Proton MR spectroscopy of cerebellitis

Single voxel proton MR spectroscopy ((1)H-MRS) of the vermis was obtained in two patients with cerebellitis. In the acute phase (1)H-MRS revealed low N-acetyl-aspartate (NAA)/creatine (Cr) and NAA/choline (Cho) and normal Cho/Cr ratios. Decrease of the concentration of NAA was confirmed by quantitative analysis in one patient. The NAA/Cr and NAA/Cho ratios and NAA concentration were increased in (1)H-MRS examinations obtained 10 and 24 months after the acute episode. (1)H-MRS demonstrates reversible metabolite changes in cerebellitis.     

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.     

Experimental hypoxic–ischemic encephalopathy: comparison of apparent diffusion coefficients and proton magnetic resonance spectroscopy

This study aims to compare the apparent diffusion coefficients (ADCs) and proton magnetic resonance spectroscopy (¹H-MRS) in the first 24 h of acute hypoxic-ischemic brain damage (HIBD) in piglets. Twenty-five 7-day-old piglets were subjected to transient bilateral common carotid artery occlusion followed by ventilation with 4% oxygen for 1 h. Diffusion-weighted imaging (DWI) and ¹H-MRS were performed on cessation of the insult or at 3, 6, 12 or 24 h after resuscitation (all n=5). ADCs, N-acetylaspartate/choline (NAA/Cho), NAA/creatine (NAA/Cr), lactate/NAA (Lac/NAA), Lac/Cho and Lac/Cr were calculated. Cerebral injury was evaluated by pathological study and Hsp70 immunohistochemical analysis. On cessation of the insult, ADCs, NAA/Cho and NAA/Cr reduced, Lac/NAA, Lac/Cho and Lac/Cr increased. From 3 to 12 h after resuscitation, ADCs, Lac/NAA, Lac/Cho and Lac/Cr recovered, NAA/Cho and NAA/Cr reduced. Twenty-four hours after resuscitation, ADCs reduced once more, Lac/NAA, Lac/Cho and Lac/Cr increased again, whereas NAA/Cho and NAA/Cr decreased continuously. Pathological study revealed mild cerebral edema on cessation of the insult and more and more severe cerebral injury after resuscitation. No Hsp70-positive cells were detected on cessation of the insult. From 3 to 12 hours after resuscitation, Hsp70-positive cells gradually increased. Twenty-four hours after resuscitation, Hsp70-positive cells decreased. Throughout the experiment, changes in NAA/Cho and pathology had the best correlation (R=–0.729). In conclusion, NAA/Cho is the most precise ratio to reflect the pathological changes of early HIBD. Transient ADCs and Lac ratios recovery do not predict the reversal of histological damage of early HIBD. Reducing astrocytic swelling is of great clinical significance.     

3-D echo planar (1)HMRS imaging in MS: metabolite comparison from supratentorial vs. central brain

To determine if metabolite ratios as measured by 3-dimensional echo planar spectroscopy imaging (3D-EPSI) from central brain regions of interest (ROI) centered at the corpus callosum reflect imaging metrics of large volumes of supratentorial brain (STB) from patients with multiple sclerosis. METHODS: 48 MS patients with relapsing-remitting, secondary progressive, and primary progressive disease underwent a 3D-EPSI sequence covering large volumes of STB. Metabolite ratios were first estimated from all voxels within a STB mask using a linear regression of N-acetylaspartate (NAA) over Creatine (Cr), NAA over choline (Cho) and Cho over Cr. Secondly, spectroscopic voxels from a central brain (CB) ROI centered at the corpus callosum were selected within the STB. Ratios were compared using Bland-Altman regression analysis and Spearman's correlation coefficients between STB versus central brain. Ratios from studied ROIs were correlated with the EDSS and compared to normal controls. RESULTS: Very strong correlations ranging from 0.884 and 0.938 (p < 0.0001) were found for all metabolite ratios between STB versus central brain. NAA/Cr ratios were similarly and negatively correlated with the EDSS across all ROIs, trends ranging from -0.257 to -0.314 (p < 0.1). NAA/Cr from all MS patients was similarly decreased compared to controls across all ROIs (p < 0.01). CONCLUSION: Metabolite ratios from a central brain ROI were statistically equivalent and highly correlated with ratios from the STB. The study of NAA/Cr using (1)HMRS from a central brain ROI centered at the corpus callosum seems to be representative of brainwide axonal changes in patients with MS.     

