摘要:

AbstractThe effects of pulsatile flow on spin phases in spin‐echo magnetic resonance imaging are considered. General expressions for the spin phases of the first four echoes are derived in terms of the Fourier coefficients of flow. These expressions are valid for any time‐dependent acceleration and, hence, are not restricted to constant acceleration. The derived expressions are then theoretically evaluated for aortic flow and examined at different points in the cardiac cycle. Our results show that rephasing may occur at certain points in the cardiac cycle for eitherevenoroddechoes depending upon the particular Fourier coefficients of the velocity function and the spin‐echo delay time. However, even‐echo rephasing is not always necessarily valid. Furthermore, the possibility of determining the flow velocities in the body with an appropriate series of imaging studies is also discussed. © 1987 Academic Pr

ISSN:0740-3194    

DOI:10.1002/mrm.1910040402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

Abstract31P surface coil NMR spectroscopy was used to evaluatein vivohigh‐energy phosphorus metabolism in the brains of mice with experimentally induced primary intracranial and subcutaneous KHT sarcomas.31P spectra of subcutaneous KHT tumors revealed a lack of detectable phosphocreatine (PCr) levels in the tumor as compared to the relatively high endogenous levels of PCr in normal mouse brain. As the intracerebral tumor size increased, there was a reduction in spectral PCr levels over a 23‐day postinoculation periodin situin the brain. No histologic or spectroscopic evidence of tumor‐associated necrosis or hypoxia was found. This study demonstrates that surface coil31P NMR spectroscopy can be used to monitor changes in highenergy phosphate metabolism associated with progressive growth of an experimentally induced mouse brain tumorin situ. © 1987 Academic Pres

ISSN:0740-3194    

DOI:10.1002/mrm.1910040403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThe soft tissue contrast obtained in fast imaging using rapidly repeated partial saturation sequences is usually based on differences inT1. We describe here an extension of the method which results in the development of clinically usefulT2‐based contrast. © 1987 Academic Press, I

ISSN:0740-3194    

DOI:10.1002/mrm.1910040404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThe pH‐dependent chemical shift behavior in31P NMR spectroscopy of inorganic phosphate (P1) and methylphosphonic acid (MeP) in solutions of various composition at 37°C are presented. An ionic strength dependent lowering of the pKa. values of bothP1and MeP is observed. 3 mmol/liter Mg2+did not affect the pH‐dependent chemical shift behavior ofP1and MeP in solutions containing 135 mmol/liter KCl and 5 mmol/liter NaCl. This finding: was reinforced by adding 5 mmol/liter 2,3‐diphosphoglycerate (2,3‐DPG) and 1.5 mmol/liter ATP to solutions with 3 mmol/liter Mg2+. The presence of these Mg+‐binding substances had no detectable effect on the chemical shift ofP1and MeP at various pH values The pH dependence of the chemical shift of MeP,P1and 2,3‐DPG in oxygenated erythrolysates was compared to protein free model solutions. No significant differences could be detected for MeP andP1whereas there was a change in the chemical shift of about 0.1–0.2 ppm for both phosphates in 2,3‐DPG. Finally intracellular pH estimated by31P NMR were compared to pH measured by electrode in freeze‐thawed hemolysates. At an extracellular pH of 7.341 ± 0.045 (SD) (n= 6) the intracellular pH was 7.160 ± 0.014 (SD) by the freeze‐thaw procedure and 7.213 ± 0.027 (SD), 7.172 ± 0.029 (SD), and 7.152 ± 0.033 (SD) estimated by the chemical shift of MeP, and 3‐phosphorus and 2‐phosphorus of 2,3‐DPG, respectiv

ISSN:0740-3194    

DOI:10.1002/mrm.1910040405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractMagnetic resonance imaging techniques have been developed to enable imaging of the live rat brain with thin (1.2‐mm) slices and microscopic pixels (115 × 115 μm). Signal‐to‐noise ratios high enough to realize the microscopic resolution are obtained with of coils designed for the subject and through the use of three dimensional Fourier spin warp imaging. The technique yields 16 contiguous slices. Correlation with fixed pathologic specimens enables unequivocal identification of gray and white matter structures in the brain of a live 200‐g rat. Structures clearly visible in the MR images include Ammon's horn, the hypothalamus, corpus callosum and substantia nigra, as well as a number of brainstem nuclei. © 1987 Academic

ISSN:0740-3194    

DOI:10.1002/mrm.1910040406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThe inhibitory effects of an aldose reductase inhibitor, sorbinil (Pfizer, NY), on cerebral glucose metabolism were investigated noninvasively in rat brain using19F nuclear magnetic resonance (NMR) spectroscopy and 2‐fluoro‐2‐deoxy‐D‐glucose (2‐FDG). Sorbinil given orally in the daily recommended doses (25 mg/kg) for man for the treatment of diabetic complications inhibited 2‐FDG flux into the aldose reductase sorbitol (ARS) pathway, demonstrated as a reduction in the intensity of the ARS index resonance as well as an increase in the resonance area ratio between the pentose monophosphate shunt (PMS) and ARS index resonances (PMS/ARS ratio). Spatial metabolite mapping using rotating frame one‐dimensional zeugmatography indicated that the inhibitory effect is spatially nonspecific. The present study is the first direct noninvasive observation of the effects of a pharmacological agent on cerebral enzymatic activities. © 1987 Aca

ISSN:0740-3194    

DOI:10.1002/mrm.1910040407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractRapid FLASH (fast low angle shot) NMR images are very sensitive to flow phenomena. In particular, a steady reflow of unsaturated spins from outside the imaging plane results in high image intensities which depend on the flip angle, the repetition time, and the flow velocity. Here we describe a technique that suppresses these signals by saturating remote spins prior to entering the imaging plane, e.g., by intercalating the FLASH sequence with slice‐selective 1–2‐1 pulse packages. Experiments have been carried out on phantoms and human extremities. Flow artifacts in the phase‐encoding direction of the images are strongly reduced. Vascular structures may be easily delineated using difference images obtained with and without flow supp

ISSN:0740-3194    

DOI:10.1002/mrm.1910040408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractT1andT2measurements of the brains of six human volunteers did not change in the presence of moderate blood alcohol levels. © 1987 Academic press, Inc

ISSN:0740-3194    

DOI:10.1002/mrm.1910040409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractAn electron paramagnetic resonance image was measured for the first time fromin vivofield gradient spectra of a living murine tumor (Cloudman S‐91 melanoma in the tail of a DBA‐2J mouse) using the paramagnetic nitroxide imaging agent 3‐carboxamido‐2,2,5,5‐tetramethylpyrroline‐l‐oxyl injected into the tail vein. The experiments were accomplished at L‐band frequency (1.55 GHz) with a single‐turn flat‐loop coil. A cross‐sectional image was obtained perpendicular to the tail axis, which clearly distinguished features to the submillimeter resolution level. © 19

ISSN:0740-3194    

DOI:10.1002/mrm.1910040410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractStrategies for estimating peak areas in31P brain spectra are discussed, and the widespread convolution difference method is analyzed. The Skilling maximum entropy method (MEM) algorithm is applied toin vivospectra and provides an estimate of the spectrum that is operator‐independent, although at the expense of some negative bias. It may be possible to overcome this bias. © 1987 Academic Press, I

ISSN:0740-3194    

DOI:10.1002/mrm.1910040411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY