Evaluation of elastic parameters for breast compression using a MRI-mammography registration approach

Patient-specific finite element (FE) models of the breast have received increasing attention due to the potential capability of fusing information from different image modalities. During the Magnetic Resonance Imaging (MRI) to X-ray mammography (MG) registration procedure, a FE model is compressed mimicking the mammographic acquisition. To develop an accurate model of the breast, the elastic properties and stress-strain relationship of breast tissues need to be properly defined. Several studies (in vivo and ex vivo experiments) have proposed a range of values associated to the mechanical properties of different tissues. This work analyse the elastic parameters (Young Modulus and Poisson ratio) obtained during the process of registering MRI to X-ray MG images. Position, orientation, elastic parameters and amount of compression are optimised using a simulated annealing algorithm, until the biomechanical model reaches a suitable position with respect to the corresponding mammogram. FE models obtained from 29 patients, 46 MRI-MG studies, were used to extract the optimal elastic parameters for breast compression. The optimal Young modulus obtained in the entire dataset correspond to 4.46 ± 1.81 kP a for adipose and 16.32 ± 8.36 kP a for glandular tissue, while the average Poisson ratio was 0.0492 ± 0.004. Furthermore, we did not find a correlation between the elastic parameters and other patient-specific factors such as breast density or patient age.