bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of a 1.5 T static magnetic field on body temperature of man
Authors: Shellock Frank G. , Schaefer Daniel J. , Gordon Christopher J. 
Published: March 2007

AbstractReports in the literature concerning the effect of static magnetic fields on the body temperature of mammals have been contradictory and confusing. A significant increase in body temperature in human subjects exposed to the static magnetic fields used in magnetic resonance imaging (MRI) would have important safety implications. Therefore, in two separate studies we determined body temperature in 20 subjects exposed to a 1.5 T static magnetic field. One group of subjects (Group I, N = 9) had sublingual pocket temperature measured immediately before and after a 60 min exposure, while another group of subjects (Group II, N = 11) had esophageal temperature determined at 2 min intervals during a 20 min exposure. No statistically significant changes in body temperatures were observed in either Group I or II subjects during exposure to the 1.5 T static Magnetic field. We conclude that a relatively intense static magnetic field has no effect on body temperature of normal human subjects. © 1986 Academic Press, Inc.
A perfusion technique for 13C NMR studies of the metabolism of 13C‐labeled substrates by mammalian cells
Authors: Lyon Robbe C. , Faustino Patrick J. , Cohen Jack S. 
Published: March 2007

AbstractWe describe an improved perfusion system designed for NMR studies with 13C‐labeled metabolites. Using this system we have monitored the uptake and metabolism of [13C]acetate and [13]Clglucose in pooled human lymphocytes cast in an agarose gel thread. © 1986 Academic Press, Inc.
Fourier imaging using rf phase encoding
Authors: Maudsley A. A. 
Published: March 2007

AbstractFourier imaging methods encode information in the amplitudes and phases of a NMR signal over multiple acquisitions. Several of the techniques that can be used for encoding this information are reviewed and a general theory of phase encoding presented. The discussion is then extended to include encoding as part of the rf excitation sequence. Radiofrequency phase encoding can be obtained using tailored excitation techniques or special‐purpose rf field gradient coils, and may be applied prior to excitation or incorporated within the excitation or refocusing pulses. This phase‐encoding method may be used for spatial and spectral discrimination, as well as being combined with other methods of image formation. An example of the proposed imaging method is described which enables Fourier imaging of short T2 signals. © 1986 Academic Press, Inc.
RARE imaging: A fast imaging method for clinical MR
Authors: Hennig J. , Nauerth A. , Friedburg H. 
Published: March 2007

AbstractBased on the principles of echo imaging, we presnet a method to acquire sufficient data for a 256 × 256 image in from 2 to 40s. The image contrast is dominated by the transverse relaxation time T2 Sampling all projections for 2D FT image reconstruction in one (or a few) echo trains leads to image artifacts due to the different T2 weighting of the echo. These artifacts cannot be described by a simple smearing out of the image in the phase direction. Proper distribution of the phase‐encoding steps on the echoes can be used to minimize artifacts and even lead to resolution enhancement. In spite of the short data acquisition times, the signal amplitudes of structures with long T2 are nearly the same as those in a conventional 2D FT experiment. Our method, therefore, is an ideal screening technique for lesions with long T2. © 1986 Academic Press, Inc.
Detection of metabolites in rabbit brain by 13C NMR spectroscopy following administration of [1‐13C]glucose
Authors: Behar K. L. , Petroff O. A. C. , Prichard J. W. , Alger J. R. , Shulman R. G. 
Published: March 2007

Abstract1H‐decoupled 13C NMR spectra (20.2 MHz) of the living rabbit brain were collected with a surface coil following the intravenous infusion of [1‐13C]glucose. Within 15 min of infusion, the α and β anomers of glucose were detected and, shortly thereafter, the carbon atoms at positions C4, C3, and C2 of glutamate and(or) glutamine. After reductions of inspired oxygen from 30 to 5%, lactate C3 was detected. The intensity of the lactate resonance rose progressively during hypoxia and later fell during recovery with oxygen. The 13C fractional isotopic enrichment of arterial blood glucose was measured by 1H NMR providing information on the rate and extent of blood glucose labeling. © 1986 Academic Press, Inc.
Correlative study of properties of water in biological systems using ultrasound and magnetic resonance
Authors: Sehgal Chandra M. , Greenleaf James F. 
Published: March 2007

