On the evaluation of the relative sensitivity of commercial TLD readers using well characterized TLD chips.
OBJECTIVE
To characterize a relative sensitivity or performance factor between two commercial thermoluminescent dosimeter (TLD) readers that can be used in inter comparing the thermoluminescent (TL) signals from the readers.


METHODS
The measurements were made with well-characterized TLD chips, TLD-100 (LiF: Mg; Ti). For illustrative purposes, we used the Harshaw TLD-5500 and the Victoreen 2800M TLD readers available in our department. A well-calibrated 6 MV beam linear accelerator was used as the source of radiation.


RESULTS
A sensitivity factor between the two readers used in the illustration was measured as 3.40 +/- 0.13 with the Harshaw TLD-5500 reader producing the superior sensitivity. In terms of measurement repeatability, we observed 2.32% +/- 1.17% reproducibility with the Victoreen 2800M TLD reader and 1.86% +/- 0.95% reproducibility with the Harshaw TLD - 5500 reader. The linearity properties of the two readers were comparable.


CONCLUSIONS
The sensitivity factor is to be interpreted as follows: when working with multiple TLD readers, in this case two, suppose the calibration of the TLD chip was performed with one of the readers, then we can use this calibration factor when measurements are made with the other reader provided we correct for differences in sensitivity with a relative sensitivity factor. This of course is true only if the TLD reader settings used at the time of measurement are similar to those used at the time of relative sensitivity characterization. Owing to a wide range of other factors that can affect the reader sensitivity, we recommend use of a relative sensitivity factor in protection level dosimetry only in situations where inaccuracies of up to 10% are acceptable.
Roland
T
T
Cancer Therapy and Research Center, Department of Medical Physics and Radiation Oncology, University of Texas Health Science Center, San Antonio, TX 78240, USA. roland@uthscsa.edu
Esquivel
C
C
Stathakis
S
S
Papanikolaou
N
N
D006801:Humans; D015203:Reproducibility of Results; D013819:Thermoluminescent Dosimetry