No abstract

After a brief theoretical description, new gradient-selected, proton-detected heteronuclear correlation sequences are introduced. The gs-HMBC and gs-Relayed-HMQC are closely related to the original gs-HMQC proposed by Hurd and John. A new approach to obtain pure absorption line shapes in gradient selected spectroscopy is used to measure phase-sensitive gs-HMQC spectra, to carry out multiplicity editing in HSQC spectra and to distinguish direct and long-range correlations in HMQC/HSQC-TOCSY spectra.

In this multinuclear NMR study myo-inositol is identified as a glia-specific marker for in vivo NMR studies. The unusually high inositol concentration may participate in the osmoregulatory system in asupcytes. Primary astrocytes also synthesize and export high amounts of hypotaurine, an intermediate of taurine synthesis. Taurine – another osmolyte – is synthesized from cysteine by astrocytes but not by primary neurons. Taurine as well as hypotaurine is accumulated by neurons from the extracellular medium. ¹³C NMR labelling results with 2-¹³C pyruvate indicate a considerable contribution of the anaplerotic pathway in primary neurons from rat. The activity is only half of the activity in primary astrocytes. The ratio of pyruvate carboxy-lase/malic enzyme activity versus pyruvate dehydrogenase activity reflects the degree of maturation. The ¹³C isotopomer ratio of glutamate and glutamine is different for pure astrocyte cultures. Therefore, the different isotopomer ratios of glutamate to glutamine obtained from intact brain studies alone do not prove TCA cycle compartimentation in the brain. Finally, the PCr/ATP ratio in primary astrocytes is 3 times higher than in primary neurons. This has to be considered in case of recovery from ischemic insults.

Summary: Middle cerebral artery occlusion was per formed in rats while the animals were inside the nuclear magnetic resonance (NMR) tomograph, Successful occlu sion was confirmed by the collapse of amplitude on an electrocorticogram, The ultrafast NMR imaging tech nique UFLARE was used to measure the apparent diffu sion coefficient (ADC) immediately after the induction of cerebral ischemia, ADC values of normal cortex and cau date-putamen were 726 ± 22 x 10-6 mm2/s and 659 ± 17 x 10-6 mm 2 /s, respectively, Within minutes of occlu sion, a large territory with reduced ADC became visible in the ipsilateral hemisphere, Over the 2 h observation period, this area grew continuously, Quantitative analysis of the ADC reduction in this region showed a gradual ADC decrease from the periphery to the core, the lowest ADC value amounting to about 60% of controL Two hours after the onset of occlusion, the regional distribu tion of ATP and tissue pH were determined with biolu minescence and fluorescence techniques, respectively. There was a depletion of A TP in the core of the ischemic Diffusion-weighted nuclear magnetic resonance (NMR) imaging (DWI) has been shown to be sensi tive to cerebral ischemia during the early, acute

No abstract

The ultra-fast application of the RARE experiment is described in detail, with special emphasis on its multifarious applications with preparation experiments that produce transverse magnetization. The factors affecting the temporal evolution of the magnetization during the experiment are described, and the implications for the slice profile when using a Gaussian refocusing pulse are experimentally examined. The choice of phase-encoding scheme for use with preparation experiments is discussed, as is the use of various phase-encoding schemes to reduce line broadening in the phase-encoding direction if a number of averages are acquired. An explanation for the decomposition of the echo are into two components if the read gradient is imbalanced is given, and the experimental conditions necessary for the coherent addition of these two echo groups are described. An alternative sequence that removes one of these groups from the acquisition window is proposed. The sensitivity of the sequence to flow and motion is investigated, and the drastic loss of signal in this situation explained. The in vivo and in vitro application of preparation experiments leading to the accurate measurement of T1, T2, diffusion constant, and magnetization transfer characteristics is presented. The implementation of zoom-imaging using spin- and stimulated-echo preparation is described, and 3D in vivo spin-echo zoom images are presented. Simple phantom experiments demonstrating the feasibility of chemical-shift selective and spectroscopic imaging are also given.

Nuclear magnetic resonance spectroscopy and imaging (MRI) play an indispensable role in science and healthcare but use only a tiny fraction of their potential. No more than ≈10 p.p.m. of all 1H nuclei are effectively detected in a 3-Tesla clinical MRI system. Thus, a vast array of new applications lays dormant, awaiting improved sensitivity. Here we demonstrate the continuous polarization of small molecules in solution to a level that cannot be achieved in a viable magnet. The magnetization does not decay and is effectively reinitialized within seconds after being measured. This effect depends on the long-lived, entangled spin-order of parahydrogen and an exchange reaction in a low magnetic field of 10−3 Tesla. We demonstrate the potential of this method by fast MRI and envision the catalysis of new applications such as cancer screening or indeed low-field MRI for routine use and remote application.

Pure parahydrogen (pH(2) ) is the prerequisite for optimal pH(2) -based hyperpolarization experiments, promising approaches to access the hidden orders of magnitude of MR signals. pH(2) production on-site in medical research centers is vital for the proliferation of these technologies in the life sciences. However, previously suggested designs do not meet our requirements for safety or production performance (flow rate, pressure or enrichment). In this article, we present the safety concept, design and installation of a pH(2) converter, operated in a clinical setting. The apparatus produces a continuous flow of four standard liters per minute of ≈98% enriched pH(2) at a pressure maximum of 50 bar. The entire production cycle, including cleaning and cooling to 25 K, takes less than 5 h, only ≈45 min of which are required for actual pH(2) conversion. A fast and simple quantification procedure is described. The lifetimes of pH(2) in a glass vial and aluminum storage cylinder are measured to be T(1C) (glass vial) =822 ± 29 min and T(1C) (Al cylinder) =129 ± 36 days, thus providing sufficiently long storage intervals and allowing the application of pH(2) on demand. A dependence of line width on pH(2) enrichment is observed. As examples, (1) H hyperpolarization of pyridine and (13) C hyperpolarization of hydroxyethylpropionate are presented.