An adaptive therapy delivery system can receive imaging information including a volumetric image comprising a target such as a tumor or one or more other structures, and can receive imaging information corresponding to one or more imaging slices comprising different portions of the target, such as imaging slices acquired at different times after acquisition of the volumetric image. The system can spatially register information from an earlier-acquired image with a portion of the target included in a later-acquired one of the imaging slices. The system can then determine an updated location of the target indicated by the spatially-registered information. Using the updated location, the system can generate an updated therapy protocol to control delivery of a therapy beam.