When reducing radiation dose to healthy tissue near a target volume, a 4D motion model (52) of a target volume is generated during CT scan data acquisition. The target volume is tracked, and tracked target volume position information (43) is provided to a motion estimation tool (48). Motion parameter information (60) output from the motion estimation tool is linked to motion phases of the target volume indicated by CT scan data. A dynamic planned target volume (PTV) (64) that covers the target volume in each motion phase is generated and linked to tracked motion parameters for each respective motion phase. A radiation dose is delivered to the PTV for each motion phase using the linked motion parameters and real-time tracking information.
