Purpose: Thermoluminescent dosimeters (TLDs) are used to measure absorbed dose to water by calibrating them to a known dose from [formula omitted], a NIST traceable standard. Energy correction factors were measured that enables the conversion of TLD measured absorbed dose from [formula omitted] to absorbed dose from 6, 9, 12, 15, and 18 MeV electron beams. Method and Materials: Energy correction factors for LiF TLD‐100 (LiF:Mg, Ti) have been determined experimentally as the ratio of thermoluminescent response in electron beams from a linac over the response from [formula omitted]. Annealed TLD‐100 chips (3 mm × 3 mm × 1mm) were irradiated using [formula omitted] and 6, 9, 12, 15, and 18 MeV electron beams from a linac. TLD irradiations were carried out in liquid water with water tight Virtual Water™ TLD holders. Using Ion chamber measurements following the AAPM's TG‐51 protocol, doses delivered to the TLDs for both [formula omitted] and linac irradiations were verified. Results: The experiments showed a average energy correction factor of 0.95 for TLD‐100 chips for 6, 9, 12, 15, and 18 MeV electron beams relative to [formula omitted]. TLD's measured the energy correction factors for electron beams with good precision in a single experiment, with the standard deviation of the mean for the energy correction factors found in each experiment ranging from 0.3% to 0.5%. However, the TLDs were found to be less precise across multiple experiments. The standard deviation of the energy correction factor from experiment to experiment ranged from 2% to 5%. Conclusions: The ability to verify and maintain strict quality control is a fundamental necessity in a radiation treatment facility. External secondary audits are an essential part of a quality assurance program. Energy correction factors allow for TLD's to provide an inexpensive and convenient method to perform external secondary audits of high energy electron beam absorbed dose calibrations.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging