Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: scientizscht on 14/09/2018 23:07:30
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Hello!
MRI has extremely strong magnetic field.
What happen if you are into an MRI and you have pacemaker? It will rip out your chest and stick to the MRI walls?
Why the naturally occurring metals and ions in your bones and body do not rip your flesh and stick in the MRI walls?
Thanks!
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If you have objects embedded in your body with a significant fraction of iron, cobalt or nickel (ie ferromagnetic elements), they will be attracted strongly to the magnet, and can cause severe tissue damage. (Ex-)Servicemen who may have small pieces of shrapnel in their eyes would be an example.
However, iron and nickel tend to corrode in the body, so metallic components put into the body tend to avoid these elements
- titanium alloys for bone supports and pacemaker cases.
- In the past, dental fillings were made of gold or amalgum (mercury, copper, tin and silver), but today they tend to be made of more ceramic materials.
- Hip replacement joints are made of titanium alloys, or chrome-cobalt alloys. Depending on the alloy, this cobalt may have various responses to magnetic field.
Joint replacements are firmly anchored in bone, so small forces won't cause damage in the way that a piece of metal would in the eye.
It would be wise to remove body piercings and earrings before having an MRI - as much because they have induced currents that could degrade the image quality.
See: https://sciencing.com/mri-compatible-metals-6924238.html
...but alancalverd is the expert here!
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I heard of a research team working on an Infra-red holographic imaging system that could be a cheaper alternative to MRI machines in countries (and small hospitals) that can't afford the purchase price and high running costs of a cryogenic MRI machine.
This system does not have any problems with ferromagnetic materials.
The IR system claims to have higher resolution than MRI, in both time and space.
See TED talk (16 minutes): https://www.ted.com/talks/mary_lou_jepsen_how_we_can_use_light_to_see_deep_inside_our_bodies_and_brains/transcript?language=en
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Thanks guys but I need deeper expertise answers. Chris, can you have more Cantab people engaged please?
According to this: https://www.google.com/m?q=neodymium+in+human+body
There is neodymium in the human body. Neodymium is the strongest magnet. I am not sure what the form of neodymium is, inside human body. But I assume even an atom of neodymium would be a magnet?
Why doesn't neodymium inside human body rip flesh to stick to the MRI walls?
What happens to people with haemochromatosis (iron deposits due to excessive iron intake or other metabolic disorders) when they have MRI?
Also you often have contrasting agent in your blood during MRI. Is this agent magnetic? If yes, why again doesn't rip your vessels to stick to MRI walls?
Due to being small molecules, the MRI generated forces are not strong?
Thanks
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Why don't neodymium inside human body doesn't rip flesh to stick to the MRI walls?
It is important to realise that ferromagnetism - the very strong attraction of metals like iron and nickel- only works with the metal itself . There is a "cooperative" effect between the many millions (or trillions or whatever) of atoms in a piece of metal.
For individual ions in solution that cooperation can't happen so the ions are barely affected by the field.
There's a sort of halfway house for some oxides where there is a long range interaction via the intervening oxide ions. That too, can only happen in solid materials.
But, essentially, the metal ions are, at most, very weakly magnetic in solution.
The effect depends on the oxidation state. I'd have to check but I think Fe(II) ions are repelled by a magnet.
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A lot of materials aren't affected by MRIs, and many pacemakers are MRI compatible these days:
https://www.bhf.org.uk/informationsupport/heart-matters-magazine/medical/ask-the-experts/pacemaker-and-mri-scan
With iron evenly distributed within tissues, the amount of iron necessary to cause the MRI to tear you apart, would have been fatal well before you ever reached the MRI. Haemochromatosis causes measurable differences on MRI scans, but there's no obvious mechanical issues that affect the patient due to the magnetic field.
The real problem is highly ferromagnetic, sharp pieces of metal within the body. A normal neodymium magnet saturates at about 0.5 Tesla, and most people that have played with them know they can pinch your fingers quite painfully. In a strong magnetic field like an MRI iron saturates at 1.5-2 Teslas, it's 3 or 4 times more magnetic than neodymium.
The pull on individual pieces goes as the product of the two strengths; the MRI would have several Tesla of field strength, and the iron would be 1.5-2, so you can imagine how strongly the field would be tugging on pieces of iron in the patient.
But if you were to divide the same amount of iron throughout the body, the pressure would divided over the whole volume and you wouldn't even notice it.
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Which bit of "the iron in your body is not attracted to magnets because it is not metal" causes people difficulty?
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Which bit of "the iron in your body is not attracted to magnets because it is not metal" causes people difficulty?
That's good to know, can we assume the same for iron nanoparticles? (Not just individual ions)
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can we assume the same for iron nanoparticles?
No, but nanoparticulate iron is spontaneously flammable and reacts with water so...
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Which bit of "the iron in your body is not attracted to magnets because it is not metal" causes people difficulty?
It's not exactly true that the 'iron in your body is not attracted to magnets', or it's deceptive, ferrohemoglobin is paramagnetic.
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Which bit of "the iron in your body is not attracted to magnets because it is not metal" causes people difficulty?
