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Fast algorithms for nonconvex compression sensing: MRI reconstruction from very few data

Description: Compressive sensing is the reconstruction of sparse images or signals from very few samples, by means of solving a tractable optimization problem. In the context of MRI, this can allow reconstruction from many fewer k-space samples, thereby reducing scanning time. Previous work has shown that nonconvex optimization reduces still further the number of samples required for reconstruction, while still being tractable. In this work, we extend recent Fourier-based algorithms for convex optimization to the nonconvex setting, and obtain methods that combine the reconstruction abilities of previous nonconvex approaches with the computational speed of state-of-the-art convex methods.
Date: January 1, 2009
Creator: Chartrand, Rick
Partner: UNT Libraries Government Documents Department

Nuclear magnetic resonance imaging with hyper-polarized noble gases

Description: This is the final report of a six-month, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The nuclei of noble gases can be hyper polarized through a laser-driven spin exchange to a degree many orders of magnitude larger than that attainable by thermal polarization without requiring a strong magnetic field. The increased polarization from the laser pumping enables a good nuclear magnetic resonance (NMR) signal from a gas. The main goal of this project was to demonstrate diffusion-weighted imaging of such hyper-polarized noble gas with magnetic resonance imaging (MRI). Possible applications include characterizing porosity of materials and dynamically imaging pressure distributions in biological or acoustical systems.
Date: October 1, 1997
Creator: Schmidt, D.M.; George, J.S.; Penttila, S.I. & Caprihan, A.
Partner: UNT Libraries Government Documents Department

Multispectral image classification of MRI data using an empirically-derived clustering algorithm

Description: Multispectral image analysis of magnetic resonance imaging (MRI) data has been performed using an empirically-derived clustering algorithm. This algorithm groups image pixels into distinct classes which exhibit similar response in the T{sub 2} 1st and 2nd-echo, and T{sub 1} (with ad without gadolinium) MRI images. The grouping is performed in an n-dimensional mathematical space; the n-dimensional volumes bounding each class define each specific tissue type. The classification results are rendered again in real-space by colored-coding each grouped class of pixels (associated with differing tissue types). This classification method is especially well suited for class volumes with complex boundary shapes, and is also expected to robustly detect abnormal tissue classes. The classification process is demonstrated using a three dimensional data set of MRI scans of a human brain tumor.
Date: August 1, 1998
Creator: Horn, K.M.; Osbourn, G.C.; Bouchard, A.M. & Sanders, J.A.
Partner: UNT Libraries Government Documents Department

Particle interations in concentrated suspensions

Description: An overview is presented of research that focuses on slow flows of suspensions in which colloidal and inertial effects are negligibly small. We describe nuclear magnetic resonance imaging experiments to quantitatively measure particle migration occurring in concentrated suspensions undergoing a flow with a nonuniform shear rate. These experiments address the issue of how the flow field affects the microstructure of suspensions. In order to understand the local viscosity in a suspension with such a flow-induced, spatially varying concentration, one must know how the viscosity of a homogeneous suspension depends on such variables as solids concentration and particle orientation. We suggest the technique of falling ball viscometry, using small balls, as a method to determine the effective viscosity of a suspension without affecting the original microstructure significantly. We also describe data from experiments in which the detailed fluctuations of a falling ball`s velocity indicate the noncontinuum nature of the suspension and may lead to more insights into the effects of suspension microstructure on macroscopic properties. Finally, we briefly describe other experiments that can be performed in quiescent suspensions (in contrast to the use of conventional shear rotational viscometers) in order to learn more about boundary effects in concentrated suspensions.
Date: June 1, 1993
Creator: Mondy, L.A.; Graham, A.L.; Abbott, J.R. & Brenner, H.
Partner: UNT Libraries Government Documents Department

