11C-methionine Positron Emission Tomography Research Articles

11C-Methionine uptake in secondary brain epilepsy

Carbon-11 methionine ((11)C-Methionine) is a radio-labeled amino acid currently utilized in Positron Emission Tomography (PET) for imaging primary and metastatic brain tumors. Its clinical use relies mostly on oncologic applications, but the tracer has the potential to investigate other non-malignant conditions. So far, very limited evidence concerns the use of (11)C-Methionine in patients suffering from seizure; however, the tracer can find a proper utilization in this setting especially as a diagnostic complement to (18)F-Fluorodeoxyglucose ((18)F-FDG). Herein we report the case of a 57-year-old patient presenting with epileptic crises secondary to a brain metastasis from bladder carcinoma, who was investigated in our institution with (11)C-Methionine PET. The scan documented the disease recurrence in the left parietal lobe associated with a diffused tracer uptake in the surrounding cerebral circumvolutions, derived from the comitial status. After surgical removal of the metastatic lesion, the patient experienced a complete recovery of symptoms and no further onset of secondary seizure.

Advantage of 11C-methionine positron emission tomography for assessing IgG4-related central nervous system lesions

Advantage of 11C-methionine positron emission tomography for assessing IgG4-related central nervous system lesions

Hypofractionated high-dose irradiation with positron emission tomography data for the treatment of glioblastoma multiforme.

This research paper presents clinical outcomes of hypofractionated high-dose irradiation by intensity-modulated radiation therapy (Hypo-IMRT) with 11C-methionine positron emission tomography (MET-PET) data for the treatment of glioblastoma multiforme (GBM). A total of 45 patients with GBM were treated with Hypo-IMRT after surgery. Gross tumor volume (GTV) was defined as the area of enhanced lesion on MRI, including MET-PET avid region; clinical target volume (CTV) was the area with 5 mm margin surrounding the GTV; planning target volume (PTV) was the area with 15 mm margin surrounding the CTV, including MET-PET moderate region. Hypo-IMRT was performed in 8 fractions; planning the dose for GTV was escalated to 68 Gy and that for CTV was escalated to 56 Gy, while keeping the dose delivered to the PTV at 40 Gy. Concomitant and adjuvant TMZ chemotherapy was administered. At a median follow-up of 18.7 months, median overall survival (OS) was 20.0 months, and median progression-free survival was 13.0 months. The 1- and 2-year OS rates were 71.2% and 26.3%, respectively. Adjuvant TMZ chemotherapy was significantly predictive of OS on multivariate analysis. Late toxicity included 7 cases of Grade 3-4 radiation necrosis. Hypo-IMRT with MET-PET data appeared to result in favorable survival outcomes for patients with GBM.

Detection of glioma recurrence by 11C-methionine positron emission tomography and dynamic susceptibility contrast-enhanced magnetic resonance imaging

This study aimed to compare the diagnostic value of ¹¹C-methionine (¹¹C-MET) PET and dynamic susceptibility contrast-enhanced (DSCE) MRI in detecting glioma recurrence by meta-analysis. Databases such as PubMed (MEDLINE included), EMBASE, Science Direct, Springerlink, EBSCO, and Cochrane Database of Systematic Review were searched for relevant original articles on the detection of recurrent glioma using DSCE MRI or ¹¹C-MET PET with or without computed tomography. No restriction was imposed over the types and grades of glioma. The included studies were assessed for methodological quality. Results from histopathological analysis and/or close clinical and/or radiological follow-up for at least 3 months were used as the reference standard. The data were extracted by two reviewers independently to analyze the sensitivity, specificity, summary receiver-operating characteristic curve, area under the curve, and heterogeneity. The present study analyzed a total of 17 selected articles including different types and grades of glioma and showed that ¹¹C-MET PET and DSCE MRI had comparable sensitivity (0.870 and 0.884, respectively), specificity (0.813 and 0.853, respectively), positive likelihood ratio (4.355 and 5.806, respectively), negative likelihood ratio (0.192 and 0.134, respectively), and diagnostic odds ratio (21.857 and 41.918, respectively) without statistically significant differences, except for the fact that DSCE MRI displayed higher area under the curve and Q* index compared with ¹¹C-MET PET (P<0.05). Both ¹¹C-MET PET and DSCE MRI are accurate tools for detecting glioma recurrence. Although DSCE MRI seems to be superior to ¹¹C-MET PET, the latter can also be used to assess glioma recurrence when the former is not available.

Analysis of progression and recurrence of meningioma using 11C-methionine PET

The recurrence rate of meningioma after surgery is high, and progression is often observed. The risk factors for recurrence and progression are not clear. We evaluated the risk factors for recurrence and progression in meningioma using (11)C-methionine (MET) positron emission tomography (PET). Thirty-seven patients (mean follow-up, 80 months) with an intracranial meningioma were enrolled. MET PET was performed before treatment between 1995 and 2010, and patients were followed up in an out-patient clinic. Surgery was performed in 33 patients, and a wait-and-see approach was taken in four patients. We evaluated the extent of tumor resection, location, WHO grade, Ki-67 labeling index, and lesion to normal ratio (LN ratio) of MET uptake. Six of the surgical cases had a recurrence, and two of the observation-only patients had tumor progression. A high LN ratio of MET uptake was a significant risk factor for recurrence and progression with univariate analysis. The area under the curve of receiver operating characteristic curve for the LN ratio of MET uptake was 0.754, and the optimal cutoff value was 3.18 (sensitivity 63 %, specificity 79 %). With multivariate analysis, a high LN ratio of MET uptake, non-gross total resection, and a high WHO grade were significant risk factors for progression and recurrence. A high LN ratio of MET uptake was a risk factor for tumor progression and recurrence. The advantage of MET PET is that it is not invasive and can easily be used to evaluate the whole tumor.

Perfusion and diffusion MRI combined with 11C-methionine PET in the preoperative evaluation of suspected adult low-grade gliomas

Perfusion and diffusion magnetic resonance imaging (pMRI, dMRI) are valuable diagnostic tools for assessing brain tumors in the clinical setting. The aim of this study was to determine the correlation of pMRI and dMRI with 11C-methionine positron emission tomography (MET PET) in suspected low-grade gliomas (LGG) prior to surgery. Twenty-four adults with suspected LGG were enrolled in an observational study and examined by MET PET, pMRI and dMRI. Histological tumor diagnosis was confirmed in 23/24 patients (18 gliomas grade II, 5 gliomas grade III). The maximum relative cerebral blood volume (rCBVmax) and the minimum mean diffusivity (MDmin) were measured in tumor areas with highest MET uptake (hotspot) on PET by using automated co-registration of MRI and PET scans. A clearly defined hotspot on PET was present in all 23 tumors. Regions with rCBVmax corresponded with hotspot regions in all tumors, regions with MDmin corresponded with hotspot regions in 20/23 tumors. The correlation between rCBVmax (r = 0.19, P = 0.38) and MDmin (r = −0.41, P = 0.053) with MET uptake in the hotspot was not statistically significant. Taken into account the difficulties of measuring perfusion abnormalities in non-enhancing gliomas, this study demonstrates that co-registered MET PET and pMRI facilitates the identification of regions with rCBVmax. Furthermore, the lack of a clear positive correlation between tumor metabolism in terms of MET uptake and tumor vascularity measured as rCBVmax suggests that combined pMRI/PET provides complementary baseline imaging data in these tumors.

The demonstration of extension of high-grade glioma beyond magnetic resonance imaging defined edema by the use of 11 C-methionine positron emission tomography

The use of magnetic resonance imaging (MRI) is the current standard for the delineation of target volumes for high-grade gliomas (HGG). While the peritumoral edema as per T2-weighted (T2W) imaging is utilized as basis to delineate the initial borders of the clinical target volume (CTV), those areas enhancing on T1-weighted (T1W) images with gadolinium contrast (T1-Gd) are considered for treatment with further boost. However, recent data has emerged concerning the use of positron emission tomography (PET) with 11 C-methionine, which seemingly provides additional information beyond MRI. We present the case of a gentleman with an inoperable HGG which was imaged with 11 C-methionine-PET ( 11 C-MET-PET)/CT as well as MRI as part of the radiotherapy treatment planning (RTP) process. The differences noted between the MRI and the PET defined volumes are presented. This being a patient who was not operated, the potentially confounding issue of surgery-induced PET-avidity is absent.

