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  • 1. 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.

  • 2.
    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)
  • 3.
    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.

  • 4.
    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)
  • 5.
    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.

  • 6.
    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.

  • 7.
    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.

  • 8. Borg, Jörgen
    et al.
    Holm, Lena
    Cassidy, J David
    Peloso, Paul M.
    Carroll, Linda J.
    von Holst, Hans
    Department of Neurosurgery, Karolinska Institutet, Stockholm, Sweden.
    Ericson, Kaj
    Diagnostic procedures in mild traumatic brain injury: results of the WHO Collaborating Centre Task Force on Mild Traumatic Brain Injury2004In: Journal of Rehabilitation Medicine, ISSN 1650-1977, E-ISSN 1651-2081, Vol. 36, no 43, p. 61-75Article in journal (Refereed)
    Abstract [en]

    We examined diagnostic procedures in mild traumatic brain injury by a systematic literature search. After screening 38,806 abstracts, we critically reviewed 228 diagnostic studies and accepted 73 (32%). The estimated prevalence of intracranial CT scan abnormalities is 5% in patients presenting to hospital with a Glasgow Coma Scale score of 15 and 30% or higher in patients presenting with a score of 13. About 1% of all treated patients with mild traumatic brain injury require neurosurgical intervention. There is strong evidence that clinical factors can predict computerized tomography scan abnormalities and the need for intervention in adults, but no such evidence for mild traumatic brain injury in children. We found evidence that skull fracture is a risk factor for intracranial lesions, but the diagnostic accuracy of radiologically diagnosed skull fracture as an indication of intracranial lesions is poor. There is only a little evidence for the diagnostic validity of cognitive testing and other diagnostic tools for mild traumatic brain injury.

  • 9. Borg, Jörgen
    et al.
    Holm, Lena
    Peloso, Paul M.
    Cassidy, J. David
    Carroll, Linda J.
    von Holst, Hans
    Department of Neurosurgery, Karolinska Institutet, Stockholm, Sweden.
    Paniak, Chris
    Yates, David
    Non-surgical intervention and cost for mild traumatic brain injury: results of the WHO Collaborating Centre Task Force on Mild Traumatic Brain Injury2004In: Journal of Rehabilitation Medicine, ISSN 1650-1977, E-ISSN 1651-2081, Vol. 36, no 43, p. 76-83Article in journal (Refereed)
    Abstract [en]

    We examined the evidence for non-surgical interventions and for economic costs for mild traumatic brain injury patients by a systematic search of the literature and a best-evidence synthesis. After screening 38,806 abstracts, we critically reviewed 45 articles on intervention and accepted 16 (36%). We reviewed 16 articles on economic costs and accepted 7 (44%). We found some evidence that early educational information can reduce long-term complaints and that this early intervention need not be intensive. Most cost studies were performed more than a decade ago. Indirect costs are probably higher than direct costs. Studies comparing costs for routine hospitalized observation vs the use of computerized tomography scan examination for selective hospital admission indicate that the latter policy reduces costs, but comparable clinical outcome of these policies has not been demonstrated. The sparse scientific literature in these areas reflects both conceptual confusion and limited knowledge of the natural history of mild traumatic brain injury.

  • 10.
    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)
  • 11. Carroll, L. J.
    et al.
    Cassidy, J. D.
    Peloso, P. M.
    Borg, J.
    von Holst, Hans
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Holm, L.
    Paniak, C.
    Pepin, M.
    Prognosis for mild traumatic brain injury: Results of the WHO Collaborating Centre Task Force on Mild Traumatic Brain Injury2004In: Journal of Rehabilitation Medicine, ISSN 1650-1977, E-ISSN 1651-2081, Vol. 36, p. 84-105Article, review/survey (Refereed)
    Abstract [en]

    We searched the literature on the epidemiology, diagnosis, prognosis, treatment and costs of mild traumatic brain injury. Of 428 studies related to prognosis after mild traumatic brain injury, 120 (28%) were accepted after critical review. These comprise our best-evidence synthesis on prognosis after mild traumatic brain injury. There was consistent and methodologically sound evidence that children's prognosis after mild traumatic brain injury is good, with quick resolution of symptoms and little evidence of residual cognitive, behavioural or academic deficits. For adults, cognitive deficits and symptoms are common in the acute stage, and the majority of studies report recovery for most within 3-12 months. Where symptoms persist, compensation/litigation is a factor, but there is little consistent evidence for other predictors. The literature on this area is of varying quality and causal inferences are often mistakenly drawn from cross-sectional studies.

