急性胆红素脑病常规MRI及~1H-MR波谱表现

目的 探讨急性胆红素脑病(acute bilirubin encephalopathy,ABE)患儿MRI特征及脑内代谢物含量与胆红素水平相关性.方法 对28例临床确诊为ABE新生儿(病例组)和15名正常新生儿(对照组)行T_1WI、T_2WI、DWI及~1H-MRS检查.~1H-MRS检查采用定点分辨率波谱序列,病例组28例均行基底节区多体素扫描,其中15例另行苍白球区单体素扫描.对照组15名新生儿均进行多体素及单体素~1H-MRS检查,测定代谢产物包括N-乙酰天冬氨酸(NAA)、肌酸复合物(Cr)、胆碱复合物(Cho)、肌醇(mI)、乳酸(Lac)、谷氨酸及谷氨酰胺复合物(Glx)浓度.并计算NAA/Cr、Cho/Cr、Lac/Cr、Glx/Cr、mI/Cr比值,应用独立两样本t检验分析两组间各代谢物浓度差异.病例组按照血清总胆红素(TSB)水平分为342.0 μmol/L513.0 μmol/L 11例共3组,对3组患儿脑内代谢物浓度进行方差分析.结果 病例组中有23例在常规MRI表现为T_1WI苍白球高信号,其余5例常规MRI表现无异常.对照组15名均无异常信号出现.~1H-MRS检查病例组15例单体素成像患儿中,7例mI峰增高,mI/Cr比值为0.74±0.23,对照组为0.57±0.20,两组差异有统计学意义(t=2.13,P=0.04);13例ABE患儿Glx波峰明显增高,Glx/Cr比值单体素为1.45±0.37,多体素为0.51±0.36,对照组为0.95±0.23、0.29±0.18,两组间比较差异具有统计学意义(t值分别为4.40、2.17,P值分别为0.00、0.03).结论 双侧苍白球对称性T_1WI高信号为ABE特征性表现,~1H-MRS可见Glx/Cr、mI/Cr升高,提示相应病理生理变化.     

氢质子磁共振波谱在早产儿脑室周围白质软化的早期预测价值

目的：探讨氢质子磁共振波谱（1H-MRS）在早产儿脑室周围白质软化（PVL）早期预测的价值。方法：对29例经常规MRI随访证实的早产儿PVL患者（病例组）和同期29例经常规MRI随访证实颅脑正常的早产儿（对照组）的头颅1H-MRS检查测得的代谢物NAA/Cr、Cho/Cr、Lac/Cr、Glx/Cr、mI/Cr进行比较和统计学分析。两组头颅1H-MRS均采用点分辨波谱（PRESS）序列,运用化学位移成像（CSI）技术行多体素检查,扫描野主要包括两侧侧脑室前后角周围白质,1H-MRS检查及首次常规MRI检查在出生后3～5天内完成,2次常规MRI随访分别在出生后第4周、8周或12周完成;用独立两样本t检验分析病例组与对照组各种代谢物比值的差异。结果：两组中均见明显的NAA、Cho、Cr、mI峰,其中Cho常为最高峰。29例病例组中,20例见较明显的Lac峰,6例见低平的Lac峰,3例未检测到Lac;18例见明显的Glx峰,10例见低平Glx峰,1例未检测到Glx峰。29例对照组中,26例见低平的Glx峰,15例见低平的Lac峰。病例组Lac/Cr、Glx/Cr明显高于对照组,差异有统计学意义（P值分别为0.005和0.002）;两组间NAA/Cr、Cho/Cr、mI/Cr差异均无统计学意义（P值分别为0.24、0.18和0.17）。结论：早产儿PVL患者早期头颅1H-MRS有特征性,Lac/Cr、Glx/Cr升高可预测PVL的发生,为临床早期干预提供帮助。     

STEAM和PRESS序列对磁共振频谱绝对定量的影响

目的:比较PRESS和STEAM序列对大脑中央前回的代谢物绝对定量的差异。方法:8例健康成年人,平均年龄26.1岁。使用PRESS序列及STEAM序列进行定量检测,实验参数为TE=30ms,TR=3000ms。扫描时间每次约30min。结果:PRESS和STEAM序列使用LCModel软件分析得出Cr的浓度存在显著的差异性,并认为实验结果与序列的特征以及受邻近代谢物峰值影响有关,而对NAA、Cho、Glx、MI、NAA/Cr、Cho/Cr、MI/Cr、Glx/Cr没有显著差异。结论:在短TE条件下,STEAM序列对绝对定量的准确性较PRESS序列稍高。在短TE情况下,Cr物质受到邻近物质峰值影响,使基线不平稳。     

