New application of diffusion tensor imaging in neurosurgery.

Diffusion tensor imaging is a MRI technique that enables the measurement of the diffusion of water in tissue in order to produce neural tract images. Advanced methods such as color coding and tractography (fiber tracking) have been used to investigate the directionality. The localization of tumors in relation to the white matter tracts (infiltration, deflection), has been one the most important initial applications. A non invasive technique for assessing tumor tissue characteristics, like tumor cell density, is required to assist preoperative surgical planning for malignant brain tumors and 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. 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. Relationships between cell density and the two key values that diffusion tensor imaging provides, fractional anisotropy and mean diffusivity, still need to be investigated. Mean diffusivity has a good negative correlation and fractional anisotropy has a good positive correlation with tumor cell density within the tumor core. Similar correlation was observed between the Ki-67, on the one hand and fractional anisotropy and mean diffusivity, on the other hand. Thus, measurement of both fractional anisotropy and mean diffusivity within the tumor core has a potential to provide detailed information on tumor cell density within the tumor.

Infiltrating growing pattern xenografts induced by glioblastoma and anaplastic astrocytoma derived tumor stem cells.

OBJECTIVE: The number of evidences regarding the role of tumor stem cells (TSC) in the initiation and progression of high-grade astrocytomas became more and more numerous in the last years. This issue has been intensively tested in glioblastoma, but little attention has been paid for anaplastic astrocytoma. The main objective of this paper was to study the morphological characteristics of the xenografts developed from glioblastoma and anaplastic astrocytoma derived cancer stem cells. METHODS: The authors of this study successfully isolated and partial characterized primary cultures of glioblastoma and anaplastic astrocytoma derived TSC. Tumors stem cells have been stereotactically inoculated in nude mice brains and the xenografts have been studied using morphological and imunohistochemistry techniques. RESULTS: The tumor xenografts which have been established in nude mice using TSC had different characteristics when compared with U87 xenografts previously developed by our group, and depend of the origin type of the tumors (glioblastoma versus anaplastic astrocytoma). The diffuse growing pattern and cells infiltration have been more pronounced in both anaplastic astrocytoma and glioblastoma derived TSC xenografts compared with U87 line xenografts. CONCLUSION: Our results support the hypothesis regarding the role of TSC in the infiltration process of glioblastoma and anaplastic astrocytoma. The extensive infiltration growing patterns of these types of xenografts make them useful models for studying the invasion mechanisms in gliomas.