Proton magnetic resonance spectroscopy of brain-stem lesions

The imaging findings of brain-stem lesions are often nonspecific and histological diagnosis is limited because of fear of complications associated with biopsy. A noninvasive method for tissue characterization is therefore highly desirable. We undertook a review of proton magnetic resonance spectroscopy (MRS) of patients with solitary brain-stem lesions to determine if MRS could characterize them. We carried out single- or multivoxel proton MRS using long echo times (135 or 270 ms) on 34 patients with solitary brain-stem lesions. We analyzed the following peaks: choline (Cho), creatine (Cr), N-acetylaspartate (NAA), and lipids/lactate (Lip) and calculated peak height ratios for Cho/Cr, NAA/Cr and Lip/Cr. The results were compared with histology in nine patients and with the presumptive diagnosis in 25. We also performed single-voxel proton MRS on the brain stem of five normal volunteers. There were differences in all ratios between controls and the patients with neoplastic and non-neoplastic lesions: Cho/Cr was low in non-neoplastic and high in neoplastic lesions (control: 1.8+/-0.1; non-neoplastic: 1.4+/-0.2; neoplastic: 2.0+/-0.2); NAA/Cr was low in non-neoplastic, and lower in neoplastic lesions (control: 2.3+/-0.1; non-neoplastic: 1.4+/-0.2; neoplastic: 1.2+/-0.1), and Lip/Cr was elevated in both neoplastic and non-neoplastic lesions (control: 0.04+/-0.02; nonneoplastic: 1.9+/-0.7; neoplastic:1.9+/-0.7).     

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.     

Apparent T(2) relaxation times of lipid and macromolecules: a study of high-grade tumor spectra

PURPOSE: To determine T(2) relaxation times of lipid and macromolecules (Lip/MMs) observed by (1)H magnetic resonance spectroscopy ((1)H MRS) of metastases (MET) and glioblastomas (GBM), so that they may be better characterized. MATERIALS AND METHODS: (1)H spectra were acquired at multiple echo times from brain lesions using point-resolved spectroscopy sequence (PRESS) at TE = 30 msec either with metabolite-nulling (six GBM and 11 MET), or without metabolite-nulling (four MET and one mucocele). All lesions were previously untreated and had subsequent histopathological classification. RESULTS: The T(2) of the 1.3-ppm Lip/MM peak was concentration-dependent, but at high concentrations it was significantly different (P = 0.015) between GBM (42 +/- 6 msec) and MET (63 +/- 18 msec). The broad 2.05-ppm and 0.09-ppm Lip/MM peaks had similar T(2)s in MET and GBM. The T(2) of the narrow 2.05-ppm Lip/MM peak sometimes observed had a T(2) of 100 +/- 17 msec in MET and 75 msec in the mucocele. CONCLUSION: We observed significantly higher T(2) of the 1.3-ppm Lip/MM peak in MET compared with GBM at high 1.3-ppm proton concentrations, in agreement with a higher 1.3/0.9-ppm peak ratio found in MET. The relatively long T(2) of the 2.05-ppm Lip/MM peak sometimes observed in MET may cause it to be confused with N-acetyl aspartate (NAA).     

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.     

In vivo and in vitro MR spectroscopic profile of central neurocytomas

This study reports in vivo and in vitro magnetic resonance spectroscopic findings in two cases of central neurocytomas (CNC) confirmed by immunohistochemistry. Volume localized in vivo proton magnetic resonance spectroscopy (MRS) was carried out before surgery using a point resolved spectroscopy (PRESS) sequence with a repetition time of six seconds and an echo time of 135 msec. Normal spectrum was obtained from gray matter from a volunteer for comparison. (1)H and (31)P in vitro MRS studies were carried out at 9.4 T on the extracts prepared from the surgically excised tumors. The in vivo spectra showed prominent glycine (Gly) and choline (Cho) and low N-acetyl aspartate compared to the normal. The Gly peak was assigned using the in vitro studies. These studies showed that the major contribution to the Cho peak observed in vivo is from phosphocholine. A combination of the presence of NAA and an increased Gly in the proton MR spectrum could be a characteristic feature of CNCs, which are rare intraventricular tumors of neuronal origin.     

原发性中枢神经系统B细胞淋巴瘤的磁共振波谱和病理对照

目的:阐明原发性中枢神经系统B细胞淋巴瘤(PCNSL)的氢质子磁共振波谱表现,并与病理进行对照。材料和方法:10例病理证实的PCNSL行磁共振常规及二维多体素波谱俭查,分析肿瘤实质、瘤周区域以及对侧的谱线,并将肿瘤实质的波谱与病理对照。结果:PCNSL的波谱表现为Cho峰升高及NAA、Cr峰的降低,1.3ppm处升高的Lip峰。瘤体和瘤周区域在Cho/Cr、Ch/NAA上有显著差异;Cho/Cr在瘤周区域2、3之间存在显著性差异,在瘤周区域2和对侧之间存在差异而在瘤周区域3和对侧之间无差异;1例病灶在瘤周区域3以远处仍可见异常谱线。HE染色和KP-1染色显示:HE染色显示肿瘤细胞密集,细胞形态较为单一;KP-1染色显示含脂质组织细胞散在分布于肿瘤细胞间。结论:PCNSL对周围浸润达到肿瘤强化边缘外15mm处,这可能对淋巴瘤的治疗有意义,而Lip峰和脂质吞噬细胞有关。     

肝脏肿瘤的活体氢质子MR波谱和病理分析

目的 研究活体肝脏氢质子MRS(1H-MRS)评价肝脏局灶性病变的价值.方法 对53例肝肿瘤患者(54个直径＞4 cm的肿瘤)和19名正常志愿者进行1H-MRS检查,分别测量满足诊断需要的正常对照组(17名)和经病理证实的良性肝脏肿瘤组(8例)和肝细胞癌(HCC)组(25例)胆碱I唪/甘油三酯亚甲基峰(Cho/Lip)比值,对结果进行方差分析和两样本间Dunnett-t检验,并通过受试者工作特征(ROC)曲线评价1H-MRS诊断HCC的敏感性和特异性.结果 正常肝脏、良性肿瘤及HCC组的Cho/Lip比值分别为0.07±0.04、0.11±0.06和0.55±0.17(F=6.58,P＜0.05),HCC组高于正常对照组和良性肝脏肿瘤组(t值分别为2.99和2.32,P值均＜0.05),正常肝脏组和良性肿瘤组Cho/Lip比值差异无统计学意义(t=1.53,P＞0.05).ROC曲线下面积为0.77,1H-MRS对诊断HCC有较高诊断价值,当Cho峰与Lip峰比值界值点为0.1时,诊断HCC的敏感性和特异性分别为80.0%和62.5%.结论肝脏局灶性病变1H-MRS分析是可行的,对于鉴别IHCC和良性肝脏肿瘤有一定的临床参考价值.     

Feasibility of quantitative intrahepatic lipid imaging applied to the magnetic resonance dual gradient echo sequence.

The quantification of intrahepatic lipids (IHLs) has attracted a great deal of interest pertaining to diagnostic treatment of type 2 diabetes mellitus. We report on an innovative approach to visualizing IHLs quantitatively by creating the best mix of the advantages of proton magnetic resonance spectroscopy (MRS) and the gradient echo (GRE) sequence on a 1.5T MR system. Proton MRS is considered to have the best precision and reliability; however, measuring a single voxel is time-consuming. On the other hand, the GRE sequence can provide information on IHLs, at least not quantitative, in a very short time. IHL images can be created from the correlation between the relative content of IHLs obtained with proton MRS and the signal intensity of GRE images with a very high correlation coefficient (R=0.992). Our approach holds great potential for quantifying fat accumulation in every possible tissue quickly and precisely.     

In vivo determination of human breast fat composition by 1H magnetic resonance spectroscopy at 7 T

The role of diet and fat consumption in the pathogenesis of breast cancer is an important subject. We report a method for noninvasive determination of lipid composition in human breast by proton magnetic resonance spectroscopy (MRS) at 7 T. Two respiratory‐triggered TE‐averaged stimulated echo acquisition mode (STEAM) acquisitions were performed on the adipose tissue of 10 healthy volunteers where the second acquisition had all gradients inverted. This acquisition protocol allows the suppression of modulation sidebands that complicate spectral analysis at the short TE_avg = 24.5 ms. The entire acquisition takes ～10 min. Ten lipid peaks were typically resolved. T₁ and T₂ were also measured and used to correct the peak intensities. The calculated average lipid composition for saturated was 28.7 ± 8.4%, monounsaturated, 48.5 ± 7.9%, and polyunsaturated, 22.7 ± 3.1%, in close agreement with reported values from subcutaneous adipose measurements. Intrasubject variability was 2.0, 1.6, and 3.6% for the saturated, monounsaturated, and polyunsaturated fractions, respectively. In conclusion, we have shown that a chemical analysis of lipids in breast tissue can be determined quite simply, quickly, and noninvasively by proton MRS at 7 T. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Detection of glutamate/glutamine resonances by 1H magnetic resonance spectroscopy at 0.5 tesla

