In quality control, the maximum allowed variation in x-ray tube output for identical settings is which percentage?

• A. +/- 5%
• B. +/- 1%
• C. +/- 2%
• D. +/- 10%

Answer: (A)

In quality control for radiography, you’re checking how consistent the x-ray output is when the technique is exactly the same. The standard tolerance used for this reproducibility is a 5% variation. This means if you repeat the same exposure settings, the measured output should stay within 5% of the baseline value. The reason this is the best answer is that it reflects a realistic balance: there will be small, normal fluctuations in generator performance (like slight changes in milliampere, timer accuracy, or kVp calibration), but these should not cause large swings in image density or patient dose. If the variation exceeds 5%, it signals a potential issue that needs investigation or calibration. The other options are either too strict, which would be routinely violated in normal operation, or too permissive, which could let meaningful changes in output go unnoticed.