What is the annual X-ray flatness change from baseline tolerance?

• A. 1%
• B. 2%
• C. Functional
• D. ±1 mm

Answer: (A)

Beam flatness measures how uniform the X-ray field is across the image, expressed as a percentage difference from the baseline beam profile. For annual quality checks, the tolerance is kept tight to preserve accurate dose delivery and consistent image quality over the year. The standard value is 1 percent, meaning the maximum change from the baseline across the field should not exceed 1%. A 2 percent change would indicate a larger deviation than normally allowed for an annual tolerance. A measurement described as ±1 mm relates to geometry or alignment, not to flatness percentage, and a non-numeric option doesn’t apply here. So the annual X-ray flatness change from baseline tolerance is 1%.