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  • 1.
    Aare, Magnus
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Evaluation of head response to ballistic helmet impacts, using FEM2003Conference paper (Refereed)
  • 2. Aare, Magnus
    et al.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Evaluation of head response to ballistic helmet impacts using the finite element method2007In: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 34, no 3, p. 596-608Article in journal (Refereed)
    Abstract [en]

    Injuries to the head caused by ballistic impacts are not well understood. Ballistic helmets provide good protection, but still, injuries to both the skull and brain occur. Today there is a lack of relevant test procedure to evaluate the efficiency of a ballistic helmet. The purpose of this project was (1) to study how different helmet shell stiffness affects the load levels in the human head during an impact, and (2) to study how different impact angles affects the load levels in the human head. A detailed finite element (FE) model of the human head, in combination with an FE model of a ballistic helmet (the US Personal Armour System Ground Troops' (PASGT) geometry) was used. The head model has previously been validated against several impact tests on cadavers. The helmet model was validated against data from shooting tests. Focus was aimed on getting a realistic response of the coupling between the helmet and the head and not on modeling the helmet in detail. The studied data from the FE simulations were stress in the cranial bone, strain in the brain tissue, pressure in the brain, change in rotational velocity and translational and rotational acceleration. A parametric study was performed to see the influence of a variation in helmet shell stiffness on the outputs from the model. The effect of different impact angles was also studied. Dynamic helmet shell deflections larger than the initial distance between the shell and the skull should be avoided in order to protect the head from the most injurious threat levels. It is more likely that a fracture of the skull bone occurs if the inside of the helmet shell strikes the skull. Oblique ballistic impacts may in some cases cause higher strains in the brain tissue than pure radial ones.

  • 3.
    Aare, Magnus
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Proposed global injury thresholds for oblique helmet impacts2003Conference paper (Refereed)
  • 4. Aare, Magnus
    et al.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Injuries from motorcycle- and moped crashes in Sweden from 1987 to 1999.2003In: Injury control and safety promotion, ISSN 1566-0974, E-ISSN 1744-4985, Vol. 10, no 3, p. 131-8Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to study injuries from motorcycle and moped crashes in Sweden from 1987 to 1999. Databases at the National Board for Health and Welfare and codes from both ICD9 and ICD10 systems were used, including patterns of age, gender, E-code and type of injury. Length of hospital stay, type of injuries and trends over time was evaluated. To get a more detailed picture of the age distribution, type of vehicle used and number of killed, data from the Swedish National Road Administration were also used. In Sweden, 27,122 individuals received in-patient care due to motorcycle and moped injuries between 1987 and 1999. The motorcycle and moped injury rate was reduced in the second half of the studied period and so were the total days of treatment per year. Males had eight times the incidence of injuries compared to females. Riders under the age of 26 and in particular those at an age of 15 had the highest incidence rate. Head injuries were the most frequent diagnosis, followed by fractures to the lower limbs. Concussion was the most frequent head injury. Focal and diffuse brain injuries combined showed the same frequency as concussion. It is concluded that more preventative strategies must be presented before the injury rate can be reduced.

  • 5.
    Antoni, Per
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hed, Yvonne
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nordberg, Axel
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Nyström, Daniel
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Hult, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Bifunctional Dendrimers: From Robust Synthesis and Accelerated One-Pot Postfunctionalization Strategy to Potential Applications2009In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 48, no 12, p. 2126-2130Article in journal (Refereed)
  • 6.
    Antoni, Per
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hed, Yvonne
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nordberg, Axel
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Nyström, Daniel
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Hult, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    One-pot dendritic growth and post-functionalization of multifunctional dendrimers: Synthesis and application2009Manuscript (preprint) (Other academic)
  • 7.
    Asplund, Maria
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Conjugated Polymers for Neural Interfaces: Prospects, possibilities and future challenges2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Within the field of neuroprosthetics the possibility to use implanted electrodes for communication with the nervous system is explored. Much effort is put into the material aspects of the electrode implant to increase charge injection capacity, suppress foreign body response and build micro sized electrode arrays allowing close contact with neurons. Conducting polymers, in particular poly(3,4-ethylene dioxythiophene) (PEDOT), have been suggested as materials highly interesting for such neural communication electrodes. The possibility to tailor the material both mechanically and biochemically to suit specific applications, is a substantial benefit with polymers when compared to metals. PEDOT also have hybrid charge transfer properties, including both electronic and ionic conduction, which allow for highly efficient charge injection.

     

    Part of this thesis describes a method of tailoring PEDOT through exchanging the counter ion used in electropolymerisation process. Commonly used surfactants can thereby be excluded and instead, different biomolecules can be incorporated into the polymer. The electrochemical characteristics of the polymer film depend on the ion. PEDOT electropolymerised with heparin was here determined to have the most advantageous properties. In vitro methods were applied to confirm non-cytotoxicity of the formed PEDOT:biomolecular composites. In addition, biocompatibility was affirmed for PEDOT:heparin by evaluation of inflammatory response and neuron density when implanted in rodent cortex.

     

    One advantage with PEDOT often stated, is its high stability compared to other conducting polymers. A battery of tests simulating the biological environment was therefore applied to investigate this stability, and especially the influence of the incorporated heparin. These tests showed that there was a decline in the electroactivity of PEDOT over time. This also applied in phosphate buffered saline at body temperature and in the absence of other stressors. The time course of degradation also differed depending on whether the counter ion was the surfactant polystyrene sulphonate or heparin, with a slightly better stability for the former.

     

    One possibility with PEDOT, often overlooked for biological applications, is the use of its semi conducting properties in order to include logic functions in the implant. This thesis presents the concept of using PEDOT electrochemical transistors to construct textile electrode arrays with in-built multiplexing. Using the electrolyte mediated interaction between adjacent PEDOT coated fibres to switch the polymer coat between conducting and non conducting states, then transistor function can be included in the conducting textile. Analogue circuit simulations based on experimentally found transistor characteristics proved the feasibility of these textile arrays. Developments of better polymer coatings, electrolytes and encapsulation techniques for this technology, were also identified to be essential steps in order to make these devices truly useful.

     

    In summary, this work shows the potential of PEDOT to improve neural interfaces in several ways. Some weaknesses of the polymer and the polymer electronics are presented and this, together with the epidemiological data, should point in the direction for future studies within this field.

  • 8.
    Asplund, Maria
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Hamedi, Mahiar
    Forchheimer, Robert
    Inganäs, Olle
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Wire electronics and woven logic, as a potential technology for neuroelectronic implantsManuscript (Other (popular science, discussion, etc.))
    Abstract [en]

    New strategies to improve neuron coupling to neuroelectronic implants are needed. In particular, to maintain functional coupling between implant and neurons, foreign body response like encapsulation must me minimized. Apart from modifying materials to mitigate encapsulation it has been shown that with extremely thin structures, encapsulation will be less pronounced. We here utilize wire electrochemical transistors (WECTs) using conducting polymer coated fibers. Monofilaments down to 10 μm can be successfully coated and weaved into complex networks with built in logic functions, so called textile logic. Such systems can control signal patterns at a large number of electrode terminals from a few addressing fibres. Not only is fibre size in the range where less encapsulation is expected but textiles are known to make successful implants because of their soft and flexible mechanical properties. Further, textile fabrication provides versatility and even three dimensional networks are possible. Three possible architectures for neuroelectronic systems are discussed. WECTs are sensitive to dehydration and materials for better durability or improved encapsulation is needed for stable performance in biological environments.

  • 9.
    Asplund, Maria
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Hamedi, Mahiar
    Inganäs, Olle
    Forchheimer, Robert
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Neural microcontacts with wire electrodes and woven logic2007Conference paper (Refereed)
  • 10.
    Asplund, Maria
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Nilsson, Mats
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Jacobsson, Anders
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Incidence of traumatic peripheral nerve injuries and amputations in Sweden between 1998 and 20062008In: Neuroepidemiology, ISSN 0251-5350, E-ISSN 1423-0208Article in journal (Refereed)
    Abstract [en]

    Background: To define the epidemiological pattern of nerve injuries and traumatic amputations in Sweden, 1998-2006, and investigate possible targets for emerging neural engineering and neuroprosthetic technologies.

    Methods: The Swedish Hospital Discharge Register was used as basis of information, including data from all public in-patient care, excluding out-patient data. ICD-10 codes were screened for nerve injuries and traumatic amputations of high incidence or in-patient care time. Selected codes, causing factors, age and gender distribution were discussed in detail, and potential targets for tailored solutions were identified.

    Results: Incidence rate was determined to 13.9 for nerve injuries and 5.21 for amputations per 100 000 person-yrs. The majority of injuries occurred at wrist and hand level although it could be concluded that these are often minor injuries requiring less than a week of hospitalization. The single most care consuming nerve injury was brachial plexus injury constituting, in average, 68 injuries and 960 hospital days annually. When minor amputations of fingers and toes were disregarded, most frequent site of amputation was between knee and ankle (24 patients / year).

    Conclusions: Based on analysis of incidence and care time, we find that brachial plexus injuries and lower leg amputations should be primary targets of these new technologies.

  • 11.
    Asplund, Maria
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Nyberg, Tobias
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Inganäs, Olle
    Electroactive polymers for neural interfaces2010In: Polymer chemistry, ISSN 1759-9954, Vol. 1, no 9, p. 1374-1391Article, review/survey (Refereed)
    Abstract [en]

    Development of electroactive conjugated polymers, for the purpose of recording and eliciting signals in the neural systems in humans, can be used to fashion the interfaces between the two signalling systems of electronics and neural systems. The design of desirable chemical, mechanical and electrical properties in the electroactive polymer electrodes, and the means of integration of these into biological systems, are here reviewed.

  • 12.
    Asplund, Maria
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Thaning, Elin
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Lundberg, J.
    Sandberg-Nordqvist, A. C.
    Kostyszyn, B.
    Inganas, O.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Toxicity evaluation of PEDOT/biomolecular composites intended for neural communication electrodes2009Article in journal (Refereed)
    Abstract [en]

    Electrodes coated with the conducting polymer poly(3,4-ethylene dioxythiophene) (PEDOT) possess attractive electrochemical properties for stimulation or recording in the nervous system. Biomolecules, added as counter ions in electropolymerization, could further improve the biomaterial properties, eliminating the need for surfactant counter ions in the process. Such PEDOT/biomolecular composites, using heparin or hyaluronic acid, have previously been investigated electrochemically. In the present study, their biocompatibility is evaluated. An agarose overlay assay using L929 fibroblasts, and elution and direct contact tests on human neuroblastoma SH-SY5Y cells are applied to investigate cytotoxicity in vitro. PEDOT: heparin was further evaluated in vivo through polymer-coated implants in rodent cortex. No cytotoxic response was seen to any of the PEDOT materials tested. The examination of cortical tissue exposed to polymer-coated implants showed extensive glial scarring irrespective of implant material (Pt:polymer or Pt). However, quantification of immunological response, through distance measurements from implant site to closest neuron and counting of ED1+ cell density around implant, was comparable to those of platinum controls. These results indicate that PEDOT: heparin surfaces were non-cytotoxic and show no marked difference in immunological response in cortical tissue compared to pure platinum controls.

  • 13.
    Asplund, Maria
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Thaning, Elin
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Lundberg, Johan
    Sandberg-Nordqvist, Ann-Christin
    Kostyszyn, Beata
    Inganäs, Olle
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Biocompatibility of PEDOT/biomolecular composites intended for neural communication electrodesManuscript (Other (popular science, discussion, etc.))
    Abstract [en]

    Electrodes of the conjugated polymer poly(3,4-ethylene dioxythiophene) (PEDOT) have been shown to possess very attractive electrochemical properties for functional electrical stimulation (FES) or recording in the nervous system. Biomolecules already present in nervous tissue, added as counter ions in PEDOT electropolymerisation, could be a route to further improve the biomaterial properties of PEDOT, eliminating the need of surfactant counter ions like docedyl benzene sulphonate (DBS) or polystyrene sulphonate (PSS) in the polymerisation process. Such PEDOT/biomolecular composites using heparin, or hyaluronic acid, have been electrochemically investigated in a previous study and have been shown to retain the attractive electrochemical properties already proven for PEDOT:PSS.

     

    The aim of the present study is to evaluate biocompatibility of these PEDOT/biomolecular composites in vitro and also evaluate PEDOT:heparin biocompatibility in cortical tissue in vivo. Hereby, we also aim to identify a suitable test protocol, that can be used in future evaluations when further material developments are made.

     

    Material toxicity was first tested on cell lines, both through a standardised agarose overlay assay on L929 fibroblasts, and through elution tests on human neuroblastoma SH-SY5Y cells. Subsequently, a biocompatibility in vivo test was performed using PEDOT:heparin coated platinum probes implanted in the cerebral cortex of Sprague-Dawley rats. Tissue was collected at three weeks and six weeks of implantation and evaluated by immunohistochemistry.

     

    No cytotoxic response was seen to any of the PEDOT:biomolecular composites tested here. Furthermore, elution tests were found to be a practical and effective way of screening materials for toxicity and had a clear advantage over the agarose overlay assay, which was difficult to apply on other cell types than fibroblasts. Elution tests would therefore be recommendable as a screening method, at all stages of material development. In the in vivo tests, the stiffness of the platinum substrate was a significant problem, and extensive glial scarring was seen in most cases irrespective of implant material. However, quantification of immunological response through distance measurements from implant site to closest neuron, and counting of macrophage densities in proximity to polymer surface, was comparable to those of platinum controls. These results indicate that PEDOT:heparin surfaces were as compatible with cortical tissue as pure platinum controls.

  • 14.
    Asplund, Maria
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Inganäs, Olle
    Composite biomolecule/PEDOT materials for neural electrodes2008In: Biointerphases, ISSN 1559-4106, Vol. 3, no 3, p. 83-93Article in journal (Refereed)
    Abstract [en]

    Electrodes intended for neural communication must be designed to meet boththe electrochemical and biological requirements essential for long term functionality. Metallic electrode materials have been found inadequate to meet theserequirements and therefore conducting polymers for neural electrodes have emergedas a field of interest. One clear advantage with polymerelectrodes is the possibility to tailor the material to haveoptimal biomechanical and chemical properties for certain applications. To identifyand evaluate new materials for neural communication electrodes, three chargedbiomolecules, fibrinogen, hyaluronic acid (HA), and heparin are used ascounterions in the electrochemical polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT). The resultingmaterial is evaluated electrochemically and the amount of exposed biomoleculeon the surface is quantified. PEDOT:biomolecule surfaces are also studiedwith static contact angle measurements as well as scanning electronmicroscopy and compared to surfaces of PEDOT electrochemically deposited withsurfactant counterion polystyrene sulphonate (PSS). Electrochemical measurements show that PEDOT:heparinand PEDOT:HA, both have the electrochemical properties required for neuralelectrodes, and PEDOT:heparin also compares well to PEDOT:PSS. PEDOT:fibrinogen isfound less suitable as neural electrode material.

  • 15.
    Brolin, Karin
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Leijonhufvud, I.
    The effect of muscle activation on neck response2005In: Traffic Injury Prevention, ISSN 1538-9588, E-ISSN 1538-957X, Vol. 6, no 1, p. 67-76Article in journal (Refereed)
    Abstract [en]

    Prevention of neck injuries due to complex loading, such as occurs in traffic accidents, requires knowledge of neck injury mechanisms and tolerances. The influence of muscle activation on outcome of the injuries is not clearly understood. Numerical simulations of neck injury accidents can contribute to increase the understanding of injury tolerances. The finite element (FE) method is suitable because it gives data on stress and strain of individual tissues that can be used to predict injuries based on tissue level criteria. The aim of this study was to improve and validate an anatomically detailed FE model of the human cervical spine by implement neck musculature with passive and active material properties. Further, the effect of activation time and force on the stresses and strains in the cervical tissues were studied for dynamic loading due to frontal and lateral impacts. The FE model used includes the seven cervical vertebrae, the spinal ligaments, the facet joints with cartilage, the intervertebral disc, the skull base connected to a rigid head, and a spring element representation of the neck musculature. The passive muscle properties were defined with bilinear force-deformation curves and the active properties were defined using a material model based on the Hill equation. The FE model's responses were compared to volunteer experiments for frontal and lateral impacts of 15 and 7 g. Then, the active muscle properties where varied to study their effect on the motion of the skull, the stress level of the cortical and trabecular bone, and the strain of the ligaments. The FE model had a good correlation to the experimental motion corridors when the muscles activation was implemented. For the frontal impact a suitable peak muscle force was 40 N/cm2 whereas 20 N/cm2 was appropriate for the side impact. The stress levels in the cortical and trabecular bone were influenced by the point forces introduced by the muscle spring elements; therefore a more detailed model of muscle insertion would be preferable. The deformation of each spinal ligament was normalized with an appropriate failure deformation to predict soft tissue injury. For the frontal impact, the muscle activation turned out to mainly protect the upper cervical spine ligaments, while the musculature shielded all the ligaments disregarding spinal level for lateral impacts. It is concluded that the neck musculature does not have the same protective properties during different impacts loadings.

  • 16.
    Brolin, Karin
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Hedenstierna, Sofia
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Bass, Cameron
    Center for Applied Biomechanics, University of Virginia, Charlottesville.
    Alem, Nabih
    US Army Aeromedical Research Laboratory, Fort Rucker.
    The importance of muscle tension on the outcome of impacts with a major vertical component2008In: International Journal of Crashworthiness, ISSN 1358-8265, E-ISSN 1754-2111, Vol. 13, no 5, p. 487-498Article in journal (Refereed)
    Abstract [en]

    The hypothesis that muscle tension protects the spine from injuries in helicopter scenarios was tested using a finite-element model of the human head and neck. It was compared with cadaver crash sled experiment with good correlation. Then, simulations were performed with a sinusoidal velocity (5-22 G) applied at T1 60° to the horizontal plane. The model with relaxed muscle activation had delayed and decreased peak head rotation compared with passive properties only. Full muscle activation decreased the injury risk for the 13.5-22 G impacts. A sensitivity study of the impact angle showed a very slight variation of the resulting neck flexion, and 1° change affected all ligament injury predictions less than 4%. Finally, simulations with helmets resulted in increased ligament and disc strains with increasing helmet mass and with an anterior or inferior shift of the centre of gravity. It is concluded that the hypothesis seems to hold.

  • 17.
    Brolin, Karin
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Nordberg, Axel
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Stability and fibre reinforced adhesive fixation of vertebral fractures in the upper cervical spine2006In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, p. 151-152Article in journal (Refereed)
  • 18. Cloots, R. J. H.
    et al.
    van Dommelen, J. A. W.
    Nyberg, Tobias
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Geers, M. G. D.
    Micromechanics of diffuse axonal injury: influence of axonal orientation and anisotropy2011In: Biomechanics and Modeling in Mechanobiology, ISSN 1617-7959, E-ISSN 1617-7940, Vol. 10, no 3, p. 413-422Article in journal (Refereed)
    Abstract [en]

    Multiple length scales are involved in the development of traumatic brain injury, where the global mechanics of the head level are responsible for local physiological impairment of brain cells. In this study, a relation between the mechanical state at the tissue level and the cellular level is established. A model has been developed that is based on pathological observations of local axonal injury. The model contains axons surrounding an obstacle (e.g., a blood vessel or a brain soma). The axons, which are described by an anisotropic fiber-reinforced material model, have several physically different orientations. The results of the simulations reveal axonal strains being higher than the applied maximum principal tissue strain. For anisotropic brain tissue with a relatively stiff inclusion, the relative logarithmic strain increase is above 60%. Furthermore, it is concluded that individual axons oriented away from the main axonal direction at a specific site can be subjected to even higher axonal strains in a stress-driven process, e.g., invoked by inertial forces in the brain. These axons can have a logarithmic strain of about 2.5 times the maximum logarithmic strain of the axons in the main axonal direction over the complete range of loading directions. The results indicate that cellular level heterogeneities have an important influence on the axonal strain, leading to an orientation and location-dependent sensitivity of the tissue to mechanical loads. Therefore, these effects should be accounted for in injury assessments relying on finite element head models.

  • 19.
    Cloots, Rudy J.H.
    et al.
    Eindhoven University of Technology, Department of Mechanical Engineering.
    van Dommelen, J.A.W.
    Eindhoven University of Technology, Department of Mechanical Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Geers, Marc
    Eindhoven University of Technology, Department of Mechanical Engineering.
    Multi-scale mechanics of traumatic brain injury: predicting axonal strains from head loads2013In: Biomechanics and Modeling in Mechanobiology, ISSN 1617-7959, E-ISSN 1617-7940, Vol. 12, no 1, p. 137-150Article in journal (Refereed)
    Abstract [en]

    The length scales involved in the development of diffuse axonal injury typically range from the head level (i.e., mechanical loading) to the cellular level. The parts of the brain that are vulnerable to this type of injury are mainly the brainstem and the corpus callosum, which are regions with highly anisotropically oriented axons. Within these parts, discrete axonal injuries occur mainly where the axons have to deviate from their main course due to the presence of an inclusion. The aim of this study is to predict axonal strains as a result of a mechanical load at the macroscopic head level. For this, a multi-scale finite element approach is adopted, in which a macro-level head model and a micro-level critical volume element are coupled. The results show that the axonal strains cannot be trivially correlated to the tissue strain without taking into account the axonal orientations, which indicates that the heterogeneities at the cellular level play an important role in brain injury and reliable predictions thereof. In addition to the multi-scale approach, it is shown that a novel anisotropic equivalent strain measure can be used to assess these micro-scale effects from head-level simulations only.

  • 20.
    Cloots, Rudy J.H.
    et al.
    Eindhoven University of Technology, Department of Mechanical Engineering.
    van Dommelen, JAW
    Eindhoven University of Technology, Department of Mechanical Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Geers, Marc
    Eindhoven University of Technology, Department of Mechanical Engineering.
    Traumatic Brain Injury at Multiple Length Scales: Relating Diffuse Axonal Injury to Discrete Axonal Impairment2010In: 2010 INTERNATIONAL IRCOBI CONFERENCE ON THE BIOMECHANICS OF INJURY PROCEEDINGS, 2010, p. 119-130Conference paper (Refereed)
  • 21. Courteille, O.
    et al.
    Ho, Johnson
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Fahlstedt, Madelen
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Fors, U.
    Felländer-Tsai, L.
    Hedman, L.
    Möller, H.
    Face validity of VIS-Ed: A visualization program for teaching medical students and residents the biomechanics of cervical spine trauma2013In: Medicine Meets Virtual Reality 20, IOS Press, 2013, p. 96-102Conference paper (Refereed)
    Abstract [en]

    This RCT study aimed to investigate if VIS-Ed (Visualization through Imaging and Simulation - Education) had the potential to improve medical student education and specialist training in clinical diagnosis and treatment of trauma patients. The participants' general opinion was reported as high in both groups (lecture vs. virtual patient (VP)). Face validity of the VIS-Ed for cervical spine trauma was demonstrated and the VP group reported higher stimulation and engagement compared to the lecture group. No significant difference in the knowledge test between both groups could be observed, confirming our null hypothesis that VIS-Ed was on par with a lecture.

  • 22.
    Eriksson, Magnus G.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Haptic Milling Simulation in Six Degrees-of-Freedom: With Application to Surgery in Stiff Tissue2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The research presented in this thesis describes a substantial part of the design of a prototypical surgical training simulator. The results are intended to be applied in future simulators used to educate and train surgeons for bone milling operations. In earlier work we have developed a haptic bone milling surgery simulator prototype based on three degrees-of-freedom force feedback. The contributions presented here constitute an extension to that work by further developing the haptic algorithms to enable six degrees-of-freedom (6-DOF) haptic feedback. Such feedback is crucial for a realistic haptic experience when interacting in a more complex virtual environment, particularly in milling applications.The main contributions of this thesis are:The developed 6-DOF haptic algorithm is based on the work done by Barbic and James, but differs in that the algorithm is modified and optimized for milling applications. The new algorithm handles the challenging problem of real-time rendering of volume data changes due to material removal, while fulfilling the requirements on stability and smoothness of the kind of haptic applications that we approach. The material removal algorithm and the graphic rendering presented here are based on the earlier research. The new 6-DOF haptic milling algorithm is characterized by voxel-based collision detection, penalty-based and constraint-based haptic feedback, and by using a virtual coupling for stable interaction.Milling a hole in an object in the virtual environment or dragging the virtual tool along the surface of a virtual object shall generate realistic contact force and torque in the correct directions. These are important requirements for a bone milling simulator to be used as a future training tool in the curriculum of surgeons. The goal of this thesis is to present and state the quality of a newly developed 6-DOF haptic milling algorithm. The quality of the algorithm is confirmed through a verification test and a face validity study performed in collaboration with the Division of Orthopedics at the Karolinska University Hospital. In a simulator prototype, the haptic algorithm is implemented together with a new 6-DOF haptic device based on parallel kinematics. This device is developed with workspace, transparency and stiffness characteristics specifically adapted to the particular procedure. This thesis is focuses on the 6-DOF haptic algorithm.

  • 23.
    Eriksson, Magnus G.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    The use of virtual reality and haptic simulators for training and education of surgical skills2006In: Simulation in Healthcare: journal of the society for simulation in healthcare, ISSN 1559-2332Article in journal (Other academic)
  • 24.
    Fahlstedt, Madelen
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Baeck, Katrien
    Mechanical Engineering Department, Biomechanics Section, Katholieke Universiteit Leuven, Belgium.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Vander Sloten, Jos
    Mechanical Engineering Department, Biomechanics Section, Katholieke Universiteit Leuven, Belgium.
    Goffin, Jan
    Mechanical Engineering Department, Biomechanics Section, Katholieke Universiteit Leuven, Belgium.
    Depreitere, Bart
    Mechanical Engineering Department, Biomechanics Section, Katholieke Universiteit Leuven, Belgium.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Influence of impact velocity and angle in a detailed reconstruction of a bicycle accident2012In: 2012 IRCOBI Conference Proceedings - International Research Council on the Biomechanics of Injury, 2012, p. 787-799Conference paper (Refereed)
    Abstract [en]

    Bicycle accidents have become the most common cause of serious injury in the traffic during the last couple of years in Sweden. The objective of this study was to investigate the effect of the input variables, initial velocity and head orientation, of a bicycle accident reconstruction on the strain levels in the brain using a detailed FE head model. The accident involved a non-helmeted 68 year old male who sustained a linear skull fracture, contusions, acute subdural hematoma, and small bleeding at the swelling (subarachnoid blood). The orientation of the head just before impact was determined from the swelling appearing in the computer tomography (CT) scans. The head model used in this study was developed at the Royal Institute of Technology in Stockholm. The stress in the cranial bone, first principal strain in the brain tissue and acceleration were determined. The model was able to predict a strain pattern that correlated well with the medical images from the victim. The variation study showed that the tangential velocity had a large effect on the strain levels in the studied case. The strain pattern indicated larger areas of high strain with increased tangential velocity especially at the more superior sections.

