MRI compatible orthosis - summary of replies
Description
Collection
Title:
MRI compatible orthosis - summary of replies
Date:
12/6/2007
Text:
Dear Colleagues:
Here is my original question, and following it are the responses: How does
one make an orthosis (a spinal orthosis, for example) MRI compatible? Is
it just a matter of no metal? Or of the type of metal? Or of the quantity of
metal? Does anyone know a source on the web where I could go to learn this?
Responses (without names): It means that there are no ferrous metals in its
composition. IT may be made of aluminum or titanium. There has been some
concern with non ferrous metals generating heat from MRI's and some halo
manufacturers are making pins of a ceramic material.
||
I have read about MRI compatible halo pins using fiberglass and ceramic tips
instead of metal (ie Jerome Medical's Resolve Halo). I believe it cannot
contain any metal whatsoever, however Jerome Medical markets their product
as electronically non-conductive materials. You may also read this thread
of a similar question at
< <URL Redacted>>
<URL Redacted>. Although the
different posters argue about their opinions, the closing statement claims
any type of metal has some magnetic response, even if it is minor, and to
avoid any type of metal in an MRI.
||
You might want to talk to these people...
< <URL Redacted>>
http://www.magneticresonancesafetytesting.com/
||
It depends on the field strength of the magnet. Most clinical magnets range
from 1.5 to 3 Tesla, these magnets do allow metal, but not ferrous metal.
Frank G. Shellock, Ph.D. writes safety manuals for MR systems. I believe he
has a website and I know he has an updated manual indicating what types of
metals are safe for certain field strengths. Let me know if you need more
info.
||
I have done this by useing plastic pop rivets and plastic D rings.
||
You need to use titanium screws to anchor your straps & buckles. The loops
on the chafe must be titanium (again) or graphite. If you want call me @ 412
599-1110 and we can discuss this further. We do many halos in our practice
and are familiar w/ these requests.
||
It would have to be all non-magnetic metal, but I doubt they would allow it,
because even a needle could destroy the machine.
||
I'm an MRI tech. Basically if you are interested in an orthosis that would
be worn during an MRI, any type of metal will cause an artifact on the
images if the metal is in the general area of the body part being scanned.
If you want the patient to be able to wear the orthosis while having a scan,
then you would need to keep it totally metal free to prevent image
degradation.
||
Iron and cobalt are the only metals that are ferromagnetic (would effect an
MRI). Theoretically, all metals that do not contain these two are fine
(aluminum, silver, gold and titanium, for examples. Most steel has iron in
it). But, and this is a huge but, the MRI, because of the huge magnetic
field it sets up, will be cause currents within the other metals, moving
them around, which would be uncomfortable, and, potentially could distort
your MRI results. I am copying my brother who works in the imaging
department of Mass General for further input if he has any. And to correct
me if I'm way off base.
||
The only criteria is that the orthosis have nothing magnetic. Any metal
rivets that are magnetic need to be changed. Also, do not forget about any
metal looped chafes.
||
Since the MRI uses Magnetic pulses, I believe any non magnetic material
would work (Aluminum, Brass, Plastic etc)
||
For a definitive answer you should contact the manufacturers of MRI
equipment. Phillips and Siemans come to mind.
||
No metal, all plastic; plastic rivets, plastic buckles.
||
I believe MRI compatible means no metal of any kind. I have made TLSO's MRI
compatible by attaching all straps etc. with plastic rivets. Personally,
I've had an MRI and was told to remove all metal items, including my wedding
ring.
||
We make them without metal, using plastic d-rings.
||
I am still a student, so I cannot offer an answer from experience, but we
did just have a lecture last week about MRI compatible HALOs. Also, with my
engineering background I would suggest that MRI compatible should include:
1. non-conductive materials. 2. any conductive materials required should not
be in contact with the skin, 3. if a conductive material does contact the
skin, it should be grounded somewhere else (this one I am not sure of but it
makes sense that if the material is not grounded elsewhere then the skin
will be the ground and thus create a burn)
||
I'm not a prosthetist or a doctor, but a mechanical engineer. I can tell you
that the major concern with metal and MRIs is the danger associated with the
movement of metal objects due to the changing magnetic field generated by
the MRI. This phenomenon is due not only to ferromagnetic attraction, but to
eddy currents that can be generated by a changing magnetic field in any
conductive metal. These electrical currents generate a magnetic field even
in non-ferrous metal. This can be observed if you drop a strong magnet into
a copper pipe. Eddy currents are generated in the pipe by the descending
magnet that oppose the magnet, causing it to fall slowly through the pipe.
This is also how some roller coaster brakes work. Besides the violent
movement of metal objects, eddy currents can generate heat in the metal, and
can also create distortions in the images generated by the MRI in their
presence. For all of these reasons, any conductive metals should be avoided.
