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  • 1.
    Alvarez, Victor
    et al.
    KTH.
    Halldin, Peter
    KTH.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    The Influence of Neck Muscle Tonus and Posture on Brain Tissue Strain in Pedestrian Head Impacts2014In: SAE Technical Papers, ISSN 0148-7191, Vol. 58Article in journal (Refereed)
    Abstract [en]

    Pedestrians are one of the least protected groups in urban traffic and frequently suffer fatal head injuries. An important boundary condition for the head is the cervical spine, and it has previously been demonstrated that neck muscle activation is important for head kinematics during inertial loading. It has also been shown in a recent numerical study that a tensed neck musculature also has some influence on head kinematics during a pedestrian impact situation. The aim of this study was to analyze the influence on head kinematics and injury metrics during the isolated time of head impact by comparing a pedestrian with relaxed neck and a pedestrian with increased tonus. The human body Finite Element model THUMS Version 1.4 was connected to head and neck models developed at KTH and used in pedestrian-to-vehicle impact simulations with a generalized hood, so that the head would impact a surface with an identical impact response in all simulations. In order to isolate the influence of muscle tonus, the model was activated shortly before head impact so the head would have the same initial position prior to impact among different tonus. A symmetric and asymmetric muscle activation scheme that used high level of activation was used in order to create two extremes to investigate. It was found that for the muscle tones used in this study, the influence on the strain in the brain was very minor, in general about 1-14% change. A relatively large increase was observed in a secondary peak in maximum strains in only one of the simulated cases. 

  • 2.
    Alvarez, Victor S
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Effect of pediatric growth on cervical spine kinematics and deformations in automotive crashes2018In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 71, p. 76-83, article id S0021-9290(18)30075-7Article in journal (Refereed)
    Abstract [en]

    Finite element (FE) models are a powerful tool that can be used to understand injury mechanisms and develop better safety systems. This study aims to extend the understanding of pediatric spine biomechanics, where there is a paucity of studies available. A newly developed and continuously scalable FE model was validated and scaled to 1.5-, 3-, 6-, 10-, 14- and 18-year-old using a non-linear scaling technique, accounting for local topological changes. The oldest and youngest ages were also scaled using homogeneous geometric scaling. To study the effect of pediatric spinal growth on head kinematics and intervertebral disc strain, the models were exerted to 3.5 g acceleration pulse at the T1 vertebra to simulate frontal, rear and side impacts. It was shown that the head rotation increases with age, but is over predicted when geometrically scaling down from 18- to 1.5-year-old and under predicted when geometrically scaling up from 1.5- to 18-year-old. The strain in the disc, however, showed a clear decrease with age in side impact and for the upper cervical spine in rear impact, indicating a higher susceptibility for neck injury at younger ages. In the frontal impact, no clear age dependence could be seen, suggesting a large contribution from changed facet joint angles, and lower levels of strain, suggesting a lower risk of injury. The results also highlight the benefit of rearward facing children in a seat limiting head lateral motion.

  • 3. Beillas, Philippe
    et al.
    Giordano, Chiara
    Alvarez, Victor
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Ying, Xingjia
    Chevalier, Marie-Christine
    Kirscht, Stefan
    Kleiven, Svein
    Development and performance of the PIPER scalable child human body models2016In: 14th International Conference on the Protection of Children in Cars, 2016Conference paper (Refereed)
  • 4. Beillas, Philippe
    et al.
    Lafon, Yoann
    Frechede, Bertrand
    Janak, Tomas
    Dupeux, Thomas
    Mear, Matthieu
    Kleiven, Svein
    Giordano, Chiara
    Alvarez, Victor
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Chawla, Anoop
    Chhabra, A
    Paruchuri, S an Singh, S
    Kaushik, D
    Mukherjee, S
    Kumar, S
    Devane, K
    Mishra, K
    Machina, G
    Jolivet, Erwan
    Lemaire, Thomas
    Faure, François
    Gilles, Benjamin
    Vimont, Ulysse
    Lecomte, Christophe
    D3. 8 Final version of the personalization and positioning software tool with documentation. PIPER EU Project2017Report (Refereed)
  • 5. Beillas, Philippe
    et al.
    Wang, Xuguang
    Lafon, Yoann
    Frechede, Bertrand
    Janak, Tomas
    Dupeux, Thomas
    Mear, Matthieu
    Pacquaut, Guillaume
    Chevalier, Marie-Christine
    Le Ruyet, Anicet
    Eichene, Alexandre
    Theodorakos, Ilias
    Yin, Xingjia
    Gardegaront, M
    Collot, Jerome
    Petit, Philippe
    Eric, Song
    Moreau, Baptiste
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Giordano, Chiara
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Strömbäck, Alvarez Victor
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    et al,
    PIPER EU Project Final publishable summary2017Report (Refereed)
  • 6.
    Brett, Calvin J.
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. DESY, Notkestr 85, D-22607 Hamburg, Germany..
    Montani, Annaclaudia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering. Politecn Milan, Dept Chem Mat & Chem Engn Giulio Natta, Piazza Leonardo da Vinci 32, I-20133 Milan, Italy..
    Schwartzkopf, M.
    DESY, Notkestr 85, D-22607 Hamburg, Germany..
    van Benthem, R. A. T. M.
    Eindhoven Univ Technol, Lab Phys Chem SPC, Groene Loper 5, NL-5600 MB Eindhoven, Netherlands.;DSM Mat Sci Ctr, Urmonderbaan 22, NL-6167 RD Geleen, Netherlands..
    Jansen, J. F. G. A.
    DSM Mat Sci Ctr, Urmonderbaan 22, NL-6167 RD Geleen, Netherlands..
    Griffini, G.
    Politecn Milan, Dept Chem Mat & Chem Engn Giulio Natta, Piazza Leonardo da Vinci 32, I-20133 Milan, Italy..
    Roth, Stephan Volkher
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Johansson, Mats K.G.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology.
    Revealing structural evolution occurring from photo-initiated polymer network formation2020In: Communications Chemistry, E-ISSN 2399-3669, Vol. 3, no 1, article id 88Article in journal (Refereed)
    Abstract [en]

    Photopolymerization is a key enabling technology offering spatial and temporal control to allow for future functional materials to be made to meet societal needs. However, gaining access to robust experimental techniques to describe the evolution of nanoscale morphology in photo-initiated polymeric systems has proven so far to be a challenging task. Here, we show that these physical transformations can be monitored and quantified at the nanoscale in situ and in real-time. It is demonstrated that the initial structural features of the liquid precursors significantly affect the final morphology and the physical properties of the resulting solid via the occurrence of local heterogeneities in the molecular mobility during the curing transformation. We have made visible how local physical arrestings in the liquid, associated with both cross-linking and vitrification, determine the length scale of the local heterogeneities forming upon curing, found to be in the 10-200nm range. Acomplete account of the structural evolution occurring during photopolymerisation is lacking. Here the physical changes occurring on the nanometer scale during photopolymerisation of acrylates are followed over time by FTIR, X-ray reflectometry, AFM, and GISAXS, offering insight into the mechanism by which initial composition influences the final morphology.

  • 7.
    Brolin, Karin
    et al.
    Lightness By Design AB, Stadsgarden 10,11tr, S-11645 Stockholm, Sweden..
    Lanner, Daniel
    MIPS AB, Kemistvagen 1B, S-18379 Taby, Sweden..
    Halldin, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering. MIPS AB, Kemistvagen 1B, S-18379 Taby, Sweden.
    Work-related traumatic brain injury in the construction industry in Sweden and Germany2021In: Safety Science, ISSN 0925-7535, E-ISSN 1879-1042, Vol. 136, article id 105147Article in journal (Refereed)
    Abstract [en]

    Work-related traumatic brain injuries (wrTBIs) in the construction industry have been studied in North America but, to the best of our knowledge, not in Europe. This study analyzed sets of public data on head injuries occurring in the construction industry from the workers' compensation systems in Sweden and Germany, 2014 - 2018. The ratio of wrTBI varied from 11% to 61% of all head injuries, with higher ratios for more severe injuries. The average yearly incidence (per 100,000 FTE) of wrTBI resulting in more than four days absence from work was nine in Sweden and 117 in Germany, as compared to 22-212 in North American studies. A limitation of studies based on workers' compensation claims is that they underestimate the true burden of wrTBI. The most frequent events leading to wrTBI were falls, followed by loss of control, failure of material agents, and body movements without stress. Falls from a height caused 35% of all wrTBI with more than 14 days off work in Sweden and 57% of all new injury pensions granted in Germany. In North American studies, 52-78% of the wrTBI were caused by falls. This highlights the relevance of fall safety measures to reduce wrTBI in the construction industry, such as avoiding work at heights, use of safety nets, education, and etcetera. The energy absorption of safety helmets mainly protects the head excluding face of which 49-62% were wrTBI, indicating that helmet testing standards should evaluate protection against TBI as well as skull fractures.

