2007 APS March Meeting Denver, Colorado
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2007 APS March Meeting Denver, Colorado http://www.aps.org/meetings/march i Monday, March 5, 2007 8:00AM - 11:00AM — Session A19 DCP: Focus Session: New Frontiers in Imaging I Colorado Convention Center 104 8:00AM A19.00001 Mobile NMR: Measuring Pixels, Images, and Spectra1 BERNHARD BLUEMICH, RWTH Aachen University — The vision of bringing nuclear magnetic resonance out of the lab to the doctor’s office, the chemical reactor, or the manufacturing site is becoming reality with the development of mobile NMR. Pioneered for well logging in the oil industry, the concept has been explored for materials testing in a more systematic way since the introduction of the NMR-MOUSE. This is a small, one-sided access NMR sensor which acquires the information of one pixel from a particular spot of a large object. As the sensor explores the stray-fields of a permanent magnet and an rf coil, the magnetic fields are inhomogeneous and the sensitive volume is limited to the region, where both fields are orthogonal and the Larmor frequency lies within the excitation bandwidth. By shaping the magnet and the coil geometries, the shape of the sensitive volume can be tailored to a thin slice or a larger volume a certain distance away from the sensor surface. In the first case, there is a strong field gradient in the depth direction, and in the second case, a homogeneous sweet spot of the field profile is desired. The first case is suitable for measuring high-resolution depth profiles, while the second case is suitable for chemical shift resolved spectroscopy and volume imaging. The basic concepts of open and closed mobile NMR sensors will be discussed along with applications from testing polymer products, cultural heritage, medical tissue, and rock cores. 1This work has been supported in part by the Miller Institute of Basic Research in Science, UC Berkeley. 8:36AM A19.00002 Ex-Situ Spectroscopic MRI , JEFFREY REIMER, UC Berkeley — Spectroscopic magnetic resonance imaging of a sample placed outside of both the radio frequency and the imaging gradient coils is presented. The sample is placed in a field with a permanent one-dimensional inhomogeneity. The imaging gradients used for phase encoding are designed to produce a static field that depends only on the transverse direction, uncoupling the effects associated with the single-sided nature of these coils. Two-dimensional imaging coupled with chemical shift information is obtained via the ex situ matching technique. Open-saddle geometry is used to match the static field profile for chemical shift information recovery. 8:48AM A19.00003 Nuclear magnetic resonance imaging with 90-nm resolution1 , M. POGGIO, C. L. DEGEN, H. J. MAMIN, D. RUGAR, IBM Research Division, Almaden Research Center, 650 Harry Rd., San Jose, CA 95120 — Using magnetic resonance force microscopy (MRFM), we demonstrate two-dimensional nuclear magnetic resonance imaging (MRI) with 90-nm lateral resolution for 19F nuclei in calcium fluoride. In terms of detectable volume, this represents a 60,000 fold improvement over the highest resolution conventional MRI. The high sensitivity of our measurement is achieved using a custom-made silicon cantilever with a 60-µN/m spring constant and a nanometer-scale FeCo magnetic tip that produces magnetic field gradients up to 14 G/nm. The spin manipulation protocol, called cyclic CERMIT, uses low duty cycle cantilever-driven adiabatic reversals to manipulate statistical spin polarization and generate a detectable cantilever frequency modulation. Work is underway to further improve measurement sensitivity, including the development of an efficient RF source aimed at reducing cantilever temperatures during imaging into the low millikelvin range. This and other improvements may allow MRFM to push deeper into the nanometer range. 1Work supported by DARPA QuIST and by the NSF through the Center for Probing the Nanoscale at Stanford University 9:00AM A19.00004 Imaging Contrast Effects in Alginate Microbeads , NINA SHAPLEY1, HOLLY HESTER- REILLY, Columbia University — We have investigated the use of alginate gel microbeads as contrast agents for the study of suspension flows in complex geometries using nuclear magnetic resonance (NMR) imaging. These deformable particles can provide imaging contrast to rigid polymer particles in a bimodal suspension (two particle sizes). Microbeads were formed of crosslinked alginate gel, with or without trapped oil droplets. Crosslinking of the aqueous sodium alginate solution or the continuous phase of an oil-in-water emulsion occurred rapidly at gentle processing conditions. The alginate microbeads exhibit both spin-spin relaxation time (T2) contrast and diffusion contrast relative to both the suspending fluid and rigid polystyrene particles. Large alginate emulsion microbeads flowing in the abrupt, axisymmetric expansion geometry can be clearly distinguished from the suspending fluid and from rigid polymer particles in both spin-echo and diffusion weighted imaging. The alginate microbeads, particularly those containing trapped emulsion droplets, offer potential as a positive contrast agent in multiple NMR imaging applications. 