zhu, Yinsu; Xu, Hai; Tang, Lijun; Xu, Yi

2012-01-01

Background. Most of current coronary CT angiography protocols are not adapted to body weight (BW) or cardiac output and no literature about influence of gender on coronary attenuation are reported with administration of a fixed iodine load per BW. Purpose. To determine the influence of body mass index (BMI) and gender on coronary arterial attenuation if contrast material dose is linearly adjusted to a patient's BW at dual-source CT coronary angiography (DSCT-CA). Material and Methods. A total of 207 consecutive patients (mean age 60.6 years) undergoing DSCT-CA were included. Contrast material (370 mg I/mL) dose calculation was randomly categorized into two groups (Group1: 1.10 mL/kg for men and women; Group 2: men 1.10 mL/kg, women 0.99 mL/kg) and flow rate was calculated as dose was divided by scan time plus 8 s. Mean arterial attenuations between men and women were compared with respect to attenuations of ascending aorta (AA) above coronary ostia, left main coronary artery (LM), proximal segments of right coronary artery (RCA), left anterior descending (LAD), and left circumflex artery (LCX) in two groups, respectively. Attenuations of coronary arteries were correlated with BW and BMI with simple linear regression. Results. The mean attenuations of AA, LM, RCA, LAD, and LCX were 407.8 ± 53.6 HU, 412.6 ± 55.4 HU, 411.4 ± 64.3 HU, 399.1 ± 56.7 HU, and 399.1 ± 60.2 HU, respectively, and there were no significant differences between men and women in group 1 (AA, P = 0.571; LM, P = 0.670; RCA, P = 0.737; LAD, P = 0.439, and LCX, P = 0.888). In group 2, the mean attenuations of AA, LM, RCA, LAD, and LCX in men were significantly higher than those in women (AA, P = 0.008; LM, P = 0.025; RCA, P = 0.017; LAD, P = 0.015, and LCX, P = 0.002). Positive linear regression between BW and attenuations of AA (R 2 = 0.047, P = 0.02), LM (R 2 = 0.036, P = 0.04), RCA (R 2 = 0.080, P 2 = 0.078, P 2 = 0.033, P = 0.05) was found in group 1, suggesting that attenuations of coronary

Assessment of endothelial function and myocardial flow reserve using 15O-water PET without attenuation correction

International Nuclear Information System (INIS)

Tuffier, Stephane; Joubert, Michael; Bailliez, Alban; Legallois, Damien; Belin, Annette; Redonnet, Michel; Agostini, Denis; Manrique, Alain

2016-01-01

Myocardial blood flow (MBF) measurement using positron emission tomography (PET) from the washout rate of 15 O-water is theoretically independent of tissue attenuation. The aim of this study was to evaluate the impact of not using attenuation correction in the assessment of coronary endothelial function and myocardial flow reserve (MFR) using 15 O-water PET. We retrospectively processed 70 consecutive 15 O-water PET examinations obtained at rest and during cold pressor testing (CPT) in patients with dilated cardiomyopathy (n = 58), or at rest and during adenosine infusion in heart transplant recipients (n = 12). Data were reconstructed with attenuation correction (AC) and without attenuation correction (NAC) using filtered backprojection, and MBF was quantified using a single compartmental model. The agreement between AC and NAC data was assessed using Lin's concordance correlation coefficient followed by Bland-Altman plot analysis. Regarding endothelial function, NAC PET showed poor reproducibility and poor agreement with AC PET data. Conversely, NAC PET demonstrated high reproducibility and a strong agreement with AC PET for the assessment of MFR. Non-attenuation-corrected 15 O-water PET provided an accurate measurement of MFR compared to attenuation-corrected PET. However, non-attenuation-corrected PET data were less effective for the assessment of endothelial function using CPT in this population. (orig.)

Attenuation maps for SPECT determined using cone beam transmission computed tomography

International Nuclear Information System (INIS)

Manglos, S.H.; Bassano, D.A.; Duxbury, C.E.; Capone, R.B.

1990-01-01

This paper presents a new method for measuring non-uniform attenuation maps, using a cone beam geometry CT scan acquired on a standard rotating gamma camera normally used for SPECT imaging. The resulting map is intended for use in non-uniform attenuation compensation of SPECT images. The method was implemented using a light-weight point source holder attached to the camera. A cone beam collimator may be used on the gamma camera, but the cone beam CT scans may also be acquired without collimator. In either implementation, the advantages include very high efficiency and resolution limited not by the collimator but by the intrinsic camera resolution (about 4 mm). Several phantoms tested the spatial uniformity, noise, linearity as a function of attenuation coefficient, and spatial resolution. Good quality attenuation maps were obtained, at least for the central slices where no truncation was present

Metal artifact reduction software used with abdominopelvic dual-energy CT of patients with metal hip prostheses: assessment of image quality and clinical feasibility.

Science.gov (United States)

Han, Seung Chol; Chung, Yong Eun; Lee, Young Han; Park, Kwan Kyu; Kim, Myeong Jin; Kim, Ki Whang

2014-10-01

The objective of our study was to determine the feasibility of using Metal Artifact Reduction (MAR) software for abdominopelvic dual-energy CT in patients with metal hip prostheses. This retrospective study included 33 patients (male-female ratio, 19:14; mean age, 63.7 years) who received total hip replacements and 20 patients who did not have metal prostheses as the control group. All of the patients underwent dual-energy CT. The quality of the images reconstructed using the MAR algorithm and of those reconstructed using the standard reconstruction was evaluated in terms of the visibility of the bladder wall, pelvic sidewall, rectal shelf, and bone-prosthesis interface and the overall diagnostic image quality with a 4-point scale. The mean and SD attenuation values in Hounsfield units were measured in the bladder, pelvic sidewall, and rectal shelf. For validation of the MAR interpolation algorithm, pelvis phantoms with small bladder "lesions" and metal hip prostheses were made, and images of the phantoms both with and without MAR reconstruction were evaluated. Image quality was significantly better with MAR reconstruction than without at all sites except the rectal shelf, where the image quality either had not changed or had worsened after MAR reconstruction. The mean attenuation value was changed after MAR reconstruction to its original expected value at the pelvic sidewall (p software with dual-energy CT decreases metal artifacts and increases diagnostic confidence in the assessment of the pelvic cavity but also introduces new artifacts that can obscure pelvic structures.

Dual energy cardiac CT.

Science.gov (United States)

Carrascosa, Patricia; Deviggiano, Alejandro; Rodriguez-Granillo, Gastón

2017-06-01

Conventional single energy CT suffers from technical limitations related to the polychromatic nature of X-rays. Dual energy cardiac CT (DECT) shows promise to attenuate and even overcome some of these limitations, and might broaden the scope of patients eligible for cardiac CT towards the inclusion of higher risk patients. This might be achieved as a result of both safety (contrast reduction) and physiopathological (myocardial perfusion and characterization) issues. In this article, we will review the main clinical cardiac applications of DECT, that can be summarized in two core aspects: coronary artery evaluation, and myocardial evaluation.

CT and MR imaging findings of sinonasal angiomatous polyps

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Zou, Jing [Department of Radiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong (China); Man, Fengyuan [Department of Radiology, Beijing Tongren Hospital, Capital Medical University, Beijing (China); Deng, Kai [Department of Radiology, Qingdao No. 4 People' s Hospital, Qingdao, Shandong (China); Zheng, Yuanyuan [Department of Radiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong (China); Hao, Dapeng, E-mail: haodp_2009@163.com [Department of Radiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong (China); Xu, Wenjian, E-mail: cjr.xuwenjian@vip.163.com [Department of Radiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong (China)

2014-03-15

Objective: To characterize the CT and MR imaging findings of patients with sinonasal angiomatous polyps (SAPs) and evaluate their respective clinical value in the diagnosis of SAP. Methods: CT and MR imaging findings of 15 patients with pathologically proven SAP were examined. Assessed image features included location, size, margin, attenuation, and change of the bony walls of the sinonasal cavity on CT, and signal intensity and enhancement pattern on MR. Results: On CT, the SAP was mostly isoattenuated with patches of slight hyperattenuation. Most lesions caused changes in the adjacent bone, including expansile remodeling (n = 8), defect or destruction (n = 7), and hyperostosis (n = 6). All lesions examined by MR showed heterogeneous isointense signal intensity on T1-weighted images and mixed obvious hyperintense and hypointense signal intensity with linear hypointense septum internally (n = 10), and hypointense peripheral rim on T2-weighted images (n = 10). Postcontrast MR images demonstrated areas of heterogeneous and marked enhancement with an unenhanced hypointense rim and septa (n = 7). Conclusions: CT and MR imaging have respective advantages in the diagnosis of SAP. Combined application of CT and MR examinations is necessary for patients with suspected SAP.

CT and MR imaging findings of sinonasal angiomatous polyps

International Nuclear Information System (INIS)

Zou, Jing; Man, Fengyuan; Deng, Kai; Zheng, Yuanyuan; Hao, Dapeng; Xu, Wenjian

2014-01-01

Objective: To characterize the CT and MR imaging findings of patients with sinonasal angiomatous polyps (SAPs) and evaluate their respective clinical value in the diagnosis of SAP. Methods: CT and MR imaging findings of 15 patients with pathologically proven SAP were examined. Assessed image features included location, size, margin, attenuation, and change of the bony walls of the sinonasal cavity on CT, and signal intensity and enhancement pattern on MR. Results: On CT, the SAP was mostly isoattenuated with patches of slight hyperattenuation. Most lesions caused changes in the adjacent bone, including expansile remodeling (n = 8), defect or destruction (n = 7), and hyperostosis (n = 6). All lesions examined by MR showed heterogeneous isointense signal intensity on T1-weighted images and mixed obvious hyperintense and hypointense signal intensity with linear hypointense septum internally (n = 10), and hypointense peripheral rim on T2-weighted images (n = 10). Postcontrast MR images demonstrated areas of heterogeneous and marked enhancement with an unenhanced hypointense rim and septa (n = 7). Conclusions: CT and MR imaging have respective advantages in the diagnosis of SAP. Combined application of CT and MR examinations is necessary for patients with suspected SAP

Phantom studies on the artifacts of barium on 18F-FDG DHC/CT images induced by X-ray attenuation correction

International Nuclear Information System (INIS)

Wang Wei; Zhu Jiarui; Wang Xinqiang; Zhao Wenrui; Chuan Ling; Xu Genxiang; Gao Chunhua; Fang Tingzheng

2007-01-01

Objective: Attenuation correction (AC) based on X-ray transmission map may result in false positive readings or artifacts on PET images, some of them due to the internal residue of high density contrast media used in diagnostic X-ray imaging. The aim of this study was to experimentally estimate the impacts of different concentrations and volumes of barium contrast on X-CT AC (CTAC) for dual-head coincidence (DHC/CT) images. Methods: A cylindrical phantom containing 18 F solution (3.7 kBq/ml), in which plastic fingertips enclosed with different concentrations (0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 2.0, 3.0 kg/L)and volumes(0.5, 1.0, 1.5, 2.0, 2.5 ml) of BaSO 4 contrast media were inserted, was used to modulate routine 18 F-fluorodeoxyglucose (FDG) imaging study on a DHC/CT scanner (GE Discovery VH). Sequential 18 F emission and X-CT transmission acquisitions followed by data processing and reconstruction were carried out in clinical settings. For comparison, both visual and quantitative analyses were performed on CTAC and non-AC (NAC) images of the phantom. Results: In NAC images, the radioactivity distribution within the whole phantom was non-uniform with lower counts in the center; the plastic fingertips were all seen as 'cold spots' with much lower counts in the contrast region than in their surrounding areas. On the contrary, in CTAC images, the radioactivity distribution within the whole phantom was almost uniform; while most plastic fingertips with media concentration ≥0.1 kg/L and volume >0.5 ml were all depicted as 'hot spots' with higher counts than in surrounding areas. Conclusions: Barium contrast with relative high concentration or large volume can induce artifacts on CTAC DHC/CT images. In clinical setting, proper interpretation of CTAC DHC/CT images should refer to NAC DHC/CT images to exclude any artifacts related to the contrast media residues. (authors)

Evaluation of radiation dose and image quality of CT scan for whole-body pediatric PET/CT: A phantom study

Energy Technology Data Exchange (ETDEWEB)

