bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bulk magnetic susceptibility shifts in nmr studies of compartmentalized samples: use of paramagnetic reagents
Authors: Chu Ksimon ‐.C. , Xu Yan , Balschi James A. , Springer Charles S. 
Published: March 2007

AbstractThe bulk magnetic susceptibility (BMS) shift of a nuclear resonance frequency caused by a paramagnetic compound is of importance in in vivo NMR, both magnetic resonance spectroscopy and magnetic resonance imaging. However, since it is a rather complicated phenomenon, it has been the source of many misinterpretations in the literature. We have reworked and organized the theory of the BMS shift. This includes accounting for the important effects of local susceptibility. We have conducted experiments on phantom samples in order to illustrate the principles involved. Our phantoms consist of capillaries and coaxial cylinders. They simulate the situations of blood vessels oriented parallel and perpendicular to the magnetic field and the interstitial spaces surrounding them. In most of our experiments, the paramagnetic compound was one of several different hyperfine shift reagents for cation resonances. These were chosen to cover a range of potencies, in both magnitude and sign, of the shifts they produce. However, we also used a reagent which was incapable of inducing a hyperfine shift and thus could cause only a BMS shift. Although we report only 23Na spectra in this paper, the latter samples simulate the cases where one observes the water 1H resonance in experiments employing hyperfine shift reagents for cations. There have been a number of such investigations recently reported in the literature. The principles considered in this paper allow us to offer new interpretations for the results of several experiments published in the last few years.
Spin‐lattice relaxation time measurements using hybrid csi–phantom study
Authors: Hornak Joseph P. , Smith Aric C. , Szumowski Jerzy 
Published: March 2007

AbstractThe spin‐lattice relaxation time T1 of multicomponent tissues is often determined by fitting relaxation data to monoexponential functions. This process can lead to large errors in the relaxation time. We describe a procedure using chemical‐shift imaging (CSI) which separates the NMR signal into water and lipid components thus allowing the two signals to be individually analyzed for relaxation times. This procedure yields more representative relaxation times than those obtained by both monoexponential and biexponential fitting schemes.
Heterotopic transplanted rat heart: a model for in vivo determination of phosphorus metabolites during ischemia and reperfusion
Authors: Rozenman Yoseph , Kantor Howard L. 
Published: March 2007

AbstractA model of heterotopic isogenic rat heart transplantation was developed in order to noninvasively observe the acute and chronic metabolic changes of ischemia. This study presents the results of 31P spectroscopy during acute global ischemia and reperfusion. The advantages of this model over other surface coil in vivo ischemia experiments are: (1) Thoracotomy for surface coil positioning is not required, thus the results are not influenced by the effect of recent major surgery. (2) Survival is not influenced by the degree of ischemic damage to the transplant, and the model enables repeated long‐term studies of the metabolic effect of reversible ischemia, and myocardial infarction. (3) The pathologic process created is homogeneous and thus the results are not complicated by variation in the severity of myocardial ischemia.
In vivo nmr diffusion spectroscopy: 31p application to phosphorus metabolites in muscle
Authors: Moonen Chrit T. W. , Van Zijl Peter C. M. , Bihan Denis Le , Despres Daryl 
Published: March 2007

AbstractApparent diffusion coefficients (Da) of individual metabolites can be studied in vivo by diffusion NMR spectroscopy using an echo sequence sensitized to molecular motion. The methods are based on the echo attenuation due to phase dispersion resulting from incoherent displacement during the diffusion time. As the displacement of metabolites by diffusion in vivo can be affected by compartment size, temperature, adsorption processes, etc., the presented methods are potentially useful in studying such phenomena in vivo. Here, the methods are applied to phosphocreatine in the rat quadriceps muscle. It is demonstrated that the displacement of phosphocreatine resembles free diffusion for short diffusion times but becomes limited as a result of boundaries due to compartmenta‐tion for longer diffusion times. The limit of the displacement indicates an apparent average size of 44 pm of the compartment in the direction of the diffusion gradient. As the gradient was applied approximately parallel (angle i 25o) to the muscle fiber, this result indicates that phosphocreatine moves freely in the cytosol but is limited by the boundaries of the muscle cells. Error analyses are performed with regard to motion artifacts and gradient performance. The methods were tested extensively for distilled water and free metabolites. © 1990 Academic Press, Inc.
Use of gel filtration in the preparation of biological fluids for magnetic resonance spectroscopy
Authors: Hoffman David W. , Venters Ronald A. , Shedd Suzanne F. , Spicer Leonard D. 
Published: March 2007

