Accuracy of detection and measurement of renal calculi: in vitro comparison of three-dimensional spiral CT, radiography, and nephrotomography.

PURPOSE: To compare accuracy of three-dimensional (3D) spiral computed tomography (CT) performed without administration of contrast material with that of radiography and linear nephrotomography in detection and measurement of renal calculi. MATERIALS AND METHODS: Fifty renal calculi within an abdominal phantom were imaged with 3D spiral CT, radiography, and linear nephrotomography. Spiral CT data were analyzed with workstation-based 3D imaging software, with a thresholding procedure based on the maximally attenuating voxel within each calculus during measurement. Measurement accuracy and detection rates were compared according to modality. Conventional and magnification-corrected measurements from radiography and linear nephrotomography were included. RESULTS: Spiral CT depicted calculi and allowed determination of the collective two-dimensional and 3D linear measurements statistically significantly more accurately than the other techniques; the mean linear measurement errors along individual axes did not exceed 3.6%. With 3D spiral CT, calculus volumes were determined with a mean error of -4.8%. CONCLUSION: 3D spiral CT enabled highly accurate determination of the volumes and all three linear dimensions of renal calculi. In addition, 3D spiral CT depicted calculi more sensitively than traditional techniques and provided new information and improved accuracy in the evaluation of nephrolithiasis.