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

International Nuclear Information System (INIS)

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

2001-01-01

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

Percutaneous CT-guided lung biopsy: sequential versus spiral scanning. A randomized prospective study

International Nuclear Information System (INIS)

Ghaye, B.; Dondelinger, R.F.; Dewe, W.

1999-01-01

The aim of this study was to evaluate in a prospective and randomized study spiral versus sequential scanning in the guidance of percutaneous lung biopsy. Fifty thoracic lesions occurring in 48 patients were biopsied by a senior and a junior operator. Six different time segments of the procedure were measured. Scanning mode versus length of procedure, pathological results, irradiation and complications were evaluated. Total duration of the procedure and of the first sampling was significantly longer with spiral CT for the senior operator (p < 0.004). No significant time difference was observed for the junior operator. Diameter of the lesion, depth of location, position of the patient and needle entry site did not influence the results. The sensitivity was 90.9, specificity 100, positive predictive value 100 and negative predictive value 60 % for spiral CT, and 94.7, 100, 100 and 85.7 % for sequential CT, respectively. Eleven pneumothoraces and ten perinodular hemorrhages were seen with spiral CT and six and ten, respectively, with sequential CT. The mean dose of irradiation was 4027 mAs for spiral CT and 2358 mAs for conventional CT. Spiral CT does neither reduce procedure time nor the rate of complications. Pathological results do not differ compared with sequential CT, and total dose of irradiation is higher with spiral scanning. (orig.)

Intra-individual diagnostic image quality and organ-specific-radiation dose comparison between spiral cCT with iterative image reconstruction and z-axis automated tube current modulation and sequential cCT

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Holger Wenz

2016-01-01

Conclusions: Spiral cCT combined with ATCM and IR allows for significant-radiation dose reduction including a reduce eye lens organ-dose when compared to a tilted sequential cCT while improving subjective and objective image quality.

The application and shielding value of low-dose CT scanning in hypoxic ischemic encephalopathy of neonate

International Nuclear Information System (INIS)

Wu Aiqin; Zheng Wenlong; Xu Chongyong; Cheng Jianmin; Chen Yu; Chen Tinggang

2006-01-01

Objective: To investigate the application and shielding value of multi-slice spiral CT scanning with low-dose in hypoxic ischemic encephalopathy (HIE) of neonate. Methods: 60 neonates with HIE diagnosed by clinic were prospectively selected and randomly divided into two groups averagely. The technical parameters were tube tension 120 kV, slice thickness and gap 6 mm, conventional tube current 250 mAs and low dose 50 mAs. Weighted CT dose index (CTDI w ) and dose length product (DLP) were compared to each other. The image noise were analyzed with water phantom of children's skull. The mean and standard deviation of CT value were statistically analyzed. The image quality was blindly evaluated in two different dose groups. Results: (1) The mAs, CTDI w and DLP in low dose group were 20 % of conventional dose group; (2) The noise of water phantom in low dose group was larger than in conventional dose group with the significant difference (t=34.533, P < 0.01 ); (3) The imaging quality in low dose group was mostly better, but inferior to conventional dose group, while there is no poor images to influence the diagnosis of HIE. Conclusions: The low dose scanning will be practical in diagnosis of HIE, and beneficial to protect the newborn which corresponds to the optimizing principle of ICRP in medical radiation protection. (authors)

Lung studies with spiral CT. pitch 1 versus pitch 2

International Nuclear Information System (INIS)

Sartoni Galloni, S.; Miceli, M.; Lipparino, M.; Burzi, M.; Gigli, F.; Rossi, M.S.; Santoli, G.; Guidarelli, G.

1999-01-01

In Spiral CT, the pitch is the ratio of the distance to tabletop travels per 360 degrees rotation to nominal slice width, expressed in mm. Performing Spiral CT examination with pitch 2 allows to reduce examination time, exposure and contrast dose, and X-ray tube overload. The authors investigated the yield of pitch 2 in lung parenchyma studies, particular relative to diagnostic image quality [it

Spiral CT scanning technique in the detection of aspiration of LEGO foreign bodies.

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Applegate, K E; Dardinger, J T; Lieber, M L; Herts, B R; Davros, W J; Obuchowski, N A; Maneker, A

2001-12-01

Radiolucent foreign bodies (FBs) such as plastic objects and toys remain difficult to identify on conventional radiographs of the neck and chest. Children may present with a variety of respiratory complaints, which may or may not be due to a FB. To determine whether radiolucent FBs such as plastic LEGOs and peanuts can be seen in the tracheobronchial tree or esophagus using low-dose spiral CT, and, if visible, to determine the optimal CT imaging technique. Multiple spiral sequences were performed while varying the CT parameters and the presence and location of FBs in either the trachea or the esophagus first on a neck phantom and then a cadaver. Sequences were rated by three radiologists blinded to the presence of a FB using a single scoring system. The LEGO was well visualized in the trachea by all three readers (both lung and soft-tissue windowing: combined sensitivity 89 %, combined specificity 89 %) and to a lesser extent in the esophagus (combined sensitivity 31 %, combined specificity 100 %). The peanut was not well visualized (combined sensitivity LEGO was 120 kV, 90 mA, 3-mm collimation, 0.75 s/revolution, and 2.0 pitch. This allowed for coverage of the cadaver tracheobronchial tree (approximately 11 cm) in about 18 s. Although statistical power was low for detecting significant differences, all three readers noted higher average confidence ratings with lung windowing among 18 LEGO-in-trachea scans. Rapid, low-dose spiral CT may be used to visualize LEGO FBs in the airway or esophagus. Peanuts were not well visualized.

Principles of spiral CT: III. Quality assurance

International Nuclear Information System (INIS)

Suess, C.; Kalender, W.A.

1998-01-01

Since its introduction in 1989 spiral CT has gained wide clinical acceptance and meanwhile it covers a large range of CT applications. This new technology, however, has not yet been recognized and acknowledged in the national or international regulations on scanner quality assurance (QA) programs. The conventional QA procedures should be extended to check the distribution of resolution and noise within the image plane. Imaging performance in the axial direction constitutes one of the major advantages of spiral scanning. Therefore, the slice sensitivity profiles and the spatial and low-contrast resolution along the z-axis have to be assessed. The high demands on table feed accuracy require additional tests. We suggest phantoms and procedures to check and quantify these parameters. Thereby, we hope to support the ongoing discussion about spiral CT quality assurance. (orig.) [de

Image Quality of 3rd Generation Spiral Cranial Dual-Source CT in Combination with an Advanced Model Iterative Reconstruction Technique: A Prospective Intra-Individual Comparison Study to Standard Sequential Cranial CT Using Identical Radiation Dose.

Science.gov (United States)

Wenz, Holger; Maros, Máté E; Meyer, Mathias; Förster, Alex; Haubenreisser, Holger; Kurth, Stefan; Schoenberg, Stefan O; Flohr, Thomas; Leidecker, Christianne; Groden, Christoph; Scharf, Johann; Henzler, Thomas

2015-01-01

To prospectively intra-individually compare image quality of a 3rd generation Dual-Source-CT (DSCT) spiral cranial CT (cCT) to a sequential 4-slice Multi-Slice-CT (MSCT) while maintaining identical intra-individual radiation dose levels. 35 patients, who had a non-contrast enhanced sequential cCT examination on a 4-slice MDCT within the past 12 months, underwent a spiral cCT scan on a 3rd generation DSCT. CTDIvol identical to initial 4-slice MDCT was applied. Data was reconstructed using filtered backward projection (FBP) and 3rd-generation iterative reconstruction (IR) algorithm at 5 different IR strength levels. Two neuroradiologists independently evaluated subjective image quality using a 4-point Likert-scale and objective image quality was assessed in white matter and nucleus caudatus with signal-to-noise ratios (SNR) being subsequently calculated. Subjective image quality of all spiral cCT datasets was rated significantly higher compared to the 4-slice MDCT sequential acquisitions (pspiral compared to sequential cCT datasets with mean SNR improvement of 61.65% (p*Bonferroni0.05spiral cCT with an advanced model IR technique significantly improves subjective and objective image quality compared to a standard sequential cCT acquisition acquired at identical dose levels.

Evaluation of image quality and dose in renal colic: comparison of different spiral-CT protocols

International Nuclear Information System (INIS)

Rimondini, A.; Mucelli, R.P.; Dalla Palma, L.; De Denaro, M.; Bregant, P.

2001-01-01

The aim of this study was to test different technical spiral-CT parameters to obtain optimal image quality with reduced X-ray dose. Images were acquired with a spiral-CT system Philips Tomoscan AVE1, using 250 mA, 120 kV, and 1-s rotational time. Three protocols were tested: protocol A with 5-mm thickness, pitch 1.6, slice reconstruction every 2.5 mm; protocol B with 3-mm thickness, pitch 1.6, slice reconstruction every 1.5 mm; and protocol C with 3-mm thickness, pitch 2, slice reconstruction every 1.5 mm. Two phantoms were employed to evaluate the image quality. Axial images were acquired, then sagittal and coronal images were reconstructed. Finally, the absorbed X-ray dose for each protocol was measured. Regarding image quality, 5-mm-thick images (protocol A) showed greater spatial resolution and lower noise compared with 3-mm-thick images (protocols B and C) on the axial plane; 3-mm reconstructed sagittal and coronal images (protocols B and C) showed an improved image quality compared with 5-mm reformatted images (protocol A). Concerning X-ray dose, the mean dose was: protocol A 19.6±0.8 mGy; protocol B 14.4±0.6 mGy; protocol C 12.5±1.0 mGy. Our study supports the use of thin slices (3 mm) combined with pitch of 1.6 or 2 in renal colic for X-ray dose reduction to the patient and good image quality. (orig.)

Spiral CT scanning technique in the detection of aspiration of LEGO foreign bodies

International Nuclear Information System (INIS)

Applegate, K.E.; Dardinger, J.T.; Herts, B.R.; Davros, W.J.; Obuchowski, N.A.; Lieber, M.L.; Maneker, A.

2001-01-01

Background:. Radiolucent foreign bodies (FBs) such as plastic objects and toys remain difficult to identify on conventional radiographs of the neck and chest. Children may present with a variety of respiratory complaints, which may or may not be due to a FB. Objective: To determine whether radiolucent FBs such as plastic LEGOs and peanuts can be seen in the tracheobronchial tree or esophagus using low-dose spiral CT, and, if visible, to determine the optimal CT imaging technique. Materials and methods: Multiple spiral sequences were performed while varying the CT parameters and the presence and location of FBs in either the trachea or the esophagus first on a neck phantom and then a cadaver. Sequences were rated by three radiologists blinded to the presence of a FB using a single scoring system. Results: The LEGO was well visualized in the trachea by all three readers (both lung and soft-tissue windowing: combined sensitivity 89 %, combined specificity 89 %) and to a lesser extent in the esophagus (combined sensitivity 31 %, combined specificity 100 %). The peanut was not well visualized (combined sensitivity < 35 %). The optimal technique for visualizing the LEGO was 120 kV, 90 mA, 3-mm collimation, 0.75 s/revolution, and 2.0 pitch. This allowed for coverage of the cadaver tracheobronchial tree (approximately 11 cm) in about 18 s. Although statistical power was low for detecting significant differences, all three readers noted higher average confidence ratings with lung windowing among 18 LEGO-in-trachea scans. Conclusion: Rapid, low-dose spiral CT may be used to visualize LEGO FBs in the airway or esophagus. Peanuts were not well visualized. (orig.)

Whole-body CT. Spiral and multislice CT. 2. tot. rev. and enl. ed.; Ganzkoerper-Computertomographie. Spiral- und Multislice-CT

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Prokop, M.; Galanski, M.; Schaefer-Prokop, C.; Molen, A.J. van der

2007-07-01

Spiral and multidetector techniques have improved the diagnostic possibilities of CT, so that image analysis and interpretation have become increasingly complex. This book represents the current state of the art in CT imaging, including the most recent technical scanner developments. The second edition comprises the current state of knowledge in cT imaging. There are new chapters on image processing, application of contrasting agents and radiation dose. All organ-specific pathological findings are discussed in full. There are hints for optimum use and interpretation of CT, including CT angiography, CT colonography, CT-IVPL, and 3D imaging. There is an introduction to cardio-CT, from calcium scoring and CTA of the coronary arteries to judgement of cardiac morphology. There are detailed scan protocols with descriptions of how to go about parameter selection. Practical hints are given for better image quality and lower radiation exposure of patients, guidelines for patient preparation and complication management, and more than 1900 images in optimum RRR quality. (orig.)

Accuracy of low dose CT in the diagnosis of appendicitis in childhood and comparison with USG and standard dose CT.

Science.gov (United States)

Yi, Dae Yong; Lee, Kyung Hoon; Park, Sung Bin; Kim, Jee Taek; Lee, Na Mi; Kim, Hyery; Yun, Sin Weon; Chae, Soo Ahn; Lim, In Seok

Computed tomography should be performed after careful consideration due to radiation hazard, which is why interest in low dose CT has increased recently in acute appendicitis. Previous studies have been performed in adult and adolescents populations, but no studies have reported on the efficacy of using low-dose CT in children younger than 10 years. Patients (n=475) younger than 10 years who were examined for acute appendicitis were recruited. Subjects were divided into three groups according to the examinations performed: low-dose CT, ultrasonography, and standard-dose CT. Subjects were categorized according to age and body mass index (BMI). Low-dose CT was a contributive tool in diagnosing appendicitis, and it was an adequate method, when compared with ultrasonography and standard-dose CT in terms of sensitivity (95.5% vs. 95.0% and 94.5%, p=0.794), specificity (94.9% vs. 80.0% and 98.8%, p=0.024), positive-predictive value (96.4% vs. 92.7% and 97.2%, p=0.019), and negative-predictive value (93.7% vs. 85.7% and 91.3%, p=0.890). Low-dose CT accurately diagnosed patients with a perforated appendix. Acute appendicitis was effectively diagnosed using low-dose CT in both early and middle childhood. BMI did not influence the accuracy of detecting acute appendicitis on low-dose CT. Low-dose CT is effective and accurate for diagnosing acute appendicitis in childhood, as well as in adolescents and young adults. Additionally, low-dose CT was relatively accurate, irrespective of age or BMI, for detecting acute appendicitis. Therefore, low-dose CT is recommended for assessing children with suspected acute appendicitis. Copyright © 2017. Published by Elsevier Editora Ltda.

Generative Adversarial Networks for Noise Reduction in Low-Dose CT.

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Wolterink, Jelmer M; Leiner, Tim; Viergever, Max A; Isgum, Ivana

2017-12-01

Noise is inherent to low-dose CT acquisition. We propose to train a convolutional neural network (CNN) jointly with an adversarial CNN to estimate routine-dose CT images from low-dose CT images and hence reduce noise. A generator CNN was trained to transform low-dose CT images into routine-dose CT images using voxelwise loss minimization. An adversarial discriminator CNN was simultaneously trained to distinguish the output of the generator from routine-dose CT images. The performance of this discriminator was used as an adversarial loss for the generator. Experiments were performed using CT images of an anthropomorphic phantom containing calcium inserts, as well as patient non-contrast-enhanced cardiac CT images. The phantom and patients were scanned at 20% and 100% routine clinical dose. Three training strategies were compared: the first used only voxelwise loss, the second combined voxelwise loss and adversarial loss, and the third used only adversarial loss. The results showed that training with only voxelwise loss resulted in the highest peak signal-to-noise ratio with respect to reference routine-dose images. However, CNNs trained with adversarial loss captured image statistics of routine-dose images better. Noise reduction improved quantification of low-density calcified inserts in phantom CT images and allowed coronary calcium scoring in low-dose patient CT images with high noise levels. Testing took less than 10 s per CT volume. CNN-based low-dose CT noise reduction in the image domain is feasible. Training with an adversarial network improves the CNNs ability to generate images with an appearance similar to that of reference routine-dose CT images.

Diagnosis of pancreatic tumors by spiral angio CT

International Nuclear Information System (INIS)

Miura, Kohi; Nakao, Norio; Takayasu, Yukio; Okawa, Tomohisa

1995-01-01

Spiral angio were performed with injection of 30 ml of contrast material at a rate of 1 ml/sec with a scan delay of 6 sec through catheter into the celiac artery while the blood flow of the superior mesenteric artery (SMA) was occluded by the inflated balloon catheter. Spiral CT scans were obtained using Somatom Plus (Siemens). Parameter for spiral CT were 24-sec acquisition time, 5 mm collimation, 5 mm/sec table incrementation. Reconstructions were performed every 5 mm. Pancreatic cancers were characteristically depicted with spiral angio CT as hypodensity relative to normal enhanced pancreatic parenchyma. On dynamic angio CT studies performed in pancreatic cancers, the area of cancer and normal parenchyma had maximum level of enhancement at 10-15 sec after injection of contrast material via catheter into the celiac, and there was no difference in enhancement between tumor and normal parenchyma. On the other hand, the lesions of cancer were revealed as hypodensity with spiral angio CT. In case of chronic pancreatitis, the enhancement of the entire pancreas obtained with spiral angio CT was homogeneous. Insulinoma in the tail of pancreas was detected by spiral angio CT but was not detected by both selective angiography and conventional CT. Three-dimensional (3-D) rendering spiral angio CT data shows the extent of vascular involvement by pancreatic cancer and provides useful information for surgical planning. Spiral angio CT is the most useful procedure for diagnosis of pancreatic tumor. (author)

Deep learning for low-dose CT

Science.gov (United States)

Chen, Hu; Zhang, Yi; Zhou, Jiliu; Wang, Ge

2017-09-01

Given the potential risk of X-ray radiation to the patient, low-dose CT has attracted a considerable interest in the medical imaging field. Currently, the main stream low-dose CT methods include vendor-specific sinogram domain filtration and iterative reconstruction algorithms, but they need to access raw data whose formats are not transparent to most users. Due to the difficulty of modeling the statistical characteristics in the image domain, the existing methods for directly processing reconstructed images cannot eliminate image noise very well while keeping structural details. Inspired by the idea of deep learning, here we combine the autoencoder, deconvolution network, and shortcut connections into the residual encoder-decoder convolutional neural network (RED-CNN) for low-dose CT imaging. After patch-based training, the proposed RED-CNN achieves a competitive performance relative to the-state-of-art methods. Especially, our method has been favorably evaluated in terms of noise suppression and structural preservation.

Enhancement pattern of small hepatic hemangioma: findings on multiphase spiral CT and dynamic MRI

International Nuclear Information System (INIS)

Choi, Byung In; Lee, Seung Koo; Kim, Myeong Jin; Chung, Jae Joon; Yoo, Hyung Sik; Lee, Jong Tae

1999-01-01

To compare the enhancement characteristics of small hemangiomas seen on multiphase spiral CT and dynamic MR imaging. Thirteen patients with 20 hepatic hemangiomas less than 25mm in diameter underwent both multiphase spiral CT and dynamic MR imaging. All lesions were assigned to one of three classified into 3 categories according to the enhancement pattern seen on multiphase spiral CT : typical delayed pooling, atypical early enhancement, or continuous low attenuation. The enhancement patterns seen on spiral CT and on dynamic MRI were correlated. On CT scans, ten lesions (50%) showed delayed pooling. Six (30%) showed early arterial enhancement and four (20%) showed continuous low attenuation. On delayed-phase MRI, all lesions showed delayed high signal intensity compared to adjacent liver parenchyma. Four of six lesions with early enhancement on CT showed peripheral globular enhancement on early arterial-phase MRI. On multiphase spiral CT scans, small hemangiomas can show variable atypical enhancement features. In this situation, contrast-enhanced dynamic MRI is helpful for the diagnosis of hemangiomas

The experimental study and clinical application on the detection of pulmonary nodules with low-dose multislice spiral CT

International Nuclear Information System (INIS)

Wu Xiaohua; Ma Daqing; Zhang Zhongjia; Ji Jingling; Zhang Yansong

2004-01-01

Objective: To investigate the detection rate of pulmonary nodules ,especially nodules ≤5 mm, in variable low-doses, and to evaluate the imaging quality of low-dose MSCT. Methods: Six postmortem specimens of patients with pneumoconiosis after necropsy were fixed at end-inspiratory volume. The fixed specimens were examined by using MSCT with standard dose (130 mA) and low-dose (50, 30, 10 mA, respectively). Low-dose MSCT scans of 40 asymptomatic volunteers and 60 patients with pulmonary metastasis were also examined with 30 mA. The numbers of pulmonary nodules less than 5 mm at standard-dose and different low-dose were recorded. Nodules were assessed by diagnostic confidence ('definite nodule', 'questionable nodule', and 'definite not nodule'). The number of images with artifact in specimens and in 40 volunteers and 60 patients with pulmonary metastasis were recorded. Results: In specimen's study, the Kappa values of groups of low-dose (50, 30, 10 mA) were 0.515, 0.242, and 0.154, respectively. The group of 50 mA had a good coincidence with standard-dose group by U test. The sensitivity of group 50, 30, 10 mA was 88.0%, 78.4%, and 75.0%, respectively. The positive predictive values of which were 98%, 94%, and 93%, respectively. The correction rates of which were 85%, 73%, and 69%, respectively. In specimens' images, subtle linear artifact was showed only in paravertebral lung field in 21 images of 31 at the group of 10 mA. Linear artifacts that affected small nodule detection were showed in lung apexes in 3 of 100 subjects. Conclusion: Low-dose MSCT is expected to improve early detection of lung cancer. Pulmonary nodules less than 5 mm could be reliably detected at 50 mA tube current in specimens. Low-dose CT (30 mA) showed satisfactory imaging quality in our study. Low-dose CT screening for lung cancer may be applied if situation permits. (authors)

Low-dose Dental-CT

International Nuclear Information System (INIS)

Gahleitner, A.; Imhof, H.; Homolka, P.; Fuerhauser, R.; Freudenthaler, J.; Watzek, G.

2000-01-01

Dental-CT is a relatively new, increasingly used investigation technique in dental radiology. Several authors have stated that the indication for Dental-CT has to be chosen on a strict basis, due to high dose values. This article describes the technique of performing dental-CT and calculates the effective dose based on published data and own measurements as well as the dose reduction potential to achieve an optimized protocol for Dental-CT investigations. (orig.) [de

Relationship between noise, dose, and pitch in cardiac multi-detector row CT.

Science.gov (United States)

Primak, Andrew N; McCollough, Cynthia H; Bruesewitz, Michael R; Zhang, Jie; Fletcher, Joel G

2006-01-01

In spiral computed tomography (CT), dose is always inversely proportional to pitch. However, the relationship between noise and pitch (and hence noise and dose) depends on the scanner type (single vs multi-detector row) and reconstruction mode (cardiac vs noncardiac). In single detector row spiral CT, noise is independent of pitch. Conversely, in noncardiac multi-detector row CT, noise depends on pitch because the spiral interpolation algorithm makes use of redundant data from different detector rows to decrease noise for pitch values less than 1 (and increase noise for pitch values > 1). However, in cardiac spiral CT, redundant data cannot be used because such data averaging would degrade the temporal resolution. Therefore, the behavior of noise versus pitch returns to the single detector row paradigm, with noise being independent of pitch. Consequently, since faster rotation times require lower pitch values in cardiac multi-detector row CT, dose is increased without a commensurate decrease in noise. Thus, the use of faster rotation times will improve temporal resolution, not alter noise, and increase dose. For a particular application, the higher dose resulting from faster rotation speeds should be justified by the clinical benefits of the improved temporal resolution. RSNA, 2006

Automatic exposure control to reduce the dose in subsecond multislice spiral CT: phantom measurements and clinical results

International Nuclear Information System (INIS)

Greess, H.; Bautz, W.; Baum, U.; Wolf, H.; Suess, C.; Kalender, W.A.

2004-01-01

Purpose: To investigate the potential of dose reduction in multislice spiral CT (MSCT) with automatic exposure control. Materials and Methods: The study was performed on a Sensation 4 multislice scanner. This prototype implementation analyzed the distribution of the attenuation along the z-axis in the lateral and sagittal directions of the digital radiogram. Depending on this distribution of the attenuation, the tube current (mA) is defined for every tube rotation. In addition, the tube current was modulated during each tube rotation. First, a three step oval water phantom was measured to evaluate the potential of this method with respect to dose reduction and image quality. In a patient study (n=26), four different scan regions (shoulder, thorax, abdomen, pelvis) were examined and dose (mAs) and image quality evaluated in comparison to examinations with a standard protocol for these regions in adults and a weight-adjusted standard protocol in children. The image quality was classified in consensus as good, sufficient and poor image quality. Results: By adapting and modulating the tube current, we substantially reduced the variation of noise in one spiral scan and in one scan region of our patient collective. The dose (average mAs) was reduced by 31% to 66% in children (mean 44%) and between 35% and 64% in adults (mean 53%), depending on the scan region. The image quality was substantially improved in regions with high attenuation and did not suffer in low attenuation regions. Conclusion: The dose can be reduced substantially by an automatic exposure control including angular tube current modulation with the same or improved image quality. (orig.) [de

Estimation of the total effective dose from low-dose CT scans and radiopharmaceutical administrations delivered to patients undergoing SPECT/CT explorations

International Nuclear Information System (INIS)

Montes, C.; Hernandez, J.; Gomez-Caminero, F.; Garcia, S.; Martin, C.; Rosero, A.; Tamayo, P.

2013-01-01

Hybrid imaging, such as single photon emission computed tomography (SPECT)/CT, is used in routine clinical practice, allowing coregistered images of the functional and structural information provided by the two imaging modalities. However, this multimodality imaging may mean that patients are exposed to a higher radiation dose than those receiving SPECT alone. The study aimed to determine the radiation exposure of patients who had undergone SPECT/CT examinations and to relate this to the Background Equivalent Radiation Time (BERT). 145 SPECT/CT studies were used to estimate the total effective dose to patients due to both radiopharmaceutical administrations and low-dose CT scans. The CT contribution was estimated by the Dose-Length Product method. Specific conversion coefficients were calculated for SPECT explorations. The radiation dose from low-dose CTs ranged between 0.6 mSv for head and neck CT and 2.6 mSv for whole body CT scan, representing a maximum of 1 year of background radiation exposure. These values represent a decrease of 80-85% with respect to the radiation dose from diagnostic CT. The radiation exposure from radiopharmaceutical administration varied from 2.1 mSv for stress myocardial perfusion SPECT to 26 mSv for gallium SPECT in patients with lymphoma. The BERT ranged from 1 to 11 years. The contribution of low-dose CT scans to the total radiation dose to patients undergoing SPECT/CT examinations is relatively low compared with the effective dose from radiopharmaceutical administration. When a CT scan is only acquired for anatomical localization and attenuation correction, low-dose CT scan is justified on the basis of its lower dose. (author)

Optimising imaging parameters in experimental spiral CT

International Nuclear Information System (INIS)

Tiitola, M.; Vehmas, T.; Kivisaari, R.P.; Kivisaari, L.

1997-01-01

Purpose: This in vitro study was conducted to analyse lesion detection and relative radiation exposure in different CT techniques. Material and Methods: We used a plastic phantom (12 x 8 x 2 cm) containing holes filled with air or fluid of varying densities to simulate lesions. This was imaged with Siemens Somatom Plus S and GE High Speed Advantage units. We varied table feeds (3 and 6 mm/s in Siemens and 3 and 4.5 mm/s in GE) and increments (2 mm and 4 mm) while keeping collimation at 3 mm. The SmartScan program of GE and the reformating algorithm of Siemens were also analysed. To evaluate the different methods, the phatnom lesions were counted by 3 observers. Radiation exposures associated with each technique were also measured. Results: The images reformatted to a coronal direction were significantly inferior (p<0.01) to those in other techniques. The use of SmartScan did not influence lesion detection, nor did changes in pitch or increment. Spiral and non-spiral techniques proved to be equal. Radiation exposure was lowest when a greater pitch or the SmartScan program was used. Conclusion: Radiation exposure in CT can be limited without significantly impairing the image quality by using low-dose techniques. Reformatting to a coronal direction should be used with care as it debases the image quality. (orig.)

Spiral CT findings of inflammatory pseudotumor of the liver

International Nuclear Information System (INIS)

Lee, Ha Jong; Nam, Kyung Jin; Lee, Ki Nam; Park, Byeong Ho; Choi, Jong Cheol; Koo, Bong Sik; Nam, Ki Dong; Kim, Chan Seong

1998-01-01

To assess the spiral CT findings of inflammatory pseudotumor of the liver(IPTL), in order to distinguish this tumor from hepatocellular carcinoma, hepatic abscess or other space occupying liver lesions. The spiral CT findings of IPTL were retrospectively evaluated in six patients. All cases were confirmed by ultrasonography-guided gun biopsy. Four patients were men and two were women, and they were aged between 37 and 74 (mean, 49) years. The site, size, and number of IPTL were assessed, and their enhancement patterns were evaluated during the arterial, portal and delayed phases of spiral CT. Five cases involved a solitary mass and in one there were multiple masses with surrounding small nodules. Four cases occurred in the right lobe and two in the left lobe. Four of five surrounding nodules were in the left lobe. During the arterial phase of spiral CT scanning, three layers were separated from four of five cases of solitary mass;they were composed of central and peripheral portions of low attenuation, and an intermediate portion of isoattenuation. Delayed enhancement of the peripheral portion was prominent during the delayed phase. In the case involving multiple masses three layers were not seen during the arterial phase, but during the delayed phase enhancement was noted. The features of three layers, as seen on spiral CT, is considered to be very specific for distinguishing IPTL from other hepatic focal lesions.=20

Lateral topography for reducing effective dose in low-dose chest CT.

Science.gov (United States)

Bang, Dong-Ho; Lim, Daekeon; Hwang, Wi-Sub; Park, Seong-Hoon; Jeong, Ok-man; Kang, Kyung Wook; Kang, Hohyung

2013-06-01

The purposes of this study were to assess radiation exposure during low-dose chest CT by using lateral topography and to compare the lateral topographic findings with findings obtained with anteroposterior topography alone and anteroposterior and lateral topography combined. From November 2011 to February 2012, 210 male subjects were enrolled in the study. Age, weight, and height of the men were recorded. All subjects were placed into one of three subgroups based on the type of topographic image obtained: anteroposterior topography, lateral topography, and both anteroposterior and lateral topography. Imaging was performed with a 128-MDCT scanner. CT, except for topography, was the same for all subjects. A radiologist analyzed each image, recorded scan length, checked for any insufficiencies in the FOV, and calculated the effective radiation dose. One-way analysis of variance and multiple comparisons were used to compare the effective radiation exposure and scan length between groups. The mean scan length in the anteroposterior topography group was significantly greater than that of the lateral topography group and the combined anteroposterior and lateral topography group (p topography group (0.735 ± 0.033 mSv) was significantly lower than that for the anteroposterior topography group (0.763 ± 0.038 mSv) and the combined anteroposterior and lateral topography group (0.773 ± 0.038) (p < 0.001). Lateral topographic low-dose CT was associated with a lower effective radiation dose and scan length than either anteroposterior topographic low-dose chest CT or low-dose chest CT with both anteroposterior and lateral topograms.

Screening for early lung cancer with low-dose spiral computed tomography: results of annual follow-up examinations in asymptomatic smokers

International Nuclear Information System (INIS)

Diederich, Stefan; Thomas, Michael; Semik, Michael; Lenzen, Horst; Roos, Nikolaus; Weber, Anushe; Heindel, Walter; Wormanns, Dag

2004-01-01

The aim of this study was analysis of incidence results in a prospective one-arm feasibility study of lung cancer screening with low-radiation-dose spiral computed tomography in heavy smokers. Eight hundred seventeen smokers (≥40 years, ≥20 pack years of smoking history) underwent baseline low-dose CT. Biopsy was recommended in nodules >10 mm with CT morphology suggesting malignancy. In all other lesions follow-up with low-dose CT was recommended. Annual repeat CT was offered to all study participants. Six hundred sixty-eight (81.8%) of the 817 subjects underwent annual repeat CT with a total of 1735 follow-up years. Follow-up of non-calcified nodules present at baseline CT demonstrated growth in 11 of 792 subjects. Biopsy was performed in 8 of 11 growing nodules 7 of which represented lung cancer. Of 174 new nodules, 3 represented lung cancer. The 10 screen-detected lung cancers were all non-small cell cancer (6 stage IA, 1 stage IB, 1 stage IIIA, 2 stage IV). Five symptom-diagnosed cancers (2 small cell lung cancer: 1 limited disease, 1 extensive disease, 3 central/endobronchial non-small cell lung cancer, 2 stage IIIA, 1 stage IIIB) were diagnosed because of symptoms in the 12-month interval between two annual CT scans. Incidence of lung cancer was lower than prevalence, screen-detected cancers were smaller, and stage I was found in 70% (7 of 10) of screen-detected tumors. Only 27% (4 of 15) of invasive procedures was performed for benign lesions; however, 33% (5 of 15) of all cancers diagnosed in the population were symptom-diagnosed cancers (3 central NSCLC, all stage III, 2 SCLC) demonstrating the limitations of CT screening. (orig.)

Assessment of pulmonary function using pixel indexes of multiple-slice spiral CT low-dose two-phase scanning in chronic obstructive pulmonary disease

International Nuclear Information System (INIS)

Zhang Lihua; Wang Yunhua; Jiang Zhongbiao; Zhang Lejun; Sun Wanli; Zhang Chunming

2012-01-01

Objective: To explore the values of pixel indexes (PI) with multiple-slice spiral CT low-dose two-phase scanning for assessing the pulmonary function in chronic obstructive pulmonary disease (COPD). Methods: Thirty-six patients with COPD (COPD group)and 30 healthy people (control group)underwent pulmonary function test (PFT). Chest 64-MSCT low-dose (50 mAs) scanning at full inspiration and expiration, routine scanning (100 mAs) at inspiration were performed. The effective dose (ED) was calculated. The lung was divided into three regions (upper, middle, lower). PI of lung were divided into five groups: -960--1024, -910--960, -800--910, -700--800, -400--700. The PI -910 (sum of the PI under -910 HU) of low-dose scanning at each region were measured and calculated using pulmo software. All PI included PIin -910 , PIiex -910 , PIin -910 -PIiex -910 , PIiex -910 /PIin -910 and (PIin -910 -PIiex -910 )/PIin -910 . All patients underwent PFT within 3 days after 64-MSCT canning, FEV1% and FEV1/FVC were selected for comparison. Results: The PIin in three regions (-960 - -1024, -910 - -960, -800 - -910) were statistically significant between normal and COPD groups (U=0.00, 57.00, 20.50, P<0.01). The PIex in all regions were statistically significant (U=0.00, 0.00, 71.52, 191.00, 6.00, P<0.01). PI -910--1024 at expiration and inspiration were correlated with FEV1% and FEV1/FVC (r=-0.548, -0.664, -0.752, -0.781, P<0.01). PIin -910 , PIex -910 ,PIiex -910 /PIin -910 , (PIin -910 -PIex -910 )/PIin -910 had a good correlation with FEV1% and FEV1/FVC (r=-0.548, -0.664, -0.752, -0.781, -0.674, -0.642, 0.674, 0.642, P<0.01). Conclusion: Pixel indexes of 64-MSCT low-dose two-phase scanning can be used to evaluate pulmonary function in COPD patients. (authors)

The effect of pitch in multislice spiral/helical CT

International Nuclear Information System (INIS)

Wang, G.; Vannier, M.W.

2000-01-01

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

Diagnosis of tracheal instability: inspiratory and expiratory spiral CT and cine CT

International Nuclear Information System (INIS)

Heussel, C.P.; Thelen, M.; Kauczor, H.U.; Hafner, B.; Lill, J.

2000-01-01

Purpose: In tracheo- and bronchomalacia, localization and determination of collapse is necessary for planning a surgical procedure. We compared inspiratory and spiral CT, cine CT, and bronchoscopy and evaluated the relevance of each method. Methods: Seventeen patients with suspected or verified tracheal stonosis or collapse underwent paired inspiratory and exspiratory spiral CT and cine CT during continuous respiration (temporal increment 100 ms). The tracheal cross-sectional area was calculated and compared. Results: In addition to bronchoscopy, further information concerning localization, extent, collapse, stability of the tracheal wall, distal portions of the stenosis, and extraluminal compressions was obtained. A significantly higher degree of tracheal collapse was seen using cine CT compared to paired spiral CT (p [de

A Monte Carlo-based method to estimate radiation dose from spiral CT: from phantom testing to patient-specific models

International Nuclear Information System (INIS)

Jarry, G; De Marco, J J; Beifuss, U; Cagnon, C H; McNitt-Gray, M F

2003-01-01

The purpose of this work is to develop and test a method to estimate the relative and absolute absorbed radiation dose from axial and spiral CT scans using a Monte Carlo approach. Initial testing was done in phantoms and preliminary results were obtained from a standard mathematical anthropomorphic model (MIRD V) and voxelized patient data. To accomplish this we have modified a general purpose Monte Carlo transport code (MCNP4B) to simulate the CT x-ray source and movement, and then to calculate absorbed radiation dose in desired objects. The movement of the source in either axial or spiral modes was modelled explicitly while the CT system components were modelled using published information about x-ray spectra as well as information provided by the manufacturer. Simulations were performed for single axial scans using the head and body computed tomography dose index (CTDI) polymethylmethacrylate phantoms at both central and peripheral positions for all available beam energies and slice thicknesses. For comparison, corresponding physical measurements of CTDI in phantom were made with an ion chamber. To obtain absolute dose values, simulations and measurements were performed in air at the scanner isocentre for each beam energy. To extend the verification, the CT scanner model was applied to the MIRD V model and compared with published results using similar technical factors. After verification of the model, the generalized source was simulated and applied to voxelized models of patient anatomy. The simulated and measured absolute dose data in phantom agreed to within 2% for the head phantom and within 4% for the body phantom at 120 and 140 kVp; this extends to 8% for the head and 9% for the body phantom across all available beam energies and positions. For the head phantom, the simulated and measured absolute dose data agree to within 2% across all slice thicknesses at 120 kVp. Our results in the MIRD phantom agree within 11% of all the different organ dose values

Floating venous thrombi: diagnosis with spiral-CT-venography; Diagnose flottierender venoeser Thromben mittels Phlebo-Spiral-CT

Energy Technology Data Exchange (ETDEWEB)

Gartenschlaeger, M. [Mainz Univ. (Germany). Klinik fuer Radiologie; Klose, K.J. [Univ. Marburg, Medizinisches Zentrum fuer Innere Medizin, Abt. Poliklinik (Germany); Schmidt, J.A. [Univ. Marburg, Medizinisches Zentrum fuer Radiologie, Abt. fuer Strahlendiagnostik (Germany)

1996-05-01

Local application of contrast agent into an ipsilateral dorsal foot vein and spiral CT were used to examine 16 consecutive cases with deep venous thrombosis proven at conventional venography; in addition, colour Doppler flow imaging was performed. At conventional venography, 8/16 thrombi appeared to be floating and the remaining 8/16 were adherent to the vessel wall. Spiral-CT showed 15/16 thrombi to be adherent to the vessel wall; the floating thrombus correlated with findings in conventional venography. At colour Doppler flow imaging 3/16 thrombi were considered floating, one of them was discordant to conventional venography. The comparison of conventional venography to spiral-CT demonstrates complete agreement for adherence to vessel wall seen in conventional venography (p=1,0) and significant discordance in cases with free-floating appearance in conventional venography. Adherence of thrombi to the wall of the vessel at conventional venography is in agreement with computed tomography. Conventional venography probably overestimates the prevalence of free floating thrombi. (orig./MG) [Deutsch] Mittels lokaler Kontrastmittelapplikation in eine ipsilaterale Fussrueckenvene und Spiral-CT wurden 16 konsekutive Faelle konventionell phlebographisch gesicherter Phlebothrombose untersucht, zusaetzlich wurde die farbkodierte Doppler-Ultraschalluntersuchung durchgefuehrt. In der konventionellen Phlebographie waren 8/16 Thromben flottierend, die uebrigen 8/16 wandadhaerent. In der Spiral-CT zeigten sich Wandadhaerenzen in 15/16 Faellen; der nachgewiesene flottierende Thrombus stimmte mit der konventionellen Phlebographie ueberein. Im farbkodierten Doppler-Ultraschall erschienen die Thromben in 3/16 Faellen flottierend, darunter ein von der konventionellen Phlebographie abweichender Befund. Der Vergleich von konventioneller und CT-Phlebographie ergab eine komplette Uebereinstimmung fuer konventionell phlebographisch nachgewiesene Wandadhaerenz und eine signifikante Abweichung

Risk-benefit analysis and cost-effectiveness analysis of lung cancer screening by spiral CT

International Nuclear Information System (INIS)

Iinuma, Takeshi

1999-01-01

Mass screening of lung cancer has been widely performed using indirect chest X-ray method in Japan. However reduction of the mortality for lung cancer is questioned. We have proposed that recently developed spiral CT should be adopted for the screening of lung cancer, since CT has an excellent detectability for small nodule. Lung Cancer Screening CT (LSCT) has been developed by author's group using spiral CT with low dose and light weight in order to make a mobile unit. In this paper risk-benefit analysis and cost-effectiveness analysis are described for the LSCT screening of lung cancer. As a risk, radiation carcinogenesis due to exposure from LSCT are compared with gain of life-expectancy by screening and men of 40 years or more and women of 45 years or more are justified. The cost per person-year is estimated for LSCT screening which is better than that of present method, although total cost is higher. The LSCT screening could be recommended if total cost is affordable. (author)

Spiral CT manifestations of spherical pneumonia

International Nuclear Information System (INIS)

Li Xiaohong; Yang Hongwei; Xu Chunmin; Qin Xiu

2008-01-01

Objective: To explore the Spiral CT manifestations and differential diagnosis of spherical pneumonia. Methods: 18 cases of spherical pneumonia and 20 cases of peripheral pulmonary carcinoma were selected, both of them were confirmed by clinic and/or pathology. The SCT findings of both groups were compared retrospectively. Results: Main spiral CT findings of spherical pneumonia were showed as followings: square or triangular lesions adjacent to pleura; with irregular shape, blurry, slightly lobulated margin, sometimes with halo sign. Small inflammatory patches and intensified vascular markings around the lesions were seen. Lesions became smaller or vanished after short-term anti-inflammatory treatment. Conclusion: Spherical pneumonia showed some characteristics on Spiral CT scan, which are helpful in diagnosis and differential diagnosis of this disease. (authors)

Measurement of lung volumes : usefulness of spiral CT

International Nuclear Information System (INIS)

Kang, Ho Yeong; Kwak, Byung Kook; Lee, Sang Yoon; Kim, Soo Ran; Lee, Shin Hyung; Lee, Chang Joon; Park, In Won

1996-01-01

To evaluate the usefulness of spiral CT in the measurement of lung volumes. Fifteen healthy volunteers were studied by both spirometer and spiral CT at full inspiration and expiration in order to correlated their results, including total lung capacity (TLC), vital capacity (VC) and residual volume (RV). 3-D images were reconstructed from spiral CT, and we measured lung volumes at a corresponding CT window range ; their volumes were compared with the pulmonary function test (paired t-test). The window range corresponding to TLC was from -1000HU to -150HU (p=0.279, r=0.986), and for VC from -910HU to -800HU (p=0.366, r=0.954) in full-inspiratory CT. The optimal window range for RV in full-expiratory CT was from -1000HU to -450HU (p=0.757, r=0.777), and TLC-VC in full-inspiratory CT was also calculated (p=0.843, r=0.847). Spiral CT at full inspiration can used to lung volumes such as TLC, VC and RV

The value of spiral CT scan on fracture of ankle joint and tarsal bones

International Nuclear Information System (INIS)

Li Zhaoli; Liang Jingyin; Pan Zhifeng

2009-01-01

Objective: To study the value of spiral CT scan on the fracture of ankle joint and tarsal bones. Methods: 43 cases with the fracture of ankle joint and tarsal bones were collected and analyzed. All the cases were examined by plain film radiography and spiral CT thin slice scan. Multi-planar reformation (MPR), surface shaded display (SSD) and other techniques of image post-processing were performed in 35 cases of them. Results: Spiral CT scan could demonstrate more fractures than plain film radiography in 28 cases(65.1%). There are 15 cases (34.9%) which are normal in plain film radiography but abnormal in Spiral CT scan. Spiral CT could demonstrate the different length, width, direction and number of linear low density shadow. SSD and MPR were performed again in the cases with avulsion fracture and fragmental fracture to demonstrate the fracture direction and the shape, size and location of fragments more clearly. Conclusion: Spiral CT thin slice scan with image post-processing techniques can play an important role in fracture of ankle joint and tarsal bones. (authors)

Low-dose CT image reconstruction using gain intervention-based dictionary learning

Science.gov (United States)

Pathak, Yadunath; Arya, K. V.; Tiwari, Shailendra

2018-05-01

Computed tomography (CT) approach is extensively utilized in clinical diagnoses. However, X-ray residue in human body may introduce somatic damage such as cancer. Owing to radiation risk, research has focused on the radiation exposure distributed to patients through CT investigations. Therefore, low-dose CT has become a significant research area. Many researchers have proposed different low-dose CT reconstruction techniques. But, these techniques suffer from various issues such as over smoothing, artifacts, noise, etc. Therefore, in this paper, we have proposed a novel integrated low-dose CT reconstruction technique. The proposed technique utilizes global dictionary-based statistical iterative reconstruction (GDSIR) and adaptive dictionary-based statistical iterative reconstruction (ADSIR)-based reconstruction techniques. In case the dictionary (D) is predetermined, then GDSIR can be used and if D is adaptively defined then ADSIR is appropriate choice. The gain intervention-based filter is also used as a post-processing technique for removing the artifacts from low-dose CT reconstructed images. Experiments have been done by considering the proposed and other low-dose CT reconstruction techniques on well-known benchmark CT images. Extensive experiments have shown that the proposed technique outperforms the available approaches.

Kidney spiral CT, indications, realization, results

International Nuclear Information System (INIS)

Braunschweig, R.; Beilicke, M.; Hundt, W.; Breiteneder, T.; Reiser, M.

1999-01-01

The introduction of spiral computed tomography (spiral CT) has vastly enriched the methodologically diversity of computer-tomographic scans. It allows for the recording of different perfusion or excretion stages of the kidney parenchyma of the urine draining paths by carrying out long-distance, phase-identical multiple examinations of the retroperitoneum. The description of the findings which are characterized by their local and contrasts behavior is possible. The following report describes the indications and technological process of kidney spiral CT using kidney-typical intravenous contrast media. Special emphasis is put on the advantages and limits of multiple phase spiral CT. Decisive preconditions are: 1. Specific clinical query, 2. selection of the corresponding phase contrasts of the kidneys and uretra or bladder, 3. exact technical and temporal adjustment of the acquisition parameters. Scanning times are in the range of seconds. The overall examination can be carried out quick and without any major strain on the part of the patient. A sound proof and a general differentiation of focal kideny lesions can be derived from the acquired data. This is also true for kidneys and ureters findings. Bladder findings can be localized and differentiated according to stage. More than two 'spiral acquisitions' should be carried out with restraint taking exposure to radiation into account. Due to the sound registration of focal lesions, its capability of reproduction and its short-time examination, the spiral CT of the kidneys can be said to be the most effective current scanning method of the retroperitoneum following clinical examinations and sonography. (orig.) [de

The potentials of spiral CT for detection of focal liver lesions; Moeglichkeiten der Spiral-CT zur Diagnostik fokaler Leberlaesionen

Energy Technology Data Exchange (ETDEWEB)

Helmberger, H. [Technische Univ. Muenchen, Klinikum rechts der Iser, Inst. fuer Roentgendiagnostik (Germany); Kersting-Sommerhoff, B. [Technische Univ. Muenchen, Klinikum rechts der Iser, Inst. fuer Roentgendiagnostik (Germany); Lenz, M. [Technische Univ. Muenchen, Klinikum rechts der Iser, Inst. fuer Roentgendiagnostik (Germany); Kirsten, R. [Technische Univ. Muenchen, Klinikum rechts der Iser, Inst. fuer Roentgendiagnostik (Germany); Bautz, W. [Technische Univ. Muenchen, Klinikum rechts der Iser, Inst. fuer Roentgendiagnostik (Germany)

1996-03-01

Spiral CT currently is the modality of choice for all aspects of diagnostic evaluation of the liver. Optimal selection of treatment should be based inter alia on the findings obtained by spiral CT with arterial application of contrast medium, as for example S-CTA (primary liver tumors), or S-CTAP (secondary liver tumors). Ultrasonography is the major supplementing modality. In the near future, MR imaging applying liver-specific contrast-enhancing agents is expected to become an important competing technique, and further developments of interest in diagnostic imaging of the liver are in the offing: it is not yet known which technique will be the modality of choice at the onset of the 21st century. (orig.) [Deutsch] Die Spiral-CT ist zur Zeit das empfehlenswerte Verfahren fuer alle Fragen der Leberdiagnostik. Zur optimalen praetherapeutischen Beurteilung der Leber sollte die Spiral-CT mit arterieller Kontrastmittelapplikation als S-CTA (primaere Lebertumoren) bzw. S-CTAP (sekundaere Lebertumoren) durchgefuehrt werden. Der US kommt ein Stellenwert als ergaenzende Methode zu. In Zukunft wird die MRT mit leberspezifischen Kontrastmitteln ein konkurrierendes Verfahren zur Spiral-CT darstellen, wobei eine weitere interessante Entwicklung auf dem Gebiet der hepatischen Bildgebung zu erwarten ist: Das diagnostische Verfahren der Wahl fuer die Leber zu Beginn des 21. Jahrhunderts ist noch nicht definiert. (orig.)

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

International Nuclear Information System (INIS)

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

2003-01-01

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

Spiral CT for evaluation of chest trauma

International Nuclear Information System (INIS)

Roehnert, W.; Weise, R.

1997-01-01

After implementation of spiral CT in our department, we carried out an analysis for determining anew the value of CT as a modality of chest trauma diagnosis in the emergency department. The retrospective study covers a period of 10 months and all emergency patients with chest trauma exmined by spiral CT. The major lesions of varying seriousness covered by this study are: pneumothorax, hematothorax, pulmonary contusion or laceration, mediastinal hematoma, rupture of a vessel, injury of the heart and pericardium. The various fractures are not included in this study. In many cases, spiral CT within relatively short time yields significant diagnostic findings, frequently saving additional angiography. A rigid diagnostic procedure cannot be formulated. Plain-film chest radiography still remains a diagnostic modality of high value. (Orig.) [de

Screenings of lung cancer with low dose spiral CT: results of a three year pilot study and design of the randomised controlled trial Italung-CT; Screening della neoplasia polmonare con TC spirale a bassa dose: risultati di uno studio pilota triennale e disegno dello studio clinico randomizzato Italung-CT

Energy Technology Data Exchange (ETDEWEB)

Picozzi, Giulia [Firenze Univ., Firenze (Italy). Radiodiagnostica I-Dipartimento di Fisiopatologia Clinica; Paci, Enrico [Azienda Ospedaliera Universitaria di Careggi, Firenze (Italy). Unita' di Epidemiologia Clinica e Descrittiva Centro per lo Studio e la Prevenzione Oncologica; Lopes Pegna, Andrea [Azienda Ospedaliera Universitaria di Careggi, Firenze (Italy). U.O. Pneumologia] [and others

2005-02-01

Purpose: To report the results of a three-year observational pilot study of lung cancer screening with low dose computed tomography (CT) and to present the study design of a randomised clinical trial named as Italung CT. Materials and methods: Sixty (47 males and 13 females, mean age 64{+-}4.5 years) heavy smokers (at least 20 packs-year) underwent three low-dose spiral CT screening tests one year apart on a single slice or multislice CT scanner. Indeterminate nodules were managed according to the recommendations of the Early Lung Cancer Action Project. Results: Indeterminate nodules were observed in 33 (55%) of the subjects (60% at the baseline screening test, 24% at the first annual test and 16% at the second annual test). The size of the largest indeterminate nodule was <5mm in diameter in 20 subjects. 10 of whom showed the nodule at the baseline test. Forty-five subjects (75%) completed the first annual test and 42 (70%) the second annual test. One (1.6%) prevalent lung cancer (adenosquamous carcinoma) and one (2.2%) incident lung cancer (small cell cancer at the first annual examination) were observed, as well as pulmonary localisation of Hodgkin's lymphoma (at the second annual test). In addition, one subject underwent lung surgery for a chondromatous hamartoma. Conclusions: The results of the pilot study are substantially in line with those of other observational studies of greater sample size. This justifies optimism about the reliability of the results in the screened arm of the Italung Ct trial which hast just began. [Italian] Scopo: Riportare i risultati di uno studio pilota osservazionale di screening della neoplasia polmonare con TC a bassa dose della durata di tre anni e presentare il disegno dello studio clinico randomizzato Italung-CT. Materiale e metodi: Sessanta (47 uomini e 13 donne, eta' media 64{+-}4,5 anni) forti fumatori (almeno 20 pacchetti/anno) sono stati sottoposti ad un esame basale e a due controlli annuali con TC single o

Fully Convolutional Architecture for Low-Dose CT Image Noise Reduction

Science.gov (United States)

Badretale, S.; Shaker, F.; Babyn, P.; Alirezaie, J.

2017-10-01

One of the critical topics in medical low-dose Computed Tomography (CT) imaging is how best to maintain image quality. As the quality of images decreases with lowering the X-ray radiation dose, improving image quality is extremely important and challenging. We have proposed a novel approach to denoise low-dose CT images. Our algorithm learns directly from an end-to-end mapping from the low-dose Computed Tomography images for denoising the normal-dose CT images. Our method is based on a deep convolutional neural network with rectified linear units. By learning various low-level to high-level features from a low-dose image the proposed algorithm is capable of creating a high-quality denoised image. We demonstrate the superiority of our technique by comparing the results with two other state-of-the-art methods in terms of the peak signal to noise ratio, root mean square error, and a structural similarity index.

