Which layer of the CR imaging plate is responsible for creating the latent image from transmitted x-ray photons exiting the patient?

• A. Protective layer
• B. Phosphor layer
• C. Conductive layer
• D. Light shield layer

Answer: (B)

The phosphor layer is where the latent image is created. When x-ray photons enter the imaging plate, the phosphor material absorbs energy and traps some of that energy in its crystal lattice, forming stored charge patterns that correspond to the x-ray exposure. This trapped energy is the latent image, kept until the plate is read by the CR system. The other layers have protective, conductive, or light-shielding roles and do not store the latent image themselves: the protective layer guards against damage, the conductive layer helps with charge management, and the light shield layer prevents ambient light from erasing the image. During reading, a laser stimulates the trapped electrons to release light, which is then converted into a digital signal.