APPLICATIONS OF TECHNOLOGY:
- In vivo diagnostic and molecular imaging
- Chemical assays
- More sensitive NMR spectra and MRI
- Enables time-of-flight imaging
- Potential for molecular imaging
Alexander Pines and colleagues at Berkeley Lab have developed a technology to increase both the sensitivity and number of possible applications of NMR/MRI with hyperpolarized Xe. The invention works by dissolving hyperpolarized Xe gas into a liquid; encoding the nuclear spins with spatial, temporal, and chemical shift information; and extracting the dissolved Xe back into a gas mixture where the (unaltered) information is decoded with high sensitivity. The technique is called Hyper-SAGE, for hyperpolarized xenon Signal Amplification by Gas Extraction.
With this technology, the signal intensity is particularly high because Xe in the gas phase: (a) is about 10 times more concentrated than in the dissolved phase; (b) can be compressed or liquefied to increase its density by several orders of magnitude; and (c) can be passed to a remote decoding microcoil with an optimized filling factor. In addition, the long longitudinal (T1) and transverse (T2) relaxation times of Xe allow for the phase transition, compression, and transfer to a remote microcoil.
The scientists tested Hyper-SAGE by using artificial membranes for the phase transitions. The signal-to-noise ratio was 3 times higher when the NMR was performed on extracted gas-phase Xe rather than aqueous Xe. These results were obtained without gas compression or optimization of the filling factor, which, when applied, will further increase the ratio by several orders of magnitude. Time-of-flight imaging was also successfully performed on a cylindrical phantom with the aqueous Xe flowing through it, as in a blood vessel.
In addition to NMR, noninvasive, high-resolution diagnostic MRI could be performed with Hyper-SAGE. Hyperpolarized Xe (known to be nontoxic) would be inhaled into the lung, which would function like the artificial membrane in the laboratory. Thus, the inhaled Xe would dissolve into the blood, circulate to a remote anatomical site where information would be encoded, and return to the lung to be exhaled and recaptured for imaging of the remote anatomical site. This technique may also allow for molecular imaging of specific cell markers.
Hyperpolarized Xe has been used for NMR and diagnostic imaging of the airspace in the lungs. However, these techniques have had limited sensitivity with low signal-to-noise ratios when the xenon is dissolved in tissues, such as in the lung or brain. The Berkeley Lab technique greatly amplifies the NMR and MRI signals and opens the door for imaging regions of the body beyond the airspace of the lungs.
DEVELOPMENT STAGE: Proven principle.
STATUS: Patent pending. Available for licensing or collaborative research.
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REFERENCE NUMBER: IB-2747