Metabolic and molecular imaging in neuro-oncology (original) (raw)
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Nuclear magnetic resonance (NMR) has been used to detect the chemicals earlier before the clinical application of magnetic resonance imaging (MRI). Since late 1980s, magnetic resonance spectroscopy (MRS) became popular with the advancement of MRI. Previous studies on in vitro NMR and in vivo MRS elucidate the effectiveness of its clinical application in different areas. We performed this study, which combines MRI and in vivo MRS, to evaluate the metabolic status of different brain tumors. We prospectively evaluated the patients with brain tumor by Single-Voxel Proton Brain Spectroscopy Exam (PROBE / SV) in 2000 and 2001. Eight glioblastoma multiformes, 5 astrocytomas, 3 meningiomas, 4 lung carcinomas with brain metastases, and 15 normal brains as the control group were included in this study. The spectra of metabolite peaks of the N-acetylaspartate (NAA), Creatine (Cr) and Choline (Cho) of the brain tumors were evaluated and compared with that of the control group. As compared with the control group, the quantitative peak ratio of NAA/Cho was significantly decreased in lesions of glioblastoma, astrocytoma, meningioma, and metastasis. The NAA/Cr and Cr/Cho peak ratios were also significantly decreased in glioblastoma and astrocytoma; on the contrary, the Cho/Cr peak ratio was increased. In patients with carcinoma of lung with brain metastasis, the NAA/Cho was significantly higher than the glioblastoma. When a focal mass lesion was detected on MRI, and the spectroscopy showed marked decrease of NAA/Cho, NAA/Cr and Cr/Cho ratios, either astrocytoma or glioblastoma should be highly considered. If the mass lesion showed higher NAA/Cho peak ratio, and the patient already had a primary malignancy, metastasis was the most likely diagnosis as compared with glioblastoma, astrocytoma and meningioma.
Emerging MR Imaging and Spectroscopic Methods to Study Brain Tumor Metabolism
Frontiers in Neurology, 2022
Proton magnetic resonance spectroscopy (1H-MRS) provides a non-invasive biochemical profile of brain tumors. The conventional 1H-MRS methods present a few challenges mainly related to limited spatial coverage and low spatial and spectral resolutions. In the recent past, the advent and development of more sophisticated metabolic imaging and spectroscopic sequences have revolutionized the field of neuro-oncologic metabolomics. In this review article, we will briefly describe the scientific premises of three-dimensional echoplanar spectroscopic imaging (3D-EPSI), two-dimensional correlation spectroscopy (2D-COSY), and chemical exchange saturation technique (CEST) MRI techniques. Several published studies have shown how these emerging techniques can significantly impact the management of patients with glioma by determining histologic grades, molecular profiles, planning treatment strategies, and assessing the therapeutic responses. The purpose of this review article is to summarize the ...
Journal of Neuro-Oncology, 2012
Magnetic resonance spectroscopic imaging (MRSI) and 18 F-fluorodeoxyglucose positron emission tomography (FDG-PET) are non-invasive imaging techniques routinely used to evaluate tumor malignancy in adults with brain tumors. We compared the metabolic activity of pediatric brain tumors using FDG-PET and MRSI. Children (n = 37) diagnosed with a primary brain tumor underwent FDG-PET and MRSI within two weeks of each other. Tumor metabolism was classified as inactive, active or highly active using the maximum choline:N-acetyl-asparate (Cho:NAA) on MRSI and the highest tumor uptake on FDG-PET. A voxel-wise comparison was used to evaluate the area with the greatest abnormal metabolism. Agreement between methods was assessed using the percent agreement and the kappa statistic (j). Pediatric brain tumors were metabolically heterogeneous on FDG-PET and MRSI studies. Active tumor metabolism was observed more frequently using MRSI compared to FDG-PET, and agreement in tumor classification was weak (j = 0.16, p = 0.12), with 42 % agreement (95 % CI = 25-61 %). Voxel-wise comparison for identifying the area of greatest metabolic activity showed overlap in the majority (62 %) of studies, though exact agreement between techniques was low (29.4 %, 95 % CI = 15.1-47.5 %). These results indicate that FDG-PET and MRSI detect similar but not always identical regions of tumor activity, and there is little agreement in the degree of tumor metabolic activity between the two techniques.
Brain tumours and their metabolic profiles by magnetic resonance spectroscopy
Malaysian Journal of Medicine and Health Sciences, 2020
Introduction: Intracranial brain tumour like meningiomas and glioblastomas are most prevalent tumour. The metastasis to the brain is one of the major issues in the tumours of the central nervous system. The diagnosis of metastatic and primary brain tumour is incomprehensible with standard magnetic resonance imaging (MRI). The magnetic resonance spectroscopy (MRS) is basically performed in standard clinical setting for diagnosing and tracking the brain tumour. Method: It is a retrospective study containing 53 patients with MRS. The patients with metastatic tumour (n=10), glioblastomas (n=8) and meningiomas (n=20) are included in the study. Single voxel technique is applied in the tumour core to determine the metabolites. The tumour N-acetyl aspartate (NAA), Choline (Cho), Creatine (Cr), Lactate, Alanine and lipids were analysed. The ratios of NAA/Cr, Cho/NAA and Cho/Cr were recorded and compared between the three tumours. The metabolites were detected between short echo time (TE) to long echo time (TE) during MRS. Results: There is a sharp fall of NAA peak in metastatic tumour. The resonance of creatine, lactate and alanine is higher in glioblastomas. A high lipid mean value of 3.13(0.17) is seen in metastatic tumour. The ROC curve shows a low NAA/Cr specificity of 46.7%, high sensitivity of 83.3% in Cho/NAA and Cho/Cr ratio. Conclusion: The metabolic profiles of metastatic brain tumour, glioblastomas and meningioma illustrate a divergence in their description that will assist in planning therapeutic and surgical intervention of these tumours.
Journal of Nuclear Medicine, 2008
The aim of this study was to determine the spatial correlation of O-(2-18 F-fluoroethyl)-L-tyrosine (18 F-FET) uptake and the concentrations of choline (Cho), creatine (Cr), and total N-acetylaspartate (tNAA) determined with proton magnetic resonance spectroscopic imaging (1 H MRSI) in cerebral gliomas for the multimodal evaluation of metabolic changes. Methods: 18 F-FET PET and 2-dimensional 1 H MRSI were performed in 15 patients with cerebral gliomas of World Health Organization (WHO) grades II-IV. PET and 1 H MRSI datasets were coregistered by use of mutual information. On the basis of their levels of 18 F-FET uptake, 4 different areas in a tumor (maximum, strong, moderate, and low 18 F-FET uptake) were defined on PET slices as being congruent with the volume of interest in the 1 H MRSI experiment. 18 F-FET uptake in lesions was evaluated as tumorto-brain ratios. Metabolite concentrations for Cho, Cr, and tNAA and Cho/tNAA ratios were computed for these 4 areas in the tumor and for the contralateral normal brain. Results: In the area with maximum 18 F-FET uptake, the concentration of tNAA (R 5 20.588) and the Cho/tNAA ratio (R 5 0.945) correlated significantly with 18 F-FET uptake. In the areas with strong and moderate 18 F-FET uptake, only the Cho/tNAA ratios (R 5 0.811 and R 5 0.531, respectively) were significantly associated with amino acid transport. At low 18 F-FET uptake, analysis of the correlations of amino acid uptake and metabolite concentrations yielded a significant result only for the concentration of Cr (R 5 0.626). No correlation was found for metabolite concentrations determined with 1 H MRSI and 18 F-FET uptake in normal brain tissue. Maximum 18 F-FET uptake and the tNAA concentration were significantly different between gliomas of WHO grades II and IV, with P values of 0.032 and 0.016, respectively. Conclusion: High 18 F-FET uptake, which is indicative of tumor cell infiltration, associates with neuronal cell loss (tNAA) and changes in ratios between parameters representing membrane proliferation and those of neuronal loss (Cho/tNAA ratio), which can be measured by 1 H MRSI. The significant correlation coefficients detected for Cr in regions with low 18 F-FET uptake suggests an association between the mechanism governing amino acid transport and energy metabolism in areas that are infiltrated by tumor cells to a lesser extent. These findings motivate further research directed at investigating the potential of 1 H MRSI to define tumor boundaries in a manner analogous to that of amino acid PET.
PET for diagnosis and therapy of brain tumors
Médecine Nucléaire, 2011
Main contribution of PET in the management of brain tumors is at the therapeutic level. Specific reasons explain this role of molecular imaging in the therapeutic management of brain tumors, especially gliomas. Gliomas are by nature infiltrating neoplasms and the interface between tumor and normal brain tissue may not be accurately defined on CT and MRI. Also, gliomas are often histologically heterogeneous with anaplastic areas evolving within a low-grade tumor, and the contrast-enhancement on CT or MRI does not represent a good marker for anaplastic tissue detection. Finally, assessment of tumor residue, recurrence or progression may be altered by different signals related to inflammation or adjuvant therapies, even on contrast-enhanced CT and MRI. These limitations of the conventional neuroimaging in delineating tumor and detecting anaplastic tissue lead to potential inaccuracy in lesion targeting at different steps of the management (diagnostic, surgical, and post-therapeutic stages). Molecular information provided by PET has proved helpful to supplement morphological imaging data in this context. 18 F-FDG (FDG) and amino-acid tracers such as 11 C-methionine (MET), provides complementary metabolic data that are independent from the anatomical MR information. These tracers help in the definition of glioma extension, in the detection of anaplastic areas and in the postoperative follow-up. Additionally, PET data have an independent prognostic value. To take advantage of PET data in glioma treatment, PET might be integrated in the planning of imageguided biopsies, radiosurgery and resection.
Overview of PET Tracers for Brain Tumor Imaging
PET Clinics, 2013
This article provides an overview of the key considerations for the development and application of molecular imaging agents for brain tumors, and the major classes of PET tracers that have been used for imaging brain tumors in humans. The most widely used PET tracers for this application are the glucose analogue 2-deoxy-2-[ 18 F]fluoro-D-glucose (18 F-FDG), radiolabeled amino acids (eg, 11 C-MET, 18 F-FET, 18 F-FDOPA), and the nucleoside analogue 3 0-deoxy-3 0-fluorothymidine (18 F-FLT). Other PET tracers that have been evaluated in patients with brain tumor include hypoxia imaging agents, [ 11 C]choline, [ 11 C]acetate, and the 68 Ga-labeled somatostatin receptor ligands DOTATOC and DOTATATE. The available data indicate that several of these classes of tracers, including radiolabeled amino acids, have imaging properties superior to those of 18 F-FDG, and can complement contrastenhanced magnetic resonance imaging for estimation of tumor volume, evaluation of nonenhancing gliomas, monitoring of response to therapy, and distinguishing recurrent tumors from treatment effects including radiation necrosis.
Metabolic imaging of low-grade gliomas with three-dimensional magnetic resonance spectroscopy
International Journal of Radiation Oncology*Biology*Physics, 2002
Purpose: The role of radiotherapy (RT) seems established for patients with low-grade gliomas with poor prognostic factors. Three-dimensional (3D) magnetic resonance spectroscopy imaging (MRSI) has been reported to be of value in defining the extent of glioma infiltration. We performed a study examining the impact MRSI would have on the routine addition of 2-3-cm margins around MRI T2-weighted hyperintensity to generate the treatment planning clinical target volume (CTV) for low-grade gliomas. Methods and Materials: Twenty patients with supratentorial gliomas WHO Grade II (7 astrocytomas, 6 oligoastrocytomas, 7 oligodendrogliomas) underwent MRI and MRSI before surgery. The MRI was contoured manually; the regions of interest included T2 hyperintensity and, if present, regions of contrast enhancement on T1-weighted images. The 3D-MRSI peak parameters for choline and N-acetyl-aspartate, acquired voxel-by-voxel, were categorized using a choline/N-acetyl-aspartate index (CNI), a tool for quantitative assessment of tissue metabolite levels, with CNI 2 being the lowest value corresponding to tumor. CNI data were aligned to MRI and displayed as 3D contours. The relationship between the anatomic and metabolic information on tumor extent was assessed by comparing the CNI contours and other MRSI-derived metabolites to the MRI T2 volume. Results: The limitations in the size of the region "excited" meant that MRSI could be used to evaluate only a median 68% of the T2 volume (range 38 -100%), leaving the volume T2c. The CNI 2 volume (median 29 cm 3 , range 10 -73) was contained totally within the T2c in 55% of patients. In the remaining patients, the volume of CNI 2 extending beyond the T2c was quite small (median 2.3 cm 3 , range 1.4 -5.2), but was not distributed uniformly about the T2c, extending up to 22 mm beyond it. Two patients demonstrated small regions of contrast enhancement corresponding to the regions of highest CNI. Other metabolites, such as creatine and lactate, seem useful for determining less and more radioresistant areas, respectively. Conclusion: Metabolically active tumor, as detected by MRSI, is restricted mainly to the T2 hyperintensity in low-grade gliomas, but can extend outside it in a limited and nonuniform fashion up to 2 cm. Therefore, a CTV including T2 and areas of CNI extension beyond the T2 hyperintensity would result in a reduction in the size and a change in the shape of the standard clinical target volumes generated by adding uniform margins of 2-3 cm to the T2 hyperintensity.