that move the jaws 215 may be able to move the jaws 215 quickly enough to adjust the width of the high energy fan beam 100 the movement of the jaws may be actuated by a controller that receives information relating to the shape and location of the treatment region further the controller may include a processor for actuating the movement of the jaws 215 further while the jaws 215 are shown as spatially independent from the collimator 220 it is also possible that the jaws 215 may be connected to the collimator or the patient so that it moves with the patient as well jaws that provide for a varying width of the high energy fan beam may also be used in systems where the collimator is not fixed to the patient for example the collimator may be fixed and stationary and the high energy fan beam is moved relative to the collimator also in another embodiment the collimator may be attached to a collimator control apparatus that may move the collimator in any direction relative to the high energy fan beam in this embodiment the collimator may be in unison with the subject or may move relative to the subject in any of these embodiments the jaws 225 may be placed anywhere along the path of the high energy fan beam in order to conform the width of the high energy fan beam to.