Carbon fiber is also conductive to some degree, but a limited search on the
internet suggests that it creates only small artifacts compared to metal,
and I couldn't find any reference to dangers associated with using it in an
MRI (found a reference to using a carbon fiber needle for interventional
procedure, e.g.). I suggest you contact the MRI lab at your hospital
specifically on this issue. Your safest bet is to use plastic, and plastic
fasteners. They should work fine if you make them big enough, and
engineering plastics like delrin or glass filled nylon should be plenty
stiff. If the MRI tech gives you the go-ahead, carbon fiber is probably your
easiest route.
||
I have had some experience regarding MRI compatibility in orthoses and in
particular Halos. The type of material is one issue , typically materials
such as aluminum, titanium, and carbon fiber have been MR compatible.
However in the last few years depending on the speed of the MR ( typically
1.5 tesla and above ) it is not merely a matter of eliminating ferrous
materials but also eliminating conductive material. This would include
getting rid of carbon fiber, titanium, and aluminum, so in the case of a
TLSO it would be of if you used nylon rivets and plastic chafes. Now having
said all of this in some hospitals still using aluminum,Titanium and carbon
are acceptable but never FERROUS material. Any way probably more than you
wanted to know but if you have any questions please email me back.
||
Make everything plastic or aluminum as a 2nd choice for fasteners! Just had
that issue at a local large hospital radiology center. It was a CTLSO and
had to be removed for steel Chicago screws and D-loops.
||
actually there are other ferromagnetic metals (e.g. Nickel). If you are
interested in determining if an inplant is MRI compatible, there is a series
of tests to measure force and torque on the item. There is a list compiled
of cleared implants. Reference Manual for Magnetic Resonance Safety,
Implants and Devices: 2007 Edition By F.G. Shellock Biomedical Research
Publishing Group. If you are concerned with more than safety but also
generating artifact free images that is *much* more difficult, as you have
to match magnetic susceptibility with the surrounding tissue, otherwise the
artifacts can be pretty bad.
David Hendricks, CPO, FAAOP - HOPE Orthopedic - Orlando, FL - 407-697-9481
- fax: 407-851-8922 - < http://www.hopeortho.com/ > www.hopeortho.com
< http://www.hopeortho.com/ >
Here is my original question, and following it are the responses: How does
one make an orthosis (a spinal orthosis, for example) MRI compatible? Is
it just a matter of no metal? Or of the type of metal? Or of the quantity of
metal? Does anyone know a source on the web where I could go to learn this?
Responses (without names): It means that there are no ferrous metals in its
composition. IT may be made of aluminum or titanium. There has been some
concern with non ferrous metals generating heat from MRI's and some halo
manufacturers are making pins of a ceramic material.
||
I have read about MRI compatible halo pins using fiberglass and ceramic tips
instead of metal (ie Jerome Medical's Resolve Halo). I believe it cannot
contain any metal whatsoever, however Jerome Medical markets their product
as electronically non-conductive materials. You may also read this thread
of a similar question at
< <URL Redacted>>
<URL Redacted>. Although the
different posters argue about their opinions, the closing statement claims
any type of metal has some magnetic response, even if it is minor, and to
avoid any type of metal in an MRI.
||
You might want to talk to these people...
< <URL Redacted>>
http://www.magneticresonancesafetytesting.com/
||
It depends on the field strength of the magnet. Most clinical magnets range
from 1.5 to 3 Tesla, these magnets do allow metal, but not ferrous metal.
Frank G. Shellock, Ph.D. writes safety manuals for MR systems. I believe he
has a website and I know he has an updated manual indicating what types of
metals are safe for certain field strengths. Let me know if you need more
info.
||
I have done this by useing plastic pop rivets and plastic D rings.
||
You need to use titanium screws to anchor your straps & buckles. The loops
on the chafe must be titanium (again) or graphite. If you want call me @ 412
599-1110 and we can discuss this further. We do many halos in our practice
and are familiar w/ these requests.
||
It would have to be all non-magnetic metal, but I doubt they would allow it,
because even a needle could destroy the machine.
||
I'm an MRI tech. Basically if you are interested in an orthosis that would
be worn during an MRI, any type of metal will cause an artifact on the
images if the metal is in the general area of the body part being scanned.
