Radioactive Implants

Overview :

Interstitial radiation therapy places the sources of radiation directly into the tumor and surrounding tissue. Most commonly used in tumors of the head, neck, prostate, and breast, it also may be used in combination with external radiation therapy. The implant may be permanent or removable. A permanent implant of radioactive seeds, such as gold or iodine, is placed directly into the organ. Over several weeks or months, the seeds slowly deliver radiation to the tumor. More commonly used is the removable implant that requires an operation under general anesthesia to place narrow, hollow stainless steel needles through the tumor. Teflon tubes are inserted through the needles, and the needles are then removed. After the patient returns to his or her room, radioactive seeds are inserted into the tubes in a procedure called afterloading. Once the desired dosage is reached, the tubes and seeds are removed.

The planning and procedures used for treatment with radioactive implants is becoming increasingly accurate and sophisticated as technology develops. Special imaging tools and computer software help physicians and radiation therapists visualize implant placements. Further, improved radiologic imaging techniques help physicians track the progress of this and other cancer therapies.

Intracavity radiation often is used for gynecologic cancers. Under general or spinal anesthesia, hollow applicators are placed directly inside the affected organ. Correct positioning is confirmed by × rays, and once the patient has returned to his or her room, a small plastic tube containing the radioactive isotope is inserted into the hollow applicator. The treatment is delivered over 48-72 hours, after which time the applicator and radioactive sources are removed. Very high doses of radiation can be delivered to the tumor, while the rapid removal of the radioactive dose limits damage to the surrounding structures.