  • 12.
    Cassidy, David J.
    et al.
    Alberta Centre for Injury Control and Research, Department of Public Health Sciences, University of Alberta, Edmonton, Alberta, Canada, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada, Section for Personal Injury Prevention, Department of Clinical Neurosciences, Karolinska Institutet, Stockholm, Sweden.
    Carrol, Linda J.
    Alberta Centre for Injury Control and Research, Department of Public Health Sciences, University of Alberta, Edmonton, Alberta, Canada.
    Peloso, Paul M.
    Department of Internal Medicine, University of Iowa Health Center, Iowa City, Iowa, USA.
    Borg, Jörgen
    Department of Neuroscience, Rehabilitation Medicine, Uppsala University, Uppsala, Sweden.
    von Holst, Hans
    Department of Neurosurgery, Karolinska Institutet, Stockholm, Sweden.
    Holm, Lena
    Section for Personal Injury Prevention, Department of Clinical Neurosciences, Karolinska Institutet, Stockholm, Sweden.
    Kraus, Jess
    Division of Epidemiology, School of Public Health, University of California, Los Angeles, California, USA.
    Coronado, Victor G.
    National Center for Injury Prevention and Control, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
    Incidence, risk factors and prevention of mild traumatic brain injury: Results of the WHO Collaborating Centre Task Force on Mild Traumatic Brain Injury2004In: Journal of Rehabilitation Medicine, ISSN 1650-1977, E-ISSN 1651-2081, Vol. 36, no 43, p. 28-60Article in journal (Refereed)
    Abstract [en]

    Objective: We undertook a best-evidence synthesis on the incidence, risk factors and prevention of mild traumatic brain injury. Methods: Medline, Cinahl, PsycINFO and Embase were searched for relevant articles. After screening 38,806 abstracts, we critically reviewed 169 studies on incidence, risk and prevention, and accepted 121 (72%).Results: The accepted articles show that 70–90% of all treated brain injuries are mild, and the incidence of hospital- treated patients with mild traumatic brain injury is about 100–300/100,000 population. However, much mild traumatic brain injury is not treated at hospitals, and the true population-based rate is probably above 600/100,000. Mild traumatic brain injury is more common in males and in teenagers and young adults. Falls and motor-vehicle colli- sions are common causes.Conclusion: Strong evidence supports helmet use to prevent mild traumatic brain injury in motorcyclists and bicyclists. The mild traumatic brain injury literature is of varying quality, and the studies are very heterogeneous. Never- theless, there is evidence that mild traumatic brain injury is an important public health problem, but we need more high- quality research into this area.

  • 13. Cassidy, David J.
    et al.
    von Holst, Hans
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Best evidence synthesis on Mild Traumatic Brain Injury: Results of the WHO collaborating centre for neurotrauma prevention, management and rehabilitation task force on Mild Traumatic Brain Injury2004In: Journal of Rehabilitation Medicine, ISSN 1650-1977, E-ISSN 1651-2081, Vol. Feb, no Supplement 43, p. 1-144Article in journal (Refereed)
  • 14.
    Courteille, Olivier
    et al.
    Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
    Fahlstedt, Madelen
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Ho, Johnson
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Hedman, Leif
    Department of Psychology, Umeå University, Umeå, Sweden.
    Fors, Uno
    Department of Computer and Systems Sciences, Stockholm University, Stockholm, Sweden.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Felländer-Tsai, Li
    Department of Clinical Science, Intervention and Technology, Division of Orthopaedics and Biotechnology, Karolin-ska Institutet, Karolinska University Hospital, Huddinge, Stockholm, Sweden.
    Möller, Hans
    Department of Clinical Science, Intervention and Technology, Division of Orthopaedics and Biotechnology, Karolin-ska Institutet, Karolinska University Hospital, Huddinge, Stockholm, Sweden.
    Learning through a virtual patient vs. recorded lecture: a comparison of knowledge retention in a trauma case2018In: International Journal of Medical Education, ISSN 2042-6372, E-ISSN 2042-6372, Vol. 9, p. 86-92Article in journal (Refereed)
    Abstract [en]

