In indirect DR detectors, what is the role of the photodiode array?

• A. Converts X-ray photons directly to electrical signal.
• B. Converts X-rays to light in the scintillator and then photodiodes convert light to electrical signal.
• C. Amplifies the electrical signal from scintillator.
• D. Stabilizes detector temperature.

Answer: (B)

In indirect DR, X-ray energy is first converted to visible light by a scintillator. The photodiode array then detects that light and converts it into an electrical signal. Each photodiode generates a current proportional to the light it receives, which is read out by the thin-film transistor (TFT) array and processed to form the image. This is different from direct DR, where X-rays are converted directly to an electrical signal by a photoconductor. The photodiodes themselves don’t amplify the signal—amplification happens in the readout electronics. Temperature stabilization is not the primary role of the photodiode array, though detectors may have temperature control to reduce noise.