title: Tract Orientation and Angular Dispersion Deviation Indicator (TOADDI): A framework for single-subject analysis in diffusion tensor imaging.
abstract: The purpose of this work is to develop a framework for single-subject analysis of diffusion tensor imaging (DTI) data. This framework is termed Tract Orientation and Angular Dispersion Deviation Indicator (TOADDI) because it is capable of testing whether an individual tract as represented by the major eigenvector of the diffusion tensor and its corresponding angular dispersion are significantly different from a group of tracts on a voxel-by-voxel basis. This work develops two complementary statistical tests based on the elliptical cone of uncertainty, which is a model of uncertainty or dispersion of the major eigenvector of the diffusion tensor. The orientation deviation test examines whether the major eigenvector from a single subject is within the average elliptical cone of uncertainty formed by a collection of elliptical cones of uncertainty. The shape deviation test is based on the two-tailed Wilcoxon-Mann-Whitney two-sample test between the normalized shape measures (area and circumference) of the elliptical cones of uncertainty of the single subject against a group of controls. The False Discovery Rate (FDR) and False Non-discovery Rate (FNR) were incorporated in the orientation deviation test. The shape deviation test uses FDR only. TOADDI was found to be numerically accurate and statistically effective. Clinical data from two Traumatic Brain Injury (TBI) patients and one non-TBI subject were tested against the data obtained from a group of 45 non-TBI controls to illustrate the application of the proposed framework in single-subject analysis. The frontal portion of the superior longitudinal fasciculus seemed to be implicated in both tests (orientation and shape) as significantly different from that of the control group. The TBI patients and the single non-TBI subject were well separated under the shape deviation test at the chosen FDR level of 0.0005. TOADDI is a simple but novel geometrically based statistical framework for analyzing DTI data. TOADDI may be found useful in single-subject, graph-theoretic and group analyses of DTI data or DTI-based tractography techniques.
authors.affiliation: National Intrepid Center of Excellence (NICoE), Bethesda, MD, USA; Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, MD, USA; NorthTide Group, LLC, USA. Electronic address: guankoac@mail.nih.gov.
authors.forename: Cheng Guan
authors.initials: CG
authors.lastname: Koay
authors.affiliation: National Intrepid Center of Excellence (NICoE), Bethesda, MD, USA; The Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA.
authors.forename: Ping-Hong
authors.initials: PH
authors.lastname: Yeh
authors.affiliation: National Intrepid Center of Excellence (NICoE), Bethesda, MD, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Ollinger
authors.affiliation: The Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA; Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, MD, USA.
authors.forename: M Okan
authors.initials: MO
authors.lastname: İrfanoğlu
authors.affiliation: Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Carlo
authors.initials: C
authors.lastname: Pierpaoli
authors.affiliation: Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Basser
authors.affiliation: National Intrepid Center of Excellence (NICoE), Bethesda, MD, USA.
authors.forename: Terrence R
authors.initials: TR
authors.lastname: Oakes
authors.affiliation: National Intrepid Center of Excellence (NICoE), Bethesda, MD, USA; National Capital Neuroimaging Consortium, Bethesda, MD, USA.
authors.forename: Gerard
authors.initials: G
authors.lastname: Riedy
mesh_terms: D000328:Adult; D001930:Brain Injuries / Q000473:pathology; D003627:Data Interpretation, Statistical; D056324:Diffusion Tensor Imaging / Q000379:methods*; D006801:Humans; D015233:Models, Statistical; D066127:White Matter / Q000473:pathology*
keywords: DTI; Elliptical cone of uncertainty; Exact Wilcoxon–Mann–Whitney p-value computation; FDR; FNR