    Objectives: To compare medical students' and residents' knowledge retention of assessment, diagnosis and treatment procedures, as well as a learning experience, of patients with spinal trauma after training with either a Virtual Patient case or a video-recorded traditional lecture. Methods: A total of 170 volunteers (85 medical students and 85 residents in orthopedic surgery) were randomly allocated (stratified for student/resident and gender) to either a video-recorded standard lecture or a Virtual Patient-based training session where they interactively assessed a clinical case portraying a motorcycle accident. The knowledge retention was assessed by a test immediately following the educational intervention and repeated after a minimum of 2 months. Participants' learning experiences were evaluated with exit questionnaires. A repeated-measures analysis of variance was applied on knowledge scores. A total of 81% (n = 138) of the participants completed both tests. Results: There was a small but significant decline in first and second test results for both groups (F-(1,F-135) = 18.154, p = 0.00). However, no significant differences in short-term and long-term knowledge retention were observed between the two teaching methods. The Virtual Patient group reported higher learning experience levels in engagement, stimulation, general perception, and expectations. Conclusions: Participants' levels engagement were reported in favor of the VP format. Similar knowledge retention was achieved through either a Virtual Patient or a recorded lecture.

  • 15.
    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)
  • 16.
    Granskog, Viktor
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Andren, Oliver C. J.
    Cai, Yanling
    Gonzalez-Granillo, Marcela
    Fellander-Tsai, Li
    von Holst, Hans
    KTH, School of Technology and Health (STH), Health Systems Engineering, Ergonomics.
    Haldosen, Lars-Arne
    Malkoch, Michael
    Linear Dendritic Block Copolymers as Promising Biomaterials for the Manufacturing of Soft Tissue Adhesive Patches Using Visible Light Initiated Thiol-Ene Coupling Chemistry2015In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 25, no 42, p. 6596-6605Article in journal (Refereed)
    Abstract [en]

    A library of dendritic-linear-dendritic (DLD) materials comprising linear poly(ethylene glycol) and hyperbranched dendritic blocks based on 2,2-bis(hydroxymethyl) propionic acid is successfully synthesized and post-functionalized with peripheral allyl groups. Reactive DLDs with pseudo-generations of 3 to 6 (G3-G6) are isolated in large scale allowing their thorough evaluation as important components for the development of biomedical adhesives. Due to their branched nature and inherent degradable ester-bonds, promising biomaterial resins are accomplished with suitable viscosity, eliminating the excessive use of co-solvents. By utilizing benign high-energy visible light initiated thiol-ene coupling chemistry, DLDs together with tris[2-(3-mercaptopropionyloxy) ethyl] isocyanurate and surgical mesh enable the fabrication of soft tissue adhesive patches (STAPs) within a total irradiation time of 30 s. The STAPs display the ability to create good adhesion to wet soft tissue and encouraging results in cytotoxicity tests. All crosslinked materials are also found to degrade after being stored in human blood plasma and phosphate buffered saline. The proposed benign methodology coupled with the promising features of the crosslinked materials is herein envisioned as a soft tissue adhesive with properties that do not exist in currently available tissue adhesives.

  • 17.
    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.

  • 18.
    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.

  • 19.
    Halldin, Peter
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Brolin, Karin
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Hedenstierna, Sofia
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Aare, Magnus
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    von Holst, Hans
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Finite element analysis of the effects of head-supported mass on neck responses: Complete phase one report, United states army european research office of the U.S army2004Report (Refereed)
  • 20.
    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)
  • 21.
    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.

  • 22.
    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)
  • 23.
    Halldin, Peter
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    von Holst, Hans
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Eriksson, Ingvar
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    An experimental head restraint concept for primary prevention of head and neck injuries in frontal collisions.1998In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 30, no 4, p. 535-43Article in journal (Refereed)
    Abstract [en]

    The Experimental Head Restraint Concept (EHRC), a 'safety belt' for the head, is designed to reduce forces to the head and neck, in frontal car crashes. The EHRC was evaluated experimentally in frontal collision for a crash severity of 11 m/s, and numerically in frontal collision for a crash severity of 11 and 15 m/s. Experimental data obtained from a frontal barrier test (11 m/s) showed a 67% reduction of the HIC value from 411 (without EHRC) to 136 (with EHRC). The same level of reduction was also obtained for the higher speed in the numerical simulation. The moment in the neck was shown in experimental configuration to increase a few percent using the EHRC, but as presented in a numerical analysis, the moment was reduced by stiffening the EHRC. The EHRC clearly has a potential role in the search for primary prevention of neurotrauma injuries in frontal related car crashes. However, there is a strong need for more advanced injury criteria for the neck in order to optimize such complex safety systems.

