@article {331, title = {Microtesla MRI with a superconducting quantum interference device}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {101}, year = {2004}, note = {P Natl Acad Sci USA823ZCTimes Cited:76Cited References Count:29}, month = {May 25}, pages = {7857-7861}, abstract = {

MRI scanners enable fast, noninvasive, and high-resolution imaging of organs and soft tissue. The images are reconstructed from NMR signals generated by nuclear spins that precess in a static magnetic field B(0) in the presence of magnetic field gradients. Most clinical MRI scanners operate at a magnetic field B(0) = 1.5 T, corresponding to a proton resonance frequency of 64 MHz. Because these systems rely on large superconducting magnets, they are costly and demanding of infrastructure. On the other hand, low-field imagers have the potential to be less expensive, less confining, and more mobile. The major obstacle is the intrinsically low sensitivity of the low-field NMR experiment. Here, we show that prepolarization of the nuclear spins and detection with a superconducting quantum interference device (SQUID) yield a signal that is independent of B(0), allowing acquisition of high-resolution MRIs in microtesla fields. Reduction of the strength of the measurement field eliminates inhomogeneous broadening of the NMR lines, resulting in enhanced signal-to-noise ratio and spatial resolution for a fixed strength of the magnetic field gradients used to encode the image. We present high-resolution images of phantoms and other samples and T(1)-weighted contrast images acquired in highly inhomogeneous magnetic fields of 132 muT; here, T, is the spin-lattice relaxation time. These techniques could readily be adapted to existing multichannel SQUID systems used for magnetic source imaging of brain signals. Further potential applications include low-cost systems for tumor screening and imaging peripheral regions of the body.

}, keywords = {system}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.0402382101}, url = {://WOS:000221652000005}, author = {McDermott, R. and Lee, S. K. and ten Haken, B. and Trabesinger, A. H. and Pines, A. and Clarke, J.} } @article {322, title = {SQUID-detected liquid state NMR in microtesla fields}, journal = {Journal of Physical Chemistry A}, volume = {108}, year = {2004}, note = {J Phys Chem A772FTTimes Cited:32Cited References Count:36}, month = {Feb 12}, pages = {957-963}, abstract = {

Nuclear magnetic resonance (NMR) experiments performed in magnetic fields on the order of microtesla yield line widths comparable to the lifetime limit even in grossly inhomogeneous magnets. The potential loss in sensitivity is overcome by combining prepolarization in fields on the order of millitesla and signal detection with a Superconducting Quantum Interference Device (SQUID). The enhanced spectral resolution attainable in microtesla fields enables NMR studies of pure liquids and solutions without the need for strong magnets. We have investigated a variety of heteronuclear systems in both the weak and strong J-coupling regimes. Six different nuclear species have been detected with the same experimental apparatus. NMR signals of thermally polarized protons were obtained in fields as low as 554 nT.

}, keywords = {water}, isbn = {1089-5639}, doi = {Doi 10.1021/Jp035181g}, url = {://WOS:000188831500005}, author = {Trabesinger, A. H. and McDermott, R. and Lee, S. K. and M{\"u}ck, M. and Clarke, J. and Pines, A.} } @article {332, title = {SQUID-detected magnetic resonance imaging in microtesla magnetic fields}, journal = {Journal of Low Temperature Physics}, volume = {135}, year = {2004}, note = {J Low Temp Phys824TWTimes Cited:37Cited References Count:34}, month = {Jun}, pages = {793-821}, abstract = {

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.

}, keywords = {mri}, isbn = {0022-2291}, doi = {Doi 10.1023/B:Jolt.0000029519.09286.C5}, url = {://WOS:000221710600023}, author = {McDermott, R. and Kelso, N. and Lee, S. K. and Mossle, M. and M{\"u}ck, M. and Myers, W. and ten Haken, B. and Seton, H. C. and Trabesinger, A. H. and Pines, A. and Clarke, J.} } @article {346, title = {Laser-polarized Xe-129 NMR and MRI at ultralow magnetic fields}, journal = {Journal of Magnetic Resonance}, volume = {157}, year = {2002}, note = {J Magn Reson600EJTimes Cited:23Cited References Count:25}, month = {Aug}, pages = {235-241}, abstract = {

Laser-polarized Xe-129 and a high-T-c superconducting quantum interference device (SQUID) are used to obtain magnetic resonance images in porous materials at a magnetic field of 2.3 mT, corresponding to a Larmor frequency of 27 kHz. Image resolution of 1 mm is obtained with gradients of only 1 mT/m. The resolution of xenon chemical shifts in different physicochemical environments at ultralow fields is also demonstrated. Details of the circulating flow optical pumping apparatus and the SQUID spectrometer are presented. (C) 2002 Elsevier Science (USA).

