Developement of a ring dosimeter using OSL technology (Optical Stimulated Luminescense)

• Grant number: 17/10525-4
• Support Opportunities: Research Grants - Innovative Research in Small Business - PIPE
• Start date: April 01, 2018
• End date: March 31, 2019
• Field of knowledge: Engineering - Biomedical Engineering
• Principal Investigator: Yvone Maria Mascarenhas
• Grantee: Yvone Maria Mascarenhas
• Company: Sapra Landauer Serviço de Assessoria e Proteção Radiológica Ltda
• CNAE: Atividades de serviços prestados principalmente às empresas não especificadas anteriormente
• City: São Carlos
• Associated researchers: Cristina Tereza Monteiro Ribeiro ; Maria de Fatima de Andrade Magon
• Associated research grant(s): 19/18131-0 - Development of a ring dosimeter using OSL technology (Optical Stimulated Luminescense), AP.PIPE
• Associated scholarship(s): 18/10405-1 - Development of a dosimetric ring using OSL (Optical Stimulated Dosimetry) technology, BP.TT

Abstract

Ionizing radiation (IR) provides a wide range of applications in society bringing significant benefits. However it has been found that ionizing radiation can also pose a risk to human health. Thus it is necessary to monitor the dose of occupationally exposed individuals (OEI). In Brazil, OEI monitoring is mandatory and currently the number of people monitored is approximately 180,000 in the country and 4 million worldwide. SAPRA-Landauer pioneered the individual external dosimetry service in Brazil using TLD technology since 1979. In 1998 the Optically Stimulated Luminescence Dosimetry (OSLD) with aluminum oxide (Al2O3:C), originally developed by Landauer Inc., a partner of SAPRA-Landauer, began to be used in several countries, mainly in the United States, France, England and Japan. In Brazil there is a certification system for individual external monitoring services (IEMS), which is regulated by the national Committee for the Evaluation of Testing and Calibration Services - CASEC / IRD / CNEN. From 2015, OSLD technology became available in Brazil with the certification obtained by SAPRA-Landauer. In some cases, such as in Nuclear Medicine (MN), X-ray interventions, catheterization, among others, the assessment of extremity and / or crystalline doses becomes particularly important. Although OSL technology has significant advantages over TLD technology, to date the OSL dosimetry is applied only to full-body monitors and wristbands. TLD typified with LiF:Mg, Ti is admittedly the only monitor available in ring dosimeters. The main restriction to the use of Al2O3:C for ring dosimetry is due to its dependence on the luminescence response from the energy of the radiation beam in the X-ray range (energy lower than 100 kV). For full body dosimeters and wristbands, this problem is circumvented with the use of more than one sensitive element and filters made from different materials. The relationship between the responses of these sensitive elements allows us to determine the average energy of the incident beam and thereby appropriately calculate the dose. Another restriction for the development of a ring using OSL is due to ergonomic reasons. Considering that this device must be comfortable for usage during working practices, the available options are limited, excluding the possibility of adopting multiple filters and sensors. The aim of this project is to develop a ring dosimeter model using OSL and Al2O3:C technology as a sensitive material, in a compatible size for its application in ring and crystalline type monitors, and low energy dependence response to the X-ray beam. In general, the methodology for this work is to develop a filter with thickness s and a central hole of diameter d. It will be studied how the behavior of the energy dependence of Al2O3:C varies according to the thickness and diameter of the hole, for different materials. Radiation tests for various exposure intensities, X-ray beam qualities and different filters will be performed. The ergonomics and material for the making of the ring will also be investigated. As a result of this first stage of the research, a filter configuration (material, thickness and orifice diameter) should be defined in order to eliminate its energy dependence for a small size detector that can be inserted into a ring. The validation of dosimetric ring adequacy is based on international standards that establishes test conditions and maximum permissible deviations in the evaluation of the dosimetric value measured Hp (0,07) obtained from a certain monitor / reader. Limiting the energy dependence of Al2O3:C to less than 30% in the (0,02 - 1.25) MeV photon range is the first step to obtain a ring dosimeter that offers the advantages related to OSL dosimetry. Such a device, worldwide unprecedented, can have great market acceptance due to the efficiency of the OSL technique. (AU)