One of the major problems with magnetic resonance imaging machines is the huge magnetic fields required to make them work and the giant superconducting magnets that generate them. These magnets usually have a field strength of around 1.5 Tesla although some designs can reach 9 T or more. That makes them expensive. So expensive, in fact, that the cost of rest of the machine is chickenfeed in comparison.
So in recent years, various groups have looked at creating images with ultra low fields of just a few tens of microteslas.
Normally, the huge magnetic field is necessary to make protons in water molecules inside the body line up. Zapping these protons with radio waves knocks them out of kilter and as they realign themselves, the protons emit radio waves that can be used to construct an image.
Ultra low field MRI gets around the need for huge magnets by using a new generation of superconducting quantum interference devices or SQUIDS to pick up the signals used to reconstruct an image.
Now Vadim Zotev and buddies at the Los Alamos National Laboratories in New Mexico have another trick up their sleeve. One of the many astounding things that magnetic resonance imaging can do is track the changing presence of carbon-13 in the body. That’s important because it shows the body’s metabolism in action so researchers can see how diseases such as cancer and diabetes change the way it functions.
Here’s the trick. Instead of using a magnetic field to align the carbon-13 nuclei inside the body, they use a technique called dynamic nuclear polarisation to align the carbon nuclei before they are injected into the body.
That should make ultra low field MRI images of metabolism in action even easier to make and paves the way for real time videos of the metabolism at work using this kind of technique
Ref: arxiv.org/abs/0911.1137: Toward Microtesla MRI of Hyperpolarized Carbon-13 for Real-Time Metabolic Imaging
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