bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vivo NMR spectroscopy of lithium‐7 in humans
Authors: Komoroski R. A. , Newton J. E. O. , Walker E. , Cardwell D. , Jagannathan N. R. , Ramaprasad S. , Sprig J. 
Published: March 2007

AbstractThe pharmacokinetics of lithium uptake was measured by 7Li NMR spectroscopy at 24.83 MHz in vivo in the brain and muscle of a normal subject and a patient suffering from bipolar affective disorder, using a modified General Electric Signa clinical magnetic resonance imaging system. Comparison was made to standard phantoms to estimate Li concentrations. The levels of Li in brain and muscle were similar, were typically less than the level in serum, and generally tracked the level in serum. The Li level at steady state in the brain of a patient suffering from schizoaffective disorder was measured over a 7‐month period. Substantial variation was seen, which showed some correlation with serum level. Serum level peaked about 2 h after a single 300‐mg dose at steady state, and muscle level, immediately thereafter. Brain level peaked considerably later at 4 h. Localized in vivo 7Li NMR spectroscopy was demonstrated by acquisition of a 125‐cm3 DRESS slice from the occipital region in less than 7 min. © 1990 Academic Press, Inc.
Transmural high energy phosphate distribution and response to alterations in workload in the normal canine myocardium as studied with spatially localized 31P NMR spectroscopy
Authors: Robitaille P‐M. , Merkle H. , Lew B. , Path G. , Hendrich K. , Lindstrom P. , From A. H. L. , Garwood M. , Bache R. J. , Uǧurbil K. 
Published: March 2007

AbstractSpatially localized phosphorus‐31 nuclear magnetic resonance (31P NMR) spectroscopy has been applied to the study of the normal canine myocardium to measure the relative content of high energy phosphates across the left ventricular wall. Transmural NMR data were acquired in five voxels spanning the wall of the left ventricle using the FLAX‐ISIS technique. The validity of the FLAX‐ISIS approach in acquiring localized spectra for transmural studies and in providing quantitative information from the localized spectra was examined rigorously by studies involving phantoms, intact rats, and the canine myocardium in vivo. The results indicated that (1) this technique yields spatially resolved spectra with partial overlap between adjacent voxels and virtually no overlap between every other voxel; (2) in the canine heart, signals from subepicardium, midwall, and sub‐endocardium can be detected separately without cross contamination; and (3) relative metabolite contents within a voxel and among voxels can be quantitated. Transmural 31P NMR spectra were acquired with cardiac gating on 29 separate animals either at early systole or late diastole, and at three different workloads with the heart rate peak systolic pressure product (RPP) increasing from 6000 mmHg/min to 35,000 mmHg/min. The data revealed that in the normal canine myocardium, the creatine phosphate (CP) content and the CP/ATP ratio was significantly lower in the subendocardium than in the subepicardium. ATP levels were transmurally constant. Both the CP content and the CP/ATP ratio measured for each voxel remained unaltered in relation to either the phase of the cardiac cycle or ∼ fourfold increase in workload. Free ADP levels calculated for each voxel showed that ADP was relatively higher in the subendocardium than the subepicardium, and in all transmural layers was higher than its apparent Km for oxidative phosphorylation. In this domain changes in ADP content with workload and MVO2 are not expected and were not observed. © 1990 Academic Press, Inc.
An ESR study of pathologic red blood cell membranes (RBCM)
Authors: Perussi Janice R. , Costa Fernando F. , Baffa Oswaldo , Zago Marco A. , Tintoand Maria H. , Tabak Marcel 
Published: March 2007

AbstractA comparative study of red blood cell membranes from normal subjects and β‐thalassemia and sickle cell anemia patients was performed by spin labeling at the lipidic and protein phase. The results show that the quantity of bound spin label is the same for sickle, thalassemic, and normal membranes. The data from 5‐doxyl stearic acid suggest an increase in fluidity for the thalassemic membrane. © 1990 Academic Press, Inc.
MR fourier transform arteriography using spectral decomposition
Authors: Cho Z. H. , Jung K. J. , Ro Y. M. 
Published: March 2007

AbstractReliable separation of arteries from other stationary tissues is accomplished through spectral decomposition by exploiting the pulsatile nature of the blood flow in the arteries. Fourier transformation of a series of projection images in the temporal direction along the cardiac cycle results in spectral images where the arteries are a part of the harmonic component images while stationary tissues and veins are represented as a dc component image. From the magnitude of the spectral images an arteriogram can be obtained by summation of the harmonic component images excluding the dc component image. This principle is applied to Fourier imaging in a cine mode data acquisition as well as line scan imaging. Since there is no need for the encoding of the flow‐sensitive gradient, this technique is free from eddy current artifacts which have been one of the major obstacles to projection angiography using the flow‐encoding gradient. © 1990 Academic Press, Inc.
Generalized MR interferography
Authors: Hennig J. 
Published: March 2007

