Enhanced 13C NMR by Thermal Mixing with Hyperpolarized 129XE

Abstract

A method of preparing a hydrogen-containing 13 C compound test sample exhibiting an enhanced 13 C nuclear magnetic resonance (NMR) signal when exposed to a 13 C NMR pulse sequence is disclosed. In the disclosed method, the hydrogen-containing 13 C compound is mixed with hyperpolarized 129 Xe in the gaseous state, and the mixture is subsequently frozen within a magnetic field. The magnetic field strength is then reduced sufficiently so that spin polarization is transferred from the hyperpolarized 129 Xe to the compound. The magnetic field strength is then increased, and the mixture is thawed to obtain the test sample.

We claim: 
     
         1 . A method of preparing a hydrogen-containing carbon-13 ( 13 C) compound test sample exhibiting an enhanced  13 C nuclear magnetic resonance (NMR) signal when exposed to a  13 C NMR pulse sequence comprising the steps of:
 (a) mixing a compound comprising hydrogen and  13 C and hyperpolarized Xenon-129 ( 129 Xe);   (b) freezing the mixture within a magnetic field;   (c) reducing the magnetic field strength sufficiently so that spin polarization is transferred from the hyperpolarized  129 Xe to the compound;   (d) increasing the magnetic field strength; and   (e) thawing the mixture to obtain a test sample exhibiting enhanced  13 C polarization when undergoing NMR analysis.   
     
     
         2 . The method of  claim 1 , wherein both the compound and hyperpolarized  129 Xe are mixed in the gas phase. 
     
     
         3 . The method of  claim 2 , wherein the compound is in the liquid phase at room temperature and pressure. 
     
     
         4 . The method of  claim 3 , wherein the compound is in the form of a vapor of the liquid phase. 
     
     
         5 . The method of  claim 1 , wherein the compound has low solubility in liquid xenon. 
     
     
         6 . The method of  claim 1 , wherein the  129 Xe is hyperpolarized by optical pumping. 
     
     
         7 . The method of  claim 1 , wherein the compound is mixed with hyperpolarized  129 Xe on a chromatographic column. 
     
     
         8 . The method of  claim 1 , wherein the mixture is frozen as a thin film. 
     
     
         9 . The method of  claim 1 , wherein the mixture is thawed by applying a radio frequency pulse to the mixture. 
     
     
         10 . The method of  claim 1 , wherein the magnetic field within which the mixture is frozen is a magnet's fringe field. 
     
     
         11 . The method of  claim 1 , wherein the step of reducing the magnetic field strength sufficiently so that spin polarization is transferred is performed by increasing the field strength of a separate electromagnet that compensates the existing magnetic field, and the step of increasing the magnetic field strength is performed by decreasing the field strength of said electromagnet. 
     
     
         12 . The method of  claim 1 , wherein the compound is a compound of biological relevance. 
     
     
         13 . The method of  claim 12 , wherein the compound of biological relevance is chosen from the group consisting of acetic acid, acetate salts, pyruvate salts, and ethanol. 
     
     
         14 . The method of  claim 13 , wherein the compound is 1- 13 C-AcH (acetic acid), Na-1- 13 C-acetate, or 2- 13 C-EtOH (ethanol). 
     
     
         15 . The method of  claim 14 , wherein the compound is 1- 13 C-AcH. 
     
     
         16 . A method for mixing a test sample having one or more hydrogen-containing  13 C compound(s) and subsequently analyzing the test sample comprising the steps of:
 (a) vaporizing a composition containing one or more compound(s) comprising hydrogen and  13 C and mixing the vapor with hyperpolarized  129 Xe;   (b) freezing the resulting mixture within a magnetic field;   (c) reducing the magnetic field strength sufficiently so that spin polarization is transferred from the hyperpolarized  129 Xe to the compound(s) within the frozen mixture;   (d) increasing the magnetic field strength;   (e) thawing the mixture to obtain a test sample;   applying a  13 C nuclear magnetic resonance (NMR) pulse sequence to the test sample; and   (g) detecting the  13 C active nuclei in the test sample by NMR spectroscopy, magnetic resonance imaging (MM), or both.   
     
     
         17 . The method of  claim 16 , wherein the one or more compound(s) comprising hydrogen and  13 C are compounds of biological relevance and that have low solubility in liquid xenon. 
     
     
         18 . The method of  claim 16 , wherein the step of thawing the mixture to obtain the test sample further comprises the step of exposing the mixture to other substances to obtain the test sample. 
     
     
         19 . A test composition comprising a hydrogen-containing carbon-13 ( 13 C) compound exhibiting an enhanced  13 C nuclear magnetic resonance (NMR) signal when exposed to a  13 C NMR pulse sequence, said test composition comprising the test sample resulting from practicing the method according to  claim 1 . 
     
     
         20 . The test composition of  claim 19 , wherein the hydrogen-containing  13 C compound is a compound of biological relevance that has low solubility in liquid xenon.