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Relative changes of the biomechanical properties of living rabbit brain tested under controlled physiologic conditions with stress-relaxation indentation

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dc.contributor.supervisor Cenkowski, Stefan (Biosystems Engineering) Del Bigio, Marc (Pathology) en_US
dc.contributor.author Kazina, Colin John
dc.date.accessioned 2014-01-16T17:41:53Z
dc.date.available 2014-01-16T17:41:53Z
dc.date.issued 2014-01-16
dc.identifier.uri http://hdl.handle.net/1993/23266
dc.description.abstract Mechanical testing of living brain with control or measurement of all potential sources of variability is difficult and not often or consistently performed. The primary objective of the current work is to compare mechanical properties of the living rabbit brain across relatively high and low groupings of arterial blood partial pressure of carbon dioxide (pCO2) and mean arterial pressure (MAP), with control or measurement of all deformation, anatomical, and other physiological variables. It is hypothesized that there are significant differences in relative viscoelastic properties of the living rabbit brain under different combinations of pCO2 and blood pressure. Stress-relaxation brain indentations were performed on seven consecutive anesthetized living rabbits, with control or measurement of all possible variables.. Five indentations were performed on each animal, with 15 minute periods of rest between each indentation, with the following relative physiological parameters: Indentation 1. Low MAP and low pCO2. Indentation 2. High MAP and low pCO2. Indentation 3. Low MAP and high pCO2. Indentation 4. High MAP and high pCO2. Indentation 5. Low MAP and low pCO2. The data were fitted to a generalized Maxwell model that incorporated two viscoelastic terms and one equilibrium elastic term. The relative stress-relaxation coefficients and material properties were determined, and compared using statistical analysis. Peak stresses encountered with relative step-loading ranged from approximately 2-4 x 103 Pa, with corresponding “instantaneous” elastic moduli approximating 4-8 x 103 Pa. A short and long Time of Relaxation was determined for each viscoelastic term of the model, and ranged from 0.03 – 1.72 s and 9.92 – 32.55 s respectively. Comparison of stress-relaxation coefficients and material properties reveals statistically significant differences in the stress coefficients and their respective elastic moduli across different combinations of pCO2 and MAP, and between the last indentation group and previous indentations. There were no significant differences found in Time of Relaxation coefficients. In conclusion, mechanical properties of step-loaded living rabbit brain are relatively dependent on pCO2 and MAP, and repetitive deformations. This may be important for further understanding of the brain in different physiological states and accurate mechanical characterization of the brain. It also highlights the need to control for these parameters during the mechanical testing of brain. en_US
dc.subject brain en_US
dc.subject biomechanics en_US
dc.title Relative changes of the biomechanical properties of living rabbit brain tested under controlled physiologic conditions with stress-relaxation indentation en_US
dc.degree.discipline Biosystems Engineering en_US
dc.contributor.examiningcommittee Zhang, Qiang (Biosystems Engineering) West, Michael (Surgery) Bilston, Lynne (University of New South Wales) en_US
dc.degree.level Doctor of Philosophy (Ph.D.) en_US
dc.description.note February 2014 en_US


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