page_title: Technetium-99m
section_title: Early medical applications in the United States
hierarchical_section_title: Technetium-99m / History / Early medical applications in the United States
caption_attribution_description: English: Technetium injection. Tc99m is contained in a shielded syringe.
context_page_description: Technetium-99m is a metastable nuclear isomer of technetium-99, symbolized as ⁹⁹ᵐTc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used medical radioisotope in the world.
  Technetium-99m is used as a radioactive tracer and can be detected in the body by medical equipment. It is well suited to the role, because it emits readily detectable gamma rays with a photon energy of 140 keV and its half-life for gamma emission is 6.0058 hours. The relatively "short" physical half-life of the isotope and its biological half-life of 1 day allows for scanning procedures which collect data rapidly but keep total patient radiation exposure low. The same characteristics make the isotope suitable only for diagnostic but never therapeutic use.
  Technetium-99m was discovered as a product of cyclotron bombardment of molybdenum. This procedure produced molybdenum-99, a radionuclide with a longer half-life, which decays to Tc-99m. At present, molybdenum-99 is used commercially as the easily transportable source of medically used Tc-99m.
context_section_description: Tc-99m remained a scientific curiosity until the 1950s when Powell Richards realized the potential of technetium-99m as a medical radiotracer and promoted its use among the medical community. While Richards was in charge of the radioisotope production at the Hot Lab Division of the Brookhaven National Laboratory, Walter Tucker and Margaret Greene were working on how to improve the separation process purity of the short-lived eluted daughter product iodine-132 from tellurium-132, its 3.2-days parent, produced in the Brookhaven Graphite Research Reactor. They detected a trace contaminant which proved to be Tc-99m, which was coming from Mo-99 and was following tellurium in the chemistry of the separation process for other fission products. Based on the similarities between the chemistry of the tellurium-iodine parent-daughter pair, Tucker and Greene developed the first technetium-99m generator in 1958. It was not until 1960 that Richards became the first to suggest the idea of using technetium as a medical tracer.
  The first US publication to report on medical scanning of Tc-99m appeared in August 1963. Sorensen and Archambault demonstrated that intravenously injected carrier-free Mo-99 selectively and efficiently concentrated in the liver, becoming an internal generator of Tc-99m. After build-up of Tc-99m, they could visualize the liver using the 140 keV gamma ray emission.
caption: A technetium injection contained in a shielded syringe
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