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Hoshizaki, Thomas Blaine
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Hoshizaki, Thomas Blaine
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Hoshizaki, Thomas Blaine
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Now showing 1 - 10 of 26
- PublicationEffect of impact surface in equestrian falls(International Society of Biomechanics in Sports (ISBS), 2016-07-22)
; ; ; ; This study examines the effect of impact surface on head kinematic response and maximum principal strain (MPS) for equestrian falls. A helmeted Hybrid III headform was dropped unrestrained onto three impact surfaces of different stiffness (steel, turf and sand) and three locations. Peak resultant linear acceleration, rotational acceleration and duration of the impact events were measured. A finite element brain model was used to calculate MPS. The results revealed that drops onto steel produced higher peak linear acceleration, rotational acceleration and MPS but lower impact durations than drops to turf and sand. However, despite lower MPS values, turf and sand impacts compared to steel impacts still represented a risk of concussion. This suggests that certification standards for equestrian helmets do not properly account for the loading conditions experienced in equestrian accidents.216 - PublicationThe influence of centric and non-centric impacts to American football helmets on the correlation between commonly metrics in brain injury research(International Research Council on the Biomechanics of Injury, 2012)
; ; ; Concussion has become recognized as an injury which can be a source of long term neurological damage. This has led to research into which metrics may be more appropriate to define risk of injury. Some researchers support the use of linear acceleration as a metric for concussion, while others suggest the use of linear and rotational acceleration as well as brain deformation metrics. The purpose of this study was to examine the relationships between these metrics using a centric and non‐centric impact protocol. A linear impactor was used to impact a Hybrid III headform fitted with different models of American football helmet using a centric and non‐centric protocol. The dynamic response was then used as input to the FE model for analysis of brain deformations. The results showed that linear acceleration was correlated to rotational acceleration and brain deformation for centric conditions, but under non‐centric conditions it was not. These results indicate that the type of methodology used will influence the relationship between the variables used to assign risk of concussion. These results also support the use of a centric/non‐centric protocol and measurement of rotational acceleration and brain deformation when it comes to the development of helmet technologies.364 - PublicationProtective Capacity of Ice Hockey Helmets against Different Impact EventsIn ice hockey, concussions can occur as a result of many different types of impact events, however hockey helmets are certified using a single injury scenario, involving drop tests to a rigid surface. The purpose of this study is to measure the protective capacity of ice hockey helmets for different impact events in ice hockey. A helmeted and unhelmeted Hybrid III headform were impacted simulating falls, elbow, shoulder and puck impacts in ice hockey. Linear and rotational acceleration and maximum principal strain (MPS) were measured. A comparison of helmeted and unhelmeted impacts found significant differences existed in most conditions (p < 0.05), however some shoulder and puck impacts showed no significant difference (p > 0.05). Impacts to the ice hockey helmet tested resulted in acceleration levels below reported ranges of concussion and TBI for falls up to 5 m/s, elbow collisions, and low velocity puck impacts but not for shoulder collisions or high velocity puck impacts and falls. The helmet tested reduced MPS below reported ranges of concussion and TBI for falls up to 5 m/s but not for the other impact events across all velocities and locations. This suggests that the ice hockey helmet tested is unable to reduce engineering parameters below reported ranges of concussion and TBI for impact conditions which do not represent a drop against a rigid surface.
749Scopus© Citations 33 - PublicationAn examination of American football helmets using brain deformation metrics associated with concussionThe sport of American football is associated with a high incidence of concussion, which research has identified may lead to long term neurological damage. As a result, it is important that protective technologies be developed to help mitigate the incidence of this type of brain trauma. This research examines how the design characteristics between different American football helmet models affect the linear and rotational acceleration responses as well as brain deformation metrics using a centric/non-centric impacting protocol. The protocol involved impacting the helmets at nine centric/non-centric sites. Brain deformation metrics were calculated using the University College Dublin Brain Trauma Model. The results revealed that design characteristics do influence the brain deformation metrics associated with incidence of concussion. Further analysis revealed that rotational acceleration was more related to brain deformation metrics than linear acceleration. These results show that when attempting to reduce brain deformation metrics, the development of rotational acceleration diminishing technologies may be beneficial. This research indicates that helmet design may be able to reduce the risk of concussive injury.
1578Scopus© Citations 55 - PublicationThe effect of acceleration signal processing for head impact numeric simulations(Springer, 2016-06)
; ; ; ; Brain injury research in sport employs a variety of physical models equipped with accelerometers. These acceleration signals are commonly processed using filters. The purpose of this research was to determine the effect of applying filters with different cutoff frequencies to the acceleration signals used as input for finite element modelling of the brain. Signals were generated from reconstructions of concussion events from American football and ice hockey in the laboratory using a Hybrid III headform. The resulting acceleration signals were used as input for the University College Dublin Brain Trauma Model after being processed with filters. The results indicated that using a filter with a cutoff of 300 Hz or higher had little effect on the resulting strain measures. In some cases there was some effect of the filters on the peak linear (8¿30g) and rotational measures (1000¿4000 rad/s2), but little effect on the finite element strain result (approximately 2¿6 %). The short duration and high magnitude accelerations, such as the puck impact, were most affected by the cutoff frequency of different filters.1754Scopus© Citations 22 - PublicationThe influence of impact angle on the dynamic response of a Hybrid III headform and brain tissue deformationThe objective of this study was to investigate the influence of impact angle on the dynamic response of a Hybrid III headform and brain tissue deformation by impacting the front and side of the headform using four angle conditions (0°, at the impact site and 5, 10 and 15° rightward rotations of the headform from 0°) as well as three additional angle conditions of -5, - 10 and -15° (leftward rotations from 0°) at the side location to examine the effects of the neckform. The acceleration-time curves were used as input into a finite element model of the brain where maximum principal strain was calculated. The study found that an impact angle of 15° significantly influencesthe results when measured using linear and rotational acceleration and maximum principal strain. When developing sophisticated impact protocols and undertaking head injury reconstruction research, it is important to be aware of impact angle.
456 - PublicationEvaluation of Dynamic Response and Brain Deformation Metrics for a Helmeted and Non-Helmeted Hybrid III Headform Using a Monorail Centric/Non-Centric Protocol(ASTM International, 2014-03-17)
; ; ; Head injuries, and concussion in particular, have become a source of interest in the sport of ice hockey. This study proposes a monorail test methodology combined with a finite element method to evaluate ice hockey helmets in a centric/non-centric protocol with performance metrics more closely associated with risk of concussion. Two conditions were tested using the protocol: (a) helmeted versus no helmet, and (b) vinyl nitrile lined hockey helmet versus expanded polypropylene lined hockey helmet. The results indicate that the impact velocities and locations produced distinct responses. Also, the protocol distinguished important design characteristics of the two helmet liner types, with the vinyl nitrile lined helmet producing lower strain responses in the cerebrum. Furthermore, it was discovered that low risk of injury peak linear and rotational acceleration values can combine to produce much higher risks of injury when using brain deformation metrics. In conclusion, the use of finite element modeling of the human brain along with a centric/non-centric protocol provides an opportunity for researchers and helmet developers to observe how the dynamic response produced by these impacts influences brain tissue deformation and injury risk. This type of centric/non-centric physical to finite element modeling methodology could be used to guide innovation for new methods to prevent concussion.542 - PublicationThe relationship between impact condition and velocity on brain tissue response(International Society of Biomechanics, 2011)
; ; Injury reconstruction is a well accepted method for investigating the relationship between the event causing brain injury and the resulting trauma to neural tissue. Understanding the effect of the impact characteristics and velocity on the brain deformations is important when interpreting brain stress and strain values obtained from reconstructions. A finite element model (UCDBTM) was used to evaluate brain tissue response under varying impact conditions using an unhelmeted Hybrid III headform. This study was designed to evaluate the relationship between impact conditions and corresponding brain tissue response variables. The results revealed that the dynamic response curve created by different impacting conditions significantly influenced the maximum principal strain and Von Mises stress of brain tissue, providing valuable insight in the limitations of accident reconstruction from descriptive data.145 - PublicationComparison of MADYMO and physical models for brain injury reconstruction(Informa UK (Taylor & Francis), 2014-05-04)
; ; Brain injury is researched using physical, mathematical, anatomical, and computational models. However, there has been little research to quantify the expected differences between these methods of brain injury research. The purpose of this research was to compare the brain deformation responses of identical traumatic brain injury (TBI) reconstructions, which were conducted first with Mathematical Dynamic Models (MADYMO) and then again with a Hybrid III headform. The ensuing finite element modelling was done using the University College Dublin Brain Trauma Model. The brain deformation parameters were analysed in discrete regions of interest which matched the TBI lesion as identified on computed tomography scans of the subject. The results indicated that overall the Hybrid III provided responses which were of considerably larger magnitude than the MADYMO simulation for all metrics analysed. The larger magnitude responses are likely a product of the more rigid nature of the Hybrid III in comparison to the MADYMO simulations. Interestingly, when the results are compared to the literature, the Hybrid III results match well with mild traumatic brain injury (mTBI) and TBI research, while the MADYMO simulations produce what would be considered very low local brain deformation responses for TBI lesions.513Scopus© Citations 8 - PublicationThe influence of acceleration loading curve characteristics on traumatic brain injuryTo prevent brain trauma, understanding the mechanism of injury is essential. Once the mechanism of brain injury has been identified, prevention technologies could then be developed to aid in their prevention. The incidence of brain injury is linked to how the kinematics of a brain injury event affects the internal structures of the brain. As a result it is essential that an attempt be made to describe how the characteristics of the linear and rotational acceleration influence specific traumatic brain injury lesions. As a result, the purpose of this study was to examine the influence of the characteristics of linear and rotational acceleration pulses and how they account for the variance in predicting the outcome of TBI lesions, namely contusion, subdural hematoma (SDH), subarachnoid hemorrhage (SAH), and epidural hematoma (EDH) using a principal components analysis (PCA). Monorail impacts were conducted which simulated falls which caused the TBI lesions. From these reconstructions, the characteristics of the linear and rotational acceleration were determined and used for a PCA analysis. The results indicated that peak resultant acceleration variables did not account for any of the variance in predicting TBI lesions. The majority of the variance was accounted for by duration of the resultant and component linear and rotational acceleration. In addition, the components of linear and rotational acceleration characteristics on the x, y, and z axes accounted for the majority of the remainder of the variance after duration.
430Scopus© Citations 26
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