Compact-bolus dynamic CT protocol with a test bolus technique in 64-MDCT coronary angiography. Comparison of fixed injection rate and duration protocol

We compared the fixed injection rate protocol (P2) with the fixed injection duration protocol (P1) for coronary CT angiography using the test bolus technique. We randomly assigned 100 patients to one of two protocols. In P1, they received 0.7 mL/kg Iohexol-350 in an injection duration of 9 s, and we selected a delay of 3 s after peak enhancement of test bolus scan. In P2, they received 0.7 mL/kg Iohexol-350 at an injection rate of 5 mL/s, and we selected a delay after peak enhancement of test bolus scan using the following formula: TID/2-2 s, where TID is the injection duration of full bolus. We compared attenuation values in the ascending aorta and coronary arteries and patient-to-patient enhancement variability at each segment. At all segments, CT attenuations of P2 were significantly greater than those of P1 (ascending aorta 400±64 vs. 368±60, P=0.01; left main trunk 399±67 vs. 369±55, P=0.02; proximal-RCA 393±66 vs. 363±56, P=0.01). There was no significant difference in patient-to-patient enhancement variability at all segments between the two groups (P>0.05). P2 yielded superior vessel enhancement and comparable patient-to-patient enhancement variability compared with P1 in thin patients. (author)