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Matemática Aplicada Semana da Pós Graduação
AN OVERVIEW OF EQUIVALENT DOSES IN EYE LENS OF
OCCUPATIONAL RADIATION WORKERS IN MEDICAL, INDUSTRIAL
AND NUCLEAR AREAS
Alexandre Roza de Lima Radiation Protection Manager
Co-authors: Dr. Francisco Cesar A Da Silva Dr. John Graham Hunt
INDUSTRIAL APPLICATIONS
INTRODUCTION
With the advancement in technology in the use of nuclear energy, the domestic nuclear scene is taking on an important role in the market and in the quality of life of the population, as much in the generation of energy as in its application in the areas of medicine and industry.
NUCLEAR APPLICATIONS
MEDICAL APPLICATIONS
Work involving medical, nuclear and industrial applications must be developed in such a way that the doses are as low
as possible, taking as policy the limitations and restrictions of such doses.
INTRODUCTION
Thus, in normal exposure, the Individual Occupational Exposure (IOE) and members of the public, do not exceed the dose limits
stipulated by the Regulatory Authority of the country.
• Finding a correlation between the effect caused by radiation and the dose of radiation received, has always troubled researches and doctors. With this intention, various researchers have tried through their scientific work to estimate doses of radiation using the technology available at the time. The most certain data was related to high doses, to radiological and nuclear accidents and to observing victims of Hiroshima and Nagasaki or experiments with guinea pigs.
• The effect of the radiation basically depends on the type of radiation energy, rate and consistency of the dose and above all, the sensitivity to radiation of the particular tissue or organ.
• The tissues most sensitive to radiation are the parts of the reproductive organs, bone marrow and the lenses of the eyes. This last effect is generating most attention on the part of researchers and doctors.
INTRODUCTION
What is Cataract?
INTRODUCTION
Catarat
Loss of transparency of the lens
So far, the cataract has been considered as a deterministic effect of a threshold dose, however the most recent epidemiology studies indicate that this type of damage also has the character of being probably being able to manifest itself by only small doses.
Normal vision Vision with Cataract
The International Commission of Radiological Protection (ICRP) analysed recent epidemiology evidence that suggested that for the lens of the eye, the threshold dose absorbed to cause biological effects is around 0.5 Gy.
INTRODUCTION
Lens opacity at the posterior subcapsular region caused by radiation
On this basis, on April 21, 2011, the ICRP has recommended changes to the occupational dose limit in planned exposure situations, reducing the eye lens dose equivalent limit from 150 mSv to 20 mSv per year, on average, during the period of 5 years, with exposure not exceeding 50 mSv in a single year.
INTRODUCTION
In face of this recommendation, t h e B r a z i l i a n N a t i o n a l Commission of Nuclear Energy (CNEN) adopted the new limit to the eyes lens through resolution CNEN n°114/2011 published on September 1, 2011.
INTRODUCTION
• Recent studies have pointed to the need for a more systematic monitoring of doses in eye lens of IOE involved in exhibitions planned, however the current studies were obtained only in exhibitions planned, such as medical, interventional medicine.
• The professionals involved in other medical, industrial and nuclear applications can be exposed to significant levels of radiation, from the point of view of radiation protection. It therefore becomes necessary to estimate the doses of radiation entering the lens of all individuals exposed occupationally.
INTRODUCTION
What should be done?
• This study aimed to show an overview about the doses in eye lens of occupational radiation workers in situations of planned exposures in the medical, industrial and nuclear areas, emphasizing applications of radiation that have the greatest radiological risks.
• A Brazilian software named “Visual Monte Carlo – VMC” applied to calculations external dose, allowing assess the impact of this new dose limit and provide for adjustments in the current scenarios is also introduced. In addition, some advices for radiation workers to avoid receiving doses higher than the established by the Regulatory Authority were recommended.
OBJECTIVE
KLEIN BE, KLEIN R, LINTON KL, FRANKE T., Diagnostic x-ray exposure and lens opacities: the Beaver Dam Eye Study. [1993]
RECENT EPIDEMILOGICAL STUDIES
DAY R, GORIN MB, ELLER AW. Prevalence of lens changes in Ukrainian children residing around Chernobyl. [1995]
RECENT EPIDEMILOGICAL STUDIES
CUCINOTTA FA, MANUEL FK, JONES J, ISZARD G, MURREY J, DJOJONEGRO B, WEAR M. Space radiation and cataracts in astronauts. [2001]
RECENT EPIDEMILOGICAL STUDIES
VANO, E., GONZALEZ, L., FERNANDEZ, J. M. AND HASKAL, Z. J. Eye lens exposure to radiation in interventional suites: caution is warranted. [2008]
RECENT EPIDEMILOGICAL STUDIES
Alterations in the subcapsular posterior of the lens, characteristics of exposure to radiation at a threshold of an effective dose less than 1 Gy were reported in cleaners of Chernobyl WORGUL [2007].
