Imaging: Nuclear *

In this paper an overview of principles involved in nuclear imaging is presented. Nuclear images are picotrial representations of the distribution of systemically administered radiopharmaceuticals. Although many radionuclides are available. 99m Tc is the most commonly used radionuclide, either in ionic form ( 99m TcO 4 ) or bound to other pharmaceuticals. Distribution within the body is by physiologic processes, dependent on the radiopharmaceutical used. Most distribution processes are organ specific rather than disease specific. Scintillation detectors are used to record the activity and disribution of an administered radiopharmaceutical and to create a representative image on film. A rectilinear scanner is an imaging system with a small detector that moves systematically, point by point, over an organ of interest. A gamma (scintillation) camera is an imaging system with a large stationary detector that encompasses a larger field of view. Nuclear imaging provides information based primarily on physiologic principles, and radiography provides infromation based primarily on anatomic or geometric principles. Examples of some scanning procedures are discussed.