MRI Safety Training

8/20/2019 MRI Safety Training

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Safety Background The MRI scanner is a very large and powerful magnet

Most clinical scanners are 1.5 - 3 Tesla scanners

3 Tesla = 3! gauss

"arths magnetic field # .5 gauss


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MRI SAFETYMagnetic Resonance Imaging (MRI) is one of the most powerful medicaldiagnostic technologies, combining strong magnetic fields with powerfulcomputer image processing.


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Function

The core of an MRI machine is a very high-strength magnet arranged to surround most of the patient$s %ody. This magnet is usually wrapped with coils of copper wire! and when electricityflows through the wire a powerful magnetic field is produced.


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Significance

• In normal MRI machines! the magnets are superconducting---their

wires have &ero resistance to the flow of electric current. The only

way to achieve superconductivity is to ma'e the magnets ultra-cold

%y su%merging them in li(uid helium) at a%out -*53 +,! the magnetassem%ly is %arely 5+, a%ove a%solute &ero. ften! this li(uid helium

is surrounded %y an insulating %lan'et of li(uid nitrogen.

ecause superconducting wires continually conduct and recalculated

the electric current without resistance! the magnetic field is present/* hours a day0 whether the MRI machine is %eing used or not.


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Considerations

• afe operation of an MRI machine re(uires managing

three main categories of potential safety issues! all

addressed %y MRI safety training programs)

1. Medical2%iological effects of high-strength magnets

/. rea2vicinity effects of high-strength magnets

3. 4ryogenic ultra-cold6 gases


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Biological magnetic issues

• There$s no evidence indicating %iological side effects from

the magnetic fields of an MRI scan! and MRI machines don$t

utili&e any ioni&ing radiation that can damage cells or 78.

9regnant patients and technicians are generally advised to

avoid MRI during the early months of pregnancy! due to a

lac' of research on potential magnetic effects on the

developing fetus. MRI operators are trained on pregnancysafety guidelines.


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Magnetic object safety• The main potential danger from MRI machines comes from the interaction of

the magnetic field with metallic o%:ects or particles. ny metal inside the

patient such as medical devices or shrapnel6 can cause severe in:uries.

Metallic o%:ects in the vicinity of an MRI room can %e attracted %y the

;fringe; magnetic field---causing them to %e suc'ed into the MRI machine at

high speed! posing a severe danger to patients. MRI training videos

demonstrate this threat.

MRI safety training outlines the methods of screening for potentiallyha&ardous metal in a patient$s %ody! and for preventing the entry of any

ferromagnetic o%:ects into the MRI room.


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Potential Projectiles E!am"les

ell phone

!eys

"lasses

#air pins $ barrettes

%ewelry

Safety pins

&aper clips

oins

&ens

&ocket knife 'ail clippers

Steeltoed boots $ shoes

ools

lipboards

'o loose metallic ob*ects should be taken into the Scan room+


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Remember# t$e magnet is A%&AYS on'

Even when the MRI Scanner is not in use,

the magnet is on. Ferromagnetic objects

should NEVER be taen into the Scan

Room.


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Cryogenic safety

• MRI operators are trained in the safe management of cryogenic

e(uipment and gases. In the event of a rapid %oil-off of the li(uid

nitrogen or li(uid helium surrounding the magnet a ;(uench;6! a

failure of the emergency venting system can cause a life-threateningo


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!earing "rotection in the MR characteristic of the switching gradient fields is the production

of acoustic noise. hen the alternating low-fre(uency currents

flow through the gradient coils! which are immersed in the high

static magnetic field ! forces are e


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Safety Issue of

Static Magnetic Field

ll non-MR personnel > study su%:ects entering

the MRI scanner room must %e screened.

4R recommends that non-emergent patients should %e screened %y two separate

individuals.

4onsider using plain-film radiographic study

to confirm the a%sence of metal fragments in

critical parts of the %ody.


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#one $% Rece&tion area

#one '% Screening interview area

#one (% )ontrol area, access

restricted with e* locs, &asse*

s*stems etc.

#one +% MR scanner room

MR &ersonnel must have saet*

training,

non-MR &ersonnel cannot have

inde&endent

access to #one ( or +.

Safety Issue of

Static Magnetic Field (ones


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Biological Effect of

Radiofre)uency Field *+,

Radioreuenc* energ* de&osited in the

bod* during an MR e/amination will be

converted into $eat-

0S"ecific Absor"tion Rate. *SAR, is

defined

as the average energ* dissi&ated in the

bod* &er unit mass and time.

1his heat gain is countered b* heat lossthrough sweat glands and cutaneous blood

vessels.


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1hermal Saet* o Subject• Resonant circuitr* can result in heating o the

ti&s o wires or leads to tem&erature in e/cess

o 23 deg ) within a ew seconds

• 4ll unnecessar* electricall* conductive

materials should be removed beore imaging.

• 4ll attached leads should be covered with

cold com&ress or ice &ac.

• 4void an* large conductive loo&s, including

limbs5do not cross arms or legs in the MR,

this orms a loo& as well6.

• )are should be taen to &lace thermal

insulation between the subject and electricall*

conductive material.


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nly items mar'ed ?MR afe@ are permitted in the magnet room. If

there is a (uestion concerning the MR safety aspect of any itemA do

not allow it to %e %rought into the magnet roomB


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The "nd

MRI Safety Training

Documents

Transcript of MRI Safety Training