Comparison of four contrast medium delivery protocols in low-iodine and low-radiation dose CT angiography of the aorta

AIM To evaluate contrast medium delivery protocols for the optimal enhancement profile of the aorta with both a reduced dose of radiation and contrast medium, called double-low computed tomography (CT) angiography (DLCTA). MATERIALS AND METHODS DLCTA was performed with 70 kVp and 200 mg iodine/kg in 205 patients following four protocols, namely slow rate (n=52), short duration (n=52), low concentration (n=50), and combined method (n=51), in comparison with a conventional group (120 kVp, 400 mg iodine/kg, n=51). The quantitative measurement of aortic attenuation, homogeneity, and subjective scores were evaluated. RESULTS Overall, in the four DLCTA groups, the radiation dose was reduced by 62%, and the iodine dose was reduced by 50%. Among the four DLCTA groups, the signal to noise ratio (SNR) and contrast to noise ratio (CNR) of the thoracic aorta were similar, but a significant difference was noted in the abdominal aorta. The short-duration group had the highest peak enhancement, least homogeneity, and worst subjective scores. Good contrast enhancement and good homogeneity were significantly more frequent in the slow-rate (86.6% and 90.4%, respectively) and low-concentration groups (78% and 96.0%, respectively). Subjective scores exhibited a trend of higher scores in the low-concentration group and lower scores in the slow-rate group (p=0.071). CONCLUSION DLCTA with 70 kVp and 200 mg iodine/kg is feasible for whole-aortic CT angiography. The low-concentration protocol is recommended owing to its most consistent optimal aortic enhancement profile. Alternatively, the slow-rate protocol can be considered for patients with limited venous access.