A radiography setting shows upright Bucky images with noise; what is most likely source?

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

Answer: (D)

When noise shows up in upright Bucky radiographs, the grid helps reduce scatter, so persistent noise is most often coming from the imaging system itself. System noise originates from the detector’s electronics and readout circuitry—things like dark current, amplifier noise, and other electronic fluctuations. This type of noise tends to be uniform across the image and does not depend strongly on the exposure level, so it can remain even when the patient is well exposed and scatter is minimized by the grid. In contrast, photon (quantum) noise depends on the number of X-ray photons and typically decreases as exposure increases, so it would lessen with higher mA or longer exposure. Scatter-related noise would mainly degrade contrast rather than appear as a uniform grain across the image. Ambient interference isn’t a typical source of image noise in this setting. Therefore, noise that persists despite the grid is most consistent with system noise.