Proton MR spectroscopy in neuroborreliosis: a preliminary study

We report results of a magnetic resonance spectroscopy (MRS) study in 12 patients with neuroborreliosis. We used a PRESS sequence, placing an 8 cm³ voxel in normal-appearing white matter of the frontal lobe. Peaks indicating N-acetylaspartate (NAA), choline (Cho), creatine (Cr), myo-inositol (mI), lipids (Lip) and lactate (Lac) were identified and ratios of NAA/Cr, Cho/Cr, mI/Cr, Lip/Cr, Lac/Cr calculated. Significant increases in Cho/Cr and Lip/Cr were noted. No abnormality was found in mean NAA/Cr and Lac/Cr, but in four patients there was a decreased NAA peak; mI/Cr ratio was slightly increased. Although the spectroscopic profile in patients with neuroborreliosis seems to be nonspecific, MRS might be useful for assessing tissue damage of the central nervous system.     

脑胶质瘤模型在体1H磁共振波谱研究

采用磁共振波谱仪在体观察大鼠C6胶质瘤的代谢及生化改变，为^1H磁共振波谱临床应用打下基础。40只Wister大鼠分为正常组（10只）和肿瘤组（30只），大鼠脑右尾状核接种C6细胞。MRI动态观察瘤组织改变，采用点分辨波谱法（PRESS：point resolved spectroscopy)行^1H磁共振波谱检测。正常大鼠^1H波谱检出N－乙酰门冬氨酸（NAA）、胆碱类化合物（Cho)、肌酸和磷酸肌酸（Cr PCr)、谷氨酸和谷氨酰胺（Glu Gln)、脂质（Lip)、乳酸（Lac)。C6胶质瘤NAA较正常组明显降低，NAA／Cho较正常组明显降低（P＜0．01），NAA／Cr较正常组也明显下降（P＜0．05），Cho/Cr明显升高（P＜0．01），Lac升高。表明高场强磁共振波谱仪可以精确观察在体大鼠C6胶质瘤的^1H磁共振波谱，对肿瘤的代谢及生化改变进行监测。     

质子磁共振波谱在脑肿瘤中的应用研究

目的 研究脑肿瘤质子磁共振波谱的不同表现及其临床应用价值。材料与方法 搜集行质子磁共振波检查并经病理追踪证实的65例脑肿瘤患者,其中Ⅰ-Ⅱ级星形细胞瘤12例,Ⅲ级星形细胞瘤6例,成胶质细胞瘤8例,胶质瘤术后复发4例,脑膜瘤9例,转移瘤17例,神经鞘瘤4例,垂体瘤4例,表皮样囊肿1例;对侧正常相应部位作为自身对照组20例。观察定点分辨选择波谱（PRESS）采集N－乙酰天门冬氨酸（STEAM）对脂质（Lip)、丙氨酸（ Ala)等短T2代谢物的显示。结果 同对照组比较脑肿瘤NAA有不同程度下降（P＜0．05）;脑外肿瘤NAA低于脑内肿瘤,脑膜瘤NAA／Cr,NAA/Cho比Ⅲ级星形细胞瘤低（P＜0．05）;NAA减少在肿瘤中心明显;在肿瘤坏死区及术后残腔几乎测不到NAA。胶质瘤实体部分Cho信号增加（P＜0．005）;成胶质细胞瘤Cho/Cr比Ⅰ－Ⅱ级星形细胞瘤高（P＜0．05）;4例肿瘤复发Cho明显升高。约21．5％的肿瘤显示Lac峰,其中高级别胶质瘤坏死区和术后残腔8例,表皮样囊肿1例,神经鞘瘤囊变区2例,肿瘤水肿区3例。约21％的未经治疗的胶质瘤出现Lip信号;转移瘤9例,脑外肿瘤11例有不同程度的Lip显示。胶质瘤Cr正常和明显减少各半,脑膜瘤Cr低或缺乏。Ala在9例脑膜瘤中有2例显示。结论 ^1HNMRS是研究脑肿瘤物质和能量代谢的有效方法,有助于脑肿瘤的诊断和鉴别诊断,能提供其组织学分级、术后复发、疗效评价等信息。     

Proton MR spectroscopy in predicting the increase of perfusion MR imaging for WHO grade II gliomas

Purpose:

To investigate the correlation between the metabolite ratios obtained from proton magnetic resonance (MR) spectroscopy and those obtained from MR perfusion parameters (relative cerebral blood volume [rCBV]) in a cohort of low‐grade glioma (LGG).