Clinical application of low-dose CT in patients with rib fractures

International Nuclear Information System (INIS)

Ge Xiaojun; Wu Hao; Hua Yanqing; Wang Mingpeng; Mao Dingbiao; Tang Ping; Hu Fei; Zhang Guozhen

2011-01-01

Objective: To evaluate images quality and diagnostic feasibility of low-dose CT in patients with traumatic rib fractures. Methods: Twenty-five patients presented with thoracic injury were underwent 64-slice spiral CT scanning in inspiration breath-hold technique. Two scan protocols were performed. In one scan protocol noise index (NI) is 11, and in another NI is 21, but the other scan parameters were no difference. The mean value of tube current, the volume CT dose index (CTDI vol ), and effective dose (ED) were recorded. Image quality was scored by 2 experienced radiologists using the 5-points scale. The numbers and degrees of rib fractures were recorded. The data were tested by using the Wilcoxon signed rank sum test. The differences of the inter-observer were determined by Kappa statistics. Results: The mean CTDIvol and ED in scan protocol with NI of 11 were (13.88±5.17) mGy and (8.14± 3.21) mSv, and that with NI of 21 were (3.91±1.57) mGy and (2.31±0.97) mSv. Compared the scan with NI of 11, there was 72% intrinsic dose reduction in the scan with NI of 21. The mean value of tube current in scan with NI of 11 and 21 were (195.88±69.33) mAs and (54.56±21.54) mAs. All patients with Ⅱ and Ⅲ degree and most patients with Ⅰ degree rib fractures that identified by the scan with NI of 11 were detected by the scan with NI of 21. There were no statistical difference between two scans with the Wilcoxon, signed rank sum test. The diagnostic acceptability and image noise score in the scan with NI of 11 were 4.9±0.2 and 4.6±0.5, and that with NI = 21 were 3.5±0.5 and 3.3±0.5. There was prefect concordance in the inter-observers in diagnostic, acceptability on finding of rib fractures, diagnostic acceptability and image noise (Kappa =0.876, 0.820, 0.792, P<0.01) between two scan protocols. Conclusion: Rib fractures can be diagnosed by the low-dose CT using the scan protocol with NI of 21. (authors)

Bibliometrics analysis of the PubMed literatures on low-dose CT

International Nuclear Information System (INIS)

Wang Qian; Xia Guanghui; Ma Xiaohong; Zhao Xinming

2012-01-01

Objective: The purposes of this study were to evaluate the developmental rule and feature in low-dose CT examinations and to provide useful references for study in the future. Materials and Methods: The journal articles on PubMed from 2002 to 2011 were processed by Thomson Data Analyzer and five aspects were analysed: time, authors, institutions, journals, countries, and keywords. Results: The number of journal articles in low-dose CT examinations were 6 433, 3165 were from US (49.2%), 112 from China (1.4%); 3664 authors (80.42%) published only one article, the famous authors published more than 4 articles; there were 9 core journals in this area. In the last decade, the number and quality of the journal articles in low -dose CT have been dramatically increased. Conclusion: The interest on the low -dose CT examination has been steadily increasing, and world famous research teams have been established. The research in low-dose CT is a multi-discipline involving medicine, medical physics, and mathematics. Cooperation between multiple scientific domains is needed for the future studies. (authors)

Dose reduction in subsecond multislice spiral CT examination of children by online tube current modulation

International Nuclear Information System (INIS)

Greess, H.; Lutze, J.; Noemayr, A.; Bautz, W.; Wolf, H.; Hothorn, T.; Kalender, W.A.

2004-01-01

The potential of online tube current modulation in subsecond multislice spiral CT (MSCT) examinations of children to reduce the dose without a loss in image quality is investigated in a controlled patient study. The dose can be reduced for oval patient sectional view without an increase in noise if the tube current is reduced where the patient diameter and, consequently, attenuation are small. We investigated a product version of an online control for tube current in a SOMATOM Sensation 4 (Siemens, Forchheim). We evaluated image quality, noise and dose reduction for examinations with online tube current modulation in 30 MSCT of thorax/abdomen and abdomen and compared mA s for tube current modulation to the mA s in standard weight-adapted children protocols. Image quality was rated as ''very good,'' ''good,'' ''diagnostic'' and ''poor'' in a consensus by three radiologists. Noise was assessed in comparison to 24 MSCT examinations without tube current modulation measured as SD in ROIs. The dose was reduced from 26 to 43% (mean 36%), depending on the patient's geometry and weight. (orig.)

Whole-body CT. Spiral and multislice CT. 2. tot. rev. and enl. ed.

International Nuclear Information System (INIS)

Prokop, M.; Galanski, M.; Schaefer-Prokop, C.; Molen, A.J. van der

2007-01-01

Spiral and multidetector techniques have improved the diagnostic possibilities of CT, so that image analysis and interpretation have become increasingly complex. This book represents the current state of the art in CT imaging, including the most recent technical scanner developments. The second edition comprises the current state of knowledge in cT imaging. There are new chapters on image processing, application of contrasting agents and radiation dose. All organ-specific pathological findings are discussed in full. There are hints for optimum use and interpretation of CT, including CT angiography, CT colonography, CT-IVPL, and 3D imaging. There is an introduction to cardio-CT, from calcium scoring and CTA of the coronary arteries to judgement of cardiac morphology. There are detailed scan protocols with descriptions of how to go about parameter selection. Practical hints are given for better image quality and lower radiation exposure of patients, guidelines for patient preparation and complication management, and more than 1900 images in optimum RRR quality. (orig.)

Dose assessment of head CT examination by volume scanning with 320-area-detector

International Nuclear Information System (INIS)

Suzuki, Shoichi; Kobayashi, Masanao

2009-01-01

CT with the 320-area-detector (320-ADCT), first presented in 2007, still requires further basic studies, particularly in the field of dose assessment, as the CT has been widely spread in clinic due to its many advantages compared with the usual spiral CT. In this paper, the assessment in the title was thereby done in human phantom and a patient with suspicious acute cerebral infarction under different scanning modes (non-spiral, spiral and volume) for their comparison. Machines for 320-ADCT, and non-spiral and spiral CT were Toshiba Aquilion ONE, and Aquilion 64-MD, respectively. Scanning of the phantom and patient was individually conducted under similar conditions of tube voltage/ current, rotation time and length with the same field of view with defined nominal slice thicknesses. Alderson human body phantom in which 240 thermoluminescent dosimeters were indwelled, was used; doses were read by the thermoluminescence dosimeter (TLD) reader model 3000 (Kyokko Co.) after scanning; and effective doses were calculated with reference to ICRP publ. 102/103 equations for patient's head to be 4.2 (64-MDCT) and 6.6 (320-ADCT) mSv, which were respectively 6.4 and 5.4 mSv when estimated using the conversion coefficient and DLP (dose length product) in the texts. It was suggested that the exposure dose at the volume scanning by 320-ADCT can be reduced in the routine examination, and in the exact diagnosis, possibly increases. These doses can be reduced further by optimization of scanning conditions by additional basic investigations. (K.T.)

Evaluation of the effective dose and image quality of low-dose multi-detector CT for orthodontic treatment planning

International Nuclear Information System (INIS)

Chung, Gi Chung; Han, Won Jeong; Kim, Eun Kyung

2010-01-01

This study was designed to compare the effective doses from low-dose and standard-dose multi-detector CT (MDCT) scanning protocols and evaluate the image quality and the spatial resolution of the low-dose MDCT protocols for clinical use. 6-channel MDCT scanner (Siemens Medical System, Forschheim, Germany), was used for this study. Protocol of the standard-dose MDCT for the orthodontic analysis was 130 kV, 35 mAs, 1.25 mm slice width, 0.8 pitch. Those of the low-dose MDCT for orthodontic analysis and orthodontic surgery were 110 kV, 30 mAs, 1.25 mm slice width, 0.85 pitch and 110 kV, 45 mAs, 2.5 mm slice width, 0.85 pitch. Thermoluminescent dosimeters (TLDs) were placed at 31 sites throughout the levels of adult female ART head and neck phantom. Effective doses were calculated according to ICRP 1990 and 2007 recommendations. A formalin-fixed cadaver and AAPM CT performance phantom were scanned for the evaluation of subjective image quality and spatial resolution. Effective doses in μSv (E2007) were 699.1, 429.4 and 603.1 for standard-dose CT of orthodontic treatment, low-dose CT of orthodontic analysis, and low-dose CT of orthodontic surgery, respectively. The image quality from the low-dose protocol were not worse than those from the standard-dose protocol. The spatial resolutions of both standard-dose and low-dose CT images were acceptable. From the above results, it can be concluded that the low-dose MDCT protocol is preferable in obtaining CT images for orthodontic analysis and orthodontic surgery.

Evaluation of the effective dose and image quality of low-dose multi-detector CT for orthodontic treatment planning

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Chung, Gi Chung; Han, Won Jeong; Kim, Eun Kyung [Department of Oral and Maxillofacial Radiology, School of Dentistry, Dankook University, Cheonan (Korea, Republic of)

2010-03-15

This study was designed to compare the effective doses from low-dose and standard-dose multi-detector CT (MDCT) scanning protocols and evaluate the image quality and the spatial resolution of the low-dose MDCT protocols for clinical use. 6-channel MDCT scanner (Siemens Medical System, Forschheim, Germany), was used for this study. Protocol of the standard-dose MDCT for the orthodontic analysis was 130 kV, 35 mAs, 1.25 mm slice width, 0.8 pitch. Those of the low-dose MDCT for orthodontic analysis and orthodontic surgery were 110 kV, 30 mAs, 1.25 mm slice width, 0.85 pitch and 110 kV, 45 mAs, 2.5 mm slice width, 0.85 pitch. Thermoluminescent dosimeters (TLDs) were placed at 31 sites throughout the levels of adult female ART head and neck phantom. Effective doses were calculated according to ICRP 1990 and 2007 recommendations. A formalin-fixed cadaver and AAPM CT performance phantom were scanned for the evaluation of subjective image quality and spatial resolution. Effective doses in {mu}Sv (E2007) were 699.1, 429.4 and 603.1 for standard-dose CT of orthodontic treatment, low-dose CT of orthodontic analysis, and low-dose CT of orthodontic surgery, respectively. The image quality from the low-dose protocol were not worse than those from the standard-dose protocol. The spatial resolutions of both standard-dose and low-dose CT images were acceptable. From the above results, it can be concluded that the low-dose MDCT protocol is preferable in obtaining CT images for orthodontic analysis and orthodontic surgery.

Feasibility of low-dose contrast medium high pitch CT angiography for the combined evaluation of coronary, head and neck arteries.

Directory of Open Access Journals (Sweden)

Zhiwei Wang

Full Text Available PURPOSE: To evaluate the image quality and radiation dose of combined heart, head, and neck CT angiography (CTA using prospectively electrocardiography (ECG-triggered high-pitch spiral scan protocol, compared with single coronary CTA. MATERIALS AND METHODS: 151 consecutive patients were prospectively included and randomly divided into three groups. Group 1 (n = 47 underwent combined heart, neck, and head CTA using prospectively ECG-triggered high-pitch spiral (Flash scan protocol with a single-phase intravenous injection of iodinated contrast and saline flush; Group 2 (n = 51 underwent single coronary CTA with Flash scan protocol; and Group 3 (n = 53 underwent single coronary CTA with prospective sequence scan protocol. All patients were examined on a dual source CT (Definition FLASH. The image quality was determined for each CT study. RESULTS: Patients of scanning protocol Group 1, 2, and 3 showed no significant differences in age, sex, heart rates, and BMI. Evaluation of coronary artery image quality showed comparable results in the three scanning protocol groups on a per patient-based analysis. In group 1, image quality was found to be sufficient to be diagnostic in all arterial segments of carotid arteries. The mean dose-length product (DLP for group 1 was 256.3±24.5 mGy×cm and was significantly higher in comparison with group 2 (93.4±19.9 mGy×cm; p < 0.001. However, there was no significant difference of DLP between group 1 and group 3 (254.1±69.9 mGy×cm. CONCLUSIONS: The combined heart, neck, and head arteries scan using prospectively electrocardiography (ECG-triggered high-pitch spiral scan protocol in 1 single examination resulted in an excellent opacification of the aorta, the carotid arteries, and the coronary arteries and provided a good image quality with low radiation dose.

Hepatic hemangioma: contrast enhancement patterns on two-phase spiral CT

International Nuclear Information System (INIS)

Yun, Eun Joo; Choi, Byung Ihn; Han, Joon Koo; Jang, Hyun Jung; Kim, Tae Kyoung; Kim, Ah Young; Lee, Ki Yeol

1998-01-01

To evaluate contrast enhancement patterns of hemangioma according to size, as seen during the arterial and portal venous phase of spiral CT. Overall, the most common enhancement pattern was peripheral high (44/82, 53.7%), during the arterial and portal venous phase. The second and third most common patterns were uniform high (11/82, 13.4%) and peripheral high-uniform high (9/82, 11.0%), also during the arterial and portal venous phase. In tumors smaller than 20 mm, low-low attenuation was seen in eight (9.8%), and iso-low attenuation in two (2.4%), during the arterial and portal venous phase, respectively. On two-phase spiral CT, the most common enhancement pattern of hemangioma was peripheral high, seen during the arterial and portal venous phase. However, a small hemangioma less than 2cm may show atypical patterns, including low and iso attenuation. (author). 23 refs., 1 tab., 4 figs

Low-dose X-ray CT reconstruction via dictionary learning.

Science.gov (United States)

Xu, Qiong; Yu, Hengyong; Mou, Xuanqin; Zhang, Lei; Hsieh, Jiang; Wang, Ge

2012-09-01

Although diagnostic medical imaging provides enormous benefits in the early detection and accuracy diagnosis of various diseases, there are growing concerns on the potential side effect of radiation induced genetic, cancerous and other diseases. How to reduce radiation dose while maintaining the diagnostic performance is a major challenge in the computed tomography (CT) field. Inspired by the compressive sensing theory, the sparse constraint in terms of total variation (TV) minimization has already led to promising results for low-dose CT reconstruction. Compared to the discrete gradient transform used in the TV method, dictionary learning is proven to be an effective way for sparse representation. On the other hand, it is important to consider the statistical property of projection data in the low-dose CT case. Recently, we have developed a dictionary learning based approach for low-dose X-ray CT. In this paper, we present this method in detail and evaluate it in experiments. In our method, the sparse constraint in terms of a redundant dictionary is incorporated into an objective function in a statistical iterative reconstruction framework. The dictionary can be either predetermined before an image reconstruction task or adaptively defined during the reconstruction process. An alternating minimization scheme is developed to minimize the objective function. Our approach is evaluated with low-dose X-ray projections collected in animal and human CT studies, and the improvement associated with dictionary learning is quantified relative to filtered backprojection and TV-based reconstructions. The results show that the proposed approach might produce better images with lower noise and more detailed structural features in our selected cases. However, there is no proof that this is true for all kinds of structures.

Evaluation of image quality and dose in thoracic spiral CT examination in patients with pulmonary carcinoma. Preliminary results

International Nuclear Information System (INIS)

Moran-Blanco, L. M.; Rodriguez-Gonzalez, R.; Calzado-Cantera, A.; Arenas de Pablo, A.; Baeza-Trujillo, M.; Cuevas-Ibanez, A.; Garcia-Castano, B.; Gomez-Leon, N.; Turrero-Nogues, A.; Moran-Penco, P.

2002-01-01

We have applied criteria for CT quality defined in the European Guidelines to a samples of thoracic CT examinations for the indication of pulmonary carcinoma of 5 institutions of the Community of Madrid that have spiral CT equipment. The selected examinations have been evaluated independently by five radiologists to determine the degree of adherence to the quality criteria for image defined in the Guidelines s for examinations of general thorax. Dosimetric measurements carried out in parallel have served to estimate the values of CT (CTDI w ) dose indices, dose-length product (DLP) and effective dose for every patient. The result show a high global adherence to the quality criteria (96%), with averages per institution being between 94% (in two institutions) and 98% (in three institutions). There are 10 of 16 criteria that are adhered to in all examinations of the sample: those which are not adhered to systematically are: two of visualization (1.1 and 1.4), with 92-96% fulfillment, and four of critical reproduction (2.6; 2.8; 2.9 and 2.10), with percentages of adherence between 91% and 96%. The average CTDI w values per institution are in the interval 12.9-19.1 mGy; those of DLP between 263 and 577 mGy cm and those of effective dose between 4.2 and 9.2 mSv. The DLP-image quality correlation in institutions with the best image quality was null in two of them and direct and moderate in the third. In both institutions with the poorest image: (Author) 20 refs

Diagnosing extracranial atherosclerotic diseases with spiral CT

International Nuclear Information System (INIS)

Moran, C.J.; Vannier, M.W.; Erickson, K.K.; Broderick, D.F.; Kido, D.K.; Yoffie, R.L.

1991-01-01

This paper reports that this discovery study was performed to determine whether extracranial carotid artery plaques could be diagnosed with a new CT technique (spiral CT) that allows nondistorted three-dimensional (3D) reconstructions in the z axis. Twenty carotid arteries were examined with spiral CT in normal volunteers and in patients suspected of having atherosclerotic plaques in the extracranial carotid arteries. The Somatom Plus CT table was advanced at a constant rate, the x-ray tube was continuously rotated, and 3D data were continuously acquired. Sixty milliliters of nonionic contrast medium was injected intravenously previous to and during the acquisition of data. The carotid bifurcations were identified in all patients. Planar images, similar to conventional intraarterial angiograms, were routinely produced from the volumetric CT data

Low-dose multislice CT in febrile neutropenic patients

International Nuclear Information System (INIS)

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

2005-01-01

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

Low-Dose X-ray CT Reconstruction via Dictionary Learning

Science.gov (United States)

Xu, Qiong; Zhang, Lei; Hsieh, Jiang; Wang, Ge

2013-01-01

Although diagnostic medical imaging provides enormous benefits in the early detection and accuracy diagnosis of various diseases, there are growing concerns on the potential side effect of radiation induced genetic, cancerous and other diseases. How to reduce radiation dose while maintaining the diagnostic performance is a major challenge in the computed tomography (CT) field. Inspired by the compressive sensing theory, the sparse constraint in terms of total variation (TV) minimization has already led to promising results for low-dose CT reconstruction. Compared to the discrete gradient transform used in the TV method, dictionary learning is proven to be an effective way for sparse representation. On the other hand, it is important to consider the statistical property of projection data in the low-dose CT case. Recently, we have developed a dictionary learning based approach for low-dose X-ray CT. In this paper, we present this method in detail and evaluate it in experiments. In our method, the sparse constraint in terms of a redundant dictionary is incorporated into an objective function in a statistical iterative reconstruction framework. The dictionary can be either predetermined before an image reconstruction task or adaptively defined during the reconstruction process. An alternating minimization scheme is developed to minimize the objective function. Our approach is evaluated with low-dose X-ray projections collected in animal and human CT studies, and the improvement associated with dictionary learning is quantified relative to filtered backprojection and TV-based reconstructions. The results show that the proposed approach might produce better images with lower noise and more detailed structural features in our selected cases. However, there is no proof that this is true for all kinds of structures. PMID:22542666

Abdominal spiral CT in children: which radiation exposure is required?

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Wormanns, D.; Diederich, S.; Lenzen, H.; Ludwig, K.; Papke, Karsten; Hagedorn, Claudia; Heindel, Walter [Muenster Univ. (Germany). Inst. fuer Klinische Radiologie; Lange, P.; Link, T.M. [Muenster Univ. (Germany). Inst. fuer Klinische Radiologie; Dept. of Radiology, Technical Univ. Muenchen (Germany)

2001-11-01

We decided to test to what extent dose reduction is possible in abdominal spiral computed tomography (CT) in young children without loss of anatomic diagnostic information. A retrospective study was performed of 30 abdominal CT examinations of children aged 3 months to 7 years. These were divided into two groups: group A with reduced radiation exposure (tube current 50 mA, CT dose index CTDI{sub FDA} {<=}0.83 mGy) and group B with standard radiation exposure (tube current {>=}100 mA, CTDI{sub FDA} {>=}1.66 mGy). Image quality was assessed using a four-part scale ('excellent', 'good', 'sufficient', 'poor') on visual image impression and visibility of 32 anatomical details. Five experienced radiologists read the CT scans independently who were blinded to the examination parameters. Differences in ranked data were evaluated with Wilcoxon's rank sum test. No difference between groups A and B was observed in visual image impression. Detail visibility was significantly lower in group A, but the differences were limited to right upper quadrant structures (portal vein, common bile duct, pancreatic head, adrenals) and to arterial branches. Significant differences in visibility rated as 'poor' were only found for the hepatic, splenic and renal arteries; all other structures showed no difference between groups A and B. A protocol with reduced radiation exposure (50 mA, CTDI{sub FDA} {<=}0.83 mGy) allowed the demonstration of most anatomic structures in abdominal spiral CT in young children. For the precise demonstration of small details (e.g. structures of the right upper quadrant), a protocol with standard radiation exposure ({>=}100 mAs) was superior. (orig.)

CT pulmonary angiography using 64-row multi-slice spiral CT: a comparative study in low tube voltage setting combined with personalized contrast agent application

International Nuclear Information System (INIS)

Zhou Xuhui; Peng Zhenpeng; Zheng Lili; Li Shurong; Yang Zhiyun; Meng Quanfei; Chen Xing

2009-01-01

Objective: To investigate the feasibility of the low tube voltage setting and personalized contrast agent application in 64-row multi-slice spiral CT pulmonary angiography. Methods: Ninety patients with high risk of pulmonary artery embolism were sequentially enrolled in the study and divided into 3 groups employing completely randomized design: (l)Regular group included 30 patients using 120 kV and fixed dose of 70 ml contrast agent, (2)Another 30 patients were in 120 kV group, using 120 kV and the contrast amount was determined according to the patient weight (1.0 ml/kg), (3) The remaining 30 patients were included in 100 kV group, using 100 kV and the contrast amount was also determined according to the patient weight(1.0 ml/kg). Administration of contrast agent was completed within 20 seconds for all the patients, followed by 20 ml of saline. The objective and subjective indexes for assessing CT image quality, CT dose index volume (CTDIvol) and effective received dose (ERD) were compared between 120 kV group and 100 kV group; then the contrast media volume, injection rate, objective CT image indexes and subjective indexes for image quality was compared between the 100 kV group and regular group. The variance analysis and post hoc test were employed for the statistical analysis. Results: Compared with 120 kV group (3.4±0.7), the image quality of 100 kV group (5.2±1.8) had higher noise (52.9%), but subjective index for the image quality demonstrated no differences (q=0.272, P=0.063) in mediastinum window while CTDIvol and ERD decreased for 34.9% [(9.5±0.0) vs (14.6±0.0) mGy] and 36.8% [(3.8±0.6) vs (2.4±0.4) mSv]. The mean CT values on pulmonary artery of 100 kV group[ (269.2±54.7) HU] were 13.4% (31.8/237.4) higher than the 120 kV group [(237.4±62.9)HU], but there was no statistical differences compared to normal group (q=0.172,P=0.260). Conclusion: Using low kV setting (100 kV) to reduce radiation dose is proved to be effective and feasible in 64-MSCT

Low-dose respiratory-gated PET/CT: based on 30 mA tube current

International Nuclear Information System (INIS)

Wu Ping; Li Sijin; Zhang Yanlan; Hao Xinzhong; Qin Zhixing; Yan Min; Cheng Pengliang; Wu Zhifang

2013-01-01

Objective: To establish a low-dose but image-comparable respiratory-gated PET/CT (RG PET/CT) protocol based on 30 mA tube current plus other improved scanning parameters, such as the tube current, the number of respiratory phase and length of breathing cycle. Methods: Twenty-six patients with 18 F-FDG-intaking lung nodules underwent one-bed standard-dose PET/CT (120 mA, 2 min/bed) and low dose RG PET/CT (30 mA, 6 respiratory phases, 1 min/phase). The radiation dose and image quality were analyzed subsequently with signal to noise ratio (SNR) for PET and the homogeneity, noise level for CT in the water phantom respectively. Otherwise the CT images were both visual evaluated by two experienced doctors. In addition, different respiratory cycle was simulated to observe its relation with radiation dose. Results: The effective dose of low-dose RG PET/CT was 4.88∼7.69 mSv [mean (5.68±0.83) mSv]. The PET SNR showed no significance between groups. The homogeneity of 30 mA is good (< 5 HU), although noise level was high, the visual character like lobulation, speculation of lung nodule was superior in some respiratory phases. The radiation dose was positively correlated with respiratory cycle. Conclusions: The performance of low-dose RG PET/CT was comparable to those of standard-dose PET/CT based on a protocol with 30 mA tube current, 6 respiratory phases and breathing state of eupnoea. It produced a much lower radiation exposure and the image quality was enough for clinical use such as delineation of tumor active target, characterization and staging of lung nodules, etc. (authors)

Low-dose helical computed tomography (CT) in the perioperative workup of adolescent idiopathic scoliosis

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Abul-Kasim, Kasim; Overgaard, Angelica; Maly, Pavel [Malmoe University Hospital, Department of Radiology, Section of Neuroradiology, University of Lund, Malmoe (Sweden); Ohlin, Acke [Malmoe University Hospital, Department of Orthopaedic Surgery, University of Lund, Malmoe (Sweden); Gunnarsson, Mikael [Malmoe University Hospital, Department of Radiation Physics, University of Lund, Malmoe (Sweden); Sundgren, Pia C. [University of Michigan Health Systems, Department of Radiology, Division of Neuroradiology, Ann Arbor (United States)

2009-03-15

The study aims were to estimate the radiation dose in patients examined with low dose spine CT and to compare it with that received by patients undergoing standard CT for trauma of the same region, as well as to evaluate the impact of dose reduction on image quality. Radiation doses in 113 consecutive low dose spine CTs were compared with those in 127 CTs for trauma. The inter- and intraobserver agreement in measurements of pedicular width, and vertebral rotation, measurements of signal-to-noise ratio and assessment of hardware status were the indicators in the evaluation of image quality. The effective dose of the low dose spine CT (0.37 mSv) was 20 times lower than that of a standard CT for trauma (13.09 mSv). This dose reduction conveyed no impact on image quality. This low dose spine CT protocol allows detailed evaluation that is necessary for preoperative planning and postoperative evaluation. (orig.)

Comparison of Adsorbed Skin Dose Received by Patients in Cone Beam Computed Tomography, Spiral and Conventional Computed Tomography Scanninng

Directory of Open Access Journals (Sweden)

Rahimi A

2011-12-01

Full Text Available Background and Aims: The evaluation of absorbed dose received by patients could give useful information for radiation risk estimation. This study was performed to compare the entrance skin dose received by patients in cone beam computed tomography (CBCT, conventional and spiral computed tomography (CT.Materials and Methods: In this experimental study, 81 calibrated TLD chips were used. the TLD chips were placed on facial, thyroid and end of sternum skin surface in patients referred for CT of the paranasal sinuses(3 TLD chips for each area to estimate the absorbed dose received by central part of radiation field, thyroid and out of field areas, respectively. The data were analyzed using one-way ANOVA and Tukey tests. Results: The dose delivered to the center of irradiated field was about 0.79±0.09 mGy in CBCT technique compared with 16.31±3.71 and 18.84±4.12 mGy for spiral and conventional CT, respectively. The received dose by the out of field areas was about 54 percent of central area dose. There was statistical significant relationship between the imaging modalities and absorbed dose received by patients (P=0.016. The least absorbed dose was for CBCT and the greatest dose was for conventional CT imaging technique.Conclusion: The dose delivered to central area of irradiated field in conventional and spiral CT imaging modalities was about 24 times greater than of that in CBCT. Also, the highest received dose was for central area of radiated field and the lowest dose was for the out of field areas.

Lung cancer screening with low-dose CT

International Nuclear Information System (INIS)

Diederich, S.; Wormanns, D.; Heindel, W.

2003-01-01

Screening for lung cancer is hoped to reduce mortality from this common tumour, which is characterised by a dismal overall survival, relatively well defined risk groups (mainly heavy cigarette smokers and workers exposed to asbestos) and a lack of early symptoms. In the past studies using sputum cytology and chest radiography have failed to demonstrate any reduction in lung cancer mortality through screening. One of the reasons is probably the relatively poor sensitivity of both these tests in early tumours. Low radiation dose computed tomography (CT) has been shown to have a much higher sensitivity for small pulmonary nodules, which are believed to be the most common presentation of early lung cancer. As, however, small pulmonary nodules are common and most are not malignant, non-invasive diagnostic algorithms are required to correctly classify the detected lesions and avoid invasive procedures in benign nodules. Nodule density, size and the demonstration of growth at follow-up have been shown to be useful in this respect and may in the future be supplemented by contrast-enhanced CT and positron emission tomography. Based on these diagnostic algorithms preliminary studies of low-dose CT in heavy smokers have demonstrated a high proportion of asymptomatic, early, resectable cancers with good survival. As, however, several biases could explain these findings in the absence of the ultimate goal of cancer screening, i.e. mortality reduction, most researchers believe that randomised controlled trials including several 10000 subjects are required to demonstrate a possible mortality reduction. Only then general recommendations to screen individuals at risk of lung cancer with low-dose CT should be made. It can be hoped that international cooperation will succeed in providing results as early as possible

Pulmonary embolism: spiral CT evaluation; Embolie pulmonaire: apport de la tomodensitometrie helicoidale

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Senac, J.P.; Vernhet, H.; Bousquet, C.; Giron, J.; Pieuchot, P.; Durand, G.; Benezet, O.; Aubas, P. [Centre Hospitalier Universitaire, 34 - Montpellier (France)

1995-06-01

Purpose: Spiral computed tomography was compared retrospectively with digital substraction pulmonary angiography (PA) in 45 patients suspected of having acute or chronic pulmonary embolism. Materials and method : 45 patients in whom the presence of acute or chronic pulmonary embolism was suspected underwent examination by spiral CT and PA. Diagnosis of pulmonary embolism was based on the direct visualization of intraluminal clots. The study of the agreement between the two methods was based on the Kappa test. In 35 cases, pulmonary emboli were proved. Acute pulmonary emboli were present in 28 cases and chronic in 7 cases. Results: Spiral computed tomography represents an excellent way to detect acute pulmonary embolism. In the chronic form, spiral CT is better than PA to detect intraluminal clots. However, Spiral CT can fail to detect small emboli in the peripheral arterial bed. In the 10 patients without pulmonary embolism, the spiral CT proved diagnosis pulmonary oedema (n=3), lymphangi-carcinoma (n=4), pleural effusion (n=3). Conclusion: This study suggest that the spiral CT examination is accurate for diagnosis of pulmonary embolism specifically in case of suspected important embolism. The advantages of spiral CT are multiple (non invasive, wide diagnosis spectrum). However, may be a limitation to is use is insufficient distal thrombi detection. This eventuality (5 to 10% in the Pioped study) justify the practice of pulmonary angiography. Spiral CT improvements should reduce this insufficiency in the next future. (Authors). 16 refs., 4 figs., 3 tabs.

Spiral CT-angiography of the aorta

NARCIS (Netherlands)

Balm, R.; Eikelboom, B. C.; van Leeuwen, M. S.; Noordzij, J.

1994-01-01

AIMS: To determine whether the new technique of CT-angiography was accurate in displaying the complex anatomy of the aorta and its major branches. METHODS: Seventeen patients with a variety of aortic pathology were examined. Using a spiral CT-scanner a volumetric scan was made during injection of

In-vitro studies to determine the degree of stenosis using spiral-CT angiography

International Nuclear Information System (INIS)

Wittenberg, G.; Lenk, G.; Jenett, M.; Elsner, H.; Kaiser, W.A.; Kellner, M.; Schultz, G.; Trusen, A.; Hahn, D.

1998-01-01

Purpose: Aim of the study was to evaluate the influence of different spiral-CT parameters for the visualisation of vascular stenoses, especially of the renal arteries. Material and methods: Models with a density equivalent to that of fat, filled with diluted contrast agent, and an inner lumen of 4, 6, 8 mm were scanned in x-, y- and z-direction. Data were acquired in up to 24 second long spiral-CT scans using different spiral-CT parameters (collimation, table speed, reconstruction algorithm, tube current). Detection of the degree of stenosis was achieved by assessment of the axial images and 3D reconstructions. Results: The best correlation between real and measured degree of stenosis was seen by using a small collimation, a low table increment and assessment of the axial images reconstructed in standard algorithm. The stenosis degrees of models directed in x- and y-direction were overestimated and those in z-direction were underestimated depending on the spiral-CT parameters. Conclusion: For optimal imaging of renal artery stenoses, collimation of 2 mm (pitch=1-2) and a reconstruction interval of 1 mm is recommended. (orig.) [de

Feasibility study of automatic tube current modulation in low-dose thoracic imaging for young children with 64-slice spiral CT

International Nuclear Information System (INIS)

Peng Yun; Li Jianyin; Zhang Qifeng; Liu Yue; Wang Bei; Zheng Jinjin

2008-01-01

Objective: To assess the feasibility of using an automatic tube current modulation (ATCM) method to obtain consistent image quality with reduced radiation dose for young children undergoing chest scans with a set of 64-slice spiral CT. Methods: Fifty young children underwent chest scans on a GE 64-slice VCT with automatic tube current modulation. The noise index (NI) for this study group was set to 8 or 9 based on the proposed reference for pediatric chest imaging in our hospital. We compared image quality and radiation dose for the study group with the age-matched control group of 50 young children acquired with standard protocol of fixed-mAs (120 and 150 mAs for under 1 and above 1 year old, respectively). The volume CT dose index(CTDIvol) values were recorded for both groups. Two experienced pediatric radiologists assessed image quality on a 5-point scale with 5 being the best. Scores greater than or equal to 3 were considered clinically acceptable. The degree of interobserver concordance was determined by Kappa statistics. Results: The average objective image noise and CTDIvol for control group was (4.78±0.58) and (6.68±0.62) mGy, respectively. For the study group the mean value of objective mAs was (41.6±11.6) (20-79 mAs) with mean CTDIvol of (2.34±0.71) mGy, and the use of ATCM produced mean noise of (7.84±0.66). The average CTDIvol with the use of NI of 8-9 was about 65% lower than that with the fixed mAs setting. The mean image quality score for the study group and control group was (3.46±0.40) and (4.65±0.46) respectively. All studies had acceptable image quality, and there was good inter-observer agreement in diagnostic acceptability (Kappa=0.474 and 0.536). Conclusion: The automatic tube current modulation method could be used to obtain consistent image quality for young children undergoing 64-slice MSCT chest scans. With proper noise level setting (NI=8 or 9), one may obtain clinically acceptable images with much reduced radiation dose. (authors)

Benefits of sinogram-affirmed iterative reconstruction in 0.4 mSv ultra-low-dose CT of the upper abdomen following transarterial chemoembolisation: comparison to low-dose and standard-dose CT and filtered back projection technique

International Nuclear Information System (INIS)

Bodelle, B.; Isler, S.; Scholtz, J.-E.; Frellesen, C.; Luboldt, W.; Vogl, T.J.; Beeres, M.

2016-01-01

Aim: To evaluate the advantage of sinogram-affirmed iterative reconstruction (SIR) compared to filtered back projection (FBP) in upper abdomen computed tomography (CT) after transarterial chemoembolisation (TACE) at different tube currents. Materials and methods: The study was approved by the institutional review board. Written informed consent was obtained from all patients. Post-TACE CT was performed with different tube currents successively varied in four steps (180, 90, 45 and 23 mAs) with 40 patients per group (mean age: 60±12 years, range: 23–85 years, sex: 70 female, 90 male). The data were reconstructed with standard FBP and five different SIR strengths. Image quality was independently rated by two readers on a five-point scale. High (Lipiodol-to-liver) as well as low (liver-to-fat) contrast-to-noise ratios (CNRs) were intra-individually compared within one dose to determine the optimal strength (S1–S5) and inter-individually between different doses to determine the possibility of dose reduction using the Kruskal–Wallis test. Results: Subjective image quality and objective CNR analysis were concordant: intra-individually, SIR was significantly (p<0.001) superior to FBP. Inter-individually, regarding different doses (180 versus 23 ref mAs), there was no significant (p=1.00) difference when using S5 SIR at 23 mAs instead of FBP. Conclusion: SIR allows for an 88% dose reduction from 3.43 to 0.4 mSv in unenhanced CT of the liver following TACE without subjective or objective loss in image quality. - Highlights: • Diagnostic image quality and radiation dose of ultra-low-dose CT of the upper abdomen using sinogram affirmed iterative reconstruction following transarterial chemoembolization in comparison to low-dose and standard dose CT and filtered back projection technique. • Ultra-low dose CT of the upper abdomen using sinogram affirmed iterative reconstruction allows for significant dose reduction by 88%. • Ultra-low dose CT of the upper abdomen

Coronary artery stent imaging with 128-slice dual-source CT using high-pitch spiral acquisition in a cardiac phantom: comparison with the sequential and low-pitch spiral mode

International Nuclear Information System (INIS)

Wolf, Florian; Loewe, Christian; Plank, Christina; Schernthaner, Ruediger; Bercaczy, Dominik; Lammer, Johannes; Leschka, Sebastian; Goetti, Robert; Marincek, Borut; Alkadhi, Hatem; Homolka, Peter; Friedrich, Guy; Feuchtner, Gudrun

2010-01-01

To evaluate coronary stents in vitro using 128-slice-dual-source computed tomography (CT). Twelve different coronary stents placed in a non-moving cardiac/chest phantom were examined by 128-slice dual-source CT using three CT protocols [high-pitch spiral (HPS), sequential (SEQ) and conventional spiral (SPIR)]. Artificial in-stent lumen narrowing (ALN), visible inner stent area (VIA), artificial in-stent lumen attenuation (ALA) in percent, image noise inside/outside the stent and CTDIvol were measured. Mean ALN was 46% for HPS, 44% for SEQ and 47% for SPIR without significant difference. Mean VIA was similar with 31% for HPS, 30% for SEQ and 33% for SPIR. Mean ALA was, at 5% for HPS, significantly lower compared with -11% for SPIR (p = 0.024), but not different from SEQ with -1%. Mean image noise was significantly higher for HPS compared with SEQ and SPIR inside and outside the stent (p < 0.001). CTDIvol was lower for HPS (5.17 mGy), compared with SEQ (9.02 mGy) and SPIR (55.97 mGy), respectively. The HPS mode of 128-slice dual-source CT yields fewer artefacts inside the stent lumen compared with SPIR and SEQ, but image noise is higher. ALN is still too high for routine stent evaluation in clinical practice. Radiation dose of the HPS mode is markedly (less than about tenfold) reduced. (orig.)

Three-dimensional spiral CT for neurosurgical planning.

Science.gov (United States)

Klein, H M; Bertalanffy, H; Mayfrank, L; Thron, A; Günther, R W; Gilsbach, J M

1994-08-01

We carried out 22 examinations to determine the value of three-dimensional (3D) volumetric CT (spiral CT) for planning neurosurgical procedures. All examinations were carried out on a of the first generation spiral CT. A tube model was used to investigate the influence of different parameter settings. Bolus injection of nonionic contrast medium was used when vessels or strongly enhancing tumours were to be delineated. 3D reconstructions were carried out using the integrated 3D software of the scanner. We found a table feed of 3 mm/s with a slice thickness of 2 mm and an increment of 1 mm to be suitable for most purposes. For larger regions of interest a table feed of 5 mm was the maximum which could be used without blurring of the 3D images. Particular advantages of 3D reconstructed spiral scanning were seen in the planning of approaches to the lower clivus, acquired or congenital bony abnormalities and when the relationship between vessels, tumour and bone was important.

Three-dimensional spiral CT for neurosurgical planning

International Nuclear Information System (INIS)

Klein, H.M.; Bertalanffy, H.; Mayfrank, L.; Thron, A.; Guenther, R.W.; Gilsbach, J.M.

1994-01-01

We carried out 22 examinations to determine the value of three-dimensional (3D) volumetric CT (spiral CT) for planning neurosurgical procedures. All examinations were carried out on a of the first generation spiral CT. A tube model was used to investigate the influence of different parameter settings. Bolus injection of nonionic contrast medium was used when vessels or strongly enhancing tumours were to be delineated. 3D reconstructions were carried out using the integrated 3D software of the scanner. We found a table feed of 3 mm/s with a slice thickness of 2 mm and an increment of 1 mm to be suitable for most purposes. For larger regions of interest a table feed of 5 mm was the maximum which could be used without blurring of the 3D images. Particular advantages of 3D reconstructed spiral scanning were seen in the planning of approaches to the lower clivus, acquired or congenital bony abnormalities and when the relationship between vessels, tumour and bone was important. (orig.)

Dual-source spiral CT with pitch up to 3.2 and 75 ms temporal resolution: image reconstruction and assessment of image quality.

Science.gov (United States)

Flohr, Thomas G; Leng, Shuai; Yu, Lifeng; Aiimendinger, Thomas; Bruder, Herbert; Petersilka, Martin; Eusemann, Christian D; Stierstorfer, Karl; Schmidt, Bernhard; McCollough, Cynthia H

2009-12-01

To present the theory for image reconstruction of a high-pitch, high-temporal-resolution spiral scan mode for dual-source CT (DSCT) and evaluate its image quality and dose. With the use of two x-ray sources and two data acquisition systems, spiral CT exams having a nominal temporal resolution per image of up to one-quarter of the gantry rotation time can be acquired using pitch values up to 3.2. The scan field of view (SFOV) for this mode, however, is limited to the SFOV of the second detector as a maximum, depending on the pitch. Spatial and low contrast resolution, image uniformity and noise, CT number accuracy and linearity, and radiation dose were assessed using the ACR CT accreditation phantom, a 30 cm diameter cylindrical water phantom or a 32 cm diameter cylindrical PMMA CTDI phantom. Slice sensitivity profiles (SSPs) were measured for different nominal slice thicknesses, and an anthropomorphic phantom was used to assess image artifacts. Results were compared between single-source scans at pitch = 1.0 and dual-source scans at pitch = 3.2. In addition, image quality and temporal resolution of an ECG-triggered version of the DSCT high-pitch spiral scan mode were evaluated with a moving coronary artery phantom, and radiation dose was assessed in comparison with other existing cardiac scan techniques. No significant differences in quantitative measures of image quality were found between single-source scans at pitch = 1.0 and dual-source scans at pitch = 3.2 for spatial and low contrast resolution, CT number accuracy and linearity, SSPs, image uniformity, and noise. The pitch value (1.6 pitch 3.2) had only a minor impact on radiation dose and image noise when the effective tube current time product (mA s/pitch) was kept constant. However, while not severe, artifacts were found to be more prevalent for the dual-source pitch = 3.2 scan mode when structures varied markedly along the z axis, particularly for head scans. Images of the moving coronary artery phantom

Dual-source spiral CT with pitch up to 3.2 and 75 ms temporal resolution: Image reconstruction and assessment of image quality

International Nuclear Information System (INIS)

Flohr, Thomas G.; Leng Shuai; Yu Lifeng; Allmendinger, Thomas; Bruder, Herbert; Petersilka, Martin; Eusemann, Christian D.; Stierstorfer, Karl; Schmidt, Bernhard; McCollough, Cynthia H.

2009-01-01

Purpose: To present the theory for image reconstruction of a high-pitch, high-temporal-resolution spiral scan mode for dual-source CT (DSCT) and evaluate its image quality and dose. Methods: With the use of two x-ray sources and two data acquisition systems, spiral CT exams having a nominal temporal resolution per image of up to one-quarter of the gantry rotation time can be acquired using pitch values up to 3.2. The scan field of view (SFOV) for this mode, however, is limited to the SFOV of the second detector as a maximum, depending on the pitch. Spatial and low contrast resolution, image uniformity and noise, CT number accuracy and linearity, and radiation dose were assessed using the ACR CT accreditation phantom, a 30 cm diameter cylindrical water phantom or a 32 cm diameter cylindrical PMMA CTDI phantom. Slice sensitivity profiles (SSPs) were measured for different nominal slice thicknesses, and an anthropomorphic phantom was used to assess image artifacts. Results were compared between single-source scans at pitch=1.0 and dual-source scans at pitch=3.2. In addition, image quality and temporal resolution of an ECG-triggered version of the DSCT high-pitch spiral scan mode were evaluated with a moving coronary artery phantom, and radiation dose was assessed in comparison with other existing cardiac scan techniques. Results: No significant differences in quantitative measures of image quality were found between single-source scans at pitch=1.0 and dual-source scans at pitch=3.2 for spatial and low contrast resolution, CT number accuracy and linearity, SSPs, image uniformity, and noise. The pitch value (1.6≤pitch≤3.2) had only a minor impact on radiation dose and image noise when the effective tube current time product (mA s/pitch) was kept constant. However, while not severe, artifacts were found to be more prevalent for the dual-source pitch=3.2 scan mode when structures varied markedly along the z axis, particularly for head scans. Images of the moving

Dual-source spiral CT with pitch up to 3.2 and 75 ms temporal resolution: Image reconstruction and assessment of image quality

Energy Technology Data Exchange (ETDEWEB)

Flohr, Thomas G.; Leng Shuai; Yu Lifeng; Allmendinger, Thomas; Bruder, Herbert; Petersilka, Martin; Eusemann, Christian D.; Stierstorfer, Karl; Schmidt, Bernhard; McCollough, Cynthia H. [Siemens Healthcare, Computed Tomography, 91301 Forchheim, Germany and Department of Diagnostic Radiology, Eberhard-Karls-Universitaet, 72076 Tuebingen (Germany); Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905 (United States); Siemens Healthcare, Computed Tomography, 91301 Forchheim (Germany); Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905 (United States)

2009-12-15

Purpose: To present the theory for image reconstruction of a high-pitch, high-temporal-resolution spiral scan mode for dual-source CT (DSCT) and evaluate its image quality and dose. Methods: With the use of two x-ray sources and two data acquisition systems, spiral CT exams having a nominal temporal resolution per image of up to one-quarter of the gantry rotation time can be acquired using pitch values up to 3.2. The scan field of view (SFOV) for this mode, however, is limited to the SFOV of the second detector as a maximum, depending on the pitch. Spatial and low contrast resolution, image uniformity and noise, CT number accuracy and linearity, and radiation dose were assessed using the ACR CT accreditation phantom, a 30 cm diameter cylindrical water phantom or a 32 cm diameter cylindrical PMMA CTDI phantom. Slice sensitivity profiles (SSPs) were measured for different nominal slice thicknesses, and an anthropomorphic phantom was used to assess image artifacts. Results were compared between single-source scans at pitch=1.0 and dual-source scans at pitch=3.2. In addition, image quality and temporal resolution of an ECG-triggered version of the DSCT high-pitch spiral scan mode were evaluated with a moving coronary artery phantom, and radiation dose was assessed in comparison with other existing cardiac scan techniques. Results: No significant differences in quantitative measures of image quality were found between single-source scans at pitch=1.0 and dual-source scans at pitch=3.2 for spatial and low contrast resolution, CT number accuracy and linearity, SSPs, image uniformity, and noise. The pitch value (1.6{<=}pitch{<=}3.2) had only a minor impact on radiation dose and image noise when the effective tube current time product (mA s/pitch) was kept constant. However, while not severe, artifacts were found to be more prevalent for the dual-source pitch=3.2 scan mode when structures varied markedly along the z axis, particularly for head scans. Images of the moving

Prospectively Electrocardiogram-Gated High-Pitch Spiral Acquisition Mode Dual-Source CT Coronary Angiography in Patients with High Heart Rates: Comparison with Retrospective Electrocardiogram-Gated Spiral Acquisition Mode

Energy Technology Data Exchange (ETDEWEB)

Sun, Kai; Ma, Rui; Wang, Li Jun [Dept. of Radiology, Baotou Central Hospital, Baotou (China); Li, Li Gang; Chen, Jiu Hong [CT BM Clinic Marketing, Siemens Healthcare, Beijing (China)

2012-11-15

To assess the image quality and effective radiation dose of prospectively electrocardiogram (ECG)-gated high-pitch spiral acquisition mode (flash mode) of dual-source CT (DSCT) coronary angiography (CTCA) in patients with high heart rates (HRs) as compared with retrospectively ECG-gated spiral acquisition mode. Two hundred and sixty-eight consecutive patients (132 female, mean age: 55 {+-} 11 years) with mean HR > 65 beats per minute (bpm) were prospectively included in this study. The patients were divided into two groups. Collection was performed in group A CTCA using flash mode setting at 20-30% of the R-R interval, and retrospectively ECG-gated spiral acquisition mode in group B. The image noise, contrast-to-noise ratio (CNR), image quality scores, effective radiation dose and influencing factors on image quality between the two groups were assessed. There were no significant differences in image quality scores and proportions of non-diagnostic coronary artery segments between two groups (image quality scores: 1.064 {+-} 0.306 [group A] vs. 1.084 {+-} 0.327 [group B], p = 0.063; proportion of non-diagnostic coronary artery segments: segment-based analysis 1.52% (group A) vs. 1.74% (group B), p = 0.345; patient-based analysis 7.5% (group A) vs. 6.7% (group B), p = 0.812). The estimated radiation dose was 1.0 {+-} 0.16 mSv in group A and 7.1 {+-} 1.05 mSv in group B (p = 0.001). In conclusion, in patients with HRs > 65 bpm without cardiac arrhythmia, the prospectively high-pitch spiral-acquisition mode with image-acquired timing set at 20-30% of the R-R interval provides a similar image quality and low rate of non-diagnostic coronary segments to the retrospectively ECG-gated low-pitch spiral acquisition mode, with significant reduction of radiation exposure.

Prospectively Electrocardiogram-Gated High-Pitch Spiral Acquisition Mode Dual-Source CT Coronary Angiography in Patients with High Heart Rates: Comparison with Retrospective Electrocardiogram-Gated Spiral Acquisition Mode

International Nuclear Information System (INIS)

Sun, Kai; Ma, Rui; Wang, Li Jun; Li, Li Gang; Chen, Jiu Hong

2012-01-01

To assess the image quality and effective radiation dose of prospectively electrocardiogram (ECG)-gated high-pitch spiral acquisition mode (flash mode) of dual-source CT (DSCT) coronary angiography (CTCA) in patients with high heart rates (HRs) as compared with retrospectively ECG-gated spiral acquisition mode. Two hundred and sixty-eight consecutive patients (132 female, mean age: 55 ± 11 years) with mean HR > 65 beats per minute (bpm) were prospectively included in this study. The patients were divided into two groups. Collection was performed in group A CTCA using flash mode setting at 20-30% of the R-R interval, and retrospectively ECG-gated spiral acquisition mode in group B. The image noise, contrast-to-noise ratio (CNR), image quality scores, effective radiation dose and influencing factors on image quality between the two groups were assessed. There were no significant differences in image quality scores and proportions of non-diagnostic coronary artery segments between two groups (image quality scores: 1.064 ± 0.306 [group A] vs. 1.084 ± 0.327 [group B], p = 0.063; proportion of non-diagnostic coronary artery segments: segment-based analysis 1.52% (group A) vs. 1.74% (group B), p = 0.345; patient-based analysis 7.5% (group A) vs. 6.7% (group B), p = 0.812). The estimated radiation dose was 1.0 ± 0.16 mSv in group A and 7.1 ± 1.05 mSv in group B (p = 0.001). In conclusion, in patients with HRs > 65 bpm without cardiac arrhythmia, the prospectively high-pitch spiral-acquisition mode with image-acquired timing set at 20-30% of the R-R interval provides a similar image quality and low rate of non-diagnostic coronary segments to the retrospectively ECG-gated low-pitch spiral acquisition mode, with significant reduction of radiation exposure.

Detection of pulmonary metastatic nodules: usefulness of low-dose multidetector CT in comparison with chest radiograph

International Nuclear Information System (INIS)

Kim, Ki Nam; Lee, Ki Nam; Yang, Doo Kyung; Lee, Soo Keol

2006-01-01

We wanted to evaluate the usefulness of low-dose multidetector CT for the detection and follow-up of pulmonary metastatic nodules in patients suffering with malignancy. We retrospectively reviewed the conventional chest radiographs and low-dose multidetector CT (low-dose CT) scans of 81 patients who had been under the diagnosis of malignancy. We reviewed the detection of pulmonary nodules and we counted the number of nodules detected by each method. The nodules were confirmed by surgical operation and by the radiologic criteria. The accuracy, sensitivity, specificity and positive and negative predictive values of each method for detecting metastatic nodules were compared with χ 2 tests. Low-dose CT depicted more nodules than did chest radiograph, and the indeterminate nodules seen on chest radiograph may be clearly benign on low-dose CT (eg. calcified granulomas or bony lesions). The accuracy of low-dose CT (75.3%) was significantly higher than that of chest radiograph (49.4%) for the detection for metastatic nodules (ρ < 0.05). Low-dose CT may provide better information than does chest radiograph for diagnosing pulmonary metastasis

Application of low-dose radiation protocols in survey CT scans

International Nuclear Information System (INIS)

Fu Qiang; Liu Ting; Lu Tao; Xu Ke; Zhang Lin

2009-01-01

Objective: To characterize the protocols with low-dose radiation in survey CT scans for localization. Methods: Eighty standard adult patients, head and body phantoms were recruited. Default protocols provided by operator's manual setting were that all the tube voltage for head, chest, abdomen and lumbar was 120 kV; the tube currents were 20,10,20 and 40 mA, respectively. Values of kV and mA in the low-dose experiments were optimized according to the device options. For chest and abdomen, the tube position were compared between default (0 degree) and 180 degree. Phantoms were scanned with above protocols, and the radiation doses were measured respectively. Paired t-test were used for comparisons of standard deviation in CT value, noise and exposure surface dose (ESD) between group with default protocols and group with optimized protocols. Results: The optimized protocols in low-dose CT survey scans were 80 kV, 10 mA for head, 80 kV, 10 mA for chest, 80 kV, 10 mA for abdomen and 100 kV, 10 mA for lumbar. The values of ESD for phantom scan in default and optimized protocols were 0.38 mGy/0.16 mGy in head, 0.30 mGy/0.20 mGy in chest, 0.74 mGy/0.30 mGy in abdomen and 0.81 mGy/0.44 mGy in lumbar, respectively. Compared with default protocols, the optimized protocols reduced the radiation doses 59%, 33%, 59% and 46% in head, chest, abdomen and lumbar. When tube position changed from 0 degree to 180 degree, the ESD were 0.24 mGy/0.20 mGy for chest; 0.37 mGy/0.30 mGy for abdomen, and the radiation doses were reduced 20% and 17%. Conclusion: A certain amount of image noise is increased in low-dose protocols, but image quality is still acceptable without problem in CT localization. The reduction of radiation dose and the radiation harm to patients are the superiority. (authors)

Automatic detection of pulmonary nodules at spiral CT: clinical application of a computer-aided diagnosis system

International Nuclear Information System (INIS)

Wormanns, Dag; Fiebich, Martin; Saidi, Mustafa; Diederich, Stefan; Heindel, Walter

2002-01-01

The aim of this study was to evaluate a computer-aided diagnosis (CAD) workstation with automatic detection of pulmonary nodules at low-dose spiral CT in a clinical setting for early detection of lung cancer. Eighty-eight consecutive spiral-CT examinations were reported by two radiologists in consensus. All examinations were reviewed using a CAD workstation with a self-developed algorithm for automatic detection of pulmonary nodules. The algorithm is designed to detect nodules with diameters of at least 5 mm. A total of 153 nodules were detected with at least one modality (radiologists in consensus, CAD, 85 nodules with diameter <5 mm, 68 with diameter ≥5 mm). The results of automatic nodule detection were compared to nodules detected with any modality as gold standard. Computer-aided diagnosis correctly identified 26 of 59 (38%) nodules with diameters ≥5 mm detected by visual assessment by the radiologists; of these, CAD detected 44% (24 of 54) nodules without pleural contact. In addition, 12 nodules ≥5 mm were detected which were not mentioned in the radiologist's report but represented real nodules. Sensitivity for detection of nodules ≥5 mm was 85% (58 of 68) for radiologists and 38% (26 of 68) for CAD. There were 5.8±3.6 false-positive results of CAD per CT study. Computer-aided diagnosis improves detection of pulmonary nodules at spiral CT and is a valuable second opinion in a clinical setting for lung cancer screening despite of its still limited sensitivity. (orig.)

Vascular imaging with spiral CT. The way to CY angiography

International Nuclear Information System (INIS)

Prokop, M.; Schaefer, C.; Kalender, W.A.; Polacin, A.; Galanski, M.

1993-01-01

Spiral CT is a technique that allows for high-quality two-dimensional angiographic projections and 3D imaging of vascular structures. The authors present the technical and methodological principles of the technique, including scan parameters and parameters of contrast application for various clinical imaging tasks. They present their experience with over 150 clinical cases using spiral CT angiography. Suitable applications of this technique include cogenital anomalies, aneurysms, dissections, stenoses, thrombi and vascular tumor involvement. Given a problem-adapted examination technique, pathologic changes in vessels of as little as 2 mm can be visualized. In some cases with complex vascular anatomy, spiral CT angiography can be superior to arterial angiography. (orig.) [de

Ultra-low-dose CT imaging of the thorax: decreasing the radiation dose by one order of magnitude

International Nuclear Information System (INIS)

Lambert, Lukas; Banerjee, Rohan; Votruba, Jiri; El-Lababidi, Nabil; Zeman, Jiri

2016-01-01

Computed tomography (CT) is an indispensable tool for imaging of the thorax and there is virtually no alternative without associated radiation burden. The authors demonstrate ultra-low-dose CT of the thorax in three interesting cases. In an 18-y-old girl with rheumatoid arthritis, CT of the thorax identified alveolitis in the posterior costophrenic angles (radiation dose = 0.2 mSv). Its resolution was demonstrated on a follow-up scan (4.2 mSv) performed elsewhere. In an 11-y-old girl, CT (0.1 mSv) showed changes of the right collar bone consistent with chronic recurrent multifocal osteomyelitis. CT (0.1 mSv) of a 9-y-old girl with mucopolysaccharidosis revealed altogether three hamartomas, peribronchial infiltrate, and spine deformity. In some indications, the radiation dose from CT of the thorax can approach that of several plain radiographs. This may help the pediatrician in deciding whether 'gentle' ultra-low-dose CT instead of observation or follow-up radiographs will alleviate the uncertainty of the diagnosis with little harm to the child. (author)

Floating venous thrombi: diagnosis with spiral-CT-venography

International Nuclear Information System (INIS)

Gartenschlaeger, M.; Schmidt, J.A.

1996-01-01

Local application of contrast agent into an ipsilateral dorsal foot vein and spiral CT were used to examine 16 consecutive cases with deep venous thrombosis proven at conventional venography; in addition, colour Doppler flow imaging was performed. At conventional venography, 8/16 thrombi appeared to be floating and the remaining 8/16 were adherent to the vessel wall. Spiral-CT showed 15/16 thrombi to be adherent to the vessel wall; the floating thrombus correlated with findings in conventional venography. At colour Doppler flow imaging 3/16 thrombi were considered floating, one of them was discordant to conventional venography. The comparison of conventional venography to spiral-CT demonstrates complete agreement for adherence to vessel wall seen in conventional venography (p=1,0) and significant discordance in cases with free-floating appearance in conventional venography. Adherence of thrombi to the wall of the vessel at conventional venography is in agreement with computed tomography. Conventional venography probably overestimates the prevalence of free floating thrombi. (orig./MG) [de

Prevalence of ligamentum arteriosum calcification on multi-section spiral CT and digital radiography.

Science.gov (United States)

Hong, Gil-Sun; Goo, Hyun Woo; Song, Jae-Woo

2012-06-01

To investigate the prevalence of ligamentum arteriosum calcification (LAC) on multi-section spiral CT and digital radiography. Five hundred and eight children and 232 adults who performed multi-section chest CT were included in this study and were divided into nine age groups: A (0-5 years), B (6-10 years), C (11-15 years), D (16-20 years), E (21-30 years), F (31-40 years), G (41-50 years), H (51-60 years), and I (61-70 years). Two radiologists assessed the presence of LAC on axial and coronal CT images, defined as focal calcific density on both or on one plane with attenuation >100 Hounsfield unit. The prevalence of LAC on CT was compared between children and adults, and between unenhanced and enhanced CT in children. The prevalence of LAC on digital radiography was evaluated in 476 children. The prevalence of definite LAC on unenhanced multi-section CT was significantly higher in children (37.8 %) than in adults (11.2 %) (P CT were 4.5, 12.8, 8.1, 19.0, 0.0, 0.0, 0.0, 2.0, and 1.9 %. In children, the prevalence of LAC was significantly higher on unenhanced than on enhanced CT (37.8 vs. 16.4 %, P children. LAC is frequently observed in children and adults on multi-section spiral CT, more frequently than previously reported. Compared with that on multi-section spiral CT, the prevalence of LAC on digital radiography is substantially low.

Low dose dynamic CT myocardial perfusion imaging using a statistical iterative reconstruction method

Energy Technology Data Exchange (ETDEWEB)

Tao, Yinghua [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States); Chen, Guang-Hong [Department of Medical Physics and Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States); Hacker, Timothy A.; Raval, Amish N. [Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53792 (United States); Van Lysel, Michael S.; Speidel, Michael A., E-mail: speidel@wisc.edu [Department of Medical Physics and Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States)

2014-07-15

Purpose: Dynamic CT myocardial perfusion imaging has the potential to provide both functional and anatomical information regarding coronary artery stenosis. However, radiation dose can be potentially high due to repeated scanning of the same region. The purpose of this study is to investigate the use of statistical iterative reconstruction to improve parametric maps of myocardial perfusion derived from a low tube current dynamic CT acquisition. Methods: Four pigs underwent high (500 mA) and low (25 mA) dose dynamic CT myocardial perfusion scans with and without coronary occlusion. To delineate the affected myocardial territory, an N-13 ammonia PET perfusion scan was performed for each animal in each occlusion state. Filtered backprojection (FBP) reconstruction was first applied to all CT data sets. Then, a statistical iterative reconstruction (SIR) method was applied to data sets acquired at low dose. Image voxel noise was matched between the low dose SIR and high dose FBP reconstructions. CT perfusion maps were compared among the low dose FBP, low dose SIR and high dose FBP reconstructions. Numerical simulations of a dynamic CT scan at high and low dose (20:1 ratio) were performed to quantitatively evaluate SIR and FBP performance in terms of flow map accuracy, precision, dose efficiency, and spatial resolution. Results: Forin vivo studies, the 500 mA FBP maps gave −88.4%, −96.0%, −76.7%, and −65.8% flow change in the occluded anterior region compared to the open-coronary scans (four animals). The percent changes in the 25 mA SIR maps were in good agreement, measuring −94.7%, −81.6%, −84.0%, and −72.2%. The 25 mA FBP maps gave unreliable flow measurements due to streaks caused by photon starvation (percent changes of +137.4%, +71.0%, −11.8%, and −3.5%). Agreement between 25 mA SIR and 500 mA FBP global flow was −9.7%, 8.8%, −3.1%, and 26.4%. The average variability of flow measurements in a nonoccluded region was 16.3%, 24.1%, and 937

Low dose dynamic CT myocardial perfusion imaging using a statistical iterative reconstruction method

International Nuclear Information System (INIS)

Tao, Yinghua; Chen, Guang-Hong; Hacker, Timothy A.; Raval, Amish N.; Van Lysel, Michael S.; Speidel, Michael A.

2014-01-01

Purpose: Dynamic CT myocardial perfusion imaging has the potential to provide both functional and anatomical information regarding coronary artery stenosis. However, radiation dose can be potentially high due to repeated scanning of the same region. The purpose of this study is to investigate the use of statistical iterative reconstruction to improve parametric maps of myocardial perfusion derived from a low tube current dynamic CT acquisition. Methods: Four pigs underwent high (500 mA) and low (25 mA) dose dynamic CT myocardial perfusion scans with and without coronary occlusion. To delineate the affected myocardial territory, an N-13 ammonia PET perfusion scan was performed for each animal in each occlusion state. Filtered backprojection (FBP) reconstruction was first applied to all CT data sets. Then, a statistical iterative reconstruction (SIR) method was applied to data sets acquired at low dose. Image voxel noise was matched between the low dose SIR and high dose FBP reconstructions. CT perfusion maps were compared among the low dose FBP, low dose SIR and high dose FBP reconstructions. Numerical simulations of a dynamic CT scan at high and low dose (20:1 ratio) were performed to quantitatively evaluate SIR and FBP performance in terms of flow map accuracy, precision, dose efficiency, and spatial resolution. Results: Forin vivo studies, the 500 mA FBP maps gave −88.4%, −96.0%, −76.7%, and −65.8% flow change in the occluded anterior region compared to the open-coronary scans (four animals). The percent changes in the 25 mA SIR maps were in good agreement, measuring −94.7%, −81.6%, −84.0%, and −72.2%. The 25 mA FBP maps gave unreliable flow measurements due to streaks caused by photon starvation (percent changes of +137.4%, +71.0%, −11.8%, and −3.5%). Agreement between 25 mA SIR and 500 mA FBP global flow was −9.7%, 8.8%, −3.1%, and 26.4%. The average variability of flow measurements in a nonoccluded region was 16.3%, 24.1%, and 937

A deep convolutional neural network using directional wavelets for low-dose X-ray CT reconstruction.

Science.gov (United States)

Kang, Eunhee; Min, Junhong; Ye, Jong Chul

2017-10-01

Due to the potential risk of inducing cancer, radiation exposure by X-ray CT devices should be reduced for routine patient scanning. However, in low-dose X-ray CT, severe artifacts typically occur due to photon starvation, beam hardening, and other causes, all of which decrease the reliability of the diagnosis. Thus, a high-quality reconstruction method from low-dose X-ray CT data has become a major research topic in the CT community. Conventional model-based de-noising approaches are, however, computationally very expensive, and image-domain de-noising approaches cannot readily remove CT-specific noise patterns. To tackle these problems, we want to develop a new low-dose X-ray CT algorithm based on a deep-learning approach. We propose an algorithm which uses a deep convolutional neural network (CNN) which is applied to the wavelet transform coefficients of low-dose CT images. More specifically, using a directional wavelet transform to extract the directional component of artifacts and exploit the intra- and inter- band correlations, our deep network can effectively suppress CT-specific noise. In addition, our CNN is designed with a residual learning architecture for faster network training and better performance. Experimental results confirm that the proposed algorithm effectively removes complex noise patterns from CT images derived from a reduced X-ray dose. In addition, we show that the wavelet-domain CNN is efficient when used to remove noise from low-dose CT compared to existing approaches. Our results were rigorously evaluated by several radiologists at the Mayo Clinic and won second place at the 2016 "Low-Dose CT Grand Challenge." To the best of our knowledge, this work is the first deep-learning architecture for low-dose CT reconstruction which has been rigorously evaluated and proven to be effective. In addition, the proposed algorithm, in contrast to existing model-based iterative reconstruction (MBIR) methods, has considerable potential to benefit from

Automated lung module detection at low-dose CT: preliminary experience

International Nuclear Information System (INIS)

Goo, Jin-Mo; Lee, Jeong-Won; Lee, Hyun-Ju; Kim, Seung-Wan; Kim, Jong-Hyo; Im, Jung-Gi

2003-01-01

To determine the usefulness of a computer-aided diagnosis (CAD) system for the automated detection of lung nodules at low-dose CT. A CAD system developed for detecting lung nodules was used to process the data provided by 50 consecutive low-dose CT scans. The results of an initial report, a second look review by two chest radiologists, and those obtained by the CAD system were compared, and by reviewing all of these, a gold standard was established. By applying the gold standard, a total of 52 nodules were identified (26 with a diameter ≤ 5 mm; 26 with a diameter > 5 mm). Compared to an initial report, four additional nodules were detected by the CAD system. Three of these, identified only at CAD, formed part of the data used to derive the gold standard. For the detection of nodules > 5 mm in diameter, sensitivity was 77% for the initial report, for the second look review, and 88% for the second look review,and 65% for the CAD system. There were 8.0 ± 5.2 false-positive CAD results per CT study. These preliminary results indicate that a CAD system may improve the detection of pulmonary nodules at low-dose CT

Low dose coronary CT angiography with 256-slice helical CT

International Nuclear Information System (INIS)

Zhang Xiaodong; Tang Binghang; Li Fangyun

2011-01-01

Objective: To compare the image quality and patient radiation dose of coronary computed tomography angiography (CCTA) received by prospectively-gated step-and-shoot (SAS) technique with those obtained by retrospectively-gated spiral ( RGS) technique on a 256-slice CT scanner. Methods: A total of 200 patients were enrolled in this study. One hundred patients underwent CCTA with SAS mode were subdivided into two groups: (1) 50 patients with an average heart rate (HR) ≤ 70 bpm were scanned with a data acquisition time window centered at the 75% of the R-R cycle (group A) and (2) 50 patients with HR > 70 bpm were scanned with the data acquisition time window centered at the 45% of the R-R cycle, including a phase tolerance of ± 5% (group B). Other 100 patients underwent CCTA with RGS mode and ECG-based tube current modulation were also subdivided into two groups: (3) 50 patients with HR ≤ 70 bpm were scanned with cardiac dose right set to phase of 75% ( group C) and (4) 50 patients with HR > 70 bpm were scanned with cardiac ose Rdight set to phases of 45% and 75% (group D). All patients were grouped in randomized order. The image quality of CCTA were evaluated using a rank scale from 1 to 4 (1: excellent; 4: non-assessable). Radiation dose of the four groups received was also estimated. The image quality between groups was compared by Mann-Whitney U test. The radiation dose between groups was compared by t test. For the 100 patients received by prospective ECG-gated CCTA, the receiver operating characteristic curve (ROC) was used to analyze the CCTA image quality and average heart rate to determine the uppercutoff of HR for obtaining diagnostic coronary images with SAS mode. A Spearman correlation analysis was also performed to analyze the correlation of HR and image quality in patients underwent CCTA with SAS mode. Results: Of 2338 coronary artery segments, excellent or good image quality (score of 1 or 2) was achieved in 96.5% (585 of 606) in group A, 77.7% (445

Hypoxic-ischemic encephalopathy in neonates and infants: an evaluation with spiral CT

International Nuclear Information System (INIS)

Zhu Linghua

2006-01-01

Objective: To evaluate spiral CT imaging in the diagnosis of hypoxic-ischemic encephalopathy (HIE) in the neonates and infants. Methods: 112 children with history of asphyxia in peri-natal period and evident clinical symptoms were evaluated with Spiral CT. CT findings were studied. Results: 46 minor cases, 57 moderate cases and 9 severe cases were found out of 112 patients. Intracranial hemorrhage was revealed in 38 cases. Mortality occurred in 1 case. Conclusion: Spiral CT is helpful for evaluating brain damage and predicting prognosis in neonates with HIE. (authors)

Seventy kilovolt ultra-low dose CT of the paranasal sinus: first clinical results

International Nuclear Information System (INIS)

Bodelle, B.; Wichmann, J.L.; Klotz, N.; Lehnert, T.; Vogl, T.J.; Luboldt, W.; Schulz, B.

2015-01-01

Aim: To evaluate the diagnostic image quality and radiation dose of low-dose 70 kV computed tomography (CT) of the paranasal sinus in comparison to 100 and 120 kV CT. Materials and methods: CT of the paranasal sinus was performed in 127 patients divided into three groups using different tube voltages and currents (70 kV/75 mAs, ultra-low dose protocol, n = 44; 100 kV/40 mAs, standard low-dose protocol, n = 42; 120 kV/40 mAs, standard protocol, n = 41). CT dose index (CTDIvol), dose–length product (DLP), attenuation, image noise and signal-to-noise ratio (SNR) were compared between the groups using Wilcoxon–Mann–Whitney U-test. Subjective diagnostic image quality was compared by using a five-point scale (1 = non-diagnostic, 5 = excellent, read by two readers in consensus) and Cohen's weighted kappa analysis for interobserver agreement. Results: Radiation dose was significantly lower with 70 kV acquisition than 100 and 120 kV (DLP: 31 versus 52 versus 82 mGy·cm; CTDI 2.33 versus 3.95 versus 6.31 mGy, all p < 0.05). Mean SNR (70 kV: 0.37; 100 kV: 0.21; 120 kV: 0.13; p < 0.05) and organ attenuation increased significantly with lower voltages. All examinations showed diagnostic image quality. Subjective diagnostic image quality was higher with standard protocols than the 70 kV protocol (120 kV: 5.0; 100 kV: 4.5; 70 kV: 3.5, p < 0.05) without significant differences with substantial interobserver agreement (κ > 0.59). Conclusion: The ultra-low dose (70 kV) CT imaging of the paranasal sinus allowed for significant dose reduction by 61% and an increased attenuation of organ structures in comparison to standard acquisition while maintaining diagnostic image quality with a slight reduction in subjective image quality. -- Highlights: •Image quality and radiation dose of 70 kV ultra-low dose CT of the paranasal sinus. •70 kV ultra-low dose CT of the paranasal sinus allows for dose reduction by 61%. •70 kV CT of the

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

Feasibility of epicardial adipose tissue quantification in non-ECG-gated low-radiation-dose CT: comparison with prospectively ECG-gated cardiac CT

Energy Technology Data Exchange (ETDEWEB)

Simon-Yarza, Isabel; Viteri-Ramirez, Guillermo; Saiz-Mendiguren, Ramon; Slon-Roblero, Pedro J.; Paramo, Maria [Dept. of Radiology, Clinica Univ. de Navarra, Pamplona (Spain); Bastarrika, Gorka [Dept. of Radiology, Clinica Univ. de Navarra, Pamplona (Spain); Cardiac Imaging Unit, Clinica Univ. de Navarra, Pamplona (Spain)], e-mail: bastarrika@unav.es

2012-06-15

Background: Epicardial adipose tissue (EAT) is an important indicator of cardiovascular risk. This parameter is generally assessed on ECG-gated computed tomography (CT) images. Purpose: To evaluate feasibility and reliability of EAT quantification on non-gated thoracic low-radiation-dose CT examinations with respect to prospectively ECG-gated cardiac CT acquisition. Material and Methods: Sixty consecutive asymptomatic smokers (47 men; mean age 64 {+-} 9.8 years) underwent low-dose CT of the chest and prospectively ECG-gated cardiac CT acquisitions (64-slice dual-source CT). The two examinations were reconstructed with the same range, field of view, slice thickness, and convolution algorithm. Two independent observers blindly quantified EAT volume using commercially available software. Data were compared with paired sample Student t-test, concordance correlation coefficients (CCC), and Bland-Altman plots. Results: No statistically significant difference was observed for EAT volume quantification with low-dose-CT (141.7 {+-} 58.3 mL) with respect to ECG-gated CT (142.7 {+-} 57.9 mL). Estimation of CCC showed almost perfect concordance between the two techniques for EAT-volume assessment (CCC, 0.99; mean difference, 0.98 {+-} 5.1 mL). Inter-observer agreement for EAT volume estimation was CCC: 0.96 for low-dose-CT examinations and 0.95 for ECG-gated CT. Conclusion: Non-gated low-dose CT allows quantifying EAT with almost the same concordance and reliability as using dedicated prospectively ECG-gated cardiac CT acquisition protocols.

Feasibility of epicardial adipose tissue quantification in non-ECG-gated low-radiation-dose CT: comparison with prospectively ECG-gated cardiac CT

International Nuclear Information System (INIS)

Simon-Yarza, Isabel; Viteri-Ramirez, Guillermo; Saiz-Mendiguren, Ramon; Slon-Roblero, Pedro J.; Paramo, Maria; Bastarrika, Gorka

2012-01-01

Background: Epicardial adipose tissue (EAT) is an important indicator of cardiovascular risk. This parameter is generally assessed on ECG-gated computed tomography (CT) images. Purpose: To evaluate feasibility and reliability of EAT quantification on non-gated thoracic low-radiation-dose CT examinations with respect to prospectively ECG-gated cardiac CT acquisition. Material and Methods: Sixty consecutive asymptomatic smokers (47 men; mean age 64 ± 9.8 years) underwent low-dose CT of the chest and prospectively ECG-gated cardiac CT acquisitions (64-slice dual-source CT). The two examinations were reconstructed with the same range, field of view, slice thickness, and convolution algorithm. Two independent observers blindly quantified EAT volume using commercially available software. Data were compared with paired sample Student t-test, concordance correlation coefficients (CCC), and Bland-Altman plots. Results: No statistically significant difference was observed for EAT volume quantification with low-dose-CT (141.7 ± 58.3 mL) with respect to ECG-gated CT (142.7 ± 57.9 mL). Estimation of CCC showed almost perfect concordance between the two techniques for EAT-volume assessment (CCC, 0.99; mean difference, 0.98 ± 5.1 mL). Inter-observer agreement for EAT volume estimation was CCC: 0.96 for low-dose-CT examinations and 0.95 for ECG-gated CT. Conclusion: Non-gated low-dose CT allows quantifying EAT with almost the same concordance and reliability as using dedicated prospectively ECG-gated cardiac CT acquisition protocols

Optimised low-dose multidetector CT protocol for children with cranial deformity

Energy Technology Data Exchange (ETDEWEB)

Vazquez, Jose Luis [Complejo Hospitalario Universitario de Vigo, Department of Radiology, Vigo, Pontevedra (Spain); Pombar, Miguel Angel [Complejo Hospitalario Universitario de Santiago, Department of Radiophysics, Santiago de Compostela, La Coruna (Spain); Pumar, Jose Manuel [Complejo Hospitalario Universitario de Santiago, Department of Radiology, Santiago de Compostela, La Coruna (Spain); Campo, Victor Miguel del [Complejo Hospitalario Universitario de Vigo, Department of Public Health, Vigo, Pontevedra (Spain)

2013-08-15

To present an optimised low-dose multidetector computed tomography (MDCT) protocol for the study of children with cranial deformity. Ninety-one consecutive MDCT studies were performed in 80 children. Studies were performed with either our standard head CT protocol (group 1, n = 20) or a low-dose cranial deformity protocol (groups 2 and 3). Group 2 (n = 38), initial, and group 3 (n = 33), final and more optimised. All studies were performed in the same 64-MDCT equipment. Cranial deformity protocol was gradationally optimised decreasing kVp, limiting mA range, using automatic exposure control (AEC) and increasing the noise index (NI). Image quality was assessed. Dose indicators such us CT dose index volume (CTDIvol), dose-length product (DLP) and effective dose (E) were used. The optimised low-dose protocol reached the following values: 80 kVp, mA range: 50-150 and NI = 23. We achieved a maximum dose reduction of 10-22 times in the 1- to 12-month-old cranium in regard to the 2004 European guidelines for MDCT. A low-dose MDCT protocol that may be used as the first diagnostic imaging option in clinically selected patients with skull abnormalities. (orig.)

Improving abdomen tumor low-dose CT images using a fast dictionary learning based processing

International Nuclear Information System (INIS)

Chen Yang; Shi Luyao; Shu Huazhong; Luo Limin; Coatrieux, Jean-Louis; Yin Xindao; Toumoulin, Christine

2013-01-01

In abdomen computed tomography (CT), repeated radiation exposures are often inevitable for cancer patients who receive surgery or radiotherapy guided by CT images. Low-dose scans should thus be considered in order to avoid the harm of accumulative x-ray radiation. This work is aimed at improving abdomen tumor CT images from low-dose scans by using a fast dictionary learning (DL) based processing. Stemming from sparse representation theory, the proposed patch-based DL approach allows effective suppression of both mottled noise and streak artifacts. The experiments carried out on clinical data show that the proposed method brings encouraging improvements in abdomen low-dose CT images with tumors. (paper)

Absorbed and effective dose from spiral and computed tomography for the dental implant planning

International Nuclear Information System (INIS)

Hong, Beong Hee; Han, Won Jeong; Kim, Eun Kyung

2001-01-01

To evaluate the absorbed and effective doses of spiral and computed tomography for the dental implant planning. For radiographic projection. TLD chips were placed in 22 sites of humanoid phantom to record the exposure to skin and the mean absorbed dose to bone marrow, thyroid, pituitary, parotid and submandibular glands and nesophages. Effective dose was calculated, using the method suggested by Frederiksen at al.. Patient situations of a single tooth gap in upper and lower midline region, edentulous maxilla and mandible were simulated for spiral tomography. 35 axial slices (maxilla) and 40 axial slices (mandible) with low and standard dose setting were used for computed tomography. All the radiographic procedures were repeated three times. The mean effective dose in case of maxilla was 0.865 mSv, 0.452 mSv, 0.136 mSv and 0.025 mSv, in spiral tomography of complete edentulous maxilla, computed tomography with standard mAs, computed tomography with low mAs and spiral tomography of a single tooth gap (p<0.05). That in case of mandible was 0.614 mSv, 0.448 mSv, 0.137 mSv and 0.036 mSv, in spiral tomography of complete edentulous mandible, computed tomography with standard mAs, computed tomography with low mAs and spiral tomography of a single tooth gap (p<0.05). Based on these results, it can be concluded that low mAs computed tomography is recommended instead of spiral tomography for the complete edentulous maxilla and mandible dental implant treatment planning

Low-dose CT: new tool for screening lung cancer?

International Nuclear Information System (INIS)

Diederich, S.; Wormanns, D.; Heindel, W.

2001-01-01

Lung cancer is the leading cause of death from malignant tumours as it is very common and has a poor prognosis at advanced tumour stages. Prognosis could be improved by treatment at early stages. As these stages are usually asymptomatic, a diagnostic test that would allow detection of early tumour stages in a population at risk could potentially reduce mortality from lung cancer. Previous approaches using chest radiography and sputum cytology in smokers have been disappointing. Fluorescent bronchoscopy and molecular markers are not yet applicable in clinical routine. Because of its high sensitivity for small pulmonary nodules, which are the most common manifestation of early lung cancer, CT appears suitable as a screening test. Low-dose examination parameters can and should be used for this purpose. From clinical practice it is well known that chest CT often demonstrates small pulmonary nodules, which do not represent lung cancer. Therefore, non-invasive diagnostic algorithms are required to avoid unnecessary biopsies in benign lesions. In preliminary studies of low-dose CT using algorithms based on size and density of detected nodules a large proportion of asymptomatic lung cancers and a large proportion of early, resectable tumour stages were found with a small proportion of invasive procedures for benign nodules. Before this technology can be recommended for broad application, however, further information is required regarding appropriate inclusion criteria (smoking habits, age groups) and screening intervals. Most importantly, further data are required to clarify whether lung cancer screening using low-dose CT can actually reduce mortality from lung cancer. (orig.)

Value of noncontrast spiral CT for suspected acute appendicitis

International Nuclear Information System (INIS)

Choi, Pil Yeob; Lee, Sang Wook; Kwon, Jae Soo; Sung, Young Soon; Rho, Myoung Ho; Chang, Jeong A.

1998-01-01

To assess the diagnostic accuracy and clinical efficacy of noncontrast spiral CT in patients with suspected acute appendicitis. Over a six-month period, 100 patients with suspected acute appendicitis were prospectively evaluated with noncontrast spiral CT. All scans were obtained from the lower body of L3 to the symphysis pubis, with 5mm or 10mm collimation and pitch of 1 or 1.5, and without intravenous or oral contrast material. Diagnosis was established by means of surgical or clinical follow-up. Prospective diagnosis based on CT findings was compared with surgical results and clinical follow-up. Acute appendicitis was confirmed in 47 of 100 patients. On the basis of the Ct findings, SI patients were prospectively interpreted as positive for appendicitis, but in six the diagnosis was false-positive. Two of the 47 with acute appendicitis were prospectively interpreted as normal. The preoperative diagnosis of acute appendicitis was, thus, 45 true-positive, 47 true-negative, six false-positive and two false-negative yielding a sensitivity of 96%, a specificity of 89%, an accuracy of 92%, a positive predictive value of 88%, and a negative predictive value of 96%. Using CT, an alternative diagnosis was established in 14 patients. Noncontrast spiral CT is a useful technique for diagnosing acute appendicitis. =20

Patient doses from CT examinations in the United Arab Emirates

International Nuclear Information System (INIS)

Janeczek, J.

2006-01-01

Full text of publication follows: The main goal of the study was to estimate effective patient doses from the 6 most common CT examinations for different types of CT scanners within the United Arab Emirates. The results were used to assess future trends in patient CT doses following rapid replacement of axial and single-slice spiral scanners by multi-slice scanners. At present all three types of scanner technology exist: axial, spiral and multi-slice with axial scanners being gradually replaced by multi-slice scanners as the medical infrastructure of the country is modernized. Altogether there are more than 30 CT scanners in the country with a population of 4 million. Out of these 11 scanners are 16-slice models with tube-current modulation system. The majority of larger United Arab Emirates hospitals have at least two CT scanners: a single slice and 4 or 16-slice scanner. The survey was carried out with data collection forms distributed to the majority of CT scanner users in the United Arab Emirates hospitals, both private and government. Effective doses for different examinations were calculated from T.L.D. measurements using an Alderson Rando phantom simulating an average size patient. Our results show that effective doses to patients initially increased with the introduction of 4-slice scanners. Multi-slice scanners with 16 and more slices have tube-current modulation system as a standard. It is routinely used by radiographers in almost all examinations resulting in patient dose reduction up to 40 % in certain examinations. Another factor affecting population dose is the increased number of patients examined using multi-slice scanners. In the United Arab Emirates there was an increase of more than 30 % in the annual number of patients examined using multi-slice scanners in comparison to single-slice scanners. This fact is attributed to the ease and speed of operation of multi-slice scanners. Rapid increase in number of CT examinations is of concern. Medical

Motion estimation and compensation in dynamic spiral CT reconstruction

International Nuclear Information System (INIS)

Kimdon, J.; Grangeat, P.; Koenig, A.; Bonnet, St.

2004-01-01

Respiratory and cardiac motion causes blurring in dynamic X-ray Computed Tomography (CT). Fast scans reduce this problem, but they require a higher radiation dose per time period to maintain the signal to noise ratio of the resulting images, thereby magnifying the health risk to the patient. As an alternative to increased radiation, our team has already developed a cone-beam reconstruction algorithm based on a dynamic particle model that estimates, predicts, and compensates for respiratory motion in circular X-ray CT. The current paper presents an extension of this method to spiral CT, applicable to modern multi-slice scanners that take advantage of the speed and dose benefits of helical trajectories. We adapted all three main areas of the algorithm: backprojection, prediction, and compensation/accumulation. In backprojection, we changed the longitudinal re-binning technique, filter direction, and the method of enforcing the data sufficiency requirements. For prediction, we had to be careful of objects appearing and disappearing as the scanner bed advanced. For compensation/accumulation, we controlled the reconstruction time and combined images to cover a greater longitudinal extent for each phase in the respiratory or cardiac cycle. Tests with moving numerical phantoms demonstrate that the algorithm successfully improves the temporal resolution of the images without increasing the dose or reducing the signal-to-noise ratio. (authors)

Low-dose CT of the paranasal sinuses with eye lens protection: effect on image quality and radiation dose

Energy Technology Data Exchange (ETDEWEB)

Hein, Eike; Rogalla, Patrik; Klingebiel, Randolph; Hamm, Bernd [Department of Diagnostic and Interventional Radiology, Charite Hospital, Humboldt-Universitaet zu Berlin (Germany)

2002-07-01

The purpose of the study was to assess the effect of lens protection on image quality and radiation dose to the eye lenses in CT of the paranasal sinuses. In 127 patients referred to rule out sinusitis, an axial spiral CT with a lens protection placed on the patients eyes was obtained (1.5/2/1, 50 mAs, 120 kV). Coronal views were reconstructed at 5-mm interval. To quantify a subjective impression of image quality, three regions of interest within the eyeball were plotted along a line perpendicular to the protection at 2, 5, and 9 mm beneath skin level on the axial images. Additionally, dose reduction of a bismuth-containing latex shield was measured using a film-dosimetry technique. The average eyeball density was 17.97 HU (SD 3.7 HU). The relative increase in CT density was 180.6 (17.7), 103.3 (11.7), and 53.6 HU (9.2), respectively. There was no diagnostic information loss on axial and coronal views observed. Artifacts were practically invisible on images viewed in a bone window/level setting. The use of the shield reduced skin radiation from 7.5 to 4.5 mGy. The utilization of a radioprotection to the eye lenses in paranasal CT is a suitable and effective means of reducing skin radiation by 40%. (orig.)

Low-dose CT of the paranasal sinuses with eye lens protection: effect on image quality and radiation dose

International Nuclear Information System (INIS)

Hein, Eike; Rogalla, Patrik; Klingebiel, Randolph; Hamm, Bernd

2002-01-01

The purpose of the study was to assess the effect of lens protection on image quality and radiation dose to the eye lenses in CT of the paranasal sinuses. In 127 patients referred to rule out sinusitis, an axial spiral CT with a lens protection placed on the patients eyes was obtained (1.5/2/1, 50 mAs, 120 kV). Coronal views were reconstructed at 5-mm interval. To quantify a subjective impression of image quality, three regions of interest within the eyeball were plotted along a line perpendicular to the protection at 2, 5, and 9 mm beneath skin level on the axial images. Additionally, dose reduction of a bismuth-containing latex shield was measured using a film-dosimetry technique. The average eyeball density was 17.97 HU (SD 3.7 HU). The relative increase in CT density was 180.6 (17.7), 103.3 (11.7), and 53.6 HU (9.2), respectively. There was no diagnostic information loss on axial and coronal views observed. Artifacts were practically invisible on images viewed in a bone window/level setting. The use of the shield reduced skin radiation from 7.5 to 4.5 mGy. The utilization of a radioprotection to the eye lenses in paranasal CT is a suitable and effective means of reducing skin radiation by 40%. (orig.)

First results of spiral CT angiography in the evaluation of carotid artery stenosis

International Nuclear Information System (INIS)

Link, J.; Mueller-Huelsbeck, S.; Brossmann, J.; Grabener, M.; Voss, C.; Heller, M.

1995-01-01

To determine the value of spiral CT angiography in Maximum Intensity Projection (MIP)-technique for evaluation of carotid artery stenosis. A comparison of the MIP technique with intraarterial DSA was done in 24 patients with 40 stenoses. Quantification of stenosis was determined according to the NASCET study: mild (0-29%), moderate (30-69%), severe (70-99%) and occlusion (100%). Totally the correlation of spiral CT angiography with DSA was 80% (r=0.93; p=0.0001). In the moderate stenosis group (r=1; p=0.1573), severe stenosis group (r=0.89; p=0.002) and the occlusion group (r=1; p=0.0009) there was a good correlation with DSA. In the mild stenosis group (r=0.55; p=0.0704) correlation of spiral CT angiography with DSA was poor. Spiral CT angiography allows an excellent delineation of calcifications. Tandem lesions and collateral flow cannot be shown with spiral CT angiography. (orig./MG) [de

Evaluation of image quality and radiation dose of thoracic and coronary dual-source CT in 110 infants with congenital heart disease

International Nuclear Information System (INIS)

Saad, Moez Ben; Rohnean, Adela; Sigal-Cinqualbre, Anne; Adler, Ghazal; Paul, Jean-Francois

2009-01-01

There are only a few reports on the diagnostic accuracy, and the technical and clinical feasibility, of multidetector CT (MDCT) in infants with congenital heart disease (CHD). To evaluate the image quality and radiation dose of DSCT in babies with CHD. From November 2006 to November 2007, 110 consecutive infants with CHD referred for pre- or postoperative CT evaluation were included. All these infants had a spiral angiothoracic DSCT scan after injection of 300 mg/ml iopromide at 0.5-1 ml/s with a power injector using a low-dose protocol (80 kVp and 10 mAs/kg). Of these infants, 34 also underwent an ECG-gated coronary CT scan for evaluation of the course of the coronary arteries. No serious adverse events were recorded. The mean dose-length product was 8±6 mGy.cm (effective dose 0.5±0.2 mSv) and 21±9 mGy.cm (effective dose 1.3±0.6 mSv) during the non-ECG-gated spiral acquisition and ECG-gated acquisition, respectively. Diagnostic quality images were achieved with the spiral acquisition in 89% of cases. Compared to the spiral mode, ECG-gated acquisition significantly improved the visualization of the coronary arteries, with a diagnostic rate of 91% and 84% for the left and right coronary arteries, respectively. DSCT together with iopromide at 300 mg/ml is a valuable tool for the routine clinical evaluation of infants with CHD. ECG-gated acquisition provides reliable visualization of the course of the coronary arteries. (orig.)

The bibliometric analysis of literatures on low-dose CT in CNKI

International Nuclear Information System (INIS)

Wang Qian; Qi Weiwei; Xia Guanghui; Zhao Xinming; Ma Xiaohong; Zhou Chunwu; Hong Nan

2013-01-01

Objective: The purposes of this study were to evaluate the characteristics and rule of the development in national low -dose CT examination, and to supply a useful reference for future studies. Materials and Methods: The journal articles in CNKI which were included by China Academic Journal Network Publishing Database (CAJD) from 2002 to 2011 were processed with Thomson Data Analyzer (TDA). Seven aspects were analyzed: time, authors, funds for scientific research, areal distribution, institutions, authors, and keywords. Results: A total 3148 journal articles on low-dose CT examination and 7352 authors were found. The cooperative rate and degree were 63, 48% and 2.34, respectively. The famous authors were those who published more than 3 articles. Authors were from 33 areas, 471 institutions of 8 systems. Beijing and Shanghai were the most productive areas, publishing 45.9% articles. There were 10 core journals in this research area, 868 articles were funded by certain grants, and number of articles was increased yearly, indicative of the importance of grant in promoting research. Conclusion: The national low-dose CT research was in the young stage compared to the international research, and the research were not evenly distributed national wide. Though the researches have involved multi-institute, multi-system, multi-discipline, the quantities and qualities of papers still have improvement space. Strengthening basic research, improving medical ethics, and optimizing clinical research methods would promote development of low-dose CT studies. (authors)

Developing low-dose C-arm CT imaging for temporomandibular joint (TMJ) disorder in interventional radiology

Energy Technology Data Exchange (ETDEWEB)

Zhu, Xiaowei; Cahill, Anne Marie [Children' s Hospital of Philadelphia, Department of Radiology, Philadelphia, PA (United States); Felice, Marc [University of Pennsylvania, Environmental Health and Radiation Safety, Philadelphia, PA (United States); Johnson, Laura [Computed Tomography Division, Siemens Healthcare Sector, Shanghai (China); Sarmiento, Marily [Siemens Medical Solutions, Angiography and X-ray Division, Hoffman Estates, IL (United States)

2011-04-15

Manufacturers have provided C-arm CT imaging technologies for applications in interventional radiology in recent years. However, clinical imaging protocols and radiation doses have not been well studied or reported. The purpose of this study is to develop low-dose settings for clinically acceptable CT imaging of temporomandibular joint in interventional radiology suites, using a C-arm imaging angiography system. CT scans were performed with a flat-panel digital C-arm angiographic system on a 5-year-old anthropomorphic phantom. The CTDI was determined for various rotation times, dose settings and Cu filter selections. The CTDI values were compared with those of conventional low-dose CT for the same phantom. The effectiveness of using Cu filters to reduce dose was also investigated. Images were reviewed by a senior radiologist for clinical acceptance. The manufacturer's default setting gave an equivalent CTDI of 4.8 mGy. Optimizing the dose settings and adding copper filtration reduced the radiation dose by 94%. This represents a 50% reduction from conventional CT. Use of Cu filters and low-dose settings significantly reduced radiation dose from that of standard settings. This phantom study process successfully guided the clinical implementation of low-dose studies for all ages at our institution. (orig.)

Demonstration of pulmonary embolism with gadolinium-enhanced spiral CT

Energy Technology Data Exchange (ETDEWEB)

Coche, E.E.; Hammer, F.D.; Goffette, P.P. [Dept. of Radiology, St. Luc University Hospital, Brussels (Belgium)

2001-11-01

The authors report a case of successful detection of pulmonary embolism using gadolinium-enhanced spiral CT (Gadodiamide, 0.4 mmol/kg, 2 ml/s, delay 18 s) in a 77-year-old woman, with previous allergy to iodinated contrast medium, and renal failure, who presented with pulmonary arterial hypertension. Doppler ultrasound of the lower limbs was first performed and revealed a deep venous thrombosis of the right lower limb. To establish if venous thrombosis was the cause of pulmonary hypertension and to confirm that pulmonary endarterectomy was not indicated in this situation, several imaging modalities were performed. Lung scintigraphy and MRI were non-diagnostic. Gadolinium-enhanced spiral CT demonstrated a large thrombus located proximally and in a segmental artery of the right lower lobe. This case illustrates the potential usefulness of gadolinium as alternative contrast agent with spiral CT to diagnose pulmonary embolism and elucidate the cause of pulmonary arterial hypertension in a patient with some contraindications for iodinated contrast medium injection. (orig.)

Demonstration of pulmonary embolism with gadolinium-enhanced spiral CT

International Nuclear Information System (INIS)

Coche, E.E.; Hammer, F.D.; Goffette, P.P.

2001-01-01

The authors report a case of successful detection of pulmonary embolism using gadolinium-enhanced spiral CT (Gadodiamide, 0.4 mmol/kg, 2 ml/s, delay 18 s) in a 77-year-old woman, with previous allergy to iodinated contrast medium, and renal failure, who presented with pulmonary arterial hypertension. Doppler ultrasound of the lower limbs was first performed and revealed a deep venous thrombosis of the right lower limb. To establish if venous thrombosis was the cause of pulmonary hypertension and to confirm that pulmonary endarterectomy was not indicated in this situation, several imaging modalities were performed. Lung scintigraphy and MRI were non-diagnostic. Gadolinium-enhanced spiral CT demonstrated a large thrombus located proximally and in a segmental artery of the right lower lobe. This case illustrates the potential usefulness of gadolinium as alternative contrast agent with spiral CT to diagnose pulmonary embolism and elucidate the cause of pulmonary arterial hypertension in a patient with some contraindications for iodinated contrast medium injection. (orig.)

Comparison of low dose with standard dose abdominal/pelvic multidetector CT in patients with stage 1 testicular cancer under surveillance

Energy Technology Data Exchange (ETDEWEB)

O' Malley, Martin E. [Joint Department of Medical Imaging, Toronto, ON (Canada); Chung, Peter; Warde, Padraig [Princess Margaret Hospital, Department of Radiation Oncology, Toronto, ON (Canada); Haider, Masoom; Jhaveri, Kartik; Khalili, Korosh [Princess Margaret Hospital, Joint Department of Medical Imaging, Toronto, ON (Canada); Jang, Hyun-Jung [Toronto General Hospital, Joint Department of Medical Imaging, Toronto, ON (Canada); Panzarella, Tony [Princess Margaret Hospital, Department of Biostatistics, Toronto, ON (Canada)

2010-07-15

To compare the image quality and acceptability of a low dose with those of standard dose abdominal/pelvic multidetector CT in patients with stage 1 testicular cancer managed by surveillance. One hundred patients (median age 31 years; range 19-83 years), 79 with seminoma and 21 with non-seminoma, underwent abdominal/pelvic imaging with low and standard dose protocols on 64-slice multidetector CT. Three reviewers independently evaluated images for noise and diagnostic quality on a 5-point scale and for diagnostic acceptability. On average, each reader scored noise and diagnostic quality of standard dose images significantly better than corresponding low dose images (p < 0.0001). One reader found all CT examinations acceptable; two readers each found 1/100 (1%) low dose examinations unacceptable. Median and mean dose-length product for low and standard dose protocols were 416.0 and 452.2 (range 122.9-913.4) and 931.9 and 999.8 (range 283.8-1,987.7) mGy cm, respectively. The low dose protocol provided diagnostically acceptable images for at least 99% of patients and achieved mean dose reduction of 55% compared with the standard dose protocol. (orig.)

Measurement of total lung capacity : a comparison of spiral CT and spirometry

International Nuclear Information System (INIS)

Chung, Kyung Il; Park, Kyung Ju; Lee, Eh Hyung; Yune, Heun Young; Suh, Jung Ho; Choe, Kyu Ok; Lim, Tae Hwan; Chung, In Hyuk

1996-01-01

To determine the potential of spiral CT as a functional imaging modality of the lung aside from its proven value in morphological depiction. Spiral CT scan was performed in ten normal female and nine normal male adults (mean age: 39, height: 163 cm, weight: 62 kg ) after single full breath-holding. Three dimensional lung images were reconstructed(minimal threshold value: -1,000HU, maximal threshold values: -150, 250, -350, -450 HU) to obtain total lung volume(TLV) on a histogram. Total lung volume measured by spiral CT was compared with TLV obtained by spirometry. Mean TLV measured by spirometry was 5.62L and TLV measured by CT at maximal threshold values of -150, -250, -350, and -450 HU was 5.53, 5.33, 5.15, and 4.98L, respectively. Mean absolute differences between the modalities of 0.17L(3%), 0.32L(5.6%), 0.48L(8.5%), 0.65L(11.5%) were statistically significant(p<0.001). Linear regression coefficients between the modalities were 0.99, 0.97, 095, and 0.94 and no statistically significant differences in accuracy of threshold levels in the estimation of lung volume(r=0.99, standard error=0.034L in all) were seen. TLV measured by spiral CT closely approximated that measured by spirometry. Spiral CT may be useful as a means of evaluating lung function

Low dose CT simulation using experimental noise model

Energy Technology Data Exchange (ETDEWEB)

Nakanishi, Satori; Zamyatin, Alexander A. [Toshiba Medical Systems Corporation, Tochigi, Otawarashi (Japan); Silver, Michael D. [Toshiba Medical Research Institute, Vernon Hills, IL (United States)

2011-07-01

We suggest a method to obtain system noise model experimentally without relying on assumptions on statistical distribution of the noise; also, knowledge of DAS gain and electronic noise level are not required. Evaluation with ultra-low dose CT data (5 mAs) shows good match between simulated and real data noise. (orig.)

Low-dose quantitative phase contrast medical CT

Science.gov (United States)

Mittone, A.; Bravin, A.; Coan, P.

2018-02-01

X-ray computed tomography (CT) is a powerful and routinely used clinical diagnostic technique, which is well tolerated by patients, and which provides high-resolution images and volumetric information about the body. However, two important limitations still affect this examination procedure: (1) its low sensitivity with respect to soft tissues, and (2) the hazards associated with x-ray exposure. Conventional radiology is based on the detection of the different photon absorption properties that characterize biological tissues, and thus the obtainable image contrast from soft and/or similar tissues is intrinsically limited. In this scenario, x-ray phase contrast imaging (XPCI) has been extensively tested and proven to overcome some of the main issues surrounding standard x-ray imaging. In addition to the absorption signal, XPCI relies on detecting the phase shifts induced by an object. Interestingly, as the order of magnitude of the phase contrast is higher than that of absorption, XPCI can, in principle, offer higher sensitivity at lower radiation doses. However, other technical aspects may counterbalance this gain, and an optimized setup and image processing solutions need to be implemented. The work presented here describes the strategies and developments we have realized, with the aim of controlling the radiation dose for the highly sensitive and quantitative XPCI-CT. Different algorithms for the phase retrieval and CT reconstruction of the XPCI data are presented. The CT algorithms we have implemented, namely the equally sloped tomography and the dictionary learning method, allow the image quality to be preserved while reducing the number of angular projections required by a factor of five. The results applied to breast imaging report accurate reconstructions at clinically compatible doses of the 3D distribution of the refractive properties of full human organs obtained by using three different phase retrieval methods. The described methodologies and the

Low-dose computed tomography scans with automatic exposure control for patients of different ages undergoing cardiac PET/CT and SPECT/CT.

Science.gov (United States)

Yang, Ching-Ching; Yang, Bang-Hung; Tu, Chun-Yuan; Wu, Tung-Hsin; Liu, Shu-Hsin

2017-06-01

This study aimed to evaluate the efficacy of automatic exposure control (AEC) in order to optimize low-dose computed tomography (CT) protocols for patients of different ages undergoing cardiac PET/CT and single-photon emission computed tomography/computed tomography (SPECT/CT). One PET/CT and one SPECT/CT were used to acquire CT images for four anthropomorphic phantoms representative of 1-year-old, 5-year-old and 10-year-old children and an adult. For the hybrid systems investigated in this study, the radiation dose and image quality of cardiac CT scans performed with AEC activated depend mainly on the selection of a predefined image quality index. Multiple linear regression methods were used to analyse image data from anthropomorphic phantom studies to investigate the effects of body size and predefined image quality index on CT radiation dose in cardiac PET/CT and SPECT/CT scans. The regression relationships have a coefficient of determination larger than 0.9, indicating a good fit to the data. According to the regression models, low-dose protocols using the AEC technique were optimized for patients of different ages. In comparison with the standard protocol with AEC activated for adult cardiac examinations used in our clinical routine practice, the optimized paediatric protocols in PET/CT allow 32.2, 63.7 and 79.2% CT dose reductions for anthropomorphic phantoms simulating 10-year-old, 5-year-old and 1-year-old children, respectively. The corresponding results for cardiac SPECT/CT are 8.4, 51.5 and 72.7%. AEC is a practical way to reduce CT radiation dose in cardiac PET/CT and SPECT/CT, but the AEC settings should be determined properly for optimal effect. Our results show that AEC does not eliminate the need for paediatric protocols and CT examinations using the AEC technique should be optimized for paediatric patients to reduce the radiation dose as low as reasonably achievable.

Enhanced dual-phase spiral CT features of polypoid ampullary carcinoma

International Nuclear Information System (INIS)

Zeng Mengsu; Yan Fuhua; Zhou Kangrong; Chen Huiming; Chen Gang; Chen Jin

2001-01-01

Objective: To understand CT features of polypoid ampullary carcinoma by enhanced dual-phase spiral CT. Methods: 15 cases of polypoid ampullary carcinoma (PAC) confirmed by surgical and pathological results were studied with thin slice enhanced dual-phase spiral CT (including arterial and portal phase scanning)with retrospective analysis, the scanning parameters were 5 mm thickness and 1.0 pitch for arterial phase scanning, and 5 mm thickness and 5 mm space for portal phase scanning. Results: All cases could display an enhanced mass as local filling defect at the site of the duodenal Vater's ampulla during arterial and portal phase scanning, the tumors ranged in size from 1 cm to 5 cm with mean of 2.3 cm, all were accompanied with dilated intrahepatic and common bile duct, enlarged gallbladder and dilated pancreatic duct, except one case which had marked atrophy of the pancreatic body and tail. Conclusion: The thin slices enhanced dual-phase spiral CT could not only accurately define the level of obstruction, but also demonstrate an enhanced mass as direct CT sign of the PAC, which is crucial for diagnosis of the PAC

Radiation dosimetry and its influencing factors for the multi-detector/slice spiral CT

International Nuclear Information System (INIS)

Bai Mei; Zheng Junzheng

2008-01-01

The Multi-Detector/Slice Spiral Computed Tomography (MDCT/MSCT)reflects the new progress in equipment and technology for radiology. Its popularized application demonstrates its advantages for clinical diagnosis. With the continuous development and growing uses of the MDCT/MSCT, the medical exposure of the patients and public has also been increasing. Therefore, assessment of the radiation dose and radiation risk from X-CT has become an increasingly important concern that should be addressed. Thus, this paper summarizes the main characteristics of the MDCT/MSCT emphasizing particularly on the radiation dosimetry, and reviews the expressions and measures of radiation dose in the MDCT/MSCT. In addition, main factors that influence radiation dose from the MDCT/MSCT are also discussed. A proper grasp of its radiation dosimetry and assessment method can significantly help radiologists, health physicists, medical physicists, X-CT engineers and manufacturers improve the management of radiation dose while optimizing the image quality in the MDCT/MSCT. (authors)

The usefulness of the adaptive dose shield for the infant CT

International Nuclear Information System (INIS)

Kojima, Hideyuki; Tsujimura, Asuka; Yabe, Hitoshi

2011-01-01

The spiral scan with a wide detector row such as the 64-detector row computed tomography (CT) system may increase radiation exposure for infants because the irradiation range is wider than the planned range. The adaptive dose shield (ADS) prevents radiation exposure greater than the planned range. We examined the usefulness of the protection effect of the ADS for the infant inner ear CT. To confirm the protection effect of the ADS, we scanned X-ray films by using the 64-detector row CT system and measured the difference of the planned range and the irradiation range. The result of that is that when the planned range was small, the protection effect for the scan ending side was inferior to the scan starting side. And also, when the gantry rotation speed and pitch factor (PF) were high values, the protection effect was inferior to a low gantry rotation speed and low PF. There was a combination of gantry rotation speed and PF at which the protection effect decreases. Due to changes of the scanning direction and PF for the infant inner ear, the crystalline lens radiation exposure dose decreased from 11.89 mGy to 4.37 mGy. In conclusion, the ADS can reduce the radiation exposure dose of an adjacent organ. Therefore, it was thought that the ADS was a useful radiation exposure reduction function for infants in the 64-detector row CT system. (author)

The role of spiral CT in pelvic trauma management

International Nuclear Information System (INIS)

Cheung, E.C.F.; Fung, K.K.L.

