Assessment of malignancy in gliomas by 3T 1H MR spectroscopy

The purpose of this study was to assess clinical 1H MR spectroscopy (MRS) as a noninvasive method for evaluating brain tumor malignancy at 3T high-field system. Using 3T MRI/MRS system, localized water-suppressed single-voxel technique in patients with brain tumor (i.e., gliomas) was employed to evaluate spectra with peaks of N-acetyl aspartate (NAA), choline-containing compounds (Cho), creatine/phosphocreatine (Cr) and lactate. On the basis of Cr, these peak areas were quantitated as a relative ratio. The variation of metabolite measurements of the designated region in 10 normal volunteers was less than 10%. Normal ranges of NAA/Cr and Cho/Cr ratios were 1.67+/-018 and 1.16+/-0.15, respectively. NAA/Cr ratio of gliomas was significantly lower than that of the normal tissues (P= .005), but Cho/Cr ratio of gliomas was significantly higher (P= .001). Cho/Cr ratio of high-grade gliomas was significantly higher than that of low-grade gliomas. The present study demonstrated that the neuronal degradation or loss was observed in all gliomas. Higher-grade glioma was correlated with higher Cho/Cr ratio, indicating a significant dependence of Cho levels on malignancy of gliomas. Our results suggest that clinical 1H MR spectroscopy could be useful to predict tumor malignancy.     

Cerebral gliomas: prospective comparison of multivoxel 2D chemical-shift imaging proton MR spectroscopy,echoplanar perfusion and diffusion-weighted MRI

Developments in MRI have made it possible to use diffusion-weighted MRI, perfusion MRI and proton MR spectroscopy (MRS) to study lesions in the brain. We evaluated whether these techniques provide useful, complementary information for grading gliomas, in comparison with conventional MRI. We studied 17 patients with histologically verified gliomas, adding multivoxel proton MRS, echoplanar diffusion and perfusion MRI the a routine MRI examination. The maximum relative cerebral blood volume (CBV), minimum apparent diffusion coefficient (ADC) and metabolic peak area ratios in proton MRS were calculated in solid parts of tumours on the same slice from each imaging data set. The mean minimum ADC of the 13 high-grade gliomas (0.92+/-0.27 x 10(-3) mm(2)/s) was lower than that of the four low-grade gliomas (1.28+/-0.15 x 10(-3) mm(2)/s) ( P<0.05). Means of maximum choline (Cho)/N-acetylaspartate (NAA), Cho/creatine (Cr), Cho/Cr in normal brain (Cr-n) and minimum NAA/Cr ratios were 5.90+/-2.62, 4.73+/-2.22, 2.66+/-0.68 and 0.40+/-0.06, respectively, in the high-grade gliomas, and 1.65+/-1.37, 1.84+/-1.20, 1.61+/-1.29 and 1.65+/-1.61, respectively, in the low-grade gliomas. Significant differences were found on spectroscopy between the high- and low-grade gliomas ( P<0.05). Mean maximum relative CBV in the high-grade gliomas (6.10+/-3.98) was higher than in the low-grade gliomas (1.74+/-0.57) ( P<0.05). Echoplanar diffusion, perfusion MRI and multivoxel proton MRS can offer diagnostic information, not available with conventional MRI, in the assessment of glioma grade.     

Low-grade gliomas and focal cortical developmental malformations: differentiation with proton MR spectroscopy