Yang, Ching-Ching, E-mail: cyang@tccn.edu.tw [Department of Medical Imaging and Radiological Sciences, Tzu-Chi College of Technology, 970, Hualien, Taiwan (China); Liu, Shu-Hsin [Department of Nuclear Medicine, Buddhist Tzu-Chi General Hospital, 970, Hualien, Taiwan and Department of Medical Imaging and Radiological Sciences, Tzu-Chi College of Technology, 970, Hualien, Taiwan (China); Mok, Greta S. P. [Biomedical Imaging Laboratory, Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Macau (China); Wu, Tung-Hsin [Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, 112, Taipei, Taiwan (China)

2014-09-15

Purpose: This study aimed to tailor the CT imaging protocols for pediatric patients undergoing whole-body PET/CT examinations with appropriate attention to radiation exposure while maintaining adequate image quality for anatomic delineation of PET findings and attenuation correction of PET emission data. Methods: The measurements were made by using three anthropomorphic phantoms representative of 1-, 5-, and 10-year-old children with tube voltages of 80, 100, and 120 kVp, tube currents of 10, 40, 80, and 120 mA, and exposure time of 0.5 s at 1.75:1 pitch. Radiation dose estimates were derived from the dose-length product and were used to calculate risk estimates for radiation-induced cancer. The influence of image noise on image contrast and attenuation map for CT scans were evaluated based on Pearson's correlation coefficient and covariance, respectively. Multiple linear regression methods were used to investigate the effects of patient age, tube voltage, and tube current on radiation-induced cancer risk and image noise for CT scans. Results: The effective dose obtained using three anthropomorphic phantoms and 12 combinations of kVp and mA ranged from 0.09 to 4.08 mSv. Based on our results, CT scans acquired with 80 kVp/60 mA, 80 kVp/80 mA, and 100 kVp/60 mA could be performed on 1-, 5-, and 10-year-old children, respectively, to minimize cancer risk due to CT scans while maintaining the accuracy of attenuation map and CT image contrast. The effective doses of the proposed protocols for 1-, 5- and 10-year-old children were 0.65, 0.86, and 1.065 mSv, respectively. Conclusions: Low-dose pediatric CT protocols were proposed to balance the tradeoff between radiation-induced cancer risk and image quality for patients ranging in age from 1 to 10 years old undergoing whole-body PET/CT examinations.

CT characteristics of thoracoabdominal localized Castleman disease

International Nuclear Information System (INIS)

Wang Rengui; Huo Meng; Wang Dandan

2010-01-01

Objective: To assess the CT characteristics of thoracoabdominal localized Castleman disease (LCD) in 55 cases and correlate with histopathologic features. Methods: Fifty-five patients with LCD proved histopathologically in thorax (n=25) and abdomen (n=30) were collected during past 20 years. The unenhanced and contrast-enhanced CT were performed in all patients. Two radiologists reviewed CT images and the CT findings were analyzed simultaneously. Results: In 54 patients with hyaline-vascular type (n=50) and mixed type (n=4) localized CD, the lesion typically presented as solitary mass (90.7%, 49 cases), with irregular or lobular or infiltrative margin (83.3%, 45 cases), central calcification (38.9%, 21 cases), marked enhancement (100%, 54 cases), focal non-necrosis low attenuation areas (72.2%, 39 cases), lymphadenopathy (70.4%, 38 cases) and dilated feeding vessels adjacent to the mass (96.3%, 52 cases). One lesion with plasma cell type localized CD presented as a mass with irregular margin, mild enhancement and central necrosis, Four morphologic patterns were classified on CT, including solitary mass with well-circumscribed margin (n=4), irregular or lobular margin (n=30), infiltrative or halo-like margin (n=16), and multiple coalescent masses (n=5). Conclusion: CT features of thoracoabdominal localized CD are closely related to the location and pathological type. LCD with hyaline-vascular and mixed type has typical CT characteristics, while LCD with plasma cell type has no typical CT findings. (authors)

Crescentic and ring-shaped opacities. CT features in two cases of bronchiolitis obliterans organizing pneumonia (BOOP)

International Nuclear Information System (INIS)

Voloudaki, A.E.; Bouros, D.E.; Froudarakis, M.E.; Datseris, G.E.; Apostolaki, E.G.; Gourtsoyiannis, N.C.

1996-01-01

Two cases of idiopathic bronchilitis obliterans organizing pneumonia (BOOP) with unusual CT findings are presented. On CT both cases exhibited crescentic and ring-shaped opacities, surrounding areas of groundglass attenuation, and associated with a nodular pattern in one patient and airspace consolidations in the second patient. CT-pathologic correlation dislosed that the central areas of groundglass attenuation corresponded to alveolar septal inflammation, in contrast to the denser periphery where granulomatous tissue in peripheral airspaces predominated. In the broad spectrum of CT findings, BOOP can exhibit specific CT features with regard to the crescentic or ring-shaped opacities with a central groundglass attenuation area. Since these features have not been described in any other disease, they might be characteristic features for the diagnosis of BOOP. (orig.)

Diagnostic value of quantitative stenosis predictors with coronary CT angiography compared to invasive fractional flow reserve

Energy Technology Data Exchange (ETDEWEB)

Wang, Rui [Heart & Vascular Center, Medical University of South Carolina, Ashley River Tower, 25 Courtenay Drive Charleston, SC 29425-2260 (United States); Department of Radiology, Beijing Anzhen Hospital, Capital Medical University, 100029 Beijing (China); Renker, Matthias [Heart & Vascular Center, Medical University of South Carolina, Ashley River Tower, 25 Courtenay Drive Charleston, SC 29425-2260 (United States); Kerckhoff Heart and Thorax Center, Benekestrasse 2-8, 61231 Bad Nauheim (Germany); Schoepf, U. Joseph, E-mail: schoepf@musc.edu [Heart & Vascular Center, Medical University of South Carolina, Ashley River Tower, 25 Courtenay Drive Charleston, SC 29425-2260 (United States); Wichmann, Julian L. [Heart & Vascular Center, Medical University of South Carolina, Ashley River Tower, 25 Courtenay Drive Charleston, SC 29425-2260 (United States); Department of Diagnostic and Interventional Radiology, University Hospital Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt (Germany); Fuller, Stephen R.; Rier, Jeremy D.; Bayer, Richard R.; Steinberg, Daniel H. [Heart & Vascular Center, Medical University of South Carolina, Ashley River Tower, 25 Courtenay Drive Charleston, SC 29425-2260 (United States); De Cecco, Carlo N. [Heart & Vascular Center, Medical University of South Carolina, Ashley River Tower, 25 Courtenay Drive Charleston, SC 29425-2260 (United States); Departments of Radiological Sciences, Oncology, and Pathology, University of Rome “Sapienza”-Polo Pontino, Latina, Viale Regina Elena, 324-00161 Roma (Italy); Baumann, Stefan [Heart & Vascular Center, Medical University of South Carolina, Ashley River Tower, 25 Courtenay Drive Charleston, SC 29425-2260 (United States); First Department of Medicine, University Medical Centre Mannheim, University of Heidelberg, Theodor-Kutzer-Ufer 1-3, 68167 Mannheim (Germany)

2015-08-15

Highlights: • Evaluation of the diagnostic performance of CCTA predictors for coronary stenosis. • TAG was unable to detect hemodynamically significant coronary lesions. • CT-FFR, LL/MLD{sup 4} and CCO provide enhanced diagnostic performance over CCTA. • CT-FFR was the best parameter. - Abstract: Objective: To evaluate the diagnostic performance of CCTA-derived stenosis predictors including CT-FFR for the detection of ischemia-inducing stenosis compared to invasive FFR. Materials and methods: Stenosis parameters were assessed using dual-source CT (DSCT). All patients underwent both CCTA and invasive FFR within 3 months and were retrospectively analyzed. Observers visually assessed all CCTA studies and performed multiple lesion measurements. Lesion length/minimal luminal diameter{sup 4} (LL/MLD{sup 4}), transluminal attenuation gradient (TAG), corrected coronary attenuation (CCO) and CT-FFR were calculated. Results: The cohort included 32 patients (58 ± 12 years, 66%male). Among 32 coronary lesions, 8 (25%) were considered hemodynamically significant with an FFR <0.80. Compared to invasive FFR, the per-vessel sensitivity and specificity of CCTA, CT-FFR, LL/MLD{sup 4}, CCO and TAG for detecting hemodynamically significant lesions were 100% and 54%, 100% and 91%, 85% and 92%, 66% and 88%, 37% and 58%, respectively. Receiver operating characteristics analysis resulted in an area under the curve of 0.91 for CT-FFR (p = 0.0005), 0.88 for LL/MLD{sup 4} (p < 0.0001), 0.85 for CCO (p < 0.0001). TAG with an AUC of 0.67 (p = 0.152) was unable to discriminate between vessels with or without hemodynamically significant lesions. Conclusion: CT-FFR, LL/MLD{sup 4} and CCO provide enhanced diagnostic performance over CCTA analysis alone for discrimination of hemodynamically significant coronary stenosis.

Split-bolus CT-urography using dual-energy CT: Feasibility, image quality and dose reduction

Energy Technology Data Exchange (ETDEWEB)

Takeuchi, Mitsuru, E-mail: m2rbimn@gmail.com [Nagoya City University Graduate School of Medical Sciences, Department of Radiology, 1 Kawasumi Mizuho-cho, Mizuho-ku, Nagoya, 467-8601 (Japan); Kawai, Tatsuya; Ito, Masato; Ogawa, Masaki [Nagoya City University Graduate School of Medical Sciences, Department of Radiology, 1 Kawasumi Mizuho-cho, Mizuho-ku, Nagoya, 467-8601 (Japan); Ohashi, Kazuya [Nagoya City University Hospital, Department of Radiology, 1 Kawasumi Mizuho-cho, Mizuho-ku, Nagoya, 467-8601 (Japan); Hara, Masaki; Shibamoto, Yuta [Nagoya City University Graduate School of Medical Sciences, Department of Radiology, 1 Kawasumi Mizuho-cho, Mizuho-ku, Nagoya, 467-8601 (Japan)

2012-11-15

Purpose: To prospectively evaluate the feasibility of dual-energy (DE) split-bolus CT-urography (CTU) and the quality of virtual non-enhanced images (VNEI) and DE combined nephrographic-excretory phase images (CNEPI), and to estimate radiation dose reduction if true non-enhanced images (TNEI) could be omitted. Patients and methods: Between August and September 2011, 30 consecutive patients with confirmed or suspected urothelial cancer or with hematuria underwent DE CT. Single-energy TNEI and DE CNEPI were obtained. VNEI was reconstructed from CNEPI. Image quality of CNEPI and VNEI was evaluated using a 5-point scale. The attenuation of urine in the bladder on TNEI and VNEI was measured. The CT dose index volume (CTDI (vol)) of the two scans was recorded. Results: The mean image quality score of CNEPI and VNEI was 4.7 and 3.3, respectively. The mean differences in urine attenuation between VNEI and TNEI were 14 {+-} 15 [SD] and -16 {+-} 29 in the anterior and posterior parts of the bladder, respectively. The mean CTDI (vol) for TNEI and CNEPI was 11.8 and 10.9 mGy, respectively. Omission of TNEI could reduce the total radiation dose by 52%. Conclusion: DE split-bolus CTU is technically feasible and can reduce radiation exposure; however, an additional TNEI scan is necessary when the VNEI quality is poor or quantitative evaluation of urine attenuation is required.

Dependent lung opacity at thin-section CT: evaluation by spirometrically-gated CT of the influence of lung volume

International Nuclear Information System (INIS)

Lee, Ki Nam; Yoon, Seong Kuk; Sohn, Choon Hee; Choi, Pil Jo; Webb, W. Richard

2002-01-01

To evaluate the influence of lung volume on dependent lung opacity seen at thin-section CT. In thirteen healthy volunteers, thin-section CT scans were performed at three levels (upper, mid, and lower portion of the lung) and at different lung volumes (10, 30, 50, and 100% vital capacity), using spirometric gated CT. Using a three-point scale, two radiologists determined whether dependent opacity was present, and estimated its degree. Regional lung attenuation at a level 2 cm above the diaphragm was determined using semiautomatic segmentation, and the diameter of a branch of the right lower posterior basal segmental artery was measured at each different vital capacity. At all three anatomic levels, dependent opacity occurred significantly more often at lower vital capacities (10, 30%) than at 100% vital capacity (p = 0.001). Visually estimated dependent opacity was significantly related to regional lung attenuation (p < 0.0001), which in dependent areas progressively increased as vital capacity decreased (p < 0.0001). The presence of dependent opacity and regional lung attenuation of a dependent area correlated significantly with increased diameter of a segmental arterial branch (r = 0.493 and p = 0.0002; r = 0.486 and p 0.0003, respectively). Visual estimation and CT measurements of dependent opacity obtained by semiautomatic segmentation are significantly influenced by lung volume and are related to vascular diameter

Differential CT features of infectious pneumonia versus bronchioloalveolar carcinoma (BAC) mimicking pneumonia

Energy Technology Data Exchange (ETDEWEB)

Kim, Tae Hoon [Yonsei University College of Medicine, Department of Radiology, Seoul (Korea); Yongdong Severance Hospital, Department of Radiology, Seoul (Korea); Kim, Sang Jin; Ryu, Young Hoon; Chung, Soo Yoon; Seo, Jae Seung; Kim, Young Jin; Choi, Byoung Wook [Yonsei University College of Medicine, Department of Radiology, Seoul (Korea); Lee, Sun Hwa [NeoDin Medical Institute, Department of Clinical Pathology, Seoul (Korea); Cho, Sang Ho [Yonsei University College of Medicine, Department of Pathology, Seoul (Korea)

2006-08-15

The purpose of this study was to evaluate retrospectively the differential CT features of bronchioloalveolar carcinoma (BAC) mimicking pneumonia and infectious pneumonia at the lung periphery. CT images were reviewed in 47 patients with focal areas of parenchymal opacification at the lung periphery. We evaluated the presence of ground-glass attenuation, marginal conspicuity of the lesion, CT angiogram sign, air-bronchogram sign, a bubble-like low-attenuation area within the lesion, presence of pleural thickening and retraction associated with the lesion, presence of pleural effusion and extra-pleural fatty hypertrophy, presence of bronchial wall thickening proximal to the lesion, and air-trapping in the normal lung near the lesion. BAC (n=18) depicted the presence of a bubble-like low-attenuation area within the lesion, whereas infectious pneumonia (n=29) represented the pleural thickening associated with the lesion and bronchial wall thickening proximal to the lesion (P<0.05). The other CT findings showed no significant differences (P>0.05). The focal areas of the parenchymal opacification on the CT images may suggest infectious pneumonia rather than BAC when they show bronchial wall thickening proximal to the lesion and pleural thickening associated with the lesion, whereas BAC is characterized as the presence of a bubble-like low attenuation area within the tumor. (orig.)

Clinical application of CT and CT-guided percutaneous transthoracic needle biopsy in patients with indeterminate pulmonary nodules

Energy Technology Data Exchange (ETDEWEB)

Cardoso, Luciana Vargas; Souza Júnior, Arthur Soares, E-mail: fabianonatividade@terra.com.br [Rio Preto-Ultra-X Radiological Diagnosis Institute, São José do Rio Preto, SP (Brazil)

2014-07-15

Objective: To investigate the clinical application of CT and CT-guided percutaneous transthoracic needle biopsy (CT-PTNB) in patients with indeterminate pulmonary nodules (IPNs). Methods: We retrospectively studied 113 patients with PNs undergoing CT and CT-PTNB. Variables such as gender, age at diagnosis, smoking status, CT findings, and CT-PTNB techniques were analyzed. Data analysis was performed with the Student's t-test for independent samples the chi-square test, and normal approximation test for comparison of two proportions. Results: Of the 113 patients studied, 68 (60.2%) were male and 78 (69%) were smokers. The diameter of malignant lesions ranged from 2.6 cm to 10.0 cm. Most of the IPNs (85%) were located in the peripheral region. The biopsied IPNs were found to be malignant in 88 patients (77.8%) and benign in 25 (22.2%). Adenocarcinoma was the most common malignant tumor, affecting older patients. The IPN diameter was significantly greater in patients with malignant PNs than in those with benign IPNs (p < 0.001). Having regular contour correlated significantly with an IPN being benign (p = 0.022), whereas spiculated IPNs and bosselated IPNs were more often malignant (in 50.7% and 28.7%, respectively). Homogeneous attenuation and necrosis were more common in patients with malignant lesions (51.9% and 26.9%, respectively). Conclusions: In our sample, CT and CT-PTNB were useful in distinguishing between malignant and benign IPNs. Advanced age and smoking were significantly associated with malignancy. Certain CT findings related to IPNs (larger diameter, spiculated borders, homogeneous attenuation, and necrosis) were associated with malignancy. (author)

Towards quantitative PET/MRI: a review of MR-based attenuation correction techniques.

Science.gov (United States)

Hofmann, Matthias; Pichler, Bernd; Schölkopf, Bernhard; Beyer, Thomas

2009-03-01

Positron emission tomography (PET) is a fully quantitative technology for imaging metabolic pathways and dynamic processes in vivo. Attenuation correction of raw PET data is a prerequisite for quantification and is typically based on separate transmission measurements. In PET/CT attenuation correction, however, is performed routinely based on the available CT transmission data. Recently, combined PET/magnetic resonance (MR) has been proposed as a viable alternative to PET/CT. Current concepts of PET/MRI do not include CT-like transmission sources and, therefore, alternative methods of PET attenuation correction must be found. This article reviews existing approaches to MR-based attenuation correction (MR-AC). Most groups have proposed MR-AC algorithms for brain PET studies and more recently also for torso PET/MR imaging. Most MR-AC strategies require the use of complementary MR and transmission images, or morphology templates generated from transmission images. We review and discuss these algorithms and point out challenges for using MR-AC in clinical routine. MR-AC is work-in-progress with potentially promising results from a template-based approach applicable to both brain and torso imaging. While efforts are ongoing in making clinically viable MR-AC fully automatic, further studies are required to realize the potential benefits of MR-based motion compensation and partial volume correction of the PET data.

Towards quantitative PET/MRI: a review of MR-based attenuation correction techniques

International Nuclear Information System (INIS)

Hofmann, Matthias; Pichler, Bernd; Schoelkopf, Bernhard; Beyer, Thomas

2009-01-01

Positron emission tomography (PET) is a fully quantitative technology for imaging metabolic pathways and dynamic processes in vivo. Attenuation correction of raw PET data is a prerequisite for quantification and is typically based on separate transmission measurements. In PET/CT attenuation correction, however, is performed routinely based on the available CT transmission data. Recently, combined PET/magnetic resonance (MR) has been proposed as a viable alternative to PET/CT. Current concepts of PET/MRI do not include CT-like transmission sources and, therefore, alternative methods of PET attenuation correction must be found. This article reviews existing approaches to MR-based attenuation correction (MR-AC). Most groups have proposed MR-AC algorithms for brain PET studies and more recently also for torso PET/MR imaging. Most MR-AC strategies require the use of complementary MR and transmission images, or morphology templates generated from transmission images. We review and discuss these algorithms and point out challenges for using MR-AC in clinical routine. MR-AC is work-in-progress with potentially promising results from a template-based approach applicable to both brain and torso imaging. While efforts are ongoing in making clinically viable MR-AC fully automatic, further studies are required to realize the potential benefits of MR-based motion compensation and partial volume correction of the PET data. (orig.)

Towards quantitative PET/MRI: a review of MR-based attenuation correction techniques

Energy Technology Data Exchange (ETDEWEB)

Hofmann, Matthias [Max Planck Institute for Biological Cybernetics, Tuebingen (Germany); University of Tuebingen, Laboratory for Preclinical Imaging and Imaging Technology of the Werner Siemens-Foundation, Department of Radiology, Tuebingen (Germany); University of Oxford, Wolfson Medical Vision Laboratory, Department of Engineering Science, Oxford (United Kingdom); Pichler, Bernd [University of Tuebingen, Laboratory for Preclinical Imaging and Imaging Technology of the Werner Siemens-Foundation, Department of Radiology, Tuebingen (Germany); Schoelkopf, Bernhard [Max Planck Institute for Biological Cybernetics, Tuebingen (Germany); Beyer, Thomas [University Hospital Duisburg-Essen, Department of Nuclear Medicine, Essen (Germany); Cmi-Experts GmbH, Zurich (Switzerland)

2009-03-15

Positron emission tomography (PET) is a fully quantitative technology for imaging metabolic pathways and dynamic processes in vivo. Attenuation correction of raw PET data is a prerequisite for quantification and is typically based on separate transmission measurements. In PET/CT attenuation correction, however, is performed routinely based on the available CT transmission data. Recently, combined PET/magnetic resonance (MR) has been proposed as a viable alternative to PET/CT. Current concepts of PET/MRI do not include CT-like transmission sources and, therefore, alternative methods of PET attenuation correction must be found. This article reviews existing approaches to MR-based attenuation correction (MR-AC). Most groups have proposed MR-AC algorithms for brain PET studies and more recently also for torso PET/MR imaging. Most MR-AC strategies require the use of complementary MR and transmission images, or morphology templates generated from transmission images. We review and discuss these algorithms and point out challenges for using MR-AC in clinical routine. MR-AC is work-in-progress with potentially promising results from a template-based approach applicable to both brain and torso imaging. While efforts are ongoing in making clinically viable MR-AC fully automatic, further studies are required to realize the potential benefits of MR-based motion compensation and partial volume correction of the PET data. (orig.)

Spiral CT during pharmacoangiography with angiotensin II in patients with pancreatic disease. Technique and diagnostic efficacy

Energy Technology Data Exchange (ETDEWEB)

Kuroda, C.; Mihara, N.; Hosomi, N.; Inoue, E.; Fujita, M. [Osaka Medical Center for Cancer and Cardiovascular Diseases (Japan). Dept. of Diagnostic Radiology; Ohigashi, H.; Ishikawa, O. [Osaka Medical Center for Cancer and Cardiovascular Diseases (Japan). Dept. of Surgery; Nakaizumi, A. [Osaka Medical Center for Cancer and Cardiovascular Deseases (Japan). Dept. of Internal Medicine; Ishiguro, S. [Osaka Medical Center for Cancer and Cardiovascular Diseases (Japan). Dept. of Pathology

1998-03-01

Purpose: To compare the diagnostic efficacy of pancreatic pharmacoangiographic CT using angiotensin II with conventional angiographic CT. Material and Methods: Eighteen patients with space-occupying pancreatic disease were examined in this study. Pharmacoangiographic CT was performed with a 1-3-{mu}/6-ml solution of angiotensin II injected through a catheter into the celiac artery during spiral CT. Results: In 17 of the 18 (94%) patients, the area of pancreatic parenchymal enhancement was the same or larger at pharmacoangiographic CT than at conventional angiographic CT. The attenuation value of the pancreatic parenchyma was significantly increased at pharmacoangiographic CT (p=0.0010). Although the attenuation value of tumors was also increased on images obtained after the injection of angiotensin II, the tumor-to-pancreas contrast was significantly greater at pharmacoangiographic CT (p=0.0479). The mean differences in attenuation between tumor and pancreas at angiographic CT with and without angiotensin II were respectively 182 HU and 115 HU. Conclusion: Pharmacoangiographic CT with angiotensin II proved superior to conventional angiographic CT in the diagnosis of pancreatic disease. We therefore recommend it as a supplementary technique at the angiographic examination of patients with suspected pancreatic tumor. (orig.).

