After passing through the patient, transmitted X-ray photons must be detected and converted into a visible or digital image. Modern radiography systems use detectors that transform X-ray energy into electrical signals that can be processed and displayed.

In digital radiography, detectors typically use scintillators or photoconductors to convert X-ray photons into light or electrical charge. These signals are then digitised to produce an image matrix representing the distribution of transmitted radiation. The efficiency of this conversion process affects image quality and radiation dose.

Important detector characteristics include detective quantum efficiency (DQE), spatial resolution, and dynamic range. High DQE detectors can produce high-quality images at lower radiation doses because they capture and convert more of the incident photon signal.

Detector physics and image formation are commonly tested in FRCR Part 1 Physics and ABR Core examinations, often in questions relating detector efficiency, signal conversion processes, and digital image properties.

The questions in this section reinforce the physical principles underlying X-ray detection and the conversion of radiation into diagnostic images.

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