title: Abnormalities in Diffusional Kurtosis Metrics Related to Head Impact Exposure in a Season of High School Varsity Football.
abstract: The purpose of this study was to determine whether the effects of cumulative head impacts during a season of high school football produce changes in diffusional kurtosis imaging (DKI) metrics in the absence of clinically diagnosed concussion. Subjects were recruited from a high school football team and were outfitted with the Head Impact Telemetry System (HITS) during all practices and games. Biomechanical head impact exposure metrics were calculated, including: total impacts, summed acceleration, and Risk Weighted Cumulative Exposure (RWE). Twenty-four players completed pre- and post-season magnetic resonance imaging, including DKI; players who experienced clinical concussion were excluded. Fourteen subjects completed pre- and post-season Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT). DKI-derived metrics included mean kurtosis (MK), axial kurtosis (K axial), and radial kurtosis (K radial), and white matter modeling (WMM) parameters included axonal water fraction, tortuosity of the extra-axonal space, extra-axonal diffusivity (Deaxial and radial), and intra-axonal diffusivity (Da). These metrics were used to determine the total number of abnormal voxels, defined as 2 standard deviations above or below the group mean. Linear regression analysis revealed a statistically significant relationship between RWE combined probability (RWECP) and MK. Secondary analysis of other DKI-derived and WMM metrics demonstrated statistically significant linear relationships with RWECPafter covariate adjustment. These results were compared with the results of DTI-derived metrics from the same imaging sessions in this exact same cohort. Several of the DKI-derived scalars (Da, MK, K axial, and K radial) explained more variance, compared with RWECP, suggesting that DKI may be more sensitive to subconcussive head impacts. No significant relationships between DKI-derived metrics and ImPACT measures were found. It is important to note that the pathological implications of these metrics are not well understood. In summary, we demonstrate a single season of high school football can produce DKI measurable changes in the absence of clinically diagnosed concussion.
authors.affiliation: 1 Advanced Neuroscience Imaging Research (ANSIR) Laboratory, Wake Forest School of Medicine , Winston-Salem, North Carolina.|2 Department of Radiology, Wake Forest School of Medicine , Winston-Salem, North Carolina.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Davenport
authors.affiliation: 4 Department of Biomedical Engineering, Wake Forest School of Medicine , Winston-Salem, North Carolina.
authors.forename: Kalyna
authors.initials: K
authors.lastname: Apkarian
authors.affiliation: 3 Department of Radiology-Neuroradiology, Wake Forest School of Medicine , Winston-Salem, North Carolina.|4 Department of Biomedical Engineering, Wake Forest School of Medicine , Winston-Salem, North Carolina.|8 Translational Science Institute, Wake Forest School of Medicine , Winston-Salem, North Carolina.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Whitlow
authors.affiliation: 4 Department of Biomedical Engineering, Wake Forest School of Medicine , Winston-Salem, North Carolina.|9 Virginia Tech-Wake Forest School of Biomedical Engineering, Wake Forest School of Medicine , Winston-Salem, North Carolina.
authors.forename: Jillian E
authors.initials: JE
authors.lastname: Urban
authors.affiliation: 13 Department of Radiology and Radiological Science, Center for Biomedical Imaging, Medical University of South Carolina , Charleston, South Carolina.
authors.forename: Jens H
authors.initials: JH
authors.lastname: Jensen
authors.affiliation: 10 MD Program, Wake Forest School of Medicine , Winston-Salem, North Carolina.
authors.forename: Eliza
authors.initials: E
authors.lastname: Szuch
authors.affiliation: 5 Department of Biostatistical Sciences, Wake Forest School of Medicine , Winston-Salem, North Carolina.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Espeland
authors.affiliation: 3 Department of Radiology-Neuroradiology, Wake Forest School of Medicine , Winston-Salem, North Carolina.|4 Department of Biomedical Engineering, Wake Forest School of Medicine , Winston-Salem, North Carolina.|9 Virginia Tech-Wake Forest School of Biomedical Engineering, Wake Forest School of Medicine , Winston-Salem, North Carolina.
authors.forename: Youngkyoo
authors.initials: Y
authors.lastname: Jung
authors.affiliation: 4 Department of Biomedical Engineering, Wake Forest School of Medicine , Winston-Salem, North Carolina.
authors.forename: Daryl A
authors.initials: DA
authors.lastname: Rosenbaum
authors.affiliation: 12 Division of Pediatric Neuropsychology, Children's National Medical Center, George Washington University School of Medicine , Rockville, Maryland.
authors.forename: Gerard A
authors.initials: GA
authors.lastname: Gioia
authors.affiliation: 7 Department of Neurosurgery, Wake Forest School of Medicine , Winston-Salem, North Carolina.|11 Childress Institute for Pediatric Trauma, Wake Forest School of Medicine , Winston-Salem, North Carolina.
authors.forename: Alexander K
authors.initials: AK
authors.lastname: Powers
authors.affiliation: 4 Department of Biomedical Engineering, Wake Forest School of Medicine , Winston-Salem, North Carolina.|8 Translational Science Institute, Wake Forest School of Medicine , Winston-Salem, North Carolina.|9 Virginia Tech-Wake Forest School of Biomedical Engineering, Wake Forest School of Medicine , Winston-Salem, North Carolina.
authors.forename: Joel D
authors.initials: JD
authors.lastname: Stitzel
authors.affiliation: 1 Advanced Neuroscience Imaging Research (ANSIR) Laboratory, Wake Forest School of Medicine , Winston-Salem, North Carolina.|2 Department of Radiology, Wake Forest School of Medicine , Winston-Salem, North Carolina.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Maldjian
mesh_terms: D000293:Adolescent; D056352:Athletes / Q000523:psychology; D001924:Brain Concussion / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000523:psychology; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005538:Football / Q000293:injuries*; D006801:Humans; D008297:Male; D012574:Schools; D012621:Seasons; D066127:White Matter / Q000000981:diagnostic imaging*
keywords: Head Impact Telemetry System; Risk Weighted Cumulative Exposure; concussion; diffusion kurtosis imaging; football