These results are inconsistent compared to ICRP 85 and ICRP 103, which report that that the threshold dose for detectable opacity was from 2 Gy in acute exposure and 4 Gy in prolonged exposure. However, this data is in agreement with the new limit of 0.5 Gy for detectable opacity that was recently proposed in ICRP 2011b.
RECENT EPIDEMILOGICAL STUDIES
Normally, individual external monitoring records the effective dose (or equivalent dose in an organ or relevant body tissue) received by each individual during a specific period. This allows the evaluation of work conditions and the comparison with the established dose limits (standards). In the case of equivalent dose in the lens, individually calibrated monitors must be used in the operational amount Hp (3). However, at the moment in Brazil there is no supply of such monitors, making an experimental study of the levels of radiation received into the lens of professionals unviable.
PHYSICAL DOSIMETRY OF EYE LENS
In EYE-D ™ the proven and reliable high-sensitive thermoluminescence detectors MCP-N (LiF:Mg,Cu,P) are applied, which assure the good energy – response and broad dose range between at least 10 µSv and 10 Sv.
Eyes lens TLD dosemeter by ORAMED for monitoring of Hp(3) doses
PHYSICAL DOSIMETRY OF EYE LENS
A Brazilian software named “Visual Monte Carlo –VMC” has also been developed using the Monte Carlo Method and a human body simulator.
MONTE CARLO METHOD
VMC and ICRP Male Simulator
The VMC photon transport algorithms have been applied to dose calculations (VMC dose calculation) and to simulating the counting geometry as applied to in-vivo measurements (VMC in-vivo). This software VMC enables to calculate the absorbed dose received by each organ and tissue relevant to the calculation of effective dose, as defined in ICRP Publication 103.
MONTE CARLO METHOD
VMC and ICRP Male Simulator
A research project is now ongoing to calculate the eye lens doses to workers in many areas of radiation applications using the VMC. The first results about this theme were presented on a paper named “Estimation of Eye Lens Dose to Industrial Gammagraphy Workers” (IRPA13 Congress, 2013).
MONTE CARLO METHOD
VMC and Positions
ü It can be inferred that the dose in the lens of the eye of those who work with radiation, albeit in the medical, nuclear or industrial area or in planned or unplanned situations of expose, has always been a concern and a motive for investigation by various researchers due to the possibility of the lens suffering cataracts.
ü But, this concern became more real after the alteration made by the ICRP on the occupational dose limit when the equivalent dose limit of the lens was reduced from 150 mSv/year to 20 mSv/year.
ü Despite this change having as its foundation planned exposures associated with medical procedures, it was observed that it was necessary to follow more systematically the doses entering the lens of the eye of workers involved in applications of radiation that had greater radiological risk, such as in nuclear and industrial areas.
CONCLUSIONS
ü The estimate of the dose in the lens resulted in the development of technology for the use of dosimeters compatible with each practical situation, because not only is an accurate device required but as well their calibration to non-conventional magnitudes.
ü To make up for this omissions, researchers are developing specific computational programs based on the Monte Carlo Method, which make it possible to estimate the dose in the lens without the necessity of advanced technology.
ü It is hoped that this study serves as a reference for subsequent works about this theme, emphasizing and stimulating new experimental and computational studies resulting in a greater certainty of the risks associated with exposure to radiation in the face of the new lens dose limits recommended by the ICRP.
CONCLUSIONS
• C.M ARAUJO LIMA, F. C. A. DA SILVA “Análise de Acidentes e Incidentes Radiológicos em Radiografia Industrial”, Monografia Pós-Graduação IRD, 2011.
• F. C. A. DA SILVA “Dosimetria Reconstrutiva de Acidentes Radiológicos usando o Método de Monte Carlo”, Tese Doutorado IRD/COPPE/UFRJ, 2003.