It's not exactly true that the 'iron in your body is not attracted to magnets', or it's deceptive, ferrohemoglobin is paramagnetic.
Because it's a delocalised system, it's hard to say if it is the iron, or the rest of the molecule, that is attracted.
I think you could replace the iron with manganese(II) and it would still be equally attracted- though manganese isn't magnetic.
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... can we assume the same for iron nanoparticles? ...
The iron in tattoo-ink can be a problem ... https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3445217/
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What about the natural metal in bones, does it get affected, even though the bone structure does not allow it to show alot?
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... can we assume the same for iron nanoparticles? ...
The iron in tattoo-ink can be a problem ... https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3445217/
True, but that's the RF component of the imaging, not the magnetic field itself.
What about the natural metal in bones,
How did you come to think that there was naturally metal in bones?
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What about the natural metal in bones,
How did you come to think that there was naturally metal in bones?
Isn't calcium a metal?
Also: "Extensive Pulsed Electromagnetic Field research shows that PEMF therapy enables bone & connective tissue regeneration"
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Calcium is a metal.
Calcium phosphate- which is a major part of bone- is a salt.
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We've been running MRI machines in clinical practice for around 40 years. The problems and patient exclusions are pretty well known.
The machines I use don't have a converging magnetic field, so they don't attract anything that isn't already magnetised. Most "open" MRI systems are reasonably safe from flying objects like oxygen bottles and screwdrivers, but we like to avoid pacemakers and aneurysm clips
Tattoo ink , idiot pins and metallic cosmetics (particularly eye shadow) are heated by the RF field and can do a lot of skin damage or worse. Nothing like an arc between the nipples to convince you that God's design of the human bosom doesn't need modification.
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We've been running MRI machines in clinical practice for around 40 years. The problems and patient exclusions are pretty well known.
The machines I use don't have a converging magnetic field, so they don't attract anything that isn't already magnetised. Most "open" MRI systems are reasonably safe from flying objects like oxygen bottles and screwdrivers, but we like to avoid pacemakers and aneurysm clips
Tattoo ink , idiot pins and metallic cosmetics (particularly eye shadow) are heated by the RF field and can do a lot of skin damage or worse. Nothing like an arc between the nipples to convince you that God's design of the human bosom doesn't need modification.
Would magnetised nanoparticles be a problem? Or is a cut off in size that makes them safe?
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Magnetic or conductive nanoparticles would absorb RF radiation from the MRI machine and get hot.
If they were spaced apart the body would simply absorb the heat from them- probably without much harm.
The magnetic field would act on magnetic particles, pretty much regardless of size.
The bigger the particles , or the bigger the bunch of small particles were, the bigger the force would be.
People have been breathing in nanoparticles of rust since the industrial revolution. The people who have MRI scans will contain nanoparticles of magnetic material.
I suspect it distorts the image very slightly, but that's all.
Why do you ask?
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Nothing like an arc between the nipples to convince you that God's design of the human bosom doesn't need modification.
I'm going to steal that line...
:-)
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Why do you ask?
To develop my understanding as always.
Thanks
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Somewhat off topic, but MRI technology has been in the news in Australia recently, as a lab in Germany used the Nuclear Magnetic Resonance (NMR) technique to analyze the chemical makeup of honey sold in shops.
They claim that many brands of honey have been adulterated with cane sugar, sugar beet or other (cheaper) syrups.
Apparently, the standard test checks if the (claimed) honey came from C3 or C4 plants, but NMR can tell far more about the chemical makeup of the honey.
It has certainly raised the profile of this technology!
Note: NMR machines for chemical analysis look very different from NMR machines used to produce whole-body images!
For an inflamatory news story, see: https://www.smh.com.au/business/consumer-affairs/new-purity-test-on-the-cards-amid-honey-adulteration-scandal-20180903-p501hc.html
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If you have objects embedded in your body with a significant fraction of iron, cobalt or nickel (ie ferromagnetic elements), they will be attracted strongly to the magnet, and can cause severe tissue damage. (Ex-)Servicemen who may have small pieces of shrapnel in their eyes would be an example.
However, iron and nickel tend to corrode in the body, so metallic components put into the body tend to avoid these elements
- titanium alloys for bone supports and pacemaker cases.
- In the past, dental fillings were made of gold or amalgum (mercury, copper, tin and silver), but today they tend to be made of more ceramic materials.
- Hip replacement joints are made of titanium alloys, or chrome-cobalt alloys. Depending on the alloy, this cobalt may have various responses to magnetic field.
Joint replacements are firmly anchored in bone, so small forces won't cause damage in the way that a piece of metal would in the eye.
It would be wise to remove body piercings and earrings before having an MRI - as much because they have induced currents that could degrade the image quality.
See: https://sciencing.com/mri-compatible-metals-6924238.html
...but alancalverd is the expert here!
Just like MRI,are dental X-ray's are harmful for your health.
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The effective dose from a single intraoral x-ray is around 10 microsievert. This is equivalent to about a days' natural background radiation and the risk of inducing a fatal cancer is less than 1 in 1,000,000, officially described as "negligible"