  • 25.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Aare, Magnus
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Improved helmet design and test methods to reduce rotational induced brain injuries2003Conference paper (Refereed)
    Abstract [en]

    Accidental impacts to the human head are often a combination of translational and rotational accelerations. The most frequent severe brain injuries from accidents are diffuse axonal injury (DAI) and subdural hematoma that both are reported to arise from rotational violence to the head. Most helmet standards used today do only take the translational accelerations into account. It is therefore suggested that an oblique impact test that measures both translational and rotational accelerations should be a complement to the helmet standards used today. This study investigates the potential to reduce the risk for DAI by improving the helmet design by use of an oblique helmet impact test rig. The method used is a detailed finite element (FE) model of the human head. The FE model is used to measure the maximum principal strain in the brain which is suggested as a measurement for the risk to get DAI. The results clearly show the importance of testing a helmet in oblique impacts. Comparing a pure vertical impact with a 45 degree oblique impact with the same initial impact energy shows that the strain in the central parts of the brain is increased with a factor of 6. It is therefore suggested that a future helmet impact standard should include a rotational component so that the helmet is designed for both radial and tangential forces. Such a test method, an oblique impact test, was used to compare two different helmet designs. One helmet was manufactured with the shell glued to the liner and one helmet was designed with a low friction layer between the shell and the liner (MIPS). It was shown that the strain in the FE model of the human head was reduced be 27% comparing the MIPS helmet to the glued helmet design.

  • 26.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Aare, Magnus
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Reduced risk for DAI by use of a new safety helmet2003Conference paper (Refereed)
    Abstract [en]

    Accidental impacts to the human head are often a combination of translational and rotational accelerations. The most frequent severe brain injuries from accidents are diffuse axonal injury (DAI) and subdural hematoma that both are reported to arise from rotational violence to the head. Most helmet standards used today do only take the translational accelerations into account. It is therefore suggested that an oblique impact test that measures both translational and rotational accelerations should be a complement to the helmet standards used today. This study investigates the potential to reduce the risk for DAI by improving the helmet design by use of an oblique helmet impact test rig. The method used is a detailed finite element (FE) model of the human head. The FE model is used to measure the maximum principal strain in the brain which is suggested as a measurement for the risk to get DAI. The results clearly show the importance of testing a helmet in oblique impacts. Comparing a pure vertical impact with a 45 degree oblique impact with the same initial impact energy shows that the strain in the central parts of the brain is increased with a factor of 6. It is therefore suggested that a future helmet impact standard should include a rotational component so that the helmet is designed for both radial and tangential forces. Such a test method, an oblique impact test, was used to compare two different helmet designs. One helmet was manufactured with the shell glued to the liner and one helmet was designed with a low friction layer between the shell and the liner (MIPS). It was shown that the strain in the FE model of the human head was reduced be 27% comparing the MIPS helmet to the glued helmet design.

  • 27.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Brolin, Karin
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Hedenstierna, Sofia
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Aare, Magnus
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Finite element analysis of the effects of head-supported mass on neck responses: Complete phase two report, United states army european research office of the U.S. army2005Report (Refereed)
  • 28.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Hedenstierna, Sofia
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Brolin, Karin
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Finite element analysis of the effects of head-supported mass on neck responses: Complete phase three report, united states army european research office of the U.S.army2006Report (Refereed)
    Abstract [en]

    The objectives for the whole project were to: I. determine the relationships between head supported mass and the risk of neck injuries. The results should be used in a Graphical user interface. In this phase three report has also the Graphical User Interface (GUI) been evaluated and the question about the how the muscle activation affect the injury risk. II. to develop and implement a 3D numerical muscle model. Results: I. The KTH neck model has successfully been used to generate results for the GUI. Results from all simulations have been reported and sent to Titan Corporation that is contracted by USAARL to program the GUI. The GUI that uses an interpolation method to calculate the neck injury risk for a general helmet with a user defined HSM configuration shows to give realistic interpolated values compared to the FE model of the neck. II. The 3D muscle model for the cervical spine includes 22 pairs of muscles. The solid muscle model showed to stabilize the vertebral column better than the spring muscle model. The model is still under evaluation and need further validation to be used in the HSM evaluation project.

  • 29.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Jakobsson, Lotta
    Chalmers tekniska högskola School of Mechanical Engineering. Institutionen för tillämpad mekanik. .
    Brolin, Karin
    Chalmers tekniska högskola School of Mechanical Engineering. Institutionen för tillämpad mekanik. .
    Palmertz, Camilla
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Investigations of Conditions that Affect Neck Compression-Flexion Injuries Using Numerical Techniques2000In: Stapp Car Crash Journal, ISSN 1532-8546Article in journal (Refereed)
  • 30.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Improved helmet design and test methods to reduce rotational induced brain injuries2009Conference paper (Other (popular science, discussion, etc.))
  • 31.
    Hedenstierna, Sofia
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    3D Finite Element Modeling of Cervical Musculature and its Effect on Neck Injury Prevention2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Injuries to the head and neck are potentially the most severe injuries in humans, since they may damage the nervous system. In accidents, the cervical musculature stabilizes the neck in order to prevent injury to the spinal column and is also a potential site for acute muscle strain, resulting in neck pain. The musculature is consequently an important factor in the understanding of neck injuries. There is however a lack of data on muscle response and little is known about the dynamics of the individual muscles. In this thesis the numerical method of Finite Elements (FE) is used to examine the importance of musculature in accidental injuries. In order to study the influence of a continuum musculature, a 3D solid element muscle model with continuum mechanical material properties was developed. It was hypothesized that a 3D musculature model would improve the biofidelity of a numerical neck model by accounting for the passive compressive stiffness, mass inertia, and contact interfaces between muscles. A solid element representation would also enable the study of muscle tissue strain injuries.

    A solid element muscle model representing a 50th percentile male was created, based on the geometry from MRI, and incorporated into an existing FE model of the spine. The passive material response was modeled with nonlinear-elastic and viscoelastic properties derived from experimental tensile tests. The active forces were modeled with discrete Hill elements. In the first version of the model the passive solid element muscles were used together with separate active spring elements. In the second version the active elements were integrated in the solid mesh with coincident nodes. This combined element, called the Super-positioned Muscle Finite Element (SMFE), was evaluated for a single muscle model before it was incorporated in the more complex neck muscle model. The main limitation of the SMFE was that the serial connected Hill-type elements are unstable due to their individual force-length relationship. The instabilities in the SMFE were minimized by the addition of passive compressive stiffness from the solid element and by the decreased gradient of the force-length relation curve.