Applications of toroids in high-pressure NMR spectroscopy

Description: Toroid detectors have distinct NMR sensitivity and imaging advantages. The magnetic field lines are nearly completely contained within the active volume element of a toroid. This results in high NMR signal sensitivity. In addition, the toroid detector may be placed next to the metallic walls of a containment vessel with minimal signal loss due to magnetic coupling with the metal container. Thus, the toroid detector is ideal for static high pressure or continuous flow monitoring systems. Toroid NMR detectors have been used to follow the hydroformylation of olefins in supercritical fluids under industrial process conditions. Supercritical fluids are potentially ideal media for conducting catalytic reactions that involve gaseous reactants, including H{sub 2}, CO, and CO{sub 2}. The presence of a single homogeneous reaction phase eliminates the gas-liquid mixing problem of alternative two-phase systems, which can limit process rates and adversely affect hydroformylation product selectivities. A second advantage of toroid NMR detectors is that they exhibit a well-defined gradient in the rf field. This magnetic field gradient can be used for NMR imaging applications. Distance resolutions of 20 {mu} have been obtained.
Date: December 1, 1995
Creator: Klingler, R.J.; Rathke, J.W. & Woelk, K.
Partner: UNT Libraries Government Documents Department

Quantifying the Diffusion of a Fluid through Membranes by RemoteDetection MRI

Description: We present a method to measure self-diffusion acrossmembranes without the need for concentration or pressure gradients.Hyperpolarized xenon in combination with remote detection of NMR allowsthe measurement of membrane permeation, even in the gas phase. Theresulting images allow quantification of the amount of fluid diffusedthrough the membrane, and represent an alternative, potentially moreprecise way of measuring a membrane diffusion coefficient. The use ofremote detection of NMR allows for non-invasive signal encoding coupledto sensitive detection, making this approach ideal for the study ofdiffusion in intact devices such as fuel cells or separationsystems.
Date: October 24, 2006
Creator: Telkki, Ville-Veikko; Hilty, Christian; Garcia, Sandra; Harel,Elad & Pines, Alexander
Partner: UNT Libraries Government Documents Department

Influence of Reactive Transport on the Reduction of U(VI) in the Presence of Fe(III) and Nitrate: Implications for U(VI) Immobilization by Bioremediation/Bioba

Description: The research in FY04 was focused in five specific topics: (1) U(VI) sorption on microbially and abiotically reduced sediments, (2) oxidation of biogenic U(IV) in presence of Fe(II), (3) U(VI) reduction by reduced sediments, (4) kinetics of U(VI) sorption on natural sediments under conditions of flow, and (5) NMR imaging of S. onidensis biofilms in porous media. Two manuscripts are currently in review, and another five (or four?) manuscripts are currently in preparation for submission.
Date: June 1, 2004
Creator: Wood, Brian D.
Partner: UNT Libraries Government Documents Department

NMR imaging and hydrodynamic analysis of neutrally buoyant non-Newtonian slurry flows

Description: The flow of solids loaded suspension in cylindrical pipes has been the object of intense experimental and theoretical investigations in recent years. These types of flows are of great interest in chemical engineering because of their important use in many industrial manufacturing processes. Such flows are for example encountered in the manufacture of solid-rocket propellants, advanced ceramics, reinforced polymer composites, in heterogenous catalytic reactors, and in the pipeline transport of liquid-solids suspensions. In most cases, the suspension microstructure and the degree of solids dispersion greatly affect the final performance of the manufactured product. For example, solid propellant pellets need to be extremely-well dispersed in gel matrices for use as rocket engine solid fuels. The homogeneity of pellet dispersion is critical to allow good uniformity of the burn rate, which in turn affects the final mechanical performance of the engine. Today`s manufacturing of such fuels uses continuous flow processes rather than batch processes. Unfortunately, the hydrodynamics of such flow processes is poorly understood and is difficult to assess because it requires the simultaneous measurements of liquid/solids phase velocities and volume fractions. Due to the recent development in pulsed Fourier Transform NMR imaging, NMR imaging is now becoming a powerful technique for the non intrusive investigation of multi-phase flows. This paper reports and exposes a state-of-the-art experimental and theoretical methodology that can be used to study such flows. The hydrodynamic model developed for this study is a two-phase flow shear thinning model with standard constitutive fluid/solids interphase drag and solids compaction stresses. this model shows good agreement with experimental data and the limitations of this model are discussed.
Date: February 1, 1995
Creator: Bouillard, J.X. & Sinton, S.W.
Partner: UNT Libraries Government Documents Department

