Assessment of muscle function using hybrid PET/MRI: comparison of (18)F-FDG PET and T2-weighted MRI for quantifying muscle activation in human subjects

PURPOSE: The aim of this study was to determine the relationship between relative glucose uptake and MRI T (2) changes in skeletal muscles following resistance exercise using simultaneous PET/MRI scans. METHODS: Ten young healthy recreationally active men (age 21 – 28 years) were injected with (18)F-FDG while activating the quadriceps of one leg with repeated knee extension exercises followed by hand-grip exercises for one arm. Immediately following the exercises, the subjects were scanned simultaneously with (18)F-FDG PET/MRI and muscle groups were evaluated for increases in (18)F-FDG uptake and MRI T (2) values. RESULTS: A significant linear correlation between (18)F-FDG uptake and changes in muscle T (2) (R (2) = 0.71) was found. for both small and large muscles and in voxel to voxel comparisons. Despite large intersubject differences in muscle recruitment, the linear correlation between (18)F-FDG uptake and changes in muscle T (2) did not vary among subjects. CONCLUSION: This is the first assessment of skeletal muscle activation using hybrid PET/MRI and the first study to demonstrate a high correlation between (18)F-FDG uptake and changes in muscle T (2) with physical exercise. Accordingly, it seems that changes in muscle T (2) may be used as a surrogate marker for glucose uptake and lead to an improved insight into the metabolic changes that occur with muscle activation. Such knowledge may lead to improved treatment strategies in patients with neuromuscular pathologies such as stroke, spinal cord injuries and muscular dystrophies.