A real-time applicator position monitoring system (RAPS) measures brachytherapy applicator displacement in real-time by computing the relative displacement between two infrared reflective targets, one attached to the applicator and the other to the patients skin. In an aspect, RAPS can be used with any brachytherapy application. RAPS measures the applicator motion during HDR brachytherapy treatment, as well as during the transfer of the patient from the imaging room (e.g., where the CT and MR scanners are located) to the HDR BT operating/treatment room.