Developments in functional neuroimaging techniques

Description: A recent review of neuroimaging techniques indicates that new developments have primarily occurred in the area of data acquisition hardware/software technology. For example, new pulse sequences on standard clinical imagers and high-powered, rapidly oscillating magnetic field gradients used in echo planar imaging (EPI) have advanced MRI into the functional imaging arena. Significant developments in tomograph design have also been achieved for monitoring the distribution of positron-emitting radioactive tracers in the body (PET). Detector sizes, which pose a limit on spatial resolution, have become smaller (e.g., 3--5 mm wide) and a new emphasis on volumetric imaging has emerged which affords greater sensitivity for determining locations of positron annihilations and permits smaller doses to be utilized. Electromagnetic techniques have also witnessed growth in the ability to acquire data from the whole head simultaneously. EEG techniques have increased their electrode coverage (e.g., 128 channels rather than 16 or 32) and new whole-head systems are now in use for MEG. But the real challenge now is in the design and implementation of more sophisticated analyses to effectively handle the tremendous amount of physiological/anatomical data that can be acquired. Furthermore, such analyses will be necessary for integrating data across techniques in order to provide a truly comprehensive understanding of the functional organization of the human brain.
Date: March 1, 1995
Creator: Aine, C.J.
Partner: UNT Libraries Government Documents Department

Global continuation for distance geometry problems

Description: Distance geometry problems arise in the interpretation of NMR data and in the determination of protein structure. The authors formulate the distance geometry problem as a global minimization problem with special structure, and show the global smoothing techniques and a continuation approach for global optimization can be used to determine solutions of distance geometry problems with a nearly 100% probability of success.
Date: March 1, 1995
Creator: More, J.J. & Wu, Zhijun
Partner: UNT Libraries Government Documents Department

Three dimensional nuclear magnetic resonance spectroscopic imaging of sodium ions using stochastic excitation and oscillating gradients

Description: Nuclear magnetic resonance (NMR) spectroscopic imaging of {sup 23}Na holds promise as a non-invasive method of mapping Na{sup +} distributions, and for differentiating pools of Na{sup +} ions in biological tissues. However, due to NMR relaxation properties of {sup 23}Na in vivo, a large fraction of Na{sup +} is not visible with conventional NMR imaging methods. An alternate imaging method, based on stochastic excitation and oscillating gradients, has been developed which is well adapted to measuring nuclei with short T{sub 2}. Contemporary NMR imaging techniques have dead times of up to several hundred microseconds between excitation and sampling, comparable to the shortest in vivo {sup 23}Na T{sub 2} values, causing significant signal loss. An imaging strategy based on stochastic excitation has been developed which greatly reduces experiment dead time by reducing peak radiofrequency (RF) excitation power and using a novel RF circuit to speed probe recovery. Continuously oscillating gradients are used to eliminate transient eddy currents. Stochastic {sup 1}H and {sup 23}Na spectroscopic imaging experiments have been performed on a small animal system with dead times as low as 25{mu}s, permitting spectroscopic imaging with 100% visibility in vivo. As an additional benefit, the encoding time for a 32x32x32 spectroscopic image is under 30 seconds. The development and analysis of stochastic NMR imaging has been hampered by limitations of the existing phase demodulation reconstruction technique. Three dimensional imaging was impractical due to reconstruction time, and design and analysis of proposed experiments was limited by the mathematical intractability of the reconstruction method. A new reconstruction method for stochastic NMR based on Fourier interpolation has been formulated combining the advantage of a several hundredfold reduction in reconstruction time with a straightforward mathematical form.
Date: December 1, 1994
Creator: Frederick, B.deB.
Partner: UNT Libraries Government Documents Department

Two-phase flow measurements by nuclear magnetic resonance (NMR). Final technical report, January 1, 1993--September 30, 1997

Description: Researchers pioneered NMR studies of concentrated suspensions starting in the late 1980`s (Majors, et al., 1989; Altobelli, et al., 1991; Abbott, et al., 1991). In those studies, they measured concentration and velocity of the liquid component either in pipe or Couette flow. If one compares these early studies of suspensions with more recent ones, imaging time has gone from 40 minutes to 8 minutes and the imaging matrix has increased from 32 x 32 to 128 x 128. In the interim, many concentrated suspension flows in both pipe and Couette geometries, with different particle sizes and shapes, and different kinds of liquids have been performed. The author summarizes the main results here and lists the publications that emanated from this grant.
Date: July 29, 1998
Creator: Fukushima, Eiichi
Partner: UNT Libraries Government Documents Department

