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.     

磁共振氢质子波谱序列PRESS和STEAM比较

目的：比较短TEPRESS与STEAM两种氢质子波语序列在脑肿瘤诊断中的优劣。方法：43例脑肿瘤的^1H—MRS，除了TE稍不同外，PRESS和STEAM序列的其他参数全部相同。结果：PRESS与STEAM在检测肿瘤Cr的浓度方面，其差异有显著性意义，其因素可能和序列的特征有关，而对NAA、Cho、mi、NAA／Cr、Cho／Cr具有良好的一致性，且PRESS波语的信噪比好，检查时间短。结论：PRESS可取代STEAM作为脑肿瘤的波语检查序列之一。     

兔肝VX2瘤活体二维多体素 1H-MRS成像STEAM和PRESS序列的比较

目的 探讨不同的定位序列对兔肝VX2瘤活体二维多体素1H-MRS(2D 1H-MRS)成像的影响. 材料与方法 兔肝VX2瘤荷瘤兔14只,于第一期(种植后第2～3周)和第二期(种植后第4周)利用1.5T磁共振扫描仪行常规MRI,并在其他参数不变的条件下分别采用激励回波采样(STEAM)和点解析波谱(PRESS)序列行活体2D 1H-MRS检查,观察不同序列波谱图的基线情况,测量主要代谢物波峰的信噪比、中心位置、半高宽和峰下积分面积比值,并进行统计学分析. 结果 (1)STEAM和PRESS序列各行25瘤次2D 1H-MRS采集,其中第一期成功率为78.6%,第二期成功率为100%,总体技术成功率为88.0%.(2)在相同时期、相同部位,不同序列所得波谱图在基线情况、代谢物波峰的信噪比、中心位置、半高宽及各个代谢物峰下积分面积的比值(包括谷氨酸胺和谷氨酸复合物(Glx)/脂质(Lip)、胆碱化合物(Cho)/Lip和糖原和葡萄糖复合物(Glyu)/Lip)差异无统计学意义(P>0.05). 结论 利用1.5T磁共振扫描仪行兔肝VX2瘤活体2D 1H-MRS检查可成功获得可析性波谱,技术成功率为88.0%.其他扫描条件和参数相同时,采用短TE(30 ms),STEAM和PRESS序列在波谱质量和检测肝内主要代谢物的敏感性方面无明显差异.     

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。     

活体质子磁共振波谱技术分析

质子磁共振波谱包括单体素1H波谱和化学位移成像两种主要形式,PRESS和STEAM两种主要的定域技术及CHESS等常见的水抑制方法.本文综述其基本原理、应用限度和J-耦合、化学位移、ppm等基本概念.     

3.0T MRI上活体鼠脑C6胶质瘤模型多体素1H MRS研究

目的探讨影响鼠脑多体素1HMRS的成像因素及在3.0TMRI上鼠脑C6胶质瘤模型各代谢物比值。方法32只正常雄性SD大鼠,体重250~300g,在右尾状核区接种C6胶质瘤细胞。利用3.0TMRI扫描机、大鼠专用线圈对鼠脑胶质瘤模型肿瘤区行二维多体素1HMRS检查,采用点分辨波谱(PRESS)序列,TR1000ms,TE35ms,视野60mm,层厚4mm,激励次数1;利用波谱后处理软件FuncTool重建C6胶质瘤Cho/Cr、Cho/NAA、NAA/Cr的比值。结果32只行多体素1HMRS检查的鼠脑胶质瘤模型中,其尾状核肿瘤区Cho/Cr的平均值为2.70±0.68、Cho/NAA为1.57±0.29、NAA/Cr为1.04±0.24。在进行多体素1HMRS检查时,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。结论用3.0TMRI行鼠脑多体素1HMRS检查切实可行,通过测定鼠脑C6胶质瘤模型各代谢物的比值,可为以后的科研工作提供有价值的参考值。     

^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 ,     

钆剂对T2WI脑肿瘤1↑H—MRSI代谢物波峰面积的影响

目的：探讨钆剂对T2WI脑肿瘤1↑H—MRSI代谢物波峰面积有无影响，为钆剂增强波谱的应用提供依据。材料和方法：在钆剂注射前后，对高级别和低级别星形细胞瘤、脑膜瘤及正常对照各4例行T2WI长TE（TE=144ms，PRESS）MRSI成像，分别记录感兴趣区内肿瘤的实性区、周围水肿区及正常表现体素的Cho、Cr及NAA代谢物波谱数据（共643个有效体素），分析增强前后代谢物波峰面积的变化。结果：钆剂注射后5—10min的长TE（TE=144ms，PRESS）MRSI显示，仅脑膜瘤组Cho峰面积下降的程度（〈10％）相比正常组有显著性差异（P〈0．05），余各组之间差异无显著意义。总体上Cho、Cr及NAA波峰的面积无明显变化。结论：钆剂注射后，脑膜瘤Cho波峰面积稍有下降，其影响机制可归于T2^＋敏感效应；总体上钆剂对T2WI长TE脑肿瘤MRSI主要代谢物波峰面积的影响甚微，可以忽略；增强波谱以Cho／Cr比值反映脑肿瘤Cho水平的变化较为可靠；应用增强后波谱完全可行。     

