Browsing by Author "Smith, Daniel R."
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Item Altered brain functional connectivity in the frontoparietal network following an ice hockey season(European Journal of Sport Science, 2022-05-08) DiFabio, Melissa S.; Smith, Daniel R.; Breedlove, Katherine M.; Pohlig, Ryan T.; Buckley, Thomas A.; Johnson, Curtis L.Sustaining sports-related head impacts has been reported to result in neurological changes that potentially lead to later-life neurological disease. Advanced neuroimaging techniques have been used to detect subtle neurological effects resulting from head impacts, even after a single competitive season. The current study used resting-state functional magnetic resonance imaging to assess changes in functional connectivity of the frontoparietal network, a brain network responsible for executive functioning, in collegiate club ice hockey players over one season. Each player was scanned before and after the season and wore accelerometers to measure head impacts at practices and home games throughout the season. We examined pre- to post-season differences in connectivity within the frontoparietal and default mode networks, as well as the relationship between the total number of head impacts sustained and changes in connectivity. We found a significant interaction between network region of interest and time point (p = .016), in which connectivity between the left and right posterior parietal cortex seed regions increased over the season (p < .01). Number of impacts had a significant effect on frontoparietal network connectivity, such that more impacts were related to greater connectivity differences over the season (p = .042). Overall, functional connectivity increased in ice hockey athletes over a season between regions involved in executive functioning, and sensory integration, in particular. Furthermore, those who sustained more impacts had the greatest changes in connectivity. Consistent with prior findings in resting-state sports-related head impact literature, these findings have been suggested to represent brain injury. Highlights: Functional connectivity of the frontoparietal network significantly increased between the pre- and post-season, which may be a compensatory mechanism driven by neural tissue injury caused by repetitive head impacts. Changes in frontoparietal network connectivity are related to head impact exposure, measured as the number of head impacts sustained in a single season. Functional connectivity of the default mode network did not change over an ice hockey season.Item In vivo estimation of anisotropic mechanical properties of the gastrocnemius during functional loading with MR elastography(Physics in Medicine & Biology, 2023-02-06) Smith, Daniel R.; Caban-Rivera, Diego A.; Williams, L. Tyler; Van Houten, Elijah E. W.; Bayly, Phil V.; Paulsen, Keith D.; McGarry, Matthew D. J.; Johnson, Curtis L.Objective. In vivo imaging assessments of skeletal muscle structure and function allow for longitudinal quantification of tissue health. Magnetic resonance elastography (MRE) non-invasively quantifies tissue mechanical properties, allowing for evaluation of skeletal muscle biomechanics in response to loading, creating a better understanding of muscle functional health. Approach. In this study, we analyze the anisotropic mechanical response of calf muscles using MRE with a transversely isotropic, nonlinear inversion algorithm (TI-NLI) to investigate the role of muscle fiber stiffening under load. We estimate anisotropic material parameters including fiber shear stiffness (${\mu }_{1}$), substrate shear stiffness (${\mu }_{2}$), shear anisotropy ($\phi $), and tensile anisotropy ($\zeta $) of the gastrocnemius muscle in response to both passive and active tension. Main results. In passive tension, we found a significant increase in ${\mu }_{1},$ $\phi ,$ and $\zeta $ with increasing muscle length. While in active tension, we observed increasing ${\mu }_{2}$ and decreasing $\phi $ and $\zeta $ during active dorsiflexion and plantarflexion—indicating less anisotropy—with greater effects when the muscles act as agonist. Significance. The study demonstrates the ability of this anisotropic MRE method to capture the multifaceted mechanical response of skeletal muscle to tissue loading from muscle lengthening and contraction.Item Individual Muscle Force Estimation in the Human Forearm Using Multi-Muscle MR Elastography (MM-MRE)(IEEE Transactions on Biomedical Engineering, 2023-06-06) Smith, Daniel R.; Helm, Cody A.; Zonnino, Andrea; McGarry, Matthew D.J.; Johnson, Curtis L.; Sergi, FabrizioObjective: To establish the sensitivity of magnetic resonance elastography (MRE) to active muscle contraction in multiple muscles of the forearm. Methods: We combined MRE of forearm muscles with an MRI-compatible device, the MREbot, to simultaneously measure the mechanical properties of tissues in the forearm and the torque applied by the wrist joint during isometric tasks. We measured shear wave speed of thirteen forearm muscles via MRE in a series of contractile states and wrist postures and fit these outputs to a force estimation algorithm based on a musculoskeletal model. Results: Shear wave speed changed significantly upon several factors, including whether the muscle was recruited as an agonist or antagonist (p = 0.0019), torque amplitude (p = <0.0001), and wrist posture (p = 0.0002). Shear wave speed increased significantly during both agonist (p = <0.0001) and antagonist (p = 0.0448) contraction. Additionally, there was a greater increase in shear wave speed at greater levels of loading. The variations due to these factors indicate the sensitivity to functional loading of muscle. Under the assumption of a quadratic relationship between shear wave speed and muscle force, MRE measurements accounted for an average of 70% of the variance in the measured joint torque. Conclusion: This study shows the ability of MM-MRE to capture variations in individual muscle shear wave speed due to muscle activation and presents a method to estimate individual muscle force through MM-MRE derived measurements of shear wave speed. Significance: MM-MRE could be used to establish normal and abnormal muscle co-contraction patterns in muscles of the forearm