Automated thermoluminescent dosimetry for simple radiographic procedures

The Harshaw 6600 reader is designed for personal monitoring using whole body cards and extremity dosemeters. The latter have the potential for use in performing a large scale patient dose survey during radiographic procedures but have not previously been used for this purpose. This system has several potential advantages: fast read-out rate, reproducible time temperature profile, no mechanical contact with the dosemeter and barcode identification. This allows individual elemental correction coefficients to be applied to each chip which thereby improves the measurement precision. This system was rigorously tested prior to use for patient dosimetry. Reproducibility, batch uniformity and minimum detectable dose were found to be 2.9%, 3.1% and 0.1 mGy respectively. Signal fading after receiving a radiation dose was found to be 25% over a three month period whilst the fading before exposure was found to be 12% over three months. The energy response of the dosemeters relative to that measured using 137Cs gamma rays was found to vary between 1.3 and 1.6 over the range 45 - 104 keV. The overall uncertainty of the results was assessed and compared with the value recommended by the National Patient Dosimetry Protocol. It was concluded that the system could be used with extremity dosemeters for large scale patient dosimetry surveys.