Quantitative aortic enhancement at arterial phase (AP). The timing of AP in Protocols B and C was early, so that contrast enhancement of the aorta was better than with the other protocols. It is suitable for the contrast imaging of the aorta in Protocols B and C. In the subgroup of body weight (BW) > 60 kg, the amount of iodine especially in Protocol-D was less than those in the other groups, and the aortic enhancement was significantly lower in Protocol-D by analysis of variance. (*; P < 0.001, **; P < 0.001, *** P = 0.0011). In the subgroups of BW ≤ 50 kg, the aortic enhancement in Protocol-C tended to be higher than those in the other groups. Error bars indicate 95% confidence interval. CT; computed tomography, HU; Hounsfield unit. -50; up to 50 kg of BW, 50 < −60; greater than 50 kg, up to 60 kg of BW, 60<; greater than 60 kg of BW.