bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of the flavonoid biochanin A on gene expression in primary human hepatocytes and human intestinal cells
Authors: Moon Young Jin , Zhang Shuzhong , Brazeau Daniel A. , Morris Marilyn E.
Published: March 2007

Biochanin A (BCA), a phytoestrogen present in plant food and herbal products, has been reported to have cancer‐preventive effects that may be mediated, in part, through effects on carcinogen metabolism. Our objective was to examine the effect of BCA on gene expression for drug‐metabolizing enzymes and transporters in human hepatocytes. Cells were exposed to 20 μM of BCA for 5 days. Gene expression was assessed by a 96‐gene human drug metabolism enzyme microarray. There were seven genes that were significantly up‐regulated, namely cytochrome P‐450 (CYP) 2A6, CYP2B6, CYP2C9, CYP2F1, multidrug resistance gene (MDR1), thromboxane A synthase 1 (TBXAS1), and SULT1A2 (sulfotransferase). Up‐regulation of MDR1, which encodes for P‐glycoprotein, was confirmed using real‐time RT‐PCR and Western analysis in hepatocytes as well as in human colon adenocarcinoma cell line (LS‐180) and the induction was dose‐dependent. BCA treatment up‐regulated genes mainly in the CYP2 family. This induction can influence the metabolism of xenobiotics, producing effects of pharmacological and toxicological importance.
Signal to Noise in Derived NMR Images
Authors: Ortendahl Douglas A. , Hylton Nola M. , Kaufman Leon , Crooks Lawrence E.
Published: March 2007

The NMR image is dependent on multiple tissue parameters: hydrogen density, relaxation times T1 and T2, and flow. From the acquired intensity images, T1, T2, and hydrogen images may be produced. The signal/noise of these derived images is critically dependent on the choice of acquisition parameters. Using the calculated T1, T2, and hydrogen images, intensity images may be calculated at arbitrary values of TE and TR, some of which (for example, short TE or TR) may be physically unacquirable.
Quadrature detection in the laboratory frame
Authors: Hoult D. I. , Chen C.‐N. , Sank V. J.
Published: March 2007

A theory of quadrature detection in the laboratory frame is developed. It is shown that the geometry of the two orthogonal coil systems needed for quadrature detection is radically different from that used with saddle‐shaped coils, and that the homogeneity of the B1 field produced upon transmission is marginally better. The opposing quadrature phase shifts needed for transmission and reception are emphasized, and the use of a quadrature hybrid is advocated as a simple and inexpensive means of interfacing the transmitter, probes, and preamplifier. Experimental results are presented which confirm the theoretical predictions, and show that up to a 40% improvement in sensitivity and a twofold reduction in transmitter power are possible, particularly in those instances where the sample is conductive—namely, imaging of humans and in vivo spectroscopy.
Magnetic field dependence of solvent proton relaxation induced by Gd3+ and Mn2+ complexes
Authors: Koenig Seymour H. , Baglin Coral , Brown Rodney D. , Fred Brewer C.
Published: March 2007

The effect of solute paramagnetic ions on the longitudinal magnetic relaxation rate 1/T1 of solvent water protons depends on magnetic field strength and on the chemical environment of the ions. The variation of 1/T1 with field has been measured for solutions of Gd3+ and Mn2+ ions in three grossly different environments near physiological pH: the hydrated aquoion; chelated by EDTA (ethylenediaminetetraacetic acid) and DTPA (diethylenetriaminepentaacetic acid); and bound to the protein concanavalin A. It is demonstrated that over the field range at which NMR imaging is currently being done, the chemical environment can alter 1/T1 of solvent protons by more than an order of magnitude. The relevance of these results to the potential utility of these ions as agents for enhancement of contrast in NMR images is discussed.
Application of linear prediction and singular value decomposition (LPSVD) to determine NMR frequencies and intensities from the FID
Authors: Barkhuijsen H. , De Beer R. , Bovee W. M. M. J. , Creyghton J. H. N. , Van Ormondt D.
Published: March 2007

A parametric spectral analysis based on linear prediction and singular value decomposition has been applied to the 31P FID of a tumor implanted in a mouse. It is found that a number of complications that may arise in in vivo FFT NMR can be circumvented. The new method yields all parameters of the spectral components, i. e., the frequency, amplitude, damping constant, and phase.
Fast fourier imaging
Authors: Uijen C. M. J. Van , Boef J. H. Den , Verschuren F. J. J.
Published: March 2007

A new NMR imaging technique, aiming at a reduction of the data acquisition time, is described in detail. The method is applicable in all multidimensional imaging situations where at least one spatial coordinate is resolved. Discussed at some length are the point‐spread function, the requird bandwidth of the NMR spectrometer, and the sampling strategy used to diminish the loss in signal‐to‐noise ratio. Experiments reveal that a reduction of the data acquisition time by at least a factor of four is attainable in practice.
31P Spin‐Lattice Relaxation Times and Resonance Linewidths of Rat Tissue in Vivo: Dependence upon the Static Magnetic Field Strength
Authors: Evelhoch Jeffrey L. , Ewy Coleen S. , Siegfried Barry A. , Ackerman Joseph J. H. , Rice David W. , Briggs Richard W.
Published: March 2007

Phosphorus‐31 NMR spin‐lattice relaxation times and resonance linewidths of rat leg muscle, brain, and liver metabolites in vivo have been examined at 1.9‐, 4.7‐, and 8.5‐ T static magnetic field strengths. The resonance linewidths expressed in ppm that have been measured are independent of field strength. The spin‐lattice relaxation times of muscle and brain phosphorus metabolites decrease linearly with increasing field strength while those of liver are constant over the range of static fields examined.
Chemical‐Shift Magnetic Resonance Imaging of Two‐Line Spectra by Gradient Reversal
Authors: Axel Leon , Glover Gary , Pelc Norbert
Published: March 2007