     The solid element musculature stabilized the vertebral column and reduced the predicted ligament strains during simulated impacts. The solid element compressive stiffness added to the passive stiffness of the cervical model. This decreased the need for additional active forces to reproduce the kinematic response of volunteers during impact. The active response of the SMFE improved model biofidelity and reduced buckling of muscles in compression. The solid element model predicted forces, strains, and energies for individual muscles and showed that the muscle response is dependent on impact direction and severity. For each impact direction, the model identified a few muscles as main load carriers that corresponded to muscles generating high EMG signals in volunteers. The single largest contributing factor to neck injury prediction was the muscle active forces. Muscle activation reduced the risk of injury in ligaments in high-energy impacts. The most urgent improvements of the solid element muscle model concerns: the stability of the SMFE; the boundary conditions from surrounding tissues; and more detailed representations of the myotendinous junctions. The model should also be more extensively validated for the kinematical response and for the muscle load predictions.

    It was concluded that a solid muscle model with continuum mechanical material properties improves the kinematical response and injury prediction of a FE neck model compared to a spring muscle model. The solid muscle model can predict muscle loads and provide insight to how muscle dynamics affect spinal stability as well as muscle acute strain injuries.

  • 32.
    Hedenstierna, Sofia
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Development of an active solid neck muscle FE model and its influence on neck injury predictionManuscript (Other academic)
  • 33.
    Hedenstierna, Sofia
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    How does a three-dimensional continuum muscle model affect the kinematics and muscle strains of a finite element neck model compared to a discrete muscle model in rear-end, frontal, and lateral impacts2008In: Spine, ISSN 0362-2436, E-ISSN 1528-1159, Vol. 33, no 8, p. E236-E245Article in journal (Refereed)
    Abstract [en]

    STUDY DESIGN. A finite element (FE) model of the human neck with incorporated continuum or discrete muscles was used to simulate experimental impacts in rear, frontal, and lateral directions. OBJECTIVE. The aim of this study was to determine how a continuum muscle model influences the impact behavior of a FE human neck model compared with a discrete muscle model. SUMMARY OF BACKGROUND DATA. Most FE neck models used for impact analysis today include a spring element musculature and are limited to discrete geometries and nodal output results. A solid-element muscle model was thought to improve the behavior of the model by adding properties such as tissue inertia and compressive stiffness and by improving the geometry. It would also predict the strain distribution within the continuum elements. METHODS. A passive continuum muscle model with nonlinear viscoelastic materials was incorporated into the KTH neck model together with active spring muscles and used in impact simulations. The resulting head and vertebral kinematics was compared with the results from a discrete muscle model as well as volunteer corridors. The muscle strain prediction was compared between the 2 muscle models. RESULTS. The head and vertebral kinematics were within the volunteer corridors for both models when activated. The continuum model behaved more stiffly than the discrete model and needed less active force to fit the experimental results. The largest difference was seen in the rear impact. The strain predicted by the continuum model was lower than for the discrete model. CONCLUSION. The continuum muscle model stiffened the response of the KTH neck model compared with a discrete model, and the strain prediction in the muscles was improved.

  • 34.
    Hedenstierna, Sofia
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Brolin, Karin
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Evaluation of a combination of continuum and truss finite elements in a model of passive and active muscle tissue2008In: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, Vol. 11, no 6, p. 627-639Article in journal (Refereed)
    Abstract [en]

    The numerical method of finite elements (FE) is a powerful tool for analysing stresses and strains in the human body. One area of increasing interest is the skeletal musculature. This study evaluated modelling of skeletal muscle tissue using a combination of passive non-linear, viscoelastic solid elements and active Hill-type truss elements, the super-positioned muscle finite element (SMFE). The performance of the combined materials and elements was evaluated for eccentric motions by simulating a tensile experiment from a published study on a stimulated rabbit muscle including three different strain rates. It was also evaluated for isometric and concentric contractions. The resulting stress-strain curves had the same overall pattern as the experiments, with the main limitation being sensitivity to the active force-length relation. It was concluded that the SMFE could model active and passive muscle tissue at constant rate elongations for strains below failure, as well as isometric and concentric contractions.

  • 35.
    Hedenstierna, Sofia
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Brolin, Karin
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Development and evaluation of a continuum neck muscle model2006In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 39, no Supplement 1, p. 150-Article in journal (Refereed)
  • 36.
    Hedenstierna, Sofia
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Siegmund, Gunter
    MEA Forensic Engineers and Scientists Ltd., Richmond, BC, Canada.
    Neck Muscle Load Distribution in Lateral, Frontal, and Rear-end Impacts: A Three-Dimensional Finite Element Analysis2009In: Spine, ISSN 0362-2436, E-ISSN 1528-1159, Vol. 34, no 24, p. 2626-2633Article in journal (Refereed)
    Abstract [en]

    Study Design. A finite element (FE) model of the human neck was used to study the distribution of neck muscle loads during multidirectional impacts. The computed load distributions were compared to experimental electromyography (EMG) recordings.

    Objective. To quantify passive muscle loads in nonactive cervical muscles during impacts of varying direction and energy, using a three-dimensional (3D) continuum FE muscle model.

    Summary of Background Data. Experimental and numerical studies have confirmed the importance of muscles in the impact response of the neck. Although EMG has been used to measure the relative activity levels in neck muscles during impact tests, this technique has not been able to measure all neck muscles and cannot directly quantify the force distribution between the muscles. A numerical model can give additional insight into muscle loading during impact.

    Methods. An FE model with solid element musculature was used to simulate frontal, lateral, and rear-end vehicle impacts at 4 peak accelerations. The peak cross-sectional forces, internal energies, and effective strains were calculated for each muscle and impact configuration. The computed load distribution was compared with experimental EMG data.

    Results. The load distribution in the cervical muscles varied with load direction. Peak sectional forces, internal energies, and strains increased in most muscles with increasing impact acceleration. The dominant muscles identified by the model for each direction were splenius capitis, levator scapulae, and sternocleidomastoid in lateral impacts, splenius capitis, and trapezoid in frontal impacts, and sternocleidomastoid, rectus capitis posterior minor, and hyoids in rear-end impacts. This corresponded with the most active muscles identified by EMG recordings, although within these muscles the distribution of forces and EMG levels were not the same.

    Conclusion. The passive muscle forces, strains, and energies computed using a continuum FE model of the cervical musculature distinguished between impact directions and peak accelerations, and on the basis of prior studies, isolated the most important muscles for each direction.

