1. D R . W A N N A J W A Z A I N I W A N M O H A M E D
R A D I O L O G I S T A N D H E A D
J P D , H Q E I I
2 4 t h J U N E 2 0 1 5
MRI SAFETY –
THE DOs AND DON’Ts
PREPARED FOR: HOSPITAL’S CME
4. WHAT IS MRI?
Magnetic Resonance Imaging is a medical
diagnostic tool to help doctors to diagnose
diseases by scanning the insides of the
human body.
a noninvasive NON-IONIZING imaging
technique.
Basic components are the magnet, gradient
coils, radio frequency coils and computer
6. MRI uses very STRONG MAGNETIC
FIELD and
Radio Frequency waves (RF)
7. In an MRI examination the patient is exposed to
the following:
• Strong Magnetic Field.
• Radio Frequency Waves (RF).
• Audible noise.
8. WHAT IS MAGNETIC FIELD?
Magnetic field is an invisible force that can
attract objects that have iron content (Fe).
The stronger the magnetic field the stronger
the force of attraction.
Objects that are not ferrous (no iron content)
will not be attracted to the magnet, eg. Wood,
plastic, gold, silver, aluminum, brass, copper.
9. WHAT IS MAGNETIC FIELD?
Magnetic field is measured in Tesla.
Avanto (Toshiba) = 1.5 Tesla
Earth = 0.00005 Tesla.
MR is 30,000 X stronger than the EARTH’s
magnetic field.
10. GENERAL MISCONCEPTIONS ABOUT
THE MAGNETIC FIELD
If the system is switched OFF, then the
magnetic field will also be off.
This is a big object. The magnet is not strong
enough to pull it.
This is a small object. Not necessary to
remove from patient or my pocket.
X
X
X
11. GENERAL KNOWLEDGE ABOUT THE
MAGNETIC FIELD’S EFFECT
The Magnetic field is very strong. It can pull
objects up to hundreds of kilograms.
A 1.0kg iron object will feel like almost
100kg inside a 1.5 TESLA magnetic field.
12. GENERAL KNOWLEDGE ABOUT THE
MAGNETIC FIELD’S EFFECT
Big objects will cause serious injuries or
even death to the people who are around or
inside the Magnet.
Small sharp objects will also cause serious
injuries or even death to the people around
or inside the Magnet.
13. TYPES OF MRI MAGNETS
PERMANENT
SUPERCONDUCTIVE
15. PERMANENT MAGNETS
Open system MRI.
Uses low magnetic field (0.2 – 0.7 T) – low
strength but safety precautions must still be
adhered to.
Do not use liquid helium as coolant.
Advantage: cheaper, no fear of
claustrophobia.
17. SUPERCONDUCTING MAGNETS
Very strong magnetic fields, typically 1T and
above – susceptible to flying objects
Uses cryogens such as liquid helium as coolant
Advantage – improved anatomic resolution,
reduced scan time with preserved image quality
Under normal working condition, is never
turned off
19. IMPORTANT KNOWLEDGE
The MAGNETIC field of a SUPERCONDUCTIVE
magnet is permanently ON (24hours).
The MAGNETIC FIELD cannot be switched off by
the user under NORMAL conditions.
(We will discuss on the Emergency condition
later).
22. SAFETY RULES
Magnetic Fringe Fields
5 Gauss Limit and Line
ACR Safety Zones
MR Compatibility
Specific Absorption Rate (SAR)
23. MAGNETIC FRINGE FIELDS
The fringe field is the peripheral magnetic
field outside of the magnet core.
Depending on the design of the magnet and
the room, a moderately large fringe field may
extend for several meters around, above, and
below an MR scanner.
Can cause interference with electronic
devices including pacemakers.
25. 5 GAUSS LIMIT AND LINE
Threshold for access to MRI areas.
1 Gauss (G) = 1 x 10-4 Tesla (0.0001 T).
5 G = 0.0005 T @ 0.5 mT
Five gauss and below are considered 'safe'
levels of static magnetic field exposure for
the general public.
26. 5 Gauss Line specifies the perimeter around a
MR scanner within which the static magnetic
fields are higher than 5 Gauss.
5 gauss safety limit is ten times higher than
the average earth magnetic field, but lower
than the magnetic field in electric trains such
as subways (up to 7 gauss).
5 GAUSS LIMIT AND LINE
27.
28. 5 GAUSS LIMIT AND LINE
Smaller fields (1-3 G) may affect nearby CT
and MRI scanners.
Older generation pacemakers may be
affected by magnetic fields exceeding 5 G.
Fringe fields of 10 G may affect computers.
Fringe fields of 30 G may magnetize your
watch and erase your credit cards!
