共查询到13条相似文献,搜索用时 15 毫秒
1.
Mika Ala-Korpela Jussi-Pekka Usenius Jyrki Keisala Aad van den Boogaart Pauli Vainio Jukka Jokisaari Seppo Soimakallio Risto Kauppinen 《Magma (New York, N.Y.)》1995,3(3-4):129-136
We present here a combination of time-domain signal analysis procedures for quantification of human brainin vivo
1H NMR spectroscopy (MRS) data. The method is based on a separate removal of a residual water resonance followed by a frequency-selective time-domain line-shape fitting analysis of metabolite signals. Calculation of absolute metabolite concentrations was based on the internal water concentration as a reference. The estimated average metabolite concentrations acquired from six regions of normal human brain with a single-voxel spin-echo technique for theN-acetylaspartate, creatine, and choline-containing compounds were 11.4±1.0,6.5±0.5, and 1.7±0.2 mmol kg–1 wet weight, respectively. The time-domain analyses ofin vivo
1H MRS data from different brain regions with their specific characteristics demonstrate a case in which the use of frequency-domain methods pose serious difficulties. 相似文献
2.
3.
Preliminaryin vivo proton spectroscopic studies of the posterior chamber of the rat eye have been undertaken at 7 T. The Spatial and Chemical shift encoded Excitation (SPACE) localization sequence was used to acquire signals from 10-µl voxels and demonstrate the presence of metabolites associated with the vitreous humor, lens, retina, and the optic nerve. LocalizedT
2 andT
1 measurements of water in the vitreous humor indicate a relatively fluid environment. Susceptibility maps are used to demonstrate the difficulties ofin vivo spectroscopic investigations in the anterior regions of the eye. Comments are made concerning the implications for spectral resolution in these regions. 相似文献
4.
Wulf-Ingo Jung 《Magma (New York, N.Y.)》1993,1(1):5-9
Spectral editing of localized proton spectra was performed using a modified version of the double spin echo PRESS sequence.
Subtraction of signals obtained with two different double spin echo sequences results in a signal the spectrum of which is
characterized by suppressed signals for uncoupled spins and enhanced coupled signals. This flip angle based localized spectral
editing process is shown to work with a gain in S/N for lactate. Experiments were carried out on a Siemens Magnetom 1.5T whole-body
imager. 相似文献
5.
Transmit/receive headcoil for optimal <Superscript>1</Superscript>H MR spectroscopy of the brain in paediatric patients at 3 T 总被引:1,自引:0,他引:1
Klomp DW van der Graaf M Willemsen MA van der Meulen YM Kentgens AP Heerschap A 《Magma (New York, N.Y.)》2004,17(1):1-4
1H magnetic resonance (MR) spectroscopy is a useful tool to obtain metabolic information from the brain in paediatric patients. To detect signals of metabolites at low concentrations or from small volumes, the signal-to-noise ratio (SNR) has to be optimized. The SNR can be increased by going to higher field strengths. However, this leads to higher spectral bandwidths, which increases the chemical shift artefact. Here we present a transmit/receive headcoil which is adapted to the dimensions of the paediatric head and enables PRESS localization with high radio-frequency (RF) bandwidths that minimize the chemical shift displacement to only 5%. In addition, since the pulse lengths are shorter with higher RF bandwidths, the echo time can be reduced to 10 ms improving SNR as well.Parts of this work have been presented at the European Society for Magnetic Resonance in Medicine and Biology in Rotterdam in 2003 相似文献
6.
