University of Michigan, Department of Radiation Oncology, Ann Arbor, Michigan.
Michigan Healthcare Professionals Radiation Oncology Institute/GenesisCare USA, Farmington Hills, Michigan.
Pract Radiat Oncol. 2022 Jul-Aug;12(4):e317-e328. doi: 10.1016/j.prro.2022.01.013. Epub 2022 Feb 24.
To assess the accuracy of dose calculations in the near-surface region for different treatment planning systems (TPSs), treatment techniques, and energies to improve clinical decisions for patients receiving whole breast irradiation (WBI).
A portable custom breast phantom was designed for dose measurements in the near-surface regions. Treatment plans of varying complexities were created at 8 institutions using 4 different TPSs on an anonymized patient data set (50 Gy in 25 fractions) and peer reviewed by participants. The plans were recalculated on the phantom data set. The phantom was aligned with predetermined shifts and laser marks or cone beam computed tomography, and the irradiation was performed using a variety of linear accelerators at the participating institutions. Dose was measured with radiochromic film placed at 0.5 and 1.0 cm depth and 3 locations per depth within the phantom. The film was scanned and analyzed >24 hours postirradiation.
The percentage difference between the mean of the measured and calculated dose across the participating centers was -0.2 % ± 2.9%, with 95% of measurements within 6% agreement. No significant differences were found between the mean of the calculated and measured dose for all TPSs, treatment techniques, and energies at all depths and laterality investigated. Furthermore, no significant differences were observed between the mean of measured dose and the prescription dose of 2 Gy per fraction.
These results demonstrate that dose calculations for clinically relevant WBI plans are accurate to within 6% of measurements in the near-surface region for various complexities, TPSs, linear accelerators, and beam energies. This work lays the necessary foundation for future studies investigating the correlation between near-surface dose and acute skin toxicities.
评估不同治疗计划系统（TPS）、治疗技术和能量在近表面区域的剂量计算准确性，以改善接受全乳放疗（WBI）患者的临床决策。
设计了一种便携式定制乳房体模，用于近表面区域的剂量测量。在匿名患者数据集（25 次分割 50Gy）上，4 个不同的 TPS 在 8 个机构中创建了不同复杂程度的治疗计划，并由参与者进行同行评审。这些计划在体模数据集上重新计算。将体模与预定的偏移量和激光标记或锥形束 CT 对齐，并在参与机构中使用各种直线加速器进行照射。在体模内的 3 个深度位置，在 0.5cm 和 1.0cm 深度处放置放射色膜以测量剂量。在照射后 >24 小时，使用扫描仪对胶片进行扫描和分析。
在参与中心之间，测量和计算剂量的平均值之间的百分比差异为-0.2%±2.9%，95%的测量值在 6%的一致性范围内。在所有研究的深度和侧别上，所有 TPS、治疗技术和能量的计算剂量与测量剂量的平均值之间没有显著差异。此外，测量剂量的平均值与 2Gy 每分次的处方剂量之间没有显著差异。
这些结果表明，对于各种复杂程度、TPS、直线加速器和束能的临床相关 WBI 计划，在近表面区域的剂量计算准确到测量值的 6%以内。这项工作为未来研究近表面剂量与急性皮肤毒性之间的相关性奠定了必要的基础。
