Predictive Models with Patient Specific Material Properties for the Biomechanical Behavior of Ascending Thoracic Aneurysms

Abstract

The aim of this study is to identify the patient-specific material properties of ascending thoracic aortic aneurysms (ATAA) using preoperative dynamic gated computed tomography (CT) scans. The identification is based on the simultaneous minimization of two cost functions, which define the difference between model predictions and gated CT measurements of the aneurysm volume at respectively systole and cardiac mid-cycle. The method is applied on five patients who underwent surgical repair of their ATAA at the University Hospital Center of St. Etienne. For these patients, the aneurysms were collected and tested mechanically using an in vitro bench. For the sake of validation, the mechanical properties found using the in vivo approach and the in vitro bench were compared. We eventually performed finite-element stress analyses based on each set of material properties. Rupture risk indexes were estimated and compared, showing promising results of the patient-specific identification method based on gated CT.

From Finite Element Meshes to Clouds of Points: A Review of Methods for Generation of Computational Biomechanics Models for Patient-Specific Applications

“…99,101,106,116 However, this review indicates that despite many years of research and development in academia and software industry, generation of patient-specific FE meshes using medical images as a source of information about organ geometry still requires input from an experienced analyst with expert knowledge of image processing and mesh generation. As discussed in sections ''Isogeometric Analysis and High Order Elements'' and ''Beyond Finite Element Meshes: Meshless Methods and Models as Clouds of Points'' methods combined with tissue classification eliminate key disadvantages associated with FE method's reliance on low-order polynomial interpolation and pave a way for automating computational grid generation.…”

Computational predictions of damage propagation preceding dissection of ascending thoracic aortic aneurysms

“…The lumen of the aneurysm is clearly visible in the DICOM file, but the aneurysm surface is not automatically detectable. The digital caliper is used to homogeneously measure the thickness of the excised aneurysm in vitro . A 2.5‐mm average wall thickness is measured on the supplied sample corresponding to the zero pressure configuration.…”

Biaxial rupture properties of ascending thoracic aortic aneurysms

“…In this study we used the Laplace law to estimate in vivo physiological conditions (in vivo stress, in vivo tangent modulus) in the bulge region of the aneurysms. Using dynamic gated CT scan and finite-element analyses, this estimation could be refined with a simulation of in vivo physiological conditions as we started to do in preliminary studies [50].…”