MRI and 18F-BPA PET-guided targeting in boron neutron capture therapy
Cairong Hu, You-Qun Lai, Ye Cao, Jian-Ji Pan, Yuan-Hao Liu, Yi-Chiao Teng, Xiaobin Xia
Abstract
In modern Boron neutron capture therapy (BNCT) treatment planning, 18 F-BPA ( 18 F-boronophenylalanine) PET (positron emission tomography) imaging is used to assess boron uptake and guide accurate dose delivery. This study evaluates the geometric and dosimetric differences between target volumes defined by MRI (magnetic resonance imaging) and PET images in accelerator-based BNCT using the NeuPex system. The GTV (gross tumor volume) was defined based on MRI (GTV MRI ) and PET images with SUV thresholds of 2.0 (GTV PET2.0 ) and 2.5 (GTV PET2.5 ) in patients with head-and-neck cancer (HNC) and malignant glioma (MG). GTV PET2.5 was approximately 50% smaller, while GTV PET2.0 showed closer volumetric agreement, with ∆V% of 23.52 ± 17.44 (HNC) and 28.71 ± 12.57 (MG), and corresponding Dice similarity coefficients of 0.71 ± 0.14 and 0.86 ± 0.17. Dosimetric analysis revealed that GTV PET2.0 achieved higher dose coverage than GTV MRI , with mean doses of 24.07 ± 6.42 Gy-Eq (HNC) and 26.36 ± 9.77 Gy-Eq (MG), and D 80 values of 19.01 ± 6.90 Gy-Eq and 21.00 ± 7.51 Gy-Eq, respectively. Tumor-to-blood ratio (TBR) and tumor-to-normal ratio (TNR) analyses further indicated substantial heterogeneity in boron uptake, with mean TBR and TNR of 2.71 ± 0.53 and 2.97 ± 0.79 for GTV PET2.0. These results suggest that GTV PET2.0 provides a balanced and biologically relevant target for BNCT planning. A TBR threshold of ≥ 2.0 is proposed as a practical criterion for patient selection. While this study focuses on geometric and dosimetric endpoints, future work correlating these findings with clinical outcomes is warranted. Overall, this study supports the integration of functional PET imaging with anatomical MRI to improve the precision and efficacy of BNCT treatment planning.