Consider an x-ray exposure results in a receptor exposure of 0.001 uGy. The resulting image is expected to display which of the following?

• A. saturation artifact
• B. quantum mottle
• C. geometric distortion
• D. excessive contrast

Answer: (B)

Quantum mottle arises when there aren’t enough photons reaching the detector. With a receptor exposure as low as 0.001 μGy, the number of detected photons is so small that random fluctuations (Poisson noise) become clearly visible, producing a grainy, mottled image and poor visibility of detail. This is exactly what quantum mottle looks like in a digital image.

Saturation artifact would occur if the exposure were too high and the image clips in the bright areas, which isn’t the case here. Geometric distortion comes from misalignment or improper positioning, not from underexposure. Excessive contrast results from processing or exposure choices that exaggerate differences in brightness, not from such an ultra-low exposure.