摘要:

AbstractNow that both magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) have reached their decadic majority, appropriate questions may be asked as to their accomplishments and prognostications for the future. This article emphasizes the approach of the metabolic biologists/physiologists to magnetic resonance biochemistry as indicated by the currently available multinuclear localized approaches. The viewpoint is emphasized that MRS is a critical care instrument where precipitious changes of oxidative metabolism lead to the well‐known stroke, heart failure, liver failure, kidney failure, etc. Generally, the gradation between the classical metabolic steady state of life and the pathway leading to cell death is a narrow one and magnetic resonance in some cases is too finely tuned to delineate the gradations of stability and instability of cell metabolism. To this point, magnetic resonance can be supplemented by other modalities that sense tissue distress. An example of a most useful and predictive measure of hypoxic stress is optical spectrophotometry which uses time resolved ranging methods to measure optical path lengths to quantitate hemoglobin deoxygenation in tissues. With such a complement, the two methods emerge as one of general importance in diagnostic procedure

ISSN:0952-3480    

DOI:10.1002/nbm.1940020503

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractMetabolites in brain and muscle of normal human volunteers have been studied by localized1H and31P NMR spectroscopyin vivo.Localization was achieved by means of stimulated echo (STEAM) sequences for both water‐suppressed1H NMR (TE = 20 ms) and31P NMR (TE = 3 ms). Volumes‐of‐interest and measuring times selected for brain spectroscopy were 8 mL and 6.5 min for1H NMR and 125 mL and 13 min for31P NMR, respectively. General problems relating to spatial localization, spectral resolution, and quantitation ofin vivoNMR data are discussed with respect to the nucleus and organs under investigation. They are correlated to studies of tissue extracts obtained at field strengths of 2.35 T (Bruker Biospec) and 7.0 T (Bruker MSL 300). Human studies were performed at 2.0 T on a whole‐body research system (Siemens Ma

ISSN:0952-3480    

DOI:10.1002/nbm.1940020504

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

Abstract1H NMR spectroscopy of human brainin vivocan be used to detect a number of cerebral metabolites includingN‐acetylaspartate, creatine + phosphocreatine and choline‐containing compounds. We have used1H NMR spectroscopy to analyse these signals in (i) biopsy material from both normal human brain and astrocytomas, and (ii) primary astrocyte cultures. On the basis of this analysis, we conclude thatin vivo1H NMR spectroscopy could play an important clinical role in the non‐invasive assessment of neuronal degeneration and proliferation of non‐neurona

ISSN:0952-3480    

DOI:10.1002/nbm.1940020505

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractTwo single‐shot localization techniques, STEAM and PRESS, are analyzed with regard to specifications forin vivolocalized proton NMR. In particular, attention is paid to optimum signal intensity per unit volume, sensitivity to motion and diffusion, shortest attainable echo time, water suppression and editing possibilities. Experimental results are shown for cat brain at 4.7 T and human brain at 1.5 T. Both STEAM and PRESS are highly effective localization methods. For long echo times, PRESS is the method of choice, because it offers a factor of two gain in signal intensity. In addition, the method is less sensitive to motion and diffusion, and not susceptible to multiple‐quantum effects. STEAM offers advantages for observation of (coupled) metabolites with shortT2, because (a) shorter TEs can be attained and (b) effective water suppression sequences can be implemented without penalty in echo time. Differences relating to editing possibilities andB1dependence, possibly important in choosing a method, are discus

ISSN:0952-3480    

DOI:10.1002/nbm.1940020506

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractMR spectra simultaneously acquired from different locations in the human body may be obtained with the SIMUVOSP technique (Simultaneous Multivolume Spectroscopy). SIMUVOSP is based on multifrequency selective RF pulses which encode positional information of the spins into the phase of the MR signal. This paper describes SIMUVOSP strategies for1H,31P and13C spectroscopy.For1H SIMUVOSP the STEAM experiment may be modified by replacing the selective RF pulses with SIMUFREX pulses (Simultaneous Multifrequency Excitation pulses). This modification allows the simultaneous spectroscopic examination of different regions in the human brain. For31P SIMUVOSP the ISIS method is combined with SIMUFRIN (Simultaneous Multifrequency Inversion) pulses, which generate the inversion of multiple regions during the RF pulse. An application of31P SIMUVOSP is the study of the metabolic heterogeneity of the high energy phosphates within the human body. For13C spectroscopy a localized polarization transfer experiment is combined with multivolume excitation. In this way SIMUVOSP on protons is extended to13C multivolume spectroscopy.

