IJCS | Volume 32, Nº6, November / December 2019

642 concepts, best practices and their effectiveness in Cardiovascular imaging. 5 Biological factors such as the sensitivity of irradiated tissues, the biodistribution of radioactive material (when administered or absorbed), age, gender and even health condition of the individuals are important. Among the various ways of estimating the exposure of individuals to ionizing radiation, the absorbed dose (which is a measure of the energy deposited by the radiation in an exposed tissue through interactionwith its molecular constituents) and the effective dose (estimated sum of absorbed doses for each organ weighted by the sensitivity to radiation and the type of radiation) are the main concepts when the objective is the evaluation of the potential biologicl effects in the diagnosis by image. These effects can be separated into deterministic and stochastic. The occurrence of deterministic effects is rare in the diagnostic routine due to the type and the amount of radiation used. Also referred today as tissue reactions, these effects are characterized by having aminimumdose below which they probably will not occur. In practice, the most observed reactions are skin lesions from prolonged exposures or fromexcessive radiation use such as invasive procedures guided by X-ray Fluoroscopy. 5,9 Stochastic effects are the most relevant for cardiology and should always be considered, although they do not represent a high risk of damages. Even in very low doses of radiation, indirect interactions (through free radicals) and direct interactions withDNA can generatemutations. Experimental difficulties have limited a precise evaluation of the effects of low doses, an unanswered research question, and limits and recommendations have been established based on data obtained from the extrapolation of large nuclear accidents and researches with human cells. 10 We are not used to dealing with probabilistic concepts and, therefore, we seek unique values for our decisionmaking. According to the lifelong risk model presented in the Biological Effects of Ionizing Radiation VII, 10 one person in 100 is expected to develop life-long cancer due to a single dose of 100 mSv above background radiation levels, while 42 people would develop cancer from other causes (Figure 3). Similarly, 1 person in 1,000 would result in a single dose of 10 mSv. In general, among professionals working with radiation, those involved with interventional techniques and, to a lesser degree, those who are involved in manipulation of radionuclides or with ergometry are the most exposed to risks. 5 Dose reductions: initiatives and advances Aware of the current role of ionizing radiations in health care and of the perspective for growth in applications and indications, several initiatives have recently been developed mainly by the International Atomic Energy Agency (IAEA). The 2012 International Conference on Radiation Protection in Medicine held in Bonn, Germany, resulted in the Bonn Call for Action that published the 10 main actions considered essential for the strengthening of radiation protection in medicine in the decade that would come. 11 In 2017, a new edition of the Conference held at the IAEA headquarters reinforced its importance. Among the actions are: to increase the implementation of the principles of justification and optimization, to strengthen the role of manufacturers and the education of health professionals, to increase the availability of information on occupational and medical exposures, and to nurture increased dialogue on risk-benefit of radiation. The IAEA also promotes training and courses, and the development of tools and applications. The QUANUM (Quality Management Audits in Nuclear Medicine Figure 3 - Expectation of developing cancer due to a single dose of 100 mSv. Source: BEIR VII 10 Fernandes et al. Ionizing radiation for cardiovascular diseases Int J Cardiovasc Sci. 2019;32(6):639-644 Viewpoint