Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri.
Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri.
Int J Radiat Oncol Biol Phys. 2021 Jul 15;110(4):1200-1209. doi: 10.1016/j.ijrobp.2021.02.034. Epub 2021 Mar 2.
To comprehensively characterize dosimetric differences between calculations with a commercial model-based dose calculation algorithm (MBDCA) and the TG-43 formalism in application to accelerated partial breast irradiation (APBI) with the strut-adjusted volume implant (SAVI) applicator.
Dose for 100 patients treated with the SAVI applicator was recalculated with an MBDCA for comparison to dose calculated via TG-43. For every pair of dose calculations, dose-volume histogram (DVH) metrics including V90%, V95%, V100%, V150%, and V200% for the PTV_EVAL were compared. Features were defined for each case including (1) applicator size, (2) ratio between PTV_EVAL contour and 1-cm rind surrounding SAVI applicator, (3) ratio between dwell time in central catheter and total dwell time, and (4) mean computed tomography (CT) number within the lumpectomy cavity. Wilcoxon rank sum tests were performed to test whether treatment plans could be stratified according to feature values into groups with statistically significant dosimetry differences between MBDCA and TG-43.
For all DVH metrics, differences between TG-43 and MBDCA calculations were statistically significant (P < .05). Minimum (maximum) relative percent differences between the MBDCA and TG-43 for V90%, V95%, and V100% were -2.1% (0.1%), -3.1% (-0.1%), and -5.0% (-0.5%), respectively. The median relative percent difference in mean PTV_EVAL dose between the MBDCA and TG-43 was -3.9%, with minimum (maximum) difference of -6.5% (-1.8%). For V90%, V95%, and V100%, plan quality worsened beyond defined thresholds in 26, 23, and 31 cases with no instances of coverage improvement. Features 1, 2, and 4 were shown to be able to stratify treatment plans into groups with statistically significant differences in dosimetry metrics between MBDCA and TG-43.
Investigated dose metrics for SAVI treatments were found to be systematically lower with MBDCA calculation in comparison to TG-43. Plans could be stratified according to several features by the magnitude of dosimetric differences between these calculations.
全面描述应用于带有支撑调整体积植入物（SAVI）施源器的加速部分乳房照射（APBI）时，商业模型为基础的剂量计算算法（MBDCA）与 TG-43 形式之间的剂量差异。
对 100 名接受 SAVI 施源器治疗的患者的剂量进行重新计算，使用 MBDCA 进行比较，与通过 TG-43 计算的剂量进行比较。对于每一对剂量计算，比较包括 PTV_EVAL 的 V90%、V95%、V100%、V150%和 V200%在内的剂量-体积直方图（DVH）指标。为每个病例定义了特征，包括（1）施源器大小，（2）PTV_EVAL 轮廓与 SAVI 施源器周围 1cm 边缘的比例，（3）中央导管内驻留时间与总驻留时间的比例，以及（4）乳腺切除腔内的平均计算机断层扫描（CT）数。进行 Wilcoxon 秩和检验，以测试是否可以根据特征值将治疗计划分层为具有统计学显著差异的 MBDCA 和 TG-43 之间的组。
对于所有 DVH 指标，TG-43 和 MBDCA 计算之间的差异均具有统计学意义（P<0.05）。MBDCA 与 TG-43 之间 V90%、V95%和 V100%的最小（最大）相对百分比差异分别为-2.1%（0.1%）、-3.1%（-0.1%）和-5.0%（-0.5%）。MBDCA 与 TG-43 之间平均 PTV_EVAL 剂量的中位数相对百分比差异为-3.9%，最小（最大）差异为-6.5%（-1.8%）。对于 V90%、V95%和 V100%，在 26、23 和 31 例中，计划质量恶化超过定义的阈值，没有覆盖改善的实例。特征 1、2 和 4 能够根据这些计算之间的剂量学指标的统计学显著差异将治疗计划分层到不同的组中。
与 TG-43 相比，SAVI 治疗的研究剂量指标用 MBDCA 计算时系统地降低。可以根据这些计算之间的剂量差异的大小，根据几个特征对计划进行分层。
