What is a practical measure to prevent Moiré patterns in DR imaging?

• A. Use a lower frequency grid to prevent aliasing.
• B. Use a higher frequency grid to prevent aliasing.
• C. Moiré cannot be prevented.
• D. Increase patient dose to overcome pattern.

Answer: (B)

Moiré patterns in DR imaging come from aliasing between the grid’s regular pattern and the detector’s sampling of the image. When the grid has a certain line density, its periodic structure can interfere with the way the detector samples, producing visible interference patterns. Using a higher-frequency grid increases the number of lead lines per centimeter, making the grid’s pattern finer. This finer grid is less likely to alias with the detector’s sampling, so moiré patterns are less likely to appear.

A lower-frequency grid would have broader, more widely spaced lines and is more prone to aliasing, which is why it wouldn’t prevent moiré. Increasing the patient dose doesn’t address the sampling interaction itself, so it won’t stop the pattern from forming.