In vivo proton magnetic resonance spectroscopy studies of human brain

In vivo localized proton magnetic resonance spectroscopy (MRS) studies of brain were performed on eighteen normal subjects using the stimulated echo (STE) sequence. The absolute concentrations and proton relaxation times of N-acetyl aspartate (NAA), total creatine (Cr) and choline (Cho) were estimated. The MRS data was quantitatively analyzed for repeatability and intersubject variability. Quantitative analysis indicates excellent spectral repeatability. Significant intersubject variations in [NAA] and [Cr] have been observed while the intersubject variability in [Cho] has been found to be fairly small. Significant intensity distortions have been observed for mixing times longer than 50 msec.     

Optical and magnetic resonance spectroscopy of stimulated recombination processes in defect studies

Optical and magnetic resonance spectroscopy is widely used in the investigation of radiation-induced processes in wide-gap solids. This paper discusses the present understanding of applications of the experimental methods of optical and thermoactivation spectroscopy in the research of new materials, for applications in radiation dosimetry and digital imaging and in the basic research into the fundamental physics and chemistry of radiation. The advantages of the simultaneous use of optical and magnetic resonance techniques for the investigation of stimulated processes are considered.     

Proton magnetic resonance imaging and phosphorus-31 magnetic resonance spectroscopy studies of bromobenzene-induced liver damage in the rat.

Respiratory-gated proton magnetic resonance imaging was used to study the response of the rat liver in situ to bromobenzene, a classic hepatotoxicant. A localized region of high proton signal intensity in the perihilar region of the liver was seen 24-48 hr after an intraperitoneal injection of bromobenzene. Localized proton magnetic resonance spectra from within this region indicated that the increased proton signal intensity was not due to accumulation of fat in the liver, but primarily due to a longer T2 for the proton resonance of water. This is consistent with acute edema in this localized region. In vivo 31P magnetic resonance spectroscopy studies of the same rat livers in situ were performed. Spectroscopic conditions were determined whereby localized, quantitative 31P spectra could be obtained. Using these methods, 10 mmol/kg bromobenzene was found after 24 hr to cause a number of statistically significant (p less than 0.05) effects: a decrease in adenosine 5'-triphosphate levels from 4.1 +/- 0.5 to 3.0 +/- 0.5 mM, a decrease in phosphodiester levels from 11.3 +/- 0.9 to 9.3 +/- 0.7 mM and an increase in the phosphomonoesters from 3.0 +/- 0.4 to 5.5 +/- 1.2 mM (mean +/- standard deviation). High resolution in vitro 31P spectra of perchloric acid extracts of these rat livers showed that the increased phosphomonoester resonance was due to a selective 4.3-fold increase in phosphocholine. Thus, our in vivo and in vitro 31P magnetic resonance spectra are consistent with the hypothesis that a phosphatidylcholine-specific phospholipase C (generating phosphocholine and diacylglycerol) is activated during tissue damage. Both the imaging and spectroscopy results obtained with bromobenzene closely resemble CCl4-induced liver changes previously reported, and may reflect a generalized response of the liver to any acutely acting toxic chemical.     

磁共振波谱与成像技术

文章简要介绍了核磁共振的基本原理,详细阐述了液体核磁共振在蛋白质结构、功能和动力学等方面的研究进展,论述了增强固体核磁共振分辨率的方法及其应用,讲述了磁共振成像的原理并综述了不同磁共振成像方法的应用研究进展,并对核磁共振的发展作了展望。     

Double-resonance circuit for nuclear magnetic resonance spectroscopy

A new double-resonance probe circuit design is described. The circuit contains no quarter-wavelength elements or equivalents, yet nonetheless achieves adequate isolation between the two input channels. It contains relatively few components, and so is both compact and efficient. It has been incorporated in two solid-state nuclear magnetic resonance (NMR) probes, with excellent results.     

Antiferromagnetic resonance studies in molecular magnetic materials

EPR spectroscopy has become an increasingly powerful tool to examine the spin states and dynamics of single-molecule magnets, but has not been exploited to probe bulk magnetically ordered phases of molecular magnets. In this article, we review the EPR spectra of antiferromagnets and canted antiferromagnets below T_N with particular reference to our own studies on the canted antiferromagnet, p-NCC₆F₄CNSSN (T_N=36 K). The antiferromagnetic resonance experiment allows the saturation of the sublattice magnetisation to be probed. In addition, the exchange and anisotropy fields (H_e and H_a), the spin-flop field (H_sf) and for canted antiferromagnets, the Dzyaloshinskii-Moriya field (H_DM), which gives rise to the spontaneous moment, can be determined.     