AbstractUltrasonic and nuclear magnetic resonance properties of media rich in water are investigated. The chemical shift of the water proton in pure water, aqueous solutions of tertiary butanol, and sodium chloride is shown to be linearly correlated to the reciprocal of sound speed in these media. A new method of determining the self‐diffusion coefficient of water by using acoustic nonlinearity and sound speed is proposed. The method is tested on a on a variety of media that include pure water, aqueous solutions of glycerol, serum albumin, egg constituents, plant tissues, frog muscle and liver, and excised human tissues. In all the cases the results are found to compare closely to diffusion coefficients measured by magnetic resonance. The results presented here indicate that the acoustic and magnetic resonance modalities, though inherently different in their origin, can provide closely related information on the properties of water. © 1986 Academic Press, Inc.
Rapid Fourier imaging using steady‐state free precession
Authors: Hawkes R. C. , Patz S. 
Published: March 2007

AbstractReversal of the read gradient in a SSFP imaging experiment allows a full spin echo to be collected in the interval τ between successive rf pulses. Orthogonal gradient pulses are used to dephase and subsequently rephase the transverse magnetization each τ enabling 2D or 3D Fourier techniques. The minimum data collection time per slice in the 3D technique is 3.1 s (128 × 256). For a 2D data collection, an oscillating bipolar sawtooth gradient is used to select the slice. Each phase‐encode value must be averaged over an equivalent portion of the oscillating slice‐selection gradient and this condition gives a minimum of 25 s for 2D data collection. Excellent slice selection is achieved with less than 5% of the signal lying outside the slice profile central lobe. Images at 0.14 T show tissue contrast may be manipulated by changing the rf pulse angle, an example of which is the presence or absence of gray/white matter contrast at rf pulse angles of 30 and 90°, respectively. The pulse angle θ dependence of five samples with different values of T2/T1 was measured and numerically calculated with good agreement between theory and experiment for θ ⩽ 90°. © 1987 Academic Press, Inc.
31P magnetic resonance spectroscopy of mesenteric ischemia
Authors: Kass Deborah A. , Banville Debra L. , Gooding Charles A. , James Thomas L. 
Published: March 2007

Abstract31P magnetic resonance spectroscopy (MRS) was performed in vivo on normal and ischemic rat intestine. Within 3 min after induction of ischemia, there is a dramatic fall in adenosine triphosphate (ATP) and rise in inorganic phosphate (Pi). Our results suggest that MRS may prove useful in the early detection of mesenteric ischemia. © 1987 Academic Press Inc.
Quadrature detection surface coil
Authors: Hyde James S. , Jesmanowicz A. , Grist Thomas M. , Froncisz W. , Kneeland J. Bruce 
Published: March 2007

AbstractA surface coil assembly consisting of two interleaved coplanar resonators that are intrinsically decoupled from each other is described for imaging at 1.5 T. Vector reception fields on‐axis at 3 cm depth are orthogonal and of equal magnitude. Both components of magnetization were received and combined resulting in a 2 1/2 improvement in signal‐to‐noise for temporomandibular joint images. © 1987 Academic Press, Inc.
Biological tissue simulation and standard testing material for MRI
Authors: De Luca F. , Maraviglia B. , Mercurio A. 
Published: March 2007

AbstractThe polyacrylamide gel is proposed here as a phantom material for NMR imaging. This substance has electrical and NMR relaxation characteristics very similar to those of biological tissues. The thermal and time stabilities also make this material a convenient standard for MRI. © 1987 Academic Press, Inc.
MR angiography by selective inversion recovery
Authors: Nishimura Dwight G. , Macovski Albert , Pauly John M. , Conolly Steven M. 
Published: March 2007

AbstractA modified inversion‐recovery sequence is introduced which performs subtraction angiography by varying time‐of‐flight effects of blood flowing into an imaged slab. The selective 180° excitation inverts different regions between measurements to isolate arterial and/or venous blood. On normal human subjects, high‐resolution carotid artery angiograms have been obtained. © 1987 Academic Press, Inc.
1H NMR relaxation measurements of human tissues in situ by spatially resolved spectroscopy
Authors: Luyten Peter R. , Anderson Charles M. , den Hollander Jan A. 
Published: March 2007

AbstractSpatially resolved spectroscopy (SPARS) is a method for obtaining high‐resolution NMR spectra of well‐defined volumes of human tissues in situ. This method was combined with the Carr‐Purcell‐Meiboom‐Gill multiple‐echo sequence for T2, and with inversion recovery for T1 relaxation measurements. Relaxation times obtained by SPARS were compared with standard CPMG and IR relaxation measurements and with imaging methods, using a number of relaxation phantoms. Spectroscopically resolved relaxation data of human bone marrow, muscle, and adipose tissue in situ were obtained. T2 measurements of human adipose tissue gave different results when using single‐echo measurements rather than the CPMG method. This difference was interpreted as a J modulation effect, which shows up in fatty acid proton resonances. This J modulation effect influences the intensity of adipose tissue in routine 1H NMR images. © 1987 Academic Press, Inc.
31P magnetization transfer studies of creatine kinase kinetics in living rabbit brain
Authors: Degani Hadessa , Alger Jeffery R. , Shulman Robert G. , Petroff Ognen A. C. , Prichard James W. 
Published: March 2007

