Prone CT Scans Research Articles

Is There a Role for Prone Computed Tomography Before Percutaneous Nephrolithotomy?

Background: The majority of percutaneous nephrolithotomies (PCNLs) are performed prone, whereas most preoperative CT scans are done supine. The purpose of this pilot study is to determine if there is utility of prone CT scans in preoperative planning for prone PCNL by identifying patient populations at risk for organ injury and tract length-related complications. Materials and Methods: To represent typical preoperative planning using CT, two-dimensional (2D)-axial-prone/supine percutaneous tract measurements were performed by minimizing the distance from the target calix to the posterior-lateral skin in a single axial plane. The minimum distance and organ interception rates for the 2D-axial planning scans were recorded. Results: A total of 60 CT colonography and 13 CT urography patients were included in analysis. There were 42 women and 31 men with unspecified pathology reports ranging in age from 27 to 86 years and in body mass index (BMI) from 17.1 to 49. Multiple logistic regression identified female gender and low BMI as predictors of organ interception on the left. On multiple linear regression comparing the difference in axial prone/supine lengths; BMI, gender, and age were not significant independent predictors of changes in tract length in any pole when prone vs supine. However, shorter supine tracts tended to lengthen when prone, and longer supine tracts tended to shorten. Conclusions: This pilot study has demonstrated that patients with long and short estimates of tract length in the supine position may have shorter and longer tracts, respectively, with repositioning to prone. Thus, prone CT may have benefit when anticipating exceptionally long (>15 cm) tract lengths. Prone scans also revealed more potential organ interceptions, particularly for low BMI and women in the left upper pole. In patients for whom prone CT demonstrates an organ interception, the urologist should consider an alternate target calix or ultrasound-guided percutaneous access to identify the most appropriate needle trajectory.

The Screw-Aorta Dilemma: Changing Patient Position in Computed Tomography Scan Is Critical in Documenting Aortic Mobility.

Retrospective chart review. To determine if obtaining a prone computed tomography (CT)-scan can better delineate a questionable screw-aorta relationship. Pedicle screw misplacement rate is reported between 6% and 15%. Studies looking at misplacements on a per patient basis show up to 14% of patients have screws at risk (impinging vital structures). A screw abutting the aorta is a management challenge and often requires vascular surgery intervention. However, CT scans routinely done in supine position may overestimate screw-aorta relationship. Change in patient position may allow the aorta to roll away and, in most cases, reveal an uncompromised aorta. This will allow safe removal of pedicle screws without any vascular intervention. One hundred eleven spinal deformity patients who underwent Posterior spinal fusion from 2004 to 2009 were evaluated. Patients with concerning screw-aorta relationship underwent additional prone CT scan. Mobility of the aorta was determined and distance was compared using prone and supine CT scans. Two thousand two hundred ninety five screws were reviewed, 36 screws in 18 patients were in proximity to the aorta. Fourteen screws (nine patients) appeared to be impinging the aorta. On prone CT, 13 out of the 14 instances the aorta moved away from the screw. The average distance at the screw level was 13.6 ± 4.8 mm in supine position and 8.9 ± 5.4 mm in prone position (P = 0.001). In one instance the relationship was unchanged on prone CT. No screw was noted to violate the lumen or distort the aorta. Supine CT scan alone is not entirely accurate in determining screw-aorta relationship. Prone-CT scan provides additional information for better delineation. This additional diagnostic step can change the treatment option by limiting the need for vascular intervention. When in doubt, the additional use of an arteriogram can allow for improved visualization. 3.

The assistance of prone position CT scan before PCNL in locating the puncture point

目的 明确术前俯卧位CT对经皮肾穿刺中通道选择有一定的辅助作用。 方法 对比同一患者的俯卧位CT与仰卧位CT中肾脏邻近器官与肾脏的相对位置及邻近器官与经皮肾穿刺通道的关系。 结果 CT中仰卧位时肾脏邻近器官与肾脏的相对位置及邻近器官与经皮肾穿刺通道的关系在患者改为俯卧位时会发生改变。这种改变在多数时候不会对穿刺通道的选择造成影响。但在少数一些患者，这种改变会对穿刺通道的选择造成影响。 结论 术前俯卧位CT对经皮肾穿刺中通道选择有一定的辅助作用。

P37. The screw-aorta dilemma: changing patient position in CT scan is critical in documenting aortic mobility

BACKGROUND CONTEXT PS misplacement rate is reported between 6-15%. Studies looking at misplacements on a per patient basis show up to 14% of patients have screws at risk (impinging vital structures). A screw abutting the aorta is a management challenge and often requires vascular surgery intervention. However, CT scans routinely done in supine position may overestimate screw-aorta relationship. Change in patient position may allow the aorta to roll away and, in most cases, reveal an uncompromised aorta. This will allow safe removal of pedicle screws without any vascular intervention. PURPOSE To assess whether prone CT helps delineate the aorta-pedicle screw relationship. STUDY DESIGN/SETTING Retrospective chart review. PATIENT SAMPLE A total of 111 patients with post-op CT, who underwent PSF for spinal deformity, from 2004-2009. OUTCOME MEASURES Distance of pedicle screw from posterior margin of Aorta. METHODS A total of 111 patients with post-op CT, who underwent PSF for spinal deformity, from 2004-2009, were evaluated. Patients with concerning screw-aorta relationship underwent a prone CT scan. Mobility of the aorta was determined by measuring between a line drawn from the posterior margin of the aorta, perpendicular to the long axis of the screw, and a parallel line passing through the anterior margin of the body of the vertebra (in mm). This distance was compared using prone and supine CT scans. Paired t-test and signed rank tests were utilized. RESULTS There were 2,295 screws were reviewed, 45 screws in 27 patients were in proximity to the aorta. Thirty-six of these were in close proximity, but not impinging (>1cm aorta-screw distance). Fourteen screws (7 patients) were impinging ( CONCLUSIONS Supine CT-scan alone is not entirely accurate in determining screw-aorta relationship. Prone-CT scan provides additional information for better delineation. This additional diagnostic step can change the treatment option by limiting the need for vascular intervention. When in doubt, the additional use of an arteriogram can allow for improved visualization. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Interactive registration between supine and prone scans in computed tomography colonography using band-height images

In computed tomographic colonography (CTC), a patient is commonly scanned twice including supine and prone scans to improve the sensitivity of polyp detection. Typically, a radiologist must manually match the corresponding areas in the supine and prone CT scans, which is a difficult and time-consuming task, even for experienced scan readers. In this paper, we propose a method of supine-prone registration utilizing band-height images, which are directly constructed from the CT scans using a ray-casting algorithm containing neighboring shape information. In our method, we first identify anatomical feature points and establish initial correspondences using local extreme points on centerlines. We then correct correspondences using band-height images that contain neighboring shape information. We use geometrical and image-based information to match positions between the supine and prone centerlines. Finally, our algorithm searches the correspondence of user input points using the matched anatomical feature point pairs as key points and band-height images. The proposed method achieved accurate matching and relatively faster processing time than other previously proposed methods. The mean error of the matching between the supine and prone points for uniformly sampled positions was 18.41±22.07mm in 20 CTC datasets. The average pre-processing time was 62.9±8.6s, and the interactive matching was performed in nearly real-time. Our supine-prone registration method is expected to be helpful for the accurate and fast diagnosis of polyps.

SU‐F‐J‐120: Evaluation of the Combined Effect of Body Orientation and Breathing On Organ Movement in Thorax Using Multi‐Step Deformable Image Registration

Purpose:Use deformable registration to map more complex anatomies that include changes associated with both different body positions and breathing, and evaluate the resultant respiratory excursions for tumors and relevant organs at risk.Methods:Same‐day exhale and inhale datasets from prone and supine 4D CT scans of lung cancer patients have been registered using the Elastix software package through a 3 step process: (1) rigid registration for bony alignment (2) deformable multiresolution B‐Spline registration of entire anatomy (3) deformable multiresolution B‐Spline registration of lung parenchyma (to improve lung vasculature alignment).Manual contours were propagated from the supine‐inhale phase to supine‐exhale, prone‐exhale and prone‐inhale, via the resulting registration transformations. Motion excursions between exhale and inhale for both body orientations were computed for tumors, heart, esophagus, vertebrae (T2, T5, T12).Results:The registration accuracy was evaluated by visual inspection of the deformed contours by physicians and minimal contour adjustments were made where deemed appropriate. The average supine [mm] / prone [mm] motion amplitudes for the initial 5‐patient sample are as follows: Tumor – 5.8/6.5, T5 – 1.4/2.0, T2 – 0.5/1.6, T12 – 1.7/2.9, Heart– 4.9/9.0, Upper esophagus – 1.6/3.8, Middle esophagus – 3.8/5.0, Lower esophagus – 4.1/6.7. Differences between prone and supine excursions for heart, esophagus, T2 and T12 were significant at 95% level (one‐sided Wilcoxon Mann‐Whitney test).On average, the right and left lung volumes increased by 10% at inhale prone and by 5% at exhale prone from their respective values in supine position.Conclusion:A multi‐step deformable registration sequence was implemented and successfully used for supine‐prone image registration of thorax. In prone position, lungs are larger, likely owing to increased pulmonary compliance and decreased compressive force of the heart on lungs when prone. Breathing motion excursion is enhanced in prone, possible consequence of rib cage stabilization and increased diaphragmatic motion.Elisabeth Weiss: Research support from Philips Healthcare and National Institutes of Health; Licensing agreement with Varian Medical Systems, UpToDate royalties.

Upright, Prone, and Supine Spinal Morphology in Adolescent Idiopathic Scoliosis

Introduction Adolescent idiopathic scoliosis patients are exposed to ten times more radiation as compared with healthy adolescents, this leads to increased risk of developing malignancies. To minimize the radiation exposure, non-ionizing imaging modalities, such as MRI, can be used, but this is acquired in supine positioning, unlike the standing X-rays that are the gold standard. As far as we know, this is the first study to compare the 2-D morphology of the spine on conventional radiographs with the 3-D morphology on supine MRI and prone CT images. The objective is to evaluate the correlation between the morphology of the spine on conventional radiographs in the upright position and 3-D supine and prone imaging modalities in patients with adolescent idiopathic scoliosis. Material and Methods 62 adolescent idiopathic scoliosis patients planned for scoliosis surgery and had undergone standard pre-operative work-up (upright radiographs, supine MRI for exclusion of neural axis abnormalities and prone CT for navigation surgery for posterior pedicle screw fixation) were included. In all three positions, Cobb angles, thoracic kyphosis, lumbar lordosis and apical vertebral rotation (2-D X-rays: method of Perdriolle, 3-D scans: semi-automatic software) were determined. In addition, on reconstructed 3-D MR and CT images, the true sagittal and coronal morphology were measured semi-automatically (previously validated technique). Chi-square tests were used for correlation analysis between the positions. Results In the thoracic and (thoraco)lumbar curves, Cobb angles correlated significantly between conventional radiographs (68 ± 15° and 44 ± 17°), supine MRI (57 ± 14° and 35 ± 16°) and prone CT (54 ± 15° and 33 ± 15°; r ≥ 0.89; p < 0.001). In the axial plane, the apical vertebral rotation showed a good correlation between the positions (upright, 22 ± 12°; prone, 20 ± 9° and supine, 16 ± 11°; r ≥ 0.56; p < 0.001). The thoracic kyphosis and lumbar lordosis on the conventional upright X-rays did not correlate with the true sagittal morphology on MRI or CT. The relation of the thoracic Cobb angle between the standing X-rays and the lying down images of moderate to severe patients is expressed by the formula: upright radiograph (°) = 10.81 + 1.01*supine MRI(°) and prone CT(°) = −3.02 + 1.00*supine MRI(°). Conclusion Although there is slight underestimation of the morphology of the 3-D spinal curvature in the supine position as compared with upright, there is a significant correlation of the deformation in all three dimensions between the different body positions and imaging modalities. Therefore, accurate estimation of the upright morphology of adolescent idiopathic scoliosis is possible, using non-ionizing supine MRI or prone CT scans.

