bluuebunny/crossref_metadata_2025_split huggingface dataset:
9.4‐T NMR microimaging studies of hepatic metastases of human colorectal tumors in nude mice
Authors: Sarkar Susanta K. , Clark Robert K. , Rycyna Robert E. , Mattingly Mark A. , Greig Russell 
Published: March 2007

AbstractWe have applied NMR microimaging at 9.4 T to detect metastatic deposits in the liver of nude mice noninvasively, using an animal model for metastatic colon cancer that mimics several aspects of the human disease. Images were obtained with a resolution of 100 X 100 X 900 μm and the tumor deposits were clearly distinguished from the normal liver tissue with excellent contrast. Comparison of NMR images with corresponding histologic sections indicates that lesions as small as 900 μm were detected. © 1989 Academic Press, Inc.
Phase‐distortion‐free in vivo surface coil proton spectroscopy
Authors: Alger J. R. , Brunetti A. 
Published: March 2007

AbstractA 1‐17 water suppression pulse sequence for phase‐distortion‐free surface coil NMR spectroscopy was constructed and tested in vivo on cat brain. The sequence produces brain spectra free of phase distortions, but some degradation of water suppression quality compared to closely related sequences which produce phase distortions was observed. © 1989 Academic Press, Inc.
Snapshot flash mri. applications to t1, t2, and chemical‐shift imaging
Authors: Haase A. 
Published: March 2007

AbstractSnapshot FLASH magnetic resonance imaging techniques have been developed to enable real‐time imaging of MR parameters. The first realization of the method is based on a 64 × 128 FLASH tomogram acquired within 200 ms, using improved MR system hardware conditions. The soft tissue contrast obtained in FLASH MRI almost disappears by using flip angles of less than 5° and repetition times of 3 ms. This work describes extensions of FLASH MRI placing conventional MR experiments before the whole imaging sequence. This creates images of any desired contrast without changing the measuring time. Examples of inversion‐recovery T1, spin‐echo T2, chemical‐shift‐selective, and spectroscopic FLASH MRI are presented. Further extensions to real‐time MRI of blood vessels, diffusion coefficients, combination with two‐dimensional MR spectroscopy experiments, and other nuclei are discussed.
Detection of metabolites in body fluids and biological tissue by a 1d soft cosy technique
Authors: Stryjewski Detlef , Oschkinat Hartmut , Leibfritz Dieter 
Published: March 2007

AbstractWith a semiselective ID COSY, related to the soft COSY sequence, metabolites with concentrations of a few millimolar can be detected, while highly abundant molecules as water or lipids are efficiently suppressed.
The crossover surface coil: an efficient in vivo nmr detector
Authors: Nagel Timothy L. , Stolk Jacob A. , Alderman Donald W. , Schoenborn Robin , Schweizer Martin P. 
Published: March 2007

AbstractThe crossover surface coil is constructed with two turns of copper foil using a unique transposition construction which incorporates an explicit center tap ground of the widened bottom layer. The coil reduces dielectric and inductive losses by effective shielding of electric fields and uniform distribution of magnetic fields for minimum Q losses upon loading of the coil. Flexible, copper foil construction permits easy conformation to tissues of interest, enhancing coil performance. Construction details of the crossover coil and Q data for coils of various sizes operating at a number of frequencies are given.
A study of optimization of the complex hyperbolic secant inversion pulses
Authors: Mao Jintong , Virapongse C. , Fitzsimmons J. R. 
Published: March 2007

AbstractThe conjugate gradient method is used to optimize the inversion slice profile produced by complex hyperbolic secant selective pulses. An improved quality is obtained for the inversion slice profile at a price, however, of a lower immunity to the amplitude variation of radiofrequency pulses.
In vitro magnetic resonance microimaging of the spinal cord
Authors: Lemaire C. , Duncan E. G. , Solsberg M. D. , Armstrong R. L. 
Published: March 2007

AbstractA 2.0‐T small animal imager equipped with 3 G/cm imaging gradient coils was used to obtain images of en bloc segments of the vertebral column containing the rat spinal cord and of a cadaveric human spinal cord. These images demonstrate the applicability of MR micro‐imaging techniques to the study of interesting problems in medicine and biology. Images of transverse sections of the spinal cord with in‐plane resolution of better than 0.1 mm were obtained from slices 1 mm thick. The images of normal and injured rat spinal cord vividly show that spinal cord injury in the rat can be visualized using MRI techniques. The MR image of the cadaveric human spinal cord shows subanachroid gray and white matter structures. A comparison with a photomicrograph indicates that it is the superior contrast of the MR image that leads to increased conspicuity. © 1990 Academic Press, Inc.
In vivo detection of injected free radicals by overhauser effect imaging
Authors: Grucker D. 
Published: March 2007

