For SID indicator accuracy, it needs to be within what tolerance of the measured value?

For SID indicator accuracy, it needs to be within what tolerance of the measured value?

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

Answer: (B)

SID indicator accuracy is about how faithfully the displayed distance matches the actual source-to-image distance. A small error changes magnification and the expected dose, so QA uses a tight tolerance. The standard tolerance is within two percent of the measured value, meaning if the true SID is 100 cm, the indicator should read between 98 and 102 cm. A looser tolerance like five or ten percent would allow noticeable geometric distortion and dose errors, while a much tighter one would be impractical. That’s why the within-two-percent range is the appropriate requirement.

SID indicator accuracy is about how faithfully the displayed distance matches the actual source-to-image distance. A small error changes magnification and the expected dose, so QA uses a tight tolerance. The standard tolerance is within two percent of the measured value, meaning if the true SID is 100 cm, the indicator should read between 98 and 102 cm. A looser tolerance like five or ten percent would allow noticeable geometric distortion and dose errors, while a much tighter one would be impractical. That’s why the within-two-percent range is the appropriate requirement.