%0 Journal Article %J Physical Review Letters %D 2011 %T Near-Zero-Field Nuclear Magnetic Resonance %A Ledbetter, M. P. %A Theis, T. %A Blanchard, J. W. %A Ring, H. %A Ganssle, P. %A Appelt, S. %A Blumich, B. %A Pines, A. %A Budker, D. %K mri %X

We investigate nuclear magnetic resonance (NMR) in near zero field, where the Zeeman interaction can be treated as a perturbation to the electron mediated scalar interaction (J coupling). This is in stark contrast to the high-field case, where heteronuclear J couplings are normally treated as a small perturbation. We show that the presence of very small magnetic fields results in splitting of the zero-field NMR lines, imparting considerable additional information to the pure zero-field spectra. Experimental results are in good agreement with first-order perturbation theory and with full numerical simulation when perturbation theory breaks down. We present simple rules for understanding the splitting patterns in near-zero-field NMR, which can be applied to molecules with nontrivial spectra.

%B Physical Review Letters %V 107 %8 Sep 1 %@ 0031-9007 %G English %U ://WOS:000294406600017 %N 10 %M WOS:000294406600017 %! Near-Zero-Field Nuclear Magnetic Resonance %R Doi 10.1103/Physrevlett.107.107601 %0 Journal Article %J Journal of Magnetic Resonance Imaging %D 2008 %T Flow in Porous Metallic Materials: A Magnetic Resonance Imaging Study %A Xu, S. J. %A Harel, E. %A Michalak, D. J. %A Crawford, C. W. %A Budker, D. %A Pines, A. %K mri %X

Purpose: To visualize flow dynamics of analytes inside porous metallic materials with laser-detected magnetic resonance imaging (MRI).Materials and Methods: We examine the flow of nuclear-polarized water in a porous stainless steel cylinder. Laser-detected MRI utilizes a sensitive optical atomic magnetometer as the detector. Imaging was performed in a remote-detection mode: the encoding was conducted in the Earth's magnetic field, and detection is conducted downstream of the encoding location. Conventional MRI (7T) was also performed for comparison.Results: Laser-detected MRI clearly showed MR images of water flowing through the sample, whereas conventional MRI provided no image.Conclusion: We demonstrated the viability of laser-detected MRI at low-field for studying porous metallic materials, extending MRI techniques to a new group of systems that is normally not accessible to conventional MRI.

%B Journal of Magnetic Resonance Imaging %V 28 %P 1299-1302 %8 Nov %@ 1053-1807 %G English %U ://WOS:000260566100033 %N 5 %M WOS:000260566100033 %! Flow in Porous Metallic Materials: A Magnetic Resonance Imaging Study %R Doi 10.1002/Jmri.21532 %0 Journal Article %J Applied Physics Letters %D 2008 %T Fluid-flow characterization with nuclear spins without magnetic resonance %A Crawford, C. W. %A Xu, S. J. %A Siegel, E. J. %A Budker, D. %A Pines, A. %K mri %X

A technique for noninvasive monitoring of flow inside metallic enclosures using laser-based atomic magnetometry is introduced. The analyte is labeled via nuclear magnetization by magnets, thereby combining the polarization and encoding steps. No radiofrequency or audiofrequency pulses are involved. We demonstrate detection of flow inside an aluminum pipe with an inner diameter of 4.9 mm that has a constriction with a diameter of 1.6 mm and a length of 6.4 mm. The results agree with a model of spin density and relaxation indicating that our technique allows for fast, quantitative, and noninvasive diagnostics of flow with potential applications discussed below. (c) 2008 American Institute of Physics.

%B Applied Physics Letters %V 93 %8 Sep 1 %@ 0003-6951 %G English %U ://WOS:000258975800042 %N 9 %M WOS:000258975800042 %! Fluid-flow characterization with nuclear spins without magnetic resonance %R Doi 10.1063/1.2977773 %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2008 %T Remote detection of nuclear magnetic resonance with an anisotropic magnetoresistive sensor %A Verpillat, F. %A Ledbetter, M. P. %A Xu, S. %A Michalak, D. J. %A Hilty, C. %A Bouchard, L. S. %A Antonijevic, S. %A Budker, D. %A Pines, A. %K mri %X

We report the detection of nuclear magnetic resonance (NMR) using an anisotropic magnetoresistive (AMR) sensor. A "remote-detection" arrangement was used in which protons in flowing water were prepolarized in the field of a superconducting NMR magnet, adiabatically inverted, and subsequently detected with an AMR sensor situated downstream from the magnet and the adiabatic inverter. AMR sensing is well suited for NMR detection in microfluidic "lab-on-a-chip" applications because the sensors are small, typically on the order of 10 mu m. An estimate of the sensitivity for an optimized system indicates that approximate to 6 x 10(13) protons in a volume of 1,000 mu m(3), prepolarized in a 10-kG magnetic field, can be detected with a signal-to-noise ratio of 3 in a 1-Hz bandwidth. This level of sensitivity is competitive with that demonstrated by microcoils in superconducting magnets and with the projected sensitivity of microfabricated atomic magnetometers.

