The Use of Resting State fMRI and CSD Tractography for Pre-operative Brain Mapping: a Cross-sectional Study

This study aims to prospectively investigate and validate the application of resting state functional MRI (rs-fMRI) and High angular resolution diffusion imaging (HARDI), particularly constrained spherical deconvolution (CSD) tractography, in presurgical functional and structural brain mapping for the purposes of neurosurgical planning, navigation and risk assessment. The main objective is to determine whether rs-fMRI and CSD tractography are capable of replacing task based fMRI (tb-fMRI) and diffusion tensor imaging (DTI) based fiber tractography (FT) using the fiber assignment by continuous tracking (FACT) algorithm for mapping the sensory-motor, language, visual, as well as higher cognitive functional and structural networks of the brain in patients with brain pathology amenable for surgical intervention. This research question will be investigated by acquiring tb-fMRI and rs-fMRI, as well as HARDI data for presurgical patients. The routine workflow of presurgical planning and risk assessment using tb-fMRI and DTI FT will be followed and used for the initial planning. Previous studies have revealed a high degree of concordance between rs-fMRI and tb-fMRI[1]-[5] as well as between CSD and DTI FT[6]-[8], but drew such conclusions from relatively small sample sizes. The aim is to incorporate the rs-fMRI and CSD results into the presurgical planning process albeit with more weight assigned to the tb-fMRI and DTI results. The study population will consist of 10 normal controls for MR imaging optimization purposes only, 150 presurgical patients from the UZ Leuven imaging department regardless of the exact type of pathology (space occupying lesions, epilepsy, vascular malformations etc.).

As tb-fMRI has previously been validated versus the gold standard of functional mapping, electrical cortical stimulation (ECS), while rs-fMRI has previously been validated against tb-fMRI. The same has been done comparing DTI and CSD. To our knowledge however, a comparative study with such a large and diverse study population attempting to cross validate all these modalities against the gold standard has not yet been done.

Image acquisition acceleration methods, such as parallel imaging (PI), simultaneous multislice acquisitions (SMS) and compressed sensing (CS) will be used whenever feasible. These acceleration methods can potentially be exploited to improve fMRI, and dMRI data quality as well as shorten acquisition time. In the case of fMRI, PI and SMS can be used to increase temporal resolution, temporal signal to noise ratio and even spatial resolution. dMRI stands to benefit from such techniques by increasing directional and/or spatial resolution.