Photomultiplier tube (Gamma camera)

Last revised by Raymond Chieng on 12 Aug 2023

The photomultiplier tube array of a Gamma camera detects the visible light produced by the scintillator, and converts it to a measurable electronic signal 1.

A series of photomultiplier tubes are mounted behind the scintillation crystal ​1.

Each photomultiplier tube is composed of a tightly sealed, evacuated glass housing ​1.

A photocathode exists at the end closest to the scintillator 1​, which absorbs the light photons produced and emits photoelectrons in the process, via the photoelectric effect .

The photoelectrons are accelerated towards an anode at the end of the photomultiplier tube, colliding into a series of dynodes along the way, with each interaction producing further photoelectrons and therefore amplifying the electronic signal 1.

The amount of light detected by a photomultiplier tube is a function of its distance from the scintillation event. Tubes that are closer to the scintillation event will have a proportionally larger signal than those further away. Therefore, the location of the signal can be determined by the position of the photomultiplier tube that receives the greatest signal.

ADVERTISEMENT: Supporters see fewer/no ads