AbstractThe kinetics of the CK reaction in the living rabbit brain was studied by three 31P magnetization transfer methods: inversion recovery (IR), inversion transfer (IT), and steadystate saturation transfer (SSST). Longitudinal relaxation rates (T−1) were determined from IR and IT experiments. The values were 0.88 ± 0.08 s−1 for PCr and 2.45 ± 0.39 s−1 for γ‐ATP. Analysis of the results of SSST experiments in which γ‐ATP was saturated yielded a forward rate constant kF of 0.53 ± 0.07 s−1. Upon saturation of PCr no change in the γ‐ATP signal could be detected in SSST. An average reverse rate constant (kR ± S.D.) of 0.52 ± 0.04 s−1 was estimated by analyzing IT data from three experiments with selective inversion of γ‐ATP. The standard error of kR was 50%. The average [PCr]/[ATP] of 1.21 ± 0.16 together with the values of kF and kR yielded a forward‐to‐reverse flux ratio of 1.23. Within our limits of accuracy this ratio was not significantly different from 1.0, thus suggesting that in the brain the forward and reverse CK fluxes are equal. © 1987 Academic Press, Inc.
Multiecho magnetic resonance angiography
Authors: Dumoulin C. L. , Souza S. P. , Feng H. 
Published: March 2007

AbstractSeveral pulse sequences which generate projected MR angiograms are presented. These pulse sequences exploit multiple‐gradient refocused echoes to obtain several independent angiograms, which can be combined or separately analyzed to provide more information than an individual angiogram. For example, a series of angiograms, each with a different projection axis, can be obtained in the time required to obtain a single angiogram using a single‐echo method. If the view angle of each echo is the same, then the acquired angiograms can be added to enhance the signal‐to‐noise ratio. Another pulse sequence simultaneously obtains two or more angiograms, sensitive to orthogonal flow components of the overall blood flow. These angiograms are then added to give an angiogram which is sensitive to flow in all directions. © 1987 Academic Press, Inc.
Proton transverse relaxation rate of 17O‐enriched water
Authors: Yeung Hong N. , Lent Arnold H. 
Published: March 2007

AbstractProton transverse relaxation rates of 17O‐enriched water at pH in the neutral range were determined with isotopic compositions of 17O varying from natural abundance to 5%. Meiboom's account of the proton T caused by the scalar interaction between the proton and 17O is generalized to accommodate new data. The generalized formulation covers 17O enrichment above the limit to which Meiboom and his co‐worker constrained all their work.
Effects of slice selection and diffusion on T2 measurement
Authors: Wong S. T. S. , Roos M. S. 
Published: March 2007

AbstractThis study examines slice selection and diffusion as sources of systematic error in T2 estimates obtained from imaging experiments. The selective refocusing pulses in a multislice, two‐echo, spin‐warp experiment cause slice profiles of sequential echoes to change in shape. This results in bias in T2 images calculated from the two‐echo data set. A method to correct the bias is presented. The effect of diffusion on T2 images obtained with typical two‐echo imaging sequences was found to be negligible. © 1987 Academic Press, Inc.
Optimizing the precision in T1 relaxation estimation using limited flip angles
Authors: Wang Henry Z. , Riederer Stephen J. , Lee James N. 
Published: March 2007

AbstractIn this article we describe the precision in the estimation of the spin–lattice relaxation time TI from MRI signals acquired for various flip angles with the repetition time TR held constant. We review the estimation procedure itself and present a model for the propagation of noise in the signal into the calculated TI. This model is verified by both Monte Carlo simulations and experimental data taken on image phantoms. Based on this model, we find that for a given TR/TI there exist two optimal flip angles that will minimize the uncertainty in the estimated TI. We also show how two optimal angles can be selected for a given range of TR/TI values. In addition, T1 estimation using the two optimal angles can be comparable to or better than using multiple evenly spaced angles. Finally, in an initial comparison with the two‐point saturation recovery method of calculating T1, results for equal total scanning time TRTot suggest that for T1 > 0.5 TRTot, the limited flip angle approach gives better TI precision whereas for TI < 0.5 TRTot, the saturation recovery approach is better. © Academic Press, Inc.
Visibility of mammalian hepatic glycogen to the NMR experiment, in vivo
Authors: Shalwitz Robert A. , Reo Nicholas V. , Becker Nancy N. , Ackerman Joseph J. H. 
Published: March 2007

