title: Human brain asymmetry in microstructural connectivity demonstrated by diffusional kurtosis imaging.
abstract: Structural asymmetry of whole brain white matter (WM) pathways, i.e., the connectome, has been demonstrated using fiber tractography based on diffusion tensor imaging (DTI). However, DTI-based tractography fails to resolve axonal fiber bundles that intersect within an imaging voxel, and therefore may not fully characterize the extent of asymmetry. The goal of this study was to assess structural asymmetry with tractography based on diffusional kurtosis imaging (DKI), which improves upon DTI-based tractography by delineating intravoxel crossing fibers. DKI images were obtained from 42 healthy subjects. By using automatic segmentation, gray matter (GM) was parcellated into anatomically defined regions of interest (ROIs). WM pathways were reconstructed with both DKI- and DTI-based tractography. The connectivity between the ROIs was quantified with the streamlines connecting the ROIs. The asymmetry index (AI) was utilized to quantify hemispheric differences in the connectivity of cortical ROIs and of links interconnecting cortical ROIs. Our results demonstrated that leftward asymmetrical ROIs and links were observed in frontal, parietal, temporal lobes, and insula. Rightward asymmetrical ROI and links were observed in superior frontal lobe, cingulate cortex, fusiform, putamen, and medial temporal lobe. Interestingly, these observed structural asymmetries were incompletely identified with DTI-based tractography. These results suggest that DKI-based tractography can improve the identification of asymmetrical connectivity patterns, thereby serving as an additional tool in the evaluation of the structural bases of functional lateralization.
authors.affiliation: Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA; Center for Biomedical Imaging, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Chu-Yu
authors.initials: CY
authors.lastname: Lee
authors.affiliation: Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA; Center for Biomedical Imaging, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Ali
authors.initials: A
authors.lastname: Tabesh
authors.affiliation: Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA; Center for Biomedical Imaging, Medical University of South Carolina, Charleston, SC, USA; Department of Neurology, Comprehensive Epilepsy Center, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Travis
authors.initials: T
authors.lastname: Nesland
authors.affiliation: Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA; Center for Biomedical Imaging, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Jens H
authors.initials: JH
authors.lastname: Jensen
authors.affiliation: Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA; Center for Biomedical Imaging, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Helpern
authors.affiliation: Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA; Center for Biomedical Imaging, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Maria V
authors.initials: MV
authors.lastname: Spampinato
authors.affiliation: Center for Biomedical Imaging, Medical University of South Carolina, Charleston, SC, USA; Department of Neurology, Comprehensive Epilepsy Center, Medical University of South Carolina, Charleston, SC, USA. Electronic address: bonilha@musc.edu.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Bonilha
mesh_terms: D000328:Adult; D001921:Brain / Q000033:anatomy & histology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D056324:Diffusion Tensor Imaging; D005260:Female; D007839:Functional Laterality; D066128:Gray Matter / Q000033:anatomy & histology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D009434:Neural Pathways / Q000033:anatomy & histology; D066127:White Matter / Q000033:anatomy & histology*
keywords: Connectivity; Connectome; Diffusion tensor imaging; Diffusional kurtosis imaging; MRI; Structural asymmetry