Nonfatal strangulation (NFS) can cause severe physical and psychological injury. Instances of NFS are correlated with a heightened risk of lethal violence between partners [1]. While NFS does not result in death, it can result in severe hypoxic brain injury (HBI) and has been shown to increase the likelihood of an eventual fatality in the relationship eightfold [1]. Unfortunately, minimal quantitative biomechanical research has been performed to study strangulation injury, and detection and diagnosis of NFS, which often relies upon visible injuries, remains challenging [2]. The effects of occluded cerebral venous flow on intracranial pressure (ICP) have not been considered in a model for HBI as opposed to the context of stroke and neonatal hypoxic-ischemic encephalopathy.
In this project, the effects of elevated ICP on the hemodynamics and structural dynamics of a diploic vein were considered. This was done by performing transient coupled fluid-structure simulations on a segment of an intracranial vein that sought to replicate the ICP surge experienced during strangulation. The vessel model was created by isolating a segment of an intracranial vessel. Using the software 3D Slicer, the skull was extracted and exported as an STL file. From there, a segment of a diploic vein was isolated and edited by importing the STL into Blender. The segment was then processed using MeshLab and Blender to make it a solid geometry and remove potential complications.
Once the vessel segment was isolated and processed, it was exported as an STL file into a commercial solver from ANSYS, Inc., Canonsburg, PA, USA. Using a coupling system of the Ansys Fluent and Mechanical models, a transient Fluid-Solid Interaction (FSI) simulation was performed by coupling ANSYS' Fluent and Mechanical models. In the simulation, blood flowed steadily through the vessel, and the data for FSI was recorded. The software was used to simulate the deformation and stress of the blood vessels caused by the blood flow for elevated intracranial pressure events for five different durations and magnitudes.
Following the FSI simulations, the total deformation, equivalent stress, dynamic pressure, static pressure, and fluid velocity were plotted. The results show that altering the pressure duration can increase average total vessel wall deformation by up to 356.35%, average equivalent stress by 331.11%, dynamic pressure by 19.28%, and decrease static pressure by 30.94%. Likewise, increasing the magnitude of pressure can also increase the dynamic pressure by 17.17 %, the maximum velocity by 16.77%, and can decrease the static pressure by 27.31%. The statistical behavior of each type of modification was unique, as altering the duration created a logarithmic plot while changing the magnitude of pressure created a second power plot. With the provided data, researchers will better understand the effects of NFS-like elevated intracranial pressure on cerebral vasculature. / Master of Science / Nonfatal strangulation (NFS) has been identified as a leading indicator of escalating partner violence. The first occurrence of NFS in an intimate partnership correlated with an 8-fold increase in the risk of future attacks that are fatal by that partner. While NFS does not result in the immediate death of the victim, it can still cause severe physical and psychological harm. This includes traumatic brain injury from lack of proper blood flow, increased intracranial pressure (ICP), and hypoxia. Quantitative research on strangulation injury has mainly been carried out by forensics researchers, resulting in a lack of understanding of the biomechanics of nonfatal strangulation. This lack of knowledge, coupled with the frequent absence of visible injuries in victims of NFS, makes diagnosing NFS events particularly difficult. This study aims to begin to fill this gap by developing a computational biomechanics model of a phenomenon that occurs during NFS. The model examines how altering the duration and magnitude of a pressure wave that mimics the increased intracranial pressure during NFS can impact the blood flow and vessel motions in an intracranial blood vessel. The blood vessel model was extracted from a computed tomography (CT) scan of a patient's skull, preprocessed, and transferred into ANSYS finite element modeling software. Fluid-solid interaction (FSI) simulations were performed in ANSYS, which allowed the study of blood pressure, blood velocity, vessel deformation, and vessel stress. The results showed that increasing either the magnitude or duration of the pressure wave caused an increase in vessel stress and deformation. The results also showed that doing either increased the maximum blood velocity and dynamic pressure while decreasing the static pressure of the blood. These results contribute toward the understanding of the biomechanics of nonfatal strangulation. The model developed in this project may serve as the foundation for more complex models in future studies.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/121067 |
| Date | 03 September 2024 |
| Creators | Davis, Nathaniel Tran |
| Contributors | Department of Biomedical Engineering and Mechanics, Staples, Anne E., Robertson, John L., VandeVord, Pamela |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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