Change search
Link to record
Permanent link

Direct link
BETA
Li, Xiaogai
Publications (10 of 18) Show all publications
Zhou, Z., Li, X., Kleiven, S., Shah, C. S. & Hardy, W. N. (2019). A Reanalysis of Experimental Brain Strain Data: Implication for Finite Element Head Model Validation. In: SAE Technical Papers: . Paper presented at SAE 62nd Stapp Car Crash Conference, STAPP 2018; Catamaran Resort Hotel San Diego; United States; 12 November 2018 through 14 November 2018. SAE International, 2019, Article ID November.
Open this publication in new window or tab >>A Reanalysis of Experimental Brain Strain Data: Implication for Finite Element Head Model Validation
Show others...
2019 (English)In: SAE Technical Papers, SAE International , 2019, Vol. 2019, article id NovemberConference paper, Published paper (Refereed)
Abstract [en]

Relative motion between the brain and skull and brain deformation are biomechanics aspects associated with many types of traumatic brain injury (TBI). Thus far, there is only one experimental endeavor (Hardy et al., 2007) reported brain strain under loading conditions commensurate with levels that were capable of producing injury. Most of the existing finite element (FE) head models are validated against brain-skull relative motion and then used for TBI prediction based on strain metrics. However, the suitability of using a model validated against brain-skull relative motion for strain prediction remains to be determined. To partially address the deficiency of experimental brain deformation data, this study revisits the only existing dynamic experimental brain strain data and updates the original calculations, which reflect incremental strain changes. The brain strain is recomputed by imposing the measured motion of neutral density target (NDT) to the NDT triad model. The revised brain strain and the brain-skull relative motion data are then used to test the hypothesis that an FE head model validated against brain-skull relative motion does not guarantee its accuracy in terms of brain strain prediction. To this end, responses of brain strain and brain-skull relative motion of a previously developed FE head model (Kleiven, 2007) are compared with available experimental data. CORrelation and Analysis (CORA) and Normalized Integral Square Error (NISE) are employed to evaluate model validation performance for both brain strain and brain-skull relative motion. Correlation analyses (Pearson coefficient) are conducted between average cluster peak strain and average cluster peak brain-skull relative motion, and also between brain strain validation scores and brain-skull relative motion validation scores. The results show no significant correlations, neither between experimentally acquired peaks nor between computationally determined validation scores. These findings indicate that a head model validated against brain-skull relative motion may not be sufficient to assure its strain prediction accuracy. It is suggested that a FE head model with intended use for strain prediction should be validated against the experimental brain deformation data and not just the brain-skull relative motion.

Place, publisher, year, edition, pages
SAE International, 2019
Series
SAE Technical Papers, ISSN 0148-7191
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:kth:diva-258835 (URN)10.4271/2018-22-0007 (DOI)2-s2.0-85065394817 (Scopus ID)
Conference
SAE 62nd Stapp Car Crash Conference, STAPP 2018; Catamaran Resort Hotel San Diego; United States; 12 November 2018 through 14 November 2018
Note

QC 20190911

Available from: 2019-09-11 Created: 2019-09-11 Last updated: 2019-11-13Bibliographically approved
Zhou, Z., Li, X. & Kleiven, S. (2019). Biomechanics of acute subdural hematoma in the elderly: A fluid-structure interaction study. Journal of Neurotrauma, 36(13), 2099-2108
Open this publication in new window or tab >>Biomechanics of acute subdural hematoma in the elderly: A fluid-structure interaction study
2019 (English)In: Journal of Neurotrauma, ISSN 0897-7151, E-ISSN 1557-9042, Vol. 36, no 13, p. 2099-2108Article in journal (Refereed) Published
Abstract [en]

Acute subdural hematoma (ASDH) due to bridging vein (BV) rupture is a frequent and lethal head injury, especially in the elderly. Brain atrophy has been hypothesized to be a primary pathogenesis associated with the increased risk of ASDH in the elderly. Though decades of biomechanical endeavours have been made to elucidate the potential mechanisms, a thorough explanation for this hypothesis appears lacking. Thus, a recently improved finite element head model, in which the brain-skull interface was modelled using a fluid-structure interaction (FSI) approach with special treatment of the cerebrospinal fluid as arbitrary Lagrangian-Eulerian fluid formulation, is used to partially address this understanding gap. Models with various degrees of atrophied brains and thereby different subarachnoid thicknesses are generated and subsequently exposed to experimentally determined loadings known to cause ASDH or not. The results show significant increases in the cortical relative motion and BV strain in the atrophied brain, which consequently exacerbates the ASDH risk in the elderly. Results of this study are suggested to be considered while developing age-adapted protecting strategies for the elderly in the future.