%B Proceedings of the National Academy of Sciences of the United States of America %V 105 %P 2271-2273 %8 Feb 19 %@ 0027-8424 %G English %U ://WOS:000253469900006 %N 7 %M WOS:000253469900006 %! Remote detection of nuclear magnetic resonance with an anisotropic magnetoresistive sensor %R Doi 10.1073/Pnas.0712129105 %0 Journal Article %J Angewandte Chemie-International Edition %D 2008 %T Temperature-controlled molecular depolarization gates in nuclear magnetic resonance %A Schroder, L. %A Chavez, L. %A Meldrum, T. %A Smith, M. %A Lowery, T. J. %A Wemmer, D. E. %A Pines, A. %K mri %B Angewandte Chemie-International Edition %V 47 %P 4316-4320 %@ 1433-7851 %G English %U ://WOS:000256364400007 %N 23 %M WOS:000256364400007 %! Temperature-controlled molecular depolarization gates in nuclear magnetic resonance %R Doi 10.1002/Anie.200800382 %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2008 %T Zero-field remote detection of NMR with a microfabricated atomic magnetometer %A Ledbetter, M. P. %A Savukov, I. M. %A Budker, D. %A Shah, V. %A Knappe, S. %A Kitching, J. %A Michalak, D. J. %A Xu, S. %A Pines, A. %K mri %X

We demonstrate remote detection of nuclear magnetic resonance (NMR) with a microchip sensor consisting of a microfluidic channel and a microfabricated vapor cell (the heart of an atomic magnetometer). Detection occurs at zero magnetic field, which allows operation of the magnetometer in the spin-exchange relaxation-free (SERF) regime and increases the proximity of sensor and sample by eliminating the need for a solenoid to create a leading field. We achieve pulsed NMR linewidths of 26 Hz, limited, we believe, by the residence time and flow dispersion in the encoding region. In a fully optimized system, we estimate that for 1 s of integration, 7 x 10(13) protons in a volume of 1 mm(3), prepolarized in a 10-kG field, can be detected with a signal-to-noise ratio of approximate to 3. This level of sensitivity is competitive with that demonstrated by microcoils in 100-kG magnetic fields, without requiring superconducting magnets.

%B Proceedings of the National Academy of Sciences of the United States of America %V 105 %P 2286-2290 %8 Feb 19 %@ 0027-8424 %G English %U ://WOS:000253469900009 %N 7 %M WOS:000253469900009 %! Zero-field remote detection of NMR with a microfabricated atomic magnetometer %R Doi 10.1073/Pnas.0711505105 %0 Journal Article %J Journal of Physical Chemistry B %D 2007 %T Quantifying the diffusion of a fluid through membranes by double phase encoded remote detection magnetic resonance imaging %A Telkki, V. V. %A Hilty, C. %A Garcia, S. %A Harel, E. %A Pines, A. %K mri %X

We demonstrate that a position correlation magnetic resonance imaging (MRI) experiment based on two phase encoding steps separated by a delay can be used for quantifying diffusion across a membrane. This method is noninvasive, and no tracer substance or concentration gradient across the membrane is required. Because, in typical membranes, the T-1 relaxation time of the fluid spins is usually much longer than the T-2 time, we developed and implemented a new position correlation experiment based on a stimulated spin-echo, in which the relaxation attenuation of the signal is dominated by T-1 instead of T-2. This enables using relatively long delays needed in the diffusion measurements. The sensitivity of the double encoded experiment detected in a conventional way is still low because of the low filling factor of the fluid inside the NMR coil around the sample. We circumvent this problem by using the remote detection technique, which significantly increases the sensitivity, making it possible to do the measurements with gaseous fluids that have a low spin-density compared to liquids. We derive a model that enables us to extract a diffusion constant characterizing the diffusion rate through the membrane from the obtained correlation images. The double phase encoded MRI method is advantageous in any kind of diffusion studies, because the propagator of fluid molecules can directly be seen from the correlation image.

