What type of radiation is used in hospitals alpha beta or gamma?

Answer 1

Amongst other uses, one in particular use is for the sterilization of an autoclave.
Another use is "irradiation" of bad cells in the body.

Gamma rays (which are high-energy photons) can be used to kill tumor cells by damaging their DNA : this is radiation therapy (aka radiotherapy).

Another use of gamma rays is to do functional imaging. A small amount of radioactivity is administered usually through intra-veinous injection. The radioactive chemical is chosen so that e.g. it is preferentially up taken by cancer cells. Then, a special device named a gamma-camera detects the radioactivity stemming from the body, creates images and allows the physician to locate the cancer cells. There are dozens of uses of gamma-rays for diagnostic imaging: finding tumors, but also finding stenosis (a abnormal narrowing of a blood vessel), haemmorage, pulmonary embolism, abnormal thyroid activity, dead cardiac cells after a heart attack, infection (by marking white blood cells with radioactive chemical)...

Answer 2

For therapeutic purposes it is usually X- ray or gamma ray therapy, but Hospitals also use the other two in certain circumstances - diagnostics and targeted cancer treatments.