1.5 T在体兔正常肌肉及VX2软组织肿瘤1H-MRS成像技术研究

目的探讨1．5T磁共振仪行在体兔正常肌肉及VX2软组织肿瘤氢质子磁共振波谱（^1H-MRS）检查的可行性及成像技术。材料与方法20只新西兰大白兔。右大腿近段肌肉内注射VX2肿瘤组织悬液0．2ml，制成肿瘤模型。分别于接种前及接种后第40d行正常大腿肌肉及肿瘤MRI和^1H-MRS成像。波谱成像序列包括单体素和多体素点解析频谱（PRESS）序列，比较不同成像条件及参数下^1H-MRS曲线，在工作站上测量胆碱（Cho）／肌酸（Cr）及脂质峰（Lipid）／Cr比值并进行统计学分析。结果所有兔正常肌肉及VX2肿瘤^1H-MRS可见Cho峰、Cr峰及Lipid峰。与正常肌肉组织相比，VX2肿瘤组织Cho峰明显增高，Lipid峰降低。肿瘤组织与正常肌肉Cho／Cr及Lipid／Cr比值差异具有统计学意义。所有兔正常肌肉和VX2肿瘤的单体素PRESS序列成像质量优于多体素PRESS序列，冠状面定位优于横断面。单体素PRESS序列半高带宽（FWHM）小于8Hz，多体素FWHM小于12Hz，成像质量较好。根据采集兴趣区大小，词整视野或采集次数可提高波谱成像质量。实时测定兔体温并设定为波谱成像时的系统温度值可有效避免波峰漂移。结论在体^1H-MRS检查兔VX2软组织肿瘤与正常肌肉^1H-MRS表现明显不同^1H-MRS有望用于软组织肿瘤的诊断。优化成像条件与参数可明显提高波谱成像质量。     

颅内囊性病变1 H MR波谱分析

目的分析颅内囊性病变^1H磁共振波谱（^1HMRS）成像特征，评价。HMRS在颅内囊性病变中的应用价值。方法52例颅内囊性病变，单体素^1HMRS采集52个病灶，其中Ⅰ-Ⅱ级星形细胞瘤8例、胶质母细胞瘤9例、转移瘤13例、脑脓肿10例、表皮样囊肿4例、蛛网膜囊肿5例、脑囊虫病3例。点分辨波谱（PRESS，TE135ms或270ms）定域序列采集病灶中心。结果（1）8例Ⅰ-Ⅱ级星形细胞瘤仅显示乳酸（Lae）峰。9例胶质母细胞瘤除了显示Lac峰外，有4例显示了低的胆碱类复合物（Cho）和氮-乙酰天冬氨酸（NAA）峰，2例显示脂质（Lip）峰。（2）转移瘤13例，7例仅显示Lae峰，6例显示Cho峰，3例显示低的NAA峰，6例显示Lip峰。（3）10例脑脓肿除了显示Lac峰，9例显示氨基酸（AA）峰，6例显示乙酸盐（Ace）峰，5例显示琥珀酸盐（Sue）峰，5例显示丙氨酸（ma）峰，2例显示Lip峰；没有显示Cho和NAA峰。（4）4例表皮样囊肿显示Lae峰，1例显示Lip峰。5例蛛网膜囊肿中2例显示低的Lae峰，1例显示Lip峰。脑囊虫病3例，显示Lac、Ace、Sue、ma峰；没有显示AA、Cho和NAA峰。结论颅内囊性病变共有Lae峰，没有特异性。AA峰结合Ace、Sue、ma峰的显示对脑脓肿诊断特异性高。Ace、Sue、AJa峰的显示提示脑寄生虫囊肿存在的可能性。MRI结合MRS有助于对颅内囊性病变的定性诊断。     

