Prospectively gated axial CT coronary angiography: comparison of image quality and effective radiation dose between 64- and 256-slice CT.

Purpose: To compare image quality and effective radiation dose for prospectively gated axial CT coronary angiography on 64- and 256-slice CT.

Methods: The patient cohort consisted of 80 consecutive patients undergoing imaging with 256-slice CT and 80 patients with 64-slice CT. The two patient groups were demographically matched according to age, gender, body mass index and heart rate. For both groups, two observers independently assessed image quality for all coronary segments on a five-point ordinal scale. The two groups were compared with regard to image quality and effective radiation dose. Image quality scores less than 3 were considered non-diagnostic.

Results: Mean effective radiation dose did not significantly differ between the two groups (3.4 +/- 0.8 mSv in both groups; p > 0.1). Vessel-based image quality was significantly better in patients undergoing 256-slice CT compared with those undergoing 64-slice CT (p < 0.001). The proportion of assessable coronary segments significantly increased from 95.6% in the 64-slice group to 98.9% in the 256-slice group (p < 0.05).

Conclusion: Prospectively gated axial CT coronary angiography performed on 256-slice CT provides significantly improved and more stable image quality at an equivalent effective radiation dose compared with 64-slice CT.