Abstract
The purpose of this study was to compare the deterministic and probabilistic tracking methods of diffusion tensor white matter fiber tractography in patients with brain tumors. We identified 29 patients with left brain tumors <2 cm from the arcuate fasciculus who underwent pre-operative language fMRI and DTI. The arcuate fasciculus was reconstructed using a deterministic Fiber Assignment by Continuous Tracking (FACT) algorithm and a probabilistic method based on an extended Monte Carlo Random Walk algorithm. Tracking was controlled using two ROIs corresponding to Broca's and Wernicke's areas. Tracts in tumoraffected hemispheres were examined for extension between Broca's and Wernicke's areas, anterior-posterior length and volume, and compared with the normal contralateral tracts. Probabilistic tracts displayed more complete anterior extension to Broca's area than did FACT tracts on the tumor-affected and normal sides (p < 0.0001). The median length ratio for tumor: normal sides was greater for probabilistic tracts than FACT tracts (p < 0.0001). The median tract volume ratio for tumor: normal sides was also greater for probabilistic tracts than FACT tracts (p = 0.01). Probabilistic tractography reconstructs the arcuate fasciculus more completely and performs better through areas of tumor and/or edema. The FACT algorithm tends to underestimate the anterior-most fibers of the arcuate fasciculus, which are crossed by primary motor fibers.
Highlights
The arcuate fasciculus is an important white matter tract that connects the frontal (Broca’s) and temporal (Wernicke’s) language regions of the brain
Our results demonstrated that the probabilistic tractography outperformed the Fiber Assignment by Continuous Tracking (FACT) tractography in estimateing the extent and degree of connectivity of the arcuate fasciculus affected by brain tumors and/or peritumoral abnormalities
We found that FACT tended to underestimate the extent of the anterior-most fibers of the arcuate fasciculus, where the fibers cross the descending corticobulbar fibers
Summary
The arcuate fasciculus is an important white matter tract that connects the frontal (Broca’s) and temporal (Wernicke’s) language regions of the brain. Diffusion tensor imaging (DTI) is an emerging magnetic resonance imaging (MRI) technique that allows visualization and characterization of white matter tracts such as the arcuate fasciculus [5,6]. Tractography algorithms utilize the DTI encoded information to reconstruct white matter tracts [10,11,12]. FACT is a streamline-based deterministic method that traces pathways from a seed region by following the primary eigenvector from one voxel to the [12,13]. The probabilistic algorithm defines pathways by generating multiple curves from seed points using a Monte Carlo simulation [14,15,16]. Probability of connectivity is assigned to individual voxels based on the frequency with which the curves traverse the voxels
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