CT chest and gantry rotation time: does the rotation time influence image quality?

ABSTRACT

BACKGROUND: Computed tomography (CT) gantry rotation time is one factor influencing image quality. Until now, there has been no report investigating the influence of gantry rotation time on chest CT image quality. PURPOSE: To investigate the influence of faster gantry rotation time on image quality and subjective and objective image parameters in chest CT imaging. MATERIAL AND METHODS: Chest CT scans from 160 patients were examined in this study. All scans were performed using a single-source mode (collimation, 128 × 0.6 mm; pitch, 1.2) on a dual-source CT scanner. Only gantry rotation time was modified, while other CT parameters were kept stable for each scan (120 kV/110 reference mAs). Patients were divided into four groups based on rotation time group 1, 1 s/ rotation (rot); group 2, 0.5 s/rot; group 3, 0.33 s/rot; group 4, 0.28 s/rot. Two blinded radiologists subjectively compared CT image quality, noise, and artifacts, as well as radiation exposure, from all groups. For objective comparison, all image datasets were analyzed by a radiologist with 5 years of experience concerning objective measurements as well as signal-to-noise ratio (SNR). RESULTS: We found that faster gantry rotation times (0.28 s/rot and 0.33 s/rot) resulted in more streak artifacts, image noise, and decreased image quality. However, there was no significant difference in radiation exposure between faster and slower rotation times (P > 0.7). CONCLUSION: Faster CT gantry rotation reduces scan time and motion artifacts. However, accelerating rotation time increases image noise and streak artifacts. Therefore, a slower CT gantry rotation speed is still recommended for higher image quality in some cases.