Short TE hydrogen-1 spectroscopic MR imaging of normal human brain: Reproducibility studies

Studies have been performed to evaluate the reproducibility of longitudinal acquisitions with short TE spectroscopic magnetic resonance (MR) imaging of human brain. In healthy volunteers, the ratios of N-acetyl-aspartate (NAA) and choline (Cho) with respect to total creatine (Cr) (creatine and phosphocreatine) have been examined in terms of voxel-to-voxel, acquisition-to-acquisition, and subject-to-subject variation. Overall coefficients of variation for NAA/Cr ratios and Cho/Cr ratios were 18% and 16%, respectively. The interacquisition variation was not statistically significant (P = .05) for either ratio. In terms of F ratios, the dominant source of variation in the NAA/Cr ratio was intersubject variability, whereas for the Cho/Cr ratio the dominant source of variation was intervoxel variability. Consequences of spectroscopic processing with spatial apodization and postacquisition water suppression and resolution enhancement were also examined. Such reproducibility studies are crucial if longitudinal spectroscopic evaluations are to be performed in a clinical setting to follow the natural course of disease states or the effects of therapy.     

Proton spectroscopic metabolite signal relaxation times in preterm infants: a prerequisite for quantitative spectroscopy in infant brain

PURPOSE: To determine relaxation times of metabolite signals in proton magnetic resonance (MR) spectra of immature brain, which allow a correction of relaxation that is necessary for a quantitative evaluation of spectra acquired with long TE. Proton MR spectra acquired with long TE allow a better definition of metabolites as N-acetyl aspartate (NAA) and lactate especially in children. MATERIALS AND METHODS: Relaxation times were determined in the basal ganglia of 84 prematurely born infants at a postconceptional age of 37.8 +/- 2.2 (mean +/- SD) weeks. Metabolite resonances were investigated using the double-spin-echo volume selection method (PRESS) at 1.5 T. T1 was determined from intensity ratios of signals obtained with TRs of 1884 and 6000 msec, measured at 3 TEs (25 msec, 136 msec, 272 msec). T2 was determined from signal intensity ratios obtained with TEs of 136 msec and 272 msec, measured at 2 TR. Taking only long TEs reduced baseline distortions by macromolecules and lipids. For myo-inositol (MI), an apparent T2 for short TE was determined from the ratio of signals obtained with TE = 25 msec and 136 msec. Intensities were determined by fitting a Lorentzian to the resonance, and by integration. RESULTS: Relaxation times were as follows: trimethylamine-containing compounds (Cho): T1 = 1217 msec/T2 = 273 msec; total creatine (Cr) at 3.9 ppm: 1010 msec/111 msec; Cr at 3.0 ppm: 1388 msec/224 msec; NAA: 1171 msec/499 msec; Lac: 1820 msec/1022 msec; MI: 1336 msec/173 msec; apparent T2 at short TE: 68 msec. CONCLUSION: T1 and T2 in the basal ganglia of premature infants do not differ much from previously published data from basal ganglia of older children and adults. T2 of Cho was lower than previous values. T2 of Cr at 3.9 ppm and Lac have been measured under different conditions before, and present values differ from these data.     

Localized 1H-MR Spectroscopy in Moyamoya Disease before and after Revascularization Surgery

Objective

To evaluate, using localized proton magnetic resonance spectroscopy (¹H-MRS), the cerebral metabolic change apparent after revascularization surgery in patients with moyamoya disease.

Materials and Methods

Sixteen children with moyamoya disease and eight age-matched normal controls underwent MR imaging, MR angiography, conventional angiography, and ^99mTc-ECD SPECT. Frontal white matter and the basal ganglia of both hemispheres were subjected to localized ¹H-MRS, and after revascularization surgery, four patients underwent follow-up ¹H-MRS.

Results

Decreased NAA/Cr ratios (1.35±0.14 in patients vs. 1.55±0.24 in controls) and Cho/Cr ratios (0.96±0.13 in patients vs. 1.10±0.11 in controls) were observed in frontal white matter. After revascularization surgery, NAA/Cr and Cho/Cr ratios in this region increased. In the basal ganglia, there is no abnormal metabolic ratios.

