Comparative viewing modalities for CT cystography L. K. Conrad, 1 E. J. Kirsh, 2 G. Steinberg, 2 G. S. Gerber, 2 W. Rosello, 3 C. Pelizzari, 3 G. S. Stacy, 1 A. H. Dachman 1 1 Department of Radiology, The University of Chicago Hospitals, 5841 S. Maryland Avenue, MC 6038, Chicago, IL 60637, USA 2 Department of Urology, The University of Chicago Hospitals, 5841 S. Maryland Avenue, MC 6038, Chicago, IL 60637, USA 3 Kurt Rossman Laboratories, Department of Radiology, The University of Chicago, 5841 South Maryland Avenue, MC 2026, Chicago, IL 60637, USA Received: 22 March 2000/Accepted: 3 May 2000 Abstract Background: To define the speed and accuracy of two different reconstructive techniques using computed to- mography (CT) cystography for the detection and mea- surement of urinary bladder masses and determine the overall ease of use. Methods: Ten patients scheduled for cystoscopy for the evaluation of hematuria or bladder masses were studied by means of thin-section CT of the air-distended bladder. Two techniques were employed by two radiologists to blindly interpret the data: conventional two-dimensional data with interactive three-dimensional problem solving (2D3DPS) and surface-shaded display (SSD) three-di- mensional images. The results were compared with the data from cystoscopy. Results: Twenty-two (100%) of 22 masses detected on cystoscopy were visualized using the reconstructive tech- niques. Both modalities were shown to have high accu- racy, but only the 2D3DPS had a sensitivity and speci- ficity of 100% for both observers at the patient-level diagnosis. The sensitivities for detecting individual masses for the two observers were 100% and 64% for 2D3DPS and 64% and 70% for SSD. Conclusion: Both methods used to display the CT data had a high sensitivity and specificity for masses, but only the 2D3DPS had a sensitivity and specificity of 100% at the patient-level diagnosis, thus making it a feasible im- aging modality for cystography. It was also preferred overall for ease of use, high accuracy, and relative low cost. Key words: Bladder, CT—Bladder neoplasms—Com- puted tomography, clinical effectiveness—Computed to- mography, image processing—Computed tomography, volume rendering—Images, interpretation. Computed tomography (CT) cystography (also called virtual cystoscopy) is an interactive method of display- ing conventional cross-sectional CT images of an air- filled urinary bladder from an endocystic perspective [1]. For virtual cystoscopy to become a clinically prac- tical means for the evaluation of the bladder, it must be acceptable to patients, technically feasible to perform in an outpatient setting, and practical for the radiologist to display and interpret in a time and cost-efficient manner. Previous investigators [1– 6] have only used a single modality for the display and interpretation of the CT data. The purpose of this study was to evaluate alternative methods of displaying CT cystoscopic data for interpre- tation. We studied both the accuracy of the technique and the user friendliness of the display method. We displayed data gathered from 10 patients who underwent CT cys- tography using two different visual presentation modali- ties. We determined the speed, ease of use, and accuracy of these two different reconstructive techniques for the detection and measurement of urinary bladder masses. Further, patient preferences for conventional cystoscopy and physician preference for both modalities were ascer- tained. Workstation based conventional two-dimensional (2D) data with interactive three-dimensional (3D) prob- lem solving (2D3DPS) and surface-shaded display (SSD) 3D images were chosen for comparison due to their wide availability and relatively low cost as compared with other modalities such as dedicated 3D virtual reality sys- tems. Correspondence to: L. K. Conrad Abdom Imaging 26:92–97 (2001) DOI: 10.1007/s002610000075 Abdominal Imaging © Springer-Verlag New York Inc. 2001