This document discusses MRI safety. It describes the three electromagnetic fields generated by MRI that can affect the human body, including the static magnetic field, gradient magnetic field, and radiofrequency field. It notes safety limits for field strength and specific absorption rate to avoid hazardous heating effects. The document also outlines safety procedures for MRI sites, including restricting access, screening patients and non-medical personnel, and precautions during scans such as avoiding loop formations of wires or limbs. Risks related to pregnancy and contrast agents are also addressed.

1. MRI SAFETY
Dr. Nikhil Arora
MD Radiodiagnosis

2. MR bio-effects
• Patient is exposed to 3 different forms of electromagnetic
field
• Static magnetic field
• Gradient magnetic field
• RF electromagnetic field
Dr. Nikhil Arora
MD Radiodiagnosis

3. Static Magnetic field
• It can raise the skin temperature.
• It causes electrical induction and cardiac effects with
elevation of T wave amplitude.
• It also has potential effects on neurons
• All these effects are not to be hazardous at field strength
<3 Tesla
• Scanning at field strength >2 Tesla cause vertigo,
headache and peripheral nerve stimulation.
Dr. Nikhil Arora
MD Radiodiagnosis

4. Gradient field
• It can cause ventricular fibrillation.
• Epileptogenic potentials.
• Visual flashes.
• Thermal effects.
• All these effects are not significant in presently used
clinical MR system.
Dr. Nikhil Arora
MD Radiodiagnosis

5. RF Magnetic field
• It leads to energy deposition and tissue heating.
• SAR ( specific absorption rate ) is measure of tissue energy deposition
• Units are watt/Kg
• FDA limit for clinical examination is SAR <0.4 W/Kg.
• Upto 4 W/Kg, no clinically hazardous effect is seen.
• SAR increases with field strength.
• There is 4 times increase in SAR at 3T as compared to 1.5 T
• Testes and eyes are more temperature sensitive organs.
Dr. Nikhil Arora
MD Radiodiagnosis

6. Acoustic Noise
• It is caused by vibration of Gradient coils.
• Noise increase with heavy duty cycles and sharper pulse
transition.
• It increases with thin slices, small FOV, less TR and less TE.
So ear phones or ear plugs must be provided to patients and
accompanying person.
Dr. Nikhil Arora
MD Radiodiagnosis

7. Safety Related Issues
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MD Radiodiagnosis

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MD Radiodiagnosis

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MD Radiodiagnosis

13. 1. MR personal / Non MR personal
• MR personal - those who are trained and educated about
MR safety and approved by the MR Medical Director of the
institution
1. Level 1 - education about their own safety
2. Level 2 - trained in broader MR safety issues.
Only MR personal have free access to Zone III and Zone IV
Dr. Nikhil Arora
MD Radiodiagnosis

14. 2. Site access restriction
ACR white paper Recommendation is MR site should be divided into 4
zones.
• Zone I - free access to general public
• Zone II - patient history and preparation (movement under supervision)
• Zone III - physically restricted from general public access. Only MR
personal will have free access to this area.
• Zone IV - MR scanner room itself and is located within ZONE III.
• Non MR personal are not allowed to enter without prior screening.
Dr. Nikhil Arora
MD Radiodiagnosis

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MD Radiodiagnosis

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MD Radiodiagnosis

17. 3) Screening of patient
and Non- MR personal
Dr. Nikhil Arora
MD Radiodiagnosis

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MD Radiodiagnosis

19. 4) Pregnancy related issues
• Electromagnetic field used for MRI may have potential to
produce development abnormalities.
• It may affect cell undergoing division, as in developing
fetus.
• Little data is available on this issue.
Dr. Nikhil Arora
MD Radiodiagnosis

20. A. Pregnant health care practitioner
She is permitted to work in and around MR environment
through all stages of pregnancy.
They are advised not to be in MRI room when sequence is
running.
Dr. Nikhil Arora
MD Radiodiagnosis

21. B. Pregnant patient
ACR white paper permits scanning of pregnant patient in any
stage of pregnancy.
If postponing MRI till end of examination is feasible then opt
that.
Written and informed consent should be taken.
Dr. Nikhil Arora
MD Radiodiagnosis

22. C. Contrast media during pregnancy
Gadolinium is known to cross placenta. It is excreted by fetal kidneys
and can re-circulate through amniotic fluid several times.
So ACR white paper recommends MR contrast medium should not
be injected.
However they allow case by case basis decision depending upon risk
benefit ratio.
Dr. Nikhil Arora
MD Radiodiagnosis

23. D. Contrast media in lactating patients
Gadolinium is excreted in human milk. So breast milk is expressed
and thrown away. Baby should not be breast fed for 36-48 hours.
Dr. Nikhil Arora
MD Radiodiagnosis

24. Precautions
• Always screen the patient and accompanying person for
any metallic objects. They can form projectile because of
strong metallic attraction. This can lead to life threatening
consequences.
Dr. Nikhil Arora
MD Radiodiagnosis

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MD Radiodiagnosis

26. Dr. Nikhil Arora
MD Radiodiagnosis

27. • Wires and coils are well insulated and are not touching
patients body.
Patient body should not be touching magnet bore. It can
cause burns.
• Avoid loop formation
Wires of pulse oxymeter, ECG leads etc should never form
loop. Loop formation can lead to induction of current and
burns. Even loop formation of body parts for example
crossed legs and arms can result in induction of current.
Dr. Nikhil Arora
MD Radiodiagnosis

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MD Radiodiagnosis

29. • In case of emergency, first step
approach must be to remove the
patient out of scanner and
resuscitate.
• Doors of scanner room should
have label picture of object that
are strictly prohibited to take
inside the scanner room.
Dr. Nikhil Arora
MD Radiodiagnosis

30. Dr. Nikhil Arora
MD Radiodiagnosis

31. Absolute Contraindication
• Internal cardiac pacemaker.
• Implantable cardiac defibrillator.
• Cochlear implant
• Neurostimulator
• Bone growth stimulator
• Drug infusion pump
• Intraocular foreign body
• Non titanium aneurysmal clip
Dr. Nikhil Arora
MD Radiodiagnosis

32. Thank you
Dr. Nikhil Arora
MD Radiodiagnosis