AbstractAnalysis of biological fluids by proton magnetic resonance spectroscopy is often complicated by dynamic range problems created from the large water resonance. Gel filtration chromatography is found to be a simple and nondestructive method for exchanging D2O for H2O and for removing low molecular weight molecules from both plasma and urine, significantly improving subsequent one‐ and two‐dimensional MRS spectra.
Proton magnetic resonance spectroscopy of human brain in vivo in the evaluation of multiple sclerosis: Assessment of the load of disease
Authors: Arnold Douglas L. , Matthews Paul M. , Francis Gordon , Antel Jack 
Published: March 2007

AbstractImage localized, water‐suppressed proton magnetic resonance spectra were obtained from affected brain in patients with multiple sclerosis. In patients with moderate to severe chronic disease, spectra revealed a decreased ratio of N‐acetylaspartate to creatine resonance intensities. A normal ratio was obtained from a large recently symptomatic MRI plaque that resolved without sequelae. We propose that the observed metabolite changes can be useful as an index of irreversible CNS injury. © 1990 Academic Press, Inc.
Quantification of regional blood flow by monitoring of exogenous tracer via nuclear magnetic resonance spectroscopy
Authors: Kim Seong‐Gi , Ackerman Joseph J. H. 
Published: March 2007

AbstractDeuterium and fluorine nuclear magnetic resonance spectroscopy have been employed for quantification of regional blood flow in concert with nonradiative, exogenous, freely diffusible tracers such as D2O and freon gas. Typically, the tracer residue washout was monitored by NMR over time following tracer administration by bolus injection or inhalation. The theory, including compartmental analysis, required to quantitatively derive volumetric tissue blood flow and perfusion is reviewed herein. Applications of NMR tissue blood flow measurement techniques to tumor, muscle, liver, and brain are presented with discussion of the advantages and disadvantages of NMR methods. © 1990 Academic Press, Inc.
Carotid‐CNS MR flow imaging
Authors: Masaryk Thomas J. , Laub Gerhard A. , Modic Michael T. , Ross Jeffrey S. , Haacke E. Mark 
Published: March 2007

AbstractThe authors present their 1‐year experience with the use of 3DFT, time‐of‐flight MR angiography for the evaluation of vascular diseases of the head and neck. Their experience with over 150 patients indicates that this examination may be performed in conjunction with standard spin‐echo imaging with only a minimal increase in patient examination time. This combined examination is most applicable to atherosclerotic disease of the carotid bifurcation, arterial occlusions of the primary and secondary branches of the intracranial circulation (particularly in pediatric patients such as those following ECMO or with sickle cell anemia), and patients with saccular berry aneurysms. This type of static, angiographic technique adds little to standard spin‐echo imaging in patients with arteriovenous fistulae, neoplasms, and giant intracranial aneurysms. Limitations of the present technique include the inability to visualize slow flow lesions (e.g., giant aneurysms) and selected high flow states (arteriovenous fistulae, some severe stenoses ). © 1990 Academic Press, Inc.
pH standardization for phosphorus‐31 magnetic resonance heart spectroscopy at different temperatures
Authors: Kost Gerald J. 
Published: March 2007

AbstractIntracellular pH typically is measured by NMR using the calibrated chemical shift of the inorganic phosphate peak in phosphorus‐31 spectra. Heart Spectroscopy experiments often require measurements of intracellular pH at temperatures from 5 to 37°C. This paper provides NMR pH calibrations for this range of temperatures, a summary of calibration data reported to date, and a discussion of the factors influencing pH Standardization. © 1990 Academic Press, Inc.
Spectral editing of tumor 13C MRS in Situ
Authors: Xue Min , Ng Thian C. , Majors Anthony 
Published: March 2007

AbstractThe editing pulse sequence DEPT (D. T. Pegg, D. M. Doddrell, and M. R. Bendall, J Chem. Phys. 77, 2745 (1982)) was modified using a scheme of various composite pulses and a 16‐step phase cycling to obtain proton‐decoupled natural‐abundance 13C edited subspectra of solid tumors. A solenoidal probe including a Faraday shield and an orthogonal saddle decoupling coil was built for this purpose. © 1990 Academic Press, Inc.
Projection images of the position‐velocity joint spin density distribution
Authors: Xiang Q. S. , Nalcioglu O. 
Published: March 2007