  • 37. Hedman, L.
    et al.
    Fahlstedt, Madelen
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Schlickum, M.
    Möller, H.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Felländer-Tsai, L.
    Training diagnosis and treatment of cervical spine trauma using a new educational program for visualization through imaging and simulation (VIS): A first evaluation by medical students2012In: Stud. Health Technol. Informatics, 2012, p. 171-174Conference paper (Refereed)
    Abstract [en]

    In this pilot study we investigated how medical students evaluated a VIS practice session. Immediately after training 43 students answered a questionnaire on the training session. They evaluated VIS as a good interactive scenario based educational tool.

  • 38.
    Ho, Johnson
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Generation of Patient Specific Finite Element Head Models2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Traumatic brain injury (TBI) is a great burden for the society worldwide and the statisticsindicates a relative constant total annual rate of TBI. It seems that the present preventativestrategies are not sufficient. To be able to develop head safety measures against accidents ine.g. sports or automobile environment, one needs to understand the mechanism behindtraumatic brain injuries. Through the years, different test subjects have been used, such ascadavers, animals and crash dummies, but there are ethical issues in animal and human testingusing accelerations at injury-level and crash dummies are not completely human-like. In aFinite Element (FE) head model, the complex shape of the intracranial components can bemodeled and mechanical entities, such as pressure, stresses and strains, can be quantified atany theoretical point. It is suggested that the size of the head, the skull-brain boundarycondition, the heterogeneity, and the tethering and suspension system can alter the mechanicalresponse of the brain. It can be seen that the shape of the skull, the composition of gray andwhite matter, the distribution of sulci, the volume of cerebrospinal fluid and geometry of othersoft tissues varies greatly between individuals. All this, suggests the development of patientspecific FE head models.A method to generate patient specific FE head model was contrived based on the geometryfrom Magnetic Resonance Imaging (MRI) scans. The geometry was extracted usingexpectation maximization classification and the mesh of the FE head model was constructedby directly converting the pixel into hexahedral elements. The generated FE model had goodelement quality, the geometrical details were more than 90 % accurate and it correlated wellwith experimental data of relative brain-skull motion. The method was thought to beautomatic but some hypothetically important anatomical structures were not possible to beextracted from medical images. This leads to investigations on the biomechanical influence ofthe cerebral vasculature, the falx and tentorium complex. It was found that biomechanicalinfluence of the cerebral vasculature was minimal, due to the convoluting geometry and thenon-linear elastic material properties of the blood vessels. It suggests that futurebiomechanical FE head model does not necessarily have to include these blood vessels. Theinclusion of falx and tentorium in an FE head model has on the other hand a substantialbiomechanical influence by affecting its surrounding tissue. Therefore, in the investigation ofthe biomechanical influence of the sulci, the falx and tentorium were manually added to theanatomically detailed 3D FE head model. The biomechanical influence of the sulci haspreviously not been studied in 3D and the results indicated an obvious reduction of the strainin the model with sulci compared to the model without sulci in all simulations, and mostinteresting was the consistent reduction of strain in the corpus callosum. The development ofgyri not only produces a larger area for synapses but also forms the sulci to protect the brainfrom external forces.Based on the results, a patient specific FE head model for traumatic brain injury predictionshould at least include the skull, cerebrospinal fluid, falx, tentorium and pia mater, in additionto the brain. With these anatomically detailed 3D models, the injury biomechanics can bebetter understood. Hopefully, the burden of TBI to the society can be alleviated with betterprotective systems and improved understanding of the patients’ condition and hence, theirmedical treatments

  • 39.
    Ho, Johnson
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    An automatic method to generate a patient specific finite element head model2006In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 39, no 1, p. S428-Article in journal (Refereed)
  • 40.
    Ho, Johnson
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Can sulci protect the brain from traumatic injury?2009In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 42, no 13, p. 2074-2080Article in journal (Refereed)
    Abstract [en]

    The influence of sulci in dynamic finite element simulations of the human head has been investigated. First, a detailed 3D FE model was constructed based on an MRI scan of a human head. A second model with a smoothed brain surface was created based on the same MRI scan as the first FE model. These models were validated against experimental data to confirm their human-like dynamic responses during impact. The validated FE models were subjected to several acceleration impulses and the maximum principle strain and strain rate in the brain were analyzed. The results suggested that the inclusion of sulci should be considered for future FE head models as it alters the strain and strain distribution in an FE model.

  • 41.
    Ho, Johnson
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Dynamic response of the brain with vasculature: A three-dimensional computational study2007In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 40, no 13, p. 3006-3012Article in journal (Refereed)
    Abstract [en]

    To date, the influence of the vasculature on the dynamic response of the brain has not been studied with a complete three-dimensional (3D) finite element head model. In this study, short duration rotational (10,000 rad/s2 with a duration of 5 ms) and translational (100G with a duration of 5 ms) acceleration impulses were applied to the 3D finite element models to study the dynamic response of the brain. The hypothesis of this study was that due to the convoluted organization and non-linear material properties of cerebral vasculature, the difference in maximum principle strain between models with and without vasculature should be minimal. The effects of non-linear material properties and the convoluted structure of the vasculature were examined by comparing the results from the 3D finite element models. The peak average strain reduction in a model with non-linear elastic vasculature and a model with linear elastic vasculature compared to a model without vasculature was 2% and 5%, respectively, indicating that the influence of the vasculature on the dynamic response of the brain is minimal.

  • 42.
    Ho, Johnson
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Investigation of the Dynamic Response Contribution of Vasculature in a 3D Finite Element Head Model2006Conference paper (Other academic)
  • 43.
    Ho, Johnson
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Investigation of the Dynamic Response Contribution of Vasculature in a 3D Finite Element Head Model2006Conference paper (Refereed)
  • 44.
    Ho, Johnson
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Automatic generation and validation of patient-specific finite element head models suitable for crashworthiness analysis2009In: International Journal of Crashworthiness, ISSN 1358-8265, E-ISSN 1754-2111, Vol. 14, no 6, p. 555-563Article in journal (Refereed)
    Abstract [en]

    A method to automatically generate finite element (FE) head models is presented in this paper. Individual variation in geometry of the head should be taken into consideration in future injury-prediction research. To avoid inter- and intra-operator variation due to manual segmentation, a robust and accurate algorithm is suggested. The current approach utilises expectation maximisation classification and skull stripping. The whole process from geometry extraction to model generation is converted into an automatic scheme. The models that are generated from the proposed method are validated in terms of segmentation accuracy, element quality and injury-prediction ability. The segmentations of the white matter and grey matter are about 90% accurate and the models have good element quality, with 94% of the elements having a Jacobian above 0.5. Using the experimental data from post-mortem human subject heads, nodal displacements were compared with the data collected from the simulations with the FE head models. The results are promising, indicating that the proposed method is good enough to generate patient-specific model for brain injury prediction. Further improvement can be made in terms of geometry accuracy and element quality.

