Changes in [¹⁸F]Fluorodeoxyglucose Activities in a Shockwave-Induced Traumatic Brain Injury Model Using Lithotripsy

We present a longitudinal study of cerebral metabolism using [¹⁸F]fluorodeoxyglucose (FDG) positron emission tomography (PET) in a rat model of shockwave-induced traumatic brain injury (SW-TBI). Anesthetized rats received 5 or 10 SW pulses to the right anterior lateral or dorsal frontal regions using SW lithotripsy. Animals were scanned for FDG uptake at baseline, 3 h post-injury, and 3 days post-injury, using a small animal PET/computed tomography (CT) scanner. FDG uptake at all time-points was quantified as the ratio of brain activity relative to peripheral activity in the left ventricle (LV) in the heart (A_brain/A_LV) for the entire brain, each hemisphere, and four cortices (motor, cingulate, somatosensory, and retrosplenial). The mixed-designed models analysis of variance (ANOVA) for the hemispheric and global FDG uptake ratio showed a significant effect of the time-of-scan (p = 0.038) and measured region (p = 6.12e-09). We also observed a significant effect of the time-of-scan (p = 0.046) and measured region (p = 2.28e-09) for the FDG uptake ratio in four cortical regions. None of the measurements (global or local) showed a significant effect for the number of SW pulses (5 or 10) or SW location (lateral or dorsal frontal regions). Our data suggest that SW-TBI causes hypermetabolism on the impact side of the rat brain at 3 h post-injury compared with the baseline measurements. However, the increase in FDG uptake by day 3 post-injury was not significant. Further studies on post-TBI metabolic changes are needed to understand better the pathophysiology of the injury.