摘要:

AbstractThe radio frequency field (B1) gradient of a surface coil can be used to obtain spectra from a series of sample regions which experience different B1field strengths. We previously reported that the sensitivity of this method, known as the surface coil rotating frame experiment (SCRFE), can be enhanced by applying a composite pulse immediately after signal acquisition to sample residualZmagnetization which is normally undetected. Initially this modified SCRFE was used to obtain spatially resolved spectra across a B1gradient of a factor of 2.5. Here we demonstrate the extension of this method to map phosphorylated metabolites across a B1gradient of a factor of close to 5. Computer simulations were used to evaluate the performance of the composite pulse, and to assist in analyzing the data. The method was used to obtain31P spectrain vivofrom various tissue layers within and beneath a murine Meth‐A tumor. The spectra differentiated between metabolite levels in tumor tissue and underlying skeletal muscle. Metabolic heterogeneity within the tumor itself was also eviden

ISSN:0952-3480    

DOI:10.1002/nbm.1940010402

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

Abstract31P spectra of rat tumours obtained with surface coils are shown to include skin signals of varying intensity. As reported previously by Stubbs, M., Rodrigues L. M., and Griffiths, J. R., (NMR in Biomedicine1, 50–55, 1988) three hepatomas (rapidly growing Morris heptoma 7777 and slow growing 9618A, and the UA hepatoma) had negligible phosphocreatine (PCr) or creatine (Cr) in acid extracts but frequently had PCr signals in surface coil spectra. Prolactinomas and mammary adenocarcinomas, which had significant PCr and Cr in extracts, showed higher PCr/NTP ratios in spectra takenin vivothan in extracts. A phantom for studying skin signalsin vivois described. A glass sphere of typical tumour size (3–4 mL) is implanted subcutaneously in the rat. Variations in skin signal with pulse duration are demonstrated with this phantom. The factors that could contribute to skin artefact in31P tumour spectra include: (i) the relative concentrations of metabolites in skin and tumour; (ii) the skin thickness, which depends on the implantation site and rat size; (iii) skin invasion by the tumour; (iv) coil design (solenoid coils and Faraday shields are unlikely to eliminate this problem); (v) pulse repetition times; (vi) pulse duration and other NMR parameters. Careful attention to these factors could reduce skin artefa

ISSN:0952-3480    

DOI:10.1002/nbm.1940010403

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractSuspensions of rabbit renal proximal tubular (PCT) cells were incubated with [2‐13C] and [3‐13C]pyruvate. The perchloric acid extracts of the cell pellets were examined by13C NMR. All experiments showed that enriched lactate, alanine, glutamate, and glutamine were the main metabolic intermediates, and that enrichment to a minor extent was found in the glutamate residue of glutathione (GSH). From these experiments, it could be deduced that PCT cells show a highly glycolytic activity, whereas enrichment of glucose exhibits gluconeogenesis. The estimation by13C NMR of the ratio of the flux into the Krebs cycle via pyruvate carboxylase to the flux via pyruvate dehydrogenase is discussed. From incubations with 10 mM13C‐labelled pyruvate, we calculated from the relative enrichments of the glutamate carbon atoms that the ratio of pyruvate carboxylase to pyruvate dehydrogenase is 1.44 ± 0.04 in rabbit renal proximal t

ISSN:0952-3480    

DOI:10.1002/nbm.1940010404

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe limited chemical shift dispersion ofin vivo31P NMR spectra obtained at the relatively low field strengths used for human applications is the cause of poor spectral resolution. This makes it difficult to obtain accurate quantitative information from overlapping resonances, and interesting resonances may be obscured. At 1.5 T unresolved1H–31P couplings contribute significantly to the linewidth ofin vivo31P NMR resonances. Therefore, proton decoupling can improve spectral resolution substantially, resulting in better resolved resonances and more reliable quantitative information. In this work it is shown that well resolved resonances of glycerophosphocholine, glycerophosphoethanolamine and phosphoethanolamine are obtained in1H decoupled31P NMR spectra of human muscle, brain, and liver. In spectra of the human heart it has been possible to resolve the myocardial Pisignal from the signals of 2,3‐diphosphoglycerate from blood. With surface coils it is difficult to achieve broadband decoupling over the entire sensitive region of the coil by using conventional decoupling sequences. This problem has been overcome by applying a train of frequency modulated inversion pulses to achieve proper decoupling despite B2inhomogeneity. Broadband1H decoupling of31P NMR spectra was possible without exceeding specific absorption rate guideli

ISSN:0952-3480    

DOI:10.1002/nbm.1940010405

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractImage localized31P magnetic resonance (MR) spectroscopy of the liver was performed in twelve normal volunteers and seven patients with hepatic tumours. The tumours which were clearly imaged by proton MR could also be distinguished from normal tissue because of spectral differences. The malignant tumours had significantly elevated phosphomonoester/inorganic phosphate and phosphomonoester/b̃‐adenosine triphosphate ratios, probably due to elevated tumour concentrations of phosphocholine and phosphoethanolamine, which are intermediates in the synthesis of membrane phospholipids. The pH values of the malignant tumours were elevated compared to normal hepatic parenchyma. Liver spectra in two patients with the commonest benign hepatic neoplasm, cavernous haemangioma, differed from both normal tissue and the malignant tumours in having a very low signal/noise ratio but apparently normal relative levels of phosphomonoest

ISSN:0952-3480    

DOI:10.1002/nbm.1940010406

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe use of four‐dimensional chemical shift imaging to monitor phosphorus metabolites within the human brain is illustrated. Saturation effects are described, and acquisition conditions are discussed in relation to quantification and sensitivity. The effects of magnetic field variations on spectral parameters are assessed and the use of a field mapping technique is illustrate

ISSN:0952-3480    

DOI:10.1002/nbm.1940010407

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractWe have refined the method for measuring the equilibrium exchange of the neutral phosphoryl compound dimethyl methylphosphonate across the human red cell membrane using31P NMR spectroscopy. Using this improved technique we measured a permeability coefficient of dimethyl methylphosphonate of 9.47 ± 1.01 × 10–5cm s–1at a concentration of 164 mM, at 25 °C. The transport at 25 °C was not saturable up to a concentration of 600 mMand was not inhibited by 4,4′‐diisothiocyano‐2,2′‐disulfonic acid,p‐chloromercuriphenyl sulfonic acid, copper ions or phloretin, or by thiourea or urea at 16 °C. The permeability was enhanced by b

ISSN:0952-3480    

DOI:10.1002/nbm.1940010408

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940010409

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940010401

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY