Chapter 15: MRI Safety

1
Chapter 15 MRI Safety

• Mark D. Herbst, MD, PhD

2
Two main sources of danger

• Magnetic field
• RF Energy
• Also
• Gradients
• Acoustic noise

3
5 Gauss Line

• Generally regarded as safe

4
Magnetic field exposure

• No demonstrated biological effects in normal
  patients
• Internal objects-ferromagnetic
• Metal in eyesblindness?
• Old steel aneurysm clips---movement/occlusion?
• Implants or prosthesesdepends on metal
  usedusually safe
• Pacemakerssome say okay, but better safe than
  sorry
• Use Shellocks book or website www.mrisafety.com

5
Magnetic field

• External objectsferromagnetic only
• Small projectiles
• Large objects can pin a patient or cause harm

6
Gradients

• More heating with higher slew rates
• 6T/sec safe
• Acoustic noiseuse earplugs or headphones

7
RF energy

• Depositing energy like in a microwave oven!
• SAR specific absorption rate (watts/kilo)
• Depends on patient weightdo not lie!
• Depends on imaging technique
• Surface burns EKG leads

8
Responsibility of the TECH

• Make sure the pt has completed a screening form
• Keep unscreened people out of danger
• Listen to the patient when they are in the
  machine
• Refuse to scan patient if it may cause harm or if
  you are unsure.