IRIDIUM IR-192 is a radioactive isotope of iridium. It can be used in brachytherapy to treat tumors by selectively delivering a cytotoxic dose of radiation to the tumor site. IRIDIUM IR-192 implants are also used. They are produced in wire form and are introduced through a catheter to the target area.

Iodide I-131 (as Sodium iodide I-131) is a radioisotopic drug used for the treatment and palliation of thyroid malignancy. Iodine-131 is notable for causing mutation and death in cells that it penetrates, which is due to its mode of beta decay. Iodide I-131 can be detected by gamma cameras for diagnostic imaging, however, it is rarely administered for diagnostic purposes only, imaging will normally be done following a therapeutic dose. Major uses of 131I include the treatment of thyrotoxicosis (hyperthyroidism) due to Graves' disease, and sometimes hyperactive thyroid nodules (abnormally active thyroid tissue that is not malignant). Iodine-131, in higher doses than for thyrotoxicosis, is used for ablation of remnant thyroid tissue following a complete thyroidectomy to treat thyroid cancer. The 131I isotope is also used as a radioactive label for certain radiopharmaceuticals that can be used for therapy, e.g. 131I-metaiodobenzylguanidine for imaging and treating pheochromocytoma and neuroblastoma. Because of the carcinogenicity of its beta radiation in the thyroid in small doses, I-131 is rarely used primarily or solely for diagnosis. Instead, the more purely gamma-emitting radioiodine iodine-123 is used in diagnostic testing. The longer half-lived iodine-125 is also occasionally used when a longer half-life radioiodine is needed for diagnosis, and in brachytherapy treatment, where the low-energy gamma radiation without a beta component makes iodine-125 useful.

Carbon C-14 is an unstable, radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Radiocarbon dating is a radiometric dating method that uses (14C) to determine the age of carbonaceous materials up to about 60,000 years old. One of the frequent uses of the technique is to date organic remains from archaeological sites. Carbon-14 can be used as a radioactive tracer in medicine. In the initial variant of the urea breath test, a diagnostic test for Helicobacter pylori, urea labeled with approximately 37 kBq (1.0 μCi) carbon-14 is fed to a patient (i.e., 37,000 decays per second). In the event of a H. pylori infection, the bacterial urease enzyme breaks down the urea into ammonia and radioactively-labeled carbon dioxide, which can be detected by low-level counting of the patient's breath. The 14C urea breath test has been largely replaced by the 13C urea breath test, which has no radiation issues.