AbstractProton dynamical polarization is a method which unites the advantages of continuous wave ESR sensitivity and pulsed NMR imaging in order to localize free radicals. Injected nitroxide has been imaged for the first time in living rats. The high sensitivity of this method to oxygen is demonstrated. © 1990 Academic Press, Inc.
Microcirculatory considerations in NMR flow imaging
Authors: Bassingthwaighte James B. 
Published: March 2007

AbstractRegional flow estimation can be accomplished either by measuring the concentration of a deposited tracer whose extraction during transit through the organ is 100%, or by observing the time course of concentration of a tracer whose transport passage through the organ is flow‐limited. The deposition method is simpler and applies not only to micro‐spheres or other large particles that lodge in the microcirculation, but also to molecular markers which are trapped. It has the advantage of having substantial time in which to observe the local concentrations by external detection. In contrast, flow‐limited markers must traverse the tissue without barrier limitation or other diffusional influence on the exchange. When the marker is limited strictly to the intravascular space, the transit time through the organ is short and observations must be made rapidly with a high resolution technique. An indicator which distributes throughout a large volume of distribution within the tissue has a slower washout, providing more time in which to make observations; tracer water is a suitable marker, except perhaps in the brain. For flow measurement by NMR, markers which fulfill these criteria without causing side effects are needed. © 1990 Academic Press, Inc.
The application of phase shifts in NMR for flow measurement
Authors: Firmin D. N. , Nayler G. L. , Kilner P. J. , Longmore D. B. 
Published: March 2007

AbstractA brief overview of the history of the application of phase shifts in NMR, and in particular NMR imaging, is presented. The imaging methods include direct phase mapping, Fourier flow imaging (where the flow data are Fourier transformed into one dimension of an image), and alternative methods, where flow‐related phase shifts are utilized for flow measurement from the magnitude of the signal. A discussion then follows of the principal errors that can affect the accuracy of the various flow imaging techniques, with particular reference to the phase mapping methods that have been used extensively in our institution. The results from a number of experiments are included to illustrate the extent of the errors and methods of removing or minimizing these effects are Suggested. © 1990 Academic Press, Inc.
A double quantum coherence transfer proton NMR spectroscopy technique for monitoring steady‐state tumor lactic acid levels in Vivo
Authors: Freeman D. M. , Sotak C. H. , Muller H. H. , Young S. W. , Hurd R. E. 
Published: March 2007

AbstractIf proton nuclear magnetic resonance (1H NMR) spectroscopy is to provide a clinically useful modality for monitoring tumor growth and treatment, the technique must be able to unambiguously detect steady‐state metabolite concentrations in human tumors and differentiate these from normal tissue levels. To address this problem, a two‐dimensional double quantum coherence transfer spectroscopy (2DDQCT) method was developed and tested in a series of tumor cell lines implanted in mice. Lactate‐edited proton NMR spectra were determined from a roughly 1‐cm3 region of interest in EMT6, RIF‐1, and fibroma. In two‐dimensional data matrix representations of the 2DDQCT experiments (double quantum frequency on the vertical axis and chemical shift on the horizontal axis) the lactate signal (330 Hz with the transmitter set at the water resonance) was well‐resolved from lipid (480 Hz, 600 Hz). The resolution in the double quantum dimension was also sufficient to conclude that a detectable level of alanine, which would reside at 358 Hz, was not present in the three tumor types. Following the NMR experiment, tumors were chemically assayed for lactate giving 8.17, 9.1, and 6.73 μmol/g wet wt for RIF‐1, EMT6, and fibroma, respectively. This technique is likely to provide a noninvasive method for monitoring the steady‐state lactic acid levels in small tumors before and after therapy, as well as in tissues with impaired oxygen delivery using clinical and research NMR Systems. © 1990 Academic Press, Inc.
MRI signal loss due to microcirculation: Phantom studies
Authors: Duewell S. , Wüthrich R. , Buck A. , von Weymarn C. , von Schulthess G. K. 
Published: March 2007

