评估在常规和 SBRT 环境中基于直线加速器的患者特定交付 QA 中更严格的伽马标准建议。
Evaluating suggested stricter gamma criteria for linac-based patient-specific delivery QA in the conventional and SBRT environments.
机构信息
Fox Chase Cancer Center, Department of Radiation Oncology, 333 Cottman Avenue, Philadelphia, PA 19111, United States.
Fox Chase Cancer Center, Department of Radiation Oncology, 333 Cottman Avenue, Philadelphia, PA 19111, United States.
出版信息
Phys Med. 2022 Aug;100:72-80. doi: 10.1016/j.ejmp.2022.06.005. Epub 2022 Jun 24.
PURPOSE
To evaluate AAPM TG-218 recommended tolerances for IMRT QA for conventional and SBRT delivery.
METHODS
QA analysis was repeated for 150 IMRT/VMAT patients with varying gamma criteria. True composite delivery was utilized, corrected for detector and output variation. Universal tolerance (TL) and action limits (AL) were compared with statistical process control (SPC) TL and AL values. Analysis was repeated as a function of plan complexity for 250 non-stereotactic body radiotherapy (SBRT) VMAT patients at 3%/2mm and a threshold of 10% and for 75 SBRT VMAT patients at 2%/2 mm and a threshold of 50% with results plotted as a function of PTV volume. Regions of failure were dose-scaled on the planning CT data sets based on delivery results.
RESULTS
The IMRT/VMAT TL and AL for gamma criteria of 3%/3 mm were 96.5% and 95.6% and for 3%/2 mm were 91.2% and 89.2%, respectively. Correlation with plan complexity for conventional fractionation VMAT was "low" for all sites with pelvis having the highest r value at -0.35. The equivalent SBRT PTV diameter ranged from 2.0 cm to 5.6 cm. Negative low correlation was found for 38 of 75 VMAT cases below AL.
CONCLUSIONS
The AL and AL are similar for 3%/2 mm. However, our 5% failure rate for AL, may result in treatment start delays approximately 2 times/month, given 40 new cases/month. VMAT QA failure at stricter criteria did not correlate strongly with plan complexity. Site-specific action limits vary less than 3% from the average. SBRT QA results do not strongly correlate with target size over the range studied.
目的
评估 AAPM TG-218 推荐的常规和 SBRT 调强放疗（IMRT）QA 容差。
方法
对 150 名接受不同伽玛标准的 IMRT/VMAT 患者进行 QA 分析。采用真正的复合传递方式，对探测器和输出变化进行校正。将通用容差（TL）和行动限（AL）与统计过程控制（SPC）TL 和 AL 值进行比较。对 250 例非立体定向体部放疗（SBRT）VMAT 患者（3%/2mm 和阈值为 10%）和 75 例 SBRT VMAT 患者（2%/2mm 和阈值为 50%）的计划复杂性进行了分析，结果作为 PTV 体积的函数进行绘制。失败区域根据传递结果在计划 CT 数据集上进行剂量缩放。
结果
IMRT/VMAT 的 TL 和 AL 伽玛标准分别为 3%/3mm 时为 96.5%和 95.6%，3%/2mm 时为 91.2%和 89.2%。对于常规分割 VMAT，所有部位的相关性均为“低”，骨盆的 r 值最高，为-0.35。等效 SBRT PTV 直径范围为 2.0cm 至 5.6cm。在低于 AL 的 75 例 VMAT 病例中，有 38 例发现负低度相关。
结论
AL 和 AL 对于 3%/2mm 相似。然而，我们的 AL 失败率为 5%，这可能导致每月约有 2 次治疗延迟，因为每月有 40 例新病例。在更严格的标准下，VMAT QA 失败与计划复杂性相关性不强。特定部位的行动限比平均值变化不到 3%。在所研究的范围内，SBRT QA 结果与靶标大小相关性不强。
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