PurposePatient‐specific quality assurance (PSQA) for vertebra stereotactic body radiation therapy (SBRT) presents challenges due to highly modulated small fields with high‐dose gradients between the target and spinal cord. This study aims to explore the use of the SRS MapCHECK® (SRSMC) for vertebra SBRT PSQA.MethodsTwenty vertebra SBRT treatment plans including prescriptions 20 Gy/1 fraction and 24 Gy/2 fractions were selected for each of Millennium (M)‐Multileaf Collimator (MLC), and high‐definition (HD)‐MLC. All 40 plans were measured using Gafchromic EBT3 film (film) and SRSMC, using the StereoPHAN phantom. Plan complexity was assessed using modulation complexity score (MCS), edge metric (EM) (mm−1), modulation factor (MU/cGy), and average leaf pair opening (ALPO) (mm) and its correlation with gamma‐pass rate was investigated. The high dose gradient between the target and the spinal cord was analyzed for film and SRSMC and compared against the treatment planning system (TPS). Applying the methodology proposed by AAPM TG‐218, action and tolerance values specific to the SRSMC for vertebra SBRT were determined for β values ranging from 5 to 8.ResultsFilm and SRSMC gamma‐pass rates showed no correlation (p > 0.05). A moderate negative correlation (R = ‐0.57, p = 0.01) is present between EM and SRSMC 3%/1 mm gamma‐pass rate for HD‐MLC plans. Both film and SRSMC accurately measured high dose gradients between the target and the spinal cord (R2 > 0.86, p ≤ 0.05). Notably, dose‐gradient of HD‐MLC plans is 22% steeper and has a smaller standard deviation to M‐MLC plans (p ≤ 0.05). Applying TG‐218, the film tolerance limit was 96% with action limit 95% for 5%/1 mm (β = 6) and for the SRSMC tolerance limit was 97% with an action limit of 96% for 4%/1 mm (β = 6).ConclusionOur findings suggest that universal TG‐218 limits may not be suitable for vertebra SBRT PSQA. This study demonstrates that SRSMC is a viable tool for vertebra SBRT PSQA, supported by TG‐218 implementation of process‐based tolerance and action limits.

中文翻译：

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使用高分辨率探测器阵列 SRS MapCHECK 对 Vertebra SBRT 进行有效的患者特异性 QA：AAPM TG-218 分析

目的椎体立体定向放射治疗 (SBRT) 的患者特异性质量保证 (PSQA) 由于目标和脊髓之间具有高剂量梯度的高度调制小射野而面临挑战。本研究旨在探索 SRS MapCHECK® (SRSMC) 在椎体 SBRT PSQA 中的应用。方法为每个 Millennium (M)-Multileaf 准直器选择 20 个椎体 SBRT 治疗计划，包括处方 20 Gy/1 分次和 24 Gy/2 分次（MLC）和高清（HD）-MLC。所有 40 个计划均使用 Gafchromic EBT3 胶片（胶片）和 SRSMC 以及 StereoPHAN 体模进行测量。使用调制复杂性得分 (MCS)、边缘度量 (EM) (mm−1)、调制因子 (MU/cGy) 和平均叶对开口 (ALPO) (mm) 及其与伽马通过率的相关性进行了研究。对胶片和 SRSMC 分析靶点和脊髓之间的高剂量梯度，并与治疗计划系统 (TPS) 进行比较。应用 AAPM TG-218 提出的方法，确定 SRSMC 对椎体 SBRT 的特定作用和耐受值，β 值范围为 5 至 8。结果胶片和 SRSMC 伽马通过率没有显示相关性（p> 0.05）。中度负相关（右= ‐0.57，p= 0.01) 存在于 HD-MLC 计划的 EM 和 SRSMC 3%/1 mm 伽马通过率之间。胶片和 SRSMC 都准确测量了目标和脊髓之间的高剂量梯度（右2> 0.86，p≤0.05）。值得注意的是，HD-MLC 计划的剂量梯度比 M-MLC 计划陡峭 22%，并且标准偏差更小（p≤0.05）。应用 TG-218，薄膜公差极限为 96%，作用极限为 95%，对于 5%/1 mm (β = 6)；对于 SRSMC，公差极限为 97%，作用极限为 96%，对于 4%/1 mm (β = 6)。结论我们的研究结果表明通用 TG-218 限制可能不适合椎骨 SBRT PSQA。这项研究表明，SRSMC 是椎骨 SBRT PSQA 的可行工具，并得到 TG-218 基于过程的耐受性和动作限制实施的支持。