轻微肝性脑病的氢质子MR波谱研究

目的 应用氢质子MR波谱(~1H-MRS)检测肝硬化患者脑内代谢物改变,评价其异常变化是否能鉴别轻微肝性脑病(MHE),并与临床神经心理测试进行相关性分析.方法 选取54例肝硬化患者(肝硬化组)和13名健康志愿者(正常对照组)完成神经心理测试,包括数字连接试验A(NCT-A)和数码-符号试验(DST),54例肝硬化患者中包括肝性脑病(HE)9例(HE组)、MHE 23例(MHE组)、无HE和MHE者22例(无HE组).所有患者和志愿者均进行常规头颅MR扫描以及枕叶皮质、左侧顶叶白质的~1H-MRS扫描,分别计算各代谢物包括N-乙酰天冬氨酸(NAA)、胆碱化合物(Cho)、肌醇(mI)和谷氨酰胺复合物(Glx)与肌酸(Cr)的比值.正常对照组与肝硬化组的代谢物比值比较采用独立样本t检验,正常对照组和肝硬化各分组间代谢物比值的比较采用单因素方差分析,组间两两比较采用非参数Mann-Whitney U检验,并用Bonferroni法进行校正.~1H-MRS代谢物比值与HE分级、神经心理测试结果、静脉血氨的相关性分析采用Spearman等级相关分析.结果 肝硬化组枕叶皮质和左顶叶白质的代谢物比值NAA/Cr、Cho/Cr/、mI/Cr、Glx/Cr值分别为1.55±0.12、0.48±0.10、0.42±0.14、2.52±0.48和1.73±0.17、0.75±0.16、0.42±0.16、2.75±0.59,其中无HE组为1.53±0.10、0.48±0.09、0.51±0.11、2.20±0.39和1.69±0.15、0.82±0.14、0.53±0.12、2.40±0.40,MHE组为1.58±0.13、0.48±0.08、0.38±0.13、2.62±0.39和1.78±0.18、0.74±0.14、0.38±0.15、2.84±0.58,HE组分别为1.54±0.12、0.50±0.13、0.29±0.07、3.04±0.31和1.70±0.19、0.62±0.16、0.29±0.07、3.37±0.38.正常对照组相应部位代谢物比值分别为1.61±0.06、0.60±0.10、0.63±0.04、2.05±0.11和1.78±0.07、1.01±0.14、0.70±0.07、1.93±0.34.与正常对照组比较,肝硬化组及肝硬化各分组的Cho/Cr、mI/Cr值均降低,Glx/Cr值均升高,差异均有统计学意义(肝硬化组与对照组比较,枕叶皮质:t值分别为3.196、9.394、-6.527,肝硬化各分组与对照组比较,F值分别为5.097、25.896、20.204,P值均＜0.01.左顶叶白质:t值分别为5.592、9.717、-6.681,F值分别为16.435、28.660、21.283,P值均＜0.01＝.枕叶皮质和左顶叶白质的Glx/Cr值在无HE组、MHE组和HE组间的差异均有统计学意义(P值均＜0.0084＝,mI/Cr值在无HE组和MHE组间比较差异也有统计学意义(P＜0.0084＝.Cho/Cr、mI/Cr值与肝硬化患者HE的严重程度成负相关(枕叶皮质Cho/Cr和mI/Cr的r值分别为-0.316和-0.740,P值均＜0.01;左顶叶白质Cho/Cr和mI/Cr的r值分别为-0.620和-0.749,P值均＜0.01＝,Glx/Cr值与其呈正相关(枕叶皮质和左顶叶白质的r值分别为0.709、0.720,P值均＜0.01＝.正常对照组NCT-A值为(49±8)s,DST值为39 ±6,肝硬化组HE、MHE、无HE组患者NCT-A值分别为(134±37)、(83±26)、(64 ±22)s,DST值分别为15±2、25±9、35±8.正常对照组和肝硬化组67例的代谢物比值Cho/Cr、mI/Cr、Clx/Cr的改变与神经心理测试有很好相关性(P＜0.01＝,其中Glx/Cr值与NCT-A为正相关(枕叶皮质r=0.570,左顶叶白质r=0.541),与DST值为负相关(枕叶皮质r=-0.642,左顶叶白质r=-0.632).各代谢物比值与静脉血氨值之间无相关性.结论 ~1H-MRS研究能显示肝硬化患者大脑皮质与白质区代谢物异常改变,以mI/Cr值和Glx/Cr值明显,并且与神经心理测试之间存在相关性,可以作为HE分级的参考,对MHE有提示作用.     

3T MRI上鼠脑多体素1H-MRS成像因素及其代谢物比值研究

目的:探讨影响鼠脑多体素1H-MRS的成像因素及在3T MRI上正常鼠脑代谢物值.材料和方法:40只正常雄性SD大鼠,体重200～250g.利用3T MRI扫描机、大鼠专用线圈对SD大鼠尾状核行二维多体素1H-MRS检查,采用点分辨波谱(PRESS)序列,TR/TE=1000ms/35ms,FOV 60mm,层厚4mm,NEX 1;利用波谱后处理软件FuncTool重建SD大鼠正常尾状核Cho/Cr、Cho/NAA、NAA/Cr的比值.结果:40只行多体素1H-MRS检查的正常SD大鼠,其尾状核Cho/Cr的平均值为0.97±0.20、Cho/NAA为0.79±0.33、NAA/Cr为1.34±0.34.在多体素1H-MRS检查中,关键要选择合适的体素位置,并对匀场进行优化,同时要恰如其分的放置饱和带.结论:在3T MRI上进行鼠脑多体素1H-MRS切实可行;通过测定正常鼠脑的代谢物比值,为以后的科研工作提供有价值的参考值.     

应用1H-MRS和LCModel研究鼻喷酒石酸布托啡诺对猪脑代谢物的影响及谷氨酸复合物的绝对定量

目的 通过氢质子磁共振波谱(1H-MRS)技术,研究鼻喷给药途径下中枢性镇痛药物对脑代谢物的影响.探讨鼻腔给药途径下1H-MRS及LCModel的应用价值.方法 本实验选取9头健康2周龄乳猪(3.612±0.371)kg,行单体素PRESS序列扫描,获得鼻喷给药前后脑代谢物的波谱分析数据,用LCModel软件自动、客观地对波谱图进行线性拟合和基线校正.结果 鼻喷酒石酸布托啡诺前1H-MRS测定动物脑谷氨酸复合物(Glx)浓度为(9.276±0.542)mmol/kg,鼻喷给药后Glx浓度为(7.283±0.540)mmol/kg.给药前后Glx浓度差异有统计学意义(t=2.826,P=0.022),而氮-乙酰天门冬氨酸(NAA)、胆碱(Cho)浓度改变无统计学意义,鼻喷给药前后NAA、Cho浓度分别为(6.094±0.384)mmol/kg:(5.530±0.346)mmol/kg(t=1.270,P=0.240)和(1.547±0.114)mmol/kg:(1.255+0.079)mmol/kg(t=1.800,P=0.110).结论 用1H-MRs技术及LCModel软件证明了Glx可能是中枢性止痛剂作用的重要神经递质.     

不同TE对3.0T质子MRS谱线及代谢物定量的影响

目的:探讨不同回波时间(TE)对脑实质谱线信噪比(SNR)、基线稳定性及代谢物相对定量的影响.方法:36例受检者,使用GE Signa Excite HD 3.0T超导磁共振扫描仪,8通道头颈联合阵列线圈.每位受检者行2～7次不等的单体素PRESS序列1 H-MRS采集共得到132条谱线.检查参数为TR 1500 ms...     

