The Balloon Immobilization Device for Radiation Treatment of the present invention includes a catheter assembly with radiopaque markers and one or more lumina. The catheter assembly consists of a flexible tube and inflatable balloon. The flexible tube has distal and proximal ends, with one or more separate lumina within and along the length of the flexible tube. At least one lumen is in fluid communication with the exterior of the flexible tube at the distal end and the interior of the inflatable balloon and at least one lumen in fluid communication with the exterior of the flexible tube at the distal end and the exterior of the flexible tube at the proximal end. The inflatable balloon varies in shape and size and is made of a radiopaque material having varying degrees of radiopacity. Radiopaque markers are located at different locations on the balloon and flexible tube.
