Preliminary Exploration of Pseudo-CT-Based Attenuation Correction for Simultaneous PET/MRI Brain Imaging in Nonhuman...

This study aimed to develop a template-based attenuation correction (AC) for the nonhuman primate (NHP) brain. We evaluated the effects of AC on positron emission tomography (PET) data quantification with two experimental paradigms by comparing the quantitative outcomes obtained using a segmentation-based AC versus template-based AC. Population-based atlas was generated from ten adult rhesus macaques. Bolus experiments using [¹⁸F]PF-06455943 and a bolus-infusion experiment using [¹¹C]OMAR were performed on a 3T Siemens PET/magnetic resonance-imaging (MRI). PET data were reconstructed with either μ map obtained from the segmentation-based AC or template-based AC. The standard uptake value (SUV), volume of distribution (V_T), or percentage occupancy of rimonabant were calculated for [¹⁸F]PF-06455943 and [¹¹C]OMAR PET, respectively. The leave-one-out cross-validation showed that the absolute percentage differences were 2.54 ± 2.86% for all region of interests. The segmentation-based AC had a lower SUV and V_T (∼10%) of [¹⁸F]PF-06455943 than the template-based method. The estimated occupancy was higher in the template-based method compared to the segmentation-based AC in the bolus-infusion study. However, future studies may be needed if a different reference tissue is selected for data quantification. Our template-based AC approach was successfully developed and applied to the NHP brain. One limitation of this study was that validation was performed by comparing two different MR-based AC approaches without validating against AC methods based on computed tomography (CT).