AbstractAn in vivo 13C NMR study was performed to investigate whether the relaxation properties of the C‐1 carbon of the glucopyranose residues of glycogen changed as the molecule increased in size. There was no change in resonance intensity or linewidth. Therefore, no significant change in T1, or T2 was observed. © Academic Press, Inc.
19F NMR imaging of blood oxygenation in the brain
Authors: Eidelberg D. , Johnson G. , Barnes D. , Tofts P. S. , Delpy D. , Plummer D. , McDonald W. I. 
Published: March 2007

AbstractPerfluorcarbon (PFC) emulsions have been developed as oxygen carrying blood substitutes. High fluorine concentrations allow them to be used in 19F NMR imaging of blood vessels. Furthermore, 19F relaxation times in PFCs are dependent on oxygen tension (pO2) so that NMR imaging may provide a noninvasive method of measuring spatially localized pO2 values in vivo. Using these principles, we have formed 19F images and calculated pO2 maps of the cat brain. © 1988 Academic Press, Inc.
Renal imaging studies at 1.5 and 9.4 T: Effects of diuretics
Authors: Sarkar Susanta K. , Holland George A. , Lenkinski Robert E. , Mattingly Mark A. , Kinter Lewis B. 
Published: March 2007

AbstractWe have studied the effects of two diuretics, selective for renal cortical (furosemide) and inner medullary (vasopressin antagonist) water handling, in rat kidney at 1.5 T and find that furosmide completely dissipates the cortical‐inner medullary T2 gradient whereas the vasopressin antagonist has little effect. This phenomenon appears to be related to changes in luminal water content. We also demonstrate the feasibility of obtaining live mouse kidney images with a resolution of 100 × 100 × 700 μm at 9.4 T. © 1988 Academic Press, Inc.
Patient anesthesia and monitoring at a 1.5‐T MRI installation
Authors: Karlik S. J. , Heatherley T. , Pavan F. , Stein J. , Lebron F. , Rutt B. , Carey L. , Wexler R. , Gelb A. 
Published: March 2007

AbstractThis paper describes the facilities successfully used to provide patient monitoring and anesthesia support in a 1.5‐T imaging installation. The requirements for the MRI site for anesthetic gases, shielded power, and radiofrequency ports are outlined. Specific modifications in anesthesia machines, anesthesia art, laryngoscope, mercury sphygmomanometer, oximeter, and remote blood pressure devices are described. Additional aspects of patient monitoring and support, e.g., electrocardiogram and pressure infusion, are also discussed. © 1988 Academic Press, Inc.
Investigation of a whole‐body receiver coil operating at liquid nitrogen temperatures
Authors: Hall A. S. , Barnard B. , McArthur P. , Gilderdale D. J. , Young I. R. , Bydder G. M. 
Published: March 2007

AbstractThis communication describes the design and application of a receiver coil operating at liquid nitrogen temperature and intended as a surface coil in a whole‐body imager. Its particular application is seen as the external receiver for parasitic internal or implanted detectors. © 1988 Academic Press, Inc.
Heating effects of metallic implants by MRI examinations
Authors: Buchli R. , Boesiger P. , Meier D. 
Published: March 2007

AbstractMagnetic radiofrequency fields applied in magnetic resonance imaging examinations induce electrical currents in metallic implants. These eddy currents may heat up the implants and thus may be capable of causing localized tissue heating. The rf power deposition and the joule heating of the implant can be calculated by solving Maxwell's equations for the specific problem. First, extreme in vitro worst‐case experiments were performed with a large and very thin aluminum sheet, which was placed in a 1.5‐T MRI device in a position parallel to the magnetic rf field. In agreement with the theoretical results the temperature rise of a thermally insulated sheet amounted to only 0.08oC after a 15‐min MRI examination at 64 MHz. No temperature rise in the aluminum sheet could be measured for a sheet immersed in a saline solution. Second, in vitro experiments with a hip joint prosthesis and an osteosynthetic plate were performed to confirm the theoretical results, which predict nearly no temperature rise in the metallic implants. No temperature rise in the implants could be measured. © 1988 Academic Press, Inc.
Human in vivo phosphate metabolite imaging with 31P NMR
Authors: Bottomley P. A. , Charles H. C. , Roemer P. B. , Flamig D. , Engeseth H. , Edelstein W. A. , Mueller O. M. 
Published: March 2007