肌萎缩侧索硬化症的~1H-MR波谱研究

目的 探讨肌萎缩侧索硬化症(ALS)患者的1H-MRS表现及其与临床评分的关系.方法 对15例临床确诊及拟诊为ALS的患者(ALS组)和15名年龄相匹配的健康志愿者(对照组)进行1H-MRS扫描,采用单体素平均TE选择性单点分辨波谱序列(TE-Averaged PRESS).扫描图像经后处理,分别获得以中央前回为中心的运动皮层和内囊后肢处的以下成分波峰:N-乙酰天门冬氨酸(NAA)、谷氨酸(Glu)、谷氨酸复合物(Glx)以及肌酸(Cr),并测量NAA/Cr、Glu/Cr和Glx/Cr峰高相对值.采用t检验比较两组间各比值的差异,并分析上述各值与ALS患者临床评分的直线相关关系.结果 ALS组运动皮层和内囊后肢的NAA/Cr值为1.91±0.34、1.53±0.17,对照分别为2.23±0.33,1.66±0.07.两组间差异有统计学意义(t值分别为4.25、2.90,P值分别为0.00、0.01).AIS组运动皮层和内囊后肢Glu/Cr为0.34±0.05、0.29±0.06,Glx/Cr为0.40±0.04、0.33±0.06,均高于对照组(Glu/Cr分别为0.30±0.03、0.25±0.04,Glx/Cr分别为0.32±0.05,0.26±0.03),两组间差异有统计学意义(t值分别为2.56、2.40、7.34、5.30,P值分别为0.02,0.03、0.00、0.00).ALS患者Norris评分值为(57±8)分,ALS功能分级评分(ALSFRS)值为(29±4)分.直线相关分析发现ALS患者运动皮层Glx/Cr值与Norris评分呈负相关(r=-0.75,P=0.00),而与ALSFRS值无相关性.结论 ALS患者谷氨酸类代谢物含量升高.(1)H-MRS可反映ALS患者脑内代谢物的变化特征.     

颞叶癫痫患者前额叶背外侧的定量质子磁共振波谱研究

目的:利用氢质子磁共振波谱(1H-MRS)研究颞叶癫痫(TLE)患者前额叶背外侧区(DLPFC)的生化改变,探讨额叶在TLE发病代谢机制中的作用.方法:纳入TLE患者(TLE组)及健康志愿者(健康对照组)各20例.根据24h视频脑电图(VEEG)所提示致痫灶所在部位将TLE组分为左侧TLE亚组及右侧TLE亚组.利用单体素1 H-MRS点分辨波谱序列(PRESS)进行扫描,并采用LCModel软件进行后处理,获取所有被试者双侧DLPFC区氮乙酰天门冬氨酸(NAA)、肌酸(Cr)、胆碱(Cho)、肌醇(Ins)及谷氨酸/谷氨酰胺复合物(Glx)的绝对浓度.然后分别对比健康对照组及TLE患者左侧DLPFC区与右侧DLPFC区、健康对照组与TLE患者同侧DLPFC区之间各代谢物浓度的差异.结果:健康对照组左右侧DLPFC区NAA浓度分别为(7.24±0.57) mmol/L、(6.76±0.87) mmol/L,左侧NAA浓度显著高于右侧(P=0.024);而TLE患者上述NAA不对称性消失,左右侧NAA浓度分别为(6.58±0.56) mmol/L、(6.31±0.62)mmol/L(P=0.092).与健康对照相比,TLE患者左侧DLPFC区NAA、Cr及Ins浓度显著降低(P=0.000、0.014、0.025),右侧DLPFC区仅Ins浓度显著降低(P=0.013),而Cho、Glx浓度在左右侧DLPFC区均无显著改变.分层分析进一步揭示左侧TLE亚组的左侧DLPFC区NAA、Cr及Ins浓度较对照组显著降低(P=0.001、0.047、0.007),右侧DLPFC区Ins浓度较对照组显著降低(P=0.002);而右侧TLE组仅有左侧DLPFC区NAA浓度显著降低(P=0.037).结论:颞叶癫痫患者的额叶也存在生化代谢异常,且以左侧额叶改变为主,说明额叶在TLE发病的代谢机制中可能起着重要作用.     

脑MRS检查影响因素分析

目的 研究不同脉冲序列、线圈类型及对比剂对磁共振波谱(MRS)代谢物的影响.资料与方法 本研究包括病例组和自愿者组.均采用GE SignaVH/i 3.0 T成像系统进行检查,MRS采用多体素点分辨波谱(PRESS)序列.病例组10例,自愿者组26名.对病例组的同一感兴趣区(ROI)进行增强前后PRESS 144(TE 144 ms)检查,并对有明显强化的肿瘤实质区进行波谱重组,共获得53个体素增强前后MRS各代谢物的数值.对自愿者组中的18名采用单通道头颅正交线圈进行MRS检查,分别采用PRESS 35(TE 35 ms)和PRESS 144(TE 144 ms)序列,ROI选择在右半卵圆中心,在检查中确保PRESS 35和PRESS 144的ROI位置完全一致.26名健康自愿者中,分别选取单通道和8通道线圈进行PRESS 144检查的自愿者各10名,对这两组右半卵圆中心同一体素区进行波谱重组.结果 (1)PRESS 144和PRESS 35在同一部位的胆碱(Cho)/肌酸(Cr)、Cho/氮-乙酰天门冬氨酸(NAA)、NAA/Cr没有差别;(2)虽然头颅单通道正交线圈和8通道相控阵线圈的信噪比(SNR)有明显差别,但线圈类型对波谱代谢物相对定量值的影响无统计学意义;(3)顺磁性对比剂会使Cho、Cr降低(无统计学意义),但对波谱各代谢物相对定量值的影响无统计学意义.结论 不同脉冲序列、线圈类型及对比剂对MRS代谢物可能会产生影响,但无统计学意义.     

Accelerated proton echo planar spectroscopic imaging (PEPSI) using GRAPPA with a 32-channel phased-array coil.

Parallel imaging has been demonstrated to reduce the encoding time of MR spectroscopic imaging (MRSI). Here we investigate up to 5-fold acceleration of 2D proton echo planar spectroscopic imaging (PEPSI) at 3T using generalized autocalibrating partial parallel acquisition (GRAPPA) with a 32-channel coil array, 1.5 cm(3) voxel size, TR/TE of 15/2000 ms, and 2.1 Hz spectral resolution. Compared to an 8-channel array, the smaller RF coil elements in this 32-channel array provided a 3.1-fold and 2.8-fold increase in signal-to-noise ratio (SNR) in the peripheral region and the central region, respectively, and more spatial modulated information. Comparison of sensitivity-encoding (SENSE) and GRAPPA reconstruction using an 8-channel array showed that both methods yielded similar quantitative metabolite measures (P > 0.1). Concentration values of N-acetyl-aspartate (NAA), total creatine (tCr), choline (Cho), myo-inositol (mI), and the sum of glutamate and glutamine (Glx) for both methods were consistent with previous studies. Using the 32-channel array coil the mean Cramer-Rao lower bounds (CRLB) were less than 8% for NAA, tCr, and Cho and less than 15% for mI and Glx at 2-fold acceleration. At 4-fold acceleration the mean CRLB for NAA, tCr, and Cho was less than 11%. In conclusion, the use of a 32-channel coil array and GRAPPA reconstruction can significantly reduce the measurement time for mapping brain metabolites.     

Utilization of glutamate/creatine ratios for proton spectroscopic diagnosis of meningiomas

Introduction Our purpose was to determine the potential of metabolites other than alanine to diagnose intracranial meningiomas on proton magnetic resonance spectroscopy (MRS). Methods Using a 1.5-T MR system the lesions were initially identified on FLAIR, and T1- and T2-weighted images. Employing standard point-resolved spectroscopy (PRESS) for single voxel proton MRS (TR 1500 ms, TE 30 ms, 128 acquisitions, voxel size 2 × 2 × 2 cm, acquisition time 3.12 min), MR spectra were obtained from 5 patients with meningiomas, from 20 with other intracranial lesions, and from 4 normal controls. Peak heights of nine resonances, including lipid, lactate, alanine, NAA (N-acetylaspartate), β/γ-Glx (glutamate + glutamine), creatine, choline, myo-inositol, and α-Glx/glutathione, were measured in all spectra. The relative quantity of each metabolite was measured as the ratio of its peak height to the peak height of creatine. Results Relative quantities of α-Glx/glutathione, β/γ-Glx, and total Glx/glutathione were significantly elevated in meningiomas compared to the 20 other intracranial lesions and the normal control brains. Alanine was found in four of five meningiomas, but lactate partially masked the alanine in three meningiomas. None of the other lesions or control brains showed an alanine peak. The one meningioma with no alanine and the three others with lactate had elevated Glx. Conclusion While alanine is a relatively unique marker for meningioma, our results support the hypothesis that the combination of glutamate/creatine ratios and alanine on proton MRS is more specific and reliable for the diagnosis of meningiomas than alanine alone.     

