FEMOSSA: Patient-specific finite element simulation of the prostate-rectum spacer placement, a predictive model for prostate cancer radiotherapy
FEMOSSA: Patient-specific finite element simulation of the prostate-rectum spacer placement, a predictive model for prostate cancer radiotherapy
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DOI：
10.1002/mp.14990
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发表时间：
2021-06-11
期刊：
影响因子：
3.8
通讯作者：
Ding, Kai
中科院分区：
文献类型：
--
作者：
Hooshangnejad, Hamed;Youssefian, Sina;Ding, Kai
目的近年来，放射治疗系统的重大进展使放射治疗（RT）成为治疗前列腺癌的一种更有效的方法。尽管如此，邻近的器官在危险（OAR）可以严重限制RT的好处。直肠-前列腺间隙中的直肠间隔器植入物在前列腺和直肠之间提供了足够的间隔，因此，有机会将潜在剂量递增至靶点并降低OAR剂量。预处理模拟的间隔器放置可以提供潜在的决策支持，以减少风险，提高疗效的间隔器放置procedure.Methods一种新的有限元法为导向的间隔器模拟算法，FEMOSSA，在这项研究中开发。我们使用有限元（FE）方法来建模和预测直肠和前列腺壁的变形，源于水凝胶注射。本研究纳入了10例前列腺癌患者，这些患者在RT治疗前接受了水凝胶植入。我们使用注射前器官轮廓来创建FE模型，并使用注射后间隔器位置来估计虚拟间隔器的分布。分配了每例患者解剖结构的特定材料属性和边界条件。然后进行有限元分析，以确定感兴趣区域（ROI）的位移矢量，并通过比较虚拟模拟轮廓与真实的注射后轮廓来验证结果。为了评估我们的方法的性能的不同方面，我们使用了三种不同的品质因数：骰子相似性系数（DSC），最近邻距离（NND）和重叠体积直方图（OVH）。最后，为了证明一个潜在的剂量测定应用FEMOSSA，预测直肠剂量虚拟间隔放置后进行了比较，对预测注射后直肠dose.Results我们的模拟显示了一个现实的变形感兴趣区。后模拟（虚拟间隔器）在前列腺和直肠壁之间创建了与注射后间隔器相同的间隔。前列腺和直肠的平均DSC分别为0.87和0.74。直肠轮廓相似系数显著增加（P < 0.01）。模拟后和注射后NND的直方图显示出相同的整体形状，并且从较低值到较高值有明显的变化，表明前列腺和直肠之间的距离增加。平均值和第5百分位数NND之间的平均差异小于2.2 mm和2.1 mm。OVH距离和相应的预测直肠剂量之间的差异是，平均小于1 mm和1.5戈伊，respectively.Conclusions FEMOSSA提供了一个逼真的模拟水凝胶注射过程，可以方便间隔放置规划和减少相关的不确定性。因此，它增加了间隔物放置过程的鲁棒性和成功率，进而提高了前列腺癌RT质量。
Purpose Major advances in delivery systems in recent years have turned radiotherapy (RT) into a more effective way to manage prostate cancer. Still, adjacency of organs at risk (OARs) can severely limit RT benefits. Rectal spacer implant in recto-prostatic space provides sufficient separation between prostate and rectum, and therefore, the opportunity for potential dose escalation to the target and reduction of OAR dose. Pretreatment simulation of spacer placement can potentially provide decision support to reduce the risks and increase the efficacy of the spacer placement procedure.Methods A novel finite element method-oriented spacer simulation algorithm, FEMOSSA, was developed in this study. We used the finite element (FE) method to model and predict the deformation of rectum and prostate wall, stemming from hydrogel injection. Ten cases of prostate cancer, which undergone hydrogel placement before the RT treatment, were included in this study. We used the pre-injection organ contours to create the FE model and post-injection spacer location to estimate the distribution of the virtual spacer. Material properties and boundary conditions specific to each patient's anatomy were assigned. The FE analysis was then performed to determine the displacement vectors of regions of interest (ROIs), and the results were validated by comparing the virtually simulated contours with the real post-injection contours. To evaluate the different aspects of our method's performance, we used three different figures of merit: dice similarity coefficient (DSC), nearest neighbor distance (NND), and overlapped volume histogram (OVH). Finally, to demonstrate a potential dosimetric application of FEMOSSA, the predicted rectal dose after virtual spacer placement was compared against the predicted post-injection rectal dose.Results Our simulation showed a realistic deformation of ROIs. The post-simulation (virtual spacer) created the same separation between prostate and rectal wall, as post-injection spacer. The average DSCs for prostate and rectum were 0.87 and 0.74, respectively. Moreover, there was a statistically significant increase in rectal contour similarity coefficient (P < 0.01). Histogram of NNDs showed the same overall shape and a noticeable shift from lower to higher values for both post-simulation and post-injection, indicative of the increase in distance between prostate and rectum. There was less than 2.2- and 2.1-mm averaged difference between the mean and fifth percentile NNDs. The difference between the OVH distances and the corresponding predicted rectal dose was, on average, less than 1 mm and 1.5 Gy, respectively.Conclusions FEMOSSA provides a realistic simulation of the hydrogel injection process that can facilitate spacer placement planning and reduce the associated uncertainties. Consequently, it increases the robustness and success rate of spacer placement procedure that in turn improves prostate cancer RT quality.