3 ms·

Isn't the resolution on these governed by the magnetic field strength (like the nuclear spectrometers in chemistry?) That's why MRI machines are so big; the mag

by swiley 6y ago

Isn't the resolution on these governed by the magnetic field strength (like the nuclear spectrometers in chemistry?) That's why MRI machines are so big; the magnets are insane (and (edit)[involve] a bizarre material: liquid helium!)

andrewnc 6y ago
Yes, but that's mainly because they use FFT for reconstruction. So you need extremely clean data. If, however, you use some significantly more sophisticated signal processing, you can side step this requirement.
- abrichr 6y ago
  Like what?
  - layoutIfNeeded 6y ago
    Maybe https://en.wikipedia.org/wiki/Compressed_sensing https://en.wikipedia.org/wiki/Compressed_sensing ?
- ska 6y ago
  Using sophisticated signal processing (which has been standard for ages at this point) gets you some gains, sure; but it's not magic and high field systems have better resolution. Worth noting: A lot of the focus on advanced signal processing has been focused on scan speed, and main field strength and homogeneity is only one factor in resolution. You need high quality gradients too, the finer the resolution the more precise everything has to be set up or you are just smearing the signal around in space.
layoutIfNeeded 6y ago
Ummmm... they're not made of liquid helium. They use superconducting magnets which need extremely low temperatures to work, and they use liquid helium for cooling them.
SimplyUnknown 6y ago
No the resolution can be set at will, down from microns to centimeters (depending on the gradient system and sequence). But! The amount of signal per voxel depends on the magnetic field strength. So with tiny voxels there is hardly any signal at low field strength so you won't see anything and you will measure mostly noise.
- lostlogin 6y ago
  You can get past this with more averages. So the real issue is that it is very slow to get high resolution at low field strengths. The flip side of this is that high field strength scanners get a lot more image artefacts than low strength systems.

by swiley 6y ago

andrewnc 6y ago

Yes, but that's mainly because they use FFT for reconstruction. So you need extremely clean data. If, however, you use some significantly more sophisticated signal processing, you can side step this requirement.

abrichr 6y ago
Like what?
- layoutIfNeeded 6y ago
  Maybe https://en.wikipedia.org/wiki/Compressed_sensing https://en.wikipedia.org/wiki/Compressed_sensing ?
ska 6y ago
Using sophisticated signal processing (which has been standard for ages at this point) gets you some gains, sure; but it's not magic and high field systems have better resolution. Worth noting: A lot of the focus on advanced signal processing has been focused on scan speed, and main field strength and homogeneity is only one factor in resolution. You need high quality gradients too, the finer the resolution the more precise everything has to be set up or you are just smearing the signal around in space.

layoutIfNeeded 6y ago

Ummmm... they're not made of liquid helium. They use superconducting magnets which need extremely low temperatures to work, and they use liquid helium for cooling them.

SimplyUnknown 6y ago

No the resolution can be set at will, down from microns to centimeters (depending on the gradient system and sequence). But! The amount of signal per voxel depends on the magnetic field strength. So with tiny voxels there is hardly any signal at low field strength so you won't see anything and you will measure mostly noise.

lostlogin 6y ago
You can get past this with more averages. So the real issue is that it is very slow to get high resolution at low field strengths. The flip side of this is that high field strength scanners get a lot more image artefacts than low strength systems.