摘要:

AbstractHigh resolution, high frequency,in vitro, proton NMR spectra of various body fluids, including urine, sweat, aqueous humour, amniotic fluid, seminal plasma, cerebrospinal fluid, synovial fluid and blood plasma are described and discussed. Applications include the detection of metabolic disorders, investigations of the biochemical basis of drug and xenobiotic metabolism, organ damage, and diagnoses for sick babies. The determination of metabolite concentrations is straightforward for fluids with a low protein content such as urine. In fluids with a high protein content such as blood plasma, it is possible to detect not only small molecules but also mobile regions of macromolecules, and to demonstrate the interaction of anions such as lactate with proteins. It seems likely that these methods will soon become established in modern pathology laboratories.

ISSN:0952-3480    

DOI:10.1002/nbm.1940020513

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe need for NMR selective pulses in magnetic resonance imaging and spectroscopy is reviewed. The shortcomings of the current generation of pulses are discussed and the need for new categories of pulse identified. Strategies for selective pulse design are outlined and two numerical optimization methods, simulated annealing and SPINCALC (a method recently introduced by us: J. T. Ngo and P. G. Morris,Magn. Reson. Med.5, 217 (1987)), are discussed in detail. Their use is illustrated and compared for the design of π/2 phase‐compensated pulses. Both methods require substantial amounts of CPU time, with simulated annealing the more demanding. Unconstrained, simulated annealing also tends to produce pulses with discontinuous waveforms. A crude two‐dimensional pulse derived from a low flip angle approximation is illustr

ISSN:0952-3480    

DOI:10.1002/nbm.1940020514

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractAn NMR spectroscopy localization method that employs an inhomogeneous surface‐spoiling magnetic field gradient has been applied to detect the13C‐{1H} signals from deep‐lying liver tissue of ratin vivo. The method requires small gradient driving currents (less than 1 amp) and short gradient periods (˜0.5–1.6 ms). Thus, it is not likely to suffer from induced eddy currents and can detect shortT2resonances. We demonstrate that by employing a pulsed surface‐spoiling gradient one can eliminate “contaminating” signals from the surface‐lying tissues (muscle, fat and skin) while still maintaining the resonance linewidth resolution for the deep‐lying tissue of interest (liver). The feasibility of using this localization approach to trace glucose conversion into

ISSN:0952-3480    

DOI:10.1002/nbm.1940020515

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe potential use of13C multilabeled substrates has been studied in biological applications usingin vivoandin vitroproton and13C NMR spectroscopy. In13C NMR spectroscopy, multilabeled compounds allow the simultaneous observation of several nuclei or increase distinctly the signal to noise ratio due to a higher degree of enrichment. Contiguous labeling of substrates leads to homonuclear13C‐13C spin couplings and provides a simple means to distinguish between endogenous stores of metabolites and metabolites derived from added substrate

ISSN:0952-3480    

DOI:10.1002/nbm.1940020516

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe use of19F chemical shift sensitive imaging techniques to monitor the biodistribution of perfluorocarbons (PFC) is discussed. For these experiments one has to study the spectroscopic properties of the PFC to be mapped for choosing high performance NMR imaging sequences. Three techniques used in our laboratory, a chemical shift selective approach, a method using spectrum simplification and a chemical shift sensitive NMR imaging method using adjusted phase encoding are discussed and illustrated by experiments.

ISSN:0952-3480    

DOI:10.1002/nbm.1940020517

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractSeveral technological problems inin vivolocalized spectroscopy of metabolism are discussed in the context of comparing data obtained by different means. Deficiencies in spectroscopy localization methods can produce spectra that are dominated by artefactual signals derived from outside of selected volumes. Such artefacts are not usually correctly accounted for by representations of the profiles of the transverse magnetization alone. Selected sensitive volumes should be defined in terms of the size of tissue contributing the major fraction of signal to an observed spectrum, which is the integrated response from the sample including any phase cancellation effects. Phase cancellation in one‐dimensional localization techniques employing excitation by an RF field with uniform phase distribution and surface coil detection such as depth resolved surface coil spectroscopy, chemical shift imaging (CSI) and rotating frame zeugmatography (RFZ) can significantly alter the effective radius of the sensitive volumes depending on the sample distribution and the extent of the homogeneous region of the magnet. Also, discrete spatial sampling in RFZ and CSI can radiate signal artefacts of around 25% into adjacent elements depending on the location and distribution of signal sources. Acquisition delays between excitation and detection and partial saturation are other major sources of systematic error. Saturation factors for metabolites are not easily obtainable on localized volumes during clinical exams on an individual basis, but may be expediently obtained as larger‐volume tissue‐averages. Better documentation of saturation effects, acquisition delays and localized volume sizes is needed to compare and validate clinical results and perfor

