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Brain Metabolites (brain + metabolite)
Selected AbstractsReduced N -acetylaspartate is consistent with axonal dysfunction in cerebral small vessel diseaseNMR IN BIOMEDICINE, Issue 3 2009Arani Nitkunan Abstract Background: Cerebral small vessel disease (SVD) is an important cause of cognitive impairment, but the pathophysiological mechanisms remain unclear. We used 1H MRS to investigate brain metabolic differences between patients with SVD and controls and correlated this with cognition. Methods: 35 patients with SVD (lacunar stroke and radiological evidence of confluent leukoaraiosis) and 35 controls underwent multi-voxel spectroscopic imaging of white matter to obtain absolute metabolite concentrations of N -acetylaspartate (NAA), total creatines, total cholines, myo -inositol, and lactate. A range of cognitive tests was performed on patients with SVD, and composite scores were calculated. Results: Scans of sufficient quality for data analysis were available in 29 cases and 35 controls. NAA was significantly reduced in patients compared with controls (lower by 7.27%, P,=,0.004). However, when lesion load within each individual voxel (mean 22% in SVD vs 5% in controls, P,<,0.001) was added as a covariate, these differences were no longer significant, suggesting that the metabolite differences arose primarily from differences in lesioned tissue. In patients with SVD, there was no correlation between cognitive scores and any brain metabolite. No lactate, an indicator of anaerobic metabolism, was detected. Conclusions: The most consistent change in SVD is a reduction in NAA, a marker of neuronal integrity. The lack of correlation with cognition does not support the use of MRS as a surrogate disease marker. Copyright © 2008 John Wiley & Sons, Ltd. [source] Impact of cerebrospinal fluid contamination on brain metabolites evaluation with 1H-MR spectroscopy: A single voxel study of the cerebellar vermis in patients with degenerative ataxiasJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2009Laura Guerrini MD PhD Abstract Purpose To investigate the impact of cerebrospinal fluid (CSF) contamination on metabolite evaluation in the superior cerebellar vermis with single-voxel 1H-MRS in normal subjects and patients with degenerative ataxias. Materials and Methods Twenty-nine healthy volunteers and 38 patients with degenerative ataxias and cerebellar atrophy were examined on a 1.5 Tesla scanner. Proton spectra of a volume of interest placed in the superior vermis were acquired using a four TE PRESS technique. We calculated N-acetyl aspartate (NAA)/creatine (Cr), choline (Cho)/Cr, and NAA/Cho ratios, T2 relaxation times and concentrations of the same metabolites using the external phantom method. Finally, concentrations were corrected taking into account the proportion of nervous tissue and CSF, that was determined as Volume Fraction (VF). Results In healthy subjects, a significant difference was observed between metabolite concentrations with and without correction for VF. As compared to controls, patients with ataxias showed significantly reduced NAA/Cr and NAA concentrations, while only corrected Cr concentration was significantly increased. The latter showed an inverse correlation with VF. Conclusion CSF contamination has a not negligible effect on the estimation of brain metabolites. The increase of Cr concentration in patients with cerebellar atrophy presumably reflects the substitutive gliosis which takes place along with loss of neurons. J. Magn. Reson. Imaging 2009;30:11,17. © 2009 Wiley-Liss, Inc. [source] Selective maximization of 31P MR spectroscopic signals of in vivo human brain metabolites at 3TJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2007Rose-Ann M. Blenman PhD Abstract Purpose To develop a short TR, short TE, large flip angle (LFA), in vivo 31P MR spectroscopy (MRS) technique at 3T that selectively maximizes the signal-to-noise ratio (SNR) of long T1 human brain metabolites implicated in bipolar disorder. Materials and Methods Two pulse sequences were evaluated for efficiency. Slice profiles acquired with the scaled, sinc-shaped, radiofrequency (RF) LFA pulses were compared to those acquired with Shinnar-Le Roux (SLR) RF LFA pulses. The SLR-based LFA pulse sequence was used to maximize the inorganic phosphate signal in a phantom, after which volunteer metabolite signals were selectively maximized and compared to their correlates acquired with conventional spin-echo methods. Results The comparison of slice profiles acquired with sinc-shaped RF LFA pulses vs. SLR RF LFA pulses showed that SLR-based pulse sequences, with their improved excitation and slice profiles, yield significantly better results. In vivo LFA spin-echo MRS implemented with SLR pulses selectively increased the 31P