@article {269, title = {Distortion-free magnetic resonance imaging in the zero-field limit}, journal = {Journal of Magnetic Resonance}, volume = {200}, year = {2009}, note = {J Magn Reson526AWTimes Cited:6Cited References Count:29}, month = {Oct}, pages = {285-290}, abstract = {

MRI is a powerful technique for clinical diagnosis and materials characterization. Images are acquired in a homogeneous static magnetic field much higher than the fields generated across the field of view by the spatially encoding field gradients. Without such a high field, the concomitant components of the field gradient dictated by Maxwell\&$\#$39;s equations lead to severe distortions that make imaging impossible with conventional MRI encoding. In this paper, we present a distortion-free image of a phantom acquired with a fundamentally different methodology in which the applied static field approaches zero. Our technique involves encoding with pulses of uniform and gradient field, and acquiring the magnetic field signals with a SQUID. The method can be extended to weak ambient fields, potentially enabling imaging in the Earth\&$\#$39;s field without cancellation coils or shielding. Other potential applications include quantum information processing and fundamental studies of long-range ferromagnetic interactions. (C) 2009 Elsevier Inc. All rights reserved.

}, keywords = {gradients}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2009.07.016}, url = {://WOS:000272260900015}, author = {Kelso, N. and Lee, S. K. and Bouchard, L. S. and Demas, V. and M{\"u}ck, M. 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 {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.} }