Radiation Dosimetry Services
Rebecca Howell, Ph.D.
Director
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)
- Cobalt-60
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 Radiation Quality Assurance Laboratory for these service needs. You may call their office at 713-745-8989, fax them at 713-794-1364 or email them at RQALab@mdanderson.org.
Reader Work
Dosimetry Process
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.
Dosimetry Data
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); 98.6% of all beams agreed within 5% and 90.9% agreed within 3%. Histograms and summary statistics for TLD/institution ratios (for the past 20 years, 2000 - 2019) are shown for All beams, and according to beam type, i.e., MV photon, Electron, and Orthovoltage beams.
Dose Ratios for Beams 01/01/2000-12/31/2019
All Beams
MV Photon Beams
Electron Beams
Orthovoltage Beams
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.
The history of the RDS independent peer review services dates back more than a half-century. We ship TLD worldwide and on-demand. We currently provide services for:
- 1,460 participating institutions in the United States and
- 163 participating institutions globally
As we look to the future, the RDS is working toward further expanding our services to additional centers all over the world to enhance safety and confidence at all radiotherapy centers.
Our Team Today
The director of RDS is Rebecca Howell. She has 20 years of clinical experience and is a tenured professor, certified by the ABR in Therapeutic Radiologic Physics and a fellow of the American Association of Physicists in Medicine.
The RDS has highly qualified and very dedicated faculty and staff, many of whom have worked at the RDS for more than thirty years. In total, the RDS has 16 faculty and staff members including medical physicists, medical dosimetrists, computational scientists, research technicians and radiological technicians, as well as accounting and administrative staff. Also, part of the RDS team are three graduate students from the Medical Physics Graduate Program at the MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences. We collaborate closely with the other sections within MD Anderson Outreach Physics, namely the Imaging and Radiation Oncology Core (IROC) Houston QA Center and the MD Anderson Accredited Dosimetry Calibration Laboratory.
History
In 1968, the Texas Regional Medical Physicists (TRMP) program began under the leadership of Robert Shalek to help its member physicists by providing services such as mailed TLD output checks, dosimetry review visits, computer-based dose calculations, equipment loans, etc. Then in 1974, the National Cancer Institute (NCI) funded the six Centers for Radiological Physics, and the TRMP was among the six. Ultimately those centers evolved to become the NCI-funded Radiological Physics Center (RPC [now IROC-Houston]), with service dedicated to radiotherapy facilities participating in NCI-funded trials.
In 1985, Shalek decided to offer services for a fee to radiotherapy facilities not monitored by the RPC. This new for-fee service was named the MD Anderson RDS. Marilyn Stovall led the RDS from 1986 until she retired in 2015 (after 65 years of service at MD Anderson). During those 30 years, the number of customers serviced by RDS grew dramatically both domestically and internationally. Upon Stovall's retirement, David Followill was appointed to be RDS' Director and Rebecca Howell as the Associate Director. After serving as the associate director of RDS for one year, Howell was promoted to director in 2016. Followill continues in his role as director of IROC Houston and Section Chief of Outreach Physics.