MRS signal, by as much as 93%, of human brain metabolites that have T1 times longer than the TR of the acquisition. Conclusion The data show that the LFA technique can be employed in vivo to maximize the signal of long T131P brain metabolites at a given TE and TR. LFAs ranging between 120° and 150° are shown to maximize the 31P signal of human brain metabolites at 3T. J. Magn. Reson. Imaging 2007. © 2007 Wiley-Liss, Inc. [source] Brain Metabolite Concentrations and Neurocognition During Short-term Recovery from Alcohol Dependence: Preliminary Evidence of the Effects of Concurrent Chronic Cigarette SmokingALCOHOLISM, Issue 3 2006Timothy C. Durazzo Background: Longitudinal studies of brain tissue metabolite recovery in short-term abstinent alcoholics have primarily investigated the frontal lobes and cerebellum with variable results. Preliminary proton magnetic resonance spectroscopic imaging (1H MRSI) suggested that chronic cigarette smoking exacerbates alcohol-induced brain injury in 1-week abstinent alcoholics. However, the potential effects of chronic cigarette smoking on the recovery of alcohol-induced brain injury have not been studied. Methods: Multislice short-echo time 1H MRSI was used to measure longitudinal changes in common brain metabolites in 25 recovering alcohol-dependent individuals (RA), retrospectively assigned to smoking (n=14) and nonsmoking (n=11) subgroups. Recovering alcohol-dependent individuals in longitudinal analyses were studied after approximately 7 and 34 days of abstinence from alcohol. In cross-sectional analyses, 36 RA (19 smokers, 17 nonsmokers) with approximately 34 days of sobriety were compared with 29 light drinkers (LD). Relationships between neurocognition and metabolite concentrations in abstinent RA were also examined. Results: Over 1 month of abstinence from alcohol, RA, as a group, showed significant increases of regional N -acetylaspartate (NAA; marker of neuronal viability) and choline-containing compounds (Cho; marker of cell membrane synthesis/turnover) primarily in frontal and parietal lobes. These increases appeared to be driven by nonsmoking RA. Cross-sectional results indicate that metabolite levels in RA at 35 days of sobriety are not significantly different from those in LD in most regions, except for lower NAA and Cho in parietal WM and subcortical structures. However, metabolite levels at that time appear to be strongly modulated by smoking status. The patterns of metabolite,neurocognition relationships were different for nonsmoking and smoking RA. Conclusions: Within the first weeks of sobriety, regional brain NAA and Cho levels increased, but metabolite levels did not normalize in all brain regions after 35 days of sobriety. Neurobiologic recovery in RA appeared to be adversely affected by chronic smoking. Greater consideration of the effects of continued cigarette smoking on the neurobiologic and neurocognitive recovery of alcohol-dependent individuals is warranted. [source] Cerebral oedema in minimal hepatic encephalopathy due to extrahepatic portal venous obstructionLIVER INTERNATIONAL, Issue 8 2010Amit Goel Abstract Background: Minimal hepatic encephalopathy (MHE) has recently been reported in patients with extrahepatic portal venous obstruction (EHPVO). Aims: To evaluate brain changes by magnetic resonance studies in EHPVO patients. Methods: Blood ammonia level, critical flicker frequency (CFF), brain metabolites on 1H-magnetic resonance (MR) spectroscopy and brain water content on diffusion tensor imaging and magnetization transfer ratio (MTR) were studied in 31 EHPVO patients with and without MHE, as determined by neuropsychological tests. CFF and magnetic resonance imaging studies were also performed in 23 controls. Results: Fourteen patients (14/31, 45%) had MHE. Blood ammonia level was elevated in all, being significantly higher in the MHE than no MHE group. CFF was abnormal in 13% (4/31) with EHPVO and in 21% (3/14) with MHE. On 1H-MR spectroscopy, increased Glx/Cr, decreased mIns/Cr, and no change in Cho/Cr were noted in patients with MHE compared with controls. Significantly increased mean diffusivity (MD) and decreased (MTR) were observed in the MHE group, suggesting presence of interstitial cerebral oedema (ICE). MD correlated positively with blood ammonia level (r=0.65, P=0.003) and Glx (r=0.60, P=0.003). Discussion: MHE was detected in 45% of patients with EHPVO while CFF was abnormal in only 13%. ICE was present in 7/10 brain regions examined, particularly in those with MHE. Hyperammonaemia elevated cerebral Glx levels correlated well with ICE. Conclusions: MHE was common in EHPVO; CFF could identify it only in a minority. ICE was present in EHPVO, particularly in those with MHE. It correlated with blood ammonia and Glx/Cr levels. Hyperammonaemia seems to contribute to ICE in