Mailed Thermoluminescent Dosimeters (TLD) for Quality Assurance
Radiation Therapy Machine Output Checks
The MD Anderson Radiation Dosimetry Services (RDS) provides independent peer reviews of beam output for radiation dose delivery systems. Specifically, we provide output checks for external beam radiation therapy machines including:
- megavoltage photon (2 - 25 MV)
- electron (4 - 20 MeV)
- orthovoltage (1.9 mm Al - 3 mm Cu HVL)
Absorbed Dose in Blood Irradiators
Thermoluminescent dosimeters (TLD) are available by mail to check the absorbed dose to the blood in irradiators used by blood banks. Packets of dosimeters are supplied; these can be placed at various locations to monitor the range of dose throughout the canister for a typical irradiation. These measurements are an independent check of the calibration of the blood irradiator as provided by the manufacturer.
Radiation Dosimetry Services also offers checks of:
- total body dosimetry
- total skin dosimetry
For information on pricing and how to order our services, please visit our Pricing and Ordering Information Page.
NOTE: We no longer offer Stereotactic Head, Single Beam or IMRT services. Please contact the MD Anderson Dosimetry Laboratory (MDADL) for these service needs. You may visit their website, call their office at 713-792-3233, fax them at 713-563-2620 or email them at firstname.lastname@example.org.
For all of the services provided by Radiation Dosimetry Services (RDS), thermoluminescent dosimeters (TLD) and associated apparatuses are mailed to and irradiated at requesting institutions. The irradiated TLD are mailed back to RDS where they are read and doses are calculated using a well-established protocol with an uncertainty of ≤ 1.5% (Kirby et al., 1992). Our TLD system is calibrated with TLD standards irradiated using a 60Co unit at the MD Anderson accredited dosimetry calibration laboratory. The TLD dose measurements are compared to the institution’s stated dose and a report is issued to the institution for each beam or dose point checked.
The majority of output checks performed by RDS show good agreement between doses measured by RDS and doses reported by the institution (RDS/institution ratio); 98.7% of all beams agreed within 5% and 91.2% agreed within 3%. Histograms and summary statistics for TLD/institution ratios (for past 15 years, 2001 - 2016) are shown below for all beams, and according to beam type, i.e. MV photon, electron, and orthovoltage beams. Click on the graphs to enlarge.
For any radiation therapy beam output check outside ± 5% for MV photon and electron beams, or ± 10% for orthovoltage beams, the institution's physicists are contacted via email by RDS technical staff. Repeat irradiations may be requested by the physicist to confirm corrective actions. Often discrepancies are indicative of incorrectly calibrated beams, misinterpreting the irradiation instructions, or errors in completing the irradiation form.
Current RDS Users
The RDS has monitored the output of radiation therapy beams and blood irradiators for over 30 years. Since 2001, RDS has monitored approximately 21,000 radiation therapy beams at 2,000 institutions in the United States and 150 institutions in other countries seeking an independent peer review verification of their radiation beam outputs.