World's most powerful MRI gets set to come online

Oct 24, 2013 by John Hewitt report
Worlds most powerful MRI. Credit: IEEE Spectrum

(Phys.org) —The most powerful MRI machine in the world is nearing completion. The new instrument will be able to generate 11.75 Tesla, a field strong enough to lift 60 metric tons. Squeezing out those last few Tesla (the previous record for field strength was around 9.4) requires extraordinary precision in the design and manufacture of the superconductor magnets at its core. As a recent article in IEEE Spectrum reports, fields of this magnitude are stronger than those used in the Large Hadron Collider which famously discovered the Higgs boson. As a research tool, a machine like this would allow the brain to be imaged in unprecedented detail—a voxel size of .1mm as compared to 1 mm previously. But as medical device makers struggle to design implants that won't move, heat up or otherwise fail in fields of that strength, the opportunity for new discovery in the brain, will by guided also by a few new challenges to be overcome.

MRI machines normally image the relatively strong signals associated with the nuclei of hydrogen. With higher field strengths it is possible to image signals from sodium or potassium, the ions that are also among the most mobile in carrying the charge associated with spikes in neurons. An area of 0.1mm still might have over 1000 neurons so this technology is not going to be imaging neuron activity individually. It may however, provide recent efforts to decode the private imagery associated with our inner thoughts and dreams with much greater accuracy than current methods. While a recent paper in Nature contains an air of optimism regarding the progress of the decoding algorithms used in these kinds of studies, cautionary tales regarding the interpretations of the results still abound.

The 270 million dollar scanner project, know as INUMAC (Imaging of Neuro disease Using high-field MR And Contrastophores), has been in development for the last seven years. Delivery was taken this summer of some 200 km of superconducting niobium-titanium wire. When cooled with superfluid helium to 1.8 Kelvins, this wire will be able to carry 1500 amps. The key to making a magnet that won't melt or vibrate itself apart, is a new winding design that permits the helium to get where it needs to for cooling, and also provides for winding alignment to micrometer precision.

Today electromagnetic devices, like precision servomotors, are no longer wound willy-nilly like a random spool of yarn, but rather put together so that each turn is in the proper place. The idea is that entire electromagnet hums coherently as a whole and creates a uniform field. A more expensive wire material, niobium-tin, would in theory carry enough current at the same diameter to create fields up to 20 Tesla, but it is much more brittle than niobium-titanium and difficult to wind.

Pushing field strengths ever higher raises a few concerns. Implant manufacturers, like Medtronic, have a tough job to do to insure the safety of their devices inside magnet bores. One indicator of the gravity of the situation, is that they have taken to naming their devices according to their tolerance of fields strong enough to turn gas cylinders in adjacent rooms into guided missiles. Their SureScan pacemaker comes with guarantee of MRI compatibility—at least up to certain fields strengths, and their spinal cord neurostimuluators, commonly used to subvert chronic pain, come with documentation that doesn't shy away from some hard-core physics.

For example, an MRI system generates three kinds of fields, each of which have different potential for interaction with a device. The static fields are present at all times around the magnet, while the three orthogonal gradient fields kick in only during the scan. A pulsed RF field is also present during the scan, and is created by a variety of different methods. We might note here that when an airplane takes-off or lands, powering down your devices in the face of the unknown is only a nuisance. Powering down an implant, if it is advised, may have more inconvenient consequences.

A final cautionary tale before leaping in to one of these new machines, is that the effects of double-digit field strength on the tissues of the body itself are not completely understood. Computer models and simulations will be invaluable in setting guidelines here, but ultimately the proof is in the pudding. Physical tests will be needed, both as reality check for the things missed by the model, and also to help indicate areas perhaps where the models might be too restrictive.

Explore further: The physics of lead guitar playing

More information: spectrum.ieee.org/biomedical/i… rful-mri-takes-shape

www.nature.com/news/brain-deco… eading-minds-1.13989

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User comments : 18

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hemitite
3.3 / 5 (7) Oct 24, 2013
That was a rather well written article: clear, informative, and elegant.
johnhew
1.7 / 5 (11) Oct 24, 2013
That was a rather well written comment. I am still searching though on your one from yesterday regarding http://medicalxpr...ies.html
cary_lewis1965
2.1 / 5 (11) Oct 24, 2013
Magneto would be so proud...
210
1 / 5 (10) Oct 24, 2013
That was a rather well written article: clear, informative, and elegant.

I MUST AGREE! It was not just the eye-popping numbers, it was also the quality of the writing, outstanding!
hemitite
1 / 5 (7) Oct 24, 2013
johnhew,

Sometimes I just give into my dark side...
bg1
not rated yet Oct 24, 2013
Who is the manufacturer and who is the customer?
johnhew
1 / 5 (10) Oct 24, 2013
bg1: The INUMAC link contains a bit of that, if you can sort it out. It is manufactured by a consortium of partners, funded by a European Consortium, will be used by several other, and it looks like at least 1 will reside somewhere.
Foundation
5 / 5 (3) Oct 24, 2013
Who is the manufacturer and who is the customer?