EHPVO. [source] Comparison of spectral fitting methods for overlapping J-coupled metabolite resonancesMAGNETIC RESONANCE IN MEDICINE, Issue 3 2010A. Gonenc Abstract There is increasing interest in the use of two-dimensional J-resolved spectroscopic acquisition (multiecho) methods for in vivo proton magnetic resonance spectroscopy due to the improved discrimination of overlapping J-coupled multiplet resonances that is provided. Of particular interest is the potential for discrimination of the overlapping resonances of glutamate and glutamine. In this study, a new time-domain parametric spectral model that makes use of all available data is described for fitting the complete two-dimensional multiecho data, and the performance of this method was compared with fitting of one-dimensional spectra obtained following averaging multiecho data (echo time-averaged) and single-echo time PRESS (Point Resolved Spectroscopy) acquired spectra. These methods were compared using data obtained from a phantom containing typical brain metabolites and a human brain. Results indicate that improved performance and accuracy is obtained for the two-dimensional acquisition and spectral fitting model. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source] Spectral phase-corrected GRAPPA reconstruction of three-dimensional echo-planar spectroscopic imaging (3D-EPSI)MAGNETIC RESONANCE IN MEDICINE, Issue 5 2007Xiaoping Zhu Abstract MR spectroscopic (MRS) images from a large volume of brain can be obtained using a 3D echo-planar spectroscopic imaging (3D-EPSI) sequence. However, routine applications of 3D-EPSI are still limited by a long scan time. In this communication, a new approach termed "spectral phase-corrected generalized autocalibrating partially parallel acquisitions" (SPC-GRAPPA) is introduced for the reconstruction of 3D-EPSI data to accelerate data acquisition while preserving the accuracy of quantitation of brain metabolites. In SPC-GRAPPA, voxel-by-voxel spectral phase alignment between metabolite 3D-EPSI from individual coil elements is performed in the frequency domain, utilizing the whole spectrum from interleaved water reference 3D-EPSI for robust estimation of the zero-order phase correction. The performance of SPC-GRAPPA was compared with that of fully encoded 3D-EPSI and conventional GRAPPA. Analysis of whole-brain 3D-EPSI data reconstructed by SPC-GRAPPA demonstrates that SPC-GRAPPA with an acceleration factor of 1.5 yields results very similar to those obtained by fully encoded 3D-EPSI, and is more accurate than conventional GRAPPA. Magn Reson Med 57:815,820, 2007. © 2007 Wiley-Liss, Inc. [source] In vivo measurement of brain metabolites using two-dimensional double-quantum MR spectroscopy,exploration of GABA levels in a ketogenic dietMAGNETIC RESONANCE IN MEDICINE, Issue 4 2003Zhiyue J. Wang Abstract A localized proton 2D double-quantum (DQ) spin-echo spectroscopy technique was implemented on 1.5 T clinical MRI scanners for the detection of ,-aminobutyrate (GABA) in the brain. The 2D approach facilitates separation of peaks overlapping with GABA in 1D DQ-filtered (DQF) spectra. This technique was applied to four normal adult volunteers and four children with intractable epilepsy. The coefficient of variation of the level of GABA and overlapping macromolecules at F2 = 3.0 ppm and F1 = 4.8 ppm was 0.08 in normal subjects. Three patients received 2D MRS scans before and after initiation of the ketogenic diet (KD): one patient showed a trend of decreasing GABA throughout the study, and two patients showed low initial GABA levels that increased over time. In addition to major metabolites and GABA, low-level metabolites (valine, leucine, and glutathione) were also identified in the 2D spectra. Magn Reson Med 49:615,619, 2003. © 2003 Wiley-Liss, Inc. [source] Pitfalls and advantages of different strategies for the absolute quantification of N -acetyl aspartate, creatine and choline in white and grey matter by 1H-MRSNMR IN BIOMEDICINE, Issue 10 2009E. Malucelli Abstract This study extensively investigates different strategies for the absolute quantitation of N -acetyl aspartate, creatine and choline in white and grey matter by 1H-MRS at 1.5,T. The main focus of this study was to reliably estimate metabolite concentrations while reducing the scan time, which remains as one of the main problems in clinical MRS. Absolute quantitation was based on the water-unsuppressed concentration as the internal standard. We compared strategies based on various experimental protocols and post-processing strategies. Data were obtained from 30 control subjects using a PRESS sequence at several TE to estimate the transverse relaxation time, T2, of the metabolites. Quantitation was performed with the algorithm QUEST using two different metabolite signal basis sets: a whole-metabolite basis