Now it is official. In two separate studies, researchers supported by the International Atomic Energy Agency (IAEA) recently concluded that interventional cardiologists and associated workers who have not used radiation protection accessories have significantly elevated incidence of radiation associated eye lens changes; and that there is urgent need to educate them in radiation protection to reduce the likelihood of cataract.
Published studies
Radiation Research (June 28, 2010) and Catheterization and Cardiovascular Interventions (June 14, 2010) two peer reviewed journals have published these studies.
There are three main forms of cataract according to its anatomic location: nuclear, cortical and posterior sub capsular (PSC). Among the three forms of age-related cataract, PSC is the least common but this form is most commonly associated with exposure to ionizing radiation. Researchers in both studies demonstrated a dose-dependent, increased risk of posterior lens opacities for interventional cardiologists and nurses when they did not use radiation protection accessories.
Larger cohort needed
Though a larger cohort is needed to confirm the findings, the results suggest that radiation protection measures for eyes must be in place.
In both studies, two independent specialists each trained in the recognition and evaluation of characteristic, radiation-induced lens changes, examined the eyes of each participant after full dilation.
The study published in Radiation Research showed that the interventional cardiologists have 3.2 times more risk than for unexposed controls. For nurses and technicians, the relative risk was 1.7 times more.
The study groups consisted of 116 exposed individuals (interventional cardiologists: 58 and associated workers :) and 93 similarly aged non-exposed individuals.
The paper published in Catheterization and Cardiovascular Interventions showed that the relative risk for interventional cardiologists was 5.7 and for nurses and paramedical staff, it was five, compared to unexposed controls. This group contained 67 physicians and nurses and 22 age and sex matched health care professionals not working in interventional medicine.
“The lens of the eye is one of the most radiosensitive tissues in the body and exposure of the lens to ionizing radiation can cause cataract” the researchers wrote in Radiation Research.
“Ionizing radiation exposure to eye lens results in characteristic progressive changes leading to opacification or clinical cataract. While initial, early stages of such opacification may not cause visual disability, the severity of such changes increases progressively with dose until vision is impaired and cataract extraction surgery is required,” the researchers warned.
“Because of its location along the visual axis of the lens, relatively minor PSC can have a great impact on vision,” the researchers cautioned.
Cataract sets in early, if the dose is larger. Cumulative x-ray doses to the lenses of interventional cardiologists and staff can be very high. They often remain close to the patients for several hours a day during cardiac interventional procedures. Patients scatter x-rays.
Combining doses
The researchers evaluated eye lens dose of each participant by combining doses measured from several catheterization laboratories with the subject's reported annual workload (number and kind of procedures carried out).
In 2007, the International Commission of Radiological Protection (ICRP), in its latest recommendation, reiterated the suggestion from recent studies that the lens of the eye may be more radiosensitive than previously considered.
Surveys during various IAEA training courses in which cardiologists from 56 countries attended indicated that only 33-77 per cent interventional cardiologists used dose measuring badges routinely. They did not use protective accessories universally.
An AERB workshop on “Radiation safety in interventional radiology including cath lab” in April 2009 highlighted the need for formal training in this important area. Taking into account its potential to deliver high radiation doses, the Atomic Energy (Radiation Protection) Rules 2004 prescribed that all such equipment must have a “license”, the highest form of regulatory documentation and control.
Interventional cardiologists must receive appropriate training and accreditation to use radiation equipment optimally without undue risk. AERB and the relevant professional associations must take the lead in achieving this objective.
Let us learn from the experience of advanced countries which acted promptly when patients suffered skin injuries. The new findings on cataract must speed up a comprehensive programme of training.
The training material is freely available at: >http://rpop.iaea.org/RPOP/RPoP/Content/AdditionalResources/Training/1_TrainingMaterial/Cardiology.htm>
Raja Ramanna Fellow, Department of Atomic Energy