  • 24.
    Hed, Yvonne
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Öberg, Kim
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Berg, Sandra
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Nordberg, Axel
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Multipurpose heterofunctional dendritic scaffolds as crosslinkers towards functional soft hydrogels and implant adhesives in bone fracture applications2013In: Journal of Materials Chemistry B, ISSN 2050-7518, Vol. 1, no 44, p. 6015-6019Article in journal (Refereed)
    Abstract [en]

    Two sets of heterofunctional dendritic frameworks displaying an inversed and exact number of ene and azide groups have successfully been synthesized and post-functionalized with biorelevant molecules. Their facile scaffolding ability enabled the fabrication of soft and azide functional dendritic hydrogels with modulus close to muscle tissue. The dendritic scaffolds are furthermore shown to be promising primers for the development of novel bone fracture stabilization adhesives with shear strengths succeeding commercial Histroacryl (R).

  • 25.
    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)
  • 26. 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.

  • 27. Hedman, Leif
    et al.
    Fahlstedt, Madelen
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Schlickum, Marcus
    Möller, Hans
    von Holst, Hans
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Felländer-Tsai, Li
    A pilot evaluation of an educational program that offers visualizations of cervical spine injuries: medical students' self-efficacy increases by training2014In: Informatics for Health and Social Care, ISSN 1753-8157, E-ISSN 1753-8165, Vol. 39, no 1, p. 33-46Article in journal (Refereed)
    Abstract [en]

    In this pilot study, a new method for visualization through imaging and simulation (VIS-Ed) for teaching diagnosis and treatment of cervical spine trauma was formatively evaluated. The aims were to examine if medical students' self-efficacy would change by training using VIS-Ed, and if so these changes were related to how they evaluated the session, and the user interface (UI) of this program. Using a one-group, pre-post course test design 43 Swedish medical students (4th year, 17 males, 26 females) practiced in groups of three participants. Overall the practice and the UI were considered as positive experiences. They judged VIS-Ed as a good interactive scenario-based educational tool. All students' self-efficacy increased significantly by training (p<0.001). Spearman's rank correlation tests revealed that increased self-efficacy was only associated with: how the session was compared to as expected (p<0.007). Students' self-efficacy increased significantly by training, but replication studies should determine if this training effect is gender-related.

  • 28.
    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.

  • 29.
    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.

  • 30.
    Höybye, Charlotte
    et al.
    Departments of Endocrinology and Diabetology, Otorhinolaryngology and Head and Neck Surgery, and Neurosurgery, Karolinska Hospital, Stockholm.
    Grenbäck, Eva
    Departments of Endocrinology and Diabetology, Otorhinolaryngology and Head and Neck Surgery, and Neurosurgery, Karolinska Hospital, Stockholm.
    Thorén, Marja
    Departments of Endocrinology and Diabetology, Otorhinolaryngology and Head and Neck Surgery, and Neurosurgery, Karolinska Hospital, Stockholm.
    Hulting, Anna-Lena
    Departments of Endocrinology and Diabetology, Otorhinolaryngology and Head and Neck Surgery, and Neurosurgery, Karolinska Hospital, Stockholm.
    Lundblad, Lars
    Departments of Endocrinology and Diabetology, Otorhinolaryngology and Head and Neck Surgery, and Neurosurgery, Karolinska Hospital, Stockholm.
    Änggård, Anders
    von Holst, Hans
    Transsphenoidal surgery in Cushing disease: 10 years of experience in 34 consecutive cases2004In: Journal of Neurosurgery, ISSN 0022-3085, E-ISSN 1933-0693, Vol. 100, p. 634-638Article in journal (Refereed)
    Abstract [en]

    Object. Cushing disease is a rare disorder. Because of their small size the adrenocorticotropic hormone (ACTH)—producing tumors are often not detectable on neuroimaging studies. To obtain a cure with transsphenoidal surgery (TSS) may therefore be difficult. In this report the authors present 10 years of experience in the treatment of patients with Cushing disease who were followed up with the same protocol and treated by the same surgeon.