Conclusion

Localized 1H-MRS revealed abnormal metabolic change in both hemispheres of children with moyamoya disease. Because of its non-invasive nature, ¹H-MRS is potentially useful for the preoperative evaluation of metabolic abnormalities and their postoperative monitoring.     

Single-voxel long TE 1H-MR spectroscopy of the normal brainstem and cerebellum

PURPOSE: To evaluate the feasibility of single voxel 1H-MRS of the CNS structures contained in the posterior cranial fossa and to determine the distribution of the normal metabolite ratios, concentrations, and T2 relaxation times in the midbrain, pons, medulla, dentate nucleus and cerebellar vermis. MATERIALS AND METHODS: A total of 147 single voxel 1H-MR spectra with a point-resolved proton spectroscopy sequence (PRESS) sequence and echo time (TE) of 136 or 272 msec were obtained in the midbrain, pons, medulla, dentate, and vermis of 31 healthy volunteers. In seven additional patients; the concentrations and T2 relaxation times of metabolites were obtained in the same locations (except the medulla) with an external phantom calibration method and a four TE PRESS technique. RESULTS: Ten (27%) of 36 spectra acquired in the medulla were of poor quality. A similar ranking of the N-acetyl aspartate (NAA)/creatine (Cr) ratio and choline(Cho)/Cr ratios in the five locations for the two TEs was observed, with the highest values in the pons (mean NAA/Cr = 4.16 +/- 0.6 and Cho/Cr =2.66 +/- 0.6 at TE 272) and the lowest values in the dentate and vermis (mean NAA/Cr = 1.66 +/- 0.2 and Cho/Cr = 1.20 +/- 0.2 at TE 272). The analysis of variance showed significant regional differences of the NAA and Cr concentrations, which had the highest values in the dentate. Non-significant regional differences were observed for the concentration of Cho and for the T2 of the metabolites. CONCLUSION: With the exception of the medulla, single voxel 1H-MRS enables an in vivo biochemical analysis of the CNS structures contained in the posterior cranial fossa. Regional differences in the metabolite ratios and concentrations must be considered when employing 1H-MRS for evaluation of diseases of the brainstem and cerebellum.     

Differentiation between high-grade glioma and metastatic brain tumor using single-voxel proton MR spectroscopy

The purpose of this study was to clarify the efficacy of single-voxel proton magnetic resonance spectroscopy (MRS) in differentiating high-grade glioma from metastasis. Thirty-one high-grade gliomas (11 anaplastic gliomas and 20 glioblastomas) and 25 metastases were studied. Proton MRS was performed using point-resolved spectroscopy with echo times (TEs) of both 136 and 30 ms. The peaks for lipid were evaluated at short TE, and those for N-acetyl-aspartate (NAA), creatine (Cr), and choline-containing compounds (Cho) were assessed at long TE. All the tumors exhibited a strong Cho peak at long TE. Twenty-one of 25 metastases showed no definite Cr peak. The remaining 4 metastases showed NAA and Cr peaks; however, the presence of NAA and relatively high NAA/Cr ratio (1.58+/-0.56) indicated normal brain contamination. All the gliomas, except for a single glioblastoma, showed a Cr peak with (n=16) or without (n=14) NAA. At short TE all metastases and glioblastomas showed definite lipid or lipid/lactate mixture, but anaplastic gliomas showed no definite lipid signal. Intratumoral Cr suggests glioma. Absence of Cr indicates metastasis. Definite lipid signal indicates cellular necrosis in glioblastoma and metastasis, and no lipid signal may exclude metastases.     

