Date of Award

8-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Bioengineering

Committee Chair/Advisor

David Karig

Committee Member

Bruce Z. Gao

Committee Member

Delphine Dean

Committee Member

Tong Ye

Committee Member

Ethan Kung

Abstract

Forces from fluid flow on a tissue or cellular boundary can drive remodeling processes through mechanotransduction pathways. In most cases, the exact mechanisms are not understood, such as in marine biofilm development or vascular remodeling. To gain a better understanding of these interactions, the flow profile at a solid boundary and the mechanical changes of that solid can be coupled together to determine the impact of fluid flow on mechanical remodeling. To achieve this, optical coherence tomography (OCT) is used to image the fluid and solid simultaneously. Fluid seeded with particles can be imaged and run through a particle image velocimetry (PIV) algorithm to acquire the velocity profile and estimate shear stress. The displacement of each material point in a solid can be tracked over time using a digital imaging correlation (DIC) algorithm, and the changes in strain can be calculated for that location. These two methods were achieved in our lab-built OCT system, using consecutive B-scans as double exposure image pairs. OCT-based PIV was performed on biofilm phantoms in laminar and turbulent flow environments, and the boundary velocity profile was determined to be a second-order polynomial in the laminar case and linear in the turbulent case, matching numerical modeling. Testing was also performed on porcine vessels using OCT-based DIC to measure the strain difference between the media and adventitia layers. As expected, the adventitia had a higher stiffness due to the ECM content. This imaging technique can provide valuable insight into the interaction between fluid flow and mechanical remodeling.

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