Hyperpolarized atoms for MRI imaging

[novawildcat]

Pardon if this is not the right forum, but does anyone here stay on top of this field? What kind of advancements have been made? Have hyperpolarized molecules reached the clinic yet for molecular imaging studies? I am interested in using 19F MRI to see where my one of my molecules that I am studying goes, however 19F has terrible signal to noise ratio, especially since fluorine is not found commonly in organisms and due also to the fact that most medicinal compounds are delivered to reach concentrations in the millimolar to nanomolar range. Thus, I was wondering if we could use a hyperpolarized F analog to do imaging studies. Do hyperpolarized compounds have half lives on the order of seconds to minutes (that would make them worthless for the studies I would need)?

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[colbgw02]

Ummmm.............yes?

 

[Neuronix]

Only certain molecules can be hyperpolarized feasibly. One fundamental barrier is the need for a long T1 (you hyperpolarize, and all that nuclear spin separation starts decaying at that rate...). 19F isn't one of those long T1 molecules. 19F is nice because it has a high gyromagnetic ratio and a high natural abundance (100%), but the problem is that there's none of it in the body naturally. So you have to deliver it in a compound to get a concentration on the order of 1mM to image with it, which typically is not a feasible concentration. But you're not going to hyperpolarize it. There's dynamic nuclear polarization, but that involves transfer of magnetization from higher gyromagnetic ratios to lower, and there's nothing you can couple to that flourine that's going to have a higher gyromagnetic ratio.

I'm not sure what half-life you're asking about. MRI is almost exclusively done with stable isotopes. T1 is just an intrinsic property of the nucleus depending on interactions in the nucleus and in the molecule. The typical hyperpolarization suspect is 13C in certain compounds (often pyruvate), though the process for hyperpolarization typically includes small concentrations of toxic byproducts so it has not been approved yet for human use. Also you have Xenon-129 and Helium-3 for lung imaging.

 

[deleted103644]

19F is hyperpolarizable (only requires a low field to do it), so it's not that impossible. As Neuronix said though, the hyperpolarized state will disappear quickly (pretty sure the OP was referring to T1 when he said "half-life") and the technique is still very experimental. I'm not sure what concentration you'd need to get with a hyperpolarized compound, but I'd wager it would still be higher than you'd like.

http://www.ncbi.nlm.nih.gov/pubmed/20614054

 

[Neuronix]

Good luck getting THAT to work in humans. Hence the hyperpolarized feasibly part.

 

[novawildcat]

Well, thanks for the excellent info guys (or gals?)!