Automated size-specific CT dose monitoring program: Assessing variability in CT dose

Energy Technology Data Exchange (ETDEWEB)

Christianson, Olav; Li Xiang; Frush, Donald; Samei, Ehsan [Clinical Imaging Physics Group, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 and Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 (United States); Clinical Imaging Physics Group, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 (United States); Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 (United States) and Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 (United States); Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 (United States); Clinical Imaging Physics Group, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 (United States); Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 (United States); Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 (United States); Medical Physics Graduate Program, Duke University, Durham, North Carolina 27705 (United States); Department of Physics, Duke University, Durham, North Carolina 27710 (United States); and Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708 (United States)

2012-11-15

Purpose: The potential health risks associated with low levels of ionizing radiation have created a movement in the radiology community to optimize computed tomography (CT) imaging protocols to use the lowest radiation dose possible without compromising the diagnostic usefulness of the images. Despite efforts to use appropriate and consistent radiation doses, studies suggest that a great deal of variability in radiation dose exists both within and between institutions for CT imaging. In this context, the authors have developed an automated size-specific radiation dose monitoring program for CT and used this program to assess variability in size-adjusted effective dose from CT imaging. Methods: The authors radiation dose monitoring program operates on an independent health insurance portability and accountability act compliant dosimetry server. Digital imaging and communication in medicine routing software is used to isolate dose report screen captures and scout images for all incoming CT studies. Effective dose conversion factors (k-factors) are determined based on the protocol and optical character recognition is used to extract the CT dose index and dose-length product. The patient's thickness is obtained by applying an adaptive thresholding algorithm to the scout images and is used to calculate the size-adjusted effective dose (ED{sub adj}). The radiation dose monitoring program was used to collect data on 6351 CT studies from three scanner models (GE Lightspeed Pro 16, GE Lightspeed VCT, and GE Definition CT750 HD) and two institutions over a one-month period and to analyze the variability in ED{sub adj} between scanner models and across institutions. Results: No significant difference was found between computer measurements of patient thickness and observer measurements (p= 0.17), and the average difference between the two methods was less than 4%. Applying the size correction resulted in ED{sub adj} that differed by up to 44% from effective dose

Presengical CT assessment of cholesteatomaclronic otitis media: review of 116 cases

International Nuclear Information System (INIS)

Lazaro, A.; Navarro, M.; Beams, B.; Fernandez, F.; Mas, F.; Domenech, A.; Moreno, A.; Bordon, F.

1995-01-01

We assess the utility of CT in the diagnosis of the sped of and complications associated with cholesteatomas of middle ear. We review retrospectively the CT studies of 116 patients who underwent surgical treatment after a preoperative diagnosis of cholesteatoma between 1988 and 1992. We compare the findings at CT and surgery, taking into account the site, extension, complications and noteworthly surgical aspects. In our study, CT disclosed the presence of a mass within the tympanic cavity in all cases (100%). Among the entire study population, there were 103 cases of cholesteatoma and 13 of chronic otitis media (COM). CT revealed signs compatible with cholesteatoma in 99 cases, 3 of which were classified as COM and 14 in which it was impossible to distinguish between COM and cholesteatoma. CT discolsed a high correlation coefficient for the detection of erosion of the ossicular chain (sensitivity, 94.4%; specificity, 63.6%) and a moderate coefficient for fistula in lateral semicircular canal (75.0% and 97.0%), rupture of the tegmen tympani (76.9% and 96.1%) and dehiscence of the osseous portion of the facial nerve canal (66.6% and 95.6%). In our experience, wich coincides with reports in the literature, we conclude that CT is currebtly an excellent imaging method for the presurgical assessment of cholesteatoma. Additional explorations are usually unneccessary. 12 refs

Measurement error in CT assessment of appendix diameter

Energy Technology Data Exchange (ETDEWEB)

Trout, Andrew T.; Towbin, Alexander J. [Cincinnati Children' s Hospital Medical Center, Department of Radiology, MLC 5031, Cincinnati, OH (United States); Zhang, Bin [Cincinnati Children' s Hospital Medical Center, Department of Biostatistics and Epidemiology, Cincinnati, OH (United States)

2016-12-15

Appendiceal diameter continues to be cited as an important criterion for diagnosis of appendicitis by computed tomography (CT). To assess sources of error and variability in appendiceal diameter measurements by CT. In this institutional review board-approved review of imaging and medical records, we reviewed CTs performed in children <18 years of age between Jan. 1 and Dec. 31, 2010. Appendiceal diameter was measured in the axial and coronal planes by two reviewers (R1, R2). One year later, 10% of cases were remeasured. For patients who had multiple CTs, serial measurements were made to assess within patient variability. Measurement differences between planes, within and between reviewers, within patients and between CT and pathological measurements were assessed using correlation coefficients and paired t-tests. Six hundred thirty-one CTs performed in 519 patients (mean age: 10.9 ± 4.9 years, 50.8% female) were reviewed. Axial and coronal measurements were strongly correlated (r = 0.92-0.94, P < 0.0001) with coronal plane measurements significantly larger (P < 0.0001). Measurements were strongly correlated between reviewers (r = 0.89-0.9, P < 0.0001) but differed significantly in both planes (axial: +0.2 mm, P=0.003; coronal: +0.1 mm, P=0.007). Repeat measurements were significantly different for one reviewer only in the axial plane (0.3 mm difference, P<0.05). Within patients imaged multiple times, measured appendix diameters differed significantly in the axial plane for both reviewers (R1: 0.5 mm, P = 0.031; R2: 0.7 mm, P = 0.022). Multiple potential sources of measurement error raise concern about the use of rigid diameter cutoffs for the diagnosis of acute appendicitis by CT. (orig.)

CT findings of pulmonary mucosa-associated lymphoid tissue lymphoma

International Nuclear Information System (INIS)

Zhang Weidong; Guan Yubao; Li Chuanxing; Wu Peihong

2010-01-01

Objective: To study the CT findings of pulmonary mucosa-associated lymphoid tissue (MALT) lymphoma. Methods: The CT examinations of 12 patients with pathologically proven pulmonary MALT lymphoma were reviewed retrospectively. Evaluated imaging findings included number, distribution, shape, attenuation and other associated findings of each lesion were evaluated. Results: Thirty-two pulmonary lesions, including consolidations, masses, nodules and lesions with ground glass attenuation, were identified in 12 patients. Multiple lesions were founded in 10 of 12 patients and solitary lesion in 2 patients. Multiple lesions found in one lung in 2 patients, and multiple lesions found in both lungs in 8 patients. Ten cases demonstrated 21 consolidation lesions with air bronchogram, and one of the ten cases demonstrated two lesions with airway dilatation. Three cases demonstrated 5 masses or nodular lesions, 3 of these 5 lesions showed air bronchogram. Two cases demonstrated 6 ground glass attenuation lesions. One case showed mediastinal and hilar lymphadenopathy. Conclusion: Pulmonary MALT lymphoma usually appears as multiple bilateral consolidations, masses, nodules with air bronchogram or lesions with ground- glass attenuation at CT imaging. The imaging findings described above and with an indolent clinical course may suggest the diagnosis of pulmonary MALT lymphoma. (authors)

Assessment of trunk muscle density using CT and its association with degenerative disc and facet joint disease of the lumbar spine.

Science.gov (United States)

Sebro, Ronnie; O'Brien, Liam; Torriani, Martin; Bredella, Miriam A

2016-09-01

The purpose of this study was (1) to evaluate the association of trunk muscle density assessed by computed tomography (CT) with age, gender, and BMI and (2) to evaluate the association between trunk muscle CT density and degenerative disc and facet joint disease of the lumbar spine. The study was IRB approved and HIPAA compliant. The study group comprised 100 subjects (mean age 44.4 ± 22.2 years, 51 % male) who underwent CT of the abdomen and pelvis without intravenous contrast. Exclusion criteria included prior abdominal or spine surgery, active malignancy and scoliosis. CTs were reviewed and the attenuation of the rectus abdominis, transverse abdominis, internal and external obliques, psoas, multifidus, longissimus and gluteus maximus were measured bilaterally at consistent levels. Degenerative disc and bilateral facet joint disease were scored using established methods. Univariate analyses were performed using linear regression. Multivariate linear regression was performed to adjust for age, gender and BMI. CT density of each trunk muscle correlated inversely with age (p degenerative disc and facet joint disease in the univariate analyses (p degenerative disc and facet joint disease respectively in the multivariate analysis. Fatty infiltration of trunk musculature increases with age and BMI. Fatty infiltration of the gluteus maximus and transverse abdominis are associated with degenerative disc and facet joint disease, independent of age, gender and BMI.

Pulmonary disease in cystic fibrosis: assessment with chest CT at chest radiography dose levels.

Science.gov (United States)

Ernst, Caroline W; Basten, Ines A; Ilsen, Bart; Buls, Nico; Van Gompel, Gert; De Wachter, Elke; Nieboer, Koenraad H; Verhelle, Filip; Malfroot, Anne; Coomans, Danny; De Maeseneer, Michel; de Mey, Johan

2014-11-01

To investigate a computed tomographic (CT) protocol with iterative reconstruction at conventional radiography dose levels for the assessment of structural lung abnormalities in patients with cystic fibrosis ( CF cystic fibrosis ). In this institutional review board-approved study, 38 patients with CF cystic fibrosis (age range, 6-58 years; 21 patients 18 years) underwent investigative CT (at minimal exposure settings combined with iterative reconstruction) as a replacement of yearly follow-up posteroanterior chest radiography. Verbal informed consent was obtained from all patients or their parents. CT images were randomized and rated independently by two radiologists with use of the Bhalla scoring system. In addition, mosaic perfusion was evaluated. As reference, the previous available conventional chest CT scan was used. Differences in Bhalla scores were assessed with the χ(2) test and intraclass correlation coefficients ( ICC intraclass correlation coefficient s). Radiation doses for CT and radiography were assessed for adults (>18 years) and children (chest CT protocol can replace the two yearly follow-up chest radiographic examinations without major dose penalty and with similar diagnostic quality compared with conventional CT.

Determination of the attenuation map in emission tomography

CERN Document Server

Zaidi, H

2002-01-01

Reliable attenuation correction methods for quantitative emission computed tomography (ECT) require accurate delineation of the body contour and often necessitate knowledge of internal anatomical structure. Two broad classes of methods have been used to calculate the attenuation map referred to as "transmissionless" and transmission-based attenuation correction techniques. While calculated attenuation correction belonging to the first class of methods is appropriate for brain studies, more adequate methods must be performed in clinical applications where the attenuation coefficient distribution is not known a priori, and for areas of inhomogeneous attenuation such as the chest. Measured attenuation correction overcomes this problem and utilizes different approaches to determine this map including transmission scanning, segmented magnetic resonance images or appropriately scaled X-ray CT scans acquired either independently on separate or simultaneously on multimodality imaging systems. Combination of data acqu...

Quantitative assessment for pneumoconiosis severity diagnosis using 3D CT images

Science.gov (United States)

Hino, Koki; Matsuhiro, Mikio; Suzuki, Hidenobu; Kawata, Yoshiki; Niki, Noboru; Kato, Katsuya; Kishimoto, Takumi; Ashizawa, Kazuto

2018-02-01

Pneumoconiosis is an occupational respiratory illness that occur by inhaling dust to the lungs. 240,000 participants are screened for diagnosis of pneumoconiosis every year in Japan. Radiograph is used for staging of severity rate in pneumoconiosis worldwide. CT imaging is useful for the differentiation of requirements for industrial accident approval because it can detect small lesions in comparison with radiograph. In this paper, we extracted lung nodules from 3D pneumoconiosis CT images by two manual processes and automatic process, and created a database of pneumoconiosis CT images. We used the database to analyze, compare, and evaluate visual diagnostic results of radiographs and quantitative assessment (number, size and volume) of lung nodules. This method was applied to twenty pneumoconiosis patients. Initial results showed that the proposed method can assess severity rate in pneumoconiosis quantitatively. This study demonstrates effectiveness on diagnosis and prognosis of pneumoconiosis in CT screening.

CT perfusion imaging in response assessment of pulmonary metastases undergoing stereotactic ablative radiotherapy

International Nuclear Information System (INIS)

Sawyer, Brooke; Pun, Emma; Tay, Huilee; Kron, Tomas; Bressel, Mathias; Ball, David; Siva, Shankar; Samuel, Michael

2015-01-01

Stereotactic ablative body radiotherapy (SABR) is an emerging treatment technique for pulmonary metastases in which conventional Response Evaluation Criteria in Solid Tumours (RECIST) may be inadequate. This study aims to assess the utility of CT perfusion imaging in response assessment of pulmonary metastases after SABR. In this ethics board-approved prospective study, 11 patients underwent a 26-Gy single fraction of SABR to pulmonary metastases. CT perfusion imaging occurred prior to and at 14 and 70 days post-SABR. Blood flow (mL/100 mL/min), blood volume (mL/100 mL), time to peak (seconds) and surface permeability (mL/100 mL/min), perfusion parameters of pulmonary metastases undergoing SABR, were independently assessed by two radiologists. Inter-observer variability was analysed. CT perfusion results were analysed for early response assessment comparing day 14 with baseline scans and for late response by comparing day 70 with baseline scans. The largest diameter of the pulmonary metastases undergoing SABR was recorded. Ten patients completed all three scans and one patient had baseline and early response assessment CT perfusion scans only. There was strong level of inter-observer agreement of CT perfusion interpretation with a median intraclass coefficient of 0.87 (range 0.20–0.98). Changes in all four perfusion parameters and tumour sizes were not statistically significant. CT perfusion imaging of pulmonary metastases is a highly reproducible imaging technique that may provide additional response assessment information above that of conventional RECIST, and it warrants further study in a larger cohort of patients undergoing SABR.

