Chen Niu1, Xin Liu2, Pan Lin2, Zhigang Min1, Wenfei Li1, Liping Guo1, Maode Wang1, Qi Li1, and Ming Zhang1
1Department of Medical Imaging, The First Affiliated Hospital of Xi'An Jiaotong University, Xi'an, China, People's Republic of, 2Institute of Biomedical Engineering, Xi'an Jiaotong University, Xi'an, China, People's Republic of
Synopsis
we evaluated a combinatorial approach that used functional activation and anatomical landmark data to define multiple ROIs for CST fiber tracking in patients with a brain tumor. Our results suggest that a combination of fMRI and DTI fiber tracking may provide a more comprehensive analysis of the CST pathway, which would be beneficial for characterizing spatial relationships between the CST pathway and the tumor. A dual ROI CST fiber tracking approach has the potential to play a critical role in preoperative planning to optimize surgical treatment and improve post-surgical outcome.Abstract
Purpose: Diffusion tensor imaging (DTI) and DT tractography techniques are widely used for identifying white matter tracts for presurgical planning1-3. However, mass effects in patients with brain tumors tend to cause anatomical distortion and compensatory functional reorganization of the cortex, which may lead to inaccurate mapping of white matter tracts4.The aim of this study was to investigate whether a different ROI definition method (the integration of fMRI and DTI) could improve the evaluation of the spatial relationship between the corticospinal tract (CST) and tumor borders for surgical planning.
Methods: 17 brain tumors patients were involved in this study. Patients were classified into three subgroups according to the spatial relationships of the lesion and the primary motor cortex (PMC)/internal capsule. Both structural images (3D FSPGR 1x1x1 mm3, 140slices) and BOLD EPI data (TR/TE = 2500/40 ms, flip angle=90°, 3.75x3.75x3mm3) were acquired. We compared 3 different ROI selection schemes for CST tractography. The pons ROI (ROI1) was manually defined on individual subject's color-coded FA map. The fMRI-based functional ROI (ROI2) was defined as the motor task activation area in the PMC in the fMRI native space for each individual. The dual approach (ROI1+ROI2) uses fMRI activation ROI2 as the seed region and anatomical ROI1 as the target region. In addition, we compared the spatial overlapping rates of different tractography methods.
Results: The results indicate that CST fiber tracking methods based only on anatomical ROI could possibly lead to distortions near tumor and may be unable to effectively localize the PMC area. In contrast, the dual ROI method enabled the tracking of fibers to reach the motor cortex. These results demonstrate that the dual ROI method can localize the entire CST fiber pathway and can accurately describe the spatial relationship between CST fiber and the tumor (Fig.1). Furthermore, we observed higher spatial overlapping rates for the tractography results when using a ROI2 selected from fMRI activation and the dual ROI method. These results illustrate higher reliability of using fMRI-guided DTT in patients with tumors compared to conventional tractography based only on anatomical ROI (Fig.2).
Discussion and Conclusion: The combination of fMRI and anatomical information enhances the identification of tracts of interest in brains with anatomical deformation, which provides neurosurgeons with a more accurate approach for visualizing and localizing white matter fiber tracts in patients with brain tumors, thus enhancing surgical performance and persevering brain function.
Acknowledgements
This research work was supported by the National Natural Science Foundation of People's Republic of China (No.61473221,No.81171318,No.30870686)
References
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