Realistic and fast simulation of anatomical deformations due to ultrasound probe pressure is of outstanding importance for testing and validation of autonomous robotic ultrasound systems. We propose a deformation model which relies on the position-based dynamics (PBD) approach to simulate the probetissue interaction and predict the displacement of internal targets during US acquisition. Performances of the patient-specific PBD anatomical model are evaluated in comparison to two different simulations relying on the traditional finite element (FE) method, in the context of breast ultrasound scanning. Localization error obtained when applying the PBD model remains below 11 mm for all the tumors even for input displacements in the order of 30 mm. The proposed method is able to achieve a better trade-off among accuracy, computation time and generalization capabilities with respect to the two FE models. Position-based dynamics approach has proved to be successful in modeling breast tissue deformations during US acquisition. It represents a valid alternative to classical FE methods for simulating the interaction between US probe and tissues
