Cervical CT angiography comparing routine noncontrast and a late venous scan as masks for automated bone subtraction: feasibility study and examination of the influence of patient motion on image quality

Abstract

Objectives: Bone subtraction techniques have been shown to enhance cranial computed tomography angiography (CTA). The aims of this study were to assess the feasibility of bone subtraction CTA (BSCTA) in cervical CTA, test whether a late venous CT (LVCT) scan can be used as bone mask instead of a low-dose nonenhanced CT (NECT), and to evaluate the impact of patient motion on image quality.

Materials and methods: Thirty-six patients underwent BSCTA for the evaluation of the neck vessels with a 64-slice CT system using commercially available software. Eighteen patients had a low-dose NECT scan before CTA, and 18 patients had an LVCT scan after CTA. Subtraction quality for vascular segments was evaluated independently by 2 examiners. Cohen's Kappa was applied to evaluate interobserver reliability, and Wilcoxon signed rank test was used to test for differences between the 2 groups. Motion between the 2 scans was measured and correlated to image quality.

Results: BSCTA using both NECT and LVCT scans as masks was successfully applied in all patients. Image quality did not differ significantly between the 2 groups, and interobserver agreement was high (k 0.5-1). Motion between the scans was highest for the jaw and hyoid, and lowest for the upper and lower spine. Decreased image quality on the subtracted images was associated with increased motion for the external carotid and vertebral artery, independent of mask type (P = 0.002-0.04).

Conclusions: BSCTA techniques can be successfully applied in the neck. If parenchymal phase imaging is indicated, the LVCT can be used as a bone subtraction mask and diagnostic scan, eg, for tumor imaging.