The Use of Teflon-embedded Calcium Sulphate

Dysprosium Thermoluminescent Dosimeters for Chest Radiography

Abstract

As part of a U.S. multi-regional pilot study conducted by the six Centers for Radiological Physics, 12-mm-diameter by 0.4-mm-thick CaSO₄:Dy Teflon-embedded discs were evaluated and used to measure patient entrance exposure on GO “average” patients at 12 clinical centers. The discs were found to have adequate sensitivity, reproducibility and linearity up to 69.7 μC kg⁻¹ (270 mR). The minimum measurable exposure was estimated as 0.4 μC kg⁻¹ (1.5 mR). All responses were corrected for energy dependence, which varied ±20% from 1.7 to 6.5 mm Al half value layer. Patient entrance exposure values ranged from 1.3 to 28 μC kg⁻¹ (5 to 110 mR), with a median value of 5.2 μC kg⁻¹ (20 mR). This value agreed with exposure measurements made on the chest radiography equipment using an ionization chamber and a phantom which simulated an “average” patient, and with published Nationwide Evaluation of X-Ray Trends (NEXT) data for the same period.