Is platinum magnetic?

[INRM]

Well, is it?

-INRM

[Rob Lister]

Originally posted by INRM
Well, is it?

-INRM

All matter is magnetic.

http://www.geo.umn.edu/orgs/irm/hg2m/hg2m_b/hg2m_b.html

[Bjorn]

Originally posted by INRM
Well, is it?

-INRM My poor google skills tells me no, but yes, because:

Platinum, when found, is fairly impure. It is always associated with small amounts of other elements, such as gold, copper, nickel, and iron, and many times contains the rare heavy metals iridium, osmium, rhodium, and palladium. These impurities can lower its specific gravity to 14, when pure platinum is 21.4. Most platinum specimens contain traces of iron, which may cause it to be slightly attracted to magnetic fields.If I read this correctly, platinum is not magnetic if it is pure/purified, although the words 'always associated with small amounts of' makes me wonder ..... :con2:

http://www.minerals.net/mineral/elements/platinum/platinum.htm

[Anders]

Originally posted by Rob Lister
All matter is magnetic.

http://www.geo.umn.edu/orgs/irm/hg2m/hg2m_b/hg2m_b.html
Yeah, Well, kind of a defintion issue...

[Benguin]

Originally posted by Anders
Yeah, Well, kind of a defintion issue...

In field geology we would not use magnetism as a test for the presence or absence of platinum. Only ferrous materials and cobalt. But then, we're talking a rough and ready science there!

[Pragmatist]

It depends on what you mean by "magnetic".

Platinum is paramagnetic with a relative susceptibility around 26E-5.

It's not ferromagnetic or diamagnetic, obviously.

Edited to correct error.

[Kumar]

Originally posted by Rob Lister
All matter is magnetic.

http://www.geo.umn.edu/orgs/irm/hg2m/hg2m_b/hg2m_b.html Interesting for me. :)

[Benguin]

Magnetism is fascinating, as is gravitational attraction.

Go google a bit on Kepler and see what you find.

[Kumar]

I want to understand more how all matters can be magnetic?

[Benguin]

Well everything is magnetic, it's just a question of how much. Same with gravity ... it always applies.

In terms of magnetism Iron (and cobalt) are just a bit special.

[INRM]

Okay, let's put it this way.

let's say I was carrying a piece of platinum. And I walked right up to an MRI... would the Platinum piece get sucked right out of my hand and go into the machine, f*cking it up all day?

-INRM

[Benguin]

No

[Rob Lister]

Originally posted by INRM
Okay, let's put it this way.

let's say I was carrying a piece of platinum. And I walked right up to an MRI... would the Platinum piece get sucked right out of my hand and go into the machine, f*cking it up all day?

-INRM

I don't know how strong the magnetic fields are in or near an MRI but I suspect you would feel a very slight tugging if you got close enough. That's just a guess. Platinum is "slightly" magnetic but I'm also not sure how to qualify that. If I cared, I'd look it up.

www.google.com

[Benguin]

Originally posted by Rob Lister
I don't know how strong the magnetic fields are in or near an MRI but I suspect you would feel a very slight tugging if you got close enough. That's just a guess. Platinum is "slightly" magnetic but I'm also not sure how to qualify that. If I cared, I'd look it up.

www.google.com

I think there'd be an attraction, but not enough to feel.

I also can't be bothered to look it up!

[Rob Lister]

Originally posted by INRM
Okay, let's put it this way.

let's say I was carrying a piece of platinum. And I walked right up to an MRI... would the Platinum piece get sucked right out of my hand and go into the machine, f*cking it up all day?

-INRM

I feel cheap for having dis'ed you in my initial reply to this question. I'm sure Benguin does as well.

Okay, here’s the deal.

Assuming the MRI is a 1.5 Tesla SIGNA machine (general electric) and assuming a one pound mass of platinum suspended on an eight inch string of number 12 nylon string from the top-front of the diagnostic plenum opening such that the mass hangs within one inch of the oval center, and assuming the machine is operating at maximum penetration, you should notice a slight pendulum-like motion of the mass which will eventually stabilize (I estimate 42.1 minutes) such that it will be 1.236 +/- .003 degrees off-plum in the direction of the plenum.

Yea, I made it up.

[Eos of the Eons]

Why do you ask?

And hey, is wood slightly magnetic too then? What about us humans?

I saw some stupid gold and copper colored "magnetic" bracelets for sale at my local Superstore. I wanted to fling them into the garbage. I was so mad they were sold in the pharmacy dept.!!!!

If magnets had any effect on our body that was in any way noticeable, you would explode in an MRI machine!!

[Benguin]

Originally posted by Rob Lister
I feel cheap for having dis'ed you in my initial reply to this question. I'm sure Benguin does as well.

Okay, here’s the deal.

Assuming the MRI is a 1.5 Tesla SIGNA machine (general electric) and assuming a one pound mass of platinum suspended on an eight inch string of number 12 nylon string from the top-front of the diagnostic plenum opening such that the mass hangs within one inch of the oval center, and assuming the machine is operating at maximum penetration, you should notice a slight pendulum-like motion of the mass which will eventually stabilize (I estimate 42.1 minutes) such that it will be 1.236 +/- .003 degrees off-plum in the direction of the plenum.

Yea, I made it up.

Ahhh, but we need the force value to determine the answer to the question (or my proposition you wouldn't feel the attraction).

[Terry]

Originally posted by INRM
Okay, let's put it this way.

let's say I was carrying a piece of platinum. And I walked right up to an MRI... would the Platinum piece get sucked right out of my hand and go into the machine, f*cking it up all day?

-INRM

When I had an MRI, they didn't make me take my platinum wedding ring off. Just as well, since at the time it would have been hard to get it over the knuckle (due to being somewhat overweight). I didn't notice any force being applied to the finger.

--Terry

[Taffer]

Originally posted by Eos of the Eons
Why do you ask?

And hey, is wood slightly magnetic too then? What about us humans?


I'd have to say yes to this. Ever see the 'floating frog' experiment where they suspended a frog in a very large magnetic field? It worked on anything at all.

[Kumar]

Originally posted by Benguin
Well everything is magnetic, it's just a question of how much. Same with gravity ... it always applies.

In terms of magnetism Iron (and cobalt) are just a bit special. Means: if all metalic & non metalic substances are magnetic to some extent? Whenther Iron(and cobalt) are just bit special or just bit more magnetic? How magnetic properties are/can be transffered to iron or other substances(all here)??:)

[Benguin]

Maybe when use the word magnetic and magnetism it's not so helpful in this context, because we all get mental images of compasses and magnets picking things up.

Magnetism is not my strongest area, I'm better with electricity and gravity, but they all work in very similar ways. If you think of electricity, I'm sure you would remember being taught early on that there are 'conductors' and 'insulators', then when you learn at a more advanced level that is chucked out as you learn the conductivity of materials is something much more varied than that. Almost anything will conduct electricity, just some things do it incredibly badly.

I understand magnetic theory is pretty much the same.

The stuff at the bottom of this link (http://chem.ufl.edu/~chm2040/Notes/Chapter_10/properties.html) explains nicely what is behind magnetic properties.

There is a good page here (http://hyperphysics.phy-astr.gsu.edu/hbase/tables/magprop.html#c2) on calculating the magnetic susceptability of various materials.

In other words, in answer to Eos' question, everything has a magnetic susceptibility, it just is negligible for most things. So you can take those magnets out of your shoes now.

[MRC_Hans]

In other words: No, Kumar. Sorry, but you cannot assume that homeopathic drugs somehow stores something magnetically.;)

Hans

[Kumar]

Originally posted by MRC_Hans
In other words: No, Kumar. Sorry, but you cannot assume that homeopathic drugs somehow stores something magnetically.;)

Hans Hello Mr.Hans,

If all substances are magnetic, we can think so. But I am not able to understand its logic as bit technical. I am just thinking that as magnetic effects is transfered into iron peice or just by rubbing--why it could not be possible in other substances if those are also somewhat magnetic. More harsh rubbing as in potentization process may mean something.:)

[Benguin]

Originally posted by Kumar
Hello Mr.Hans,

If all substances are magnetic, we can think so. But I am not able to understand its logic as bit technical. I am just thinking that as magnetic effects is transfered into iron peice or just by rubbing--why it could not be possible in other substances if those are also somewhat magnetic. More harsh rubbing as in potentization process may mean something.:)

Well you could speculate, but you are looking to find a theory to prove a phenomenon for which no evidence exists.