Musculoskeletal tumors: use of proton MR spectroscopic imaging for characterization

PURPOSE: To determine the value of multivoxel proton magnetic resonance spectroscopic imaging (MRSI) in distinguishing malignant skeletal tumors from benign tumors and normal bone marrow using the metabolite choline (Cho) as a marker for malignancy. MATERIALS AND METHODS: Pathologic specimens obtained from 13 patients who had undergone wide resection for skeletal tumors underwent evaluation by MRSI at 1.5 T. Coronal T1-weighted gradient-echo sequence obtained for localization purposes (TR/TE = 250/1.8 msec, field of view [FOV] = 18 x 18), and single-slice MRSI (TR/TE = 2000/272 msec, FOV = 18 x 18, 10-mm slice-thickness) were performed. Water, lipid, and Cho images were reconstructed from MRSI data. Cho signal was measured in each specimen and expressed relative to background noise level (signal-to-noise ratio [SNR]) where noise was measured between 7.0 and 9.0 ppm. Cho SNRs were compared between areas containing malignant tumor and nonmalignant tissue (benign lesion or normal bone marrow) as determined by histopathology. RESULTS: Specimens included 13 skeletal sarcomas (seven osteosarcomas, three chondrosarcomas, one malignant fibrous histiocytoma, one fibrosarcoma, and one leiomyosarcoma). All specimens included a sample of normal bone marrow and two specimens also contained benign lesions. All sarcomas demonstrated a signal at 3.2 ppm assigned to Cho-containing metabolites in areas of malignancy. Peak Cho SNR was significantly different for areas containing histologically-proven malignancy compared to nonmalignant tissue (9.8 +/- 5.1 vs. 2.7 +/- 1.4, respectively, P < 0.002). CONCLUSION: These preliminary results indicate that MRSI at 1.5 T is a promising noninvasive method of differentiating malignant skeletal tumors from nonmalignant tissue. Using MRSI, Cho can be detected in skeletal tumors and may serve as a marker for malignancy.     

Optimal Pulse Sequence for Ferumoxides-Enhanced MR Imaging Used in the Detection of Hepatocellular Carcinoma: A Comparative Study Using Seven Pulse Sequences

Objective

To identify the optimal pulse sequence for ferumoxides-enhanced magnetic resonance (MR) imaging in the detection of hepatocelluar carcinomas (HCCs).

Materials and Methods

Sixteen patients with 25 HCCs underwent MR imaging following intravenous infusion of ferumoxides. All MR studies were performed on a 1.5-T MR system, using a phased-array coil. Ferumoxides (Feridex IV) at a dose of 15 µmol/Kg was slowly infused intravenously, and axial images of seven sequences were obtained 30 minutes after the end of infusion. The MR protocol included fast spin-echo (FSE) with two echo times (TR3333 8571/TE18 and 90-117), singleshot FSE (SSFSE) with two echo times (TR∞/TE39 and 98), T2*-weighted gradient-recalled acquisition in the steady state (GRASS) (TR216/TE20), T2*-weighted fast multiplanar GRASS (FMPGR) (TR130/TE8.4-9.5), and T2*-weighted fast multiplanar spoiled GRASS (FMPSPGR) (TR130/TE8.4-9.5). Contrast-to-noise ratios (CNRs) of HCCs determined during the imaging sequences formed the basis of quantitative analysis, and images were qualitatively assessed in terms of lesion conspicuity and image artifacts. The diagnostic accuracy of all sequences was assessed using receiver operating characteristic (ROC) analysis.

Results

Quantitative analysis revealed that the CNRs of T2*-weighted FMPGR and T2*-weighted FMPSPGR were significantly higher than those of the other sequences, while qualitative analysis showed that image artifacts were prominent at T2*-weighted GRASS imaging. Lesion conspicuity was statistically significantly less clear at SSFSE imaging. In term of lesion detection, T2*-weighted FMPGR, T2*-weighted FMPSPGR, and proton density FSE imaging were statistically superior to the others.

Conclusion

T2*-weighted FMPGR, T2*-weighted FMPSPGR, and proton density FSE appear to be the optimal pulse sequences for ferumoxides-enhanced MR imaging in the detection of HCCs.     

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.     

