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Title: Modelling deformation in the failing heart
Author: Nasopoulou, Anastasia
ISNI:       0000 0004 6058 1070
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2016
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Accurate estimation of myocardial stiness is an essential step in the development of realistic patient specic models of the heart, and can provide a reliable biomarker for disease stratication. Current methods for the estimation of myocardial material parameters are limited by the low identiability with clinically available data. This PhD work addresses the general problem of the compromise that needs to be made between model delity and parameter identiability. Parameter estimation is aected by the quality of clinical data used, the level of realism (or complexity) in the mathematical model of the ventricular mechanics, and the strategy adopted for comparing the data derived observations to the outputs of the model. This work focuses on the last aspect aecting parameter estimation, and proposes a novel cost function (CF), a novel criteria to compare data and model that improves the identiability of parameters without any loss of model delity. Using a popular transversely isotropic law for modelling the myocardium, we focus on the reported coupling between the two main parameters, the coecients of the linear and exponential part of the strain energy. The hypothesis investigated is that these two coecients can be decoupled by a novel CF that is based on the analysis of the strain energy stored in the myocardium and the external work performed while lling the ventricle. We then investigate the ability of the novel and existing CFs to dissociate the coupled material parameters. In this context, four geometry based CFs, that can be readily obtained from clinically available imaging data, were examined together with the novel CF. Finite element (FE) models of the myocardium in diastole were constructed from both synthetic and clinically derived datasets and parameter sweep simulations over the two main parameters of the material law were conducted. Our results showed that all geometry based CFs conducted to the same coupling of the parameters, both in silico and in the clinical data derived models. In both these models however, the energy based CF managed to isolate one of the parameters, and therefore in conjunction with one of the other geometry based CFs can uniquely identify the parameter set. In conclusion, we introduce a novel pipeline of a combination of CF that can be used for unique estimation of material parameters of passive myocardium within a standard FE framework. We demonstrate the method's accuracy in silico and also its applicability to clinical datasets.
Supervisor: Niederer, Steven Alexander ; Lamata de la Orden, Pablo ; Smith, Nicolas Peter Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available