Which tolerance applies to annual TBI/TSET output calibration?

• A. ±1% from baseline
• B. 2% from baseline
• C. 0% tolerance
• D. ±2% from baseline

Answer: (B)

The key idea is how much the machine’s output is allowed to drift from the established reference value over a year. For annual TBI/TSET output calibration, the accepted drift is two percent from the baseline. This means the measured output must stay within baseline ±2%. The baseline comes from the initial calibration or the most recent approved re-calibration, serving as the reference for long-term stability. Staying within ±2% ensures the delivered dose remains within clinically acceptable limits despite normal instrument drift and measurement uncertainty. If the annual measurement falls outside this range, a recalibration and recheck are warranted. A zero tolerance is impractical due to inherent measurement noise; ±1% would be stricter than typical practice for this annual check, while ±2% aligns with standard expectations.