1999-01-01

Rapid and accurate assessment of pelvic injury is critical for good patient management. Plain X-ray is often used as a preliminary evaluation of the injury but this may not give adequate diagnosis of the acetabulum fracture, subtle fracture of the pelvic bone and the associated soft tissue injuries. Nowadays, spiral CT has taken an increasing role in the evaluation of pelvic trauma. It gives a rapid assessment of the bone and soft tissue injuries as compared to conventional CT. Besides, 2-D (multiplanar imaging) and 3-D image reconstruction with multiple angle views, provide the maximum information which facilitates detailed pelvic trauma evaluation. Three cases were used to illustrate the role of spiral CT in pelvic trauma management. Copyright (1999) Blackwell Science Pty Ltd

Measurement of slice sensitivity profile for a 64-slice spiral CT system

International Nuclear Information System (INIS)

Liu Chuanya; Qin Weichang; Wang Wei; Lu Chuanyou

2006-01-01

Objective: To measure and evaluate slice sensitivity profile (SSP) and the full width at half-maximum(FWHM) for a 64-slice spiral CT system. Methods: Using the same CT technique and body mode as those used for clinical CT, delta phantom was scanned with Somatom Sensation 64-slice spiral CT. SSPs and FWHM were measured both with reconstruction slice width of 0.6 mm at pitch=0.50, 0.75, 1.00, 1.25, 1.50 and with reconstruction slice width of 0.6, 1.0, 1.5 mm at pitch=1 respectively. Results: For normal slice width of 0. 6 mm, the measured FWHM, i.e. effective slice width, is 0.67, 0.67, 0.66, 0.69, 0.69 mm at different pitch. All the measured FWHM deviate less than 0.1 mm from the nominal slice width. The measured SSPs are symmetrical, bell-shaped curves without far-reaching tails, and show only slight variations as a function of the spiral pitch. When reconstruction slice width increase, relative SSP become wider. Conclusions: The variation of pitch hardly has effect all on SSP, effective slice width, and z-direction spatial resolution for Sensation 64-slice spiral CT system, which is helpful to optimize CT scanning protocol. (authors)

Comparative analysis of multi-slice spiral CT and positron emission tomography-CT in evaluation of axillary lymph nodes in breast cancer patients

International Nuclear Information System (INIS)

Sun Xianchang; Zhang Ruyi; Liu Qingwei; Zhao Suhong; Zu Degui; Li Xin

2008-01-01

Objective: To evaluate and compare spiral CT and positron emission tomography-CT (PET-CT) in characterization of of axillary lymph nodes in breast cancer patients. Methods: Forty patients with pathologically proven breast cancer underwent contrast-enhanced spiral CT of the breast and axilla, 13 of them also underwent PET-CT examination. One hundred and fifty-eight axillary lymph nodes were found in the 40 patients through contrast enhanced spiral CT, while 57 lymph nodes were found in the 13 patients through PET-CT. Three radiologists rated the lymph nodes found in CT images on a five-point scale. If the score was equal to or greater than 3, it was defined as positive (metastatic), otherwise negative. Visual observation and semiquantitative analysis were used to classify lymph nodes in PET-CT images. The results of spiral CT observation and PET-CT observation of lymph nodes were compared with pathological results. The relative value of CT and PET-CT was analyzed. Exact probability statistics were employed. Results: One hundred and fifty eight lymph nodes of 40 patients were detected by spiral CT, 91 of them were diagnosed as positive and 67 as negative Among the lymph nodes found in spiral CT, 99 were positive and 59 were negative pathologicall. A total of 57 lymph nodes were found by PET-CT. Thirty-nine of them were defined as positive and 18 as negative. Among the lymph nodes found in PET-CT, 39 were positive and 18 were negative pathologically. The sensitivity, specificity, accuracy, positive and negative predictive values in CT prediction in axillary lymph nodes metastases were 88.89%, 94.91%, 91.14%, 96.70%, and 83.58%, respectively. The sensitivity, specificity, accuracy, positive and negative predictive values in PET-CT prediction in axillary lymph nodes metastases were 97.44%, 94.44%, 96.49%, 97.44%, and 94.44%, respectively. PET-CT had no significant difference with spiral CT in sensitivity, accuracy, positive and negative predictive values for detection

Optimized imaging quality and radiation dose for coronary artery angiography using 128-slice, dual-source Flash Spiral CT under the natural heart rate

International Nuclear Information System (INIS)

Xue Yuejun; Qian Nong; Shao Yanhui; Pan Changjie; Rong Weiliang; Xu Yiqun; Tao Zhiwei

2011-01-01

Objective: To compare the quality and radiation doses of coronary artery angiography under the natural heart rate condition between Flash spiral heart mode and prospective electrocardiogram- triggering sequence mode using dual-source, in order to choose personalized low doses of coronary artery scanning mode. Methods: Sixty patients who underwent coronary angiography (CTA) on a 128-slice, dual- source CT scanner were divided into 2 group i.e, group A (27 cases) and group B (33 cases). Flash spiral heart scan mode was employed for group A. Inclusion criteria included: heart rate 75 bpm), date acquisition was set at 30%-50% of the R-R interval. (3) At the arrhythmias, premature beat, fibrillation atrial, date acquisition was set at 20%-90% of the R-R interval. In both groups, patients with a BMI ≥ 25.0 kg/m 2 were examined with a tube voltage of 120 kV, while the other patients with a BMI 2 were examined with a tube voltage of 100 kV. The BMI was (24.6±1.0) kg/m 2 in group A, while that was (24.6±0.9) kg/m 2 in group B. In both groups, all images were transferred to the workstation for further processing and analysis. The imaging quality of coronary artery segments and the radiation dose were compared with t test. Results: A total of 336 coronary artery segments were evaluated in group A and 412 segments were evaluated in group B. The imaging quality of coronary artery segments were scored. Excellent or good was achieved in 98.2% (330 of 336) artery segments in group A, and that was 98.1% (404 of 412) in group B. There was no statistical difference in imaging quality between the two groups (t=0.513, P=0.608). The average effective dose was (0.74±0.29) mSv in group A, whereas that was (3.67± 1.37) mSv in group B. There was a significant difference between the two groups (t=-10.858, P= 0.000). Conclusions: The personalized low doses coronary artery scanning mode can substantially reduce radiation damage while preserving good imaging quality. (authors)

Spiral computed tomography phase-space source model in the BEAMnrc/EGSnrc Monte Carlo system: implementation and validation

International Nuclear Information System (INIS)

Kim, Sangroh; Yoshizumi, Terry T; Yin Fangfang; Chetty, Indrin J

2013-01-01

Currently, the BEAMnrc/EGSnrc Monte Carlo (MC) system does not provide a spiral CT source model for the simulation of spiral CT scanning. We developed and validated a spiral CT phase-space source model in the BEAMnrc/EGSnrc system. The spiral phase-space source model was implemented in the DOSXYZnrc user code of the BEAMnrc/EGSnrc system by analyzing the geometry of spiral CT scan—scan range, initial angle, rotational direction, pitch, slice thickness, etc. Table movement was simulated by changing the coordinates of the isocenter as a function of beam angles. Some parameters such as pitch, slice thickness and translation per rotation were also incorporated into the model to make the new phase-space source model, designed specifically for spiral CT scan simulations. The source model was hard-coded by modifying the ‘ISource = 8: Phase-Space Source Incident from Multiple Directions’ in the srcxyznrc.mortran and dosxyznrc.mortran files in the DOSXYZnrc user code. In order to verify the implementation, spiral CT scans were simulated in a CT dose index phantom using the validated x-ray tube model of a commercial CT simulator for both the original multi-direction source (ISOURCE = 8) and the new phase-space source model in the DOSXYZnrc system. Then the acquired 2D and 3D dose distributions were analyzed with respect to the input parameters for various pitch values. In addition, surface-dose profiles were also measured for a patient CT scan protocol using radiochromic film and were compared with the MC simulations. The new phase-space source model was found to simulate the spiral CT scanning in a single simulation run accurately. It also produced the equivalent dose distribution of the ISOURCE = 8 model for the same CT scan parameters. The MC-simulated surface profiles were well matched to the film measurement overall within 10%. The new spiral CT phase-space source model was implemented in the BEAMnrc/EGSnrc system. This work will be beneficial in estimating the

Spiral computed tomography phase-space source model in the BEAMnrc/EGSnrc Monte Carlo system: implementation and validation.

Science.gov (United States)

Kim, Sangroh; Yoshizumi, Terry T; Yin, Fang-Fang; Chetty, Indrin J

2013-04-21

Currently, the BEAMnrc/EGSnrc Monte Carlo (MC) system does not provide a spiral CT source model for the simulation of spiral CT scanning. We developed and validated a spiral CT phase-space source model in the BEAMnrc/EGSnrc system. The spiral phase-space source model was implemented in the DOSXYZnrc user code of the BEAMnrc/EGSnrc system by analyzing the geometry of spiral CT scan-scan range, initial angle, rotational direction, pitch, slice thickness, etc. Table movement was simulated by changing the coordinates of the isocenter as a function of beam angles. Some parameters such as pitch, slice thickness and translation per rotation were also incorporated into the model to make the new phase-space source model, designed specifically for spiral CT scan simulations. The source model was hard-coded by modifying the 'ISource = 8: Phase-Space Source Incident from Multiple Directions' in the srcxyznrc.mortran and dosxyznrc.mortran files in the DOSXYZnrc user code. In order to verify the implementation, spiral CT scans were simulated in a CT dose index phantom using the validated x-ray tube model of a commercial CT simulator for both the original multi-direction source (ISOURCE = 8) and the new phase-space source model in the DOSXYZnrc system. Then the acquired 2D and 3D dose distributions were analyzed with respect to the input parameters for various pitch values. In addition, surface-dose profiles were also measured for a patient CT scan protocol using radiochromic film and were compared with the MC simulations. The new phase-space source model was found to simulate the spiral CT scanning in a single simulation run accurately. It also produced the equivalent dose distribution of the ISOURCE = 8 model for the same CT scan parameters. The MC-simulated surface profiles were well matched to the film measurement overall within 10%. The new spiral CT phase-space source model was implemented in the BEAMnrc/EGSnrc system. This work will be beneficial in estimating the spiral

Evaluation of 16 detector row spiral CT in diagnosing pulmonary embolism

International Nuclear Information System (INIS)

Yu Xiaokun; Li Lei

2008-01-01

Objective: To investigate the value of 16 detector row spiral CT in the diagnosis of pulmonary embolism(PE). Methods: Imaging data of 20 patients (plain 16 detector row spiral CT scanning plus enhanced scanning imaging) highly suspected of PE was retrospectively analyzed. Results: Among the 20 cases, embolism was showed in 13 patients on 16 detector row spiral CT pulmonary angiography (MSCTPA). 6 cases of the 13 PE's patients have masculine findings on plain MSCT scanning images. Localized tenuous lung markings, dilated pulmonary artery, 'mosaic' sign, pleural or pericardial effusion, local high attenuation centrally in the pulmonary arteries and lung infarction occurred respectively. Conclusion: MSCTPA may be an effective, simple and safe technique for the diagnosis of PE. It was a reliable means in defecting PE However, for the cases unfit for contrast media and cases only suitable for unenhanced CT because of nonspecific heart-pulmonary symptom, noticeable abnormal signs of plain MSCT scanning could suggest the occurrence of pulmonary embolism. (authors)

Reduction of the unnecessary dose from the over-range area with a spiral dynamic z-collimator: comparison of beam pitch and detector coverage with 128-detector row CT.

Science.gov (United States)

Shirasaka, Takashi; Funama, Yoshinori; Hayashi, Mutsukazu; Awamoto, Shinichi; Kondo, Masatoshi; Nakamura, Yasuhiko; Hatakenaka, Masamitsu; Honda, Hiroshi

2012-01-01

Our purpose in this study was to assess the radiation dose reduction and the actual exposed scan length of over-range areas using a spiral dynamic z-collimator at different beam pitches and detector coverage. Using glass rod dosimeters, we measured the unilateral over-range scan dose between the beginning of the planned scan range and the beginning of the actual exposed scan range. Scanning was performed at detector coverage of 80.0 and 40.0 mm, with and without the spiral dynamic z-collimator. The dose-saving ratio was calculated as the ratio of the unnecessary over-range dose, with and without the spiral dynamic z-collimator. In 80.0 mm detector coverage without the spiral dynamic z-collimator, the actual exposed scan length for the over-range area was 108, 120, and 126 mm, corresponding to a beam pitch of 0.60, 0.80, and 0.99, respectively. With the spiral dynamic z-collimator, the actual exposed scan length for the over-range area was 48, 66, and 84 mm with a beam pitch of 0.60, 0.80, and 0.99, respectively. The dose-saving ratios with and without the spiral dynamic z-collimator for a beam pitch of 0.60, 0.80, and 0.99 were 35.07, 24.76, and 13.51%, respectively. With 40.0 mm detector coverage, the dose-saving ratios with and without the spiral dynamic z-collimator had the highest value of 27.23% with a low beam pitch of 0.60. The spiral dynamic z-collimator is important for a reduction in the unnecessary over-range dose and makes it possible to reduce the unnecessary dose by means of a lower beam pitch.

Improvement in printing technique of spiral CT three-dimensional colour image

International Nuclear Information System (INIS)

Wang Yicheng; Liu Feng; Zhang Ling

2005-01-01

Objective: To investigate the printing technique of spiral CT three-dimensional (3D) colour image. Methods: The 3D colour images of 136 patients were printed, with the equipment of Marconi spiral CT, personnel computer, colour ink printer, and network switchboard. Results: All printed images were satisfied by this method. Conclusion: This technique is economic, simple, and useful, and can meet the need for clinical diagnosis and operation. (authors)

TU-F-CAMPUS-I-01: Investigation of the Effective Dose From Bolus Tracking Acquisitions at Different Anatomical Locations in the Chest for CT

Energy Technology Data Exchange (ETDEWEB)

Nowik, P; Bujila, R; Merzan, D [Dept. of Medical Physics, Karolinska University Hospital, Stockholm (Sweden)

2015-06-15

Purpose: Stationary table acquisitions (Bolus tracking) in X-ray Computed Tomography (CT) can Result in dose length products (DLP) comparable to spiral scans. It is today unclear whether or not the effective dose (E) for Bolus Tracking can be approximated using target region specific conversion factors (E/DLP). The purpose of this study was to investigate how E depends on the anatomical location of the Bolus Tracking in relation to Chest CT scans with the same DLP. Methods: Effective doses were approximated for the ICRP 110 adult Reference Male (AM) and adult Reference Female (FM) computational voxel phantoms using software for CT dose approximations (pre-simulated MC data). The effective dose was first approximated for a Chest CT scan using spiral technique and a CTDIvol (32 cm) of 6 mGy. The effective dose from the spiral scan was then compared to E approximated for contiguous Bolus Tracking acquisitions (1 cm separation), with a total collimation of 1 cm, over different locations of the chest of the voxel phantoms. The number of rotations used for the Bolus Tracking acquisitions was adjusted to yield the same DLP (32 cm) as the spiral scan. Results: Depending on the anatomical location of the Bolus Tracking, E ranged by factors of 1.3 to 6.8 for the AM phantom and 1.4 to 3.3 for the AF phantom, compared to the effective dose of the spiral scans. The greatest E for the Bolus Tracking acquisitions was observed for anatomical locations coinciding with breast tissue. This can be expected as breast tissue has a high tissue weighting factor in the calculation of E. Conclusion: For Chest CT scans, the effective dose from Bolus Tracking is highly dependent on the anatomical location where the scan is administered and will not always accurately be represented using target region specific conversion factors.

The anal verge: localization with multi-slice spiral CT

International Nuclear Information System (INIS)

Wang Wei; Tang Guangjian

2010-01-01

Objective: To determine and evaluate the method of localization of anal verge by multislice spiral CT. To provide an imaging reference for operative guidance of low-rectal cancer. Methods Forty eight consecutive adult patients suspected of abnormalities other than rectal disease were evaluated with abdominal and pelvic CT scans since August, 2009. They were divided into two groups based on sex and age. There were 23 men and 25 women. The ages of young group were 28 to 50 years and the average age was 41 years. The ages of elderly group were 52 to 81 years and the average age was 64 years. A small cotton ball dipped with contrast media was put at the anal verge as a marker and CT scans were performed with 64-slice spiral CT scanner. The distances between the cotton balls and the lower margin of the pubis combination (La), the lower margin of the Sth sacral vertebra (Lb), the inferior aperture of minor pelvis (Lc) and the lower margin of the basement of external anal sphincter (Ld) were measured on the mid- sagittal images obtained by MPR. The averages, the standard deviations (s), the 95% and 80% confidence intervals of La, Lb, Lc and Ld were calculated. We took the intervals of ±1.96 s or ±1.28 s 0.05) between two different sex groups [male group, (10.0±1.2) mm], female group, (9.6±1.2) mm and between two age groups [young group, (9.6±1.2) mm, elderly group, (9.9±1.3) mm]. Conclusions: The lower margin of the basement of external anal sphincter was a useful anatomic landmark for localizing the anal verge, and could be definitely identified on the middle sagittal pelvic CT image. The distance between the structure and anal verge is constant enough and can be used in measuring distance from low rectal lesion to the anal verge. (authors)

Initial clinical experience with spiral CT angiography in the abdomen

International Nuclear Information System (INIS)

Gaa, J.; Stehling, M.K.; Costello, P.

1993-01-01

The latest developments in modern CT instruments, offering scanning times of a second, opened up new possibilities in CT imaging in combination with the spiral technique. The data set normally taken with single-breath-hold technique is free of respiratory artefacts and thus is a good basis for accurate 3D image reconstruction. Spiral CTA allows a non-invasive 3D imaging of various blood vessels. Patients with abdominal aortic aneurysms of aorto-iliac bypass can be examined as outpatients within 15 minutes. (orig.) [de

Low-dose non-enhanced CT versus full-dose contrast-enhanced CT in integrated PET/CT studies for the diagnosis of uterine cancer recurrence

Energy Technology Data Exchange (ETDEWEB)

Kitajima, Kazuhiro [Institute of Biomedical Research and Innovation, Department of PET Diagnosis, Kobe (Japan); Kobe University Graduate School of Medicine, Department of Radiology, Kobe (Japan); Suzuki, Kayo [Institute of Biomedical Research and Innovation, Department of PET Diagnosis, Kobe (Japan); Nakamoto, Yuji [Kyoto University Hospital, Department of Diagnostic Radiology, Kyoto (Japan); Onishi, Yumiko; Sakamoto, Setsu; Sugimura, Kazuro [Kobe University Graduate School of Medicine, Department of Radiology, Kobe (Japan); Senda, Michio [Institute of Biomedical Research and Innovation, Department of Molecular Imaging, Kobe (Japan); Kita, Masato [Kobe City Medical Center General Hospital, Department of Obstetrics and Gynecology, Kobe (Japan)

2010-08-15

To evaluate low-dose non-enhanced CT (ldCT) and full-dose contrast-enhanced CT (ceCT) in integrated {sup 18}F-fluorodeoxyglucose (FDG) PET/CT studies for restaging of uterine cancer. A group of 100 women who had undergone treatment for uterine cervical (n=55) or endometrial cancer (n=45) underwent a conventional PET/CT scans with ldCT, and then a ceCT scan. Two observers retrospectively reviewed and interpreted the PET/ldCT and PET/ceCT images in consensus using a three-point grading scale (negative, equivocal, or positive) per patient and per lesion. Final diagnoses were obtained by histopathological examination, or clinical follow-up for at least 6 months. Patient-based analysis showed that the sensitivity, specificity and accuracy of PET/ceCT were 90% (27/30), 97% (68/70) and 95% (95/100), respectively, whereas those of PET/ldCT were 83% (25/30), 94% (66/70) and 91% (91/100), respectively. Sensitivity, specificity and accuracy did not significantly differ between two methods (McNemar test, p=0.48, p=0.48, and p=0.13, respectively). There were 52 sites of lesion recurrence: 12 pelvic lymph node (LN), 11 local recurrence, 8 peritoneum, 7 abdominal LN, 5 lung, 3 supraclavicular LN, 3 liver, 2 mediastinal LN, and 1 muscle and bone. The grading results for the 52 sites of recurrence were: negative 5, equivocal 0 and positive 47 for PET/ceCT, and negative 5, equivocal 4 and positive 43 for PET/ldCT, respectively. Four equivocal regions by PET/ldCT (local recurrence, pelvic LN metastasis, liver metastasis and muscle metastasis) were correctly interpreted as positive by PET/ceCT. PET/ceCT is an accurate imaging modality for the assessment of uterine cancer recurrence. Its use reduces the frequency of equivocal interpretations. (orig.)

Evaluation of an exposed-radiation dose on a dual-source cardiac computed tomography examination with a prospective electrocardiogram-gated fast dual spiral scan

International Nuclear Information System (INIS)

Matsubara, Kosuke; Koshida, Kichiro; Koshida, Haruka; Sakuta, Keita; Hayashi, Hiroyuki; Takata, Tadanori; Horii, Junsei; Kawai, Keiichi; Yamamoto, Tomoyuki

2012-01-01

We evaluated exposed-radiation doses on dual-source cardiac computed tomography (CT) examinations with prospective electrocardiogram (ECG)-gated fast dual spiral scans. After placing dosimeters at locations corresponding to each of the thoracic organs, prospective ECG-gated fast dual spirals and retrospective ECG-gated dual spiral scans were performed to measure the absorbed dose of each organ. In the prospective ECG-gated fast dual spiral scans, the average absorbed doses were 5.03 mGy for the breast, 9.96 mGy for the heart, 6.60 mGy for the lung, 6.48 mGy for the bone marrow, 9.73 mGy for the thymus, and 4.58 mGy for the skin. These values were about 5% of the absorbed doses for the retrospective ECG-gated dual spiral scan. However, the absorbed dose differed greatly at each scan, especially in the external organs such as the breast. For effective and safe use of the prospective ECG-gated fast dual spiral scan, it is necessary to understand these characteristics sufficiently. (author)

Dual source multidetector CT-angiography before transcatheter aortic valve implantation (TAVI) using a high-pitch spiral acquisition mode

Energy Technology Data Exchange (ETDEWEB)

Wuest, W.; Anders, K.; May, M.S.; Uder, M. [University of Erlangen, Department of Radiology, Erlangen (Germany); Schuhbaeck, A.; Gauss, S.; Marwan, M.; Arnold, M.; Muschiol, G.; Daniel, W.G.; Achenbach, S. [University of Erlangen, Department of Cardiology, Erlangen (Germany); Ensminger, S. [University of Erlangen, Department of Cardiac Surgery, Erlangen (Germany)

2012-01-15

Transcatheter Aortic Valve Implantation (TAVI) is an alternative to surgical valve replacement in high risk patients. Angiography of the aortic root, aorta and iliac arteries is required to select suitable candidates, but contrast agents can be harmful due to impaired renal function. We evaluated ECG-triggered high-pitch spiral dual source Computed Tomography (CT) with minimized volume of contrast agent to assess aortic root anatomy and vascular access. 42 patients (82 {+-} 6 years) scheduled for TAVI underwent dual source (DS) CT angiography (CTA) of the aorta using a prospectively ECG-triggered high-pitch spiral mode (pitch = 3.4) with 40 mL iodinated contrast agent. We analyzed aortic root/iliac dimensions, attenuation, contrast to noise ratio (CNR), image noise and radiation exposure. Aortic root/iliac dimensions and distance of coronary ostia from the annulus could be determined in all cases. Mean aortic and iliac artery attenuation was 320 {+-} 70 HU and 340 {+-} 77 HU. Aortic/iliac CNR was 21.7 {+-} 6.8 HU and 14.5 {+-} 5.4 HU using 100 kV (18.8 {+-} 4.1 HU and 8.7 {+-} 2.6 HU using 120 kV). Mean effective dose was 4.5 {+-} 1.2 mSv. High-pitch spiral DSCTA can be used to assess the entire aorta and iliac arteries in TAVI candidates with a low volume of contrast agent while preserving diagnostic image quality. (orig.)

Spiral CT scanning plan to generate accurate Fe models of the human femur

International Nuclear Information System (INIS)

Zannoni, C.; Testi, D.; Capello, A.

1999-01-01

In spiral computed tomography (CT), source rotation, patient translation, and data acquisition are continuously conducted. Settings of the detector collimation and the table increment affect the image quality in terms of spatial and contrast resolution. This study assessed and measured the efficacy of spiral CT in those applications where the accurate reconstruction of bone morphology is critical: custom made prosthesis design or three dimensional modelling of the mechanical behaviour of long bones. Results show that conventional CT grants the highest accuracy. Spiral CT with D=5 mm and P=1,5 in the regions where the morphology is more regular, slightly degrades the image quality but allows to acquire at comparable cost an higher number of images increasing the longitudinal resolution of the acquired data set. (author)

MR appearance of cartilage defects of the knee: preliminary results of a spiral CT arthrography-guided analysis

International Nuclear Information System (INIS)

Berg, B.C. vande; Lecouvet, F.E.; Maldague, B.; Malghem, J.

2004-01-01

The aim of this study was to determine signal intensity patterns of cartilage defects at MR imaging. The MR imaging (3-mm-thick fat-suppressed intermediate-weighted fast spin-echo images) was obtained in 31 knees (21 male and 10 female patients; mean age 45.5 years) blindly selected from a series of 252 consecutive knees investigated by dual-detector spiral CT arthrography. Two radiologists determined in consensus the MR signal intensity of the cartilage areas where cartilage defects had been demonstrated on the corresponding reformatted CT arthrographic images. There were 83 cartilage defects at spiral CT arthrography. In 52 (63%) lesion areas, the MR signal intensity was higher than that of adjacent normal cartilage with signal intensity equivalent to (n=31) or lower than (n=21) that of articular fluid. The MR signal intensity was equivalent to that of adjacent normal cartilage in 17 (20%) lesion areas and lower than that of adjacent cartilage in 8 (10%) lesion areas. In 6 (7%) lesion areas, mixed low and high signal intensity was observed. The MR signal intensity of cartilage defects demonstrated on spiral CT arthrographic images varies from low to high on fat-suppressed intermediate-weighted fast spin-echo MR images obtained with our equipment and MR parameters. (orig.)

Comparative analysis between spiral CT and pathology of pulmonary nodules

International Nuclear Information System (INIS)

Wang Kaifu; Zhang Zhanqing

2007-01-01

Objective: To explore the value of spiral CT in the diagnosis of atypical pulmonary nodules. Methods: CT, clinic and histopathologic data of 72 patients with atypical pulmonary nodules confirmed by surgical resection in 41 cases and/or biopsy in 31 cases were retrospectively analyzed. Results: CT scans demonstrated slight lobulation in 34 cases, irregular margin in 50 cases, long speculate in 10 cases, air-bronchogram in 2 case, vacuole in 2 case. 38 pulmonary cancer, 22 pulmonary tuberculosis and 12 pulmonary inflammatory pseudotumors were diagnosed with spiral CT. However, 30 pulmonary cancer, 30 pulmonary tuberculosis and 12 pulmonary inflammatory pseudotumors were confirmed by histopathology. The overall accurate diagnostic rate of pulmonary cancer was 66.7% (20/30), pulmonary tuberculosis was 60%(18/30), pulmonary inflammatory pseudotumors was 16.7%(2/12). 40 cases were diagnosed correctly and 32 cases were misdiagnosed with CT in 72 cases of atypical pulmonary nodules. The misdiagnostic rate of CT was 44.4%. 10 cases of lung cancer were misdiagnosed, including 4 cases of tuberculosis (long speculate or irregular margin) and 6 cases of inflammatory pseudotumors (irregular margin or long speculate or air-bronchogram). 12 cases of tuberculosis were misdiagnosed, including 8 cases lung cancer (slight lobulation) and 4 cases of inflammatory pseudotumors (slight lobulation). 10 cases inflammatory pseudotumor were misdiagnosed as lung cancer (slight lobulation). Conclusion: Spiral CT was very useful in the localization and morphological describing, but difficult in qualitative diagnosing of atypical pulmonary nodules, exactly diagnosis was relied on surgery and biopsy. (authors)

Convolutional auto-encoder for image denoising of ultra-low-dose CT

Directory of Open Access Journals (Sweden)

Mizuho Nishio

2017-08-01

Conclusion: Neural network with convolutional auto-encoder could be trained using pairs of standard-dose and ultra-low-dose CT image patches. According to the visual assessment by radiologists and technologists, the performance of our proposed method was superior to that of large-scale nonlocal mean and block-matching and 3D filtering.

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...

Gamma regularization based reconstruction for low dose CT

International Nuclear Information System (INIS)

Zhang, Junfeng; Chen, Yang; Hu, Yining; Luo, Limin; Shu, Huazhong; Li, Bicao; Liu, Jin; Coatrieux, Jean-Louis

2015-01-01

Reducing the radiation in computerized tomography is today a major concern in radiology. Low dose computerized tomography (LDCT) offers a sound way to deal with this problem. However, more severe noise in the reconstructed CT images is observed under low dose scan protocols (e.g. lowered tube current or voltage values). In this paper we propose a Gamma regularization based algorithm for LDCT image reconstruction. This solution is flexible and provides a good balance between the regularizations based on l 0 -norm and l 1 -norm. We evaluate the proposed approach using the projection data from simulated phantoms and scanned Catphan phantoms. Qualitative and quantitative results show that the Gamma regularization based reconstruction can perform better in both edge-preserving and noise suppression when compared with other norms. (paper)

Three phase dynamic CT with double spiral CT: utility of determination of stomach cancer stage

International Nuclear Information System (INIS)

Jung, Min Ha; Kim, Hong In; Kim, Tae Hyung; Lee, Ki Yeol; Cho, June Il; Park, Cheol Min; Cha, In Ho

1997-01-01

To evaluate the utility of three phases of spiral CT in the diagnosis of stomach cancer. Between August 1994 and March 1995, thirty eight patients with stomach cancer, demonstrated on spiral CT, underwent surgery. Twenty-eight cases were advanced and ten were early. There were 27 men, and 11 women, and their average age was 52.8 years old (33-77). After ingestion of 600-700ml of water, 120-140ml of nonionic contrast material was injected intravenously. Spiral CT scanning was performed in 10mm slice thickness and of 10mm/sec table speed. Three phase image were obtained at 25sec (arterial phase), 60-65sec (venous phase) and 4min (equilibrium phase) after the start of bolus injection. On each phase, CT findings were compared with pathologic results, and tumor detectibility, depth of tumor invasion and lymph node metastasis was analysed. Thirty of the 38 carcinomas (79%) were detected on the arterial phase, 33 (81%) on the venous phase and 30 (79%) on the equilibrium phase. Depth of tumor invasion was measured accurately in 27 of 38 cases (71%) : T1-4/10 (40%), T2-8/11 (73%), T3-13/15 (87%), T4-2/2 (100%). We overstaged one case of T1 as T2 and two cases of T2 as T3, and understaged one case of T2 as T1 and two cases of T3 as T2. Among the 16 enlarged lymph nodes larger than 8mm, 13 cases were positive on pathologic examination and the sensitivity was 65%. With three-phase spiral CT scanning, we obtained 71% accuracy of depth of tumor invasion. The venous phase is most useful for tumor detection and for determining depth of tumor invasion and lymph node metastasis

A study of parameters in spiral CT volumetry using balloon phantoms

International Nuclear Information System (INIS)

Lee, Hak Jong; Han, Joon Koo

2001-01-01

To evaluate the effects of threshold values, reconstruction interval, slice thickness and table speed on the spiral CT volumetry. Two phantoms made of a balloon and diluted contrast media underwent spiral CT scanning with section thicknesses of 5, 7 and 10 mm and table speeds of 5, 8 and 10 mm with scans of 5 mm section thickness, 7, 10, and 14 mm with scans of 7 mm section thickness, and 10, 15, and 20 mm with scans of 10 mm section thickness. The volumetric values of phantom A and B were obtained at varying threshold values and a reconstruction interval of 5 and 10 mm for all scans. Volumes were also determined with the threshold value fixed and a reconstruction interval of 1, 5, 7 and 10 mm, respectively. Three-dimensional display and volumetric measurements were obtained using reconstructed images. The effects of threshold value, reconstruction interval, slice thickness and table speed on volumetry were analyzed. Volumetric values varied according to threshold values. Where a threshold value was low, value increased as pitch increased, but where a the threshold value was high, value decreased as pitch increased. With varying threshold values, measurement errors in CT volumetry were 1.6 to 9.0%. Volume decreased as reconstruction interval increased. Where the table speed/ slice thickness ratio was constant, volume was constant though slice thickness differed. At fixed threshold values, variation in the reconstruction interval was statistically more significant than variation in slice thickness or table speed (p<0.05, Kruskal-Wallis one-way ANOVA). Among serveral spiral scanning and image reconstruction parameters including threshold value, reconstruction interval, slice thickness, and table speed, threshold value most affected the result obtained. At fixed threshold values, the reconstruction interval used had more effect on CT volumetry than other parameters

Design of wireless data transmission system for spiral CT

International Nuclear Information System (INIS)

Wang Jue; Wang Fuquan; Liu Huaili

2010-01-01

A new wireless data transmission scheme based on UWB was proposed after studying the structure and character of spiral CT transmission system, the system was designed and validated. Using UWB device as wireless module to realize wireless data transmission. Using FPGA as main controller to meet the requirement of timing control for system module. Using two pieces of SDRAM in pingpang operation to realize large capacity storage mechanism. Using USB 2.0 interface to realize high-speed connection with UWB module. The results show that the transmission speed of the system arrival at 16.87 M bit ps within 3 meters, and the precision is 100%, it can be used for line-array spiral CT. (authors)

Dose and image quality in low-dose CT for urinary stone disease: added value of automatic tube current modulation and iterative reconstruction techniques

International Nuclear Information System (INIS)

Soenen, Olivier; Balliauw, Christophe; Oyen, Raymond; Zanca, Federica

2017-01-01

The aim of this study was to compare dose and image quality (IQ) of a baseline low-dose computed tomography (CT) (fix mAs) vs. an ultra-low-dose CT (automatic tube current modulation, ATCM) in patients with suspected urinary stone disease and to assess the added value of iterative reconstruction. CT examination was performed on 193 patients (103 baseline low-dose, 90 ultra-low-dose). Filtered back projection (FBP) was used for both protocols, and Sinogram Affirmed Iterative Reconstruction (SAFIRE) was used for the ultra-low-dose protocol only. Dose and ureter stones information were collected for both protocols. Subjective IQ was assessed by two radiologists scoring noise, visibility of the ureter and overall IQ. Objective IQ (contrast-to-noise ratio, CNR) was assessed for the ultra-low-dose protocol only (FBP and SAFIRE). The ultra-low-dose protocol (ATCM) showed a 22% decrease in mean effective dose ( p < 0.001) and improved visibility of the pelvic ureter (p = 0.02). CNR was higher for SAFIRE (p < 0.0001). SAFIRE improves the objective IQ, but not the subjective IQ for the chosen clinical task. (authors)

Effects of sparse sampling schemes on image quality in low-dose CT

International Nuclear Information System (INIS)

Abbas, Sajid; Lee, Taewon; Cho, Seungryong; Shin, Sukyoung; Lee, Rena

2013-01-01

Purpose: Various scanning methods and image reconstruction algorithms are actively investigated for low-dose computed tomography (CT) that can potentially reduce a health-risk related to radiation dose. Particularly, compressive-sensing (CS) based algorithms have been successfully developed for reconstructing images from sparsely sampled data. Although these algorithms have shown promises in low-dose CT, it has not been studied how sparse sampling schemes affect image quality in CS-based image reconstruction. In this work, the authors present several sparse-sampling schemes for low-dose CT, quantitatively analyze their data property, and compare effects of the sampling schemes on the image quality.Methods: Data properties of several sampling schemes are analyzed with respect to the CS-based image reconstruction using two measures: sampling density and data incoherence. The authors present five different sparse sampling schemes, and simulated those schemes to achieve a targeted dose reduction. Dose reduction factors of about 75% and 87.5%, compared to a conventional scan, were tested. A fully sampled circular cone-beam CT data set was used as a reference, and sparse sampling has been realized numerically based on the CBCT data.Results: It is found that both sampling density and data incoherence affect the image quality in the CS-based reconstruction. Among the sampling schemes the authors investigated, the sparse-view, many-view undersampling (MVUS)-fine, and MVUS-moving cases have shown promising results. These sampling schemes produced images with similar image quality compared to the reference image and their structure similarity index values were higher than 0.92 in the mouse head scan with 75% dose reduction.Conclusions: The authors found that in CS-based image reconstructions both sampling density and data incoherence affect the image quality, and suggest that a sampling scheme should be devised and optimized by use of these indicators. With this strategic

Estimation of absorbed dose of radiosensitive organs and effective sose in patients underwent abdominopelvic spiral CT scan using impact CT patient dosimetry

Directory of Open Access Journals (Sweden)

Ayoub Amirnia

2017-05-01

Full Text Available Background: Due to the presence of radiosensitive organs in the abdominopelvic region and increasing the number of requests for CT scan examinations, concerns about increasing radiation doses in patients has been greatly elevated. Therefore, the goal of this study was to determine the absorbed dose of radiosensitive organs and the effective dose in patients underwent abdominopelvic CT scan using ImPACT CT patient dosimetry Calculator (version 1.0.4, Imaging Performance Assessment on Computed Tomography, www.impactscan.org. Methods: This prospective cross-sectional study was conducted in Imam Reza Hospital from November to February 2015 February 2015 in the Imam Reza Hospital, in Urmia, Iran. The demographic and dosimetric information of 100 patients who underwent abdominopelvic CT scan in a 6-slice CT scanner were obtained through the data collection forms. The demographic data of the patients included age, weight, gender, and BMI. The dosimetric parameters included pitch value, CT dose volume index (CTDIvol, dose-length product (DLP, tube voltage, tube current, exposure time, collimation size, scan length, and scan time. To determine the absorbed dose of radiosensitive organs and also the effective dose in patients, ImPACT CT patient dosimetry calculator was used. Results: The results of this study demonstrated that the mean and standard deviation (SD of patients' effective dose in abdominopelvic CT scan was 4.927±0.164 mSv. The bladder in both genders had the greatest mean organ dose, which was 64.71±17.15 mGy for men and 77.56±18.48 mGy for women (P<0.001. Conclusion: The effective dose values of this examination are in the same range as previous studies, as well as International Commission on Radiological Protection (ICRP recommendations. However, the radiation dose from CT scan has the largest contribution to the medical imaging. According to the ALARA principle, it is recommended that the scan parameters, especially mAs, should be

Absorbed dose in CT. Comparison by CT dose index

International Nuclear Information System (INIS)

Yamamoto, Kenji; Akazawa, Hiroshi; Andou, Takashi

2002-01-01

Few reports have discussed the absorbed dose on CT units with increased scanning capacity even with the current widespread adoption of multi-slice CT units. To compare and investigate the dose indexes among CT units, we measured the absorbed dose on CT units operating in Nagano Prefecture Japan. The measurements showed proportionality between phantom absorbed dose and the exposured mAs values in conventional scanning operation. Further, the measurements showed that the absorbed dose in the center of the phantom differed by about 2.1-fold between the highest and lowest levels on individual CT units. Within a single company, multi-slice CT units of the same company gave absorbed doses of about 1.3 to 1.5 times those of conventional single-slice CT units under the same exposured conditions of conventional scanning. When the scanning pitch was reduced in helical scanning, the absorbed dose at the center of the phantom increased. (author)

Accuracy of lung nodule volumetry in low-dose CT with iterative reconstruction: an anthropomorphic thoracic phantom study.

Science.gov (United States)

Doo, K W; Kang, E-Y; Yong, H S; Woo, O H; Lee, K Y; Oh, Y-W

2014-09-01

The purpose of this study was to assess accuracy of lung nodule volumetry in low-dose CT with application of iterative reconstruction (IR) according to nodule size, nodule density and CT tube currents, using artificial lung nodules within an anthropomorphic thoracic phantom. Eight artificial nodules (four diameters: 5, 8, 10 and 12 mm; two CT densities: -630 HU that represents ground-glass nodule and +100 HU that represents solid nodule) were randomly placed inside a thoracic phantom. Scans were performed with tube current-time product to 10, 20, 30 and 50 mAs. Images were reconstructed with IR and filtered back projection (FBP). We compared volume estimates to a reference standard and calculated the absolute percentage error (APE). The APE of all nodules was significantly lower when IR was used than with FBP (7.5 ± 4.7% compared with 9.0 ±6.9%; p volumetry in low-dose CT by application of IR showed reliable accuracy in a phantom study. Lung nodule volumetry can be reliably applicable to all lung nodules including small, ground-glass nodules even in ultra-low-dose CT with application of IR. IR significantly improved the accuracy of lung nodule volumetry compared with FBP particularly for ground-glass (-630 HU) nodules. Volumetry in low-dose CT can be utilized in patient with lung nodule work-up, and IR has benefit for small, ground-glass lung nodules in low-dose CT.

SU-F-I-31: Reproducibility of An Automatic Exposure Control Technique in the Low-Dose CT Scan of Cardiac PET/CT Exams

Energy Technology Data Exchange (ETDEWEB)

Park, M; Rosica, D; Agarwal, V; Di Carli, M; Dorbala, S [Brigham and Women’s Hospital and Harvard Medical School, Boston, MA (United States)

2016-06-15

Purpose: Two separate low-dose CT scans are usually performed for attenuation correction of rest and stress N-13 ammonia PET/CT myocardial perfusion imaging (PET/CT). We utilize an automatic exposure control (AEC) technique to reduce CT radiation dose while maintaining perfusion image quality. Our goal is to assess the reproducibility of displayed CT dose index (CTDI) on same-day repeat CT scans (CT1 and CT2). Methods: Retrospectively, we reviewed CT images of PET/CT studies performed on the same day. Low-dose CT utilized AEC technique based on tube current modulation called Smart-mA. The scan parameters were 64 × 0.625mm collimation, 5mm slice thickness, 0.984 pitch, 1-sec rotation time, 120 kVp, and noise index 50 with a range of 10–200 mA. The scan length matched with PET field of view (FOV) with the heart near the middle of axial FOV. We identified the reference slice number (RS) for an anatomical landmark (carina) and used it to estimate axial shift between two CTs. For patient size, we measured an effective diameter on the reference slice. The effect of patient positioning to CTDI was evaluated using the table height. We calculated the absolute percent difference of the CTDI (%diff) for estimation of the reproducibility. Results: The study included 168 adults with an average body-mass index of 31.72 ± 9.10 (kg/m{sup 2}) and effective diameter was 32.72 ± 4.60 cm. The average CTDI was 1.95 ± 1.40 mGy for CT1 and 1.97 ± 1.42mGy for CT2. The mean %diff was 7.8 ± 6.8%. Linear regression analysis showed a significant correlation between the table height and %diff CTDI. (r=0.82, p<0.001) Conclusion: We have shown for the first time in human subjects, using two same-day CT images, that the AEC technique in low-dose CT is reproducible within 10% and significantly depends on the patient centering.

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

Staging of gastric adenocarcinoma using two-phase spiral CT: correlation with pathologic staging

International Nuclear Information System (INIS)

Seo, Tae Seok; Lee, Dong Ho; Ko, Young Tae; Lim, Joo Won

1998-01-01

To correlate the preoperative staging of gastric adenocarcinoma using two-phase spiral CT with pathologic staging. One hundred and eighty patients with gastric cancers confirmed during surgery underwent two-phase spiral CT, and were evaluated retrospectively. CT scans were obtained in the prone position after ingestion of water. Scans were performed 35 and 80 seconds after the start of infusion of 120mL of non-ionic contrast material with the speed of 3mL/sec. Five mm collimation, 7mm/sec table feed and 5mm reconstruction interval were used. T-and N-stage were determined using spiral CT images, without knowledge of the pathologic results. Pathologic staging was later compared with CT staging. Pathologic T-stage was T1 in 70 cases(38.9%), T2 in 33(18.3%), T3 in 73(40.6%), and T4 in 4(2.2%). Type-I or IIa elevated lesions accouted for 10 of 70 T1 cases(14.3%) and flat or depressed lesions(type IIb, IIc, or III) for 60(85.7%). Pathologic N-stage was NO in 85 cases(47.2%), N1 in 42(23.3%), N2 in 31(17.2%), and N3 in 22(12,2%). The detection rate of early gastric cancer using two-phase spiral CT was 100.0%(10 of 10 cases) among elevated lesions and 78.3%(47 of 60 cases) among flat or depressed lesions. With regard to T-stage, there was good correlation between CT image and pathology in 86 of 180 cases(47.8%). Overstaging occurred in 23.3%(42 of 180 cases) and understaging in 28.9%(52 of 180 cases). With regard to N-stage, good correlation between CT image and pathology was noted in 94 of 180 cases(52.2%). The rate of understaging(31.7%, 57 of 180 cases) was higher than that of overstaging(16.1%, 29 of 180 cases)(p<0.001). The detection rate of early gastric cancer using two-phase spiral CT was 81.4%, and there was no significant difference in detectability between elevated and depressed lesions. Two-phase spiral CT for determing the T-and N-stage of gastric cancer was not effective;it was accurate in abont 50% of cases understaging tended to occur.=20

Simple pulmonary eosinophilia detected at low-dose CT for lung cancer screening

Energy Technology Data Exchange (ETDEWEB)

Jeon, Kyung Nyeo; Bae, Kyung Soo; Kim, Ho Cheol [Gyeongsang National University Hospital, Jinju (Korea, Republic of)] (and others)

2006-05-15

The aim of this study was to evaluate the frequency, radiologic findings and clinical significance of the simple pulmonary eosinophilia (SPE) that was diagnosed among the asymptomatic patients who underwent low-dose CT scans for the early detection of lung cancer. From June 2003 to May 2005, 1,239 asymptomatic patients (1,275 examinations) who visited the health promotion center in our hospital and who underwent low-dose CT were enrolled in this study. SPE was defined as the presence of > 500 eosinophils per microliter of peripheral blood and the presence of abnormal parenchymal lesions such as nodules, airspace consolidation or areas of ground-glass attenuation (GGA) on CT, and there was spontaneous resolution or migration of the lesions on the follow-up examination. We analyzed the CT findings of SPE and we investigated the relationship between the occurrence of SPE and the season, smoking and the presence of parasite infestation. 36 patients were finally diagnosed as having SPE; this was 24% of the 153 patients who were diagnosed with parasite infestation and 2.8% of the total low-dose CT scans. These 36 patients consisted of 31 men and 5 women with a mean age 45.7 years. There was no significant relationship between SPE and the presence of parasite infestation, smoking or gender. Among the patients with peripheral blood eosinophilia, the eosinophil count was significantly higher in the patients with SPE than that in the patients without pulmonary infiltration ({rho} < 0.05). SPE more frequently occurred in winter and spring than in summer and autumn ({rho} < 0.05). The CT findings were single or multiple nodules in 18 patients, nodules and focal GGA in 9 patients and GGA only in 9 patients. Most of the nodules were less than 10 mm (88%, 49/56) in diameter and they showed an ill-defined margin (82%, n = 46); 30% of the nodules (n = 17) showed a halo around them. Simple pulmonary eosinophilia can be suggested as the cause if single or multiple ill-defined nodules

Simple pulmonary eosinophilia detected at low-dose CT for lung cancer screening

International Nuclear Information System (INIS)

Jeon, Kyung Nyeo; Bae, Kyung Soo; Kim, Ho Cheol

2006-01-01

The aim of this study was to evaluate the frequency, radiologic findings and clinical significance of the simple pulmonary eosinophilia (SPE) that was diagnosed among the asymptomatic patients who underwent low-dose CT scans for the early detection of lung cancer. From June 2003 to May 2005, 1,239 asymptomatic patients (1,275 examinations) who visited the health promotion center in our hospital and who underwent low-dose CT were enrolled in this study. SPE was defined as the presence of > 500 eosinophils per microliter of peripheral blood and the presence of abnormal parenchymal lesions such as nodules, airspace consolidation or areas of ground-glass attenuation (GGA) on CT, and there was spontaneous resolution or migration of the lesions on the follow-up examination. We analyzed the CT findings of SPE and we investigated the relationship between the occurrence of SPE and the season, smoking and the presence of parasite infestation. 36 patients were finally diagnosed as having SPE; this was 24% of the 153 patients who were diagnosed with parasite infestation and 2.8% of the total low-dose CT scans. These 36 patients consisted of 31 men and 5 women with a mean age 45.7 years. There was no significant relationship between SPE and the presence of parasite infestation, smoking or gender. Among the patients with peripheral blood eosinophilia, the eosinophil count was significantly higher in the patients with SPE than that in the patients without pulmonary infiltration (ρ < 0.05). SPE more frequently occurred in winter and spring than in summer and autumn (ρ < 0.05). The CT findings were single or multiple nodules in 18 patients, nodules and focal GGA in 9 patients and GGA only in 9 patients. Most of the nodules were less than 10 mm (88%, 49/56) in diameter and they showed an ill-defined margin (82%, n = 46); 30% of the nodules (n = 17) showed a halo around them. Simple pulmonary eosinophilia can be suggested as the cause if single or multiple ill-defined nodules or

Use of spiral CT and the contrast medium iohexol to determine in one session aortorenal morphology and the relative glomerular filtration rate of each kidney

International Nuclear Information System (INIS)

Frennby, B.; Almen, T.

2001-01-01

The aim of this study was to determine the relative glomerular filtration rate (GFR), i.e. the GFR of each kidney in percent of total GFR, by spiral CT. In 41 patients, who were part of a follow-up program after endoluminal stent grafting of aortic aneurysm, spiral CT with the contrast medium iohexol was used to evaluate the morphology of the aorta and kidneys. The opportunity was taken to utilize the already injected iohexol to determine the relative GFR with an extra CT sequence. In each patient two determinations were made, 6 or 12 months apart. The amount of a GFR marker accumulating in Bowman's space, tubuli, and renal pelvis within 2-3 min after i.v. injection, before any marker had left the kidney via the ureter, was defined as proportional to the GFR of that kidney. The renal accumulation of iohexol was obtained by spiral CT using 10-mm collimation and a table speed of 10 mm/s (pitch ratio 1:1) from the upper to the lower poles. The correlation coefficient between the relative GFR of each kidney determined at the first and second examination was excellent (r=0.99) with a median (range) difference of 1% (0-6%) of total GFR. The radiation dose calculated as the mean absorbed dose to the kidneys was 50 mGy and the effective dose 5 mSv. The morphology of aorta and kidneys and the relative GFR of each kidney can be determined in one session with spiral CT using iohexol as both angiographic contrast medium and as a GFR marker. It is also possible to take some plasma samples in the same session to determine iohexol concentration to calculate the body clearance of iohexol (or take plasma and urine samples to calculate the renal clearance of iohexol). (orig.)

Virtual gastroscopy using spiral CT in gastric lesions

International Nuclear Information System (INIS)

Shin, Sang Soo; Kang, Heoung Keun; Jeong, Yong Yeon; Yoon, Man Won; Song, Sang Gook; Jeong, Gwang Woo

1998-01-01

To compare virtual gastroscopy using spiral CT with conventional endoscopy for the detection and evaluation of gastric lesions. During a previous six-month period, 30 patients with pathologically-proven gastric lesions underwent conventional endoscopy and virtual gastroscopy using spiral CT. There were 18 cases of advanced gastric carcinoma, eight benign ulcers, and four submucosal tumors(two leiomyomas, two lymphomas). Source images of virtual gastroscopy were three-dim-ensionally reconstructed within an Advantage Windows Workstation and virtual gastroscopic images were obtained using Navigator Software. On analysis, images were graded according to their quality(excellent, good, poor). Virtual gastroscopic images were interpreted by two radiologists blinded to conventional endoscopic findings, and were subsequently compared with endoscopic findings in terms of detectability and findings. In the cases of advanced gastric carcinoma, lesions were classified according to Borrmann's system. For virtual gastroscopy, overall image quality was excellent in 21 cases(70%), good in five(17%), and poor in four(13%). Lesions were detected in 25 cases(83%). Among the 18 advanced gastric carcinomas, virtual gastroscopy image quality was excellent in 14 cases(78%), good in two(11%), and poor in two(11%). Lesions were detected in 16 cases(89%). Two Borrmann type IV cases were not detected. Among the eight benign ulcers, virtual gastroscopy image quality was excellent in three cases(38%), good in three(38%), and poor in two(25%). The detection of lesion was possible in five cases(63%). In all submucosal tumors, virtual gastroscopy image quality was excellent. Lesions were detected in all cases. Virtual gastroscopy using spiral CT is safe and noninvasive, and for the evaluation of gastric lesions may be complementary to axial CT. It successfully detects gastric lesions, and in depicting the pattern of gastric folds its image quality is excellent.=20

A new approximate algorithm for image reconstruction in cone-beam spiral CT at small cone-angles

International Nuclear Information System (INIS)

Schaller, S.; Flohr, T.; Steffen, P.

1996-01-01

This paper presents a new approximate algorithm for image reconstruction with cone-beam spiral CT data at relatively small cone-angles. Based on the algorithm of Wang et al., our method combines a special complementary interpolation with filtered backprojection. The presented algorithm has three main advantages over Wang's algorithm: (1) It overcomes the pitch limitation of Wang's algorithm. (2) It significantly improves z-resolution when suitable sampling schemes are applied. (3) It avoids the waste of applied radiation dose inherent to Wang's algorithm. Usage of the total applied dose is an important requirement in medical imaging. Our method has been implemented on a standard workstation. Reconstructions of computer-simulated data of different phantoms, assuming sampling conditions and image quality requirements typical to medical CT, show encouraging results

Can low-dose CT with iterative reconstruction reduce both the radiation dose and the amount of iodine contrast medium in a dynamic CT study of the liver?

Energy Technology Data Exchange (ETDEWEB)

Takahashi, Hiroto; Okada, Masahiro; Hyodo, Tomoko; Hidaka, Syojiro; Kagawa, Yuki; Matsuki, Mitsuru; Tsurusaki, Masakatsu; Murakami, Takamichi, E-mail: murakami@med.kindai.ac.jp

2014-04-15

Purpose: To investigate whether low-dose dynamic CT of the liver with iterative reconstruction can reduce both the radiation dose and the amount of contrast medium. Materials and methods: This study was approved by our institutional review board. 113 patients were randomly assigned to one of two groups. Group A/group B (fifty-eight/fifty-five patients) underwent liver dynamic CT at 120/100 kV, with 0/40% adaptive statistical iterative reconstruction (ASIR), with a contrast dose of 600/480 mg I/kg, respectively. Radiation exposure was estimated based on the manufacturer's phantom data. The enhancement value of the hepatic parenchyma, vessels and the tumor-to-liver contrast of hepatocellular carcinomas (HCCs) were compared between two groups. Two readers independently assessed the CT images of the hepatic parenchyma and HCCs. Results: The mean CT dose indices: 6.38/4.04 mGy, the dose-length products: 194.54/124.57 mGy cm, for group A/group B. The mean enhancement value of the hepatic parenchyma and the tumor-to-liver contrast of HCCs with diameters greater than 1 cm in the post-contrast all phases did not differ significantly between two groups (P > 0.05). The enhancement values of vessels in group B were significantly higher than that in group A in the delayed phases (P < 0.05). Two reader's confidence levels for the hepatic parenchyma in the delayed phases and HCCs did not differ significantly between the groups (P > 0.05). Conclusions: Low-dose dynamic CT with ASIR can reduce both the radiation dose and the amount of contrast medium without image quality degradation, compared to conventional dynamic CT without ASIR.

