Gradient Fields
Faraday's law establishes a relationship between the changes of a magnetic field over time and electrical fields. Therefore, switching gradient fields induces an electrical field in conducting material or tissue. Resulting eddy currents can heat materials or tissue. In vivo, also peripheral nerve stimulation may result due to shifts of charges dissipating the resting membrane potential of the nerve fibers.
When the gradient coil is used at a high gradient duty cycle, the inner surface of the gradient coil can heat up and remain hot for some time.
Read and follow the warnings listed below when operating the MR instrument. Prior to use of accessories within the gradient field, read section Accessories below.
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Risk of burns The magnetic fields created in the Gradient Coil (gradient fields) can cause burns when running MR scans. - •
- Do not enter the gradient field with your extremities while running MR scans.
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- Do not bring conducting material into the gradient field since it heats up.
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- Do not touch the surface of the Gradient Coil or the RF Coil while or shortly after running MR scans since the surface might be hot.
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Peripheral nerve stimulation Fast switching magnetic fields created in the gradient coil (gradient fields) can cause nerve stimulation. - •
- Do not enter the gradient field with your extremities while running MR scans.
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Risk of short circuit because of condensate Setting the cooling seed point of the gradient cooling water below 18°C or inappropriate environmental conditions increase the risk of water condensation. - •
- Operate the instrument in the environmental conditions specified in the System Owner Manual or in the Operating Instructions (where applicable).
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- Do not regulate the temperature of the gradient cooling water below 18 ºC.
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Harm to the animal by increased body temperature High gradient duty cycle and fast gradient switching schemes applied for a long duration lead to high temperatures at the inner surface of the gradient coil. Depending on the animal setup and the remaining air circulation, a lethal heating of the animal can occur. In case of scanning animals with high gradient slew rates, be aware of potential nerve stimulations in the animal. - •
- We recommend to use an animal monitoring system to monitor vital signs (for example heart rate, respiratory rate, body temperature, …).
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