the disclosure is directed to catheter devices and methods for controlled application of irradiation to tissue adjacent a body site , such as cavity after removal of tissue , e . g . cancer . the catheter device includes an inflatable balloon having at least two layers . the inflatable balloon has an expansion of more than 25 % and less than 200 % when inflated from the un - inflated condition to a turgid condition , preferably more than 50 % and less than 150 %. in the turgid condition the polymeric material of the balloon layers are at or near the elastic limit of the balloon layer material . the balloon may contain or be formed of or be coated with radiopaque material to facilitate positional or symmetry verification .