A method of chemical‐shift imaging is described using the invariance of chemical shifts to changes in magnetic field gradients used for frequency encoding of position in imaging. This enables separation of the effects on the observed signal of chemical shift from the effects of different positions along the imaging gradient when the signal is observed with different gradients. A simple implementation for a two‐line spectrum is presented using signals observed with normal and reversed imaging gradients. This is used to create “fat” and “water” images of the thigh.© 1985 Academic Press,Inc.
Chemical‐Shift Imaging
Authors: Guilfoyle D. N. , Mansfield P.
Published: March 2007

The echo‐planar shift mapping (EPSM) technique, a variant of echo‐planar imaging (EPI), is evaluated with theoretical studies using computer simulations and with experimental studies using fluorine resonances in phantoms. In situations where the signal‐to‐noise ratio permits, it is shown that EPSM can produce in a few seconds chemical‐shift spectra at all points in a specified spin‐density image corresponding to a selected slice. Applications of this technique are likely to be for proton and fluorine chemical‐shift measurements and rapid studies of magnetic field inhomogeneities produced by magnet nonalignment and field shifts around magnetic materials.© 1985 Academic Press,Inc.© 1985 Academic Press,Inc.
An Improved Saddle Coil for MR Imaging in Resistive Magnet Systems
Authors: Doornbos Johannes , Booijen Paul E. , Grimbergen Harry A. A. , Falke Theo H. M.
Published: March 2007

The design of a two‐turn radiofrequency coil for MR imaging at 0.15 T is presented. The use of well‐isolated copper tube (instead of the usual wire) as conductor material resulted in an open, patient friendly construction. Furthermore, the Q value and signalto‐noise ratio of the tube‐type coil were increased as compared to the corresponding values in the case of a geometrically similar wire‐type coil.© 1985 Academic Press,Inc.
Phase Alterations of Spin Echoes by Motion along Magnetic Field Gradients
Authors: Wendt III Richard E. , Murphy Paul H. , Ford Joseph J. , Bryan R. Nick , Burdine John A.
Published: March 2007

Using a Taylor series expansion of the phase shift of a moving isochromatic spin group in the presence of a magnetic field gradient, the refocusing effects of the Carr‐Purcell‐Meiboom‐Gill pulse sequence on stationary nuclei and those with constant, rectilinear velocity are readily demonstrated. Continuing the analysis to higher orders of motion reveals that nuclei with a constant, rectilinear acceleration have a phase shift at the spin echoes which increases linearly with echo number. Constant, rectilinear jerk (the time rate of change of acceleration) leads to an increase in phase shift from echo to echo which is quadratic in nature with an overlying reduction of the odd‐numbered echoes by a constant amount. Motion parameters may be measured by parameter identification techniques. These principles may be applied to phase‐sensitive NMR imaging.© 1985 Academic Press,Inc.
Magnetic Resonance Imaging the Velocity Vector Components of Fluid Flow
Authors: Feinberg David A. , Crooks Lawrence E. , Sheldon Phillip , Iii John Hoenninger , Watts Jeffrey , Arakawa Mitsuaki
Published: March 2007

Encoding the Precession phase angle of proton nuclei for Fourier analysis has produced accurate measurement of fluid velocity vector components by MRI. A Pair of identical gradient pulses separated in time by exactly ½ TE, are used to linearly encode the phase of flow velocity vector components without changing the phase of stationary nuclei, Two‐dimensional Fourier transformation of signals gave velocity density images of laminar flow in angled tubes which were in agreement with the laws of vector addition. These Velocity profile images provide a quantitative method for the investigation of fluid dynamics and hemodynamics.© 1985 Academic Press,Inc.
Hepatic gluconeogenesis from alanine: 13C nuclear magnetic resonance methodology for in vivo studies
Authors: Stromski M. E. , Arias‐Mendoza F. , Alger J. R. , Shulman R. G.
Published: March 2007

This paper describes an experimental protocol designed to optimize 13C NMR spectra from the liver of the living anesthetized rat at 1.9 T. The protocol involves the use of a Helmholtz NMR coil which is positioned around the liver after surgical exposure. 1H decoupling is facilitated by double tuning this coil to both the 1H and the 13C frequencies. The protocol was shown to be suitable for studying the hepatic metabolism of 13C‐labeled substrates in vivo by investigating the metabolism of [3‐13C] alanine. Labeled glucose, glutamate, glutamine, and aspartate were formed and detected by 13C NMR in vivo in this experiment. The labeling patterns in these metabolites provided evidence that the major flow of alanine carbon into the Krebs cycle is via the pyruvate carboxylase reaction rather than through pyruvate dehydrogenase. © 1986 Academic Press, Inc.
Suppression of water and other noncoupled spins by homonuclear polarization transfer in magnetic resonance imaging
Authors: Dumoulin Charles L.
Published: March 2007

The water component of an NMR image is suppressed by selectively detecting only those protons which are coupled to other protons. Selectivity is obtained by polarization transfer between the coupled spins. Since spin‐spin coupling is independent of magnetic field strength, the suppression obtainable by polarization transfer is independent of chemical shift. Consequently, this technique does not require extremely homogeneous magnetic field for the separation of water and lipid signals. In addition, water suppression by this technique is independent of T1 and T2. Suppression of the water signal intensity has been observed experimentally to be as high as a factor of 100. Suppression is limited only by instrumental imperfections. © 1986 Academic Press, Inc.
Quadrature‐multiplexed rf excitation for information doubling in NMR imaging
Authors: Ra J. B. , Hilal S. K. , Cho Z. H. , Park H. W. , Cho M. H.
Published: March 2007

