Iobenguane I-131 is a radioactive therapeutic agent. The drug contains radioactive isotope I-131, which decays by electron emission with a half-life of about 8 days. By the chemical structure, iobenguane is similar to the neurotransmitter norepinephrine and is subject to the same uptake and regulation pathways. After intravenous administration, iobenguane I-131 accumulates within pheochromocytoma and paraganglioma cells, and radiation from the radioactive decay causes cell death and tumor necrosis. Iobenguane I-131 was approved by the FDA for the treatment of adult and pediatric patients with iobenguane scan positive, unresectable, locally advanced or metastatic pheochromocytoma or paraganglioma who require systemic anticancer therapy. Iobenguane I-131 is investigated in clinical trials as a treatment of neuroblastoma, ganglioneuroblastoma and other tumors of neuroendocrinal origin.

Iofetamine hydrochloride I-123 is a radiopharmaceutical for cerebral perfusion imaging. lofetamine is the N-isopropyl derivative of amphetamine with iodine 123(1123) at the para position to serve as the tracer. This configuration was systematically derived by Winchell et al. to provide sufficient brain uptake and retention for brain imaging, which typically requires an acquisition time of 25-40 minutes. After experimental intraarterial injection the drug has a high extraction ratio (> 90 percent) in the brain. Iofetamine hydrochloride I-123 permits cerebral blood perfusion imaging with single photon emission computed tomography (SPECT). Iofetamine is an amphetamine analog that is rapidly taken up by the lungs, then redistributed principally to the liver and brain. The precise mechanism of localization has not been determined, but is believed to result from nonspecific receptor binding. Brain uptake peaks at 30 minutes postinjection and remains relatively constant through 60 minutes. The drug is metabolized and excreted in the urine, with negligible activity remaining at 48 hours. When compared with CT in stroke patients, visualization may be performed sooner after symptom onset and a larger zone of involvement may be evident with iofetamine. Localization of seizure foci and diagnosis of Alzheimer's disease may also be possible. As CT has revolutionized noninvasive imaging of brain anatomy, SPECT with iofetamine permits routine cerebral blood flow imaging. Iofetamine hydrochloride I-123 under the brand name Spectamine was approved for use in the United States as a diagnostic aid in determining the localization of and in the evaluation of non-lacunar stroke and complex partial seizures, as well as in the early diagnosis of Alzheimer's disease in 1987. However it was discontinued in USA.

XENON XE-127, a radioactive gas, was developed at Brookhaven National Laboratory in 1973 for lung ventilation imaging. It appears to be preferable to xenon-133 because of the higher counting rates, lower patient radiation dose, and longer shelf life. However, its production ceased in 1993 due to various reasons.

Krypton Kr 81m is radiolabeled noble gas suitable only for inhalation in diagnostic studies. Krypton Kr 81m used for Imaging ventilated regions of the lung, Combined with pulmonary perfusion scintigraphy for diagnosis of pulmonary embolism and other conditions. Krypton Kr 81m diffuses easily, passing through cell membranes and exchanging freely between blood and tissue. It is distributed in the lungs in a manner similar to air, thus representing the regions of the lung that are aerated. The gamma photons of krypton Kr 81m can then be employed to obtain counts per minute per lung or region of the lung, or to display their distribution as a scan.

Cyanocobalamin Co-58 is radiopharmaceutical derivative of an essential vitamin B12. Radioactive isotope Co-58 has a half-life of 72 days and produces hard gamma radiation when it decays to Fe-58. In the 1960s, cyanocobalamin Co-58 was used in western European countries for the diagnosis of liver diseases: hepatitis, parenchymal liver disease, lead poisoning, and other condition. Its use was superseded by cyanocobalamin Co-57, which is marketed used for the diagnosis of pernicious anemia and as a diagnostic adjunct in other defects of intestinal vitamin B12 absorption.

Cyanocobalamin Co 57 is a manufactured form of radiolabeled vitamin B indicated as an adjunct in diagnosing intestinal cyanocobalamin malabsorption syndromes due to lack of intrinsic factor (IF) or other defects in intestinal absorption (e.g., blind loop syndrome and diverticulitis, celiac disease, Crohn's disease, lesions in the small intestine, severe pancreatitis, tropical sprue).

Iodocholesterol I-131 is a radioiodine-labeled cholesterol analog used as a diagnostic agent for Cushing's syndrome, hyperaldosteronism, and pheochromocytoma. Iodocholesterol I-131 accumulates in tissues where steroid hormones are produced, including the adrenal glands the ovaries and the testes. After binding to low-density lipoprotein (LDL) receptors on adrenocortical cells, Iodocholesterol I-131 is internalized. As cholesterol is the precursor for all adrenocortical steroid hormones, areas of hormonal hypersecretion can be visualized using scintigraphy and the adrenocortical function can be assessed.

Fluoroethylcholine ion F-18 is ethylcholine labeled with fluorine F 18, a positron-emitting isotope. Fluorine F18 fluoroethylcholine incorporates into tumor cells through an active, carrier-mediated transport mechanism for choline and then is phosphorylated intracellularly by choline kinase, yielding a phosphoryl derivative, and finally is integrated into cellular phospholipids, probably primarily into a phosphatidyl derivative; concentration of this agent in tumor cells as various fluorine F 18 fluoroethylcholine derivatives enables tumor imaging using positron emission tomography (PET). Choline kinase, the enzyme responsible for the phosphorylation of choline, is frequently up-regulated in human tumor cell lines. F18-fluoroethylcholine is used for imaging of prostate cancer and brain tumors, mainly in Europe and Japan.

Iometopane (RTI-55, beta-CIT) is a cocaine congener, binding to the neuronal dopamine and serotonin reuptake transporters affinity of Kd = 0.3 nM. Radiopharmaceutical forms of RTI-55 are used in single-photon emission computer tomography. Radioisotops 123I and 125I are favored, but 124I also used as a positron emitter to diagnose Parkinson's Disease.

Technetium Tc 99m Gluconate is a radiopharmaceutical agent that has been used for the diagnosis of kidney disease. Although Technetium Tc 99m Gluconate is of a hydrophilic character, it shows high plasma protein binding (50–70%). Therefore, both glomerular filtration and tubular excretion by the kidneys occur with slow pharmacokinetics, and only 70% of the injected activity is washed out after one day. This is the reason why Technetium Tc 99m Gluconate is no longer used for renal studies. Owing to its low stability, Technetium Tc 99m Gluconate is used (i) for red blood cell labeling and (ii) as a ligand exchange partner for labeling other molecules