PURPOSE: To assess proton magnetic resonance (MR) spectroscopy in differentiating between low-grade gliomas and focal cortical developmental malformations (FCDMs). MATERIALS AND METHODS: Eighteen patients with seizures and a cortical brain lesion on MR images were studied with proton MR spectroscopy. A metabolite ratio analysis was performed, and the metabolite signals in the lesion core were compared with those in the contralateral centrum semiovale and in the corresponding brain sites in 18 control subjects to separately obtain the changes in N-acetylaspartate (NAA), choline-containing compounds (Cho), and creatine-phosphocreatine (Cr). Ten patients had a low-grade glioma (three, oligodendrogliomas; three, oligoastrocytomas; three, astrocytomas; and one, pilocytic astrocytoma), and eight had FCDM (five, focal cortical dysplasias and three, dysembryoplastic neuroepithelial tumors). Linear discriminant analysis and Student t test were used for statistical comparisons. RESULTS: Loss of NAA and increase of Cho were more pronounced in low-grade gliomas than in FCDMs (NAA, -72% +/- 15 [+/- SD] vs -29% +/- 22, P <.001; Cho, 117% +/- 56 vs 21% +/- 66, P <.01). Changes in NAA and Cho helped differentiate low-grade gliomas from FCDMs, and changes in Cho and Cr helped differentiate astrocytomas from oligodendrogliomas and oligoastrocytomas. Metabolite NAA/Cho and NAA/Cr ratios helped differentiate low-grade gliomas from FCDMs but did not differentiate glioma subtypes. CONCLUSION: MR spectroscopy allows distinction between low-grade gliomas and FCDMs and between low-grade glioma subtypes. Metabolite changes are more informative than are metabolite ratios.     

Proton MR spectroscopy of pediatric cerebellar tumors.

PURPOSETo investigate the role of proton MR spectroscopy in pediatric cerebellar tumor diagnosis.METHODSSingle voxel pulse sequences with long echo time (135 or 270 milliseconds, voxel size 8 to 19 cm3), were used to obtain proton spectra of primary pediatric cerebellar tumors. Eleven primitive neuroectodermal tumors (patient age, 2 to 12 years; mean, 7 years), 11 low-grade astrocytomas (age, 2 to 16 years; mean, 9 years), 4 ependymomas (age, 1 to 6 years; mean, 4 years), 1 mixed glioma ependymo-astrocytoma (age, 11 years), 1 anaplastic ependymoma (age, 7 years), 1 ganglioglioma (age, 14 years), and 1 malignant teratoma (age, 6 days) were studied. Control cerebellum spectra were acquired from five patients without abnormality in cerebellum (age, 2 to 15 years; mean, 8 years). The signal intensities from choline-containing compounds (Cho), creatine/phosphocreatine (Cr), N-acetyl-aspartate (NAA), and lactate (Lac) were quantified. The mean and standard deviation of metabolite ratios were calculated.RESULTSThe control spectra ratios (NAA:Cho = 1.49 +/- 0.36, Cr:Cho = 1.13 +/- 0.23) were distinct from the tumor spectra (NAA:Cho = 0.41 +/- 0.27 and Cr:Cho = 0.37 +/- 0.23). Most of primitive neuroectodermal tumors had low NAA:Cho (0.17 +/- 0.09) and Cr:Cho (0.32 +/- 0.19). Compared with primitive neuroectodermal tumors, low-grade astrocytomas and ependymomas had higher NAA:Cho ratio (0.63 +/- 0.19 and 0.39 +/- 0.12). The Cr:Cho ratio was higher for ependymomas (0.60 +/- 0.20) than for astrocytomas (0.27 +/- 0.12) and primitive neuroectodermal tumors. No NAA was found in the malignant teratoma. Lac:Cho ratio was 0.66 +/- 0.40, 0.58 +/- 0.30, and 0.08 +/- 0.12 for astrocytoma, ependymoma, and primitive neuroectodermal tumor, respectively. Lactate was elevated in the mixed glioma ependymo-astrocytoma, ganglioglioma, and teratoma. The NAA and lactate signals were sometimes obscured by lipids in the spectra. Discriminant analysis was carried out using NAA:Cho and Cr:Cho ratios to differentiate the three major tumor types. The sensitivity/specificity values for diagnosing astrocytoma, ependymoma, and primitive neuroectodermal tumor were found to be 0.91/0.84, 0.75/0.92, and 0.82/0.89, respectively, based on this study.CONCLUSIONIn many cases, proton MR spectroscopy can be used to help differentiate cerebellar primitive neuroectodermal tumor, low-grade astrocytoma, and ependymoma.     

