Abstract: A system for providing therapeutic radiation to a predetermined tissue region within a body cavity of a living being utilizes an applicator arrangement which may, in a specific embodiment, comprise a pair of colpostats in conjunction with a tandem. The colpostats and tandem are formed of a material which is transparent to an imaging modality, such as CT scanning. Imaging-transparent source carriers containing dummy, or test, sources are placed in the colpostats. After the location of the colpostats, for example, has been determined, by imaging, the dummy source carriers are removed therefrom and replaced with selected source carriers containing actual radiation sources. The radiation source carriers further contain shielding which controls the strength and radiation pattern of the emitted radiation, all of which may be selected in response to the image.