  • 8. Cecchi, N. J.
    et al.
    Domel, A. G.
    Liu, Y.
    Rice, E.
    Lu, R.
    Zhan, X.
    Zhou, Z.
    Raymond, S. J.
    Sami, S.
    Singh, H.
    Rangel, I.
    Watson, L. P.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Zeineh, M.
    Camarillo, D. B.
    Grant, G.
    Identifying Factors Associated with Head Impact Kinematics and Brain Strain in High School American Football via Instrumented Mouthguards2021In: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 49, no 10, p. 2814-2826Article in journal (Refereed)
    Abstract [en]

    Repeated head impact exposure and concussions are common in American football. Identifying the factors associated with high magnitude impacts aids in informing sport policy changes, improvements to protective equipment, and better understanding of the brain’s response to mechanical loading. Recently, the Stanford Instrumented Mouthguard (MiG2.0) has seen several improvements in its accuracy in measuring head kinematics and its ability to correctly differentiate between true head impact events and false positives. Using this device, the present study sought to identify factors (e.g., player position, helmet model, direction of head acceleration, etc.) that are associated with head impact kinematics and brain strain in high school American football athletes. 116 athletes were monitored over a total of 888 athlete exposures. 602 total impacts were captured and verified by the MiG2.0’s validated impact detection algorithm. Peak values of linear acceleration, angular velocity, and angular acceleration were obtained from the mouthguard kinematics. The kinematics were also entered into a previously developed finite element model of the human brain to compute the 95th percentile maximum principal strain. Overall, impacts were (mean ± SD) 34.0 ± 24.3 g for peak linear acceleration, 22.2 ± 15.4 rad/s for peak angular velocity, 2979.4 ± 3030.4 rad/s2 for peak angular acceleration, and 0.262 ± 0.241 for 95th percentile maximum principal strain. Statistical analyses revealed that impacts resulting in Forward head accelerations had higher magnitudes of peak kinematics and brain strain than Lateral or Rearward impacts and that athletes in skill positions sustained impacts of greater magnitude than athletes in line positions. 95th percentile maximum principal strain was significantly lower in the observed cohort of high school football athletes than previous reports of collegiate football athletes. No differences in impact magnitude were observed in athletes with or without previous concussion history, in athletes wearing different helmet models, or in junior varsity or varsity athletes. This study presents novel information on head acceleration events and their resulting brain strain in high school American football from our advanced, validated method of measuring head kinematics via instrumented mouthguard technology.

  • 9. Darragh, Walsh
    et al.
    Zhou, Zhou
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Jamie, Kearns
    David, Newport
    John, Mulvihill
    Mechanical Properties of the Cranial Meninges: A Systematic Review2021In: Journal of Neurotrauma, ISSN 0897-7151, E-ISSN 1557-9042, Vol. 38, no 13, p. 1748-1761Article in journal (Refereed)
    Abstract [en]

    The meninges are membranous tissues that are pivotal in maintaining homeostasis of the central nervous system. Despite the importance of the cranial meninges in nervous system physiology and in head injury mechanics, our knowledge of the tissues' mechanical behavior and structural composition is limited. This systematic review analyzes the existing literature on the mechanical properties of the meningeal tissues. Publications were identified from a search of Scopus, Academic Search Complete, and Web of Science and screened for eligibility according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The review details the wide range of testing techniques employed to date and the significant variability in the observed experimental findings. Our findings identify many gaps in the current literature that can serve as a guide for future work for meningeal mechanics investigators. The review identifies no peer-reviewed mechanical data on the falx and tentorium tissues, both of which have been identified as key structures in influencing brain injury mechanics. A dearth of mechanical data for the pia-arachnoid complex also was identified (no experimental mechanics studies on the human pia-arachnoid complex were identified), which is desirable for biofidelic modeling of human head injuries. Finally, this review provides recommendations on how experiments can be conducted to allow for standardization of test methodologies, enabling simplified comparisons and conclusions on meningeal mechanics.

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  • 10. Fahlstedt, M.
    et al.
    Bergström, J.
    Lanner, D.
    Halldin, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    How Efficient are the Rotational Impact Tests in ECE R22.06 Motorcycle Helmet Test Standard to Decrease the Rotational-Induced Brain Injuries?2022In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI, International Research Council on the Biomechanics of Injury , 2022, p. 912-923Conference paper (Refereed)
    Abstract [en]

    Head injuries are among the most common injuries in motorcycle accidents, where the helmet is the main protection. Until recently, the test standards have only evaluated protection against linear impacts. Evaluating protection against rotational impacts has been recently introduced. The objective of this study was to evaluate how current motorcycle helmets perform in ECE R22.06 rotational impact tests. The rotational impact tests were performed on three helmet models and the linear impact tests were performed on one helmet model. All the helmets passed the rotational impact tests. The maximum value for the experimental tests was 4.5 krad/s2 for PRA and 0.48 for BrIC compared to the threshold values of 10.4 krad/s2 and 0.78. In the linear impact tests five out of twenty-two impact tests failed the threshold for peak linear acceleration or head injury criterion. The results from this study suggest that motorcycle helmets will be more optimised towards reducing linear-induced injuries and not rotational-induced injuries in the newly introduced test standard ECE R22.06. This is not responding to the protection requirements when evaluating the accident statistics, which shows that rotational-induced injuries are as common or even more common than linear-induced injuries in helmeted motorcycle accidents. 

  • 11.
    Fahlstedt, Madelen
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Abayazid, F.
    Imperial College, Dyson School of Design Engineering.
    Panzer, M. B.
    University of Virginia, Department of Mechanical and Aerospace Engineering.
    Trotta, A.
    University Collge Dublin, School of Mechanical & Materials Engineering.
    Zhao, W.
    Worcester Polytechnic Institute, Department of Mechanical Engineering.
    Ghajari, M.
    Imperial College, Dyson School of Design Engineering.
    Gilchrist, M. D.
    University College Dublin, School of Mechanical & Materials Engineering.
    Ji, S.
    Worcester Polytechnic Institute, Department of Mechanical Engineering.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Annaidh, A. N.
    University College Dublin, School of Mechanical & Materials Engineering.
    Halldin, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Ranking and Rating Bicycle Helmet Safety Performance in Oblique Impacts Using Eight Different Brain Injury Models2021In: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686Article in journal (Refereed)
    Abstract [en]

    Bicycle helmets are shown to offer protection against head injuries. Rating methods and test standards are used to evaluate different helmet designs and safety performance. Both strain-based injury criteria obtained from finite element brain injury models and metrics derived from global kinematic responses can be used to evaluate helmet safety performance. Little is known about how different injury models or injury metrics would rank and rate different helmets. The objective of this study was to determine how eight brain models and eight metrics based on global kinematics rank and rate a large number of bicycle helmets (n=17) subjected to oblique impacts. The results showed that the ranking and rating are influenced by the choice of model and metric. Kendall’s tau varied between 0.50 and 0.95 when the ranking was based on maximum principal strain from brain models. One specific helmet was rated as 2-star when using one brain model but as 4-star by another model. This could cause confusion for consumers rather than inform them of the relative safety performance of a helmet. Therefore, we suggest that the biomechanics community should create a norm or recommendation for future ranking and rating methods.

