What makes up the capture area of a detector element (DEL)?

• A. Top electrode, detection layer, and bottom electrode
• B. Capture area, storage capacitor, and thin film transistor (TFT) gate
• C. Thin film transistor (TFT) gate, detection layer, and storage capacitor
• D. Top electrode, capture area, and bottom electrode

Answer: (A)

The capture area is the part of each detector element that actually absorbs X-rays and creates a measurable electrical signal. It is the sandwich that directly collects charge: the detection layer sits between the two electrodes—the top electrode and the bottom electrode. When X-ray photons interact in the detection layer, they produce charge carriers, and the applied bias across those electrodes sweeps those charges to form the signal you read out. The readout components, namely the thin film transistor (TFT) and storage capacitor, are responsible for storing and transferring that signal but do not themselves constitute the area where X-rays are captured. So the capture area is made up of the top electrode, the detection layer, and the bottom electrode.