Proton magnetic resonance spectroscopy of brain tumors correlated with pathology

RATIONALE AND OBJECTIVES: Evaluate proton magnetic resonance spectroscopy ((1)H-MRS) for assessing and grading brain tumors. MATERIALS AND METHODS: The research was done at Detroit Medical Center in a 1.5-T Siemens MR magnet using single-voxel or multivoxel MRS. This study consisted of 27 patients: 10 females and 17 males ages 22-83 years (average age 43.8). The data were recorded for three peaks-N-acetyl aspartate (NAA), choline (Cho), creatine (Cr)-which were used to calculate the ratios Cho/NAA and Cho/Cr. RESULTS: Abnormal spectra were seen in 25 patients and normal spectra in 2. In 16 patients with brain astrocytoma of various grades, the pathology grading was correlated with Cho/NAA and Cho/Cr. These values were 6.53 and 3.35 for nine patients with Grade 4 astrocytoma; 1.85 and 1.62 for three patients with Grade 3 astrocytoma; 2.21 and 1.50 for three patients with Grade 2 astrocytoma; and 1.45 and 1.49 for one patient with Grade 1 astrocytoma. The remaining nine patients with abnormal spectra were also correlated with pathology. CONCLUSION: MRS ratios can be used to differentiate malignant and nonmalignant lesions from normal brain tissue. In general, high-grade astrocytoma have higher Cho/NAA and Cho/Cr ratios compared with low-grade astrocytoma.     

1 H-MRS对低级别和高级别脑胶质瘤鉴别诊断的作用及病理级别相关性的研究

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。资料与方法 搜集经临床手术、病理证实的脑胶质瘤36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Siemens Sonata 1．5T超导磁共振扫描仪,多体素扫描,点分辨表面线圈法,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。低级别、高级别脑胶质瘤的肿瘤组织分别和对侧正常脑组织的NAA／Cr、Cho／Cr、NAA／Cho比值存在非常显著性差异（P〈0．01）;低级别脑胶质瘤和高级别脑胶质瘤的肿瘤组织的NAA／Cr、Cho／Cr、NAA／Cho比值存在显著性差异（P〈0．05）。脑胶质瘤的NAA／Cho、Cho／Cr、NAA／Cr比值与病理级别相关,其中NAA／Cho和Cho／cr比值反映肿瘤级别较稳定;NAA／Cr、NAA／Cho比值存在负相关关系（相关系数rs分别为-0．663,-0．851）,Cho／Cr比值存在正相关关系（相关系数rs为0．858）。结论 ^1H—MRS与MRI相结合能提高脑胶质瘤术前诊断的准确性。^1H-MRS可评价脑胶质瘤的分级,反映脑胶质瘤代谢特性以及肿瘤生长潜能。     

Asymmetry and gender effect in functionally lateralized cortical regions: a proton MRS imaging study

PURPOSE: to compare metabolite concentrations and ratios in gray matter regions known for their anatomical/functional asymmetry and evaluate gender effect. MATERIALS AND METHODS: Proton MRS imaging was performed at 1.5 T with TR/TE 2300/280 msec in 20 healthy right-handed subjects (mean age 29.6 +/- 5.3 years, 10 men). Concentrations of N-acetyl aspartate (NAA), choline (Cho), and creatine (Cr), and the peak area ratios NAA/Cho, NAA/Cr, and Cho/Cr were evaluated in hippocampal and parahippocampal gyri, thalamus, insula, Broca's and Wernicke's areas (and corresponding contralateral areas), primary and secondary visual areas, temporal, inferior parietal, cingulate, supplemental motor, dorsolateral prefrontal, and sensorimotor areas. Linear mixed-effects regression models were used for statistical analyses. RESULTS: NAA concentration and NAA/Cho were higher in the left thalamus by 21.9% and 20%, respectively (both P < 0.001). NAA concentration was 13% higher in the region contralateral to Wernicke's area (P < 0.02). No gender differences were found. CONCLUSION: Metabolite concentrations and ratios were symmetric and gender independent in most brain regions, however small hemispheric side differences in the thalamus and in Wernicke's area were found.     

