Department of Radiotherapy, Anshan Cancer Hospital, Anshan, Liaoning, China.
Department of Oncology Ward 2, Hebei General Hospital, Shijiazhuang, Hebei, China.
J Appl Clin Med Phys. 2021 Jun;22(6):60-70. doi: 10.1002/acm2.13287. Epub 2021 May 24.
To investigate the dose-effect of Auto Flash Margin (AFM) on breast cancer's superficial tissues based on the Treatment Planning System (TPS) in the breast-conserving radiotherapy plan.
A total of 16 breast-conserving patients with early stage breast cancer were selected, using the X-ray Voxel Monte Carlo (XVMC) algorithm. Then, every included case plan was designed using a 2 cm-AFM (the value of AFM is 2 cm) and N-AFM (without AFM). Under the condition of ensuring the same configuration of #MU and collimator, the absorbed dose after a simulated inspiratory motion was calculated again using the new plan center, which moved backward to the linac source. The dose difference between the measurement points between AFM and N-AFM groups was compared.
In the dose results, PTV of the AFM group was superior to that of the N-AFM group, PTV , PTV , Lung_Ipsi , Lung_Ipsi , and Body . Also, the dose results of the N-AFM group were significantly higher than those of the AFM group. However, there was no significant difference between Lung_Contra , Heart , and Breast_Contra in the two groups. In the collimator alignments at the same angle between groups, the AFM group formed an apparent air region outside the collimator compared with the N-AFM group. In the XVMC algorithm feature parameter, the AFM group had less #MU, higher QE, and slightly longer optimization time. The #segments of both groups were close to the 240 control points preset by the plan. The validation results of EBT3 film in both groups were more significant than 95%, meeting the clinical plan's application requirements. The difference in film results between groups was mainly reflected in the dose distribution at the near-source. 4DCT was used to summarize the maximum and minimum inspiratory motion distances of 7.31 ± 0.45 and 3.42 ± 0.91 mm respectively.
These results suggest that the AFM function application could significantly reduce the possibility of insufficient tumor target caused by inspiratory motion and ensure sufficient tumor target exposure.
基于乳腺保乳放疗计划的治疗计划系统（TPS），研究自动闪光边界（AFM）对乳腺癌浅表组织的剂量效应。
选择了 16 例早期乳腺癌的保乳患者，采用 X 射线体素蒙特卡罗（XVMC）算法。然后，对每一个纳入的病例计划，使用 2cm-AFM（AFM 值为 2cm）和 N-AFM（无 AFM）进行设计。在保证相同的 MU 和准直器配置的情况下，用新的计划中心（向后移动到直线加速器源）再次计算模拟吸气运动后的吸收剂量。比较 AFM 和 N-AFM 两组之间测量点的剂量差异。
在剂量结果中，AFM 组的 PTV 优于 N-AFM 组，PTV、PTV、Lung_Ipsi、Lung_Ipsi 和 Body。此外，N-AFM 组的剂量结果明显高于 AFM 组。然而，两组之间的 Lung_Contra、Heart 和 Breast_Contra 没有显著差异。在两组相同角度的准直器对准情况下，与 N-AFM 组相比，AFM 组在准直器外部形成了明显的空气区域。在 XVMC 算法特征参数中，AFM 组的 MU 较少，QE 较高，优化时间略长。两组的#segments 都接近计划预设的 240 个控制点。两组的 EBT3 胶片验证结果均大于 95%，符合临床计划的应用要求。两组胶片结果的差异主要反映在近源处的剂量分布。4DCT 用于总结 7.31±0.45mm 和 3.42±0.91mm 的最大和最小吸气运动距离。
这些结果表明，AFM 功能的应用可以显著降低吸气运动引起的肿瘤靶区不足的可能性，确保肿瘤靶区充分暴露。
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