摘要:

AbstractThis study reports the firstin vivoresults using an MR contrast agent manganese dipyridoxal diphosphate (Mn‐DPDP) designed to estimate the functional status of the hepatocyte. Thirty New Zealand white rabbits were studied in groups of 5 as follows: No. 1, control, MRI scans only; No. 2 MRI before and up to 90 min following 50 μmol/kg of Mn‐DPDP iv; No. 3, rabbits received 9.3 g ethanol/kg and MRI; No. 4, as in No. 3 but following Mn‐DPDP; No. 5, MRI as in No. 2 but 18 h. following 1000 mg/kg Dgalactosamine used to induce hepatocyte necrosis; and No. 6, rabbits received D‐galactosamine and Mn‐DPDP. In this study significant ethanol‐and D‐galactosamine‐induced hepatocyte damage was indicated by the increased SGPT serum levels in the rabbit. The use of Mn‐DPDP allowed detection of early hepatocyte necrosis in these animals whereas conventional spin‐echo MRI did not. The fact that D‐galactosamine curves with and without Mn‐DPDP were not significantly different indicated virtually no membrane transport or metabolism of Mn‐DPDP in the liver. Ethanol curves were not normal, but there was still considerable residual Mn‐DPDP metabolism. Mn‐DPDP appears to be an attractive agent in assessing hepatocyte functi

ISSN:0740-3194    

DOI:10.1002/mrm.1910100102

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

年代:1989

数据来源: WILEY

摘要:

AbstractAdiabatic pulses have been employed in spectroscopic imaging and relaxation rate measurements at 4.7 T to demonstrate the feasibility of obtaining spectroscopic data from the complete sensitive volume of a surface coil using the surface coil as a transmitter and receiver. With conventionalB1sensitive pulses, spectroscopic localization or imaging techniques, such as chemical‐shift imaging, yield resonance intensities that are distorted severely as a function of space, and maximal signal is detected from a small region within the complete sensitive volume of the coil. With adiabatic pulses, however, this problem is eliminated completely. In addition, a new method of spatial localization is introduced. This method, referred to as FLAX‐ISIS, is a derivative of longitudinally modulated Fourier series window and ISIS approaches and utilizes adiabatic inversion and excitation pulses. The method allows construction of localized spectra for multiple regions along the surface coil axis by postacquisition data manipulation of a single set of free induction decays. These techniques were applied to the study of the myocardium using an implanted surface coil in an instrumented closed‐chest canine model and in an open‐chest preparation. The results demonstrate that one‐dimensional techniques are adequate for transmural detection of metabolites provided signal origin is restricted to a column perpendicular to the left ventricle wall. © 1989 Academic

ISSN:0740-3194    

DOI:10.1002/mrm.1910100103

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe objective of this work is refinement of an MR angiography technique via postprocessing removal of phase errors which inhibit static signal subtraction. Projective views of the object are obtained using interleaved flow‐compensated and noncompensated gradient waveforms. Complex subtraction of data sets is required since a projection dephase pulse is used for static signal suppression. This renders the difference image susceptible to systematic phase errors which are modeled asa smoothly varying multiplicative phase function. The error function is estimated by comparison of heavily spatial filtered renditions of the object acquired without projection dephasing in order to minimize influence of flow. The phase correction is then applied to high‐resolution data sets collected with projection dephasing to enhance flow sensitivity. The technique is demonstrated by improvement of MR angiograms of rats acquired on a 2‐T, 31‐cm‐bore system. © 1989 Academic

ISSN:0740-3194    

DOI:10.1002/mrm.1910100104

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

年代:1989

数据来源: WILEY

摘要:

Abstract31P NMR spectroscopy was used to monitor the metabolic response of the tibialis anterior muscle group to transcutaneous nerve stimulation of the peroneal nerve at a rate of 4 Hz for 5 min in human volunteers (n= 8). It is demonstrated that this technique can be used as a method of investigating effort‐free and compensation‐independent skeletal muscle exercise. © 1989 Academic Press,

ISSN:0740-3194    

DOI:10.1002/mrm.1910100105

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

年代:1989

数据来源: WILEY

摘要:

AbstractBecause clinical studies have indicated that shear in fluids may be one of the major causes of magnetic resonance image artifacts, we imaged an apparatus that would separate the effects of shear from the plethora of other motion artifacts. The apparatus contained fluid between two concentric cylinders. To produce shear, we turned the outer cylinder. To produce motion without shear, we turned both cylinders as one. Shear rates near 200 s−1(similar to those in large arteries) can cause pixel intensities either to increase 40% or decrease to background levels. Increases can occur when the velocities are nearly parallel to the phase‐encoding gradient. Decreases can occur when velocities are in the direction of the frequency gradient. The decreases are similar to those predicted from phase dispersion within a “voxel” so long as the voxel's phase warp does not exceed 2π. © 1989 Academic P

ISSN:0740-3194    

DOI:10.1002/mrm.1910100106

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

年代:1989

数据来源: WILEY

摘要:

AbstractFlow velocity distributions or spectra may be obtained by NMR imaging using an anisotropic three‐dimensional Fourier transform pulse sequence in which the low‐resolution direction encodes perpendicular velocity. Velocity spectra from regions of interest covering the entire lumens of pipes in a flow phantom containing straight sections, a jet, and a constriction suggest that velocity spectra provide useful information even when the vessels are not spatially well‐resolved. The flow in the phantom was characterized and limited measurements were made. © 1989 Academic Pres

ISSN:0740-3194    

DOI:10.1002/mrm.1910100107

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

年代:1989

数据来源: WILEY

摘要:

AbstractAlthough the measurement of the pH of biological systems using the31P NMR response of inorganic phosphate is well known, sometimes in blood absolute determination of the intensity and position ofthePiresonance is precluded by overlap from the doublet resonance of 2,3‐diphosphoglycerate. Three techniques which overcome this problem by eliminating the doublet are described and their sensitivity to the experimental parameters is assessed. © 1989 Academic Press, I

ISSN:0740-3194    

DOI:10.1002/mrm.1910100108

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

年代:1989

数据来源: WILEY

摘要:

AbstractA perfusion culture system has been developed for31P NMR study of human uveal melanoma metabolism by adapting the Vitafiber I cartridge system (Amicon).31P NMR spectra collected weekly during periods of up to 10 weeks demonstrated increasing levels of phosphorus metabolites as the anchorage‐dependent cells grew to tissue‐like density. © 1989 Academic Press,

ISSN:0740-3194    

DOI:10.1002/mrm.1910100109

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

年代:1989

数据来源: WILEY

摘要:

AbstractPhosphorus‐31 nuclear magnetic resonance (31P NMR) has been applied to study the canine heart prior to and during regional myocardial ischemia induced by partial flow reduction in the left anterior descending coronary artery (LAD). NMR data were acquired in a transmural fashion by restricting the signal to a column perpendicular to the heart wall usingB0gradients and obtaining spectroscopic spatial resolution along the third dimension using theB1gradient and adiabatic excitation. With this approach, transmural spectra were accumulated in five separate voxels spanning the wall of the left ventricle from the epicardium to the endocardium. In the normal canine myocardium the levels of high‐energy phosphates CP and ATP were relatively constant throughout the left ventricular wall, with only minor evidence of free inorganic phosphate in any of the transmural voxels. However, during sustained partial occlusion of the LAD, significant regional differences between the epi‐ and the endocardium were noted. The data demonstrate the importance of studying cardiac bioenergetics with transmural differentiation. © 1989 Academic Pres

ISSN:0740-3194    

DOI:10.1002/mrm.1910100110

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

年代:1989

数据来源: WILEY

摘要:

AbstractTwo‐dimensional1H–31P correlation spectroscopy and relaxation time measurements of intact diseased pancreas were performed in order to identify an unknown peak appearing at −0.18 ± 0.04 ppm in a31P NMR spectrum of taurocholate‐induced experimental acute pancreatitis in rats. The signal was identified as a solubilized lecithin taurocholate Complex. © 1989 Academic P

ISSN:0740-3194    

DOI:10.1002/mrm.1910100111

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

年代:1989

数据来源: WILEY