Picano et al. BMC Cancer 2012, 12:157 http://www.biomedcentral.com/1471-2407/12/157 Page 3 of 13 Figure 2 The dose-effect relationship between radiation exposure and cancer (left side) and radiation exposure and atherosclerosis (right side). The solid line indicates the epidemiological evidence, which is conclusive for cancer risk above 50 mSv and for atherosclerosis risk above 500 mSv. The dashed line indicates the dose range with absent or inconclusive evidence. Freely adapted from refs 3 (BEIR VII, 2006) and 7 (ICRP publication 103, 2007). high-volume cath labs have an annual exposure equivalent to around 5 mSv (below apron) per year, two to three times higher than that of diagnostic radiologists [4] (Figure 1b) and a projected professional lifetime attributable excess cancer risk of 1 in 100 [17]. Of special concern, in interven- tional cardiologists the head organ dose is 10- to 20-fold higher than the dose recorded beneath the apron [18,19] (Figure 2). Annual exposure to the cardiologist's head is on the order of magnitude of 100 microsieverts per single ablation procedure [18] and in the range of 20–30 mSv per year [19] or much higher if a ceiling-suspended screen is not used [20,21]. Radiation from the fluoroscopy tube is scattered by the patient while the cardiac intervention is underway and can reach the physician’s head, which is often unprotected, even if a lead apron is worn to protect the torso. The left side of the operator is more exposed than the right side in most cases due to the usual layout of an interventional room, where the radiologist or cardiolo- gist operates from the right side of the patient. Scattered radiation comes from the patient and is more intense when the x-ray tube is on his/her left. This implies that the lifetime estimated organ dose for a busy interventional cardiologist after 25 years of work in the catheterization la- boratory is in the order of magnitude of 1 to 3 Sv as scatter dose measured at the head with a dosimeter and the brain dose that could approximately be a 20–25% of the “external dose” (Figure 2). Unfortunately, the practice of interven- tional cardiology is sometimes accompanied by suboptimal perception of radiation risk and by negligent use of radi- ation protection tools [22-24]. Radioprotection awareness by operators is dramatically effective in reducing profes- sional exposure by 90% [20]. Today, in most cardiology imaging laboratories and in interventional radiology fluor- oscopy rooms, overhead radiation shields, thyroid shields, and leaded aprons are employed to reduce the radiation doses to the operators head and neck. It is rare that unpro- tected radiologists or cardiologist would do an angiog- raphy procedure. Unfortunately, this was not the most common situation in the past, and still today is not the rule in all and every laboratory [22-24]. Brain cancer risk The central dogma of radioprotection is that biological effects of ionizing radiation are a direct consequence of DNA damage occurring in directly irradiated cells. This remains a useful approach in radioprotection, although in experimental models of mice medulloblastoma, brain can- cer increases in spite of lead shields for protecting mouse