A method and system may include a therapeutic agent having a radioactive source enclosed by a container. The container may be placed within a cavity of a medical device for treating animal tissue. The method and system allows a radioactive source to be manufactured in such a manner so as to control and spatially modulate the delivery of radiation doses to a treatment area of animal tissue, such as for tissue of humans. From the container, radiation doses and/or a radiation field are produced by the radiation source. The geometry and size of the radiation doses are controlled by the geometry of the container and the geometry of the radiation source as well as the type, number, and geometry of holes/slots in either the source material and/or a surface of the container.
