Amplification of Xenon NMR and MRI by remote detection

A novel technique is proposed in which a nuclear magneticresonance (NMR) spectrum or magnetic resonance image (MRI) is encoded andstored as spin polarization and is then moved to a different physicallocation to be detected. Remote detection allows the separateoptimization of the encoding and detection steps, permitting theindependent choice of experimental conditions, and excitation anddetection methodologies. In the first experimental demonstration of thistechnique, we show that NMR signal can be amplified by taking diluted129Xe from a porous sample placed inside a large encoding coil, andconcentrating it into a smaller detection coil. In general, the study ofNMR active molecules at low concentration that have low physical fillingfactor is facilitated by remote detection. In the second experiment, MRIinformation encoded in a very low field magnet (4-7mT) is transferred toa high field magnet (4.2 T) in order to be detected under optimizedconditions. Furthermore, remote detection allows the utilization ofultra-sensitive optical or superconducting detection techniques, whichbroadens the horizon of NMR experimentation

Sensitivity Quantification of Remote Detection NMR and MRI

A sensitivity analysis of the remote detection NMR technique is presented. With remote detection, information about a sample is encoded onto a mobile sensor fluid, which facilitates a spatial separation of encoding and detection of spin magnetization. This approach can be interpreted as a two-dimensional NMR experiment, therefore the same general formalism can be used for a sensitivity analysis. Even though remote detection is a point-by-point experiment, the sensitivity does not scale unfavorably with the number of detected points compared to transient detection. It is proportional to the relative sensitivity between the remote detector and the circuit that is used for encoding. The influence of the different signal decay times is analyzed, and the distinction between spectroscopy and imaging experiments is made

Sensitivity Quantification of Remote Detection NMR and MRI

A sensitivity analysis of the remote detection NMR technique is presented. With remote detection, information about a sample is encoded onto a mobile sensor fluid, which facilitates a spatial separation of encoding and detection of spin magnetization. This approach can be interpreted as a two-dimensional NMR experiment, therefore the same general formalism can be used for a sensitivity analysis. Even though remote detection is a point-by-point experiment, the sensitivity does not scale unfavorably with the number of detected points compared to transient detection. It is proportional to the relative sensitivity between the remote detector and the circuit that is used for encoding. The influence of the different signal decay times is analyzed, and the distinction between spectroscopy and imaging experiments is made

Multiphase imaging of gas flow in a nanoporous material using remote detection NMR

Pore structure and connectivity determine how microstructured materials perform in applications such as catalysis, fluid storage and transport, filtering, or as reactors. We report a model study on silica aerogel using a recently introduced time-of-flight (TOF) magnetic resonance imaging technique to characterize the flow field and elucidate the effects of heterogeneities in the pore structure on gas flow and dispersion with Xe-129 as the gas-phase sensor. The observed chemical shift allows the separate visualization of unrestricted xenon and xenon confined in the pores of the aerogel. The asymmetrical nature of the dispersion pattern alludes to the existence of a stationary and a flow regime in the aerogel. An exchange time constant is determined to characterize the gas transfer between them. As a general methodology, this technique provides new insights into the dynamics of flow in porous media where multiple phases or chemical species may be present

Laser-polarized {sup 129}Xe NMR and MRI at ultra-low magnetic fields

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