Magnetic resonance imaging and magnetic resonance spectroscopy in a patient with amyotrophic lateral sclerosis and frontotemporal dementia

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) have been investigated in a single neurodegenerative disease manifesting as either amyotrophic lateral sclerosis (ALS) or frontotemporal dementia (FTD) alone, but have not been examined in combined disorders such as ALS with FTD (ALS-FTD). To our knowledge, this study is the first attempt to demonstrate relationship between MRI abnormalities and MR spectroscopic metabolite changes of the motor cortex, frontal white matter and corticospinal tract in a patient with the diagnosis of ALS with probable upper motor neuron signs (ALS-PUMNS) and FTD. Patient presented underwent MRI of the brain and MRS. The ratio of N-acetylaspartate (NAA) to creatine (Cr), choline to Cr, myo-inositol (ml) to Cr and glutamate-glutamine (Glx) to Cr were derived from peak area measurement. Spectra from the right motor cortex, frontal white matter and corticospinal tract were obtained. MR images were evaluated for sulcus centralis enlargement, corticospinal tract hyperintensity and frontal lobes atrophy. Spectra showed reduced NAA/Cr and Glx/Cr ratio, yet the ratio of Cho/Cr exhibited significant elevation. MR images revealed sulcus centralis enlargement, high signal intensity of corticospinal tract and atrophy of both frontal lobes. Proton spectroscopic metabolic changes in a current patient fully correlate with previously reported MRS metabolic changes in ALS alone. Surprisingly, normal ml (glial marker) values have been found in almost all measured voxels of interest except in the frontal white matter. These findings differ from the previous findings in ALS or FTD alone. In conclusion, these findings support the concept that ALS, FTD and ALS-FTD may represent different manifestations of a single pathological continuum.     

磁共振波谱分析在颅脑胶质瘤分级中的应用研究

目的 分析脑胶质瘤的氢质子磁共振波谱（proton magnetic resonance spectroscopy,1H-MRS）表现及其临床意义;探讨脑胶质瘤的1H-MRS特点与其病理级别相关性.方法 搜集经临床手术、病理证实的脑胶质瘤病例49例,按照WHO诊断标准分成两组：低级别脑胶质瘤组、高级别脑胶质瘤组.所有患者在术前行1H-MRs检查,均在MR非增强成像的基础上获得.使用Philips Achieva 1.5T超导磁共振扫描仪,单体素或多体素扫描,点分辨法,检测不同区域代谢物变化.结果 脑胶质瘤的1H-MRS表现：肌酸（Cr）轻度下降,N-乙酰天门冬氨酸（NAA）显著下降,胆碱（Cho）显著增高.低、高级别脑胶质瘤的肿瘤组织与对侧止常脑组织的NAA、Cho、NAA/Cr、NAA/Cho值存在显著性差异（P〈0.05）;低级别和高级别脑胶质瘤的肿瘤组织的NAA/Cr、NAA/Cho值存在显著性差异（P〈0.05）.脑胶质瘤的NAA/Cho、Cho/Cr、NAA/Cr值与病理级别相关,其中NAA/Cho和NAA/Cr值反映肿瘤级别较稳定;NAA/Cr、NAA/Cho值呈负相关关系,Cho/Cr值呈正相关关系.结论 ：1H-MRS结合MKI能提高脑胶质瘤术前诊断的准确性.1H-MRS能对胶质瘤进行分级,反映胶质瘤代谢特性以及肿瘤生长潜能.     

Differences between Spinocerebellar Ataxias and Multiple System Atrophy-Cerebellar Type on Proton Magnetic Resonance Spectroscopy

Purpose

A broad spectrum of diseases can manifest cerebellar ataxia. In this study, we investigated whether proton magnetic resonance spectroscopy (MRS) may help differentiate spinocerebellar ataxias (SCA) from multiple systemic atrophy- cerebellar type (MSA-C).

