%0 Journal Article %J Journal of Magnetic Resonance %D 2009 %T Distortion-free magnetic resonance imaging in the zero-field limit %A Kelso, N. %A Lee, S. K. %A Bouchard, L. S. %A Demas, V. %A Mück, M. %A Pines, A. %A Clarke, J. %K gradients %X

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'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'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.

%B Journal of Magnetic Resonance %V 200 %P 285-290 %8 Oct %@ 1090-7807 %G English %U ://WOS:000272260900015 %N 2 %M WOS:000272260900015 %! Distortion-free magnetic resonance imaging in the zero-field limit %R Doi 10.1016/J.Jmr.2009.07.016 %0 Journal Article %J Journal of Magnetic Resonance %D 2006 %T SQUID-detected microtesla MRI in the presence of metal %A Mossle, M. %A Han, S. I. %A Myers, W. R. %A Lee, S. K. %A Kelso, N. %A Hatridge, M. %A Pines, A. %A Clarke, J. %K nmr %X

In magnetic resonance imaging performed at fields of I T and above, the presence of a metal insert can distort the image because of susceptibility differences within the sample and modification of the radiofrequency fields by screening currents. Furthermore, it is not feasible to perform nuclear magnetic resonance (NMR) spectroscopy or acquire a magnetic resonance image if the sample is enclosed in a metal container. Both problems can be overcome by substantially lowering the NMR frequency. Using a microtesla imaging system operating at 2.8 kHz, with a superconducting quantum interference device as the signal detector, we have obtained distortion-free images of a phantom containing a titanium bar and three-dimensional images of an object enclosed in an aluminum can; in both cases high-field images are inaccessible. (c) 2005 Elsevier Inc. All rights reserved.

%B Journal of Magnetic Resonance %V 179 %P 146-151 %8 Mar %@ 1090-7807 %G English %U ://WOS:000236977600019 %N 1 %M WOS:000236977600019 %! SQUID-detected microtesla MRI in the presence of metal %R Doi 10.1016/J.Jmr.2005.11.005 %0 Journal Article %J Ieee Transactions on Applied Superconductivity %D 2005 %T SQUID-detected in vivo MRI at microtesla magnetic fields %A Mossle, M. %A Myers, W. R. %A Lee, S. K. %A Kelso, N. %A Hatridge, M. %A Pines, A. %A Clarke, J. %K nmr %X

We use a low transition temperature (T(c)) Super-conducting Quantum Interference Device (SQUID) to perform in vivo magnetic resonance imaging (MRI) at magnetic fields around 100 microtesla, corresponding to proton Larmor frequencies of about 5 kHz. In such low fields, broadening of the nuclear magnetic resonance lines due to inhomogeneous magnetic fields and susceptibility variations of the sample are minimized, enabling us to obtain high quality images. To reduce environmental noise the signal is detected by a second-order gradiometer, coupled to the SQUID, and the experiment is surrounded by a 3-mm thick Al shield. To increase the signal-to-noise ratio (SNR), we prepolarize the samples in a field up to 100 mT. Three-dimensional images are acquired in less than 6 minutes with a standard spin-echo phase-encoding sequence. Using encoding gradients of similar to 100 mu T/m we obtain three-dimensional images of bell peppers with a resolution of 2 x 2 x 8 mm(3). Our system is ideally suited to acquiring images of small, peripheral parts of the human body such as hands and arms. In vivo images of an arm, acquired at 132 mu T, show 24-mm sections of the forearm with a resolution of 3 x 3 mm(2). and a SNR of 10. We discuss possible applications of MRI at these low magnetic fields.

%B Ieee Transactions on Applied Superconductivity %V 15 %P 757-760 %8 Jun %@ 1051-8223 %G English %U ://WOS:000229765300170 %N 2 %M WOS:000229765300170 %! SQUID-detected in vivo MRI at microtesla magnetic fields %R Doi 10.1109/Tasc.2005.850043 %0 Journal Article %J Magnetic Resonance in Medicine %D 2005 %T SQUID-detected MRI at 132 mu T with T(1)-weighted contrast established at 10 mu T-300 mT %A Lee, S. K. %A Mossle, M. %A Myers, W. %A Kelso, N. %A Trabesinger, A. H. %A Pines, A. %A Clarke, J. %K dispersion %X

T(1)-weighted contrast MRI with prepolarization was detected with a superconducting quantum interference device (SQUID). A spin evolution period in a variable field between prepolarization and detection enabled the measurement of T(1) in fields between 1.7 muT and 300 mT; T, dispersion curves of agarose gel samples over five decades in frequency were obtained. SQUID detection at 5.6 kHz drastically reduces the field homogeneity requirements compared to conventional field-cycling methods using Faraday coil detection. This allows T(1) dispersion measurements to be easily combined with MRI, so that T(1) in a wide range of fields can be used for tissue contrast. Images of gel phantoms with T(1)-weighted contrast at four different fields between 10 muT and 300 mT demonstrated dramatic contrast enhancement in low fields. A modified inversion recovery technique further enhanced the contrast by selectively suppressing the signal contribution for a specific value of the low-field T(1). Published 2004 Wiley-Liss, Inc.

