An Anthropometric-Based Subject-Specific Finite Element Model of the Human Breast for Predicting Large Deformations.

Silvia Pianigiani,Bernardo Innocenti,Leonardo Ruggiero

doi:10.3389/fbioe.2015.00201

Abstract

The large deformation of the human breast threatens proper nodules tracking when the subject mammograms are used as pre-planning data for biopsy. However, techniques capable of accurately supporting the surgeons during biopsy are missing. Finite element (FE) models are at the basis of currently investigated methodologies to track nodules displacement. Nonetheless, the impact of breast material modeling on the mechanical response of its tissues (e.g., tumors) is not clear. This study proposes a subject-specific FE model of the breast, obtained by anthropometric measurements, to predict breast large deformation. A healthy breast subject-specific FE parametric model was developed and validated by Cranio-caudal (CC) and Medio-Lateral Oblique (MLO) mammograms. The model was successively modified, including nodules, and utilized to investigate the effect of nodules size, typology, and material modeling on nodules shift under the effect of CC, MLO, and gravity loads. Results show that a Mooney–Rivlin material model can estimate healthy breast large deformation. For a pathological breast, under CC compression, the nodules displacement is very close to zero when a linear elastic material model is used. Finally, when nodules are modeled, including tumor material properties, under CC, or MLO or gravity loads, nodules shift shows ~15% average relative difference.

Highlights

Predicting the mechanical behavior of soft biological tissues is essential for several bioengineering applications
For all performed dynamic explicit Finite element (FE) simulations, the ratio of the kinetic energy to the internal energy showed to be below 5%, quasi-static conditions are assumed due to the negligible influence of the dynamic effect (Han et al, 2012).Considering the healthy subject clinical condition, i.e., absence of nodules, the linear elastic modeling approach provides unrealistic deformation predictions, while the Mooney–Rivlin and neo-Hookean material models show to be able to estimate breast-plates compression with the same accuracy
The impact of nodules linear elastic vs. hyperelastic Mooney–Rivlin material modeling was evaluated tracking the displacement of the nodes within the nodules geometrical partitions

Summary

Introduction

Predicting the mechanical behavior of soft biological tissues is essential for several bioengineering applications. Estimation of the mechanical behavior of the human breast is fundamental to provide surgeons relevant information to be used in the operation theater. Determining the position shift of tumors during biopsy procedures would aid the surgeons to localize and remove cancerous tissues in a more effective way. The highly non-linear deformation, to which the breast tissue is subjected to, makes tumors localization, upon gravity or compression loads application, a challenging target (Pathmanathan et al, 2008). The surgeon must be capable of localizing, precisely and accurately, the tumor that is subjected to shifting its position whether the subject moves with respect to the operation theater coordinate reference system (i.e., absolute reference system). According to the clinical setting, the subject local coordinate reference system changes in function of standing, prone, and supine postures. Each subject postural configuration is strictly related to a specific clinical procedure

Methods

Results

Discussion

Conclusion