Which artifact is most associated with extremely low receptor exposure?

• A. Quantum mottle
• B. Motion artifact
• C. Geometric distortion
• D. Pixel dropout

Answer: (A)

Low receptor exposure leads to quantum mottle. When there aren’t enough x-ray photons reaching the detector, the signal becomes dominated by random fluctuations in photon arrival. This quantum noise shows up as a grainy, mottled texture across the image because each pixel’s value is based on a small, variable number of photons. As exposure increases, more photons arrive and the noise diminishes, yielding a smoother, more uniform image.

Motion artifact, on the other hand, comes from the patient moving during exposure and appears as blur rather than a grainy texture. Geometric distortion results from misalignment or improper distance/angle, causing shapes to be stretched or distorted. Pixel dropout is due to detector defects or data loss, leading to missing or abnormal pixels. So the grainy appearance tied to underexposure is the hallmark of quantum mottle.