Fractional anisotropy value by diffusion tensor magnetic resonance imaging as a predictor of cell density and proliferation activity of glioblastomas.

BACKGROUND In vivo, water diffusion displays directionality due to presence of complex microstructural barriers in tissue. The extent of directionality of water diffusion can be expressed as a fractional anisotropy (FA) value using diffusion tensor magnetic resonance imaging (DTI). The FA value has been suggested as an indicator of the cell density of astrocytic tumors. The aim of the present study was to confirm beyond doubt that FA values indicate cell density even when limited in glioblastomas and to determine whether the FA value of a given patient predicts proliferation activity in the individual glioblastoma. METHODS We performed DTI in 19 patients with glioblastoma and measured the FA values of tumor and normal brain regions prior to computed tomography-guided stereotactic biopsy. Differences in mean FA value between normal brain regions and glioblastoma lesion were compared. Cell density and MIB-1 indices were examined using tumor specimens obtained from biopsies. Correlation among FA values, cell density, and MIB-1 indices was also evaluated. RESULTS The mean FA value significantly differed between normal brain regions and glioblastoma lesions. Positive correlation was observed between FA value and cell density (r = 0.73, P < 0.05) and between FA value and MIB-1 index (r = 0.80, P < 0.05). CONCLUSIONS Our results suggest that the FA value of glioblastoma as determined by DTI prior to surgery is a good predictor of cell density and, consequently, proliferation activity.