Equivalent image quality between continuous-bed-motion < and > step and shoot acquisition methods in positron emission tomography

Objectives: Recently, continuous bed motion (CBM) has become clinically available for commercial PET/CT systems. CBM needs to determine bed speed instead of acquisition time per bed as done in the conventional step and shoot (SS), and a conversion table calculated using the noise equivalent count (NEC) has usually used to determine scan time. This study aimed to compare the image quality between CBM using an NEC-based conversion table and the SS acquisition methods. Methods: Nine bed-speed settings for CBM were derived from SS acquisition times per bed using NEC based conversion table provided by manufacture. A National Electrical Manufacturers Association (NEMA) body phantom containing six spheres (10- to 37-mm diameter) was used for the evaluation of the image quality. The background region of body phantom was filled with 4.22 kBq/ml of fluorodeoxyglucose (FDG), and the six spheres were prepared with 4-times the concentration of the background region. The percent background variability (N), percent contrast in the hot image (QH), QH/N ratio (QH/N) and maximum standardized uptake values (SUVmax) in each of the spheres, and coefficient of variation in the background region (CVbackground) were the physical parameters used for evaluation. Furthermore, a five-point scale was used for the visual evaluation performed on each image of a slices in which all spheres were clearly detected most. Results: On physical and visual evaluations, no significant differences were observed between CBM and SS for any of the parameters, except QH/N at a sphere size of 10 mm (p = 0.003). Conclusion: Although a significant difference between CBM and SS was observed for one of the physical parameters evaluated, results from the other parameters, as well as the visual evaluation, did not indicate a significant difference. We conclude that CBM using a NEC based conversion table provides an image quality that is equivalent to that obtained by SS acquisition methods.