Abstract
The literature on biological effects of magnetic and electromagnetic fields commonly utilized in magnetic resonance imaging systems is surveyed here. After an introduction on the basic principles of magnetic resonance imaging and the electric and magnetic properties of biological tissues, the basic phenomena to understand the bio-effects are described in classical terms. Values of field strengths and frequencies commonly utilized in these diagnostic systems are reported in order to allow the integration of the specific literature on the bio-effects produced by magnetic resonance systems with the vast literature concerning the bio-effects produced by electromagnetic fields. This work gives an overview of the findings about the safety concerns of exposure to static magnetic fields, radio-frequency fields, and time varying magnetic field gradients, focusing primarily on the physics of the interactions between these electromagnetic fields and biological matter. The scientific literature is summarized, integrated, and critically analyzed with the help of authoritative reviews by recognized experts, international safety guidelines are also cited.
Highlights
Safety issues and discussions about potential hazards associated with magnetic resonance imaging (MRI) systems and procedures have been extremely controversial over the past decade: partly because of the disputed assertions about the role of electromagnetic fields in carcinogenesis or the promotion of abnormalities in growth and development [1,2,3]; partly because the assumption that MRI was inherently a safe procedure had reduced the importance of the publication of negative results [4]
The MR environment may be unsafe for patients with certain implants, primarily due to movement or dislodgment of objects made from ferromagnetic materials [9], and because of heating and induction of electrical currents, which may present risks to patients with implants or external devices [10]
There is no evidence of health hazards associated with exposure of patients to strong static magnetic fields, we report here several physical mechanisms of interaction between tissues and static magnetic fields that could lead to potential pathological effects
Summary
Safety issues and discussions about potential hazards associated with magnetic resonance imaging (MRI) systems and procedures have been extremely controversial over the past decade: partly because of the disputed assertions about the role of electromagnetic fields in carcinogenesis or the promotion of abnormalities in growth and development [1,2,3]; partly because the assumption that MRI was inherently a safe procedure had reduced the importance of the publication of negative results [4]. GG The term v × B can be seen as a motion-induced electric field, and it can produce biological effects by disrupting physiological electrical signals of the human body, such as neuronal conduction and biopotentials It was reported [31] that ECGs of monkeys exposed to a strong static magnetic field showed field-induced morphological changes in T-wave shape. Several of these studies have been carried out on laboratory animals to determine thermoregulatory reactions of living systems to tissue heating associated with exposure to RF radiation These experiments do not apply directly to the conditions that occur during MRI procedures, because the pattern of RF absorption, or the coupling of radiation to biological tissues, depends on the body size, on the anatomical features, the duration of the exposure, the sensitivity of tissues, and several other factors. The ICNIRP Safety Guidelines [67] permit humans to be exposed to electric fields that are over ten times stronger than radiation limits applicable to all electronic consumer products presently on the market
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