Achievements of true whole-body imaging using a faster acquisition of the lower extremities in variable-speed continuous bed motion

Abstract

Variable-speed continuous bed motion 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT), a reliable imaging technique, allows setting the bed motion speed for arbitrary sections of the body. The purpose of this study was to evaluate the relationship between the PET image quality and the bed speed following shortening of the scanning time for the lower extremities to achieve whole-body acquisition optimization of the examination time. Four sets of images were created by editing four-phase dynamic whole-body PET/CT images acquired at a bed speed of 6 and 14 mm/s in the trunk and lower extremities, respectively. The signal-to-noise ratio (SNR) was calculated using regions of interest in the liver, gluteus muscles, thigh, and lower legs, and the relationship between the bed speed and the SNR was assessed. The number of patients with findings in the lower extremities among 967 cases was evaluated. Based on this relationship between the SNR and bed motion speed, it is reasonable to increase the speed of the lower extremities by up to three times that of the trunk. The findings from whole-body FDG-PET imaging revealed that the number of patients with detected lesions in the lower extremities was 6.6% (64/967), bone metastases were found in 2.6%, soft lesions in 1.8%, and inflammation in 2.3%. Images of the lower extremities, which have a better SNR than the trunk, can be acquired at a faster bed speed using the variable-speed continuous bed motion PET.