A prospective trial comparing FDG-PET/CT and CT to assess tumor response to cetuximab in patients with incurable squamous cell carcinoma of the head and neck

International Nuclear Information System (INIS)

Adkins, Douglas; Ley, Jessica; Dehdashti, Farrokh; Siegel, Marilyn J; Wildes, Tanya M; Michel, Loren; Trinkaus, Kathryn; Siegel, Barry A

2014-01-01

Computed tomography (CT), the standard method to assess tumor response to cetuximab in incurable squamous cell carcinoma of the head and neck (SCCHN), performs poorly as judged by the disparity between high disease control rate (46%) and short time to progression (TTP) (70 days). F-18 fluorodeoxyglucose positron emission tomography (FDG-PET)/CT is an alternative method to assess tumor response. The primary objective of this prospective trial was to evaluate the metabolic response of target lesions, assessed as the change in maximum standardized uptake value (SUV max ) on FDG-PET/CT before and after 8 weeks (cycle 1) of cetuximab. Secondary objectives were to compare tumor response by CT (RECIST 1.0) and FDG-PET/CT (EORTC criteria) following cycle 1, and determine TTP with continued cetuximab administration in patients with disease control by CT after cycle 1 but stratified for disease control or progression by FDG-PET/CT. Among 27 patients, the mean percent change of SUV max of target lesions after cycle 1 was −21% (range: +72% to −81%); by FDG-PET/CT, partial response (PR)/stable disease (SD) occurred in 15 patients (56%) and progression in 12 (44%), whereas by CT, PR/SD occurred in 20 (74%) and progression in 7 (26%). FDG-PET/CT and CT assessments were discordant in 14 patients (P = 0.0029) and had low agreement (κ = 0.30; 95% confidence interval [CI]: 0.12, 0.48). With disease control by CT after cycle 1, median TTP was 166 days (CI: 86, 217) if the FDG-PET/CT showed disease control and 105 days (CI: 66, 159) if the FDG-PET/CT showed progression (P < 0.0001). Median TTP of the seven patients whose post cycle 1 CT showed progression compared to the 12 whose FDG-PET/CT showed progression were similar (53 [CI: 49, 56] vs. 61 [CI: 50, 105] days, respectively). FDG-PET/CT may be better than CT in assessing benefit of cetuximab in incurable SCCHN

Predicting factors for conversion from fluoroscopy guided Percutaneous transthoracic needle biopsy to cone-beam CT guided Percutaneous transthoracic needle biopsy

International Nuclear Information System (INIS)

Lee, Kang Ji; Han, Young Min; Jin, Gong Yong; Song, Ji Soo

2015-01-01

To evaluate the predicting factors for conversion from fluoroscopy guided percutaneous transthoracic needle biopsy (PTNB) to cone-beam CT guided PTNB. From January 2011 to December 2012, we retrospectively identified 38 patients who underwent cone-beam CT guided PTNB with solid pulmonary lesions, and 76 patients who underwent fluoroscopy guided PTNB were matched to the patients who underwent cone-beam CT guided PTNB for age, sex, and lesion location. We evaluated predicting factors such as, long-axis diameter, short-axis diameter, anterior-posterior diameter, and CT attenuation value of the solid pulmonary lesion affecting conversion from fluoroscopy guided PTNB to cone-beam CT guided PTNB. Pearson χ 2 test, Fisher exact test, and independent t test were used in statistical analyses; in addition, we also used receiver operating characteristics curve to find the proper cut-off values affecting the conversion to cone-beam CT guided PTNB. Short-axis, long-axis, anterior-posterior diameter and CT attenuation value of the solid pulmonary lesion in patients who underwent fluoroscopy guided PTNB were 2.70 ± 1.57 cm, 3.40 ± 1.92 cm, 3.06 ± 1.81 cm, and 35.67 ± 15.70 Hounsfield unit (HU), respectively. Short-axis, long-axis, anterior-posterior diameter and CT attenuation value of the solid pulmonary lesion in patients who underwent cone-beam CT guided PTNB were 1.60 ± 1.30 cm, 2.20 ± 1.45 cm, 1.91 ± 1.99 cm, and 18.32 ± 23.11 HU, respectively. Short-axis, long-axis, anterior-posterior diameter, and CT attenuation value showed a significantly different mean value between the 2 groups (p = 0.001, p < 0.001, p = 0.003, p < 0.001, respectively). Odd ratios of CT attenuation value and short-axis diameter of the solid pulmonary lesion were 0.952 and 0.618, respectively. Proper cut-off values affecting the conversion to cone-beam CT guided PTNB were 1.65 cm (sensitivity 68.4%, specificity 71.1%) in short-axis diameter and 29.50 HU (sensitivity 65.8%, specificity 65.8%) in

Direct assessment of lung function in COPD using CT densitometric measures

International Nuclear Information System (INIS)

Gu, Suicheng; Leader, Joseph; Gur, David; Pu, Jiantao; Zheng, Bin; Chen, Qihang; Sciurba, Frank; Kminski, Naftali

2014-01-01

To investigate whether lung function in patients with chronic obstructive pulmonary disease (COPD) can be directly predicted using CT densitometric measures and assess the underlying prediction errors as compared with the traditional spirometry-based measures. A total of 600 CT examinations were collected from a COPD study. In addition to the entire lung volume, the extent of emphysema depicted in each CT examination was quantified using density mask analysis (densitometry). The partial least square regression was used for constructing the prediction model, where a repeated random split-sample validation was employed. For each split, we randomly selected 400 CT exams for training (regression) purpose and the remaining 200 exams for assessing performance in prediction of lung function (e.g., FEV1 and FEV1/FVC) and disease severity. The absolute and percentage errors as well as their standard deviations were computed. The averaged percentage errors in prediction of FEV1, FEV1/FVC%, TLC, RV/TLC% and DLco% predicted were 33%, 17%, 9%, 18% and 23%, respectively. When classifying the exams in terms of disease severity grades using the CT measures, 37% of the subjects were correctly classified with no error and 83% of the exams were either correctly classified or classified into immediate neighboring categories. The linear weighted kappa and quadratic weighted kappa were 0.54 (moderate agreement) and 0.72 (substantial agreement), respectively. Despite the existence of certain prediction errors in quantitative assessment of lung function, the CT densitometric measures could be used to relatively reliably classify disease severity grade of COPD patients in terms of GOLD. (paper)

Role of CT in hybrid imaging. Point of view of the medical physicist

International Nuclear Information System (INIS)

Gardin, I.; Hapdey, S.

2010-01-01

The recent introduction of hybrid systems SPECT/CT and PET/CT in nuclear medicine, greatly improved the diagnostic accuracy for particular clinical indications, due to the possible attenuation correction of functional images and the availability of helpful anatomic information. The introduction of CT in the nuclear diagnostic process results in a significant increase of the patient dose. This increase should be justified and optimized considering both the clinical question and the CT settings available on these systems. The choice of CT settings directly affects the effective dose. It varies basically as the square of the tube voltage, linearly with the length of the scan and the product of the current by the rotation time of the tube. It is also inversely proportional to the pitch. For attenuation correction, the literature shows that it is possible to use a low CT tube current without significant effect on tumor FDG uptake or lesion size. Conversely low CT voltage must be used with caution, depending on the algorithm implemented in the CT hybrid device to transform CT Hounsfield units to the attenuation map at the appropriate energy. The radiation dose for anatomic correlation can be substantially lower than for diagnostic-quality CT. It is possible to reduce the patient's radiation dose by a factor of 2 or 3 by acquiring a low-dose PET/CT scan for anatomic correlation of adequate image quality if compared with diagnostic 18 FDG PET/CT. Using specific CT settings, the effective dose can range 7.3-11.3 mSv depending on the patient weight and age. (authors)

Evaluation of Dixon Sequence on Hybrid PET/MR Compared with Contrast-Enhanced PET/CT for PET-Positive Lesions

International Nuclear Information System (INIS)

Jeong, Ju Hye; Cho, Ihn Ho; Kong, Eun Jung; Chun, Kyung Ah

2014-01-01

Hybrid positron emission tomography and magnetic resonance (PET/MR) imaging performs a two-point Dixon MR sequence for attenuation correction. However, MR data in hybrid PET/MR should provide anatomic and morphologic information as well as an attenuation map. We evaluated the Dixon sequence of hybrid PET/MR for anatomic correlation of PET-positive lesions compared with contrast-enhanced PET/computed tomography (CT) in patients with oncologic diseases. Twelve patients underwent a single injection, dual imaging protocol. PET/CT was performed with an intravenous contrast agent (85±13 min after 18 F-FDG injection of 403± 45 MBq) and then (125±19 min after injection) PET/MR was performed. Attenuation correction and anatomic allocation of PET were performed using contrast-enhanced CT for PET/CT and Dixon MR sequence for hybrid PET/MR. The Dixon MR sequence and contrast-enhanced CT were compared for anatomic correlation of PET-positive lesions (scoring scale ranging from 0 to 3 for visual ratings). Additionally, standardized uptake values (SUVs) for the detected lesions were assessed for quantitative comparison. Both hybrid PET/MR and contrast-enhanced PET/CT identified 55 lesions with increased FDG uptake in ten patients. In total, 28 lymph nodes, 11 bone lesions, 3 dermal nodules, 3 pleural thickening lesions, 2 thyroid nodules, 1 pancreas, 1 liver, 1 ovary, 1 uterus, 1 breast, 1 soft tissue and 2 lung lesions were present. The best performance was observed for anatomic correlation of PET findings by the contrast-enhanced CT scans (contrast-enhanced CT, 2.64± 0.70; in-phase, 1.29±1.01; opposed-phase, 1.29±1.15; water-weighted, 1.71±1.07; fat weighted, 0.56±1.03). A significant difference was observed between the scores obtained from the contrast-enhanced CT and all four coregistered Dixon MR images. Quantitative evaluation revealed a high correlation between the SUVs measured with hybrid PET/MR (SUVmean, 2.63±1.62; SUVmax, 4.30±2.88) and contrast-enhanced PET/CT

Evaluation of Dixon Sequence on Hybrid PET/MR Compared with Contrast-Enhanced PET/CT for PET-Positive Lesions

Energy Technology Data Exchange (ETDEWEB)

Jeong, Ju Hye; Cho, Ihn Ho; Kong, Eun Jung; Chun, Kyung Ah [Yeungnam Univ. Hospital, Daegu (Korea, Republic of)

2014-03-15

Hybrid positron emission tomography and magnetic resonance (PET/MR) imaging performs a two-point Dixon MR sequence for attenuation correction. However, MR data in hybrid PET/MR should provide anatomic and morphologic information as well as an attenuation map. We evaluated the Dixon sequence of hybrid PET/MR for anatomic correlation of PET-positive lesions compared with contrast-enhanced PET/computed tomography (CT) in patients with oncologic diseases. Twelve patients underwent a single injection, dual imaging protocol. PET/CT was performed with an intravenous contrast agent (85±13 min after {sup 18}F-FDG injection of 403± 45 MBq) and then (125±19 min after injection) PET/MR was performed. Attenuation correction and anatomic allocation of PET were performed using contrast-enhanced CT for PET/CT and Dixon MR sequence for hybrid PET/MR. The Dixon MR sequence and contrast-enhanced CT were compared for anatomic correlation of PET-positive lesions (scoring scale ranging from 0 to 3 for visual ratings). Additionally, standardized uptake values (SUVs) for the detected lesions were assessed for quantitative comparison. Both hybrid PET/MR and contrast-enhanced PET/CT identified 55 lesions with increased FDG uptake in ten patients. In total, 28 lymph nodes, 11 bone lesions, 3 dermal nodules, 3 pleural thickening lesions, 2 thyroid nodules, 1 pancreas, 1 liver, 1 ovary, 1 uterus, 1 breast, 1 soft tissue and 2 lung lesions were present. The best performance was observed for anatomic correlation of PET findings by the contrast-enhanced CT scans (contrast-enhanced CT, 2.64± 0.70; in-phase, 1.29±1.01; opposed-phase, 1.29±1.15; water-weighted, 1.71±1.07; fat weighted, 0.56±1.03). A significant difference was observed between the scores obtained from the contrast-enhanced CT and all four coregistered Dixon MR images. Quantitative evaluation revealed a high correlation between the SUVs measured with hybrid PET/MR (SUVmean, 2.63±1.62; SUVmax, 4.30±2.88) and contrast

Clinical and pulmonary thin-section CT findings in acute Klebsiella Pneumoniae pneumonia

International Nuclear Information System (INIS)

Okada, Fumito; Ando, Yumiko; Honda, Koichi; Nakayama, Tomoko; Kiyonaga, Maki; Ono, Asami; Tanoue, Shuichi; Maeda, Toru; Mori, Hiromu

2009-01-01

The aim of this study was to assess the clinical and pulmonary thin-section CT findings in patients with acute Klebsiella pneumoniae pneumonia. We retrospectively evaluated thin-section CT examinations performed between January 1991 and December 2007 from 962 patients with acute Klebsiella pneumoniae pneumonia. Seven hundred and sixty-four cases with concurrent infectious diseases were excluded. Thus, our study group comprised 198 patients (118 male, 80 female; age range 18-97 years, mean age 61.5). Underlying diseases and clinical findings were assessed. Parenchymal abnormalities were evaluated along with the presence of enlarged lymph nodes and pleural effusion. CT findings in patients with acute Klebsiella pneumoniae pneumonia consisted mainly of ground-glass attenuation (100%), consolidation (91.4%), and intralobular reticular opacity (85.9%), which were found in the periphery (96%) of both sides of the lungs (72.2%) and were often associated with pleural effusion (53%). The underlying conditions in patients with Klebsiella pneumoniae pneumonia were alcoholism or smoking habit. (orig.)