AbstractGeneralized MR interferography allows the measurement of parameters which affect the phase of the MR signal. Interference is generated by the simultaneous generation of two echoes in one excitation cycle. Local variations of the signal phase are transformed into displacement of the stripe pattern generated by interference. A number of possible experiments based on this principle are presented. The resulting interferographic images allow the fast determination of parameters such as field inhomogeneity, susceptibility, flow, and motion. © 1990 Academic Press, Inc.
Motion‐insensitive, steady‐state free precession imaging
Authors: Zur Y. , Wood M. L. , Neuringer L. J. 
Published: March 2007

AbstractSteady‐state free precession (SSFP) pulse sequences employing gradient reversal echoes and short repetition time (TR) between successive rf excitation pulses offer high signal‐to‐noise ratio per unit time. However, SSFP sequences are very sensitive to motion. A new SSFP method is presented which avoids the image artifacts and loss of signal intensity due to motion. The pulse sequence is designed so that the time integral of each of the three gradients is zero over each TR time interval. The signal then consists of numerous echoes which are superimposed. These echoes are isolated by combining the data from N different scans. In each scan a specific phase shift is added during every TR interval. Each of these N isolated echoes produces a motion‐insensitive, artifact‐free image. Because all the echoes are sampled simultaneously, the signal‐to‐noise ratio per unit time in this SSFP method is higher than in existing SSFP techniques which sample only one echo at a time. The new method was implemented and used to produce both two‐ and three‐dimensional images of the head and cervical spin of a human patient. In these images the high signal intensity of cerebrospinal fluid is preserved regardless of its motion. Further work is required to evaluate the imaging parameters (TR, TE, rf tip angle) so as to give optimal tissue contrast for the various echoes. © 1990 Academic Press, Inc.
Visualization of altered myocardial lipids by 1H NMR chemical‐shift imaging following ischemic insult
Authors: Bouchard Alain , Doyle Mark , Wolkowicz Paul E. , Wilson Randall , Evanochko William T. , Pohost Gerald M. 
Published: March 2007

AbstractAcute myocardial infarction is associated with an accumulation of lipids. Spectroscopic and chemical‐shift imaging strategies which can depict the spatial distribution of these chemical species are evolving. The present study was undertaken to test whether the Dixon method could detect spatially lipids known to accumulate in myocardium after an ischemic insult. Seven dogs underwent a 24‐h coronary artery occlusion (LAD = 4, Cx = 3). Post mortem, hearts were removed and imaged ex vivo. Myocardial samples were also evaluated by high‐resolution 1H NMR spectroscopy. Lipid images revealed regions of increased signal intensity, in the regions corresponding to the myocardial infarction, particularly in the periphery of the infarction. An increase in mobile lipids was observed by 1H NMR spectroscopy of myocardial samples with moderately reduced blood flow and corresponding to regions with increased signal intensity on the lipid image. This study shows that chemical‐shift imaging may be useful for detecting alterations in myocardial lipid levels following an ischemic insult. © 1991 Academic Press, Inc.
Acute Myocardial Infarction: Comparison of T2‐Weighted and T1‐Weighted Gadolinium‐DTPA Enhanced MR Imaging
Authors: Matheijssen Niels A. A. , de Roos Albert , Van Wall Ernst E. Der , Doornbos Joost , Van Ijkman Paul R. M. D , Bruschke Albert V. G. , van voorthuisen Ad E. 
Published: March 2007

