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» MRI Safety

Exposures, limits, safe systems of work. This section explores safety issues in magnetic resonance imaging.

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SAR Levels

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What is the relationship between the SAR and (i) static magnetic field strength? (ii) RF pulse flip angle? What kind of pulse sequence therefore gives the greatest concern for RF heating effects?

At high fields, the SAR is proportional to (i) the square of the static magnetic field strength and (ii) the square of the RF pulse flip angle being used.

For these reasons fast spin echo sequences give the greatest concern for RF effects. They use a train of 180° refocussing RF pulses.

Further reading on this topic:
Books: MRI From Picture to Proton p190, Q&A in MRI p304-305

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