Exceptional brain PET images from the NeuroEXPLORER: scans with targeted radiopharmaceuticals and comparison to HRRT.

Abstract

Current brain-dedicated positron emission tomography (PET) systems (e.g., the High-Resolution Research Tomograph, HRRT) are unable to accurately and precisely measure pharmacologically-specific signals in small brain regions due to insufficient image resolution and sensitivity. The NeuroEXPLORER (NX), a new ultra-high-performance brain-dedicated scanner, promises to address these needs. Seven healthy individuals underwent paired scans on the HRRT and NX with targeted radiopharmaceuticals (¹⁸F-FDG; ¹⁸F-SynVesT-1; ¹⁸F-FPEB; ¹⁸F-Flubatine; ¹¹C-PHNO; ¹⁸F-FE-PE2I; ¹¹C-DASB). Early (0-10 min) and late standard uptake value (SUV) images were visually compared between scanners. The exceptional spatial resolution of the NX can be appreciated in the details of the cortical ribbon and subcortical nuclei (e.g., mediodorsal thalamus) for ¹⁸F-FDG (glucose metabolism), ¹⁸F-SynVesT-1 (synaptic density), ¹⁸F-FPEB (glutamate receptors mGluR5), which have high uptake across gray matter. Tracers with more focal uptake targeting the dopamine system (¹¹C-PHNO, ¹⁸F-FE-PE2I) displayed unprecedented anatomical detail (e.g., in the D₃ receptor-rich mammillo-thalamic tract and anteroventral thalamus). Similarly, ¹⁸F-Flubatine (β₂^* nicotinic acetylcholine receptors) displayed clear uptake in the brainstem (e.g., inferior olivary nuclei), and ¹¹C-DASB (serotonin transporters) markedly improved delineation of raphe nuclei in the brainstem and multiple cortical areas (e.g., temporal poles, subcallosal area). High-resolution early images of tracer delivery could be obtained from all tracers, especially those with high extraction. We compared measurements of tracer uptake between an ultra-high-performance brain-dedicated PET system (NX) and the previous state-of-the-art system (HRRT) in the same subjects for seven different tracers, demonstrating a substantial gain in image detail, especially for small brain structures. We also discussed the implications of this technology for basic and clinical brain PET research and potential healthcare applications. Not applicable.