ISSN:0952-3480    

DOI:10.1002/nbm.1940020507

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractIt is demonstrated that it is possible to acquire two volume selective1H NMR spectra of human brainin vivo, consisting of voxels of 1.5 × 1.5 × 1.5 cm3, within 14 min with a good S/N ratio. This is mainly achieved by the application of a PRESS sequence generating a spin‐echo of the VOI at 135 ms in conjunction with the STABLE technique by which two spectra can be recorded in an interlaced mode. TheBohomogeneity over such small voxels is considerably higher than over larger voxels. With these methodological improvements it is possible to observe morphological heterogeneity of tumors. The results indicate that spectral changes seem to correlate with the metabolic state of the tumor rather than the tumor type. Additionally the spectrum of a patient with multiple sclerosis suggests that even differentiation between tumors and other lesions might not be possi

ISSN:0952-3480    

DOI:10.1002/nbm.1940020508

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

Abstract1H NMR spectroscopy of brain extracts was used to investigate the metabolic changes that take place during development of the neonatal rat brain. Data were obtained over the range 1–21 days. The concentration ofN‐acetylaspartate rose by a factor of 9 during this period, the most rapid rise occurring after day 9. The total creatine concentration rose from days 1–21, with a large increase between days 1 and 5. Taurine concentration rose until day 5, then fell from days 5–21. The concentration of choline‐containing compounds fell during the 21 day period. The results are discussed in relation to brain development and conventional biochemical data. A major conclusion in relation to spectroscopy of children is that interpretation of changes seen in disease will require adequate data from age‐match

ISSN:0952-3480    

DOI:10.1002/nbm.1940020509

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractA lactate map of the rat kidney is presented, using a four‐dimensional spectroscopic imaging technique in connection with a double resonance editing scheme. A voxel size of 12 μL has been obtained, and we show that eddy currents do not affect the line shape of an individual vox

ISSN:0952-3480    

DOI:10.1002/nbm.1940020510

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractSpectroscopic imaging and single voxel localization are compared with respect to the signal to noise ratio per unit time and unit volume. It is shown experimentally that, when using the same experiment time and the same voxel size, both methods give similar results. In order to investigate the localization limits of spectroscopic imaging, lipid distribution in a single large cell was measured and correlated with gradient echo microscopy.

ISSN:0952-3480    

DOI:10.1002/nbm.1940020511

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractFor the validation of volume‐selective1H and31P NMR spectroscopy of the brain methods are required that allow high resolution quantitative mapping of tissue pH and metabolites on intact brain slices. The following techniques are proposed for this purpose. Tissue pH is imaged on cryostat sections ofin situfrozen brains, using umbelliferone as a fluorescent pH indicator (Csibaet al, Brain Res289, 334–337 (1983)). Regional tissue ATP content is measured in adjacent cryostat sections, using the luciferine/luciferase system of fireflies for evoking substrate‐specific bioluminescence (Kogure and Furones Alonso,Brain Res.154, 273–284 (1978)). Lactate content is imaged in a similar way by inducing substrate‐specific bioluminescence with lactate dehydrogenase and luciferase from vibrio Fischeri (Paschen,J. Cereb. Blood Flow Metab.5, 609–612 (1985)). The spatial resolution of these techniques is better than 100m̈, as exemplified in experimental brain tumors and brain infarct of cats.The applicability of biochemical mapping for the validation of NMR spectroscopy was tested in a global brain ischemia model of cat by correlating surface coil31P and1H spectra with the corresponding regional biochemical data, measured in the sensitive volume of the coil. Correlation coefficients werer= 0.907, 0.852 and 0.924 for pH, lactate and ATP, respectively. These results demonstrate that the biochemical measurements obtained by bioluminescence and fluoroscopic imaging correlate closely with the NMR data and, therefore, are appropriate for the validation of more complex applications, such as volume‐selective spectroscopy of brain infa

ISSN:0952-3480    

DOI:10.1002/nbm.1940020512

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY