Value of multislice helical CT scans and maximum-intensity-projection images to improve detection of ureteral stones at abdominal radiography.

Abstract

The purpose of this study was to assess the improvement in the detection of ureteral stones on abdominal radiographs when the stones were viewed on multislice helical CT scans and maximum-intensity-projection (MIP) images. The study included 72 patients with renal colic who underwent abdominal radiography and multislice helical CT. For each patient, a frontal MIP image was generated, and the stone, when present, was marked with a cross on the transverse CT scan. The cross appeared automatically on the corresponding MIP image. The CT examination was used as the standard of reference. The presence and location of ureteral stones on the abdominal radiographs were assessed during three interpretation sessions. In the first session, the abdominal radiographs were viewed alone. In the second, they were viewed with the transverse CT scans. In the third, the abdominal radiographs were viewed with the CT scans and the MIP images. Ureteral stones were present in 58 patients. The percentage of stones detected on the abdominal radiographs was 45% when the radiographs were viewed alone, 66% when they were viewed with the CT scans (p = 0.002 vs radiographs alone), and 78% when viewed with the CT scans and MIP images (p = 0.016 vs radiographs with CT scans). The sensitivity of stone detection on abdominal radiographs was greatest when the interpreters viewed the radiographs in conjunction with the CT scans and MIP images.