29. ACR SAFETY ZONES
The American College of Radiology has
defined four safety zones within MRI
facilities.
Zone I, II, III, IV.
Correspond to levels of increasing magnetic
field exposure (and hence potential safety
concern).
30. ZONE I
All areas freely
accessible to the
general public
without supervision.
Magnetic fringe
fields in this area
are less than 5
Gauss (0.5 mT).
ZONE II
Still a public area,
but the interface
between unregulated
Zone I and the
strictly controlled
Zones III and IV. MR
safety screening
typically occurs here
under technologist
supervision.
ZONE III
An area near the
magnet room where
the fringe, gradient,
or RF magnetic
fields are sufficiently
strong to present a
physical hazard to
unscreened patients
and personnel.
ZONE IV
Synonymous with
the MR magnet
room itself. Has
the highest field
(and greatest risk)
and from which
all ferromagnetic
objects must be
excluded.
31. MRI COMPATIBILITY
MR Safe
The potential for injury of the individual.
“When the device is introduced or used in the
MRI environment it does not pose an
increased safety risk to the patient or other
personnel”
32. MRI COMPATIBILITY
MR Compatible
The potential for damage to the device and its
associated components, the function of the
device that will be affected during the MR
procedure, and/or the potential source of image
artifacts.
“When the device is introduced or used in the
MRI environment, it is MR safe that it performs
its intended function without performance
degradation, and that it does not adversely affect
the function of the MRI scanner (e.g. no
significant image artifacts or noise)”
35. SCREENING GUIDELINES
Absolute Contraindications
Relative Contraindications
Post-op period
Contrast media and NSF
Pregnancy
36. ABSOLUTE CONTRAINDICATIONS
Electronically, magnetically, and
mechanically activated implants.
Ferromagnetic or electronically operated
active devices like automatic cardioverter
defibrillators.
37. Cardiac pacemakers.
Metallic splinters in the eye.
Ferromagnetic haemostatic clips in the
central nervous system.
ABSOLUTE CONTRAINDICATIONS
38. RELATIVE CONTRAINDICATIONS
Cochlear implants.
Other pacemakers, e.g. for the carotid sinus.
Insulin pumps and nerve stimulators.
Lead wires or similar wires.
39. Prosthetic heart valves (in high fields, if
dehiscence is suspected).
Haemostatic clips (body).
Non-ferromagnetic stapedial implants.
RELATIVE CONTRAINDICATIONS
40. POST OP PERIOD
If the metallic object is a “passive implant”
(i.e. there is no electronically- or
magnetically-activated component associated
with the operation of the device) and it is
made from nonferromagnetic material, the
patient may undergo an MR procedure
immediately after implantation.
41. POST OP PERIOD
For an implant or device that exhibits
“weakly magnetic” qualities, it may be
necessary to wait a period of six weeks after
implantation before performing an MR
procedure.
However, patients with implants or devices
that are “weakly magnetic” but rigidly fixed
in the body (e.g., bone screws, other
orthopedic implants, or other devices) may
be studied immediately after implantation.
42. CONTRAST MEDIA AND NSF
Nephrogenic Systemic Fibrosis (NSF)
NSF has been observed in patients with
severe kidney disease or dysfunction
receiving GBCA.
Characterized by extensive thickening and
hardening of the skin with fibrotic nodules
and plaques.
43. CONTRAST MEDIA AND NSF
The disease is progressive and can be
associated with a fatal outcome with still no
definitive cure.
Should not use if GFR < 30 mL/min/1.73m2.
Some GBCAs [gadodiamide (Omniscan);
gadopentetate dimeglumine (Magnevist);
gadoversetamide (OptiMARK) ] are
specifically contraindicated for use in
patients at risk of NSF.
44. CONTRAST MEDIA AND NSF
Other approved agents (Ablavar, Eovist,
MultiHance,ProHance) should be used in
patients at risk of NSF only if the diagnostic
information is essential and not available
with non-contrast enhanced MRI or other
imaging modalities.
Post MRI – advice for several days
haemodialysis with increased rate and
volume to enhance elimination of GBCA.
45. PREGNANCY
Safety Committee of the Society for Magnetic
Resonance Imaging in 1991:
“MR imaging may be used in pregnant women if other
non-ionizing forms of diagnostic imaging are
inadequate or if the examination provides important
information that would otherwise require exposure
to ionizing radiation (e.g., fluoroscopy, CT, etc.).
Pregnant patients should be informed that, to date,
there has been no indication that the use of clinical
MR imaging during pregnancy has produced
deleterious effects.”
46. PREGNANCY
Relatively few studies performed in pregnant
human subjects exposed to MR imaging or
the MR environment.
