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Water Signal (water + signal)
Selected AbstractsIn vivo proton spectroscopy without solvent suppressionCONCEPTS IN MAGNETIC RESONANCE, Issue 4 2001David B. Clayton Abstract In 1H MR spectroscopy of the human brain, it is common practice to suppress the solvent signal prior to acquisition. This reduces the large dynamic range which is otherwise required of the MR receiver and digitizer in order to detect the dilute metabolite resonances in the presence of the much larger water signal. However, complete solvent suppression is not always obtainable, particularly over large volumes and in superficial regions containing large susceptibility gradients. In this work, it demonstrated that modern commercial MR scanners possess the dynamic range necessary to adequately resolve the 1H metabolites in unsuppressed spectra. Moreover, a postacquisition method is presented which can completely remove the intact water signal and accurately quantitate the metabolite peaks. Preserving the water signal in in vivo spectroscopy has several useful benefits, such as providing a high signal-to-noise ratio internal concentration, frequency, and line shape reference. Comparison is made between suppressed and unsuppressed spectra from both a phantom and the human brain acquired at 4 T. © 2001 John Wiley & Sons, Inc. Concepts Magn Reson 13: 260,275, 2001 [source] 13C-NMR detection of STD spectraMAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2010Christoph Räuber Abstract We have investigated the use of 13C for the detection of saturation transfer difference (STD) NMR spectra. By detecting the STD spectrum in the 13C channel it is possible to eliminate the residual water signal in the STD-NMR spectrum. We have employed an INEPT transfer in order to shift the magnetization from the proton channel to 13C. As a sample system to check our method we have used human serum albumin and phenylalanine. We have shown that such a transfer can be accomplished and gives reasonable signal intensities. Copyright © 2009 John Wiley & Sons, Ltd. [source] Noninvasive temperature mapping with MRI using chemical shift water-fat separationMAGNETIC RESONANCE IN MEDICINE, Issue 5 2010Brian J. Soher Abstract Tissues containing both water and lipids, e.g., breast, confound standard MR proton reference frequency-shift methods for mapping temperatures due to the lack of temperature-induced frequency shift in lipid protons. Generalized Dixon chemical shift,based water-fat separation methods, such as GE's iterative decomposition of water and fat with echo asymmetry and least-squares estimation method, can result in complex water and fat images. Once separated, the phase change over time of the water signal can be used to map temperature. Phase change of the lipid signal can be used to correct for non-temperature-dependent phase changes, such as amplitude of static field drift. In this work, an image acquisition and postprocessing method, called water and fat thermal MRI, is demonstrated in phantoms containing 30:70, 50:50, and 70:30 water-to-fat by volume. Noninvasive heating was applied in an Off1-On-Off2 pattern over 50 min, using a miniannular phased radiofrequency array. Temperature changes were referenced to the first image acquisition. Four fiber optic temperature probes were placed inside the phantoms for temperature comparison. Region of interest (ROI) temperature values colocated with the probes showed excellent agreement (global mean ± standard deviation: ,0.09 ± 0.34°C) despite significant amplitude of static field drift during the experiments. Magn Reson Med 63:1238,1246, 2010. © 2010 Wiley-Liss, Inc. [source] Eliminating spurious lipid sidebands in 1H MRS of breast lesionsMAGNETIC RESONANCE IN MEDICINE, Issue 2 2002Patrick J. Bolan Abstract Detecting metabolites in breast lesions by in vivo 1H MR spectroscopy can be difficult due to the abundance of mobile lipids in the breast which can produce spurious sidebands that interfere with the metabolite signals. Two-dimensional J -resolved spectroscopy has been demonstrated in the brain as a means to eliminate these artifacts from a large water signal; coherent sidebands are resolved at their natural frequencies, leaving the noncoupled metabolite resonances in the zero-frequency trace of the 2D spectrum. This work demonstrates that using the zero-frequency trace,or equivalently the average of spectra acquired with different echo times,can be used to separate noncoupled metabolite signals from the lipid-induced sidebands. This technique is demonstrated with simulations, phantom studies, and in several breast lesions. Compared to the conventional approach using a single echo time, echo time averaging provides increased sensitivity for the study of small and irregularly shaped lesions. Magn Reson Med 48:215,222, 2002. © 2002 Wiley-Liss, Inc. [source] k-space analysis of point-resolved spectroscopy (PRESS) with regard to spurious echoes in in vivo1H MRSNMR IN BIOMEDICINE, Issue 2 2009G. Starck Abstract The spurious echo artefact, not uncommon in 1H MRS in the brain, comes from refocusing outer volume signal. Application of MRS in small volumes in susceptibility-affected regions often results in large shim gradients. The artefact problem is accentuated when the global effect of the shim gradient shifts the water resonance outside the water suppression band in the outer volume. This scenario brings the issue of spurious echoes once again to the fore. In this paper, spurious