If grid lines are parallel to the scanning laser, the moiré pattern will not be present.

• A. True
• B. False
• C. Not enough information
• D. Only with high kVp

Answer: (A)

Moiré patterns come from aliasing between a regular grid (like a grid line pattern) and the imaging system’s sampling or readout pattern. The scanning laser reads the plate line by line in a fixed direction. When the grid lines run parallel to that scanning direction, the sampling aligns with the grid’s periodicity, so there isn’t a varying phase relationship that would produce a beat pattern across the readout. In this orientation, the grid’s modulation is effectively carried through the scan without creating the interference bands that characterize moiré.

If the grid were oriented differently relative to the scan, especially at angles or with frequencies that don’t line up neatly with the scanner’s sampling, aliasing could occur and moiré patterns might appear. In practice, awareness of grid orientation and frequency helps minimize these artifacts.