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PostPosted: Wed Oct 01, 2008 2:20 am 
I was shot in the leg by an airgun at close range in 1945. Since the pellet was in the fleshy upper part of the leg, the doctors decided not to remove the pellet. It is, I suppose, still there. Recently I developed sciatica and have been recommended for an MRI scan of my back. The people doing the scan asked me if I had any metal in my body. I mentioned the pellet. They then decided that there was a risk, because of the powerful magnets' attraction for the metal. But surely lead is not subject to the attraction of magnets. Your discussion of the composition of pellets makes me wonder whether the presence of other metals would make a difference. Does anybody have information on this?


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PostPosted: Wed Oct 01, 2008 2:56 am 
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I'm sure the chemists/metallurgists amongst us can answer this, but from what i can remember, lead pellets have a tiny bit of antimony, some tin and a wee bit of zinc. I have no idea of the proportions and there must be more trace elements.
Lead is not magnetic but I'm not sure about any of the trace elements that are in its make up. Whether these will be attracted by the scanner is in my view doubtful.
Don't they scan when some one has been shot, or is it just X-Ray?


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PostPosted: Wed Oct 01, 2008 3:03 am 
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Can anyone guarantee what the composition was of the pellet that hit you 63 years ago. I would very much doubt it.

Whatever happens, not that you will have any option, take the advice from the MRI specialists. They will be highly unlikely to do the scan if there is even a remote risk of magnetic material.


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PostPosted: Wed Oct 01, 2008 6:47 am 
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Some things to consider:

A changing electrical field through non-ferous metal will set up a current, that will in turn create some magnetism. Ever seen a spinning horseshoe magnet suspended over an aluminum disc that is free to rotate? The disc will spin, being drawn around by the magnetism set up by the current induced by the horseshoe magnet.

Another effect of the induced current is heat generated in the metal.

If lead is left in the body, does it chemically seal itself off from leaching? If so, would that seal be affected by the induced currents and/or the heat?

Take Care,
Ed Hall


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PostPosted: Wed Oct 01, 2008 8:34 am 
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I was hit in the eye by some lead from an adjacent shooter many years ago. I was asked the same question prior to having an upper body MRI and I described the incident. The doctors did an x-ray of my left eye to determine if any lead had been left behind. The answer was none and I had the MRI. My impression was that the heating effect described by Ed Hall was the issue, especially in the eye.


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 Post subject: MRI safety
PostPosted: Wed Oct 01, 2008 1:29 pm 
Healthcare providers are, because of the beloved lawyers (you win, I win; you lose, I win), punitive damages and mischievous litigants, absolutely paranoid about exposing patients to avoidable risk. Unfortunately, the legal environment of some countries makes this attitude necessary for self-preservation. Please therefore allow me to remain anonymous: I'm a recently retired radiologist member of this forum. (And, in case you were wondering, I never had any case brought against me, thank goodness!)

The two risks from embedded metal in MRI are heating (due to eddy currents) and displacement due to the huge magnetic fields. In a simple bit of the body, with little in the way of sensitive clockwork, and strong structural tissues, displacement realistically isn't a risk. The heating effect, on a small lump, is likewise neglegible. Plenty of people get scanned intentionally, who are known to have metal structures within them. For practical purposes, as long as the metal is known to be "MRI-friendly", ie not ferro-magnetic, it's safe. This goes for aneurysm clips in the brain, and not just for those within politicians!

There was a paper, some years ago, addressing the risks to attending personnel, etc, in the vicinity of MRI scanners. It was advised that firearms should not be taken into the scanning room! (Yes, it was an American paper!). If I remember correctly, there was one incident where a handgun was caused to discharge as a result of the magnetic field.


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 Post subject: spelling!
PostPosted: Wed Oct 01, 2008 1:36 pm 
Oops! Can't edit as a guest. Apologies, Negligible, not neglegible - the brain knows, but the body doesn't respond!


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 Post subject: mri
PostPosted: Wed Oct 01, 2008 11:17 pm 
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I would seek a second opinion about the MRI scan. My mother had a hip replacement about 10 years ago but she had to have a MRI scan of her lower back and legs for exactly the same reasons as you. Now if a great lump of metalwork in her hip was ok to go in the scanner, then I'd suspect a lead pellet would be of no concern. As always though, talk to a proper specialist who can give you the relevant advice.

Rob.


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PostPosted: Thu Oct 02, 2008 11:51 am 
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The big issue is the fact that they don't know for certain what the pellet is, it could be a steel BB, iron shot gun shot, they don't know so they won't take a risk.