I can tell the difference between a magnetised bit of iron and an unmagnetised one. It might be possible, with equipment sensitive enough, to tell if a something fairly unsusceptible like wood has had prolonged exposure to a strong magnetic field, I don't know. It wouldn't be possible with a fluid.

There is no way to tell the difference between a bit of water and a succussed remedy because there is no difference. When you've found a way of telling the difference with any statistical reliability then we can talk about theories as to what's going on.

Did you forget the Hanneman quote I gave you already?

[Kumar]

Benguin,

Thanks for information. You want to say that their may not be any measurable effects in most of other substances than iron( cobalt).

Btw, which substances can interfere MRI imaging?

Did you forget the Hanneman quote I gave you already?

But who agrees here, with Dr. Hanneman's other quotes? If you all would had agreed, it would have saved lot of time & energy to me & others. :)

[Kumar]

Sorry, I got details of banned items on MRI here. (http://www.nlm.nih.gov/medlineplus/ency/article/003335.htm) But I want to know that if MRI based images of body parts are due to the presence of iron in body parts or it takes imaging effeced by other body substances also?? I want to know the basis of target parts for taking their images?

[MRC_Hans]

Originally posted by Kumar
Hello Mr.Hans,

If all substances are magnetic, we can think so. But I am not able to understand its logic as bit technical. I am just thinking that as magnetic effects is transfered into iron peice or just by rubbing--why it could not be possible in other substances if those are also somewhat magnetic. More harsh rubbing as in potentization process may mean something.:) No, because that is one of the special things with iron and a few other metals: They can be magnetized, and retain a magnet field. Other substances (like water, alcohol, and lactose) cannot retain a magnet field.

There are several more holes in the thesis, but this is really enough to dismiss it.

Hans

[The Don]

Originally posted by Kumar
Sorry, I got details of banned items on MRI here. (http://www.nlm.nih.gov/medlineplus/ency/article/003335.htm) But I want to know that if MRI based images of body parts are due to the presence of iron in body parts or it takes imaging effeced by other body substances also?? I want to know the basis of target parts for taking their images?
courtesy of howstuffworks.com

http://electronics.howstuffworks.com/mri1.htm

[Rolfe]

Kumar thinks that MRI works because there is iron in all the tissues.

:hb:

Rolfe.

[MRC_Hans]

Originally posted by The Don
courtesy of howstuffworks.com

http://electronics.howstuffworks.com/mri1.htm Very interesting article, thank you! Apart from explaining how MRI scans work in a very understandable way, it indirectly delivers another ground shot to Kumar's newest thesis: Since you can place a human in a 2 tesla magnet field :eek: without appreciable side effects, it is evident that in the unlikely event that some kind of magnetic effect exists in hom. remedies, there is not a snowball's chance in heII that some infinitesimal effect could have any influence on the body.

It is also a bit of a slap in the face of other magnet therapies.

Hans

[Benguin]

Originally posted by MRC_Hans
No, because that is one of the special things with iron and a few other metals: They can be magnetized, and retain a magnet field. Other substances (like water, alcohol, and lactose) cannot retain a magnet field.

There are several more holes in the thesis, but this is really enough to dismiss it.

Hans

Well aside from the material issues, I can't see how it is possible for a magnetic field to be created in a fluid, I'm not sure what you'd get if you could create a fluid of pulverised magnetic iron, but I'd be surprised if it would be anything.

Can I just point out, in case I confused anyone with talking about magnetic properties of all materials, that magnet therapy is utter steaming gonads that makes me laugh like a hyena.

