<unk>  <unk>  is a type of tomography involving radioactive<unk> s. Types include positron<unk>  tomography (PET) and Single-photon<unk>  (SPECT). The imaging agent used in SPECT emits gamma rays, as opposed to the positron emitters (such as 18F) used in PET. There are a range of radiotracers (such as 99mTc, 111In, 123I, 201Tl) that can be used, depending on the specific application.
Emission computed tomography
Pulmonary examination
PET response criteria in solid tumors
Cardiac examination
Electron beam computed tomography
Operation of computed tomography
Medicine chest 
Medicine chest