Purpose: To determine the energy correction factor for TLD‐100 chips comparing 6 MV and 10 MV photon beams produced by a Varian Linac to [formula omitted] energy. Method and Materials: The energy correction for the difference in thermoluminescent (TL) response for 6 and 10 MV photons from a linac compared to [formula omitted] energies were measured with LiF TLD‐100 (LiF:Mg, Ti) thermoluminescent dosimeters (TLDs). This energy correction and dose dependence were determined by irradiating TLD‐100 chips (3 mm × 3 mm × 1mm) to varying doses (100–300 cGy) using [formula omitted] and 6 and 10 MV photons from a Varian linac. TLD irradiations were done in liquid water with water tight Virtual Water™ TLD holders. Doses delivered to the TLDs for both [formula omitted] and linac irradiations were verified with ion chamber measurements following the AAPM's TG‐51 protocol. [formula omitted] TLD irradiations were also done in air with a PMMA holder. Monte Carlo methods were used to determine the absorbed dose to water at the same location where the TLDs were irradiated. Results: The energy correction factor was determined to be the ratio of linac TL output to the dose delivered by the linac divided by the [formula omitted] TL output. The results of the test showed less than a two percent correction for both the 6 and 10 MV beam with standard deviation of the mean of less than 0.2 percent. No dose dependence was seen in the range of 100 to 300 cGy. Conclusion: The energy correction factor for TLDs allows TLDs to be used as a secondary verification of linac outputs relative to a [formula omitted] standard.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging