Dose modulated retrospective ECG-gated versus non-gated 64-row CT angiography of the aorta at the same radiation dose: comparison of motion artifacts, diagnostic confidence and signal-to-noise-ratios.

PURPOSE: To compare ECG-gated and non-gated CT angiography of the aorta at the same radiation dose, with regard to motion artifacts (MA), diagnostic confidence (DC) and signal-to-noise-ratios (SNRs).

MATERIALS AND METHODS: Sixty consecutive patients prospectively randomized into two groups underwent 64-row CT angiography, with or without dose-modulated ECG-gating, of the entire aorta, due to several pathologies of the ascending aorta. MA and DC were both assessed using a four-point scale. SNRs were calculated by dividing the mean enhancement by the standard deviation. The dose-length-product (DLP) of each examination was recorded and the effective dose was estimated.

RESULTS: Dose-modulated ECG-gating showed statistically significant advantages over non-gated CT angiography, with regard to MA (p<0.001) and DC (p<0.001), at the aortic valve, at the origin of the coronary arteries, and at the dissection membrane, with a significant correlation (p<0.001) between MA and DC. At the aortic wall, however, ECG-gated CT angiography showed statistically significant fewer MA (p<0.001), but not a statistically significant higher DC (p=0.137) compared to non-gated CT angiography. At the supra-aortic vessels and the descending aorta, the ECG-triggering showed no statistically significant differences with regard to MA (p=0.861 and 0.526, respectively) and DC (p=1.88 and 0.728, respectively). The effective dose of ECG-gated CT angiography (23.24mSv; range, 18.43-25.94mSv) did not differ significantly (p=0.051) from that of non-gated CT angiography (24.28mSv; range, 19.37-29.27mSv).

CONCLUSION: ECG-gated CT angiography of the entire aorta reduces MA and results in a higher DC with the same SNR, compared to non-gated CT angiography at the same radiation dose.