A quadrature multiplexed pulse sequence to double the data information in a given acquisition time is proposed for NMR tomography. This technique takes advantage of the Hermitian property of the Fourier transform operation in NMR imaging. The proposed technique uses two rf pulses with 90° phase difference simultaneously applied for the excitation of the spins in two different slices. The method results in truly simulaneous data acquisition coming from two different anatomical slices which can be separated into the real and imaginary parts of the image domain. This technique, therefore, also allows us either to reduce the experiment time by half or double the number of slices in the same examination time, depending on the applied imaging scheme. As a preliminary study, simultancous dual‐slice imaging of a human head using a conventional single‐slice imaging scheme was performed. © 1986 Academic Press, Inc.
A modified saturation‐recovery approximation for multiple spin‐echo pulse sequences
Authors: Lee James N. , Riederer Stephen J.
Published: March 2007

In equations describing multiple spin‐echo pulse sequences, the T1 dependence is often approximated by a saturation‐recovery expression, which is valid only when the repetition time TR is much greater than the time required for the echoes. A slight modification of this approximation greatly increases its accuracy for small TR values. © 1986 Academic Press, Inc.
Spin‐lattice relaxation (T1) times of cerebral white matter in multiple sclerosis
Authors: Lacomis David , Osbakken Mary , Gross George
Published: March 2007

Magnetic resonance imaging was used to evaluate the cerebral white matter of three subject groups: (1) 22 patients with known multiple sclerosis (MS) (11 with disease of shorter duration (0–5 years) and 11 with disease of longer duration (>5 years)); (2) 9 patients with suspected MS; and (3) 12 normal volunteers. Transverse spin‐echo (SE) 30/ 500 and 120/1000 radiofrequency pulse sequences were used for anatomic localization and plaque identification, respectively, while combined spin echo‐inversion recovery was used for T1 determination. T1 values were calculated for grossly normal cerebral white matter in the frontal, parietal, and occipital lobes of normal volunteers and MS patients, and for plaques in MS patients. When compared with normals, the T1 values of plaquefree areas from definite MS patients (shorter and longer duration disease groups combined) were significantly longer in the frontal lobe (MS = 374 ± 34 ms, Normal = 352 ± 39 ms, P < 0.05) and in the occipital lobe (MS = 414 ± 37, Normal = 378 ± 40, P < 0.02). Although the T1 values of the shorter duration MS group were longer than those of normals, the difference was not statistically significant. Thus, the significant difference between the definite MS group (both shorter and longer duration) is more heavily weighted by the longer duration MS group. T1 values in patients with suspected MS without plaques were not significantly different from those of normals. In diagnosed MS patients, T1 values of plaques were significantly longer than T1 values of corresponding normal areas (P < 0.05). In conclusion, plaque‐free white matter in patients with clinically diagnosed MS has longer T1 values than white matter in normals, suggesting the presence of biophysical abnormalities which are not seen on other routine imaging modalities. These differences may be accentuated as the disease progresses. Thus, it may be possible in the future to evaluate MS disease activity based on T1 characteristics of normal appearing white matter. © 1986 Academic Press, Inc.
Monoclonal antibodies labeled with polymeric paramagnetic ion chelates
Authors: Shreve Paul , Aisen Alex M.
Published: March 2007

Polymeric paramagnetic ion chelate molecules were synthesized and covalently linked to monoclonal antibodies. The labeled antibodies retained their antigen binding capacity in vitro while carrying up to an average of 50 paramagnetic ion chelates, enabling specifically bound antibody concentrations less than 2.0 μM to significantly reduce proton longitudinal relaxation times. © 1986 Academic Press, Inc.
A computer simulation of nuclear magnetic resonance imaging
Authors: Summers Ronald M. , Axel Leon , Israel Solomon
Published: March 2007

A modular, user‐friendly computer simulation of NMR imaging was created for the DEC VAX computer. This simulation is novel in that complex imaging phenomena, such as chemical shifts and flow, may be easily studied. Other features include spin warp and backprojection imaging, movie generation, and simulation of image contrast, composite pulse sequences, motion artifacts, aliasing, selective excitation, field inhomogeneity, noise and signal averaging. The simulation incorporates fast Fourier transform and graphics modules for processing and display of one‐and two‐dimensional images. Examples which illustrate features of the program are shown. The simulation is a useful tool for both the sophisticated and the beginning user of NMR imaging. It serves as a drawing board for studying MRI phenomena and a teaching program for demonstrating basic techniques. © 1986 Academic Press, Inc.
Liposome delivery of NMR contrast agents for improved tissue imaging
Authors: Magin R. L. , Wright S. M. , Niesman M. R. , Chan H. C. , Swartz H. M.
Published: March 2007

Large unilamellar liposomes containing the paramagnetic contrast agent manganese chloride were shown to selectively enhance the intensity of the proton NMR signal from the livers of experimental mice. The kinetics of the observed effect indicate that the liposomes are rapidly removed from the circulation and deposited in high concentration within the liver. This process is known to involve the phagocytic activity of macrophages. These results show that liposomes could provide a useful and efficient vehicle for delivering NMR contrast agents to organs like the liver, spleen, and bone marrow. It may also be possible to use liposomes to selectively deliver contrast agents to tissue regions of developing pathology that are rich in macrophage activity. © 1986 Academic Press, Inc.
Projection angiograms of blood labeled by adiabatic fast passage
Authors: Dixon W. Thomas , Du Leila N. , Faul David D. , Gado Mokhtar , Rossnick Susan
Published: March 2007

