PET or micro-PET and SPECT or micro-SPECT

Nuclear imaging uses low doses of radioactive substances linked to compounds used by the body's cells or compounds that recognize specific epitopes at the target cells. Using special detection equipment, the radioactive substances can be traced in the body to report where and when they accumulate, providing the radiologist with functional information about organs and tissues .
In PET (Positron Emission Tomography), radiotracers contain isotopes which emit positrons upon nuclear decay (most commonly F-18), while SPECT (Single Photon Emission Computed Tomography) relies on gamma-rays emitting radiotracers.
In microPET/SPECT, the instrumentation is implemented with accessories or with a technical set-up optimized for small animal studies.