In computed radiography, the latent image is stored in which layer of the cassette?

• A. Scintillation layer
• B. Conductor layer
• C. Photo-stimulable phosphor layer
• D. Protective layer

Answer: (C)

In computed radiography, the latent image is stored in the photo-stimulable phosphor layer. When the plate is exposed to X-rays, electrons are trapped in defect sites within the europium-doped phosphor material, forming a stored (latent) image. This energy remains as trapped charges until the plate is later scanned with a laser, which stimulates the phosphor to release the stored energy as visible light that is then detected and converted to a digital image. The other layers serve different roles: a protective layer guards the surface, a conductor layer helps dissipate static electricity, and a scintillation layer (not used to store the latent image in CR) would simply produce light in response to X-rays rather than store it.