Breast-conserving surgery is the most acceptable operation for breast cancer removal from an invasive and psychological point of view. Before the surgical procedure, a preoperative MRI is performed in the prone configuration, while the surgery is achieved in the supine position. This leads to a considerable movement of the breast, including the tumor, between the two poses, complicating the surgeon's task. In this work, a simulation pipeline allowing the computation of patient-specific geometry and the prediction of personalized breast material properties was put forward. Through image segmentation, a finite element model including the subject-specific geometry is established. By first computing an undeformed state of the breast, the geometrico-material model is calibrated by surface acquisition in the intra-operative stance. Using an elastic corotational formulation, the patient-specific mechanical properties of the breast and skin were identified to obtain the best estimates of the supine configuration. The final results are a Mean Absolute Error of 4.00mm for the mechanical parameters E_breast = 0.32 kPa and E_skin = 22.72 kPa, congruent with the current state-of-the-art. The Covariance Matrix Adaptation Evolution Strategy optimizer converges on average between 5 to 30 min depending on the initial parameters, reaching a simulation speed of 20s. To our knowledge, our model offers one of the best compromises between accuracy and speed. Satisfactory results were obtained for the estimation of breast deformation from preoperative to intra-operative configuration. Furthermore, we have demonstrated the clinical feasibility of such applications using a simulation framework that aims at the smallest disturbance of the actual surgical pipeline.

翻译：保乳手术从创伤和心理角度看是乳腺癌切除中最可接受的手术方式。术前需在俯卧位进行磁共振成像，而手术则在仰卧位完成。这导致乳房（包括肿瘤）在两种体位间发生显著位移，增加了外科医生的操作难度。本研究提出了一种仿真管道，可实现患者特异性几何结构的计算及个性化乳房材料属性的预测。通过图像分割建立包含个体特异性几何结构的有限元模型，首先计算乳房的未变形状态，再通过术中姿态的表面采集对几何-材料模型进行标定。采用弹性共旋公式，识别患者特异性乳房和皮肤力学参数以获得仰卧位构型的最优估计。最终结果为：力学参数E_breast = 0.32 kPa、E_skin = 22.72 kPa对应的平均绝对误差为4.00毫米，与当前最新技术水平一致。协方差矩阵自适应进化策略优化器根据初始参数不同，平均收敛时间为5至30分钟，仿真速度达20秒。据我们所知，本模型在精度与速度之间实现了最佳平衡之一。从术前到术中构型的乳房变形估计取得了满意结果。此外，我们通过旨在最小化实际手术管道干扰的仿真框架，验证了此类应用的临床可行性。