Proton MR spectroscopy of cerebral gliomas at 3 T: spatial heterogeneity, and tumour grade and extent

This study aimed to evaluate the usefulness of proton MR spectroscopic imaging ((1)H-MRSI) at 3 T in differentiating high- from low-grade gliomas, and tumour from necrosis, oedema or normal tissue. Forty-four patients with brain gliomas and four with meningiomas were retrospectively reviewed. The normalised metabolites choline (nCho), N-acetylaspartate (nNAA), creatine (nCr) and lactate/lipids (nLL), and the metabolite ratios Cho/NAA, NAA/Cr and Cho/Cr were calculated. Necrotic-appearing areas showed two spectroscopic patterns: "necrosis" with variable nCho and high nLL, and "cystic necrosis" with variable nLL or nonevident peaks. Peri-enhancing oedematous-appearing areas showed three spectroscopic patterns ("tumour" with abnormal Cho/NAA, "oedema" with normal Cho/NAA and "tumour/oedema" with normal nCho and abnormal Cho/NAA) in gliomas, and one ("oedema") in meningiomas. Peri-enhancing or peri-tumour normal-appearing areas showed two patterns ("infiltrated" with abnormal nCho and/or Cho/NAA and "normal" with normal spectra) in gliomas and one ("normal") in meningiomas. Discriminant analysis showed that classification accuracy between high- and low-grade glioma masses was better with normalised metabolites or all parameters together than metabolite ratios and that among peri-enhancing areas was much better with normalised metabolites. The analysis of spatial distribution of normalised metabolites by 3-T (1)H-MRSI helps to discriminate among different tissues, offering information not available with conventional MRI.     

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.     

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 of delayed cerebral radiation in monkeys and humans after brachytherapy.

PURPOSETo determine whether radiation necrosis can be differentiated from residual/recurrent tumor by proton MR spectroscopy.METHODSWe studied the effects of interstitial brachytherapy on the brains of healthy monkeys and in humans with glioblastoma multiforme. The effects of radiation therapy on normal brain tissue in monkeys were assessed with sequential proton MR spectroscopic studies 1 week to 6 months after brachytherapy. Proton MR spectroscopy was also performed in five patients with residual/recurrent glioblastoma multiforme (three of whom had radiation necrosis after brachytherapy), seven patients with newly diagnosed untreated glioblastoma multiforme, and 16 healthy volunteers, who served as a control group.RESULTSIn monkeys, the ratio of N-acetylaspartate (NAA) to creatine-phosphocreatine (Cr) and the ratio of choline-containing compounds (Cho) to Cr of the reference point were significantly lower 1 week after brachytherapy than before treatment. The ratio of NAA to Cho of the irradiated area tended to be higher 1 week after brachytherapy than before irradiation. These peak metabolic ratios showed characteristic changes 6 months after treatment. In two of three monkeys, lipid signal was elevated 6 months after irradiation. In the clinical study, the ratio of NAA to Cho in the area of radiation necrosis was significantly different from that in glioblastoma multiforme when compared with the contralateral hemisphere after irradiation. In addition, lipid signal was detected in all patients with radiation necrosis.CONCLUSIONIt might be possible to use proton MR spectroscopy to differentiate radiation necrosis from residual/recurrent glioblastoma multiforme on the basis of comparisons with the contralateral hemisphere after radiation therapy.     

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.     

