What term refers to the individual pixel into which x-ray energy is deposited during exposure?

• A. Electron well
• B. Pixel cell
• C. Voxel
• D. Crystal site

Answer: (A)

Think of the detector as a grid of tiny charge-collection regions. When x-ray energy is absorbed in one of those regions, it creates electron-hole pairs. The freed electrons are pulled into a localized region under the electrode called a potential well, or specifically an electron well, within that pixel. This well is where the charge from that exposure is stored before it’s read out and converted into a digital signal. So the individual location where energy from a single exposure is deposited and its resulting charge is held is best described as an electron well.

The term pixel cell would refer to the physical detector element itself, not the exact charge-collection site. A voxel is used for three-dimensional imaging (volume element, as in CT), and crystal site isn’t the terminology used for the charge collection region in digital detectors.