The value of spiral CT thin imaging reconstruction in the diagnosis of obstructive jaundice

International Nuclear Information System (INIS)

Huang Zhi; Liu Zhang; Yang Chaoxiang; Lin Chengye; Zhang Li; Li Yuxiang; Ma Yunyan; Xiao Haisong; Lu Zhifeng; Wang Bo; Zhou Yunhong

2009-01-01

Objective: To approach the value of spiral CT thin imaging reconstruction in the diagnosis of obstructive jaundice in order to improve the correctness of the diagnosis. Methods: Analysis the cases' clinical manifestation and the CT images, who were diagnosed as obstructive jaundice by operation. All of cases had high-resolution computed tomograyhy scan. The thickness and the interval is 5mm, reconstructed the thickness and the interval to 1 mm and 1.5 mm, then send the images to the workstation and MRR were processed. Analysis the date with the pathology. Results: Spiral CT thin imaging reconstruction have 98% and 93% in the accuracy of location and characterization in the obstruction. Conclusion: The spiral CT thin imaging reconstruction is a good method to improve the accuracy of location and characterization in the obstructive jaundice. (authors)

Evaluation of radiation doses delivered in different chest CT protocols

International Nuclear Information System (INIS)

Gorycki, Tomasz; Lasek, Iwona; Kamiński, Kamil; Studniarek, Michał

2014-01-01

There are differences in the reference diagnostic levels for the computed tomography (CT) of the chest as cited in different literature sources. The doses are expressed either in weighted CT dose index (CTDI VOL ) used to express the dose per slice, dose-length product (DLP), and effective dose (E). The purpose of this study was to assess the radiation dose used in Low Dose Computer Tomography (LDCT) of the chest in comparison with routine chest CT examinations as well as to compare doses delivered in low dose chest CT with chest X-ray doses. CTDI VOL and DLP doses were taken to analysis from routine CT chest examinations (64 MDCT TK LIGHT SPEED GE Medical System) performed in 202 adult patients with FBP reconstruction: 51 low dose, 106 helical, 20 angio CT, and 25 high resolution CT protocols, as well as 19 helical protocols with iterative ASIR reconstruction. The analysis of chest X-ray doses was made on the basis of reports from 44 examinations. Mean values of CTDI VOL and DLP were, respectively: 2.1 mGy and 85.1 mGy·cm, for low dose, 9.7 mGy and 392.3 mGy·cm for helical, 18.2 mGy and 813.9 mGy·cm for angio CT, 2.3 mGy and 64.4 mGy·cm for high resolution CT, 8.9 mGy. and 317.6 mGy·cm for helical ASIR protocols. Significantly lower CTDI VOL and DLP values were observed for low dose and high resolution CT versus the remaining CT protocols; doses delivered in CT ASIR protocols were also lower (80–81%). The ratio between medial doses in low dose CT and chest X-ray was 11.56. Radiation dose in extended chest LDCT with parameters allowing for identification of mediastinal structures and adrenal glands is still much lower than that in standard CT protocols. Effective doses predicted for LDCT may exceed those used in chest X-ray examinations by a factor of 4 to 12, depending on LDCT scan parameters. Our results, as well as results from other authors, suggest a possibility of reducing the dose by means of iterative reconstruction. Efforts towards further dose

Assessment of pancreatic adenocarcinoma: use of low-dose whole pancreatic CT perfusion and individualized dual-energy CT scanning

International Nuclear Information System (INIS)

Li, Hai-ou; Guo, Jun; Li, Xiao; Qi, Yao-dong; Wang, Xi-ming; Xu, Zhuo-dong; Liu, Cheng; Chen, Jiu-hong

2015-01-01

The objective of this study was to investigate the value of low-dose whole pancreatic computed tomography (CT) perfusion integrated with individualized dual-energy CT (DECT) scanning in the diagnosis of pancreatic adenocarcinoma. Twenty patients with pancreatic adenocarcinoma underwent pancreatic CT perfusion as well as individualized dual-phase DECT pancreatic scans. Perfusion characteristics of non-tumourous pancreatic parenchyma and pancreatic adenocarcinoma were analysed. Weighted-average 120 kVp images and the optimal monoenergetic images in dual phase were reconstructed and the contrast noise ratio (CNR) of pancreas-to-tumour were compared. There were significant difference on blood flow as well as blood volume between pancreatic adenocarcinoma and the non-tumourous pancreatic parenchyma (P < 0.05), whereas no difference on permeability (P > 0.05). CNRs of pancreas-to-tumour in individualized pancreatic phase were significantly higher than those in venous phase (P < 0.05), and CNRs of optimal monoenergetic images were higher than those on weighted-average 120 kVp images (P < 0.05) in both phase. Total effective radiation dose of CT examination was around 9.32–13.75 mSv. Low-dose whole pancreatic CT perfusion can provide functional information, and the individualized pancreatic phase DECT scan is the optimal method for detecting pancreatic adenocarcinomas. The integration of the two techniques has great value in clinical application.

Diagnostic accuracy of low-dose versus ultra-low-dose CT for lumbar disc disease and facet joint osteoarthritis in patients with low back pain with MRI correlation

Energy Technology Data Exchange (ETDEWEB)

Lee, Sun Hwa [Inje University College of Medicine, Department of Emergency Medicine, Sanggye Paik Hospital, Nowon-gu (Korea, Republic of); Yun, Seong Jong; Jo, Hyeon Hwan; Kim, Dong Hyeon [Republic of Korea Air Force, Department of Radiology, Aerospace Medical Center, Cheongwon-gun, Chungcheongbuk-do (Korea, Republic of); Song, Jae Gwang [Republic of Korea Air Force, Department of Orthopedic Surgery, Aerospace Medical Center, Cheongwon-gun, Chungcheongbuk-do (Korea, Republic of); Park, Yong Sung [Kyung Hee University Hospital at Gangdong, Kyung Hee University School of Medicine, Department of Radiology, Seoul (Korea, Republic of)

2018-04-15

To compare the image quality, radiation dose, and diagnostic performance between low-dose (LD) and ultra-low-dose (ULD) lumbar-spine (L-spine) CT with iterative reconstruction (IR) for patients with chronic low back pain (LBP). In total, 260 patients with chronic LBP who underwent L-spine CT between November 2015 and September 2016 were prospectively enrolled. Of these, 143 underwent LD-CT with IR and 117 underwent ULD-CT with IR. The patients were divided according to their body mass index (BMI) into BMI1 (<22.9 kg/m{sup 2}), BMI2 (23.0-24.9 kg/m{sup 2}), and BMI3 (≥25 kg/m{sup 2}) groups. Two blinded radiologists independently evaluated the signal-to-noise ratio (SNR), qualitative image quality, and final diagnoses (lumbar disc disease and facet joint osteoarthritis). L-spine MRIs interpreted by consensus were used as the reference standard. All data were statistically analyzed. ULD protocol showed significantly lower SNR for all patients (p < 0.001) except the vertebral bodies and lower qualitative image quality for BMI3 patients (p ≤ 0.033). There was no statistically significant difference between ULD (sensitivity, 95.1-98.1%; specificity, 92.5-98.7%; accuracy, 94.6-98.0%) and LD protocols (sensitivity, 95.6-100%; specificity, 95.5-98.9%; accuracy, 97.4-98.1%), (all p≥0.1) in the BMI1 and BMI2; while dose was 60-68% lower with the ULD protocol. Interobserver agreements were excellent or good with regard to image quality and final diagnoses. For the BM1 and BMI2 groups, ULD-CT provided an acceptable image quality and exhibited a diagnostic accuracy similar to that of LD-CT. These findings suggest that it is a useful diagnostic tool for patients with chronic LBP who exhibit a BMI of <25 kg/m{sup 2}. (orig.)

Diagnostic accuracy of low-dose versus ultra-low-dose CT for lumbar disc disease and facet joint osteoarthritis in patients with low back pain with MRI correlation

International Nuclear Information System (INIS)

Lee, Sun Hwa; Yun, Seong Jong; Jo, Hyeon Hwan; Kim, Dong Hyeon; Song, Jae Gwang; Park, Yong Sung

2018-01-01

To compare the image quality, radiation dose, and diagnostic performance between low-dose (LD) and ultra-low-dose (ULD) lumbar-spine (L-spine) CT with iterative reconstruction (IR) for patients with chronic low back pain (LBP). In total, 260 patients with chronic LBP who underwent L-spine CT between November 2015 and September 2016 were prospectively enrolled. Of these, 143 underwent LD-CT with IR and 117 underwent ULD-CT with IR. The patients were divided according to their body mass index (BMI) into BMI1 (<22.9 kg/m 2 ), BMI2 (23.0-24.9 kg/m 2 ), and BMI3 (≥25 kg/m 2 ) groups. Two blinded radiologists independently evaluated the signal-to-noise ratio (SNR), qualitative image quality, and final diagnoses (lumbar disc disease and facet joint osteoarthritis). L-spine MRIs interpreted by consensus were used as the reference standard. All data were statistically analyzed. ULD protocol showed significantly lower SNR for all patients (p < 0.001) except the vertebral bodies and lower qualitative image quality for BMI3 patients (p ≤ 0.033). There was no statistically significant difference between ULD (sensitivity, 95.1-98.1%; specificity, 92.5-98.7%; accuracy, 94.6-98.0%) and LD protocols (sensitivity, 95.6-100%; specificity, 95.5-98.9%; accuracy, 97.4-98.1%), (all p≥0.1) in the BMI1 and BMI2; while dose was 60-68% lower with the ULD protocol. Interobserver agreements were excellent or good with regard to image quality and final diagnoses. For the BM1 and BMI2 groups, ULD-CT provided an acceptable image quality and exhibited a diagnostic accuracy similar to that of LD-CT. These findings suggest that it is a useful diagnostic tool for patients with chronic LBP who exhibit a BMI of <25 kg/m 2 . (orig.)

Cystic Fibrosis: Are Volumetric Ultra-Low-Dose Expiratory CT Scans Sufficient for Monitoring Related Lung Disease?

DEFF Research Database (Denmark)

Loeve, Martine; Lequin, Maarten H; Bruijne, Marleen de

2009-01-01

Purpose: To assess whether chest computed tomography (CT) scores from ultra-low-dose end-expiratory scans alone could suffice for assessment of all cystic fibrosis (CF)-related structural lung abnormalities. Materials and Methods: In this institutional review board–approved study, 20 patients...... with CF aged 6–20 years (eight males, 12 females) underwent low-dose end-inspiratory CT and ultra-low-dose end-expiratory CT. Informed consent was obtained. Scans were randomized and scored by using the Brody-II CT scoring system to assess bronchiectasis, airway wall thickening, mucus plugging......-Altman plots. Results: Median age was 12.6 years (range, 6.3–20.3 years), median forced expiratory volume in 1 second was 100% (range, 46%–127%) of the predicted value, and median forced vital capacity was 99% (range, 61%–123%) of the predicted value. Very good agreement was observed between end...

On the use of Monte Carlo-derived dosimetric data in the estimation of patient dose from CT examinations

International Nuclear Information System (INIS)

Perisinakis, Kostas; Tzedakis, Antonis; Damilakis, John

2008-01-01

The purpose of this work was to investigate the applicability and appropriateness of Monte Carlo-derived normalized data to provide accurate estimations of patient dose from computed tomography (CT) exposures. Monte Carlo methodology and mathematical anthropomorphic phantoms were used to simulate standard patient CT examinations of the head, thorax, abdomen, and trunk performed on a multislice CT scanner. Phantoms were generated to simulate the average adult individual and two individuals with different body sizes. Normalized dose values for all radiosensitive organs and normalized effective dose values were calculated for standard axial and spiral CT examinations. Discrepancies in CT dosimetry using Monte Carlo-derived coefficients originating from the use of: (a) Conversion coefficients derived for axial CT exposures, (b) a mathematical anthropomorphic phantom of standard body size to derive conversion coefficients, and (c) data derived for a specific CT scanner to estimate patient dose from CT examinations performed on a different scanner, were separately evaluated. The percentage differences between the normalized organ dose values derived for contiguous axial scans and the corresponding values derived for spiral scans with pitch=1 and the same total scanning length were up to 10%, while the corresponding percentage differences in normalized effective dose values were less than 0.7% for all standard CT examinations. The normalized organ dose values for standard spiral CT examinations with pitch 0.5-1.5 were found to differ from the corresponding values derived for contiguous axial scans divided by the pitch, by less than 14% while the corresponding percentage differences in normalized effective dose values were less than 1% for all standard CT examinations. Normalized effective dose values for the standard contiguous axial CT examinations derived by Monte Carlo simulation were found to considerably decrease with increasing body size of the mathematical phantom

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

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

Energy Technology Data Exchange (ETDEWEB)

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.

Radiation dose-reduction strategies in thoracic CT.

Science.gov (United States)

Moser, J B; Sheard, S L; Edyvean, S; Vlahos, I

2017-05-01

Modern computed tomography (CT) machines have the capability to perform thoracic CT for a range of clinical indications at increasingly low radiation doses. This article reviews several factors, both technical and patient-related, that can affect radiation dose and discusses current dose-reduction methods relevant to thoracic imaging through a review of current techniques in CT acquisition and image reconstruction. The fine balance between low radiation dose and high image quality is considered throughout, with an emphasis on obtaining diagnostic quality imaging at the lowest achievable radiation dose. The risks of excessive radiation dose reduction are also considered. Inappropriately low dose may result in suboptimal or non-diagnostic imaging that may reduce diagnostic confidence, impair diagnosis, or result in repeat examinations incurring incremental ionising radiation exposure. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Clinical application of the three-dimensional reconstruction of spiral CT pneumocolon

International Nuclear Information System (INIS)

Yu Shenping; Li Ziping; Xu Dasheng; Lin Erjian; Lin Peizhang; Xu Qiaolan

2000-01-01

Objective: To evaluate the clinical role of the 3 types of reconstruction of the spiral CT pneumocolon in the diagnosis of colon lesions. Methods: Three types of reconstruction with spiral CT pneumocolon including air cast imaging (ACI), CT virtual endoscopy (CTVE), and multiple planner reconstruction (MPR) in 34 patients with colorectal cancer or polyps were correlated with surgical pathology respectively. Results: Among the 34 patients, 30 was colorectal cancer and 6 was polyps (2 of which in the proximal lumen of 2 colon cancer). (1) Comparison between the 3 types of the spiral CT pneumocolon reconstruction and pathology in colorectal cancer. 1) ACI: tumor patterns: coincide (n =22), anti-coincide (n = 8); tumor extension: coincide (n = 24), anti-coincide (n = 6); tumor size: coincide (n = 28), anti-coincide (n = 2). 2) CTVE: tumor patterns: coincide (n = 26), anti-coincide (n = 4); tumor extension: coincide (n = 25), anti-coincide ( n 5); tumor size: coincide (n = 23), anti-coincide (n = 7). 3) MPR: tumor patterns: coincide (n = 24), anti-coincide (n = 6); tumor extension: coincide (n = 30), anti-coincide (n = 0); tumor size: coincide (n = 26), anti-coincide (n = 4). (2) Comparison between the 3 types of the spiral CT pneumocolon reconstruction and pathology in colorectal polyps: the lesions were displayed in 4 (ACI) and in 6 (CTVE and MPR). Conclusion: (1) For the diagnosis of colorectal cancers: CTVE was the best means to display the tumor patterns, MPR most correct to judge the tumor extension, and ACI most suitable to measure the tumor size. (2) For the diagnosis of colorectal polyps, ACI can be used for oriented diagnosis, CTVE can well display the intra-luminal three-dimensional structure and can be used for characteristic diagnosis, MPR can be used for differential diagnosis

Synchronized control of spiral CT scan for security inspection device

International Nuclear Information System (INIS)

Wang Jue; Jiang Zenghui; Wang Fuquan

2008-01-01

In security inspection system of spiral CT, the synchronization between removing and rotating, and the scan synchronization between rotating and sampling influence quality of image reconstruction, so it is difficulty and important that how to realize synchronized scan. According to the controlling demand of multi-slice Spiral CT, the method to realize synchronized scan is given. a synchronized control system is designed, in which we use a industrial PC as the control computer, use magnetic grids as position detectors, use alternating current servo motor and roller motor as drivers respectively drive moving axis and rotating axis. This method can solve the problem of synchronized scan, and has a feasibility and value of use. (authors)

Functioning islet cell tumor of the pancreas. Localization with dynamic spiral CT

International Nuclear Information System (INIS)

Chung, M.J.; Choi, B.I.; Han, J.K.; Chung, J.W.; Han, M.C.; Bae, S.H.

1997-01-01

Purpose: The purpose of this study was to evaluate the usefulness of dynamic spiral CT, including multidimensional reformation, in the detection and localization of islet cell tumors of the pancreas. Material and Methods: Seven patients with histopathologically proven functioning islet cell tumors of the pancreas were studied with 2-phase contrast-enhanced spiral CT. Scanning of the arterial phase and late phase was started 30 s and 180 s, respectively, after injection of 100 ml of contrast medium at a rate of 3 ml/s. Results: Axial images in the arterial phase depicted the lesions in 5 patients, but in the late phase in only one patient. Multiplanar reformatted images of the arterial phase depicted the lesions in all 7 patients. Maximal intensity projection images demonstrated all lesions with information of their relationship to the vascular structure. Conclusion: Dynamic spiral CT with scanning during the arterial phase and retrospective multidimensional reformation is useful for preoperative detection and localization of small islet cell tumors of the pancreas. (orig.)

Clinical utility of coronary CT angiography with low-dose chest CT in the evaluation of patients with atypical chest pain: a preliminary report

International Nuclear Information System (INIS)

Lim, Soo Jin; Choo, Ki Seok; Kim, Chang Won

2008-01-01

To determine the clinical utility of coronary CT angiography (CCTA) with low-dose chest CT in the evaluation of patients with atypical chest pain. Ninety-six patients (mean age 60.2 years; age range, 41-68 years; 70 males) were referred for CCTA with low-dose chest CT (16-slice MDCT, Siemens) for an evaluation of atypical chest pain. When significant stenoses (lumen diameter reduction > 50%) were detected on CCTA, invasive coronary angiography (CA) was performed as the standard of reference. In all patients, medical chart review or telephone contact with patients was used to evaluate the contribution of CCTA with low-dose chest CT to the final clinical diagnosis, at least 6 months after performing CCTA. Among 96 patients, seven patients (7%) had significant stenoses as detected on CCTA, whereas two patients (2%) had significant stenoses and five patients had insignificant stenoses or no stenosis, as detected on conventional catheter angiography. In 18 (19%) of the 89 patients without significant stenosis detected on CCTA, this protocol provided additional information that suggested or confirmed an alternate clinical diagnosis. In patients with atypical chest pain, CCTA with low-dose chest CT could help to exclude ischemic heart disease and could provide important ancillary information for the final diagnosis

Prospective ECG triggering versus low-dose retrospective ECG-gated 128-channel CT coronary angiography: comparison of image quality and radiation dose

International Nuclear Information System (INIS)

Feng, Q.; Yin, Y.; Hua, X.; Zhu, R.; Hua, J.; Xu, J.

2010-01-01

Aim: To evaluate image quality and radiation dose for 128-detector prospective electrocardiogram (ECG)-gated computed tomography coronary angiography (CTCA) compared with a low-dose retrospective ECG-gated imaging protocol. Materials and methods: Thirty-one and 47 patients suspected of having coronary artery disease were enrolled into groups examined using prospective and low-dose retrospective ECG-gated CT protocols respectively. All examinations were performed on a 128-detector CT system (Definition AS, Siemens Healthcare, Forchheim, Germany). Prospective CTCA was performed using following parameters: tube voltage 100 kV; tube current 205 mAs; centre of acquisition window 70% of the RR interval. The tube current for low-dose retrospective ECG-gated CTCA was full dose during 40-70% of the RR interval and partial dose for the rest of RR interval. The pitch varied between 0.2 and 0.5 depending on heart rate and patient size. Image quality of coronary arteries was evaluated using a four-point grading scale. The signal-to-noise ratios (SNRs) of enhanced arteries and myocardium were also measured, corresponding contrast-to-noise ratios (CNRs) were calculated, and the radiation doses received were recorded. Results: There was a significant difference in the image quality scores between the retrospective and prospective gating protocols (Chi-square = 15.331, p = 0.009). There was no significant difference between the SNRs of the contrasted artery and myocardium in these two groups, but the CNRs were increased in the prospective group. The mean radiation dose of prospective gating group was 2.71 ± 0.67 mSv (range, 1.67-3.59 mSv), which was significantly lower than that of the retrospective group (p < 0.001). Conclusion: Prospective CT angiography can achieve lower radiation dose than that of low-dose retrospective CT angiography, with preserved image quality.

Prospective ECG triggering versus low-dose retrospective ECG-gated 128-channel CT coronary angiography: comparison of image quality and radiation dose

Energy Technology Data Exchange (ETDEWEB)

Feng, Q.; Yin, Y.; Hua, X.; Zhu, R.; Hua, J. [Department of Radiology, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai (China); Xu, J., E-mail: xujianr@hotmail.co [Department of Radiology, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai (China)

2010-10-15

Aim: To evaluate image quality and radiation dose for 128-detector prospective electrocardiogram (ECG)-gated computed tomography coronary angiography (CTCA) compared with a low-dose retrospective ECG-gated imaging protocol. Materials and methods: Thirty-one and 47 patients suspected of having coronary artery disease were enrolled into groups examined using prospective and low-dose retrospective ECG-gated CT protocols respectively. All examinations were performed on a 128-detector CT system (Definition AS, Siemens Healthcare, Forchheim, Germany). Prospective CTCA was performed using following parameters: tube voltage 100 kV; tube current 205 mAs; centre of acquisition window 70% of the RR interval. The tube current for low-dose retrospective ECG-gated CTCA was full dose during 40-70% of the RR interval and partial dose for the rest of RR interval. The pitch varied between 0.2 and 0.5 depending on heart rate and patient size. Image quality of coronary arteries was evaluated using a four-point grading scale. The signal-to-noise ratios (SNRs) of enhanced arteries and myocardium were also measured, corresponding contrast-to-noise ratios (CNRs) were calculated, and the radiation doses received were recorded. Results: There was a significant difference in the image quality scores between the retrospective and prospective gating protocols (Chi-square = 15.331, p = 0.009). There was no significant difference between the SNRs of the contrasted artery and myocardium in these two groups, but the CNRs were increased in the prospective group. The mean radiation dose of prospective gating group was 2.71 {+-} 0.67 mSv (range, 1.67-3.59 mSv), which was significantly lower than that of the retrospective group (p < 0.001). Conclusion: Prospective CT angiography can achieve lower radiation dose than that of low-dose retrospective CT angiography, with preserved image quality.

Value of multi-slice spiral CT MPVR reconstruction in the diagnosis of acute appendicitis

International Nuclear Information System (INIS)

Wang Kang; Zhao Zehua; Wang Zhi; Wang Weizhong; Xu Songsen; Zhang Miao; Liu Wenjin; Zhang Guozhen; Feng Dianxu

2005-01-01

Objective: To investigate the value of multi-slice spiral CT MPVR reconstruction in the diagnosis of acute appendicitis. Methods: A total of 39 patients with clinically suspected acute appendicitis underwent surgery from February, 2002 to September, 2003. They were prospectively examined before surgery with routine CT scanning and MPVR reconstruction spiral CT. 31 cases of appendicitis were confirmed after appendectomy. CT scans and surgery-pathology reports were evaluated on a five-grade scale from hyperemic-edematous appendix to abscess (normal appendix: 0 grade). Results: The results of spiral CT MPVR reconstruction were compared with the surgical and pathologic findings at appendectomy, yielding an accuracy of 87.2%, sensitivity of 90.3%, specificity of 75%, positive predictive value of 93.3%, and negative predictive value of 66.7%, respectively. Results of routine CT yielded an accuracy of 38.5%, sensitivity of 38.7%, specificity of 37.5%, positive predictive value of 70.6%, and negative predictive value of 13.6%, respectively. MPVR reconstruction signs of 28 patients with acute appendicitis included enlarged appendix ( > 6 mm) (96.4%), appendicoliths (26.7%), caecal apical thickening (36.7%), periappendiceal inflammation (71.4%), and abscess (10.7%). Conclusion: The use of spiral CT MPVR reconstruction in patients with equivocal clinical presentation suspected of having acute appendicitis can lead to a significant improvement in the preoperative diagnosis and maybe a decrease in surgical-pathologic severity of appendiceal disease. (authors)

Smoking habits in the randomised Danish Lung Cancer Screening Trial with low-dose CT

DEFF Research Database (Denmark)

Ashraf, Haseem; Saghir, Zaigham; Dirksen, Asger

2014-01-01

BACKGROUND: We present the final results of the effect of lung cancer screening with low-dose CT on the smoking habits of participants in a 5-year screening trial. METHODS: The Danish Lung Cancer Screening Trial (DLCST) was a 5-year screening trial that enrolled 4104 subjects; 2052 were randomised...... to annual low-dose CT (CT group) and 2052 received no intervention (control group). Participants were current and ex-smokers (≥4 weeks abstinence from smoking) with a tobacco consumption of ≥20 pack years. Smoking habits were determined annually. Missing values for smoking status at the final screening...... round were handled using two different models. RESULTS: There were no statistically significant differences in annual smoking status between the CT group and control group. Overall the ex-smoker rates (CT + control group) significantly increased from 24% (baseline) to 37% at year 5 of screening (p

CT patterns of fungal pulmonary infections of the lung: Comparison of standard-dose and simulated low-dose CT

International Nuclear Information System (INIS)

Christe, Andreas; Lin, Margaret C.; Yen, Andrew C.; Hallett, Rich L.; Roychoudhury, Kingshuk; Schmitzberger, Florian; Fleischmann, Dominik; Leung, Ann N.; Rubin, Geoffry D.; Vock, Peter; Roos, Justus E.

2012-01-01

Purpose: To assess the effect of radiation dose reduction on the appearance and visual quantification of specific CT patterns of fungal infection in immuno-compromised patients. Materials and methods: Raw data of thoracic CT scans (64 × 0.75 mm, 120 kVp, 300 reference mAs) from 41 consecutive patients with clinical suspicion of pulmonary fungal infection were collected. In 32 patients fungal infection could be proven (median age of 55.5 years, range 35–83). A total of 267 cuboids showing CT patterns of fungal infection and 27 cubes having no disease were reconstructed at the original and 6 simulated tube currents of 100, 40, 30, 20, 10, and 5 reference mAs. Eight specific fungal CT patterns were analyzed by three radiologists: 76 ground glass opacities, 42 ground glass nodules, 51 mixed, part solid, part ground glass nodules, 36 solid nodules, 5 lobulated nodules, 6 spiculated nodules, 14 cavitary nodules, and 37 foci of air-space disease. The standard of reference was a consensus subjective interpretation by experts whom were not readers in the study. Results: The mean sensitivity and standard deviation for detecting pathological cuboids/disease using standard dose CT was 0.91 ± 0.07. Decreasing dose did not affect sensitivity significantly until the lowest dose level of 5 mAs (0.87 ± 0.10, p = 0.012). Nodular pattern discrimination was impaired below the dose level of 30 reference mAs: specificity for fungal ‘mixed nodules’ decreased significantly at 20, 10 and 5 reference mAs (p < 0.05). At lower dose levels, classification drifted from ‘solid’ to ‘mixed nodule’, although no lesion was missed. Conclusion: Our simulation data suggest that tube current levels can be reduced from 300 to 30 reference mAs without impairing the diagnostic information of specific CT patterns of pulmonary fungal infections

A simple method for estimating the effective dose in dental CT. Conversion factors and calculation for a clinical low-dose protocol

International Nuclear Information System (INIS)

Homolka, P.; Kudler, H.; Nowotny, R.; Gahleitner, A.; Wien Univ.

2001-01-01

An easily appliable method to estimate effective dose including in its definition the high radio-sensitivity of the salivary glands from dental computed tomography is presented. Effective doses were calculated for a markedly dose reduced dental CT protocol as well as for standard settings. Data are compared with effective doses from the literature obtained with other modalities frequently used in dental care. Methods: Conversion factors based on the weighted Computed Tomography Dose Index were derived from published data to calculate effective dose values for various CT exposure settings. Results: Conversion factors determined can be used for clinically used kVp settings and prefiltrations. With reduced tube current an effective dose for a CT examination of the maxilla of 22 μSv can be achieved, which compares to values typically obtained with panoramic radiography (26 μSv). A CT scan of the mandible, respectively, gives 123 μSv comparable to a full mouth survey with intraoral films (150 μSv). Conclusion: For standard CT scan protocols of the mandible, effective doses exceed 600 μSv. Hence, low dose protocols for dental CT should be considered whenever feasable, especially for paediatric patients. If hard tissue diagnoses is performed, the potential of dose reduction is significant despite the higher image noise levels as readability is still adequate. (orig.) [de

Adaptive iterative dose reduction (AIDR) 3D in low dose CT abdomen-pelvis: Effects on image quality and radiation exposure

International Nuclear Information System (INIS)

Ang, W C; Hashim, S; Karim, M K A; Bahruddin, N A; Salehhon, N; Musa, Y

2017-01-01

The widespread use of computed tomography (CT) has increased the medical radiation exposure and cancer risk. We aimed to evaluate the impact of AIDR 3D in CT abdomen-pelvic examinations based on image quality and radiation dose in low dose (LD) setting compared to standard dose (STD) with filtered back projection (FBP) reconstruction. We retrospectively reviewed the images of 40 patients who underwent CT abdomen-pelvic using a 80 slice CT scanner. Group 1 patients ( n =20, mean age 41 ± 17 years) were performed at LD with AIDR 3D reconstruction and Group 2 patients ( n =20, mean age 52 ± 21 years) were scanned with STD using FBP reconstruction. Objective image noise was assessed by region of interest (ROI) measurements in the liver and aorta as standard deviation (SD) of the attenuation value (Hounsfield Unit, HU) while subjective image quality was evaluated by two radiologists. Statistical analysis was used to compare the scan length, CT dose index volume (CTDI vol ) and image quality of both patient groups. Although both groups have similar mean scan length, the CTDI vol significantly decreased by 38% in LD CT compared to STD CT ( p <0.05). Objective and subjective image quality were statistically improved with AIDR 3D ( p <0.05). In conclusion, AIDR 3D enables significant dose reduction of 38% with superior image quality in LD CT abdomen-pelvis. (paper)

Low dose CT perfusion in acute ischemic stroke

International Nuclear Information System (INIS)

Murphy, Amanda; Symons, Sean; Jakubovic, Raphael; Zhang, Liying; Aviv, Richard I.; So, Aaron; Lee, Ting-Yim

2014-01-01

The purpose of this investigation is to determine if CT perfusion (CTP) measurements at low doses (LD = 20 or 50 mAs) are similar to those obtained at regular doses (RD = 100 mAs), with and without the addition of adaptive statistical iterative reconstruction (ASIR). A single-center, prospective study was performed in patients with acute ischemic stroke (n = 37; 54 % male; age = 74 ± 15 years). Two CTP scans were performed on each subject: one at 100 mAs (RD) and one at either 50 or 20 mAs (LD). CTP parameters were compared between the RD and LD scans in regions of ischemia, infarction, and normal tissue. Differences were determined using a within-subjects ANOVA (p 0.05). CTP-derived CBF and CBV are not different at 50 mAs compared to 100 mAs, even without the addition of ASIR. Current CTP protocols can be modified to reduce the effective dose by 50 % without altering CTP measurements. (orig.)

Hyaline cartilage thickness in radiographically normal cadaveric hips: comparison of spiral CT arthrographic and macroscopic measurements.

Science.gov (United States)

Wyler, Annabelle; Bousson, Valérie; Bergot, Catherine; Polivka, Marc; Leveque, Eric; Vicaut, Eric; Laredo, Jean-Denis

2007-02-01

To assess spiral multidetector computed tomographic (CT) arthrography for the depiction of cartilage thickness in hips without cartilage loss, with evaluation of anatomic slices as the reference standard. Permission to perform imaging studies in cadaveric specimens of individuals who had willed their bodies to science was obtained from the institutional review board. Two independent observers measured the femoral and acetabular hyaline cartilage thickness of 12 radiographically normal cadaveric hips (from six women and five men; age range at death, 52-98 years; mean, 76.5 years) on spiral multidetector CT arthrographic reformations and on coronal anatomic slices. Regions of cartilage loss at gross or histologic examination were excluded. CT arthrographic and anatomic measurements in the coronal plane were compared by using Bland-Altman representation and a paired t test. Differences between mean cartilage thicknesses at the points of measurement were tested by means of analysis of variance. Interobserver and intraobserver reproducibilities were determined. At CT arthrography, mean cartilage thickness ranged from 0.32 to 2.53 mm on the femoral head and from 0.95 to 3.13 mm on the acetabulum. Observers underestimated cartilage thickness in the coronal plane by 0.30 mm +/- 0.52 (mean +/- standard error) at CT arthrography (P cartilage thicknesses at the different measurement points was significant for coronal spiral multidetector CT arthrography and anatomic measurement of the femoral head and acetabulum and for sagittal and transverse CT arthrography of the femoral head (P cartilage thickness from the periphery to the center of the joint ("gradients") were found by means of spiral multidetector CT arthrography and anatomic measurement. Spiral multidetector CT arthrography depicts cartilage thickness gradients in radiographically normal cadaveric hips. (c) RSNA, 2007.

Dose-reduced CT with model-based iterative reconstruction in evaluations of hepatic steatosis: How low can we go?

Energy Technology Data Exchange (ETDEWEB)

Yasaka, Koichiro, E-mail: koyasaka@gmail.com [Department of Radiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655 (Japan); Katsura, Masaki [Department of Radiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655 (Japan); Akahane, Masaaki [NTT Medical Center Tokyo, 5-9-22 Higashi-Gotanda, Shinagawa-ku, Tokyo 141-8625 (Japan); Sato, Jiro [Department of Radiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655 (Japan); Matsuda, Izuru [Kanto Rosai Hospital, 1-1 Kizukisumiyoshi-cho, Nakahara-ku, Kawasaki, Kanagawa 211-8510 (Japan); Ohtomo, Kuni [Department of Radiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655 (Japan)

2014-07-15

Purpose: To determine whether dose-reduced CT with model-based iterative image reconstruction (MBIR) is a useful tool with which to diagnose hepatic steatosis. Materials and methods: This prospective clinical study approved by our Institutional Review Board included 103 (67 men and 36 women; mean age, 64.3 years) patients who provided written informed consent to undergo unenhanced CT. Images of reference-dose CT (RDCT) with filtered back projection (R-FBP) and low- and ultralow-dose CT (dose-length product; 24 and 9% of that of RDCT) with MBIR (L-MBIR and UL-MBIR) were reconstructed. Mean CT numbers of liver (CT[L]) and spleen (CT[S]), and quotient (CT[L/S]) of CT[L] and CT[S] were calculated from selected regions of interest. Bias and limits of agreement (LOA) of CT[L] and CT[L/S] in L-MBIR and UL-MBIR (vs. R-FBP) were assessed using Bland–Altman analyses. Diagnostic methods for hepatic steatosis of CT[L] < 48 Hounsfield units (HU) and CT[L/S] < 1.1 were applied to L-MBIR and UL-MBIR using R-FBP as the reference standard. Results: Bias was larger for CT[L] in UL-MBIR than in L-MBIR (−3.18 HU vs. −1.73 HU). The LOA of CT[L/S] was larger for UL-MBIR than for L-MBIR (±0.425 vs. ±0.245) and outliers were identified in CT[L/S] of UL-MBIR. Accuracy (0.92–0.95) and the area under the receiver operating characteristics curve (0.976–0.992) were high for each method, but some were slightly lower in UL-MBIR than L-MBIR. Conclusion: Dose-reduced CT reconstructed with MBIR is applicable to diagnose hepatic steatosis, however, a low dose of radiation might be preferable.

Detecting airway remodeling in COPD and emphysema using low-dose CT imaging

Science.gov (United States)

Rudyanto, R.; Ceresa, M.; Muñoz-Barrutia, A.; Ortiz-de-Solorzano, C.

2012-03-01

In this study, we quantitatively characterize lung airway remodeling caused by smoking-related emphysema and Chronic Obstructive Pulmonary Disease (COPD), in low-dose CT scans. To that end, we established three groups of individuals: subjects with COPD (n=35), subjects with emphysema (n=38) and healthy smokers (n=28). All individuals underwent a low-dose CT scan, and the images were analyzed as described next. First the lung airways were segmented using a fast marching method and labeled according to its generation. Along each airway segment, cross-section images were resampled orthogonal to the airway axis. Next 128 rays were cast from the center of the airway lumen in each crosssection slice. Finally, we used an integral-based method, to measure lumen radius, wall thickness, mean wall percentage and mean peak wall attenuation on every cast ray. Our analysis shows that both the mean global wall thickness and the lumen radius of the airways of both COPD and emphysema groups were significantly different from those of the healthy group. In addition, the wall thickness change starts at the 3rd airway generation in the COPD patients compared with emphysema patients, who display the first significant changes starting in the 2nd generation. In conclusion, it is shown that airway remodeling happens in individuals suffering from either COPD or emphysema, with some local difference between both groups, and that we are able to detect and accurately quantify this process using images of low-dose CT scans.

Intracranial aneurysms: evaluation in 200 patients with spiral CT angiography

International Nuclear Information System (INIS)

Young, N.; Kingston, R.J.; Markson, G.; Dorsch, N.W.C.; McMahon, J.

2001-01-01

The goal of this study was to assess the usefulness of spiral CT angiography (CTA) with three- dimensional reconstructions in defining intracranial aneurysms, particularly around the Circle of Willis. Two hundred consecutive patients with angiographic and/or surgical correlation were studied between 1993 and 1998, with CTA performed on a GE HiSpeed unit and Windows workstation. The following clinical situations were evaluated: conventional CT suspicion of an aneurysm; follow-up of treated aneurysm remnants or of untreated aneurysms; subarachnoid haemorrhage (SAH) and negative angiography; family or past aneurysm history; and for improved definition of aneurysm anatomy. Spiral CTA detected 140 of 144 aneurysms, and an overall sensitivity of 97%, including 30 of 32 aneurysms 3 mm or less in size. In 38 patients with SAH and negative angiography, CTA found six of the seven aneurysms finally diagnosed. There was no significant artefact in 17 of 23 patients (74%) with clips. The specificity of CTA was 86% with 8 false-positive cases. Spiral CTA is very useful in demonstrating intracranial aneurysms. (orig.)

CT dose reduction in children

International Nuclear Information System (INIS)

Vock, Peter

2005-01-01

World wide, the number of CT studies in children and the radiation exposure by CT increases. The same energy dose has a greater biological impact in children than in adults, and scan parameters have to be adapted to the smaller diameter of the juvenile body. Based on seven rules, a practical approach to paediatric CT is shown: Justification and patient preparation are important steps before scanning, and they differ from the preparation of adult patients. The subsequent choice of scan parameters aims at obtaining the minimal signal-to-noise ratio and volume coverage needed in a specific medical situation; exposure can be divided in two aspects: the CT dose index determining energy deposition per rotation and the dose-length product (DLP) determining the volume dose. DLP closely parallels the effective dose, the best parameter of the biological impact. Modern scanners offer dose modulation to locally minimise exposure while maintaining image quality. Beyond the selection of the physical parameters, the dose can be kept low by scanning the minimal length of the body and by avoiding any non-qualified repeated scanning of parts of the body. Following these rules, paediatric CT examinations of good quality can be obtained at a reasonable cost of radiation exposure. (orig.)

Quantitative assessment of pulmonary function using low dose multi-slice spiral CT in smoker

International Nuclear Information System (INIS)

Chen Huai; Zeng Qingsi; Zheng Jinping; Guan Yubao; Zhang Chaoliang; Cen Renli

2012-01-01

Objective: To evaluate the clinical feasibility of low dose MSCT for quantitative assessment of pulmonary function in smokers. Methods: One hundred and forty-six patients with chronic objective pulmonary disease (COPD) including 109 smokers (74.6%) and 37 non-smokers (25.3%) underwent pulmonary function test and low-dose MSCT scan. All data were analyzed using computer-aided lung analysis software. Pulmonary function parameters from low-dose MSCT were compared between smokers and non-smokers and also compared with pulmonary function test in non-smokers (Pearson test). Results: In smokers, the average volume at full inspiratory phase (Vin) was (5125 ± 862 ) ml, mean lung attenuation was (-902 ± 26) HU, mean lung density was (0.0984 ± 0.0260 ) g/cm 3 , emphysema volume was (2890 ±1370) ml. The average volume at full expiratory phase (Vex) was (2756 ±1027) ml, mean lung attenuation was (-811 ±62) HU, mean lung density was (0.1878 ±0.0631) g/cm 3 , emphysema volume was (685 ±104) ml. In non-smokers, the average Vin was (3734 ± 759) ml, mean lung attenuation was (-876 ±40) HU,mean lung density was (0.1244 ±0.0401)g/cm 3 , emphysema volume was ( 1503 ± 1217) ml. The average Vex was (1770 ± 679) ml, mean lung attenuation was (-765 ± 56) HU, mean lung density was (0.2360 ± 0.0563) g/cm 3 , emphysema volume was (156 ± 45) ml. There were significant differences between smokers and non-smokers (P<0.01). The Vex/Vin was correlated with residual volume/total lung capacity (RV/TLC, r=0.60, P<0.01), and Vin was correlated with TLC (r=0.58, P<0.01), Vex with RV (r=0.59, P<0.01). Pixel index (PI) -950 in was correlated with FEV 1% pre and FEV1/FVC% (r=-0.53, -0.62, respective, P<0.01), Pl-950ex was correlated with FEV1 % pre and FEV1/FVC% (r=-0.71, -0.77, respective, P<0.01). Conclusion: Low-dose MSCT can be a potential imaging tool for quantitative pulmonary function assessment in smokes. (authors)

The evaluation of radioprotection with low dose CT scanning in normal rabbits brain

International Nuclear Information System (INIS)

Zhang Shuqing; Gong Shenchu; Wang Tianle; Shen Yunxia; Cui Lei

2008-01-01

Objective: To determine wheather a lower radiation dose technique and various pitch could be used in CT of the rabbits' brain without jeopardizing the diagnostic accuracy of the images, and determine the evaluation of radioprotection with low dose CT scanning. Methods: Fifteen rabbits underwent CT using 200 mAs, 110 mAs or 70 mAs,and pitch 1.0 or 1.5. Anatomy details and the confidence level in reaching a diagnosis were evaluated by two radiologists in a double-blinded manner using a 4-point scoring system. The CTDI w of every group were compared. Results: For both reader there was no statistically significant difference between 6 group total score of 1-6 anatomical detail and each of 6 anatomical detail although score for each of 6 anatomical detail. The CTDI w of 70 mAs, in pitch 1.5 group decreased about 76.7%. Conclusion: Radiation dose reduction in brain CT is feasible in clinical use, and quality of images can be re- served. It plays an important role in radiation protection. (authors)

Low-dose CT pulmonary angiography on a 15-year-old CT scanner: a feasibility study

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Moritz Kaup

2016-12-01

Full Text Available Background Computed tomography (CT low-dose (LD imaging is used to lower radiation exposure, especially in vascular imaging; in current literature, this is mostly on latest generation high-end CT systems. Purpose To evaluate the effects of reduced tube current on objective and subjective image quality of a 15-year-old 16-slice CT system for pulmonary angiography (CTPA. Material and Methods CTPA scans from 60 prospectively randomized patients (28 men, 32 women were examined in this study on a 15-year-old 16-slice CT scanner system. Standard CT (SD settings were 100 kV and 150 mAs, LD settings were 100 kV and 50 mAs. Attenuation of the pulmonary trunk, various anatomic landmarks, and image noise were quantitatively measured; contrast-to-noise ratios (CNR and signal-to-noise ratios (SNR were calculated. Three independent blinded radiologists subjectively rated each image series using a 5-point grading scale. Results CT dose index (CTDI in the LD series was 66.46% lower compared to the SD settings (2.49 ± 0.55 mGy versus 7.42 ± 1.17 mGy. Attenuation of the pulmonary trunk showed similar results for both series (SD 409.55 ± 91.04 HU; LD 380.43 HU ± 93.11 HU; P = 0.768. Subjective image analysis showed no significant differences between SD and LD settings regarding the suitability for detection of central and peripheral PE (central SD/LD, 4.88; intra-class correlation coefficients [ICC], 0.894/4.83; ICC, 0.745; peripheral SD/LD, 4.70; ICC, 0.943/4.57; ICC, 0.919; all P > 0.4. Conclusion The LD protocol, on a 15-year-old CT scanner system without current high-end hardware or post-processing tools, led to a dose reduction of approximately 67% with similar subjective image quality and delineation of central and peripheral pulmonary arteries.

Usefulness of low dose oral contrast media in FDG PET/CT

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An, Y. S.; Yun, J. G.; Lee, M. H.; Cho, C. W.; Yun, S. N [Ajou University Medical Center, Suwon (Korea, Republic of)

2004-07-01

Oral contrast media might help in interpreting PET/CT images, allowing better discrimination between physiologic and pathologic abdominal uptake. The aim of this study was to evaluate the usefulness of low dose oral contrast on FDG PET/CT. A total of 435 cancer patients received 200mL of oral Barium with water(200mL) immediately before FDG injection. PET images were reconstructed using attenuation correction and iterative reconstruction. The FDG uptake in gastrointestinal(GI) tract were analyzed by visual and semiquantitative method in transaxial, coronal and sagittal planes. Seventy patients(16%, 113 sites) of 435 images showed high FDG uptake(pSUV>4.0) : 50(74%, 84 sites) with diffuse uptake and 20(26%, 29sites) with focal uptake. The most common distribution site of oral contrast media was small bowel (n=27, 39%) and others were small bowel with transverse colon(n=6, 8%), small bowel with ascending and sigmoid colon(n=6, 8%) and etc. In PET/CT images, FDG uptake coexisted with oral contrast was showed in 26 patients(54%) with diffuse pattern and 9(45%) with focal pattern, and by sites, those were 38(45%) and 9(31%), respectively. In small bowel regions, the most common distribution site, the proportion of coexistence reached as high as 61% (29 in the total 47 sites). Application of low dose contrast agent can be helpful in the evaluation of intestinal uptake in FDG PET/CT image.

Usefulness of low dose oral contrast media in FDG PET/CT

International Nuclear Information System (INIS)

An, Y. S.; Yun, J. G.; Lee, M. H.; Cho, C. W.; Yun, S. N

2004-01-01

Oral contrast media might help in interpreting PET/CT images, allowing better discrimination between physiologic and pathologic abdominal uptake. The aim of this study was to evaluate the usefulness of low dose oral contrast on FDG PET/CT. A total of 435 cancer patients received 200mL of oral Barium with water(200mL) immediately before FDG injection. PET images were reconstructed using attenuation correction and iterative reconstruction. The FDG uptake in gastrointestinal(GI) tract were analyzed by visual and semiquantitative method in transaxial, coronal and sagittal planes. Seventy patients(16%, 113 sites) of 435 images showed high FDG uptake(pSUV>4.0) : 50(74%, 84 sites) with diffuse uptake and 20(26%, 29sites) with focal uptake. The most common distribution site of oral contrast media was small bowel (n=27, 39%) and others were small bowel with transverse colon(n=6, 8%), small bowel with ascending and sigmoid colon(n=6, 8%) and etc. In PET/CT images, FDG uptake coexisted with oral contrast was showed in 26 patients(54%) with diffuse pattern and 9(45%) with focal pattern, and by sites, those were 38(45%) and 9(31%), respectively. In small bowel regions, the most common distribution site, the proportion of coexistence reached as high as 61% (29 in the total 47 sites). Application of low dose contrast agent can be helpful in the evaluation of intestinal uptake in FDG PET/CT image

Algorithm of pulmonary emphysema extraction using low dose thoracic 3D CT images

Science.gov (United States)

Saita, S.; Kubo, M.; Kawata, Y.; Niki, N.; Nakano, Y.; Omatsu, H.; Tominaga, K.; Eguchi, K.; Moriyama, N.

2006-03-01

Recently, due to aging and smoking, emphysema patients are increasing. The restoration of alveolus which was destroyed by emphysema is not possible, thus early detection of emphysema is desired. We describe a quantitative algorithm for extracting emphysematous lesions and quantitatively evaluate their distribution patterns using low dose thoracic 3-D CT images. The algorithm identified lung anatomies, and extracted low attenuation area (LAA) as emphysematous lesion candidates. Applying the algorithm to 100 thoracic 3-D CT images and then by follow-up 3-D CT images, we demonstrate its potential effectiveness to assist radiologists and physicians to quantitatively evaluate the emphysematous lesions distribution and their evolution in time interval changes.

Efficacy of spiral CT in the evaluation of peritoneal seeding of gastric cancer

International Nuclear Information System (INIS)

Choi, Hyuck Jae; Han, Joon Koo; Kim, Tae Kyoung; Kim, Ah Young; Lee, Joon Woo; Moon, Min Hoan; Yang, Han Kwang; Choi, Byung Ihn

2001-01-01

To determine usefulness of spiral CT in the preoperative evaluation of peritoneal seeding from a gastric carcinoma. From a database of 411 consecutive patients with surgically proven advanced gastric cancinoma obtained over a six-month period, 17 with peritoneal seeding and a control group of 24 without peritoneal seeding underwent spiral CT scanning with 7-8 mm scan thickness and interval during the portal phase. Preoperative CT images were analyzed by two readers who reached a consensus with regard to the presence and location of the ascites, thickening of the parietal peritoneum, and changes in the omentum and mesentery. Ascites was present in 47% (8/17) of patients with peritoneal seeding the right subhepatic space (n=6, 35%) and right paracolic gutter (n=5, 29%)-but not the cul-de-sac (n=2, 12%)-were common sites of fluid collection. Permeative changes in the omentum and mesentery were seen in 18% (3/17) and 12% (2/17) of patients, respectively. Among five controls with false positive results, ascites in the cul-de-sac was present in three (two males and one female, 12%) while omental nodules and a thickened peritoneum were found in two (8%) and one (4%), respectively. In nine controls with false negative results, small disseminated nodules were seen in the mesentery and omentum at surgical field. The sensitivity and specificity of spiral CT were 47% (8/17) and 79% (19/24), respectively. In terms of sensitivity and specificity, spiral CT is not especially accurate in distinguishing peritoneal seeding from gastric carcinoma

Helical CT for lung-cancer screening. 3. Fundamental study for ultra-low-dose CT by application of small tube current and filter

International Nuclear Information System (INIS)

Itoh, Shigeki; Koyama, Shuji; Tusaka, Masatoshi; Maekoshi, Hisashi; Satake, Hiroko; Ishigaki, Takeo.

1996-01-01

In order to develop ultra-low-dose helical CT for lung cancer screening, the effect of reduction of the tube current to 20 mA and application of a 10 mm thick aluminium filter upon radiation dose and image quality was evaluated with a phantom. Exposure dose at the center of a gantry and absorbed dose at the center of an acrylic phantom at 20 mA with the filter were 15% and 29% of the dose at 50 mA without the filter, respectively. For reduction of absorbed dose, reduction of the tube current was more useful than application of the filter. Image noise at 20 mA with the filter was double that at 50 mA without the filter. Neither reduction of the tube current nor application of the filter changed full width at half maximum on section sensitivity of the Z-axis. Although reduction of the tube current did not affect the difference in CT values between an acrylic sphere and styroform, application of the filter caused a reduction of 4.5% in the difference in CT values. Neither reduction of the tube current nor application of the filter affected the contrast resolution of the high-contrast phantom; however, that of the low-contrast phantom deteriorated. Although improvement of the filter and evaluation of clinical images are necessary, reduction of the tube current to 20 mA and application of the aluminium filter appear to be a promising method for ultra-low-dose helical CT of the lung. (author)

Thin-section CT vs spiral CT in candidates for lung volume reduction surgery: a comparison based on radiologists' subjective preferences

International Nuclear Information System (INIS)

Cederlund, K.; Hoegberg, S.; Rasmussen, E.; Svane, B.; Bergstrand, L.

2001-01-01

The aim of this study was to investigate whether high-resolution (HRCT) or spiral CT was preferred in evaluating severe emphysema in patients undergoing lung volume reduction surgery (LVRS), whether there is any difference in this regard between the cranial and caudal part of the lung, and whether the degree of emphysema has an impact on the radiologists' preference. The study was performed by letting four radiologists compare images obtained with the two techniques (film pairs) and decide which technique they preferred or if the techniques were considered as equal in evaluating emphysema. In evaluation of 188 film pairs, the HRCT images were preferred in 56 %, spiral CT in 19 % and the techniques considered as equal in 25 %. Spiral CT images were preferred more often in the caudal part of the lung and in more advanced emphysema compared with the HRCT images. The study confirms our clinical assumption that use of both CT techniques are valuable in evaluating advanced emphysema and there may be technical as well as histopathological reasons for this. (orig.)

Malignant focal hepatic lesions complicating underlying liver disease: dual-phase contrast-enhanced spiral CT sensitivity and specificity in orthotopic liver transplant patients

International Nuclear Information System (INIS)

Mortele, K.J.; De Keukeleire, K.; Praet, M.; Van Vlierberghe, H.; Hemptinne, B. de; Ros, P.R.

2001-01-01

The aim of this study was to determine the accuracy of contrast-enhanced biphasic spiral CT as a screening tool in the preoperative evaluation of orthotopic liver transplant (OLT) patients. Spiral-CT examinations were performed before liver transplantation in 53 patients. Scans were retrospectively reviewed and compared with pathologic findings in fresh-sectioned livers. When findings between spiral CT and pathology were discordant, formalized livers were reexamined with lesion-by lesion evaluation. Fresh pathologic evaluation revealed 23 liver lesions (16 HCC, 7 macro-regenerative nodules). Malignancy was identified in 13 of 53 patients (24.5%). Pre-transplantation spiral CT depicted 27 liver lesions (23 HCC, 4 macro-regenerative nodules). Malignancy was suspected in 14 patients (26.4%). In 10 of 53 (18.9%), spiral CT and pathologic evaluation were discordant. Subsequent retrospective pathologic evaluation showed malignancy in 4 additional patients. Spiral CT compared with the retrospective pathologic findings revealed 36 real-negative, 14 real-positive, 0 false-positive, and 3 false-negative patients with malignancy. Sensitivity and specificity of spiral CT in detection of malignancy was 82 and 100%, respectively. Contrast-enhanced biphasic spiral CT is an accurate technique in the evaluation of patients preceding OLT. Routine fresh-sectioned liver pathologic findings are not as sensitive as previously estimated. (orig.)

The potentials of spiral CT for detection of focal liver lesions

International Nuclear Information System (INIS)

Helmberger, H.; Kersting-Sommerhoff, B.; Lenz, M.; Kirsten, R.; Bautz, W.

1996-01-01

Spiral CT currently is the modality of choice for all aspects of diagnostic evaluation of the liver. Optimal selection of treatment should be based inter alia on the findings obtained by spiral CT with arterial application of contrast medium, as for example S-CTA (primary liver tumors), or S-CTAP (secondary liver tumors). Ultrasonography is the major supplementing modality. In the near future, MR imaging applying liver-specific contrast-enhancing agents is expected to become an important competing technique, and further developments of interest in diagnostic imaging of the liver are in the offing: it is not yet known which technique will be the modality of choice at the onset of the 21st century. (orig.) [de

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

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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.)

Parotid-Absorbed Doses: A Comparison Between Spiral Tomography and Panoramic

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Ehsan Hekmatian

2016-07-01

Full Text Available Background Jaws spiral tomography and panoramic radiography have wide applications in dentistry, and the parotid gland is one of the most sensitive organs of the head and neck. Objectives The aim of this study was to evaluate and compare the parotid-absorbed dose in spiral tomography and panoramic radiographs using a thermoluminescent dosimeter. Materials and Methods A radiation analog dosimetry phantom was placed in a Cranex Tome radiograph device, and a parotid absorbed dose was measured in both techniques. Thermoluminescent dosimeters were placed bilaterally in the parotid region (on the tube side and the opposite side. Spiral tomography dosimetry was done for the upper and lower jaws in the anterior and posterior regions. Each region contained four slices of 2 mm and four slices of 4 mm in thickness. The results were analyzed by a Wilcoxon test. Results For the tube side parotid, the average absorbed doses in spiral tomography of the anterior and posterior parts of the maxilla and mandible, with the 2 mm slice thickness, were 1.70/1.40 and 1.65/1.60 mGy, respectively. The average absorbed doses with the 4mm slices were 1.65/1.70 and 1.75/1.57 mGy, respectively. For the opposite parotid, the average absorbed dose in spiral tomography of the anterior and posterior parts of the maxilla and mandible, with the 2 mm slice thickness, were 1.40/1.30 and 1.40/1.67 mGy, respectively. The average absorbed doses with the 4mm slices were 1.50/1.66 and 1.40/1.50 mGy, respectively. The average absorbed dose of the panoramic radiograph was 1.40 mGy. Conclusions There was no statistically significant difference in the parotid absorbed dose between spiral tomography and a panoramic radiograph (P value = 0.18. The overall results of this study were similar to other studies.

Pulmonary sequestration: diagnosis with three dimensional reconstruction using spiral CT

International Nuclear Information System (INIS)

Nie Yongkang; Zhao Shaohong; Cai Zulong; Yang Li; Zhao Hong; Zhang Ailian; Huang Hui

2003-01-01

Objective: To evaluate the role of three dimensional (3D) reconstruction using spiral CT in the diagnosis of pulmonary sequestration. Methods: Ten patients with pulmonary sequestration were analyzed. The diagnoses were confirmed by angiography in 2 patients, by operation in 2 patients, and by CT angiography in 6 patients. All patients were examined with Philips SR 7000 or GE Lightspeed Plus scanner. CT images were transferred to a workstation and 3D reconstruction was performed. All images were reviewed and analyzed by two radiologists. Results: Among 10 patients, the pulmonary sequestration was in the right lower lobe in 1 patient and in the left lower lobe in 9 patients. Anomalous systemic arteries originated from thoracic aorta in 8 patients and from celiac artery in 2 patients. On plain CT scan, there were 4 patients with patchy opacities, 3 patients with hilar mass accompanying vascular engorgement and profusion in adjacent parenchyma, 2 patients with finger-like appendage surrounded by hyper-inflated lung, and 1 patient with lung mass-like lesion. Enhanced CT revealed anomalous systemic arteries in 9 patients and drainage vein in 7 patients. Maximum intensity projection (MIP) and curvilinear reconstruction could depict the abnormal systemic artery and drainage vein in sequestration. Surface shadow display (SSD) and volume rendering (VR) could delineate the anomalous systemic artery. Conclusion: 3D reconstruction with enhanced spiral CT can depict anomalous systemic artery and drainage vein and it is the first method of choice in diagnosing pulmonary sequestration

Fuzzy-neural network in the automatic detection and volumetry of the spleen on spiral CT scans

International Nuclear Information System (INIS)

Heitmann, K.R.; Mainz Univ.; Rueckert, S.; Heussel, C.P.; Thelen, M.; Kauczor, H.U.; Uthmann, T.

2000-01-01

Purpose: To assess spleen segmentation and volumetry in spiral CT scans with and without pathological changes of splenic tissue. Methods: The image analysis software HYBRIKON is based on region growing, self-organized neural nets, and fuzzy-anatomic rules. The neural nets were trained with spiral CT data from 10 patients, not used in the following evaluation on spiral CT scans from 19 patients. An experienced radiologist verified the results. The true positive and false positive areas were compared in terms to the areas marked by the radiologist. The results were compared with a standard thresholding method. Results: The neural nets achieved a higher accuracy than the thresholding method. Correlation coefficient of the fuzzy-neural nets: 0.99 (thresholding: 0.63). Mean true positive rate: 90% (thresholding: 75%), mean false positive rate: 5% (thresholding>100%). Pitfalls were caused by accessory spleens, extreme changes in the morphology (tumors, metastases, cysts), and parasplenic masses. Conclusions: Self-organizing neural nets combined with fuzzy rules are ready for use in the automatic detection and volumetry of the spleen in spiral CT scans. (orig.) [de

Comparison of spiral CT angiography with conventional digital subtraction angiography in the evaluation of renal transplant donors: a pilot study

International Nuclear Information System (INIS)

Chu, C.; Young, N.; Lau, H.

2001-01-01

Conventional digital subtraction renal arteriography (IA-DSA) has been traditionally used as the preoperative imaging modality for assessment of renal vascular anatomy for renal transplant donors. This study evaluates the potential use of spiral CT angiography in replacing IA-DSA in the preoperative assessment of this group of patients. Seven patients underwent both spiral CT angiography and IA-DSA between October 1997 and April 1998. It is concluded that spiral CT angiography can demonstrate the number, length and location of renal arteries and it is suggested that spiral CT angiography can potentially replace IA-DSA in the preoperative assessment of renal donors. Copyright (2001) Blackwell Science Pty Ltd

Pitfalls in the use of spiral CT for identification of intracranial aneurysms

International Nuclear Information System (INIS)

Young, N.; Kingston, R.J.; Dorsch, N.W.C.

1999-01-01

We describe problems encountered in our first 136 patients, with 95 aneurysms, who underwent spiral CT for investigation of possible aneurysms involving the circle of Willis and adjacent major vessels, and who had surgical and/or angiographic confirmation. There were seven false-positive cases, of which the first three could be explained by operator inexperience. There were four false negatives, all small aneurysms; two were not seen because of operator error and two were hidden by an adjacent larger aneurysm. Clip artefacts prevented diagnostic studies in six of 21 postoperative studies. One aneurysm was outside the CT field of view, being on a pericallosal artery. One basilar artery tip aneurysm was excluded from the field of the CT study because of a planning error. Inspection of the axial source images is critical if the diagnosis of small or thrombosed aneurysms is to be made. Close attention to image acquisition and computer modelling is required to reduce errors in spiral CT angiography of intracranial aneurysms. (orig.)

The findings and the role of axial CT imaging and 3D imaging of gastric lesion by spiral CT

International Nuclear Information System (INIS)

Lee, Dong Ho; Ko, Young Tae

1996-01-01

The purpose of this study is to assess the efficacy of axial CT imaging and 3D imaging by spiral CT in the detection and evaluation of gastric lesion. Seventy-seven patients with pathologically-proven gastric lesions underwent axial CT and 3D imaging by spiral CT. There were 49 cases of advanced gastric carcinoma(AGC), 21 of early gastric carcinoma (EGC), three of benign ulcers, three of leiomyomas, and one case of lymphoma. Spiral CT was performed with 3-mm collimation, 4.5mm/sec table feed, and 1-1.5-mm reconstruction interval after the ingestion of gas. 3D imaging was obtained using the SSD technique, and on analysis a grade was given(excellent, good, poor). Axial CT scan was performed with 5-mm collimation, 7mm/sec table feed, and 5-mm reconstruction interval after the ingestion of water. Among 49 cases of AGC, excellent 3D images were obtained in seven patients (14.3%), good 3D images in 30(61.2%), and poor 3D images in 12(24.5%). Among the 12 patients with poor images, the cancers were located at the pyloric antrum in eight cases, were AGC Borrmann type 4 in three cases, and EGC-mimicking lesion in one case. Using axial CT scan alone, Borrmann's classification based tumor morphology were accurately identified in 67.3% of cases, but using 3D imaging, the corresponding figure was 85.7%. In 33 cases receiving surgery, good correlation between axial CT scan and pathology occurred in 72.7% of T class, and 69.7% of N class. Among 21 cases of EGC, excellent 3D images were obtained in three patients (14.3%), good 3D images in 14 (66.7%), and poor 3D images in two (9.5%). The other two cases of EGC were not detected. By axial CT scan, no tumor was detected in four cases, and there were two doubtful cases. 3D images of three benign ulcers were excellent in one case and good in two. 3D images of three leiomyomas and one lymphoma were excellent. Combined axial CT imaging and 3D imaging by spiral CT has the potential to accurately diagnose gastric lesions other than AGC

Wedge-shaped parenchymal enhancement peripheral to the hepatic hemangioma : two-phase spiral CT findings

International Nuclear Information System (INIS)

Kim, Kyoung Won; Kim, Tae Kyoung; Han, Joon Koo; Kim, Ah Young; Lee, Hyun Ju; Song, Chi Sung; Choi, Byung Ihn

2000-01-01

To determine the incidence of hepatic hemangiomas associated with wedge-shaped parenchymal enhancements adjacent to the tumors as seen on two-phase spiral CT images obtained during the hepatic arterial phase and to characterize the two-phase spiral CT findings of those hemangiomas. One hundred and eight consecutive hepatic hemangiomas in 63 patients who underwent two-phase spiral CT scanning during an 11-month period were included in this study. Two-phase spiral CT scans were obtained during the hepatic arterial phase (30-second delay) and portal venous phase (65-second delay) after injection of 120 mL of contrast material at a rate of 3 mL/sec. We evaluated the frequency with which wedge-shaped parenchymal enhancement was adjacent to the hemangiomas during the hepatic arterial phase and divided hemangiomas into two groups according to whether or not wedge-shaped parenchymal enhancement was noted (Group A and Group B). The presence of such enhancement in hemangiomas was correlated with tumor size and the grade of intratumoral enhancement. In 24 of 108 hemangiomas, wedge-shaped parenchymal enhancement adjacent to hepatic tumors was seen on two-phase CT images obtained during the hepatic arterial phase. Mean hemangioma size was 22mm in group A and 24mm in group B. There was no statistically significant relationship between lesion size and the presence of wedge-shaped parenchymal enhancement adjacent to a hemangioma. In 91.7% and 100% of tumors in Group A, and in 9.6% and 17.8% in Group B, hemangiomas showed more than 50% intratumoral enhancement during the arterial and portal venous phase, respectively. Wedge-shaped parenchymal enhancements peripheral to hepatic hemangiomas was more frequently found in tumors showing more than 50% intratumoral enhancement during these two phases (p less than 0.01). Wedge-shaped parenchymal enhancements is not uncommonly seen adjacent to hepatic hemangiomas on two-phase spiral CT images obtained during the hepatic arterial phase. A

Thin-section CT vs spiral CT in candidates for lung volume reduction surgery: a comparison based on radiologists' subjective preferences

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Cederlund, K.; Hoegberg, S.; Rasmussen, E.; Svane, B. [Dept. of Thoracic Radiology, Karolinska Hospital, Stockholm (Sweden); Bergstrand, L. [Dept. of Radiology, Danderyds Hospital (Sweden)

2001-03-01

The aim of this study was to investigate whether high-resolution (HRCT) or spiral CT was preferred in evaluating severe emphysema in patients undergoing lung volume reduction surgery (LVRS), whether there is any difference in this regard between the cranial and caudal part of the lung, and whether the degree of emphysema has an impact on the radiologists' preference. The study was performed by letting four radiologists compare images obtained with the two techniques (film pairs) and decide which technique they preferred or if the techniques were considered as equal in evaluating emphysema. In evaluation of 188 film pairs, the HRCT images were preferred in 56 %, spiral CT in 19 % and the techniques considered as equal in 25 %. Spiral CT images were preferred more often in the caudal part of the lung and in more advanced emphysema compared with the HRCT images. The study confirms our clinical assumption that use of both CT techniques are valuable in evaluating advanced emphysema and there may be technical as well as histopathological reasons for this. (orig.)

The optimal parameter for radiation dose in pediatric low dose abdominal CT: cross-sectional dimensions versus body weight

International Nuclear Information System (INIS)

Jung, Yoon Young; Goo, Hyun Woo

2008-01-01

To investigate the best parameter between cross-sectional dimensions and body weight in pediatric low dose abdominal CT. One hundred and thirty six children consecutively underwent weight-based abdominal CT. The subjects consisted of group 1 (79 children, weight range 10.0-19.9 kg) and group 2 (57 children, weight range 20.0-39.9 kg). Abdominal cross-sectional dimensions including circumference, area, anteroposterior diameters and transverse diameters were calculated. Image noise (standard deviation of CT density) was measured by placing a region of interest in the posterior segment of the right hepatic lobe on a CT image at the celiac axis. The measured image noise was correlated with the cross-sectional abdominal dimensions and body weight for subjects in each group. In group 1 subjects,area, circumference, transverse diameter, anteroposterior diameter, and body weight showed a significant positive correlation with image noise in descending order(γ = 0.63, 0.62, 0.61, 0.51, and 0.49; ρ < 0.0001). In group 2 subjects, transverse diameter, circumference, area, anteroposterior diameter, and body weight showed a significant positive correlation with image noise in descending order (γ = 0.83, 0.82, 0.78, 0.71, and 0.71; ρ < 0.0001). Cross-sectional dimensions such as area, circumference, and transverse diameter showed a higher positive correlation with image noise than body weight for pediatric low dose abdominal CT

Low-dose dual-energy cone-beam CT using a total-variation minimization algorithm

International Nuclear Information System (INIS)

Min, Jong Hwan

2011-02-01

Dual-energy cone-beam CT is an important imaging modality in diagnostic applications, and may also find its use in other application such as therapeutic image guidance. Despite of its clinical values, relatively high radiation dose of dual-energy scan may pose a challenge to its wide use. In this work, we investigated a low-dose, pre-reconstruction type of dual-energy cone-beam CT (CBCT) using a total-variation minimization algorithm for image reconstruction. An empirical dual-energy calibration method was used to prepare material-specific projection data. Raw data at high and low tube voltages are converted into a set of basis functions which can be linearly combined to produce material-specific data using the coefficients obtained through the calibration process. From much fewer views than are conventionally used, material specific images are reconstructed by use of the total-variation minimization algorithm. An experimental study was performed to demonstrate the feasibility of the proposed method using a micro-CT system. We have reconstructed images of the phantoms from only 90 projections acquired at tube voltages of 40 kVp and 90 kVp each. Aluminum-only and acryl-only images were successfully decomposed. We evaluated the quality of the reconstructed images by use of contrast-to-noise ratio and detectability. A low-dose dual-energy CBCT can be realized via the proposed method by greatly reducing the number of projections

Low-dose megavoltage cone-beam CT for radiation therapy

International Nuclear Information System (INIS)

Pouliot, Jean; Bani-Hashemi, Ali; Chen, Josephine; Svatos, Michelle; Ghelmansarai, Farhad; Mitschke, Matthias; Aubin, Michele; Xia Ping; Morin, Olivier; Bucci, Kara; Roach, Mack; Hernandez, Paco; Zheng Zirao; Hristov, Dimitre; Verhey, Lynn

2005-01-01

Purpose: The objective of this work was to demonstrate the feasibility of acquiring low-exposure megavoltage cone-beam CT (MV CBCT) three-dimensional (3D) image data of sufficient quality to register the CBCT images to kilovoltage planning CT images for patient alignment and dose verification purposes. Methods and materials: A standard clinical 6-MV Primus linear accelerator, operating in arc therapy mode, and an amorphous-silicon (a-Si) flat-panel electronic portal-imaging device (EPID) were employed. The dose-pulse rate of a 6-MV Primus accelerator beam was windowed to expose an a-Si flat panel by using only 0.02 to 0.08 monitor units (MUs) per image. A triggered image-acquisition mode was designed to produce a high signal-to-noise ratio without pulsing artifacts. Several data sets were acquired for an anthropomorphic head phantom and frozen sheep and pig cadaver heads, as well as for a head-and-neck cancer patient on intensity-modulated radiotherapy (IMRT). For each CBCT image, a set of 90 to 180 projection images incremented by 1 deg to 2 deg was acquired. The two-dimensional (2D) projection images were then synthesized into a 3D image by use of cone-beam CT reconstruction. The resulting MV CBCT image set was used to visualize the 3D bony anatomy and some soft-tissue details. The 3D image registration with the kV planning CT was performed either automatically by application of a maximization of mutual information (MMI) algorithm or manually by aligning multiple 2D slices. Results: Low-noise 3D MV CBCT images without pulsing artifacts were acquired with a total delivered dose that ranged from 5 to 15 cGy. Acquisition times, including image readout, were on the order of 90 seconds for 180 projection images taken through a continuous gantry rotation of 180 deg . The processing time of the data required an additional 90 seconds for the reconstruction of a 256 3 cube with 1.0-mm voxel size. Implanted gold markers (1 mm x 3 mm) were easily visible for all exposure

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

International Nuclear Information System (INIS)

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

2003-01-01

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

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

Virtual Colonoscopy Screening With Ultra Low-Dose CT and Less-Stressful Bowel Preparation: A Computer Simulation Study

Science.gov (United States)

Wang, Jing; Wang, Su; Li, Lihong; Fan, Yi; Lu, Hongbing; Liang, Zhengrong

2008-10-01

Computed tomography colonography (CTC) or CT-based virtual colonoscopy (VC) is an emerging tool for detection of colonic polyps. Compared to the conventional fiber-optic colonoscopy, VC has demonstrated the potential to become a mass screening modality in terms of safety, cost, and patient compliance. However, current CTC delivers excessive X-ray radiation to the patient during data acquisition. The radiation is a major concern for screening application of CTC. In this work, we performed a simulation study to demonstrate a possible ultra low-dose CT technique for VC. The ultra low-dose abdominal CT images were simulated by adding noise to the sinograms of the patient CTC images acquired with normal dose scans at 100 mA s levels. The simulated noisy sinogram or projection data were first processed by a Karhunen-Loeve domain penalized weighted least-squares (KL-PWLS) restoration method and then reconstructed by a filtered backprojection algorithm for the ultra low-dose CT images. The patient-specific virtual colon lumen was constructed and navigated by a VC system after electronic colon cleansing of the orally-tagged residue stool and fluid. By the KL-PWLS noise reduction, the colon lumen can successfully be constructed and the colonic polyp can be detected in an ultra low-dose level below 50 mA s. Polyp detection can be found more easily by the KL-PWLS noise reduction compared to the results using the conventional noise filters, such as Hanning filter. These promising results indicate the feasibility of an ultra low-dose CTC pipeline for colon screening with less-stressful bowel preparation by fecal tagging with oral contrast.

Evaluation of spiral CT in staging of colon and rectum carcinoma

International Nuclear Information System (INIS)

Hundt, W.; Braunschweig, R.; Reiser, M.

1999-01-01

The purpose of our study was to evaluate the capability of a subsecond spiral-CT scanner using two contrast medium phases in staging of colorectal cancer. In our study we included 37 patients with proven rectum or colon carcinoma. Spiral CT was performed following tap-water enema of the colon in the arterial and venous phases of contrast medium enhancement. Our results were compared with the findings of pathological examination after surgery. The tumor's size and extension were evaluated in the arterial and venous phases, the lymph nodes in the venous phase of the CT scan. The tumor was in the rectum (n = 14), sigma (n = 11), descending colon (n = 6), and cecum (n = 6). Two-phase spiral CT had a sensitivity of 97.2 % in the arterial phase and 89.1 % in the venous phase in detecting the carcinoma. The staging results were in the arterial phase in 30 of 37 cases (81.0 %) and in the venous phase in 24 of 37 cases (64.8 %) according to pathology. In 27 of 32 patients (84.3 %) lymph nodes were detected. The correct classification of the N-stage was possible in 23 of 34 cases (67.6 %). The combined use of arterial and venous phases in staging of colorectal cancer can improve the T- and N-stage classification in comparison with using only one contrast medium phase. The arterial phase is superior compared with the venous phase for local tumor staging and the venous phase is used for lymph node assessment. (orig.) (orig.)

Influence of Ultra-Low-Dose and Iterative Reconstructions on the Visualization of Orbital Soft Tissues on Maxillofacial CT.

Science.gov (United States)

Widmann, G; Juranek, D; Waldenberger, F; Schullian, P; Dennhardt, A; Hoermann, R; Steurer, M; Gassner, E-M; Puelacher, W

2017-08-01

Dose reduction on CT scans for surgical planning and postoperative evaluation of midface and orbital fractures is an important concern. The purpose of this study was to evaluate the variability of various low-dose and iterative reconstruction techniques on the visualization of orbital soft tissues. Contrast-to-noise ratios of the optic nerve and inferior rectus muscle and subjective scores of a human cadaver were calculated from CT with a reference dose protocol (CT dose index volume = 36.69 mGy) and a subsequent series of low-dose protocols (LDPs I-4: CT dose index volume = 4.18, 2.64, 0.99, and 0.53 mGy) with filtered back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR)-50, ASIR-100, and model-based iterative reconstruction. The Dunn Multiple Comparison Test was used to compare each combination of protocols (α = .05). Compared with the reference dose protocol with FBP, the following statistically significant differences in contrast-to-noise ratios were shown (all, P ≤ .012) for the following: 1) optic nerve: LDP-I with FBP; LDP-II with FBP and ASIR-50; LDP-III with FBP, ASIR-50, and ASIR-100; and LDP-IV with FBP, ASIR-50, and ASIR-100; and 2) inferior rectus muscle: LDP-II with FBP, LDP-III with FBP and ASIR-50, and LDP-IV with FBP, ASIR-50, and ASIR-100. Model-based iterative reconstruction showed the best contrast-to-noise ratio in all images and provided similar subjective scores for LDP-II. ASIR-50 had no remarkable effect, and ASIR-100, a small effect on subjective scores. Compared with a reference dose protocol with FBP, model-based iterative reconstruction may show similar diagnostic visibility of orbital soft tissues at a CT dose index volume of 2.64 mGy. Low-dose technology and iterative reconstruction technology may redefine current reference dose levels in maxillofacial CT. © 2017 by American Journal of Neuroradiology.

CTA-enhanced perfusion CT: an original method to perform ultra-low-dose CTA-enhanced perfusion CT

Energy Technology Data Exchange (ETDEWEB)

Tong, Elizabeth; Wintermark, Max [University of Virginia, Department of Radiology, Neuroradiology Division, Charlottesville, VA (United States)

2014-11-15

Utilizing CT angiography enhances image quality in PCT, thereby permitting acquisition at ultra-low dose. Dynamic CT acquisitions were obtained at 80 kVp with decreasing tube current-time product [milliamperes x seconds (mAs)] in patients suspected of ischemic stroke, with concurrent CTA of the cervical and intracranial arteries. By utilizing fast Fourier transformation, high spatial frequencies of CTA were combined with low spatial frequencies of PCT to create a virtual PCT dataset. The real and virtual PCT datasets with decreasing mAs were compared by assessing contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and noise and PCT values and by visual inspection of PCT parametric maps. Virtual PCT attained CNR and SNR three- to sevenfold superior to real PCT and noise reduction by a factor of 4-6 (p < 0.05). At 20 mAs, virtual PCT achieved diagnostic parametric maps, while the quality of real PCT maps was inadequate. At 10 mAs, both real and virtual PCT maps were nondiagnostic. Virtual PCT (but not real PCT) maps regained diagnostic quality at 10 mAs by applying 40 % adaptive statistical iterative reconstruction (ASIR) and improved further with 80 % ASIR. Our new method of creating virtual PCT by combining ultra-low-dose PCT with CTA information yields diagnostic perfusion parametric maps from PCT acquired at 20 or 10 mAs with 80 % ASIR. Effective dose is approximately 0.20 mSv, equivalent to two chest radiographs. (orig.)

Lung nodule detection performance in five observers on computed tomography (CT) with adaptive iterative dose reduction using three-dimensional processing (AIDR 3D) in a Japanese multicenter study: Comparison between ultra-low-dose CT and low-dose CT by receiver-operating characteristic analysis

Energy Technology Data Exchange (ETDEWEB)

Nagatani, Yukihiro, E-mail: yatsushi@belle.shiga-med.ac.jp [Department of Radiology, Shiga University of Medical Science, Otsu 520-2192, Shiga (Japan); Takahashi, Masashi; Murata, Kiyoshi [Department of Radiology, Shiga University of Medical Science, Otsu 520-2192, Shiga (Japan); Ikeda, Mitsuru [Department of Radiological and Medical Laboratory Science, Nagoya University Graduate School of Medicine, Nagoya 461-8673, Aichi (Japan); Yamashiro, Tsuneo [Department of Radiology, Graduate School of Medical Science, University of the Ryukyus, Nishihara 903-0215, Okinawa (Japan); Miyara, Tetsuhiro [Department of Radiology, Graduate School of Medical Science, University of the Ryukyus, Nishihara 903-0215, Okinawa (Japan); Department of Radiology, Okinawa Prefectural Yaeyama Hospital, Ishigaki 907-0022, Okinawa (Japan); Koyama, Hisanobu [Department of Radiology, Kobe University Graduate School of Medicine, Kobe 650-0017, Hyogo (Japan); Koyama, Mitsuhiro [Department of Radiology, Osaka Medical College, Takatsuki 569-8686, Osaka (Japan); Sato, Yukihisa [Department of Radiology, Osaka University Graduate School of Medicine, Suita 565-0871, Osaka (Japan); Department of Radiology, Osaka Medical Center of Cancer and Cardiovascular Diseases, Osaka 537-8511, Osaka (Japan); Moriya, Hiroshi [Department of Radiology, Ohara General Hospital, Fukushima 960-8611 (Japan); Noma, Satoshi [Department of Radiology, Tenri Hospital, Tenri 632-8552, Nara (Japan); Tomiyama, Noriyuki [Department of Radiology, Osaka University Graduate School of Medicine, Suita 565-0871, Osaka (Japan); Ohno, Yoshiharu [Department of Radiology, Kobe University Graduate School of Medicine, Kobe 650-0017, Hyogo (Japan); Murayama, Sadayuki [Department of Radiology, Graduate School of Medical Science, University of the Ryukyus, Nishihara 903-0215, Okinawa (Japan)

2015-07-15

Highlights: • Using AIDR 3D, ULDCT showed comparable LND of solid nodules to LDCT. • Using AIDR 3D, LND of smaller GGN in ULDCT was inferior to that in LDCT. • Effective dose in ULDCT was about only twice of that in chest X-ray. • BMI values in study population were mostly in the normal range body habitus. - Abstract: Purpose: To compare lung nodule detection performance (LNDP) in computed tomography (CT) with adaptive iterative dose reduction using three dimensional processing (AIDR3D) between ultra-low dose CT (ULDCT) and low dose CT (LDCT). Materials and methods: This was part of the Area-detector Computed Tomography for the Investigation of Thoracic Diseases (ACTIve) Study, a multicenter research project being conducted in Japan. Institutional Review Board approved this study and informed consent was obtained. Eighty-three subjects (body mass index, 23.3 ± 3.2) underwent chest CT at 6 institutions using identical scanners and protocols. In a single visit, each subject was scanned using different tube currents: 240, 120 and 20 mA (3.52, 1.74 and 0.29 mSv, respectively). Axial CT images with 2-mm thickness/increment were reconstructed using AIDR3D. Standard of reference (SOR) was determined based on CT images at 240 mA by consensus reading of 2 board-certificated radiologists as to the presence of lung nodules with the longest diameter (LD) of more than 3 mm. Another 5 radiologists independently assessed and recorded presence/absence of lung nodules and their locations by continuously-distributed rating in CT images at 20 mA (ULDCT) and 120 mA (LDCT). Receiver-operating characteristic (ROC) analysis was used to evaluate LNDP of both methods in total and also in subgroups classified by LD (>4, 6 and 8 mm) and nodular characteristics (solid and ground glass nodules). Results: For SOR, 161 solid and 60 ground glass nodules were identified. No significant difference in LNDP for entire solid nodules was demonstrated between both methods, as area under ROC

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

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

International Nuclear Information System (INIS)

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

2010-01-01

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

Investigation of ultra low-dose scans in the context of quantum-counting clinical CT

Science.gov (United States)

Weidinger, T.; Buzug, T. M.; Flohr, T.; Fung, G. S. K.; Kappler, S.; Stierstorfer, K.; Tsui, B. M. W.

2012-03-01

In clinical computed tomography (CT), images from patient examinations taken with conventional scanners exhibit noise characteristics governed by electronics noise, when scanning strongly attenuating obese patients or with an ultra-low X-ray dose. Unlike CT systems based on energy integrating detectors, a system with a quantum counting detector does not suffer from this drawback. Instead, the noise from the electronics mainly affects the spectral resolution of these detectors. Therefore, it does not contribute to the image noise in spectrally non-resolved CT images. This promises improved image quality due to image noise reduction in scans obtained from clinical CT examinations with lowest X-ray tube currents or obese patients. To quantify the benefits of quantum counting detectors in clinical CT we have carried out an extensive simulation study of the complete scanning and reconstruction process for both kinds of detectors. The simulation chain encompasses modeling of the X-ray source, beam attenuation in the patient, and calculation of the detector response. Moreover, in each case the subsequent image preprocessing and reconstruction is modeled as well. The simulation-based, theoretical evaluation is validated by experiments with a novel prototype quantum counting system and a Siemens Definition Flash scanner with a conventional energy integrating CT detector. We demonstrate and quantify the improvement from image noise reduction achievable with quantum counting techniques in CT examinations with ultra-low X-ray dose and strong attenuation.

Lung nodule detection performance in five observers on computed tomography (CT) with adaptive iterative dose reduction using three-dimensional processing (AIDR 3D) in a Japanese multicenter study: Comparison between ultra-low-dose CT and low-dose CT by receiver-operating characteristic analysis.

Science.gov (United States)

Nagatani, Yukihiro; Takahashi, Masashi; Murata, Kiyoshi; Ikeda, Mitsuru; Yamashiro, Tsuneo; Miyara, Tetsuhiro; Koyama, Hisanobu; Koyama, Mitsuhiro; Sato, Yukihisa; Moriya, Hiroshi; Noma, Satoshi; Tomiyama, Noriyuki; Ohno, Yoshiharu; Murayama, Sadayuki

2015-07-01

To compare lung nodule detection performance (LNDP) in computed tomography (CT) with adaptive iterative dose reduction using three dimensional processing (AIDR3D) between ultra-low dose CT (ULDCT) and low dose CT (LDCT). This was part of the Area-detector Computed Tomography for the Investigation of Thoracic Diseases (ACTIve) Study, a multicenter research project being conducted in Japan. Institutional Review Board approved this study and informed consent was obtained. Eighty-three subjects (body mass index, 23.3 ± 3.2) underwent chest CT at 6 institutions using identical scanners and protocols. In a single visit, each subject was scanned using different tube currents: 240, 120 and 20 mA (3.52, 1.74 and 0.29 mSv, respectively). Axial CT images with 2-mm thickness/increment were reconstructed using AIDR3D. Standard of reference (SOR) was determined based on CT images at 240 mA by consensus reading of 2 board-certificated radiologists as to the presence of lung nodules with the longest diameter (LD) of more than 3mm. Another 5 radiologists independently assessed and recorded presence/absence of lung nodules and their locations by continuously-distributed rating in CT images at 20 mA (ULDCT) and 120 mA (LDCT). Receiver-operating characteristic (ROC) analysis was used to evaluate LNDP of both methods in total and also in subgroups classified by LD (>4, 6 and 8 mm) and nodular characteristics (solid and ground glass nodules). For SOR, 161 solid and 60 ground glass nodules were identified. No significant difference in LNDP for entire solid nodules was demonstrated between both methods, as area under ROC curve (AUC) was 0.844 ± 0.017 in ULDCT and 0.876 ± 0.026 in LDCT (p=0.057). For ground glass nodules with LD 8mm or more, LNDP was similar between both methods, as AUC 0.899 ± 0.038 in ULDCT and 0.941 ± 0.030 in LDCT. (p=0.144). ULDCT using AIDR3D with an equivalent radiation dose to chest x-ray could have comparable LNDP to LDCT with AIDR3D except for smaller ground

Advanced single-slice rebinning for tilted spiral cone-beam CT

International Nuclear Information System (INIS)

Kachelriess, Marc; Fuchs, Theo; Schaller, Stefan; Kalender, Willi A.

2001-01-01

Future medical CT scanners and today's micro CT scanners demand cone-beam reconstruction algorithms that are capable of reconstructing data acquired from a tilted spiral trajectory where the vector of rotation is not necessarily parallel to the vector of table increment. For the medical CT scanner this case of nonparallel object motion is met for nonzero gantry tilt: the table moves into a direction that is not perpendicular to the plane of rotation. Since this is not a special application of medical CT but rather a daily routine in head exams, there is a strong need for corresponding reconstruction algorithms. In contrast to medical CT, where the special case of nonperpendicular motion is used on purpose, micro CT scanners cannot avoid aberrations of the rotational axis and the table increment vector due to alignment problems. Especially for those micro CT scanners that have the lifting stage mounted on the rotation table (in contrast to setups where the lifting stage holds the rotation table), this kind of misalignment is equivalent to a gantry tilt. We therefore generalize the advanced single-slice rebinning algorithm (ASSR), which is considered a very promising approach for medical cone-beam reconstruction due to its high image quality and its high reconstruction speed [Med. Phys. 27, 754-772 (2000)], to the case of tilted gantries. We evaluate this extended ASSR approach (which we will denote as ASSR + , for convenience) in comparison to the original ASSR algorithm using simulated phantom data for reconstruction. For the case of nonparallel object motion ASSR + shows significant improvements over ASSR, however, its computational complexity is slightly increased due to the broken symmetry of the spiral trajectory

Early clinical phase of patient's management after polytrauma using 1- and 4-slice helical CT; Fruehes klinisches Management nach Polytrauma mit 1- und 4-Schicht-Spiral-CT

Energy Technology Data Exchange (ETDEWEB)

Kloeppel, R.; Kahn, T. [Klinik und Poliklinik fuer Diagnostische Radiologie, Universitaetsklinikum Leipzig (Germany); Schreiter, D. [Chirurgische Intensivtherapieabteilung, Zentrum fuer Chirurgie, Universitaetsklinikum Leipzig (Germany); Dietrich, J. [Abt. Neuroradiologie der Klinik und Poliklinik fuer Diagnostische Radiologie, Universitaetsklinikum Leipzig (Germany); Josten, C. [Klinik und Poliklinik fuer Unfall- und Wiederherstellungschirurgie, Zentrum fuer Chirurgie, Universitaetsklinikum Leipzig (Germany)

2002-07-01

In the early clinical phase the comprehensive imaging of patients with multiple trauma using helical CT is already established. Aim of this study was to assess whether MSCT may improve the patient management and the diagnostic results.The procedure is designed as follows: after life-thretening treatment x-ray of chest and ultrasound are carried out in the emergency room. Then the patient is moved to CT. From 1998 to december 2000 241 patients were examined using a single slice helical CT (Somatom plus 4), in 2001 79 patients using a 4-slice helical CT (Somatom VZ, Siemens Med.Sol.). After CT selected radiograms of the extremities were taken.359 of 360 procedures were carried out successfully. Excluding 1 case (death during 1-sl. h CT) all relevant lesions of head, neck, and body were diagnosed. Although the patients had an injury severity score of {approx}30. The change from 1slice-helical CT to 4 slice-helical CT allowed us to reduce the stay in the CT room from 28 to 16 min. The total lethality decreased by {approx}4%.Advantages for the patient arose from the standardized examination protocol using multislice CT. If integrated in an interdisciplinary management concept, it is a good compromise between examination time, comprehensive diagnostic imaging, life-saving therapeutic procedures, and therapy planning. (orig.) [German] Die klinische Erstversorgung Polytraumatisierter schliesst inzwischen in vielen Unfallkliniken den fruehzeitigen Einsatz der Spiral-CT ein. Kann die neuerlich eingefuehrte Mehrschicht-Spiral-CT Ergebnisse und Patientenmanagement weiter verbessern?Nach lebensrettenden Sofortmassnahmen, Thoraxroentgen und Notsonographie im Schockraum erfolgte die CT: Von 1998-2000 wurden 241 Patienten mit einem 1-Schicht-Spiral-CT (Somatom plus 4) und in 2001 79 Patienten mit einem 4-Schicht-Spiral-CT (Somatom VZ, beide Siemens Med. Sol.) untersucht. Klinisch ausgewaehlte Extremitaetenaufnahmen wurden ergaenzt.359 von 360 Untersuchungen verliefen erfolgreich

TU-EF-204-07: Add Tube Current Modulation to a Low Dose Simulation Tool for CT Systems

International Nuclear Information System (INIS)

Ding, Y.; Wen, G.; Brown, K.; Klahr, P.; Dhanantwari, A.

2015-01-01

Purpose: We extended the capabilities of a low dose simulation tool to model Tube-Current Modulation (TCM). TCM is widely used in clinical practice to reduce radiation dose in CT scans. We expect the tool to be valuable for various clinical applications (e.g., optimize protocols, compare reconstruction techniques and evaluate TCM methods). Methods: The tube current is input as a function of z location, instead of a fixed value. Starting from the line integrals of a scan, a new Poisson noise realization at a lower dose is generated for each view. To validate the new functionality, we compared simulated scans with real scans in image space. Results: First we assessed noise in the difference between the low-dose simulations and the original high-dose scan. When the simulated tube current is a step function of z location, the noise at each segment matches the noise of 3 separate constant-tube-current-simulations. Secondly, with a phantom that forces TCM, we compared a low-dose simulation with an equivalent real low-dose scan. The mean CT number of the simulated scan and the real low-dose scan were 137.7±0.6 and 137.8±0.5 respectively. Furthermore, with 240 ROIs, the noise of the simulated scan and the real low-dose scan were 24.03±0.45 and 23.99±0.43 respectively, and they were not statistically different (2-sample t-test, p-value=0.28). The facts that the noise reflected the trend of the TCM curve, and that the absolute noise measurements were not statistically different validated the TCM function. Conclusion: We successfully added tube-current modulation functionality in an existing low dose simulation tool. We demonstrated that the noise reflected an input tube-current modulation curve. In addition, we verified that the noise and mean CT number of our simulation agreed with a real low dose scan. The authors are all employees of Philips. Yijun Ding is also supported by NIBIB P41EB002035 and NIBIB R01EB000803

Usefulness of low dose oral contrast media in 18F-FDG PET/CT

International Nuclear Information System (INIS)

An, Young Sil; Yoon, Joon Kee; Hong, Seon Pyo; Joh, Chul Woo; Yoon, Seok Nam

2006-01-01

The standard protocol using large volume of oral contrast media may cause gastrointestinal discomfort and contrast-related artifacts in PET/CT. The aim of this study was to evaluate the usefulness of low dose oral contrast in 18 F-FDG PET/CT. We retrospectively reviewed the whole-body PET/CT images in a total of 435 patients. About 200 ml of oral contrast agent (barium sulfate) was administered immediately before injection of 18 F-FDG. The FDG uptake of intestines was analyzed by visual and semi-quantitative method on transaxial, coronal and saggital planes. Seventy (16%, 113 sites) of 435 images showed high FDG uptake (peak SUV > 4); 50 (74%, 84 sites) with diffuse and 20 (26%, 29 sites) with focal uptake. The most commonly delivered site of oral contrast media was small bowel (n = 27, 39%). On PET/CT images, FDG uptake coexisted with oral contrast media in 26 patients (54%, 38 sites) with diffuse pattern and 9 (45%, 9 sites) with focal pattern, and by sites, those were 38 (45%) and 9 (31%), respectively. In small bowel regions, the proportion of coexistence reached as high as 61% (29/47 sites). A visual analysis of available non-attenuation corrected PET images of 27 matched regions revealed no contrast-related artifact. We concluded that the application of low dose contrast media could be helpful in the evaluation of abdominal uptake in the FDG PET/CT image

Low-dose CT of the paranasal sinuses. Minimizing X-ray exposure with spectral shaping

Energy Technology Data Exchange (ETDEWEB)

Wuest, Wolfgang [Friedrich-Alexander-University Erlangen-Nuremberg, Radiological Institute, Erlangen (Germany); Radiological Institute, Erlangen (Germany); May, Matthias; Saake, Marc; Brand, Michael; Uder, Michael; Lell, Michael [Friedrich-Alexander-University Erlangen-Nuremberg, Radiological Institute, Erlangen (Germany)

2016-11-15

Shaping the energy spectrum of the X-ray beam has been shown to be beneficial in low-dose CT. This study's aim was to investigate dose and image quality of tin filtration at 100 kV for pre-operative planning in low-dose paranasal CT imaging in a large patient cohort. In a prospective trial, 129 patients were included. 64 patients were randomly assigned to the study protocol (100 kV with additional tin filtration, 150mAs, 192 x 0.6-mm slice collimation) and 65 patients to the standard low-dose protocol (100 kV, 50mAs, 128 x 0.6-mm slice collimation). To assess the image quality, subjective parameters were evaluated using a five-point scale. This scale was applied on overall image quality and contour delineation of critical anatomical structures. All scans were of diagnostic image quality. Bony structures were of good diagnostic image quality in both groups, soft tissues were of sufficient diagnostic image quality in the study group because of a high level of noise. Radiation exposure was very low in both groups, but significantly lower in the study group (CTDI{sub vol} 1.2 mGy vs. 4.4 mGy, p < 0.001). Spectral optimization (tin filtration at 100 kV) allows for visualization of the paranasal sinus with sufficient image quality at a very low radiation exposure. (orig.)

Spectrotemporal CT data acquisition and reconstruction at low dose

International Nuclear Information System (INIS)

Clark, Darin P.; Badea, Cristian T.; Lee, Chang-Lung; Kirsch, David G.

2015-01-01

Purpose: X-ray computed tomography (CT) is widely used, both clinically and preclinically, for fast, high-resolution anatomic imaging; however, compelling opportunities exist to expand its use in functional imaging applications. For instance, spectral information combined with nanoparticle contrast agents enables quantification of tissue perfusion levels, while temporal information details cardiac and respiratory dynamics. The authors propose and demonstrate a projection acquisition and reconstruction strategy for 5D CT (3D + dual energy + time) which recovers spectral and temporal information without substantially increasing radiation dose or sampling time relative to anatomic imaging protocols. Methods: The authors approach the 5D reconstruction problem within the framework of low-rank and sparse matrix decomposition. Unlike previous work on rank-sparsity constrained CT reconstruction, the authors establish an explicit rank-sparse signal model to describe the spectral and temporal dimensions. The spectral dimension is represented as a well-sampled time and energy averaged image plus regularly undersampled principal components describing the spectral contrast. The temporal dimension is represented as the same time and energy averaged reconstruction plus contiguous, spatially sparse, and irregularly sampled temporal contrast images. Using a nonlinear, image domain filtration approach, the authors refer to as rank-sparse kernel regression, the authors transfer image structure from the well-sampled time and energy averaged reconstruction to the spectral and temporal contrast images. This regularization strategy strictly constrains the reconstruction problem while approximately separating the temporal and spectral dimensions. Separability results in a highly compressed representation for the 5D data in which projections are shared between the temporal and spectral reconstruction subproblems, enabling substantial undersampling. The authors solved the 5D reconstruction

Spiral CT features and anatomic basis of posterior pararenal space involvement in acute pancreatitis

International Nuclear Information System (INIS)

Min Pengqiu; Yan Zhihan; Yang Hengxuan; Liu Zaiyi; Song Bin; Wu Bing; Zhang Jin; Liu Rongbo

2005-01-01

Objective: To evaluate spiral CT features and anatomic basis of the posterior pararenal space (PPS) involvement in acute pancreatitis (AP). Methods: CT images of 87 cases with AP were retrospectively studied with focus on spiral CT features, incidence of the PPS involvement, and its correlations with the posterior renal fascia or lateroconal fascia. Results: Our study showed that the incidence of the PPS involvement was 47% (41/87), with Grade A 53% (46/87), Grade B 24%(21/87), and Grade C 23% (20/87), and Grade 0 53% (46/87), Grade I 22% (19/87), and Grade II 25% (22/87), respectively. The pancreatitis fluid collection in the PPS was continuous with that in the anterior pararenal space or with the fluid between the two laminae of the posterior renal fascia. In 3 follow-up cases, pseudocysts in the PPS were continuous with that in anterior pararenal space below the cone of renal fascia. Conclusion: Spiral CT features of the PPS involvement varies from mild inflammatory changes to fluid collection or phlegmonous mass. Fluid within anterior pararenal space in AP flows into the PPS by three routes. (authors)

CT dose management

International Nuclear Information System (INIS)

Zasheva, Ts.; Georgiev, E.; Kirova, G.

2013-01-01

Full text: Introduction: In recent decades Computed Tomography established itself as one of the most common study with a very wide range of applications and techniques of scanning. Best diagnostic value of the method resist to the risks of ionizing radiation, as statistics show that CT is one of the main sources of continuously increasing dose to the population. What you will learn: The physical parameters of the X-ray tube and the principles of image reconstruction; The relationship between variables parameters and the received dose; The ratio between the force and voltage of the current to the image quality, Influence of the used contrast medium to the physical properties of the image, The ratio of patient BMI to image processing, Effective use of knowledge for the optimal CT protocol. Discussions: The goal to reduce the dose received by the patient during a CT scan while keeping the diagnostic quality of the image puts to the test as handset X-ray producers and technicians who need to master the technique of study protocol forming as well as to balance the harm - benefit ratio. Among the most popular techniques are these of dose modulation, low-dose computed tomography at the expense of a reduction of the current or voltage intensity, and control of the number of post-processing algorithms for the image reconstruction. Conclusion: The training of radiologists and X-ray technicians plays a major role in optimizing of technical parameters in view of the reduction of the dose for the patient, while maintaining the diagnostic quality of the image

Comparison of prospective electrocardiography-gating high-pitch mode and without electrocardiography-synchronization high-pitch mode acquisition for the image quality and radiation doses of the aortic using dual-source CT

International Nuclear Information System (INIS)

Li Jian; Huan Yi; Zhao Hongliang; Wang Ying; Liu Ying; Wei Mengqi; Shi Mingguo; Zheng Minwen

2013-01-01

Objective: To evaluate the application of prospective ECG-gating Flash spiral scan mode dual-source CT in aortography, and compare it's image quality and radiation dose with without ECG-synchronization high-pitch spiral scanning mode. Methods: Fifty consecutive patients (Group A) with suspected aortic dissection or after operations for the aortic dissection were scanned with prospective ECG-gated high-pitch scan and another 50 consecutive patients (Group B) were analyzed by non-ECG-gated high-pitch scan. Image quality of the aortic was assessed by two independent readers. Image noise was measured, radiation dose estimates were calculated. The imaging quality of the aortic and the radiation dose were compared with Mann-whitney U and t test. Results: The average image quality score [(1.18 ± 0.40) in group A and (1.23 ± 0.31) in group B] showed no significant difference between group A and group B (U = 1.20, P = 0.23). The mean radiation dose of group A was lower than that of group B [(1.49 ± 0.38) mSv in group A, (2.79 ± 0.54) mSv in group B, t = 13.677, P < 0.05]. Conclusion: Prospective ECG-gated dual source CT Flash spiral scanning with low radiation dose and good image quality in the aortic dissection with high value of clinical application. (authors)

Low-dose computed tomography image restoration using previous normal-dose scan

International Nuclear Information System (INIS)

Ma, Jianhua; Huang, Jing; Feng, Qianjin; Zhang, Hua; Lu, Hongbing; Liang, Zhengrong; Chen, Wufan

2011-01-01

Purpose: In current computed tomography (CT) examinations, the associated x-ray radiation dose is of a significant concern to patients and operators. A simple and cost-effective means to perform the examinations is to lower the milliampere-seconds (mAs) or kVp parameter (or delivering less x-ray energy to the body) as low as reasonably achievable in data acquisition. However, lowering the mAs parameter will unavoidably increase data noise and the noise would propagate into the CT image if no adequate noise control is applied during image reconstruction. Since a normal-dose high diagnostic CT image scanned previously may be available in some clinical applications, such as CT perfusion imaging and CT angiography (CTA), this paper presents an innovative way to utilize the normal-dose scan as a priori information to induce signal restoration of the current low-dose CT image series. Methods: Unlike conventional local operations on neighboring image voxels, nonlocal means (NLM) algorithm utilizes the redundancy of information across the whole image. This paper adapts the NLM to utilize the redundancy of information in the previous normal-dose scan and further exploits ways to optimize the nonlocal weights for low-dose image restoration in the NLM framework. The resulting algorithm is called the previous normal-dose scan induced nonlocal means (ndiNLM). Because of the optimized nature of nonlocal weights calculation, the ndiNLM algorithm does not depend heavily on image registration between the current low-dose and the previous normal-dose CT scans. Furthermore, the smoothing parameter involved in the ndiNLM algorithm can be adaptively estimated based on the image noise relationship between the current low-dose and the previous normal-dose scanning protocols. Results: Qualitative and quantitative evaluations were carried out on a physical phantom as well as clinical abdominal and brain perfusion CT scans in terms of accuracy and resolution properties. The gain by the use

Radiation exposure in multi-slice versus single-slice spiral CT: results of a nationwide survey

International Nuclear Information System (INIS)

Brix, G.; Nagel, H.D.; Stamm, G.; Veit, R.; Lechel, U.; Griebel, J.; Galanski, M.

2003-01-01

Multi-slice (MS) technology increases the efficacy of CT procedures and offers new promising applications. The expanding use of MSCT, however, may result in an increase in both frequency of procedures and levels of patient exposure. It was, therefore, the aim of this study to gain an overview of MSCT examinations conducted in Germany in 2001. All MSCT facilities were requested to provide information about 14 standard examinations with respect to scan parameters and frequency. Based on this data, dosimetric quantities were estimated using an experimentally validated formalism. Results are compared with those of a previous survey for single-slice (SS) spiral CT scanners. According to the data provided for 39 dual- and 73 quad-slice systems, the average annual number of patients examined at MSCT is markedly higher than that examined at SSCT scanners (5500 vs 3500). The average effective dose to patients was changed from 7.4 mSv at single-slice to 5.5 mSv and 8.1 mSv at dual- and quad-slice scanners, respectively. There is a considerable potential for dose reduction at quad-slice systems by an optimisation of scan protocols and better education of the personnel. To avoid an increase in the collective effective dose from CT procedures, a clear medical justification is required in each case. (orig.)

Realistic simulation of reduced-dose CT with noise modeling and sinogram synthesis using DICOM CT images

International Nuclear Information System (INIS)

Won Kim, Chang; Kim, Jong Hyo

2014-01-01

Purpose: Reducing the patient dose while maintaining the diagnostic image quality during CT exams is the subject of a growing number of studies, in which simulations of reduced-dose CT with patient data have been used as an effective technique when exploring the potential of various dose reduction techniques. Difficulties in accessing raw sinogram data, however, have restricted the use of this technique to a limited number of institutions. Here, we present a novel reduced-dose CT simulation technique which provides realistic low-dose images without the requirement of raw sinogram data. Methods: Two key characteristics of CT systems, the noise equivalent quanta (NEQ) and the algorithmic modulation transfer function (MTF), were measured for various combinations of object attenuation and tube currents by analyzing the noise power spectrum (NPS) of CT images obtained with a set of phantoms. Those measurements were used to develop a comprehensive CT noise model covering the reduced x-ray photon flux, object attenuation, system noise, and bow-tie filter, which was then employed to generate a simulated noise sinogram for the reduced-dose condition with the use of a synthetic sinogram generated from a reference CT image. The simulated noise sinogram was filtered with the algorithmic MTF and back-projected to create a noise CT image, which was then added to the reference CT image, finally providing a simulated reduced-dose CT image. The simulation performance was evaluated in terms of the degree of NPS similarity, the noise magnitude, the bow-tie filter effect, and the streak noise pattern at photon starvation sites with the set of phantom images. Results: The simulation results showed good agreement with actual low-dose CT images in terms of their visual appearance and in a quantitative evaluation test. The magnitude and shape of the NPS curves of the simulated low-dose images agreed well with those of real low-dose images, showing discrepancies of less than +/−3.2% in

The experimental study on bowel ischemia in closed loop obstruction by using multi-phase spiral CT

International Nuclear Information System (INIS)

Zhang Xiaoming; Yang Hanfeng; Huang Xiaohua; Tang Xianying; Jian Pu; Yang Zhengwei; Zhou Jiyong; Zhao Zongwen

2005-01-01

Objective: To evaluate the bowel ischemia in experimental closed loop obstruction by using multi-phase spiral CT. Methods: Twenty-four New Zealand rabbits of both sexes (mean age, 4 months, and mean body weight, 2.5-3.0 kg) were divided randomly into three groups with each group containing 8 rabbits. After clamping 10-15 cm segments of small bowel and their veins for 0.5 hours (Group A), 1-2 hours (Group B), and 3-5 hours (Group C), respectively, multi-phase spiral CT was performed at baseline, and at arterial, venous, and delayed phases after intravenous contrast administration. Then the rabbits were sacrificed to observe their surgical and histological changes. Two radiologists, blinded to the animal model classification and their histological results, individually reviewed the CT images to observe the CT appearances of the closed loop. Statistical significance criteria was determined by P 0.05) at baseline, however, they were significantly different (P<0.05) at all phases after enhancement. Among rabbits without necrotic closed loop, 11 of 13 had continuous enhancement at all phases, while only 1 of 11 rabbits with necrotic closed loop showed continuous enhancement (P<0.05). Conclusion: The ischemia of bowel wall in different phases after clamping small bowel and their veins can be evaluated by using enhanced multi-phase spiral CT. Continuous enhancement of bowel wall in multi-phase spiral CT can be seen prominently in the early bowel ischemia, but necrotic bowel shows no enhancement. (authors)

Low-dose CT imaging of a total hip arthroplasty phantom using model-based iterative reconstruction and orthopedic metal artifact reduction

Energy Technology Data Exchange (ETDEWEB)

Wellenberg, R.H.H.; Streekstra, G.J.; Maas, M. [Academic Medical Center, Department of Radiology, Amsterdam (Netherlands); Boomsma, M.F.; Osch, J.A.C. van [Department of Radiology, Zwolle (Netherlands); Vlassenbroek, A. [Philips Medical Systems, Brussels (Belgium); Milles, J. [Philips Medical Systems, Eindhoven (Netherlands); Edens, M.A. [Department of Innovation and Science, Zwolle (Netherlands); Slump, C.H. [University of Twente, MIRA Institute for Biomedical Technology and Technical Medicine, Enschede (Netherlands)

2017-05-15

To compare quantitative measures of image quality, in terms of CT number accuracy, noise, signal-to-noise-ratios (SNRs), and contrast-to-noise ratios (CNRs), at different dose levels with filtered-back-projection (FBP), iterative reconstruction (IR), and model-based iterative reconstruction (MBIR) alone and in combination with orthopedic metal artifact reduction (O-MAR) in a total hip arthroplasty (THA) phantom. Scans were acquired from high- to low-dose (CTDI{sub vol}: 40.0, 32.0, 24.0, 16.0, 8.0, and 4.0 mGy) at 120- and 140- kVp. Images were reconstructed using FBP, IR (iDose{sup 4} level 2, 4, and 6) and MBIR (IMR, level 1, 2, and 3) with and without O-MAR. CT number accuracy in Hounsfield Units (HU), noise or standard deviation, SNRs, and CNRs were analyzed. The IMR technique showed lower noise levels (p < 0.01), higher SNRs (p < 0.001) and CNRs (p < 0.001) compared with FBP and iDose{sup 4} in all acquisitions from high- to low-dose with constant CT numbers. O-MAR reduced noise (p < 0.01) and improved SNRs (p < 0.01) and CNRs (p < 0.001) while improving CT number accuracy only at a low dose. At the low dose of 4.0 mGy, IMR level 1, 2, and 3 showed 83%, 89%, and 95% lower noise values, a factor 6.0, 9.2, and 17.9 higher SNRs, and 5.7, 8.8, and 18.2 higher CNRs compared with FBP respectively. Based on quantitative analysis of CT number accuracy, noise values, SNRs, and CNRs, we conclude that the combined use of IMR and O-MAR enables a reduction in radiation dose of 83% compared with FBP and iDose{sup 4} in the CT imaging of a THA phantom. (orig.)

