Knill Cory, Loughery Brian, Sandhu Raminder
Department of Radiation Oncology, Corewell Health William Beaumont University Hospital, Royal Oak, Michigan 48073, USA.
Med Dosim. 2023;48(3):176-180. doi: 10.1016/j.meddos.2023.03.006. Epub 2023 Apr 22.
The stereotactic treatment of single cranial targets using noncoplanar volumetric modulated arc therapy (VMAT) allows for effective dose delivery to the target, while sparing normal brain tissue. In this study, the dosimetric effect of adding dynamic jaw tracking and automatic collimator angle selection in the optimization of single target cranial VMAT plans was investigated. Twenty-two cranial targets, previously treated with VMAT without dynamic jaw tracking and automatic collimator angle optimization (CAO) were chosen for replanning. Target volumes ranged from 0.441cc to 25.863cc with doses between 18Gy and 30Gy delivered in 1 to 5 fractions. Original plans were reoptimized with automatic CAO, keeping all other objectives the same (CAO plans). Next, original plans were reoptimized with both dynamic jaw tracking and CAO (DJT plans). Original, CAO, and DJT target doses were compared using the Paddick gradient index (GI) and the Paddick inverse conformity index (ICI), while normal tissue dose was compared using the volume of the normal brain receiving 5Gy, 10Gy, and 12Gy. The normal tissue volume was normalized to target size to allow cross comparison between plans. A one-sided t-test was performed to determine whether the changes in the plan metrics were statistically significant. CAO plans had improved GIs compared to the originals (p = 0.03) with insignificant changes in other plan metrics (p > 0.20). The addition of dynamic jaw tracking in DJT plans greatly improved ICIs and normal brain metrics (p < 0.01) compared to the CAO plans with minor improvement in ICIs (p = 0.07). The combined effect of adding dynamic jaw tracking and collimator optimization led to improvements in all metrics of the DJT plans when compared to the original (p < 0.02). The addition of dynamic jaw tracking and CAO led to improvements in both target and normal tissue dose metrics for single-target noncoplanar cranial VMAT plans.
使用非共面容积调强弧形治疗（VMAT）对单个颅脑靶点进行立体定向治疗，可在保护正常脑组织的同时，有效地将剂量传递至靶点。在本研究中，我们调查了在优化单个靶点颅脑VMAT计划时添加动态准直器跟踪和自动准直器角度选择的剂量学效果。选择22个先前接受过未采用动态准直器跟踪和自动准直器角度优化（CAO）的VMAT治疗的颅脑靶点进行重新计划。靶体积范围为0.441立方厘米至25.863立方厘米，剂量在18Gy至30Gy之间，分1至5次给予。原始计划采用自动CAO重新优化，保持所有其他目标不变（CAO计划）。接下来，原始计划同时采用动态准直器跟踪和CAO进行重新优化（DJT计划）。使用帕迪克梯度指数（GI）和帕迪克逆适形指数（ICI）比较原始、CAO和DJT靶区剂量，同时使用接受5Gy、10Gy和12Gy照射的正常脑组织体积比较正常组织剂量。将正常组织体积归一化至靶区大小，以便在不同计划之间进行交叉比较。进行单侧t检验以确定计划指标的变化是否具有统计学意义。与原始计划相比，CAO计划的GI有所改善（p = 0.03），而其他计划指标变化不显著（p > 0.20）。与CAO计划相比，DJT计划中添加动态准直器跟踪极大地改善了ICI和正常脑指标（p < 0.01），ICI略有改善（p = 0.07）。与原始计划相比，添加动态准直器跟踪和准直器优化的联合效果使DJT计划的所有指标均得到改善（p < 0.02）。添加动态准直器跟踪和CAO可改善单靶点非共面颅脑VMAT计划的靶区和正常组织剂量指标。