Kummy-wummy ... the molecules in a fluid are moving about constantly, even in an apparently static fluid. Magnetic alignment can only occur for a transient moment before it will disappear through random rearrangment of the molecules in the fluid.

In any case, any effect as remote and weak as would occur through succussing two non-susceptible materials (water, duck's liver) is likely to be overridden by the earth's magnetic fields.

There is nothing latent to be seen ... here, an experiment for you;
1. Take two pieces of iron
2. magnetise one
3. Melt them both
4. Allow them both to solidify
5. Find a way to tell which is which by analysing their different magnetic properties.
6. Phone Randi up and collect your million.

Try not to burn yourself, or set fire to anything. I'd feel guilty.

[INRM]

I remember hearing a risk like if you got metal bits in your eyes or something, and went into an MRI, the magnet could move the metal and cut your nerves and blind you. They do an X-ray of your eye.

Does this X-ray include your whole head, or just your eyes?

'Cause I was exposed to a whole lot of dust, some got into my ears even. What would happen then?

-INRM

[Benguin]

Originally posted by INRM
I remember hearing a risk like if you got metal bits in your eyes or something, and went into an MRI, the magnet could move the metal and cut your nerves and blind you. They do an X-ray of your eye.

Does this X-ray include your whole head, or just your eyes?

'Cause I was exposed to a whole lot of dust, some got into my ears even. What would happen then?

-INRM

It's if you're likely to have been exposed to airborne iron filings and such like. The medline link Kumar gave covers it well.

[The Don]

Originally posted by MRC_Hans
Very interesting article, thank you! Apart from explaining how MRI scans work in a very understandable way, it indirectly delivers another ground shot to Kumar's newest thesis: Since you can place a human in a 2 tesla magnet field :eek: without appreciable side effects, it is evident that in the unlikely event that some kind of magnetic effect exists in hom. remedies, there is not a snowball's chance in heII that some infinitesimal effect could have any influence on the body.

It is also a bit of a slap in the face of other magnet therapies.

Hans
Surely, the weaker the field, the stronger the effect

[fishbob]

'Cause I was exposed to a whole lot of dust, some got into my ears even. What would happen then? Probably get a massive aneurism, your head would explode, and somebody would have to hose out the MRI machine.

[Matabiri]

Originally posted by Benguin
Magnetism is not my strongest area, I'm better with electricity and gravity, but they all work in very similar ways.

At the risk of being highly pedantic, as I understand it electricity and magnetism work in the same way, gravity works differently...

[HopkinsMedStudent]

I wear my platinum wedding ring into the MRI scanner room every day and I havent noticed any force being pulled on it. I dont know how pure the ring is, but if theres any impurities in it, they are not of sufficient magnitude to produce a noticeable force in a standard 1.5T field.

Welders and other people who work with metal cutting can accumulate very small particles of iron or other ferromagnetic metals into their eyes. If put into an MRI machine, they may be able to feel heat or pain in their eyes, so of course you are supposed to exclude anybody who fits this profile from getting a scan.

Some older tattoos used iron in the mettalic inks which could cause skin burns. However, most of the tattoos of the last 20 years or so use iron-free inks, so if its a recent tattoo the chances are greater of having no complications. We use a voice monitor to make sure that there is no local RF heating for people with tattoos, and if there is, we immediately cancel the scan. We've never had any serious burns with tattooed patients, just some minor pain that subsided immediately after leaving the scanner room.

Kumar,

MRI has NOTHING to do with imaging iron. Conventional MR scanning is based on hydrogen, not iron. MR spectroscopy uses other species such as sodium for example, but iron is not one of them.

[Kumar]

Originally posted by The Don
courtesy of howstuffworks.com

http://electronics.howstuffworks.com/mri1.htm Don, Interesting site in easy language thanks. It appears by understanding this site that when this much magnetic effect can not effect then other possibily can not be possible. But, this is the only mystry of homeopathy & TRS alike how a needle can effect when a sword can not effect. We may continue accordingly.

[Rob Lister]

Originally posted by Kumar
Don, Interesting site in easy language thanks. It appears by understanding this site that when this much magnetic effect can not effect then other possibily can not be possible. But, this is the only mystry of homeopathy & TRS alike how a needle can effect when a sword can not effect. We may continue accordingly.

