Influence of respiratory motion on image quality of 4D-CBCT / 中华放射肿瘤学杂志

ABSTRACT

Objective@#To investigate the relationship between the image quality of 4D cone beam CT (4D-CBCT) and the characteristic parameters of respiratory motion.@*Methods@#Catphan 500 was fixed on the Mapcheck XY/4D table by a fixation device. The control platform was utilized to simulate the static and 19 motion states. A synergy accelerator was adopted to perform 4D-CBCT scan of the image quality detection module under different motion states. By analyzing the geometric accuracy, spatial resolution, low-contrast visibility, CT value uniformity and motion position accuracy of the images of the 10 phases of the reconstructed images, the relationship among the image quality of 4D-CBCT, motion direction, amplitude and cycle was analyzed.@*Results@#4D-CBCT images could not be properly reconstructed in the static state or only in the left-right (LR) direction. The image quality was significantly worse than that in the SI direction. The contrast-to-noise ratio (CNR) was decreased as the motion cycle was increased. When the cycle was increased from 2 s to 6 s, the CNR was significantly declined from 3.33 to 1.72(P<0.01), whereas respiratory motion exerted no significant effect upon the geometric accuracy, spatial resolution and sagittal position.@*Conclusions@#The CNR, horizontal and vertical geometric accuracy and motion position accuracy of 4D-CBCT image quality are significantly affected by respiratory motion, whereas spatial resolution and sagittal geometric accuracy are not significantly influenced by respiratory motion.4D-CBCT requires the intervention of periodical motion in the SI direction. Excessively slow or absence of periodical motion can influence the image quality and even the images cannot be accurately reconstructed.4D-CBCT image reconstruction equally requires the intervention of periodical motion in the SI direction. The image quality is simultaneously affected by the amplitude and cycle of respiratory motion. For 4D-CBCT scan, the respiratory cycle of<6 s and an amplitude of>0.75 cm are recommended.