AbstractIn order to study perfusion effects in MRI under different conditions we developed two different kinds of phantoms. The first phantom exhibits linear capillary flow with several capillaries within one voxel. The second consists of an anion exchange resin with beads forcing the spins to change directions such that they undergo accelerations and decelerations. Both phantoms were imaged with standard spin‐echo sequences and signal intensities were quantified at various echo times. Qualitative and quantitative agreements of the data with the results obtained by computations of signal toss due to spin‐phase phenomena are excellent, thus suggesting that perfusion effects can be fully understood using these phenomena. It is argued that the phantoms used in conjunction with conventional spin‐echo sequences represent a realistic model for studying true capillary networks in conjunction with specialized perfusion sequences. © 1990 Academic Press, Inc.
Sensory stimulation by time‐varying magnetic fields
Authors: Cohen Mark S. , Weisskoff Robert M. , Rzedzian Richard R. , Kantor Howard L. 
Published: March 2007

AbstractWhen two human volunteers were imaged with magnetic field gradient dB/dt of 61 T/s RMS, the subjects reported, to our surprise, feeling muscular twitches synchronous with gradient pulses over repeated experiments. No adverse or sustained effects were seen. Experiments in a canine, intended to assess the safety of MR imaging with dB/dt of up to 66 T/s RMS, failed to induce detectable changes in the electrocardiogram or to show any signs of gross response to gradient pulsing. Although these data are preliminary, and largely anecdotal, they suggest a level above which such stimulation may occur. We believe that this is the first report of direct human stimulation in an MRI device and that determination of the stimulation threshold may have impact on the selection of appropriate operating points for magnetic imaging systems. © 1990 Academic Press, Inc.
Spin echo 31P spectroscopic imaging in the human brain
Authors: Maudsley A. A. , Twieg D. B. , Sappey‐Marinier D. , Hubesch B. , Hugg J. W. , Matson G. B. , Weiner M. W. 
Published: March 2007

AbstractSpectroscopic imaging of phosphorus metabolites in the human brain has been carried out with two data acquisition methods: by observation of the free induction decay (FID) signal and by a short spin echo sequence. The resultant spectral images and spatially resolved spectra are compared. Spin echo observation is found to provide spectra of superior quality, and by suitably selecting the sequence timing, no significant increase in T2 losses, as compared with the FID method, is encountered. 31P images with approximately 3.5 cm spatial resolution are obtained within times of 37 min at 2.0 T field strength. © 1990 Academic Press, Inc.
Phosphate metabolite imaging and concentration measurements in human heart by nuclear magnetic resonance
Authors: Bottomley Paul A. , Hardy Christopher J. , Roemer Peter B. 
Published: March 2007

AbstractCardiac‐gated phosphorus (31P) nuclear magnetic resonance (NMR) spectroscopic imaging with surface coils resolves in three dimensions the spatial distribution of high energy phosphate metabolites in the human heart noninvasively. 31P spectra derive from 6‐ to 14‐cm3 volumes of myocardium in the anterior left ventricle, septum, and apex, at depths of up to about 8 cm from the chest, as identified by proton (1H) NMR anatomical images acquired without moving the subject. Spectroscopic images are acquired in 9 to 21 min at 1.5 T. Metabolite concentrations are quantified with reference to a standard located outside the chest, yielding normal in vivo concentrations of phosphocreatine and adenosine triphosphate of about 11.0 ± 2.7 (SD) and 6.9 ± 1.6 μmol/g of wet heart tissue, respectively. High energy phosphate contents did not vary significantly with location in the normal myocardium, but 2,3‐diphosphoglycerate signals from blood varied with Subject and location. © 1990 Academic Press, Inc.
Relaxometry of brain: Why white matter appears bright in MRI
Authors: Koenig S. H. , Brown R. D. , Spiller M. , Lundbom N. 
Published: March 2007