Quantitative proton MR spectroscopic imaging of the mesial temporal lobe

PURPOSE: To evaluate variations in regional metabolite concentrations in the anterior mesial temporal lobe (ATL), and compare metabolite concentrations between the allocortex and neocortex using quantitative proton MR spectroscopic imaging (MRSI). MATERIALS AND METHODS: Metabolite concentrations and ratios were measured in 20 healthy young subjects with the use of a multislice spin-echo (SE) sequence (TR/TE=2300/280 msec). Quantitation of MRSI data was performed by means of the phantom replacement methodology. RESULTS: The highest choline (Cho) concentration (4.1 +/- 1.1 mM) was found in the ATL (P=0.0015 compared to the middle mesial temporal lobe (MTL), and P=0.0008 compared to the posterior mesial temporal lobe (PTL)). The ATL also had a higher Cho/creatine (Cr) ratio and a lower N-acetyl aspartate (NAA)/Cho ratio compared to other examined regions (P <0.0001 and P < or = 0.052, respectively). In the allocortical regions, the average Cho concentration (3.5 +/- 0.8 mM) was 68% higher, and the NAA concentration (9.5 +/- 1.8 mM) was 13% lower than in the neocortex (P <10(-6) and P <0.008, respectively). Cho/Cr was 64% higher, NAA/Cr 14% lower, and NAA/Cho 47% lower in the allocortex than in the neocortex (P <10(-6), P=0.013, and P <10(-6), respectively). CONCLUSION: The mesial temporal lobe shows high levels of Cho, which presumably reflect a difference in cellular composition between the allocortex and neocortex. Regional metabolite variations must be considered when pathological conditions involving the mesial temporal lobe are evaluated.     

3T 1H-MR spectroscopy in grading of cerebral gliomas: comparison of short and intermediate echo time sequences

BACKGROUND AND PURPOSE: Echo time (TE) can have a large influence on the spectra in proton MR spectroscopy ((1)H-MR spectroscopy). The purpose of this study was to comparatively assess the diagnostic value of 3T single-voxel (1)H-MR spectroscopy with short or intermediate TEs in grading cerebral gliomas. METHODS: Single voxel (1)H-MR spectroscopy was performed at 3T in 35 patients with cerebral glioma. The spectra were obtained with both short (35 ms) and intermediate TEs (144 ms). Metabolite ratios of choline (Cho)/creatine (Cr), Cho/N-acetylaspartate (NAA), lipid and lactate (LL)/Cr and myo-inositol (mIns)/Cr were calculated and compared between short and intermediate TEs in each grade. After receiver operating characteristic curve analysis, diagnostic accuracy for each TE in differentiating high-grade glioma from low-grade glioma was compared. RESULTS: At short TE, Cho/Cr and Cho/NAA ratios were significantly lower, and LL/Cr and mIns/Cr were significantly higher, compared with those at intermediate TE, regardless of tumor grade. Lactate inversion at intermediate TE was found in only 2 patients. At both TEs, there were significant differences in Cho/Cr and LL/Cr ratios between low- and high-grade gliomas. Diagnostic accuracy was slightly higher at short TE alone or combined with intermediate TE than intermediate TE alone (85.7% versus 82.9%). CONCLUSION: Metabolite ratios were significantly different between short and intermediate TE. Cho/Cr and LL/Cr ratios at either TE were similarly useful in differentiating high-grade gliomas from low-grade gliomas. If only a single spectroscopic sequence can be acquired, short TE seems preferable because of poor lactate inversion at intermediate TE on 3T single-voxel (1)H-MR spectroscopy.     

Usefulness of Cho/Cr ratio in proton MR spectroscopy for differentiating residual/recurrent glioma from non-neoplastic lesions

PURPOSE: We evaluated the clinical usefulness of the Cho/Cr ratio of proton MR spectroscopy(1H-MRS) to differentiate residual/recurrent glioma from non-neoplastic lesions. PATIENTS AND METHODS: 20 cases of glioma were involved in this study(astrocytoma grade I-II: 7, oligodendroglioma: 1, astrocytoma grade III: 2, glioblastoma: 10). Seven of the patients underwent surgical resection only, 4 underwent surgical resection and radiotherapy(40-60 Gy), and 9 underwent surgical resection and radiotherapy with concurrent chemotherapy(14-60 Gy). 1H-MRS was performed on a 1.5 Tesla clinical MR unit using a 3D-chemical shift imaging sequence(1500 msec/270 msec/1 (TR/TE/excitations), and the Cho/Cr ratio was calculated in the voxel where neoplastic lesion was most suspected on MRI. The presence of lactate + lipid peak was also evaluated. All spectra were obtained after the contrast enhanced study. RESULTS: Cho/Cr ratios were significantly higher in cases of residual/recurrent tumors(mean +/- SD = 1.70 +/- 0.96) than in non-neoplastic lesions(mean +/- SD = 1.04 +/- 1.16) (Mann-Whitney U-test p = 0.047). If a Cho/Cr ratio of more than 1.5 was used as a marker of tumor presence, its sensitivity was 64%, specificity 83%, and accuracy 70%. One false-positive case that of radiation necrosis whose spectrum showed a high Cho/Cr ratio with markedly elevated lactate + lipid peak. CONCLUSION: The Cho/Cr ratio of 1H-MRS provides additional information to MRI in differentiating residual/recurrent gliomas from non-neoplastic lesions.     

