Which component is the smallest sensing unit that converts radiation interactions into an electrical signal in digital radiography?

• A. Pixels
• B. Voxels
• C. Display monitor matrix
• D. Detector elements (DELs)

Answer: (D)

In digital radiography, the smallest sensing unit that directly converts radiation interactions into an electrical signal is the detector element. Each detector element is a tiny sensor in the detector array that captures X-ray interactions and produces an electrical signal, using either indirect conversion (scintillator plus photodiode readout) or direct conversion (a photoconductor like selenium with readout). These detector elements form a 2D array that is sampled to create the final image as a grid of pixels. Voxels are 3D elements used in CT, and the display monitor matrix refers to how the image is shown on the monitor, not how the radiation is detected. Therefore the detector element is the correct unit responsible for converting radiation into an electrical signal.