MECHANICAL CHARACTERIZATION OF PORCINE AORTA USING MAGNETIC RESONANCE IMAGING
Flamini, Vittoria (2010) MECHANICAL CHARACTERIZATION OF PORCINE AORTA USING MAGNETIC RESONANCE IMAGING. PhD thesis, Dublin City University.
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Determination of aortic mechanical properties in a non-invasive way would be an important step in predicting the onset and development of one of the most fatal degenerative cardiovascular diseases: abdominal aortic aneurysm(AAA). The approach presented in this work to achieve this goal couples Magnetic Resonance Imaging (MRI) with Finite Element (FE) analysis to define a model of aortic mechanical behaviour. In particular, the aortic fibrous
structure was analysed using Diffusion Tensor MRI, the results of which showed that fibres could be tracked in the aortic tissue, and that their angles measured ( 15◦) are in accordance with the angles reported in literature.
DTI was also applied to a frozen aorta, where the structural parameters obtained were different from those for fresh tissue thus indicating the potential of DTI to measure damage in aortic tissue. MRI was also used for characterization of aortic tissue deformation, using Phase Contrast MRI (PC MRI). With this technique circumferential strains were measured in an aorta, which on average ranged between 0.95-4.7%, in accordance with the range found in vivo from literature. A mechanical constitutive model was implemented, initially based on the structural information from DTI and uniaxial test data, in a finite element (FE) model. Strains estimated in the model under applied physiological pressure were compared with the strains measured using PC MRI. Material parameters of the constitutive model were changed iteratively until the strains matched, thus obtaining the material constants necessary to characterize the behaviour of the aorta non-invasively. This thesis clearly demonstrates the feasibility of a novel approach to mechanical characterization of aortas, based on the use of innovative MRI techniques. Moreover, the application of DTI to both fresh and frozen tissue, which clearly identified differences in the tissues at the fibre level, demonstrates the potential of DTI as a diagnostic tool for degenerative arterial diseases such as AAAs.
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