Proton MR spectroscopy of tumefactive demyelinating lesions

BACKGROUND AND PURPOSE: Tumefactive demyelinating lesions (TDLs) can simulate intracranial neoplasms in clinical presentation and MR imaging appearance, and surgical biopsy is often performed in suspected tumors. Proton MR spectroscopy has been applied in assessing various intracranial diseases and is increasingly used in diagnosis and clinical management. Our purpose was to determine if multivoxel proton MR spectroscopy can be used to differentiate TDLs and high-grade gliomas. METHODS: Conventional MR images, proton MR spectra, and medical records were retrospectively reviewed in six patients with TDLs diagnosed by means of biopsy or by documented clinical improvement, with or without supporting laboratory testing and follow-up imaging. Proton MR spectra of 10 high-grade gliomas with similar conventional MR imaging appearances were used for comparison. In contrast-enhancing, central, and perilesional areas of each lesion, peak heights of N-acetylaspartate (NAA), choline (Cho), and creatine (Cr) were measured and the lactate peak noted. Cho/Cr and NAA/Cr ratios of corresponding regions in TDLs and gliomas were compared. RESULTS: No significant differences in mean Cho/Cr ratios were found in the corresponding contrast-enhancing, central, or perilesional areas of TDLs and gliomas. The mean central-region NAA/Cr ratio in gliomas was significantly lower than that of TDLs, but mean NAA/Cr ratios in other regions were not significantly different. A lactate peak was identified in four of six TDLs and three of 10 gliomas. CONCLUSION: In the cases examined, the NAA/Cr ratio in the central region of TDLs and high-grade gliomas differed significantly. However, overall metabolite profiles of both lesions were similar; this finding emphasizes the need for the cautious interpretation of spectroscopic findings.     

3.0T ~1H-MRS在脑内高级别星形细胞瘤及单发转移瘤鉴别诊断中的价值

目的:探讨多体素氢质子磁共振波谱(1 H-MRS)对脑高级别星形细胞瘤、单发脑转移瘤的鉴别诊断价值。方法:收集经手术、活检病理证实的颅脑肿瘤患者37例,其中高级别星形细胞瘤(Ⅲ~Ⅳ级)17例(间变性星形细胞瘤5例,胶质母细胞瘤12例),脑单发转移瘤20例。37例行颅脑常规MRI检查及多体素1 H-MRS分析,分析肿瘤实质强化区、强化边缘区、对侧相应正常区域脑组织的生化代谢物及其比值,并进行对照。结果:1脑高级别星形细胞瘤、脑转移瘤1 H-MRS与对侧相应正常区域对比均表现为Cho峰升高,NAA、Cr峰下降。12例胶质母细胞瘤中,显示Lip峰者11例。20例脑转移瘤中,11例见Lac峰升高,9例Lip峰升高。2高级别星形细胞瘤肿瘤实体区的Cho/NAA明显高于脑转移瘤(P0.05);高级别星形细胞瘤瘤周水肿的Cho/Cr、Cho/NAA明显高于脑转移瘤(P0.05)。结论:3.0T1 H-MRS分析对高级别星形细胞瘤、脑单发转移瘤的诊断和鉴别诊断有重要价值,可作为一种非损伤性的鉴别手段;肿瘤瘤周水肿带的波谱更有利于胶质瘤与转移瘤的鉴别。     

脑胶质瘤周围区的~1H-MRS研究

目的应用多体素氢质子磁共振波谱(1H-MRS)探讨胶质瘤周围区脑代谢改变的特点,评价多体素1H-MRS在胶质瘤周围区的应用价值。方法23例病理证实的脑胶质瘤病人分为低级别组(WHOⅠ～Ⅱ级)13例和高级别组(WHOⅢ～Ⅳ级)10例,所有病例术前均行多体素1H-MRS检查,测量肿瘤实质区、周围区及对侧正常脑组织区代谢产物的相对定量,进行统计学比较。结果多体素1H-MRS显示高级别胶质瘤的周围区与实质区NAA/Cr、Cho/Cr、NAA/Cho值差异有统计学意义(P值均为0.00)。高级别胶质瘤周围区与对侧正常脑组织区NAA/Cr、Cho/Cr、NAA/Cho、Glx/Cr值差异均有统计学意义(P值均为0.00);低级别胶质瘤周围区与实质区NAA/Cr、Cho/Cr、NAA/Cho值差异均有统计学意义(P值均为0.00);低级别胶质瘤周围区与对侧正常脑组织区Cho/Cr、NAA/Cho值差异均有统计学意义(P值分别为0.02、0.00);高级别与低级别胶质瘤实质区NAA/Cr、NAA/Cho、Cho/Cr、Glx/Cr值差异均有统计学意义(P值分别为0.00、0.00、0.03、0.00);高级别与低级别胶质瘤周...     