Application of NMR spectroscopy and multidimensional imaging to the gelcasting process and in-situ real-time monitoring of cross-linking polyacrylamide gels

Description: In the gelcasting process, a slurry of ceramic powder in a solution of organic monomers is cast in a mold. The process is different from injection molding in that it separates mold-filling from setting during conversion of the ceramic slurry to a formed green part. In this work, NMR spectroscopy and imaging have been conducted for in-situ monitoring of the gelation process and for mapping the polymerization. {sup 1}H nuclear magnetic resonance spectra have been obtained during polymerization of a premix of soluble reactive methacrylamide (monomer) and N, N`-methylene bisacrylamide (cross-linking molecules). The premix was polymerized by adding ammonium persulfate (initiator) and tetramethyl-ethylene-diamine (accelerator) to form long-chain, cross-linked polymers. The time-varying spin-lattice relaxation times T{sub 1} during polymerization have been studied at 25 and 35{degrees}C, and the variation of spectra and T{sub 1} with respect to extent of polymerization has been determined. To verify homogeneous polymerization, multidimensional NMR imaging was utilized for in-situ monitoring of the process. The intensities from the images are modeled and the correspondence shows a direct extraction of T{sub 1} data from the images.
Date: April 1, 1995
Creator: Ahuja, S.; Dieckman, S.L. & Gopalsami, N.
Partner: UNT Libraries Government Documents Department

NMR analysis on microfluidic devices by remote detection

Description: We present a novel approach to perform high-sensitivity NMR imaging and spectroscopic analysis on microfluidic devices. The application of NMR, the most information rich spectroscopic technique, to microfluidic devices remains a challenge because the inherently low sensitivity of NMR is aggravated by small fluid volumes leading to low NMR signal, and geometric constraints resulting in poor efficiency for inductive detection. We address the latter by physically separating signal detection from encoding of information with remote detection. Thereby, we use a commercial imaging probe with sufficiently large diameter to encompass the entire device, enabling encoding of NMR information at any location on the chip. Because large-diameter coils are too insensitive for detection, we store the encoded information as longitudinal magnetization and flow it into the outlet capillary. There, we detect the signal with optimal sensitivity using a solenoidal microcoil, and reconstruct the information encoded in the fluid. We present a generally applicable design for a detection-only microcoil probe that can be inserted into the bore of a commercial imaging probe. Using hyperpolarized 129Xe gas, we show that this probe enables sensitive reconstruction of NMR spectroscopic information encoded by the large imaging probe while keeping the flexibility of a large coil.
Date: August 15, 2005
Creator: McDonnell, Erin E.; Han, SongI; Hilty, Christian; Pierce,Kimberly & Pines, Alexander
Partner: UNT Libraries Government Documents Department

Molecular medicine: Synthesis and in-vivo detection of agents for use in boron neutron capture therapy. Final report, May 1, 1993--April 30, 1996

Description: During the early stages of this project, the author developed the first whole-body boron MRI technique. They found that, for the first time, information concerning both the location and the quantity of boron present in living tissues could be obtained through the use of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) respectively. However, it was also discovered that boron MRI was not without problems. Both naturally occurring isotopes of boron (boron-10 and boron-11) possess magnetic moments, making them amenable to MR detection. The author found that there are difficulties in obtaining boron MRI images which are a consequence of the inherently poor magnetic resonance characteristics of the boron nucleus. The magnetogyric ratios of both boron-10 and boron-11 are smaller than those of hydrogen, which makes boron much less sensitive to magnetic resonance detection. In addition, both isotopes of boron posses nuclear electric quadrupole moments which serve to shorten their magnetization relaxation times; this causes the MR signal to broaden and decay rapidly, often before the receiver coils can collect the MR information. The rapid rate of signal decay is enhanced in biological systems which leads to further signal loss and a decrease in the signal to noise ratio (SNR).
Date: August 1, 1997
Creator: Kabalka, G.W.
Partner: UNT Libraries Government Documents Department