Materials and Methods:

Patients underwent prospectively conventional MR, proton magnetic resonance spectroscopy (¹HMRS), and perfusion‐weighted images (PWI). Statistical analyses were performed to determine the correlative and independent predictive factors of rCBVmax and the metabolite ratio thresholds with optimum sensitivity and specificity.

Results:

Thirty‐one patients were included in this study. Linear correlations were observed between the metabolic ratios (lactate [Lac]/creatine [Cr], choline [Cho]/N‐acetyl‐aspartate [NAA], free‐lipids/Cr) and rCBVmax (P < 0.05). These metabolic ratios were determined to be independent predictive factors of rCBVmax (P = 0.027, 0.011 and 0.032, respectively). According to the receiver operating characteristic curves, the cutoff values of the metabolic ratios to discriminate between the two populations of rCBVmax (<1.7 versus = 1.7) were 1.72, 1.54, and 1.40, respectively, with a sensitivity = 75% and a specificity >95% for Lac/Cr.

Conclusion:

This study demonstrated consistent correlations between the data from ¹HMRS and PWI. The Lac/Cr ratio predicts regional hemodynamic changes, which are themselves a useful biomarker of clinical prognosis in patients with LGG. As such, this ratio may provide a new parameter for making improved clinical decisions. J. Magn. Reson. Imaging 2012;35:543‐550. © 2011 Wiley Periodicals, Inc.     

头颈部良性神经源性肿瘤1H MRS的表现特点

目的：探讨头颈部良性神经源性肿瘤在单体素^1H MRS上的表现特点。材料和方法：共收集经单体素。HMRS检查，并经手术病理证实的头颈部神经源性肿瘤14例（神经鞘瘤11例，神经纤维瘤2例，颈动脉体瘤1例）。采用点分析波谱法（PRESS：TE=144ms，14例）和激励回波法（STEAM：TE=30ms，11例）进行。HMRS空间定位，以胆碱和脂质代谢物为标准评价所有肿瘤。波谱图上，胆碱和脂质分别在3．2ppm和0．9—1．4ppm区域识别。结果：采用PRESS后，14例神经源性肿瘤中检测出胆碱代谢物者11例，检出脂质代谢物者6例。胆碱和脂质代谢物同时检出者5例，仅检出胆碱者6例，仅检出脂质者1例，胆碱和脂质均未检出者2例。采用STEAM后，11例肿瘤中检出胆碱代谢物和脂质者分别为3例和8例。结论：头颈部良性神经源性肿瘤的单体素。HMRS表现具有多样性，多数肿瘤以长TEPRESS上胆碱峰的显示为特点，长TEPRESS能较STEAM更好地检出良性神经源性肿瘤内的胆碱代谢物。     