controlling hand and wrist function.Item Mechanical evaluation of structure and function in fibrous soft tissue using MR elastography(University of Delaware, 2022) Smith, Daniel R.Human soft tissues are highly complex networks comprised of a variety of components that contribute to the overall functionality of the tissue, but these structures can be disrupted through injury or pathology, leading to tissue dysfunction. Magnetic resonance elastography (MRE) is a developing imaging technique that has shown promise in evaluating human soft tissues in-vivo by providing mechanical property estimates that are sensitive to structural changes in these tissues, including sensitivity to pathological changes. While MRE has proved to be an effective technique in much of human soft tissue, fibrous soft tissues, such as brain white matter and skeletal muscle, cause standard assumptions of mechanical isotropy to fail, resulting in data-model mismatches and inaccurate evaluations of tissue integrity and health. In this thesis, we propose to develop and test an MRE method to evaluate the health of fibrous soft tissues by evaluating structural and functional changes from pathology or injury. ☐ 5203 The first part of work focuses on the assessing the viability of using a nearly incompressible, transversely isotropic (NITI) material model to accurately estimate the anisotropic material properties of human white matter. This NITI material model uses three independent material parameters to describe tissue response, but the definition of these parameters with MRE requires more information than is typically generated. To generate the necessary data, we utilize a technique called multi-excitation MRE, which uses multiple actuators to generate unique complex waveforms throughout the brain. Through analysis of these waveforms, we show that multiexcitation MRE provides sufficient information to estimate the NITI independent material parameters throughout white matter, ensuring repeatable and reliable parameters measures. Additionally, we estimate these parameters using the recently developed transversely isotropic, nonlinear inversion algorithm (TI-NLI) and combine multiexcitation MRE wave motion data and white matter fiber directions, as defined by diffusion tensor imaging (DTI) data. Using a population of healthy young subjects, we assess the parameter’s sensitivity to structural variances in white matter by quantifying the anisotropic parameters within individual white matter tracts across the population as well as the heterogeneity within a single tract. By capturing this heterogeneity across WM, this technique indicates an ability to capture structural variances caused by other sources, including degradation from injury or pathology or recovery through applied therapies. ☐ 5203 Although structural variations provide can provide significant information about soft tissue health, skeletal muscle has primarily been evaluated through functional measures of health, such as tissue loading. In the second half of this work, we aim to evaluate MRE’s capacity to measure functional outcomes like loading by capturing in-vivo estimates of skeletal muscle tension response and force production. Using multi-muscle MRE (MM-MRE), we provide in-vivo measurements of functional changes through three primary factors: correlation between combined muscle load and shear stiffness parameter outcomes; significant shear stiffness differences between muscles during agonist and antagonist actions; and variation of shear stiffness outcomes with different levels of initial loading due to muscle length. We then applied TI-NLI to skeletal muscle to quantify the anisotropic variations during passive muscle lengthening and isometric contractions and found unique parameter responses between the two conditions. These unique responses indicate anisotropic MRE’s capacity to provide a multifaceted approach to analyzing response to functional measures and provide a valuable tool for evaluating further changes in response due to injury-based or pathological changes to skeletal muscle.Item Relationships between aggression, sensation seeking, brain stiffness, and head impact exposure: Implications for head impact prevention in ice hockey(Brain and Behavior, 2022-04-23) DiFabio, Melissa S.; Smith, Daniel R.; Breedlove, Katherine M.; Buckley, Thomas A.; Johnson, Curtis L.Objectives: The objectives of this study were to (1) examine the relationship between the number of head impacts sustained in a season of men's collegiate club ice hockey and behavioral traits of aggression and sensation seeking, and (2) explore the neural correlates of these behaviors using neuroimaging. Design: Retrospective cohort study. Methods: Participants (n = 18) completed baseline surveys to quantify self-reported aggression and sensation-seeking tendencies. Aggression related to playing style was quantified through penalty minutes accrued during a season. Participants wore head impact sensors throughout a season to quantify the number of head impacts sustained. Participants (n = 15) also completed baseline anatomical and magnetic elastography neuroimaging scans to measure brain volumetric and viscoelastic properties. Pearson correlation analyses were performed to examine relationships between (1) impacts, aggression, and sensation seeking, and (2) impacts, aggression, and sensation seeking and brain volume, stiffness, and damping ratio, as an exploratory analysis. Results: Number of head impacts sustained was significantly related to the number of penalty minutes accrued, normalized to number of games played (r = .62, p < .01). Our secondary, exploratory analysis revealed that number of impacts, sensation seeking, and aggression were related to stiffness or damping ratio of the thalamus, amygdala, hippocampus, and frontal cortex, but not volume. Conclusions: A more aggressive playing style was related to an increased number of head impacts sustained, which may provide evidence for future studies of head impact prevention. Further, magnetic resonance elastography may aid to monitor behavior or head impact exposure. Researchers should continue to examine this relationship and consider targeting behavioral modification programs of aggression to decrease head impact exposure in ice hockey.