1. A radiation therapy method comprising: performing a plurality of radiation treatment sessions on a subject, each radiation treatment session employing a parameterized radiation treatment plan having parameters with initial values of the parameters of the radiation treatment plan generated based on one or more planning images of the subject acquired prior to performing the plurality of radiation treatment sessions, at least some radiation treatment sessions including: acquiring one or more treatment images of the subject prior to performing the radiation treatment plan, registering the one or more treatment images with the one or more planning images using a voxel-based elastic function, adjusting the initial values of the parameters of the radiation treatment plan prior to performing the radiation treatment plan based on elastic deformation indicated by the voxel-based elastic function to produce adjusted radiation treatment plan parameter values, subsequent to the adjusting, storing the adjusted radiation treatment plan parameter values in a treatment plan parameters memory, and subsequent to the acquiring, registering, adjusting, and storing, performing the radiation treatment plan using the adjusted radiation treatment plan parameter values stored in the treatment plan parameters memory.