脑胶质瘤病的MRI及MRS研究

目的 :回顾性分析大脑胶质瘤病磁共振成像 (MRI)及磁共振波谱 (MRS)特点 ,以探讨两者对本病诊断的临床价值。方法 :综合 7例患者的临床表现、影像学特点及病理诊断 ,均符合大脑胶质瘤病诊断标准。常规行SE序列平扫及增强。其中 3例行MRS研究 ,二维多体素、点分辨法 (PRESS)、TE 14 4ms。结果 :所有病例均侵犯 2个脑叶或以上。病变区呈长T2 、稍长T1异常信号 ,受累区脑组织肿胀 ,占位效应轻。 3例增强扫描见小结节或片状强化 ,4例无明显强化。 3例MRS表现均有不同程度NAA降低 ,Cho上升 ,Cho/Cr和Cho/NAA的比值上升。结论 :MRI是目前诊断大脑胶质瘤病的首选影像学方法 ,MRS对于鉴别诊断有较大价值。     

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...     

Intracranial tumors in children: small single-voxel proton MR spectroscopy using short- and long-echo sequences

We report preliminary experience using single-voxel, proton MR spectroscopy (MRS) employing small voxels of interest, in combination with short and long echo-time protocols, for the assessment of primary intracranial tumors in children. We examined 23 children with primary intracranial tumors detected by MRI, and 32 controls with similar ages, using MRS on a 1.5 T system. Localized single-voxel (3.7±1.3 cc) proton spectra were obtained with short-echo (2,000/18), stimulated-echo (STEAM) and long-echo (2,000/270) spin-echo (PRESS) protocols. All spectra were evaluated qualitatively; 10 tumor and 19 control spectra were processed for peak area quantification. Small voxels of interest were able to account for tissue heterogeneity. Combined acquisition of short- and long-echo spectra increased the number of detectable metabolites. The solid portion of all tumors exhibited reducedN-acetyl-aspartate (NAA), strong contribution from cholines (Cho) and inositols or glycine, minimal presence of total creatine (tCr), enhanced broad mobile lipid resonances and accumulated lactate. Calculated selected metabolite ratios of Cho/tCr and Cho/NAA were substantially increased from control values. The cystic portions of the masses showed only lipid and lactate peaks.     

Maturation of the human fetal brain as observed by 1H MR spectroscopy.

Proton MRS was used to monitor cerebral metabolite tissue levels in 35 normal fetuses during development in the gestational age range of 30-41 weeks. First, MRI in three orthogonal orientations was performed. A volume of interest (VOI) (15-43 cc) of fetal brain tissue was then selected for (1)H MRS. For localization, two pulse sequences (stimulated echo acquisition mode (STEAM) at TE = 20 ms, and point-resolved spectroscopy (PRESS) at TE = 135 ms) were applied. The MR spectra of the brain showed signals for inositol (Ino), choline (Cho), creatine (Cr), and N-acetyl (NA) compounds. From 30 to 41 weeks the absolute tissue level of NA, and the ratios of NA/Cr and NA/Cho increased, whereas the ratio of Cho/Cr decreased. These changes reflect maturation of the brain. Considering the diagnostic value of proton MRS in pediatric neurology, this new approach may also be useful for characterizing pathological conditions in the fetal brain.     

软组织肿瘤的MR灌注成像与MR波谱成像的比较研究

目的 通过分析软组织肿瘤同一病例相同感兴趣区的MR灌注加权成像(MR-PWI)及MR氢质子波谱(1H-MRS)的功能影像信息,比较两者用于软组织肿瘤的定性诊断价值.方法 研究同时行MR-PWI、1H-MRS的全身各部位软组织肿瘤共40例.比较MR-PWI及1H-MRS各参数在良、恶性肿瘤中的差异,进而对2种诊断方法进行评价.所获数据采用t检验或配对四格表确切概率法分析.结果 MR-PWI良、恶性软组织肿瘤的血流量(BF)值差异有统计学意义(t=2.531,P<0.05),血容量(BV)及平均通过时间(MTT)值差异均无统计学意义(t值分别为1.587和1.732,P值均>0.05);以BF值=4.35 ml·100 mg-1·min-1为阈值,MR-PWI诊断恶性肿瘤的敏感度为81.8%(18/22),特异度为72.2%(13/18).良、恶性软组织肿瘤的时间信号曲线(TIC)类型比较:Ⅰ a型在良性肿瘤中占3/18,在恶性肿瘤中占17/22;Ⅰ b型在良性肿瘤中占12/18,在恶性肿瘤中占3/22;Ⅰ c型在恶性肿瘤中占2/22.Ⅱ型在良性肿瘤中占3/18.良、恶性软组织肿瘤的胆碱(Cho)、肌酸复合物(Cr)、脂质(Lip)值差异均无统计学意义(t值分别为1.332、1.637、1.986,P值均>0.05),而Cho/Cr比值的差异有统计学意义(t=2.927,P<0.05);以Cho/Cr比值=3.22为阈值,1H-MRS诊断恶性肿瘤的敏感度为86.4%(19/22),特异度为88.9%(16/18).1H-MRS谱线比较:18例良性及17例恶性软组织肿瘤在2.0～2.1ppm(×10-6)处均未出现异常峰,而2例恶性神经鞘瘤和3例恶性纤维组织细胞瘤均在2.0～2.1ppm处出现异常峰.MR-DWI与1H-MRS用于恶性肿瘤诊断准确度的差异无统计学意义(X2=0.125,P>0.05).结论 软组织肿瘤的MR-PWI的BF值、1H-MRS的Cho/Cr比值有利于软组织肿瘤良、恶性的鉴别;软组织肿瘤的TIC形态有助于肿瘤良、恶性的鉴别.MR-PWI和1H-MRS两者用于诊断恶性软组织肿瘤的准确度无明显差异,1H-MRS诊断恶性软组织肿瘤的敏感度和特异度较高.     