ISSN:0952-3480    

DOI:10.1002/nbm.1940020518

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractClinical studies using31P and1H MRS with a whole body 2.0 T MRI/MRS system are described. In most cases, techniques to quantitate absolute molar concentrations of metabolites in various organs were used. In the brain, AIDS, chronic stroke, and white matter lesions were associated with alterations of brain31P metabolites. Epilepsy was associated with increased pH in the seizure focus. In the heart, dilated cardiomyopathy was associated with increased PDE/ATP while PCr/ATP was unchanged. In the liver, alcoholic hepatitis and cirrhosis were associated with diminished hepatic ATP while alcoholic hepatitis had increased pH and cirrhosis had decreased pH. This allowed differentiation of normal liver, alcoholic hepatitis, and alcoholic cirrhosis without biopsy. In the prostate, malignancy was associated with increased PME/ATP and decreased PCr/ATP. The PME/PCr was greatly increased in malignant prostate with no overlap in normals. Other cancers outside the brain had increased PME and effective treatment was often associated with diminished PME.1H MRS of the brain was performed using ISIS and outer volume suppression pulses for volume localization. Excellent high resolution1H water‐suppressed spectra were obtained at echo times as short as 30 ms, showing well resolved peaks for lactate,N‐acetylaspartate, glutamate, choline, creatinine, and inositol.1H MRS demonstrated that the uptake of ethanol by the brain was slower than the rise of ethanol in blood.31P spectroscopic imaging of the brain with resolution of 2.25 × 2.25 × 2.5 cm produced metabolic images and high resolution spectra from desired regions of interest. The research activities in this laboratory over the past two years demonstrate the wealth of metabolic information that can be obtained clinically with MRS. Technical advances in the area of proton MRS and spectroscopic imaging should improve the ability to detect metabolic alterations produced by human di

ISSN:0952-3480    

DOI:10.1002/nbm.1940020519

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractA procedure for obtainingT1values for phosphorous metabolites in localized regions of human subjects, using a standard 1.5 T MR imager, is described.31P spectra andT1values localized to the liver, and to abdominal and calf muscle of healthy volunteers were obtained by means of a multi‐slice spectroscopy technique, consisting of a chemical shift imaging (CSI) sequence with aB1‐insensitive excitation and one dimension of phase encoding, used in conjunction with a surface coil. An examination consisting of proton imaging, shimming and collection of31P progressive saturation spectroscopic data forT1determination required 1h to perform. Shimming on the signal from the body region detected by the surface coil gave spectra of excellent spectral resolution. Quantification of all peaks in the localized31P spectra was carried out with the PIQABLE algorithm, andT1values were calculated for inorganic phosphate (Pi), the phosphodiester region, and the ATP α‐, b̃‐ and γ peaks of liver, and for calf muscle Pi, phosphocreatine (PCr), and the three ATP peaks. The precisions of the measurement and of the entire process for obtaining and quantifying localized spectra by one‐dimensional CSI were determined, and the accuracy ofT1values obtained by this means was verified. The temporal variation inT1values obtained in a series of examinations of a single normal subject was also assessed. The consistency of theT1values obtained in this study within vivoT1values obtained by other techniques is a stringent test of accuracy of localized spectra obtai

ISSN:0952-3480    

DOI:10.1002/nbm.1940020520

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractSurface coils with strong coupling for both31P and1H were used to measure metabolite concentrations byin vivoNMR spectroscopy. Tissue water was used as an internal concentration reference and the31P and1H spatial sensitivities of the coils were matched. For such coils, sample loading does not necessarily have a significant effect on absolute quantitation results. The coils had proportionality constants which were almost independent of loading and the1H and31P flip angles at the coil centre produced by fixed length pulses were approximately equal over the range of loading conditions encounteredin vivo. For 7 normal infants, of gestational plus postnatal age (GPA) 35 to 37 weeks, the nucleotide triphosphate concentration in the cerebral cortex was 3.7 ± 0.6 mmol/L wet tissue (mean ± SD). Further studies of normal infants down to 26 weeks GPA indicated that phosphorus metabolite concentrations increased significantly with GPA during this period. Concentrations were often low in the cerebral cortices of birth asphyxiated infants. In order to provide corroboration for the results from neonatal brain, data were acquired also from the resting, unexercised forearm muscles of 6 young adults and the measured adenosine triphosphate concentration was 6.3 ± 0.8Mmol/L wet tiss

ISSN:0952-3480    

DOI:10.1002/nbm.1940020521

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractA combination of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) has been used to follow the time course of changes resulting from forebrain ischemia in the rat. The31P MRS demonstrates that the level of high energy metabolites decreases significantly during the 10 min ischemic period but returns to normal after 1 h of reperfusion. MRI shows no change after 1 h of reperfusion but significant changes in the striatum after 24 h and in the hippocampus after 48 h. These changes correlate well with histopathology. Diabetic rats have shown the effect of hyperglycemia in accentuation of ischemic and post ischemic pH changes. Conversely, diabetic rats maintained severely hypoglycemic with insulin showed little variation in pH during or following the ischemic insult. The results emphasize the importance of both MRS and MRI in following the temporal profile and distribution of ischemic neuronal injury.

ISSN:0952-3480    

DOI:10.1002/nbm.1940020522

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY