Define quantum mottle and its relationship to exposure.

• A. Quantum mottle is graininess due to insufficient photon flux; increasing exposure reduces mottle and improves image uniformity.
• B. Quantum mottle is caused by overexposure, increasing patient dose.
• C. Quantum mottle refers to motion blur artifacts.
• D. Quantum mottle is caused by detector saturation and reduces image contrast.

Answer: (A)

Quantum mottle is graininess in an image caused by too few photons reaching the detector. When photon counts are low, the random nature of photon arrival creates fluctuations that appear as specks or noise. Increasing exposure adds more photons, which reduces these random fluctuations and yields a more uniform image with a better signal-to-noise ratio. Keep in mind this improves image quality but also increases patient dose, so the exposure should be adjusted to minimize mottle while staying within ALARA principles. The other options describe different problems—overexposure, motion blur, and detector saturation—that are not the same as quantum mottle.