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Purpose: We investigated the amount of patient dose reduction in the thyroid, lens of the eye and the breast when using bismuth protections in multislice computed tomography (CT) exams as well as their influence on the quality of diagnostic images., Materials and Methods: The radiation dose was measured by using thermoluminescence dosimeters. The study was conducted on the two CT scanners installed in our radiology department (64 and eight slices). The shield effects on the CT image were evaluated by measuring the signal-to-noise ratio in a phantom and in vivo, and by verifying the presence of artefacts on patients' images. The obtained organ-dose reduction factors were used to evaluate the effects of shielding on the effective dose., Results: The shielding attenuation ranged from 30% to 60% depending on the CT scan protocols and organs. The difference between shielded and unshielded signal-to-noise ratio was statistically significant but within the standard requirements for quality assurance. Results were in agreement with the radiologists' perception of image quality. The use of the shields allowed up to 38% reduction of effective dose., Conclusions: Use of bismuth shields significantly decreases both organ and effective radiation dose, with a consequent reduction in health risk for the patient, quantified in 1.4 fewer cases of radiation-induced tumours every 5 years in our centre (12,100 exams/year), in agreement with the risk factors proposed by Publication 60 of the International Commission on Radiological Protection (ICRP). The relative inexpensiveness of these protections, their easy application and their substantial lack of influence on image quality suggest their massive introduction into routine clinical practice.

Purpose: The purpose of the study was to evaluate the efficacy of a bismuth shield (Attenurad F&L Medical Products, Vandergrift, PA) in reducing the dose to surface organs during Computed Tomography (CT) examinations. The shield was evaluated for reduction of the dose to breast during chest examinations and reduction of the dose to the lens of the eye during brain examinations., Materials and Methods: The dose was measured on patients (10 for the eye and 30 for the breast), and on an anthropomorphic phantom (Alderson Rando). The reduction of image quality was evaluated both qualitatively by an expert radiologist, and in terms of increased noise on the phantom images (Rando)., Results: The use of the protective device reduced the dose by 34% to the breast and 50% to the lens. These figures are confirmed by the measurements taken both on patients and on the anthropomorphic phantom. The protective device reduced image quality in the regions immediately beneath it, but in the cases considered, those regions were of no diagnostic interest, while in the brain and lung regions, the quality is only slightly reduced, always allowing a correct diagnostic evaluation. Numerical analysis also led to the conclusion that a modest increase in noise is only statistically significant for the anterior portions of the lung. When present, the artifacts appeared outside the field of clinical interest. That is mainly due to the use of a foam pad (0.7 - 1 cm thick) to protect the breast., Discussion and Conclusions: The protection proved effective both in the case of breast and of lens, leading to a significant reduction in dose, without excessively affecting image quality. The shield proved easy to use, and did not increase the examination time.

According to recent surveys made by the International Commission on Radiological Protection (ICRP) and the World Health Organization (WHO), it has been estimated that in temperate regions people spend only 20% of their time outdoors and spend the remaining 80% indoors (homes, schools, other buildings). It is therefore important to establish whether radiation sources exist inside buildings in order to assess risk for the population. The 238U and 232Th radioactive chains are of particular importance because of Radon and Radon daughter production and 40K as component of building materials. It has been estimated that about 4.5% of lung cancers observed in the population are associated with exposure to Radon daughters. In order to comply with international regulations it is estimated that 1.5% of the existing dwellings in temperate regions need to be improved.