Material and Methods

This prospective study recruited 156 patients with ataxia, including spinocerebellar ataxia (SCA) types 1, 2, 3, 6 and 17 (N = 94) and MSA-C (N = 62), and 44 healthy controls. Single voxel proton MRS in the cerebellar hemispheres and vermis were measured. The differences were evaluated using nonparametric statistic tests.

Results

When compared with healthy controls, the cerebellar and vermis NAA/Cr and NAA/Cho were lower in all patients(p<0.002). The Cho/Cr was lower in SCA2 and MSA-C (p<0.0005). The NAA/Cr and Cho/Cr were lower in MSA-C or SCA2 comparing with SCA3 or SCA6. The MRS features of SCA1 were in between (p<0.018). The cerebellar NAA/Cho was lower in SCA2 than SCA1, SCA3 or SCA6 (p<0.04). The cerebellar NAA/Cho in MSA-C was lower than SCA3 (p<0.0005). In the early stages of diseases (SARA score<10), significant lower NAA/Cr and NAA/Cho in SCA2, SCA3, SCA6 or MSA-C were observed comparing with healthy controls (p<0.017). The Cho/Cr was lower in MSA-C or SCA2 (p<0.0005). Patients with MSA-C and SCA2 had lower NAA/Cr and Cho/Cr than SCA3 or SCA6 (p<0.016).

Conclusion

By using MRS, significantly lower NAA/Cr, Cho/Cr and NAA/Cho in the cerebellar hemispheres and vermis were found in patients with ataxia (SCAs and MSA-C). Rapid neuronal degeneration and impairment of membrane activities were observed more often in patients with MSA-C than those with SCA, even in early stages. MRS could also help distinguish between SCA2 and other subtypes of SCAs. MRS ratios may be of use as biomarkers in early stages of disease and should be further assessed in a longitudinal study.     

Detecting neuronal dysfunction of hand motor cortex in ALS: A MRSI study

Background: Although hand motor cortex (HMC) has been constantly used for identification of primary motor cortex in magnetic resonance spectroscopy (MRS) studies of amyotrophic lateral sclerosis (ALS), neurochemical profiles of HMC have never been assessed independently. As HMC has a constant location and the clinic–anatomic correlation between hand motor function and HMC has been established, we hypothesize that HMC may serve as a promising region of interest in diagnosing ALS.

Patients and methods: Fourteen ALS patients and 14 age- and gender-matched healthy controls (HC) were recruited in this study. An optimized magnetic resonance spectroscopic imaging (MRSI) method was developed and for each subject bilateral HMC areas were scanned separately (two-dimensional multi-voxel MRSI, voxel size 0.56?cm³). N-acetyl aspartate (NAA)–creatine (Cr) ratio was measured from HMC and the adjacent postcentral gyrus.

Results: Compared with HC, NAA/Cr ratios from HMC and the postcentral gyrus were significantly reduced in ALS. However, in each group the difference of NAA/Cr ratios between HMC and the postcentral gyrus was not significant. Limb predominance of HMC was not found in either ALS or HC. In ALS, there was a significant difference in NAA/Cr ratio between the most affected HMC and the less affected HMC. A positive relationship between NAA/Cr ratio of HMC and the severity of hand strength (assessed by finger tapping speed) was demonstrated.

Conclusion: Neuronal dysfunction of HMC can differentiate ALS patients from HC when represented as reduced NAA/Cr ratio. Postcentral gyrus could not serve as normal internal reference tissue in diagnosing ALS. Asymmetrical NAA/Cr ratios from bilateral HMC may serve as a promising diagnostic biomarker of ALS at the individual level.     

Proton magnetic resonance spectroscopy in diagnostics of epilepsy

Present paper presents proton MRS investigation results. The investigation was carried out with Magnetom Vision device. Twenty-five patients in the age of 20-44 years suffering with generalization epileptic fits validated by EEG (no visible changes on MRT) were examined. In all cases independently on the localization of the changes, decreasing of NAA and increasing of Cho were recorded. At one side temporal lobe injury recorded by EEG at the damaged part decreasing of NAA/Cr and NAA/Cho + Cr ratios were registered. Patients with bilateral changes registered by EEG showed non-equal changes of metabolite concentration on both sides. Examination of patients suffering with distinct symptoms of temple epileptics has shown ipsilaterality decrease of NAA and Cr concentration. But on the injured side NAA/Cr ratio decrease was more distinct. In general, the laterality was recorded in 14 patients out of 22 with pathological changes registered by proton MRS and in 10 patients out of 14 the above mentioned changes corresponds to the side of the fit initiation. In the patients with bilaterality changes NAA/Cr ratio asymmetry was recorded in all cases, but the most distinctly in the medium part of the temple lobe. Comparison of data recorded in 8 patients suffering with one side fit complex has shown significant asymmetry of metabolites which was observed in ipsilaterality and contra laterality NAA ratio obtained in hippocampal areas. Difference in NAA ratio obtained between left and right sides are 19-25%. Left-right ratio of other metabolites corresponded to that ratio in the control group and was symmetrical.     

磁共振波谱分析与帕金森病患者Hoehn&Yahr分级的相关性研究

目的:探讨磁共振波谱分析(MRS)与帕金森病(PD)HoehnYahr分级之间的相关性。方法:选择2016年9月-2017年8月我院收治的60例PD患者为研究对象,根据HoehnYahr分级将患者分为早期PD组32例、中期PD组18例、晚期PD组10例,并选择同时期在门诊进行健康体检的20例志愿者作为对照组。对各组研究对象的双侧基底节、双侧额叶、双侧丘脑区进行MRS,并分析PD患者HoehnYahr分级与MRS的关系。结果:晚期PD组双侧基底节、双侧额叶、双侧丘脑区NAA/Cr、NAA/Cho、Cho/Cr比值均低于中期PD组、早期PD组、对照组,且中期PD组低于早期PD组、对照组,早期PD组低于对照组,差异有统计学意义(P0.05)。通过Spearman相关性分析显示,MRS检测出PD患者NAA/Cr、NAA/Cho、Cho/Cr比值与HoehnYahr分级间呈负相关性(P0.05)。结论:MRS与PD患者的HoehnYahr分级具有负相关性,并且可通过MRS预测患者疾病的严重程度,以对其进行相应的治疗以及预后评估。     

In vitro study of astrocytic tumour metabolism by proton magnetic resonance spectroscopy

In vivo magnetic resonance spectroscopy (MRS) studies of glial brain tumours reported that higher grade of astrocytoma is associated with increased level of choline-containing compounds (Cho) and decreased levels of N-acetylaspartate (NAA) and creatine and phosphocreatine (Cr). In this work, we studied the metabolism of glioma tumours by in vitro proton magnetic resonance spectroscopy (1H-MRS). 1H-MR spectra were recorded in vitro from perchloric acid extracts of astrocytoma (WHO II) and glioblastoma multiforme (WHO IV) samples. We observed differences between astrocytoma and glioblastoma multiforme in the levels of Cho, alanine, lactate, NAA, and glutamate/glutamine. In astrocytoma samples, we found higher MR signal of NAA and lower signal of Cho and alanine. MR spectra of glioblastoma samples reported significantly higher levels of lactate and glutamate/glutamine. In contrast, levels of Cr were the same in both tumour types. We also determined NAA/Cr and Cho/Cr ratios in the tumour samples. The NAA/Cr ratio was higher in astrocytomas than in glioblastomas multiforme. Conversely, the Cho/Cr ratio was higher in glioblastoma multiforme. The results indicate that MRS is a promising method for distinguishing pathologies in human brain and for pre-surgical grading of brain tumours.     

Linear Associations between Clinically Assessed Upper Motor Neuron Disease and Diffusion Tensor Imaging Metrics in Amyotrophic Lateral Sclerosis

Objective

To assess the relationship between clinically assessed Upper Motor Neuron (UMN) disease in Amyotrophic Lateral Sclerosis (ALS) and local diffusion alterations measured in the brain corticospinal tract (CST) by a tractography-driven template-space region-of-interest (ROI) analysis of Diffusion Tensor Imaging (DTI).

