Analyzing spatial distribution between (18)F-fluorodeoxyglucose and (18)F-boronophenylalanine positron emission tomography to investigate selection indicators for boron neutron capture therapy

BACKGROUND: (18)F-FDG PET is often utilized to determine BNCT selection due to the limited availability of (18)F-BPA PET, which is performed by synthesizing (18)F into the boron drug used for BNCT, although the uptake mechanisms between those are different. Additionally, only a few non-spatial point parameters, such as maximum SUV (SUV(max)), have reported a correlation between those in previous studies. This study aimed to investigate the spatial accumulation pattern between those PET images in tumors, which would be expected to either show higher uptake on (18)F-BPA PET or be utilized in clinical, to verify whether (18)F-FDG PET could be used as a selection indicator for BNCT. METHODS: A total of 27 patients with 30 lesions (11 squamous cell carcinoma, 9 melanoma, and 10 rhabdomyosarcoma) who received (18)F-FDG and (18)F-BPA PET within 2 weeks were enrolled in this study. The ratio of metabolic tumor volumes (MTVs) to GTV, histogram indices (skewness/kurtosis), and the correlation of total lesion activity (TLA) and non-spatial point parameters (SUV(max), SUV(peak), SUV(min), maximum tumor-to-normal tissue ratio (T(max)/N), and T(min)/N) were evaluated. After local rigid registration between those images, distances of locations at SUV(max) and the center of mass with MTVs on each image and similarity indices were also assessed along its coordinate. RESULTS: In addition to SUV(max), SUV(peak), and T(max)/N, significant correlations were found in TLA. The mean distance in SUV(max) was [Formula: see text] and significantly longer than that in the center of mass with MTVs. The ratio of MTVs to GTV, skewness, and kurtosis were not significantly different. However, the similarities of MTVs were considerably low. The similarity indices of Dice similarity coefficient, Jaccard coefficient, and mean distance to agreement for MTV40 were [Formula: see text] , [Formula: see text] , and [Formula: see text] cm, respectively. Furthermore, it was worse in MTV50. In addition, spatial accumulation patterns varied in cancer types. CONCLUSIONS: Spatial accumulation patterns in tumors showed low similarity between (18)F-FDG and (18)F-BPA PET, although the various non-spatial point parameters were correlated. In addition, the spatial accumulation patterns were considerably different in cancer types. Therefore, the selection for BNCT using (18)F-FDG PET should be compared carefully with using (18)F-FBPA PET. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40658-022-00514-7.