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.     

Diagnostic potential of short echo time MR spectroscopy of gliomas with single-voxel and point-resolved spatially localised proton spectroscopy of brain

Accurate neuroimaging grading of gliomas is useful for management, but techniques such as MRI and CT are not sufficiently reliable. Necrosis is a consistent, decisive prognostic factor and the key diagnostic criterion for glioblastoma multiforme. MR spectroscopy (MRS) allows noninvasive measurement of metabolites in brain tumours and mobile lipids reflect necrosis. However, short echo-time (TE) spectroscopy has been required for reliable assessment of lipids, since their relaxation times are very short. Recent advances have made it possible to perform short-TE MRS. We attempted to evaluate the significance of short TE spectroscopy as part of routine imaging for diagnosis and grading of gliomas. We performed TE 30 ms MRS in 25 patients with gliomas (grade II six; grade III three; grade IV, 16) and in 19 areas of healthy white matter using proton brain examination/single voxel (PROBE/SV) and point-resolved spatially localised spectroscopy (PRESS). With short-TE spectroscopy, lipid signals were detected in all 16 tumours of grade IV, one grade II (P = 0.0002) and none of grade III (P = 0.001). TE 136 ms MRS, carried out in 20 of these cases, showed lipid signals in only four of 14 grade IV tumours and in none of the other six. N-acetylaspartate/choline (NAA/Cho) ratios were always more than 1.0 in healthy tissues and less than 1.0 in all but one of the gliomas. The mean creatine (Cr)/Cho ratio in each tumour grade was significantly lower than in the healthy tissues. The mean Cr/Cho ratio was also significantly lower in grade IV than in grade II tumours (P < .0005). Considerable overlap in Cr/Cho ratio was observed between grade II and grades III and IV gliomas at long but less so at short-TE MRS. We conclude that short-TE MRS with PROBE/SV and PRESS is of value in grading gliomas. Received: 25 June 2000 Accepted: 1 September 2000     

1.5 T磁共振兔VX2肝癌活体二维多体素1H-MRS应用初探

目的探讨应用1.5 T磁共振仪对兔VX2肝癌进行活体二维多体素氢质子磁共振波谱（1H-MRS）检查的可行性,对所得1H-MRS图作初步观察. 材料与方法采用经腹腔瘤块种植法建立兔VX2肝癌模型,利用1.5 T磁共振仪进行常规MR平扫和二维多体素1H-MRS,包括激励回波采样模式（STEAM）和点分辨波谱（PRESS）序列检查,初步比较肿瘤实质、瘤周和邻近正常肝组织的1H-MRS图的差别.扫描结束次日处死动物,取其相应位置肝脏组织块进行病理组织学分析. 结果建立兔VX2肝癌模型共计16只,均按照计划进行了MR平扫和二维多体素1H-MRS检查,共24瘤次,其中22瘤次获得令人满意的1H-MRS图,技术成功率达到92.0%.1H-MRS图上可见4个主要的波峰,包括脂质（Lip）、谷氨酰胺和谷氨酸复合物（Glx）、胆碱（Cho）、糖原和葡萄糖复合物（Glyu）.发现瘤周和邻近正常肝组织内Cho峰和Glyu峰较肿瘤实质内的要高,Lip峰稍降低.其他参数相同的情况下,STEAM和PRESS序列在本研究1H-MRS扫描中所得波谱谱图无明显区别. 结论应用1.5 T磁共振仪对兔VX2肝癌进行活体二维多体素1H-MRS检查是可行的.