The optimal dose of the contrast media for spiral CT portography

International Nuclear Information System (INIS)

Zhang Jiansheng; Xiao Peiyu; Meng Xiaochun; Xu Chuan

2007-01-01

Objective: To investigate the optimal dose of the contrast media in SCTP. Methods: 40 healthy patients were divided into 2 groups according to their body weight (20 cases in group A with weight below 60kg, 20 cases in group B with weight over 70kg). They all received 90ml contrast media at a rate of 4.0 ml/sec in the contrast-enhanced CT ex- amination. And non-cirrhosis cases, liver cirrhosis without ascites cases and liver cirrhosis with ascites cases were selected respectively, 60 patients in each group. Then, the patients of each group were randomly divided into 3 sub-groups, 20 cases in each of them, which respectively received 1.5ml/kg, 2.0ml/kg, 2.5ml/kg contrast media at a rate of 4.0 ml/sec in the contrast-enhanced CT examination. The effect of the dose of the contrast material on the imaging quality of portal vein system in patients with different weight and different state of illness was analyzed. Results: In 40 healthy patients, the density difference between portal vein and hepatic parenchyma was significantly higher in Group A than in Group B (P 0.05), and both of them showed significant difference while using 1.5ml/kg contrast media (P 0.05), and they both had significant difference when using 1.5ml/kg contrast media (P< 0.05). Besides these, the imaging quality of portal vein branches and collateral vessels were better in 2.0ml/kg group than others. Conclusion: The patient's body weight and the state of liver disease influenced the extent of portal vein enhancement. To calculate the dose of contrast media according to patient's weight is crucial for ensuring the imaging quality of portal vein system. 2.0ml/kg contrast media can provide a better effect. (authors)

Spiral-CT-angiography of acute pulmonary embolism: factors that influence the implementation into standard diagnostic algorithms

International Nuclear Information System (INIS)

Bankier, A.; Herold, C.J.; Fleischmann, D.; Janata-Schwatczek, K.

1998-01-01

Purpose: Debate about the potential implementation of Spiral-CT in diagnostic algorithms of pulmonary embolism are often focussed on sensitivity and specificity in the context of comparative methodologic studies. We intend to investigate whether additional factors might influence this debate. Results: The factors availability, acceptance, patient-outcome, and cost-effectiveness-studies do have substantial influence on the implementation of Spiral-CT in the diagnostic algorithms of pulmonary embolism. Incorporation of these factors into the discussion might lead to more flexible and more patient-oriented algorithms for the diagnosis of pulmonary embolism. Conclusion: Availability of equipment, acceptance among clinicians, patient-out-come, and cost-effectiveness evaluations should be implemented into the debate about potential implementation of Spiral-CT in routine diagnostic imaging algorithms of pulmonary embolism. (orig./AJ) [de

Virtual endoscopy using spiral CT in patients with carcinomas of the hypopharynx and larynx

International Nuclear Information System (INIS)

Song, Sang Gook; Seo, Jeong Jin; Chung, Tae Woong; Kim, Hyeong Kil; Jeong, Gwang Woo; Jeong, Yong Yeon; Kang, Heoung Keun; Cho, Jae Sik

2000-01-01

To compare the usefulness of virtual endoscopy using spiral CT with that of laryngoscopy in the detection and evaluation of laryngeal and pharyngeal carcinomas. Twenty-four patients with pathologically proven laryngeal and pharyngeal carcinomas underwent laryngoscopy and virtual endoscopy using spiral CT. Eleven of the carcinomas were supraglottic, five were glottic, and eight were hypopharyngeal. Source images obtained by spiral CT were transmitted to an independent workstation and virtual endoscopic images were obtained using Navigator software. These were graded according to their quality (good, fair, bad), and were interpreted by two radiologists who were blinded to the conventional endoscopic findings. These latter were subsequently compared with the virtual endoscopic findings in terms of similarity to laryngoscopic examination and detectability of lesions. The overall image quality of virtual endoscopy was good in 16 cases (67%), fair in eight (33%), and bad in no case. Among the 11 supraglottic carcinomas, image quality was good in seven cases (64%), and fair in four (36%). In four of the five glottic carcinomas (80%) quality was good, and in one case (20%) it was fair, while among the eight hypopharyngeal carcinomas, quality was good in five cases (63%), and fair in three (37%). Overall, detection of the lesion was possible in 23 cases (96%). Due to the small size of the lesion, the one case of glottic carcinoma was not detected. Virtual endoscopy using spiral CT is a safe and noninvasive method, and also successfully detects laryngeal and pharyngeal lesions, with good image quality. For the evaluation of laryngeal and hypopharyngeal carcinoma, its use ma complement that of axial CT. (author)

Early detection of lung cancer using ultra-low-dose computed tomography in coronary CT angiography scans among patients with suspected coronary heart disease.

Science.gov (United States)

Zanon, Matheus; Pacini, Gabriel Sartori; de Souza, Vinicius Valério Silveiro; Marchiori, Edson; Meirelles, Gustavo Souza Portes; Szarf, Gilberto; Torres, Felipe Soares; Hochhegger, Bruno

2017-12-01

To assess whether an additional chest ultra-low-dose CT scan to the coronary CT angiography protocol can be used for lung cancer screening among patients with suspected coronary artery disease. 175 patients underwent coronary CT angiography for assessment of coronary artery disease, additionally undergoing ultra-low-dose CT screening to early diagnosis of lung cancer in the same scanner (80kVp and 15mAs). Patients presenting pulmonary nodules were followed-up for two years, repeating low-dose CTs in intervals of 3, 6, or 12 months based on nodule size and growth rate in accordance with National Comprehensive Cancer Network guidelines. Ultra-low-dose CT identified 71 patients with solitary pulmonary nodules (41%), with a mean diameter of 5.50±4.00mm. Twenty-eight were >6mm, and in 79% (n=22) of these cases they were false positive findings, further confirmed by follow-up (n=20), resection (n=1), or biopsy (n=1). Lung cancer was detected in six patients due to CT screening (diagnostic yield: 3%). Among these, four cases could not be detected in the cardiac field of view. Most patients were in early stages of the disease. Two patients diagnosed at advanced stages died due to cancer complications. The addition of the ultra-low-dose CT scan represented a radiation dose increment of 1.22±0.53% (effective dose, 0.11±0.03mSv). Lung cancer might be detected using additional ultra-low-dose protocols in coronary CT angiography scans among patients with suspected coronary artery disease. Copyright © 2017 Elsevier B.V. All rights reserved.

Shallow and deep breath lung tumor volume as estimated by spiral volumetric CT in comparison to standard axial CT using virtual simulation

International Nuclear Information System (INIS)

Quader, M.A.; Kalend, A.M.; Deutsch, M.; Greenberger, J.S.

1995-01-01

Purpose/Objective: In order to assess an individual patient tumor volume (TV) margins that are sufficient to design a beam-eye-view (BEW) conformal portal, the radiographic extent of gross tumor volume (GTV) dimensions and its fluctuation with breathing are measured by fast spiral CT scanning of patients treated for Stage II, III lung cancers using 5-6 field multi-collimated conformal beams. Materials and Methods: Over the course of conformal radiotherapy for lung cancer, a full thorax CT scans of the patient were taken by conventional axial CT scanning with patients immobilized in the treatment position and breathing normally. Patient(s) with good pulmonary function test (PFT) status were selected to perform deep breathing and re-scanned by fast spiral techniques in order to re-acquire the tomographic variation in the (GTV) with breathing. A Picker spiral ZAP-100 software running on the AQSim-PQ-2000 was used with a variable helical pitch of 1.0, 1.5 and 2.0. The variable pitch spirals were limited to tumor bed, diaphragm and lung apex area for measurements. Effect of breathing motion along x,y,z direction were then assessed for each beam-eye-view portal as seen in digitally reconstructed radiography (DRR) at the treated gantry angle. Results: Comparison of axial and spiral scans shows the progression of lung and diaphram motion with breathing can be gauged better in spiral scans. The movement of the diaphragm during shallow breathing has been found to be 2-3cm by measuring the distance between the most inferior and superior slices where diaphragm is present. The variation of the tumor dimensions along AP/PA and lateral direction seems to be less sensitive to breathing than those along inferior-superior direction. Conclusion: The fast spiral CT scanning is sensitive to patient lung motion and can be used to determine the fluctuations of the gross tumor volume with breathing. The extent of the fluctuation is location dependent and increases as one moves from the

A framework to measure myocardial extracellular volume fraction using dual-phase low dose CT images

International Nuclear Information System (INIS)

Liu, Yixun; Summers, Ronald M.; Yao, Jianhua; Liu, Songtao; Sibley, Christopher T.; Bluemke, David A.; Nacif, Marcelo S.

2013-01-01

Purpose: Myocardial extracellular volume fraction (ECVF) is a surrogate imaging biomarker of diffuse myocardial fibrosis, a hallmark of pathologic ventricular remodeling. Low dose cardiac CT is emerging as a promising modality to detect diffuse interstitial myocardial fibrosis due to its fast acquisition and low radiation; however, the insufficient contrast in the low dose CT images poses great challenge to measure ECVF from the image. Methods: To deal with this difficulty, the authors present a complete ECVF measurement framework including a point-guided myocardial modeling, a deformable model-based myocardium segmentation, nonrigid registration of pre- and post-CT, and ECVF calculation. Results: The proposed method was evaluated on 20 patients by two observers. Compared to the manually delineated reference segmentations, the accuracy of our segmentation in terms of true positive volume fraction (TPVF), false positive volume fraction (FPVF), and average surface distance (ASD), were 92.18% ± 3.52%, 0.31% ± 0.10%, 0.69 ± 0.14 mm, respectively. The interobserver variability measured by concordance correlation coefficient regarding TPVF, FPVF, and ASD were 0.95, 0.90, 0.94, respectively, demonstrating excellent agreement. Bland-Altman method showed 95% limits of agreement between ECVF at CT and ECVF at MR. Conclusions: The proposed framework demonstrates its efficiency, accuracy, and noninvasiveness in ECVF measurement and dramatically advances the ECVF at cardiac CT toward its clinical use

A framework to measure myocardial extracellular volume fraction using dual-phase low dose CT images

Energy Technology Data Exchange (ETDEWEB)

Liu, Yixun; Summers, Ronald M.; Yao, Jianhua, E-mail: JYao@cc.nih.gov [Clinical Image Processing Service, Radiology and Imaging Sciences, NIH Clinical Center, Bethesda, Maryland 20892 (United States); Liu, Songtao; Sibley, Christopher T.; Bluemke, David A. [Radiology and Imaging Sciences, NIH Clinical Center, Bethesda, Maryland 20892-1182 and Molecular Biomedical Imaging Laboratory, National Institute of Biomedical Imaging and Bioengineering, NIH Clinical Center, Bethesda, Maryland 20892 (United States); Nacif, Marcelo S. [Radiology and Imaging Sciences, NIH Clinical Center, Bethesda, Maryland 20892-1182 (United States)

2013-10-15

Purpose: Myocardial extracellular volume fraction (ECVF) is a surrogate imaging biomarker of diffuse myocardial fibrosis, a hallmark of pathologic ventricular remodeling. Low dose cardiac CT is emerging as a promising modality to detect diffuse interstitial myocardial fibrosis due to its fast acquisition and low radiation; however, the insufficient contrast in the low dose CT images poses great challenge to measure ECVF from the image. Methods: To deal with this difficulty, the authors present a complete ECVF measurement framework including a point-guided myocardial modeling, a deformable model-based myocardium segmentation, nonrigid registration of pre- and post-CT, and ECVF calculation. Results: The proposed method was evaluated on 20 patients by two observers. Compared to the manually delineated reference segmentations, the accuracy of our segmentation in terms of true positive volume fraction (TPVF), false positive volume fraction (FPVF), and average surface distance (ASD), were 92.18% ± 3.52%, 0.31% ± 0.10%, 0.69 ± 0.14 mm, respectively. The interobserver variability measured by concordance correlation coefficient regarding TPVF, FPVF, and ASD were 0.95, 0.90, 0.94, respectively, demonstrating excellent agreement. Bland-Altman method showed 95% limits of agreement between ECVF at CT and ECVF at MR. Conclusions: The proposed framework demonstrates its efficiency, accuracy, and noninvasiveness in ECVF measurement and dramatically advances the ECVF at cardiac CT toward its clinical use.

Pulmonary spheral tuberculosis: features and clinical significance of spiral dynamic CT

International Nuclear Information System (INIS)

Xie Ruming; Ma Daqing; Li Tieyi; Chen Yi; Lu Fudong; Zhou Xinhua

2001-01-01

Objective: To assess the features and clinical significance of spiral dynamic CT in patients with pulmonary spheral tuberculosis. Methods: The 54 foci in 42 patients with pulmonary spheral tuberculosis were studied. Thin-sections at 2 mm thickness and 2 mm interval through the nodular center were obtained before and after administration of contrast material. Results: In 54 pulmonary spheral tuberculosis, maximum enhanced CT value in 51 (94.4%, 51/54) foci was less than 20 HU, and more than 20 HU in the other 3(5.6%, 3/54) foci. 27(50.0%, 27/54) foci showed no any enhancement, 24, (44%, 24/54) foci showed capsular enhancement, 1(1.9%, 1/54) focus showed peripheral enhancement and 2(3.7%, 2/54) foci showed extensive enhancement. The accuracy of the correct diagnosis was 25.9% in terms of plain CT and 94.4% in terms of enhanced CT scanning. The difference was significant (x 2 = 50.1, P < 0.05). The curative effect of extensive enhanced foci and peripheral enhanced foci was optimal, capsular enhanced foci was second, and non-enhanced foci was barely satisfactory. Conclusion: Spiral dynamic CT technique may improve the accuracy of diagnosing pulmonary spheral tuberculosis. No enhancement and/or capsular enhancement were suggestive of tuberculosis. The enhancing character of foci might contribute to assess the curative effect of anti-tuberculosis

Novel iterative reconstruction method with optimal dose usage for partially redundant CT-acquisition

International Nuclear Information System (INIS)

Bruder, H; Raupach, R; Sunnegardh, J; Allmendinger, T; Klotz, E; Stierstorfer, K; Flohr, T

2015-01-01

In CT imaging, a variety of applications exist which are strongly SNR limited. However, in some cases redundant data of the same body region provide additional quanta.Examples: in dual energy CT, the spatial resolution has to be compromised to provide good SNR for material decomposition. However, the respective spectral dataset of the same body region provides additional quanta which might be utilized to improve SNR of each spectral component. Perfusion CT is a high dose application, and dose reduction is highly desirable. However, a meaningful evaluation of perfusion parameters might be impaired by noisy time frames. On the other hand, the SNR of the average of all time frames is extremely high.In redundant CT acquisitions, multiple image datasets can be reconstructed and averaged to composite image data. These composite image data, however, might be compromised with respect to contrast resolution and/or spatial resolution and/or temporal resolution. These observations bring us to the idea of transferring high SNR of composite image data to low SNR ‘source’ image data, while maintaining their resolution.It has been shown that the noise characteristics of CT image data can be improved by iterative reconstruction (Popescu et al 2012 Book of Abstracts, 2nd CT Meeting (Salt Lake City, UT) p 148). In case of data dependent Gaussian noise it can be modelled with image-based iterative reconstruction at least in an approximate manner (Bruder et al 2011 Proc. SPIE 7961 79610J).We present a generalized update equation in image space, consisting of a linear combination of the previous update, a correction term which is constrained by the source image data, and a regularization prior, which is initialized by the composite image data. This iterative reconstruction approach we call bimodal reconstruction (BMR).Based on simulation data it is shown that BMR can improve low contrast detectability, substantially reduces the noise power and has the potential to recover spatial

Novel iterative reconstruction method with optimal dose usage for partially redundant CT-acquisition

Science.gov (United States)

Bruder, H.; Raupach, R.; Sunnegardh, J.; Allmendinger, T.; Klotz, E.; Stierstorfer, K.; Flohr, T.

2015-11-01

In CT imaging, a variety of applications exist which are strongly SNR limited. However, in some cases redundant data of the same body region provide additional quanta. Examples: in dual energy CT, the spatial resolution has to be compromised to provide good SNR for material decomposition. However, the respective spectral dataset of the same body region provides additional quanta which might be utilized to improve SNR of each spectral component. Perfusion CT is a high dose application, and dose reduction is highly desirable. However, a meaningful evaluation of perfusion parameters might be impaired by noisy time frames. On the other hand, the SNR of the average of all time frames is extremely high. In redundant CT acquisitions, multiple image datasets can be reconstructed and averaged to composite image data. These composite image data, however, might be compromised with respect to contrast resolution and/or spatial resolution and/or temporal resolution. These observations bring us to the idea of transferring high SNR of composite image data to low SNR ‘source’ image data, while maintaining their resolution. It has been shown that the noise characteristics of CT image data can be improved by iterative reconstruction (Popescu et al 2012 Book of Abstracts, 2nd CT Meeting (Salt Lake City, UT) p 148). In case of data dependent Gaussian noise it can be modelled with image-based iterative reconstruction at least in an approximate manner (Bruder et al 2011 Proc. SPIE 7961 79610J). We present a generalized update equation in image space, consisting of a linear combination of the previous update, a correction term which is constrained by the source image data, and a regularization prior, which is initialized by the composite image data. This iterative reconstruction approach we call bimodal reconstruction (BMR). Based on simulation data it is shown that BMR can improve low contrast detectability, substantially reduces the noise power and has the potential to recover

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

African Journals Online (AJOL)

STORAGESEVER

2010-06-07

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

Submillisievert standard-pitch CT pulmonary angiography with ultra-low dose contrast media administration: A comparison to standard CT imaging.

Science.gov (United States)

Suntharalingam, Saravanabavaan; Mikat, Christian; Stenzel, Elena; Erfanian, Youssef; Wetter, Axel; Schlosser, Thomas; Forsting, Michael; Nassenstein, Kai

2017-01-01

To evaluate the image quality and radiation dose of submillisievert standard-pitch CT pulmonary angiography (CTPA) with ultra-low dose contrast media administration in comparison to standard CTPA. Hundred patients (56 females, 44 males, mean age 69.6±15.4 years; median BMI: 26.6, IQR: 5.9) with suspected pulmonary embolism were examined with two different protocols (n = 50 each, group A: 80 kVp, ref. mAs 115, 25 ml of contrast medium; group B: 100 kVp, ref. mAs 150, 60 ml of contrast medium) using a dual-source CT equipped with automated exposure control. Objective and subjective image qualities, radiation exposure as well as the frequency of pulmonary embolism were evaluated. There was no significant difference in subjective image quality scores between two groups regarding pulmonary arteries (p = 0.776), whereby the interobserver agreement was excellent (group A: k = 0.9; group B k = 1.0). Objective image analysis revealed that signal intensities (SI), signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the pulmonary arteries were equal or significantly higher in group B. There was no significant difference in the frequency of pulmonary embolism (p = 0.65). Using the low dose and low contrast media protocol resulted in a radiation dose reduction by 71.8% (2.4 vs. 0.7 mSv; pcontrast agent volume can obtain sufficient image quality to exclude or diagnose pulmonary emboli while reducing radiation dose by approximately 71%.

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

Directory of Open Access Journals (Sweden)

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.

Evaluation of chronic infectious interstitial pulmonary disease in children by low-dose CT-guided transthoracic lung biopsy

Energy Technology Data Exchange (ETDEWEB)

Heyer, Christoph M.; Lemburg, Stefan P.; Kagel, Thomas; Nicolas, Volkmar [Ruhr-University of Bochum, Institute of Diagnostic Radiology, Interventional Radiology and Nuclear Medicine, BG Clinics Bergmannsheil, Bochum (Germany); Mueller, Klaus-Michael [Ruhr-University of Bochum, Institute of Pathology, BG Clinics Bergmannsheil, Bochum (Germany); Nuesslein, Thomas G.; Rieger, Christian H.L. [Ruhr-University of Bochum, Pediatric Hospital, Bochum (Germany)

2005-07-01

Children with chronic infectious interstitial lung disease often have to undergo open lung biopsy to establish a final diagnosis. Open lung biopsy is an invasive procedure with major potential complications. Transthoracic lung biopsy (TLB) guided by computed tomography (CT) is a less-invasive well-established procedure in adults. Detailing the role of low-dose CT-guided TLB in the enhanced diagnosis of chronic lung diseases related to infection in children. A group of 11 children (age 8 months to 16 years) underwent CT-guided TLB with a 20-gauge biopsy device. All investigations were done under general anaesthesia on a multidetector CT scanner (SOMATOM Volume Zoom, Siemens, Erlangen, Germany) using a low-dose protocol (single slices, 120 kV, 20 mAs). Specimens were processed by histopathological, bacteriological, and virological techniques. All biopsies were performed without major complications; one child developed a small pneumothorax that resolved spontaneously. A diagnosis could be obtained in 10 of the 11 patients. Biopsy specimens revealed chronic interstitial alveolitis in ten patients. In five patients Chlamydia pneumoniae PCR was positive, in three Mycoplasma pneumoniae PCR was positive, and in two Cytomegalovirus PCR was positive. The average effective dose was 0.83 mSv. Low-dose CT-guided TLB can be a helpful tool in investigating chronic infectious inflammatory processes in children with minimal radiation exposure. It should be considered prior to any open surgical procedure performed for biopsy alone. In our patient group no significant complication occurred. A disadvantage of the method is that it does not allow smaller airways and vessels to be assessed. (orig.)

Effect of Localizer Radiography Projection on Organ Dose at Chest CT with Automatic Tube Current Modulation.

Science.gov (United States)

Saltybaeva, Natalia; Krauss, Andreas; Alkadhi, Hatem

2017-03-01

Purpose To calculate the effect of localizer radiography projections to the total radiation dose, including both the dose from localizer radiography and that from subsequent chest computed tomography (CT) with tube current modulation (TCM). Materials and Methods An anthropomorphic phantom was scanned with 192-section CT without and with differently sized breast attachments. Chest CT with TCM was performed after one localizer radiographic examination with anteroposterior (AP) or posteroanterior (PA) projections. Dose distributions were obtained by means of Monte Carlo simulations based on acquired CT data. For Monte Carlo simulations of localizer radiography, the tube position was fixed at 0° and 180°; for chest CT, a spiral trajectory with TCM was used. The effect of tube start angles on dose distribution was investigated with Monte Carlo simulations by using TCM curves with fixed start angles (0°, 90°, and 180°). Total doses for lungs, heart, and breast were calculated as the sum of the dose from localizer radiography and CT. Image noise was defined as the standard deviation of attenuation measured in 14 circular regions of interest. The Wilcoxon signed rank test, paired t test, and Friedman analysis of variance were conducted to evaluate differences in noise, TCM curves, and organ doses, respectively. Results Organ doses from localizer radiography were lower when using a PA instead of an AP projection (P = .005). The use of a PA projection resulted in higher TCM values for chest CT (P chest CT. © RSNA, 2016 Online supplemental material is available for this article.

A PC program for estimating organ dose and effective dose values in computed tomography

International Nuclear Information System (INIS)

Kalender, W.A.; Schmidt, B.; Schmidt, M.; Zankl, M.

1999-01-01

Dose values in CT are specified by the manufacturers for all CT systems and operating conditions in phantoms. It is not trivial, however, to derive dose values in patients from this information. Therefore, we have developed a PC-based program which calculates organ dose and effective dose values for arbitrary scan parameters and anatomical ranges. Values for primary radiation are derived from measurements or manufacturer specifications; values for scattered radiation are derived from Monte Carlo calculations tabulated for standard anthropomorphic phantoms. Based on these values, organ doses can be computed by the program for arbitrary scan protocols in conventional and in spiral CT. Effective dose values are also provided, both with ICRP 26 and ICRP 60 tissue-weighting coefficients. Results for several standard CT protocols are presented in tabular form in this paper. In addition, potential for dose reduction is demonstrated, for example, in spiral CT and in quantitative CT. Providing realistic patient dose estimates for arbitrary CT protocols is relevant both for the physician and the patient, and it is particularly useful for educational and training purposes. The program, called WinDose, is now in use at the Erlangen University hospitals (Germany) as an information tool for radiologists and patients. Further extensions are planned. (orig.)

Visual classification of emphysema heterogeneity compared with objective measurements: HRCT vs spiral CT in candidates for lung volume reduction surgery

International Nuclear Information System (INIS)

Cederlund, K.; Hoegberg, S.; Rasmussen, E.; Svane, B.; Bergstrand, L.; Tylen, U.; Aspelin, P.

2002-01-01

The aim of this study was to investigate whether spiral CT is superior to high-resolution computed tomography (HRCT) in evaluating the radiological morphology of emphysema, and whether the combination of both CT techniques improves the evaluation in patients undergoing lung volume reduction surgery (LVRS). The material consisted of HRCT (with 2-mm slice thickness) and spiral CT (with 10-mm slice thickness) of 94 candidates for LVRS. Selected image pairs from these examinations were evaluated. Each image pair consisted of one image from the cranial part of the lung and one image from the caudal part. The degree of emphysema in the two images was calculated by computer. The difference between the images determined the degree of heterogeneity. Five classes of heterogeneity were defined. The study was performed by visual classification of 95 image pairs (spiral CT) and 95 image pairs (HRCT) into one of five different classes of emphysema heterogeneity. This visual classification was compared with the computer-based classification. Spiral CT was superior to HRCT with 47% correct classifications of emphysema heterogeneity compared with 40% for HRCT-based classification (p<0.05). The combination of the techniques did not improve the evaluation (42%). Spiral CT is superior to HRCT in determining heterogeneity of emphysema visually, and should be included in the pre-operative CT evaluation of LVRS candidates. (orig.)

Visual classification of emphysema heterogeneity compared with objective measurements: HRCT vs spiral CT in candidates for lung volume reduction surgery

Energy Technology Data Exchange (ETDEWEB)

Cederlund, K.; Hoegberg, S.; Rasmussen, E.; Svane, B. [Department of Thoracic Radiology, Karolinska Hospital, Stockholm (Sweden); Bergstrand, L. [Department of Radiology, Danderyds Hospital, Danderyd (Sweden); Tylen, U. [Deparment of Radiology, Sahlgrenska University Hospital, Gothenberg (Sweden); Aspelin, P. [Department of Radiology, Huddinge University Hospital, Huddinge (Sweden)

2002-05-01

The aim of this study was to investigate whether spiral CT is superior to high-resolution computed tomography (HRCT) in evaluating the radiological morphology of emphysema, and whether the combination of both CT techniques improves the evaluation in patients undergoing lung volume reduction surgery (LVRS). The material consisted of HRCT (with 2-mm slice thickness) and spiral CT (with 10-mm slice thickness) of 94 candidates for LVRS. Selected image pairs from these examinations were evaluated. Each image pair consisted of one image from the cranial part of the lung and one image from the caudal part. The degree of emphysema in the two images was calculated by computer. The difference between the images determined the degree of heterogeneity. Five classes of heterogeneity were defined. The study was performed by visual classification of 95 image pairs (spiral CT) and 95 image pairs (HRCT) into one of five different classes of emphysema heterogeneity. This visual classification was compared with the computer-based classification. Spiral CT was superior to HRCT with 47% correct classifications of emphysema heterogeneity compared with 40% for HRCT-based classification (p<0.05). The combination of the techniques did not improve the evaluation (42%). Spiral CT is superior to HRCT in determining heterogeneity of emphysema visually, and should be included in the pre-operative CT evaluation of LVRS candidates. (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

Ultra-low-dose lung screening CT with model-based iterative reconstruction: an assessment of image quality and lesion conspicuity.

Science.gov (United States)

Ju, Yun Hye; Lee, Geewon; Lee, Ji Won; Hong, Seung Baek; Suh, Young Ju; Jeong, Yeon Joo

2018-05-01

Background Reducing radiation dose inevitably increases image noise, and thus, it is important in low-dose computed tomography (CT) to maintain image quality and lesion detection performance. Purpose To assess image quality and lesion conspicuity of ultra-low-dose CT with model-based iterative reconstruction (MBIR) and to determine a suitable protocol for lung screening CT. Material and Methods A total of 120 heavy smokers underwent lung screening CT and were randomly and equally assigned to one of five groups: group 1 = 120 kVp, 25 mAs, with FBP reconstruction; group 2 = 120 kVp, 10 mAs, with MBIR; group 3 = 100 kVp, 15 mAs, with MBIR; group 4 = 100 kVp, 10 mAs, with MBIR; and group 5 = 100 kVp, 5 mAs, with MBIR. Two radiologists evaluated intergroup differences with respect to radiation dose, image noise, image quality, and lesion conspicuity using the Kruskal-Wallis test and the Chi-square test. Results Effective doses were 61-87% lower in groups 2-5 than in group 1. Image noises in groups 1 and 5 were significantly higher than in the other groups ( P image quality was best in group 1, but diagnostic acceptability of overall image qualities in groups 1-3 was not significantly different (all P values > 0.05). Lesion conspicuities were similar in groups 1-4, but were significantly poorer in group 5. Conclusion Lung screening CT with MBIR obtained at 100 kVp and 15 mAs enables a ∼60% reduction in radiation dose versus low-dose CT, while maintaining image quality and lesion conspicuity.

SU-F-I-12: Region-Specific Dictionary Learning for Low-Dose X-Ray CT Reconstruction

International Nuclear Information System (INIS)

Xu, Q; Han, H; Xing, L

2016-01-01

Purpose: Dictionary learning based method has attracted more and more attentions in low-dose CT due to the superior performance on suppressing noise and preserving structural details. Considering the structures and noise vary from region to region in one imaging object, we propose a region-specific dictionary learning method to improve the low-dose CT reconstruction. Methods: A set of normal-dose images was used for dictionary learning. Segmentations were performed on these images, so that the training patch sets corresponding to different regions can be extracted out. After that, region-specific dictionaries were learned from these training sets. For the low-dose CT reconstruction, a conventional reconstruction, such as filtered back-projection (FBP), was performed firstly, and then segmentation was followed to segment the image into different regions. Sparsity constraints of each region based on its dictionary were used as regularization terms. The regularization parameters were selected adaptively according to different regions. A low-dose human thorax dataset was used to evaluate the proposed method. The single dictionary based method was performed for comparison. Results: Since the lung region is very different from the other part of thorax, two dictionaries corresponding to lung region and the rest part of thorax respectively were learned to better express the structural details and avoid artifacts. With only one dictionary some artifact appeared in the body region caused by the spot atoms corresponding to the structures in the lung region. And also some structure in the lung regions cannot be recovered well by only one dictionary. The quantitative indices of the result by the proposed method were also improved a little compared to the single dictionary based method. Conclusion: Region-specific dictionary can make the dictionary more adaptive to different region characteristics, which is much desirable for enhancing the performance of dictionary learning

SU-F-I-12: Region-Specific Dictionary Learning for Low-Dose X-Ray CT Reconstruction

Energy Technology Data Exchange (ETDEWEB)

Xu, Q; Han, H; Xing, L [Stanford University School of Medicine, Stanford, CA (United States)

2016-06-15

Purpose: Dictionary learning based method has attracted more and more attentions in low-dose CT due to the superior performance on suppressing noise and preserving structural details. Considering the structures and noise vary from region to region in one imaging object, we propose a region-specific dictionary learning method to improve the low-dose CT reconstruction. Methods: A set of normal-dose images was used for dictionary learning. Segmentations were performed on these images, so that the training patch sets corresponding to different regions can be extracted out. After that, region-specific dictionaries were learned from these training sets. For the low-dose CT reconstruction, a conventional reconstruction, such as filtered back-projection (FBP), was performed firstly, and then segmentation was followed to segment the image into different regions. Sparsity constraints of each region based on its dictionary were used as regularization terms. The regularization parameters were selected adaptively according to different regions. A low-dose human thorax dataset was used to evaluate the proposed method. The single dictionary based method was performed for comparison. Results: Since the lung region is very different from the other part of thorax, two dictionaries corresponding to lung region and the rest part of thorax respectively were learned to better express the structural details and avoid artifacts. With only one dictionary some artifact appeared in the body region caused by the spot atoms corresponding to the structures in the lung region. And also some structure in the lung regions cannot be recovered well by only one dictionary. The quantitative indices of the result by the proposed method were also improved a little compared to the single dictionary based method. Conclusion: Region-specific dictionary can make the dictionary more adaptive to different region characteristics, which is much desirable for enhancing the performance of dictionary learning

Emphysema Quantification Using Low Dose Chest CT: Changes in Follow-Up Examinations of Asymptomatic Smokers

Energy Technology Data Exchange (ETDEWEB)

Jang, Eun Ho; Sun, Joo Sung; Kang, Doo Kyung [Dept. of Radiology, Ajou University School of Medicine, Suwon (Korea, Republic of); Park, Kwang Joo; Park, Kyung Joo [Dept. of Pulmolary Medicine, Ajou University School of Medicine, Suwon (Korea, Republic of)

2012-01-15

To evaluate the changes of emphysema quantification in a follow-up low dose CT compared with pulmonary function test (PFT) results in asymptomatic smokers. We selected 66 asymptomatic smokers (> 40 years old) who underwent a follow-up low dose CT at least one year after the first CT as well as PFT within the same time period. Emphysema quantification was performed using an automated measurement software and an emphysema index (EI) was calculated using multiple threshold values (-970--900 HU). The interval change of EI ({Delta} EI) was compared with the change in the PFT values. Mean follow-up %forced expiratory volume in 1 second (88.1), %forced vital capacity (FVC) (89.5) and forced expiratory flow between 25 and 75% of vital capacity (3.21) were significantly lower compared with the values of initial tests (93.3, 93.1, 3.48). The mean EIs (2.4-25.6%) increased on follow-up CTs compared with initial EIs (2.1-24.5%), though the increase was not statistically significant. In a group with a follow-up period of 2 years or more (n = 32), EI significantly increased when using -900 HU as the threshold. The ({Delta} EIs were poorly correlated with the ({Delta} PFT values, but significantly correlated with ({Delta} FVC (r = -0.32--0.27). Emphysema quantification using low dose CT was not effective for the evaluation of short-term changes in less than a 2-year period, but may be used for long term follow-up series in asymptomatic smokers.

Computer-aided detection of early interstitial lung diseases using low-dose CT images

Energy Technology Data Exchange (ETDEWEB)

Park, Sang Cheol; Kim, Soo Hyung [School of Electronics and Computer Engineering, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Tan, Jun; Wang Xingwei; Lederman, Dror; Leader, Joseph K; Zheng Bin, E-mail: zhengb@upmc.edu [Department of Radiology, University of Pittsburgh, Pittsburgh, PA 15213 (United States)

2011-02-21

This study aims to develop a new computer-aided detection (CAD) scheme to detect early interstitial lung disease (ILD) using low-dose computed tomography (CT) examinations. The CAD scheme classifies each pixel depicted on the segmented lung areas into positive or negative groups for ILD using a mesh-grid-based region growth method and a multi-feature-based artificial neural network (ANN). A genetic algorithm was applied to select optimal image features and the ANN structure. In testing each CT examination, only pixels selected by the mesh-grid region growth method were analyzed and classified by the ANN to improve computational efficiency. All unselected pixels were classified as negative for ILD. After classifying all pixels into the positive and negative groups, CAD computed a detection score based on the ratio of the number of positive pixels to all pixels in the segmented lung areas, which indicates the likelihood of the test case being positive for ILD. When applying to an independent testing dataset of 15 positive and 15 negative cases, the CAD scheme yielded the area under receiver operating characteristic curve (AUC = 0.884 {+-} 0.064) and 80.0% sensitivity at 85.7% specificity. The results demonstrated the feasibility of applying the CAD scheme to automatically detect early ILD using low-dose CT examinations.

MO-DE-207A-09: Low-Dose CT Image Reconstruction Via Learning From Different Patient Normal-Dose Images

Energy Technology Data Exchange (ETDEWEB)

Han, H; Xing, L [Stanford University, Palo Alto, CA (United States); Liang, Z [Stony Brook University, Stony Brook, NY (United States)

2016-06-15

Purpose: To investigate a novel low-dose CT (LdCT) image reconstruction strategy for lung CT imaging in radiation therapy. Methods: The proposed approach consists of four steps: (1) use the traditional filtered back-projection (FBP) method to reconstruct the LdCT image; (2) calculate structure similarity (SSIM) index between the FBP-reconstructed LdCT image and a set of normal-dose CT (NdCT) images, and select the NdCT image with the highest SSIM as the learning source; (3) segment the NdCT source image into lung and outside tissue regions via simple thresholding, and adopt multiple linear regression to learn high-order Markov random field (MRF) pattern for each tissue region in the NdCT source image; (4) segment the FBP-reconstructed LdCT image into lung and outside regions as well, and apply the learnt MRF prior in each tissue region for statistical iterative reconstruction of the LdCT image following the penalized weighted least squares (PWLS) framework. Quantitative evaluation of the reconstructed images was based on the signal-to-noise ratio (SNR), local binary pattern (LBP) and histogram of oriented gradients (HOG) metrics. Results: It was observed that lung and outside tissue regions have different MRF patterns predicted from the NdCT. Visual inspection showed that our method obviously outperformed the traditional FBP method. Comparing with the region-smoothing PWLS method, our method has, in average, 13% increase in SNR, 15% decrease in LBP difference, and 12% decrease in HOG difference from reference standard for all regions of interest, which indicated the superior performance of the proposed method in terms of image resolution and texture preservation. Conclusion: We proposed a novel LdCT image reconstruction method by learning similar image characteristics from a set of NdCT images, and the to-be-learnt NdCT image does not need to be scans from the same subject. This approach is particularly important for enhancing image quality in radiation therapy.

MO-DE-207A-09: Low-Dose CT Image Reconstruction Via Learning From Different Patient Normal-Dose Images

International Nuclear Information System (INIS)

Han, H; Xing, L; Liang, Z

2016-01-01

Purpose: To investigate a novel low-dose CT (LdCT) image reconstruction strategy for lung CT imaging in radiation therapy. Methods: The proposed approach consists of four steps: (1) use the traditional filtered back-projection (FBP) method to reconstruct the LdCT image; (2) calculate structure similarity (SSIM) index between the FBP-reconstructed LdCT image and a set of normal-dose CT (NdCT) images, and select the NdCT image with the highest SSIM as the learning source; (3) segment the NdCT source image into lung and outside tissue regions via simple thresholding, and adopt multiple linear regression to learn high-order Markov random field (MRF) pattern for each tissue region in the NdCT source image; (4) segment the FBP-reconstructed LdCT image into lung and outside regions as well, and apply the learnt MRF prior in each tissue region for statistical iterative reconstruction of the LdCT image following the penalized weighted least squares (PWLS) framework. Quantitative evaluation of the reconstructed images was based on the signal-to-noise ratio (SNR), local binary pattern (LBP) and histogram of oriented gradients (HOG) metrics. Results: It was observed that lung and outside tissue regions have different MRF patterns predicted from the NdCT. Visual inspection showed that our method obviously outperformed the traditional FBP method. Comparing with the region-smoothing PWLS method, our method has, in average, 13% increase in SNR, 15% decrease in LBP difference, and 12% decrease in HOG difference from reference standard for all regions of interest, which indicated the superior performance of the proposed method in terms of image resolution and texture preservation. Conclusion: We proposed a novel LdCT image reconstruction method by learning similar image characteristics from a set of NdCT images, and the to-be-learnt NdCT image does not need to be scans from the same subject. This approach is particularly important for enhancing image quality in radiation therapy.

Studies on image quality, high contrast resolution and dose for the axial skeleton and limbs with a new, dedicated CT system (ISO-C-3D)

International Nuclear Information System (INIS)

Rock, C.; Kotsianos, D.; Linsenmaier, U.; Fischer, T.

2002-01-01

Purpose: Evaluation of 3D-CT imaging of the axial skeleton and different joints of the lower and upper extremities with a new dedicated CT system (ISO-C-3D) based on a mobile isocentric C-arm image amplifier. Material and Methods: 27 cadaveric specimes of different joints of the lower and upper extremities and of the spinal column were examined with 3D-CT imaging (ISO-C-3d). All images were evaluated by 3 radiologists for image quality using a semiquantitative score (score value 1: poor quality; score value 4: excellent quality). In addition, dose measurements and measurements of high contrast resolution were performed in comparison to conventional and low-dose spiral CT using a high contrast phantom (Catphan, Phantom Laboratories). Results: Adequate image quality (mean score values 3-4) could be achieved with an applied dose comparable to low-dose CT in smaller joints such as wrist, elbow, ankle and knee. A remarkably inferior image quality resulted in imaging of the hip, lumbar and thoracic spine (mean score values 2-3) in spite of almost doubling the dose (dose increased by 85 percent). The image quality of shoulder examinations was insufficient (mean score value 1). Phantom studies showed a high-contrast resolution comparable to helical CT in the xy-axis (9 lp/cm). Conclusion: Preliminary results show, that image quality of C-arm-based CT-imaging (ISO-C-3D) seems to be adequate in smaller joints. ISO-C-3D images of the hip and axial skeleton show a decreased image quality, which does not seem to be sufficient for diagnosing subtle fractures. (orig.) [de

Radiation dose in cardiac SPECT/CT: An estimation of SSDE and effective dose

International Nuclear Information System (INIS)

Abdollahi, Hamid; Shiri, Isaac; Salimi, Yazdan; Sarebani, Maghsoud; Mehdinia, Reza; Deevband, Mohammad Reza; Mahdavi, Seied Rabi; Sohrabi, Ahmad; Bitarafan-Rajabi, Ahmad

2016-01-01

Aims: The dose levels for Computed Tomography (CT) localization and attenuation correction of Single Photon Emission Computed Tomography (SPECT) are limited and reported as Volume Computed Tomography Dose Index (CTDIvol) and Dose-Length Product (DLP). This work presents CT dose estimation from Cardiac SPECT/CT based on new American Association of Physicists in Medicine (AAPM) Size Specific Dose Estimation (SSDE) parameter, effective dose, organ doses and also emission dose from nuclear issue. Material and methods: Myocardial perfusion SPECT/CT for 509 patients was included in the study. SSDE, effective dose and organ dose were calculated using AAPM guideline and Impact-Dose software. Data were analyzed using R and SPSS statistical software. Spearman-Pearson correlation test and linear regression models were used for finding correlations and relationships among parameters. Results: The mean CTDIvol was 1.34 mGy ± 0.19 and the mean SSDE was 1.7 mGy ± 0.16. The mean ± SD of effective dose from emission, CT and total dose were 11.5 ± 1.4, 0.49 ± 0.11 and 12.67 ± 1.73 (mSv) respectively. The mean ± SD of effective dose from emission, CT and total dose were 11.5 ± 1.4, 0.49 ± 0.11 and 12.67 ± 1.73 (mSv) respectively. The spearman test showed that correlation between body size and organ doses is significant except thyroid and red bone marrow. CTDIvol was strongly dependent on patient size, but SSDE was not. Emission dose was strongly dependent on patient weight, but its dependency was lower to effective diameter. Conclusion: The dose parameters including CTDIvol, DLP, SSDE, effective dose values reported here are very low and below the reference level. This data suggest that appropriate CT acquisition parameters in SPECT/CT localization and attenuation correction are very beneficial for patients and lowering cancer risks.

Radiation dose in cardiac SPECT/CT: An estimation of SSDE and effective dose

Energy Technology Data Exchange (ETDEWEB)

Abdollahi, Hamid, E-mail: Hamid_rbp@yahoo.com [Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Shiri, Isaac [Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Salimi, Yazdan [Biomedical Engineering and Medical Physics Department, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran (Iran, Islamic Republic of); Sarebani, Maghsoud; Mehdinia, Reza [Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Deevband, Mohammad Reza [Biomedical Engineering and Medical Physics Department, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran (Iran, Islamic Republic of); Mahdavi, Seied Rabi [Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Radiation Biology Research Center, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Sohrabi, Ahmad [Department of Biostatistics, School of Public Health, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Bitarafan-Rajabi, Ahmad, E-mail: bitarafan@hotmail.com [Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Department of Nuclear Medicine, Rajaei Cardiovascular, Medical and Research Center, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of)

2016-12-15

Aims: The dose levels for Computed Tomography (CT) localization and attenuation correction of Single Photon Emission Computed Tomography (SPECT) are limited and reported as Volume Computed Tomography Dose Index (CTDIvol) and Dose-Length Product (DLP). This work presents CT dose estimation from Cardiac SPECT/CT based on new American Association of Physicists in Medicine (AAPM) Size Specific Dose Estimation (SSDE) parameter, effective dose, organ doses and also emission dose from nuclear issue. Material and methods: Myocardial perfusion SPECT/CT for 509 patients was included in the study. SSDE, effective dose and organ dose were calculated using AAPM guideline and Impact-Dose software. Data were analyzed using R and SPSS statistical software. Spearman-Pearson correlation test and linear regression models were used for finding correlations and relationships among parameters. Results: The mean CTDIvol was 1.34 mGy ± 0.19 and the mean SSDE was 1.7 mGy ± 0.16. The mean ± SD of effective dose from emission, CT and total dose were 11.5 ± 1.4, 0.49 ± 0.11 and 12.67 ± 1.73 (mSv) respectively. The mean ± SD of effective dose from emission, CT and total dose were 11.5 ± 1.4, 0.49 ± 0.11 and 12.67 ± 1.73 (mSv) respectively. The spearman test showed that correlation between body size and organ doses is significant except thyroid and red bone marrow. CTDIvol was strongly dependent on patient size, but SSDE was not. Emission dose was strongly dependent on patient weight, but its dependency was lower to effective diameter. Conclusion: The dose parameters including CTDIvol, DLP, SSDE, effective dose values reported here are very low and below the reference level. This data suggest that appropriate CT acquisition parameters in SPECT/CT localization and attenuation correction are very beneficial for patients and lowering cancer risks.

Radiation exposure during paediatric CT in Sudan: CT dose, organ and effective doses

International Nuclear Information System (INIS)

Suliman, I.I.; Khamis, H.M.; Ombada, T.H.; Alzimami, K.; Alkhorayef, M.; Sulieman, A.

2015-01-01

The purpose of this study was to assess the magnitude of radiation exposure during paediatric CT in Sudanese hospitals. Doses were determined from CT acquisition parameters using CT-Expo 2.1 dosimetry software. Doses were evaluated for three patient ages (0-1, 1-5 and 5-10 y) and two common procedures (head and abdomen). For children aged 0-1 y, volume CT air kerma index (C vol ), air Kerma-length product and effective dose (E) values were 19.1 mGy, 265 mGy.cm and 3.1 mSv, respectively, at head CT and those at abdominal CT were 8.8 mGy, 242 mGy.cm and 7.7 mSv, respectively. Those for children aged 1-5 y were 22.5 mGy, 305 mGy.cm and 1.1 mSv, respectively, at head CT and 12.6 mGy, 317 mGy.cm, and 5.1 mSv, respectively, at abdominal CT. Dose values and variations were comparable with those reported in the literature. Organ equivalent doses vary from 7.5 to 11.6 mSv for testes, from 9.0 to 10.0 mSv for ovaries and from 11.1 to 14.3 mSv for uterus in abdominal CT. The results are useful for dose optimisation and derivation of national diagnostic reference levels. (authors)

PET/CT in malignant melanoma: contrast-enhanced CT versus plain low-dose CT

International Nuclear Information System (INIS)

Pfluger, Thomas; Schneider, Vera; Fougere, Christian la; Bartenstein, Peter; Weiss, Mayo; Melzer, Henriette Ingrid; Coppenrath, Eva; Berking, Carola

2011-01-01

The aim of this study was to evaluate the diagnostic value of contrast-enhanced CT (CECT) versus non-enhanced low-dose CT (NECT) in the staging of advanced malignant melanoma with 18 F-fluordeoxyglucose (FDG) positron emission tomography (PET)/CT. In total, 50 18 F-FDG PET/CT examinations were performed in 50 patients with metastasized melanoma. For attenuation correction, whole-body NECT was performed followed by diagnostic CECT with contrast agent. For the whole-body PET, 18 F-FDG was applied. Criteria for evaluation were signs of vital tumour tissue (extent of lesions, contrast enhancement, maximum standardized uptake value >2.5). Findings suspicious for melanoma were considered lesions. NECT, CECT and 18 F-FDG PET were evaluated separately, followed by combined analysis of PET/NECT and PET/CECT. Findings were verified histologically and/or by follow-up (>6 months). Overall, 232 lesions were analysed, and 151 proved to be metastases. The sensitivity of NECT, CECT, PET, PET/NECT and PET/CECT was 62, 85, 90, 97 and 100%, and specificity was 52, 63, 88, 93 and 93%, respectively. Compared to CECT, NECT obtained additional false-negative results: lymph node (n = 19) and liver/spleen metastases (n = 9). Misinterpreted physiological structures mainly caused additional false-positive findings (n = 17). In combined analysis of PET/NECT, six false-positive [other tumours (n = 2), inflammatory lymph nodes (n = 2), inflammatory lung lesion (n = 1), blood vessel (n = 1)] and five false-negative findings [liver (n = 3), spleen (n = 1), lymph node metastases (n = 1)] remained. On PET/CECT, six false-positive [inflammatory lymph nodes (n = 3), other tumours (n = 2), inflammatory lung lesion (n = 1)] and no false-negative findings occurred. However, additional false findings on PET/NECT (6 of 232) did not change staging compared to PET/CECT. Our results indicate that it is justified to perform PET/NECT instead of PET/CECT for melanoma staging. (orig.)

Low-Dose Contrast-Enhanced Breast CT Using Spectral Shaping Filters: An Experimental Study.

Science.gov (United States)

Makeev, Andrey; Glick, Stephen J

2017-12-01

Iodinated contrast-enhanced X-ray imaging of the breast has been studied with various modalities, including full-field digital mammography (FFDM), digital breast tomosynthesis (DBT), and dedicated breast CT. Contrast imaging with breast CT has a number of advantages over FFDM and DBT, including the lack of breast compression, and generation of fully isotropic 3-D reconstructions. Nonetheless, for breast CT to be considered as a viable tool for routine clinical use, it would be desirable to reduce radiation dose. One approach for dose reduction in breast CT is spectral shaping using X-ray filters. In this paper, two high atomic number filter materials are studied, namely, gadolinium (Gd) and erbium (Er), and compared with Al and Cu filters currently used in breast CT systems. Task-based performance is assessed by imaging a cylindrical poly(methyl methacrylate) phantom with iodine inserts on a benchtop breast CT system that emulates clinical breast CT. To evaluate detectability, a channelized hoteling observer (CHO) is used with sums of Laguerre-Gauss channels. It was observed that spectral shaping using Er and Gd filters substantially increased the dose efficiency (defined as signal-to-noise ratio of the CHO divided by mean glandular dose) as compared with kilovolt peak and filter settings used in commercial and prototype breast CT systems. These experimental phantom study results are encouraging for reducing dose of breast CT, however, further evaluation involving patients is needed.