%B Journal of Physical Chemistry B %V 111 %P 13929-13936 %8 Dec 20 %@ 1520-6106 %G English %U ://WOS:000251615400011 %N 50 %M WOS:000251615400011 %! Quantifying the diffusion of a fluid through membranes by double phase encoded remote detection magnetic resonance imaging %R Doi 10.1021/Jp076760e %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2005 %T Microfluidic gas-flow profiling using remote-detection NMR %A Hilty, C. %A McDonnell, E. E. %A Granwehr, J. %A Pierce, K. L. %A Han, S. I. %A Pines, A. %K mri %X

We have used nuclear magnetic resonance (NMR) to obtain spatially and temporally resolved profiles of gas flow in microfluidic devices. Remote detection of the NMR signal both overcomes the sensitivity limitation of NMR and enables time-of-flight measurement in addition to spatially resolved imaging. Thus, detailed insight is gained into the effects of flow, diffusion, and mixing in specific geometries. The ability for noninvasive measurement of microfluidic flow, without the introduction of foreign tracer particles, is unique to this approach and is important for the design and operation of microfluidic devices. Although here we demonstrate an application to gas flow, extension to liquids, which have higher density, is implicit.

%B Proceedings of the National Academy of Sciences of the United States of America %V 102 %P 14960-14963 %8 Oct 18 %@ 0027-8424 %G English %U ://WOS:000232811800006 %N 42 %M WOS:000232811800006 %! Microfluidic gas-flow profiling using remote-detection NMR %R Doi 10.1073/Pnas.0507566102 %0 Journal Article %J Physical Review Letters %D 2005 %T Time-of-flight flow imaging using NMR remote detection %A Granwehr, J. %A Harel, E. %A Han, S. %A Garcia, S. %A Pines, A. %A Sen, P. N. %A Song, Y. Q. %K mri %X

A time-of-flight imaging technique is introduced to visualize fluid flow and dispersion through porous media using NMR. As the fluid flows through a sample, the nuclear spin magnetization is modulated by rf pulses and magnetic field gradients to encode the spatial coordinates of the fluid. When the fluid leaves the sample, its magnetization is recorded by a second rf coil. This scheme not only facilitates a time-dependent imaging of fluid flow, it also allows a separate optimization of encoding and detection subsystems to enhance overall sensitivity. The technique is demonstrated by imaging gas flow through a porous rock.

%B Physical Review Letters %V 95 %8 Aug 12 %@ 0031-9007 %G English %U ://WOS:000231247300028 %N 7 %M WOS:000231247300028 %! Time-of-flight flow imaging using NMR remote detection %R Doi 10.1103/Physrevlett.95.075503 %0 Journal Article %J Physical Review Letters %D 2004 %T Hyperpolarized xenon nuclear spins detected by optical atomic magnetometry %A Yashchuk, V. V. %A Granwehr, J. %A Kimball, D. F. %A Rochester, S. M. %A Trabesinger, A. H. %A Urban, J. T. %A Budker, D. %A Pines, A. %K mri %X

We report the use of an atomic magnetometer based on nonlinear magneto-optical rotation with frequency-modulated light to detect nuclear magnetization of xenon gas. The magnetization of a spin-exchange-polarized xenon sample (1.7 cm(3) at a pressure of 5 bars, natural isotopic abundance, polarization 1%), prepared remotely to the detection apparatus, is measured with an atomic sensor. An average magnetic field of similar to10 nG induced by the xenon sample on the 10 cm diameter atomic sensor is detected with signal-to-noise ratio similar to10, limited by residual noise in the magnetic environment. The possibility of using modern atomic magnetometers as detectors of nuclear magnetic resonance and in magnetic resonance imaging is discussed. Atomic magnetometers appear to be ideally suited for emerging low-field and remote-detection magnetic resonance applications.

%B Physical Review Letters %V 93 %8 Oct 15 %@ 0031-9007 %G English %U ://WOS:000224533300012 %N 16 %M WOS:000224533300012 %! Hyperpolarized xenon nuclear spins detected by optical atomic magnetometry %R Doi 10.1103/Physrevlett.93.160801 %0 Journal Article %J Journal of Low Temperature Physics %D 2004 %T SQUID-detected magnetic resonance imaging in microtesla magnetic fields %A McDermott, R. %A Kelso, N. %A Lee, S. K. %A Mossle, M. %A Mück, M. %A Myers, W. %A ten Haken, B. %A Seton, H. C. %A Trabesinger, A. H. %A Pines, A. %A Clarke, J. %K mri %X