AbstractMagnetic resonance images were obtained from 32 patients with acute myocardial infarction, using a four‐echo technique (echo time (TE) = 30, 60, 90, and 120 ms) pre‐gadolinium(Gd)‐DTPA injection and a TE = 30 ms sequence pre‐ and post‐Gd‐DTPA. Intensity ratios of infarcted and normal myocardium were calculated, as were contrast‐to‐noise and signal‐to‐noise ratios. The four intensity ratios pre‐Gd‐DTPA were 1.20 ±0.15, 1.42 ± 0.22, 1.78 ± 0.38, and 1.99 ± 0.60 for TE = 30, 60, 90, and 120 ms, respectively, and 1.42 ± 0.19 post‐Gd‐DTPA (p = NS for post‐Gd‐DTPA vs TE = 60, p = 0.007 for TE = 90 vs TE = 120, p < 0.0001 for all other comparisons). The four contrast‐to‐noise ratios pre‐Gd‐DTPA were 1.69 ± 0.97, 2.69 ± 1.13, 3.17 ± 1.15, and 2.90 ± 1.09 for TE = 30, 60, 90, and 120 ms, respectively, and 2.71 ± 1.26 post‐Gd‐DTPA (p = NS for post‐Gd‐DTPA vs TE = 60, 90, and 120, p = NS for TE = 120 vs TE = 60 and 90, p< 0.01 for all other comparisons). The four signal‐to‐noise ratios pre‐Gd‐DTPA were 8.67 ± 1.47, 6.52 ± 0.76, 5.20 ± 0.64, 4.17 ± 0.53 for TE = 30, 60, 90, and 120 ms, respectively, and 9.17 ± 1.92 post‐Gd‐DTPA (p = 0.03 for post‐Gd‐DTPA vs TE = 30, p < 0.0001 for all other comparisons). In conclusion, the detectabilities of acute myocardial infarction were similar at TE = 60 ms and at Gd‐DTPA enhanced short‐TE MR imaging. However, image quality proved to be superior using the Gd‐DTPA enhanced short‐TE technique. © 1991 Academic Press, Inc.
Multiple echo SSFP sequences
Authors: Mizumoto Chris T. , Yoshitome Eiji 
Published: March 2007

AbstractWe report a new type of SSFP imaging sequences for acquiring higher‐order echoes. Spins excited during a cycle have, in a sense, a phase memory such that they can be refocused several cycles down the line, and since the spins are pulsed under a steady‐state condition, the resulting echoes have very complicated T1 and T2 dependencies. A steady‐state equation, which describes the T1 and T2 dependencies for the higher‐order echoes, is presented, and the intensity of each echo is calculated and compared with the experimental results. Although the signal intensity of the higher‐order echoes are weaker than the FID or the CE‐FAST echo, these echoes may be used to obtain images with different contrast dependencies previously unobtainable with either of the two signals. © 1991 Academic Press. Inc.
A progressive gradient moment nulling design technique
Authors: Pipe James G. , Chenevert Thomas L. 
Published: March 2007

AbstractA method is presented for designing motion‐compensated gradients in a progressive manner. The method is easily applicable to many types of waveforms, and can compensate for any order of motion. It can be implemented graphically or numerically. Underlying theory and examples of its application are provided. © 1991 Academic Press, Inc.
MR angiography without subtraction
Authors: Zur Y. , Zou X. , Neuringer L. J. 
Published: March 2007

AbstractA new NMR method for producing angiograms with strong suppression of the static spin signal and without the need for subtraction is described and demonstrated. A velocity‐selective pulse sequence was implemented whereby the magnetization of all stationary spins is driven to the —z axis and is not detected, while maximizing the signal intensity of the moving spins. A theory of the method is presented and gives good agreement with experimental results obtained on a flow phantom. It is shown theoretically and experimentally that high‐quality velocity‐independent angiograms of the head and neck can be obtained with strong suppression of static spin signal when TR ∼ T1. The method can be extended to produce three‐dimensional angiograms. © 1991 Academic Press, Inc.
19F NMR imaging of cerebral blood flow
Authors: Branch Craig A. , Helpern J. A. , Ewing James R. , Welch K. M. A. 
Published: March 2007

AbstractTechniques for the quantitative imaging assessment of cerebral blood flow are presented in a cat using 19F NMR imaging of trifluoromethane. The input function of the indicator was acquired noninvasively, while its uptake and clearance were followed in 2‐cc volume voxels from images acquired at 67 sintervals. A single compartment model yielded normal cerebral blood flow estimates. © 1991 Academic Press, Inc.
Multiexponential proton relaxation in model cellular systems
Authors: Menon R. S. , Rusinko M. S. , Allen P. S. 
Published: March 2007

AbstractWater proton relaxation measurements obtained from model cellular systems composed of red blood cell (RBC) ghosts are presented. The purpose of the investigation was to evaluate hypotheses concerning the possible sources of multiple exponential components in similar relaxation measurements made on tissue. Both laboratory frame transverse and longitudinal relaxation rates, as well as rotating frame relaxation rates, were measured in preparations of RBC ghosts and “extracellular fluid” that were, (a) uniformly mixed or (b) compartmentalized by layering, as the concentration of serum albumin was varied in the “extracellular fluid.” The data show that although transmembrane exchange is too fast to give rise to multiexponential relaxation, multiple components can result from compartmentalization at the level of the cellular organization and do not necessarily require different tissue types. In addition, the data clearly demonstrate the importance of protein adsorption to cellular membranes as a determinant of the concentration of freely mobile solute protein molecules in tissue fluids. © 1991 Academic Press, Inc.
magnetic resonance imaging of lipid deposits in human atheroma via a stimulated‐echo diffusion‐weighted technique
Authors: Altbach Maria I. , Mattingly Mark A. , Brown Michael F. , Gmitro Arthur F. 
Published: March 2007