    Methods. Thirty-four patients, 26 of them female and eight of them male (mean age 40 years, range 13–74 years) were studied. All had obvious clinical signs and symptoms of Cushing syndrome. Magnetic resonance (MR) imaging was performed in all patients, and inferior petrosal sinus (IPS) sampling was done in 14.

    In 12 patients MR imaging indicated a pituitary tumor; 10 were microadenomas and two were macroadenomas. In six patients with no visible tumor, the results of IPS sampling supported the diagnosis. All patients underwent TSS; the mean follow-up duration was 6 ± 0.5 years. Selective adenomectomy was performed in 32 and hemihypophysectomy in the other two patients. A cure was obtained in 31 patients (91%) after one TSS and in two more patients after further TSS; one patient was not cured despite two TSSs and one underwent bilateral adrenalectomy. Disease recurrence was seen in two patients after 3 years, and they were successfully treated with stereotactic gamma knife surgery. Half of the patients had an ACTH deficiency postoperatively, whereas one third had other pituitary hormone insufficiencies. There were no serious complications attributable to the surgical intervention.

    Conclusions. Transsphenoidal surgery with selective adenomectomy is an effective and safe treatment for Cushing disease. In the patients presented in this study, the surgical outcome seemed to depend on careful preoperative evaluation and the surgeon's experience. For optimal results in this rare disease the authors therefore suggest that the endocrinological, radiological, and surgical procedures be coordinated in a specialized center.

  • 31. 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)
  • 32.
    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.

  • 33.
    Kleiven, Svein
    et al.
    KTH, Superseded Departments, Aeronautical Engineering.
    Peloso, Paul M.
    von Holst, Hans
    KTH, Superseded Departments, Aeronautical Engineering.
    The epidemiology of head injuries in Sweden from 1987 to 20002003In: Injury control and safety promotion, ISSN 1566-0974, E-ISSN 1744-4985, Vol. 10, no 3, p. 173-180Article in journal (Refereed)
    Abstract [en]

    The purpose of the present study was to evaluate the variability in the annual head injury incidence rate in Sweden from 1987 to 2000. It was hypothesized that the annual incidence rate would decrease over time due to a variety of primary preventive strategies that have been introduced in Swedish society. We used the Hospital Discharge Register at the National Board for Health and Welfare and head injury codes 800-804, and 850-854 from ICD9 system and S2.0-S2.9, and S6.0-S6.9 codes from ICD-10 system. We evaluated the patterns of age, gender, external cause of injury (E-code), type of injury, length of hospital stay, and trends over time. Head injuries due to transportation collision were reduced over the 14-year period analysis. Falls persisted as the dominant cause of head injury. Overall, men had 2.1 times the incidence of head injury compared to women. There was a decline in younger ages experiencing a head injury over this interval, while the number of head injuries among elderly people increased over time. Concussion was about three times more frequent than fractures. Hematoma and diffuse or focal contusions had a much lower incidence rate than concussion. Concussions and fractures decreased over time. Diffuse or focal injuries showed a steady rate of occurrence over the study interval while hematoma increased. Although length of hospital stay varied widely from zero to more than 50 days, 73.6% of hospital days were confined to two days or less. The incidence rate is stable over this time frame. While head injuries attributable to transportation accidents decreased, falls made up an increasing proportion of head injuries. Since we observed an increase in head injuries among elderly, primary prevention strategies may need to be targeted at this age group, and at preventing falls.

  • 34.
    Kleiven, Svein
    et al.
    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).
    CONSEQUENCES OF BRAIN SIZE FOLLOWING IMPACT IN PREDICTION OF SUBDURAL HEMATOMA EVALUATED WITH NUMERICAL TECHNIQUES2001In: IRCOBI (International Research Council on the Biokinetics of Impacts), 2001, p. 161-172Conference paper (Refereed)
  • 35.
    Kleiven, Svein
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    von Holst, Hans
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Consequences of head size following trauma to the human head2002In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 35, no 2, p. 153-160Article in journal (Refereed)
    Abstract [en]

    The objective of the present study was to evaluate whether variation of human head size results in different outcome regarding intracranial responses following a direct impact. Finite Element models representing different head sizes and with various element mesh densities were created. Frontal impacts towards padded surfaces as well as inertial loads were analyzed. The variation in intracranial stresses and intracranial pressures for different sizes of the geometry and for various element meshes were investigated. A significant correlation was found between experiment and simulation with regard to intracranial pressure characteristics. The maximal effective stresses in the brain increased more than a fourfold, from 3.6 kPa for the smallest head size to 16.3 kPa for the largest head size using the same acceleration impulse. When simulating a frontal impact towards a padding, the head injury criterion (HIC) value varies from the highest level of 2433 at a head mass of 2.34 kg to the lowest level of 1376 at a head mass of 5.98 kg, contradicting the increase in maximal intracranial stresses with head size. The conclusion is that the size dependence of the intracranial stresses associated with injury, is not predicted by the HIC. It is suggested that variations in head size should be considered when developing new head injury criteria.