  • 12.
    Fahlstedt, Madelen
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Halldin, Peter
    MIPS AB, Stockholm, Sweden.
    The difference in ranking of bike helmets when using different finite element head models2019In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI, International Research Council on the Biomechanics of Injury , 2019, p. 660-661Conference paper (Refereed)
  • 13.
    Fahlstedt, Madelen
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Current Playground Surface Test Standards Underestimate Brain Injury Risk for Children2019In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380Article in journal (Refereed)
    Abstract [en]

    Playgrounds surface test standards have been introduced to reduce the number of fatal and severe injuries. However, these test standards have several simplifications to make it practical, robust and cost-effective, such as the head is represented with a hemisphere, only the linear kinematics is evaluated and the body is excluded. Little is known about how these simplifications may influence the test results. The objective of this study was to evaluate the effect of these simplifications on global head kinematics and head injury prediction for different age groups. The finite element human body model PIPER was used and scaled to seven different age groups from 1.5 up to 18 years old, and each model was impacted at three different playground surface stiffness and three head impact locations. All simulations were performed in pairs, including and excluding the body. Linear kinematics and skull bone stress showed small influence if excluding the body while head angular kinematics and brain tissue strain were underestimated by the same simplification. The predicted performance of the three different playground surface materials, in terms of head angular kinematics and brain tissue strain, was also altered when including the body. A body and biofidelic neck need to be included, together with suitable head angular kinematics based injury thresholds, in future physical or virtual playground surface test standards to better prevent brain injuries.

  • 14.
    Fahlstedt, Madelen
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    The Influence of the Body on Head Kinematics in Playground Falls for Different Age Groups2018In: Proceedings of International Research Council on Biomechanics of Injury (IRCOBI) Conference, 2018Conference paper (Refereed)
  • 15.
    Fahlstedt, Madelen
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Meng, Shiyang
    MIPS AB, Kemistvagen 1B, S-18379 Taby, Sweden..
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Influence of Strain post-processing on Brain Injury Prediction2022In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 132, article id 110940Article in journal (Refereed)
    Abstract [en]

    Finite element head models are a tool to better understand brain injury mechanisms. Many of the models use strain as output but with different percentile values such as 100th, 95th, 90th, and 50th percentiles. Some use the element value, whereas other use the nodal average value for the element. Little is known how strain post-processing is affecting the injury predictions and evaluation of different prevention systems. The objective of this study was to evaluate the influence of strain output on injury prediction and ranking.& nbsp;Two models with different mesh densities were evaluated (KTH Royal Institute of Technology head model and the Total Human Models for Safety (THUMS)). Pulses from reconstructions of American football impacts with and without a diagnosis of mild traumatic brain injury were applied to the models. The value for 100th, 99th, 95th, 90th, and 50th percentile for element and nodal averaged element strain was evaluated based on peak values, injury risk functions, injury predictability, correlation in ranking, and linear correlation.& nbsp;The injury risk functions were affected by the post-processing of the strain, especially the 100th percentile element value stood out. Meanwhile, the area under the curve (AUC) value was less affected, as well as the correlation in ranking (Kendall's tau 0.71-1.00) and the linear correlation (Pearson's r2 0.72-1.00). With the results presented in this study, it is important to stress that the same post-processed strain should be used for injury predictions as the one used to develop the risk function.

  • 16.
    Giordano, Chiara
    et al.
    KTH.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Development of an Unbiased Validation Protocol to Assess the Biofidelity of Finite Element Head Models used in Prediction of Traumatic Brain Injury2016In: SAE Technical Papers, SAE International , 2016, no NovemberConference paper (Refereed)
    Abstract [en]

    This study describes a method to identify laboratory test procedures and impact response requirements suitable for assessing the biofidelity of finite element head models used in prediction of traumatic brain injury. The selection of the experimental data and the response requirements were result of a critical evaluation based on the accuracy, reproducibility and relevance of the available experimental data. A weighted averaging procedure was chosen in order to consider different contributions from the various test conditions and target measurements based on experimental error. According to the quality criteria, 40 experimental cases were selected to be a representative dataset for validation. Based on the evaluation of response curves from four head finite element models, CORA was chosen as a quantitative method to compare the predicted time history response to the measured data. Optimization of the CORA global settings led to the recommendation of performing curve comparison on a fixed time interval of 0-30 ms for intracranial pressure and at least 0-40 ms for brain motion and deformation. The allowable maximum time shift was adjusted depending on the shape of the experimental curves (DMAX = 0.12 for intracranial pressure, DMAX = 0.40 for brain motion and DMAX = 0.25 for brain deformation). Finally, bigger penalization of ratings was assigned to curves with fundamentally incorrect shape compared to those having inaccuracies in amplitude or time shift (cubic vs linear). This rigorous approach is necessary to ensure confidence in the model results and progress in the usage of finite element head models for traumatic brain injury prediction. 

  • 17.
    Giordano, Chiara
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Evaluation of Axonal Strain as a Predictor for Mild Traumatic Brain Injuries Using Finite Element Modeling2014In: SAE Technical Papers, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    Finite element (FE) models are often used to study the biomechanical effects of traumatic brain injury (TBI). Measures based on mechanical responses, such as principal strain or invariants of the strain tensor, are used as a metric to predict the risk of injury. However, the reliability of inferences drawn from these models depends on the correspondence between the mechanical measures and injury data, as well as the establishment of accurate thresholds of tissue injury. In the current study, a validated anisotropic FE model of the human head is used to evaluate the hypothesis that strain in the direction of fibers (axonal strain) is a better predictor of TBI than maximum principal strain (MPS), anisotropic equivalent strain (AESM) and cumulative strain damage measure (CSDM). An analysis of head kinematics-based metrics, such as head injury criterion (HIC) and brain injury criterion (BrIC), is also provided. Logistic regression analysis is employed to compare binary injury data (concussion/no concussion) with continuous strain/kinematics data. The threshold corresponding to 50% of injury probability is determined for each parameter. The predictive power (area under the ROC curve, AUC) is calculated from receiver operating characteristic (ROC) curve analysis. The measure with the highest AUC is considered to be the best predictor of mTBI.Logistic regression shows a statistical correlation between all the mechanical predictors and injury data for different regions of the brain. Peaks of axonal strain have the highest AUC and determine a strain threshold of 0.07 for corpus callosum and 0.15 for the brainstem, in agreement with previously experimentally derived injury thresholds for reversible axonal injury. For a data set of mild TBI from the national football league, the strain in the axonal direction is found to be a better injury predictor than MPS, AESM, CSDM, BrIC and HIC. 

  • 18.
    Gomez-Alvarez, Marcelo
    et al.
    Karolinska Inst, Dept Clin Sci Intervent & Technol, Unit Audiol, Alfred Nobels Alle 10, S-14183 Stockholm, Sweden..
    Gourevitch, Boris
    Sorbonne Univ Paris, Inst Pasteur, INSERM, Unite Genet & Physiol Audit, Paris, France.;CNRS, Paris, France..
    Felix, Richard A., II
    Washington State Univ, Vancouver, WA USA..
    Nyberg, Tobias
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Hernandez-Montiel, Hebert L.
    Univ Autonoma Queretaro, Clin Sistema Nervioso, Lab Neurobiol & Bioingn Celular, Santiago De Queretaro, Mexico..
    Magnusson, Anna K.
    Karolinska Inst, Dept Clin Sci Intervent & Technol, Unit Audiol, Alfred Nobels Alle 10, S-14183 Stockholm, Sweden..
    Temporal information in tones, broadband noise, and natural vocalizations is conveyed by differential spiking responses in the superior paraolivary nucleus2018In: European Journal of Neuroscience, ISSN 0953-816X, E-ISSN 1460-9568, Vol. 48, no 4, p. 2030-2049Article in journal (Refereed)
    Abstract [en]

    Communication sounds across all mammals consist of multiple frequencies repeated in sequence. The onset and offset of vocalizations are potentially important cues for recognizing distinct units, such as phonemes and syllables, which are needed to perceive meaningful communication. The superior paraolivary nucleus (SPON) in the auditory brainstem has been implicated in the processing of rhythmic sounds. Here, we compared how best frequency tones (BFTs), broadband noise (BBN), and natural mouse calls elicit onset and offset spiking in the mouse SPON. The results demonstrate that onset spiking typically occurs in response to BBN, but not. BFT stimulation, while spiking at the sound offset occurs for both stimulus types. This effect of stimulus bandwidth on spiking is consistent with two of the established inputs to the SPON from the octopus cells (onset spiking) and medial nucleus of the trapezoid body (offset spiking). Natural mouse calls elicit two main spiking peaks. The first spiking peak, which is weak or absent with BFT stimulation, occurs most consistently during the call envelope, while the second spiking peak occurs at the call offset. This suggests that the combined spiking activity in the SPON elicited by vocalizations reflects the entire envelope, that is, the coarse amplitude waveform. Since the output from the SPON is purely inhibitory, it is speculated that, at the level of the inferior colliculus, the broadly tuned first peak may improve the signal-to-noise ratio of the subsequent, more call frequency-specific peak. Thus, the SPON may provide a dual inhibition mechanism for tracking phonetic boundaries in social-vocal communication.

  • 19.
    Halldin, Peter
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Fahlstedt, Madelen
    How sensitive are different headform design parameters in oblique helmeted impacts?2018In: Proceedings of International Research Council on Biomechanics of Injury (IRCOBI) Conference, 2018Conference paper (Refereed)
  • 20.
    Huang, Qi
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Finite Element Analysis of Energy-Absorbing Floors for Reducing Head Injury Risk during Fall Accidents2023In: Applied Sciences, E-ISSN 2076-3417, Vol. 13, no 24, article id 13260Article in journal (Refereed)
    Abstract [en]

    Featured Application: The results proposed a new approach to evaluate the protection effectiveness of energy-absorbing floors for fall-related injury prevention. Also, it could help to reduce the huge associated costs related to fall-related injuries among the children and elderly population. Energy-absorbing floor (EAF) has been proposed as one of several biomechanically effective strategies to mitigate the risk of fall-related injuries by decreasing peak loads and enhancing system energy absorption. This study aims to compare the protective capacity of four commercially available EAF products (Igelkott Floor, Kradal, SmartCells, and OmniSports) in terms of head impacts using the finite element (FE) method. The stress–strain curves acquired from mechanical tests were applied to material models in LS-Dyna. The established FE models were then validated using Hybrid III or hemispheric drop tests to compare the acceleration–time curves between experiments and simulations. Finally, the validated FE models were utilized to simulate a typical pedestrian fall accident scenario. It was demonstrated that EAFs can substantially reduce the peak forces, acceleration, and velocity changes during fall-related head impacts. Specifically, in the accident reconstruction scenario, SmartCells provided the largest reduction in peak linear acceleration and skull fracture risk, while Igelkott Floor provided the largest reduction in peak angular velocity and concussion risk. This performance was caused by different energy absorption mechanisms. Consequently, the results can contribute to supporting the implementation of EAFs and determine the effectiveness of various protective strategies for fall-related head injury prevention.

  • 21.
    Huang, Qi
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Lindgren, Natalia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    A method for obtaining case-specific buck models based on vehicle side-view image for pedestrian collision simulations2023In: IRCOBI 2023 - Conference Proceedings, International Research Council on the Biomechanics of Injury, International Research Council on the Biomechanics of Injury , 2023, p. 499-500Conference paper (Refereed)
  • 22.
    Huang, Qi
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Lindgren, Natalia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Zhou, Zhou
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    A method for generating case-specific vehicle models from a single-view vehicle image for accurate pedestrian injury reconstructions2024In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 200, article id 107555Article in journal (Refereed)
    Abstract [en]

    Developing vehicle finite element (FE) models that match real accident-involved vehicles is challenging. This is related to the intricate variety of geometric features and components. The current study proposes a novel method to efficiently and accurately generate case-specific buck models for car-to-pedestrian simulations. To achieve this, we implemented the vehicle side-view images to detect the horizontal position and roundness of two wheels to rectify distortions and deviations and then extracted the mid-section profiles for comparative calculations against baseline vehicle models to obtain the transformation matrices. Based on the generic buck model which consists of six key components and corresponding matrices, the case-specific buck model was generated semi-automatically based on the transformation metrics. Utilizing this image-based method, a total of 12 vehicle models representing four vehicle categories including family car (FCR), Roadster (RDS), small Sport Utility Vehicle (SUV), and large SUV were generated for car-to-pedestrian collision FE simulations in this study. The pedestrian head trajectories, total contact forces, head injury criterion (HIC), and brain injury criterion (BrIC) were analyzed comparatively. We found that, even within the same vehicle category and initial conditions, the variation in wrap around distance (WAD) spans 84–165 mm, in HIC ranges from 98 to 336, and in BrIC fluctuates between 1.25 and 1.46. These findings highlight the significant influence of vehicle frontal shape and underscore the necessity of using case-specific vehicle models in crash simulations. The proposed method provides a new approach for further vehicle structure optimization aiming at reducing pedestrian head injury and increasing traffic safety.

  • 23. Huber, C. M.
    et al.
    Patton, D. A.
    Maheshwari, J.
    Zhou, Zhou
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Arbogast, K. B.
    Finite Element Simulations of a Concussion Case in High School Soccer2022In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI, International Research Council on the Biomechanics of Injury , 2022, p. 616-617Conference paper (Refereed)
  • 24. Ji, S.
    et al.
    Ghajari, M.
    Mao, H.
    Kraft, R. H.
    Hajiaghamemar, M.
    Panzer, M. B.
    Willinger, R.
    Gilchrist, M. D.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Stitzel, J. D.
    Use of Brain Biomechanical Models for Monitoring Impact Exposure in Contact Sports2022In: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 50, no 11, p. 1389-1408Article in journal (Refereed)
    Abstract [en]

    Head acceleration measurement sensors are now widely deployed in the field to monitor head kinematic exposure in contact sports. The wealth of impact kinematics data provides valuable, yet challenging, opportunities to study the biomechanical basis of mild traumatic brain injury (mTBI) and subconcussive kinematic exposure. Head impact kinematics are translated into brain mechanical responses through physics-based computational simulations using validated brain models to study the mechanisms of injury. First, this article reviews representative legacy and contemporary brain biomechanical models primarily used for blunt impact simulation. Then, it summarizes perspectives regarding the development and validation of these models, and discusses how simulation results can be interpreted to facilitate injury risk assessment and head acceleration exposure monitoring in the context of contact sports. Recommendations and consensus statements are presented on the use of validated brain models in conjunction with kinematic sensor data to understand the biomechanics of mTBI and subconcussion. Mainly, there is general consensus that validated brain models have strong potential to improve injury prediction and interpretation of subconcussive kinematic exposure over global head kinematics alone. Nevertheless, a major roadblock to this capability is the lack of sufficient data encompassing different sports, sex, age and other factors. The authors recommend further integration of sensor data and simulations with modern data science techniques to generate large datasets of exposures and predicted brain responses along with associated clinical findings. These efforts are anticipated to help better understand the biomechanical basis of mTBI and improve the effectiveness in monitoring kinematic exposure in contact sports for risk and injury mitigation purposes. 

