[Optimal scan timing in 64-row MDCT angiography of the lower extremities: 2-point ROI detection bolus-tracking...

In CT angiography of the lower extremities, we have developed a 2-point ROI detection bolus-tracking method (2ROI-BTM) to provide the optimal contrast medium concentration and reduce contrast medium. The time to reach the ankle from the abdominal aorta was 22.5 s (95% central range, 14.6-40.1 s). The mean scan time was 13.6 s (range, 11.5-15.0 s). In the 2ROI-BTM (n=78), the mean CT number was 516 HU in the aorta, 427 HU in the popliteal artery, and 323 HU in the tibial artery. Compared with the TIM (n=66), the CT number was low in only 3% or less of cases, and the usual contrast medium dose of 20 ml for test injection could be reduced. With the 2ROI-BTM, the optimal scan timing can be determined more easily than with the TIM, allowing the contrast medium dose to be reduced by 26% and providing contrast enhancement with superior reproducibility of morphological characteristics for the generation of 3D images.