Occupational Eye Lens Dose in Interventional Radiology and Cardiology: New Insights

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, 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.