Objectives: To achieve the efficient usage of contrast material (CM) in high-pitch CT aortography, an appropriate duration of the CM injection is crucial. We used a modification of the double-level test bolus method for determination of proper injection duration with the aim of evaluating the image quality of tailored-duration CM injection compared with that of a fixed duration.
Materials and methods: The institutional review board approved retrospective review of 80 consecutive subjects who had undergone high-pitch 70-kVp CT aortography with a modified double-level test bolus method. The interval between peak enhancement at the aortic root and femoral artery was derived from the time/attenuation curves. A total of 40 subjects underwent CT aortography with individually set duration time from the results. The remaining subjects underwent CT aortography with a fixed-duration time. The density values at several parts of the aorta were assessed. The differences in image quality and CM amount used for each method were assessed by Welch test.
Results: The injection duration was almost 50% shorter (median, 15 seconds; range, 11-25 seconds) when individually tailored. The mean CM amount was reduced by 50% (46.2-23.9 mL, P < 0.01). The range of mean CT attenuation throughout the aorta was not significantly different between the 2 methods (316-327 HU and 305-321 HU, P > 0.05, respectively).
Conclusions: The modified double-level test bolus method in high-pitch CT aortography can significantly reduce the amount of CM without adversely affecting image quality.