bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractLarge 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

AbstractA 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

Abstract[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

AbstractA 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

AbstractHigh‐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

AbstractA 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractA 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

AbstractPrincipal 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

AbstractAdiabatic 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

AbstractThe 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

AbstractAn 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

AbstractA 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

AbstractA 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

AbstractA 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

AbstractThe 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

AbstractGiven 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

AbstractWhen 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

AbstractWith 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

AbstractNMR 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

AbstractIrreversible 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

AbstractA 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

AbstractPhosphatidylcholine, 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

AbstractMetabolic 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.