Yttrium is a soft, silvery metal. Yttrium is often used as an additive in alloys. It increases the strength of aluminium and magnesium alloys. It is also used in the making of microwave filters for radar and has been used as a catalyst in ethene polymerisation. Yttrium-aluminium garnet (YAG) is used in lasers that can cut through metals. It is also used in white LED lights. Yttrium oxide is added to the glass used to make camera lenses to make them heat and shock resistant. It is also used to make superconductors. Yttrium oxysulfide used to be widely used to produce red phosphors for old-style colour television tubes. Radioactive isotope yttrium-90 is used in targeted tumor radiotherapy and nuclear medicine imaging of yttrium-90 radioactivity with bremsstrahlung imaging and positron emission tomography.

Fluorine is a chemical element with symbol F and atomic number 9. Fluorine is the lightest of the halogens, a group of compounds including chloride, bromine, iodine and astatine. Under standard conditions, it exists as a highly toxic pale yellow diatomic gas. Fluorine is the most electronegative element, making it extremely reactive. It reacts with nearly all other elements, except for helium and neon. Fluorine is a vital element in the nuclear energy industry, has been used in commercial applications, such as refrigeration, and was used to make chemical weapons. Fluorine-containing drugs are used in medicine as anesthetics, antibiotics, anti-cancer and anti-inflammatory agents, psychopharmaceuticals, and in many other applications.

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.