technetium-99m

A radioisotope of technetium that decays by isomeric transition, emitting an essentially monoenergetic gamma ray of 142 keV with a half-life of 6.01 hr. It is usually obtained from a radionuclide generator of molybdenum-99 and is used to prepare radiopharmaceuticals for scanning the brain, parotid, thyroid, lungs, blood pool, liver, heart, spleen, kidney, lacrimal drainage apparatus, bone, and bone marrow.

- ^99mTc diphosphonate a radionuclide complex used for bone scans.

- ^99mTc-DTPA a radionuclide chelate complex used for renal imaging and function testing; also known as ^99mTc pentatate. [diethylene triamine pentaacetic acid]

- ^99mTc sestamibi a lipophilic cationic complex of a ^99mTc-labeled isonitrite, used as a radionuclide in several organs (e.g., brain, bone, thyroid, breast) for the detection of cancer, or in the heart for identifying coronary artery occlusion. It has superseded Tl-201 in cardiac imaging and in experimental breast imaging.

- ^99mTc sulfur colloid a particulate radionuclide complex taken up by the reticuloendothelial system; used for imaging the liver and spleen.

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n.

an isotope of the artificial radioactive element technetium. It emits gamma radiation only, with no beta particles, at a convenient energy for detection by a gamma camera and has a short half-life. For these reasons it is widely used in nuclear medicine as a tracer for the examination of many organs (see scintigram). Symbol: Tc-99m.