Glioma grading: sensitivity, specificity, and predictive values of perfusion MR imaging and proton MR spectroscopic imaging compared with conventional MR imaging

BACKGROUND AND PURPOSE: Sensitivity, positive predictive value (PPV), and negative predictive value (NPV) of conventional MR imaging in predicting glioma grade are not high. Relative cerebral blood volume (rCBV) measurements derived from perfusion MR imaging and metabolite ratios from proton MR spectroscopy are useful in predicting glioma grade. We evaluated the sensitivity, specificity, PPV, and NPV of perfusion MR imaging and MR spectroscopy compared with conventional MR imaging in grading primary gliomas. METHODS: One hundred sixty patients with a primary cerebral glioma underwent conventional MR imaging, dynamic contrast-enhanced T2*-weighted perfusion MR imaging, and proton MR spectroscopy. Gliomas were graded as low or high based on conventional MR imaging findings. The rCBV measurements were obtained from regions of maximum perfusion. Metabolite ratios (choline [Cho]/creatine [Cr], Cho/N-acetylaspartate [NAA], and NAA/Cr) were measured at a TE of 144 ms. Tumor grade determined with the three methods was then compared with that from histopathologic grading. Logistic regression and receiver operating characteristic analyses were performed to determine optimum thresholds for tumor grading. Sensitivity, specificity, PPV, and NPV for identifying high-grade gliomas were also calculated. RESULTS: Sensitivity, specificity, PPV, and NPV for determining a high-grade glioma with conventional MR imaging were 72.5%, 65.0%, 86.1%, and 44.1%, respectively. Statistical analysis demonstrated a threshold value of 1.75 for rCBV to provide sensitivity, specificity, PPV, and NPV of 95.0%, 57.5%, 87.0%, and 79.3%, respectively. Threshold values of 1.08 and 1.56 for Cho/Cr and 0.75 and 1.60 for Cho/NAA provided the minimum C2 and C1 errors, respectively, for determining a high-grade glioma. The combination of rCBV, Cho/Cr, and Cho/NAA resulted in sensitivity, specificity, PPV, and NPV of 93.3%, 60.0%, 87.5%, and 75.0%, respectively. Significant differences were noted in the rCBV and Cho/Cr, Cho/NAA, and NAA/Cr ratios between low- and high-grade gliomas (P <.0001,.0121,.001, and.0038, respectively). CONCLUSION: The rCBV measurements and metabolite ratios both individually and in combination can increase the sensitivity and PPV when compared with conventional MR imaging alone in determining glioma grade. The rCBV measurements had the most superior diagnostic performance (either with or without metabolite ratios) in predicting glioma grade. Threshold values can be used in a clinical setting to evaluate tumors preoperatively for histologic grade and provide a means for guiding treatment and predicting postoperative patient outcome.     