The linear combination of model spectra (LCModel) calculation of a parameter for long-term quality control,k
T, was introduced, representing the ratio of the temporal and nominal intensities of CH3 groups of lactate and acetate in a quality control phantom. This procedure is a part of the quality assurance of the scanner
using fully automatic measurement and calculation ofk
T parameters, and utilizing Shewhart regulation control charts for continuous evaluation of the magnetic resonance (MR) scanner
setting. The application of thek
T parameter for the correction of in vivo data increases the precision of molar concentration determination by about 4%. This
was tested by the quantitative in vivo MR determination of the molar concentrations of 13 prominent metabolites (N-acetylaspartate (NAA),N-acetylaspartylgutamate, creatine and phosphocreatine (Cr), choline-containing compounds (Cho), myo-inositol, scyllo-inositol.,
γ-aminobutyric acid, glutamine, glutamate, glucose, lactate, alanine, taurine) in the white matter and hippocampus of the
brain in groups of volunteers, using a short echo time stimulated echo acquisition mode sequence (echo time =10 ms) and the
LCModel technique. The repeatability of the measurement of prominent metabolites such as NAA, Cr and Cho was found to be around
10% (relative standard deviation,n=6); precision in a group of volunteers (n=20 and 28, respectively) was in the range of approximately 13–20%. For other metabolites, which are measured with a lower
signal-to-noise ratio, the precision can be much lower. 相似文献
7.
Comparison of in vivo1H MRS of human brain tumours with1H HR-MAS spectroscopy of intact biopsy samples in vitro 总被引:3,自引:1,他引:3
Sarah J. Barton Franklyn A. Howe Andrew M. Tomlins Simon A. Cudlip Jeremy K. Nicholson B. Anthony Bell John R. Griffiths 《Magma (New York, N.Y.)》1999,8(2):121-128
High resolution magic angle spinning (MAS)1H nuclear magnetic resonance (NMR) spectroscopy has been employed to study intact human brain tumour tissue and comparison
with the corresponding in vivo spectrum has been made. Two dimensional1H MAS-NMR measurements, including J-resolved and homonuclear shift correlation spectra, were obtained to aid metabolite signal
assignment. MAS gave greatly improved line-shape and reduced line-width in comparison to conventional high resolution in vivo1H MRS of intact tissue, permitting the simultaneous detection of cellular lipids and metabolites. The technique provides the
most direct method for comparison of in vivo spectra with high resolution spectra in vitro and hence allows more reliable
peak assignment of in vivo1H MRS spectra. 相似文献
8.
1H MR spectroscopy is routinely used for lateralization of epileptogenic lesions. The present study deals with the role of
relaxation time corrections for the quantitative evaluation of long (TE=135 ms) and short echo time (TE=10 ms) 1H MR spectra
of the hippocampus using two methods (operator-guided NUMARIS and LCModel programs). Spectra of left and right hippocampi
of 14 volunteers and 14 patients with epilepsy were obtained by PRESS (TR/TE=5000/135 ms) and STEAM (TR/TE=5000/10 ms) sequences
with a 1.5-T imager. Evaluation was carried out using Siemens NUMARIS software and the results were compared with data from
LCModel processing software. No significant differences between the two methods of processing spectra with TE=135 ms were
found. The range of relaxation corrections was determined. Metabolite concentrations in hippocampi calculated from spectra
with TE=135 ms and 10 ms after application of correction coefficients did not differ in the range of errors and agreed with
published data (135 ms/10 ms: NAA=10.2±0.6/10.4±1.3 mM, Cho=2.4±0.1/2.7±0.3 mM, Cr=12.2±1.3/11.3±1.3 mM). When relaxation
time corrections were applied, quantitative results from short and long echo time evaluation with LCModel were in agreement.
Signal intensity ratios obtained from long echo time spectra by NUMARIS operator-guided processing also agreed with the LCModel
results. 相似文献
9.
4. Conclusions Combined respiratory and cardiac triggering improves the localization accuracy and spectral quality in cardiac1H-MRS dramatically leading to substantially increased spectral reproducibility. The best practical realization of double triggering turned out to be the use of the ECG amplitude when making use of the fact that it is modulated by respiration. In spite of the spectral quality achieved in most subjects, we still fail to record satisfactory spectra in a minority of subjects. The reasons for this are not understood at present but must be some particulars of either a given subject or the experimental setup. The cardiac1H-MR spectra contain quantifiable contributions from creatine, TMA, lipids, and probably taurine. It is possible that the spectral contributions of creatine are subject to dipolar coupling similar to the observations for skeletal muscle. 相似文献
10.
