Comparison of TLD calibration methods for dosimetry

Abstract

For the purpose of dose measurement using a high‐dose rate 192Ir source, four methods of thermoluminescent dosimeter (TLD) calibration were investigated. Three of the four calibration methods used the 192Ir source. Dwell times were calculated to deliver 1 Gy to the TLDs irradiated either in air or water. Dwell time calculations were confirmed by direct measurement using an ionization chamber. The fourth method of calibration used 6 MV photons from a medical linear accelerator, and an energy correction factor was applied to account for the difference in sensitivity of the TLDs in 192Ir and 6 M V. The results of the four TLD calibration methods are presented in terms of the results of a brachytherapy audit where seven Australian centers irradiated three sets of TLDs in a water phantom. The results were in agreement within estimated uncertainties when the TLDs were calibrated with the 192Ir source. Calibrating TLDs in a phantom similar to that used for the audit proved to be the most practical method and provided the greatest confidence in measured dose. When calibrated using 6 MV photons, the TLD results were consistently higher than the 192Ir−calibrated TLDs, suggesting this method does not fully correct for the response of the TLDs when irradiated in the audit phantom.PACS number: 87

Australasian brachytherapy audit: Results of the ‘end‐to‐end’ dosimetry pilot study

“…Details of the calibration process are described by Haworth et al . Briefly, the TLDs were calibrated using a modified version of the audit phantom.…”

“…). Details of the uncertainties associated with the calibration process are contained in the publication of Haworth et al . and are summarised in Table .…”

“…The total uncertainty is the sum in quadrature of all the components and does not include the uncertainty in the thermoluminescent dosimeter ( TLD ) reading (0.7%). For further details on how these factors were derived, the reader is referred to Haworth et al …”

Avaliação de parâmetros dosimétricos de fontes de braquiterapia utilizando simulação Monte Carlo e dosimetria gel polimérica

“…Atualmente, muitos sistemas dosimétricos têm sido estudados com o objetivo de determinação experimental de dose em sistemas de planejamento em radioterapia, dentre eles a câmara de ionização, dosímetros termoluminescentes (TLDs) filmes radiocrômicos e dosímetro gel polimérico (ROMANO et al, 1996;MCJURY et al, 2000;PERONI et al, 2007;DEMPSEY, 2010;HAWORTH et al, 2013). Porém, dosimetria em braquiterapia é de grande complexidade, devido ao alto gradiente de dose em regiões muito próximas à fonte, ao tamanho dos dosímetros utilizados experimentalmente e à alta dependência energética dos mesmos (KARAISKOS et al, 1998).…”

“…Os dosímetros comumente utilizados para tal fim são os dosímetros termoluminescentes e os filmes dosimétricos (SCHWOB, ORION, 2007;SHARMA, JURSINIC, 2013;LUCAS, AUBINEAU-LANIÈCE, LOURENÇO, 2014). Estes, porém, não apresentam as características necessárias de resolução espacial e possibilidade de obtenção de distribuições tridimensionais de dose (TEDGREN, HEDMAN, GRINDBORG, 2011;HAWORTH, BUTLER, WIFERT, 2013;MORRISON, GEETHA, SLOBODA, 2014).…”