Dosimetry Data
Between 1995 and 2025 Radiation Dosimetry Services (RDS) monitored nearly 300,000 beams at radiotherapy centers worldwide, including 105,223 MV photon, 179,223 MeV electron, and 3,130 orthovoltage beams, with more than 1.4 million TLD analyzed. The overwhelming majority of output checks demonstrate strong agreement between RDS measured doses and those reported by the institution (RDS-to-institution ratio):
- For photon beams, 99.3% of beams agreed within 5%, and 94.0% agreed within 3%.
- For electron beams, 98.9% of beams agreed within 5%, and 91.6% agreed within 3%.
Acceptance Criteria: ±5% for MV Photons and MeV Electrons; ±10% for Orthovoltage
These criteria are grounded in established uncertainty analysis. The RDS TLD-protocol (MV Photons and MeV Electrons) has a standard error of approximately 1.3% (Kirby et al., 1992). Based on this uncertainty, dose agreement within ±5% of the stated value corresponds to a confidence level of approximately 93%. Accordingly, results outside ±5% are highly likely to reflect a true discrepancy. For orthovoltage beams, a wider threshold of ±10% is applied due to greater uncertainty, primarily driven by energy correction factors for orthovoltage photon beams.
Out-of-Criteria Results
For any radiation therapy beam output check outside ±5% for MV photon and MeV electron beams, or ±10% for orthovoltage beams, RDS technical staff promptly contact the institution’s physicists by email or phone. Discrepancies may be attributable to calibration issues, but often are a result of misinterpretation of irradiation instructions, errors in completing the irradiation form or mis-irradiation (set-up error) etc. The RDS team welcomes direct communication with physicists to support timely investigation and resolution of out-of-criteria results.