1. A magnetic resonance (MR) guided radiotherapy device, comprising: a bore-type magnet configured to generate a static magnetic field in an examination region, the magnet being configured with a magnet radiation translucent region which allows radiation beams to travel radially through the bore-type magnet into a subject disposed therein; a split-type gradient coil defining a gap including a gradient coil radiation translucent region aligned to the magnet radiation translucent region, the split-type coil being configured to apply selected magnetic field gradient pulses across the imaging region; a radiofrequency (RF) coil configured to induce and manipulate magnetic resonance in a subject in the examination region and/or acquire magnetic resonance data from the examination region; a radiation source disposed laterally to the bore-type magnet, the radiation source being positioned to transmit the radiation beams through the magnet and gradient coil radiation translucent regions to an isocenter of the bore-type magnet; a scanner controller configured to control the gradient coil and RF coil to generate an image representation; and a processor configured to: acquire a pre-treatment representation of a target volume and at least one non-target volume; determine physical contours and positions of the target and non-target volumes based on image processing techniques and/or models that describe at least one of the volumes separate from the pre-treatment representation and based on the pre-treatment representation; administer a treatment of a plurality of radiation doses, each of the radiation doses include a plurality of radiation beam trajectories and at least one radiation beam geometry; acquire at least one treatment image representation of the target volume and the at least one non-target volume, wherein the processor is configured to acquire the treatment image representation after at least one of the plurality of radiation doses; determine physical contours and positions of the target and non-target volumes based on image processing techniques and/or models that describe at least one of the volumes separate from the treatment representation and based on the treatment representation; and determine an actual radiation dose delivered to each region of the target and non-target volumes based on changes between the determined physical contours and positions of the target and non-target volumes from the pre-treatment representation and the determined physical contours and positions of the target and non-target volumes from the treatment image representations, the radiation beam trajectories, and the at least one radiation beam geometry.