Amorphous Selenium is used in which imaging system?

• A. Direct DR
• B. Indirect DR
• C. Radiographic film
• D. CR

Answer: (A)

Amorphous selenium is used as a direct conversion detector in direct digital radiography. In this approach, X-ray photons interact directly with the selenium layer and create an electrical charge at the detector element, which is then collected by the TFT array for readout. This direct conversion eliminates the intermediate light emission step, reducing light spread and preserving spatial resolution. In indirect DR, the X-rays first convert to visible light in a scintillator (like CsI or gadolinium oxysulfide), and that light is then detected by a silicon photodiode—this adds light diffusion and can slightly blur the image compared with direct conversion. Radiographic film and CR use completely different imaging chains (film or phosphor plates with laser scanning, respectively). So, the material is used in direct DR because of its ability to convert X-rays straight into an electrical signal.