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MR SAFETY-GRADIENT FIELDS

Physics

MR SAFETY-GRADIENT FIELDS

1. Electric fields are produced perpendicular to the gradient fields.
2. These electric fields induce eddy currents in conductive tissues causing stimulation.
3. An eddy current is an electric current induced in a conductor when that conductor is exposed to a changing magnetic field.
4. Can cause unpleasant effects: peripheral nerve stimulation, muscle contraction, cardiac arrhythmias (very rare), flashing visual lights, metallic taste sensation.
5. These effects are not seen below 20 T/sec.
6. As a precaution, MRI is avoided during the first trimester of pregnancy.


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REFERENCES

1. Bushberg, J. T. (2012). The essential physics of medical imaging. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. Find it at Amazon
2. Heggie, J. C., Liddell, N. A., & Maher, K. P. (1997). Applied imaging technology. Melbourne: St. Vincents Hospital.

Ⓒ A. Manickam 2018

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