If you want the patient to be able to wear the orthosis while having a scan,
then you would need to keep it totally metal free to prevent image
degradation.
||
Iron and cobalt are the only metals that are ferromagnetic (would effect an
MRI). Theoretically, all metals that do not contain these two are fine
(aluminum, silver, gold and titanium, for examples. Most steel has iron in
it). But, and this is a huge but, the MRI, because of the huge magnetic
field it sets up, will be cause currents within the other metals, moving
them around, which would be uncomfortable, and, potentially could distort
your MRI results. I am copying my brother who works in the imaging
department of Mass General for further input if he has any. And to correct
me if I'm way off base.
||
The only criteria is that the orthosis have nothing magnetic. Any metal
rivets that are magnetic need to be changed. Also, do not forget about any
metal looped chafes.
||
Since the MRI uses Magnetic pulses, I believe any non magnetic material
would work (Aluminum, Brass, Plastic etc)
||
For a definitive answer you should contact the manufacturers of MRI
equipment. Phillips and Siemans come to mind.
||
No metal, all plastic; plastic rivets, plastic buckles.
||
I believe MRI compatible means no metal of any kind. I have made TLSO's MRI
compatible by attaching all straps etc. with plastic rivets. Personally,
I've had an MRI and was told to remove all metal items, including my wedding
ring.
||
We make them without metal, using plastic d-rings.
||
I am still a student, so I cannot offer an answer from experience, but we
did just have a lecture last week about MRI compatible HALOs. Also, with my
engineering background I would suggest that MRI compatible should include:
1. non-conductive materials. 2. any conductive materials required should not
be in contact with the skin, 3. if a conductive material does contact the
skin, it should be grounded somewhere else (this one I am not sure of but it
makes sense that if the material is not grounded elsewhere then the skin
will be the ground and thus create a burn)
||
I'm not a prosthetist or a doctor, but a mechanical engineer. I can tell you
that the major concern with metal and MRIs is the danger associated with the
movement of metal objects due to the changing magnetic field generated by
the MRI. This phenomenon is due not only to ferromagnetic attraction, but to
eddy currents that can be generated by a changing magnetic field in any
conductive metal. These electrical currents generate a magnetic field even
in non-ferrous metal. This can be observed if you drop a strong magnet into
a copper pipe. Eddy currents are generated in the pipe by the descending
magnet that oppose the magnet, causing it to fall slowly through the pipe.
This is also how some roller coaster brakes work. Besides the violent
movement of metal objects, eddy currents can generate heat in the metal, and
can also create distortions in the images generated by the MRI in their
presence. For all of these reasons, any conductive metals should be avoided.
Carbon fiber is also conductive to some degree, but a limited search on the
internet suggests that it creates only small artifacts compared to metal,
and I couldn't find any reference to dangers associated with using it in an
MRI (found a reference to using a carbon fiber needle for interventional
procedure, e.g.). I suggest you contact the MRI lab at your hospital
specifically on this issue. Your safest bet is to use plastic, and plastic
fasteners. They should work fine if you make them big enough, and
engineering plastics like delrin or glass filled nylon should be plenty
stiff. If the MRI tech gives you the go-ahead, carbon fiber is probably your
easiest route.
||
I have had some experience regarding MRI compatibility in orthoses and in
particular Halos. The type of material is one issue , typically materials
such as aluminum, titanium, and carbon fiber have been MR compatible.
However in the last few years depending on the speed of the MR ( typically
1.5 tesla and above ) it is not merely a matter of eliminating ferrous
materials but also eliminating conductive material. This would include
getting rid of carbon fiber, titanium, and aluminum, so in the case of a
TLSO it would be of if you used nylon rivets and plastic chafes. Now having
said all of this in some hospitals still using aluminum,Titanium and carbon
are acceptable but never FERROUS material. Any way probably more than you
wanted to know but if you have any questions please email me back.
||
Make everything plastic or aluminum as a 2nd choice for fasteners! Just had
that issue at a local large hospital radiology center. It was a CTLSO and
had to be removed for steel Chicago screws and D-loops.
||
actually there are other ferromagnetic metals (e.g. Nickel). If you are
interested in determining if an inplant is MRI compatible, there is a series
of tests to measure force and torque on the item. There is a list compiled
of cleared implants. Reference Manual for Magnetic Resonance Safety,
Implants and Devices: 2007 Edition By F.G. Shellock Biomedical Research
Publishing Group. If you are concerned with more than safety but also
generating artifact free images that is *much* more difficult, as you have
to match magnetic susceptibility with the surrounding tissue, otherwise the
artifacts can be pretty bad.
David Hendricks, CPO, FAAOP - HOPE Orthopedic - Orlando, FL - 407-697-9481
- fax: 407-851-8922 - < http://www.hopeortho.com/ > www.hopeortho.com
< http://www.hopeortho.com/ >
Citation
“MRI compatible orthosis - summary of replies,” Digital Resource Foundation for Orthotics and Prosthetics, accessed November 24, 2024, https://library.drfop.org/items/show/228826.