Systematic feasibility analysis of a quantitative elasticity estimation for breast anatomy using supine/prone patient postures.

Breast elastography is a critical tool for improving the targeted radiotherapy treatment of breast tumors. Current breast radiotherapy imaging protocols only involve prone and supine CT scans. There is a lack of knowledge on the quantitative accuracy with which breast elasticity can be systematically measured using only prone and supine CT datasets. The purpose of this paper is to describe a quantitative elasticity estimation technique for breast anatomy using only these supine/prone patient postures. Using biomechanical, high-resolution breast geometry obtained from CT scans, a systematic assessment was performed in order to determine the feasibility of this methodology for clinically relevant elasticity distributions. A model-guided inverse analysis approach is presented in this paper. A graphics processing unit (GPU)-based linear elastic biomechanical model was employed as a forward model for the inverse analysis with the breast geometry in a prone position. The elasticity estimation was performed using a gradient-based iterative optimization scheme and a fast-simulated annealing (FSA) algorithm. Numerical studies were conducted to systematically analyze the feasibility of elasticity estimation. For simulating gravity-induced breast deformation, the breast geometry was anchored at its base, resembling the chest-wall/breast tissue interface. Ground-truth elasticity distributions were assigned to the model, representing tumor presence within breast tissue. Model geometry resolution was varied to estimate its influence on convergence of the system. A priori information was approximated and utilized to record the effect on time and accuracy of convergence. The role of the FSA process was also recorded. A novel error metric that combined elasticity and displacement error was used to quantify the systematic feasibility study. For the authors' purposes, convergence was set to be obtained when each voxel of tissue was within 1 mm of ground-truth deformation. The authors' analyses showed that a ∼97% model convergence was systematically observed with no-a priori information. Varying the model geometry resolution showed no significant accuracy improvements. The GPU-based forward model enabled the inverse analysis to be completed within 10-70 min. Using a priori information about the underlying anatomy, the computation time decreased by as much as 50%, while accuracy improved from 96.81% to 98.26%. The use of FSA was observed to allow the iterative estimation methodology to converge more precisely. By utilizing a forward iterative approach to solve the inverse elasticity problem, this work indicates the feasibility and potential of the fast reconstruction of breast tissue elasticity using supine/prone patient postures.

TU‐A‐12A‐06: Intra‐Observer Variability in Delineation of Target Volumes in Breast Radiotherapy and Its Effect On Accuracy of Deformation Measurements

Purpose:In breast radiotherapy, the target volume may change during treatment and need adaptation of the treatment plan. This is possible for both tumour bed (TB) and whole breast (WB) target volumes. Delineation of the target (to detect changes) is also subject to uncertainty due to intra‐ and inter‐observer variability. This work measured the uncertainty, due to intraobserver variability, in the quantification of tissue deformation.Methods:Datasets consisting of paired prone and supine CT scans of three patients were used. Significant deformation in target volumes is expected between prone and supine patient positions. The selected cases had 1) no seroma, 2) some seroma, and 3) large seroma. The TB and WB were outlined on each dataset three times by one clinician. Delineation variability was defined as the standard deviations of the distances between observer outlines. For each target volume and each case, tissue deformation between prone and supine delineations was quantified using the Dice similarity coefficient (DSC) and the average surface distance (ASD). The uncertainty in the tissue deformation (due to delineation variability) was quantified by measuring the ranges of DSC and ASD using all combinations of pairs of outlines (9 pairs).Results:For the TB, the range of delineation variability was 0.44‐1.16 mm. The deformation, DSC and ASD, (and uncertainty in measurement) of the TB between prone and supine position of the cases were: 1) 0.21 (0.17‐0.28) and 12.4 mm (11.8‐13 mm); 2) 0.54 (0.51‐0.57) and 3.3 mm (3.1‐3.5 mm); 3) 0.62 (0.61‐0.64) and 4.9 mm (4.6‐5.2 mm). WB deformation measurements were subject to less uncertainty due to delineation variability than TB deformation measurements.Conclusion:For the first time, the uncertainty, due to observer variability, in the measurement of the deformation of breast target volumes was investigated. Deformations in these ranges would be difficult to detect.This work was supported in part by Cancer Research‐UK under Programme Grant C46/A10588 and in part by the National Institute for Health Research (NIHR) through funding of the biomedical research imaging centre. P. Juneja is supported by the EPSRC Platform Grant EP/H046526/1.

The effects of different body positions of low-dose expiratory phase spiral CT on the diagnosis of pulmonary air trapping after stem cell transplantation

Objective To explore the effects of different body positions at the expiratory phase thin-section multi-slice spiral CT on the diagnosis of pulmonary air trapping after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Methods Thirty-one allo-HSCT patients underwent the expiratory phase low-dose MSCT lung scanning at supine and prone positions to detect whether they have air trapping lesion,the volume percent of air trapping region (CT value≤-700 HU at expiratory phase) against the whole lung was measured by using GE workstation after grading.Statistical analysis on lesion detection rate was performed with Mc Nemar test and volume percent with rank sum test. Results Air trapping regions were observed in 8 patients (25.8%,8/31) who performed CT scan at the supine position,while 15 cases (48.4%,15/31) were positive for prone position CT scan.Seven cases showed positive results at both body positions.Statistical significance in the positive detection rate at supine and prone positions was found (χ2=4.00,P=0.039).The volume fraction of the two positions was 13 for supine position and 21 for prone position with statistical significance (Z=-3.37,P=0.001).Sensitivity at prone position CT scan to detect air trapping was much higher than that at supine position CT scan. Conclusion For allo-HSCT patients with chronic rejection reaction,performing expiratory phase thin-section CT scan and prone position scan can not only improve the detection rate of lung forepart lesions,but also preliminarily evaluate the severity of the air trapping,which can provide a basis for the early diagnosis and treatment in clinics. Key words: Lung diseases; Stem cell transplantation; Graft rejection; Tomography,Xray computed

Automated teniae coli detection and identification on computed tomographic colonography

Computed tomographic colonography (CTC) is a minimally invasive technique for colonic polyps and cancer screening. Teniae coli are three bands of longitudinal smooth muscle on the colon surface. Teniae coli are important anatomically meaningful landmarks on human colon. In this paper, the authors propose an automatic teniae coli detection method for CT colonography. The original CTC slices are first segmented and reconstructed to a 3D colon surface. Then, the 3D colon surface is unfolded using a reversible projection technique. After that the unfolded colon is projected to a 2D height map. The teniae coli are detected using the height map and then reversely projected back to the 3D colon. Since teniae are located at the junctions where the haustral folds meet, the authors apply 2D Gabor filter banks to extract features of haustral folds. The maximum response of the filter banks is then selected as the feature image. The fold centers are then identified based on local maxima and thresholding on the feature image. Connecting the fold centers yields a path of the folds. Teniae coli are extracted as lines running between the fold paths. The authors used the spatial relationship between ileocecal valve (ICV) and teniae mesocolica (TM) to identify the TM, then the teniae omentalis (TO) and the teniae libera (TL) can be identified subsequently. The authors tested the proposed method on 47 cases of 37 patients, 10 of the patients with both supine and prone CT scans. The proposed method yielded performance with an average normalized root mean square error (RMSE) ( ± standard deviation [95% confidence interval]) of 4.87% ( ± 2.93%, [4.05% 5.69%]). The proposed fully-automated teniae coli detection and identification method is accurate and promising for future clinical applications.