儿童神经元蜡样质脂褐素沉积病的MRI及MRS表现

目的：分析婴儿型和晚期婴儿型神经元蜡样质脂褐素沉积病（NCL）的MRI、磁共振波谱（^1H—MRS）表现。方法：对2例婴儿型和8例晚期婴儿型NCL患儿行磁共振平扫和磁共振波谱检查。总结分析各种特征性影像表现及N-乙酰天门冬氨酸（NAA）、总肌酸（Cr）、胆碱复合物（Cho）、NAA／Or、Cho／Cr比值的变化规律。结果：10例患儿都表现为逐渐进展的脑萎缩,婴儿型以大脑萎缩为早期表现,晚期婴儿型以小脑萎缩为早期表现。2例婴儿型病例及病史4～5年的晚期婴儿型患儿可见大脑半球白质的异常高信号,脑室旁白质最为明显。婴儿型病例见双侧丘脑和基底节核团T2WI低信号。8例发现颅骨板障明显增厚。磁共振波谱显示随着病程延长,晚期婴儿型病例的NAA／Cr比值逐渐降低,Cho／Cr值未见明显变化。婴儿型病例末观测到NAA峰,Cho／Cr水平降低,肌醇（mi）水平明显增高。结论：MRI和^1H—MRS可以敏感地发现婴儿型和晚期婴儿型患儿脑内的异常改变9有助于NCL的诊断和分型,并可以评价疾病的严重程度,监测病情变化。     

青年抑郁症患者基底节和丘脑3D 1H-MRS研究

目的:探讨青年抑郁症患者基底节和丘脑可能存在的神经生化异常.方法:对44例青年抑郁症患者(抑郁症组)和40例年龄和性别匹配的健康志愿者(对照组)进行常规MRI扫描和三维氢质子MR波谱(3D 1H-MRS)检查,测量双侧基底节和丘脑的 N-乙酰天门冬氨酸(NAA)、胆碱复合物(Cho)、肌醇(mI)和肌酸(Cr)的绝对值,并计算它们与Cr的比值.对两组实验对象各代谢物及其比值进行统计学分析.结果:①抑郁症组双侧豆状核和尾状核头部Cho/Cr、mI/Cr明显高于对照组,差异有显著性意义(P＜0.05),而NAA/Cr在两组间差异无统计学意义(P＞0.05);②抑郁症组丘脑NAA/Cr、Cho/Cr和mI/Cr与对照组相比,差异无统计学意义(P＞0.05).结论:青年抑郁症患者基底节区豆状核和尾状核头部的Cho/Cr、mI/Cr增高,可能构成该病的神经生物学基础.     

T1, T2, and concentrations of brain metabolites in neonates and adolescents estimated with H-1 MR spectroscopy

The protein and lipid content of the human brain increases dramatically from infancy to adolescence. The authors investigated whether this change influences the relaxation behavior of metabolites measurable with hydrogen-1 magnetic resonance (MR) spectroscopy. H-1 MR spectroscopy was performed in eight neonates and eight adolescents at 1.5 T with STEAM (stimulated-echo acquisition mode) sequences. Five spectra were obtained in each volume of interest with different TE and TR values. T1 and T2 were subsequently calculated. T1 and T2 for inositols, choline-containing compounds (Cho), phosphocreatine plus creatine (PCr + Cr), and N-acetylaspartate (NAA) did not differ significantly between the two subject groups. Metabolite concentrations were estimated by using the fully relaxed water signal as an internal standard. Mean estimated concentrations of NAA and PCr + Cr were higher in the adolescent group, whereas the concentration of Cho was lower. The concentration of inositols was similar in the two groups.     

