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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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Decreasing SAR

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What options are open to the operator to decrease SAR, if SAR limits are exceeded?

If SAR limits are exceeded the scanner will say so. (It works out the SAR for you; that's why it needs the patient's weight.) If SAR limits are exceeded, the operator may increase the repetition time, reduce the number of slices or reduce the flip angle. All these affect the duty cycle: the percentage of the time in an imaging sequence during which RF pulses are applied.

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

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