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QUESTIONS
» MRI Safety

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

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MRI Safety Q&A

These questions are concerned with MRI safety.

Choose a question...
  1. Explain the differences between the following terms:
    • MR safe
    • MR compatible
  2. Why are pacemakers an absolute contraindication to MRI?
  3. What advice would you give to a medical doctor about scanning a pregnant woman?
  4. Can a pregnant staff member enter the scanning room?
  5. What would you advise for a 2-months-pregnant patient who comes for a scan with cord compression?
  6. Under what conditions would you allow a patient with an implant with ferromagnetic components to be to be scanned?
  7. What would you advise about scannning a sheet-metal worker?
  8. Why might a patient complain of a heating effect on their eyelids?
  9. What are magnetophosphenes? When and why do they occur?
  10. Techniques which employ fast gradient switching (e.g. echo-planar imaging) can cause peripheral nerve stimulation. Are the cardiac or respiratory systems at risk? Why / why not? What is the limit of exposure to sinusoidal or pulsed magnetic fields by which we can adequately avoid peripheral nerve or cardiac muscle stimulation?
  11. What is SAR? How can it be calculated?
  12. Which two body parts are regarded as particularly heat-sensitive?
  13. 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?
  14. What procedure would you advise if a patient crashes (cardiac arrest) in the scanning room?
  15. Why can the ECG be misleading when a patient is in the scanner? In what way is it misleading?
  16. What is quenching?
  17. When is the highest risk of quenching?
  18. How might a quench damage the magnet?
  19. In the event of a magnet quench with cryogen leakage, what should be done to get the patient out? What risk is there to the patient if they remain in the room (3 risks)?
  20. What area is the Controlled Area?
  21. What advice should you give regarding the screening of a patient with no recorded medical history and who is unconscious or unresponsive?
  22. How does the fringe field vary with distance from the magnet?
  23. Can people with aneurysm clips be scanned?
  24. What about artificial heart valves? Are they safe for MRI?
  25. What about stents, filters and coils?

UK related:

Choose a question...
  1. What current MRI safety guidelines are available? (UK relevant)
  2. What are the upper and lower limits of the two level approach for patients and volunteers, for the static magnetic field? (UK)
  3. What are the upper limits for authorised staff, for the static magnetic field? (UK)
  4. What are the upper limits for the general public, for the static magnetic field? (UK)
  5. What are the limits on whole-body temperature rise at the (i) uncontrolled level? (ii) upper level? (UK)
  6. What is the upper level SAR for scans less than 15 mins, for the whole body? (UK)
  7. What is the restriction on SAR (peak in any one kilogram) for scans greater than 30 mins, for the head? the trunk? the limbs? (UK)

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