Determination of optically stimulated luminescence dosimetric characteristics and suitability for entrance surface dose assessement in diagnostic x-ray examinations

The availability of Optically Stimulated Luminescence (OSL) dosimeter system developed by Landauer Inc. (Glenwood IL) has greatly improved radiation dosimetry application in the medical field. Recent studies with OSL dosimeters (nanoDots) gave much emphases to patient radiation exposure in radiother...

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Main Author:	Musa, Yahaya
Format:	Thesis
Language:	English
Published:	2018
Subjects:	QC Physics
Online Access:	http://eprints.utm.my/id/eprint/81634/1/YahayaMusaPFS2018.pdf
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spelling	my-utm-ep.816342019-09-10T01:50:14Z Determination of optically stimulated luminescence dosimetric characteristics and suitability for entrance surface dose assessement in diagnostic x-ray examinations 2018 Musa, Yahaya QC Physics The availability of Optically Stimulated Luminescence (OSL) dosimeter system developed by Landauer Inc. (Glenwood IL) has greatly improved radiation dosimetry application in the medical field. Recent studies with OSL dosimeters (nanoDots) gave much emphases to patient radiation exposure in radiotherapy but ignoring the potential risks from radiographic examinations. This study focused on the measurement of entrance surface dose (ESD) resulting from radiographic examination. Monitoring procedures have been developed by the International Atomic Energy Agency (IAEA) to estimate ESD, while considering exposure parameters and patient’s characteristics. However, dosimetric properties of the OSL system must be characterized to ascertain its suitability for ESD measurements in medical radiography due to energy dependence and over-response factors of the Al2O3 material. This thesis consists of three phases: 1) evaluating stability of the new OSL dosimetry system, 2) characterizing the nanoDots in radiographic energy range from 40 kV to 150 kV with typical doses ranging from 0 to 20 mGy, and 3) assessing suitability of the nanoDots for ESD measurement in routine X-ray examinations. The dosimetric characteristics of the nanoDots in the above energy range are presented in this study, including repeatability, reproducibility, signal depletion, element correction factor, linearity, angular and energy dependence, and dose measurement accuracy. Experimental results showed repeatability of below 5% and reproducibility of less than 2%. OSL signals after sequential readouts were reduced by approximately 0.5% per readout and having good linearity for doses between 5 – 20 mGy. The nanoDots OSL dosimeter showed significant angular and energy dependence in this energy range, and corresponding energy correction factors were determined in the range of 0.76 – 1.12. ESDs were determined in common diagnostic X-ray examinations using three different methods including direct (measured on phantom/patient) and indirect (without phantom) measurements with nanoDots OSL dosimeters, and CALDose_X 5.0 software calculations. Results from direct and indirect ESD measurements showed good agreement within relative uncertainties of 5.9% and 12%, respectively, in accordance with the International Electrotechnical Commission (IEC) 61674 specifications. However, the measured results were below ESDs calculated with CALDose_X 5.0 software. Measured eye and gonad doses were found to be significant compared to ESDs during anterior-posterior (AP) abdomen and AP skull examinations, respectively. The results obtained in this research work indicate the suitability of utilizing nanoDots OSL dosimeter for entrance surface dose assessment during diagnostic X-ray examinations. 2018 Thesis http://eprints.utm.my/id/eprint/81634/ http://eprints.utm.my/id/eprint/81634/1/YahayaMusaPFS2018.pdf application/pdf en public http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:124969 phd doctoral Universiti Teknologi Malaysia Physics
institution	Universiti Teknologi Malaysia
collection	UTM Institutional Repository
language	English
topic	QC Physics
spellingShingle	QC Physics Musa, Yahaya Determination of optically stimulated luminescence dosimetric characteristics and suitability for entrance surface dose assessement in diagnostic x-ray examinations
description	The availability of Optically Stimulated Luminescence (OSL) dosimeter system developed by Landauer Inc. (Glenwood IL) has greatly improved radiation dosimetry application in the medical field. Recent studies with OSL dosimeters (nanoDots) gave much emphases to patient radiation exposure in radiotherapy but ignoring the potential risks from radiographic examinations. This study focused on the measurement of entrance surface dose (ESD) resulting from radiographic examination. Monitoring procedures have been developed by the International Atomic Energy Agency (IAEA) to estimate ESD, while considering exposure parameters and patient’s characteristics. However, dosimetric properties of the OSL system must be characterized to ascertain its suitability for ESD measurements in medical radiography due to energy dependence and over-response factors of the Al2O3 material. This thesis consists of three phases: 1) evaluating stability of the new OSL dosimetry system, 2) characterizing the nanoDots in radiographic energy range from 40 kV to 150 kV with typical doses ranging from 0 to 20 mGy, and 3) assessing suitability of the nanoDots for ESD measurement in routine X-ray examinations. The dosimetric characteristics of the nanoDots in the above energy range are presented in this study, including repeatability, reproducibility, signal depletion, element correction factor, linearity, angular and energy dependence, and dose measurement accuracy. Experimental results showed repeatability of below 5% and reproducibility of less than 2%. OSL signals after sequential readouts were reduced by approximately 0.5% per readout and having good linearity for doses between 5 – 20 mGy. The nanoDots OSL dosimeter showed significant angular and energy dependence in this energy range, and corresponding energy correction factors were determined in the range of 0.76 – 1.12. ESDs were determined in common diagnostic X-ray examinations using three different methods including direct (measured on phantom/patient) and indirect (without phantom) measurements with nanoDots OSL dosimeters, and CALDose_X 5.0 software calculations. Results from direct and indirect ESD measurements showed good agreement within relative uncertainties of 5.9% and 12%, respectively, in accordance with the International Electrotechnical Commission (IEC) 61674 specifications. However, the measured results were below ESDs calculated with CALDose_X 5.0 software. Measured eye and gonad doses were found to be significant compared to ESDs during anterior-posterior (AP) abdomen and AP skull examinations, respectively. The results obtained in this research work indicate the suitability of utilizing nanoDots OSL dosimeter for entrance surface dose assessment during diagnostic X-ray examinations.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Musa, Yahaya
author_facet	Musa, Yahaya
author_sort	Musa, Yahaya
title	Determination of optically stimulated luminescence dosimetric characteristics and suitability for entrance surface dose assessement in diagnostic x-ray examinations
title_short	Determination of optically stimulated luminescence dosimetric characteristics and suitability for entrance surface dose assessement in diagnostic x-ray examinations
title_full	Determination of optically stimulated luminescence dosimetric characteristics and suitability for entrance surface dose assessement in diagnostic x-ray examinations
title_fullStr	Determination of optically stimulated luminescence dosimetric characteristics and suitability for entrance surface dose assessement in diagnostic x-ray examinations
title_full_unstemmed	Determination of optically stimulated luminescence dosimetric characteristics and suitability for entrance surface dose assessement in diagnostic x-ray examinations
title_sort	determination of optically stimulated luminescence dosimetric characteristics and suitability for entrance surface dose assessement in diagnostic x-ray examinations
granting_institution	Universiti Teknologi Malaysia
granting_department	Physics
publishDate	2018
url	http://eprints.utm.my/id/eprint/81634/1/YahayaMusaPFS2018.pdf
_version_	1747818376450801664

Determination of optically stimulated luminescence dosimetric characteristics and suitability for entrance surface dose assessement in diagnostic x-ray examinations

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