Evaluation of different cerebral mass lesions by perfusion-weighted MR imaging

PURPOSE: To investigate the contribution of perfusion-weighted MR imaging (PWI) by using the relative cerebral blood volume (rCBV) ratio in the differential diagnosis of various intracranial space-occupying lesions. MATERIALS AND METHODS: This study involved 105 patients with lesions (high-grade glioma (N=26), low-grade glioma (N=11), meningioma (N=23), metastasis (N=25), hemangioblastoma (N=6), pyogenic abscess (N=4), schwannoma (N=5), and lymphoma (N=5)). The patients were examined with a T2*-weighted (T2*W) gradient-echo single-shot EPI sequence. The rCBV ratios of the lesions were obtained by dividing the values obtained from the normal white matter. Statistical analysis was performed with the Mann-Whitney U-test. A P-value less than 0.05 was considered statistically significant. RESULTS: The rCBV ratio was 5.76+/-3.35 in high-grade gliomas, 1.69+/-0.51 in low-grade gliomas, 8.02+/-3.89 in meningiomas, 5.27+/-3.22 in metastases, 11.36+/-4.41 in hemangioblastomas, 0.76+/-0.12 in abscesses, 1.10+/-0.32 in lymphomas, and 3.23+/-0.81 in schwannomas. The rCBV ratios were used to discriminate between 1) high- and low-grade gliomas (P<0.001), 2) hemangioblastomas and metastases (P<0.05), 3) abscesses from high-grade gliomas and metastases (P<0.001), 4) schwannomas and meningiomas (P<0.001), 5) lymphomas from high-grade gliomas and metastases (P<0.001), and 6) typical meningiomas and atypical meningiomas (P<0.01). CONCLUSION: rCBV ratios can help discriminate intracranial space-occupying lesions by demonstrating lesion vascularity. It is possible to discriminate between 1) high- and low-grade gliomas, 2) hemangioblastomas and other intracranial posterior fossa masses, 3) abscesses from high-grade gliomas and metastases, 4) schwannomas and meningiomas, 5) lymphomas and high-grade gliomas and metastases, and 6) typical and atypical meningiomas.     

Multiparametric 3T MR approach to the assessment of cerebral gliomas: tumor extent and malignancy

Introduction Contrast-enhanced MR imaging is the method of choice for routine assessment of brain tumors, but it has limited sensitivity and specificity. We verified if the addition of metabolic, diffusion and hemodynamic information improved the definition of glioma extent and grade.Methods Thirty-one patients with cerebral gliomas (21 high- and 10 low-grade) underwent conventional MR imaging, proton MR spectroscopic imaging (¹H-MRSI), diffusion weighted imaging (DWI) and perfusion weighted imaging (PWI) at 3 Tesla, before undergoing surgery and histological confirmation. Normalized metabolite signals, including choline (Cho), N-acetylaspartate (NAA), creatine and lactate/lipids, were obtained by ¹H-MRSI; apparent diffusion coefficient (ADC) by DWI; and relative cerebral blood volume (rCBV) by PWI.Results Perienhancing areas with abnormal MR signal showed 3 multiparametric patterns: “tumor”, with abnormal Cho/NAA ratio, lower ADC and higher rCBV; “edema”, with normal Cho/NAA ratio, higher ADC and lower rCBV; and “tumor/edema”, with abnormal Cho/NAA ratio and intermediate ADC and rCBV. Perienhancing areas with normal MR signal showed 2 multiparametric patterns: “infiltrated”, with high Cho and/or abnormal Cho/NAA ratio; and “normal”, with normal spectra. Stepwise discriminant analysis showed that the better classification accuracy of perienhancing areas was achieved when regarding all MR variables, while ¹H-MRSI variables and rCBV better differentiated high- from low-grade gliomas.Conclusion Multiparametric MR assessment of gliomas, based on ¹H-MRSI, PWI and DWI, discriminates infiltrating tumor from surrounding vasogenic edema or normal tissues, and high- from low-grade gliomas. This approach may provide useful information for guiding stereotactic biopsies, surgical resection and radiation treatment.     

Disarrangement of fiber tracts and decline of neuronal density correlate in glioma patients--a combined diffusion tensor imaging and 1H-MR spectroscopy study