Visceral Organ-to-Percutaneous Tract Distance Is Shorter When Patients Are Placed in the Prone Position on Bolsters Compared with the Supine Position

Percutaneous nephrolithotomy (PCNL) in the prone position is associated with a 0.1% risk of colon injury, yet there have not been any reported cases of colon injury with supine PCNL. The aim of the present study was to prospectively compare CT scans of patients performed in both supine and prone positions on bolsters. Sixteen consecutive patients (mean age 55, 12 men) with 19 renal units (3 bilateral) who presented for PCNL underwent preoperative supine (without bolsters) and prone (with bolsters) noninfused CT scans. Axial images through lower pole calices containing stones necessitating percutaneous access were then analyzed. Percutaneous access was planned based on both supine and prone CT scans. Skin-to-stone distance (cm), angle of the percutaneous tract to the anterior-posterior axis (degrees), and visceral organ-to-tract distance (cm) were measured. Visceral organ-to-tract distance was significantly shorter in the prone position when compared with the supine position (2.8 cm vs 3.5 cm, P=0.04). In three renal units, visceral organ-to-tract distance in the prone position was less than 0.4 cm. Furthermore, the prone position was associated with significantly shorter skin-to-stone distance (7.6 cm vs 9.0 cm, P=0.0005) and significantly wider angles (40 degrees vs 35 degrees, P=0.02). Small sample size and simulation of the percutaneous access tract are two limitations of the present study. When prone PCNL is contemplated, preoperative planning CT scans that are performed in the prone position with bolsters provide better preoperative assessment of colon-to-percutaneous renal tract distance.

A support vector machine (SVM) for predicting preferred treatment position in radiotherapy of patients with breast cancer

NYU 05-181 protocol compared the CT simulation in both supine and prone positions for 400 patients with breast cancer (200 left-breast and 200 right-breast) to identify which setup is better at sparing heart and lung involvement in the treatment process. The results demonstrated that all right-breast patients benefited from the prone treatment position, while for left-breast patients, 85% were better treated prone and 15% were better treated supine. Using the clinical data collected from this protocol, the authors aimed at developing an automated tool capable of identifying which of the left-breast cancer patients are better treated supine without obtaining a second CT scan in the supine position. Prone CT scans from 198 of the 200 left-breast cancer patients enrolled in NYU 05-181 protocol were deidentified and exported to a dedicated research planning workstation. Three-dimensional geometric features of the organs at risk and tumor bed were extracted. A two-stage classifier was used to classify patients into the prone class or the supine class. In the first stage, the authors use simple thresholding to divide the patients into two groups based on their in-field heart volume. For patients with in-field heart volume < or = 0.1 cc, the prone position was chosen as the preferred treatment position. Patients with in-field heart volume > 0.1 cc will be further classified in the second stage by a weighted support vector machine (SVM). The weight parameters of the SVM were adjusted to maximize the specificity [true-supine/(true-supine+false-prone)] at the cost of lowering but still maintaining reasonable sensitivity [true-prone/(true-prone+false-supine)]. The authors used K-fold cross validations to test the performance of the SVM classifier. A feature selection algorithm was also used to identify features that give the best classification performance. After the first stage, 49 of the 198 left-breast cancer patients were found to have > 0.1 cc of in-field heart volume. The three geometric features of heart orientation, distance between heart and tumor, and in-field lung were selected by the feature selection algorithm in the second stage of the two-stage classifier to give the best predefined weighted accuracy. The overall sensitivity and specificity of the proposed method were found to be 90.4% and 99.3%, respectively. Using two-stage classification, the authors reduced the proportion of prone-treated patients that need a second supine CT scan down to 16.3/170 or 9.6%, as compared to 21/170 or 12.4% when the authors use only the first stage (thresholding) for classification. The authors' study showed that a feature-based classifier is feasible for predicting the preferred treatment position, based on features extracted from prone CT scans. The two-stage classifier achieved very high specificity at an acceptable expense of sensitivity.

Pedicle Screws Adjacent to the Aorta: Is Prone CT Scan Helpful?

Pedicle Screws Adjacent to the Aorta: Is Prone CT Scan Helpful?