The above post should win some kind of award somewhere.

No, not the language award.

Possibly, the anti-language award.

[Rolfe]

But, this is the only mystry of homeopathy & TRS alike how a needle can effect when a sword can not effect. We may continue accordingly.No, we may continue accordingly when we have some evidence that homoeopathy and TRS do effect.

Oh, that was "mass existing belief", not to be denied.

Sorry, not going back into that revolving door again thank you.

Rolfe.

[INRM]

Originally posted by HopkinsMedStudent
I wear my platinum wedding ring into the MRI scanner room every day and I havent noticed any force being pulled on it. I dont know how pure the ring is, but if theres any impurities in it, they are not of sufficient magnitude to produce a noticeable force in a standard 1.5T field.

Welders and other people who work with metal cutting can accumulate very small particles of iron or other ferromagnetic metals into their eyes. If put into an MRI machine, they may be able to feel heat or pain in their eyes, so of course you are supposed to exclude anybody who fits this profile from getting a scan.

Some older tattoos used iron in the mettalic inks which could cause skin burns. However, most of the tattoos of the last 20 years or so use iron-free inks, so if its a recent tattoo the chances are greater of having no complications. We use a voice monitor to make sure that there is no local RF heating for people with tattoos, and if there is, we immediately cancel the scan. We've never had any serious burns with tattooed patients, just some minor pain that subsided immediately after leaving the scanner room.

Kumar,

MRI has NOTHING to do with imaging iron. Conventional MR scanning is based on hydrogen, not iron. MR spectroscopy uses other species such as sodium for example, but iron is not one of them.

i know this sounds so dumb, but would CA++ set off an MRI's magnet?

Or is that just regular ol' calcium?

[HopkinsMedStudent]

Originally posted by INRM
i know this sounds so dumb, but would CA++ set off an MRI's magnet?

Or is that just regular ol' calcium?

Both regular calcium and Ca2+ have fully paired electron orbitals, so for all practical purposes calcium is immune to the effects of the magnetic field.

For an element to react to a magnetic field in an MR scanner, it must have unpaired electrons, this is because paired electrons (spin up and spin down) cancel each other's magnetic moment out to result in zero net magnetic moment per atom.

Diamagnetic objects have interactions with the MR magnetic field that are too weak to produce substantial force. Every material has some diamagnetic properties. Diamagnetic objects in a magnetic field generates a very small repulsive force.

Paramagnetic objects have unpaired electrons in which each atom produces a net magnetic moment. However, across the whole object, the magnetic moments are oriented in a random fashion, and therefore, there are no large magnetic domains.

All ferromagnetic objects are also paramagnetic. HOWEVER, in addition to being paramagnetic, instead of having their magnetic moments spread randomly throughout the sample, they have large magnetic domains that comprise trillions of atoms with the same magnetic moment. These large magnetic domains interact with an external magnetic field to generate a noticeable force on the object. All paramagnetic materials generate forces in a magnetic field, but the paramagnetic forces are observable only in a microenvironment, whereas ferromagnetic forces produce a net force vector for the whole object. So if you took an iron wrench into the MR scanner room you would feel the magnet trying to pull it out of your grasp.

On a macroscopic level, the only dangerous items in the context of MR scanners are ferromagnetic objects. Paramagnetic materials dont transition into the large magnetic domains that draw a substantial force from the magnetic field.

[phildonnia]

What a coincidence; as I read this post, I happen to have both a few grams of platinum on my finger and a small Nd magnet in a drawer. I've never noticed any reaction between the two.

For a more accurate test, I was able to balance my wedding ring on edge on a flat table. I was unable to disturb it in the slightest by waving the magnet nearby.

[Benguin]

Originally posted by Matabiri
At the risk of being highly pedantic, as I understand it electricity and magnetism work in the same way, gravity works differently...

Well yes. The main differences being my levels of understanding.

I was thinking about fields when I said that;
Magnetic fields
Electric fields,
Gravitational fields.