^1HMRS在脑梗塞中的临床应用

目的　应用氢质子磁共振波谱 (1HMRS)和化学位移成像 (chemicalshiftimaging ,CSI)研究人脑梗塞中代谢物随时间的变化规律 ,评价1HMRS在脑梗塞中的临床应用价值。材料与方法　 2 8例脑梗塞患者根据发作时间将其分为 :超急性期 (6小时内 ) 2例 ;急性期 (6小时后至 2天内 ) 6例 ;亚急性期 (2天后至 6周内 ) 12例 ;慢性期 (6周后 ) 8例。将正常对侧相同部位 2 0例作为自身对照组。应用定点分辨选择波谱 (pointedresolvedselectivespectroscopy ,PRESS) /TE 13 5msCSI和两侧相对应部位PRESS/TE 13 5ms单体素采集。测算N 乙酰天门冬氨酸 (NAA)、肌酸 (Cr)、含胆碱类化合物 (Cho)与对照组的比值及同侧NAA/Cho、NAA/Cr、Lac/Cho(乳酸 /含胆碱类化合物 )的变化。结果　超急性期 2例出现Lac而NAA、Cho、Cr改变不明显 ;急性期 5例Lac增加 ,NAA开始减少 ,Cr稍降低 ,Cho未见明显改变 ;亚急性期Lac进一步增加 ,2例复查患者 2周后Lac开始下降 ,但仍维持较高浓度 ,NAA继续减少 ,Cr降低 ,Cho稍减少 ;慢性期NAA、Cr进一步减少 ,3例在病灶区仍检测到一定浓度Lac ,5例未见明显的Lac ,3例 6个月后病灶边缘Cho浓度比对侧高 ,5例Cho降低。另外 3例亚急性期、2例慢性期明显脂肪峰。同对照组比较 ,2 8例患者总的NAA下降最明显 ,     

Comments on "Ensuring safety of implanted devices under MRI using reversed polarization"

A 3‐T study is presented, comparing the ability of two ¹H spectroscopy pulse sequences, Carr–Purcell point resolved spectroscopy (CPRESS; TE = 45 msec), and conventional PRESS (TE = 35 msec), to separate between groups of 20 normal control (NC) and 20 mild cognitive impairment (MCI) subjects. Both sequences showed higher myo‐inositol (mI) and mI/N‐acetyl‐aspartate (NAA) levels in the posterior cingulate gyrus of the MCI subjects. The increased intrasubject repeatability of mI and mI/NAA CPRESS measurements (～6% vs. 9% for PRESS) translated into decreased intraclass variability. A 22% intraclass mI PRESS variability was reduced to 16% for CPRESS, and an 18% intraclass mI/NAA PRESS variability was reduced to 12% for CPRESS for the group of NC subjects. Similar results were observed for the MCI subjects. Decreased intraclass variability led to improved separation between NC and MCI subjects (P = 0.017 for PRESS and P < 0.0001 for CPRESS mI/NAA, the best NC/MCI discriminant for each method). Seventy‐five percent sensitivity at eighty percent specificity was demonstrated by mI/NAA CPRESS measurements in separating NC from MCI subjects. High correlations were also observed between subject performance on a number of neuropsychological tests (probing verbal memory, visuoconstruction performance, and visual motor integration) and the mI/NAA ratio; higher correlation coefficients (with stronger statistical significance) were consistently evident for CPRESS than for PRESS data. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Characterization of intervertebral disc degeneration by high-resolution magic angle spinning (HR-MAS) spectroscopy.

The goal of this study was to determine the ability of high-resolution magic angle spinning (HR-MAS) NMR spectroscopy to distinguish different stages of intervertebral disc degeneration (IVDD). 17 discs were removed from human cadavers and analyzed them using 1D and 2D (total correlation spectroscopy (TOCSY)) (1)H HR-MAS spectroscopy, and T(1) and T(2) relaxation time measurements to determine the chemical composition and changes in chemical environment of discs with increasing levels of degeneration (Thompson grade). Among the significant findings were that spectra were very similar for samples taken from annular and nuclear regions of discs, and that visually apparent changes were observed in the spectra of the annular and nuclear samples from discs with increasing Thompson grade. Area ratios of the N-acetyl to choline (Cho) regions, and Cho to carbohydrate (Carb) regions of the spectra allowed us to discriminate between discs of increasing Thompson grade with minimal overlap of individual ratios. Changes in T(1) and T(2) relaxation times of the chemical constituents of disc spectra were not significantly correlated to the degree of degeneration. The results of this study support the feasibility of using in vivo spectroscopy for detecting chemical changes associated with disc degeneration.     