%B Magnetic Resonance in Medicine %V 53 %P 9-14 %8 Jan %@ 0740-3194 %G English %U ://WOS:000226380700003 %N 1 %M WOS:000226380700003 %! SQUID-detected MRI at 132 mu T with T(1)-weighted contrast established at 10 mu T-300 mT %R Doi 10.1002/Mrm.20316 %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2004 %T Microtesla MRI with a superconducting quantum interference device %A McDermott, R. %A Lee, S. K. %A ten Haken, B. %A Trabesinger, A. H. %A Pines, A. %A Clarke, J. %K system %X

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.

%B Proceedings of the National Academy of Sciences of the United States of America %V 101 %P 7857-7861 %8 May 25 %@ 0027-8424 %G English %U ://WOS:000221652000005 %N 21 %M WOS:000221652000005 %! Microtesla MRI with a superconducting quantum interference device %R Doi 10.1073/Pnas.0402382101 %0 Journal Article %J Journal of Physical Chemistry A %D 2004 %T SQUID-detected liquid state NMR in microtesla fields %A Trabesinger, A. H. %A McDermott, R. %A Lee, S. K. %A Mück, M. %A Clarke, J. %A Pines, A. %K water %X

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.

%B Journal of Physical Chemistry A %V 108 %P 957-963 %8 Feb 12 %@ 1089-5639 %G English %U ://WOS:000188831500005 %N 6 %M WOS:000188831500005 %! SQUID-detected liquid state NMR in microtesla fields %R Doi 10.1021/Jp035181g %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 Journal of Magnetic Resonance %D 2002 %T Laser-polarized Xe-129 NMR and MRI at ultralow magnetic fields %A Wong-Foy, A. %A Saxena, S. %A Moule, A. J. %A Bitter, H. M. L. %A Seeley, J. A. %A McDermott, R. %A Clarke, J. %A Pines, A. %K atoms %X

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).

%B Journal of Magnetic Resonance %V 157 %P 235-241 %8 Aug %@ 1090-7807 %G English %U ://WOS:000178377400009 %N 2 %M WOS:000178377400009 %! Laser-polarized Xe-129 NMR and MRI at ultralow magnetic fields %R Doi 10.1006/Jmre.2002.2592 %0 Journal Article %J Science %D 2002 %T Liquid-state NMR and scalar couplings in microtesla magnetic fields %A McDermott, R. %A Trabesinger, A. H. %A Mück, M. %A Hahn, E. L. %A Pines, A. %A Clarke, J. %K resonance %X

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.

%B Science %V 295 %P 2247-2249 %8 Mar 22 %@ 0036-8075 %G English %U ://WOS:000174561700039 %N 5563 %M WOS:000174561700039 %! Liquid-state NMR and scalar couplings in microtesla magnetic fields %R Doi 10.1126/Science.1069280 %0 Journal Article %J Journal of the American Chemical Society %D 2001 %T Resolution of Xe-129 chemical shifts at ultralow magnetic field %A Saxena, S. %A Wong-Foy, A. %A Moule, A. J. %A Seeley, J. A. %A McDermott, R. %A Clarke, J. %A Pines, A. %K adsorption %B Journal of the American Chemical Society %V 123 %P 8133-8134 %8 Aug 22 %@ 0002-7863 %G English %U ://WOS:000170494200027 %N 33 %M WOS:000170494200027 %! Resolution of Xe-129 chemical shifts at ultralow magnetic field %R Doi 10.1021/Ja011064s %0 Journal Article %J Ieee Transactions on Applied Superconductivity %D 1999 %T High-T-c SQUIDs for low-field NMR and MRI of room temperature samples %A Schlenga, K. %A McDermott, R. F. %A Clarke, J. %A de Souza, R. E. %A Wong-Foy, A. %A Pines, A. %K frequencies %X

We have constructed a high-T-c SQUID spectrometer to detect NMR signals from samples at room temperature in magnetic fields up to 3 mT. The multiloop SQUID magnetometer has a system noise of about 30 fT/Hz(1/2) at the relevant frequencies of 2 to 100 kHz, The magnetometer is operated in vacuum at 77 K, and is separated from the sample, which is less than 1.5 mm away, by a sapphire window, In a magnetic field of 2 mT we can detect the proton spin echo at 86 kHz without signal averaging. This sensitivity enables us to obtain one-dimensional images. In addition, we present data on hyperpolarized Xe-129, which has an optically pumped polarization of several percent.

%B Ieee Transactions on Applied Superconductivity %V 9 %P 4424-4427 %8 Jun %@ 1051-8223 %G English %U ://WOS:000081964500386 %N 2 %M WOS:000081964500386 %! High-T-c SQUIDs for low-field NMR and MRI of room temperature samples %R Doi 10.1109/77.784006 %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 Journal of the Brazilian Chemical Society %D 1999 %T NMR and MRI obtained with high transition temperature DC SQUIDs %A de Souza, R. E. %A Schlenga, K. %A Wong-Foy, A. %A McDermott, R. %A Pines, A. %A Clarke, J. %K system %X

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'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.