You are correct about gravity being different, but the physics one uses to play with it is very similar.

I was wrong to say they work the same way, just that we can model them very similarly.

I remember finding it all fascinating when I was taught about 14 years ago ... I regret forgetting most of it, maybe I should read a book!

[anor277]

Just on a point(less?) of clarification; the magnetism (ferromagnetism) we commonly refer to arises from spinning electrons. The magnetic field measured by a MRI or NMR machine derives from nuclear spins (some orders of magnitude less intense than that propagated by electrons). I believe the MRI machine in medical use responds to the nuclei in hydrogen (one of the most MRI receptive nuclei and of course a major component of biological entities) to give a powerful diagnostic tool. The nucleus in a proton can be either spin aligned (alpha – lower energy state) or spin unaligned (beta) with respect to the permanent magnetic field supplied by the electromagnetic in the MRI machine. Flipping the protons from one state to the other is a process requiring very little energy yet the instruments are sensitive enough to measure the transitions.

As an aside, MRI (or Nuclear Magnetic Resonance - they changed the name to Magnetic Resonance Imaging to keep those pesky nuclei out of hospitals) was 1st used to characterize the shifts of small(ish) organic molecules (which of course contain protons) in solution. Even a relatively simple molecule can give rise to a complicated (and characteristic) NMR spectrum. It is beyond me how the spectra of a human body supplied by an MRI machine can give interpretable results but they demonstrably can.

[SGT]

Originally posted by Rob Lister
All matter is magnetic.

http://www.geo.umn.edu/orgs/irm/hg2m/hg2m_b/hg2m_b.html

In the same way, we could say that all substances are water soluble. What varies is the level of solubility.
When we say that glass is insoluble in water, what we really mean is that the silicate ions, that are in solution, are so few that we can ignore them.
I wonder what is the point in a homeopathic preparation where there are more particles of glass then of the 'active' principle in the water.
By the way, the distilled water used in the preparation has other impurities besides glass. What is the therapeutic effect of all these impurities?

[Rolfe]

Originally posted by SGT
By the way, the distilled water used in the preparation has other impurities besides glass. What is the therapeutic effect of all these impurities? Been there (http://www.randi.org/vbulletin/showthread.php?s=&threadid=38285)
seen that (http://www.randi.org/vbulletin/showthread.php?s=&threadid=38170)
done that (http://www.randi.org/vbulletin/showthread.php?s=&threadid=39349)
bought the t-shirt (http://www.randi.org/vbulletin/showthread.php?s=&threadid=39060).

Rolfe.

[INRM]

I know this sounds SO neurotic...

but, can you answer this question anyway?

1.) I sucked in some dust yesterday, and a chunk that had a metallic taste to it. Is that a danger?

2.) I've been playing with a lot of magnets, and then I scratched the back of my neck... nothing will happen will it, even if a piece of the magnet ( a small sliver) was on, or slightly in my skin... if I walk into the MRI room, will it get sucked forward, through my brain-stem and kill me instantly? Or will it have no effect, or will it burn a little?

I'm so scared.

-INRM

[Benguin]

We can't help you. Tell the radiologists before your scan, and they'll come up with an appropriate course of action.

[HopkinsMedStudent]

Originally posted by anor277
I believe the MRI machine in medical use responds to the nuclei in hydrogen (one of the most MRI receptive nuclei and of course a major component of biological entities) to give a powerful diagnostic tool.

Yes. The key to MRI is that there are billions of atoms of hydrogen in a small packed volume in our bodies. Thats absolutely key, because as you suggested, the magnetic flux generated by hydrogen protons is very small, so you need trillions of them concentrated in a small space to get good signal.

The nucleus in a proton can be either spin aligned (alpha – lower energy state) or spin unaligned (beta) with respect to the permanent magnetic field supplied by the electromagnetic in the MRI machine.