Prospective motion correction for magnetic resonance spectroscopy using single camera Retro-Grate reflector optical tracking

Purpose:

To introduce and evaluate a method of prospective motion correction for localized proton magnetic resonance spectroscopy (1H‐MRS) using a single‐camera optical tracking system.

Materials and Methods:

Five healthy participants were scanned at 3T using a point‐resolved spectroscopic sequence (PRESS) with a motion‐tracking module and phase navigator. Head motion in six degrees was tracked with a Retro‐Grate Reflector (RGR) tracking system and target via a mirror mounted inside the bore. Participants performed a series of three predetermined motion patterns during scanning.

Results:

Left–right rotation (Rz) (average 12°) resulted in an increase in the total choline to total creatine ratio (Cho/Cr) of +14.6 ± 1.5% (P = 0.0009) for scans without correction, but no change for scans with correction (+1.1 ± 1.5%; P = 0.76). Spectra with uncorrected Z‐translations showed large lipid peaks (skull) with changes in Cho/Cr of ?13.2 ± 1.6% (P = 0.02, no motion correction) and ?2.2 ± 2.4% (P = 0.51) with correction enabled. There were no significant changes in the ratios of N‐acetylaspartate, glutamate+glutamine, or myo‐inositol to creatine compared to baseline scans for all experiments.

Conclusion:

Prospective motion correction for 1H‐MRS, using single‐camera RGR tracking, can reduce spectral artifacts and quantitation errors in Cho/Cr ratios due to head motion and promises improved spectral quality and reproducibility. J. Magn. Reson. Imaging 2011. © 2011 Wiley‐Liss, Inc.

     

Lactate,N-acetylaspartate,choline and creatine concentrations,and spin-spin relaxation in thalamic and occipito-parietal regions of developing human brain

Previous studies of the brains of normal infants demonstrated lower lactate (Lac)/choline (Cho), Lac/creatine (Cr), and Lac/N-acetylaspartate (Naa) peak-area ratios in the thalamic region (predominantly gray matter) compared with occipitoparietal (mainly unmyelinated white matter) values. In the present study, thalamic Cho, Cr, and Naa concentrations between 32–42 weeks' gestational plus postnatal age were greater than occipito-parietal: 4.6 ± 0.8 (mean ± SE), 10.5 ± 2.0, and 9.0 ± 0.7 versus 1.8 ± 0.6, 5.8 ± 1.5, and 3.4 ± 1.1 mmol/kg wet weight, respectively: Lac concentrations were similar, 2.7 ± 0.6 and 3.3 ± 1.3 mmol/kg wet weight, respectively. In the thalamic region, Cho and Naa T₂s increased, and Cho and Lac concentrations decreased, during development. Lower thalamic Lac peak-area ratios are principally due to higher thalamic concentrations of Cho, Cr, and Naa rather than less Lac. The high thalamic Cho concentration may relate to active myelination; the high thalamic Naa concentration may be due to advanced gray-matter development including active myelination. Lac concentration is higher in neonatal than in adult brain.     

磁共振波谱在星形细胞肿瘤术前分级中的价值

目的 研究磁共振波谱(MRS)在星形细胞肿瘤术前分级中的价值. 方法 52例患者均经病理证实,其中弥漫性星形细胞瘤(WHO 2级)20例,间变性星形细胞瘤(WHO 3级)14例,胶质母细胞瘤(WHO 4级)18例.MRS采用多体素PRESS序列.结果 ①星形细胞肿瘤在MRS上常表现为Cho升高、NAA降低,级别越高变化越明显.在高度恶性星形细胞肿瘤中还可出现Lip峰.②对病例组中32例高度恶性星形细胞肿瘤采用Pearson相关回归分析法显示,肿瘤实质区的Cho/Cr(r＝0.656,P=0.000)、Lip1.3/Cr(r＝0.559,P=0.001)及Glx/Cr(r＝0.482,P=0.005)均与肿瘤的病理分级呈显著正相关;Cho/NAA(r＝0.395,P=0.025)、Lip0.9/Cr(r＝0.386,P=0.029)与病理分级呈正相关.③当Cho/Cr＝2时,诊断WHO 4级星形细胞肿瘤的敏感性为94.4%,特异性为64.3%,阳性预测值为77.3%,阴性预测值为90%.④当Lip1.3/Cr＝0.526时,诊断为WHO 4级星形细胞肿瘤的敏感性为88.9%,特异性为92.9%,阳性预测值为94.1%,阴性预测值为86.7%. 结论 MRS是一种有潜力的方法,有助于对肿瘤术前进行分级.     

