Small nuclei identification with a hemispherical brain PET

Abstract

Background To confirm the performance of the first hemispherical positron emission tomography (PET) for the brain (Vrain) that we developed to visualise the small nuclei in the deep brain area, we compared 18F-fluorodeoxyglucose (FDG) brain images with whole-body PET images. Methods Ten healthy male volunteers (aged 22–45 years) underwent a representative clinical whole-body PET, followed by Vrain each for 10 min. These two scans were initiated 30 min and 45 min after FDG injection (4.1 ± 0.5 MBq/kg), respectively. First, we visually identified the small nuclei and then compared their standardised uptake values (SUVs) with the participants’ age. Next, the SUVs of each brain region, which were determined by applying a volume-of-interest template for anatomically normalised PET images, were compared between the brain images with the Vrain and those with the whole-body PET images. Results Small nuclei, such as the inferior colliculus, red nucleus, and substantia nigra, were more clearly visualised in Vrain than in whole-body PET. The anterior nucleus and dorsomedial nucleus in the thalamus and raphe nucleus in the brainstem were identified in Vrain but not in whole-body PET. The SUVs of the inferior colliculus and dentate gyrus in the cerebellum positively correlated with age (Spearman’s correlation coefficient r = 0.811, p = 0.004; r = 0.738, p = 0.015, respectively). The SUVs of Vrain were slightly higher in the mesial temporal and medial parietal lobes than those in whole-body PET. Conclusions This was the first time that the raphe nuclei, anterior nuclei, and dorsomedial nuclei were successfully visualised using the first hemispherical brain PET. Trial registration Japan Registry of Clinical Trials, jRCTs032210086, Registered 13 May 2021, https://jrct.niph.go.jp/latest-detail/jRCTs032210086.

A conformal TOF–DOI Prism‐PET prototype scanner for high‐resolution quantitative neuroimaging

“…26 Besides HRRT, hemispherical brain PET (Vrain) also has high spatial resolution and improves visualization of small nuclei such as the raphe nucleus. 27 However, they did not evaluate the visualization capability of the LC regions which are < 3 mm in size.…”

“…In another recent serotonergic system study using HRRT, small brain regions such as the raphe nuclei (RN) were excluded from any quantitative analysis due to PVE caused by a combination of limited spatial resolution and sensitivity 26 . Besides HRRT, hemispherical brain PET (Vrain) also has high spatial resolution and improves visualization of small nuclei such as the raphe nucleus 27 . However, they did not evaluate the visualization capability of the LC regions which are < 3 mm in size.…”

Visualization of small brain nuclei with a high-spatial resolution, clinically available whole-body PET scanner

“…It has been considered that conventional WB PET scanners are inadequate to evaluate small brain structures, including brainstem nuclei, because of their relatively poor spatial resolution. Indeed, several reports have described PET-tracer uptake in the brainstem nuclei using head-dedicated PET scanners [ 12 , 13 , 16 ]. For example, Takahashi et al described that FDG uptake in small brainstem nuclei such as the IC, RN, and MRN were more clearly detected by a brain-dedicated PET system with a hemispherical shape than by WB PET [ 12 ].…”

“…Indeed, several reports have described PET-tracer uptake in the brainstem nuclei using head-dedicated PET scanners [ 12 , 13 , 16 ]. For example, Takahashi et al described that FDG uptake in small brainstem nuclei such as the IC, RN, and MRN were more clearly detected by a brain-dedicated PET system with a hemispherical shape than by WB PET [ 12 ]. Thus, to the best of our knowledge, the present study is the first to clarify the utility of WB SiPM-PET with application of dedicated OSEM with TOF and PSF reconstruction to detect physiological FDG uptake in and around the brainstem (including ION, DN, MRN, IC, MB, RN, STN, LGN, MGN, and SC) with reference to the anatomical locations on 3D-MRI.…”

“…A PET scanner developed with a silicon photomultiplier (SiPM) and time-of-flight (TOF) capability [ 5 , 6 ] in combination with full 3D image reconstruction with resolution modeling (point-spread function [PSF] reconstruction) enables generation of high-resolution images [ 7 – 11 ]. Recent articles have indicated that 18 F-fluorodeoxyglucose ( 18 F-FDG) uptake in the small structures of the brain can be visualized using state-of-the-art, brain-dedicated SiPM-PET scanners [ 12 – 15 ] that outperform previous-generation brain-dedicated PET scanners, in terms of both spatial resolution and detection sensitivity [ 16 , 17 ]. In our previous study, we compared the partial volume correction (PVC) performance of PSF reconstruction with MR-based PVC performance for measurements of FDG uptake in the cerebral cortex [ 11 ].…”