set (WhoM) and a basis set in which the singlet signals were split from the coupled signals (MSM). The basis sets were simulated in vivo for each TE used. Metabolites' T2s were then determined by fitting the estimated signal amplitudes of the metabolites obtained at different TEs. Then the absolute concentrations (mM) of the metabolites were assessed for each subject using the estimated signal amplitudes and either the mean estimated relaxation times of all subjects (mean protocol, MP) or the T2 estimated from the spectra derived from the same subject (individual protocol, IP). Results showed that MP represents a less time-consuming alternative to IP in the quantitation of brain metabolites by 1H-MRS in both grey and white matter, with a comparable accuracy when performed by MSM. It was also shown that the acquisition time might be further reduced by using a variant of MP, although with reduced accuracy. In this variant, only one water-suppressed and one water-unsuppressed spectra were acquired, drastically reducing the duration of the entire MRS examination. However, statistical analysis highlights the reduced accuracy of MP when performed using WhoM, particularly at longer echo times. Copyright © 2009 John Wiley & Sons, Ltd. [source] The apparent dependence of the diffusion coefficient of N-acetylaspartate upon magnetic field strength: evidence of an interaction with NMR methodologyNMR IN BIOMEDICINE, Issue 8 2003David N. Guilfoyle Abstract An inverse relationship between applied magnetic field strength and the apparent diffusion coefficient (ADC) of several important brain metabolites including N -acetyl- l -aspartate (NAA), choline and creatine, measured in vivo using proton magnetic resonance spectroscopy (MRS), has been reported. In this investigation, using phantom studies of NAA at magnetic field strengths of 3 and 7,T, these observations have been verified under controlled MRS conditions in vitro, and the ADC of NAA has been found to vary inversely with magnetic field strength, decreasing at a rate of 2.5%/T at 20°C. We have also assessed whether the effect is a function of a systemic bias in methodology, or if the effect is actually on the rate of molecular diffusion. This was done using an MRS-independent method for measurement of molecular diffusion in NAA phantoms at 0, 0.025 and 7,T applied magnetic field strengths. As a result, it has been demonstrated that the observed apparent magnetic field dependence of the ADC of NAA is a consequence of the NMR measurement and is apparently not a real effect on molecular diffusion. Copyright © 2003 John Wiley & Sons, Ltd. [source] Increased glutamate/glutamine compounds in the brains of patients with fibromyalgia: A magnetic resonance spectroscopy studyARTHRITIS & RHEUMATISM, Issue 6 2010Manuel Valdés Objective Fibromyalgia (FM) has been defined as a systemic disorder that is clinically characterized by pain, cognitive deficit, and the presence of associated psychopathology, all of which are suggestive of a primary brain dysfunction. This study was undertaken to identify the nature of this cerebral dysfunction by assessing the brain metabolite patterns in patients with FM through magnetic resonance spectroscopy (MRS) techniques. Methods A cohort of 28 female patients with FM and a control group of 24 healthy women of the same age were studied. MRS techniques were used to study brain metabolites in the amygdala, thalami, and prefrontal cortex of these women. Results In comparison with healthy controls, patients with FM showed higher levels of glutamate/glutamine (Glx) compounds (mean ± SD 11.9 ± 1.6 arbitrary units [AU] versus 13.4 ± 1.7 AU in controls and patients, respectively; t = 2.517, 35 df, corrected P = 0.03) and a higher Glx:creatine ratio (mean ± SD 2.1 ± 0.4 versus 2.4 ± 1.4, respectively; t = 2.373, 35 df, corrected P = 0.04) in the right amygdala. In FM patients with increased levels of pain intensity, greater fatigue, and more symptoms of depression, inositol levels in the right amygdala and right thalamus were significantly higher. Conclusion The distinctive metabolic features found in the right amygdala of patients with FM suggest the possible existence of a neural dysfunction in emotional processing. The results appear to extend previous findings regarding the dysfunction in pain processing observed in patients with FM. [source] Corrected values of brain metabolites for the article: ,Abnormal cellular energy and phospholipid metabolism in the left dorsolateral prefrontal cortex of medication-free individuals with bipolar disorder: an in vivo1H MRS study'BIPOLAR DISORDERS, Issue 7 2008Benicio N. Frey No abstract is available for this article. [source] Quantification of brain metabolitesACTA NEUROPSYCHIATRICA, Issue 3 2009Jim Lagopoulos No abstract is available for this article. [source] |