Quantitative measurement of N‐acetyl‐aspartyl‐glutamate at 3 T using TE‐averaged PRESS spectroscopy and regularized lineshape deconvolution

This article introduces regularized lineshape deconvolution in conjunction with TE‐averaged PRESS spectroscopy to measure N‐acetyl‐aspartyl‐glutamate (NAAG). Averaging different echo times suppressed the signals of multiplets from strongly coupled spin systems near 2 ppm; thus, minimizing the interfering signals to detect the acetyl proton signal of NAAG. Signal distortion was corrected by lineshape deconvolution, and Tikhonov regularization was introduced to reduce noise amplification arising from deconvolution; as a result, spectral resolution was enhanced without significantly sacrificing signal‐to‐noise ratio (SNR). This new approach was used to measure NAAG in the two regions of interest of healthy volunteers, dominated by gray matter and white matter, respectively. The acetyl proton signal of NAAG was directly quantified by fitting the deconvoluted spectra to a Voigt‐lineshape spectral model function, yielding the NAAG–N‐acetyl‐aspartate (NAA) ratios of 0.11 ± 0.02 for the gray matter voxels (n = 8) and 0.18 ± 0.02 for the white matter voxels (n = 12). Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Human brain MR spectroscopy thermometry using metabolite aqueous‐solution calibrations

Purpose:

To estimate absolute brain temperature using proton MR spectroscopy (¹H‐MRS) and mean brain–body temperature difference of healthy human volunteers.

Materials and Methods:

Chemical shift difference between temperature‐dependent water spectral line position and temperature‐stable metabolite spectral reference was used for the estimations of absolute brain temperature. Temperature calibrations constants were obtained from the spectra of the N‐acetyl aspartate (NAA line at ～2.0 ppm), glycero‐phosphocholine (GPC line at ～3.2 ppm), and creatine (Cr line at ～3.0 ppm) aqueous solutions with pH values within physiologically pertinent ranges. Single‐voxel PRESS sequence (TR/TE 2000/80 ms) was used for this purpose. Brain temperature was determined by averaging the temperatures computed from water‐Cho, water‐Cr, and water‐NAA chemical shift differences.

Results:

The mean brain temperature of 18 healthy volunteers was 38.1 ± 0.4°C and mean brain–body (rectal) temperature difference was 1.3 ± 0.4°C.

Conclusion:

Improved accuracy of the temperature constants and averaging the temperatures computed from water‐Cho, water‐Cr, and water‐NAA chemical shift differences increased the reliability of the brain temperature estimations. J. Magn. Reson. Imaging 2010;31:807–814. ©2010 Wiley‐Liss, Inc.     

Comparative reliability of proton spectroscopy techniques designed to improve detection of J‐coupled metabolites

Improved detection of J‐coupled neurometabolites through the use of modified proton magnetic resonance spectroscopy (1H‐MRS) techniques has recently been reported. TE‐averaged point‐resolved spectroscopy (PRESS) uses the J modulation effects by averaging FIDs with differing echo times to improve detection of glutamate, while standard PRESS detection of glutamate can be improved by using an appropriate single echo determined from J‐modulation simulations. In the present study, the reliabilities of TE‐averaged PRESS, standard PRESS with TE = 40 ms, and standard PRESS with TE = 30 ms in detecting metabolite levels in the cingulate gyrus of the human brain at 3T were compared in six subjects. TE‐averaged PRESS measures showed a mean variability of 9% for N‐acetyl aspartate, choline, and creatine, compared with < 4% for the 30‐ and 40‐ms PRESS techniques. The coefficients of variation for glutamate were 10%, 7%, and 5% for TE‐averaged, 30‐ms, and 40‐ms PRESS, respectively. PRESS with a TE of 40 ms also demonstrated improved reliability for GABA and glutamine concentrations. These results show that with the appropriate selection of echo time standard PRESS can be a reliable ¹H‐MRS technique for the measurement of J‐coupled neurometabolites in the human brain and, moreover, compares favorably with at least one J‐edited technique. Magn Reson Med 60:964–969, 2008. © 2008 Wiley‐Liss, Inc.     

