1. A method of dynamically tracking one or more targets within an anatomical region and delivering therapeutic radiation to the targets, while the anatomical region undergoes a periodic motion characterized by a motion cycle P, the anatomical region including one or more reference structures, the method comprising: monitoring the periodic motion to measure the cycle P; determining in real time the locations, within the moving anatomical region, of the targets relative to the reference structure; and delivering radiation treatment in real time to the targets, as the anatomical region undergoes the periodic motion.