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- All Subjects: Particle Image Velocimetry
- Creators: Pizziconi, Vincent
Currently, cerebral aneurysm risk evaluation and treatment planning in clinical practice is largely based on geometric features of the aneurysm including the dome size, dome-to-neck ratio, and parent vessel geometry. Hemodynamics, on the other hand, although known to be deeply involved in cerebral aneurysm initiation and progression, are considered to a lesser degree. Previous work in the field of biofluid mechanics has demonstrated that geometry is a driving factor behind aneurysmal hemodynamics.
The goal of this research is to develop a more combined geometric/hemodynamic basis for informing clinical decisions. Geometric main effects were analyzed to quantify contributions made by geometric factors that describe cerebral aneurysms (i.e., dome size, dome-to-neck ratio, and inflow angle) to clinically relevant hemodynamic responses (i.e., wall shear stress, root mean square velocity magnitude and cross-neck flow). Computational templates of idealized bifurcation and sidewall aneurysms were created to satisfy a two-level full factorial design, and examined using computational fluid dynamics. A subset of the computational bifurcation templates was also translated into physical models for experimental validation using particle image velocimetry. The effects of geometry on treatment were analyzed by virtually treating the aneurysm templates with endovascular devices. The statistical relationships between geometry, treatment, and flow that emerged have the potential to play a valuable role in clinical practice.
The purpose of this study is to collect baseline internal and external pressure data for the three most commonly used pelvic circumferential compression devices (PCCD). Unstable pelvic fractures as a result of automobile accidents, falls, and other traumatic injuries mortality rate [3]. Early use of pelvic circumferential compression devices can mitigate fatal outcomes [4]-[5]. Prolonged eternal pressure above 9.3kPa can result in long-term soft tissue damage and pressure ulcers [7]. This study hypothesizes that the application of the three most commonly used PCCDs would result in the same mean maximum point pressure exertion. To study this, internal and external, both analog and digital, pressure apparati were used to collect data. The results of this data collection demonstrate a discrepancy in the pressure distribution between right and left greater trochanters within each PCCD. Additionally, the results suggest there is an effect of internal packing on the pressure exertion externally at the two greater trochanters within each PCCD. Lastly, the differences in pressure exertion between each PCCD, internally and externally, were inconclusive as some compared metrics resulted in statistically significant results while others did not. The methodologies employed in this study can be improved through fixation of pressure collection instruments, utilization of digital pressure mats, and removal of confounding factors. The results of this study indicate that digitized, discrete data over a fixed time interval may be clinically useful, suggesting that a digital data collection would yield more reliable data. Additionally, internally mounted pressure sensor data will provide more precise results than the analog method employed herein, as well as provide insight towards bone reduction and displacement following the application of PCCDs. Finally, the information gathered from this study can be utilized to improve upon existing technologies to create a more innovative solution.
The purpose of this study is to collect baseline internal and external pressure data for the three most commonly used pelvic circumferential compression devices (PCCD). Unstable pelvic fractures as a result of automobile accidents, falls, and other traumatic injuries mortality rate [3]. Early use of pelvic circumferential compression devices can mitigate fatal outcomes [4]-[5]. Prolonged eternal pressure above 9.3kPa can result in long-term soft tissue damage and pressure ulcers [7]. This study hypothesizes that the application of the three most commonly used PCCDs would result in the same mean maximum point pressure exertion. To study this, internal and external, both analog and digital, pressure apparati were used to collect data. The results of this data collection demonstrate a discrepancy in the pressure distribution between right and left greater trochanters within each PCCD. Additionally, the results suggest there is an effect of internal packing on the pressure exertion externally at the two greater trochanters within each PCCD. Lastly, the differences in pressure exertion between each PCCD, internally and externally, were inconclusive as some compared metrics resulted in statistically significant results while others did not. The methodologies employed in this study can be improved through fixation of pressure collection instruments, utilization of digital pressure mats, and removal of confounding factors. The results of this study indicate that digitized, discrete data over a fixed time interval may be clinically useful, suggesting that a digital data collection would yield more reliable data. Additionally, internally mounted pressure sensor data will provide more precise results than the analog method employed herein, as well as provide insight towards bone reduction and displacement following the application of PCCDs. Finally, the information gathered from this study can be utilized to improve upon existing technologies to create a more innovative solution.
particularly emergent class of cardiovascular diseases and account for significant cardiovascular morbidity and mortality worldwide. Computational simulations of aortic flows are growing increasingly important as tools for gaining understanding of these pathologies and for planning their surgical repair. In vitro experiments are required to validate these simulations against real world data, and a pulsatile flow pump system can provide physiologic flow conditions characteristic of the aorta.
This dissertation presents improved experimental techniques for in vitro aortic blood flow and the increasingly larger parts of the human cardiovascular system. Specifically, this work develops new flow management and measurement techniques for cardiovascular flow experiments with the aim to improve clinical evaluation and treatment planning of aortic diseases.
The hypothesis of this research is that transient flow driven by a step change in volume flux in a piston-based pulsatile flow pump system behaves differently from transient flow driven by a step change in pressure gradient, the development time being substantially reduced in the former. Due to this difference in behavior, the response to a piston-driven pump can be predicted in order to establish inlet velocity and flow waveforms at a downstream phantom model.
The main objectives of this dissertation were: 1) to design, construct, and validate a piston-based flow pump system for aortic flow experiments, 2) to characterize temporal and spatial development of start-up flows driven by a piston pump that produces a step change from zero flow to a constant volume flux in realistic (finite) tube geometries for physiologic Reynolds numbers, and 3) to develop a method to predict downstream velocity and flow waveforms at the inlet of an aortic phantom model and determine the input waveform needed to achieve the intended waveform at the test section. Application of these newly improved flow management tools and measurement techniques were then demonstrated through in vitro experiments in patient-specific coarctation of aorta flow phantom models manufactured in-house and compared to computational simulations to inform and execute future experiments and simulations.