AbstractNMR images of subintimal lipid deposits within the vessel walls of atherosclerotic human aortas were obtained at 37 and 27°C at 4.7 T. A combination of a stimulated‐echo and pulsed‐field gradients was used for suppressing the mobile tissue water relative to the less mobile tissue lipids. At 27°C there was also a substantial reduction of the subintimal lipid signal intensity, which is consistent with the characteristic phase transition of cholesteryl esters in human atheroma. These results represent the first direct detection of lipid deposits in nonprotruding atherosclerotic lesions with NMR imaging. © 1991 Academic Press, Inc.
GRASE (Gradient‐and Spin‐Echo) imaging: A novel fast MRI technique
Authors: Oshio Koichi , Feinberg David A. 
Published: March 2007

AbstractA fast multi‐section MR imaging technique is described. Gradient‐ and spin‐echo (GRASE) imaging utilizes the speed advantages of gradient refocusing while overcoming the image artifacts arising from static field inhomogeneity and chemical shift. Image contrast is determined by the T2 contrast in the Hahn spin echoes. A novel k‐space trajectory temporally modulates signals and demodulates artifacts. © 1991 Academic Press, Inc.
The magnetic field dependence of proton spin relaxation in tissues
Authors: Bryant Robert G. , Mendelson Daniel Ari , Lester Cathy Coolbaugh 
Published: March 2007

AbstractThe magnetic field dependence of water‐proton relaxation is reported for a simple protein solution, a cross‐linked protein solution, and a series of rat tissues, fresh, dried and rehydrated. The shape of the magnetic field dependence associated with water proton relaxation in tissues is accounted for by magnetic dipole‐dipole interactions between the mobile water spins and the immobile spin populations of the nonrotating components of the tissue coupling the behavior of the immobilized spin system to that of the mobile water spin system. The effect of this coupling is to impart the field dependence of the relaxation associated with the immobilized spin population to that of the mobile water spins that are observed in most relaxation and imaging experiments. © 1991 Academic Press, Inc.
High‐resolution 1H NMR imaging of regional ischemia in the isolated perfused rabbit heart at 4.7 T
Authors: Chatham John C. , Ackerman Stacey , Blackband Stephen J. 
Published: March 2007

AbstractHigh‐resolution 1H NMR images of the isolated perfused rabbit heart were recorded before and after the induction of regional ischemia while the heart was arrested. On T2‐weighted images the ischemic region appeared darker than the surrounding tissue and a 28% reduction in T2 was measured from the images. Infusion of an NMR contrast agent demonstrated that the hypointense region on the T2‐weighted image was from the ischemic region, which was further confirmed by histological analysis of the heart. It is proposed that the decreased T2 in the ischemic region may be a consequence of changes in water compartmentalization. It is possible that these changes may be used to follow the evolution of tissue injury during ischemia, and therefore provide information regarding the transition between reversible to irreversible injury in the isolated perfused heart. © 1991 Academic Press, Inc.
Transverse relaxivity of particulate MRI contrast media: From theories to experiments
Authors: Muller Robert N. , Gillis Pierre , Moiny Francis , Roch Alain 
Published: March 2007

AbstractComputer simulations and experimental approach have been used to characterize the properties of particulate MRI contrast agents with special attention paid to the influence of particle size. Up to approximately 50 nm, an increase of the particle diameter leads to a strong enhancement of the transverse magnetization decay rate. For larger grains or aggregates, the decay rate measured without spin‐echo formation reaches a plateau. When observed through a spin‐echo sequence, the transverse magnetization decay rate becomes slower on increasing the particle size or on shortening the echo time. For these large particles, multiexponential decay rates are observed. Definition and measurement of relaxivity in such systems is discussed. © 1991 Academic Press, Inc.
A new lipophilic gadolinium chelate as a tissue‐specific contrast medium for MRI
Authors: Weinmann H.‐J. , Schuhmann‐Giampieri G. , Schmitt‐Willich H. , Vogler H. , Frenzel T. , Gries H. 
Published: March 2007

