Continuous Bed Motion in a Silicon Photomultiplier–Based Scanner Provides Equivalent Spatial Resolution and Image Quality in Whole-Body PET Images at Similar Acquisition Times Using the Step-and-Shoot Method

Abstract

This study investigated the spatial resolution and image quality of the continuous-bed-motion (CBM) method in a sensitive silicon photomultiplier-based PET/CT system compared with the traditional step-and-shoot (SS) method. Methods: A PET/CT scanner was used in this study. Data acquisition using the SS method was performed for 3 min per bed position. In the CBM method, the bed speed ranged from 0.5 to 3.3 mm/s. The acquisition time equivalent to the SS method was 1.1 mm/s for 2-bed-position ranges and 0.8 mm/s for 7-bed-position ranges. The spatial resolution was investigated using 18 F point sources and evaluated using the full width at half maximum. Image quality was investigated using a National Electrical Manufacturers Association International Electrotechnical Commission body phantom with 6 spheres 10, 13, 17, 22, 28, and 37 mm in inner diameter. The radioactivity concentration ratio of the 18 F solution in all spheres and the background was approximately 4:1. The detectability of each sphere was visually evaluated using a 5-step score. Image quality was physically evaluated using the noise-equivalent count rate, contrast percentage of the 10-mm hot sphere, background variability percentage, and contrast-to-noise ratio. Results: The spatial resolution was not affected by the difference in acquisition methods or bed speeds. The detectability of the 10-mm sphere with a bed speed of 2.2 mm/s or faster was significantly inferior to that of the SS 2-bed-position method. In evaluating image quality, we observed no significant difference in contrast percentage among the acquisition methods or speeds in the CBM method. However, the increasing bed speed in the CBM method increased the background variability percentage and decreased the noise-equivalent count rate. When comparing the SS 2-bedposition method with the CBM method at 0.8 mm/s, we observed no significant differences in any parameters. Conclusion: In whole-body PET images obtained with a silicon photomultiplier-based PET/CT scanner, the CBM method provides spatial resolution and image quality equivalent to the SS method, with the same acquisition time.