伽玛刀放射外科的等中心与扇区时长联合优化（ISDO）

文献信息

中文摘要

背景： 当前的伽玛刀（GK）治疗计划算法通常使用几何启发式方法而非剂量驱动优化来确定等中心位置。等中心要么自动放置（使用质心、基于骨架或基于曲率的算法），要么由计划者手动放置，随后在固定等中心位置下进行单独的扇区时长优化（SDO）。由于等中心选择与剂量学优化是分离的，SDO步骤常受次优等中心配置的约束，限制了可实现的计划质量，并导致不必要的长束流开启时间（BOT）。
方法： 我们引入了一个等中心与扇区时长联合优化框架（ISDO），用剂量驱动的等中心与扇区时长联合优化替代启发式等中心放置。该框架包括用于等中心选择的L_{2,1/2}组稀疏模型，以及用于交付效率的显式BOT正则化。所选等中心通过SDO模块进一步细化，随后经过后处理阶段，将优化后的扇区-准直器模式转换为可交付的射束配置。该框架使用12例GK病例进行评估，涵盖多种临床适应证，包括动静脉畸形、前庭神经鞘瘤、脑膜瘤和垂体腺瘤。
结果： 在计划质量相似或更好的情况下，ISDO计划使用更少或相等的射束数，并显著减少了BOT。在所有病例中，ISDO将射束数减少了15.06%，BOT减少了20.77%。在靶区覆盖相似的情况下，选择性和Paddick适形指数分别增加了5.77%和5.82%，R50和D2cm分别减少了6.45%和5.23%。危及器官（OAR）的最大剂量和平均剂量也分别减少了16.0%和28.8%。
结论： 通过将等中心选择直接纳入BOT感知的逆向计划框架，并通过L_{2,1/2}组稀疏项驱动等中心选择，所提出的ISDO方法比当前临床GK治疗计划方法实现了更高效、更适形的GK计划。

英文摘要

Current Gamma Knife (GK) treatment planning algorithms typically determine isocenter locations using geometric heuristics rather than dose-driven optimization. Isocenters are either placed automatically (using center-of-mass, skeleton-based, or curvature-based algorithms) or manually by planners, followed by a separate sector duration optimization (SDO) with fixed isocenter locations. Since the isocenter selection is separate from the dosimetry optimization, the SDO step is often constrained by a suboptimal isocenter configuration, limiting achievable plan quality and leading to unnecessarily long beam-on time (BOT).
Approach. We introduce an integrated isocenter and sector duration optimization framework (ISDO) that replaces heuristic isocenter placement with a dose-driven joint isocenter and sector duration optimization. The framework includes an L_{2,1/2\ } group-sparsity model for isocenter selection and an explicit BOT regularization for delivery efficiency. The selected isocenters are further refined through an SDO module, followed by a post-processing stage that converts the optimized sector-collimator patterns into deliverable shot configuration. The framework was evaluated using 12 GK cases spanning a variety of clinical indications, including arteriovenous malformation, vestibular schwannoma, meningioma, and pituitary adenoma.
Main results. With similar or better plan quality, ISDO plans used fewer or equal shots and substantially reduced the BOT. Across all cases, ISDO reduced the number of shots by 15.06% and BOT by 20.77%. With similar target coverage, the selectivity and Paddick conformity index increased by 5.77% and 5.82%, and R50 and D2cm decreased by 6.45% and 5.23%. The maximum and mean doses of organs-at-risk (OARs) were also reduced by 16.0% and 28.8% respectively.
Significance. By incorporating isocenter selection directly into the BOT-aware inverse-planning framework and driving the isocenter selection through an L_{2,1/2\ } group sparsity term, the proposed ISDO method achieved more efficient and conformal GK plans than current clinical GK treatment planning approaches.
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