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Retrospective evaluation of lens injuries and dose study

What is RELID

An international study called RELID (Retrospective Evaluation of Lens Injuries and Dose) was initiated by the IAEA in 2008. RELID has two components namely, evaluation of dose and evaluation of radiation injury.

The evaluation of radiation dose to the eye is not a straightforward issue. The current measurement techniques are not adequately developed and are not available for routine use to know radiation dose to the eye lens. Thus retrospective estimations become necessary. The Form for retrospective evaluation of dose needs to be filled by the staff to help estimate radiation dose. The participant is asked to provide information on number of years of work in interventional lab, use of protective screens and eye wears, work load with fluoroscopy time and cine details as well as other information pertaining to technique that may have bearing on the radiation dose to the eye lens. Based on this information, the radiation dose is estimated. Availability of personal monitoring badge data helps in correlation. The location of the staff in the interventional room is also taken into account.

The ophthalmologist tests the eyes and scores the posterior subcapsular opacities using Merriam-Focht scores. The scoring is 0.5, 1.0, 1.5, etc. This is done separately for each eye. The quantification of opacity score helps in comparison with the estimated radiation dose and establish correlation.

Eye testing exercises conducted

A number of eye testing exercises have been conducted since September 2008: 

Place: Bogota, Colombia
Date: 25-26 September 2008
Regional/national organization involved: Latin American Society on Interventional Cardiology
RELID report Colombia in English, in Spanish

Place: Kuala Lumpur, Malaysia
Date: 17-19 April 2009
Regional/national organization involved: National Heart Association of Malaysia

Place: Montevideo, Uruguay    
Date: 16-17 April 2009
Regional/national organization involved: Latin American Society on Interventional Cardiology
RELID report Uruguay in English, in Spanish

Place: Varna, Bulgaria
Date: 11-12 July 2009
Regional/national organization involved: National Centre of Radiation Biology and Radiation Protection
RELID report Bulgaria 

Place: Sofia, Bulgaria
Date: 13-15 July 2009
Regional/national organization involved: National Centre of Radiation Biology and Radiation Protection
RELID report Bulgaria 

Place: Bangkok, Thailand
Date: 23-24 December 2009    

Place: Buenos Aires, Argentina
Date: 11-13 August 2010
Regional/national organization involved: Latin American Society on Interventional Cardiology
RELID report Argentina in English, in Spanish

Place: Kuala Lumpur, Malaysia
Date: 6-7 May 2011
Regional/national organization involved: National Heart Association of Malaysia

About IAEA cataract study

The lens of the eye is one of the radiosensitive tissues in the body. Radiation induced cataract has been demonstrated among staff involved with interventional procedures using X rays. A number of studies suggest there may be significant risk of lens opacities in populations exposed to low doses of ionizing radiation. These include those undergoing CT scans, astronauts, radiologic technologists, radiotherapy besides data from atomic bomb survivors  and those exposed in Chernobyl accident.

These observations have clear implications for those working in interventional rooms. Interventionalists and paramedical staff (nurses and to some extent radiographers) remain near the X ray source and within a high scatter radiation field for several hours a day during interventional procedures. During typical working conditions and if radiation protection tools are not routinely used, X-ray exposure to the eyes of interventional physicians and paramedical personnel working in interventional and catheterization laboratories can be high.

The cataract has so far been considered to be a deterministic effect with threshold. The International Commission on Radiological Protection (ICRP) and the U.S. National Council on Radiation Protection and Measurements (NCRP)  have published threshold values, for detectable opacities of 5 Sv for protracted exposures and 0.5 to 2 Sv for acute exposure.

The Commission has now reviewed recent epidemiological evidence and has issued a statement after its meeting on 21st April 2011.

According to this statement, the threshold in absorbed dose for the lens of the eye is now considered to be 0.5 Gy.Estimations indicate that cumulative lifetime occupational doses received by interventionalists and some paramedical staff may exceed these currently accepted international standards unless specific measures are taken.

In its 2007 recommendations the ICRP stated that ‘‘new data on the radiosensitivity of the eye with regard to visual impairment are expected ... because of the uncertainty concerning this risk, there should be particular emphasis on optimization in situations of exposure of the eyes”. The most recent ICRP statement for tissue reactions continues to recommend that optimization should be applied in any exposure situation and for any category of exposure.

Subcapsular posterior lens changes, characteristic of radiation exposure with a dose-effect threshold significantly less than 1 Gy were recently reported in Chernobyl cleanup workers. These findings are inconsistent with the 2000 and 2007 ICRP threshold of 5 Gy for ‘‘detectable opacities’’ from protracted exposures. However, these data agree with the new threshold of 0.5 Gy for detectable lens opacities that was recently proposed in the ICRP statement.

The regular and appropriate use of the personnel monitoring device by interventionalists is largely lacking. In surveys conducted by the IAEA during various training courses, in which cardiologists from over 56 countries have participated, responses indicate that only 33-77% of interventional cardiologists utilize radiation badges routinely.