ISSN: 1755-5191

Imaging in Medicine

Short Communication - Imaging in Medicine (2016) Volume 8, Issue 1

Occupational eye lens dose in interventional radiology and cardiology: new insights

Efstathios P Efstathopoulos*

Department of Radiology, Medical School, National and Kapodistrian University of Athens,

Corresponding Author:
Efstathios P Efstathopoulos
Department of Radiology
Medical School, National and Kapodistrian University of Athens
Athens 12462, Greece
Tel: +30 210 5831818
E-mail: stathise@med.uoa.gr

Abstract

Interventional radiology and cardiology procedures deliver high radiation dose to physicians and interventional suite staff. Nowadays the interest has been focused on occupational dose to the lens of the eye. Recent epidemiological studies have shown that radiation-induced cataract is observed in lower dose threshold than the previous considered by ICRP 103. Based on these studies, in 2011, ICRP reduced the annual occupational dose limit for the lens of the eye to 20 mSv while the dose threshold was determined 0.5 Gy. Many reports have demonstrated that the occupational ocular dose may exceed the new annual limit if radiation protection equipment is not used. New considerations regarding the dose to the eye necessitate the education of medical personnel on radiation protection issues and the dosimetry of the lens in clinical routine.

Keywords

Occupational eye lens; Interventional radiology; Cardiology

The advances in digital imaging and the improvement in interventional tools and devices like catheters and stents have expanded the use of interventional procedures. During the period 1998-2008, the total number of interventional procedures increased by 78% [1]. Interventional radiology [IR] and cardiology [IC] procedures deliver high radiation doses both to patients and medical personnel, which has raised serious concerns regarding the harmful effects of ionizing radiation. Lately, the interest has focused on the occupational dose to the lens of the eye. It is well known that ionizing radiation is associated with posterior sub-capsular cataract [PSC] and cortical opacities [2]. Interventional radiologists, cardiologists and other medical staff who stand close to patient and the x-ray source during the fluoroscopy-guided procedures are at high risk concerning radiationassociated cataract, especially when the lens of the eye is unprotected. Ciraj-Bjelac et al. [3], showed that there is a strong correlation between radiationinduced cataract and exposure to medical staff working in IC when the protection tools are not used. More specifically, the investigators found that 52% of interventional cardiologists and 45% of nurses had posterior lens opacities while this quota amounted 9% for the control group. In a similar study conducted by Vano et al. [4], eye lens changes appeared to 38% of interventional cardiologists, 21% of nurses and 12% of unexposed controls. According to International Commission of Radiological Protection [ICRP] publication 103 [5], cataract formation is considered a deterministic effect with a threshold dose of 0.5-2 Gy for acute exposure and 5-6 Gy for chronic exposure. In the same report [5], the recommended annual

occupational equivalent dose for the lens of the eye is 150 mSv. However, recent epidemiological studies based on atomic bomb survivors [6,7] and Chernobyl cleanup workers [8,9] suggest a lower dose threshold for radiationinduced cataract than the previously proposed by ICRP 103. Nakashima et al. [6], in a reanalysis for radiation cataractogenesis among atomic bomb survivors, determine a threshold of 0.6 Sv for cortical cataract and 0.7 Sv for PSC whereas in a similar study, Neriishi et al. [7] gave a dose threshold from 0 to 0.8 Gy. An evaluation study among Chernobyl clean-up workers 12 and 14 yr after the accident [8] determined the threshold of cataract under 1 Gy. Particularly interesting are the low radiation dose studies. Chodick et al. [9], in a prospective study among radiologic technologists, showed a correlation between exposure to low dose ionizing radiation and the risk of developing cataract. These studies raised the concern regarding radiationinduced character and in 2011 ICRP published ‘’The Statement on Tissue Reactions’’ [10]. In this statement the threshold for the lens of the eye is determined 0.5 Gy whereas the equivalent dose limit was decreased by 87%. The new dose limit for the lens of the eye is now considered 20 mSv/year for occupational exposure. The dose for the lens of the eye varies among medical staff performing IR/IC procedures and depends on several factors such as the type of procedure, the exposure parameters [kVp, mAs, fluoroscopy time, magnification], the patient size, the position and the angle of the x-ray tube, the position of the operator and the use of radiation protection devices. Efstathopoulos et al. [11] investigating the occupational doses in 25 diagnostic and therapeutic IR/IC procedures concluded that the interventionists receive 64-1129 μSv to the lens of the eye and the nurses 4- 16 μSv. The investigators also found that the annual eye dose was 8.2 mSv for the interventional cardiologist and 0.5 mSv for the interventional radiologist with the highest workload while the corresponding dose was 27.9 mSv for the interventional radiologist who performed vertebroplasties. In a retrospective study, including 129 interventional cardiologists and electrophysiologists who worked for an average of 22 years, Jacob et al. [12] estimated the cumulative dose to the lens from 25 to 1600 mSv. In addition, Vano et al. [13] found that the cumulative eye dose for the catheterization laboratory staff ranged from 0.1 to 18.9 Sv. It is obvious from all these studies that the dose to the lens of the eye can exceed the new annual limit for personnel working in IR/IC. A pan-European project, called ORAMED [The Optimization of Radiation Protection for Medical Staff] project [14], that included six different countries and more than 1300 IR/IC procedures revealed that eye lens doses range from 10 μSv to 4 mSv per procedure, the cumulative annual eye lens dose from less than 1 mSv to 150 mSv whereas the 24% of medical personnel exceeds the new annual limit of 20 mSv. The results of the studies highlight the need for education and training of medical staff involved with IC/IR procedures on radiation protection issues. Physicians and other medical personnel should have deep knowledge about radiation protection principles and rules, be aware of the radiation-associated risk and use properly the radiation protection equipment. It has been proved that the use of radiation protection eyeglasses reduces the dose to the lens by 83-90% [14]. However, it is impressive that only 31% of interventional radiologists wear lead eyeglasses during interventional procedures [14]. In addition, Pantos et al. [15] showed that the dose to the eyes of the primary operator performed catheter ablation procedures was below 9 μSv per procedure when the interventionist used lead glasses and ceiling protection shield. New considerations concerning the radiation dose to the lens of the eye require more epidemiological studies especially at low radiation doses in order to have a more clear answer whether radiation-associated cataract is a deterministic or a non-threshold based effect. In addition, it is significantly important the establishment of an effective method for the dosimetry for the lens of the eye in clinical routine.

References

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