Picano et al. BMC Cancer 2012, 12:157 http://www.biomedcentral.com/1471-2407/12/157 low mitotic activity, thus considered radio-resistant accord- ing to a fundamental law of radiobiology (“law of Bergonié and Tribondeau”, 1906). In fact, the brain is one of the main target organs of radiation exposure in the catheterization lab [4,5], and is usually unprotected due to the myth of its radio-resistance [6]. The brain and head effects of LDR may include stochastic and deterministic effects. Stochastic or probabilistic effects of low-dose radiation consist primarily of cancer, which is the main effect recognized at a regula- tory and radioprotection level [7]. In theory, stochastic effects may well include other non-cancer effects such as neuro-vascular and neuro-degenerative effects, for which there is clear experimental evidence [8]. Another clinically relevant radiation effect on the head is eye cataract, previ- ously thought to be deterministic (tissue reactions) and cur- rently recognized as possibly stochastic in nature, and occurring at much lower radiation exposure level than previously thought [9]. In general, there is a striking lack of evidence systematically collected in exposed medical professionals. Radiation exposure of interventional cardiologists Medical radiation from x-rays and nuclear medicine is the largest manmade source of radiation exposure in Western countries, accounting for a mean effective dose of 3.0 mSv per capita per year, corresponding to a cardiological risk of 150 chest x-rays [10,11]. Of this equivalent 150 chest x-rays from medical radiation (except radiotherapy), almost one- half come from cardiology procedures [11]. Interventional radiology and interventional cardiology account for about 14% (0.43 of 3.0 mSv) of overall exposure to the average US citizen for the radiological year 2006 [11]. Each procedure involves a relatively large radiation exposure for the patient, which in each exam may range from 7 to 56 mSv, around an average reference dose of 15 mSv for a percutaneous coronary intervention or a cardiac radiofrequency ablation [12]. The high levels of patient exposure also imply a signifi- cant professional exposure for the interventional cardiolo- gist, who needs to operate near the patient and the radiation source. The single dose per procedure of the oper- ator is on the order of magnitude of one thousandth of the exposure of the patient [13] (Figure 1a). Effective occupa- tional doses per procedure range from 0.02 to 38 microSv for diagnostic catheterization, 0.2 to 31.2 microSv for percu- taneous coronary intervention, 0.2–9.6 microSv for abla- tion, 0.3–17.4 microSv for pacemaker or intracardiac defibrillation implantations [14] and may reach even higher values per procedure up to 50 microSv for dilation of chronic total occlusion and up to 100 microSv transcutane- ous aortic valve [15] and up to 200 microSv per single pro- cedure of endovascular thoraco-abdominal aneurysm repair [16]. The measurement over personal protective devices ranged from 0.4–1,100 microSv at the eye level, 1.2–580 microSv at the thyroid level, 32–750 microSv at the trunk Page 2 of 13 Figure 1 (a) The range of radiation exposure of interventional cardiologists per single procedure: diagnostic coronary angiography, percutaneous coronary angioplasty, cardiac ablation, cardiac pacemakers, intracardiac defibrillator or implantation, transcutaneous aortic valve implantation, dilation of chronic coronary total occlusion and endovascular thoraco- abdominal aneurysm repair. From original data of references 14– 16. There is substantial variability in operator dose across procedures and within each procedure. On the y-axis, a log scale is used. Right side: The annual radiation exposure for different specialists. Interventional cardiologists are by far the most exposed (modified from Vano E et?al., 1998, ref. 4). (b) The map of radiation exposure in the cardiac interventionalist. There are “hot regions” of higher exposure in the eye, thyroid and brain that should be carefully protected by glasses, collars and cap. Radiation exposure on the left is almost double that on the right side (modified from Vano E et?al., 1998, ref. 4). Right side: Estimated cumulative dose after 20 years of professional life in the cardiac cath lab: the whole body dose (below lead apron) is around 100 mSv; the head dose is 10 times higher, and in the head, the left head dose is twice that of the right side dose. Obviously, in this order of magnitude there are substantial variations (up to 10 times) depending on years of exposure, volume of activity, type of procedure, technology used, protection habits and radiation awareness. level, and 0.4–790 microSv at head level, whereas measure- ments under the apron at the trunk levels ranged from 0 to 23 microSv [14]. Each operator does hundreds or thou- sands of procedures each year, and therefore the cumula- tive dose in a professional lifetime is not negligible. The most active and experienced interventional cardiologists in