What is the best contrast injection protocol for 64-row multi-detector cardiac computed tomography?

Abstract

Objective: To determine the optimal contrast injection protocol for 64-MDCT coronary angiography.

Materials and methods: One hundred and fifty consecutive patients scheduled to undergo retrospectively electrocardiographically gated 64-MDCT. Each 30 patients were assigned to use a different contrast protocol: group 1: uniphasic protocol (contrast injection without saline flush); group 2: biphasic protocol (contrast injection with saline flush); group 3A, 3B and 3C: triphasic protocol (contrast media+different saline diluted contrast media+saline flush). Image quality scores and artifacts were compared and evaluated on both transaxial and three-dimensional coronary artery images among each contrast protocol.

Results: Among the triphasic protocol groups, group 3A (30%:70% contrast media-saline mixture was used in second phase) used the least contrast media and had the least frequency of streak artifacts, but there were no significant differences in coronary artery attenuation, image quality, visualization right and left heart structures. Among the uniphasic protocol group (group 1), biphasic protocol group (group 2) and triphasic protocol subgroup (group 3A), there were no significant differences in image quality scores of coronary artery (P=0.18); uniphasic protocol group had the highest frequency of streak artifacts (20 cases) (P<0.05) and had the most amount contrast media (67.0+/-5.3 ml); biphasic protocol group had the least amount of contrast media (59.9+/-4.9 ml) (P<0.05) and had the highest attenuation of left main coronary artery and right coronary artery (P<0.01), but had the least amount of clear visualization right heart structure (6 cases); triphasic protocol group (group 3A) had the most amount of clear visualization right heart structures (29 cases) were the most among the three groups (P<0.05).

Conclusion: Biphasic protocol are superior to the traditional uniphasic protocols for using the least total contrast media, having the least Streak artifacts and without image quality degradation. However, it is also important to visualize the right atrium and ventricle, so triphasic protocol (30%:70% contrast media-saline mixture was used in second phase) should be used for 64-MDCT coronary CT angiography.