signals of the point-resolved spectroscopy (PRESS) sequence are analysed using the concept of k-space. This new approach facilitates a more geometrical view of the problem, well suited for studying the effect of gradient spoiling and refocusing of signal. Several spoiling options are shown, and the probability of the global effects of shimming being a primary cause of the artefact is discussed. Fourier transform analysis of realistic slice profiles, combined with the k-space description of spurious echoes, shows that unsuppressed water signal in outer regions greatly increases the demands on spoiling. Gradient spoiling adequate for artefact suppression at a given size of MRS volume may not be sufficient at a smaller size. Several ways to improve PRESS measurements with regard to suppression of spurious signal are discussed. Copyright © 2008 John Wiley & Sons, Ltd. [source] In vivo microfocal computed tomography and micro,magnetic resonance imaging evaluation of antiresorptive and antiinflammatory drugs as preventive treatments of osteoarthritis in the ratARTHRITIS & RHEUMATISM, Issue 9 2010Michael D. Jones Objective To determine whether treatment with an antiresorptive drug in combination with an antiinflammatory drug reduces periarticular bone and soft tissue adaptations associated with the progression of posttraumatic secondary osteoarthritis (OA). Methods We used in vivo microfocal computed tomography (micro-CT) to map bony adaptations and in vivo micro,magnetic resonance imaging (micro-MRI) to examine joint inflammation in a rat model of surgically induced OA secondary to knee triad injury. We examined the arthroprotective effects of the bisphosphonates alendronate and risedronate and the nonsteroidal antiinflammatory drug (NSAID) meloxicam. Results Micro-CT revealed reduced levels of periarticular trabecular bone loss in animals with knee triad injury treated with the bisphosphonate drugs alendronate or risedronate, or the NSAID meloxicam, compared with untreated animals. Alendronate treatment reduced bony osteophyte development. While risedronate as a monotherapy did not positively impact osteophytogenesis, combination therapy with risedronate and meloxicam reduced osteophyte severity somewhat. Micro-MRI revealed an increased, diffuse water signal in the epiphyses of untreated rats with knee triad injury 8 weeks after surgery, suggestive of a bone marrow lesion,like stimulus. In contrast, meloxicam-treated rats showed a significant reduction in fluid signal compared with both bisphosphonate-treated groups 8 weeks after surgery. Histologic analysis qualitatively confirmed the chondroprotective effect of both bisphosphonate treatments, showing fewer degradative changes compared with untreated rats with knee triad injury. Conclusion Our findings indicate that select combinations of bisphosphonate and NSAID drug therapy in the early stages of secondary OA preserve trabecular bone mass and reduce the impact of osteophytic bony adaptations and bone marrow lesion,like stimulus. Bisphosphonate and NSAID therapy may be an effective disease-modifying drug regimen if administered early after the initial injury. [source] Online assessment of biofilm development, sloughing and forced detachment in tube reactor by means of magnetic resonance microscopyBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2010Michael Wagner Abstract Magnetic resonance microscopy (MRM) was successfully applied for non-invasive online monitoring of biofilm development, sloughing, and forced detachment. Biofilm cultivation was performed in a tube reactor directly placed in the MRM scanner. Based on the differences in relaxation time of free and bound protons, the distributed water signal was allocated to the bulk and the biofilm phase. The velocity of the flowing water in the tube reactor was measured in all three directions (x, y, and z) at spatial resolutions of 78,µm. From the velocity data, maps of flow gradients (shear rates) were derived. The experiments showed that a more compact biofilm structure is sloughed off in total with nearly no biomass left on the substratum. Continued biofilm cultivation resulted in filamentous biofilm structures, which did not show any sloughing. Experiments at higher Reynolds numbers were performed in order to force biofilm detachment. Continuous measuring of proton velocity and biomass was used to characterize the different stages of biofilm development. The measurements revealed that biofilms are able to resist extremely high local shear stress being raised up to factor of 20 compared to the mean local shear stress acting on the complete biofilm surface. The maximum local shear stress of single biofilm structures exposed to flow was found to be on average seven times higher compared to the mean local shear stress of the entire biofilm surface. MRM was able to visualize and quantify the development of biofilms and interaction of biofilms with the surrounding fluid at the meso-scale. It is suggested that detachment and sloughing depends on both internal and external structural parameters. Biotechnol. Bioeng. 