Technetium was the first synthetic radioactive element, occurring in nature only in trace amounts as a fission product of uranium ores; it therefore has no traditional metallurgical, structural, or civilian industrial uses. Its real, and today almost its only, large-scale application lies in nuclear medicine. Technetium-99m is the most widely used medical radioisotope in hospitals worldwide, employed in bone scans and in myocardial perfusion, thyroid, renal, brain, and tumor imaging. A technetium-99m-labeled drug is injected intravenously, and a gamma camera or SPECT system acquires images that reveal tumor metastases, the extent of a myocardial infarction, renal function, and bone lesions. Tc-99m has a half-life of about six hours and a gamma-ray energy well matched to imaging—enough to penetrate the body for detection without exposing the patient to excessive radiation—and these are the fundamental reasons it has become the workhorse nuclide of nuclear medicine. Beyond medical imaging, metallic technetium and its alloys have no large-scale industrial consumption. It has respectable corrosion resistance and could in principle serve as a special alloy additive, but its high price and radioactivity have kept it out of the materials market; within the nuclear industry it is studied only as an object of spent-fuel reprocessing and of long-term behavior studies of high-level radioactive waste.
Technetium dioxide (TcO2) is one of the most stable oxides of technetium, a black or gray powder studied mainly as a chemical form of technetium in nuclear-fuel reprocessing and in immobilization research on high-level waste; it currently has no civilian products. Ammonium pertechnetate (NH4TcO4), which resembles potassium perchlorate in appearance, is the most important intermediate in technetium chemistry. It is obtained by dissolving irradiated targets, followed by solvent extraction and crystallization, and serves as the feedstock for preparing other technetium compounds and Tc-99m medical generators. What is actually injected into the patient in the clinic is Tc-99m pertechnetate (the pertechnetate anion, TcO4-), eluted from a molybdenum-99 generator; combined with various cold kits such as methylenediphosphonate, methoxyisobutylisonitrile, and diethylenetriaminepentaacetic acid, it forms complete sets of radiopharmaceuticals for bone, myocardial, and dynamic renal imaging.
