implant /im″plant, implant″/ [L, implantare, to set into] , 1. (in radiotherapy) an encapsulated radioactive substance embedded in tissue for therapy. Seeds containing iodine-125 may be implanted permanently in prostate and chest tumors, and seeds of iridium-192 in ribbons or wire may be embedded temporarily in head and neck cancers. Sealed sources of cesium-137 or radium-226 may be implanted in the body cavity temporarily in the treatment of gynecological malignancies; strontium-90 in sealed sources may be embedded for a brief period (usually less than 2 minutes) in the treatment of eye tumors; needles containing radium-226 may be used as temporary interstitial implants. Patients with radioactive implants are isolated from other patients whenever possible. 2. (in surgery) material inserted or grafted into an organ or structure of the body. The implant may be of tissue, such as in a blood vessel graft, or of an artificial substance, such as in a hip prosthesis, a cardiac pacemaker, or a container of radioactive material.
