In 1970, Eckelman and Richards presented the first "kit" containing all the ingredients required to release the Tc, "milked" from the generator, in the chemical form to be administered to the patient.
Technetium-99m is used in 20 million diagnostic nuclear medical procedures every year. Approximately 85% of diagnostic imaging procedures in nuclear medicine use this isotope as radioactive tracer. Klaus Schwochaus book Technetium' lists 31 radiopharmaceuticals based on Tc for imaging and functional studies of the brain, myocardium, thyroid, lungs, liver, gallbladder, kidneys, skeleton, blood, and tumors. A more recent review is also available.
Depending on the procedure, the Tc is tagged (or bound to) a pharmaceutical that transports it to its required location. For example, when Tc is chemically bound to exametazime (HMPAO), the drug is able to cross the blood–brain barrier and flow through the vessels in the brain for cerebral blood-flow imaging. This combination is also used for labeling white blood cells (Tc labeled WBC) to visualize sites of infection. Tc sestamibi is used for myocardial perfusion imaging, which shows how well the blood flows through the heart. Imaging to measure renal function is done by attaching Tc to mercaptoacetyl triglycine (MAG3); this procedure is known as a MAG3 scan.
Technetium-99m (Tc-99m) can be readily detected in the body by medical equipment because it emits 140.5 keV gamma rays (these are about the same wavelength as emitted by conventional X-ray diagnostic equipment), and its half-life for gamma emission is six hours (meaning 94% of it decays to Tc in 24 hours). Besides, it emits virtually no beta radiation, thus keeping radiation dosage low. Its decay product, Tc, has a relatively long half-life (211,000 years) and emits little radiation. The short physical half-life of Tc and its biological half-life of 1 day with its other favourable properties allows scanning procedures to collect data rapidly and keep total patient radiation exposure low. Chemically, technetium is selectively concentrated in thyroid, salivary glands, and stomach and excluded from cerebrospinal fluid. Combination with perchlorate abolishes its selectiveness.