AbstractA new concept of phase encoding called position‐velocity combined oblique Fourier phase encoding is introduced. It encodes both spatial and velocity information in a single oblique direction in the position‐velocity space. Using this method, two‐dimensional projection images of the three‐dimensional position‐velocity joint spin density distribution along different directions can be obtained. These projection images can provide detailed information on the flow system under study. The imaging of the two‐dimensional projection is less time consuming compared to three‐dimensional Fourier flow imaging and can be easily implemented on a conventional magnetic resonance imaging scannner. © 1990 Academic Press, Inc.
An apparatus for applying a mechanical massage to rat hearts inside a wide‐bore NMR spectrometer
Authors: Kushnir Tammar , Schwalb Herzl , Yaroslavsky Esther , Borman Joseph B. , Uretzky Gideon , Navon Gil 
Published: March 2007

AbstractA device for applying mechanical massage to the isolated perfused rat heart inside a wide‐bore NMR spectrometer was developed. This device exerts a squeezing pressure on a fibrillating heart placed inside a NMR spectrometer without interfering with the NMR measurements. It appears that the apparatus is important for obtaining reliable results in the postischemic reperfusion period. © 1990 Academic Press, Inc.
Cooperative T1 and T2 effects on contrast using a new driven inversion spin‐echo (DISE) MRI pulse sequence
Authors: Conturo Thomas E. , Kessler Robert M. , Beth Albert H. 
Published: March 2007

AbstractA pulse sequence is presented for obtaining a single image with combined T1/T2 weighting. T2 relaxation is made to increase intensity, in cooperation with the effect of T1 relaxation, by providing T2 weighting with a 90°‐180°‐90° driven inversion pulse triplet in an inversion recovery method. Unlike the inversion spin‐echo method having a short inversion time (TI), signals in the new driven inversion spin‐echo (DISE) method need not be negative and the most T1‐sensitive region of the recovery curve can be used. Selecting sensitivity to one relaxation time does not degrade the sensitivity to the other relaxation time. T1 sensitivity is thus extended to longer echo times (TE intervals), T2 sensitivity is extended to longer TI intervals, and the combined Tl / T2‐weighted technique with intermediate TE and T1 has highly cooperative and near‐maximal T1 and T2 effects on contrast. Intensity is not multiplicatively degraded by T1 and T2weighting so that the signal‐to‐noise of the combined T1/T2 ‐weighted method is high. High intensity and TI and T2 cooperatively occur for a much wider range of relaxation times, and especially for images heavily weighted to the pathologic intermediate and long T1 and T2 Rgime. © 1990 Academic Press, Inc.
NMR visibility of 39K and 35Cl in erythrocytes and kidney tubules
Authors: Boulanger Y. , Vinay P. 
Published: March 2007

AbstractThe NMR visibility of 39K and 35Cl has been investigated in erythrocytes and in dog renal tubules. In erythrocytes, the 39K NMR visibility was determined by comparing the signal intensities before and after hemolysis with water and by comparing the NMR and flame photometry results. Both procedures showed a NMR visibility of 100% for intracellular potassium. The visibility of intracellular chloride in erythrocytes was estimated at 40% by monitoring the intensity of the35Cl signal as a function of the hematocrit value. In the case of kidney proximal tubules, the 39K visibility appeared to be very low but could not he accurately determined due to the low sensitivity of the nucleus. The 35Cl signals for intracellular chloride in renal tubules were too broad to be detected. © 1990 Academic Press, Inc.
Spatial mapping of 23Na NMR signals by two‐dimensional rotating frame imaging
Authors: Boehmer John P. , Metz Kenneth R. , Mao Jintong , Briggs Richard W. 
Published: March 2007

AbstractThe reconstruction of two‐dimensional spatial images with 0.5‐mm resolution using radio frequency gradients generated by an NMR coil system rotated about the sample is demonstrated for 23Na. The method retains chemical shift, should be capable of mapping T1 and T2 information, and might offer sensitivity advantages for nuclides with short T2. © 1990 Academic Press, Inc.
Analysis of diabetic cataractogenesis using chemical‐shift nuclear magnetic resonance microscopy
Authors: Cheng Hong‐Ming , Aguayo James B. , Moore Gregory J. , Mattingly Mark 
Published: March 2007