No published reports on persons exposed to
magnetic fields, including staff at MR
departments, have a higher incidence of
genetic damage to their children than found
in the average population.
47. PREGNANCY
Should only be used if their usage is considered
critical and the potential benefits justify the
potential risk to the unborn fetus.
Should use agents believed to be at low risk for
the development of NSF at the lowest possible
dose to achieve diagnostic results.
Therefore, their use should not be limited,
particularly given the important clinical reasons
for MRI examinations during pregnancy.
49. HAZARDS, RISKS AND SIDE EFFECTS
Magnetic Forces
Magnetic Shielding
Acoustic Noise
Claustrophobia
Quenching
Contrast media
Absorbed Dose
Cardiac Risks
Magnetohydrodynamic Effects
Nerve Conductivity
50. MAGNETIC FORCES
The “MISSILE EFFECT”:
Very dramatic and dangerous phenomenon.
Occurs when a metal object is pulled into the
magnet with great force ( >20 mph).
Can be a lethal danger if one is hit by an
unrestrained object in flight.
Could also be trapped in between.
51. MAGNETIC FORCES
The “MISSILE EFFECT”:
Many objects including wrenches, hammers, IV
poles, oxygen bottles, crash carts, floor buffers,
wheelchairs, tool boxes, stretchers, mop buckets
… even a policeman’s handgun, have been
involved in accidents.
Could damage the MRI machine.
52. Boy, 6, Killed in Freak MRI Accident
July 31, 2001
A 6-year-old boy died after undergoing an MRI exam at a New York-area hospital
when the machine's powerful magnetic field jerked a metal oxygen tank across the
room, crushing the child's head.
The force of the device's 10-ton magnet is about 30,000 times as powerful as Earth's
magnetic field, and 200 times stronger than a common refrigerator magnet.
The canister fractured the skull and injured the brain of the young patient, Michael
Colombini, of Croton-On-Hudson, N.Y., during the procedure Friday. He died of the
injuries on Sunday, the hospital said.
The routine imaging procedure was performed after Colombini underwent surgery
for a benign brain tumor last week. Westchester Medical Center officials said he was
under sedation at the time of the deadly accident.
Hospital Takes ‘Full Responsibility’ FIRST FATAL MRI
ACCIDENT
56. MAGNETIC FORCES
Torque
Twisting and pulling force on objects.
Objects may be pulled or twisted out of position
and will tend to align along the magnet’s field
lines.
Internal injuries can result if this involves an
implant, prosthesis, surgical staples, aneurysm
clips, etc.
57. ACOUSTIC NOISE
Caused by the interactions of the magnetic
field created by pulses of the current through
the gradient coil with the main magnetic
field.
Loudest noise range between 110-120dB.
Noise levels increase with field strength.
58. ACOUSTIC NOISE
May create discomfort, anxiety, and even
temporary hearing loss.
Disposable earplugs and/or headphones are
recommended in high-field systems.
60. CLAUSTROPHOBIA
A psychological reaction to being confined in a
relatively small area.
Reported in about 1-4% of cases as a reason to
interrupt the MRI examination.
Short and wide open MRI are advantageous.
Can be overcome by detailed explanation, careful
attention, special equipment, sedatives.
61. QUENCHING
Quenching the magnet is DEACTIVATING THE
MAGNETIC FIELD OF THE MAGNET.
A quench is an escalating reaction to heat.
It causes the cryogens (helium) to boil off
rapidly, which in turn causes the loss of the static
magnetic field.
May occur unexpectedly or from pressing the
EMERGENCY button.
62. QUENCHING
As the superconductive magnet becomes
resistive, heat will be released.
To protect patients and operators, the
evaporated helium requires emergency venting
systems – quench pipe through the roof or the
wall.
If large amounts of helium gas escapes into the
examination room – risk of frostbites,
asphyxiation and injury due to panic.
63. QUENCHING
Large quantities can completely displace
oxygen from the entire room and if inhaled
may cause loss of consciousness within 10
seconds with the possibility of asphyxia and
death.
Patients and staff must therefore be
evacuated immediately from the scanner
room if a quench occurs.
64.
65. CONTRAST MEDIA
Gadolinium based contrast agents (GBCA)
are extremely well tolerated by the vast
majority of patients.
Reactions resembling an “allergic” response
are very unusual and vary in frequency from
0.004% to 0.7%.
Severe, life-threatening anaphylactoid or
nonallergic anaphylactic reactions are
exceedingly rare (0.001% to 0.01%).
66. CONTRAST MEDIA
The frequency of acute adverse reactions is
about 8 times higher in patients with a
previous reaction to gadolinium-based
contrast media.
Persons with asthma and various other
allergies to food or medications are at greater
risk, with reports of adverse reaction rates as
high as 3.7%.