  • 45.
    Ho, Johnson
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    The influence of the falx and tentorium: A 3D computational study of impacts using detailed FE head modelsManuscript (Other academic)
    Abstract [en]

    The influence of the falx and tentorium on biomechanics of the head during impact was studied in the current study with finite element analysis. A study of such has not been done previously in 3D. Three detailed 3D finite element models were created based on images of a healthy person with a normal size head. Two of the models contained the addition of falx and tentorium with different material properties. The models were subjected to coronal and sagittal rotational impulses applied to the skull. The acceleration of the impulse was large enough to theoretically induce diffuse axonal injuries (DAI). Strain distributions in the brain of the different models were compared and the findings indicated that the falx induced large strain to the surrounding brain tissues, especially to the corpus callosum in coronal rotation. The tentorium seemed to constrain motion of the cerebellum while inducing large strain in the brain stem in both rotations. Lower strains in the different lobes while higher strains in the brain stem and corpus callosum which are the classical site for DAI, were found in the model with falx and tentorium. The result indicated the need of modeling dura mater with non-linear elastic material model, which otherwise would have been too stiff. The non-sliding interface of the protruding dura mater is suspected to induce too large strains in adjacent areas and needed to investigate further.

  • 46. Inganäs, Olle
    et al.
    Asplund, Maria
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Hamedi, Mahiar
    Forchheimer, Robert
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Neural Contacts with Conjugated Polymers in Fibre Geometries2007Conference paper (Refereed)
  • 47.
    Ioakeimidou, Foteini
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Olwal, Alex
    KTH, School of Computer Science and Communication (CSC).
    Nordberg, Axel
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    3D Visualization and Interaction with Spatiotemporal X-ray Data to Minimize Radiation in Image-guided Surgery2011In: 2011 24TH INTERNATIONAL SYMPOSIUM ON COMPUTER-BASED MEDICAL SYSTEMS (CBMS) / [ed] Olive, M; Solomonides, T, NEW YORK, NY: IEEE , 2011Conference paper (Refereed)
    Abstract [en]

    Image-guided surgery (IGS) often depends on X-ray imaging, since pre-operative MRI, CT and PET scans do not provide an up-to-date internal patient view during the operation. X-rays introduce hazardous radiation, but long exposures for monitoring are often necessary to increase accuracy in critical situations. Surgeons often also take multiple X-rays from different angles, as X-rays only provide a distorted 2D perspective from the current viewpoint. We introduce a prototype IGS system that augments 2D X-ray images with spatiotemporal information using a motion tracking system, such that the use of X-rays can be reduced. In addition, an interactive visualization allows exploring 2D X-rays in timeline views and 3D clouds where they are arranged according to the viewpoint at the time of acquisition. The system could be deployed and used without time-consuming calibration, and has the potential to improve surgeons' spatial awareness, while increasing efficiency and patient safety.

  • 48.
    Juntikka, Rickard
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Hallström, Stefan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Optimization of single skin surfaces for head injury prevention - a comparison of optima calculated for global versus local injury thresholds2004In: International Journal of Crashworthiness, ISSN 1358-8265, E-ISSN 1754-2111, Vol. 9, no 4, p. 365-379Article in journal (Refereed)
    Abstract [en]

    This paper describes optimizations of material properties for a bonnet-like plate using finite element calculations and the Euro-NCAP pedestrian head impact test. Four different head models were used for the impact simulations, a Euro-NCAP dummy head, a Hybrid III dummy head and two biomechanical head models exhibiting different mechanical properties for the brain tissue. The objective function was to minimize the displacement of the bonnet plate while satisfying constraints on the head injury criterion (HIC), the resultant contact force and, for the human head models, the strain in the brain tissue. An investigation was also conducted of the kinematics of the head models during impact, evaluating the energy distribution and the apparent mass. The analysis gave at hand that optimization of the plate with respect to impact with the Euro-NCAP and Hybrid III head models reached substantially, different results compared to impact with the biomechanical head models. For the latter case, the stiffness of the brain tissue influenced which constraints were active in the final solution. The investigation of the kinematics at impact showed that a substantial portion of energy was confined within the brain during impact for the biomechanical head models. The apparent mass at impact coincided with the actual mass for the rigid dummy heads while for the human head models it was roughly the mass of the skull only.

  • 49. Kasai, Nahoko
    et al.
    Shimada, Akiyoshi
    Nyberg, Tobias A.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Torimitsu, Keiichi
    An Electrochemical Sensor Array and Its Application to Real-Time Brain Slice Imaging2009In: Electronics and Communications in Japan, ISSN 1942-9533, Vol. 92, no 9, p. 217-221Article in journal (Refereed)
    Abstract [en]

    An electrochemical sensing system using a planar microelectrode array has been developed for monitoring biological molecules with relatively high spatial and temporal resolution. This allows noninvasive real-time imaging of biological molecules released from tissue. In this study, we establish a multichannel hydrogen peroxide (H2O2) sensing system to monitor the real-time H2O2 distribution in tissue using a planar sensor array. H2O2 is known to be associated with the pathology of neurological diseases because it is a by-product of degenerative reactions involving reactive oxygen species, which are a major cause of oxidative stress in mammalian cells. The sensor array is based on a 64-channel ITO electrode array composed of 50 x 50 mu m electrodes modified with an enzyme (horseradish peroxidase) and an electron transfer mediator. We place a cultured rat hippocampal slice on the array and measure the current at each sensor using a multipotentiostat. When we introduce bicuculline into the solution as a stimulant in the presence of a catalase inhibitor, we can observe a distinct increase in the H2O2 concentration. This real-time H2O2 distribution monitoring system is a powerful tool with which to explore the neuronal cell death mechanism in biological systems.

  • 50.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    A Parametric Study of Energy Absorbing Foams for Head Injury Prevention2007In: The 20th ESV Conference Proceedings, 2007Conference paper (Refereed)
    Abstract [en]

    This paper describes a parametric study of foammaterial properties for interior car surfaces usingfinite element calculations. Two different headmodels were used for the impact simulations, aHybrid III dummy head and a biomechanical headmodel. The objective was to study the head injurycriterion (dummy) (HIC(d)), the angular velocity, theresultant acceleration and, for the human headmodels, the strain in the brain tissue and the stress inthe skull for a variation in foam material propertiessuch as stiffness, plateau stress and energyabsorption. The analysis gave at hand that the bestchoice of material properties with respect to impactusing the Hybrid III head model reached differentresults compared to an impact with the biomechanicalhead model. For a purely perpendicular impact, theHIC(d) for the head model managed to predict thestrain level in the brain quite well. Even though theHIC reached acceptable levels for both aperpendicular and oblique impact towards a 31 kg/m3EPP padding, the maximum strain in the human headmodel for an oblique impact was almost twicesuggested allowable levels. The difference in thestrain in the brain between an oblique andperpendicular impact when impacted with sameinitial velocity towards the same padding was notpredicted by the HIC(d).

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