NONLINEAR VISCOELASTIC MODELING OF BREAST TISSUE BY EMPLOYING NONLINEAR GENERALIZED STANDARD SOLID MODEL BASED ON EXPERIMENTAL DATA

The main purpose of the present study is to characterize the nonlinear viscoelastic behavior of breast tissue by employing nonlinear generalized standard solid model.For this aim, a uniaxial compression test is carried out clinically on 5 cases and an overall number of 47 points are examined from different regions of the breast. The output of the experiments is the mechanical compressive stress versus strain while the rate of loading is set to 1 mm/s. Relation between the experimental stress and strain can determine the tncchanical behavior of breast tissue. Therefore, the experimental data are fitted to the transfer function of the nonlinear generalized standard solid model and the related coefficients are obtained for every case. Fitness of the employed nonlinear model to the experimental data is evaluated by the match percentage and mean squared error (MSE). Match percentage values over 98% and MSE values less than 0.] indicates that this model can properly characterize the nonlinear time-dependent of the breast tissue. Moreover, results show that there is significant difference between the Inechanical stress in healthy breast regions and hIInor- included points as a sensible increase is perceived in the mechanical stress by the presence of a tumor. Consequently. this model can also be used for tumor detection in breast tissue.

Keywords:

viscoelasticity , breast tissue. Nonlinear generalized standard solid model , transfer function , tumor detection