WE‐C‐BRB‐02: A Support Vector Machine (SVM) Classifier Identifies From Prone CT Simulation the Optimal Set Up for Breast Radiotherapy

Purpose: To determine optimal (prone vs. supine) treatment positions for breast radiotherapy by classifying geometric features extracted from prone CT scans. Method and Materials: CT scans from patients enrolled in NYU 05‐181 Protocol were studied to discern predicting factors for optimizing treatment positions for breast radiotherapy. Each of the 400 patients accrued for this protocol underwent CT simulation and planning in both supine and prone positions. The treatment set up was chosen based on maximum sparing of heart and lung. Since the results demonstrated that most patients were best treated prone, we studied whether a support vector machine (SVM) classifier could successfully predict optimal position based on a single prone CT scan and limit a second supine CT only to the minority of women best treated supine. To build this classifier, prone CT scans of NYU 05‐181 were de‐identified and exported in DICOM RT format. Three‐dimensional shape and distance features were computed from organs at risk and the planning target volume in the CT scans. We used a k‐fold cross validation procedure to test the performance of the SVM classifier. Results: Images of 36 patients (23 prone‐treated and 13 supine‐treated) were used. Preliminary results indicate that breast volume, heart and lung involvement in the treatment field are significant predicting factors. A weighting of 1:5 (prone‐treated: supine‐treated) was used when determining the soft margin hyper plane of the SVM classifier. The purpose is to increase the specificity [true‐supine/ (true‐supine+false‐prone)] of the classifier since patients classified as prone will not receive a validation supine CT scan. A sensitivity [true‐prone/(true‐prone+false‐supine)] of 87% and a specificity of 92% was achieved using 11 geometric features and the SVM classifier. Conclusion: Preliminary data support the use of a feature‐based classification to predict the optimal treatment position from prone CT scans.

Extracolonic Tumors of the Gastrointestinal Tract Detected Incidentally at Screening CT Colonography

The aim of this article is to report our experience with incidental detection of extracolonic tumors of the gastrointestinal tract identified prospectively at screening CT colonography. A total of 2014 patients (1097 females, 917 males; mean age, 56.9 years) underwent primary CT colonography evaluation at our institution over an 18-month period. Following cathartic preparation and colonic distention, supine and prone multidetector CT scans were obtained with thin-collimation low-dose technique without intravenous contrast. We reviewed our database for lesions of the extracolonic gastrointestinal tract that were detected during the prospective reading. Focal extracolonic gastrointestinal tract lesions were prospectively detected in 10 (0.5 percent) of 2014 patients (8 females; 2 males; mean age, 58.5 years). All patients were asymptomatic. Tumor locations included ileum (n = 3), stomach (n = 3), jejunum (n = 2), and appendix (n = 2). Mean tumor size was 2.2 (range, 0.8-3.4) cm. Lesions in eight patients were subsequently confirmed by conventional or capsule endoscopy and/or by intravenous contrast-enhanced CT. Seven lesions were surgically excised and one was removed at endoscopy; two patients with lipomas did not undergo further evaluation or treatment. Final diagnoses were benign in all cases and included lipoma (n = 3), small-bowel hamartoma (n = 2), appendiceal mucinous cystadenoma (n = 2), gastric leiomyoma (n = 1), small-bowel lymphangioma (n = 1), and gastric fundic gland polyp (n = 1). Incidental extracolonic tumors of the gastrointestinal tract detected at screening CT colonography were all asymptomatic and benign but often prompted more invasive workup. Although the incidence of these tumors was relatively low, widespread population screening with CT colonography would result in new surgical referrals for these findings.

Ct Image Fusion as a Tool for Measuring in 3D the Setup Errors during Conformal Radiotherapy for Prostate Cancer

The importance of optimal daily patient positioning has been stressed in order to ensure treatment reproducibility and gain in accuracy and precision. We report our data on the 3D setup uncertainty during radiation therapy for prostate cancer using the CT image fusion technique. Ten consecutive patients scheduled for radiation therapy for prostate cancer underwent 5 prone position CT scans using an individualized immobilization cast. These different setups were analyzed using the image fusion module of the ERGO 3D-Line Medical System (Milan, Italy) treatment planning system. The isocenter and the body marker displacements were measured. The 3D isocenter dislocations were quantified: systematic error was sigma(3D) = 3.9 mm, whereas random error was sigma(3D) = 1 mm. The mean of the minimum displacements was 0.2 +/- 1 mm showing that the immobilization device used allows an accurate setup to be obtained. Single direction errors were also measured showing systematic errors, sigma(AP), = 2.6 mm, sigma(LL) = 0.6 mm, SigmaSI = 3 mm in the anterior-posterior, latero-lateral, superior-inferior direction, respectively. Related random errors were sigma(AP), = 1 mm, sigma(LL) = 0.6 mm, sigma(SI) = 1.2 mm. In terms of accuracy, our uncertainties are similar to those reported in the literature. By applying the CT image fusion technique, a 3D study on setup accuracy was performed. We demonstrated that the use of an individualized immobilization system for prostate treatment is adequate to obtain good setup accuracy, as long as a high-quality positioning control method, such as the stereoscopic X-ray-based positioning system, is used.

