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Abstract: 11C-methionine positron emission tomography (11C-methionine PET) provides accurate detection of brain tumors. Several reports have analyzed the correlation between uptake of 11C-methionine and Ki-67 index or microvessel density non-stereotactically and suggested that 11C-methionine uptake reflects both proliferation potential and angiogenic capability in gliomas. As gliomas possess heterogeneous histological architecture, non-stereotactic comparison of the histology and 11C-methionine PET image may not be accurate. In the present study, the correlation between 11C-methionine uptake and cell or microvessel density was analyzed using histological specimens obtained by stereotactic biopsy, and an exact local comparison of 11C-methionine PET image and histological specimens was conducted. The tumor/normal tissue (T/N) ratio of 11C-methionine positron emission tomography was found to correlate better with cell density (R =0.747, p =0.000042) and Ki-67 index (R =0.675, p =0.00041) than with microvessel density (R =0.467, p =0.025) in a histological comparison using a stereotactic image. Furthermore, multiple linear regression analysis revealed that cell density was the key determinant for predicting 11C-methionine level while microvessel density was not. These results suggest that cell density contributes more to 11C-methionine uptake than microvessel density in glioma tissues and that the previously reported correlation of 11C-methionine uptake and microvessel density in glioma patients requires reevaluation. [Copyright &y& Elsevier]

Abstract: Multimodal imaging is one of the necessary steps in the treatment of malignant brain tumors, and use of magnetic resonance imaging (MRI) and positron emission tomography (PET) are the current gold standard technique for the morphological and biological assessment of malignant brain tumors. In addition, fractional anisotropy (FA) obtained from diffusion tensor imaging (DTI) and 11C-methionine PET are useful to determine the tumor border at the tumor and white matter interface. Although there is no question of their value, a universally accepted cut-off value to discriminate normal and abnormal tissue has not been established. In this study we attempted to calculate and determine the cut-off values in FA and 11C-methionine PET that will allow delineation of the tumor border at the tumor and white matter interface by combining these two modalities. We were able to determine individual cut-off values for 11 patients, and then found an average cut-off value in the T/N ratio of 11C-methionine PET of 1.27 and in FA of 0.26, values similar to those previously confirmed by histological study. Moreover, reconstructing images delineating the tumor border was possible combining these two imaging modalities. We propose that the combined analysis of DTI and 11C-methionine PET has the potential to improve tumor border imaging in glioma patients, providing important information for establishing neurosurgical strategies. [Copyright &y& Elsevier]

Abstract: A noninvasive technique for assessing tumor tissue characteristics is required to assist preoperative surgical planning for malignant brain tumors. Preoperative information on tumor cell density within a tumor would help better define the target for tumor biopsy, resulting in more accurate diagnosis and grading of malignant brain tumors. One possible source of this information is diffusion tensor imaging (DTI), although to date studies have focused on its ability to delineate white matter fiber tracks by fiber-tracking and to detect tumor infiltration around the tumor and normal white matter interface. However, the use of DTI for providing information on cell density has also been examined, although with the controversial results. In addition the exact relationships between cell density and the two key values that DTI provides, namely fractional anisotropy (FA) and mean diffusivity (MD), still need to be investigated. In the present study we performed a retrospective investigation of tumor cell density and FA and MD values in biopsy cases. We found that FA has a good positive correlation (R =0.75) and MD has a good negative correlation (R =0.70) with tumor cell density within the tumor core. Similar correlation was observed between the Ki-67 labeling index and FA (R =0.71) and MD (R =0.62). Thus, measurement of both FA and MD within the tumor core has a potential to provide detailed information on tumor cell density within the tumor. Although data obtained from DTI should be interpreted carefully and comprehensively with other imaging modalities such as positron emission tomography, DTI seems to be informative for planning the best biopsy target containing the highest cell density. [Copyright &y& Elsevier]