  • 25. Ji, Z.
    et al.
    Wan, Y.
    Zhao, Z.
    Wang, Teng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Yu, M.
    Wang, H.
    Fan, S.
    Liu, Z.
    Liu, C.
    Polydopamine and Magnesium Ions Loaded 3D-Printed Ti-6Al-4V Implants Coating with Enhanced Osteogenesis and Antibacterial Abilities2022In: Advanced Materials Technologies, E-ISSN 2365-709X, Vol. 7, no 12, article id 2200598Article in journal (Refereed)
    Abstract [en]

    3D printing has been applied in the fabrication of Ti-6Al-4V implants due to its high processing efficiency and flexibility. However, the biological inertness of 3D-printed Ti-6Al-4V implant surface limits its further clinical application. This paper aims to improve the biocompatibility of 3D-printed Ti-6Al-4V implants through multi-scale composite structure and bioactive coating. The samples are prepared by selective laser melting (SLM). The multi-scale composite structure is constructed by acid etching and anodic oxidation, and then the bioactive coating is added by hydrothermal treatment. The results indicate that acid etching removes the residuals on the surface and builds micron-/sub-micron structures. Anodic oxidation superimposes TiO2 nanotube arrays with a diameter of ≈80 nm, forming the multi-scale composite structure. The polydopamine-magnesium ion coating is added by hydrothermal treatment on the basis of retaining the multi-scale composite structure. After modification, the surface wettability and corrosion resistance are improved, and the roughness is slightly reduced. Regarding the biocompatibility of the modified 3D-printed Ti-6Al-4V implant, its admirable osteogenic induction performance is verified on osteoblasts (MC3T3-E1). Also, the addition of magnesium ions achieves better antibacterial properties. The results provide new target points for the surface modification of 3D-printed Ti-6Al-4V implant to attain better clinical performance. 

  • 26.
    Ji, Zhenbing
    et al.
    Shandong Univ, Natl Demonstrat Ctr Expt Mech Engn Educ, Sch Mech Engn, Key Lab High Efficiency & Clean Mfg, Jinan, Peoples R China..
    Wan, Yi
    Shandong Univ, Natl Demonstrat Ctr Expt Mech Engn Educ, Sch Mech Engn, Key Lab High Efficiency & Clean Mfg, Jinan, Peoples R China..
    Wang, Hongwei
    Shandong First Med Univ, Coll Artificial Intelligence & Big Data Med Sci, Tai An, Peoples R China..
    Yu, Mingzhi
    Univ Coll Dublin, Ctr Micro Nano Mfg Technol MNMT Dublin, Sch Mech & Mat Engn, Dublin, Ireland..
    Zhao, Zihe
    Shandong Univ, Natl Demonstrat Ctr Expt Mech Engn Educ, Sch Mech Engn, Key Lab High Efficiency & Clean Mfg, Jinan, Peoples R China..
    Wang, Teng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Ma, Guoxuan
    Shandong Univ, Natl Demonstrat Ctr Expt Mech Engn Educ, Sch Mech Engn, Key Lab High Efficiency & Clean Mfg, Jinan, Peoples R China..
    Fan, Shiyuan
    Shandong Univ, Natl Demonstrat Ctr Expt Mech Engn Educ, Sch Mech Engn, Key Lab High Efficiency & Clean Mfg, Jinan, Peoples R China..
    Liu, Zhanqiang
    Shandong Univ, Natl Demonstrat Ctr Expt Mech Engn Educ, Sch Mech Engn, Key Lab High Efficiency & Clean Mfg, Jinan, Peoples R China..
    Effects of surface morphology and composition of titanium implants on osteogenesis and inflammatory responses: a review2023In: Biomedical Materials, ISSN 1748-6041, E-ISSN 1748-605X, Vol. 18, no 4, article id 042002Article, review/survey (Refereed)
    Abstract [en]

    Titanium and its alloys have been widely used in bone tissue defect treatment owing to their excellent comprehensive properties. However, because of the biological inertness of the surface, it is difficult to achieve satisfactory osseointegration with the surrounding bone tissue when implanted into the body. Meanwhile, an inflammatory response is inevitable, which leads to implantation failure. Therefore, solving these two problems has become a new research hotspot. In current studies, various surface modification methods were proposed to meet the clinical needs. Yet, these methods have not been classified as a system to guide the follow-up research. These methods are demanded to be summarized, analyzed, and compared. In this manuscript, the effect of physical signal regulation (multi-scale composite structure) and chemical signal regulation (bioactive substance) generated by surface modification in promoting osteogenesis and reducing inflammatory responses was generalized and discussed. Finally, from the perspective of material preparation and biocompatibility experiments, the development trend of surface modification in promoting titanium implant surface osteogenesis and anti-inflammatory research was proposed.

  • 27. Kapeliotis, M.
    et al.
    Musigazi, G.
    Famaey, N.
    Depreitere, B.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Vander Sloten, J.
    Assessment of bridging vein rupture associated with acute subdural hematoma through finite elements analysis after biofidelic position adaptation2018In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI, International Research Council on the Biomechanics of Injury , 2018, p. 695-696Conference paper (Refereed)
  • 28.
    Kapeliotis, Markos
    et al.
    Katholieke Univ Leuven, Biomech Sect, Leuven, Belgium. usigazi, Gracia Umuhire; Depreitere, Bart.
    Musigazi, Gracia Umuhire
    Famaey, Nele
    Depreitere, Bart
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Vander Sloten, Jos
    The sensitivity to inter-subject variability of the bridging vein entry angles for prediction of acute subdural hematoma2019In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 92, p. 6-10Article in journal (Refereed)
    Abstract [en]

    Acute subdural hematoma (ASDH) is one of the most frequent traumatic brain injuries (TBIs) with high mortality rate. Bridging vein (BV) ruptures is a major cause of ASDH. The KTH finite element head model includes bridging veins to predict acute subdural hematoma due to BV rupture. In this model, BVs were positioned according to Oka et al. (1985). The aim of the current study is to investigate whether the location and entry angles of these BVs could be modelled using data from a greater statistical sample, and what the impact of this improvement would be on the model's predictive capability of BV rupture. From the CT angiogram data of 78 patients, the relative position of the bridging veins and their entry angles along the superior sagittal sinus was determined. The bridging veins were repositioned in the model accordingly. The performance of the model, w.r.t. BV rupture prediction potential was tested on simulations of full body cadaver head impact experiments. The experiments were simulated on the original version of the model and on three other versions which had updated BV positions according to mean, maximum and minimum entry angles. Even though the successful prediction rate between the models stayed the same, the location of the rupture site significantly improved for the model with the mean entry angles. Moreover, the models with maximum and minimum entry angles give an insight of how BV biovariability can influence ASDH. In order to further improve the successful prediction rate, more biofidelic data are needed both with respect to bridging vein material properties and geometry. Furthermore, more experimental data are needed in order to investigate the behaviour of FE head models in depth.

  • 29.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Biomechanics and Prevention2020In: Management of Severe Traumatic Brain Injury, Springer, 2020Chapter in book (Refereed)
    Abstract [en]

    Injury statistics have found the most common accident situation to be an oblique impact. An oblique impact will give rise to both linear and rotational head kinematics. The low shear modulus and nearly incompressible properties of brain tissue make it to deform primarily in shear for a given impact. This gives a large sensitivity of the brain to rotational loading and a small sensitivity to linear kinematics. Therefore, rotational kinematics is the best indicator of TBI risk. A radial impact, such as in fall accidents, causes substantially higher stresses in the skull with an associated higher risk of skull fractures and TBIs secondary to those impacts.

  • 30.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Biomechanics of traumatic brain injuries and head injury criteria2011In: 2011 IUTAM Symposium on Impact Biomechanics in Sport, Symposium Proceedings, International Union of Theoretical and Applied Mechanics , 2011Conference paper (Refereed)
  • 31.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Hip fracture risk functions for elderly men and women in sideways falls2020In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 105, article id 109771Article in journal (Refereed)
    Abstract [en]

    Falls among the elderly cause a huge number of hip fractures world-wide. The objective is to generate hip fracture force risk functions for elderly women and men in sideways falls which can be used for determining effectiveness of fall prevention measures as well as for individual assessment of fracture risk at the clinics. A literature survey was performed and ten publications were identified who contained several hundred individual femoral neck fracture forces in sideways fall for both elderly women and men. Theoretical distributions were tested for goodness of fit against the pooled dataset with the Anderson-Darling test (AD-test) and root mean square errors (RMSE) were extracted. According to the AD-test, a Weibull distribution is a plausible model for the distribution of hip fracture forces. A simple, exponential two-parameter Weibull function was therefore proposed, having a RMSE below 2.2% compared to the experimental distribution for both men and women. It was demonstrated that elderly women only can endure nearly half the proximal femur force for 5 and 10% fracture risk as elderly men. It should be noted though, that women were found to have significantly lesser body height and body weight which would produce less impact force during falls from standing height. The proposed sex-specific hip fracture risk functions can be used for biomechanically optimizing hip protectors and safety floors and for determining their effectiveness as a fall prevention measure.

