Dosimetry Process

A Straightforward and Efficient TLD Mail Audit Process

1. For all radiation dosimetry service (RDS) services, thermoluminescent dosimeters (TLD) — along with associated phantoms (electrons) or platforms (photons) for irradiation — are shipped to participating institutions. Medical physicists (or their delegates) perform irradiations, delivering 3 Gy (or 300 MU), according to RDS instructions, and return the irradiated TLD to RDS for analysis.
2. At RDS, TLD are read, and doses are calculated using a well-established protocol with uncertainty of ≤1.5% (Kirby et al., 1992). The system is calibrated with TLD standards irradiated by RDS staff at an independent, accredited calibration laboratory on irradiators calibrated using NIST-traceable dosimetry equipment.
3. Measured TLD doses are compared with the institution’s stated doses, and a detailed report is issued for each beam or dose point evaluated.

Turnaround Time

Our normal turnaround time for a report is two weeks from receipt of irradiated TLD at our office.  A minimum seven-day interval is maintained between TLD irradiation and readout to ensure optimal accuracy. This period allows the signal to stabilize and enables the application of appropriate correction factors, as signal fading can otherwise lead to higher dosimetric uncertainty.

For time-sensitive output checks, RDS will perform readout exactly seven days post-irradiation (rush service). If rush service is required, please indicate this on the data sheet and contact RDS directly to ensure timely processing. Overnight shipping of TLDs can also be arranged to further expedite the turnaround time.

Quality Assurance (QA) and Independent Validation of RDS Measurements

The RDS maintains a comprehensive quality assurance program to ensure the accuracy, consistency and long-term stability of its TLD dosimetry system.

• TLD batches are commissioned according to the American Association of Physicists in Medicine Report-191.
• TLD batches are periodically evaluated to ensure consistency and reproducibility.
• TLD standards and control capsules are irradiated weekly by RDS staff at an independent calibration laboratory using radiation units calibrated with NIST-traceable dosimetry equipment, ensuring traceability of reported doses. Standards are read at the beginning, middle and end of each session, with an additional control read mid-session to verify system performance and reading stability.
• RDS performs routine intercomparisons with IROC-Houston across the photon and electron clinical beam energies to maintain alignment with external references.
• RDS participates annually in the International Atomic Energy Agency (IAEA) “blind check” and reference irradiation program. Over the past five years, RDS audit results have demonstrated excellent agreement with IAEA reference doses, with a mean difference of 0.73% ± 0.05%, well within 1%.

This multi-layered QA framework provides independent validation and reinforces confidence in the accuracy of all RDS measurements.