Computed tomography angiography of the carotid arteries at low kV settings: a prospective randomised trial assessing radiation dose and diagnostic confidence.

Abstract

To assess radiation dose and diagnostic image quality of a low-dose (80 kV) versus a standard-dose (120 kV) protocol for computed tomography angiography (CTA) of the supra-aortic arteries. 64-slice CTA of the supra-aortic arteries was performed in 42 consecutive patients using randomly either 80 or 120 kV at 300 absolute mAs. Intravascular attenuation values, contrast-to-noise (CNR) and signal-to-noise ratio (SNR) measurements were performed at three levels. Two readers assessed image quality by using a four-point scale. The effective dose (ED) was calculated to assess the differences in radiation exposure. Intravascular attenuation values at 80 kV were higher in the common carotid artery, the carotid bifurcation and the internal carotid artery (p < 0.001). CNR and SNR differed at the internal carotid artery, with higher values in the 80-kV group (p > 0.05). Both readers revealed a significantly better image quality at 120 kV only at the common carotid artery (p < 0.001; p = 0.007). Mean ED was significantly lower at 80-kV (1.23 ± 0.09 vs. 3.99 ± 0.33 mSv; p < 0.001). Tube voltage reduction to 80 kV in CTA of the supra-aortic arteries allows for significant radiation dose reduction but has limitations at the level of the common carotid artery.