Consortium to develop the medical uses of NMR imaging, NMR spectroscopy, and positron emission tomography. Final technical report

Description: The goal of this work is to, perform clinically relevant studies using a new whole-body 4.1 T NMR imaging spectrometer. Initially we will develop and approach for the assessment of the severity of skeletal muscle involvement in ischemic peripheral vascular disease.
Date: June 1, 1998
Creator: Pohost, G.M.
Partner: UNT Libraries Government Documents Department

BrainMap `95 workshop

Description: The fourth annual BrainMap workshop was held at La Mansion del Rio Hotel in San Antonio December 3--4, 1995. The conference title was ``Human Brain Mapping and Modeling.`` The meeting was attended by 137 registered participants and 30 observers from 82 institutions representing 12 countries. The meeting focused on the technical issues associated with brain mapping and modeling. A total of 23 papers were presented covering the following topics: spatial normalization and registration; functional image analysis; metanalysis and modeling; and new horizons in biological databases. The full program with abstracts was available on the Research Imaging Center`s web site. A book will be published by John Wiley and Sons prior to the end of 1998.
Date: December 31, 1995
Partner: UNT Libraries Government Documents Department

Multi-Modality Phantom Development

Description: Multi-modality imaging has an increasing role in the diagnosis and treatment of a large number of diseases, particularly if both functional and anatomical information are acquired and accurately co-registered. Hence, there is a resulting need for multi modality phantoms in order to validate image co-registration and calibrate the imaging systems. We present our PET-ultrasound phantom development, including PET and ultrasound images of a simple prostate phantom. We use agar and gelatin mixed with a radioactive solution. We also present our development of custom multi-modality phantoms that are compatible with PET, transrectal ultrasound (TRUS), MRI and CT imaging. We describe both our selection of tissue mimicking materials and phantom construction procedures. These custom PET-TRUS-CT-MRI prostate phantoms use agargelatin radioactive mixtures with additional contrast agents and preservatives. We show multi-modality images of these custom prostate phantoms, as well as discuss phantom construction alternatives. Although we are currently focused on prostate imaging, this phantom development is applicable to many multi-modality imaging applications.
Date: March 20, 2009
Creator: Huber, Jennifer S.; Peng, Qiyu & Moses, William W.
Partner: UNT Libraries Government Documents Department

Magnetic resonance imaging of solvent transport in polymer networks

Description: The spectroscopic technique of magnetic resonance imaging (MRI) has recently provided a new window into transport of solvents in polymer networks. Diffusion of solvent as a rate-controlling phenomenon is paramount to understanding transport in many important industrial and biological processes, such as upgrading fossil fuels, film casting and coating, development of photoresists, design of drug-delivery systems, development of solvent resistant polymers, etc. By MRI mapping the migration of solvent molecules through various polymer specimens, researchers Robert Botto and George Cody of Argonne National Laboratory, with support from the Division of Chemical Sciences at DOE, were able to characterize and distinguish between different modes of transport behavior associated with fundamentally different types of polymer systems. The method was applied to rubbers, glassy polymers, and coals. In polymers shown to undergo a glass transition from a rigid to rubbery state, a sharply defined solvent front was observed that propagated through specimens in the manner of a constant velocity shock wave. This behavior was contrasted with a smooth solvent concentration gradient found in polymer systems where no glass transition was observed. The results of this analysis have formed the basis of a new model of anomalous transport in polymeric solids and are helping to ascertain fundamental information on the molecular architectures of these materials.
Date: February 1, 1995
Creator: Botto, R.E. & Cody, G.D.
Partner: UNT Libraries Government Documents Department

An on-line NMR technique with a programmable processor

Description: Nuclear magnetic resonance (NMR) spectroscopy is used to determine molecular content of materials, mainly in laboratory measurements. The reduced cost of fast computer processors, together with recent break throughs in digital signal processor technology, has facilitated the on-line use of NMR by allowing modifications of the available technology. This paper describes a system and an algorithm for improving the on-line operations. It is base on the time-domain NMR signal detected by the controller and some prior knowledge of chemical signal patterns. The desired signal can be separated from a composite signal by using an adaptive line enhancer (ALE) filter. This technique would be useful for upgrading process procedures in on-line manufacturing.
Date: July 1, 1995
Creator: Razazian, K.; Dieckman, S.L. & Raptis, A.C.
Partner: UNT Libraries Government Documents Department