%B Journal of the Brazilian Chemical Society %V 10 %P 307-312 %8 Jul-Aug %@ 0103-5053 %G English %U ://WOS:000083873500009 %N 4 %M WOS:000083873500009 %! NMR and MRI obtained with high transition temperature DC SQUIDs %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 %0 Journal Article %J Review of Scientific Instruments %D 1997 %T Low magnetic field dynamic nuclear polarization using a single-coil two-channel probe %A TonThat, D. M. %A Augustine, M. P. %A Pines, A. %A Clarke, J. %K nmr %X

We describe the design and construction of a single-coil, two-channel probe for the detection of low-field magnetic resonance using dynamic nuclear polarization (DNP). The high-frequency channel of the probe, which is used to saturate the electron spins, is tuned to the electron Larmor frequency, 75 MHz at 2.7 mT, and matched to 50 Omega. Low-field, H-1 nuclear magnetic resonance (NMR) is detected through the second, low-frequency channel at frequencies <1 MHz. The performance of the probe was tested by measuring the DNP of protons in a manganese (II) chloride solution at 2.7 mT. At the proton NMR frequency of 120 kHz, the signal amplitude was enhanced over the value without DNP by a factor of about 200. (C) 1997 American Institute of Physics.

%B Review of Scientific Instruments %V 68 %P 1527-1531 %8 Mar %@ 0034-6748 %G English %U ://WOS:A1997WP24700033 %N 3 %M WOS:A1997WP24700033 %! Low magnetic field dynamic nuclear polarization using a single-coil two-channel probe %R Doi 10.1063/1.1147641 %0 Journal Article %J Chemical Physics Letters %D 1997 %T SQUID detected NMR of laser-polarized xenon at 4.2 K and at frequencies down to 200 Hz %A TonThat, D. M. %A Ziegeweid, M. %A Song, Y. Q. %A Munson, E. J. %A Appelt, S. %A Pines, A. %A Clarke, J. %K relaxation %X

A spectrometer based on a dc SQUID (superconducting quantum interference device) was used to record nuclear magnetic resonance signals from laser-polarized Xe-129 at 4.2 K and at frequencies ranging from about 200 Hz to 110 kHz in magnetic fields varying from about 0.02 to 9 mT. The Xe-129 resonance linewidths were found to increase with increasing magnetic field, and, at a given field, to increase with higher Xe-129 concentration. The spin-lattice relaxation times were observed to decrease from similar to 8000 s at 5 mT to similar to 2000 s at fields below 0.05 mT. Such long relaxation times make possible a variety of spin polarization transfer experiments. (C) 1997 Published by Elsevier Science B.V.

%B Chemical Physics Letters %V 272 %P 245-249 %8 Jun 27 %@ 0009-2614 %G English %U ://WOS:A1997XH44000017 %N 3-4 %M WOS:A1997XH44000017 %! SQUID detected NMR of laser-polarized xenon at 4.2 K and at frequencies down to 200 Hz %R Doi 10.1016/S0009-2614(97)88016-5 %0 Journal Article %J Physical Review Letters %D 1992 %T Pulsed Fourier-Transform Nqr of N-14 with a Dc Squid %A Hurlimann, M. D. %A Pennington, C. H. %A Fan, N. Q. %A Clarke, J. %A Pines, A. %A Hahn, E. L. %K nh4clo4 %X

The zero-field free induction decay of solid ammonium perchlorate at 1.5 K has been directly detected with a dc superconducting quantum interference device. The Fourier-transform spectrum consists of three sharp lines at 17.4, 38.8, and 56.2 kHz arising from pure N-14 nucLear quadrupole resonance transitions. The absence of splittings and resonance transitions from dipolar-coupled proton spins is attributed to reorientation of the ammonium groups by quantum tunneling in combination with motional averaging in the three proton levels characterized by the irreducible representation T. The measured N-14 spin-spin relaxation time is 22+/-2 ms and the spin-lattice relaxation time is 63+/-6 ms.

%B Physical Review Letters %V 69 %P 684-687 %8 Jul 27 %@ 0031-9007 %G English %U ://WOS:A1992JE75400034 %N 4 %M WOS:A1992JE75400034 %! Pulsed Fourier-Transform Nqr of N-14 with a Dc Squid %R Doi 10.1103/Physrevlett.69.684 %0 Journal Article %J Ieee Transactions on Magnetics %D 1989 %T Nuclear Magnetic-Resonance with Dc Squid Preamplifiers %A Fan, N. Q. %A Heaney, M. B. %A Clarke, J. %A Newitt, D. %A Wald, L. L. %A Hahn, E. L. %A Bielecki, A. %A Pines, A. %B Ieee Transactions on Magnetics %V 25 %P 1193-1199 %8 Mar %@ 0018-9464 %G English %U ://WOS:A1989T670600113 %N 2 %M WOS:A1989T670600113 %! Nuclear Magnetic-Resonance with Dc Squid Preamplifiers %R Doi 10.1109/20.92510