Methods

This cross-sectional study included 34 patients with ALS, on whom DTI was performed. Clinical measures were separately obtained including the Penn UMN Score, a summary metric based upon standard clinical methods. After normalizing all DTI data to a population-specific template, tractography was performed to determine a region-of-interest (ROI) outlining the CST, in which average Mean Diffusivity (MD) and Fractional Anisotropy (FA) were estimated. Linear regression analyses were used to investigate associations of DTI metrics (MD, FA) with clinical measures (Penn UMN Score, ALSFRS-R, duration-of-disease), along with age, sex, handedness, and El Escorial category as covariates.

Results

For MD, the regression model was significant (p = 0.02), and the only significant predictors were the Penn UMN Score (p = 0.005) and age (p = 0.03). The FA regression model was also significant (p = 0.02); the only significant predictor was the Penn UMN Score (p = 0.003).

Conclusions

Measured by the template-space ROI method, both MD and FA were linearly associated with the Penn UMN Score, supporting the hypothesis that DTI alterations reflect UMN pathology as assessed by the clinical examination.     

Prediction of Neurological Impairment in Cervical Spondylotic Myelopathy using a Combination of Diffusion MRI and Proton MR Spectroscopy

Purpose

In the present study we investigated a combination of diffusion tensor imaging (DTI) and magnetic resonance spectroscopic (MRS) biomarkers in order to predict neurological impairment in patients with cervical spondylosis.

Methods

Twenty-seven patients with cervical spondylosis were evaluated. DTI and single voxel MRS were performed in the cervical cord. N-acetylaspartate (NAA) and choline (Cho) metabolite concentration ratios with respect to creatine were quantified, as well as the ratio of choline to NAA. The modified mJOA scale was used as a measure of neurologic deficit. Linear regression was performed between DTI and MRS parameters and mJOA scores. Significant predictors from linear regression were used in a multiple linear regression model in order to improve prediction of mJOA. Parameters that did not add value to model performance were removed, then an optimized multiparametric model was established to predict mJOA.

Results

Significant correlations were observed between the Torg-Pavlov ratio and FA (R² = 0.2021, P = 0.019); DTI fiber tract density and FA, MD, Cho/NAA (R² = 0.3412, P = 0.0014; R² = 0.2112, P = 0.016; and R² = 0.2352, P = 0.010 respectively); along with FA and Cho/NAA (R² = 0.1695, P = 0.033). DTI fiber tract density, MD and FA at the site of compression, along with Cho/NAA at C2, were significantly correlated with mJOA score (R² = 0.05939, P < 0.0001; R² = 0.4739, P < 0.0001; R² = 0.7034, P < 0.0001; R² = 0.4649, P < 0.0001). A combination biomarker consisting of DTI fiber tract density, MD, and Cho/NAA showed the best prediction of mJOA (R² = 0.8274, P<0.0001), with post-hoc tests suggesting fiber tract density, MD, and Cho/NAA were all significant contributors to predicting mJOA (P = 0.00053, P = 0.00085, and P = 0.0019, respectively).

Conclusion

A linear combination of DTI and MRS measurements within the cervical spinal cord may be useful for accurately predicting neurological deficits in patients with cervical spondylosis. Additional studies may be necessary to validate these observations.     

MEG responses during rhythmic finger tapping in humans to phasic stimulation and their interpretation based on neural mechanisms