BACKGROUND AND PURPOSE: Diffusion tensor imaging (DTI) and MR spectroscopy are noninvasive, quantitative tools for the preoperative assessment of gliomas with which the quantitative parameter fractional anisotropy (FA) and the concentration of neurometabolites N-acetylaspartate (NAA), choline (Cho), creatine (Cr) of the brain can be determined. Measurements of FA and NAA reflect the integrity of fiber tracts and the presence of neurons, respectively. This investigation examines changes of FA and NAA and compares these different aspects in architecture of gliomas after spatial coregistration. METHODS: DTI and chemical shift (1)H-MR spectroscopy was performed in 34 healthy volunteers and 69 patients with histologically confirmed (n = 48) or morphologically suspected (n = 21) non-necrotic brain glioma. Volumes of interest (VOIs) were placed in the tumor center (TC), the tumor border (TB), the normal-appearing white matter adjacent to the tumors (TNWM), and in the white matter of the contralateral hemisphere (NWMC). Median FA values and NAA/Cr and NAA/Cho ratios were calculated in the patients' VOIs and the gray and white matter of the volunteers. Correlations of FA values and NAA ratios were calculated. RESULTS: Continuous changes of FA and NAA from the tumor center to the periphery (the adjacent white matter and the contra-lateral hemisphere, respectively) were observed, where median values were: TC: 0.73 +/- 0.45, 0.47 +/- 0.58, 0.17 +/- 0.15 (NAA/Cr, NAA/Cho, FA); TB: 1.06 +/- 0.53, 1.00 +/- 0.15, 0.23 +/- 0.08; TNWM: 1.42 +/- 2.48, 1.21 +/- 0.95, 0.34 +/- 0.09; and NWMC: 1.63 +/- 0.72, 1.56 +/- 1.34, 0.38 +/- 0.08. Correlation of median FA values and NAA ratios in the cumulative group of patients was high (r = 0.99 [NAA/Cr], 0.95 [NAA/ Cho] at P < .01). Correlation between the individual NAA ratios and the FA values was moderate (r = 0.53 [NAA/Cr], 0.51 [NAA/Cho] at P < .01). CONCLUSION: In gliomas, the degree of tissue organization decreases continuously from the surrounding tissue toward the center of the tumor accompanied by a concordant decrease of NAA. This uniform behavior of FA and NAA reflects a decreasing integrity of both neuronal structures and fibers.     

Characterization of intracranial mass lesions with in vivo proton MR spectroscopy.

PURPOSETo assess the use of in vivo proton MR spectroscopy for characterization of intracranial mass lesions and to ascertain its reliability in grading of gliomas.METHODSOne hundred twenty patients with intracranial masses were subjected to volume selective spectroscopy using stimulated echo acquisition mode (echo time, 20 and 270 milliseconds) and spin echo (echo time, 135 milliseconds) sequences. The intracranial lesions were grouped into intraaxial and extraaxial, as judged with MR imaging. Assignment of resonances was confirmed in two samples each of brain abscess, epidermoid cyst, and tuberculoma using ex vivo high-resolution MR spectroscopy.RESULTSThe in vivo spectra appeared distinct compared with normal brain in all the cases. All high-grade gliomas (n = 37) showed high choline and low or absent N-acetyl-L-aspartate and creatine along with lipid and/or lactate, whereas low-grade gliomas (n = 23) were characterized by low N-acetyl-aspartate and creatine and high choline and presence of only lactate. N-acetyl-aspartate/choline ratio was significantly lower and choline/creatine ratio was significantly higher in high-grade gliomas than in low-grade gliomas. Presence of lipids suggested a higher grade of malignancy. All metastases (n = 7) showed lipid and lactate, whereas choline was visible in only four cases. Epidermoids showed resonances from lactate and an unassigned resonance at 1.8 ppm. Meningiomas could be differentiated from schwannomas by the presence of alanine in the former. Among the infective masses, pyogenic abscesses (n = 6) showed resonances only from cytosolic amino acids, lactate, alanine, and acetate; and tuberculomas (n = 11) showed only lipid resonances.CONCLUSIONSIn vivo proton MR spectroscopy, helps in tissue characterization of intracranial mass lesions. Spectroscopy is a reliable technique for grading of gliomas when N-acetyl-aspartate/choline and choline/creatine ratios and presence of lipids are used in combination.     

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.     

Measurements of diagnostic examination performance using quantitative apparent diffusion coefficient and proton MR spectroscopic imaging in the preoperative evaluation of tumor grade in cerebral gliomas

Purpose

Tumor grading is very important both in treatment decision and evaluation of prognosis. While tissue samples are obtained as part of most therapeutic approaches, factors that may result in inaccurate grading due to sampling error (namely, heterogeneity in tissue sampling, as well as tumor-grade heterogeneity within the same tumor specimen), have led to a desire to use imaging better to ascertain tumor grade. The purpose in our study was to evaluate the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), area under the curve (AUC), and accuracy of diffusion-weighted MR imaging (DWI), proton MR spectroscopic imaging (MRSI) or both in grading primary cerebral gliomas.

