The invention provides a method for locating radioactive material implanted in a living body, the method having the steps of implanting a stent into the body, the stent containing the radioactive material; imaging the body to determine a first position of the stent relative to remote points on the body; determining a second position of the stent at a second time later than the time of the implanting step; and measuring the distance between said first position and said second position. Also provided is a system for determining movement of a radiation source implanted in a living body, the device having a radiographic film overlaying a region of the body so as to oppose the radiation source, whereby the film is positioned relative to a reference point on the body; a grid disposed between the film and the body; and a radio-opaque substrate overlaying the film.