What type of noise cannot be reduced

• A. Quantum noise
• B. System noise
• C. Scatter
• D. Ambient noise

Answer: (D)

Ambient noise refers to background fluctuations coming from the surrounding environment and outside the imaging signal itself. Because this noise originates from external sources—like room conditions or stray background radiation—it persists regardless of how you adjust exposure or process the image. You can lessen its impact only through physical controls such as shielding or improving environmental conditions, but you can’t remove it through the imaging process alone. In contrast, other noise sources are tied to the signal or the detector and can be reduced by increasing photon flux, improving electronics, or using anti-scatter measures. So ambient noise is the type that cannot be reduced by typical imaging adjustments.