Department of Physics and Atmospheric Science, Dalhousie University, Canada.
Department of Radiation Oncology, Dalhousie University, Canada.
Phys Med Biol. 2023 Jul 21;68(15). doi: 10.1088/1361-6560/ace23f.
. Non-coplanar arc geometry optimizations that take advantage of beam's eye view (BEV) geometric overlap information have been proven to reduce dose to healthy organs-at-risk (OARs). Recently, a metric called mean arc distance (MAD) has been developed that quantifies the arc geometry sampling of 4space. The purpose of this research is to combine improved BEV overlap information with MAD to generate static couch lung stereotactic body radiotherapy (SBRT) treatment plans deliverable on a C-arm linear accelerator.. An algorithm utilizing the Moller-Trumbore ray-triangle intersection method was employed to compute a cost surrogate for dose to overlapping OARs using distances interpolated onto a PDD. Cost was combined with MAD for 100 000 random combinations of arc trajectories. A pathfinding algorithm for arc selection was created, balancing the contributions of MAD and 4cost for the final trajectory. This methodology was evaluated for 18 lung SBRT patients. Cases were also planned with arcs from a clinical treatment template protocol for dosimetric and plan quality comparison. Results were evaluated using dose constraints in the context of RTOG0915.. Five of six OARs had maximum dose reductions when planned with the arc trajectory optimization algorithm. Significant maximum dose reductions were found for esophagus (7.41 ± 0.91 Gy,= 0.00019), trachea (5.56 ± 1.55 Gy,= 0.0025), spinal cord (2.87 ± 1.13 Gy,= 0.039), large bronchus (3.47 ± 1.49 Gy,= 0.0075), and aorta (3.13 ± 0.99 Gy,= 0.012). Mean dose to contralateral lung was also significantly reduced (0.50 ± 0.06 Gy,= 0.00019). There were two significant increases in OAR doses: mean dose to ipsilateral lung (0.40 ± 0.09,= 0.00086) and V5to ipsilateral lung (1.95 ± 0.70%,= 0.011). Paddick conformity index increased by 0.03 ± 0.02 (= 0.14), remaining below a limit of 1.2 for both techniques.. Static couch non-coplanar optimization yielded maximum dose reductions to OARs while maintaining target conformity for lung SBRT.
. 利用视线（BEV）几何重叠信息的非共面弧几何优化已被证明可以降低健康器官-风险（OAR）的剂量。最近，开发了一种称为平均弧距（MAD）的度量标准，用于量化 4 空间的弧几何采样。本研究的目的是结合改进的 BEV 重叠信息和 MAD 生成可在 C 臂直线加速器上交付的静态胸廓立体定向体部放疗（SBRT）治疗计划。. 利用 Moller-Trumbore 射线-三角形相交方法的算法，通过在 PDD 上插值距离来计算重叠 OAR 剂量的成本替代物。成本与 MAD 相结合，用于 100000 个随机的弧轨迹组合。创建了一种用于弧选择的寻路算法，为最终轨迹平衡 MAD 和 4cost 的贡献。该方法在 18 例肺部 SBRT 患者中进行了评估。还使用临床治疗模板协议中的弧来规划病例，以进行剂量学和计划质量比较。结果在 RTOG0915 的背景下使用剂量限制进行了评估。当使用弧轨迹优化算法规划时，五个 OAR 中有六个达到了最大剂量降低。食道（7.41±0.91Gy，=0.00019）、气管（5.56±1.55Gy，=0.0025）、脊髓（2.87±1.13Gy，=0.039）、大支气管（3.47±1.49Gy，=0.0075）和主动脉（3.13±0.99Gy，=0.012）的最大剂量显著降低。对侧肺的平均剂量也显著降低（0.50±0.06Gy，=0.00019）。有两个 OAR 剂量显著增加：同侧肺的平均剂量（0.40±0.09，=0.00086）和同侧肺的 V5（1.95±0.70%，=0.011）。Paddick 适形指数增加了 0.03±0.02（=0.14），两种技术的适形指数均保持在 1.2 以下。. 静态胸廓非共面优化在保持肺 SBRT 靶标适形性的同时，降低了 OAR 的最大剂量。
