gms | German Medical Science

Objective: Diffuse tumor infiltration poses a problem in therapy planning. Gliomas grow diffusely throughout and along white matter structures. Glioma-related changes in structural integrity and metabolism are not detectable by standard magnetic resonance (MR) imaging. Fiber density mapping (FDM) is a new approach for post-processing of diffusion tensor imaging (DTI) data. The aim of this study was to investigate differences in metabolism of fiber tract alterations between gliomas grade II-IV by correlation of fiber density values with metabolite concentrations measured by Fiber density mapping (FDM) and MR spectroscopic imaging (MRSI).

Method: FDM and MRSI were performed in 48 patients with gliomas WHO grade II-IV. FDM data were used for the definition of fiber tracts in tumoral and peritumoral areas. Structural integrity of fiber tracts was assessed as fiber density ipsi-to-contralateral ratio (FD ICR). Metabolite concentrations for choline-containing compounds (Cho) and N-acetyl-aspartate (NAA) were computed and correlated to FD ICR values after co-registration with anatomical MRI.

Results: In tumoral areas Cho concentrations of altered fiber tracts were significantly different between low- and high-grade glioma and showed different courses for the correlations of FD ICR and Cho. In high-grade glioma, increasing fiber destruction was associated with a massive progression in cell membrane proliferation. Peritumoral fiber structures showed significantly decreased NAA concentrations for all patients, but only patients with glioblastoma multiforme (GBM) had significantly decreased fiber density compared to the contralateral side. Glioma WHO grade II and III had significantly higher peritumoral FD ICR than GBMs.

Conclusions: A multi-parametrical MR imaging strategy providing information about both structural integrity and metabolism of the tumor is required for a detailed assessment of glioma-related fiber tract alterations. This in turn is essential for treatment planning.