In CR imaging, the latent image known as the stored image is held in which layer of the imaging plate?

• A. PSP layer
• B. Conductor layer
• C. IP reader/digitizer
• D. Protective layer

Answer: (A)

In computed radiography, the stored (latent) image is held in the photostimulable storage phosphor (PSP) layer of the imaging plate. When X-rays expose the plate, energy is captured by the phosphor grains and electrons are trapped in metastable states, creating the stored signal of the image. The other layers don’t store the image: the protective layer only shields the plate, the conductor layer helps dissipate static electricity, and the reader/digitizer is the external device that scans and converts the stored signal into a digital image. During readout, a laser scans the PSP layer, releasing the trapped energy as light in proportion to the stored energy, which is then detected and digitized to form the image. The latent image is erased after reading so the plate can be reused.