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Quantifying Relative Surface Level Brain Motion in Postmortem Human Subjects Using High-Frequency B-Mode Ultrasound

Tesny, Angela Clara
http://rave.ohiolink.edu/etdc/view?acc_num=osu1650296600260485

Abstract Details

2022, Doctor of Philosophy, Ohio State University, Mechanical Engineering.
Motor vehicle crashes are a leading cause of bleeding head injury, especially in the elderly population. Acute subdural hematomas (ASDH) are particularly lethal. The increased frequency of ASDH with age has been attributed to the rupture of bridging veins, necessitating a better understanding of the relationship between rotational kinematics and bridging vein failure. As bridging veins run from the surface of the cortex through the meninges and into the dural sinuses, any relative motion between the brain and the skull may result in the shearing of the bridging veins, resulting in ASDH. The increased atrophy in the elderly population compared to their younger counterparts results in an initial strain on the bridging veins, suggesting one of the reasons why the elderly population is more susceptible to ASDH from bridging vein failure. Previous studies have quantified whole brain motion under a variety of dynamic loading conditions. Further, finite element (FE) models of the brain have been utilized to supplement the investigation of the brain’s susceptibility to injury; however, the experimental brain data currently used to validate these models are lacking surface-level validation data. The objective of this dissertation is to provide experimental brain displacement data at the surface of the brain to contribute to further validation of FE models and aid in the investigation of the relationship between head kinematics and brain displacement that could result in an ASDH in the elderly. Surface-level brain displacements were quantified in this dissertation work using high-frequency, Brightness-mode (B-mode) ultrasound due to its advantages of noninvasiveness and high resolution. However, the use of ultrasound to quantify displacement while the probe is rotating under high rates has not yet been validated. As an initial objective of this dissertation work, the ultrasound was validated under the same conditions that it was utilized for quantifying brain displacement in postmortem human subject (PMHS). A custom validation fixture was fabricated to replicate brain motion under rotation in a PMHS. Rather than tracking human tissue samples, a three-dimensional (3D) phantom was created. Displacement of the 3D printed tracking phantom was compared to displacement obtained from a linear potentiometer. On average, the difference between the measurement systems was 0.05 mm, or a 1.5% difference. Combined with an NRMSD value of 0.08, these results indicate that the accuracy of the ultrasound as a measurement system is not influenced by high-rate rotation, and thus can be utilized to quantify brain displacement in PMHS. Displacements between surface-level brain tissues and the skull were quantified using high-frequency, B-mode ultrasound in five PMHS. Each subject underwent pre-test magnetic resonance (MR) imaging and brain parenchymal fraction (BPF) was calculated. Brain temperature of each subject was monitored and controlled throughout both preparation and testing, as lower temperatures have been shown to reduce the effects of postmortem degradation. The head of each subject was removed at the C6-C7 vertebral level, and artificial cerebrospinal fluid (aCSF) was reintroduced via the subarachnoid space. A small window was opened through the skull for the ultrasound to image the underlying tissue at 3 cm posterior to the bregma and 3 cm lateral to the centerline. The head was secured in a cage that ensured uniform rotation in the sagittal plane in an anterior-posterior direction. A custom rotation fixture delivered repeatable pulses over a wide range of input kinematics. Each subject’s brain was brought to physiological intracranial pressure before each rotation test. All rotation tests across all five subjects were complete within 56 hours postmortem. The moment of inertia (MOI) of each subject was calculated post-test. Tissue tracking video sequences collected by B-mode ultrasound were analyzed using a commercial video tracking software. Peak brain displacements were quantified at the surface of the cortex, 1 mm deep into the cortex, and 2 mm deep into the cortex. This dissertation provides over 300 displacement curves from five subjects varying in age, sex, and anthropometry that can be used to improve and validate human body models. Subject-specific parameters such as the postmortem time at which the rotation test was conducted, BPF, and MOI were all significant predictors of peak brain displacement. These data provided in this dissertation provide another step towards understanding subdural hematoma injury risk based on kinematic input.
Yun-Seok Kang, PhD (Advisor)
Rebecca Dupaix, PhD (Committee Member)
Alan Litsky, PhD (Committee Member)
John Bolte IV, PhD (Committee Member)
333 p.
Biomechanics; Biomedical Engineering; Mechanical Engineering; Medical Imaging
subdural hematoma; brain; injury; biomechanics; brain motion; brain displacement; PMHS; ultrasound; motor vehicle crash

Recommended Citations

Citations

  • Tesny, A. C. (2022). Quantifying Relative Surface Level Brain Motion in Postmortem Human Subjects Using High-Frequency B-Mode Ultrasound [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1650296600260485

    APA Style (7th edition)

  • Tesny, Angela. Quantifying Relative Surface Level Brain Motion in Postmortem Human Subjects Using High-Frequency B-Mode Ultrasound. 2022. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1650296600260485.

    MLA Style (8th edition)

  • Tesny, Angela. "Quantifying Relative Surface Level Brain Motion in Postmortem Human Subjects Using High-Frequency B-Mode Ultrasound." Doctoral dissertation, Ohio State University, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=osu1650296600260485

    Chicago Manual of Style (17th edition)

osu1650296600260485
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This open access ETD is published by The Ohio State University and OhioLINK.
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