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Result : Searchterm 'Safety' found in 2 terms [ ] and 55 definitions [ ]
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If a device is to be labeled MR Safe, the following information should be provided:
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Data demonstrating that when the device is introduced or used in the MRI environment (i.e. the MRI scan room) it does not pose an increased safety risk to the patient or other personnel,
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a scientifically-based rationale for why data are not necessary to prove the safety of the device in the MR environment (for example, a passive device made entirely of a polymer known to be nonreactive in strong magnetic fields).
If a device is to be labeled MR Compatible, the following information should be provided:
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Data demonstrating that when the device is introduced or used in the MRI environment, it is MR safe that it performs its intended function without performance degradation, and that it does not adversely affect the function of the MRI scanner (e.g. no significant image artifacts or noise). Any image artifact or noise due to the medical device should be quantified (e.g., % volume affected, signal to noise ratio),
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a scientifically-based rationale for why data are not necessary to prove the compatibility of the device in the MRI environment.
Test Conditions:
The static magnetic field strength ( Gauss (G) or Tesla (T)) to which the device was tested and demonstrated to be MRI 'safe', 'compatible', or 'intended for use in' should be related to typical machine ratings (e.g. 0.5 T, 1.5 T, 2.0 T, and shielded or unshielded magnet, etc).
The same conditions should be used for the spatial gradient ( field strength per unit distance (i.e., G/cm)) in which the device was tested and demonstrated to be 'safe', 'compatible', or 'intended for use in'.
Also the RF transmitter power used during testing of the device, should be related to this typical machine ratings. | | | | • For this and other aspects of MRI safety see our InfoSheet about MRI Safety. | | | • Patient-related information is collected in our MRI Patient Information.
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• View the NEWS results for 'MR Compatibility' (2).
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The subacute risks and side effects of magnetic and RF fields (for patients and staff) have been intensively examined for a long time, but there have been no long-term studies following persons who have been exposed to the static magnetic fields used in MRI. However, no permanent hazardous effects of a static magnetic field exposure upon human beings have yet been demonstrated.
Temporary possible side effects of high magnetic and RF fields:
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Varying magnetic fields can induce so-called magnetic phosphenes that occur when an individual is subject to rapid changes of 2-5 T/s, which can produce a flashing sensation in the eyes. This temporary side effect does not seem to damage the eyes. Static field strengths used for clinical MRI examinations vary between 0.2 and 3.0 tesla;; field changes during the MRI scan vary in the dimension of mT/s. Experimental imaging units can use higher field strengths of up to 14.0 T, which are not approved for human use.
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The Radio frequency pulses mainly produce heat, which is absorbed by the body tissue. If the power of the RF radiation is very high, the patient may be heated too much. To avoid this heating, the limit of RF exposure in MRI is up to the maximum specific absorption rate (SAR) of 4 W/kg whole body weight (can be different from country to country). For MRI safety reasons, the MRI machine starts no sequence, if the SAR limit is exceeded.
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Very high static magnetic fields are needed to reduce the conductivity of nerves perceptibly. Augmentation of T waves is observed at fields used in standard imaging but this side effect in MRI is completely reversible upon removal from the magnet. Cardiac arrhythmia threshold is typically set to 7-10 tesla. The magnetohydrodynamic effect, which results from a voltage occurring across a vessel in a magnetic field and percolated by a saline solution such as blood, is irrelevant at the field strengths used.
The results of some animal and cellular studies suggest the possibility that electromagnetic fields may act as co-carcinogens or tumor promoters, but the data are inconclusive.
Up to 45 tesla, no important effects on enzyme systems have been observed. Neither changes in enzyme kinetics, nor orientation changes in macromolecules have been conclusively demonstrated.
There are some publications associating an increase in the incidence of leukemia with the location of buildings close to high-current power lines with extremely low-frequency (ELF) electromagnetic radiation of 50-60 Hz, and industrial exposure to electric and magnetic fields but a transposition of such effects to MRI or MRS seems unlikely.
Under consideration of the MRI safety guidelines, real dangers or risks of an exposure with common MRI field strengths up to 3 tesla as well as the RF exposure during the MRI scan, are not to be expected.
For more MRI safety information see also Nerve Conductivity,
Contraindications, Pregnancy
and Specific Absorption Rate.
See also the related poll result: ' In 2010 your scanner will probably work with a field strength of' | | | |
• View the DATABASE results for 'MRI Risks' (9).
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• View the NEWS results for 'MRI Risks' (3).
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The national regulatory boards decided to limit the threshold for access to MRI areas to 5 gauss.
It is of special interest for the observer of bureaucratic procedures that the 5 gauss safety limit is ten times higher than the average earth magnetic field, but lower than the magnetic field in electric trains such as subways (up to 7 gauss).
For example, the fields measured on the surface of the receiver of a telephone are 35 gauss and of an audio headset 100 gauss. | | | |
• View the DATABASE results for '5 Gauss Limit' (3).
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During the MRI scan an augmentation of T waves is observed at fields used in standard imaging but this possible MRI side effect is completely reversible upon removal from the magnet. A field strength dependent increase in the amplitude of the ECG in rats has been observed during exposure to high homogeneous stationary magnetic fields, but this side effect is not transferable to standard imaging situations for humans.
The minimum level at which augmentation can be observed is 0.3 T and increases by higher field strength.
An augmentation in T-wave amplitude can occur instantaneously and is immediately reversible after exposure to the magnetic field ceased. There should be no abnormalities in the ECG in the later follow-up. Augmentation of the signal amplitude in the T-wave segment may result from superimposed electrical potential.
No circulatory alterations coincide with the ECG changes. Therefore, no biological risks are believed to be associated with them.
For more MRI safety information see also Contraindications
and MRI Risks. | | | |
• View the DATABASE results for 'Cardiac Risks' (2).
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Most of the used materials are non-magnetic, for this case there is no risk for movement caused through the magnetic field.
If the cardiac stent is outside the region of the radio frequency pulse, also the risk of e.g. heating is low. | | | |
• View the DATABASE results for 'Cardiac Stent' (4).
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