3205 - Feasibility Study of Multi-B-Value DWI Functional MRI-Based Biologically-Guided Lattice Radiotherapy
Presenter(s)
R. Zhang1, T. Dai2, and Y. Yin2; 1Department of Graduate,Shandong First Medical University & Shandong Academy of Medical Sciences, jinan, Shandong, China, 2Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China
Purpose/Objective(s): Lattice radiotherapy (LRT) improves tumor control via spatially fractionated high-dose boosting, but conventional geometric-based LRT ignores tumor biological heterogeneity. Multi-b-value diffusion-weighted imaging (DWI) enables noninvasive identification of radioresistant subvolumes characterized by low apparent diffusion coefficient (ADC) and altered intravoxel incoherent motion (IVIM). We aimed to evaluate the technical, dosimetric, and clinical feasibility of multi-b-value DWI functional MRI-guided biologically-guided lattice radiotherapy (BG-LRT) for bulky solid tumors.
Materials/Methods: Twenty patients with bulky solid tumors (=5 cm) underwent 3.0T multi-b-value DWI (b=0,100,400,800,1200 s/mm²) for ADC and IVIM parametric mapping. Radioresistant subvolumes were defined as low-ADC/hypoperfusion regions. Lattice boost vertices were automatically registered to biological targets, and VMAT plans were generated. Endpoints included registration accuracy, dosimetric quality, workflow efficiency, acute toxicity, and early tumor response. Conventional LRT plans were created for comparison.
Results: Biologically defined subvolumes were successfully identified in all patients. Mean target registration error was 1.2±0.3 mm. BG-LRT achieved significantly higher biological target coverage (98.2±1.1% vs. 91.5±2.3%, P<0.001) and superior conformity index (0.82±0.04 vs. 0.75±0.05, P<0.01) compared with conventional LRT, with comparable PTV coverage and normal tissue sparing. Total workflow time was =4 hours. No =Grade 3 acute toxicities were observed. Early objective response rate was 75%.
Conclusion: Multi-b-value DWI-based BG-LRT is technically feasible, dosimetrically robust, and clinically safe. This strategy enables precise biological targeting of radioresistant subvolumes within bulky tumors and supports efficient clinical implementation. Functional MRI-guided lattice radiotherapy represents a promising paradigm for personalized, biologically adaptive radiation therapy.