A surface coil on the neck causes adiabatic fast passage in blood as it flows by through a magnetic field gradient. This allows separation of blood and stationary tissue images of the head. Coronal and sagittal images of a volunteer are presented showing the vertebral and common, internal and external carotid arteries in projection views. © 1986 Academic Press, Inc.
Synthesis of [guanidino‐13C]creatine and measurement of the creatine phosphokinase reaction in vitro by 13C NMR spectroscopy
Authors: Han Chung H. , Sillerud Laurel O.
Published: March 2007

[guanidino‐13C]Creatine has been synthesized by reaction involving synthesis of [13C]cyanamide followed by its condensation with sarcosine. The creatine guanidino carbon 13C NMR frequency shifts upon the formation of phosphocreatine by 0.83 ppm with a splitting (2JCP = 3.3 Hz) due to two‐bond phosphorus‐carbon coupling. The high 13C enrichment (99%) at the guanidino carbon of creatine gave rise to an adequate signal‐to‐noise ratio for both creatine and phosphocreatine so that a study of the time course of the creatine phosphokinase reaction could be performed and provided the means for a determination of the Km (15.5 mM) of the reaction. © 1986 Academic Press, Inc.
The field dependence of NMR imaging. I. Laboratory assessment of signal‐to‐noise ratio and power deposition
Authors: Chen C‐N. , Sank V. J. , Cohen S. M. , Hoult D. I.
Published: March 2007

A method is proposed for measuring on the bench the NMR signal‐to‐noise ratio of rf probes, (over the range 1–100 MHz) and also the power deposited in patients during the imaging experiment. The technique is based on the principle of reciprocity, in that a direct relationship exists between the magnetic field generated (upon transmission) by a matched probe coil and the signal‐to‐noise ration delivered by the same coil when used as a receiver. The construction and use of a calibrated sense coil for measuring the field is described, and the precautions and theory necessary for accurate measurement and understanding are outlined. Finally, the method is verified by comparison with a direct spectral measure of sensitivity obtained from a small doped water sample placed in NMR imaging equipment. © 1986 Academic Press, Inc.
1H NMR studies of urine during fasting: Excretion of ketone bodies and acetylcarnitine
Authors: Bales John R. , Bell Jimmy D. , Nicholson Jeremy K. , Sadler Peter J.
Published: March 2007

High‐resolution 1H NMR spectroscopy has been applied to a study of urine from five normal human subjects during a 48‐h period of fasting and for 22 h thereafter. The excretion rates of all three ketone bodies (acetoacetate, 3‐D‐hydroxybutyrate, and acetone), acetylcaritine, and sarcosine during this period were measured. Parallel increases in the excretion of the ketone bodies and acetylcarnitine were observed during fasting with little change in the output of creatinine and sarcosine. © 1986 Academic Press, Inc.
Some results of high‐flow‐velocity NMR imaging using selection gradient
Authors: Cho Z. H. , Oh C. H. , Mun C. W. , Kim Y. S.
Published: March 2007

A simple and new flow velocity measurement technique using conventional spin‐echo sequence is proposed and its applications to a preclinical result are presented. This technique utilizes the phase velocity encoding effect due to 180° rf and its corresponding selection gradient. This phase encoding and its phase velocity relations have been obtained by numerical solution of the Bloch equation. A flow velocity measurement obtained with a volunteer using this proposed technique indicates close agreement with other previously measured values.
Liposomes containing paramagnetic macromolecules as MRI contrast agents
Authors: Navon G. , Panigel R. , Valensin G.
Published: March 2007

The use of paramagnetic ions, bound to macromolecules and trapped in liposomes, as MRI contrast agents is suggested. As an example, the system of Mn2+ bound to serum proteins was tested. The binding of the metal ions to the macromolecules enhances their relaxation and at the same time decreases their rate of diffusion out of the liposomes. The use of liposomes is expected to reduce the potential toxicity of the paramagnetic ions and allows their targeting toward specific tissues. © 1986 Academic Press, Inc.
Localization of unaffected spins in NMR imaging and spectroscopy (LOCUS spectroscopy)
Authors: Haase Axel
Published: March 2007

A new method for the localization of NMR spectra in vivo is presented. Herein a series of selective 90° pulses with different carrier frequencies in the presence of magnetic field gradients is saturating spins of unwanted regions. Only spins in the region of interest are left unaffected. The LOCUS (localization of unaffected spins) spectrum of this region is measured by a single 90° excitation pulse. The FLASH imaging sequence combined with the LOCUS technique allows the identification of the region of interest. © 1986 Academic Press, Inc.
Effects of selective pulses on the measurement of T2 and apparent diffusion in multiecho MRI
Authors: Majumdar S. , Gore J. C.
Published: March 2007

The effects of using spatially selective and nonuniform radiofrequency pulses on the apparent T2 of a train of multiple echoes have been calculated by computer simulation. It is demonstrated that the use of selective pulses produces errors in estimates of T2 in imaging experiments because regions of the slice are effectively off resonance and therefore receive spin rotations less than in an ideal case. Components of the transverse magnetization that are incompletely rotated by 180° refocusing pulses produce longitudinal components that are later returned to the transverse plane and add to subsequent echoes. These so‐called ghost components influence the precise value of T2 estimated, but even when completely removed the resultant estimate is too short. The apparent T2 is influenced by the magnitude of the nutation angle inhomogeneity across the slice and paradoxically is not always more accurate with larger numbers of echoes. The reduction of apparent T2 caused by increasing the slice‐selection gradient across a thin slab of material replicates the effects previously ascribed to diffusion and affords an alternative explanation for these without recourse to motion of the Spins. © 1987 Academic Press, Inc.
Anatomical interpretation of MR scans of the brain
Authors: Vanier M. , Ethier R. , Clark J. , Peters T. M. , Olivier A. , Melanson D.
Published: March 2007

