  Background: Mammography is a specific type of breast imaging that uses
low-dose X-rays to detect cancer in early stage. During the exam, the women
breast is compressed between two plates in order to even out the breast
thickness and to spread out the soft tissues. This technique improves exam
quality but can be uncomfortable for the patient. The perceived discomfort can
be assessed by the means of a breast biomechanical model. Alternative breast
compression techniques may be computationally investigated trough finite
elements simulations.Methods: The aim of this work is to develop and evaluate a
new biomechanical Finite Element (FE) breast model. The complex breast anatomy
is considered including adipose and glandular tissues, muscle, skin, suspensory
ligaments and pectoral fascias. Material hyper-elasticity is modeled using the
Neo-Hookean material models. The stress-free breast geometry and
subject-specific constitutive models are derived using tissues deformations
measurements from MR images.Findings: The breast geometry in three breast
configurations were computed using the breast stress-free geometry together
with the estimated set of equivalent Young's modulus (Ebreast_r=0.3 kPa,
Ebreast_l=0.2 kPa, Eskin=4 kPa, Efascia=120 kPa). The Hausdorff distance
between estimated and measured breast geometries for prone, supine and supine
tilted configurations is equal to 2.17 mm, 1.72mm and 5.90mm
respectively.Interpretation: A subject-specific breast model allows a better
characterization of breast mechanics. However, the model presents some
limitations when estimating the supine tilted breast configuration. The results
show clearly the difficulties to characterize soft tissues mechanics at large
strain ranges with Neo-Hookean material models.