多体素MRS在星形细胞瘤中的应用价值

目的探讨多体素MRS在不同级别星形细胞瘤术前诊断的应用价值。方法搜集22例病理证实的脑星形细胞瘤,分为高、低级别2组,行MR常规、增强扫描及MRS检查,比较Cho/Cr、NAA/Cr、Cho/NAA比值及Lac、Lip情况。结果高级别组表现为Cho明显增高,NAA及Cr明显降低,低级别组表现为Cho轻到中度不等增高和NAA不同程度的降低,高、低级别组间Cho/Cr、NAA/Cr以及Cho/NAA比值差别有意义。肿瘤周边水肿区与对侧正常脑组织间Cho/Cr、Cho/NAA比值差别有意义,NAA/Cr比值差别无统计学意义。高级别组中有11例出现Lac峰,7例出现Lip峰,低级别组中仅有2例出现Lac峰,无Lip峰出现。结论多体素H-MRS在术前全面评价星形细胞瘤不同级别间的鉴别诊断及确定肿瘤边界形态方面有重要的临床意义。     

In vivo 3.0‐tesla magnetic resonance T1ρ and T2 relaxation mapping in subjects with intervertebral disc degeneration and clinical symptoms

The purpose of this study is (1) to determine the correlation between T_1ρ and T₂ and degenerative grade in intervertebral discs using in vivo 3.0‐T MRI, and (2) to determine the association between T_1ρ and T₂ and clinical findings as quantified by the SF‐36 Questionnaire and Oswestry Disability Index. Sixteen subjects participated in this study, and each completed SF‐36 and Oswestry Disability Index questionnaires. MRI T_1ρ and T₂ mapping was performed to determine T_1ρ (77 discs) and T₂ (44 discs) in the nucleus of the intervertebral disc, and T₂‐weighted images were acquired for Pfirrmann grading of disc degeneration. Pfirrmann grade was correlated with both T_1ρ (r = ?0.84; P < 0.01) and T₂ (r = ?0.61; P < 0.01). Mixed‐effects models demonstrate that only T_1ρ was associated with clinical questionnaires (R²_SF‐36 = 0.55, R²_O.D.I. = 0.56; P < 0.05). Although the averaged values of T_1ρ and T₂ were significantly correlated, they presented differences in spatial distribution and dynamic range, thus suggesting different sensitivities to tissue composition. This study suggests that T_1ρ may be sensitive to early degenerative changes (corroborating previous studies) and clinical symptoms in intervertebral disc degeneration. Magn Reson Med 63:1193–1200, 2010. © 2010 Wiley‐Liss, Inc.     

Selective excitation of two‐dimensional arbitrarily shaped voxels with parallel excitation in spectroscopy

Parallel excitation is being studied intensively for applications in MR imaging and in particular for selecting arbitrary shapes as regions of interest. In this work, parallel excitation was applied to arbitrarily shaped voxel selection in spectroscopy and investigated for different excitation k‐space trajectories (radial, rectilinear, and spiral) and acceleration factors. Each trajectory was segmented into multiple excitations to increase the overall bandwidth during target selection. Acceleration by parallel excitation was used to decrease the number of segments. Evaluation of spatial and spectral localization of the target of interest was performed in simulation and phantom experiments, and was compared with the point resolved spectroscopy (PRESS) experiment with standard voxels. The selective excitation experiments demonstrated excellent spatial localization and a broad frequency response, although PRESS was superior in direct comparisons with respect to signal‐to‐noise ratio (SNR) and outer volume suppression. Extensive SNR variation was observed dependent on trajectory (8%–90%), with the preferred radial case producing approximately 40%–60% SNR of the PRESS case. Accelerated trajectories at R = 4 provided comparable artifact signal and target excitation accuracy compared with their nonaccelerated counterparts; however, further acceleration (R = 8) resulted in increased artifact (33% increase at R = 8). Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.     