AbstractThe remarkable success of magnetic resonance imaging of adult brain relates to the unusually large ratio of the longitudinal relaxation rates 1 / T1 of white and gray matter, ∼2:1 at physiological temperature and traditional imaging fields. Several investigators have conjectured that myelin is the source of the greater 1 / T1 of white matter without, however, suggesting details of the molecular mechanisms responsible. From measurements of the magnetic field dependence of 1 / T1 (NMRD profiles) of adult and neonatal gray and white matter at 5 and 35°C, we find a thermally activated contribution to the NMRD profile of adult white matter that is not present in the profiles of either adult gray or neonatal gray and white matter. We attribute this contribution to myelin and develop a quantitative model that accounts for the unique relaxation behavior of myelinated white matter. We find that myelin water, 15% of the total, has a relatively short T1 that arises from an unexpectedly large interaction with myelin lipid; when cast in terms of an interaction over the entire myelin bilipid‐water interface, it is sevenfold greater than the analogous protein‐water interfacial interaction. Its magnitude remains to be accounted for, but cholesterol, known to alter the relaxation rates of lipid protons, may play an important role. The contribution of myelin to 1/T1 at physiological temperatures is attributed to thermally activated transmembrane diffusion of water and, hence, more rapid mixing of axonal and the rapidly relaxing myelin water molecules. © 1990 Academic Press, Inc.
Functional cerebral imaging by susceptibility‐contrast NMR
Authors: Belliveau John W. , Rosen Bruce R. , Kantor Howard L. , Rzedzian Richard R. , Kennedy David N. , McKinstry Robert C. , Vevea James M. , Cohen Mark S. , Pykett Ian L. , Brady Thomas J. 
Published: March 2007

AbstractIn vivo measurement of cerebral physiology by dynamic contrast‐enhanced NMR is demonstrated. Time‐resolved images of the cerebral transit of paramagnetic contrast agent were acquired using a new ultrafast NMR imaging technique and a novel mechanism of image contrast based on microscopic changes in tissue magnetic susceptibility. Global hypercapnia in dogs was used to establish the relationship between susceptibility‐induced signal change and brain blood volume, and the response of gray and white matter to this microvascular stimulus was measured. © 1990 Academic Press, Inc.
Is the detection of fucose cancer markers by 2D 1H NMR unequivocal?
Authors: Phillips P. S. , Herring F. G. 
Published: March 2007

AbstractFucose is believed to be a marker for cancer that may be detectable by the 2D proton NMR (COSY) of human plasma. However, the COSY technique is time consuming and prone to error. These problems may be alleviated by using the SUPERCOSY pulse sequence; this technique shows that there are many other cross peaks in the region (1.3, 4.2 ppm) which are not readily distinguishable from fucose. © 1990 Academic Press, Inc.
In Vivo13C imaging enhanced by polarization transfer
Authors: Ueshima Yasuhiro , Yamai Satoshi , Ikehira Hiroo , Hashimoto Takahiro , Mori Kazuya , Maki Takeshi , Fukuda Hiroshi , Tateno Yuklo 
Published: March 2007

AbstractCarbon‐13 NMR imaging has been combined with 1H‐13C polarization transfer to improve image quality. Natural‐abundance carbon images of Fischer rat bodies were obtained within a few minutes. Next 13C‐labeled glucose was administered orally to rats, and spatial distributions of glucose and its derivatives were observed with this technique. © 1990 Academic Press, Inc.
Effects of velocity profile of to‐and‐fro pulsatile flow on magnetic resonance signal intensity
Authors: Fujita N. , Harada K. , Murakami T. , Akai Y. , Kozuka T. 
Published: March 2007

AbstractThe effects of to‐and‐fro pulsatile flow, i.e., an oscillatory fluid motion with no net flow, on signal intensity in gated spin‐echo magnetic resonance imaging are considered both theoretically and experimentally. On the basis of hydrodynamic principles, to‐and‐fro pulsatile flow at large Womersley numbers consists of uniform inner flow and boundary‐layer‐type flow adjacent to a tube wall. Therefore, the velocity profile is “trapezoidal” rather than parabolic at all times during the pulsation period. Contrary to the absence of phase dispersion and loss of signal within the inner flow where no velocity gradient exists, large velocity differences cause phase dispersion and, hence, loss of signal within the boundary layer, whose thickness is inversely proportional to the Womersley number. An understanding of these features of to‐and‐fro pulsatile flow provides the theoretical basis of cerebrospinal fluid flow phenomena in magnetic resonance imaging, since this type of flow exists in cerebrospinal fluid pathways. © 1990 Academic Press, Inc.
A DANTE tagging sequence for the evaluation of translational sample motion
Authors: Mosher Timothy J. , Smith Michael B. 
Published: March 2007

AbstractA magnetic resonance imaging sequence that is sensitive to translational motion such as that seen with cardiac contraction is presented. The sequence employs DANTE radiofrequency excitation with a continuous magnetic field gradient to generate a grid pattern of lines. There is improved line resolution and reduced eddy‐current formation over Current techniques. © 1990 Academic Press, Inc.
Improved metabolite editing by the 1D soft COSY technique with 270° Gaussian‐shaped pulses
Authors: Stryjewski Detlef , Leibfritz Dieter 
Published: March 2007

