Purpose

Low-dose-rate permanent-seed (LDR-PS) brachytherapy has shown a great potential for treating breast cancer. An implantation scheme indicating the template pose and needle trajectories is determined before the operation. However, when performing the pre-planned scheme intraoperatively, a change of the patient’s posture will cause seed placements away from the desired locations. Hence, the implantation scheme should update based on the current patient’s posture.

Methods

A numerical method of optimizing the implantation scheme for the LDR-PS breast brachytherapy is presented here. The proposed algorithm determines the fewest needle trajectories and template poses for delivering the seeds to the intraoperative desired locations. The clinical demand, such as the minimum distance between the chest wall and the needle, is considered in the optimization process.

Results

The method was simulated for a given LDR-PS brachytherapy procedure to evaluate the optimal scheme as the number of the template poses changing. The optimization parameters of the needles’ number and the implantation errors are used to adjust the algorithm outcome. The results show that the implantation schemes obtained by our method have a satisfactory accuracy in the cases of 2 or 3 template poses. The computation time is about 76s to 150s according to the number of the template poses from 1 to 3.

Conclusion

The proposed method can find the optimal implantation scheme corresponding to the current desired seed locations immediately once there is a change of patient’s posture. This work can be applied to the robot-assisted LDR-PS breast brachytherapy for improving the operation accuracy and efficiency.

中文翻译：

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近距离放射治疗中种子植入计划的术中优化

目的

低剂量率永久种子（LDR-PS）近距离放射疗法已显示出治疗乳腺癌的巨大潜力。在手术之前确定指示模板姿势和针轨迹的植入方案。但是，在术中执行预先计划的方案时，患者姿势的改变将导致种子放置远离所需位置。因此，植入方案应基于当前患者的姿势进行更新。

方法

本文介绍了一种优化LDR-PS乳房近距离放射疗法植入方案的数值方法。提出的算法确定了用于将种子输送到术中所需位置的最少针头轨迹和模板姿势。在优化过程中会考虑临床需求，例如胸壁和针头之间的最小距离。

结果

对于给定的LDR-PS近距离放射治疗程序，对该方法进行了仿真，以评估随着模板姿势数量变化而优化的方案。针数和植入误差的优化参数用于调整算法结果。结果表明，通过我们的方法获得的植入方案在2个或3个模板姿势的情况下具有令人满意的精度。根据模板姿势的数量（从1到3），计算时间约为76s至150s。

结论

一旦患者的姿势发生变化，所提出的方法可以立即找到与当前所需种子位置相对应的最佳植入方案。这项工作可以应用于机器人辅助的LDR-PS乳房近距离放射治疗，以提高手术的准确性和效率。