Noninvasive evaluation of cerebral glioma grade by using multivoxel 3D proton MR spectroscopy

Objective

To determine whether metabolite ratios in multivoxel 3D proton MR spectroscopy (¹H MRS) is different between low-grade and high-grade gliomas and may be useful for glioma grading.

Materials and Methods

Thirty-nine patients (23 male and 16 female; 22-75 years old; mean age, 44.92±12.65 years) suspected of having gliomas underwent 3D ¹H MRS examinations. Metabolite ratios [choline (Cho)/creatine (Cr), N-acetylaspartate (NAA)/Cr and Cho/NAA] were measured. Tumor grade was determined by using the histopathologic grading. Receiver operating characteristic analysis of metabolite ratios was performed, and optimum thresholds for tumor grading were determined. The resulting sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for identifying high-grade gliomas were calculated.

Results

Diagnostic-quality 3D ¹H MRS with readily quantifiable Cho, Cr and NAA peaks was obtained in 94.87% of the cases. The Cho/Cr and Cho/NAA ratios were significantly higher in high-grade than in low-grade glioma (P<.001), whereas the NAA/Cr ratios were significantly lower in high-grade than in low-grade glioma (P<.001). Receiver operating characteristic analysis demonstrated a threshold value of 2.04 for Cho/Cr ratio to provide sensitivity, specificity, PPV and NPV of 84.00%, 83.33%, 91.30% and 71.43%, respectively. Threshold value of 2.20 for Cho/NAA ratio resulted in sensitivity, specificity, PPV and NPV of 88.00%, 66.67%, 84.62% and 72.73%, respectively. Overall diagnostic accuracy was not statistically significantly different between Cho/Cr and Cho/NAA ratios (χ²=0.093, P=.76).

Conclusion

Metabolite ratios of low-grade gliomas were significantly different from high-grade gliomas. Cho/Cr and Cho/NAA ratios could have the superior diagnostic performance in predicting the glioma grade.     

Brain metabolite alterations demonstrated by proton magnetic resonance spectroscopy in diabetic patients with retinopathy

Due to the homology between retinal and cerebral microvasculatures, retinopathy is a putative indicator of cerebrovascular dysfunction. This study aimed to detect metabolite changes of brain tissue in type 2 diabetes mellitus (T2DM) patients with diabetic retinopathy (DR) using proton magnetic resonance spectroscopy (¹H-MRS). Twenty-nine T2DM patients with DR (DR group), thirty T2DM patients without DR (DM group) and thirty normal controls (NC group) were involved in this study. Single-voxel ¹H-MRS (TR: 2000 ms, TE: 30 ms) was performed at 3.0 T MRI/MRS imager in cerebral left frontal white matter, left lenticular nucleus, and left optic radiation. Our data showed that NAA/Cr ratios of the DR group were significantly lower than those of the DM group in the frontal white matter and optic radiation. In the lenticular nucleus, MI/Cr ratios were significantly higher in the DM group than those in the NC group, while MI/Cr ratios were significantly lower in the DR group than those in the DM group. In the frontal white matter, NAA/Cho ratios were found to be decreased in the DR group as compared to the NC group. Additionally, our finding indicated that NAA/Cr ratios were negatively associated with DR severity in both the frontal white matter and optic radiation. A decrease in NAA indicated neuronal loss and the likely explanation for a decrease in MI was glial loss. In conclusion, we inferred that cerebral neurons and glia cells were damaged in patients with DR. Our data support that DR is associated with brain tissue damage.     

