Which QC test is commonly used in digital radiography to assess detector uniformity across the image field?

• A. Dark Noise
• B. Detector Uniformity/Flat-Field
• C. Spatial Resolution
• D. Repeat-Rate Monitoring

Answer: (B)

Detector uniformity across the image field is assessed with a detector uniformity (flat-field) test. The idea is to expose the detector with a uniform X-ray field and look at the resulting image for any shading or variations in brightness that shouldn’t be there. If the detector responds equally everywhere, the image would be a single, uniform gray. Real detectors often show pixel-to-pixel gain differences or dead/hot regions, which show up as nonuniformities. This test identifies those variations so a correction map (gain calibration) can be applied to produce uniform brightness and reliable image quality across the field.

Other tests measure different aspects: dark noise checks the electronic noise when no exposure is made, spatial resolution assesses sharpness and detail, and repeat-rate monitoring looks at consistency of technique or exposure between exams. None of those directly quantify how uniformly the detector responds across the image field like the flat-field test does.