Midfield proton magnetic resonance spectroscopy (MRS) provides a noninvasive method to monitor glutamate and glutamine (Glx) levels in vivo. Experiments to detect the γ and β resonances of Glx have been performed by using commercial 0.5 T and 1.5 T MR scanners on seven patients with elevated blood ammonia and eight normal volunteers. Compared with the spectral sensitivity obtained on an otherwise identical system operating at 1.5 T, the singlet resonance of N-acetyl aspartate (NAA) was decreased by a factor of 1.48, which is significantly less than expected using the ratio of Boltzman populations at the two field strengths. However, the resonances of Glx at 0.5 T increased in signal-to-noise ratio (SNR) by a factor of 2. The increased SNR of Glx is principally due to improved B ₀ main-field homogeneity and collapse of the strongly J -coupled Glx resonances. Our preliminary results suggest that midfield proton MRS will provide significant clinical utility in the detection of Glx levels in human brain.     

兔肝VX2瘤活体二维多体素1H-MRS动态分析及病理对照研究

目的 探讨兔肝VX2瘤活体二维多体素1H-MRS动态变化特征.材料与方法对14只兔肝VX2瘤荷瘤兔分两期进行活体2D 1H-MRS和常规MRI检查,观察肿瘤中心部分、肿瘤周围部分与瘤周正常肝组织的代谢物波峰变化,测量代谢物峰下积分面积比值.取MRS检查相应部位标本进行常规病理学检查,并进行PAS染色,测量积分光密度.结果 肿瘤中心部分的脂质(Lip)、胆碱化合物(Cho)和糖原和葡萄糖复合物(Glyu)波峰与瘤周正常肝组织差别较大.肿瘤周围部分除Lip峰高于瘤周正常肝组织以外,Cho和Glyu峰差异不大.肿瘤中心部分的Cho/Lip和Glyu/Lip值均较瘤周正常肝组织低(P<0.05),肿瘤周围部分与瘤周正常肝组织无显著性差异(P>0.05).第二期三个部位的Glx/Lip、Cho/Lip、Glyu/Lip比值均较第一期明显降低(P<0.05).瘤周正常肝组织PAS染色积分光密度值与Glyu/Lip值之间存在显著线性相关关系(r=0.627,P<0.05).结论 活体2D 1H-MRS能动态显示兔肝VX2瘤不同区域和不同时期主要代谢物的变化,在一定程度上反映了肝组织糖原储备及肿瘤的生长、增殖、坏死情况.     

Investigation of stroke in sickle cell disease by1H nuclear magnetic resonance spectroscopy

Summary Localized proton nuclear magnetic resonance spectroscopy (MRS), obtained with stimulated echo and spin echo sequences, MR imaging (MRI) and MR angiography (MRA) were used to study the brain in 13 children and adolescents with sickle cell disease. Regions of interest (ROI) studied by MRS included regions appearing normal on MRI as well as regions showing complications of sickle cell disease, including focal deep white matter areas of high signal intensity (deep white matter ischemia, DWMI) seen on long TR images, focal atrophic brain areas, and infarcts. The findings in these studies are summarized as follows: Normal-appearing regions on MRI have normal MRS. In ROI including small areas of DWMI, lactate elevation was not detected, but the levels ofN-acetyl-aspartate (NAA) appeared slightly elevated. In areas of DWMI 1–2 cm in size, reduced blood flow could be seen on MRA and lactate elevation could be detected with MRS. When blood flow to a DWMI region was normal, NAA was reduced and there was little lactate elevation, as cell death had already occurred. ROI consisting of atrophic tissue had reduced NAA levels but total creatine levels were not changed. Sometimes lipids, presumably from broken cell membrane, could be detected. In regions of past massive stroke, all metabolites were absent except for small amounts of lactate or lipids.     

3-T proton magnetic resonance spectroscopy of central neurocytoma: 3 case reports and review of the literature

Central neurocytoma (CNC), first described by Hassoun et al in 1982, is a rare neuronal tumor of the central nervous system, accounting for 0.25% to 0.5% of all central nervous system tumors. To our knowledge, there are only 5 published articles reporting the magnetic resonance spectroscopy (MRS) findings of neurocytomas. The 3-T proton MRS findings of 3 cases with CNC confirmed by immunohistochemical stains are reported here. Increased choline (Cho)/creatine (Cr) ratios with decreased N-acetylaspartate (NAA)/Cr ratios were observed in all 3 cases, but only 1 case had an increased peak at 3.55 ppm known as glycine (Gly). The other case with an increased alanine peak at 1.5 ppm had a poor prognosis. Therefore, we conclude that the presence of a Gly peak may suggest the diagnosis of CNC but that the absence of Gly does not exclude the diagnosis of CNC.     

Automated MR spectroscopy of intra- and extraventricular neurocytomas.

PURPOSE: We evaluated the automated magnetic resonance spectroscopic (MRS) characteristics of intra- and extraventricular neurocytomas. MATERIALS AND METHODS: One extra- and 4 intraventricular neurocytomas were studied. Automated single-voxel proton MRS was performed with a 1.5 T MR scanner. The results of 6 total automated MR spectra were analyzed for each tumor. RESULTS: Lactate resonance was detected as a doublet in 3 MR spectra of 2 intraventricular neurocytomas. A peak corresponding to N-acetylaspartate (NAA) was small in 5 MR spectra of 4 intraventricular neurocytomas. Creatine (Cr) resonance was detected in all 6 MR spectra. Prominent choline (Cho) resonance was found in all 6 MR spectra. The myoinositol (MI) and/or glycine (Gly) peaks were large in 3 MR spectra of 2 intraventricular neurocytomas. CONCLUSION: The presence of the NAA signal and high MI and/or Gly signals may be characteristic features of intraventricular neurocytomas. A combination of prominent Cho resonance and detectable Cr resonance is a common feature of both intra- and extraventricular neurocytomas.     

Proton magnetic resonance spectroscopy reflects cellular proliferative activity in astrocytomas

We examined whether proton magnetic resonance spectroscopy (MRS) could provide accurate information on histological grade and cell proliferation in astrocytomas. We studied 23 patients with astrocytomas: five grade II, 10 grade III and eight with grade IV (glioblastoma multiforme). We performed proton MRS and determined the Ki-67 labeling index (LI), a tumour proliferation marker, in the same areas of the astrocytomas, and examined the statistical relationship between proton MRS and Ki-67 LI. The N-acetylaspartate (NAA)/creatine-phosphocreatine (Cr) and NAA/choline (Cho)-containing compound ratios were always significantly lower and the Cho/Cr ratios significantly higher than those for normal brain. The Cho/Cr ratio correlated positively and the NAA/Cho ratio inversely with Ki-67 LI. These findings suggest that the Cho signal in proton MRS reflects cellular proliferation. In Kaplan-Meier survival analysis, there was no significant difference between high (> 2.0, 14 cases) and low (< 2.0, 9 cases) Cho/cr ratio groups. Received: 24 December 1998/Accepted: 11 August 1999     

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.     

Use of phosphorus-31 MR spectroscopy to monitor response to chemotherapy in non-Hodgkin lymphoma

Two patients with non-Hodgkin lymphoma of the femur were examined with 31P magnetic resonance spectroscopy (MRS) and proton magnetic resonance imaging before and during treatment with chemotherapy. Prior to treatment, 31P MRS of the tumor showed that in comparison to normal skeletal muscle, phosphocreatine was reduced, and phosphomonoesters (PME) and phosphodiesters were elevated. The 31P spectrum became similar to that of normal muscle after 40 days of treatment in both cases. Following the initial dose of chemotherapy, an increase in PME relative to adenosine triphosphate was observed within 48 h in one patient. Magnetic resonance showed a change in the soft tissue component of both tumors and 6-12 months later there was no clinical evidence of any recurrence. Magnetic resonance spectroscopy with 31P may prove to be a sensitive technique for monitoring therapeutic response of tumors.     

Tumor characterization using unconventional MR modalities

This article reviews many of the promising new magnetic resonance (MR) modalities for the characterization of tumor structure and metabolism, excluding 31P magnetic resonance spectroscopy (MRS). The report focuses on recent work with localized proton MRS, MR imaging of diffusion and perfusion, and work on imaging bound pools of sodium ions. The technical problems associated with these methods are discussed, along with the unique information each provides. Many of these techniques have already been used in studies of human disease, or are of sufficient importance that clinical applications are imminent.     

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.