Abstract: Objective  To determine the clinical value of 320-slice spiral CT in the measurement of ureteral calculi.
  Methods  All patients who underwent unenhanced 320 multi-slice CT scan for the evaluation of ureteral colic were evaluated. Maximal stone diameter was measured respectively in 2 dimension in axial and reformatted coronal sections.
  Results  The average maximum diameter and maximum area of the calculus measured in the coronal reconstruction image group of 100 patients were larger than the cross-sectional image(P＜0.05）. The volume of the stone was 24-3 060 mm3. There was 37% underestimation of maximal stone diameter in axial plane for all stones as compared with measurement on coronal reconstruction.
  Conclusion  Measuring the ureteric stone diameter on axial plane of 320 multi-slice computed tomography(MSCT） scan underestimates size of ureteric stone,coronal reformatted plane be used size estimation. The volume measurement of calculi after volume rendering(VR）  reconstruction is helpful for the clinical selection of follow-up treatment for ureteral calculi.

Key words: ureteral calculi, tomography, spiral computed, image processing, computer-assisted