magnet safety training center for in vivo microscopy v1.4

Magnet Safety Training Center for In Vivo Microscopy

V1.4

Your Magnet Safety Team

Larry HedlundGary Cofer

Bastiaan Driehuys

Updated: May 15, 2012

Center forCenter forIn VivoIn Vivo

MicroscopyMicroscopyNCRRNCRR

General MRI Hazards

• An MRI scanner creates a magnetic field that is 30,000-150,000 times stronger than the earth’s magnetic field and is always onalways on

• While hazards to people with pace-makers and implants tend to be emphasized, projectile hazardsprojectile hazards are most worrisome for us

• Within a few feet of the magnet, the field gradient can rip steel rip steel objectsobjects out of your hand

• The onset of this zone is very rapidvery rapid and non-linear

• Objects can reach speeds of 80mph80mph before slamming into the magnet (or you)



Unique Issues to CIVM

• We have the following differences: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

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



Why Bother With Magnet Safety?

• A magnet projectile presents a very real possibility of serious injury or deathserious injury or death

• Impact of the magnet by a projectile could result in 3 months of system down timesystem down time

• Repair costs leave less moneyless money for science– ($450,000 to replace a 7T magnet)

• Serious incidents lead to more onerous onerous safety rules safety rules and less scienceand less science



How Fast Will Objects Fly?

Notable Observations:

• Vobj =45mph at 2T– Equivalent to 7-story free-fall


• Terminal velocity facts:– Scales as square root of B0

– independent of mass*

• Impact energy– Scales with mass

– Scales linearly with B0(See appendix for math if interested)

Forces on Objects!

B0=7T, radius=20cm

• 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



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



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



Our Magnet Policies

1. NO EQUIPMENT brought into lab without sign-off and Labeling by magnet safety representative

2. NOBODY WORKS IN THIS MRI LAB until they have completed this magnet safety training1. And Documented it by signing their name on the wiki

3. VISITORS and AFTER HOURS WORK have separate policies

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

Weekends and After Hours

The magnet laboratories are available from 7:30 AM to 5:00 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.



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 don’t get between it and the magnet



Labels Used in Our Lab

Labels are on clipboard by 2T console. To print more, see Magnet Safety Page on Wiki



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)

A recent incident (Jan 2011)

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”

Motor/pump stuck to 7T

Rigging required to remove pump from 7T

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?

• Don’t 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

Another recent incident (April 2012)

• Situation:

• Janitor working on buffing floors

• Received instruction to stay away from Magnet

• Still got buffer sucked into the magnet

Janitor’s Buffer Stuck to 7T

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



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 SafetyWiki page to verify that you have completed this

Appendix for Physicists and Engineers



How Fast Will Objects Fly?

Potential Energy of ObjectStuck in Magnet

Potential Energy of ObjectRemoved from Magnet

Difference must be kinetic energy prior to impact



Projectile Velocity Estimates

• Notable Observations:



• Terminal velocity facts:– Scales as square root of B0

– independent of mass*

• Impact energy– Scales with mass

– Scales linearly with B0

Conserve Energy

Treat object as iron chunk:

Velocity scales as sqrt(B0)



Gradient Spatial Profile Estimates

Estimate scanner as dipole loop

Gradient from dipole loop

Peak gradient strength

B0=7T, radius=20cm

Force in field gradient

azB

1. Peak gradient at roughly 10-20cm from edge of scanner2. Peak gradient strength proportional to B0 and inverse of bore

size



Forces!

Force on object

B0=7T, radius=20cm

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

magnet safety training center for in vivo microscopy v1.4

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