A method of determining a treatment parameter, includes determining an accumulated dose at a target region that undergoes motion, determining an accumulated dose at a critical region, and determining the treatment parameter based on the determined accumulated dose at the target region and the determined accumulated dose at the critical region, wherein the act of determining the treatment parameter is performed during a treatment session. A method of determining a treatment parameter, includes tracking a position of a target, delivering radiation to the target based on the tracked position, and compensating for an inaccuracy of the tracked position by using information regarding a delivered dose to determine a treatment parameter for a next beam delivery.