AbstractRecently we proposed Gaussian‐shaped pulses to overcome the dynamic range problem within a 1D Soft COSY pulse sequence for the editing of metabolites in their natural environment. Similar to the development of the application of a COSY technique, the ECZOTIC sequence was introduced for the same purpose. A brief comparison of the abilities of both sequences is given in the first part of this communication, and the second part deals with the improvement of phase behavior within 1D Soft COSY by use of 270° pulses. © 1990 Academic Press, Inc.
Signal‐to‐noise in phase angle reconstruction: Dynamic range extension using phase reference offsets
Authors: Conturo Thomas E. , Smith Gregory D. 
Published: March 2007

AbstractThe dynamic range of phase‐reconstructed magnetic resonance images is compared to that of magnitude‐reconstructed images. From analysis of propagation of errors, the phase angle noise is phase‐independent and given in radians by σ (|I|)/|I|, the noise‐to‐signal ratio of the corresponding magnitude‐reconstructed image. As the phase can range from minus π to π the phase angle dynamic range is 2π times that of the signal magnitude. These results agree with experiment, verifying that the noise in the two receiver channels is uncorrelated. An artifact‐free technique is presented for correcting phase spillover, which further extends the phase angle dynamic range. The reconstruction‐based reference phase is adjusted on a local basis so that the boundary of phase wraparound is reconstructed near the center of the [ − π, π] interval. For a particular flow study, the phase signal‐to‐noise was extended over twofold by spillover correction, to a value 15 times that of the magnitude signal‐to‐noise. © 1990 Academic Press, Inc.
A simple method of generating variable T1 contrast images using temporally reordered phase encoding
Authors: Norris David G. , Böttcher Uwe , Leibfritz Dieter 
Published: March 2007

AbstractA rapid method of generating T1 images by means of an inversion pulse followed by a fast low‐angle imaging experiment is presented. The T1 contrast is manipulated by a temporal reordering of the phase‐encoding gradient, resulting in an almost completely free choice of T1 contrast, without any extra restriction on the size of the data acquisition matrix. The intrinsic rapidity of the sequence renders it insensitive to motion artifacts and lends itself to multipoint T1 calculations. The method is particularly well suited to high‐field imaging. © 1990 Academic Press, Inc.
The proton NMR of blood plasma and the test for cancer
Authors: Herring F. G. , Phillips P. S. , Pritchard H. , Silver H. , Whittal K. P. 
Published: March 2007

AbstractThe water‐suppressed proton NMR spectra of plasma from healthy controls and cancer patients have been recorded along with the high‐density lipoprotein (HDL) and triglyceride (TG) levels in the plasma. The dependence of the average of methylene and methyl resonance linewidths on the HDL/TG ratio is demonstrated. It is shown that the deranged lipoprotein levels caused by the presence of cancer lead to the serological test for cancer proposed by Fossel. The work provides the formation for a complete understanding of the proposed serological test for cancer. However, the wide variation in lipoprotein composition in the plasma from both healthy adults and cancer patients means that the serological test proposed by Fossel cannot be used as a screen for cancer. © 1990 Academic Press, Inc.
Gadolinium (III) complex equilibria: The implications for Gd(III) MRI contrast agents
Authors: Jackson Graham E. , Wynchank Sinclair , Woudenberg Marianne 
Published: March 2007

AbstractA computer model of blood plasma which has allowed the effect of Gd(III) contrast agents to be simulated has been developed. Initial binding of Gd(III) is to transferrin. At high concentration the metal ion binds to citrate and salicylate. At a concentrate of 10−3 M, GdCl3 is predicted to effect a redistribution of the in vivo Zn(II), Ca(II), and Fe(II) complexes present in blood plasma. There is little effect on the Cu(II) distribution. At a concentration below lo−5 M EDTA and DTPA have little effect on the free Gd(III) metal ion concentration. Above this concentration though, the metal ion is bound aimost exclusively to the EDTA or DTPA. An attempt is made to relate the toxicity of GdCl3, [Gd(EDTA)]−, and [Gd(DTPA)]2− to the thermodynamic stability of these complexes. The effect of substitution kinetics is also discussed. © 1990 Academic Press, Inc.