Photopeak

The photopeak refers to the region of the pulse height spectrum caused by the complete photoelectric absorption of Gamma rays by the scintillator crystal of a Gamma camera.

The energy value of the photopeak(s) should correspond to the characteristic energies of the Gamma rays emitted by the radionuclide that is being measured in the nuclear medicine study.

The photopeak is typically spread over a range instead of a single value. This is due to statistical fluctuations that are at least partially determined by the sensitivity of the detector.

A pulse height analyzer is typically used to select for the photopeak(s) of interest, rejecting all other energy values of the pulse height spectrum.