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

ANALYSIS OF THE EFFECT OF CONSIDERING GRAVITY IN X-RAY
MAMMOGRAPHY SIMULATION
M. Alajami 1 , J.A. Solves-Llorens 1 , F. Martínez-Martínez 1 , M.J. Rupérez 1 , C.
Monserrat 1 , V. Naranjo 1 , M. García 2 , E. Feliu 2 and M. Lloret 3
1. ABSTRACT
This work proves that prone gravity-loaded breast taken directly from a MRI (magnetic
resonance image) should not be used as an approximation of unloaded reference state
for X-ray mammography simulation. In this work, an approximation to the zero-strain
state of the breast is used for comparing the simulation of the breast compression during
an X-ray mammography in two cases, when gravity is considered and when it is not.
The committed error is measured for four different biomechanical models taken from
the literature and the simulation is performed for six patients. On the other hand, the
compression forces obtained for the used linear elastic, Neo-Hookean, and Mooney-
Rivlin models were unrealistic, whereas more realistic forces were obtained for the
polynomial model.
2. INTRODUCTION
Currently, the most common imaging modalities used to diagnose breast cancer is the
X-ray mammography, magnetic resonance imaging (MRI), and ultrasound. Each
imaging modality displays the information about the breast tissues differently.
Researchers have found that a combination of these imaging modalities leads to a more
effective diagnosis and management of the breast cancer [1]. Therefore, image
registration techniques have been developed for tracking and assessing a specific region
of the tissue across different views [2]. In most cases biomechanical models based on
the finite element methods (FEM) were chosen to register MRI with X-ray
mammograms [2-4] due to its accuracy. To register MRI to mammograms data, MRI is
used to build the model of the breast. The prone gravity-loaded deformed configuration
was commonly used as the reference state for the standing up configuration [2, 3].
However, during MR, the patient lies prone with the breasts hanging down under
gravity. Therefore, for more realistic simulations, stress-free state is needed to be the
reference state.
Few publications talk about this unloaded zero-strain configuration. Some groups have
solved an inverse elasticity problem to get the reference state [5, 6]. However, the
provided algorithms present a high computational cost. Rajagopal et al. [7, 8], identified
the reference state by acquiring MRIs of the breast under neutral buoyancy (immersed
in water). However, this is out of the clinical protocol. Pérez Del Palomar et al. [9]
1 Instituto Interuniversitario de Investigación en Bioingenieria y Tecnología Orientada al Ser Humano
(UPV) Universitat Politècnica de València, Spain.
2 Hospital Clínica Benidorm, Benidorm, Alicante, Spain.
3 Hospital Universitario y Politécnico La Fe, Valencia, Spain.