AbstractGd‐Ethoxybenzyl‐DTPA (Gd‐EOB‐DTPA) is a highly water‐soluble paramagnetic contrast agent. Due to its protein binding of about 10% and its lipophilic residue, Gd‐EOB‐DTPA exhibits both renal (30% of the dose) and hepatobiliary (70%) excretion in rats. Despite its lipohilic character, the compound displays a low toxicity (LD50 = 7.5 mmol/kg). T1‐relaxivity of 5.3 liters mmol−1 s−1 in water, 8.7 liters mmol−1 s−1 in plasma, and 16.9 liters mmol−1 s−1 in rat liver together with the hepatocellular uptake explain the liverspecific contrast enhancement of Gd‐EOB‐DTPA. The diagnostic dose is considerably lower than the amount of Magnevist used in abdominal imaging. The preclinical studies suggest its clinical role as being a hepatobiliary contrast agent for MRI. © 1991 Academic Press, Inc.
A new macrocyclic MRI contrast agent: Gd MCTA complex
Authors: Schaefer Michel , Meyer Dominique , Beaute Sylvie , Doucet Didier 
Published: March 2007

AbstractA new macrocyclic complex Gd‐MCTA has been synthesized which exhibits a higher LD 50 compared to Gd‐DOTA. These two complexes show comparable NMRD profiles. © 1991 Academic Press, Inc.
Clinical experience with contrast enhanced echo‐planar imaging of the brain
Authors: Worthington B. S. , Bullock P. , Stehlings M. , Gowlnad P. , Firth J. L. , Mansfield P. 
Published: March 2007

AbstractThe overall effects of intravenous Gd‐DTPA on tissue signal in intracranial tumors are complex depending on dose, time of administration, pulse sequence, and tissue structure. Ultrahigh speed EPI permits the kinetics of tissue enhancement in intracranial tumors to be studied during the “wash‐in” equilibrium and “wash‐out” phases. Ongoing studies employing dynamic scanning have shown it to be a valuble adjunct to a morphological study of tumors, providing an assessment of vascularity which is important in planning resction; and demonstrating areas with maximal breakdown of the blood‐brain barrier which are most suitable for stereotactic biopsy. There are grounds for anticipating that the alalysis of the temporal profil of enhancement may allow discrimination between different tumor types and provide information on factors which relate to the malignant potential of a single type. © 1991 Academic Press, Inc.
Susceptibility contrast imaging of cerebral blood volume: Human experience
Authors: Rosen B. R. , Belliveau J. W. , Aronen H. J. , Kennedy D. , Buchbinder B. R. , Fischman A. , Gruber M. , Glas J. , Weisskoff R. M. , Cohen M. S. , Hochberg F. H. , Brady T. J. 
Published: March 2007

AbstractMagnetic resonance (MR) can offer a unique window on the structure/function relationships in the brain, by utilizing the established link between tissue function, metabolism, and hemodynamics. This report focuses on recent applications of MR‐based crebral blood volume (CBV) imaging in humans. Our methodology uses high‐speed “single‐shot” or echo planar imaging techniques, which provide the necessary temporal resolution for maping the rapid cerebral transit of contrast agents. These MR CBV mapping techniques have been used to study normal human brain task activation and in the clinical study of patients with brain tumors. In the latter, positron emission tomography imaging was used for functional metabolic and CBV correlation. Susceptibility contrast CBV imaging should allow us to improve our understanding of the relationship between the detailed physiology and morphology of the microvascular bed and functional attributes of the brain. These techniques can be applied to understanding fundamental questions of cognitive neuroscience and can aid in improving diagnostic sensitivity and specificity in various neuropathologies. © 1991 Academic Press, Inc.
Liposomes as MR contrast agents: Pros and cons
Authors: Unger Evan , Shen De Kang , Wu Guanli , Fritz Thomas 
Published: March 2007

AbstractLiposomes are generally thought of as being useful for entrapping drugs within their internal aqueous space. When used with MR contrast agents, this has the drawback that water flux across the membrance bilayer is limiting to contrast enhancement. This can be partially overcome by making the liposomes very small, such that surface area is relatively great compared to internal volume, thereby facilitating water exchange. Alternatively the membranes can be designed to be permeable to water but this may render the vesicles unstable in serum. Another approach is to incorporate the contrast agents into the lipid bilayer. By designing novel complexes of manganese with the ligands incorporated onto dual acyl chains, we have achieved R1 and R2 values of over 20/mmol sec−1 or more than five times higher than Gd‐DTPA. Hepatic metastasis detection is significantly improved in rats at doses of only 10 μmol/kg manganese. Membrane‐bound manganese complexes function as highly effective liver imaging agents and merit further study for development as agents to undergo human clinical trials. © 1991 Academic Press, Inc.