Technetium-99m is a metastable nuclear isomer of technetium-99, symbolized as 99mTc. The "m" indicates that this is a metastable nuclear isomer. It is a gamma ray emitting isotope used in radioactive isotope medical tests, for example as a radioactive tracer that medical equipment can detect in the body. It is well suited to the role because it emits readily detectable 140 keV gamma rays (these are about the same wavelength emitted by conventional X-ray diagnostic equipment), and its half-life f… (More on Technetium-99m)