A stereotactic method of brain localization is applied to magnetic resonance imaging for the interpretation of brain structures. This proportional grid system developed by Talairach is based on two intracerebral structures, the anterior and posterior commissures. It takes into account individual variations in brain size and shape. In an experimental study on cadavers we demonstrated that his system permitted accurate identification of cortical structures on CT scan. In this paper, we describe its application to MR. It provides, on a routine basis, a simple reliable method of anatomical interpretation. The use of this grid system is made easier by the fact that both commissures are seen on midsagittal MR Scans. © 1987 Academic Press, Inc.
The utility of principal component analysis for the image display of brain lesions. A preliminary, comparative study
Authors: Schmiedl Udo , Ortendahl Douglas A. , Mark Alexander S. , Berry Isabelle , Kaufman Leon
Published: March 2007

Principal component analysis (PCA), a common tool from multivariate statistical analysis, has been implemented into the computer display system of a MR imaging device. PCA allows the calculation of images in which the information in a defined region of interest inherent in the basic acquired images is condensed. PCA image calculation has been applied to acquired MR studies of 13 patients with brain lesions. The appearance of the brain lesions on the resultant PCA images was scored in comparison to the acquired images before and after administration of Gd‐DTPA as well as to other calculated images including T1, T2 hydrogen density, and contrast‐optimized images. The conspicuity of a lesion and the number of distinguishable components within a lesion were slightly supenor on PCA than on the acquired images. PCA is an analytical tool for MR imaging that should be helpful in revealing information that is inherent in, but not readily visible on, standard acquired MR images. © 1987 Academic Press, Inc.
Adiabatic refocusing pulse which compensates for variable of power and off‐resonance effects
Authors: Robin Bendall M. , Garwood Michael , Uǧurbil Kâmil , Pegg David T.
Published: March 2007

Adiabatic 180° inversion rf pulses can be converted to 180° refocusing pulses by inverting the effective field midway during the pulse. Suitable pulses retain insensitivity to large variations in the rf field strength and act over a reasonable spectral width. Such pulses may find application in studies utilizing surface coils. © 1987 Academic Press, Inc.
The in vivo contour plot. An improved representation of stimulus experiments
Authors: Offermann Werner , Kuhn Winfried , Soboll Sibylle , Ishikawa Toshihisa , Leibfritz Dieter
Published: March 2007

The in vivo contour plot is a superior representation of the data from stimulus experiments. Its performance is illustrated by four examples, viz., necrosis of a superfused rat heart, anoxia on perfused mouse liver, ischemiae on Langendorff heart in the presence and absence of a Ca antagonist, and the internal stimulus of the cardiac cycle. The in vivo contour plot visualizes line intensities (metabolite concentrations), line positions (pH), and linewidths, as well as the time derivatives of these parameters in any available number of Spectra. © 1987 Academic Press, Inc.
Comparison of lactate concentration determinations in ischemic and hypoxic rat brains by in vivo and in vitro1H NMR spectroscopy
Authors: Chang L.‐H. , Pereira B. M. , Weinstein P. R. , Keniry M. A. , Murphy‐Boesch J. , Litt L. , James T. L.
Published: March 2007

An experimental protocol for the quantitation of lactate is demonstrated for in vivo 1H NMR surface coil spectroscopy. The in vivo lactate concentration can be calculated by comparing the in vivo and in vitro ratios of lactate and N‐acetylaspartate (NAA) NMR signals. With this protocol, approximately 25% of lactate present in the hypoxic or ischemic rat brain is observed by NMR. © 1987 Academic press Inc.
Hepatobiliary MR contrast agents: 5‐substituted iron‐EHPG derivatives
Authors: Lauffer Randall B. , Vincent Alice C. , Padmanabhan Sreenivasan , Villringer Arno , Saini Sanjay , Elmaleh David R. , Brady Thomas J.
Published: March 2007

A series of iron(III) ethylenebis(2‐hydroxypheny1)glycine [Fe(EHPG)]‐ derivatives have been examined for their role as paramagnetic hepatobiliary contrast agents for magnetic resonance (MR) imaging. The 5‐substituted complexes, Fe(5‐Me‐EHPG)−, Fe(5‐Cl‐EHPG)−, and Fe(5‐Br‐EHPG)−, have been compared to the parent compound in rat bio‐distribution and MR imaging studies; correlative in vitro parameters for the complexes, including octanol‐buffer partition coefficients and albumin binding affinity, have also been obtained. The three new derivatives exhibited higher degrees of lipophilicity and albumin binding affinity and varying degrees of improvement in liver‐to‐blood and bile‐to‐liver concentration ratios measured at 30 min postinjection. The 5‐C1 complex had the best overall performance in terms of these tissue ratios as well as in terms of total biliary excretion. Sequential MR images of rats after administration of the complexes revealed subtle pharmacokinetic differences among the derivatives and, in general, correlated well with and complemented the biodistribution results. This study points to the sensitivity of hepatocellular uptake and excretion to simple chemical modifications and, moreover, demonstrates the importance of screening multiple derivatives to select optimal hepatobiliary MR imaging agents. © 1987 Academic press, Inc.
A UHF probe for NMR micro‐imaging experiments
Authors: Fan M. , Gonord P. , Kan S. , Taquin J.
Published: March 2007

