Purpose: Postinjection transmission positron emission tomography (PET) may be useful for shortening the total scan time. In this study, the effect of post-transmission scanning was assessed using PET on a phantom (NU4) and actual rat brain.
Methods: Transmission was performed using (57)Co for 15 min. After a 15-min pre-transmission scan, emission PET was performed in list mode for 1 h, followed by an additional 15-min post-transmission scan. To compare the pre-transmission and post-transmission results, we measured nonuniformity, the recovery coefficient, and the spillover ratio (SOR) using NU4 and rat phantoms. The authors also assessed cerebral glucose metabolism using (18)F-fluorodeoxyglucose (FDG) PET and the binding potential for (18)F-fluorinated N-3-fluoropropyl-2-β-carboxymethoxy-3-β-(4-iodophenyl)nortropane (FP-CIT) in rat brain for differences between pre-transmission and post-transmission scanning.
Results: Nonuniformity and the SORs for air and water were comparable on the pre-transmission and post-transmission scans. With FDG-PET, after attenuation and scatter corrections no differences were observed in the brain regions on the pre-transmission and post-transmission scans. With FP-CIT-PET, the binding potentials were also not significantly different.
Conclusions: In the present study, we validated a post-transmission method for PET of the rat brain. Post-transmission PET was reliable, and the results were comparable to those of pre-transmission PET. Post-transmission PET eliminates the early tracer uptake time in the PET imaging, making it possible to determine uptake in the conscious subject, which may provide more realistic, "normal" metabolic measurements. Thus, post-transmission PET may be a useful option for increasing the number of subjects who can be evaluated.