title: Improved identifiability of myocardial material parameters by an energy-based cost function.
abstract: Myocardial stiffness is a valuable clinical biomarker for the monitoring and stratification of heart failure (HF). Cardiac finite element models provide a biomechanical framework for the assessment of stiffness through the determination of the myocardial constitutive model parameters. The reported parameter intercorrelations in popular constitutive relations, however, obstruct the unique estimation of material parameters and limit the reliable translation of this stiffness metric to clinical practice. Focusing on the role of the cost function (CF) in parameter identifiability, we investigate the performance of a set of geometric indices (based on displacements, strains, cavity volume, wall thickness and apicobasal dimension of the ventricle) and a novel CF derived from energy conservation. Our results, with a commonly used transversely isotropic material model (proposed by Guccione et al.), demonstrate that a single geometry-based CF is unable to uniquely constrain the parameter space. The energy-based CF, conversely, isolates one of the parameters and in conjunction with one of the geometric metrics provides a unique estimation of the parameter set. This gives rise to a new methodology for estimating myocardial material parameters based on the combination of deformation and energetics analysis. The accuracy of the pipeline is demonstrated in silico, and its robustness in vivo, in a total of 8 clinical data sets (7 HF and one control). The mean identified parameters of the Guccione material law were [Formula: see text] and [Formula: see text] ([Formula: see text], [Formula: see text], [Formula: see text]) for the HF cases and [Formula: see text] and [Formula: see text] ([Formula: see text], [Formula: see text], [Formula: see text]) for the healthy case.
authors.affiliation: Department of Biomedical Engineering, Division of Imaging Sciences and Biomedical Engineering, King's College London, London, UK.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Nasopoulou
authors.affiliation: Cardiovascular Department, Guy's and St. Thomas' NHS Foundation Trust, London, UK.
authors.forename: Anoop
authors.initials: A
authors.lastname: Shetty
authors.affiliation: Department of Biomedical Engineering, Division of Imaging Sciences and Biomedical Engineering, King's College London, London, UK.
authors.forename: Jack
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Biomedical Engineering, Division of Imaging Sciences and Biomedical Engineering, King's College London, London, UK.
authors.forename: David
authors.initials: D
authors.lastname: Nordsletten
authors.affiliation: Cardiovascular Department, Guy's and St. Thomas' NHS Foundation Trust, London, UK.
authors.forename: C Aldo
authors.initials: CA
authors.lastname: Rinaldi
authors.affiliation: Department of Biomedical Engineering, Division of Imaging Sciences and Biomedical Engineering, King's College London, London, UK. pablo.lamata@kcl.ac.uk.
authors.forename: Pablo
authors.initials: P
authors.lastname: Lamata
authors.affiliation: Department of Biomedical Engineering, Division of Imaging Sciences and Biomedical Engineering, King's College London, London, UK. steven.niederer@kcl.ac.uk.
authors.forename: Steven
authors.initials: S
authors.lastname: Niederer
mesh_terms: D000465:Algorithms; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D020342:Finite Element Analysis; D006333:Heart Failure / Q000175:diagnosis / Q000473:pathology; D006352:Heart Ventricles / Q000473:pathology; D006801:Humans; D008954:Models, Biological; D009206:Myocardium / Q000473:pathology*; D015203:Reproducibility of Results
keywords: Myocardium; Parameter estimation; Passive constitutive equations; Patient-specific modelling