1. A method of brachytherapy, the method comprising: positioning an applicator ( 100 ) into a target region ( 200 ), the applicator having a plurality of hollow channels ( 110 ); moving a tracking device ( 175 ) through at least a portion of the plurality of channels; obtaining a position of one or more of the plurality of channels based at least in part on the movement of the tracking device; localizing the position of the one or more of the plurality of channels in an image using position measurements from the tracking device; and generating a brachytherapy plan for administering a radiation dose based on the position of the one or more of the plurality of channels.