Low-Dose and Standard-Dose Unenhanced Helical Computed Tomography for the Assessment of Acute Renal Colic: Prospective Comparative Study

Energy Technology Data Exchange (ETDEWEB)

Kim, Bong Soo; Hwang, Im Kyung; Choi, Yo Won; Namkung, Sook; Kim, Heung Cheol; Hwang, Woo Cheol; Choi, Kuk Myung; Park, Ji Kang; Han, Tae Il; Kang, Weechang [Cheju National Univ. College of Medicine, Jeju (Korea, Republic of). Dept. of Diagnostic Radiology

2005-11-01

Purpose: To compare the efficacy of low-dose and standard-dose computed tomography (CT) for the diagnosis of ureteral stones. Material and Methods: Unenhanced helical CT was performed with both a standard dose (260 mAs, pitch 1.5) and a low dose (50 mAs, pitch 1.5) in 121 patients suspected of having acute renal colic. The two studies were prospectively and independently interpreted for the presence and location of ureteral stones, abnormalities unrelated to stone disease, identification of secondary signs, i.e. hydronephrosis and perinephric stranding, and tissue rim sign. The standard-dose CT images were interpreted by one reviewer and the low-dose CT images independently by two reviewers unaware of the standard-dose CT findings. The findings of the standard and low-dose CT scans were compared with the exact McNemar test. Interobserver agreements were assessed with kappa analysis. The effective radiation doses resulting from two different protocols were calculated by means of commercially available software to which the Monte-Carlo phantom model was given. Results: The sensitivity, specificity, and accuracy of standard-dose CT for detecting ureteral stones were 99%, 93%, and 98%, respectively, whereas for the two reviewers the sensitivity of low-dose CT was 93% and 95%, specificity 86%, and accuracy 92% and 94%. We found no significant differences between standard-dose and low-dose CT in the sensitivity and specificity for diagnosing ureter stones ( P >0.05 for both). However, the sensitivity of low-dose CT for detection of 19 stones less than or equal to 2 mm in diameter was 79% and 68%, respectively, for the two reviewers. Low-dose CT was comparable to standard-dose CT in visualizing hydronephrosis and the tissue rim sign. Perinephric stranding was far less clear on low-dose CT. Low-dose CT had the same diagnostic performance as standard-dose CT in diagnosing alternative diseases. Interobserver agreement between the two low-dose CT reviewers in the diagnosis of

Low-dose celiac CT angiography with fixed current-time product

International Nuclear Information System (INIS)

Yu Hong; Li Huimin; Li Xiaolin; Zhu Shiqiang; Zhang Jiaming; Wang Xiangming; Zou Xiaofeng

2009-01-01

Objective: To characterize the feasibility of low-dose CT angiography on 16-slice multi-slice computed tomography (16-MSCT), and its relationship to the noise in the pre-contrast image and enhancement value. Methods: Forty-three consecutive patients (male 21, female 22, mean age 59 years, median age 56 years) underwent abdominal 16-MSCT (Toshiba Aquilion 16) with constant scanning parameters including 120 kVp, a 0.5-second gantry rotation time, a pitch of 0.938: 1, and 16 x 1-mm detector collimation. The mA was set at 200 in the pre-contrast scan and 160 in the contrast-enhanced scan. The arterial phase images were retrospectively reconstructed with 1-mm slice thickness, 0.8 mm interval. The pre-contrast noise was defined as the standard deviation (SD) of the aorta at the level of right posterior crura of diaphragm. The enhancement of aorta was also measured at level of celiac artery. The volume rendering of CT angiography was made and classified into three grades (excellent, good, bad). Receiver operating characteristic curve (ROC) was used to evaluate the relationship between the image quality of CT angiography and noise in the pre-contrast image and enhancement value. Results: Twenty-five cases had the aorta enhancement between 300.0-400.0 HU. The sensitivity and specificity of excellent CTA image was 75% and 62%, respectively when the SD was 12.00. Eighteen cases had the aorta enhancement more than 400.0 HU. The sensitivity and specificity of excellent CTA image was all 100% when the SD was 12.25, and 100% and 75%, respectively when the SD was 13.35. The area under curve of CTA image quality and enhancement in receiver-operated characteristic analysis was 0.907. The enhancement was more than 356.7 HU when the sensitivity and specificity of excellent CTA image was 100% and 60%, respectively, and 389.8 HU when 78% and 80%. When the enhancement was more than 442.4 HU, the specificity of excellent CTA image was 100%. Conclusions: MSCT angiography with low radiation

Emphysema quantification and lung volumetry in chest X-ray equivalent ultralow dose CT - Intra-individual comparison with standard dose CT.

Science.gov (United States)

Messerli, Michael; Ottilinger, Thorsten; Warschkow, René; Leschka, Sebastian; Alkadhi, Hatem; Wildermuth, Simon; Bauer, Ralf W

2017-06-01

To determine whether ultralow dose chest CT with tin filtration can be used for emphysema quantification and lung volumetry and to assess differences in emphysema measurements and lung volume between standard dose and ultralow dose CT scans using advanced modeled iterative reconstruction (ADMIRE). 84 consecutive patients from a prospective, IRB-approved single-center study were included and underwent clinically indicated standard dose chest CT (1.7±0.6mSv) and additional single-energy ultralow dose CT (0.14±0.01mSv) at 100kV and fixed tube current at 70mAs with tin filtration in the same session. Forty of the 84 patients (48%) had no emphysema, 44 (52%) had emphysema. One radiologist performed fully automated software-based pulmonary emphysema quantification and lung volumetry of standard and ultralow dose CT with different levels of ADMIRE. Friedman test and Wilcoxon rank sum test were used for multiple comparison of emphysema and lung volume. Lung volumes were compared using the concordance correlation coefficient. The median low-attenuation areas (LAA) using filtered back projection (FBP) in standard dose was 4.4% and decreased to 2.6%, 2.1% and 1.8% using ADMIRE 3, 4, and 5, respectively. The median values of LAA in ultralow dose CT were 5.7%, 4.1% and 2.4% for ADMIRE 3, 4, and 5, respectively. There was no statistically significant difference between LAA in standard dose CT using FBP and ultralow dose using ADMIRE 4 (p=0.358) as well as in standard dose CT using ADMIRE 3 and ultralow dose using ADMIRE 5 (p=0.966). In comparison with standard dose FBP the concordance correlation coefficients of lung volumetry were 1.000, 0.999, and 0.999 for ADMIRE 3, 4, and 5 in standard dose, and 0.972 for ADMIRE 3, 4 and 5 in ultralow dose CT. Ultralow dose CT at chest X-ray equivalent dose levels allows for lung volumetry as well as detection and quantification of emphysema. However, longitudinal emphysema analyses should be performed with the same scan protocol and

Usefulness evaluation of low-dose for emphysema: Compared with high-resolution CT

Energy Technology Data Exchange (ETDEWEB)

Lee, Won Jeong [Dept. of Radiological Technology, Daejeon Health Institute of Technology, Daejeon (Korea, Republic of)

2016-09-15

The purpose of this study was to evaluate the usefulness of low-dose CT (LDCT) for emphysema compared with high-resolution CT (HRCT). Measurements of radiation dose and noise were repeated 3 times in same exposure condition which was similar with obtaining HRCT and LDCT images. We analysed reading results of 146 subjects. Six images per participants selected for emphysema grading. Emphysema was graded for all 6 zones on the left and right sides of the lungs by the consensus reading of two chest radiologists using a 4-point scale. Between the HRCT and LDCT images, diagnostic differences and agreements for emphysema were analyzed by McNemar's and unweighted kappa tests, and radiation doses and noise by a Mann-Whitney U-test, using the SPSS 19.0 program. Radiation dose from HRCT was significantly higher than that of LDCT, but the noise was significantly lower in HRCT than in LDCT. Diagnostic agreement for emphysema between HRCT and LDCT images was excellent (k-value=0.88). Emphysema grading scores were not significantly different between HRCT and LDCT images for all six lung zones. Emphysema grading scores from LDCT images were significantly correlated with increased scores on HRCT images (r=0.599, p < 0.001). Considering the tradeoff between radiation dose and image noise, LDCT could be used as the gold standard method instead of HRCT for emphysema detection and grading.

Evaluation of the low dose cardiac CT imaging using ASIR technique

Science.gov (United States)

Fan, Jiahua; Hsieh, Jiang; Deubig, Amy; Sainath, Paavana; Crandall, Peter

2010-04-01

Today Cardiac imaging is one of the key driving forces for the research and development activities of Computed Tomography (CT) imaging. It requires high spatial and temporal resolution and is often associated with high radiation dose. The newly introduced ASIR technique presents an efficient method that offers the dose reduction benefits while maintaining image quality and providing fast reconstruction speed. This paper discusses the study of image quality of the ASIR technique for Cardiac CT imaging. Phantoms as well as clinical data have been evaluated to demonstrate the effectiveness of ASIR technique for Cardiac CT applications.

Three-dimensional spiral CT of craniofacial malformations in children

International Nuclear Information System (INIS)

Binaghi, S.; Gudinchet, F.

2000-01-01

Objective. To assess the value of three-dimensional CT (3D CT) in the diagnosis and management of suspected paediatric craniofacial malformations. Materials and methods. Twenty-eight children (12 girls, 16 boys) with a mean age of 4 years, suffering from craniofacial or cervical malformations, underwent craniofacial spiral CT. 3D reformatting was performed using an independent workstation. Results. 3D CT allowed the preoperative evaluation of 16 patients with craniosynostosis and the post-surgical management of 2 patients. 3D CT clearly depicted malformations of the skull base involving the petrous bone in seven patients (four cases of Goldenhar-Gorlin syndrome, one case of Treacher-Collins syndrome and two cases of Crouzon's disease). Four patients with craniofacial clefts were also evaluated. Radiological findings were confirmed by the clinical and intraoperative findings in all patients that underwent surgical treatment. Movement artefacts and ''Lego effect'' related to abrupt change of cranial vault border were encountered and are discussed. Conclusions. 3D CT of the skull can safely and reliably identify paediatric craniofacial malformations involving bone, and it should be used as morphological mapping to help the surgeon in planning surgical treatment. (orig.)

Development of low-dose protocols for thin-section CT assessment of cystic fibrosis in pediatric patients.

LENUS (Irish Health Repository)

O'Connor, Owen J

2010-12-01

To develop low-dose thin-section computed tomographic (CT) protocols for assessment of cystic fibrosis (CF) in pediatric patients and determine the clinical usefulness thereof compared with chest radiography.

Routine chest and abdominal high-pitch CT: An alternative low dose protocol with preserved image quality

International Nuclear Information System (INIS)

Amacker, Nadja A.; Mader, Caecilia; Alkadhi, Hatem; Leschka, Sebastian; Frauenfelder, Thomas

2012-01-01

Objective: To investigate the radiation dose and image quality of the high-pitch dual source computer tomography (DSCT) for routine chest and abdominal scans. Methods: 130 consecutive patients (62 female, 68 male, median age 55 years) were included. All patients underwent 128-slice high-pitch DSCT (chest n = 99; abdomen n = 84) at a pitch of 3.2. Two observers independently rated image quality using a 4-point score (1: excellent to 4: non-diagnostic). Image noise was measured and operational radiation dose quantities were recorded. An additional group of 132 patients (chest, n = 80; abdomen n = 52) scanned with standard-pitch CT matched for age, gender, and body mass index (BMI) served as control group. Results: Interobserver agreement for image quality rating was good (k = 0.74). Subjective image quality of high-pitch CT was diagnostic in all patients (median score chest; 2, median score abdomen: 2). Image noise of high-pitch CT was comparable to standard-pitch for the chest (p = 0.32) but increased in the abdomen (p < 0.0001). For high-pitch CT radiation dose was 4.4 ± 0.9 mSv (chest) and 6.5 ± 1.2 mSv (abdomen). These values were significantly lower compared to standard-pitch CT (chest: 5.5 ± 1.2 mSv; abdomen: 11.3 ± 3.8 mSv). Conclusion: Based on the technical background high-pitch dual source CT may serve as an alternative scan mode for low radiation dose routine chest and abdominal CT.

Body packers on your examination table: How helpful are plain x-ray images? A definitive low-dose CT protocol as a diagnosis tool for body packers.

Science.gov (United States)

Schulz, B; Grossbach, A; Gruber-Rouh, T; Zangos, S; Vogl, Th J; Eichler, K

2014-12-01

To analyze the clinical value and radiation dose of plain x-rays and CT in examining patients suspected of ingesting drug-filled packets. Thirty-eight patients with suspected internal concealment of drug-filled packets who were examined with plain x-rays or CT or both were included in the study. CT studies were performed using low-dose and standard-dose techniques. All radiographic images were analysed by two radiologists regarding identification of the packets and estimating the effective radiation dose from standard- and low-dose CT versus conventional x-ray examinations. Descriptive calculations were made regarding the number and density of packs and radiation dosage. The diagnostic performance of both radiologists with standard- and low-dose CT was calculated by analysing differences in the mean number of packs found. Thirty-one patients were positively identified as body packers with an average of 13 packs (min: n = 1, max: n = 58, total: n = 390); seven patients were not concealing drug packets. X-ray images were taken of 24 patients prior to CT, thus allowing a direct comparison between the two methods. The correct diagnosis was made in 42%, in 33% the radiologists were uncertain, and in 25% of drug packets were either not or wrongly identified. X-ray imaging had a positive predictive value of 20% with a negative predictive value of 81%. A total of 55 CT examinations were performed on all patients with a mean effective dose of 2 mSv (low dose) versus 9.3 mSv (standard dose). The visibility of packets on low-dose CT images compared to high-dose CT was not reduced: the radiologists identified 385 and 381 of the packets, respectively, with no difference regarding the examination technique (p = 0.24 and p = 0.253, respectively). The radiodensity of all drug-filled packets at CT ranged from 26-292 HU (mean 181.2 HU). X-ray imaging of supposed body packers leads to a significant risk of diagnostic errors and additional need for CT. Instead, a single abdominal low-dose

Low dose CT reconstruction via L1 norm dictionary learning using alternating minimization algorithm and balancing principle.

Science.gov (United States)

Wu, Junfeng; Dai, Fang; Hu, Gang; Mou, Xuanqin

2018-04-18

Excessive radiation exposure in computed tomography (CT) scans increases the chance of developing cancer and has become a major clinical concern. Recently, statistical iterative reconstruction (SIR) with l0-norm dictionary learning regularization has been developed to reconstruct CT images from the low dose and few-view dataset in order to reduce radiation dose. Nonetheless, the sparse regularization term adopted in this approach is l0-norm, which cannot guarantee the global convergence of the proposed algorithm. To address this problem, in this study we introduced the l1-norm dictionary learning penalty into SIR framework for low dose CT image reconstruction, and developed an alternating minimization algorithm to minimize the associated objective function, which transforms CT image reconstruction problem into a sparse coding subproblem and an image updating subproblem. During the image updating process, an efficient model function approach based on balancing principle is applied to choose the regularization parameters. The proposed alternating minimization algorithm was evaluated first using real projection data of a sheep lung CT perfusion and then using numerical simulation based on sheep lung CT image and chest image. Both visual assessment and quantitative comparison using terms of root mean square error (RMSE) and structural similarity (SSIM) index demonstrated that the new image reconstruction algorithm yielded similar performance with l0-norm dictionary learning penalty and outperformed the conventional filtered backprojection (FBP) and total variation (TV) minimization algorithms.

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

International Nuclear Information System (INIS)

Kazama, Masahiro; Saito, Yasuo

2015-01-01

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

Low dose CT perfusion in acute ischemic stroke.

Science.gov (United States)

Murphy, Amanda; So, Aaron; Lee, Ting-Yim; Symons, Sean; Jakubovic, Raphael; Zhang, Liying; Aviv, Richard I

2014-12-01

The purpose of this investigation is to determine if CT perfusion (CTP) measurements at low doses (LD = 20 or 50 mAs) are similar to those obtained at regular doses (RD = 100 mAs), with and without the addition of adaptive statistical iterative reconstruction (ASIR). A single-center, prospective study was performed in patients with acute ischemic stroke (n = 37; 54% male; age = 74 ± 15 years). Two CTP scans were performed on each subject: one at 100 mAs (RD) and one at either 50 or 20 mAs (LD). CTP parameters were compared between the RD and LD scans in regions of ischemia, infarction, and normal tissue. Differences were determined using a within-subjects ANOVA (p test post hoc analysis (p 50 mAs, there was no significant difference between cerebral blood flow (CBF), cerebral blood volume (CBV), or time to maximum enhancement (Tmax) values for the RD and LD scans in the ischemic, infarcted, or normal contralateral regions (p LD scans for all parameters in the ischemic and normal tissue regions (p > 0.05). CTP-derived CBF and CBV are not different at 50 mAs compared to 100 mAs, even without the addition of ASIR. Current CTP protocols can be modified to reduce the effective dose by 50 % without altering CTP measurements.

Spiral CT in kidney: assumption of renal function by objective evaluation of renal cortical enhancement

International Nuclear Information System (INIS)

Choi, Bo Yoon; Lee, Jong Seok; Lee, Joon Woo; Myung, Jae Sung; Sim, Jung Suk; Seong, Chang Kyu; Kim, Seung Hyup; Choi, Guk Myeong; Chi, Seong Whi

2000-01-01

To correlate the degree of renal cortical enhancement, objectively evaluated by means of spiral CT with the serum level of creatinine, and to determine the extent to which this degree of enhancement may be used to detect renal parenchymal disease. Eighty patients (M:F = 50:30; age + 25-19, (mean 53) years) with available serum level of creatinine who underwent spiral CT between September and October 1999 were included in this study. In fifty patients the findings suggested hepatic or biliary diseases such as hepatoma, biliary cancer, or stone, while in thirty, renal diseases such as cyst, hematoma, or stone appeared to be present. Spiral CT imaging of the cortical phase was obtained at 30-40 seconds after the injection of 120 ml of non-ionic media at a rate of 3 ml/sec. The degree of renal cortical enhancement was calculated by dividing the CT attenuation number of renal cortex at the level of the renal hilum by the CT attenuation number of aorta at the same level. The degree of renal cortical enhancement was compared with the serum level of creatinine, and the degree of renal cortical enhancement in renal parenchymal disease with that of the normal group. Among eighty patients there were five with renal parenchymal disease and 75 with normal renal function. The ratio of the CT attenuation number of renal cortex to that of aorta at the level of the renal hilum ranged between 0.49 and 0.99 (mean, 0.79; standard deviation, 0.15). while the serum level of creatinine ranged between 0.6 and 3.2 mg/dl. There was significant correlation (coefficient of -0.346) and a statistically significant probability of 0.002 between the ratio of the CT attenuation numbers and the serum level of creatinine. There was a significant difference (statistically significant probability of less than 0.01) between those with renal parenchymal disease and the normal group. The use of spiral CT to measure the degree of renal cortical enhancement provides not only an effective index for

Spiral CT and optimization of the modalities of the iodinated intravenous contrast material: Experimental studies in human pathology

International Nuclear Information System (INIS)

Bonaldi, V.

1998-01-01

Spiral (or helical) CT represents the most recent improvement in the field of computed assisted tomography (CAT scan). The capabilities of this new imaging modality are much superior to these of conventional CT scanning; then result from the rapid acquisition and from the volumetric nature of the derived data set. The short time of data acquisition had made mandatory the revision of protocols for intravenous administration of iodinated contrast material. By the means of several studies, carried out on pathologic and healthy patients, we have attempted to improve knowledge in factors influencing CT attenuation values after injection of contrast material, in the aim of improving contrast administration performed during spiral CT scanning. Anatomical landmarks that we have studied till now have been liver, the pancreas, the kidney and the cervical spine. In addition, a paired based methodology has been used. The volumetric set of data derived from spiral CT scanning leads to optimal post-processing tasks, the most interesting being related to cine-display and multiplanar reformatting; both modalities have been evaluated, about the pancreas and the musculo-skeletal system respectively. Conversely, this new modality, as for other imaging modalities, is responsible for additional costs derived from restless increase in the number of images to be dealt with and from the occurrence of new tasks (in post-processing particularly). The place of spiral CT in diagnostic strategies among other modern imaging modalities should be assessed, especially with respect to Magnetic Resonance Imaging (MRI). (author)

Intra-arterial Ultra-low-Dose CT Angiography of Lower Extremity in Diabetic Patients

Energy Technology Data Exchange (ETDEWEB)

Özgen, Ali, E-mail: draliozgen@hotmail.com [Yeditepe University Hospital, Department of Radiology (Turkey); Sanioğlu, Soner [Yeditepe University Hospital, Department of Cardiovascular Surgery (Turkey); Bingöl, Uğur Anıl [Yeditepe University Hospital, Department of Plastic Surgery (Turkey)

2016-08-15

PurposeTo image lower extremity arteries by CT angiography using a very low-dose intra-arterial contrast medium in patients with high risk of developing contrast-induced nephropathy (CIN).Materials and MethodsThree cases with long-standing diabetes mellitus and signs of lower extremity atherosclerotic disease were evaluated by CT angiography using 0.1 ml/kg of the body weight of contrast medium given via 10-cm-long 4F introducer by puncturing the CFA. Images were evaluated by an interventional radiologist and a cardiovascular surgeon. Density values of the lower extremity arteries were also calculated. Findings in two cases were compared with digital subtraction angiography images performed for percutaneous revascularization. Blood creatinine levels were followed for possible CIN.ResultsIntra-arterial CT angiography images were considered diagnostic in all patients and optimal in one patient. No patient developed CIN after intra-arterial CT angiography, while one patient developed CIN after percutaneous intervention.ConclusionIntra-arterial CT angiography of lower extremity might be performed in selected patients with high risk of developing CIN. Our limited experience suggests that as low as of 0.1 ml/kg of the body weight of contrast medium may result in adequate diagnostic imaging.

Establishment of an orthotopic lung cancer model in nude mice and its evaluation by spiral CT.

Science.gov (United States)

Liu, Xiang; Liu, Jun; Guan, Yubao; Li, Huiling; Huang, Liyan; Tang, Hailing; He, Jianxing

2012-04-01

To establish a simple and highly efficient orthotopic animal model of lung cancer cell line A549 and evaluate the growth pattern of intrathoracic tumors by spiral CT. A549 cells (5×10(6) mL(-1)) were suspended and inoculated into the right lung of BALB/c nude mice via intrathoracic injection. Nude mice were scanned three times each week by spiral CT after inoculation of lung cancer cell line A549. The survival time and body weight of nude mice as well as tumor invasion and metastasis were examined. Tissue was collected for subsequent histological assay after autopsia of mice. The tumor-forming rate of the orthotopic lung cancer model was 90%. The median survival time was 30.7 (range, 20-41) days. The incidence of tumor metastasis was 100%. The mean tumor diameter and the average CT value gradually increased in a time-dependent manner. The method of establishing the orthotopic lung cancer model through transplanting A549 cells into the lung of nude mice is simple and highly successful. Spiral CT can be used to evaluate intrathoracic tumor growth in nude mice vividly and dynamically.

Borrmann type IV adenocarcinoma versus gastric lymphoma : spiral CT evaluation

International Nuclear Information System (INIS)

Seo, Bo Kyoung; Kim, Yun Hwan; Shin, Kue Hee; Hong, Suk Joo; Kim, Hong Weon; Park, Cheol Min; Chung, Kyoo Byung; Cho, Hyun Deuk

1999-01-01

To distinguish the spiral CT findings of Borrmann type IV adenocarcinoma from those of gastric lymphoma with diffuse gastric wall thickening. We retrospectively reviewed the spiral CT scans of 30 patients with Borrmann type IV adenocarcinoma and nine with gastric lymphoma with diffuse gastric wall thickening. In all patients the respective condition was pathologically confirmed by gastrectomy. CT scanning was performed after peroral administration of 500-700ml of water. A total of 120-140 ml bolus of nonionic contrast material was administered intravenously at a flow rate of 3 ml/sec and two-phase images were obtained at 35-45 sec(early phase) and 180 sec(delayed phase) after the start of bolus injection. Spiral CT was performed with 10mm collimation, 10mm/sec table feed and 10mm reconstruction. We evaluated the degree and homogeneity of enhancement of thickened entire gastric wall, and the enhancement pattern of gastric inner layer, as seen on early-phase CT scans. On early and delayed views, the thickness of gastric wall and the presence of perigastric fat infiltration were determined. The enhancement patterns of gastric inner layer were classified as either continuous or discontinuous thick enhancement, thin enhancement, or nonenhancement. The thickness of gastric wall was 1.2-3.5cm(mean 2.2cm) in cases of adenocarcinoma and 1.2-7.6cm(mean 4cm) in lymphoma. Perigastric fat infiltration was seen in 24 patients with adenocarcinoma(80%) and four with lymphoma(44%). In those with adenocarcinoma, the degree of enhancement of entire gastric wall was hyperdense in fifteen patients(50%) and isointense in eleven (37%). Seven patients with lymphoma(78%)showed hypodensity. In those with adenocarcinoma, continuous thick enhancement of gastric inner layer was seen in 18 patients(60%) and discontinuous thick enhancement in nine(30%). In lymphoma cases, no thick enhancement was observed. Thin enhancement of gastric inner layer was demonstrated in three patients with

Clinical application of 16-slice spiral CT in reconstruction imaging of coronary artery for diagnosing coronary disense

International Nuclear Information System (INIS)

Mao Xinbo; Zhu Xinjin; Zeng Huiliang; Chen Xueguang

2005-01-01

Objective: An evaluation of the reconstructed imaging of coronary arteries with 16-slice spiral CT in diagnosis of coronary disease. Methods: The reconstructed images of coronary arteries obtained on a 16-slice spiral CT scanner were reviewed in 60 cases, on which the following techniques were applied: retrospective ECG-gating, Segment method with 75% R-R interval, volume rendering technique (VRT), maximum intensity projection (MIP), mulfiplanar reconstruction (MPR), curved planar reconstruction (CPR) and CT virtual endoscopy (CTVE). Results: In all 60 cases, different stages of CHD were revealed in 21 cases; none abnormality was found in 33; and images were in poor quality in 2 cases, which was available for diagnosis. There were 4 stents planted in 4 cases: soft plaque suspected in lcase, patent in 2 and occlude in 1. Conclusion: The reconstructed imaging of coronary arteries with 16-slice spiral CT is superior modality in evaluation of severe coronary stenosis, plaques, and the pantency of the intra-luminal stents, which is an efficient and non-invasive imaging in diagnosis of early-stage CHD and screening in high risk population. (authors)

Dose calculation with respiration-averaged CT processed from cine CT without a respiratory surrogate

International Nuclear Information System (INIS)

Riegel, Adam C.; Ahmad, Moiz; Sun Xiaojun; Pan Tinsu

2008-01-01

. The average maximum and mean γ indices were very low (well below 1), indicating good agreement between dose distributions. Increasing the cine duration generally increased the dose agreement. In the follow-up study, 49 of 50 patients had 100% of points within the PTV pass the γ criteria. The average maximum and mean γ indices were again well below 1, indicating good agreement. Dose calculation on RACT from cine CT is negligibly different from dose calculation on RACT from 4D-CT. Differences can be decreased further by increasing the cine duration of the cine CT scan.

The diagnostic value of multi-slice spiral CT virtual bronchoscopy in tracheal and bronchial disease

International Nuclear Information System (INIS)

Han Ying; Ma Daqing

2006-01-01

Objective: To assess the diagnostic value of multi-slice spiral CT virtual bronchoscopy (CTVB) in tracheal and bronchial disease. Methods: Forty-two patients including central lung cancer (n=35), endobronchial tuberculosis (n=3), intrabronchial benign tumor (n=3), and intrabronchial foreign body (n=1) were examined by using multi-slice spiral CT examinations. All the final diagnosis were proved by pathology except 1 patient with endoluminal foreign body was proved by clinic. All patients were scanned on GE Lightspeed 99 scanner, using 10 mm collimation, pitch of 1.35, and reconstructed at 1 mm intervals and 1.25 mm thickness. The chest images of transverse CT and virtual bronchoscopy were viewed by two separate radiologists who were familiar with the tracheal and bronchial anatomy. Results: Among the 42 patients, the tumor of trachea and bronchial lumen appeared as masses in 22 of 35 patients with central lung cancer and bronchial stenosis was found in 13 of 35 patients with central lung cancer, and bronchial wall thickening was revealed on transverse CT in all 35 cases. 3 patients of endobronchial tuberculosis showed bronchial lumen narrowing on CTVB, the bronchial wall thickening was revealed on transverse CT, and the length of the wall thickening was long. 3 patients with intrabronchial benign tumor showed nodules in trachea and bronchial lumen on CTVB, and without wall thickening on transverse CT. CTVB could detect the occlusion of bronchial lumen in 1 patient with intrabronchial foreign body and CTVB was able to visualize the areas beyond stenosis, and the bronchial wall was without thickening on transverse CT. Conclusion: Multi- slice spiral CTVB could reflect the morphology of tracheal and bronchial disease. Combined with transverse CT, it could provide diagnostic reference value for bronchial disease. (authors)

Volume-artifact reduction modality by helical CT of the anterior, middle and posterior carnial fossae. Comparison with conventional CT; Volumen-Artefakt-Reduktionstechnik mittels Spiral-CT in der vorderen, mittleren und hinteren Schaedelgrube. Vergleich mit der konventionellen kranialen CT

Energy Technology Data Exchange (ETDEWEB)

Dorenbeck, U.; Finkenzeller, T.; Hill, K.; Feuerbach, S.; Link, J. [Regensburg Univ. (Germany). Inst. fuer Roentgendiagnostik

2000-04-01

Purpose: The object of this study was to determine the extent to which a new volume-artifact reduction (VAR) modality using helical CT was able to reduce artifacts in the anterior, middle and posterior fossae in comparison with conventional CT (sequential mode). Methods: In a prospective, randomized trial, 50 patients underwent helical CT (VAR) and 50 underwent sequential CT. The results were evaluated by three radiologists; influences on image quality where scaled between 1 (no artifact) and 4 (not assessable). Eight regions of the anterior, middle and posterior fossae were evaluated. Results: On average, artifacts were scaled at 2.5 in helical CT (VAR) and 3.1 in conventional CT. Significant differences were seen at the eyeball, anterior to the petrosol bone, at the internal occipital crest, and at the level of the transverse sinus (p<0.005). Conclusions: Helical CT with the VAR modality is superior to conventional, sequential CT in the area of the anterior, middle and posterior fossae. (orig.) [German] Ziel: Das Ziel dieser Studie war herauszufinden, inwieweit ein neuer Volumen-Artefakt-Reduktionsmodus (VAR) im Spiral-CT in der vorderen, mittleren und hinteren Schaedelgrube gegenueber der Einzelschicht-CT zu einer Artefaktverringerung beitragen kann. Methoden: In einer prospektiven randomisierten Studie wurden 50 Untersuchungen mit Spiral-CT und 50 mit Einzelschicht-CT bezueglich Artefakten verglichen. Die Auswertung erfolgte durch drei Radiologen, die Bildqualitaet wurde in einer Skala zwischen 1 (kein Artefakt) und 4 (Beurteilung der Region wegen Artefakten nicht moeglich) angegeben. Acht anatomische Regionen in der vorderen, mittleren und hinteren Schaedelgrube wurden auf Beeintraechtigung durch Artefakte untersucht. Ergebnisse: Im Durchschnitt betrug die Bewertung fuer die Artefaktbeeintraechtigung beim Spiral-CT (VAR) 2,5 gegenueber 3,1 bei der Einzelschicht-CT. Der VAR-Modus ermoeglichte in der mittleren und hinteren Schaedelgrube sowie im Balbus oculi

TU-H-207A-08: Estimating Radiation Dose From Low-Dose Lung Cancer Screening CT Exams Using Tube Current Modulation

International Nuclear Information System (INIS)

Hardy, A; Bostani, M; McMillan, K; Zankl, M; Cagnon, C; McNitt-Gray, M

2016-01-01

Purpose: The purpose of this work is to estimate effective and lung doses from a low-dose lung cancer screening CT protocol using Tube Current Modulation (TCM) across patient models of different sizes. Methods: Monte Carlo simulation methods were used to estimate effective and lung doses from a low-dose lung cancer screening protocol for a 64-slice CT (Sensation 64, Siemens Healthcare) that used TCM. Scanning parameters were from the AAPM protocols. Ten GSF voxelized patient models were used and had all radiosensitive organs identified to facilitate estimating both organ and effective doses. Predicted TCM schemes for each patient model were generated using a validated method wherein tissue attenuation characteristics and scanner limitations were used to determine the TCM output as a function of table position and source angle. The water equivalent diameter (WED) was determined by estimating the attenuation at the center of the scan volume for each patient model. Monte Carlo simulations were performed using the unique TCM scheme for each patient model. Lung doses were tallied and effective doses were estimated using ICRP 103 tissue weighting factors. Effective and lung dose values were normalized by scanspecific 32 cm CTDIvol values based upon the average tube current across the entire simulated scan. Absolute and normalized doses were reported as a function of WED for each patient. Results: For all ten patients modeled, the effective dose using TCM protocols was below 1.5 mSv. Smaller sized patient models experienced lower absolute doses compared to larger sized patients. Normalized effective and lung doses showed some dependence on patient size (R2 = 0.77 and 0.78, respectively). Conclusion: Effective doses for a low-dose lung screening protocol using TCM were below 1.5 mSv for all patient models used in this study. Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical

TU-H-207A-08: Estimating Radiation Dose From Low-Dose Lung Cancer Screening CT Exams Using Tube Current Modulation

Energy Technology Data Exchange (ETDEWEB)

Hardy, A; Bostani, M [University of California, Los Angeles, Los Angeles, CA (United States); McMillan, K [Mayo Clinic, Rochester, MN (United States); Zankl, M [Helmholtz Zentrum Munchen, Neuherberg (Germany); Cagnon, C [UCLA Medical Center, Los Angeles, CA (United States); McNitt-Gray, M [UCLA School of Medicine, Los Angeles, CA (United States)

2016-06-15

Purpose: The purpose of this work is to estimate effective and lung doses from a low-dose lung cancer screening CT protocol using Tube Current Modulation (TCM) across patient models of different sizes. Methods: Monte Carlo simulation methods were used to estimate effective and lung doses from a low-dose lung cancer screening protocol for a 64-slice CT (Sensation 64, Siemens Healthcare) that used TCM. Scanning parameters were from the AAPM protocols. Ten GSF voxelized patient models were used and had all radiosensitive organs identified to facilitate estimating both organ and effective doses. Predicted TCM schemes for each patient model were generated using a validated method wherein tissue attenuation characteristics and scanner limitations were used to determine the TCM output as a function of table position and source angle. The water equivalent diameter (WED) was determined by estimating the attenuation at the center of the scan volume for each patient model. Monte Carlo simulations were performed using the unique TCM scheme for each patient model. Lung doses were tallied and effective doses were estimated using ICRP 103 tissue weighting factors. Effective and lung dose values were normalized by scanspecific 32 cm CTDIvol values based upon the average tube current across the entire simulated scan. Absolute and normalized doses were reported as a function of WED for each patient. Results: For all ten patients modeled, the effective dose using TCM protocols was below 1.5 mSv. Smaller sized patient models experienced lower absolute doses compared to larger sized patients. Normalized effective and lung doses showed some dependence on patient size (R2 = 0.77 and 0.78, respectively). Conclusion: Effective doses for a low-dose lung screening protocol using TCM were below 1.5 mSv for all patient models used in this study. Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical

MO-DE-207A-05: Dictionary Learning Based Reconstruction with Low-Rank Constraint for Low-Dose Spectral CT

International Nuclear Information System (INIS)

Xu, Q; Liu, H; Xing, L; Yu, H; Wang, G

2016-01-01

Purpose: Spectral CT enabled by an energy-resolved photon-counting detector outperforms conventional CT in terms of material discrimination, contrast resolution, etc. One reconstruction method for spectral CT is to generate a color image from a reconstructed component in each energy channel. However, given the radiation dose, the number of photons in each channel is limited, which will result in strong noise in each channel and affect the final color reconstruction. Here we propose a novel dictionary learning method for spectral CT that combines dictionary-based sparse representation method and the patch based low-rank constraint to simultaneously improve the reconstruction in each channel and to address the inter-channel correlations to further improve the reconstruction. Methods: The proposed method has two important features: (1) guarantee of the patch based sparsity in each energy channel, which is the result of the dictionary based sparse representation constraint; (2) the explicit consideration of the correlations among different energy channels, which is realized by patch-by-patch nuclear norm-based low-rank constraint. For each channel, the dictionary consists of two sub-dictionaries. One is learned from the average of the images in all energy channels, and the other is learned from the average of the images in all energy channels except the current channel. With average operation to reduce noise, these two dictionaries can effectively preserve the structural details and get rid of artifacts caused by noise. Combining them together can express all structural information in current channel. Results: Dictionary learning based methods can obtain better results than FBP and the TV-based method. With low-rank constraint, the image quality can be further improved in the channel with more noise. The final color result by the proposed method has the best visual quality. Conclusion: The proposed method can effectively improve the image quality of low-dose spectral

MO-DE-207A-05: Dictionary Learning Based Reconstruction with Low-Rank Constraint for Low-Dose Spectral CT

Energy Technology Data Exchange (ETDEWEB)

Xu, Q [Xi’an Jiaotong University, Xi’an (China); Stanford University School of Medicine, Stanford, CA (United States); Liu, H; Xing, L [Stanford University School of Medicine, Stanford, CA (United States); Yu, H [University of Massachusetts Lowell, Lowell, MA (United States); Wang, G [Rensselaer Polytechnic Instute., Troy, NY (United States)

2016-06-15

Purpose: Spectral CT enabled by an energy-resolved photon-counting detector outperforms conventional CT in terms of material discrimination, contrast resolution, etc. One reconstruction method for spectral CT is to generate a color image from a reconstructed component in each energy channel. However, given the radiation dose, the number of photons in each channel is limited, which will result in strong noise in each channel and affect the final color reconstruction. Here we propose a novel dictionary learning method for spectral CT that combines dictionary-based sparse representation method and the patch based low-rank constraint to simultaneously improve the reconstruction in each channel and to address the inter-channel correlations to further improve the reconstruction. Methods: The proposed method has two important features: (1) guarantee of the patch based sparsity in each energy channel, which is the result of the dictionary based sparse representation constraint; (2) the explicit consideration of the correlations among different energy channels, which is realized by patch-by-patch nuclear norm-based low-rank constraint. For each channel, the dictionary consists of two sub-dictionaries. One is learned from the average of the images in all energy channels, and the other is learned from the average of the images in all energy channels except the current channel. With average operation to reduce noise, these two dictionaries can effectively preserve the structural details and get rid of artifacts caused by noise. Combining them together can express all structural information in current channel. Results: Dictionary learning based methods can obtain better results than FBP and the TV-based method. With low-rank constraint, the image quality can be further improved in the channel with more noise. The final color result by the proposed method has the best visual quality. Conclusion: The proposed method can effectively improve the image quality of low-dose spectral

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

International Nuclear Information System (INIS)

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.)

Inter- and intrascanner variability of pulmonary nodule volumetry on low-dose 64-row CT : an anthropomorphic phantom study

NARCIS (Netherlands)

Xie, X.; Willemink, M. J.; Zhao, Y.; de Jong, P. A.; van Ooijen, P. M. A.; Oudkerk, M.; Greuter, M. J. W.; Vliegenthart, R.

Objective: To assess inter- and intrascanner variability in volumetry of solid pulmonary nodules in an anthropomorphic thoracic phantom using low-dose CT. Methods: Five spherical solid artificial nodules [diameters 3, 5, 8, 10 and 12mm; CT density 1100 Hounsfield units (HU)] were randomly placed

Radiation dose in CT are meeting the challenge

International Nuclear Information System (INIS)

Wang Jun

2003-01-01

Despite comprising only 2% of all examinations, CT contributed around 20% of the collective dose to the population from diagnostic imaging. An abdominal examination in an adult with an effective dose of 10 mSv has been estimated to increase the lifetime risk of fatal cancer by 1 in 2000. Children are 10 times more sensitive to the effects of radiation than middle aged adults. Girls are more sensitive than boys. Variations in CT practice, ease of using, urgency in multislice CT, unawaring of the 'uncoupling effect' in CT may be contributing to increasing in radiation dose. We must train and have an awareness of emerging materials and the implied changes in practice, with revision of protocols to take account of advances. The 'as low as reasonably achievable (ALARA) ' principle applies just as much to CT as it does to conventional radiography

Dual-energy CT for the characterization of urinary calculi: In vitro and in vivo evaluation of a low-dose scanning protocol

International Nuclear Information System (INIS)

Thomas, C.; Patschan, O.; Nagele, U.; Stenzl, A.; Ketelsen, D.; Tsiflikas, I.; Reimann, A.; Brodoefel, H.; Claussen, C.; Kopp, A.; Heuschmid, M.; Schlemmer, H.P.; Buchgeister, M.

2009-01-01

The efficiency and radiation dose of a low-dose dual-energy (DE) CT protocol for the evaluation of urinary calculus disease were evaluated. A low-dose dual-source DE-CT renal calculi protocol (140 kV, 46 mAs; 80 kV, 210 mAs) was derived from the single-energy (SE) CT protocol used in our institution for the detection of renal calculi (120 kV, 75 mAs). An Alderson-Rando phantom was equipped with thermoluminescence dosimeters and examined by CT with both protocols. The effective doses were calculated. Fifty-one patients with suspected or known urinary calculus disease underwent DE-CT. DE analysis was performed if calculi were detected using a dedicated software tool. Results were compared to chemical analysis after invasive calculus extraction. An effective dose of 3.43 mSv (male) and 5.30 mSv (female) was measured in the phantom for the DE protocol (vs. 3.17/4.57 mSv for the SE protocol). Urinary calculi were found in 34 patients; in 28 patients, calculi were removed and analyzed (23 patients with calcified calculi, three with uric acid calculi, one with 2,8-dihyxdroxyadenine-calculi, one patient with a mixed struvite calculus). DE analysis was able to distinguish between calcified and non-calcified calculi in all cases. In conclusion, dual-energy urinary calculus analysis is effective also with a low-dose protocol. The protocol tested in this study reliably identified calcified urinary calculi in vivo. (orig.)

Dual-energy CT for the characterization of urinary calculi: In vitro and in vivo evaluation of a low-dose scanning protocol.

Science.gov (United States)

Thomas, C; Patschan, O; Ketelsen, D; Tsiflikas, I; Reimann, A; Brodoefel, H; Buchgeister, M; Nagele, U; Stenzl, A; Claussen, C; Kopp, A; Heuschmid, M; Schlemmer, H-P

2009-06-01

The efficiency and radiation dose of a low-dose dual-energy (DE) CT protocol for the evaluation of urinary calculus disease were evaluated. A low-dose dual-source DE-CT renal calculi protocol (140 kV, 46 mAs; 80 kV, 210 mAs) was derived from the single-energy (SE) CT protocol used in our institution for the detection of renal calculi (120 kV, 75 mAs). An Alderson-Rando phantom was equipped with thermoluminescence dosimeters and examined by CT with both protocols. The effective doses were calculated. Fifty-one patients with suspected or known urinary calculus disease underwent DE-CT. DE analysis was performed if calculi were detected using a dedicated software tool. Results were compared to chemical analysis after invasive calculus extraction. An effective dose of 3.43 mSv (male) and 5.30 mSv (female) was measured in the phantom for the DE protocol (vs. 3.17/4.57 mSv for the SE protocol). Urinary calculi were found in 34 patients; in 28 patients, calculi were removed and analyzed (23 patients with calcified calculi, three with uric acid calculi, one with 2,8-dihyxdroxyadenine-calculi, one patient with a mixed struvite calculus). DE analysis was able to distinguish between calcified and non-calcified calculi in all cases. In conclusion, dual-energy urinary calculus analysis is effective also with a low-dose protocol. The protocol tested in this study reliably identified calcified urinary calculi in vivo.

Dual-energy CT for the characterization of urinary calculi: In vitro and in vivo evaluation of a low-dose scanning protocol

Energy Technology Data Exchange (ETDEWEB)

Thomas, C. [University of Tuebingen, Department of Diagnostic and Interventional Radiology, Tuebingen (Germany); Department of Diagnostic and Interventional Radiology, Tuebingen (Germany); Patschan, O.; Nagele, U.; Stenzl, A. [University of Tuebingen, Department of Urology, Tuebingen (Germany); Ketelsen, D.; Tsiflikas, I.; Reimann, A.; Brodoefel, H.; Claussen, C.; Kopp, A.; Heuschmid, M.; Schlemmer, H.P. [University of Tuebingen, Department of Diagnostic and Interventional Radiology, Tuebingen (Germany); Buchgeister, M. [University of Tuebingen, Medical Physics, Department of Radiation Oncology, Tuebingen (Germany)

2009-06-15

The efficiency and radiation dose of a low-dose dual-energy (DE) CT protocol for the evaluation of urinary calculus disease were evaluated. A low-dose dual-source DE-CT renal calculi protocol (140 kV, 46 mAs; 80 kV, 210 mAs) was derived from the single-energy (SE) CT protocol used in our institution for the detection of renal calculi (120 kV, 75 mAs). An Alderson-Rando phantom was equipped with thermoluminescence dosimeters and examined by CT with both protocols. The effective doses were calculated. Fifty-one patients with suspected or known urinary calculus disease underwent DE-CT. DE analysis was performed if calculi were detected using a dedicated software tool. Results were compared to chemical analysis after invasive calculus extraction. An effective dose of 3.43 mSv (male) and 5.30 mSv (female) was measured in the phantom for the DE protocol (vs. 3.17/4.57 mSv for the SE protocol). Urinary calculi were found in 34 patients; in 28 patients, calculi were removed and analyzed (23 patients with calcified calculi, three with uric acid calculi, one with 2,8-dihyxdroxyadenine-calculi, one patient with a mixed struvite calculus). DE analysis was able to distinguish between calcified and non-calcified calculi in all cases. In conclusion, dual-energy urinary calculus analysis is effective also with a low-dose protocol. The protocol tested in this study reliably identified calcified urinary calculi in vivo. (orig.)

Image quality and radiation dose of low dose coronary CT angiography in obese patients: Sinogram affirmed iterative reconstruction versus filtered back projection

International Nuclear Information System (INIS)

Wang, Rui; Schoepf, U. Joseph; Wu, Runze; Reddy, Ryan P.; Zhang, Chuanchen; Yu, Wei; Liu, Yi; Zhang, Zhaoqi

2012-01-01

Purpose: To investigate the image quality and radiation dose of low radiation dose CT coronary angiography (CTCA) using sinogram affirmed iterative reconstruction (SAFIRE) compared with standard dose CTCA using filtered back-projection (FBP) in obese patients. Materials and methods: Seventy-eight consecutive obese patients were randomized into two groups and scanned using a prospectively ECG-triggered step-and-shot (SAS) CTCA protocol on a dual-source CT scanner. Thirty-nine patients (protocol A) were examined using a routine radiation dose protocol at 120 kV and images were reconstructed with FBP (protocol A). Thirty-nine patients (protocol B) were examined using a low dose protocol at 100 kV and images were reconstructed with SAFIRE. Two blinded observers independently assessed the image quality of each coronary segment using a 4-point scale (1 = non-diagnostic, 4 = excellent) and measured the objective parameters image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Radiation dose was calculated. Results: The coronary artery image quality scores, image noise, SNR and CNR were not significantly different between protocols A and B (all p > 0.05), with image quality scores of 3.51 ± 0.70 versus 3.55 ± 0.47, respectively. The effective radiation dose was significantly lower in protocol B (4.41 ± 0.83 mSv) than that in protocol A (8.83 ± 1.74 mSv, p < 0.01). Conclusion: Compared with standard dose CTCA using FBP, low dose CTCA using SAFIRE can maintain diagnostic image quality with 50% reduction of radiation dose.

Generalized multi-dimensional adaptive filtering for conventional and spiral single-slice, multi-slice, and cone-beam CT

International Nuclear Information System (INIS)

Kachelriess, Marc; Watzke, Oliver; Kalender, Willi A.

2001-01-01

In modern computed tomography (CT) there is a strong desire to reduce patient dose and/or to improve image quality by increasing spatial resolution and decreasing image noise. These are conflicting demands since increasing resolution at a constant noise level or decreasing noise at a constant resolution level implies a higher demand on x-ray power and an increase of patient dose. X-ray tube power is limited due to technical reasons. We therefore developed a generalized multi-dimensional adaptive filtering approach that applies nonlinear filters in up to three dimensions in the raw data domain. This new method differs from approaches in the literature since our nonlinear filters are applied not only in the detector row direction but also in the view and in the z-direction. This true three-dimensional filtering improves the quantum statistics of a measured projection value proportional to the third power of the filter size. Resolution tradeoffs are shared among these three dimensions and thus are considerably smaller as compared to one-dimensional smoothing approaches. Patient data of spiral and sequential single- and multi-slice CT scans as well as simulated spiral cone-beam data were processed to evaluate these new approaches. Image quality was assessed by evaluation of difference images, by measuring the image noise and the noise reduction, and by calculating the image resolution using point spread functions. The use of generalized adaptive filters helps to reduce image noise or, alternatively, patient dose. Image noise structures, typically along the direction of the highest attenuation, are effectively reduced. Noise reduction values of typically 30%-60% can be achieved in noncylindrical body regions like the shoulder. The loss in image resolution remains below 5% for all cases. In addition, the new method has a great potential to reduce metal artifacts, e.g., in the hip region

Pulmonary emphysema quantitation with Computed Tomography. Comparison between the visual score with high resolution CT, expiratory density mask with spiral CT and lung function studies

International Nuclear Information System (INIS)

Zompatori, Maurizio; Battaglia, Milva; Rimondi, Maria Rita; Vivacqua, Donatella; Biscarini, Manuela; Fasano, Luca; Pacilli, Angela Maria Grazia; Guerrieri, Aldo; Fabbri, Mario; Cavina, Mauro

1997-01-01

CT is the most accurate method to detect pulmonary emphysema in vivo. They compared prospectively two different methods for emphysema quantitation in 5 normal volunteers and 20 consecutive patients with chronic obstructive pulmonary disease (COPD). All subjects were submitted to function tests and HRCT; three scans were acquired at preselected levels during inspiration. The type and extent of pulmonary emphysema were defined by two independent observers under blind conditions. Disagreements were subsequently settled by consent. All subjects were also examined with expiratory spiral CT using a density mask program, at two different cut-off levels (-850,-900 HU). Visual score and expiratory spiral density mask values (-850 HU) were significantly correlated (r = 0.86), but the visual extent of emphysema was always higher than shown by expiratory spiral CT. The emphysema extent assessed with both CT methods correlated with the function result of expiratory airflow obstruction and gas diffusion impairment (visual score versus forced expiratory volume in one second: r = -0.81, versus single breath carbon monoxide diffusion: r = -0.78. Spiral expiratory density mask -850 HU versus forced expiratory volume in one second: r = -0.85 versus single breath carbon monoxide diffusion: r = -0.77). When -900 HU was used as the cut-off value for the expiratory density mask, the correlation with single breath carbon monoxide diffusion worsened (r = -0.56). Visual score and expiratory density mask -850 HU gave similar results and permitted COPD patients to be clearly distinguished from normal controls (p < 0.01). They believe the true residual volume should lie somewhere in between the CT value and the function results with the helium dilution technique and conclude that the extent of pulmonary emphysema can be confidently assessed with CT methods. Finally, the simple visual score may be as reliable as such highly sophisticated new methods as the spiral expiratory density mask

Evaluation of a low-dose CT protocol with oral contrast for assessment of acute appendicitis

Energy Technology Data Exchange (ETDEWEB)

Platon, Alexandra; Jlassi, Helmi; Becker, Christoph D.; Poletti, Pierre-Alexandre [University Hospital of Geneva, Department of Radiology, Geneva 14 (Switzerland); Rutschmann, Olivier T. [University Hospital of Geneva, Emergency Center, Geneva (Switzerland); Verdun, Francis R. [University Institute for Radiation Physics, Lausanne (Switzerland); Gervaz, Pascal [University Hospital of Geneva, Clinic of Digestive Surgery, Geneva (Switzerland)

2009-02-15

The aim of this study was to evaluate a low-dose CT with oral contrast medium (LDCT) for the diagnosis of acute appendicitis and compare its performance with standard-dose i.v. contrast-enhanced CT (standard CT) according to patients' BMIs. Eighty-six consecutive patients admitted with suspicion of acute appendicitis underwent LDCT (30 mAs), followed by standard CT (180 mAs). Both examinations were reviewed by two experienced radiologists for direct and indirect signs of appendicitis. Clinical and surgical follow-up was considered as the reference standard. Appendicitis was confirmed by surgery in 37 (43%) of the 86 patients. Twenty-nine (34%) patients eventually had an alternative discharge diagnosis to explain their abdominal pain. Clinical and biological follow-up was uneventful in 20 (23%) patients. LDCT and standard CT had the same sensitivity (100%, 33/33) and specificity (98%, 45/46) to diagnose appendicitis in patients with a body mass index (BMI) {>=} 18.5. In slim patients (BMI < 18.5), sensitivity to diagnose appendicitis was 50% (2/4) for LDCT and 100% (4/4) for standard CT, while specificity was identical for both techniques (67%, 2/3). LDCT may play a role in the diagnostic workup of patients with a BMI {>=} 18.5. (orig.)

Evaluation of a low-dose CT protocol with oral contrast for assessment of acute appendicitis

International Nuclear Information System (INIS)

Platon, Alexandra; Jlassi, Helmi; Becker, Christoph D.; Poletti, Pierre-Alexandre; Rutschmann, Olivier T.; Verdun, Francis R.; Gervaz, Pascal

2009-01-01

The aim of this study was to evaluate a low-dose CT with oral contrast medium (LDCT) for the diagnosis of acute appendicitis and compare its performance with standard-dose i.v. contrast-enhanced CT (standard CT) according to patients' BMIs. Eighty-six consecutive patients admitted with suspicion of acute appendicitis underwent LDCT (30 mAs), followed by standard CT (180 mAs). Both examinations were reviewed by two experienced radiologists for direct and indirect signs of appendicitis. Clinical and surgical follow-up was considered as the reference standard. Appendicitis was confirmed by surgery in 37 (43%) of the 86 patients. Twenty-nine (34%) patients eventually had an alternative discharge diagnosis to explain their abdominal pain. Clinical and biological follow-up was uneventful in 20 (23%) patients. LDCT and standard CT had the same sensitivity (100%, 33/33) and specificity (98%, 45/46) to diagnose appendicitis in patients with a body mass index (BMI) ≥ 18.5. In slim patients (BMI < 18.5), sensitivity to diagnose appendicitis was 50% (2/4) for LDCT and 100% (4/4) for standard CT, while specificity was identical for both techniques (67%, 2/3). LDCT may play a role in the diagnostic workup of patients with a BMI ≥ 18.5. (orig.)

Low-tube-voltage selection for non-contrast-enhanced CT: Comparison of the radiation dose in pediatric and adult phantoms.

Science.gov (United States)

Shimonobo, Toshiaki; Funama, Yoshinori; Utsunomiya, Daisuke; Nakaura, Takeshi; Oda, Seitaro; Kiguchi, Masao; Masuda, Takanori; Sakabe, Daisuke; Yamashita, Yasuyuki; Awai, Kazuo

2016-01-01

We used pediatric and adult anthropomorphic phantoms to compare the radiation dose of low- and standard tube voltage chest and abdominal non-contrast-enhanced computed tomography (CT) scans. We also discuss the optimal low tube voltage for non-contrast-enhanced CT. Using a female adult- and three differently-sized pediatric anthropomorphic phantoms we acquired chest and abdominal non-contrast-enhanced scans on a 320-multidetector CT volume scanner. The tube voltage was set at 80-, 100-, and 120 kVp. The tube current was automatically assigned on the CT scanner in response to the set image noise level. On each phantom and at each tube voltage we measured the surface and center dose using high-sensitivity metal-oxide-semiconductor field-effect transistor detectors. The mean surface dose of chest and abdominal CT scans in 5-year olds was 4.4 and 5.3 mGy at 80 kVp, 4.5 and 5.4 mGy at 100 kV, and 4.0 and 5.0 mGy at 120 kVp, respectively. These values were similar in our 3-pediatric phantoms (p > 0.05). The mean surface dose in the adult phantom increased from 14.7 to 19.4 mGy for chest- and from 18.7 to 24.8 mGy for abdominal CT as the tube voltage decreased from 120 to 80 kVp (p voltage and the low tube voltage technique can be used for non-contrast-enhanced chest- and abdominal scanning. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.