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Is there a good reason we aren't seeing REBCO magnets in all new MRI machines? Seems like not needing liquid helium would be a pretty big win for hospitals?
by gpm 3y ago
Is there a good reason we aren't seeing REBCO magnets in all new MRI machines? Seems like not needing liquid helium would be a pretty big win for hospitals?
- fabian2k 3y agoThey probably still can't carry the necessary current without helium cooling. There are some NMR spectrometers (which work essentially by the same principles as MRI machines) with high-temperature superconductors, but those are still cooled by helium. The lower the temperature is the more current you can pack into those. Could also be that it doesn't make economic sense yet, they're still pretty new compared to classical superconductors.
- refulgentis 3y agoYes: Commonwealth Fusion essentially is buying the world's supply of it. MRIs are a more mature market, i.e. > 1 units, and need to justify component switches not just for feasibility, but for profitability. Swapping out a known-good for something in such short supply isn't feasible, it's more expensive than liquid helium. Source: https://spectrum.ieee.org/fusion-2662267312 https://spectrum.ieee.org/fusion-2662267312 "Over two years, the team managed to buy up most of the world’s supply of 4-millimeter-wide HTS tape"
- actionfromafar 3y agoCommonwealth Fusion is such a Fallout name
- deprecative 3y agoTodd is in shambles that he can't use the name.
- fragmede 3y ago[flagged]
- cyberax 3y ago> Is there a good reason we aren't seeing REBCO magnets in all new MRI machines? REBCO tapes are still very brittle, and MRI machines are notorious for the amount of banging they produce when active.
- andbberger 3y ago??? the gradient coils make the noise, and due to field homogeneity requirements, it is safe to assume the superconducting coil is not moved by the gradient coils
- alacritas0 3y agohomogeneity is only optimized for a small volume within the bore. Regardless, the superconducting coils will still experience a change in Lorentz forces as sequences are run, and noise from other components will still be "heard" by the main magnet
- cyberax 3y agoIt's still very much affected by the vibrations, and the electromagnetic forces from the gradient coils.
- caymanjim 3y agoMRIs don't consume much helium. Keeping them topped off is a trivial expense compared to the rest of the costs of the machine and operation. If there were a new design that didn't require helium, it would also have to cost less than current machines to make sense.
- 7speter 3y agoWait, isn't the byproduct of fusion helium anyway?
- willis936 3y agoYeah but you'd power a city for a year for 100 kg of helium.
- ta988 3y agoA single MRI needs around 1000 liters, 1L is roughly 130g. For those who wonder prices vary between $15-35 per liter. Recent MRIs have recycling systems that reduce refill needs by 90% when they work properly.
- willis936 3y agoSo about $15k for 100 kg?
- Tuna-Fish 3y agoFusion produces much, much less helium than that. D-T fusion that produces 100kg of He-4 would produce something like 25PJ of net primary energy. If you managed to turn 20% of that into electricity, you'd have 5PJ. This is within an order of magnitude of the yearly electricity consumption of the entire world.
- willis936 3y agoI do actually have receipts. For example numbers I picked Washington DC, which has 700k people that each use an average of 600 kWh per month. That's 5 TWh / year, which I rounded up to 10 TWh. This yields 475 m^3 of helium, which is 85 kg. I rounded up to 100. DC is a modest city and all of humanity uses 15000 TWh / year (of heat). This "100 kg / city / year" estimate is even on the lower end since I started with electric consumption and never put in the factor of 3 to convert to thermal. Your mass-energy conversion number is within error of mine, but your estimate of how much power we use is much lower. https://www.wolframalpha.com/input?i=%2810+TWh%29+%2F+%2817.59+MeV%29+%2F+%28avogadro%27s+number+1%2Fmol%29+*+%284.002602+g%2Fmol%29+%2F+%280.1786+g+%2F+liter%29 https://www.wolframalpha.com/input?i=%2810+TWh%29+%2F+%2817....
- ororroro 3y agoThere are already non-venting systems that use a reasonable amount of helium (7L) to manufacture and don't require refilling. It just was not a design consideration previously. https://www.philips.com.au/healthcare/resources/landing/the-next-mr-wave/sealed-mr-technology https://www.philips.com.au/healthcare/resources/landing/the-...
- pfdietz 3y agoI would say it's because the technology has not been matured enough. I would also say the reason CFS has been getting funding is not because of fusion (although, hey, why not take that longshot bet), but because of the value of being able to make these magnets for non-fusion applications.