A long solenoid is capable of producing, at least theoretically, a B, field that is relatively more homogeneous than other known structures. This paper describes the design of a UHF probe incorporating a one‐turn solenoid associated with a pair of parallel‐plate transmission line feeders and presents a practical example used in a 360‐MHz spectrometer for micro‐imaging experiments. Numerical evaluation of the solenoid inductance using King's method for direct calculation of elliptic integrals is also included. © 1987 Academic press, Inc.
A simple field map for shimming
Authors: Mackenzie I. S. , Robinson E. M. , Wells A. N. , Wood B.
Published: March 2007

A field‐mapping procedure based on volume‐selective spectroscopy is described. For proton NMR the method may be used to optimize magnet shimming, on the sample under investigation, prior to spectroscopy or imaging experiments. Examples of field maps obtained on our 4.7‐T system, using phantoms and biological samples of up to 6 cm in diameter, are presented. © 1987 Academic Press, Inc.
Tumor imaging with anti‐CEA antibody labeled 19F emulsion
Authors: Shimizu Masahiro , Kobayashi Tetsuro , Morimoto Hideki , Matsuura Nariaki , Shimano Takashi , Nomura Nobuhiko , Itoh Souichi , Yamazaki Masaru , Iriguchi Norio , Yamamoto Tohru , Yamai Satoshi , Furuta Tadaaki , Maki Takeshi , Mori Takesada
Published: March 2007

The possibility of using 19MRI for detection of tumors using a 2‐T NMR system was examined in animals. Anticarcino‐embryonic antigen (CEA) antibody conjugated with perfluorochemical (perfluorotributylamine, FTBA) was administered to nude mouse inoculated with LOVO, a CEA‐producing human cancer cell line. Tumor imaging based on the 19F NMR was examined after excision of the tumors from nude mice (ex vivo). The imaging pattern of the tumor coincided with the antibody distribution determined immunohistologically. © 1987 Academic Press, Inc.
A phospholipid spin label used as a liposome‐associated MRI contrast agent
Authors: Grant Chris W. M. , Barber Kathryn R. , Florio Eugene , Karlik Stephen
Published: March 2007

Given current clinical use of phospholipid bilayer structures (liposomes/vesicles) as non‐toxic drug delivery vehicles, we have addressed the possibility of employing the phospholipids themselves as MRI contrast agents. To this end we have synthesized phosphatidylcholine with a nitroxide spin label replacing one methyl residue of the choline headgroup. This material was mixed with natural phosphatidylcholine in mole ratios from 150 to 1:1 and used to prepare sonicated unilamellar vesicles in saline. Expected structural features of these vesicles were verified by freeze‐fracture electron microscopy. Proton T1 values of saline were readily decreased to less than 0.3 s by such preparations, yielding a net relaxivity of 0.6 M−1 s−1. The approach seems to be a realistic way of firmly associating a contrast agent of minimal toxicity with ordinary liposomes/vesicles in a manner that is not subject to leakage. © 1987 Academic Press, Inc.
On the calculation of magnetization slice profiles for NMR imaging and in vivo spectroscopy
Authors: Bulsing J. Mark , Galloway Graham J. , Brereton Ian M. , Doddrellt David M.
Published: March 2007

When developing new techniques for NMR imaging and in vivo spectroscopy it is a major advantage to be able to calculate the magnetization slice profiles, at any point during a pulse sequence in the presence of a field gradient. While this has frequently been done by treating the problem as a number of discrete resonances, it is sometimes necessary to consider the continuous nature of the magnetization profiles. This paper describes a method used to simulate the free‐induction decay at any point during the NMR experiment. © Academic Press, Inc.
Nitroxides as potential contrast enhancing agents for MRI application: Influence of structure on the rate of reduction by rat hepatocytes, whole liver homogenate, subcellular fractions, and ascorbate
Authors: Keana John F. W. , Pou Sovitj , Rosen Gerald M.
Published: March 2007

With an eye toward the development of nitroxides as potential contrast enhancing agents for MRI applications, we have compared the rates of reduction of 24 nitroxides of diverse structures by rat whole liver homogenate, hepatocytes, subcellular fractions, and ascorbate (10 eq excess). Our results indicate that five‐membered ring nitroxides and α‐carboxy α‐aryl tert‐butyl nitroxides are significantly more resistant toward bioreduction than six‐membered ring and heterocyclic‐substituted nitroxides in all systems. In the case of six‐membered ring nitroxides the presence of either negatively charged or positively charged groups increases the susceptibility toward ascorbate reduction. The presence of carboxylate groups tends to enhance the resistance of all the nitroxides toward reduction by liver homogenate, hepatocytes, and subcellular fractions. trans‐Azethoxyl nitroxides exhibited the best overall resistance toward bioreduction. The T1 relaxivities of selected nitroxides were measured and found to be similar. © Academic Press, Inc.
Indirect monitoring of carbon‐13 metabolism with NMR: Analysis of perfusate with a closed‐loop flow system
Authors: O'leary Daniel J. , Hawkes Susan P. , Wade Chas. G.
Published: March 2007

