Photomultiplier tube (Gamma camera)

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, which absorbs the light photons produced and emits photoelectrons in the process, via the photoelectric effect ¹. 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.