Gamma camera

Scintigraphy ("scint") is the use of gamma cameras to capture emitted radiation from internal radioisotopes to create two-dimensional[1] images.

SPECT (single photon emission computed tomography) imaging, as used in nuclear cardiac stress testing, is performed using gamma cameras.

A gamma camera consists of one or more flat crystal planes (or detectors) optically coupled to an array of photomultiplier tubes in an assembly known as a "head", mounted on a gantry.

The highly efficient capture method of this combination for detecting gamma rays was discovered in 1944 by Sir Samuel Curran[3][4] whilst he was working on the Manhattan Project at the University of California at Berkeley.

The electronic circuit connecting the photodetectors is wired so as to reflect the relative coincidence of light fluorescence as sensed by the members of the hexagon detector array.

All the PMTs simultaneously detect the (presumed) same flash of light to varying degrees, depending on their position from the actual individual event.

[2]: 112  The total sum of the voltages from each photomultiplier, measured by a pulse height analyzer is proportional to the energy of the gamma ray interaction, thus allowing discrimination between different isotopes or between scattered and direct photons.

Large amounts of radiation must be present so as to provide enough exposure for the camera system to detect sufficient scintillation dots to form a picture.

[2]: 128 Other methods of image localization (pinhole, rotating slat collimator with CZT) have been proposed and tested;[12] however, none have entered widespread routine clinical use.