Cerebral bone subtraction CT angiography using 80kVp and sinogram-affirmed iterative reconstruction: contrast medium and radiation dose reduction with improvement of image quality.

Abstract

The purpose of this study was to evaluate the feasibility of a contrast medium (CM), radiation dose reduction protocol for cerebral bone-subtraction CT angiography (BSCTA) using 80-kVp and sinogram-affirmed iterative reconstruction (SAFIRE). Seventy-five patients who had undergone BSCTA under the 120- (n=37) or the 80-kVp protocol (n=38) were included. CM was 370mgI/kg for the 120-kVp and 296mgI/kg for the 80-kVp protocol; the 120- and the 80-kVp images were reconstructed with filtered back-projection (FBP) and SAFIRE, respectively. We compared effective dose (ED), CT attenuation, image noise, and contrast-to-noise ratio (CNR) of two protocols. We also scored arterial contrast, sharpness, depiction of small arteries, visibility near skull base/clip, and overall image quality on a four-point scale. ED was 62% lower at 80- than 120-kVp (0.59±0.06 vs 1.56±0.13mSv, p<0.01). CT attenuation of the internal carotid artery (ICA) and middle cerebral artery (MCA) was significantly higher on 80- than 120-kVp (ICA: 557.4±105.7 vs 370.0±59.3 Hounsfield units (HU), p<0.01; MCA: 551.9±107.9 vs 364.6±62.2 HU, p<0.01). The CNR was also significantly higher on 80- than 120-kVp (ICA: 46.2±10.2 vs 36.9±7.6, p<0.01; MCA: 45.7±10.0 vs 35.7±9.0, p<0.01). Visibility near skull base and clip was not significantly different (p=0.45). The other subjective scores were higher with the 80- than the 120-kVp protocol (p<0.05). The 80-kVp acquisition with SAFIRE yields better image quality for BSCTA and substantial reduction in the radiation and CM dose compared to the 120-kVp with FBP protocol.