A method for coating a substrate with a radioisotope comprising is disclosed. The method comprises immersing the substrate within a solution containing a .gamma., .beta..sup.+, .alpha. or .beta..sup.- emitting radioisotope, then exposing the immersed substrate to tuned vibrational cavitation (i.e. ultrasonic) to produce a coated substrate, followed by baking the coated substrate at a temperature below the recrystallization temperature of the substrate. Following this step, the substrate is rinsed and dried. Substrates coated using the method of this invention exhibit very low rates of leaching of the coated radioisotope, and are suitable for use within medical applications.