Hattingen E Lanfermann H Menon S Neumann-Haefelin T de Rochement RD Stamelou M Höglinger GU Magerkurth J Pilatus U 《Magma (New York, N.Y.)》2009,22(1):43-52
OBJECT: To evaluate if combined (1)H and (31)P MR spectroscopic imaging (MRSI) before and after treatment of severe internal carotid artery (ICA) stenosis detects significant changes in energy metabolism in the basal ganglia of both hemispheres. MATERIALS AND METHODS: A group of 14 patients with high-grade ICA stenosis and 11 healthy control subjects were examined with 2D (1)H MRSI and 3D (31)P MRSI at 3 T before and after treatment of severe ICA stenosis. Spectroscopic data were processed with LCModel and jMRUI software. Changes of the phosphorylated metabolites, pH, N-acetyl-acetate, creatine and choline-containing compounds prior/post intervention were analyzed and patients' data were compared with that of control subjects. RESULTS: Untreated patients had significantly higher Adenosindiphosphate (ADP) in basal ganglia ipsi- and contralateral to the side of ACI stenosis compared to controls. After treatment, ADP of both hemispheres significantly decreased by approximately 20% compared to the pre-treatment values. Further, significant decreases of phosphorylated metabolites prior/post intervention were found for patients compared to controls. CONCLUSION: This spectroscopic study reveals that unilateral high-grade ICA stenosis has an effect on cerebral high-energy metabolism of both hemispheres, which is at least partially reversible after treatment. Therefore the restoration of blood flow in high-grade ICA stenosis recovers the impaired energy balance of the brain. 相似文献
11.
Hattingen E Lanfermann H Quick J Franz K Zanella FE Pilatus U 《Magma (New York, N.Y.)》2009,22(1):33-41
OBJECT: To investigate glycine (Gly) concentrations in low- and high-grade gliomas based on (1)H MR spectroscopic imaging (MRSI) with short and long echo time (TE). Myoinositol (MI) and Gly appear at the same resonance frequency of 3.56 ppm, but due to strong coupling the MI signal dephases more rapidly. Therefore, their contribution to the 3.56 ppm signal should be distinguishable comparing MRSI data acquired at short and long TE. MATERIALS AND METHODS: (1)H MRSI (TE = 30 and 144 ms) was performed at 3 T in 29 patients with histopathological confirmed World Health Organization (WHO) grade II-IV gliomas and in FIVE healthy subjects. All spectra from the gliomas revealed increase of the 3.56 ppm resonance in the short TE spectra. Signal intensities of Gly and MI were differentiated either by analysing the short to long TE ratio of the resonance or by performing a weighted difference. Gly concentrations were compared between high-grade (WHO III-IV) and low-grade gliomas. RESULTS: High-grade gliomas showed significantly higher Gly concentrations compared to low-grade gliomas. CONCLUSION: Appropriate data processing of short and long TE (1)H MRSI provides a tool to distinguish and to quantify Gly and MI concentrations in gliomas. As Gly seems to be a marker of malignancy, more dedicated spectroscopic methods to differentiate these metabolites are justified. 相似文献
12.
Yijing Lin Hidekatsu Yokoyama Shin-ichi Ishida Nobuaki Tsuchihashi Tateaki Ogata 《Magma (New York, N.Y.)》1997,5(2):99-103
The flexible surface-coil-type resonator (FSCR) operating in a 700 MHz microwave electron spin resonance (ESR) system was
applied to measure the nitroxide radicals at a specific area in rats. The FSCR was composed of a single-turn coil with a diameter
of 5 mm and two flexible coaxial lines of 450 mm in length. For an endoscope-like application, the FSCR was inserted into
the rectum of the rat and sequential changes in the ESR signals of the intravenously injected nitroxide radical (4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl;
TEMPOL or 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-yloxy; carbamoyl-PROXYL) were measured. The ESR signal intensity of
the nitroxide decreased according to first-order kinetics. For a stethoscope-like application, the FSCR was placed at several
sites on the abdominal skin of the rats receiving a subcutaneous injection of carbamoyl-PROXYL, and diffusion and/or metabolism
of the radical in the skin was observed. 相似文献