Interindividual,repositioning, and time‐of‐day effects on single voxel proton MR spectroscopy of the anterior cingulate cortex

Purpose:

To measure interindividual, repositioning, and time‐of‐day effects of single voxel PRESS (P oint RES olved S pectroscopy) proton magnetic resonance spectroscopy (¹H‐MRS) acquisition of the anterior cingulate cortex (AC) in healthy human subjects.

Materials and Methods:

AC ¹H‐MRS measurements were performed in 15 healthy adult volunteers using a short echo PRESS sequence (GE Healthcare 3 Tesla, TE/TR = 30/2500 ms, 192 acquisitions, 6 cm³ voxels). For each individual, a total of eight spectra were obtained during two identical scanning sessions separated by 3.5 h. In each, two consecutive AC spectra were acquired. After the first two scans, the subject left the scanner, then immediately returned for repositioning and acquisition of two more consecutive spectra. The subject then left the imaging centre to return 3.5 h later for a repeated procedure. Spectroscopic postprocessing was done using LCmodel. Interindividual, repositioning and time‐of‐day effects were measured using restricted maximum likelihood (REML) models of variance components analysis, where response variables were levels of creatine/phosphocreatine (Cr), N‐acetyl‐aspartate (NAA), myo‐inositol (mI), choline (Cho), and the glutamate‐glutamine complex (Glx).

Results:

Interindividual effects were markedly higher than time‐of‐day and repositioning effects for all metabolites.

Conclusion:

Our findings show that ¹H‐MRS measurements of the AC are sensitive to interindividual differences, while time of day and repositioning are markedly less important. J. Magn. Reson. Imaging 2010;32:276–282. © 2010 Wiley‐Liss, Inc.     

质子磁共振波谱对脑肿瘤的鉴别诊断价值

目的初步探讨氢质子磁共振波谱(1H-MRS)对不同脑肿瘤的诊断及鉴别诊断价值.材料和方法39例颅内肿瘤分别行常规MRI及1H-MRS检查,将肿瘤实质与对侧相应部位及正常对照组行对照研究.检查方法为PRESS序列,主要观察代谢物为氮-乙酰天门冬氨酸(NAA)、含胆碱的化合物(Cho)、肌酸(Cr/PCr)、乳酸(Lac)和脂类(Lipids).结果几乎所有肿瘤波谱均呈现NAA峰降低,Cho升高,Cho/Cr及Cho/NAA比值升高,与正常组织相比有显著性差异(p＜0.05).低度恶性胶质瘤组8例Cho/Cr、NAA/Cr、NAA/Cho代谢物比值分别为1.87±0.45、1.13±0.26、0.74±0.21;高度恶性胶质瘤组7例的代谢物比值的均值分别为2.75±1.17、1.07±0.31和0.62±0.28;脑膜瘤组11例,其代谢物比值的均值分别为6.04±2.15、0和0;转移瘤组10例,其代谢物比值的均值分别为2.32±1.08、1.22±0.17和1.23±0.46.胶质瘤组2例术后与术前比较Cho/Cr比值有明显降低.淋巴瘤1例放疗后较放疗前Cho/Cr比值降低;听神经鞘瘤1例见升高的Cho峰;蛛网膜囊肿1例仅见Lac峰.结论H1-MRS对脑肿瘤的诊断及鉴别诊断、治疗后随访、手术后疗效的评价均有重要价值,可作为一种非损伤性的辅助诊断手段.     

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 ataxias

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.