BACKGROUND

Permanent breast seed implant (PBSI) brachytherapy is a promising treatment that has the potential to be widely utilized with increased standardization, optimization, and robustness. Excellent early efficacy and very high patient acceptance were reported, however, to further evaluate and improve planning strategies, a framework to quantify plan robustness to implant uncertainties is necessary.

PURPOSE

In this study, we aim to quantify clinical seed displacement using an automated algorithm and develop and validate a PBSI post-implant dosimetry simulation framework to evaluate PBSI plan robustness to implant uncertainties.

METHODS AND MATERIALS

Clinical PBSI seed displacements were quantified for 63 consecutive patients. A PBSI simulator was developed in Matlab (2020) by resampling clinical seed displacements and computing a range of possible post-implant dosimetry outcomes under various seed displacement scenarios. Simulations were performed retrospectively on 63 previous clinical plans to evaluate plan robustness to seed displacement.

RESULTS

Mean seed displacement for the whole cohort was 10 ± 6 mm. A clinical seed displacement database was established and a user interface was developed for the simulation framework. For all clinical plans, the median (range) value of simulated median ETV V90 in various seed displacement scenarios was 97.8% (87.5–100%).

CONCLUSIONS

A PBSI postimplant dosimetry simulation framework was developed and validated. Simulation results showed that the current PTV planning margin is sufficient to provide adequate postimplant dose coverage of ETV. This simulator can be used to evaluate plan robustness to seed displacement and will facilitate future research in improving PBSI planning methods.

中文翻译：

---

用于永久性乳腺粒子植入近距离放射治疗稳健性评估的植入后剂量测定模拟框架

背景

永久性乳腺粒子植入（PBSI）近距离放射治疗是一种很有前途的治疗方法，随着标准化、优化和稳健性的提高，有可能得到广泛应用。据报道，早期疗效优异，患者接受度非常高，但是，为了进一步评估和改进计划策略，需要一个量化计划对植入不确定性的鲁棒性的框架。

目的

在本研究中，我们的目标是使用自动化算法量化临床种子位移，并开发和验证 PBSI 植入后剂量测定模拟框架，以评估 PBSI 计划对植入不确定性的稳健性。

方法和材料

对 63 名连续患者的临床 PBSI 粒子位移进行了量化。通过对临床种子位移进行重新采样并计算各种种子位移场景下一系列可能的植入后剂量测定结果，在 Matlab (2020) 中开发了 PBSI 模拟器。对 63 个之前的临床计划进行了回顾性模拟，以评估计划对种子位移的稳健性。

结果

整个队列的平均种子位移为 10 ± 6 毫米。建立了临床种子置换数据库，并为模拟框架开发了用户界面。对于所有临床计划，各种种子置换场景中模拟中位 ETV V90 的中位（范围）值为 97.8% (87.5–100%)。

结论

开发并验证了 PBSI 植入后剂量测定模拟框架。模拟结果表明，当前的 PTV 规划余量足以提供足够的 ETV 植入后剂量覆盖。该模拟器可用于评估计划对种子位移的鲁棒性，并将促进未来改进 PBSI 计划方法的研究。