Aliasing in DR imaging and how can it be prevented?

• A. Aliasing Occurs When Sampling Frequency Is Insufficient to Represent High-Frequency Structures; Prevent With Appropriate Sampling, Higher Grid Frequency, and Proper Alignment
• B. Aliasing Is Not Preventable
• C. Aliasing Occurs Due to Patient Motion
• D. Aliasing Is a Type of Random Noise From the Detector

Answer: (A)

Aliasing occurs when the detector’s sampling rate isn’t high enough to capture the finest details in the image. In digital radiography, the image is sampled into discrete pixels; if some structures have spatial frequencies higher than half of that sampling rate (the Nyquist limit), those details fold back and distort the image. Preventing this relies on increasing sampling capability—smaller pixel size or a higher-resolution detector—and using a grid with higher line density. Proper alignment of the grid with the detector also helps, so the grid’s pattern doesn’t interact with the sampling in a way that produces moiré or aliasing artifacts. Aliasing is not primarily caused by motion or by random detector noise; those issues are separate concerns.