Which material is responsible for storing the latent within the CR imaging plate?

• A. Helium-neon
• B. Rare-earth metals
• C. Amorphous selenium (a-Se)
• D. Photo-stimulable phosphor (PSP)

Answer: (D)

Latent image storage in computed radiography happens in the imaging plate’s photostimulable phosphor layer. When x-rays expose the plate, electrons are excited and trapped in defect sites within the phosphor lattice, creating a stored energy pattern that represents the image but isn’t visible yet. This trapped-energy material is the photostimulable phosphor itself. During readout, a laser supplies energy to release those trapped electrons; as they return to ground state, they emit light that is captured by the scanner to form the digital image. Amorphous selenium is used in direct radiography to convert x-ray energy directly to an electric signal, not to store a latent image in PSP. While dopants in PSP may include rare-earth elements, the essential storage medium is the photostimulable phosphor layer. A helium-neon laser is used to stimulate during readout, not to store the latent energy.