}, keywords = {atoms}, isbn = {1090-7807}, doi = {Doi 10.1006/Jmre.2002.2592}, url = {://WOS:000178377400009}, author = {Wong-Foy, A. and Saxena, S. and Moule, A. J. and Bitter, H. M. L. and Seeley, J. A. and McDermott, R. and Clarke, J. and Pines, A.} } @article {357, title = {Liquid-state NMR and scalar couplings in microtesla magnetic fields}, journal = {Science}, volume = {295}, year = {2002}, note = {Science534ADTimes Cited:140Cited References Count:20}, month = {Mar 22}, pages = {2247-2249}, abstract = {

We obtained nuclear magnetic resonance (NMR) spectra of liquids in fields of a few microtesla, using prepolarization in fields of a few millitesta and detection with a dc superconducting quantum interference device (SQUID). Because the sensitivity of the SQUID is frequency independent, we enhanced both signal-to-noise ratio and spectral resolution by detecting the NMR signal in extremely tow magnetic fields, where the NMR tines become very narrow even for grossly inhomogeneous measurement fields. In the absence of chemical shifts, proton-phosphorous scalar (J) couplings have been detected, indicating the presence of specific covalent bonds. This observation opens the possibility for \"pure J spectroscopy\" as a diagnostic tool, for the detection of molecules in low magnetic fields.

}, keywords = {resonance}, isbn = {0036-8075}, doi = {Doi 10.1126/Science.1069280}, url = {://WOS:000174561700039}, author = {McDermott, R. and Trabesinger, A. H. and M{\"u}ck, M. and Hahn, E. L. and Pines, A. and Clarke, J.} } @article {365, title = {Resolution of Xe-129 chemical shifts at ultralow magnetic field}, journal = {Journal of the American Chemical Society}, volume = {123}, year = {2001}, note = {J Am Chem Soc463TWTimes Cited:9Cited References Count:39}, month = {Aug 22}, pages = {8133-8134}, keywords = {adsorption}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja011064s}, url = {://WOS:000170494200027}, author = {Saxena, S. and Wong-Foy, A. and Moule, A. J. and Seeley, J. A. and McDermott, R. and Clarke, J. and Pines, A.} } @article {383, title = {Low-field magnetic resonance imaging with a high-T-c dc superconducting quantum interference device}, journal = {Applied Physics Letters}, volume = {75}, year = {1999}, note = {Appl Phys Lett259URTimes Cited:49Cited References Count:19}, month = {Dec 6}, pages = {3695-3697}, abstract = {

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].

}, keywords = {mri}, isbn = {0003-6951}, doi = {Doi 10.1063/1.125432}, url = {://WOS:000083912800035}, author = {Schlenga, K. and McDermott, R. and Clarke, J. and de Souza, R. E. and Wong-Foy, A. and Pines, A.} } @article {387, title = {NMR and MRI obtained with high transition temperature DC SQUIDs}, journal = {Journal of the Brazilian Chemical Society}, volume = {10}, year = {1999}, note = {J Brazil Chem Soc259BETimes Cited:11Cited References Count:30}, month = {Jul-Aug}, pages = {307-312}, abstract = {

We have measured nuclear magnetic resonance (NMR) signals from several samples at room temperature in magnetic fields ranging from about 0.05 mT to 2 mT using a spectrometer based on a high-T-c de SQUID (high transition temperature de Superconducting QUantum Interference Device). We are able to observe proton signals from 1 mL of mineral oil in 2 mT in a single transient. The sensitivity of this system has also allowed the detection of proton NMR at magnetic fields as low as 0.059 mT, which is comparable to the Earth\&$\#$39;s field. Such results make possible a number of new experiments in magnetic resonance imaging (MRI). We present a two-dimensional image of a phantom filled with mineral oil obtained in a field of 2 mT.

}, keywords = {system}, isbn = {0103-5053}, url = {://WOS:000083873500009}, author = {de Souza, R. E. and Schlenga, K. and Wong-Foy, A. and McDermott, R. and Pines, A. and Clarke, J.} }