1Membership Pending 9:12AM A19.00005 , EIICHI FUKUSHIMA, New Mexico Resonance — No abstract available. 9:48AM A19.00006 Spin Sorting: Apparent Longitudinal Relaxation without Spin Transitions , MARK CONRADI, YULIN CHANG, JASON WOODS, SUSAN CONRADI, Washington University, DEPARTMENT OF PHYSICS TEAM — Nuclear spins experience forces in the presence of a magnetic field gradient. The forces cause the spin-up and spin-down nuclei to move in opposite directions, resulting in a flow of longitudinal magnetization. The effect can generate local longitudinal spin magnetization, though it does not involve transitions (flipping) of spins. This phenomenon, spin sorting, competes with true spin-lattice relaxation and is generally not observable when T1 is short. We present our calculations of 3 the longitudinal magnetization of diffusing spins with long T1 ( He) in magnetic field gradients and compare the calculations with experimental results. We show that the longitudinal spin magnetization due to spin sorting can be dominant at short times in such a system. We also show how this phenomenon can potentially be used to generate nuclear magnetizations larger than thermal equilibrium. 10:00AM A19.00007 Spin-Exchange Optical Pumping of Solid Alkali Compounds1 , BRIAN PATTON, Princeton University Physics Department, KIYOSHI ISHIKAWA, Graduate School of Material Science, University of Hyogo, Japan, YUAN-YU JAU, WILLIAM HAPPER, Princeton University Physics Department — Spin-exchange optical pumping of noble gases has been used for many years to create highly non- equilibrium spin populations, with applications ranging from fundamental physics[1] to medical imaging[2]. In this procedure, angular momentum is transferred from circularly-polarized laser light to the electron spins of an alkali vapor and ultimately to the nuclei of a gas such as 3He or 129Xe. Here we show experimentally that a similar process can be used to polarize the nuclei of a solid film of cesium hydride which coats the walls of an optical pumping cell. We present nuclear magnetic resonance (NMR) data which demonstrate that the nuclear polarization of 133Cs in CsH can be enhanced above the Boltzmann limit in a 9.4-Tesla magnetic field. Possible spin-exchange mechanisms will be discussed, as well as the extension of this technique to other compounds. [1] T. W. Kornack, R. K. Ghosh, and M. V. Romalis, Phys. Rev. Lett. 95, 23080 (2005). [2] M. S. Conradi, D. A. Yablonskiy, et al., Acad. Radiol. 12, 1406 (2005). 1This work was supported by AFOSR. 10:12AM A19.00008 Hyperpolarized water as an authentic magnetic resonance imaging con- trast agent.1 , SONGI HAN, EVAN MCCARNEY, BRANDON ARMSTRONG, University of California Santa Barbara — Water itself in a highly 1H spin-polarized state is proposed as a contrast agent free contrast agent to visualize its macroscopic evolution in aqueous media by magnetic resonance imaging (MRI). Hyper-polarization suggests an ideal contrast mechanism to highlight the ubiquitous and specific function of water in physiology, biology and materials because the physiological, chemical and macroscopic function of water is not altered by the degree of magnetization. We present an approach that is capable of enhancing the 1H MRI signal by up to two orders of magnitude, instantaneously, under ambient conditions, at 0.35 Tesla, by utilizing highly electron spin-polarized nitroxide radicals that are covalently immobilized onto a porous, water-saturated, gel matrix. The continuous polarization of radical-free flowing water allowed us to distinctively visualize vortices in model reactors and dispersion patterns through porous media utilizing the remotely enhanced liquids to obtain unusually high image contrast (RELIC). 1The work was supported by the Dreyfus New Faculty Award and through the MRL program of the National Science Foundation under Grant No. DMR00-80034. 10:24AM A19.00009 Latest Developments in Dynamic MRI of Multi-Phase Systems , LYNN GLADDEN, University of Cambridge — In recent years there has been increasing interest in applying magnetic resonance techniques in areas of engineering and chemical technology. Central to many engineering applications is the need to characterise both hydrodynamics and chemical reaction in optically opaque three-dimensional environments; thus MRI is uniquely well-suited to such studies. This presentation addresses the application of MRI techniques which have sufficiently fast data acquisition