Clinical and pulmonary thin-section CT findings in acute Klebsiella Pneumoniae pneumonia

Energy Technology Data Exchange (ETDEWEB)

Okada, Fumito [Oita University Faculty of Medicine, Department of Diagnostic and Interventional Radiology, Oita (Japan); Oita University Faculty of Medicine, Department of Radiology, Oita (Japan); Ando, Yumiko; Honda, Koichi; Nakayama, Tomoko; Kiyonaga, Maki; Ono, Asami; Tanoue, Shuichi; Maeda, Toru; Mori, Hiromu [Oita University Faculty of Medicine, Department of Diagnostic and Interventional Radiology, Oita (Japan)

2009-04-15

The aim of this study was to assess the clinical and pulmonary thin-section CT findings in patients with acute Klebsiella pneumoniae pneumonia. We retrospectively evaluated thin-section CT examinations performed between January 1991 and December 2007 from 962 patients with acute Klebsiella pneumoniae pneumonia. Seven hundred and sixty-four cases with concurrent infectious diseases were excluded. Thus, our study group comprised 198 patients (118 male, 80 female; age range 18-97 years, mean age 61.5). Underlying diseases and clinical findings were assessed. Parenchymal abnormalities were evaluated along with the presence of enlarged lymph nodes and pleural effusion. CT findings in patients with acute Klebsiella pneumoniae pneumonia consisted mainly of ground-glass attenuation (100%), consolidation (91.4%), and intralobular reticular opacity (85.9%), which were found in the periphery (96%) of both sides of the lungs (72.2%) and were often associated with pleural effusion (53%). The underlying conditions in patients with Klebsiella pneumoniae pneumonia were alcoholism or smoking habit. (orig.)

Emergencies in the retroperitoneum: assessment of spread of disease by helical CT

Energy Technology Data Exchange (ETDEWEB)

Scialpi, M. E-mail: michelescialpi@libero.it; Scaglione, M.; Angelelli, G.; Lupattelli, L.; Resta, M.C.; Resta, M.; Rotondo, A

2004-04-01

Acute pancreatitis, leaking abdominal aortic aneurysm, and renal trauma frequently occur in the setting of patients with abdominal nontraumatic and traumatic injury; it represents the most urgent conditions that may determine the presence of fluid collections or haematoma in the retroperitoneum. Single spiral CT and multidetector-row CT (MDCT) play an important role in diagnosis of retroperitoneal emergencies, providing useful informations on the type, site, extent and management of the fluid collections. An accurate CT assessment requires the awareness of the existence of dissectable retroperitoneal fascial planes. Fluid collections or haematoma tends to escape the retroperitoneal site of origin into planes extend from the diaphragm to the pelvic floor. We assess the multicompartimental anatomy of the retroperitoneum and the pathway of spread of the most frequent retroperitoneal fluid collections or haematoma by helical CT.

CT during selective arteriography: anatomical assessment of unruptured intracranial aneurysms before endovascular treatment

International Nuclear Information System (INIS)

Nomura, M.; Kida, S.; Uchiyama, N.; Yamashima, T.; Yamashita, J.; Sanada, J.; Yoshikawa, J.; Matsui, O.

2001-01-01

Our aim was to investigate the usefulness of helical CT during selective angiography (CT arteriography) in pretreatment assessment of unruptured intracranial aneurysms. We studied 47 unruptured aneurysms in 34 prospectively recruited patients for whom endovascular embolisation was initially considered. As pretreatment assessment, we performed rotational digital subtraction angiography (DSA) followed by CT arteriography. The findings on axial source images (axial images) and reconstructed three-dimensional CT angiography (3D-CTA) of CT arteriography were compared to those of rotational DSA, with particular attention to the neck of the aneurysm and arterial branches adjacent to it. Information provided by CT arteriography was more useful than that of rotational DSA as regards the neck in 25 (53 %) of 47 cases and as regards branches in 18 (49 %) of 37 aneurysms. On axial images, small arteries such as the anterior choroidal artery were seen in some cases. CT arteriography can provide valuable additional information about unruptured aneurysms, which cannot be obtained by rotational DSA alone. This technique is useful for obtaining anatomical information about aneurysm anatomy and for deciding the therapeutic strategy. (orig.)

Iterative model reconstruction: Improved image quality of low-tube-voltage prospective ECG-gated coronary CT angiography images at 256-slice CT

Energy Technology Data Exchange (ETDEWEB)

Oda, Seitaro, E-mail: seisei0430@nifty.com [Department of Cardiology, MedStar Washington Hospital Center, 110 Irving Street, NW, Washington, DC 20010 (United States); Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto, 860-8556 (Japan); Weissman, Gaby, E-mail: Gaby.Weissman@medstar.net [Department of Cardiology, MedStar Washington Hospital Center, 110 Irving Street, NW, Washington, DC 20010 (United States); Vembar, Mani, E-mail: mani.vembar@philips.com [CT Clinical Science, Philips Healthcare, c595 Miner Road, Cleveland, OH 44143 (United States); Weigold, Wm. Guy, E-mail: Guy.Weigold@MedStar.net [Department of Cardiology, MedStar Washington Hospital Center, 110 Irving Street, NW, Washington, DC 20010 (United States)

2014-08-15

Objectives: To investigate the effects of a new model-based type of iterative reconstruction (M-IR) technique, the iterative model reconstruction, on image quality of prospectively gated coronary CT angiography (CTA) acquired at low-tube-voltage. Methods: Thirty patients (16 men, 14 women; mean age 52.2 ± 13.2 years) underwent coronary CTA at 100-kVp on a 256-slice CT. Paired image sets were created using 3 types of reconstruction, i.e. filtered back projection (FBP), a hybrid type of iterative reconstruction (H-IR), and M-IR. Quantitative parameters including CT-attenuation, image noise, and contrast-to-noise ratio (CNR) were measured. The visual image quality, i.e. graininess, beam-hardening, vessel sharpness, and overall image quality, was scored on a 5-point scale. Lastly, coronary artery segments were evaluated using a 4-point scale to investigate the assessability of each segment. Results: There was no significant difference in coronary arterial CT attenuation among the 3 reconstruction methods. The mean image noise of FBP, H-IR, and M-IR images was 29.3 ± 9.6, 19.3 ± 6.9, and 12.9 ± 3.3 HU, respectively, there were significant differences for all comparison combinations among the 3 methods (p < 0.01). The CNR of M-IR was significantly better than of FBP and H-IR images (13.5 ± 5.0 [FBP], 20.9 ± 8.9 [H-IR] and 39.3 ± 13.9 [M-IR]; p < 0.01). The visual scores were significantly higher for M-IR than the other images (p < 0.01), and 95.3% of the coronary segments imaged with M-IR were of assessable quality compared with 76.7% of FBP- and 86.9% of H-IR images. Conclusions: M-IR can provide significantly improved qualitative and quantitative image quality in prospectively gated coronary CTA using a low-tube-voltage.

CT and MRI findings of cyclosporine-related encephalopathy and hypertensive encephalopathy

International Nuclear Information System (INIS)

Yamamoto, Akira; Hayakawa, Katsumi; Houjyou, Makoto

2002-01-01

We present the MRI and CT findings of one child with cyclosporine-related encephalopathy, and one child with hypertensive encephalopathy following cyclosporine-related encephalopathy. The imaging findings were shown well on T2-weighted and fluid-attenuated inversion recovery (FLAIR) MR images. Cyclosporine-related encephalopathy was distributed predominantly in the posterior white matter. Hypertensive encephalopathy showed similar changes of CT attenuation, but with wider distribution. These two disorders seem to have the same pathogenesis. (orig.)

Respiratory management of CT-transmission for accuracy fusion in PET/CT. A comparison between normal expiration and free breathing in 600 experiences

International Nuclear Information System (INIS)

Osawa, Atsushi; Takiguchi, Tomohiro; Tamura, Shintaro; Ohashi, Takashi; Miwa, Kenta; Akimoto, Kenta; Wagatsuma, Kei

2010-01-01

Image misregistration can occur in fusion positron emission tomography (PET)/CT, because of motion artifacts caused by the management of respiration. The standard imaging protocol of the CT component of PET/CT is normal expiration (NormExp) or free breathing (FB). The objective of this study was to compare NormExp and FB for the optimal breathing protocol for PET/CT scans. A total of 600 consecutive patients were examined using lutetium oxyorthosilicate (LSO)-based PET/CT. CT was acquired during NormExp (id est (i.e.), the level reached when the patient exhaled without forcing expiration and then held the breath) in 300 patients and during FB in 300 patients. The profile of liver measured along body axis was assessed. The distance of profile centers between the PET image and the CT image was measured. The misalignment between profile centers (PET) and profile centers (CT) was compared between NormExp and FB using the histogram of patients. An F test was used to test if the variances of two misalignments are equal. Next, the relationship between misalignment and age was evaluated in two managements of respiration. There was no significant difference between NormExp and FB in the histogram. However, significant misalignments (>10 cm) were found with NormExp. Patient age may have influenced the mismatch. FB is recommended for geriatric patients during acquisition of attenuation correction CT data sets. (author)

Intraoperative CT in the assessment of posterior wall acetabular fracture stability.

Science.gov (United States)

Cunningham, Brian; Jackson, Kelly; Ortega, Gil

2014-04-01

Posterior wall acetabular fractures that involve 10% to 40% of the posterior wall may or may not require an open reduction and internal fixation. Dynamic stress examination of the acetabular fracture under fluoroscopy has been used as an intraoperative method to assess joint stability. The aim of this study was to demonstrate the value of intraoperative ISO computed tomography (CT) examination using the Siemens ISO-C imaging system (Siemens Corp, Malvern, Pennsylvania) in the assessment of posterior wall acetabular fracture stability during stress examination under anesthesia. In 5 posterior wall acetabular fractures, standard fluoroscopic images (including anteroposterior pelvis and Judet radiographs) with dynamic stress examinations were compared with the ISO-C CT imaging system to assess posterior wall fracture stability during stress examination. After review of standard intraoperative fluoroscopic images under dynamic stress examination, all 5 cases appeared to demonstrate posterior wall stability; however, when the intraoperative images from the ISO-C CT imaging system demonstrated that 1 case showed fracture instability of the posterior wall segment during stress examination, open reduction and internal fixation was performed. The use of intraoperative ISO CT imaging has shown an initial improvement in the surgeon's ability to assess the intraoperative stability of posterior wall acetabular fractures during stress examination when compared with standard fluoroscopic images. Copyright 2014, SLACK Incorporated.

Evaluation of a direct motion estimation/correction method in respiratory-gated PET/MRI with motion-adjusted attenuation.

