Date of Graduation

5-2023

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering (MSBME)

Degree Level

Graduate

Department

Biomedical Engineering

Advisor/Mentor

Morten O. Jensen

Committee Member

Hanna Jensen

Second Committee Member

Paul Millett

Keywords

Biomechanics, Finite Element, Micro CT, Mitral Valve

Abstract

The mitral valve serves a critical role in healthy cardiac function by ensuring the unidirectional flow of oxygenated blood from the left atrium into the left ventricle. It experiences the highest pressures found within the heart and its closure is the result of a complex interaction of several different structures that, furthermore, are unique to each individual. Despite the valve’s vital role however, the specific function of these constituent structures is not fully understood. This, confounded by its asymmetric, personalized nature, make surgical interventions for the mitral valve far less effective than for its neighboring aortic valve. Efforts to overcome this have been made through the lens of computational simulation, in which the valve is studied virtually and procedures may be planned. The quality and reliability of these simulation results are only as good as the inputs that the simulation model receives. This study proposes and evaluates a workflow by which high-quality biomechanical inputs are obtained for computational input and validation. To account for individual variation, all steps are performed on the same valve such that a direct correspondence is made between geometry, stress/load distribution and the resulting coaptation. Ultrasound in vivo measurements are made so that custom tailored mounting hardware can be manufactured. This hardware is used to support the valve in a physiologically appropriate manner for µCT imaging in both the open and closed configurations. Scanning within a fluid medium, to prevent tissue desiccation and other detrimental effects, is made possible through a DiceCT tissue staining procedure. High resolution, 3D imagery is obtained for the open valve whereas only a relatively quick set of projection images is obtained for the closed configuration. Registration between open and closed imagery is accomplished by localizing aluminum oxide fiducial markers that are bound to the leaflet surface. Subsequent image analysis is performed to isolate the tissue and place the data in the proper format for computational use. The valve is then closed under known pressure while chordal forces/strains are simultaneously recorded to provide loading conditions. The effectiveness of the workflow is illustrated through two animal experiments. Incomplete results were obtained from the first experiment as the tissue degraded significantly during a prolonged period of µCT downtime. The second experiment resulted in good quality ultrasound imagery, leading to the creation of customized mounting hardware, yet the remainder of the process was still in progress at the final stages of this document. Computational modeling is still ongoing, yet some preliminary results are presented which show the geometry from the first animal experiment tending towards closure.

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