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PostPosted: Thu Oct 02, 2008 10:51 pm 
Further to my previous contribution (retired radiologist, with years of MRI experience)...

A pellet, even if iron, in the leg would not worry a sensible MRI team.


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PostPosted: Fri Oct 03, 2008 12:51 pm 
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Anonymous wrote:
Further to my previous contribution (retired radiologist, with years of MRI experience)...

A pellet, even if iron, in the leg would not worry a sensible MRI team.


My point was there are many things that people could call a "pellet" which would include a steel BB which would be a problem.


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PostPosted: Fri Oct 03, 2008 1:07 pm 
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Richard H wrote:
Anonymous wrote:
Further to my previous contribution (retired radiologist, with years of MRI experience)...

A pellet, even if iron, in the leg would not worry a sensible MRI team.


My point was there are many things that people could call a "pellet" which would include a steel BB which would be a problem.


My point was that it doesn't matter what anyone on here thinks. If the MRI team (or their legal team) don't want to do it then it won't be done.


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PostPosted: Sat Oct 04, 2008 2:36 am 
Retired radiologist again.

Look, you can listen to, and be confused by, the opinions freely given in this forum, but, if you are going to act upon them, you would like to know the knowledge-base from which the contributors draw their opinions, wouldn't you?

Medicine, in spite of the legal parasites' best efforts, is generally evidence-based. It is not based on hearsay, ignorant opinion or whim. Healthcare professionals make decisions from knowledge drawn from international literature, which is peer-revued and evidence-based. It's a rather different environment from this forum.

You can ask a professional (a radiologist, not a technician, who may, sadly, blindly follow department 'policy') about the risks - assume the worst-case, that it's a soft iron fragment, sitting bang up against the femoral artery in your leg. Enough shrapnel- and medically inserted metallic structure-containing patients have been scanned without mishap to provide evidence that metal bits inside the body does NOT mean no MRI scans! It depends what it is and where. Whilst absence of evidence of risk isn't the same as evidence of absence of risk, there is a wealth of MRI safety literature on which you can expect, nay demand, that a decision is made about whether to scan you.

You could also go elsewhere, and forget to tell anyone about the pellet... It all depends how much you want the diagnostic investigation.


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PostPosted: Thu Oct 09, 2008 2:23 pm 
I've worked with MRI units for over a decade. Our routine with any foreign body is to xray first. This provides information about the existance, compositon, shape, size and location of the object. Usually a lead lead or steel pellet would likely be safe in an MRI unit up to 1.5 Tesla. The operator should be made aware of any foreign body so that you will be put into the magnet slowly. The greatest amout of torquing will occur near the mouth of the bore. You will be requested to monitor the area where the foreign body is and inform the staff of any discomfort, pain or noticable heat/warmth. The operator will can make changes to phase direction, bandwidth and gradient strength to lessen the distortion caused by the metal, and possibly improve the quality of your study. Have your test done at a modern centre, and discuss your situation with an experienced Radiologist.


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PostPosted: Fri Oct 24, 2008 2:10 pm 
I am another retired radiologist with experience in supervising and interpreting MRI scans. The reply from "Guest" (retired radiologist) is correct regarding the risks of metal FB's being heating and displacement of the FB near sensitive structures. There is an additional risk as well: induced currents in wires (think cardiac pacemakers, implanted cardiac defibrillators and neurological stimulators).

In addition, there is another consideration that is not really a risk to the patient but is a factor detrimental to the diagnostic quality of the exam. When a metallic object is adjacent to the site being imaged, the "local" magnetic field is changed, resulting in distortion of the image. Depending upon the size (mass) of the metallic object, the quantity of ferromagnetic substance (iron) in the metal and the distance to the structure being imaged, this image distortion can be significant enough that the scan is useless, or the distortion could be negligible.

In the case cited above, a small pellet of any kind that has been present for years and whose location is not close to the lumbar spine or to the distribution of the sciatic nerve would pose no problem with regard to image quality. As previously stated, such a pellet would also not be of concern for patient safety.

The presence of a metallic foreign body, even a ferromagnetic foreign body, is not necessarily a contraindication to an MRI examination. The determination to perform the exam depends upon the particular circumstances.

The following statement, copied from a previous reply, is NOT correct:
"They will be highly unlikely to do the scan if there is even a remote risk of magnetic material."

As a practical matter, an experienced radiologist should make this determination. If you suspect that an MRI scan was refused because of unreasonable blind adherence to a safety protocol, you should request to speak with the radiologisit and directly ask his or her opinion (as suggested by "Toyno" above).


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