Magnet Safety Training Center for In Vivo Microscopy V1.4

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Magnet Safety Training Center for In Vivo
MicroscopyV1.4
Updated May 15, 2012

• Your Magnet Safety Team
• Larry Hedlund
• Gary Cofer
• Bastiaan Driehuys

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General MRI Hazards

• An MRI scanner creates a magnetic field that is
  30,000-150,000 times stronger than the earths
  magnetic field and is always on
• While hazards to people with pace-makers and
  implants tend to be emphasized, projectile
  hazards are most worrisome for us
• Within a few feet of the magnet, the field
  gradient can rip steel objects out of your hand
• The onset of this zone is very rapid and
  non-linear
• Objects can reach speeds of 80mph before slamming
  into the magnet (or you)

Center for In Vivo Microscopy
NCRR
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Unique Issues to CIVM

• Compared to other magnet facilities like
• A clinical 1.5T MRI suite
• An NMR spectroscopy facility

• We have the following differences
• Higher field strengths than clinical (7T vs 1.5T)
• Force on objects scales with field strength
• Larger magnet bores than NMR spectroscopy
• The magnet reach scales with bore size
• Equipment and Tools used in MRI suite
• Providing a handy supply of magnetic projectiles

Center for In Vivo Microscopy
NCRR
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Why Bother With Magnet Safety?

• A magnet projectile presents a very real
  possibility of serious injury or death
• Impact of the magnet by a projectile could result
  in 3 months of system down time
• Repair costs leave less money for science
• (450,000 to replace a 7T magnet)
• Serious incidents lead to more onerous safety
  rules and less science

Center for In Vivo Microscopy
NCRR
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How Fast Will Objects Fly?
Center for In Vivo Microscopy
(See appendix for math if interested)
NCRR
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Forces on Objects!
B07T, radius20cm

• Objects can be pulled with 50-300x their normal
  gravitational weight
• Within 1 meter of scanners tools can slip off
  surfaces and start accelerating
• Peak force occurs roughly 10-20cm from magnet
  entrance

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CIVM Incidents and Hazards

• Peristaltic Pump stuck to 2 Tesla magnet,
• Chair stuck to 7T magnet.
• Surgical tools ripped from ventilator cart, stuck
  to 7T magnet
• Compressed Nitrogen Tank stuck to 2 Tesla
  Magnet
• Fan stuck to 2 Tesla Magnet
• Hand-tools stuck to 7 Tesla Magnet
• Other Hazards motors, power supplies (in all
  electronics), drill bits, cylinder caps, razor
  blades, screws

Center for In Vivo Microscopy
NCRR
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Personal Safety and Nuissances

• Persons with pace makers and infusion pumps
  should consult their physician before working in
  this laboratory
• Remove watches, wallets, and cell phones before
  entering laboratory.
• Most jewelry (gold, silver, diamond) is safe in
  the magnet environment

Center for In Vivo Microscopy
NCRR
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Our Magnet Policies

• NO EQUIPMENT brought into lab without sign-off
  and Labeling by magnet safety representative
• NOBODY WORKS IN THIS MRI LAB until they have
  completed this magnet safety training
• And Documented it by signing their name on the
  wiki
• VISITORS and AFTER HOURS WORK have separate
  policies

Center for In Vivo Microscopy
NCRR
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What About Visitors?

• Visitors may enter the MRI lab only when
  accompanied by trained CIVM personnel
• Instruct visitors briefly about MRI hazards
• Visitors must stay at least 10 feet away from
  magnets (close to the door is good)
• Visitors may never assist or work in the lab
• Visitors may not enter the lab after hours

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Weekends and After Hours

• The magnet laboratories are available from 730
  AM to 500 PM Monday through Friday. Use on
  nights or weekends requires written permission
  from the Center Director
• It is advisable never to bring any magnet hazards
  into the lab after hours
• No visitors are allowed in the MRI labs after
  hours.

