Multiscale Mechano-Biological Finite Element Modelling of Oncoplastic Breast Surgery—Numerical Study towards Surgical Planning and Cosmetic Outcome Prediction

Abstract

Surgical treatment for early-stage breast carcinoma primarily necessitates breast conserving therapy (BCT), where the tumour is removed while preserving the breast shape. To date, there have been very few attempts to develop accurate and efficient computational tools that could be used in the clinical environment for pre-operative planning and oncoplastic breast surgery assessment. Moreover, from the breast cancer research perspective, there has been very little effort to model complex mechano-biological processes involved in wound healing. We address this by providing an integrated numerical framework that can simulate the therapeutic effects of BCT over the extended period of treatment and recovery. A validated, three-dimensional, multiscale finite element procedure that simulates breast tissue deformations and physiological wound healing is presented. In the proposed methodology, a partitioned, continuum-based mathematical model for tissue recovery and angiogenesis, and breast tissue deformation is considered. The effectiveness and accuracy of the proposed numerical scheme is illustrated through patient-specific representative examples. Wound repair and contraction numerical analyses of real MRI-derived breast geometries are investigated, and the final predictions of the breast shape are validated against post-operative follow-up optical surface scans from four patients. Mean (standard deviation) breast surface distance errors in millimetres of 3.1 (±3.1), 3.2 (±2.4), 2.8 (±2.7) and 4.1 (±3.3) were obtained, demonstrating the ability of the surgical simulation tool to predict, pre-operatively, the outcome of BCT to clinically useful accuracy.

A Model to Predict Cosmetic Outcome after Breast Conservation Surgery

“…The first step was to create a Finite Element Model (FEM) of the breast, using the method described by Vavourakis et al [16]. Vavourakis' BCS simulator models the 3D post-surgical shape of the breast by coupling a physiological model of tissue recovery with a Mooney-Rivlin biomechanical model of pose estimation.…”

“…Vavourakis' model [16] simulates the wound healing process, by taking the volume excised during surgery as input data. This volume depends on the tumor position and size, and therefore, a virtual surgery has to occur in which all FE inside the volume to excise are re-labelled as damaged.…”

“…The breast volume was next meshed in Gmsh [19], by inserting uniformly distributed points inside the object, subsequently connecting them with tetrahedron elements. To complete the creation of the FEM, distinct boundary conditions and material properties were assigned to the surface mesh [16]. The Breast Imaging Reporting and Data System (BI-RADS) [20] was used for weighting the material property values.…”

“…However, each technique is usually designed for specialized applications: estimate pose transformation [5]- [10], model breast deformation [11] [12] [13] [14], predict the healing process of the breast after tumor removal [15] [16], among others. Vavourakis et al [16], proposed a 3D surgical simulator to predict a patient-specific outcome after BCS. This simulator relies on a coupled multiscale Finite Element (FE) numerical procedure to solve two mathematical models: a biochemical model for wound healing and angiogenesis, and a biomechanical model for soft tissues and pose estimation.…”

“…In this paper, we build on Vavourakis' [16] techniques to develop an algorithm that predicts BCS outcomes. This algorithm was tested on 135 women, and the results from the 3D prediction are compared against actual clinical outcomes at 3 and 12 months.…”