What is the percentage of the detector element (DEL) devoted to the detection layer called?

• A. Amorphous selenium
• B. Amorphous silicon
• C. Fill factor
• D. Dexel

Answer: (C)

Fill factor is the percentage of a detector element that is active, meaning the portion of the pixel area that actually participates in detecting x-rays. In a flat-panel detector, each detector element (DEL) includes an active detection region plus non-active areas such as gaps or guard structures. The fill factor is calculated as the active detection area divided by the total DEL area, expressed as a percentage. A higher fill factor means more of the pixel is sensitive to x-rays, which improves signal collection and can enhance spatial resolution because there are fewer dead spaces between elements.

The listed materials describe what the detection layer might be made of (for example, amorphous selenium or amorphous silicon in different detector designs) or refer to a single detector element (dexel). These are not the percentage that represents how much of the DEL is devoted to detection, which is exactly what fill factor measures.