To evaluate GRID UNIFORMITY and GRID ALIGNMENT, what is the recommended method?

• A. Use a high-contrast phantom
• B. Produce a radiograph of a homogeneous phantom at clinical KVP and density ~1.20
• C. Expose a flat-field image with no phantom
• D. Rely on visual inspection of the grid

Answer: (B)

To evaluate grid uniformity and alignment, imaging a homogeneous phantom at clinical technique is the most effective approach. A uniform phantom provides consistent attenuation, so any variation seen on the radiograph is attributable to the grid itself rather than the subject. Using clinical kilovoltage and aiming for a density around 1.20 ensures the exposure level is representative of a real patient image, giving enough contrast and signal to reveal subtle grid lines and any misalignment or nonuniform transmission.

Using a high-contrast phantom would emphasize subject contrast rather than grid performance, making it harder to detect grid issues. Exposing a flat-field image with no phantom removes attenuation entirely, which can mask how the grid behaves under typical imaging conditions. Relying solely on visual inspection is subjective and may miss subtle misalignments or uniformity problems that a properly exposed, uniform background would reveal.

So, producing a radiograph of a homogeneous phantom at clinical technique provides the most accurate, practical assessment of both grid uniformity and grid alignment.