<prompt> Gamma Rays are used in?CT scanDEXA ScanFluoroscopyPET Scan  <response>: PET Scan uses Gamma Rays. Gamma Rays are used in SCINTIGRAPHY STUDIESTc99m radioisotope studies,SPECTSingle Photon Emission Computerised Tomography studies and PET scan Positron Emission Tomography, Bone scan Tc99m-MDP studies All other investigations given in the options use X rays. 