AbstractPhosphorus (31P) spectroscopic images showing the distribution of high‐energy phosphate metabolites in the human brain have been obtained at 1.5 T in scan times of 8.5 to 34 min at 27 and 64 cm3 spatial resolution using pulsed phase‐encoding gradient magnetic fields and three‐dimensional Fourier transform (3DFT) techniques. Data were acquired as free induction decays with a quadrature volume NMR detection coil of a truncated geometry designed to optimize the signal‐to‐noise ratio on the coil axis on the assumption that the sample noise represents the dominant noise source, and self‐shielded magnetic field gradient coils to minimize eddy‐current effects. The images permit comparison of metabolic data acquired simultaneously from different locations in the brain, as well as metabolite quantification by inclusion of a vial containing a standard of known 31P concentration in the image array. Values for the NMR visible adenosine triphosphate in three individuals were about 3 mM of tissue. The ratio of NMR detectable phosphocreatine to ATP in brain was 1.15 ± 0.17 SD in these experiments. Potential sources of random and systematic error in these and other 31P measurements are identified. © 1988 Academic Press, Inc.
Reactive hyperemia monitored on rat muscle using perfluorocarbons and 19F NMR
Authors: Authier Bertrand 
Published: March 2007

AbstractPerfluorinated blood substitutes can be detected by 19F NMR in vivo in small concen‐ trations. Reactive hyperemia was induced in rat leg by the transient application of a tourniquet, causing a 50% increase in 19F NMR signal. These results show that this method can be used to monitor the kinetics of tissue perfusion. © 1988 Academic Press, Inc.
Electron spin resonance imaging of tissues with lipid‐rich areas
Authors: Bačič G. , Walczak T. , Demsar F. , Swartz H. M. 
Published: March 2007

AbstractElectron spin resonance imaging and spectroscopy of lipid‐rich samples were studied at 9 GHz. Using both lipid‐ and aqueous‐soluble nitroxides good delincation of fat‐ and muscle‐rich regions of tissue was obtained. Several different principles can be used to differentiate between these types of tissues and potentially between different types of lip‐ids. These principles include lipophilicity of nitroxides, viscosity (which is higher in lipids), oxygen solubility (oxygen is four times more soluble in lipids), and the distribution of paramagnetic metal ions. These techniques have potential applicability for directly studying metabolism and oxygen concentration in tissues by ESR techniques and for investigating potential contrast agents for in vivo NMR techniques. © 1988 Academic Press, Inc.
Boron‐11 MRI and MRS of intact animals infused with a boron neutron capture agent
Authors: Kabalka George W. , Davis Mark , Bendel Peter 
Published: March 2007

AbstractBoron neutron capture therapy (BNCT) depends on the delivery of boron‐containing drugs to a targeted lesion. Currently, the verification and quantification of in vivo boron content is a difficult problem. Boron‐11 spectroscopy was utilized to confirm the presence of a dimeric sulfhydryl dodecaborane BNCT agent contained in an intact animal. Spectroscopy experiments revealed that the decay time of transverse magnetization of the boron‐11 spins was less than 1 ms which precluded the use of a 2DFT imaging protocol. A back‐projection protocol was developed and utilized to generate the first boron‐11 image of a BNCT agent in the liver of an intact Fisher 344 rat. © 1988 Academic Press, Inc.
A method for correctly setting the rf flip angle
Authors: Perman William H. , Bernstein Matt A. , Sandstrom John C. 
Published: March 2007

AbstractCurrently the accepted method for setting the correct rf power levels to achieve 90° and 180° rf pulses for MR imaging is to peak the echo amplitude of a rf spin‐echo sequence. The echo amplitude of this α‐2α pulse sequence is proportional to sin3(α) and has a relatively broad maximum. Recently another method for setting the rf flip angle by maximizing the ratio of the stimulated echo to the primary echo amplitudes (in a 3α sequence) demonstrated accuracy similar to that of the spin‐echo method using a shorter repetition time. We present a new, more sensitive, and more accurate method for setting the correct rf power levels for 90° and 180° rf pulses. In this method, based upon the stimulated echo pulse sequence, we are able to accurately set the rf power to within ±0.1 dB by minimizing the signal amplitude of the third spin echo. This null method works for both selective and nonselective rf pulses of flip angle 90° or 180°, allowing the user to accurately adjust the relative amplitudes of the four rf pulse types within a single pulse sequence. © 1989 Academic Press, Inc.