  • 36.
    Kleiven, Svein
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    von Holst, Hans
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Consequences of Reduced Brain Volume Following Impact in Prediction of Subdural Hematoma Evaluated with Numerical Techniques2002In: Traffic Injury Prevention, ISSN 1538-9588, E-ISSN 1538-957X, Vol. 3, no 4, p. 303-310Article in journal (Refereed)
    Abstract [en]

    Detailed and parameterized models of the adult human head were created using the finite element method. Different sizes of the brain and the subdural space were generated, and the models were impacted toward padded surfaces in the frontal, temporal, and occipital direction. The present results show for the first time that, by reducing the brain size and thereby increasing the volume in the subdural space in the finite element model, a significant increase in relative motion was found between the skull and brain which correlated with the reduction of brain size.

  • 37.
    Kleiven, Svein
    et al.
    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).
    Evaluation of Head Injury Criteria2002Report (Other academic)
  • 38.
    Kleiven, Svein
    et al.
    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).
    Influence of Direction and Duration of Impact to the Human Head2002Conference paper (Refereed)
  • 39.
    Kleiven, Svein
    et al.
    KTH, Superseded Departments, Biotechnology.
    von Holst, Hans
    KTH, Superseded Departments, Biotechnology.
    Review and Evaluation of Head Injury Criteria2003Conference paper (Refereed)
  • 40.
    Li, Xiaogai
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Ho, Johnson
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    3-D Finite Element Modeling of Brain Edema: Initial Studies on Intracranial Pressure Using COMSOL Multiphysics2009In: COMSOL Conference, 2009Conference paper (Refereed)
    Abstract [en]

    Brain edema is one of the most common consequences of serious traumatic brain injuries which is usually accompanied with increased Intracranial Pressure (ICP) due to water content increment. A three dimensional finite element model of brain edema is used to study intracranial pressure in this paper. Three different boundary conditions at the end of Cerebral Spinal Fluid (CSF) were used to investigate the boundary condition effects on the volume-pressure curve based on the current model. Compared with the infusion experiments, results from the simulations show that exponential pressure boundary condition model corresponds well with the experiment

  • 41.
    Li, Xiaogai
    et al.
    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).
    Ho, Johnson
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Three Dimensional Poroelastic Simulation of Brain Edema: Initial studies on intracranial pressure2010In: IFMBE Proceedings, 2010, 2010, p. 1478-1481Conference paper (Refereed)
    Abstract [en]

    Brain edema is one of the most common consequences of serious head injury because of the enhancement of water content and thus the increased brain volume. Once the brain compensation mechanisms have been exhausted, the intracranial pressure (ICP) will increase exponentially because the brain is enclosed in the rigid skull. Previous research suggests that the poroelastic theory provides a solution for studying the fluid flow in the brain. In this paper, poroelastic theory is used to study the intracranial pressure distribution due to traumatic brain edema by a detailed 3D finite element brain model.

  • 42.
    Li, Xiaogai
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Ho, Johnson
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Three Dimensional Poroelastic Simulation of Brain Edema: Initial Studies on Intracranial Pressure Using Comsol Multiphysics2009In: Proceedings of European Comsol Conference, Milan, Italy, October 7 - 9, 2009Conference paper (Refereed)
  • 43.
    Li, Xiaogai
    et al.
    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).
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Decompressive craniotomy causes significant strain increase in axonal fiber tracts2012In: Journal of clinical neuroscience, ISSN 0967-5868, E-ISSN 1532-2653, Vol. 20, no 4, p. 509-513Article in journal (Refereed)
    Abstract [en]

    Background

    Decompressive craniotomy allows expansion of the swollen brain outside the skull, resulting in axonal stretch, which might lead to neural injury and consequently cause unfavorable outcome for the patients. The aim of this study was to assess and quantify the axonal deformation at both pre- and post-craniotomy period in order to provide more insight into the mechanical effects on the axonal fibers upon such a treatment.

