Speakers
Description
Introduction
Almost 20% of the occupationally exposed workers assessed are interventional radiology professionals. Although lens of the eye radiological surveillance is not mandatory, implementing this type of dosimetry in the country is an important asset in prevention of lens of the eye injuries due to radiation. The aim of this study was to evaluate DXT-100 extremity dosemeters suitability for lens of the eye dosimetry by compliance of IEC 62387 for photon radiation requirements of Coefficent of variation (CV) and Non linearity.
Materials and Methods
Element correction coefficients were determined previously at the laboratory using a 0.5 mCi Sr-90 source incorporated in TLD Reader according to user´s manual.
68 DXT-100 Thermo Fisher ® dosemeters where assembled on a 42mg/cm2 cap with an orange holder attached to a band and delivered to the national SSDL to be irradiated with a Cs-137 source at reference conditions for measuring Hp(3). (Fig 1)
Figure 1. Left: Hp(3) dosemeter assambled Right: dosemeters allocated in water phantom for irradiation
Table 1. Evaluated dose values
Dose values (w=16) were selected considering IEC 62387 section 11.3.2 (Table 1). For each dose value, 4 DXT-100 dosemeters were irradiated. 4 DXT-100 were assigned to background measurement.
All readings were performed in a Harshaw 6600 plus model with acquisition set up and Time Temperature Profile as suggested in user´s manual.
Coefficient of variation was calculated as follow (eq 3.3 IEC 62387):
s= standard deviation, G = average dose for each dose value n. For Non Linearity doses from 0.1 to 100 mSv where evaluated. Percentage of relative response was calculated (eq. 3.35, IEC 62387): where R = reader value, R0= dose delivered
Results and Discussion
Coefficient of Variation
Results are shown inTable 2. Requirements are met when CV is equal or below c1 column for w-2 evaluated doses and the last 2 (no adjacent doses) equal or below c2 column.
Table 2. Calculated Coefficient of Variation for Hp(3) (*)not met
In general, requirements were met with or without ecc correction. When ecc where applied better CV values where obtained. Three evaluated doses (shown in red) didn´t met the requirements. In these cases, further analysis with a greater number of dosemeters tested would be needed.
Non Linearity
Non linearity shall be between -9% and +11%. Results are shown in table 3.
Table 3. Relative response -non linearity (difference in %)
(*)not met
Better linearity was achieved when ecc´s where applied.
Conclusion
DXT-100 extremity dosemeters are suitable for Hp(3) determination in terms of coefficient of variation and Non linearity requirements of IEC 62387. Best results were obtained when no ecc´s were applied.
Further type test- angle of incidence,energy dependence - must be perform. The use of DXT-100 for evaluate Hp(3) will allow to set national reference levels for lens of the eye.
References
IEC 62387:2012 Radiation Protection Instrumentation Passive integrating dosemeter systems for personal and environmental monitoring of photon and beta radiation
Norma UY 100, 2018. Basic Regulation for Radiological Safety and Radioprotection.
Harshaw 6600 plus TLD Reader Operator´s Manual
| Speakers email | analaura.garcia@miem.gub.uy |
|---|---|
| Speakers affiliation | Personal External Dosimetry Laboratory- Ministry of Industry, Energy and Mining |
| Name of Member State/Organization | Uruguay/Ministry of Industry, Energy and Mining-National Regulatory Authority in Radioprotection |
