In an indirect capture flat-panel detector, which component converts the visible light into electrons?

• A. Photodiode
• B. TFT array
• C. Scintillation layer
• D. Amorphous selenium (A-Se) detector

Answer: (A)

In indirect capture detectors, the light produced by the scintillator after x-ray interaction is the key signal that needs to be transformed into an electrical one. The component that does this conversion from visible light to electrons is the photodiode. It senses the scintillator’s visible photons and releases electrons, creating a charge that the TFT array then collects and routes for readout. The scintillation layer’s job is to produce the light, while the TFT array manages the charge and readout, and amorphous selenium is used in direct conversion detectors to convert x-rays straight to charge without a scintillator.