Infantile tuberous sclerosis changes in the brain: proton MR spectroscopy findings.

A parietal hamartoma of a three-month-old boy with tuberous sclerosis was studied with magnetic resonance (MR) imaging, and proton MR spectroscopy. MR spectra were obtained with the single-voxel PRESS (point resolved spectroscopy; TR = 1500 ms, TE = 135 ms) sequence, in a 8 cc region of interest. Apparently low NAA/Cho (0.28), and NAA/Cr (0.37) ratios were noted in the hamartoma, that could suggest a neoplasm. The lesion and the surrounding brain tissue were studied again after seven months with spectroscopic imaging using the chemical shift sequence (TR = 1500 ms. TE = 40 ms). This study revealed apparently improved NAA/Cho (2.63), NAA/Cr (2.13) ratios in the hamartoma compared to the initial examination at three months of age, excluding the possibility of a neoplasm.     

Proton MR spectroscopic measurement of neurometabolites in hepatic encephalopathy during oral lactulose therapy.

BACKGROUND AND PURPOSEMR imaging and MR spectroscopy are increasingly being used to determine response to pharmacologic therapy. Hepatic encephalopathy (HE) is characterized by abnormal cerebral metabolites, yet the response to lactulose and other anti-HE measures is still primarily determined by using arbitrary categorical clinical rating scales, rather than MR spectroscopy. The purpose of this study was to determine whether MR spectroscopy could demonstrate relevant neurometabolic changes associated with lactulose therapy and thereby provide further support for the use of MR spectroscopy in clinical trials.METHODSTen control subjects and 23 patients with grades I to III HE were studied by proton MR spectroscopy with imaging parameters of 2000/26 (TR/TE). Metabolic ratios were calculated for myo-inositol (mI)/creatine (Cre), choline (Cho)/Cre, (glutamine + glutamate) (Glx)/Cre, N-acetylaspartate (NAA)/Cre, and (Cho + mI)/Glx. A time series design trial was used in which eight patients with HE were compared before and after lactulose therapy (60 mL by mouth three times per day).RESULTSRelative to control subjects, HE was characterized by 43%, 64%, and 5% reductions, respectively, in mI/Cre, (Cho + mI)/Glx, and Cho/Cre. In comparison, Glx/Cre was increased by 75% and NAA/Cre was not changed. Therapy with lactulose was associated with increases of 29%, 37%, and 7%, respectively, in mI/Cre, (Cho + mI)/Glx, and Cho/Cre, as well as respective decreases of 15% and 42%, respectively, in Glx/Cre and HE grade. NAA/Cre did not change with lactulose therapy.CONCLUSIONMR spectroscopy detects neurometabolic changes associated with pharmacologic therapy for HE. The metabolic ratios ml/Cre and (Cho + mI)/Glx are the most sensitive measures of lactulose effect. These data support the expanded use of MR spectroscopy as an adjunctive technique in pharmaceutical development and clinical trials for HE.     

Proton MR spectroscopy in Rett syndrome.

Seven patients (mean age 7.7yr) with Rett syndrome, a condition with progressive regression of psychomotor development are included in this study. Proton MR spectroscopy images were obtained with the multivoxel chemical-shift imaging mode (TR=1500ms, TE=40ms). Spectra from 224 voxels in the brain parenchyma were studied. N-acetyl aspartate (NAA), creatine (Cr), choline (Cho), and myoinositol (mI) peaks were quantitatively evaluated, and NAA/Cr, NAA/Cho, and Cho/Cr, mI/Cr ratios were calculated. Five age-matched normal cases were available as controls. In three patients with Rett syndrome spectroscopy findings were normal, and the metabolite ratios were similar to control cases. In the remaining four patients with the syndrome prominent decrease of the NAA peak was the main finding resulting in decreases in NAA/Cr (1.14+/-17), and NAA/Cho (1.08+/-27) ratios (p<0.0001). Cho/Cr ratios (0.93+/-26), and mI/Cr ratios (0.88+/-36) were normal compared to controls. There was no correlation between spectroscopic changes and clinical status of the patients. The findings suggested that not only reduced neuronal-dendritic arborizations but also decreased neuronal function could contribute to spectroscopy changes in Rett syndrome.     