Hydrodynamic particle migration in small-amplitude, oscillatory, circular couette flow: The limits of reversibility

Description: Initially well-mixed suspensions of large spherical particles in viscous Newtonian fluids subjected to continuous nonhomogeneous shear flows demix and establish large concentration gradients. A number of experimental studies have determined that the particles migrate to the low shear-rate region in one-dimensional flow fields. Other investigators have proposed mechanisms to model the migration caused by the presence of nonuniform shear gradients. Here, we report on the shear-induced migration of particles in the annular space between two coaxial cylinders (a wide-gap Couette), with the inner cylinder oscillating and the outer cylinder fixed. In these experiments, the conditions are such that colloidal and inertial forces do not exert an appreciable effect on the suspensions of neutrally bouyant spherical particles in Newtonian liquids. Nuclear magnetic resonance (NMR) imaging is used to measure the concentration profile during the demixing of the initially well-mixed suspensions.
Date: January 1, 1992
Creator: Brenner, H. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Chemical Engineering); Altobelli, S.A. (Lovelace Medical Foundation, Albuquerque, NM (United States)); Graham, A.L.; Abbott, J.R. (Los Alamos National Lab., NM (United States)) & Monday, L.A. (Sandia National Labs., Albuquerque, NM (United States))
Partner: UNT Libraries Government Documents Department

Review of progress in quantitative NDE. [Nondestructive Evaluation (NDE)]

Description: This booklet is composed of abstracts from papers submitted at a meeting on quantitative NDE. A multitude of topics are discussed including analysis of composite materials, NMR uses, x-ray instruments and techniques, manufacturing uses, neural networks, eddy currents, stress measurements, magnetic materials, adhesive bonds, signal processing, NDE of mechanical structures, tomography,defect sizing, NDE of plastics and ceramics, new techniques, optical and electromagnetic techniques, and nonlinear techniques. (GHH)
Date: January 1, 1991
Partner: UNT Libraries Government Documents Department

An instrument control and data analysis program for NMR imaging and spectroscopy

Description: We describe a software environment created to support real-time instrument control and signal acquisition as well as array-processor based signal and image processing in up to five dimensions. The environment is configured for NMR imaging and in vivo spectroscopy. It is designed to provide flexible tools for implementing novel NMR experiments in the research laboratory. Data acquisition and processing operations are programmed in macros which are loaded in assembled from to minimize instruction overhead. Data arrays are dynamically allocated for efficient use of memory and can be mapped directly into disk files. The command set includes primitives for real-time control of data acquisition, scalar arithmetic, string manipulation, branching, a file system and vector operations carried out by an array processor. 6 figs.
Date: January 1, 1988
Creator: Roos, M.S.; Mushlin, R.A.; Veklerov, E.; Port, J.D.; Ladd, C. & Harrison, C.G.
Partner: UNT Libraries Government Documents Department

Absolute calibration in vivo measurement systems

Description: Lawrence Livermore National Laboratory (LLNL) is currently investigating a new method for obtaining absolute calibration factors for radiation measurement systems used to measure internally deposited radionuclides in vivo. Absolute calibration of in vivo measurement systems will eliminate the need to generate a series of human surrogate structures (i.e., phantoms) for calibrating in vivo measurement systems. The absolute calibration of in vivo measurement systems utilizes magnetic resonance imaging (MRI) to define physiological structure, size, and composition. The MRI image provides a digitized representation of the physiological structure, which allows for any mathematical distribution of radionuclides within the body. Using Monte Carlo transport codes, the emission spectrum from the body is predicted. The in vivo measurement equipment is calibrated using the Monte Carlo code and adjusting for the intrinsic properties of the detection system. The calibration factors are verified using measurements of existing phantoms and previously obtained measurements of human volunteers. 8 refs.
Date: February 1, 1991
Creator: Kruchten, D.A. & Hickman, D.P.
Partner: UNT Libraries Government Documents Department