NMR studies of living cells and of perfused organs almost invariably require a major effort in the design of either the probe or the support system. For enriched 13C studies of metabolism, it is sometimes possible to use a simpler approach, one amenable to use in narrow‐bore high‐resolution NMR spectrometers. Since some of the metabolic changes are reflected by changes in the chemical composition of the media, it may be necessary to provide only for NMR measurements of the perfusate. A simple apparatus is described which allows NMR measurement of the perfusate. A commercially available concentric NMR tube, modified to incorporate flow, is inserted in the flow loop and placed in the spectrometer. An example is given of the metabolism of 13C‐enriched glucose to lactate by chick embryo fibroblasts grown in a hollow fiber bundle assembly. © Academic Press, Inc.
31P NMR characterization of graded traumatic brain injury in rats
Authors: Vink Robert , McIntosh Tracy K. , Yamakami Iwao , Faden Alan I.
Published: March 2007

Irreversible tissue injury following central nervous system trauma is believed to result from both mechanical disruption at the time of primary insult, and more delayed “autodestructive” processes. These delayed events are associated with various biochemical changes, including alterations in phosphate energy metabolism and intracellular pH. Using 31P NMR, we have monitored the changes in phosphorus energy metabolism and intracellular pH in a single hemisphere of the rat brain over an 8‐h period following graded, traumatic, fluid percussion‐induced brain injury. Following trauma the ratio of phosphocreatine to inorganic phosphate (PCr/Pi) declined in each injury group. This decline was transitory with low injury (1.0 ± 0.5 atm), biphasic with moderate (2.1 ± 0.4 atm) and high (3.9 ± 0.9 atm) injury, and sustained following severe injury (5.9 ± 0.7 atm). The initial PCr/Pi decline in the moderate and high injury groups was associated with intracellular acidosis; however, the second decline occurred in the absence of any pH changes. Alterations in ATP occurred only in severely injured animals and such changes were associated with marked acidosis and 100% mortality rate. After 4 h, the posttraumatic PCr/Pi ratio correlated linearly with the severity of injury. We suggest that a reduced posttraumatic PCr/Pi ratio may be indicative of altered mitochondrial energy production and may predict a reduced capacity of the cell to recover from traumatic injury. © 1988 Academic Press, Inc.
Monitoring of acutely III patients during nuclear magnetic resonance imaging: Use of a Time‐varying filter electrocardiographic gating device to reduce gradient artifacts
Authors: Rokey Roxann , Wendt Richard E. , Johnston Donald L.
Published: March 2007

A time‐varying filter electrocardiographic gating device designed to reduce NMR‐induced gradient artifacts during NMR imaging of the acutely ill cardiac patient is described. When used in conjunction with multiple electrocardiographic display monitors, accurate assessment of the electrocardiogram for morphologic changes and arrhythmias during all phases of the NMR examination is possible. © 1988 Academic Press, Inc.
Phospholipid profile of the human brain: 31P NMR spectroscopic study
Authors: Kwee Ingrid L. , Nakada Tsutomu
Published: March 2007

Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, sphingomyelin, and ethanolamine plasmalogen represent the six most abundant phospholipids of brain cell membrane. The ratio of the phospholipid contents (phospholipid profile) of the brain is remarkably consistent under various metabolic conditions and alteration of the phospholipid profile is believed to reflect changes in the membrane system. We describe here a simple but sensitive method to analyze the phospholipid profile of the human brain utilizing the acidified chloroform‐methanol lipid extraction method of Folch et al. and 31P nuclear magnetic resonance (NMR) spectroscopy. Unique regional phospholipid profiles were consistently obtained. Although the large chemical‐shift anisotropy of the 31P confined to rigid structures such as the cell membrane precludes direct observation of phospholipid profiles in living tissue, a reflection of the membrane phospholipid profiles can nevertheless be obtained by studying “NMR visible” water soluble intermediate metabolites of membrane phospholipids in vivo. © 1988 Academic Press, Inc.
Fluorine‐19 NMR imaging of glucose metabolism
Authors: Nakada Tsutomu , Kwee Ingrid L. , Card Peter J. , Matwiyoff Nicholas A. , Griffey Beatrice V. , Griffey Richard H.
Published: March 2007

Metabolic imaging reflecting glucose metabolism in the glycolytic and aldose reductase sorbitol (ARS) pathways was performed noninvasively in rat using fluorinated glucose analogs, 2‐fluoro‐2‐deoxy‐D‐glucose (2‐FDG) or 3‐fluoro‐3‐deoxy‐D‐glucose (3‐FDG), and fluorine‐19 (19F) nuclear magnetic resonance (NMR) imaging. I9F images of 2‐FDG‐6‐phosphate, a main metabolite of 2‐FDG in the glycolytic pathway, showed high glucose utilization in the brain, spinal cord, and heart. Images of 3‐fluoro‐3‐deoxy‐D‐sorbitol (3‐FDSL), a main metabolite of 3‐FDG in the ARS pathway, demonstrated the heterogeneous nature of the spatial distribution of aldose reductase activities, being highest in the brain and lens. The extremely low toxicity of 3‐FDG indicates promise for clinical application of 3‐FDG NMR imaging. © 1988 Academic Press, Inc.
Modulation of water proton relaxation rates by liposomes containing paramagnetic materials
Authors: Bačić G. , Niesman M. R. , Bennett H. F. , Magin R. L. , Swartz H. M.
Published: March 2007