  • 32.
    Kleiven, Svein
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Eriksson, Anders
    Umeå Univ, Dept Community Med & Rehabil Forens Med, Umeå, Sweden..
    Lynoe, Niels
    Karolinska Inst, Dept Learning Informat Management & Eth, Ctr Healthcare Eth, Stockholm, Sweden..
    Does High-Magnitude Centripetal Force and Abrupt Shift in Tangential Acceleration Explain High Risk of Subdural Hemorrhage?2022In: NEUROTRAUMA REPORTS, ISSN 2689-288X, Vol. 3, no 1, p. 248-249Article in journal (Refereed)
  • 33.
    Kleiven, Svein
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Sahandifar, Pooya
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Upright trunk and lateral or slight anterior rotation of the pelvis cause the highest proximal femur forces during sideways falls2022In: Frontiers in Bioengineering and Biotechnology, E-ISSN 2296-4185, Vol. 10, article id 1065548Article in journal (Refereed)
    Abstract [en]

    Whole-body models are historically developed for traffic injury prevention, and they are positioned accordingly in the standing or sitting configuration representing pedestrian or occupant postures. Those configurations are appropriate for vehicle accidents or pedestrian-vehicle accidents; however, they are uncommon body posture during a fall accident to the ground. This study aims to investigate the influence of trunk and pelvis angles on the proximal femur forces during sideways falls. For this purpose, a previously developed whole-body model was positioned into different fall configurations varying the trunk and pelvis angles. The trunk angle was varied in steps of 10 degrees from 10 to 80 degrees, and the pelvis rotation was changed every 5 degrees from -20 degrees (rotation toward posterior) to +20 degrees (rotation toward anterior). The simulations were performed on a medium-size male (177 cm, 76 kg) and a small-size female (156 cm, 55 kg), representative for elderly men and women, respectively. The results demonstrated that the highest proximal femur force measured on the femoral head was reached when either male or female model had a 10-degree trunk angle and +10 degrees anterior pelvis rotation.

  • 34.
    Kleiven, Svein
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Sahandifar, Pooya
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Upright trunk and slight anterior rotation of the pelvis cause the highest proximal femur forces during sideways fallsIn: Heliyon, E-ISSN 2405-8440Article in journal (Other academic)
    Abstract [en]

    Whole-body models are historically developed for traffic injury prevention, and they are positioned accordingly in the standing or sitting configurations representing pedestrian or occupant postures. Those configurations are appropriate for vehicle accidents or pedestrian-vehicle accidents; however, they are uncommon body posture during a fall accident to the ground. This study aims to investigate the influence of trunk and pelvis angles on the proximal femur forces during sideways falls. For this purpose, a previously developed whole-body model was positioned into different fall configurations varying the trunk and pelvis angles. The trunk angle was varied in steps of 10 degrees from 10 to 80 degrees, and the pelvis rotation was changed every 5 degrees from -20 degrees (rotation toward posterior) to +20 degrees (rotation toward anterior). The simulations were performed on a medium-size male (177 cm, 76 kg) and a small-size female (156 cm, 55 kg), representative for elderly men and women, respectively. The results demonstrated that the highest proximal femur force measured on the femoral head was reached when either male or female model had a 10-degree trunk angle and +10 degree anterior pelvis rotation.

  • 35. Laic, R. A. G.
    et al.
    Kapeliotis, M.
    Famaey, N.
    Depreitere, B.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Vander Sloten, J.
    Quantifying biovariability in position and diameter of bridging veins to improve acute subdural hematoma prediction in FE head models2021In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI, International Research Council on the Biomechanics of Injury , 2021, p. 337-352Conference paper (Refereed)
    Abstract [en]

    Bridging veins (BV) rupture is a major cause of Acute Subdural Hematoma. This study aims to quantify their biovariability to better understand their properties and increase the biofidelity of finite element (FE) head models. The number of BV and their measured diameters were manually counted in CT angiograms from 67 patients. A mixed linear model was used for the statistical analysis and the results were implemented in the KTH FE head model. LS-DYNA simulations were used to evaluate the amount of successful BV rupture predictions. The false positive and false negative predictions were also counted. The human brain has a mean of 23,18 BV, with diameters ranging between 0,37 and 3,24 mm. In the initial version of the KTH model two BV mechanical properties datasets gave a 6/8 successful prediction rate with one false positive and one false negative and one dataset gave a 7/8 successful prediction rate with one false negative. For the updated version all sets gave a 7/8 successful prediction rate with one false negative. The number of BV and BV diameter size is segment dependent, but not hemisphere dependent. The implementation of these findings in the FE head model is a good preliminary attempt to increase BV rupture predictability.

  • 36. Laic, R. A. G.
    et al.
    Kapeliotis, M.
    Famaey, N.
    Depreitere, B.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Vander Sloten, J.
    Quantifying biovariability in position and diameter of bridging veins to improve acute subdural hematoma prediction in FE head models2022In: Proceedings of Science, Sissa Medialab Srl , 2022, p. 337-352Conference paper (Refereed)
    Abstract [en]

    Bridging veins (BV) rupture is a major cause of Acute Subdural Hematoma. This study aims to quantify their biovariability to better understand their properties and increase the biofidelity of finite element (FE) head models. The number of BV and their measured diameters were manually counted in CT angiograms from 67 patients. A mixed linear model was used for the statistical analysis and the results were implemented in the KTH FE head model. LS-DYNA simulations were used to evaluate the amount of successful BV rupture predictions. The false positive and false negative predictions were also counted. The human brain has a mean of 23,18 BV, with diameters ranging between 0,37 and 3,24 mm. In the initial version of the KTH model two BV mechanical properties datasets gave a 6/8 successful prediction rate with one false positive and one false negative and one dataset gave a 7/8 successful prediction rate with one false negative. For the updated version all sets gave a 7/8 successful prediction rate with one false negative. The number of BV and BV diameter size is segment dependent, but not hemisphere dependent. The implementation of these findings in the FE head model is a good preliminary attempt to increase BV rupture predictability.

  • 37. Laksari, Kaveh
    et al.
    Kurt, Mehmet
    Babaee, Hessam
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Camarillo, David
    Mechanistic Insights into Human Brain Impact Dynamics through Modal Analysis2018In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 120Article in journal (Refereed)
    Abstract [en]

    Although concussion is one of the greatest health challenges today, our physical understanding of the cause of injury is limited. In this Letter, we simulated football head impacts in a finite element model and extracted the most dominant modal behavior of the brain’s deformation. We showed that the brain’s deformation is most sensitive in low frequency regimes close to 30 Hz, and discovered that for most subconcussive head impacts, the dynamics of brain deformation is dominated by a single global mode. In this Letter, we show the existence of localized modes and multimodal behavior in the brain as a hyperviscoelastic medium. This dynamical phenomenon leads to strain concentration patterns, particularly in deep brain regions, which is consistent with reported concussion pathology.

  • 38.
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Biomechanical Visualizations as aNew Tool for CRS Awareness: A booklet introducing the theoretical background2020Other (Other (popular science, discussion, etc.))
    Download full text (pdf)
    fulltext
  • 39.
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Subject-Specific Head Model Generation by Mesh Morphing: A Personalization Framework and Its Applications2021In: Frontiers in Bioengineering and Biotechnology, E-ISSN 2296-4185, Vol. 9, article id 706566Article in journal (Refereed)
    Abstract [en]

    Finite element (FE) head models have become powerful tools in many fields within neuroscience, especially for studying the biomechanics of traumatic brain injury (TBI). Subject-specific head models accounting for geometric variations among subjects are needed for more reliable predictions. However, the generation of such models suitable for studying TBIs remains a significant challenge and has been a bottleneck hindering personalized simulations. This study presents a personalization framework for generating subject-specific models across the lifespan and for pathological brains with significant anatomical changes by morphing a baseline model. The framework consists of hierarchical multiple feature and multimodality imaging registrations, mesh morphing, and mesh grouping, which is shown to be efficient with a heterogeneous dataset including a newborn, 1-year-old (1Y), 2Y, adult, 92Y, and a hydrocephalus brain. The generated models of the six subjects show competitive personalization accuracy, demonstrating the capacity of the framework for generating subject-specific models with significant anatomical differences. The family of the generated head models allows studying age-dependent and groupwise brain injury mechanisms. The framework for efficient generation of subject-specific FE head models helps to facilitate personalized simulations in many fields of neuroscience.

  • 40.
    Li, Xiaogai
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Improved safety standards are needed to better protect younger children at playgrounds2018In: Scientific Reports, E-ISSN 2045-2322, Vol. 8, no 1, article id 15061Article in journal (Refereed)
    Abstract [en]

    Playground-related traumatic brain injuries (TBIs) in children remain a considerable problem world-wide and current safety standards are being questioned due to historical reasons where the injury thresholds had been perpetuated from automobile industry. Here we investigated head injury mechanisms due to falls on playgrounds using a previously developed and validated age-scalable and positionable whole body child model impacted at front, back and side of the head simulating head-first falls from 1.59 meters (m). The results show that a playground material passing the current testing standards (HIC < 1000 and resultant linear acceleration <200g) resulted in maximum strain in the brain higher than known injury thresholds, thus not offering sufficient protection especially for younger children. The analysis highlights the age dependence of head injuries in children due to playground falls and the youngest have a higher risk of brain injury and skull fracture. Further, the results provide the first biomechanical evidence guiding age-dependent injury thresholds for playground testing standards. The results also have direct implications for novel designs of playground materials for a better protection of children from TBIs. Only making the playground material thicker and more compliant is not sufficient. This study represents the first initiative of using full body human body models of children as a new tool to improve playground testing standards and to better protect the children at playgrounds.

  • 41.
    Li, Xiaogai
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Sandler, Håkan
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Infant skull fractures: Accident or abuse?: Evidences from biomechanical analysis using finite element head models2019In: Forensic Science International, ISSN 0379-0738, E-ISSN 1872-6283, Vol. 294, p. 173-182Article in journal (Refereed)
    Abstract [en]

    Abusive Head Trauma (AHT) is considered by some authors to be a leading cause of traumatic death in children less than two years of age and skull fractures are commonly seen in cases of suspected AHT. Today, diagnosing whether the observed fractures are caused by abuse or accidental fall is still a challenge within both the medical and the legal communities and the central question is a biomechanical question: can the described history explain the observed fractures? Finite element (FE) analysis has been shown a valuable tool for biomechanical analysis accounting for detailed head geometry, advanced material modelling, and case-specific factors (e.g. head impact location, impact surface properties). Here, we reconstructed two well-documented suspected abuse cases (a 3- and a 4-month-old) using subject-specific FE head models. The models incorporate the anatomical details and age-dependent anisotropic material properties of infant cranial bones that reflect the grainy fibres radiating from ossification centres. The impact locations are determined by combining multimodality images. The results show that the skull fracture patterns in both cases of suspected abuse could be explained by the described accidental fall history, demonstrating the inherent potential of FE analysis for providing biomechanical evidence to aid forensic investigations. Increased knowledge of injury mechanisms in children may have enormous medico-legal implications world-wide. 

  • 42.
    Li, Xiaogai
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    von Holst, Hans
    Finite element modeling of decompressive craniectomy (DC) and its clinical validation2015In: Advances in Biomedical Sciences and Engineering, ISSN 2377-035X, Vol. 2, no 1, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Decompressive craniectomy (DC) is a reliable neurosurgical approach to reduce a pathologically increased intracranial pressure after neurological diseases such as severe traumatic brain injury (TBI) and stroke. The procedure has substantially reduced the mortality rate but at the expense of increased neurological cognitive impairments. Finite Element (FE) modeling in the past decades has become an important tool to develop innovative treatment strategies in various areas of the clinical neuroscience field. The aim of this study was to develop patient-specific FE models to simulate DC surgery and validate the models against patients' clinical data. The FE models were created based on the Computed Tomography (CT) images of six patients treated with DC. Brain tissue was modeled as poroelastic material. To validate the model prediction, the motion of brain surface at the DC area from the simulation was compared with the measured values from medical images which were derived from image registration. The results from the computational simulations gave a reliable prediction of brain surface motion at DC area for all the six patients evaluated. Both the deformation pattern and the quantitative values of the brain surface displacement from the model simulation were found in good agreement with measured values from medical images. The developed FE model and its validation in this study is a prerequisite for future investigations aiming at finding optimal treatment for a specific patient which hopefully will significantly improve patients' outcome.

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  • 43.
    Li, Xiaogai
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    von Schantz, Anna
    Mips AB, Täby, Sweden.
    Fahlstedt, Madelen
    Mips AB, Täby, Sweden.
    Halldin, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Evaluating child helmet protection and testing standards: A study using PIPER child head models aged 1.5, 3, 6, and 18 years2024In: PLOS ONE, E-ISSN 1932-6203, Vol. 19, no 1 January, article id e0286827Article in journal (Refereed)
    Abstract [en]

    The anatomy of children’s heads is unique and distinct from adults, with smaller and softer skulls and unfused fontanels and sutures. Despite this, most current helmet testing standards for children use the same peak linear acceleration threshold as for adults. It is unclear whether this is reasonable and otherwise what thresholds should be. To answer these questions, helmet-protected head responses for different ages are needed which is however lacking today. In this study, we apply continuously scalable PIPER child head models of 1.5, 3, and 6 years old (YO), and an upgraded 18YO to study child helmet protection under extensive linear and oblique impacts. The results of this study reveal an age-dependence trend in both global kinematics and tissue response, with younger children experiencing higher levels of acceleration and velocity, as well as increased skull stress and brain strain. These findings indicate the need for better protection for younger children, suggesting that youth helmets should have a lower linear kinematic threshold, with a preliminary value of 150g for 1.5-year-old helmets. However, the results also show a different trend in rotational kinematics, indicating that the threshold of rotational velocity for a 1.5YO is similar to that for adults. The results also support the current use of small-sized adult headforms for testing child helmets before new child headforms are available.

  • 44.
    Li, Xiaogai
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Yuan, Qiantailang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Lindgren, Natalia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Huang, Qi
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Fahlstedt, Madelen
    Mips AB, Taby, Sweden..
    Östh, Jonas
    Volvo Cars Safety Ctr, Gothenburg, Sweden.;Chalmers Univ Technol, Dept Mech & Maritime Sci, Div Vehicle Safety, Gothenburg, Sweden..
    Pipkorn, Bengt
    Chalmers Univ Technol, Dept Mech & Maritime Sci, Div Vehicle Safety, Gothenburg, Sweden.;Autol Res, Vargarda, Sweden..
    Jakobsson, Lotta
    Volvo Cars Safety Ctr, Gothenburg, Sweden.;Chalmers Univ Technol, Dept Mech & Maritime Sci, Div Vehicle Safety, Gothenburg, Sweden..
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Personalization of human body models and beyond via image registration2023In: Frontiers in Bioengineering and Biotechnology, E-ISSN 2296-4185, Vol. 11, article id 1169365Article in journal (Refereed)
    Abstract [en]

    Finite element human body models (HBMs) are becoming increasingly important numerical tools for traffic safety. Developing a validated and reliable HBM from the start requires integrated efforts and continues to be a challenging task. Mesh morphing is an efficient technique to generate personalized HBMs accounting for individual anatomy once a baseline model has been developed. This study presents a new image registration-based mesh morphing method to generate personalized HBMs. The method is demonstrated by morphing four baseline HBMs (SAFER, THUMS, and VIVA+ in both seated and standing postures) into ten subjects with varying heights, body mass indices (BMIs), and sex. The resulting personalized HBMs show comparable element quality to the baseline models. This method enables the comparison of HBMs by morphing them into the same subject, eliminating geometric differences. The method also shows superior geometry correction capabilities, which facilitates converting a seated HBM to a standing one, combined with additional positioning tools. Furthermore, this method can be extended to personalize other models, and the feasibility of morphing vehicle models has been illustrated. In conclusion, this new image registration-based mesh morphing method allows rapid and robust personalization of HBMs, facilitating personalized simulations.