2010;107: 172,181. © 2010 Wiley Periodicals, Inc. [source] Fat-water separation in dynamic objects using an UNFOLD-like temporal processingJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2010Riad Ababneh PhD Abstract Purpose To separate fat and water signals in dynamic imaging. Because important features may be embedded in fat, and because fat may take part in disease processes, separating fat and water signals may be of great importance in a number of clinical applications. This work aims to achieve such separation at nearly no loss in temporal resolution compared to usual, nonseparated acquisitions. In contrast, the well-known 3-point Dixon method may cause as much as a 3-fold reduction in temporal resolution. Materials and Methods The proposed approach involves modulating the echo time TE from frame to frame, to force fat signals to behave in a conspicuous manner through time, so they can be readily identified and separated from water signals. The strategy is inspired from the "unaliasing by Fourier encoding the overlaps in the temporal direction" (UNFOLD) method, although UNFOLD involves changes in the sampling function rather than TE, and aims at suppressing aliased material rather than fat. Results The method was implemented at 1.5 T and 3 T, on cardiac cine and multiframe steady-state free precession sequences. In addition to phantom results, in vivo results from volunteers are presented. Conclusion Good separation of fat and water signals was achieved in all cases. J. Magn. Reson. Imaging 2010;32:962,970. © 2010 Wiley-Liss, Inc. [source] High-resolution magic angle spinning proton NMR analysis of human prostate tissue with slow spinning ratesMAGNETIC RESONANCE IN MEDICINE, Issue 3 2003Jennifer L. Taylor Abstract The development of high-resolution magic angle spinning (HR-MAS) NMR spectroscopy for intact tissue analysis and the correlations between the measured tissue metabolites and disease pathologies have inspired investigations of slow-spinning methodologies to maximize the protection of tissue pathology structures from HR-MAS centrifuging damage. Spinning sidebands produced by slow-rate spinning must be suppressed to prevent their complicating the spectral region of metabolites. Twenty-two human prostatectomy samples were analyzed on a 14.1T spectrometer, with HR-MAS spinning rates of 600 Hz, 700 Hz, and 3.0 kHz, a repetition time of 5 sec, and employing various rotor-synchronized suppression methods, including DANTE, WATERGATE, TOSS, and PASS pulse sequences. Among them, DANTE, as the simplest scheme, has shown the most potential in suppression of tissue water signals and spinning sidebands, as well as in quantifying metabolic concentrations. Magn Reson Med 50:627,632, 2003. © 2003 Wiley-Liss, Inc. [source] Compartmental relaxation and diffusion tensor imaging measurements in vivo in ,-carrageenan-induced edema in rat skeletal muscle,NMR IN BIOMEDICINE, Issue 6 2008Reuben H. Fan Abstract Integrated diffusion tensor T2 measurements were made on normal and edematous rat muscle, and the data were fitted with one- and two-compartment models, respectively. Edematous muscle exhibited a short-lived component (T2,=,28,±,6,ms), with diffusion characteristics similar to that of normal muscle, and a long-lived component (T2,=,96,±,27,ms), with greater mean apparent diffusion coefficient (ADC) and lower fractional anisotropy (FA). With this two-component description of diffusion and relaxation, values of ADC and FA estimated with a conventional pulsed-gradient spin-echo sequence will depend on the echo time, relative fraction of short-lived and long-lived water signals, and the intrinsic ADC and FA values within the tissue. On the basis of the relative differences in water diffusion properties between long-lived and short-lived water signals, as well as the similarities between the short-lived component and normal tissue, it is postulated that these two signal components largely reflect intracellular and extracellular water. Copyright © 2007 John Wiley & Sons, Ltd. [source] Direct metabolic fingerprinting of commercial herbal tinctures by nuclear magnetic resonance spectroscopy and mass spectrometry,PHYTOCHEMICAL ANALYSIS, Issue 4 2009Matteo Politi Abstract Introduction Tinctures are widely used liquid pharmaceutical preparations traditionally obtained by maceration of one or more medicinal plants in ethanol,water solutions. Such a process results in the extraction of virtually hundreds of structurally diverse compounds with different polarities. Owing to the large chemical diversity of the constituents present in the herbal tinctures, the analytical tools used for the quality control of tinctures are usually optimised only for the detection of single chemical entities or specific class of compounds. Objective In order to overcome the major limitations of the current methods used for analysis of tinctures, a new methodological approach based on NMR spectroscopy and MS spectrometry has been tested with different commercial tinctures. Methodology Diffusion-edited 1H-NMR (1D DOSY) and 1H-NMR with suppression of the ethanol and water signals have been applied here for the first time to the direct analysis of commercial herbal tinctures derived from Echinacea purpurea, Hypericum perforatum, Ginkgo biloba and Valeriana officinalis. The direct injection of the tinctures in the MS detector in order to obtain the corresponding metabolic profiles was also performed. Results Using both NMR and MS methods it was possible, without evaporation or separation steps, to obtain a metabolic fingerprint able to distinguish between tinctures prepared with different plants. Batch-to-batch homogeneity, as well as degradation after the expiry date of a batch, was also investigated. Conclusion The techniques proposed here represent fast and convenient direct analyses of medicinal herbal tinctures. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||