Yes, interestingly a typical field strength of 1.5T is only sufficient to tip a tiny minority of the total spins in the direction of the aligned field. Its on the order of one excess spin per million. This is somewhat unfortunate, because you could get much better signal if ALL the spins lined up parallel to the field. Higher field strengths give better images because a higher field causes more of the spins to line up parallel to the field. However, there are engineering design problems to building high field strength magnets that are also suitable for human imaging purposes.

A lot of people are claustrophobic, so they cant be scanned in a regular closed bore system. We have open MRIs that use 2 panels instead of a bore system, but the field strength for those is much less than conventional MRI (0.5T - 1.0T max). As a result, the images from the open MRI systems are not as good as the closed bore systems.

Flipping the protons from one state to the other is a process requiring very little energy yet the instruments are sensitive enough to measure the transitions.

Yeah as I said the key is that although the magnetic flux measurable from one proton is very small, there are trillions and trillions of hydrogen protons in a small volume size, so when you add up a small signal from such a large number of protons, the resulting flux is measurable by the coils in the MR scanner.


It is beyond me how the spectra of a human body supplied by an MRI machine can give interpretable results but they demonstrably can.

MRI is basically an NMR system with 3 magnetic gradient fields. With magnetic gradient fields, you can spatially encode the magnetic spin flux generated by the sample. NMR systems use RF pulses to generate signal from the sample, but it doesnt have any gradient fields to parse out WHERE in the sample those spin flux contributions are coming from, so the overall result for NMR is a spin reading of the whole sample.

With 3 gradient fields as is typical for an MRI system, you can control which part of the sample gets excited (slice select) and then use the 2 other gradients to get an x,y encoded matrix of magnetic flux. Its very cool stuff. The guys who won last year's Nobel Prize for Medicine were the engineers/physicists who discovered the use of gradients to turn NMR systems into a true imaging system.

[pgwenthold]

Originally posted by HopkinsMedStudent
Yes. The key to MRI is that there are billions of atoms of hydrogen in a small packed volume in our bodies. Thats absolutely key, because as you suggested, the magnetic flux generated by hydrogen protons is very small, so you need trillions of them concentrated in a small space to get good signal.



Small correction: MRI does not measure magnetic flux of H nuclei. It only uses a magnetic field to split the energies of the nuclear spin states, and then uses normal EM radiation to carry out the spectroscopy.

MRI itself is a little more complicated than that, using relaxation times to identify the environment of the protons, but it is still the decay of EM absorption.

[HopkinsMedStudent]

Originally posted by pgwenthold
Small correction: MRI does not measure magnetic flux of H nuclei.

Fair enough, I should have used the term "field" or "moment" instead of "flux." I was just trying to emphasize that the individual signal contribution from a single proton is very small, so you need lots of them to generate sufficient signal that can be captured by the receive coil in the scanner.

PET scans are much better than MRI in terms of sensitivity, because it can use a much smaller number of nuclei to get good signal. However, MRI is much better in terms of spatial resolution. Usually when we want to do a PET scan we cross register is with MR images so that we can take advantage of the great spatial resolution of MRI and the great sensitivity that PET offers.

[Crotchety Englishman]

My interest was tweaked when I read this thread as my doctoral thesis was on doping palladium and platinum with small amounts of ferromagnetic ions (things like iron, nickel and cobalt) in order to drive them through an enhanced paramagnetic state to ferromagnetism. Strongly ferromagnetic ions like cobalt and iron cause small domains of ferromagnetism to occur while nickel atoms only do this when the doped atoms are close enough to form doublets and triplets. Less than 2.5% of doped nickel will cause the entire palladium crystal to flip into a ferromagnetic state with a much smaller amount of iron causing this. Platinum I seem to remember needed even less. Platinum and especially palladium had rather odd magnetic behaviour due to very high electron-electron interactions.

I am also aware of an accident at a lab whereby a wrench was accidently let loose and pulled into the bore of a superconducting magnet. The major problem is that the forces on the windings can exceed design specs resulting in them moving within their potting material. The movement can not only crack the wire but cause enough frictional heating to cause the magnet to quench. If that wasn't enough to damage the magnet, the chances are that the windings are no longer positioned precisely and the homogenity of the magnetic field is messed up rendering the experiment impossible.