AbstractWe here report the analysis of single rabbit lenses under high‐glucose stress using four‐dimensional 13C nuclear magnetic resonance (NMR) spectroscopy (three spatial and one chemical‐shift). We have produced spatial maps of lenticular metabolites (glucose, sorbitol, and lactate) with submillimeter in‐plane resolution. The production of sorbitol and its inhibition are also presented. This is the first study to report regional tissue metabolism. We expect further improvements in spatial resolution and acquisition times that will enable localized kinetic studies in intact tissues. © 1991 Academic Press, Inc.
19F nuclear magnetic resonance imaging of drug distribution in vivo: The disposition of an antifolate anticancer drug in mice
Authors: Maxwell R. J. , Frenkiel T. A. , Newell D. R. , Bauer C. , Griffiths J. R. 
Published: March 2007

AbstractThe application of 19F nuclear magnetic resonance imaging to the study of drug distribution in vivo is discussed. CB3988 (C2‐desamino‐C2‐methyl‐N 10‐propargyl‐2′‐trifluoromethyl‐5,8‐dideazafolic acid) is a fluorinated representative of a class of quinazoline an‐tifolates which act as inhibitors of thymidylate synthase and which are being evaluated for the treatment of human cancer. 19 F images were obtained in vivo from the abdomen of mice following intravenous injection of CB3988 (500 mg/kg). Time resolutions of 4 and 20 min were achieved for two‐ and three‐dimensional imaging, respectively. These images were consistent with the presence of high concentrations of drug (up to 26 mg/ml) in the gall bladder, urinary bladder, and small intestine, as confirmed ex vivo by extraction and HPLC analysis. The results indicate the potential value of 19F NMR imaging in pharmacokinetic Studies. © 1991 Academic Press, Inc.
Multisite Saturation transfer using DANTE and continuous wave
Authors: Clark Joseph F. , Harris Gale I. , Dillon Patrick F. 
Published: March 2007

AbstractThe DANTE pulse sequence was modified to produce selective resonance saturation similar to that produced by the continuous wave (CW) technique. A combined DANTE and CW saturation technique can be used to perform multisite saturation transfer experiments because of the similar saturation produced by the two techniques. © 1991 Academic Press, Inc.
In Vivo Brain Water Determination by T1 Measurements: Effect of Total Water Content, Hydration Fraction, and Field Strength
Authors: Fatouros P. P. , Marmarou A. , Kraft K. A. , Inao S. , Schwarz F. P. 
Published: March 2007

AbstractThis work is concerned with the accurate quantification of brain water content under routine clinical conditions. Gelatin solutions of varying water content are first employed as a model of an edematous brain and longitudinal relaxation measurements are performed at proton Larmor frequencies of 5, 41, 63, and 100 MHz. These are followed with in vivo measurements in an experimental animal model of brain edema at 41 MHz. The results underscore the dominant role of total water content Win the relaxation process and verify the expected linearity between 1/T1 and 1/W. A scheme is presented and experimentally verified at 41 MHz for deducing the exact relationship of 1/T1 vs 1/W at any frequency. Knowledge of this relationship along with precise measurements of 1/T1 at a given field strength permits quantitative in vivo measures of brain water content to be obtained with a precision of about 0.01. It is concluded that routine, accurate, and noninvasive brain water measurements are possible by magnetic resonance imaging in a clinical environment. © 1991 Academic Press, Inc.
Hepatic transport of the magnetic resonance imaging contrast agent Fe(III)‐N‐(3‐Phenylglutaryl)desferrioxamine B
Authors: Hoener Betty‐Ann , Tzika A. Aria , Englestad Barry L. , White David L. 
Published: March 2007

AbstractWe have studied the hepatic transport of Fe(III)‐N‐(3‐phenylglutaryl)desferrioxamine B (Fe‐PGDF). Using 59Fe‐PGDF in biliary cannulated rats we have shown that 32 ± 2% of an iv bolus dose was excreted into the bile. In animals pretreated with a saturating dose of taurocholate, oxyphenonium, or bromosulfophthalein (BSP), 25 ± 6%, 23 ± 1%, or 1.6 ± 0.8% of the dose, respectively, was excreted into the bile. Magnetic resonance images indicated that BSP blocked uptake of Fe‐PGDF by the hepatocytes. Possible enterohepatic recycling of 59Fe‐PGDF was investigated in linked rat experiments. All of the material excreted into the bile of the donor, 28 ± 10% of the dose, was recovered in the gastrointestinal tract of the recipient, but none was found in its bile or urine. These results suggested that uptake of Fe‐PGDF by the hepatocytes occurred via the BSP transporter and that no enterohepatic recycling of the contrast agent occurred. © 1991 Academic Press, Inc.
A reduced power selective adiabatic spin‐echo pulse sequence
Authors: Conolly Steven , Glover Gary , Nishimura Dwight , Macovski Albert 
Published: March 2007

