[Optimal technique of virtual cystoscopy on single-detector helical CT, and clinical application].

The optimal technique of virtual cystoscopy (VC) was determined on single-detector helical CT using a bladder phantom, and its clinical utility was evaluated. A phantom simulating the urinary bladder with 2 dome-shaped polyps (diameters 5 and 10 mm) was constructed. Imaging specifications were as follows: collimation, 3 and 5 mm; pitch 1; reconstruction interval, 1 and 2 mm. The polyps were positioned parallel and perpendicular to the scanning direction. Using these data sets, virtual cystoscopic images were generated by a voxel transmission technique. The threshold values were changed from -950 HU to -250 HU. Three radiologists evaluated visualization of the polyps in terms of proportion and shape on different collimations, threshold values, and location, for each size of polyp. Results indicated that the optimal technique of VC was as follows: collimation 3 mm, pitch 1:1, reconstruction interval 1 mm, and threshold value from -550 HU to -500 HU. VC depicted 13 (81.3%) of 16 lesions on the urinary bladder and prostate diseases noted on conventional cystoscopy using the optimal scanning technique. VC enabled evaluation of the accurate shape of lesions and their relation to adjacent mucosa.