RESUMEN
O método de cálculo numérico TLM (Transmission Line Matrix Method) é aplicado no estudo da interação das ondas eletromagnéticas de radiofreqüência (RF) irradiados pelas antenas dos telefones celulares com a cabeça do usuário. É feito o cálculo da distribuição espacial do campo elétrico e da taxa de absorção específica (SAR) para um modelo bidimensional (2D), onde a antena do telefone é modelada por um dipolo elétrico operando na freqüência de 835 MHz e com uma potência de 0,6 W, sendo estes valores práticos dos telefones celulares analógicos. Para simular a cabeça humana foi utilizado um modelo oval multicamadas, onde foram considerados os parâmetros elétricos da pele, do crânio e do cérebro. São avaliadas as situações onde a antena é colocada a 1,5 cm e 5 cm do modelo da cabeça, tanto para polarização TE quanto TM dos campos. Os resultados obtidos da SAR para as diferentes situações analisadas são discutidos e comparados com os valores limites estabelecidos pelas normas internacionais, observando-se que para determinadas circunstâncias estes valores são ultrapassados.
Asunto(s)
Radiación no Ionizante , Teléfono , Fuentes de Radiación , Simulación por Computador , Factores de Riesgo , Seguridad de Equipos/tendencias , Telecomunicaciones/normas , Vías de Exposición a la RadiaciónRESUMEN
There are few books on radiation protection for radiologic technologists. Several recent issues make the appearance of this text timely: (1) the Committee on Bioeffects of Ionizing Radiation (BEIR) now estimates the risk of radiation injury to the population to be greater than they had previously estimated; (2) current studies are now concerned with the bioeffects of low-level radiation, which is characteristic of diagnostic radiology; (3) based on a close examination of the radiation data on the Hiroshima and Nagasaki atom bomb survivors, the International Commission of Radiological Protection (ICRP) recently revised its recommendations on radiation protection and lowered the annual dose limit to the whole body for radiation workers from 50 mSv to 20 mSv; (4) the introduction of new imaging techniques, such as magnetic resonance imaging (MRI), requires an understanding of the bioeffects of exposure to magnetic fields and radio waves, as well as a thorough knowledge of the safety issues surrounding the use of these techniques to image the human body; and (5) quality control is an effective dose reduction tool and is now considered an essential element of radiation protection programs. Keeping these recent developments in mind, the purpose of this book is to: 1) Provide a current and thorough overview of the bioeffects of radiation. 2) Provide comprehensive coverage of the physical principles and technical aspects of radiation protection in diagnostic radiology. 3) Explore the hazards and safety considerations of MRI. 4) Explain the role of quality assurance/quality control in radiation protection. 5) Describe the recent recommendations and new developments in radiation protection for patients undergoing diagnostic X-ray examinations. 6) Summarize the results of various dose studies in X-ray imaging, including computed tomography and mammography