Technetium-99m

Technetium-99m (99mTc) is a metastable nuclear isomer of technetium-99 (itself an isotope of technetium), 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.

medical test

Colloquially a technetium cow, or moly cow, a device used to extract the short-lived Tc-99m