Manually adjusted versus vendor-preset definition of metabolite boundaries impact on proton metabolite ratios

RATIONALE AND OBJECTIVES: Metabolite peak boundary definition is an important postprocessing step in proton magnetic resonance spectroscopy (1H-MRS). We compare metabolite ratios calculated using three different postprocessing strategies: software-rendered default peak boundaries, manually adjusted peak boundaries and a curve-fitting program. The first two of these methods are commercially available. MATERIALS AND METHODS: A total of 42 spectra acquired on a 1.5-T MR unit using two-dimensional chemical shift proton MR spectroscopy (TR/TE = 1500/144 ms) were analyzed. Choline (Cho), creatine (Cr), and N-acetylaspartate (NAA) relative concentrations were derived and the following metabolite ratios were calculated: Cho/Cr, Cho/NAA, and NAA/Cr. Metabolite concentrations/ratios were calculated using (a) default peak boundaries rendered by commercially available, postprocessing software (Functool 2000, version 2.6.0); (b) manually adjusted peak boundaries by an experienced spectroscopist, using an option offered by the same commercially available software; and (c) an offline in-house curve-fitting program. Measurements obtained with method (c) were considered as the "gold standard." Paired t-tests comparing default and adjusted metabolite ratios, as well as default and adjusted ratios with their respective curve-fit values were used for statistical analysis. RESULTS: Significant differences between default and manually adjusted values were found for Cho/Cr ratios <1.5 and for all Cho/NAA ratios. For Cho/Cr ratios <1.5, significant differences between default and curve-fit values were present; this was not the case when comparing manually adjusted and curve-fit values. Default and manually adjusted Cho/NAA ratios were significantly higher than corresponding curve-fit ratios. Manually adjusted values were, however, closer to the curve-fit values. No significant differences were noted between default and adjusted NAA/Cr values; default and manually adjusted ratios were significantly lower than curve-fit ratios. CONCLUSION: There can be significant differences in metabolite ratios calculated using default and manually adjusted peak limits in proton MR spectroscopy. Furthermore, Cho/Cr and NAA/Cho adjusted metabolite ratios are closer to curve-fit values, which are considered the most accurate of the three.     

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     

In vivo proton MR spectroscopy of primary and nodal nasopharyngeal carcinoma

BACKGROUND AND PURPOSE: The aim of this study was to determine the feasibility of performing in vivo proton ((1)H) MR spectroscopy of nasopharyngeal carcinoma (NPC) and to document the (1)H spectrum of this cancer. METHODS: Twenty-seven patients with NPC lesions >1 cm(3) underwent localized (1)H MR spectroscopy performed at 1.5 T. Water-suppressed spectra from both primary tumors (nine cases) and metastatic nodes (18 cases) were obtained at TE 136 and 272. Spectra were analyzed in the time domain by using a nonlinear least squares fitting algorithm with incorporation of previous knowledge. Choline (Cho)/creatine (Cr) ratios for primary NPC and metastatic nodes were calculated and compared. Spectra from normal neck muscle of five volunteers were acquired as control data. RESULTS: (1)H MR spectroscopy was successfully obtained in seven (78%) of nine primary tumors and 16 (89%) of 18 metastatic nodes. Intense lipid signals in the range of 0.89 to 2.02 ppm were observed in 95% of spectra at TE 136 and 91% of spectra at TE 272. At TE 136, Cho/Cr for metastatic nodes (5.3 +/- 1.6) was significantly higher than the ratio for primary (2.6 +/- 0.5) NPC lesions (P =.02). Cho/Cr ratios for NPC lesions were higher than those for normal neck muscles, for which values ranged from 0 to 0.97 and 0 to 1.1 at TE 136 and 272, respectively. CONCLUSION: (1)H MR spectroscopy is a feasible technique for the evaluation of NPC tumors >1 cm(3). Cho/Cr ratios for the lesions were high compared with those for normal neck muscle.