Comparison of diffusion signal models for fiber tractography in eloquent glioma surgery - determination of accuracy under awake craniotomy conditions.

OBJECTIVE Fiber tractography(FT) has become an important non-invasive tool to ensure maximal safe tumor resection in eloquent glioma surgery. Intraoperatively applied FT is still predominantly based on Diffusion Tensor Imaging(DTI). However, reconstruction schemes of high angular resolution diffusion imaging(HARDI) data for high resolution fiber tractography(HRFT) are gaining increasing attention. The aim of this prospective study was to compare the accuracy of sophisticated HRFT-models compared with DTI-FT. METHODS Ten patients with eloquent gliomas underwent surgery under awake craniotomy conditions. The localization of acquisition points(AP), representing deteriorations during intraoperative electrostimulation(IOM) and neuropsychological mapping, were documented. The offsets of AP to the respective fiber bundle were calculated. Probabilistic QBI- and CSD-FT were compared to DTI-FT for the major language-associated fiber bundles (superior longitudinal fasciclus (SLF) II-IV, inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus/medial longitudinal fasciculus (ILF/MLF). RESULTS Among 186 offset values, 46% were located closer than 10mm to the estimated fiber bundle (CSD:36%; DTI:40% and QBI:60%). Moreover, only 10 offsets were further away than 30mm (5%). Lowest mean min-offsets (SLF: 7.7±7.9mm; IFOF: 12.7±8.3mm; ILF/MLF: 17.7±6.7mm) were found for QBI, indicating a significant advantage compared with CSD or DTI (p<0.001), respectively. No significant differences were found between CSD-, and DTI-FT offsets (p=0.105), albeit for the compound SLF exclusively (p<0.001). CONCLUSIONS Comparing HRFT techniques QBI and CSD with DTI, QBI delivered significantly better results with lowest offsets and good correlation to IOM results. Besides, QBI-FT was feasible for neurosurgical pre- and intraoperative applications. Our findings suggest that a combined approach of QBI-FT and IOM under awake craniotomy is considerable for best preservation of neurological function in the presented setting. Overall, the implementation of selected HRFT models into neuronavigation systems seems to be a promising tool in glioma surgery.