• A. R. LIMA, F. C. A. DA SILVA, J.G. HUNT “Estimativa de Dose Equivalente nos Cristalinos dos Operadores de Gamagrafia Industrial usando o Método Monte Carlo”, IRPA, 2013.
• J.G. HUNT, “Calibração de um Sistema de Medida in vivo através da Simulação da Fonte de Radiação e do Detector utilizando-se a Técnica de Monte Carlo”, Tese de Doutorado, UERJ, 1998.
• TAHUATA. L., SALATI, I.P.A., PRINZIO, R.DI., PRINZIO, M.A.R.R.DI., “Radioproteção e Dosimetria: Fundamentos - 5ª Revisão – IRD/CNEN, 2013
• COMISSÃO NACIONAL DE ENERGIA NUCLEAR. NN – 3.01. Diretrizes Básicas de Proteção Radiológica, Resolução nº 114, 2011.
• INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION 2000. Radiopathology of skin and eye and radiation risk. ICRP PUBLICATION 85. ANN. ICRP 30.
• INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION 2007 Recommendations of the International Commission on Radiological Protection ICRP Report 103; Ann. ICRP 37
REFERENCES
• INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION 2011 Statement on tissue reactions ICRP Ref 4825-3093-1464
• INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION 2012Recommendations of the International Commission on Radiological Protection ICRP Report 118 (116-134)
• RELID (Retrospective Evaluation of Lens Injuries and Dose). Available on: http://rpop.iaea.org/RPOP/RPoP/Content/News/relid-cataract-study.htm(last accessed on 12 March 2013).
• HOME by INFOMEDICA WIKI http://pt-br.infomedica.wikia.com/wiki/Catarata • HOME by Radiation Effects Research Foundation
http://www.rerf.jp/radefx/early_e/cataract.html • KLEIN BE, KLEIN R, LINTON KL, FRANKE T., Diagnostic x-ray exposure and lens
opacities: the Beaver Dam Eye Study. Am J Public Health Apr;83(4):588-90 (1993). • DAY R, GORIN MB, ELLER AW. Prevalence of lens changes in Ukrainian children
residing around Chernobyl. Health Phys. May;68(5):632-42 (1995) • HALL P, GRANATH F, LUNDELL M, OLSSON K, HOLM LE. Lenticular opacities in
individuals exposed to ionizing radiation in infancy. Radiat Res. Aug;152(2):190-5 (1999)
• CUCINOTTA FA, MANUEL FK, JONES J, ISZARD G, MURREY J, DJOJONEGRO B, WEAR M. Space radiation and cataracts in astronauts. Radiat Res. Nov;156(5 Pt 1):460-6 (2001)
REFERENCES
• RASTEGAR N, ECKART P, MERTZ M. Radiation-induced cataract in astronauts and cosmonauts. Graefes Arch Clin Exp Ophthalmol. Jul;240(7):543-7 (2002)
• NERIISHI, K., NAKASHIMA, E., MINAMOTO, A., FUJIWARA, S., AKAHOSHI, M., MISHIMA, H. K., KITAOKA, T. AND SHORE, R. E. Postoperative cataract cases among atomic bomb survivors: radiation dose response and threshold. Radiat. Res. 168, 404–408 (2007).
• NAKASHIMA, E., NERIISHI, K. AND MINAMOTO, A. A re-analysis of atomic bomb cataract data, 2000–2002: a threshold analysis. Health Phys. 90, 154–160 (2006).
• WORGUL, B. V. ET AL. Cataracts among Chernobyl cleanup workers: implications regarding permissible eye exposure. Radiat. Res. 167, 233–243 (2007).
• VANO, E., GONZALEZ, L., FERNANDEZ, J. M. AND HASKAL, Z. J. Eye lens exposure to radiation in interventional suites: caution is warranted. Radiology 248, 945–953 (2008).
• E. BORMUSOV ET AL., Non-Thermal Electromagnetic Radiation Damage to Lens Epithelium. Open Ophthalmol J. 2: 102-106 (2008)
• BEHRENS, J. ENGELHARDT, M. FIGEL, O. HUPE, M. JORDAN AND R. Hp(0.07) photon dosemeters for eye lens dosimetry:calibration on a rod vs. A slab phantomR Seifert Radiation Protection Dosimetry Vol. 148, No. 2, pp. 139–142 (2012).
• Catálogo da RADCARD s.c., EYE-D ™, http://oramed-fp7.eu/
REFERENCES
