IJCS | Volume 32, Nº6, November / December 2019

640 Figure 1 - Evolution of the number of procedures with ionizing radiation in the Brazilian Unified Health System (SUS). Codes of procedures: 0204 (Conventional Radiology), 0208 (Nuclear Medicine), 0210 (Interventional Radiology) e 0211 (Cardiac Catheterization). Source: DATASUS – Portal da Saúde 3 Code 0204 Code 0208 Code 0210 Code 0211 275,000 250,000 225,000 200,000 175,000 150,000 125,000 100,000 75,000 50,000 25,000 0 Brazilian National Commission for Nuclear Energy (CNEN, from Portuguese: Comissão Nacional de Energia Nuclear ) regulation NN-3.01 8 and presented in Table 1. Poor understanding of these concepts and of the risks involved can lead to failures across the chain of decisions and increase the potential risks for patients and workers. Table 1 - Basic requirements for radiation protection Justification No practice or source associated with this practice is accepted by CNEN, unless the practice produces benefits to exposed individuals or to society sufficient to compensate for the corresponding detriment, taking into account social and economic factors, among other relevant factors. Medical exposures must be justified considering the diagnostic and therapeutic benefits they will produce in relation to corresponding detriment, taking into account the risks and benefits of available alternative techniques that do not involve exposure. Optimization Related to the exposures caused by a particular source associated with a practice, radiation protection should be optimized so that the magnitude of individual doses, the number of exposed persons, and the likelihood of exposures occurring remain as low as reasonably achievable, taking into account economic and social factors. In case of medical exposures of patients, the medical optimization of radiation protection should be understood as the application of the dose of radiation necessary and sufficient to achieve the intended purposes. Limitation The normal exposure of individuals should be restricted in such a way that neither the effective dose nor the equivalent dose in the organs or tissues of interest, caused by the possible combination of exposures originated from authorized practices, exceeds the specified dose limit except to special circumstances authorized by CNEN. These dose limits do not apply to medical exposures. Source: CNEN regulation 3.01 - Basic Guidelines for Radiation Protection 8 Risk assessment and biological effects of radiation Risk assessment involves the understanding of specific factors of each technique such as: the type of radiation, the intensity or quantity used, the time of exposure and possible effects. Recently, a consensus paper was published, the result of a task force of the American College of Cardiology, which reviewed Fernandes et al. Ionizing radiation for cardiovascular diseases Int J Cardiovasc Sci. 2019;32(6):639-644 Viewpoint