    Methods

    Displacement fields representing the structural changes in whole brain were obtained by a nonlinear image registration method based on the three-dimensional CT imaging data sets of a patient both before and after decompressive craniotomy. Axonal fiber tracts together with their orientations were extracted from diffusion weighted (DW) images from a healthy brain and adapted to the patient’s brain by image registration. The deformation of the brain tissue in the form of Lagrangian finite strain tensor for the entire brain was then calculated from the displacement field. Based on the obtained brain tissue strain tensor and the axonal fiber tracts, 1st principal strain was extracted at axonal fibers. Furthermore, other axonal deformation measures, i.e., axonal strain, and axonal effective shear strain were also quantified.

    Results

    Greatest axonal fiber displacement (up to 12 mm) was found predominantly located in the treated part of the craniotomy, accompanied by a large axonal deformation, e.g., 1st principal strain up to 0.49. This indicated the extent of axonal fiber stretching due to the neurosurgical intervention. Other strain measures, such as axonal strain and axonal effective shear strain also showed an increased level at the treated part for post-craniotomy compared to that found in the pre-craniotomy period.

    Conclusions

    The distortion (stretching or shearing) of axonal fibers at the treated part of the craniotomy may influence the axonal fibers in such a way that the neurochemical events are jeopardized. It is suggested that such a quantitative model may clarify some of the potential problems with such a treatment. Also, by further development of the technology it is quite possible to judge the outcome of strain levels already before the decompressive craniotomy is performed. This may have the possibility to optimize the size as well as the area of craniotomy.

  • 44.
    Li, Xiaogai
    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.
    Influence of gravity for optimal head positions in the treatment of head injury patients2011In: Acta Neurochirurgica, ISSN 0001-6268, Vol. 153, no 10, p. 2057-2064Article in journal (Refereed)
    Abstract [en]

    BACKGROUND:

    Brain edema is a major neurological complication of traumatic brain injury (TBI), commonly including a pathologically increased intracranial pressure (ICP) associated with poor outcome. In this study, gravitational force is suggested to have a significant impact on the pressure of the edema zone in the brain tissue and the objective of the study was to investigate the significance of head position on edema at the posterior part of the brain using a finite element (FE) model.

    METHODS:

    A detailed FE model including the meninges, brain tissue and a fully connected cerebrospinal fluid (CSF) system was used in this study. Brain tissue was modelled as a poroelastic material consisting of an elastic solid skeleton composed of neurons and neuroglia, permeated by interstitial fluid. The effect of head positions (supine and prone position) due to gravity was investigated for a localized brain edema at the posterior part of the brain.

    RESULTS:

    The water content increment at the edema zone remained nearly identical for both positions. However, the interstitial fluid pressure (IFP) inside the edema zone decreased around 15% by having the head in a prone position compared with a supine position.

    CONCLUSIONS:

    The decrease of IFP inside the edema zone by changing patient position from supine to prone has the potential to alleviate the damage to central nervous system nerves. These observations indicate that considering the patient's head position during intensive care and at rehabilitation might be of importance to the treatment of edematous regions in TBI patients.

  • 45.
    Li, Xiaogai
    et al.
    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). Karolinska institutet.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Influences of brain tissue poroelastic constants on intracranial pressure (ICP) during constant-rate infusion2013In: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, Vol. 16, no 12, p. 1330-1343Article in journal (Refereed)
    Abstract [en]

    A 3D finite element (FE) model has been developed to study the mean intracranial pressure (ICP) response during constant-rate infusion using linear poroelasticity. Due to the uncertainties in the poroelastic constants for brain tissue, the influence of each of the main parameters on the transient ICP infusion curve was studied. As a prerequisite for transient analysis, steady-state simulations were performed first. The simulated steady-state pressure distribution in the brain tissue for a normal cerebrospinal fluid (CSF) circulation system showed good correlation with experiments from the literature. Furthermore, steady-state ICP closely followed the infusion experiments at different infusion rates. The verified steady-state models then served as a baseline for the subsequent transient models. For transient analysis, the simulated ICP shows a similar tendency to that found in the experiments, however, different values of the poroelastic constants have a significant effect on the infusion curve. The influence of the main poroelastic parameters including the Biot coefficient alpha, Skempton coefficient B, drained Young's modulus E, Poisson's ratio nu, permeability kappa, CSF absorption conductance C-b and external venous pressure p(b) was studied to investigate the influence on the pressure response. It was found that the value of the specific storage term S-epsilon is the dominant factor that influences the infusion curve, and the drained Young's modulus E was identified as the dominant parameter second to S-epsilon. Based on the simulated infusion curves from the FE model, artificial neural network (ANN) was used to find an optimised parameter set that best fit the experimental curve. The infusion curves from both the FE simulation and using ANN confirmed the limitation of linear poroelasticity in modelling the transient constant-rate infusion.