Science.gov (United States)

Bousse, Alexandre; Manber, Richard; Holman, Beverley F; Atkinson, David; Arridge, Simon; Ourselin, Sébastien; Hutton, Brian F; Thielemans, Kris

2017-06-01

Respiratory motion compensation in PET/CT and PET/MRI is essential as motion is a source of image degradation (motion blur, attenuation artifacts). In previous work, we developed a direct method for joint image reconstruction/motion estimation (JRM) for attenuation-corrected (AC) respiratory-gated PET, which uses a single attenuation-map (μ-map). This approach was successfully implemented for respiratory-gated PET/CT, but since it relied on an accurate μ-map for motion estimation, the question of its applicability in PET/MRI is open. The purpose of this work is to investigate the feasibility of JRM in PET/MRI and to assess the robustness of the motion estimation when a degraded μ-map is used. We performed a series of JRM reconstructions from simulated PET data using a range of simulated Dixon MRI sequence derived μ-maps with wrong attenuation values in the lungs, from -100% (no attenuation) to +100% (double attenuation), as well as truncated arms. We compared the estimated motions with the one obtained from JRM in ideal conditions (no noise, true μ-map as an input). We also applied JRM on 4 patient datasets of the chest, 3 of them containing hot lesions. Patient list-mode data were gated using a principal component analysis method. We compared SUV max values of the JRM reconstructed activity images and non motion-corrected images. We also assessed the estimated motion fields by comparing the deformed JRM-reconstructed activity with individually non-AC reconstructed gates. Experiments on simulated data showed that JRM-motion estimation is robust to μ-map degradation in the sense that it produces motion fields similar to the ones obtained when using the true μ-map, regardless of the attenuation errors in the lungs (PET/MRI clinical datasets. It provides a potential alternative to existing methods where the motion fields are pre-estimated from separate MRI measurements. © 2017 University College London (UCL). Medical Physics published by Wiley Periodicals, Inc

ASSESSING AEROBIC NATURAL ATTENUATION OF TRICHLOROETHENE AT FOUR DOE SITES

International Nuclear Information System (INIS)

Koelsch, Michael C.; Starr, Robert C.; Sorenson, Kent S. Jr.

2005-01-01

A 3-year Department of Energy Environmental Science Management Program (EMSP) project is currently investigating natural attenuation of trichloroethane (TCE) in aerobic groundwater. This presentation summarizes the results of a screening process to identify TCE plumes at DOE facilities that are suitable for assessing the rate of TCE cometabolism under aerobic conditions. In order to estimate aerobic degradation rates, plumes had to meet the following criteria: TCE must be present in aerobic groundwater, a conservative co-contaminant must be present and have approximately the same source as TCE, and the groundwater velocity must be known. A total of 127 TCE plumes were considered across 24 DOE sites. The four sites retained for the assessment were: (1) Brookhaven National Laboratory, OU III; (2) Paducah Gaseous Diffusion Plant, Northwest Plume; (3) Rocky Flats Environmental Technology Site, Industrialized Area--Southwest Plume and 903 Pad South Plume; and (4) Savannah River Site, A/M Area Plume. For each of these sites, a co-contaminant derived from the same source area as TCE was used as a nonbiodegrading tracer. The tracer determined the extent to which concentration decreases in the plume can be accounted for solely by abiotic processes such as dispersion and dilution. Any concentration decreases not accounted for by these processes must be explained by some other natural attenuation mechanism. Thus, ''half-lives'' presented herein are in addition to attenuation that occurs due to hydrologic mechanisms. This ''tracer-corrected method'' has previously been used at the DOE's Idaho National Engineering and Environmental Laboratory in conjunction with other techniques to document the occurrence of intrinsic aerobic cometabolism. Application of this method to other DOE sites is the first step to determining whether this might be a significant natural attenuation mechanism on a broader scale. Application of the tracer-corrected method to data from the Brookhaven

How to distinguish between bleeding and coagulated extradural hematomas on the plain CT scanning

International Nuclear Information System (INIS)

Petersen, O.F.; Espersen, J.O.

1984-01-01

Four types of extradural hematoma could be separated at examination of the plain CT scan in 54 extradural hematomas. Two major groups appear: the still bleeding hematoma showing either generally low attenuation values of ''holes'', and a coagulated homogenous type with generally high attenuation values. The attenuation values of the bleeding-liquid part of hematoma - were correlated to hemoglobin concentration in blood, to which clots were not related. Seven extradural hematomas grew and coagulated on repeated preoperative CT scans. In two cases intravenous contrast was given to the bleeding type of hematoma, and the contrast media appeared in ''holes'', but not in areas of high attenuation value. It is easy to distinguish between the different types of hematoma on the plain CT scan, and the separation by eye between the still bleeding and the coagulated extradural hematoma seems reliable. (orig.)

Cardiac causes of pulmonary arterial hypertension: assessment with multidetector CT

Energy Technology Data Exchange (ETDEWEB)

Hoey, Edward T.D.; Gopalan, Deepa; Agrawal, S.K.B. [Papworth Hospital, Cambridge (United Kingdom); Screaton, Nicholas J. [Papworth Hospital, Cambridge (United Kingdom); Papworth Hospital NHS Trust, Diagnostic Centre, Department of Radiology, Papworth Everard, Cambridgeshire (United Kingdom)

2009-11-15

The causes of pulmonary arterial hypertension (PAH) are diverse and include multiple congenital and acquired cardiac diseases as well as diseases primarily affecting the pulmonary vasculature, lung, pleura and chest wall. The traditional role of CT in evaluating PAH includes assessment of pulmonary vasculature and lung parenchyma with limited assessment of the heart. Advances in multidetector CT technology with improved spatial and temporal resolution now permit accurate delineation of cardiac morphology. CT pulmonary angiography (CTPA) is widely utilised in the workup of patients with suspected pulmonary vascular disease and can identify both pulmonary and cardiac causes. As the initial presentation for CTPA is often precipitated by nonspecific, unexplained symptoms and therefore undertaken by a general radiologist, it is important that a systematic approach to the interpretation of these studies, including cardiac evaluation, is routinely adopted. This paper reviews the CT evaluation in pulmonary hypertension with a particular focus on the cardiac causes, their subclassification into congenital systemic to pulmonary shunts and secondary to left heart disease, and their imaging features. It emphasises the use of a systematic approach to interpretation of CTPA examinations both in patients with known PAH and those with previously unsuspected disease. (orig.)

Cardiac causes of pulmonary arterial hypertension: assessment with multidetector CT

International Nuclear Information System (INIS)

Hoey, Edward T.D.; Gopalan, Deepa; Agrawal, S.K.B.; Screaton, Nicholas J.

2009-01-01

The causes of pulmonary arterial hypertension (PAH) are diverse and include multiple congenital and acquired cardiac diseases as well as diseases primarily affecting the pulmonary vasculature, lung, pleura and chest wall. The traditional role of CT in evaluating PAH includes assessment of pulmonary vasculature and lung parenchyma with limited assessment of the heart. Advances in multidetector CT technology with improved spatial and temporal resolution now permit accurate delineation of cardiac morphology. CT pulmonary angiography (CTPA) is widely utilised in the workup of patients with suspected pulmonary vascular disease and can identify both pulmonary and cardiac causes. As the initial presentation for CTPA is often precipitated by nonspecific, unexplained symptoms and therefore undertaken by a general radiologist, it is important that a systematic approach to the interpretation of these studies, including cardiac evaluation, is routinely adopted. This paper reviews the CT evaluation in pulmonary hypertension with a particular focus on the cardiac causes, their subclassification into congenital systemic to pulmonary shunts and secondary to left heart disease, and their imaging features. It emphasises the use of a systematic approach to interpretation of CTPA examinations both in patients with known PAH and those with previously unsuspected disease. (orig.)

Assessment of trunk muscle density using CT and its association with degenerative disc and facet joint disease of the lumbar spine

International Nuclear Information System (INIS)

Sebro, Ronnie; O'Brien, Liam; Torriani, Martin; Bredella, Miriam A.

2016-01-01

The purpose of this study was (1) to evaluate the association of trunk muscle density assessed by computed tomography (CT) with age, gender, and BMI and (2) to evaluate the association between trunk muscle CT density and degenerative disc and facet joint disease of the lumbar spine. The study was IRB approved and HIPAA compliant. The study group comprised 100 subjects (mean age 44.4 ± 22.2 years, 51 % male) who underwent CT of the abdomen and pelvis without intravenous contrast. Exclusion criteria included prior abdominal or spine surgery, active malignancy and scoliosis. CTs were reviewed and the attenuation of the rectus abdominis, transverse abdominis, internal and external obliques, psoas, multifidus, longissimus and gluteus maximus were measured bilaterally at consistent levels. Degenerative disc and bilateral facet joint disease were scored using established methods. Univariate analyses were performed using linear regression. Multivariate linear regression was performed to adjust for age, gender and BMI. CT density of each trunk muscle correlated inversely with age (p < 0.001) and BMI (p < 0.001). CT density of each trunk muscle correlated inversely with degenerative disc and facet joint disease in the univariate analyses (p < 0.001); however, only the gluteus maximus and the transverse abdominis remained significant predictors of degenerative disc and facet joint disease respectively in the multivariate analysis. Fatty infiltration of trunk musculature increases with age and BMI. Fatty infiltration of the gluteus maximus and transverse abdominis are associated with degenerative disc and facet joint disease, independent of age, gender and BMI. (orig.)

Lesion detection performance: comparative analysis of low-dose CT data of the chest on two hybrid imaging systems.

Science.gov (United States)

Jessop, Maryam; Thompson, John D; Coward, Joanne; Sanderud, Audun; Jorge, José; de Groot, Martijn; Lança, Luís; Hogg, Peter

2015-03-01

Incidental findings on low-dose CT images obtained during hybrid imaging are an increasing phenomenon as CT technology advances. Understanding the diagnostic value of incidental findings along with the technical limitations is important when reporting image results and recommending follow-up, which may result in an additional radiation dose from further diagnostic imaging and an increase in patient anxiety. This study assessed lesions incidentally detected on CT images acquired for attenuation correction on two SPECT/CT systems. An anthropomorphic chest phantom containing simulated lesions of varying size and density was imaged on an Infinia Hawkeye 4 and a Symbia T6 using the low-dose CT settings applied for attenuation correction acquisitions in myocardial perfusion imaging. Twenty-two interpreters assessed 46 images from each SPECT/CT system (15 normal images and 31 abnormal images; 41 lesions). Data were evaluated using a jackknife alternative free-response receiver-operating-characteristic analysis (JAFROC). JAFROC analysis showed a significant difference (P detection, with the figures of merit being 0.599 (95% confidence interval, 0.568, 0.631) and 0.810 (95% confidence interval, 0.781, 0.839) for the Infinia Hawkeye 4 and Symbia T6, respectively. Lesion detection on the Infinia Hawkeye 4 was generally limited to larger, higher-density lesions. The Symbia T6 allowed improved detection rates for midsized lesions and some lower-density lesions. However, interpreters struggled to detect small (5 mm) lesions on both image sets, irrespective of density. Lesion detection is more reliable on low-dose CT images from the Symbia T6 than from the Infinia Hawkeye 4. This phantom-based study gives an indication of potential lesion detection in the clinical context as shown by two commonly used SPECT/CT systems, which may assist the clinician in determining whether further diagnostic imaging is justified. © 2015 by the Society of Nuclear Medicine and Molecular Imaging

Clinical analysis of CT features in 200 neonates with hypoxic-ischemic encephalopathy (HIE)

International Nuclear Information System (INIS)

Zhang Fan

2003-01-01

Objective: To analyze the CT features of HIE in neonates. Methods: CT scanning was performed in 200 neonates with HIE. Results: The CT features in 200 HIE were hypo-attenuated substantia alba, accompanied with intra-cranial hemorrhage, widened cavity of septum pellucidum and cerebral infarction. In total 200 cases, mild HIE was found in 118 cases, moderate HIE was revealed in 67 cases and severe condition was observed in 15 cases. Intra-cranial hemorrhage was noted in 87 cases. Conclusion: The cerebral injury should be diagnosed by the findings of hypo-attenuated substantia alba and intracranial hemorrhage on CT scan, combined with clinical histories and manifestations of intro-uterine neonate asphyxia

[F-18]2-fluoro-2-deoxyglucose (FDG) positron emission tomography after limb salvage surgery: post-surgical appearance, attenuation correction and local complications

