Abdominal aortic aneurysms at multi-detector row helical CT: optimization with interactive determination of scanning delay and contrast medium dose.

Abstract

To prospectively evaluate a technique for optimizing aortoiliac enhancement at multi-detector row helical computed tomography (CT) with both the scanning delay and contrast medium dose determined by using an interactive method. Forty-five patients with abdominal aortic aneurysm were randomized to undergo multi-detector row helical CT with either an interactive protocol (n = 23) or a standard protocol (n = 22). Scanning delays in all patients were determined with automated triggering. Patients in the standard protocol group received 150 mL of contrast medium intravenously at 4 mL/sec. The same injection rate was used for the interactive protocol group, but the dose was reduced with discontinuation of injection at start of scanning. Quantities of contrast medium used and contrast-enhanced aortic attenuation achieved were compared. Aortoiliac enhancement was evaluated qualitatively by using a five-point scale (1 = poor, 5 = excellent). Quantitative and qualitative data were analyzed with the two-tailed t test and Wilcoxon rank sum test, respectively, to determine significance of differences (P <.05). Data from six patients were excluded because of technical errors. Data were analyzed from 20 patients in the interactive protocol group and 19 in the standard protocol group. Mean contrast medium volume was 107 mL +/- 20 (standard deviation) in the interactive protocol group and 148 mL +/- 3 in the standard protocol group (P <.001). Mean contrast-enhanced attenuation at initial, peak, and final measurements was 257 HU +/- 38, 285 HU +/- 46, and 269 HU +/- 54, respectively, for the interactive protocol group, and 261 HU +/- 65, 288 HU +/- 66, and 269 HU +/- 61 for the standard protocol group (P >.05). Mean qualitative enhancement scores for interactive and standard protocol groups were 4.47 and 4.44, respectively (P =.47). The interactive method is a simple, efficient, and reproducible way to optimize aortoiliac enhancement while reducing contrast medium dose.