Author: Hao Gao, Xue Hong, Harold Li, Yuting Lin, Jufri Setianegara, Xin Tong, Chao Wang, Weijie Zhang, Ya-Nan Zhu 👨🔬
Affiliation: Department of Radiation Oncology, University of Kansas Medical Center 🌍
Purpose: Lattice radiotherapy (LATTICE) is a form of spatially fractionated radiation therapy (SFRT) designed to deliver high radiation doses to specific tumor regions (vertices) while sparing surrounding healthy tissues. Traditional LATTICE uses rigid vertex patterns, such as cubic or hexagonal grids, which limits adaptability for irregularly shaped tumors or those near critical organs, potentially causing unexpected hotspots or under-treatment. This study introduces a novel planning method with fully flexible vertex placement and joint optimization of vertex positions and dose distribution to improve precision and treatment quality.
Methods: The proposed method integrates vertex positioning with other treatment variables, such as proton spot weights or photon fluences, into a constrained optimization framework. Vertex positions are treated as variables subject to guidelines on spacing between centers and proximity to target boundaries. This allows dynamic adjustments of vertex placement to optimize dose distribution while maintaining treatment efficacy.
Results: Plans generated using the proposed method (NEW) were compared to conventional LATTICE plans. For each anatomical location (abdominal and lung cancer cases), 100 conventional LATTICE plans with varying vertex placements were created. From these, three plans were selected for comparison, termed BEST, MID, and WORST, corresponding to the smallest, median, and largest total optimization objective f, respectively. NEW plans demonstrated comparable or superior quality to conventional plans. For example, in photon LATTICE abdomen plans, f values were 1.92 (NEW), 2.79 (WORST), 2.27 (MID), and 1.96 (BEST), reflecting a 31.2% improvement from WORST to NEW. Similarly, the peak-to-valley dose ratio (PVDR) values were 5.88 (NEW), 3.00 (WORST), 4.33 (MID), and 5.16 (BEST), showing improvements of 96.0% from WORST to NEW.
Conclusion: This study introduces a novel LATTICE planning approach featuring fully flexible vertex positioning integrated with dose optimization. Compared to traditional LATTICE techniques, the proposed method enhances target PVDR while providing improved sparing of organs at risk.