Energy Technology Data Exchange (ETDEWEB)

Gelfand, Michael J.; Sharp, Susan E. [Cincinnati Children' s Hospital Medical Center, Department of Radiology, Nuclear Medicine Division, Cincinnati, OH (United States)

2015-08-15

Metal endoprostheses and internal fixation devices cause significant artifacts on CT after limb salvage surgery; positron emission tomography (PET) images should be evaluated for artifacts. (1) To describe [F-18]2-fluoro-2-deoxyglucose (FDG) PET uptake patterns after limb salvage surgery. (2) To determine whether metal endoprostheses and fixation hardware cause significant artifacts on CT attenuation-corrected PET that interfere with diagnostic use of PET/CT after limb salvage surgery. We reviewed 92 studies from 18 patients ages 5-21 years. Diagnoses were osteogenic sarcoma in 14, Ewing sarcoma in 3, and malignant peripheral nerve sheath tumor originating in bone in 1. Nine patients had distal femur/knee endoprostheses, five had lower-extremity bone allografts secured by large metal plates and four had upper-extremity limb salvage procedures. Maximum standardized uptake value was calculated at lower-extremity soft-tissue-endoprosthesis interfaces. In 15 patients with PET/CT imaging, the first PET/CT scan after limb salvage surgery was reviewed for metal artifacts on CT images and for artifacts at locations on PET corresponding to the CT metal artifacts. Increased FDG uptake was consistently present at soft-tissue interfaces with endoprostheses, allografts and internal fixation devices, with little or no FDG uptake at cemented endoprosthesis-bone interfaces. Maximum standardized uptake value at margins of femur/knee endoprostheses ranged from 1.4 to 5.7. In four patients with distal femur/knee endoprostheses, minimal artifact was noted on attenuation-corrected PET images, but image interpretation was not affected. In the other 11 patients who had CT attenuation correction, we detected no artifacts caused by the attenuation correction. CT attenuation correction did not cause artifacts that affected interpretation of attenuation-corrected PET images. (orig.)

[F-18]2-fluoro-2-deoxyglucose (FDG) positron emission tomography after limb salvage surgery: post-surgical appearance, attenuation correction and local complications

International Nuclear Information System (INIS)

Gelfand, Michael J.; Sharp, Susan E.

2015-01-01

Metal endoprostheses and internal fixation devices cause significant artifacts on CT after limb salvage surgery; positron emission tomography (PET) images should be evaluated for artifacts. (1) To describe [F-18]2-fluoro-2-deoxyglucose (FDG) PET uptake patterns after limb salvage surgery. (2) To determine whether metal endoprostheses and fixation hardware cause significant artifacts on CT attenuation-corrected PET that interfere with diagnostic use of PET/CT after limb salvage surgery. We reviewed 92 studies from 18 patients ages 5-21 years. Diagnoses were osteogenic sarcoma in 14, Ewing sarcoma in 3, and malignant peripheral nerve sheath tumor originating in bone in 1. Nine patients had distal femur/knee endoprostheses, five had lower-extremity bone allografts secured by large metal plates and four had upper-extremity limb salvage procedures. Maximum standardized uptake value was calculated at lower-extremity soft-tissue-endoprosthesis interfaces. In 15 patients with PET/CT imaging, the first PET/CT scan after limb salvage surgery was reviewed for metal artifacts on CT images and for artifacts at locations on PET corresponding to the CT metal artifacts. Increased FDG uptake was consistently present at soft-tissue interfaces with endoprostheses, allografts and internal fixation devices, with little or no FDG uptake at cemented endoprosthesis-bone interfaces. Maximum standardized uptake value at margins of femur/knee endoprostheses ranged from 1.4 to 5.7. In four patients with distal femur/knee endoprostheses, minimal artifact was noted on attenuation-corrected PET images, but image interpretation was not affected. In the other 11 patients who had CT attenuation correction, we detected no artifacts caused by the attenuation correction. CT attenuation correction did not cause artifacts that affected interpretation of attenuation-corrected PET images. (orig.)

Gadolinium-DTPA and gadodiamide as an alternative contrast medium for CT

International Nuclear Information System (INIS)

Engelbrecht, V.; Koch, J.A.; Rassek, M.; Moedder, U.

1996-01-01

To evaluate the effect of intravenously applied gadolinium-based contrast medium in computed tomographic (CT) studies. Serial dilutions of iohexol 300, Gd-DTPA and gadodiamide were scanned with CT in a phantom study using water filled tubes. For quantification of X-ray attenuation, the mean Hounsfield units (HU) were calculated from the CT scans. Five patients with contraindications against iodine contrast agents were examined with abdominal or thoracic CT before and after application of 0.2 mmol/kg body weight of a gadolinium-based contrast agent. In these patients attenuation values were obtained in ROI from unenhanced and enhanced CT scans. The phantom study revealed a 38,4% enhancement for Gd-DTPA and a 35.7% enhancement for gadodiamide scaled on the reference measurements with iohexol 300. Thus, 130.2 ml Gd-DTPA or 140.1 ml gadodiamide are needed to achieve the same attenuation as an i.v. injection of 50 ml iohexol 300. Consequently the corresponding dose of 1 mmol/kg body weight would exceed the manufacturer's recommended dose. In four patients with complete thoracic or abdominal CT, i.v. applied gadolinium-based contrast medium (0.2 mmol/kg) yielded no visible advantage. In these patients parenchymal enhancement did not exceed 25%. Dynamic CT of a patient with focal liver lesion revealed an arterial enhancement peak of 75%. Sufficient parenchymal enhancement in CT studies cannot be achieved with the available gadolinium-based contrast mediums. They might be helpful if only short time vascular enhancement is required. (orig.) [de

Optimizing radiation exposure for CT localizer radiographs

Energy Technology Data Exchange (ETDEWEB)

Bohrer, Evelyn; Maeder, Ulf; Fiebich, Martin [Univ. of Applied Sciences, Giessen (Germany). Inst. of Medical Physics and Radiation Protection-IMPS; Schaefer, Stefan; Krombach, Gabriele A. [Univ. Hospital Giessen (Germany). Dept. of Radiology; Noel, Peter B. [Technische Univ. Muenchen (Germany). Dept. of Diagnostic and Interventional Radiology

2017-08-01

The trend towards submillisievert CT scans leads to a higher dose fraction of localizer radiographs in CT examinations. The already existing technical capabilities make dose optimization of localizer radiographs worthwhile. Modern CT scanners apply automatic exposure control (AEC) based on attenuation data in such a localizer. Therefore not only this aspect but also the detectability of anatomical landmarks in the localizer for the desired CT scan range adjustment needs to be considered. The effective dose of a head, chest, and abdomen-pelvis localizer radiograph with standard factory settings and user-optimized settings was determined using Monte Carlo simulations. CT examinations of an anthropomorphic phantom were performed using multiple sets of acquisition parameters for the localizer radiograph and the AEC for the subsequent helical CT scan. Anatomical landmarks were defined to assess the image quality of the localizer. CTDI{sub vol} and effective mAs per slice of the helical CT scan were recorded to examine the impact of localizer settings on a helical CT scan. The dose of the localizer radiograph could be decreased by more than 90% while the image quality remained sufficient when selecting the lowest available settings (80 kVp, 20 mA, pa tube position). The tube position during localizer acquisition had a greater impact on the AEC than the reduction of tube voltage and tube current. Except for the use of a pa tube position, all changes of acquisition parameters for the localizer resulted in a decreased total radiation exposure. A dose reduction of CT localizer radiograph is necessary and possible. In the examined CT system there was no negative impact on the modulated helical CT scan when the lowest tube voltage and tube current were used for the localizer.

Assessment of endothelial function and myocardial flow reserve using {sup 15}O-water PET without attenuation correction

Energy Technology Data Exchange (ETDEWEB)

Tuffier, Stephane; Joubert, Michael; Bailliez, Alban [EA 4650, Normandie Universite, Caen (France); Legallois, Damien [EA 4650, Normandie Universite, Caen (France); Caen University Hospital, Department of Cardiology, Caen (France); Belin, Annette [Caen University Hospital, Department of Cardiac Surgery, Caen (France); Redonnet, Michel [Rouen University Hospital, Department of Cardiac Surgery, Rouen (France); Agostini, Denis [EA 4650, Normandie Universite, Caen (France); Caen University Hospital, Department of Nuclear Medicine, Caen (France); Manrique, Alain [EA 4650, Normandie Universite, Caen (France); Caen University Hospital, Department of Nuclear Medicine, Caen (France); Cyceron PET Centre, Caen (France)

2016-02-15

Myocardial blood flow (MBF) measurement using positron emission tomography (PET) from the washout rate of {sup 15}O-water is theoretically independent of tissue attenuation. The aim of this study was to evaluate the impact of not using attenuation correction in the assessment of coronary endothelial function and myocardial flow reserve (MFR) using {sup 15}O-water PET. We retrospectively processed 70 consecutive {sup 15}O-water PET examinations obtained at rest and during cold pressor testing (CPT) in patients with dilated cardiomyopathy (n = 58), or at rest and during adenosine infusion in heart transplant recipients (n = 12). Data were reconstructed with attenuation correction (AC) and without attenuation correction (NAC) using filtered backprojection, and MBF was quantified using a single compartmental model. The agreement between AC and NAC data was assessed using Lin's concordance correlation coefficient followed by Bland-Altman plot analysis. Regarding endothelial function, NAC PET showed poor reproducibility and poor agreement with AC PET data. Conversely, NAC PET demonstrated high reproducibility and a strong agreement with AC PET for the assessment of MFR. Non-attenuation-corrected {sup 15}O-water PET provided an accurate measurement of MFR compared to attenuation-corrected PET. However, non-attenuation-corrected PET data were less effective for the assessment of endothelial function using CPT in this population. (orig.)

Impact of low-energy CT imaging on selection of positive oral contrast media concentration.

Science.gov (United States)

Patino, Manuel; Murcia, Diana J; Iamurri, Andrea Prochowski; Kambadakone, Avinash R; Hahn, Peter F; Sahani, Dushyant V

2017-05-01

To determine to what extent low-energy CT imaging affects attenuation of gastrointestinal tract (GIT) opacified with positive oral contrast media (OCM). Second, to establish optimal OCM concentrations for low-energy diagnostic CT exams. One hundred patients (38 men and 62 women; age 62 ± 11 years; BMI 26 ± 5) with positive OCM-enhanced 120-kVp single-energy CT (SECT), and follow-up 100-kVp acquisitions (group A; n = 50), or 40-70-keV reconstructions from rapid kV switching-single-source dual-energy CT (ssDECT) (group B; n = 50) were included. Luminal attenuation from different GIT segments was compared between exams. Standard dose of three OCM and diluted solutions (75%, 50%, and 25% concentrations) were introduced serially in a gastrointestinal phantom and scanned using SECT (120, 100, and 80 kVp) and DECT (80/140 kVp) acquisitions on a ssDECT scanner. Luminal attenuation was obtained on SECT and DECT images (40-70 keV), and compared to 120-kVp scans with standard OCM concentrations. Luminal attenuation was higher on 100-kVp (328 HU) and on 40-60-keV images (410-924 HU) in comparison to 120-kVp scans (298 HU) in groups A and B (p < 0.05). Phantom: There was an inverse correlation between luminal attenuation and X-ray energy, increasing up to 527 HU on low-kVp and 999 HU on low-keV images (p < 0.05). 25% and 50% diluted OCM solutions provided similar or higher attenuation than 120 kVp, at low kVp and keV, respectively. Low-energy CT imaging increases the attenuation of GIT opacified with positive OCM, permitting reduction of 25%-75% OCM concentration.

CT evaluation of the bile ducts in patients with fatty liver

International Nuclear Information System (INIS)

Quint, L.E.; Glazer, G.M.

1984-01-01

Computed tomographic (CT) evaluation of the bile ducts in the fatty liver can be difficult, since hepatic attenuation decreases with increased triglyceride content, and liver parenchyma may become isodense with bile. Forty-seven patients with fatty infiltration of the liver were retrospectively identified. In 7 of these patients, attenuation of liver and bile differed by less than 10 HU. In 2 patients, dilated intrahepatic ducts were invisible using CT, because bile was isodense with fatty liver parenchyma. Thus, the fatty liver presents a potential pitfall in CT evaluation of the bile ducts. For maximal accuracy scans should be obtained both before and after administration of intravenous urographic contrast material