I don't know anything about MRI machines, but couldn't they be built with high temperature superconductors and use liquid nitrogen? If anything this feels like a cost issue not a pure technology issue...
It IS a technology issue. High-TC superconductors are basically ceramics, meaning that they are brittle. And a good simulation of MRI experience is being inside a trash can that other people hit with baseball bats.
We are only now starting to get high-TC superconductors in the form of tape, but it's not yet ready to replace low-TC superconductors.
BTW, it's also the reason we're hearing about so many new fusion startups trying to utilize it. It _should_ provide an order of magnitude cost decreases compared to liquid-helium. But it's still something that only startups are using.
And modern MRI machines are not that expensive either, mass production made them surprisingly affordable. A top-of-the-line machine is around $700k, and mid-range devices are $300-$400k (and now I want one in my backyard...).
So the savings on high-TC supeconductors would not be that impressive overall.
There's apparently even a robust second-hand market for them: https://bimedis.com/search/search-items/magnetic-resonance-i...
NMR spectrometers work on essentially the same mechanism as MRIs, just in a very different form factor. It might even work for MRIs without helium because they have a much lower field (~3-6T) compared to the ~28T of the highest field NMR spectrometer.
The high-temperature superconductors are still pretty new for this field, it took a while to figure out manufacturing them on a scale and quality that could be used for these large magnets.
That's a real understatement :)
A typical NMR spectrometer needs to hold a test tube, and an MRI machine kinda has to hold a whole human.
> "Balloon Grade" Helium represents a slightly impure Helium. While there is no scientific definition of this quality, it is often accepted that the purity of "Balloon Grade" Helium is around 99%
https://www.quantum-technology.com/recover/balloon-grade-hel...
Sounds high, but not pure enough for MRI applications, and it isn't currently economical to reliquefy without shipping it to a processor.
> Manufacturers have stated that this wasted helium is considered a ‘recycled product’ as it would have been lost to the environment had it not been captured and re-purposed. If the balloon market demand declined, manufacturers would have to re-evaluate other markets and consider the possibilities of re-liquefying it. Re-liquefying is currently considered uneconomical from the locations of where the filling application take place.
https://www.partysafe.eu/balloon-and-gas-helium
Also it's small, but not insignificant, sector of the market:
> "A reasonable estimate is that latex 'party' balloons and their foil equivalent account for between 5% and 7% of the total helium usage."
https://www.theguardian.com/science/shortcuts/2012/dec/11/sh...
How does that work?