Molality as a unit of measure for expressing 1H MRS brain metabolite concentrations in vivo

Absolute concentrations of cerebral metabolite in in vivo 1H magnetic resonance spectroscopy studies (1H-MRS) are widely reported in molar units as moles per liter of tissue, or in molal units as moles per kilogram of tissue. Such measurements require external referencing or assumptions as to local water content. To reduce the scan time, avoid assumptions that may be invalid under specific pathologies, and provide a universally accessible referencing procedure, we suggest that metabolite concentrations from 1H-MRS measurements in vivo be reported in molal units as moles per kilogram of tissue water. Using internal water referencing, a two-compartment water model, a simulated brain spectrum for peak identification, and a spectroscopic bi-exponential spin-spin relaxation segmentation technique, we measured the absolute concentrations for the four common 1H brain metabolites: choline (Cho), myo-inositol (mIno), phosphocreatine + creatine (Cr), and N-acetyl-aspartate (NAA), in the hippocampal region (n = 26) and along the Sylvian fissure (n = 61) of 35 healthy adults. A stimulated echo localization method (20 ms echo time, 10 ms mixing time, 4 s repetition time) yielded metabolite concentrations, uncorrected for metabolite relaxation or contributions from macromolecule resonances, that were expectantly higher than with molar literature values. Along the Sylvian fissure the average concentrations (coefficient of variation (CV)) in mmoles/kg of tissue water were 17.6 (12%) for NAA, 14.2 (9%) for Cr, 3.6 (13%) for Cho, and 13.2 (15%) for mIno. Respective values for the hippocampal region were 15.7 (20%), 14.7 (16%), 4.6 (19%), and 17.7 (26%). The concentrations of the two regions were significantly different (p 相似文献   

Occupational prolonged organic solvent exposure in shoemakers: brain MR spectroscopy findings

Our purpose was to investigate, by magnetic resonance (MR) spectroscopy, the metabolite changes in the brains of subjects in the shoemaking industry who had been chronically exposed to organic solvents. A total of 49 male subjects and 30 age-matched healthy volunteers underwent detailed neurological and psychiatric examinations. All subjects had long-echo [repetition time (TR) 2000 ms, echo time (TE) 136 ms] single-voxel MR spectroscopy. Voxels (15 x 15 x 15 mm(3)) were placed in the parietal white matter, thalamus, and basal ganglia. N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios were calculated. There was no significant difference between the study subjects and the control group in NAA/Cr ratios obtained from thalamus, basal ganglia, and parietal white matter. Cho/Cr ratios in thalamus, basal ganglia, and parietal white matter were found to be significantly increased compared to controls. There was a positive correlation between basal ganglia Cho/Cr ratio and duration of exposure (r = 0.63). MR spectroscopy should be performed to reveal metabolite changes and determine the degree of brain involvement in solvent-related industry workers.     

Magnetic resonance spectroscopy study of proton metabolite level changes in sensorimotor cortex after upper limb replantation-revascularization

We aimed to investigate the changes in proton metabolite levels at the motor and somatosensory cortex by magnetic resonance spectroscopy (MRS) after upper extremity replantation or revascularization. Nine patients who referred to our clinic suffering from major total (two) and subtotal (seven) amputation of the upper extremity were enrolled in this study. Mean time value between the injury and operation was 5.1 h. Mean follow-up period or mean time between the injury and MRS analysis was 26.2 months (ranging from 7 to 41 months). Voxels (TR: 2000; TE: 136 ms) were placed onto locations in the bilateral precentral and postcentral cortex area of the cerebral hemispheres that represent the upper extremity. Contralateral sides of the brain hemisphere that represent the injured extremity were accounted as control groups. Metabolite ratios [NAA (N-acetyl aspartate)/Cr (creatine) and Cho (choline)/Cr] of the motor and somatosensory cortex were calculated. The NAA/Cr and Cho/Cr metabolite ratios between the two groups were found to be insignificant, and these results may indicate that there is no remarkable somatosensorial cortex disruption or demyelination in these patients. Fifty-six percent of patients were found as functional according to Chen's scale.     

Absolute Quantification Using Turbo Spectroscopic Imaging in Multiple Sclerosis Patients

One of the drawbacks of scanning patients using multiple-voxel spectroscopic imaging is the long acquisition time. This is especially true when one is interested in obtaining absolute metabolite concentrations which requires acquisition of unsuppressed water spectra in addition to the suppressed spectra. In our experiment, turbo spectroscopic imaging (TSI) method with acquisition of three echoes per excitation was applied to reduce scanning time without lowering the spatial resolution. In 15 relapsing-remitting multiple sclerosis patients (mean age 37.07 years, mean disease duration 7.67 years), an MRSI scan at the level of centrum semiovale was obtained. The scan time was approximately 7 min including the unsuppressed spectra. Tissue water was used as an internal concentration reference to obtain absolute metabolite concentrations of N-acetyl-aspartate (NAA), creatine (Cr), and choline (Cho). The peak areas were corrected for differences in transversal and longitudinal relaxation times and a water concentration of 55.5 M was assumed. A three-dimensional high-resolution T ₁ scan was acquired and used to segment tissue in gray matter (GM), white matter (WM), and cerebrospinal fluid using FSL’S FAST segmentation method (a software library of the automated segmentation tool by the Center of Functional MRI of the Brain, Oxford, UK). Finally, a regression analysis was employed to address the metabolite concentrations and ratios in GM and WM, respectively. Our study shows that the metabolite concentrations (NAA, Cho, Cr) and metabolite ratios (NAA/Cr and Cho/Cr) in GM and WM obtained using the methods discussed earlier are comparable to the results found in other studies of similar patient groups. It also shows that TSI method can be used to obtain the absolute metabolite ratios in a reasonable scan time.     

Straightforward relative quantitation and age-related human standards of N-acetylaspartate at the centrum semiovale level by CSI (1)H-MRS

1H-MRS was aimed to monitor metabolite concentrations in homogeneous interaxial slices of cerebral matter at the centrum semiovale level in healthy volunteers. NAA (N-acetylaspartate + N-acetylglutamate), Cr (creatine + phosphocreatine), and Cho (choline + acetylcholine) were evaluated by resonance integrations. Using Cr as an internal standard, NAA/Cr ratio was considered as a relative measure of concentration. CSI sequence explored volunteer's interaxial slices of white and gray matter by means of 8 x 8 matrices of (1)H-NMR spectra. NAA/Cr integral ratios were averaged over the whole spectral matrix to obtain the Index of NAA at Centrum Semiovale (INACS) of each individual. Indexes of the sixty-eight healthy volunteers, divided into three groups by age, showed good intraindividual reproducibility, and were virtually unaffected by small shifts or bendings of the interaxial slice analyzed. The INACSs were used to estimate Age-Sectorial INACS Ranges (ASIR), the intervals that, on the basis of a normal statistical distribution, should comprise 95% of the age-matched healthy population. Individual INACSs, compared to accurately defined ASIRs taken as standards, could early detect subtle, diffuse neuronal or axonal damage within centrum semiovale interaxial slices. Periodic inspection of INACS could also allow monitoring of progressive neuronal or axonal degeneration.     

Quantification of cerebral metabolites in glioma patients with proton MR spectroscopy using T2 relaxation time correction

This study was aimed to investigate the significance of absolute concentration of metabolites in glioma patients using proton MR spectroscopy (MRS) with T2 relaxation time correction using three different echo times. The absolute concentrations of metabolites in 7 normal subjects and in 23 gliomas (10 low-grade, 13 high-grade) were obtained by proton MRS using a tissue water signal as an internal standard. The signal intensities of metabolites and tissue water were corrected by T2 relaxation time. In low-grade glioma, the T2 relaxation time of NAA was shorter, and T2 relaxation time of water was prolonged as compared to normal subjects (p < 0.001). In high-grade glioma, the T2 relaxation time of NAA (p < 0.001) and T2 relaxation time of Cr (p < 0.01) were shorter, and T2 relaxation time of water (p < 0.001) was prolonged as compared to normal subjects. Moreover, high-grade gliomas revealed a shorter T2 relaxation time of Cr than low-grade gliomas (p < 0.05). In glioma, NAA and Cr concentration were decreased, and Cho were increased as compared to normal subjects. Moreover, high-grade glioma revealed a significant lower Cr (p < 0.001) and Cho (p < 0.01) concentration compared to low-grade gliomas. Low Cr concentration is the most reliable indicator of malignancy in glioma. Cho concentration did not correlate with malignancy in gliomas.     

Serial Precision of Metabolite Peak Area Ratios and Water Referenced Metabolite Peak Areas in Proton MR Spectroscopy of the Human Brain

The precision of cerebral proton magnetic resonance spectroscopy (MRS) measurements is critical both in the clinical setting and for research purposes. Marshall et al. have recently concluded that “disappointing in vivo repeatability…is likely to limit” the ability of MRS to detect modest changes. We present here a comprehensive study of the precision of short- and long-term metabolite peak area ratios and water referenced metabolite peak areas for long echo time point resolved spectroscopy (PRESS) spectra (repetition time (TR) = 2000 ms, echo time (TE) = 136 ms) acquired from the occipital lobes of normal volunteers and a phantom using a conventional whole body 1.5 T MR system and conventional acquisition and analysis protocols. Short-term in vitro precision determined by five repeat scans on five occasions was excellent as measured by a mean coefficient of variation (NAA/Cho = 1.3%, NAA/Cr + PCr = 1.0%, Cho/Cr + PCr = 1.6%, NAA/H₂O = 0.5%, Cho/H₂O = 1.2%, Cr + PCr/H₂O = 0.8%). Long term in vitro precision using 100 spectra acquired over 2 years was also very good (NAA/Cho = 2.7%, NAA/Cr + PCr = 1.4%, Cho/Cr + PCr = 2.2%, NAA/H₂O = 1.5%, Cho/H₂O = 2.4%, Cr + PCr/H₂O = 1.5%). Short-term in vivo precision determined by five repeat scans in a single scanning session on eight subjects was also excellent (NAA/Cho = 5.2%, NAA/Cr + PCr = 3.0%, Cho/Cr + PCr = 6.6%, NAA/H₂O = 1.4%, Cho/H₂O = 4.9%, Cr + PCr/H₂O = 2.7%) and only worsened slightly for long-term in vivo precision determined by five repeat scans on eight subjects over 3 months (NAA/Cho = 5.2%, NAA/Cr + PCr = 4.8%, Cho/Cr + PCr = 7.7%, NAA/H₂O = 2.5%, Cho/H₂O = 6.4%, Cr + PCr/H₂O = 3.8%). We attribute the excellent precision reported here to the use of highly automated techniques for voxel shimming, water suppression and peak area measurements. These results allow us to repudiate Marshall’s assertion regarding disappointing repeatability of in vivo MRS.     

Single-voxel proton MR spectroscopy in toluene abuse

Inhalation of toluene, which is an organic solvent, causes toxic encephalopathy characterized by cognitive impairment, cerebellar and extra-pyramidal symptoms. We studied cranial MR images and single-voxel MR spectroscopy of 22 toluene abusers and age-matched control subjects. The mean age of the abusers and mean duration of abuse were 18,1 years and 47 months, respectively. We got three MR spectra from the centrum semiovale, cerebellum and thalamus by using STEAM sequence with a TE value of 30 ms. N-acetyl aspartate (NAA)/Creatine (Cr), Choline (Cho)/Cr, myo-inositol (mI)/Cr peak integral ratios were calculated. NAA/Cr in the cerebellum and centrum semiovale of the abusers were significantly lower than those of the control subjects. mI/Cr in centrum semiovale and cerebellum were higher in toluene abusers. No significant difference was found in the metabolite ratios of the thalami. The association of NAA/Cr and mI/Cr ratios in cerebellum and centrum semiovale with the duration of abuse was significant. Normal level of NAA in thalamus, which was a neuron rich gray matter structure, might imply that toluene inhalation did not cause direct neuronal injury. Selective reduction of NAA and increased level of mI in white matter supported the theory of that axonopathy and gliosis were the main mechanisms of pathophysiology in chronic toluene encepholopathy. Insignificance of elevation of Cho/Cr ratios demonstrated that toluene inhalation did not cause active demyelination.     

Intraindividual variability of striatal (1)H-MRS brain metabolite measurements at 3 T

PURPOSE: To measure possible positional and diurnal physiological effects on brain metabolites in single-voxel proton magnetic resonance spectroscopy ((1)H-MRS) measurements of the right and left striatum. METHODS: (1)H-MRS measurements were performed in 10 healthy adult volunteers using a short echo PRESS sequence (TE=30 ms, TR=3000 ms). Each individual was scanned during both morning and afternoon hours. Regions of interest were right and left striatum. To control for systematic drift in scanner performance, (1)H-MRS measurements of a standard phantom solution were also acquired. Statistical analysis was performed using a repeated measures analysis of variance that included three within-subject factors: metabolite (N-acetyl-aspartate [NAA] or creatine [Cr]), laterality (left or right caudate) and time (morning or afternoon). RESULTS: A significant interaction (P<.016) between time of day and metabolite levels was observed. Further exploration of this finding revealed a significant difference between morning and afternoon levels of NAA (P<.044) but not Cr. In addition, no significant morning-to-afternoon differences were observed for the (1)H-MRS phantom measurements. CONCLUSIONS: Systematic variation due to scanner performance does not account for the changes observed in repeated measurements of striatal NAA levels. This difference may be accounted for by either repositioning effects or circadian physiological effects. Further studies are required to learn whether time of day standardization of (1)H-MRS acquisitions may contribute to improved reproducibility of measurements.     

Magnetic resonance spectroscopy of the brain in neurologically asymptomatic HIV-infected patients

The CNS involvement is frequently found in human immunodeficiency virus (HIV) infection. The purpose of our study was to determine whether proton magnetic resonance spectroscopy (MRS) could detect early brain involvement in neurologically asymptomatic HIV-infected patients with normal MR imagings and to find the correlation between MRS and the immune status. We performed MRS in 30 HIV seropositive neurologically asymptomatic patients with normal MRI and compared the MRS findings with 13 controls. A statistically significant reduction in N-acetylaspartate (NAA)/creatine (Cr) and N-acetylaspartate (NAA)/choline (Cho) in both centrum semiovale (p < 0.005) and thalamic areas (p < 0.05) was found. There is no statistically significant difference as to choline (Cho)/creatine (Cr) and myoinositol (mI)/creatine (Cr) ratios in both regions. The difference of NAA/Cr was more pronounced in the white matter than in the gray matter. As for the immune status, there was a trend towards correlation between CD4 counts and NAA/Cr but devoid of statistical significance. Our results suggest that MRS is more sensitive than conventional MR imaging in detecting CNS involvement in neurologically asymptomatic HIV patients and may, therefore, be used for early detection of brain damage induced by HIV.     

A (1)H magnetic resonance spectroscopy study of aging in parietal white matter: implications for trials in multiple sclerosis

1H magnetic resonance spectroscopy (MRS) provides a unique tool to detect and quantify brain metabolites. In multiple sclerosis it can be used to investigate axonal loss or dysfunction through measurement of N-acetyl aspartate (NAA), a neuronal marker. Previous studies in adults have reported variable effects of aging on metabolite concentrations but have predominantly focused on changes in the elderly. This study has examined a younger adult age group to provide a reference database more applicable to the multiple sclerosis population. Single voxel (1)H MRS was carried out in 44 subjects between 22 and 62 years of age. Sixteen subjects underwent repeat examination after one year. Absolute concentrations of NA (the sum of NAA and N-acetyl aspartate glutamate), NAA, creatine/phosphocreatine (Cr), choline containing compounds (Cho) and myo-inositol (mI) were measured. NA, NAA and mI concentrations did not correlate with age but there were significant correlations between age and Cr (r = 0.43, p = 0.004) and Cho (r = 0.38, p = 0. 011) concentrations. No significant differences in metabolite concentrations were seen over one year. This study provides evidence that age-related changes of metabolite concentrations occur even in a young to middle aged adult population. This emphasizes the need to perform absolute quantification of metabolite concentrations rather than ratios and the importance of age-matching in (1)H MRS studies of multiple sclerosis.     

Brain metabolite changes in alcoholism: An in vivo proton magnetic resonance spectroscopy (MRS) study

Image-guided, single voxel, localized proton magnetic resonance (MR) spectroscopy was performed to assess the brain metabolite changes in 10 (n = 10) alcoholic patients in the frontal lobe, cerebellum, and thalamus regions. The spectra obtained were characterized by a reduced N-acetyl-aspartate (NAA) to choline (Cho) (p < .01) and NAA to total creatine (Cr + PCr) (p < .01) ratios relative to age-matched (n = 27) controls. These decreased ratios correspond to depleted concentration of the metabolite levels such as NAA and Cho. Reduction of NAA is consistent with the neuronal loss while reduction in Cho suggests significant changes in the membrane lipids of alcoholics.     

Brain metabolite concentration ratios in vivo: multisite reproducibility by single-voxel 1H MR spectroscopy

Ten normal subjects were scanned identically at three separate sites (Little Rock, Houston, and New Orleans) to evaluate the reproducibility of brain metabolite ratios in single-voxel (1)H point-resolved spectroscopy sequence (PRESS) magnetic resonance (MR) spectroscopy in vivo. All scans were processed by a single individual at a single site. Coefficients of variation of the measured metabolite ratios generally were in the range found for previous single-voxel, single-site reproducibility studies. No differences were found among the sites for ratios of N-acetylaspartate to creatine (NAA/Cr) or choline to Cr (Cho/Cr) in left thalamus by multivariate ANOVA. Metabolite ratios of Cr or Cho relative to local brain H(2)O did not vary among the sites. However, by multivariate ANOVA, NAA/H(2)O differed between Little Rock and New Orleans, but not between those sites and Houston. Intraclass correlation coefficients suggested reasonable reproducibility between Little Rock and New Orleans, but not between those sites and Houston.     

广泛性焦虑大鼠前额叶皮质和海马磁共振波谱的研究

以广泛性焦虑大鼠为研究载体,探讨其前额叶皮质和海马组织质子磁共振波谱(1H-MRS)的变化及意义.大鼠分为正常组和模型组各8只,采用慢性情绪应激的方法建立广泛性焦虑大鼠模型,以国际公认的高架十字迷宫试验对其进行评价,在活体状态下,通过pharmascan70/16超导磁共振仪(7.0T)检测双侧海马及前额叶皮质N-乙酰天门冬氨酸(NAA)、胆碱(Cho)、谷氨酸(Glu)、肌酸(Cr)等代谢物水平,分别计算NAA、Cho和Glu与Cr的比值,进而对脑组织代谢进行定性及定量分析.正常组与广泛性焦虑组双侧海马及左侧前额叶皮质代谢物无明显差异(P0.05),广泛性焦虑大鼠右侧前额叶皮质NAA、Cho相对浓度较正常组显著降低(P0.05),Glu相对浓度则明显升高(P0.05).慢性焦虑情绪的产生可能与右侧前额叶皮质兴奋性神经递质谷氨酸的浓度升高、神经元的损伤或数量减少及细胞内信号转导的异常有关.