H Magnetic resonance imaging and P magnetic resonance spectroscopy in experimental filariasis

¹H Magnetic resonance imaging and ³¹P magnetic resonance spectroscopy (MRS) have been carried out in experimental rodent filariasis, i.e., Acanthocheilonema viteae infection in the rodent host, Mastomys coucha. The T₂-weighted image of the infected host shows fine hyperintense thread like structures of adult filariid nests in the cervical region. ³¹P MRS of normal and infected hosts, localized over the same region of interest, show seven major peaks corresponding to phosphomonoesters (including glucose-6-phosphate, fructose-6-phosphate, fructose-1-6-diphosphate, phosphorylcholine, and adenine monophosphate or AMP), inorganic phosphate, glycerophosphorylcholine, phosphoenolpyruvate, phosphocreatine and nucleoside di- and tri-phosphates. Concentrations of phosphomonoesters (PMEs) are higher in the normal rodent compared with the infected ones. In vivo ³¹P MRS provides a non-invasive assessment of tissue bioenergetics and phospholipid metabolism.     

Generalization of the lineshape useful in magnetic resonance spectroscopy

A new lineshape function is derived from the Tsallis distribution to describe electron paramagnetic resonance (EPR) spectra, and possibly nuclear magnetic resonance (NMR) spectra as well. This lineshape generalizes the Gaussian and Lorentzian lineshapes that are widely used in simulations. The main features of this lineshape function are presented: the normalization, moments, and first derivative. A number of experimental EPR spectra are compared with the results of simulations employing the new lineshape function. The results show that the new lineshape often provides a better approximation of the experimental spectrum. It is also shown that the new parameter of the lineshape function can be used to quantify the intermolecular spin-spin interactions.     

New developments in nuclear magnetic resonance using noise spectroscopy

In the 30 years since Ernst and Kaiser introduced the idea of incoherent radiation fields and their application to NMR spectroscopy, relatively few researchers have exploited the advantages of noise spectroscopy. Some recent applications of one-dimensional noise spectroscopy in NMR are presented which display a versatility which commonly is not appreciated. Excitation schemes are discussed which demonstrate both broadband and narrowband features, and demonstrate both theoretically and experimentally how noise spectroscopy allows for the observation of distortion-free broadline spectra in solids whichmay not be amenable to techniques more traditionally used in pulsed NMR experiments. It is argued that these applications of noise spectroscopy deserve a more common place in the experimentalists arsenal.     

The role of magnetic resonance spectroscopy in clinical medicine

This article presents a view which emphasises the particular perspective of a clinician who has close involvement in magnetic resonance spectroscopy (MRS) and is directed towards readers who wish to understand the likely role of MRS in clinical medicine. Many more complete reviews already exist, including two review articles from our group. Another review would hardly be justifiable and those readers seeking such an article should consult Refs. 1–5. This will be more in the nature of a personal overview of the topic and one which will touch upon some of the problems which accrue from the interactions of scientists with little appreciation of clinical medicine with clinicians who have little understanding of the complexities of the NMR experiment. Moreover, the discussion will be confined to situations where MRS is likely to impinge directly on problems of day-to-day clinical management, as opposed to situations where the results of MRS research lead to an improved understanding of particular disease states, but where there is no need for each and every patient who is a potential benificiary of the technique to undergo an MRS examination.     

Proton magnetic resonance studies of TiCuH

The TiCuH structure can be described as alternating layers of TiH₂ and Cu atoms and, thus, corresponds to a two-dimensional analog of metal hydrides with CaF₂- type structures. Measurements of the proton relaxation times for TiCuH yield an activation energy of 0.79 eV for hydrogen diffusion. This result strongly suggests the H-atoms in TiCuH jump directly between the tetrahedral sites rather than through the vacant octahedral sites as proposed for H-atom jumps in f.c.c. TiH_x. In addition, the Korringa constant and hydrogen diffusion rate for TiCuH are compared with similar parameters for TiH_x and several ternary titanium hydrides.     

89Yttrium nuclear magnetic resonance studies

With a Fourier-transform spectrometer, especially developed for nuclei with weak NMR signals, the lines of⁸⁹Y have been investigated in aqueous solutions of Y(NO₃)₃, YCl₃, and Y(ClO₄)₃. The concentration dependence of the chemical shifts of the⁸⁹Y resonance frequencies in these solutions were measured. Using this dependence, the Larmor frequency of the⁸⁹Y³⁺ ion solely surrounded by water was determined by extrapolation. The Larmor frequency of⁸⁹Y was referred to those of²H,³⁹K, and⁷³Ge with high accuracy. The magnetic moment of the⁸⁹Y³⁺ ion purely surrounded by H₂O molecules is μ(⁸⁹Y³⁺) = ?0.1368523(4) μ_N. The concentration dependence of Y(NO₃)₃ solutions in D₂O yields the solvent isotope effect δ(⁸⁹Y³⁺ in D₂O)?δ(⁸⁹Y³⁺ in H₂O)= ?(4.3±0.5)ppm. The⁸⁹Y relaxation times T₁ and T₂ of a 3 molal aqueous Y(NO₃)₃ solution were determined in the pH range ?0.5...+1.25. T₁ 190...90 s is nearly constant in this range, whereas the transverse relaxation rate T₂ ^?1 increases strongly with increasing pH; this effect seems to be due to the chemical exchange of the hydrated Y³⁺ ion between a monomer and a polymer site.