Which material in gamma cameras is responsible for converting gamma photons into visible light?

• A. Light pipe
• B. PMTs
• C. Crystal
• D. Collimator

Answer: (C)

The scintillation crystal is responsible for converting gamma photons into visible light. When a gamma photon interacts in the crystal, it deposits energy and the crystal re-emits that energy as a burst of visible light. That light is then detected by photodetectors (often PMTs) and transformed into an electrical signal for imaging. The crystal chosen, like NaI(Tl), is used because it produces a strong, well-tatched light output for the common gamma energies used in nuclear medicine. The light pipe merely transports that light to the detectors, the PMTs convert the light to electricity, and the collimator shapes the field of view without producing light.