1. A system, comprising: a model to represent a volumetric deformation of a brain, stored in a memory, corresponding to brain tissue that has been displaced or shifted by at least one of disease, surgery or anatomical changes; and a fusion engine, executed by a processor, to employ the model to perform a coarse fusion to align a first three-dimensional image of a patient's brain with respect to a second three-dimensional image of the patient's brain after a region of the brain has been displaced or shifted, wherein the coarse function comprises: determining an initial volume of at least one selected anatomic region in the first three-dimensional image of the patient's brain and another volume of the at least one selected anatomic region in the second three-dimensional image of the patient's brain; computing shrinkage or growth factors from the first three-dimensional image of the patient's brain based on a difference between the initial volume and the another volume for the at least one selected anatomic region; generating a mapping between the first and second three-dimensional images of the patient's brain based on the computed shrinkage or growth factors and at least one volume parameter of the model to provide feedback that compensates for distortion between the first and second three-dimensional images of the patient's brain; and adjusting one or more points on a displacement vector of the model extending through the at least one selected anatomic region to compensate for spatial deformations that occur between the first and second image of the patient's brain based on the mapping.