AbstractWe introduce a selective adiabatic pulse sequence suitable for generating selective spin‐echoes for both MR imaging and spectroscopy. The technique is simple; one uses the echo generated by any pair of identical selective adiabatic inversion pulses. The nonlinear phase across the slice is compensated perfectly by the second π pulse. This compensation is immune to RF inhomogeneity and nonlinearity. For imaging applications, we concentrate on a reduced‐power version of the pulse sequence in which time is traded off variably for RF amplitude in the presence of a time‐varying gradient. This technique, known as variable‐rate excitation, mildly degrades the off‐resonant slice profile when applied to amplitude‐modulated pulses. We present theoretical explanations and experimental results that show that the variable‐rate adiabatic pulses are immune to off‐resonant degradation of the magnitude normally encountered in MR imaging. © 1991 Academic Press. Inc.
Comparison of human polymorphonuclear leukocytes from peripheral blood and purulent exudates by high resolution 1H MRS
Authors: May George L. , Sztelma Krystyna , Sorrell Tania C. , Mountford Carolyn E. 
Published: March 2007

AbstractHuman pus samples from various sites, including soft tissue and pleural cavity, as well as sputum from patients with cystic fibrosis have been analyzed by 1H magnetic resonance spectroscopy (MRS) and found to generate high resolution spectra. Assignments have been made for neutral lipid, amino acids, taurine, and lactate. Human peripheral blood polymorphonuclear leukocytes have also been examined and a similar spectrum containing these lipid and metabolite resonances was detected in cells stimulated with lipopolysaccharide. In unstimulated cells, only resonances from taurine and lactate were observed, suggesting that the presence of the lipid and metabolite resonances is an indicator of cellular activation of polymorphonuclear leukocytes. This is the first report of 1H MRS applied to intact human polymorphonuclear leukocytes and extends available documentation as to which types of normal and/or diseased tissue contain MR visible molecules. © 1991 Academic Press, Inc.
Diffusion of water in tissues and MRI
Authors: Hazlewood U. F. , Rorschach H. E. , Lin C. 
Published: March 2007

AbstractThe purpose of this paper is to present an overview of the diffusive behavior of water in biological tissues. The analysis shows that obstructive barriers would have to occupy very large volume fractions in order to account for the reduction in the diffusion coefficient (D) observed in biological systems. Generally, most models lead to the supposition that a substantial fraction (20–40%) of the cell water is hydration water, or that the diffusion coefficient of the cytoplasmic water is reduced substantially from the free water value. Thus, the conclusion that a substantial fraction of cell water has diffusive properties that are altered by the macromolecules of the cytoplasm seems inescapable. The impact of these findings on MRI remain to be determined. © 1991 Academic Press, Inc.
Analytical solution and verification of diffusion effect in SSFP
Authors: Carney C. E. , Wong S. T. S. , Patz S. 
Published: March 2007

AbstractAssuming that the SSFP magnetization response maintains a steady state which is penodic in the presence of diffusion, we can solve for the diffusion effect in such sequences. Formulating a Fourier series decomposition solution to the Bloch‐Torrey equation and imposing the steady‐state condition, analytical expressions describing the signal decay due to diffusion are developed. Magnetization responses for any system and sequence parameters can then be obtained. Also, sensitivity to b factor changes is quite different than standard diffusion measurement techniques. Assumptions made in the solution are verified via finite difference solutions and simulations of the Bloch‐Torrey equation.
Studies of restricted diffusion in heterogeneous media containing variations in susceptibility
Authors: Zhong Jianhui , Gore John C. 
Published: March 2007

AbstractMeasurements of water self‐diffusion in heterogeneous media by pulsed gradient spin‐echo methods depend on the precise choice of experimental parameters. This variation may reflect the presence of restricted or anisotropic diffusion, or the presence of intrinsic magnetic field gradients. In experiments at 2.0 T, restricted diffusion effects have been demonstrated in freshly excised tissues with an effective barrier radius of order 10 μm. In samples with intrinsic susceptibility variations such as tissues or gels containing dispersions of iron oxide particles, the reduction of apparent diffusion coefficient with diffusion interval can be used to estimate the degree of heterogeneity of the magnetic field in the sample. The implications of these effects for diffusion‐weighted MRI as well as their use to derive novel tissue parameters are discussed. © 1991 Academic Press, Inc.