Invited Commentary

Invited Commentary

425P - Clinical Impact of [11C]-Methionine Positron Emission Tomography on the Treatment of Primary and Recurrent Gliomas

ABSTRACT Purpose To assess whether 11C-methionine positron emission tomography (11C-MET PET) has a clinical significance in the management of glioma patients. Patients and methods Fifty-three patients with histologically proven primary gliomas (16 grade II, 15 grade III, and 22 grade IV) were investigated repeatedly with 11C-MET PET. A total of 249 PET scans were performed, with a median of 4 scans for each patient. Functional imaging with PET was compared with concurrent MRI or CT. Results We registered high sensibility and specificity in the management of glioma patients. The mean 11C-MET uptake index results significantly correlated with histological grade. The overall survival (OS) of GBM patients who underwent 11C-MET PET serial controls and parallel CT or MRI scans resulted to be 29.24 months, significantly higher compared to OS of GBM who underwent CT or MRI alone during follow up. Conclusion 11C-MET PET allowed the detection of malignant progression in low grade glioma patients and the assessment of post-surgery status in both low and anaplastic gliomas with high sensibility and specificity. Thus, 11C-MET PET expresses its maximum potential in earlier disclosing recurrence during the long-term follow-up of GBM patients, with a relevant impact on therapeutic course and survival of these patients. Disclosure All authors have declared no conflicts of interest.

Usefulness of 11C-Methionine Positron Emission Tomography in Differential Diagnosis between Recurrent Tumours and Radiation Necro-sis in Patients with Glioma: An Overview

Usefulness of 11C-Methionine Positron Emission Tomography in Differential Diagnosis between Recurrent Tumours and Radiation Necro-sis in Patients with Glioma: An Overview

Usefulness of 11C-Methionine Positron Emission Tomography in Differential Diagnosis between Recurrent Tumours and Radiation Necro-sis in Patients with Glioma: An Overview

Usefulness of 11C-Methionine Positron Emission Tomography in Differential Diagnosis between Recurrent Tumours and Radiation Necro-sis in Patients with Glioma: An Overview

Diagnostic Value of 11C-Methionine (MET) and 18F-Fluorothymidine (FLT) Positron Emission Tomography in Recurrent High-Grade Gliomas; Differentiation from Treatment-Induced Tissue Necrosis

We retrospectively evaluated the usefulness of combined measurement of L-methyl-[11C]methionine (MET) and 3'-deoxy-3'-[18F]fluorothymidine (FLT) positron emission tomography (PET) in the differential diagnosis between recurrent gliomas and necrotic lesions. Twenty-one patients with high-grade glioma, previously treated with surgery and radiotherapy with chemotherapy and first radiological suspicion of recurrence were enrolled. The uptake was assessed by the maximum standardized uptake value (SUVmax) and lesion-to-normal tissue count density ratio (L/N ratio). Of the 21 lesions, 15 were diagnosed recurrent gliomas and six were necrotic lesions. The average SUVmax was not significantly different between recurrent gliomas and necrotic lesions on either MET-PET or FLT-PET. The average L/N ratio of recurrent gliomas (3.36 ± 1.06) was significantly higher than that of necrotic lesions (2.18 ± 0.66) on MET-PET (p < 0.01) and the average L/N ratio of recurrent gliomas (7.01 ± 2.26) was also significantly higher than that of necrotic lesions (4.60 ± 1.23) on FLT-PET (p < 0.01). ROC curve analysis showed that the areas under the curves were high but not different between MET- and FLT-PET. PET studies using MET and FLT are useful in the differentiation of recurrent glioma from treatment-induced necrotic lesion. However, there is no complementary information in the differentiation with simultaneous measurements of MET- and FLT-PET.

Quantitative volumetric analysis of gliomas with sequential MRI and 11C-methionine PET assessment: patterns of integration in therapy planning

The aim of the study was to evaluate the volumetric integration patterns of standard MRI and (11)C-methionine positron emission tomography (PET) images in the surgery planning of gliomas and their relationship to the histological grade. We studied 23 patients with suspected or previously treated glioma who underwent preoperative (11)C-methionine PET because MRI was imprecise in defining the surgical target contour. Images were transferred to the treatment planning system, coregistered and fused (BrainLAB). Tumour delineation was performed by (11)C-methionine PET thresholding (vPET) and manual segmentation over MRI (vMRI). A 3-D volumetric study was conducted to evaluate the contribution of each modality to tumour target volume. All cases were surgically treated and histological classification was performed according to WHO grades. Additionally, several biopsy samples were taken according to the results derived either from PET or from MRI and analysed separately. Fifteen patients had high-grade tumours [ten glioblastoma multiforme (GBM) and five anaplastic), whereas eight patients had low-grade tumours. Biopsies from areas with high (11)C-methionine uptake without correspondence in MRI showed tumour proliferation, including infiltrative zones, distinguishing them from dysplasia and radionecrosis. Two main PET/MRI integration patterns emerged after analysis of volumetric data: pattern vMRI-in-vPET (11/23) and pattern vPET-in-vMRI (9/23). Besides, a possible third pattern with differences in both directions (vMRI-diff-vPET) could also be observed (3/23). There was a statistically significant association between the tumour classification and integration patterns described above (p < 0.001, κ = 0.72). GBM was associated with pattern vMRI-in-vPET (9/10), low-grade with pattern vPET-in-vMRI (7/8) and anaplastic with pattern vMRI-diff-vPET (3/5). The metabolically active tumour volume observed in (11)C-methionine PET differs from the volume of MRI by showing areas of infiltrative tumour and distinguishing from non-tumour lesions. Differences in (11)C-methionine PET/MRI integration patterns can be assigned to tumour grades according to the WHO classification. This finding may improve tumour delineation and therapy planning for gliomas.

Clinical characteristics of meningiomas assessed by 11C-methionine and 18F-fluorodeoxyglucose positron-emission tomography

The clinical course of meningioma varies from case to case, despite similar characteristics on magnetic resonance (MR) imaging. Functional imaging including (11)C-methionine and (18)F-fluorodeoxyglucose (FDG) positron-emission tomography (PET) has been widely studied for noninvasive preoperative evaluation of brain tumors. However, few reports have examined correlations between meningiomas and findings on (11)C-methionine and FDG PET. The objective of this study was to clarify the relationship between tumor characteristics and (11)C-methionine and FDG uptake in meningiomas. For 68 meningiomas in 51 cases, (11)C-methionine uptake was evaluated by measuring both mean and maximum tumor/normal (T/N) ratio for the whole area of the tumors. FDG uptake in 44 of those meningiomas was also analyzed. Tumor size was measured volumetrically, and tumor-doubling time was estimated. Histopathological evaluation was performed in 19 surgical cases. Mean and maximum T/N ratios of (11)C-methionine PET were significantly higher in skull-base lesions than in non-skull-base lesions. Correlations of mean and maximum T/N ratio of (11)C-methionine PET with tumor-doubling time, MIB-1 labeling index, microvessel density and World Health Organization grading were not significant. Mean T/N ratio of (11)C-methionine PET correlated significantly with tumor volume according to logarithm regression modeling (P < 0.0001, R = 0.544). However, mean and maximum T/N ratio of FDG-PET correlated with none of the tumor characteristics described above. These results suggest that (11)C-methionine uptake correlates with tumor volume, but not with tumor aggressiveness.

Evaluation of Segmental Pancreatic Function Using 11C-Methionine Positron Emission Tomography for Safe Living Donor Operation of Pancreas Transplantation

For a safe living pancreas donoration for transplantation, we evaluated the function of the residual pancreas head using 11C-methionine positron emission tomography (PET) in 13 cases before and after distal pancreatectomy. After 6 hours of fasting, we intravenously administered 11C-methionine (370 to 740 MBq), performing PET at 30 minutes thereafter. 11C-methionine PET uptake in the pancreas head was expressed as a standardized uptake value (SUV) for comparison before versus after surgery: 17.3 ± 2.5 versus 17.4 ± 4.9, respectively, demonstrating no significant difference. However, the changes in SUVs of the residual pancreas head showed three patterns after surgery. The SUVs were elevated in three donors after surgery, hypermetabolite type; maintained in five donors, normometabolite type; and decreased in five donors hypometabolite type. The percentages of subjects with a postoperative HbA1c value more than 5.8%, the upper normal limit, were 33% in hypermetabolite type; 40% in the normometabolite type; and 60% in the hypometabolite type. Although diabetes mellitus has not developed in any of the 13 donors, the pancreatic head function after distal pancreatectomy was slightly decreased, especially among the hypometabolite type. To avoid postoperative diabetes mellitus for a prolonged period, donors who show decreased SUVs after surgery should be strictly followed. In conclusion, 11C-methionine PET may be a potent modality to evaluate segmental pancreatic function for a safe living donor pancreatectomy.

Imaging 18F-fluorodeoxy glucose/11C-methionine uptake decoupling for identification of tumor cell infiltration in peritumoral brain edema

Discriminating tumor infiltrative and vasogenic brain edema in malignant gliomas is important although challenging in clinical settings. This study challenged this issue by performing voxel-wise analysis of (18)F-fluorodeoxy glucose (FDG) and (11)C-methionine positron emission tomography (PET) in peritumoral brain edemas. The authors studied ten malignant glioma and nine meningioma patients with peritumoral brain edema. A voxel-wise analysis of FDG and (11)C-methionine PET was performed in order to quantify the correlation between uptake of these tracers in normal brain tissue and peritumoral brain edema. Decoupling score of the uptake of two tracers was calculated as the z-score from the estimated correlation between uptake of the two tracers in normal brain tissue. The decoupling score was also converted into images for visual inspection. Average decoupling score in the peritumoral brain edema was calculated and compared between those obtained from malignant gliomas and meningiomas. FDG and (11)C-methionine uptake showed a reproducible linear correlation in normal brain tissue. This correlation was preserved in peritumoral edema of meningioma, but not in that of malignant gliomas. In malignant gliomas, higher (11)C-methionine uptake compared to that estimated by the FDG uptake in normal brain tissue was observed, thus suggesting that decoupling was caused by tumor infiltration. Visual inspection of the decoupling score enabled discrimination of tumor infiltrative and vasogenic edema. The average decoupling scores of the peritumoral brain edema in malignant gliomas were significantly higher than those in meningiomas (2.9 vs. 0.7, P = 0.0003). As a conclusion, FDG/(11)C-methionine uptake decoupling score can be used for the discrimination of tumor infiltrative and vasogenic brain edema. The proposed method also suggests the possibility of accurately detecting tumor infiltration into brain tissues in gliomas, providing significant information for treatment planning and follow-up.

11C‐methionine uptake and intraoperative 5‐aminolevulinic acid‐induced fluorescence as separate index markers of cell density in glioma

The extent of tumor resection is acknowledged as 1 of the prognostic factors for glioma. 5-Aminolevulinic acid (5-ALA)-induced fluorescence guidance and neuronavigation integrated with (11) C-methionine positron emission tomography (PET) are widely utilized under the expectation of improving the extent of resection. These 2 novel approaches are beneficial for glioma resections, and the combination of these approaches appears rational. However, biological characteristics reflecting 5-ALA-induced fluorescence and (11) C-methionine uptake have not been clearly elucidated, and studies about the relationship between 5-ALA-induced fluorescence and (11) C-methionine uptake have been limited. The present study aimed to clarify this issue. Data from 11 consecutive patients harboring astrocytic tumors were analyzed: 2 grade II and 2 grade III, and 7 grade IV tumors were included. Thirty samples from these patients were obtained from the relative periphery of each tumor. Relationships among histology, 5-ALA-induced fluorescence and (11) C-methionine uptake were analyzed by stereotactic sampling and image analysis. Uptake of (11) C-methionine correlated with cell density (R(2) = 0.322, P = .0059). Cell density was higher in fluorescence-positive areas than in negative areas (2760 ± 1080 vs 1450 ± 1380/mm(2) , P = .0132). Although both (11) C-methionine uptake and fluorescence seemed to correlate with cell density, no significant difference in (11) C-methionine uptake was seen between fluorescence-positive and -negative areas (P = .367). Multiple linear regression analysis revealed (11) C-methionine uptake and 5-ALA-induced fluorescence as independent indices for tumor cell density. These results indicate that 5-ALA fluorescence and (11) C-methionine PET image are separate index markers for cytoreduction surgery of gliomas.