Materials and methods

We performed conventional MR imaging (MR), DWI, and MRSI in 74 patients with newly diagnosed brain gliomas: 59 patients had histologically verified high-grade gliomas: 37 glioblastomas multiform (GBM) and 22 anaplastic astrocytomas (AA), and 15 patients had low-grade gliomas. Apparent diffusion coefficient (ADC) values of tumor and peritumoral edema, and ADC ratios (ADC in tumor or peritumoral edema to ADC of contralateral white matter, as well as ADC in tumor to ADC in peritumoral edema) were determined from three regions of interest. The average of the mean, maximum, and minimum for ADC variables was calculated for each patient. The metabolite ratios of Cho/Cr and Cho/NAA at intermediate TE were assessed from spectral maps in the solid portion of tumor, peritumoral edema and contralateral normal-appearing white matter. Tumor grade determined with the two methods was then compared with that from histopathologic grading. Logistic regression and receiver operating characteristic (ROC) curve analysis were performed to determine optimum thresholds for tumor grading. Measures of diagnostic examination performance, such as sensitivity, specificity, PPV, NPV, AUC, and accuracy for identifying high-grade gliomas were also calculated.

Results

Statistical analysis demonstrated a threshold minimum ADC tumor value of 1.07 to provide sensitivity, specificity, PPV, and NPV of 79.7%, 60.0%, 88.7%, and 42.9% respectively, in determining high-grade gliomas. Threshold values of 1.35 and 1.78 for peritumoral Cho/Cr and Cho/NAA metabolite ratios resulted in sensitivity, specificity, PPV, and NPV of 83.3%, 85.1%, 41.7%, 97.6%, and 100%, 57.4%, 23.1% and 100% respectively for determining high-grade gliomas. Significant differences were noted in the ADC tumor values and ratios, peritumoral Cho/Cr and Cho/NAA metabolite ratios, and tumoral Cho/NAA ratio between low- and high-grade gliomas. The combination of mean ADC tumor value, maximum ADC tumor ratio, peritumoral Cho/Cr and Cho/NAA metabolite ratios resulted in sensitivity, specificity, PPV, and NPV of 91.5%, 100%, 100% and 60% respectively.

Conclusion

Combining DWI and MRSI increases the accuracy of preoperative imaging in the determination of glioma grade. MRSI had superior diagnostic performance in predicting glioma grade compared with DWI alone. The predictive values are helpful in the clinical decision-making process to evaluate the histologic grade of tumors, and provide a means of guiding treatment.     

Analysis of the spatial characteristics of metabolic abnormalities in newly diagnosed glioma patients

PURPOSE: To evaluate the role of 3D MR spectroscopic imaging (MRSI) as a tool for characterizing heterogeneity within a lesion in glioma patients. MATERIALS AND METHODS: Forty-nine patients with newly diagnosed glioma were studied with 3D water-suppressed proton (1-H) MRSI. Signal intensities from choline (Cho), creatine (Cr), N-acytel aspartate (NAA), and lactate/lipid (LL) were estimated from the spectra. Regions of interest (ROIs) corresponding to the metabolic abnormalities were defined and compared with the anatomic lesions. RESULTS: This study showed that the tumor burden measured with either the volumes of the metabolic abnormalities or the metabolic levels in the most abnormal voxels was correlated with the degree of malignancy of the tumor. The volumes of elevated Cho and decreased NAA were useful for distinguishing low-grade from high-grade lesions. The volume of abnormal LL was correlated with the existence of necrosis and with the volume of contrast-enhancing lesions in high-grade lesions. The differences in the volume of abnormal LL were also statistically significant between patients in each grade. CONCLUSION: These 3D-MRSI data provide important additional information to conventional MRI for evaluating and characterizing gliomas.