Abstract

The objective of this work is to study the influence of different fluids of the tympanic cavity into the biomechanical behavior of the middle ear. The 3 D computer model of the tympanic ossicular chain was built using images from computed tomography (CT). After construction of the tympanic ossicular chain model, it was adapted the simulation by placing the passage to the external auditory canal and to the tympanic cavity.

The discretization of the model was made using the finite element method based on ABAQUS software. The mechanical properties were extracted from previous works. The umbo and the stapes footplate displacements, for a sound pressure level of 105 dB applied in tympanic membrane were obtained, comparing the tympanic ossicular chain and the different levels of external and internal pressure in the middle ear (liquid and air). The results demonstrate that the biomechanical behavior of the middle ear is different for different levels of pressure tested in this model. When using liquid, displacements are of lower amplitude when compared with the results obtained with air.

 

Abstract

The main purpose of this publication is the proper determination of the fractional order at the Zener viscoelastic models and the analysis of the implications derived from the accuracy in obtaining this. The procedure is performed using the numerical method of Levenberg-Marquardt from values reported in the literature. The parameters used are obtained from an artery segment using a stress relaxation test. After determining the fractional order is proceeded to find the model solution using, the function of Mittag-Leffler with two parameters and the convolution operation in order to compare the behavior of the fractional model vs the integer order and identify their key differences. The displacements present on the artery are obtained, under the stimulus of a normal blood pulse and two dissimilar, simulating the effect in blood flow caused by an arrhythmia and by mechanical ventilation process. Finally the dynamic response from the pulses is analyzed using the convolution operation and Gauss Kronrod numeric method, where the solutions accuracy obtained by the fractional model is observed, an compared with the integer order model.

Abstract

Computational modeling of the cardiovascular system plays an increasingly important role in biomedicine, as it allows for non-invasive investigations of the status-quo and studying the influence of different treatment options available. The goal is to incorporate patient-specific datasets to obtain socalled digital twins to increase relevance of virtual surgery and support clinical decision making. In this context, aortic dissection is particularly challenging, since the overall system behavior strongly depends on the interplay between tissue deformation and blood flow, giving rise to a fully coupled fluid-structure interaction problem. To account for the complex physics, several additional modeling aspects such as prestress, advanced constitutive models respecting fibre orientation and suitable boundary conditions for the fluid and solid phases have to be considered. Within this study, these special techniques are applied to a patient-specific dataset, for which first results are presented highlighting their relevance.