18F-FDG-PET/CT for assessment of volume and global metabolic activity of the thigh muscles: A CT-based segmentation methodology

96 Purpose: To develop a new imaging methodology for assessing and monitoring the effects of therapeutic interventions in muscular diseases. We present a CT-based tissue segmentation method for determining volume and global uptake of 18F-fluorodeoxyglucose (FDG) in the thigh muscles and correlate these parameters with BMI and age.Materials and Methods:A total of 71 subjects (36 males, mean age 48 years, range 21-75) from a prospective clinical trial [NCT01724749] were included. All subjects underwent FDG-PET/CT imaging 180 min after intravenous injection of the tracer. The upper and lower boundaries of the ROI were set 5 cm below the greater trochanter and 5 cm above the intercondylar notch, respectively. Using OsiriX MD software (Pixmeo SARL, Bernex, Switzerland), a 3D growing region algorithm with a neighborhood Hounsfield unit of 1 and 150 was used to highlight the muscle. The volumes (cm3) of the left and right muscle groups were independently measured using CT-based segmentation, determined by multiplying area of the ROI with slice thickness and the FDG uptake, expressed as the average mean standardized uptake value (average SUVmean). Results: There was no significant difference in muscle volume between the two sides: left 3606.5±1195.6 cm3, right 3633.5±1215.7 cm3, p=0.36. In contrast, a small, but statistically significant, difference was noted in the metabolic activity expressed as the average SUVmean of the two muscle groups: left 0.60±0.13, right 62±0.14, p