1. A method for hierarchical registration of a blood vessel model to blood vessel image data, the method comprising: (a) mapping a vascular model for a subject to a target vascular image for the subject using a global rigid transformation; (b) hierarchically mapping individual vessel branches in the model using piecewise rigid transformations to form a piecewise-rigid-transformed vascular model; and (c) hierarchically mapping individual vessel branches in the piecewise-rigid-transformed vascular model to the target image using piecewise deformable transformations to form a piecewise-deformably-transformed vascular model.