Structural and functional connectivity are emerging as important tools for oncological neurological imaging. In particular, brain tumor patients have benefited from functional and structural neurological imaging for the guidance of surgical treatment. More recently, diffusion MRI (dMRI) has emerged as a unique and vital tool for surgeons when using intra-operative electrical stimulation (IES) mapping of eloquent white matter pathways to be spared during tumor resection. Magnetic source imaging (MSI) and functional MRI (fMRI) have likewise been used to inform mapping over cortical areas. The overarching goal of this proposal is to improve preoperative delineation of cortical and white matter regions that are vital to motor function, and to use functional and structural connectivity to predict those cortical and subserving white matter pathways at risk for postoperative clinical deficits. Despite tremendous advances in acquisition and post-processing algorithms, there is still substantial need for improvement in preoperative fiber tracking with diffusion MRI. In particular, conventional diffusion tensor imaging (DTI) algorithms have poor ability to delineate the lateral portions of the corticospinal tract (CST) serving motor function due to the complexity in white matter structure leading to these areas. We have investigated the ability of more advanced dMRI methods including probabilistic and high-angular resolution diffusion MRI (HARDI) and our initial results show promise. However, these advances need to be verified systematically and our preliminary data also indicate that incorporating a novel preoperative motor MSI method that accurately localizes the motor cortices, increases our ability to confidently delineate the CST with dMRI fiber tracking. Therefore, based on these data, we hypothesize that probabilistic HARDI fiber tracking with MSI will improve on current methods to pre-operatively delineate the CST in brain tumor patients. Recent developments in structural and functional connectivity analyses now promise even greater potential for these techniques to not only improve delineation of eloquent regions, but also to determine the functional impact of these regions. Our preliminary data indicate the ability of MSI preoperative measures of functional connectivity to predict those cortical sensorimotor regions that may lead to post-operative deficit. To this end, dMRI may be used to extend this cortical information to include the subserving white matter pathways that are at risk for post-operative deficit. Based on these data, we hypothesize that integrating functional and structural connectivity will provide even greater benefit for preoperative mapping of motor pathways by providing potential prognostic information on the functional impact of these pathways.
Combining structural and functional connectivity from probabilistic high-angular resolution diffusion MRI and magnetic source imaging will improve preoperative delineation and characterization of eloquent primary motor areas and their subserving white matter pathways at risk for postoperative functional deficits in brain tumor patients.
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