 The phase-resetting experiment was applied to human periodic finger tapping to understand how its rhythm is controlled by the internal neural clock that is assumed to exist. In the experiment, the right periodic tapping movement was disturbed transiently by a series of left finger taps in response to impulsive auditory cues presented randomly at various phases within the tapping cycle. After each left finger tap, the original periodic tapping was reestablished within several tapping cycles. Influences of the disturbance on the periodic right finger tapping varied depending on the phase of the periodic right finger tapping at which each left finger tap was made. It was confirmed that the periodic tapping was disturbed not by the auditory cues but by the left finger taps. Based on this fact, in this paper each single left tap was considered as the stimulus, and the phase of the periodic tapping of the right index finger when the left tap was executed as the phase of the stimulus. Responses of the neural activities (magnetoencephalography, MEG), the tapping movement, and the corresponding muscle activities (electromyography) were simultaneously measured. Phase-resetting curves (PRCs) representing the degree of phase reset as a function of the phase of the stimulus were obtained both for the left sensorimotor cortex MEG response and for the right index finger tapping response. The shapes of both PRCs were similar, suggesting that the phase reset of the left sensorimotor cortex activities and that of the finger tapping rhythm were the same. Four out of eight subjects showed type-0 reset in Winfree's definition, and the others showed type-1 reset. For general limit-cycle oscillators, type-0 reset is obtained for relatively strong perturbations and type 1 for weak perturbations. It was shown that the transient response of MEG to the single left tap stimuli in type-0 subjects, where the phase was progressively reset, were different from those in type-1 subjects. Based on detailed analysis of the differences, a neural network model for the phase reset of the tapping rhythm is proposed. Received: 10 February 2000 / Accepted in revised form: 15 January 2002     

当归注射液对脑缺血/再灌注神经元代谢物的影响

目的：研究当归注射液对脑缺血／再灌注时神经元代谢物及血流速度的作用,阐明当归对脑缺血损伤神经修复过程的影响。方法：雄性SD大鼠69只,体重150～170g,随机分成假手术组(n=4)、缺血损伤组(n=30)和当归治疗组(n=35)。制作右大脑中动脉血供阻断(MCA0)模型。缺血2h后,当归治疗组立即腹腔注射当归注射液(5g／kgbw)。在再灌注后3～4h和5～6h,以磁共振成像(MRI)技术研究大脑T2加权成像(T2WI)和局域质子谱(^1H MRS)的变化,观察当归对成像和神经元代谢物N-乙酰天门冬氨酸(NAA)、肌酸／磷酸肌酸(Cr／PCr)和胆碱(Cho)的影响。激光多普勒血流仪观察当归注射液对血流速度的影响,测定脑表面血管密度。结果：与缺血损伤组比较,当归治疗组的高信号强度区信号减弱、体积小,NAA值大,Cr/NAA和Cho/NAA比值小,再灌注时的血流速度显著加快,单位面积内的血管长度增加。结论：当归注射液加快缺血脑组织的血液循环,改善神经元的代谢。     

Convex-Envelope Based Automated Quantitative Approach to Multi-Voxel 1H-MRS Applied to Brain Tumor Analysis

Background

Magnetic Resonance Spectroscopy (MRS) can measure in vivo brain tissue metabolism that exhibits unique biochemical characteristics in brain tumors. For clinical application, an efficient and versatile quantification method of MRS would be an important tool for medical research, particularly for exploring the scientific problem of tumor monitoring. The objective of our study is to propose an automated MRS quantitative approach and assess the feasibility of this approach for glioma grading, prognosis and boundary detection.

Methods

An automated quantitative approach based on a convex envelope (AQoCE) is proposed in this paper, including preprocessing, convex-envelope based baseline fitting, bias correction, sectional baseline removal, and peak detection, in a total of 5 steps. Some metabolic ratios acquired by this quantification are selected for statistical analysis. An independent sample t-test and the Kruskal-Wallis test are used for distinguishing low-grade gliomas (LGG) and high-grade gliomas (HGG) and for detecting the tumor, peritumoral and contralateral areas, respectively. Seventy-eight cases of pre-operative brain gliomas with pathological reports are included in this study.

Results

Cho/NAA, Cho/Cr and Lip-Lac/Cr (LL/Cr) calculated by AQoCE in the tumor area differ significantly between LGG and HGG, with p≤0.005. Using logistic regression combining Cho/NAA, Cho/Cr and LL/Cr to generate a ROC curve, AQoCE achieves a sensitivity of 92.9%, a specificity of 72.2%, and an area under ROC curve (AUC) of 0.860. Moreover, both Cho/NAA and Cho/Cr in the AQoCE approach show a significant difference (p≤0.019) between tumoral, peritumoral, and contralateral areas. The comparison between the results of AQoCE and Siemens MRS processing software are also discussed in this paper.

Conclusions

The AQoCE approach is an automated method of residual water removal and metabolite quantification. It can be applied to multi-voxel ¹H-MRS for evaluating brain glioma grading and demonstrating characteristics of brain glioma metabolism. It can also detect infiltration in the peritumoral area. Under the limited clinical data used, AQoCE is significantly more versatile and efficient compared to the reference approach of Siemens.     

Perception of the consequences of self-action is temporally tuned and event driven

It has been proposed that in order to increase the salience of sensations with an external cause, sensations that are predictable based on one's own actions are attenuated [1 and 2]. This may explain why self-imposed tickle [3 and 4] or constant forces [5] are perceived as less intense than the same stimuli externally imposed. Here, subjects used their right index finger to tap a force sensor mounted above their left index finger. When a motor generated a tap on the left finger synchronously with the right tap, simulating contact between the fingers, the perception of force in the left finger was attenuated compared to the same tap experienced during rest. Attenuation gradually reduced as the left tap was either delayed or advanced relative to the active right tap. However, no attenuation was seen to left taps triggered by right-finger movements that stopped above or passed wide of the sensor. We conclude that there is a window of sensory attenuation that is broadly temporally tuned and centered on the time at which the fingers would normally make contact. That is, predictive tactile sensory attenuation is linked to specific external events arising from movement rather than to the movement per se.     

兔实验性肝性脑病1H磁共振波谱初步研究

目的:研究兔实验性肝性脑病1H磁共振波谱(magnetic resonance spectroscopy,MRS)变化。方法:将24只兔子随机分三组:对照组,肝硬化组,肝性脑病组,各8只。肝性脑病组采用四氯化碳(CCl4)联合内毒素方法制作肝性脑病兔子模型,肝硬化组采用CCl4制作肝硬化模型。分别在第4、6、8、10、12周取肝脏病理活检,第12周测量血氨值,并进行兔子脑组织的MRS扫描。计算N-乙酰天门冬氨酸(N-acetyl asparte,NAA)、肌酸(creatine,Cr)、胆碱(choline,Cho)、肌醇(myo-inositol,mI)和谷氨酰胺复合物(glutamine and glutamate,Glx)的峰下面积,计算NAA/Cr、Cho/Cr、mI/Cr、Glx/Cr。结果:与对照组及肝硬化组相比,肝性脑病组兔血氨上升,脑部MRS显示Glx/Cr升高,Cho/Cr降低,差异显著(P0.05)。与对照组相比,肝硬化组血氨以及MRS改变无统计学意义。结论:兔实验性肝性脑病1H磁共振波谱存在变化。     

BMI and Neuronal Integrity in Healthy,Cognitively Normal Elderly: A Proton Magnetic Resonance Spectroscopy Study

Recent studies associated excess body weight with brain structural alterations, poorer cognitive function, and lower prefrontal glucose metabolism. We found that higher BMI was related to lower concentrations of N‐acetyl‐aspartate (NAA, a marker of neuronal integrity) in a healthy middle‐aged cohort, especially in frontal lobe. Here, we evaluated whether NAA was also associated with BMI in a healthy elderly cohort. We used 4 Tesla proton magnetic resonance spectroscopy (¹H MRS) data from 23 healthy, cognitively normal elderly participants (69.4 ± 6.9 years; 12 females) and measured concentrations of NAA, glutamate (Glu, involved in cellular metabolism), choline‐containing compounds (Cho, involved in membrane metabolism), and creatine (Cr, involved in high‐energy metabolism) in anterior (ACC) and posterior cingulate cortices (PCC). After adjustment for age, greater BMI was related to lower NAA/Cr and NAA/Cho ratios (β < ?0.56, P < 0.008) and lower Glu/Cr and Glu/Cho ratios (β < ?0.46, P < 0.02) in ACC. These associations were not significant in PCC (β > ?0.36, P > 0.09). The existence of an association between NAA and BMI in ACC but not in PCC is consistent with our previous study in healthy middle‐aged individuals and with reports of lower frontal glucose metabolism in young healthy individuals with elevated BMI. Taken together, these results provide evidence that elevated BMI is associated with neuronal abnormalities mostly in frontal brain regions that subserve higher cognitive functions and impulse control. Future studies need to evaluate whether these metabolite abnormalities are involved in the development and maintenance of weight problems.     

Correlation of diffusion and metabolic alterations in different clinical forms of multiple sclerosis

Diffusion tensor imaging (DTI) and MR spectroscopic imaging (MRSI) provide greater sensitivity than conventional MRI to detect diffuse alterations in normal appearing white matter (NAWM) of Multiple Sclerosis (MS) patients with different clinical forms. Therefore, the goal of this study is to combine DTI and MRSI measurements to analyze the relation between diffusion and metabolic markers, T2-weighted lesion load (T2-LL) and the patients clinical status. The sensitivity and specificity of both methods were then compared in terms of MS clinical forms differentiation. MR examination was performed on 71 MS patients (27 relapsing remitting (RR), 26 secondary progressive (SP) and 18 primary progressive (PP)) and 24 control subjects. DTI and MRSI measurements were obtained from two identical regions of interest selected in left and right centrum semioval (CSO) WM. DTI metrics and metabolic contents were significantly altered in MS patients with the exception of N-acetyl-aspartate (NAA) and NAA/Choline (Cho) ratio in RR patients. Significant correlations were observed between diffusion and metabolic measures to various degrees in every MS patients group. Most DTI metrics were significantly correlated with the T2-LL while only NAA/Cr ratio was correlated in RR patients. A comparison analysis of MR methods efficiency demonstrated a better sensitivity/specificity of DTI over MRSI. Nevertheless, NAA/Cr ratio could distinguish all MS and SP patients groups from controls, while NAA/Cho ratio differentiated PP patients from controls. This study demonstrated that diffusivity changes related to microstructural alterations were correlated with metabolic changes and provided a better sensitivity to detect early changes, particularly in RR patients who are more subject to inflammatory processes. In contrast, the better specificity of metabolic ratios to detect axonal damage and demyelination may provide a better index for identification of PP patients.     

Direct determination of the N-acetyl-L-aspartate synthesis rate in the human brain by (13)C MRS and [1-(13)C]glucose infusion

A non-invasive (13)C magnetic resonance spectroscopy (MRS) technique is described for the determination of the N-acetyl-L-aspartate (NAA) synthesis rate, V(NAA), in the human brain in vivo. In controls, the mean V(NAA) was 9.2 +/- 3.9 nmol/min/g. In Canavan disease, where [NAA] is increased (p < 0.001) and [aspartate] is deceased (p < 0.001), V(NAA) was significantly reduced to 3.6 +/- 0.1 nmol/min/g (p < 0.001). These rates are in close agreement with the activity of the biosynthetic enzyme measured in vitro in animals, and with the rate of urinary excretion of NAA in human subjects with Canavan disease. The present result is consistent with the regulation of NAA synthesis by the activity of a single enzyme, L-aspartate-N-acetyltransferase, in vivo, and with its control in Canavan disease by limited substrate supply and/or product inhibition. The (13)C MRS technique provides the means for further determination of abnormal rates of neuronal NAA synthesis among neurological disorders in which low cerebral [NAA] has been identified.     

磁共振波谱成像结合扩散加权成像在脑胶质瘤及脑转移瘤鉴别诊断中的意义

目的:评估磁共振波谱成像(Proton Magnetic Resonance Spectroscopy,1H-MRS)联合磁共振扩散加权成像(Diffusion Weighted Imaging,DWI)在鉴别脑胶质瘤及孤立的脑转移瘤中的作用。方法:应用3.0T磁共振扫描仪,对临床手术确诊及组织病理学诊断证实的49例脑肿瘤患者(35例多形性胶质母细胞瘤,14例脑转移瘤)进行常规磁共振成像、磁共振波谱成像及磁共振扩散加权成像,并并对获得的数据进一步测量瘤内及瘤周区的代谢比、N-乙酰天门冬氨酸(NAA)、胆碱(Cho)、肌酸(Cr)值以及表观弥散系数(ADC值),分析两肿瘤组之间不同参数的统计学差异。此外,我们研究了感兴趣区域(ROI)的大小对肿瘤区域的病变扩散性能潜在影响。结果:胶质母细胞瘤瘤周N-乙酰天门冬氨酸(NAA)、肌酸(Cr),胆碱(Cho)/Cr,Cho/NAA和r CBV显著高于颅内转移瘤(P0.05);ADC值在两肿瘤组之间无显著差异(P0.05)。结论:在瘤周区1H-MRS有助于鉴别胶质母细胞瘤与单发的脑转移瘤。在瘤内扩散性的定量特性依赖ROI大小的设置。     

弥散加权成像联合磁共振波谱分析在脑梗死中的应用研究

目的探讨脑梗死弥散加权成像（DWI）和磁共振波谱分析（MRS）的特点和影响因素,及二者对评估脑梗死的临床价值。方法采用Philips Achieva 1.5T双梯度超导磁共振扫描仪,对72例临床疑是脑梗死患者行常规T1WI、T2WI、FLAIR、DWI、MRS检查,在工作站上测定梗死核心区、内缘区、外缘区、周围区和镜像区的ADC值和代谢物Lac、NAA、Cr、Cho、NAA/Cr、Lac/Cr、Lac/NAA值。结果 DWI显示的梗死灶范围较常规MRI像更加准确、清晰;超急性期、急性期、亚急性期和慢性期梗死核心区的Lac/Cr值和Lac/NAA值高于对侧镜像区,ADC值和NAA/Cr值低于对侧镜像区,存在统计学差异（P〈0.05）;DWI的影响因素有b值、扩散系数、T2穿透效应和各向异性等,MRS的影响因素有磁场均匀性、压水压脂性能、体素、TE与TR、组织代谢物浓度和波谱采集链等。结论 DWI结合MRS能更加全面地评估缺血半暗带,更精确地对脑梗死进行分期和定位。     

The Value of Proton Magnetic Resonance Spectroscopy in High-Intensity Focused Ultrasound Treatment of Experimental Liver Cancer

High-intensity focused ultrasound (HIFU) is a rapidly developing, non-invasive technique for local treatment of solid tumors that produce coagulative tumor necrosis. This study is aimed to investigate the feasibility of proton magnetic resonance spectroscopy (MRS) on early assessing treatment of HIFU ablation in rabbit with VX2 liver tumor. HIFU ablation was performed on normal liver and VX2 tumor in rabbit, and MRS was performed on normal liver and VX2 tumor before and 2 days after 100% HIFU ablation or 80% ablation in tumor volume. Choline (Cho) and choline/lipid (Cho/Lip) ratios between complete and partial HIFU ablation of tumor were compared. Tissues were harvested and sequentially sliced to confirm the necrosis. In normal liver, the Cho value liver was not obviously changed after HIFU (P > .05), but the Cho/Lip ratio was decreased (P < .05). Cho in liver VX2 tumor was much higher than that in normal liver (P < .001). Cho and Cho/Lip ratio were significantly decreased in tumor after complete HIFU ablation and partial HIFU ablation, and the Cho value in complete HIFU tumor ablation did not show any difference from that in normal liver after HIFU (P > .05); however, the Cho value in partial ablation was still higher than that in normal liver before or in tumor after complete HIFU treatment due to the residual part of tumors, and Cho/Lip ratio is lower than that in complete HIFU treatment (P < .001). The changes in MRS parameters were consistent with histopathologic changes of the tumor tissues after treatment. MRS could differentiate the complete tumor necrosis from residual tumor tissue, when combined with magnetic resonance imaging. We conclude that MRS may be applied as an important, non-invasive biomarker for monitoring the thoroughness of HIFU ablation.