  • 46.
    Liljemalm, Rickard
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Nyberg, Tobias
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Heating during infrared neural stimulation2013In: Lasers in Surgery and Medicine, ISSN 0196-8092, E-ISSN 1096-9101, Vol. 45, no 7, p. 469-481Article in journal (Refereed)
    Abstract [en]

    Background and Objective Infrared neural stimulation (INS) has recently evoked interest as an alternative to electrical stimulation. The mechanism of activation is the heating of water, which induces changes in cell membrane potential but may also trigger heat sensitive receptors. To further elucidate the mechanism, which may be dependent on cell type, a detailed description of the temperature distribution is necessary. A good control of the resulting temperature during INS is also necessary to avoid excessive heating that may damage the cells. Here we present a detailed model for the heating during INS and apply it for INS of in vitro neural networks of rat cerebral cortex neurons. Study Design/Materials and Methods A model of the heating during INS of a cell culture in a non-turbid media was prepared using multiphysics software. Experimental parameters such as initial temperature, beam distribution, pulse length, pulse duration, frequency and laser-cell distance were used. To verify the model, local temperature measurements using open pipette resistance were conducted. Furthermore, cortical neurons in culture were stimulated by a 500 mW pulsed diode laser (wavelength 1,550 nm) launched into a 200 μm multimodal optical fiber positioned 300 μm from the glass surface. The radiant exposure was 5.2 J/cm2. Results The model gave detailed information about the spatial and temporal temperature distribution in the heated volume during INS. Temperature measurements using open pipette resistance verified the model. The peak temperature experienced by the cells was 48°C. Cortical neurons were successfully stimulated using the 1,550 nm laser and single cell activation as well as neural network inhibition were observed. Conclusion The model shows the spatial and temporal temperature distribution in the heated volume and could serve as a useful tool for future studies of the heating during INS.

  • 47.
    Liljemalm, Rickard
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Nyberg, Tobias
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Heating during optical stimulation of neurons2011Conference paper (Refereed)
  • 48.
    Liljemalm, Rickard
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Nyberg, Tobias
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Optical Stimulation of Neurons2011Conference paper (Refereed)
  • 49.
    Maria, Asplund
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Thaning, Elin
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Inganäs, Olle
    Biomolecular and Organic Electronics IFM, and Center of Organic Electronics, Linköping University, SE-581 83 Linköping, Sweden.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Electroactive Polymers for Neural Interfaces: New Materials2007Conference paper (Refereed)
  • 50. Mordaka, J.
    et al.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Van Schijndel-De Nooij, M.
    De Lange, R.
    Casanova, L. J. G.
    Carter, E. L.
    Von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    The importance of rotational kinematics in pedestrian head to windshield impacts2007In: International Research Council on the Biomechanics of Injury - 2007 International IRCOBI Conference on the Biomechanics of Injury, Proceedings, 2007, p. 83-94Conference paper (Refereed)
    Abstract [en]

    The objective of the present study was to analyze the effect of angular kinematics on head injury in pedestrian head-to-windshield impacts. Three cases of pedestrian head impacts were simulated with FE head and windshield models. The initial impact conditions were obtained from pedestrian accident reconstructions carried out using multi-body pedestrian and car models. The results from the FE head model were compared with injuries reported in the database. Maximum principal strain was chosen as the injury indicator. After successful head injury predictions, the initial velocities were varied and as a result different peak angular velocities and accelerations were simulated. The results showed that increased peak change in angular velocity caused higher maximal principal strain in the brain and in consequence higher probability of Diffuse Axonal Injury (DAI), and Acute Subdural Haematoma (ASDH). A dramatic, three-fold increase in the strain levels in the brain was found when doubling the impact velocity. This paper presents work performed within the framework of a European Commission 6 th framework project (APROSYS).

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