Rare-earth intensifying screens require films sensitive to which color spectrum?

• A. Blue-Violet
• B. Blue-Green
• C. Red
• D. Infrared

Answer: (B)

Rare-earth screens use phosphors that emit green light when exposed to X-rays. To get the most image density from that light, the film must be sensitive to green wavelengths (the blue-green portion of the spectrum). This green-sensitive pairing with rare-earth screens increases image speed and lowers patient dose. If a blue-sensitive film were used, it wouldn’t respond as well to the green emission, reducing exposure efficiency. Older calcium tungstate screens emit blue light and were paired with blue-sensitive film, but rare-earth screens are designed for green sensitivity, hence the need for films sensitive to the blue-green spectrum.