Low-dose coronary CT angiography with prospective ECG triggering: validation of a contrast material protocol adapted...

The aim of the study was to validate a body mass index (BMI)-adapted contrast material protocol to compensate for the effect of BMI on coronary attenuation during low-dose coronary CT angiography with prospective ECG triggering.

One hundred forty patients underwent prospectively ECG-triggered coronary CT angiography for clinical indications. The following BMI-adapted contrast material protocol was used for imaging of 70 consecutively registered patients: BMI < 17.5, 50 mL contrast material at 4.0 mL/s; 17.5-22.4, 55 mL at 4.0 mL/s; 22.5-24.9, 65 mL at 4.0 mL/s; 25.0-27.4, 80 mL at 4.5 mL/s; 27.5-29.9, 80 mL at 5.0 mL/s; 30.0-34.9, 85 mL at 5.0 mL/s; 35.0-40.0, 95 mL at 5.0 mL/s; > 40, 105 mL at 5.0 mL/s. Seventy patients matched for BMI who had previously undergone routine coronary CT angiography with a fixed contrast material dosage of 80 mL at 5 mL/s served as the reference group. Vessel attenuation in the left main and proximal right coronary arteries was measured and correlated with BMI, and the results in the two protocol groups were compared.

The groups were well matched for BMI. The mean BMI in the nonadapted protocol group was 26.5 +/- 4.0 (standard deviation) (range, 18.9-36.5), and that in the BMI-adapted protocol group was 26.7 +/- 4.2 (range, 18.2-37.2) (p not significant). The mean amount of contrast material used was smaller in the BMI-adapted group (73.9 +/- 11.2 vs 80.0 +/- 0 mL; p < 0.01). Mean coronary artery attenuation did not differ significantly between the two groups (386 +/- 102 HU vs 385 +/- 64 HU; p not significant). Without BMI adaptation, coronary attenuation correlated strongly with BMI (r = -0.63; p < 0.001). With the BMI-adapted protocol, however, there was no correlation between BMI and coronary attenuation (r = -0.24; p not significant).

We validated a BMI-adapted contrast material protocol that results in adequate coronary vessel attenuation independent of individual BMI despite a significant reduction in overall amount of contrast material used.