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Generation of Patient Specific Finite Element Head Models
KTH, School of Technology and Health (STH), Neuronic Engineering.ORCID iD: 0000-0001-9785-2071
2008 (English)Doctoral 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

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , vi, 39 p.
Series
Trita-STH : report, ISSN 1653-3836 ; 2008:7
Keyword [en]
Injury Prevention, Patient Specific, Finite Element Head Model, Anatomical Structures
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-9585ISBN: 978-91-7415-191-6 (print)OAI: oai:DiVA.org:kth-9585DiVA: diva2:126650
Public defence
2008-12-12, Lecture hall 3-221, Alfred Nobels Allé 10, Huddinge, 13:00 (English)
Opponent
Supervisors
Note
QC 20100811Available from: 2008-11-21 Created: 2008-11-19 Last updated: 2010-08-11Bibliographically approved
List of papers
1. Automatic generation and validation of patient-specific finite element head models suitable for crashworthiness analysis
Open this publication in new window or tab >>Automatic generation and validation of patient-specific finite element head models suitable for crashworthiness analysis
2009 (English)In: International Journal of Crashworthiness, ISSN 1358-8265, Vol. 14, no 6, 555-563 p.Article in journal (Refereed) Published
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.

Keyword
human head model; finite element analysis; automatic model generation; localised brain motion
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-9580 (URN)10.1080/13588260902895708 (DOI)000274698300004 ()2-s2.0-71449118841 (Scopus ID)
Note
QC 20100810. Uppdaterad från manuskript till artikel i tidskrift (20100810).Available from: 2008-11-19 Created: 2008-11-19 Last updated: 2010-08-10Bibliographically approved
2. Dynamic response of the brain with vasculature: A three-dimensional computational study
Open this publication in new window or tab >>Dynamic response of the brain with vasculature: A three-dimensional computational study
2007 (English)In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 40, no 13, 3006-3012 p.Article in journal (Refereed) Published
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.

Keyword
Human head model, Finite element analysis, Cerebral blood vessels, Traumatic brain injury
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-9584 (URN)10.1016/j.jbiomech.2007.02.011 (DOI)000250277800023 ()2-s2.0-34548513569 (Scopus ID)
Note
QC 20100811Available from: 2008-11-19 Created: 2008-11-19 Last updated: 2010-08-11Bibliographically approved
3. The influence of the falx and tentorium: A 3D computational study of impacts using detailed FE head models
Open this publication in new window or tab >>The influence of the falx and tentorium: A 3D computational study of impacts using detailed FE head models
(English)Manuscript (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.

Keyword
Finite element model, biomechanics, falx, tentorium
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-9582 (URN)
Note
QC 20100811Available from: 2008-11-19 Created: 2008-11-19 Last updated: 2010-08-11Bibliographically approved
4. Can sulci protect the brain from traumatic injury?
Open this publication in new window or tab >>Can sulci protect the brain from traumatic injury?
2009 (English)In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 42, no 13, 2074-2080 p.Article in journal (Refereed) Published
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.

Keyword
Human head model, Finite element analysis, Cerebral convolution, Traumatic brain injury, diffuse axonal injury, white-matter, head impact, model, segmentation, epidemiology, simulations, primate, mater
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-18837 (URN)10.1016/j.jbiomech.2009.06.051 (DOI)000270478000010 ()2-s2.0-69449098153 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved

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