Place, publisher, year, edition, pages
Mary Ann Liebert, 2019
National Category
Medical and Health Sciences Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-243833 (URN)10.1089/neu.2018.6143 (DOI)000473049600431 ()30717617 (PubMedID)2-s2.0-85068219142 (Scopus ID)
Note

QC 20190212

Available from: 2019-02-06 Created: 2019-02-06 Last updated: 2019-11-14Bibliographically approved
Zhou, Z., Li, X. & Kleiven, S. (2019). Biomechanics of periventricular injury. Journal of Neurotrauma
Open this publication in new window or tab >>Biomechanics of periventricular injury
2019 (English)In: Journal of Neurotrauma, ISSN 0897-7151, E-ISSN 1557-9042Article in journal (Other academic) Submitted
National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-263069 (URN)
Note

QCR 20191029

Available from: 2019-10-29 Created: 2019-10-29 Last updated: 2019-11-13Bibliographically approved
Zhou, Z., Li, X., Kleiven, S. & Hardy, W. N. (2019). Brain Strain from Motion of Sparse Markers. Stapp Car Crash Journal, 63
Open this publication in new window or tab >>Brain Strain from Motion of Sparse Markers
2019 (English)In: Stapp Car Crash Journal, ISSN 1532-8546, Vol. 63Article in journal (Refereed) Published
Abstract [en]

Brain strain secondary to head impact or inertial loading is closely associated with pathologic observations in the brain. The only experimental brain strain under loading close to traumatic level was calculated by imposing the experimentally measured motion of markers embedded in the brain to an auxiliary model formed by triad elements (Hardy et al., 2007). However, fidelity of this strain calculation as well as the suitability of using triad elements for three-dimensional strain estimation remains to be verified. Therefore, this study proposes to use tetrahedron elements as a new approach to estimate the brain strain. Fidelity of this newly-proposed approach along with the previous triad-based approach is evaluated with the aid of a finite element (FE) head model by numerically replicating the experimental impacts and strain estimation procedures. Strain in the preselected brain elements obtained from the whole head simulation exhibits good correlation with its tetra estimation which exceeds triad estimation, indicating that the tetra approach more accurately estimates the strain in the preselected region. The newly calculated brain strain curves using tetra elements provide better representation of the experimental brain deformation and can be used for strain validation of FE head models.

National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-263068 (URN)
Note

QCR 20191029

Available from: 2019-10-29 Created: 2019-10-29 Last updated: 2019-10-30Bibliographically approved
Fahlstedt, M., Kleiven, S. & Li, X. (2019). Current Playground Surface Test Standards Underestimate Brain Injury Risk for Children. Journal of Biomechanics
Open this publication in new window or tab >>Current Playground Surface Test Standards Underestimate Brain Injury Risk for Children
2019 (English)In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380Article in journal (Refereed) Published
Abstract [en]

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

National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-250703 (URN)10.1016/j.jbiomech.2019.03.038 (DOI)000469156200001 ()2-s2.0-85064461545 (Scopus ID)
Note

QC 20190625

Available from: 2019-05-03 Created: 2019-05-03 Last updated: 2019-11-14Bibliographically approved
Li, X., Sandler, H. & Kleiven, S. (2019). Infant skull fractures: Accident or abuse?: Evidences from biomechanical analysis using finite element head models. Forensic science international, 294, 173-182
Open this publication in new window or tab >>Infant skull fractures: Accident or abuse?: Evidences from biomechanical analysis using finite element head models
2019 (English)In: Forensic science international, Vol. 294, p. 173-182Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Abusive Head Trauma; Multiple skull fractures; Finite element head model; Ossification centers; Impact location
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-259171 (URN)10.1016/j.forsciint.2018.11.008 (DOI)000454861200029 ()2-s2.0-85057577148 (Scopus ID)
Note

QC 20190923

Available from: 2019-09-12 Created: 2019-09-12 Last updated: 2019-10-09Bibliographically approved
Zhou, Z., Li, X., Kleiven, S., Shah, C. & Hardy, W. (2018). A reanalysis of experimental brain strain data: implication for finite element head model validation. Stapp Car Crash Journal, 62, 293-318
Open this publication in new window or tab >>A reanalysis of experimental brain strain data: implication for finite element head model validation
Show others...
2018 (English)In: Stapp Car Crash Journal, ISSN 1532-8546, Vol. 62, p. 293-318Article in journal (Refereed) Published
Abstract [en]

Relative motion between the brain and skull and brain deformation are biomechanics aspects associated with many types of traumatic brain injury (TBI). Thus far, there is only one experimental endeavor (Hardy et al., 2007) reported brain strain under loading conditions commensurate with levels that were capable of producing injury. Most of the existing finite element (FE) head models are validated against brain-skull relative motion and then used for TBI prediction based on strain metrics. However, the suitability of using a model validated against brain-skull relative motion for strain prediction remains to be determined. To partially address the deficiency of experimental brain deformation data, this study revisits the only existing dynamic experimental brain strain data and updates the original calculations, which reflect incremental strain changes. The brain strain is recomputed by imposing the measured motion of neutral density target (NDT) to the NDT triad model. The revised brain strain and the brain-skull relative motion data are then used to test the hypothesis that an FE head model validated against brainskull relative motion does not guarantee its accuracy in terms of brain strain prediction. To this end, responses of brain strain and brain-skull relative motion of a previously developed FE head model (Kleiven, 2007) are compared with available experimental data. CORrelation and Analysis (CORA) and Normalized Integral Square Error (NISE) are employed to evaluate model validation performance for both brain strain and brain-skull relative motion. Correlation analyses (Pearson coefficient) are conducted between average cluster peak strain and average cluster peak brain-skull relative motion, and also between brain strain validation scores and brain-skull relative motion validation scores. The results show no significant correlations, neither between experimentally acquired peaks nor between computationally determined validation scores. These findings indicate that a head model validated against brain-skull relative motion may not be sufficient to assure its strain prediction accuracy. It is suggested that a FE head model with intended use for strain prediction should be validated against the experimental brain deformation data and not just the brain-skull relative motion.

Place, publisher, year, edition, pages
NLM, 2018
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:kth:diva-242238 (URN)30608998 (PubMedID)2-s2.0-85059498927 (Scopus ID)
Note

QC 20190514

Available from: 2019-01-29 Created: 2019-01-29 Last updated: 2019-11-13Bibliographically approved
Zhou, Z., Li, X. & Kleiven, S. (2018). Fluid–structure interaction simulation of the brain–skull interface for acute subdural haematoma prediction. Biomechanics and Modeling in Mechanobiology, 18(1), 155-173
Open this publication in new window or tab >>Fluid–structure interaction simulation of the brain–skull interface for acute subdural haematoma prediction
2018 (English)In: Biomechanics and Modeling in Mechanobiology, ISSN 1617-7959, E-ISSN 1617-7940, Vol. 18, no 1, p. 155-173Article in journal (Refereed) Published
Abstract [en]

Traumatic brain injury is a leading cause of disability and mortality. Finite element-based head models are promising tools for enhanced head injury prediction, mitigation and prevention. The reliability of such models depends heavily on adequate representation of the brain–skull interaction. Nevertheless, the brain–skull interface has been largely simplified in previous three-dimensional head models without accounting for the fluid behaviour of the cerebrospinal fluid (CSF) and its mechanical interaction with the brain and skull. In this study, the brain–skull interface in a previously developed head model is modified as a fluid–structure interaction (FSI) approach, in which the CSF is treated on a moving mesh using an arbitrary Lagrangian–Eulerian multi-material formulation and the brain on a deformable mesh using a Lagrangian formulation. The modified model is validated against brain–skull relative displacement and intracranial pressure responses and subsequently imposed to an experimentally determined loading known to cause acute subdural haematoma (ASDH). Compared to the original model, the modified model achieves an improved validation performance in terms of brain–skull relative motion and is able to predict the occurrence of ASDH more accurately, indicating the superiority of the FSI approach for brain–skull interface modelling. The introduction of the FSI approach to represent the fluid behaviour of the CSF and its interaction with the brain and skull is crucial for more accurate head injury predictions.

Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2018
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:kth:diva-233858 (URN)10.1007/s10237-018-1074-z (DOI)000457974500012 ()2-s2.0-85053071855 (Scopus ID)
Note

QC 20180906

Available from: 2018-08-30 Created: 2018-08-30 Last updated: 2019-10-30Bibliographically approved
Li, X. & Kleiven, S. (2018). Improved safety standards are needed to better protect younger children at playgrounds. Scientific Reports, 8(1), Article ID 15061.
Open this publication in new window or tab >>Improved safety standards are needed to better protect younger children at playgrounds
2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, no 1, article id 15061Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Neurosciences
Identifiers
urn:nbn:se:kth:diva-237094 (URN)10.1038/s41598-018-33393-z (DOI)000446856000009 ()30305685 (PubMedID)2-s2.0-85054699576 (Scopus ID)
Note

QC 20181022

Available from: 2018-10-24 Created: 2018-10-24 Last updated: 2019-09-11Bibliographically approved
Fahlstedt, M., Kleiven, S. & Li, X. (2018). The Influence of the Body on Head Kinematics in Playground Falls for Different Age Groups. In: Proceedings of International Research Council on Biomechanics of Injury (IRCOBI) Conference: . Paper presented at IRCOBI.
Open this publication in new window or tab >>The Influence of the Body on Head Kinematics in Playground Falls for Different Age Groups
2018 (English)In: Proceedings of International Research Council on Biomechanics of Injury (IRCOBI) Conference, 2018Conference paper, Published paper (Refereed)
National Category
Other Medical Sciences
Research subject
Applied Medical Technology
Identifiers
urn:nbn:se:kth:diva-248778 (URN)2-s2.0-85061107724 (Scopus ID)
Conference
IRCOBI
Note

QC 20190418

Available from: 2019-04-10 Created: 2019-04-10 Last updated: 2019-11-14Bibliographically approved
Organisations

Search in DiVA

Show all publications