What chemical is found in a computed radiography cassette?

• A. Silver halide
• B. Photostimulable phosphor
• C. Developer solution
• D. Fixer

Answer: (B)

In computed radiography, the cassette houses a plate made of a photostimulable phosphor. When X-rays hit this phosphor, energy is stored as trapped electrons in the material. Later, a laser in the CR reader stimulates those trapped electrons to release the stored energy as light, which is detected to form the image. The most common material is europium-doped barium fluorobromide (BaFBr:Eu2+), a solid phosphor embedded in the imaging plate inside the cassette. This is different from silver halide crystals used in traditional film radiography, and from developer solution or fixer chemicals used in film processing. So the chemical found in a computed radiography cassette is the photostimulable phosphor.