67. CONTRAST MEDIA
At risk patients should be covered with oral
prednisolone.
Breast-feeding mothers
Less than 0.04% of the iv dose is excreted
into the breast milk in the first 24 hours.
Expected systemic dose absorbed by the
infant from the breast milk is less than
0.0004%.
68. CONTRAST MEDIA
The available data suggest that it is safe for
the mother and infant to continue breast-
feeding after receiving such an agent.
If the mother remains concerned about any
potential ill effects to the infant, she may
abstain from breast-feeding from the time of
contrast administration for a period of 12 to
24 hours.
69. CONTRAST MEDIA
Gadolinium-based contrast agent in pregnancy
Current radiology practices and
recommendations discourage the use of
gadolinium-based contrast agents during
pregnancy because their safety for the fetus
has not been proven.
Because it is unclear how GBCAs will affect
the fetus, these agents should be
administered only with caution.
72. GENERAL SAFETY INFORMATION
Ensure system is operated by qualified
personnel only.
Provide safety training for medical and
non-medical staff.
Warning signs must be clear in MR area.
Report accidents to proper authorities.
73. GENERAL SAFETY INFORMATION
Keep MR door closed at all times.
MR area must be a restricted zone.
Create EMERGENCY plan for evacuation.
Call service to notify incident of emergency.
Do not use unapproved accessories or
software.
74.
75. SAFETY GUIDELINES
SAFETY INFORMATION FOR NON-MEDICAL
STAFF – Engineers, Cleaners, Rescue Workers:
Warning signs must be observed.
DO NOT enter MR room unless given
permission.
Use non-magnetic tools, equipment in MR
room.
76.
77. SAFETY GUIDELINES
SAFETY INFORMATION FOR MEDICAL STAFF
– Doctors, MR Technologists, Nurses:
Observe warning signs.
Do not enter MR room unless authorized by
person on duty.
All equipment must be checked for MR
compatibility.
78. SAFETY GUIDELINES
Patients must be screened.
Personnel must be screened if they are not
familiar with the MR environment before.
Record patients’ data, eg weight, age,
correctly.
79. SAFETY GUIDELINES
Proceed with extra caution:
Claustrophobic patients.
Children.
Elderly patients.
Persons that have less sensation.
Persons that cannot communicate.
Unconscious, sedated or intensive care
patients.
Pregnant women.
80. SAFETY GUIDELINES
DO NOT PERFORM MR EXAMINATION IF
PATIENT HAS METALLIC AND
ELECTRICALLY CONDUCTIVE DEVICES
OR IMPLANTS THAT MAY BE AFFECTED
BY ELECTROMAGNETIC FIELDS. Eg
Pacemakers, aneurysm clips, implanted
defibrillators.
81. SAFETY GUIDELINES
EMERGENCY PLAN
Emergency plans should be devised and
discussed with emergency staff.
Emergency phone numbers must be
available.
Location maps for :
Emergency buttons.
Emergency exits.
82. SAFETY GUIDELINES
In the event of an EMERGENCY or ACCIDENT:
Remove patients and personnel from MR Room.
Notify emergency staff.
DO NOT PRESS QUENCH BUTTON if no one is
stuck inside the Magnet.
(No immediate danger to patients or staff)
83. SAFETY GUIDELINES
EMERGENCY RUN DOWN UNIT (ERDU) or
‘QUENCH’ BUTTON can only be pressed if:
Life threatening to patient or staff – stuck by
magnetic objects inside magnet and cannot
be removed.
Safety personnel such as a fireman needs to
put out a fire in the MRI room.
84. SAFETY GUIDELINES
DO NOT PRESS QUENCH button if:
an object is stuck but not life threatening.
Inform the hospital authorities for next
course of action.
85. SAFETY GUIDELINES
Other EMERGENCY Buttons that can be
activated anytime if required are:
ELECTRICAL STOP button – to shutdown the
MR in an emergency situation e.g. Fire, flood.
Patient TABLE STOP button – to remove
patient from magnet by pulling table
manually.
86. Incident Injury or
Death
Damage to
MR
Damage to
personal
belonging
Person
resposible e
Quench
O2 tank NO YES NO Doctor No.Ramp
down
O2 tank NO YES NO Nurse No. Ramp
down
Wheelchair NO YES NO Ragiographer NO
Video camera NO YES YES Camera-man
Radiographer
NO
Helium tank YES YES YES Engineer NO. Ramp
down.
Hearing aid NO NO YES Radiographer NO
Magnetic
sandbags
NO YES YES Doctor NO
O2 tank
holder
NO YES NO Radiographer YES (not
necessary)
REPORTED INCIDENTS IN M’SIA:
