High-resolution in utero SV2A PET imaging of the nonhuman primate brain using the NeuroEXPLORER.

The NeuroEXPLORER (NX), a next generation brain-dedicated PET scanner, has demonstrated improved spatial resolution and sensitivity compared with previous PET scanners. In this study, we performed synaptic vesicle glycoprotein 2A (SV2A) PET, an in vivo marker of synaptic density, to evaluate the performance of the NX in both fetal and maternal brains of four pregnant rhesus macaques. Results were compared with the previously acquired PET images using miniEXPLORER and Biograph mCT for fetal and maternal brains (four pregnant monkeys per scanner). The NX demonstrated superior performance compared with the other scanners, providing improved image clarity and higher distribution volume ratios (DVRs), which were significant in the occipital region and putamen of the fetal brain (p < 0.05, FDR uncorrected), as well as across all regions in the maternal brain (p < 0.05, FDR corrected). The percentage difference in mean regional DVR between maternal and fetal brains ranged from 36.1% in the amygdala to 78.3% in the occipital lobe in the NX, which may reflect regional differences in the phase of synaptic development. This study highlights the NX as a promising non-invasive tool for investigating in utero synaptic development. The presence of in utero motion emphasizes the necessity of motion correction for reliable PET quantification.