Dynamic 11C-methionine PET analysis has an additional value for differentiating malignant tumors from granulomas: an experimental study using small animal PET

We evaluated whether the dynamic profile of L-(11)C-methionine (11C-MET) may have an additional value in differentiating malignant tumors from granulomas in experimental rat models by small animal positron emission tomography (PET). Rhodococcus aurantiacus and allogenic rat C6 glioma cells were inoculated, respectively, into the right and left calf muscles to generate a rat model bearing both granulomas and tumors (n=6). Ten days after the inoculations, dynamic 11C-MET PET was performed by small animal PET up to 120 min after injection of 11C-MET. The next day, after overnight fasting, the rats were injected with 18F-2-deoxy-2-fluoro-D-glucose (18F-FDG), and dynamic 18F-FDG PET was performed up to 180 min. The time-activity curves, static images, and mean standardized uptake value (SUV) in the lesions were calculated. 11C-MET uptake in the granuloma showed a slow exponential clearance after an initial distribution, while the uptake in the tumor gradually increased with time. The dynamic pattern of 11C-MET uptake in the granuloma was significantly different from that in the tumor (p<0.001). In the static analysis of 11C-MET, visual assessment and SUV analysis could not differentiate the tumor from the granuloma in all cases, although the mean SUV in the granuloma (1.48±0.09) was significantly lower than that in the tumor (1.72±0.18, p<0.01). The dynamic patterns, static images, and mean SUVs of 18F-FDG in the granuloma were similar to those in the tumor (p=NS). Dynamic 11C-MET PET has an additional value for differentiating malignant tumors from granulomatous lesions, which deserves further elucidation in clinical settings.

Use of Positron Emission Tomography in the Evaluation of Diffuse Intrinsic Brainstem Gliomas in Children

Diffuse intrinsic brainstem gliomas (DIBSGs) in children remain difficult tumors to treat and have a very poor prognosis. Intensifying both chemotherapy and radiation programs have been attempted without success. Positron emission tomography (PET) has been used to differentiate benign from malignant tumors and may predict outcome. To determine whether PET can characterize a specific metabolic pattern of DIBSGs and correlate this with patient survival. We conducted a retrospective review of patients with DIBSGs and PET scans at diagnosis. Data for ¹⁸[F] fluorodeoxyglucose (FDG) and ¹¹C-methionine (CMET) PET scans were collected. Treatment and survival were reviewed. We identified 30 patients with DIBSGs, 25 of whom had FDG and/or CMET PET scans. Scans showed both focal and generalized metabolic activity, and the patterns showed no correlation with survival. Patients with both FDG and CMET positive scans had a mean survival of 380 days, whereas those negative for both isotopes had a mean survival of 446 days. There was no specific PET pattern identified in this DIBSG cohort but a trend toward improved survival was noted with absence of FDG and CMET metabolism. Metabolically active areas may suggest potential sites for biopsy. We believe that biopsy is essential for improving therapy for this patient population.

Discrimination between low-grade oligodendrogliomas and diffuse astrocytoma with the aid of 11C-methionine positron emission tomography

The diagnostic usefulness of (11)C-methionine PET scans in gliomas is still controversial. The authors investigated the clinical significance of (11)C-methionine PET findings in preoperative diagnosis of histological type and grade. The tissue uptake of (11)C-methionine was assessed using PET in 70 patients with histologically confirmed intracerebral gliomas. The ratio of maximum standard uptake values in tumor areas to the mean standard uptake values in the contralateral normal brain tissue (tumor/normal tissue [T/N] ratio) was calculated and correlated with tumor type, histological grade, contrast enhancement on MR imaging, Ki 67 labeling index, and 1p/19q status. The T/N ratio was significantly increased as tumor grade advanced in astrocytic tumors (WHO Grade II vs Grade III, p = 0.0011; Grade III vs Grade IV, p = 0.0007). Among Grade II gliomas, the mean T/N ratio was significantly higher in oligodendroglial tumors than in diffuse astrocytomas (DAs) (p < 0.0001). All T/N ratios for oligodendroglial tumors were ≥ 1.46, and those for DA were consistently < 1.46, with the exception of 2 cases of gemistocytic astrocytoma. The Ki 67 labeling index significantly correlated with T/N ratio in astrocytic tumors, but not in oligodendrogliomas. Oligodendroglial tumors without 1p/19q deletion had a significantly higher T/N ratio than those with the codeletion. In combination with Gd-enhanced MR imaging, 67% of nonenhanced tumors with a T/N ratio of ≥ 1.46 were proved to be Grade II oligodendrogliomas. These results clearly show that (11)C-methionine PET T/N ratios in Grade II oligodendrogliomas were higher than those in DAs independently of their proliferative activity. This information contributes to preoperative differential diagnoses of histological type, especially in suspected low-grade gliomas.