posted by Boo Boo .
Technetium-99m emits only gamma radiation. Why would this type of radiation be used in diagnostic imaging rather than an isotope that also emits beta or alpha radiation?
The half life of Tc-99 is small, about 6 hours and it is excreted from the body in about a day.
An isotope that emits alpha and beta radiation in addition to gamma rays, would cause much more internal cellular damage, even if its half life and intensity were similar to that of Tc-99.