Construction and evaluation of F-18 FDG PET probabilistic MAP for voxel based analysis of the rat brain

The purpose of this study was to develop F-18 FDG PET and MRI template for normal rat brain. Also, feasibility of SPM in detailed regional analysis of molecular changes in the rat brain was explored for F-18 FDG PET imaging of a model of traumatic brain injury (TBI). Ten normal rats were scanned with PET and MRI. The PET images were acquired with 3D mode using microPET focus 120 scanner after injection of 37 MBq F-18 FDG. T2-weighted MR images were acquired using 4.7T MRI system. A MRI-based spatial normalization was used. The PET images were coregistered to T2-weighted MR images. Maximum mutual information (MMI) registrations and affine spatial normalizations were performed using SPM2. The spatial normalization of the MRI to the standard MRI was applied to the integral images. The normalized PET images were averaged voxel wise to create PET template. Eight TBI model rats were subjected to a moderate lateral fluid percussion injury. At 2 days, 1 week, 3 weeks and 5 weeks post FPI, PET images of 8 TBI rats were acquired 4 times. TBI PET images were realigned, spatially normalized to a created PET-template and smoothed (8 mm FWHM). To assess the extent and severity of significant hypo metabolic lesions in TBI compared to normal controls were obtained by a two-sided t-test of SPM (uncorrected p < 0.001, 50 voxels). Visually acceptable PET and MRI templates were created. Registration errors were negligible when MMI procedure was used to register a translated or rotated image volume. Thirty-two PET studies of 8 TBI model subjects were obtained. SPM analysis showed injured distribution of decrease F-18 FDG uptake in TBI rats compared with normal rats. In SPM analysis, the extent and severity of significant hypo metabolic lesions were decreased according to a significant effect of time. At 5 weeks injured animals showed F-18 FDG uptake recovery using SPM analysis. These results indicate that voxel-based method will be useful for future longitudinal studies of rat brain