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Working with Magnet Hazards

• Ensure the magnet hazard has been labeled
• Ensure that someone else is present when you move
  a magnet hazard in the lab
• When moving a magnet hazard dont get between it
  and the magnet

Center for In Vivo Microscopy
NCRR
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Labels Used in Our Lab
Center for In Vivo Microscopy
Labels are on clipboard by 2T console. To print
more, see Magnet Safety Page on Wiki
NCRR
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If You Do Get Something Stuck

• Evacuate the lab
• Seek medical help (if appropriate)
• Contact magnet safety team member for removal of
  object
• (get a camera and take a picture so we can update
  this presentation)

Center for In Vivo Microscopy
NCRR
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A recent incident (Jan 2011)
Rigging required to remove pump from 7T
Motor/pump stuck to 7T

• Situation
• Senior Scientist (MRI professor) visiting CIVM
• Had worked at CIVM many times in the past
• Carried motor/pump close to 7T before it was
  ripped from him
• Assumed it was safe because advertised as
  MR-compatible

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What went wrong?

• Despite a 5yr magnet safety training program at
  CIVM, the visitor had not completed the training.
• The object he brought in to the lab had not been
  screened for magnetic content and had not been
  labeled as being a magnet hazard.

(Evan was not the guilty party)

• What can you do?
• Dont be shy about asking anybody you see in the
  magnet lab if they have completed our magnet
  safety training
• Be vigilant about possible magnet hazards. If
  they are needed in the lab, make sure they are
  labeled as hazards

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Another recent incident (April 2012)
Janitors Buffer Stuck to 7T

• Situation
• Janitor working on buffing floors
• Received instruction to stay away from Magnet
• Still got buffer sucked into the magnet

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What went wrong?

• Janitor had gotten close to Bruker 7T, and 2T
  without problems
• Assumed the 7T in rm 141 would be the same
• But the 7T in room 141 is UNSHIELDED

• What can you do?
• Be ware that the reach of the 7T in rm 141
  reaches 10x further than the Bruker 7T (16ft
  reach vs 1-2 ft reach)
• Our current safety presentation is geared towards
  scientists. We need another solution for
  non-scientists
• Need a Visceral Poster for Non-Scientists

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Fact Review

• Ferrous objects are our biggest hazard
• Objects can reach 45mph in the 2T magnet and
  83mph in the 7T magnet
• 1 meter from magnets, the magnetic force becomes
  equal to gravitational force
• Objects can be pulled (accelerated) with 50-300x
  their normal gravitational pull
• Labeling and your vigilance are our best defense
  against a serious accident

Please sign/date training record on the Magnet
Safety Wiki page to verify that you have
completed this
Center for In Vivo Microscopy
NCRR
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Appendix for Physicists and Engineers
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How Fast Will Objects Fly?
Potential Energy of Object Stuck in Magnet
Potential Energy of Object Removed from Magnet
Difference must be kinetic energy prior to impact
Center for In Vivo Microscopy
NCRR
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Projectile Velocity Estimates
Conserve Energy

• Notable Observations
• Vobj 45mph at 2T
• Equivalent to 7-story free-fall
• Vobj 83mph at 7T
• Equivalent to 23-story free-fall
• Terminal velocity facts
• Scales as square root of B0
• independent of mass
• Impact energy
• Scales with mass
• Scales linearly with B0

Treat object as iron chunk
Velocity scales as sqrt(B0)
Center for In Vivo Microscopy
NCRR
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Gradient Spatial Profile Estimates
B07T, radius20cm
Force in field gradient
Estimate scanner as dipole loop
Gradient from dipole loop
Peak gradient strength

1. Peak gradient at roughly 10-20cm from edge of
   scanner
2. Peak gradient strength proportional to B0 and
   inverse of bore size

Center for In Vivo Microscopy
NCRR
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Forces!
B07T, radius20cm
Force on object
Point where magnetic force gravitational force

1. Within 1m of scanners tools can slip off surfaces
   and start accelerating into the magnet
2. Objects can be pulled with 50-300x their normal
   gravitational weight at peak gradient point

Center for In Vivo Microscopy
NCRR