  • 45.
    Li, Xiaogai
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Zhou, Zhou
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    An anatomically detailed and personalizable head injury model: Significance of brain and white matter tract morphological variability on strain2021In: Biomechanics and Modeling in Mechanobiology, ISSN 1617-7959, E-ISSN 1617-7940Article in journal (Refereed)
    Abstract [en]

    Finite element head (FE) models are important numerical tools to study head injuries and develop protection systems. The generation of anatomically accurate and subject-specific head models with conforming hexahedral meshes remains a significant challenge. The focus of this study is to present two developmental works: first, an anatomically detailed FE head model with conforming hexahedral meshes that has smooth interfaces between the brain and the cerebrospinal fluid, embedded with white matter (WM) fiber tracts; second, a morphing approach for subject-specific head model generation via a new hierarchical image registration pipeline integrating Demons and Dramms deformable registration algorithms. The performance of the head model is evaluated by comparing model predictions with experimental data of brain–skull relative motion, brain strain, and intracranial pressure. To demonstrate the applicability of the head model and the pipeline, six subject-specific head models of largely varying intracranial volume and shape are generated, incorporated with subject-specific WM fiber tracts. DICE similarity coefficients for cranial, brain mask, local brain regions, and lateral ventricles are calculated to evaluate personalization accuracy, demonstrating the efficiency of the pipeline in generating detailed subject-specific head models achieving satisfactory element quality without further mesh repairing. The six head models are then subjected to the same concussive loading to study the sensitivity of brain strain to inter-subject variability of the brain and WM fiber morphology. The simulation results show significant differences in maximum principal strain and axonal strain in local brain regions (one-way ANOVA test, p < 0.001), as well as their locations also vary among the subjects, demonstrating the need to further investigate the significance of subject-specific models. The techniques developed in this study may contribute to better evaluation of individual brain injury and the development of individualized head protection systems in the future. This study also contains general aspects the research community may find useful: on the use of experimental brain strain close to or at injury level for head model validation; the hierarchical image registration pipeline can be used to morph other head models, such as smoothed-voxel models.

  • 46. Li, Y. Q.
    et al.
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering. Southern Methodist University, United States.
    Gao, X. -L
    Modeling of advanced combat helmet under ballistic impact2015In: Journal of applied mechanics, ISSN 0021-8936, E-ISSN 1528-9036, Vol. 82, no 11, article id 111004Article in journal (Refereed)
    Abstract [en]

    The use of combat helmets has greatly reduced penetrating injuries and saved lives of many soldiers. However, behind helmet blunt trauma (BHBT) has emerged as a serious injury type experienced by soldiers in battlefields. BHBT results from nonpenetrating ballistic impacts and is often associated with helmet back face deformation (BFD). In the current study, a finite element-based computational model is developed for simulating the ballistic performance of the Advanced Combat Helmet (ACH), which is validated against the experimental data obtained at the Army Research Laboratory. Both the maximum value and time history of the BFD are considered, unlike existing studies focusing on the maximum BFD only. The simulation results show that the maximum BFD, the time history of the BFD, and the shape and size of the effective area of the helmet shell agree fairly well with the experimental findings. In addition, it is found that ballistic impacts on the helmet at different locations and in different directions result in different BFD values. The largest BFD value is obtained for a frontal impact, which is followed by that for a crown impact and then by that for a lateral impact. Also, the BFD value is seen to decrease as the oblique impact angle decreases. Furthermore, helmets of four different sizes - extra large, large, medium, and small - are simulated and compared. It is shown that at the same bullet impact velocity the small-size helmet has the largest BFD, which is followed by the medium-size helmet, then by the large-size helmet, and finally by the extra large-size helmet. Moreover, ballistic impact simulations are performed for an ACH placed on a ballistic dummy head form embedded with clay as specified in the current ACH testing standard by using the validated helmet model. It is observed that the BFD values as recorded by the clay in the head form are in good agreement with the experimental data.

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  • 47.
    Lindgren, Natalia
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Fahlstedt, Madelen
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Influence of Headform on Assessments and Ratings of the Protective Performance of Bicycle Helmets2022In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI, International Research Council on the Biomechanics of Injury , 2022, p. 892-911Conference paper (Refereed)
    Abstract [en]

    Numerous helmet rating methods have been proposed to assess the safety and effectiveness of bicycle helmets. The methods usually involve a series of experimental impact tests using an Anthropomorphic Test Device (ATD) headform. There are several headforms available for the purpose and this study sought to assess how the choice of headform influences the safety assessment and ratings of bicycle helmets by following four proposed rating programs using three commonly used headforms. 19 head impact cases were evaluated computationally using the National Operating Committee on Standards for Athletic Equipment (NOCSAE) headform, Hybrid III (HIII) headform, and standard EN960 headform. The results show that for most oblique impact cases, EN960 produced considerably lower Peak Angular Acceleration (PAA), Peak Angular Velocity (PAV) and head injury risk compared to HIII and NOCSAE. This implies that the safety performance of bicycle helmets could be rated higher when using uncoated metal headforms compared to rubber-coated ones. The different headforms' tendency to produce varying rotational motion in oblique impacts raises questions about which of the headforms are suitable for such impact tests. The results presented in this study emphasize the occasional contradictions in helmet ratings presented by helmet rating programs. 

  • 48.
    Lindgren, Natalia
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Yuan, Qiantailang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Pipkorn, Bengt
    Autol Res, Vargarda, Sweden..
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Li, Xiaogai
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Development of personalizable female and male pedestrian SAFER human body models2024In: Traffic Injury Prevention, ISSN 1538-9588, E-ISSN 1538-957X, Vol. 25, no 2, p. 182-193Article in journal (Refereed)
    Abstract [en]

    ObjectivesVulnerable road users are globally overrepresented as victims of road traffic injuries. Developing biofidelic male and female pedestrian human body models (HBMs) that represent diverse anthropometries is essential to enhance road safety and propose intervention strategies.MethodsIn this study, 50th percentile male and female pedestrians of the SAFER HBM were developed via a newly developed image registration-based mesh morphing framework. The performance of the HBMs was evaluated by means of a set of cadaver experiments, involving subjects struck laterally by a generic sedan buck.ResultsIn simulated whole-body pedestrian collisions, the personalized HBMs effectively replicate trajectories of the head and lower body regions, as well as head kinematics, in lateral impacts. The results also demonstrate the personalization framework's capacity to generate personalized HBMs with reliable mesh quality, ensuring robust simulations.ConclusionsThe presented pedestrian HBMs and personalization framework provide robust means to reconstruct and evaluate head impacts in pedestrian-to-vehicle collisions thoroughly and accurately.

  • 49.
    Lindgren, Natalia
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Yuan, Qiantailang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Pipkorn, Bengt
    Autoliv Research, Vårgårda, Sweden..
    Kleiven, Svein
    Autoliv Research, Vårgårda, Sweden..
    Li, Xiaogai
    Autoliv Research, Vårgårda, Sweden..
    Subject-Specific Pedestrian SAFER Human Body Models using a Rapid and Landmark-Free Mesh Morphing Method2023In: IRCOBI 2023 - Conference Proceedings, International Research Council on the Biomechanics of Injury, International Research Council on the Biomechanics of Injury , 2023, p. 523-524Conference paper (Refereed)
  • 50.
    Majdolhosseini, Maryam
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Zhou, Zhou
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Villa, Alessandra
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for High Performance Computing, PDC.
    Which part of axonal membrane is the most vulnerable: A molecular dynamics/Finite Element study2023In: European Biophysics Journal, ISSN 0175-7571, E-ISSN 1432-1017, Vol. 52, no SUPPL 1, p. S39-S39Article in journal (Other academic)
123 1 - 50 of 115
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