Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA.
J Appl Clin Med Phys. 2021 Apr;22(4):82-91. doi: 10.1002/acm2.13216. Epub 2021 Mar 5.
To validate an MR-compatible version of the ScandiDos Delta Phantom+ on a 0.35T MR guided linear accelerator (MR-Linac) system and to determine the effect of plan complexity on the measurement results.
METHODS/MATERIALS: 36 clinical treatment plans originally delivered on a 0.35T MR linac system were re-planned on the Delta Phantom+ MR geometry following our clinical quality assurance (QA) protocol. The QA plans were then measured using the Delta Phantom+ MR and the global gamma pass rates were compared to previous results measured using a Sun Nuclear ArcCHECK-MR. Both 3%/3mm and 2%/2mm global gamma pass rates with a 20% dose threshold were recorded and compared. Plan complexity was quantified for each clinical plan investigated using 24 different plan metrics and each metric's correlation with the overall 2%/2mm global gamma pass rate was investigated using Pearson correlation coefficients.
Both systems demonstrated comparable levels of gamma pass rates at both the 3%/3mm and 2%/2mm level for all plan complexity metrics. Nine plan metrics including area, number of active MLCs, perimeter, edge metric, leaf segment variability, complete irradiation area outline, irregularity, leaf travel index, and unique opening index were moderately (|r| > 0.5) correlated with the Delta 2%/2mm global gamma pass rates whereas those same metrics had weak correlation with the ArcCHECK-MR pass rates. Only the perimeter to area ratio and small aperture score (20 mm) metrics showed moderate correlation with the ArcCHECK-MR gamma pass rates.
The MR-compatible version of the ScandiDos Delta Phantom+ MR has been validated for clinical use on a 0.35T MR-Linac with results being comparable to an ArcCHECK-MR system in use clinically for almost five years. Most plan complexity metrics did not correlate with lower 2%/2mm gamma pass rates using the ArcCHECK-MR but several metrics were found to be moderately correlated with lower 2%/2mm global gamma pass rates for the Delta Phantom+ MR.
在 0.35T 磁共振引导线性加速器（MR-Linac）系统上验证 ScandiDos Delta Phantom+ 的 MR 兼容版本，并确定计划复杂性对测量结果的影响。
方法/材料：根据我们的临床质量保证（QA）协议，对最初在 0.35T MR 直线加速器系统上交付的 36 个临床治疗计划进行重新规划，然后在 Delta Phantom+MR 几何形状上对 QA 计划进行测量，并将全局伽马通过率与之前使用 Sun Nuclear ArcCHECK-MR 测量的结果进行比较。记录并比较了 20%剂量阈值下的 3%/3mm 和 2%/2mm 全局伽马通过率。使用 24 种不同的计划指标对每个临床计划进行量化，并使用 Pearson 相关系数研究每个指标与整体 2%/2mm 全局伽马通过率之间的相关性。
两种系统在所有计划复杂性指标下，在 3%/3mm 和 2%/2mm 水平上均表现出可比的伽马通过率。包括面积、活跃的多叶准直器数量、周长、边缘指标、叶片段变异性、完全照射区域轮廓、不规则性、叶片行程指数和独特开口指数在内的 9 个计划指标与 Delta 2%/2mm 全局伽马通过率中度相关（|r|>0.5），而这些相同的指标与 ArcCHECK-MR 通过率弱相关。只有周长与面积比和小孔径评分（20mm）指标与 ArcCHECK-MR 伽马通过率中度相关。
ScandiDos Delta Phantom+MR 的 MR 兼容版本已在 0.35T MR-Linac 上验证可用于临床，其结果与临床上使用近五年的 ArcCHECK-MR 系统相当。使用 ArcCHECK-MR 时，大多数计划复杂性指标与较低的 2%/2mm 伽马通过率不相关，但发现几个指标与 Delta Phantom+MR 的较低的 2%/2mm 全局伽马通过率中度相关。
