What is the acceptable variation in the constancy of linac output compared to the benchmark values?

The acceptable variation in the constancy of linear accelerator (linac) output is typically set at 3% when compared to benchmark values. This standard is established to ensure that the delivered radiation dose remains accurate and consistent, which is critical for effective patient treatment and safety.

A variation of 3% is considered a reasonable threshold that balances accuracy with practical variability in daily operations and measurements. Deviations beyond this level may indicate equipment issues or changes in performance that could affect treatment efficacy, prompting further investigation or recalibration of the linac.

Maintaining this level of constancy helps uphold quality assurance protocols in radiation therapy, ensuring that patients receive the prescribed dose with minimal risk of underdosing or overdosing. Thus, the choice of a 3% variation is grounded in both clinical safety and the technological capabilities of modern radiotherapy systems.