2.3. Thermoluminescent dosimeters
Twenty-six thermoluminescent dosimeters were used (TLD-100 consisting of LiF: Mg, Ti). The TLDs were calibrated at known values of exposure, ranging from 1 to 15 mGy, in diagnostic radiology qualities, with computed tomography protocols RQT8, RQT9 and RQT10. Industrial x-ray equipment was used for this calibration: a Pantak/Seifert 160HS ISOVOLT property of the Institute of Nuclear Energy Research (IPEN) in São Paulo, Brazil. All readings (calibration and measurements) were performed on a Harshaw TLD reader, model QS 3500™, with the aid of WinREMS™ software coupled to a data acquisition system. The dose response curve was determined from the calibration with a coefficient of variation of 8%. The measurement of the dose was determined in each TLD because of the dose–response curves, presented in Fig. 2, corrected by the calibration factor of the dosimeter and the reference light at the time of reading. The result had the maximum uncertainty of the order of 10%.