ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

For all these models, C1 = µ/2, µ is the initial shear modulus of the material, C10,
C01, C20, C11, C02 are material constants characterizing the deviatoric
deformations, d, d1, d2 are incompressibility parameters, I1, I2 are the first and
the second deviatoric strain invariants respectively, and J is determinant of the
deformation gradient.
Regarding the skin, a polynomial form obtained from [9] was used for all the
hyperelastic models with the following parameters: C10=31, C01=30, C11=22.5, C20=50
and C02=60 Pa. The density of skin, fat, and glandular tissues was taken from [9, 11],
and it was 1000, 920 and 1040 Kg/m3, respectively.
The following two cases (Fig. 1) were used to simulation CC mammography of six
patients referred to as P1-P6, with age ranged from of from 37 to 77:
Case A: The prone configuration (breast position when MRI is performed) was used as
the reference state for patient standing up position (breast position when mammography
is performed); the gravity force is ignored in this case.
Case B: From the prone configuration, the zero-strain state was calculated, and used as
a reference state for patient standing up position; the gravity force is applied in this case.
Figure1. Steps for the X-ray mammography simulation.
To study the effect of gravity, the breast of the six patients were scanned on a 1.5T
Philips ACHIEVE, with TR = 5000 ms, TE = 120 ms, flip angle = 90 °, matrix size =
448x512, and slice thickness = 2 mm . The resulting scan images were segmented into
three tissues: skin, fat, and glandular tissue. The segmented DICOM was used to
generate the volume of the breast by using the commercial package Simpleware 4.2.
The filters used to get more realistic 3D image data were Gaussian smoothing, cavity
fill and Island removal filter. After getting the 3D image data of the breast, Simpleware
was used again to mesh the volume. The fat and glandular tissues were meshed with
tetrahedral elements, while the skin was meshed with a triangular shell of 3 mm of