An apparatus includes a scanner (102, 104) and a scanning motion monitor (100). A motion modeler (116) uses data from the scanning motion monitor (100) and the scanner (102, 104) to generate a motion model which describes motion of a region of interest of an object. A treatment planner (112) uses image data from the scanner (102, 104) to establish a treatment plan for the object. A treatment device 114, which operates in conjunction with a treatment motion monitor (108), uses the motion model to compensate for motion of the object during application of the treatment.