1. A computer-implemented method of modelling an organ, the method comprising: obtaining a 3D shape model, corresponding to a patient, comprising a 3D blood vessel structure of the organ; obtaining an influence of a 3D blood vessel tree indicating the 3D blood vessel structure on a deformation of the 3D shape model, wherein the 3D shape model is compartmentalized into areas based on the influence; receiving a 2D image, corresponding to the patient, of the organ; extracting a 2D blood vessel structure from the 2D image; deforming the 3D blood vessel tree based on the 2D blood vessel structure; and generating a 3D patient-specified shape model fit to the 2D image by deforming the 3D shape model based on the deformed 3D blood vessel tree, the influence and the areas.