Virtual colonoscopy

Computed tomographic colonography (CTC) is a safe and reliable imaging examination of the colon interpreted by radiologists. First described by Vining and colleagues 1 Vining DJ Gelfand DW Non-invasive colonoscopy using helical CT scanning, 3D reconstruction and virtual reality. Syllabus: 23rd annual meeting. Society of Gastrointestinal Radiologists, Maui, Hawaii1994 Google Scholar in 1994, the technique developed from the need for a noninvasive screening examination for colon cancer that would be more acceptable to patients than conventional colonoscopy. CTC is done after colonic cleansing. Air or CO2 is insufflated through a rectal catheter. Prone and supine helical thin-section CT scans of the abdomen and pelvis during a breath-hold are obtained, and three-dimensional reconstructions are made. Th Gluecker and colleagues 2 Gluecker Th Dorta G Keller W Jornod P Meuli R Schnyder P Performance of multidetector computed tomography colonography compared with conventional colonoscopy. Gut. 2002; 51: 207-211 Crossref PubMed Scopus (48) Google Scholar recently compared CTC with conventional colonoscopy in 50 patients with a history of polyps or colon cancer, unexplained abdominal pain, or iron-deficiency anaemia. Sensitivity for detecting lesions of 10 mm or larger was 82% with CTC compared with conventional colonoscopy. These and other 3 Macari M Bini EJ Xue X et al. Colorectal neoplasms: prospective comparison of thin section low dose multidetector row CT colonography and conventional colonoscopy for detection. Radiology. 2002; 224: 383-392 Crossref PubMed Scopus (203) Google Scholar data show that multidetector helical CT performs well in detection of polyps that are 10 mm or greater.

ACCEPTABILITY OF VIRTUAL COLONOSCOPY AS A COMMUNITY BASED CRC SCREENING TEST IN ASYMPTOMATIC AVERAGE RISK SUBJECTS

Objectives The acceptability of virtual colonoscopy (VC) in an average risk colorectal cancer (CRC) screening population is unknown. Our aims were to (1) assess acceptability of VC and (2) compare this with colonoscopy (CY), in a community based screening programme.Methods Randomly selected asymptomatic average risk subjects aged 50–54 or 65–69 years were invited to participate in a VC based CRC screening programme. Virtual colonoscopy involved a sodium picosulfate (picolax) based bowel preparation, hyoscine butylbromide (buscopan) injection, rectal insertion of Foley's catheter, inflation of the bowel by CO2 and supine and prone CT scans. Of 174 (M:F 91:83) subjects who have completed screening by VC, 43 had a positive VC and underwent CY on the same day. CY subjects received a mean sedation of midazolam 3.4 mg, pethidine 59 mg. All participants completed questionnaires following their procedure (s).Results Visual analogue scale questionnaire results (median scores). (0 = most favourable, 100 = least favourable) Pain Tolerated General satisfaction Level of embarrassment How likely to do again All VC n = 174 16 11 6 7 5 VC and CY n = 43 VC 17 17 7.5 5 4 CY 4 5 2.5 2 2 Was procedure better, worse or similar to expected? Better (%) Similar (%) Worse (%) All VC n = 174 50 43 7 CY n = 43 88 9 3 VC CY No preference Preferred procedure (n = 43) 7 14 22 Conclusion VC is a highly acceptable screening test. The vast majority of subjects would readily have either VC or CY again.