T2 measurement and quantification of glutamate in human brain in vivo.

The proton NMR transverse relaxation time T(2) of glutamate (Glu) in human brain was measured by means of spectrally selective refocusing at 3.0 T in vivo. An 81.4-ms-long dual-band Gaussian 180 degrees RF pulse, designed for refocusing at 2.35 and 3.03 ppm, was employed within point-resolved spectroscopy (PRESS) to generate the Glu C4-proton target multiplet and the total creatine (tCr) singlet. Six optimal echo times (TEs) between 128 and 380 ms were selected from numerical analysis of the filtering performance for effective detection of the Glu signal with minimal contamination from glutamine (Gln), N-acetylaspartate (NAA), and glutathione (GSH). The magnetization of Glu and tCr was extracted from spectral fitting of experimental and calculated spectra. Apparent T(2) values of Glu and tCr were estimated as 201 +/- 18 and 164 +/- 12 ms for the medial prefrontal (PF) cortex, and 198 +/- 22 and 169 +/- 15 ms (mean +/- SD, N = 5) for the left frontal (LF) cortex, respectively. With water segmentation data, the magnetization values of Glu and tCr of the two adjacent voxels, calculated from the T(2) values and spectra following the thermal equilibrium magnetization, were combined to give the Glu and tCr concentrations as 10.37 +/- 1.06 and 8.87 +/- 0.56 mM for gray matter (GM), and 5.06 +/- 0.57 and 5.16 +/- 0.45 mM (mean +/- SD, N = 5) for white matter (WM), respectively.     

APP/PS1转基因阿尔茨海默病小鼠的MR波谱定量分析

目的 利用MRS探讨APP/PS1转基因阿尔茨海默病(AD)小鼠脑内代谢物的变化及对早期AD的诊断价值.方法 35只APP/PS1双转基因AD小鼠(实验组)和20只野生型小鼠(对照组)分别在3、6、9月龄时采用7.0 T高场强MR仪行1H-MRS,测量小鼠大脑皮质及海马区N-乙酰天冬氨酸(NAA)、肌醇(mI)和肌酸(Cr)的峰下面积,计算NAA/Cr和mI/Cr比值,并与病理结果进行对照.分别以各月龄AD小鼠的NAA/Cr比值的95%可信区间的上限及mI/Cr比值的95%可信区间的下限作为阈值,比较其对AD小鼠的敏感度、特异度和准确度.两组间NAA/Cr和mI/Cr比值的比较采用独立样本t检验.结果 3、6、9月龄AD小鼠的mI/Cr比值分别为0.68±0.03、0.72±0.04、0.77±0.04,对照组分别为0.63±0.04、0.64±0.03、0.64±0.04,两组间差异均有统计学意义(t值分别为2.814、5.146、14.437,P值均<0.01),3月龄时ml/Cr比值即明显升高,病理检查显示大脑皮质及海马区出现星形胶质细胞的增生、活化;3、6、9月龄AD小鼠的NAA/Cr比值分别为1.17±0.08、1.04±0.05、0.90±0.05,对照组分别为1.18 ±0.07、1.16 ±0.07、1.18±0.08,3月龄时,两组间差异无统计学意义(t=0.752,P>0.05),6、9月龄时两组间差异有统计学意义(t值分别为-8.514、-5.646,P值均<0.05),6月龄时NAA/Cr比值明显降低,病理检查显示AB沉积斑块出现.mI诊断3、6及9月龄AD小鼠的敏感度分别为80%(28/35)、84%(26/31)、85%(23/27);特异度为85%(17/20)、94%(17/18)、100%(16/16);准确度为82%(45/55)、88%(43/49)、91%(39/43);NAA诊断6、9月龄AD小鼠的敏感度分别为84%(26/31)、89%(24/27);特异度为89%(16/18)、100%(16/16);准确性为86%(42/49)、93%(40/43).结论 mI、NAA是评价早期AD的高敏感度、高特异度的指标,且mI的变化早于NAA,1H-MRS定量分析为早期AD的诊断提供了重要依据.