Investigation of image guidance strategy for intermittent breath-hold cone beam CT

Abstract

Objective To develop a practical image acquisition strategy using intermittent breath-hold cone beam computed tomography (CBCT). Methods A breathing phantom was used to simulate the movement of tumor near the diaphragm during free breathing and breath hold and scanned by conventional breath-hold CBCT and type Ⅰ/Ⅱ intermittent breath-hold CBCT. In the conventional breath-hold CBCT, scan paused and free breathing occurred at the break of breath hold and free breathing was not included in the scan. In the intermittent breath-hold CBCT, one scan covered several breath holds separated by free breathing in a ratio of 3 vs1. Image quality and three-dimensional registration accuracy were quantitatively compared between conventional breath-hold CBCT and type Ⅰ/Ⅱ intermittent breath-hold CBCT. Comparison of image quality parameters between conventional breath-hold CBCT and intermittent breath-hold CBCT was made by paired t test. Results Motion artifacts arose in type I and Ⅱ intermittent breath-hold CBCT scans. There were no significant differences in the reconstructed pixel value or uniformity between intermittent breath-hold CBCT and conventional breath-hold CBCT (P>0.05, and P=0.02, 0.53). Compared with conventional breath-hold CBCT images, the signal-to-noise ratios of type I and Ⅱ intermittent breath-hold CBCT images were reduced by 30% and 60%, respectively (P<0.05). The registration error was up to 0.4 cm in the anterior-posterior direction and less than 0.1 cm in other directions. Conclusions The phantom study shows that intermittent breath-hold CBCT does not significantly reduce image quality or registration accuracy compared with conventional breath-hold CBCT. The feasibility of intermittent breath-hold CBCT in clinical application needs to be further validated among a large number of patients. Key words: Breath-hold; Tomography, X-ray computed, cone beam; Respiratory motion