The manufacturer of the superconductor is Luvata ( http://www.luvata.com ). The customer is a French-German consortium.
I believe this is the official site of the scanner: http://portal.uni...e/inumac
RobL
1 / 5 (4) Oct 25, 2013
'Cooled to 1.8 Kelvin' wow! That's cold, don't want that He (l) pipe to burst! .... I wonder what they do with all the waste heat? They could heat the building?
axemaster
not rated yet Oct 25, 2013
I got to play with the field of a cyclotron recently, set at partial power (~1 Tesla). That's an very strong field capable of generating really terrifying forces (i.e. accelerating iron objects to extreme speeds, bending steel, causing pieces of copper to nearly defy gravity). I can't even imagine something >10T. When they say "strong enough to turn gas cylinders in adjacent rooms into guided missiles", they really mean it.
antialias_physorg
5 / 5 (1) Oct 25, 2013
At those kinds of filed strengths you get all kinds of issues which can lead to patients not to be able to use these.

Piercings and metal implants are obvious (with piercings usually being removable...and emergency staff are charged to look for that stuff on unconscious patients in all kinds of places now). What is sometimes forgotten is that some types of tattoos are made used a metal based ink. This can heat up and cause serious burns.
don't want that He (l) pipe to burst!

The cooling systems are fitted with an emergency conduit to the outside. E.g. in the case of quenching the stuff is vented (expensive, but better than blowing up the room in any case)
Mike_Massen
1 / 5 (1) Nov 16, 2013
:hmmm: Would those with Hemochromatosis have to be concerned ?

Yes the static field is huge - mind boggling !

What is the nature of the dynamic field in terms of intensity, frequency etc ?

I earnestly hope the commenters can follow the good writing with their own thoughtful opinions, offer educative input and interesting rational discussion instead of angry opinionated barking such as on other threads - now and then aye 210 ?

johnhew
not rated yet Nov 18, 2013
what are the additional concerns with hemochromatosis?
Mike_Massen
not rated yet Nov 24, 2013
johnhew asked
"what are the additional concerns with hemochromatosis?"
Increased amount of Fe in the body & not necessarily evenly distributed. Free Fe as we know is magnetic, oxidised Fe as Ferrous is generally non-magnetic whereas Ferric in such minerals as magnetite is magnetic.

With hemochromatosis its entirely possible the distribution & different valance states of iron throughout the body could result in localised movement/heating where Ferric is concentrated & even if not concentrated moves in response to the static fields & can heat up in the dynamic fields in any number of random locations causing unknown damage to fine structures.

It might be worth noting that we cannot make full use of Fe ingested unless we have good intake of Copper as the key enzyme for metabolising Iron is Ferroxidase which is a Cu based enzyme.

The problem is Cu & Fe are co-antagonists, many pathogens use Fe as a catalyst for food production however, Cu discourages bacteria significantly !
antialias_physorg
not rated yet Nov 24, 2013
Something was bugging me about my own argument (and the hemochromatosis argument) here, so I went back to my lecture notes to look some stuff up.

The problem with induced heat arises with the dynamic part of the field, only, the static part (which is what the 11.75 tesla field is) doesn't heat up anything at all (it is 'only' a problem for metal implants, as they get attracted/ripped from the patient).
So the heating issue for this powerful new MRI isn't any worse than for the old ones as the readout/signal field strength isn't increased.

It might even be less as you can use lower dynamic fields to get the same signal strength as before (however you probably want to get better resolution, so the heating issue is probably on the same order as before)

..and of course you shouldn't move the patient quickly while (s)he's in there and the field is turned on.
Mike_Massen
not rated yet Nov 24, 2013
"Something was bugging me.."
uttered antialias_physorg,
many assumptions bug me antialias_physorg, Eg. those with hemochromatosis won't have particulate agglomerations of Fe moved internally damaging tissues.

antialias_physorg speculated thus
".. the static part (which is what the 11.75 tesla field is) doesn't heat up anything at all
I wouldn't be so quick to believe that, as red blood cells move Fe through the body & are also subject to vortices through many difficult areas, Eg heart, might there be localised heating & this is not so easily dissipated without harm during the period of exposure ?

What of the fine capillaries in the brain as they give up oxygen, could brain cells be subject to local heating effects close to capillaries ?

Worth considering as ~ a quarter of the cells in the human body are red blood cells with Fe.

What of the intra/inter cellular fluids, higher the static field the greater chance of unknown effects re protein synthesis, protease etc
antialias_physorg
not rated yet Nov 24, 2013
The heating happens due to a differential (either the magnetic field changing or a magnetic particle moving within a static field). The main heating that is a medically relevant issue happens at the Gigahertz scale.
Blood flow/vortices don't move fast enough to cause significant heating in even such a strong field.
You can google for the frog levitation experiment in a 16T field that suffered no ill effects due to heating.
Mike_Massen
not rated yet Nov 24, 2013
antialias_physorg murmered, messed the tech
"The heating happens due to a differential (either the magnetic field changing or a magnetic particle moving within a static field)."
Friction !
You missed a point, pulling particulates through tissues can create heat, see my point re agglomeration.

antialias_physorg continued with
"The main heating that is a medically relevant issue happens at the Gigahertz scale."
That's primarily microwaves, negligible evidence of instrumented work done in respect of (high) static fields & local motion for appreciable period.

antialias_physorg guessed
"Blood flow/vortices don't move fast enough to cause significant heating in even such a strong field."
Wouldnt bet on it, effect has local maxima & cumulative.

antialias_physorg Frog experiment you offer is for a "cold blooded creature" for relatively short periods, frog couldn't communicate effects Eg. headaches & humans are far more complex !

Careful, assumptions can kill !