Liposomes containing paramagnetic chemicals have significant potential for enhancing the effectiveness and selectivity of contrast agents in magnetic resonance imaging. We have studied the interactions of water, liposomes, and contrast agents using NMR and ESR. We find that the permeability of liposomes to water is of major importance in determining the effects of these systems on water proton relaxation. Key factors include (1) liposome composition, which determines the phospholipid membrane phase behavior as a function of temperature; (2) liposome structure (unilamellar or multilamellar); (3) location of the contrast agent in the liposome (aqueous space or lipid membrane); and (4) binding of contrast agents by liposomes. By appropriate selection of these factors it is possible to obtain effective proton relaxation enhancement in a manner suitable for particular experimental or clinical needs for contrast in MRI. For maximum relaxivity using lipophilic nitroxides, the optimum system appears to be 5‐doxyl stearate in multilamellar vesicles with a membrane composition that gives a phase transition temperature slightly above body temperature. © 1988 Academic Press, Inc.
A new steady‐state imaging sequence for simultaneous acquisition of two MR images with clearly different contrasts
Authors: Bruder H. , Fischer H. , Graumann R. , Deimling M.
Published: March 2007

We present a new steady‐state imaging sequence, which simultaneously allows in a single acquisition the formation of two MR images with clearly different contrasts. The contrast of the first image is FISP‐like, whereas the second image is strongly T2‐weighted. In principle the T2 values in the image can be calculated from the combination of the first and second images. We also show calculated T2 images. © 1988 Academic Press, Inc.
A magnetic resonance imaging study of experimental cerebral edema and its response to dexamethasone
Authors: Barnes D. , McDonald W. I.
Published: March 2007

Vasogenic edema following cortical freezing, and its response to dexamethasone were studied in cats. The time course of the edema shown by MRI was the same as that observed by invasive techniques. Dexamethasone retards early edema formation and may reduce its total volume, but does not accelerate its disappearance. © 1988 Academic Press, Inc.
Relaxivity and binding of Mn2+ ions in solutions of phosphatidylserine vesicles
Authors: Koenig Seymour H. , Brown Rodney D. , Kurland Robert , Ohkit Shinpei
Published: March 2007

We report the magnetic field dependence (NMRD profiles) of 1/T1, of solvent protons in solutions of unilamellar phosphatidylserine vesicles with added Mn2+ ions, including studies of the variation of the profiles with temperature, extent of coverage of available binding sites by Mn2+ ions, ionic strength, and competition with (nonparamagnetic) Ca2+ ions. In addition, we sketch the theory of screening of the negative surface charges of the vesicles due to both specific binding of Mn2+ ions and nonspecific effects of other mobile solute ions. The major result is that the NMRD profiles, although qualitatively similar, vary systematically as the parameters of the solutions are altered, in a manner consistent with the theory of screening. The profiles of the Mn2+‐vesicle complexes are much like those of Mn2+‐protein complexes that have the ions in an octahedral ligand environment. In addition, we find that the profiles are similar to those reported for Mn2+ ions in packed liver cells and liver tissue, supporting a previous conjecture that available Mn2+ in liver binds to the polar head groups of cell membranes, saturating these sites before binding elsewhere. Again, it is evident that results for in vitro model systems can be extrapolated reliably to tissue behavior. © 1988 Academic Press, Inc.
Averaging error in NMR slice profile measurements
Authors: Selikson Mark , Fearon Thomas
Published: March 2007

Slice thickness is a primary operational parameter in the evaluation of the performance of an MRI system with regard to providing accurate imaging of a slice of tissue. Of the various methods that have been utilized to evaluate slice thickness, a continuous high‐signal ramp has gained the most support as the method of choice. However, problems with the accuracy of the measurement method have been associated with the finite thickness of the ramp. This report considers the accuracy of the measurement method as a function of ramp width. © 1988 Academic Press, Inc.
A volume‐localized, two‐dimensional NMR method for the determination of lactate using zero‐quantum coherence created in a stimulated echo pulse sequence
Authors: Sotak Christopher H.
Published: March 2007

A volume‐localized, two‐dimensional NMR method which unambiguously measures lactate protons in the presence of interfering lipid resonances is presented. This technique employs the stimulated echo method for spatial selection and was used to observe lactic acid levels in a subcutaneously implanted RIF‐1 tumor at a concentration of 9.6 mM.. © 1988 Academic Press, Inc.
Concurrent measurements of cerebral blood flow, sodium, lactate, and high‐energy phosphate metabolism using 19F, 23Na, 1H, and 31P nuclear magnetic resonance spectroscopy
Authors: Eleff Scott M. , Schnall Mitchell D. , Ligetti Laszlo , Osbakken Mary , Subramanian Harihara , Chance Britton , Leigh John S.
Published: March 2007

A new NMR technique for nondestructive, noninvasive, nonradioactive concurrent measurements of blood flow and several energy‐dependent metabolites were applied to in situ cat brain during high cerebral blood flow states (seizures) and low flow states (carotid occlusion plus hemorrhagic shock). An inductively coupled, quadruple‐tuned surface coil with a 50‐ohm match at all relevant frequencies was used for both excitation and receiving. A broadband spectometer was used to measure the 31P spectrum (PCr, ATP, Pi, and pH), a water‐suppressed 1H spectrum (lactate), 23Na, and 19F (blood flow via CHF3 washout). Each nucleus was excited at an independently determined rate. Sodium, with a short T1, was excited more frequently than phosphorus. The results qualitatively agreed with other techniques. Blood flow greatly increased during seizures with a 10% decrease in the Na signal, minimal lactate accumulation, no pH shift, and a change in the PCr‐to‐Pi ratio from 3.4 to 1.7. During carotid occlusion plus hypotension blood flow, PCr and ATP decreased to less than 10% of baseline values. Changes in PCr and Pi preceded parallel changes in Na and ATP. These experiments demonstrated the feasibility of concurrent measurements of physiologically induced changes in high‐energy phosphates, lactate, sodium, and blood flow from the same volume of brain, in a nondestructive manner using NMR spectroscopy. © 1988 Academic Press, Inc.