We describe studies of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) of liquid samples at room temperature in microtesla magnetic fields. The nuclear spins are prepolarized in a strong transient field. The magnetic signals generated by the precessing spins, which range in frequency from tens of Hz to several kHz, are detected by a low-transition temperature dc SQUID (Superconducting QUantum Interference Device) coupled to an untuned, superconducting flux transformer configured as an axial gradiometer. The combination of prepolarization and frequency-independent detector sensitivity results in a high signal-to-noise ratio and high spectral resolution (similar to 1 Hz) even in grossly inhomogeneous magnetic fields. In the NMR experiments, the high spectral resolution enables us to detect the 10-Hz splitting of the spectrum of protons due to their scalar coupling to a P-31 nucleus. Furthermore, the broadband detection scheme combined with a non-resonant field-reversal spin echo allows the simultaneous observation of signals from protons and P-31 nuclei, even though their NMR resonance frequencies differ by a factor of 2.5. We extend our methodology to MRI in microtesla fields, where the high spectral resolution translates into high spatial resolution. We demonstrate two-dimensional images of a mineral oil phantom and slices of peppers, with a spatial resolution of about 1 mm. We also image an intact pepper using slice selection, again with 1-mm, resolution. A further experiments we demonstrate T-1-contrast imaging of a water phantom, some parts of which were doped with a paramagnetic salt to reduce the longitudinal relaxation time T-1. Possible applications of this MRI technique include screening for tumors and integration with existing multichannel SQUID systems for brain imaging.

%B Journal of Low Temperature Physics %V 135 %P 793-821 %8 Jun %@ 0022-2291 %G English %U ://WOS:000221710600023 %N 5-6 %M WOS:000221710600023 %! SQUID-detected magnetic resonance imaging in microtesla magnetic fields %R Doi 10.1023/B:Jolt.0000029519.09286.C5 %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2001 %T Functionalized xenon as a biosensor %A Spence, M. M. %A Rubin, S. M. %A Dimitrov, I. E. %A Ruiz, E. J. %A Wemmer, D. E. %A Pines, A. %A Yao, S. Q. %A Tian, F. %A Schultz, P. G. %K mri %X

The detection of biological molecules and their interactions is a significant component of modern biomedical research. In current biosensor technologies, simultaneous detection is limited to a small number of analytes by the spectral overlap of their signals. We have developed an NMR-based xenon biosensor that capitalizes on the enhanced signal-to-noise, spectral simplicity, and chemical-shift sensitivity of laser-polarized xenon to detect specific biomolecules at the level of tens of nanomoles. We present results using xenon "functionalized" by a biotin-modified supramolecular cage to detect biotin-avidin binding. This biosensor methodology can be extended to a multiplexing assay for multiple analytes.

%B Proceedings of the National Academy of Sciences of the United States of America %V 98 %P 10654-10657 %8 Sep 11 %@ 0027-8424 %G English %U ://WOS:000170966800030 %N 19 %M WOS:000170966800030 %! Functionalized xenon as a biosensor %R Doi 10.1073/Pnas.191368398 %0 Journal Article %J Applied Physics Letters %D 1999 %T Low-field magnetic resonance imaging with a high-T-c dc superconducting quantum interference device %A Schlenga, K. %A McDermott, R. %A Clarke, J. %A de Souza, R. E. %A Wong-Foy, A. %A Pines, A. %K mri %X

A spectrometer incorporating a high transition temperature dc superconducting quantum interference device (SQUID) is used to obtain nuclear magnetic resonance signals from protons in mineral oil at room temperature in fields up to 3 mT. The spatial separation between the SQUID magnetometer at 77 K and the sample at room temperature is less than 1 mm. At 2 mT, the signal is easily resolved in a single scan. Two-dimensional images of samples consisting of pieces of lucite or glass immersed in mineral oil are obtained at 2 mT. (C) 1999 American Institute of Physics. [S0003-6951(99)03649-9].

%B Applied Physics Letters %V 75 %P 3695-3697 %8 Dec 6 %@ 0003-6951 %G English %U ://WOS:000083912800035 %N 23 %M WOS:000083912800035 %! Low-field magnetic resonance imaging with a high-T-c dc superconducting quantum interference device %R Doi 10.1063/1.125432 %0 Journal Article %J Applied Physics Letters %D 1998 %T Low field magnetic resonance images of polarized noble gases obtained with a dc superconducting quantum interference device %A Augustine, M. P. %A Wong-Foy, A. %A Yarger, J. L. %A Tomaselli, M. %A Pines, A. %A TonThat, D. M. %A Clarke, J. %K mri %X

Using a low transition temperature superconducting quantum interference device as a detector, we have obtained magnetic resonance images of laser-polarized He-3 gas and solid Xe-129 at 4.2 K in magnetic fields as low as 0.54 mT (He-3) and 1 mT (Xe-129), corresponding to Larmor frequencies of 17.6 and 11.8 kHz, respectively. The experimental resolution of the images is similar to 500 mu m for He-3 ill the gas phase and similar to 950 mu m for Xe-129 in the solid state. (C) 1998 American Institute of Physics.

%B Applied Physics Letters %V 72 %P 1908-1910 %8 Apr 13 %@ 0003-6951 %G English %U ://WOS:000073054300038 %N 15 %M WOS:000073054300038 %! Low field magnetic resonance images of polarized noble gases obtained with a dc superconducting quantum interference device %R Doi 10.1063/1.121223