1. A method of estimating an organ deformation model, the method comprising: generating at least one 3D organ shape model of an organ of a subject based on at least one non-real time medical image representing a deformation state of the organ of the subject; generating a deformation space for the organ of the subject based on the at least one 3D organ shape model and prior knowledge regarding the organ; and estimating a 3D organ deformation model of the organ of the subject based on a real-time medical image of the organ of the subject and the deformation space.