Since TLD-100 response varies significantly with radiation energy, to perform accurate dosimetry for BT treatments with Ir-192, calibration was performed indirectly by exposing the dosimeters to three different radiation fields:
The batch of 20 TLDs was randomly divided into four groups of 5 dosimeters. One group was used for radiation background, while the remaining groups were irradiated with known radiation doses of 0.5, 1.5, and 5 Gy, with each one being exposed to the three radiation fields. For each exposure, a graph of reading vs dose was plotted and, through a linear fit the calibration factor (CF), was evaluated as the slope of the line.
A graph of CF vs energy was then plotted and the factor for Ir-192 was obtained as linear interpolation [55 (link),56 (link),57 (link)].
250 kV X-ray spectrum with 1 mm Cu added filtration (HVL = 2.1 mm Cu) with a Siemens Stabilipan 2 X-ray tube (Eaverage = 114 keV obtained with software TASMICS [52 (link)]).
Cesium-137 (Cs-137) with Gammacell® 40 Exactor by Best Theratronics (Eaverage = 662 keV).
Cobalt-60 (Co-60) with the Gammacell® 220 provided by Atomic Energy of Canada Limited (Eaverage = 1250 keV).
The batch of 20 TLDs was randomly divided into four groups of 5 dosimeters. One group was used for radiation background, while the remaining groups were irradiated with known radiation doses of 0.5, 1.5, and 5 Gy, with each one being exposed to the three radiation fields. For each exposure, a graph of reading vs dose was plotted and, through a linear fit the calibration factor (CF), was evaluated as the slope of the line.
A graph of CF vs energy was then plotted and the factor for Ir-192 was obtained as linear interpolation [55 (link),56 (link),57 (link)].
Free full text: Click here
