The Effect of Attenuation and Scatter Correction in Rat Brain PET

Attenuation correction (AC) and scatter correction (SC) are problematic issues for animal positron emission tomography (PET). In this study, the effects of AC and SC were assessed using PET on a phantom and actual rat brain. Transmission (TX) was performed using ⁵⁷Co for 15 min. After a 15 min TX scan, emission (EM) PET was performed in list mode for 1 h. To assess the effects of AC and SC, the spillover ratio (SOR) was measured using a rat-sized NEMA NU4 image-quality phantom; statistical parametric mapping (SPM) was performed to assess the effects of AC and SC in the rat brain using 18^F-FDG (FDG). In addition, the binding potential (BP) was compared for ¹⁸F-FP-CIT (FP-CIT) PET. SPM was used to compare PET images to which AC and SC were applied, and BP was used for FP-CIT PET. The SORs of air and water decreased after AC and SC. SPM for FDG PET after AC showed a significant increase in FDG-measured activity in the cerebellum and occipital cortex. After AC/SC, a significant decrease in FDG-measured activity was observed in the frontal and temporal cortices. For FP-CIT PET of the rat brain, the BP decreased by 26% after AC because the FP-CIT uptake increased more in the cerebellum than in the striatum owing to AC. After AC and SC, the mean BP increased by 61%. AC and AC/SC were found to be necessary components of the artifact correction process for both FDG PET and FP-CIT PET of rat brains.