Vehicle comfort in oscillatory conditions is a multifaceted phenomenon affected by various factors including road conditions, driving speed, and driving mode, among others. Vibrations experienced during driving, irrespective of their intensity or waveform, significantly impact driving comfort. The Seat-to-Head Frequency Response Function (STHT) represents a complex connection between head movements and vibrations transmitted through the seat and headrest interface. In this study, an artificial neural network model was created to replicate the STHT function based on experimental data collected from twenty healthy male participants.

The main aim of this study was to evaluate the impact of simulated aortic stenosis on velocity and shear stress distribution within the patient-specific heart model by using computational Finite Element (FE) method. The three-dimensional (3D) patient-specific model of heart, including surrounding arterial and vein structures, was reconstructed based on Computed Tomography (CT) scan images in order to obtain the 3D FE mesh. Computational Fluid Dynamics (CFD) analysis was performed, with applied equivalent material characteristics and boundary conditions. Using one patient-specific heart model with clinically confirmed hypertrophic cardiomyopathy, three different cases were simulated: (i) without aortic stenosis, (ii) with 30% of aortic stenosis (mild aortic stenosis), and (iii) with 70% of aortic stenosis (severe aortic stenosis). The initial results of the study (velocity and shear stress distribution) were quantified concerning anatomical patient's structures and simulating different degrees of aortic stenosis to analyse the blood flow patterns, as well as the correlation between shear stress and aortic and left ventricular remodelling. It was found that gradient of shear stress distribution increases with stenosis degree, especially in the ascending aorta which can lead to different aortopathies and endothelial diseases. Due to the difficulties in obtaining such characteristics in vitro or in vivo, the performed computational analysis gave better insight into the biomechanics of the heart and aortic stenosis that is needed to achieve improvements in surgical repair techniques and presurgical planning.

Femoro-popliteal “by-pass” is indicated in the advanced stage of peripheral arterial occlusive disease. Indications for surgical treatment are set on the basis of the clinical picture, “ankle-brachial index” and angiographic findings. By the method of finite element analysis, three-dimensional models can be made on the basis of scanning angiography, on which we can measure different physical quantities and calculate the value of the “ankle-brachial index”. The aim is to show the hemodynamics of arteries by the method of finite element analysis (FEA) based on preoperative and postoperative scan angiography as well as physical quantities that can be measured in this way. In this review, the hemodynamics of femoro-popliteal “by-pass” on the preoperative and postoperative model are presented. The models obtained by FEA show: pressure, shear stress, velocities, and streamlines. Pressure, “ankle-brachial index”, compared with the values measured on the patient, with FEA results preoperatively and postoperatively. Postoperatively, higher values of pressure and “ankle-brachial index” were measured on the patient and on the models. The values shown in the models are significantly correlated with the values measured on the patient. Shear stress and velocity values are significantly reduced on postoperative models. The streamlines show a dominant anterior tibial artery. The values of physical quantities measured on the patient and on the models obtained by the FEA method correlate to a significant extent.

Cardiovascular diseases are the leading cause of death in the world with an incidence of about 30% of total mortality. It is a disease of the blood vessels of the heart that most often occurs due to the process of atherosclerosis. The process of atherosclerosis leads to narrowing of the coronary arteries, and thus to a reduced supply of blood or oxygen to the heart muscle. A fractional flow reserve (FFR) indicates the severity of blood flow blockages in the coronary arteries and allows physicians to identify which specific lesion or lesions are responsible for patient ischemia. In this paper, we studied the values of the FFR, using numerical simulations, on the geometries obtained by reconstructing the angiogram images.

In this report we present basic steps in the 3D reconstruction process of DICOM images and application of our finite element (FE) numerical procedure for loose coupling solid-fluid interaction, to simulate a complete heartbeat cycle for a realistic model of the left heart side. Passive mechanical stresses are calculated using an orthotropic material model based on the experimental investigation of passive material properties of the myocardium, while active stresses are calculated using the Hunter material model. The basic equations for solid mechanics, fluid dynamics, and muscle activation are summarized and model applicability is illustrated on a complex realistic model which includes a left atrium, ventricle, mitral and aortic valves (which serve as fluid domain) coupled with solid wall with realistic fiber directions.

The aim of this work was to evaluate the impact of Bicuspid Aortic Valve (BAV), on displacements, Von Mises stress, shear stress and pressure distribution within the aortic root by using computational Finite Element (FE) method. The three-dimensional (3D) patient-specific geometry of dilated aortic root with BAV was reconstructed based on Computed Tomography (CT) scan images, in order to obtain the 3D finite element mesh. Two types of analyses: i) structural analysis and ii) computational fluid dynamics (CFD) were performed, with applied equivalent material characteristics of BAV and boundary conditions. The initial results for this single case, displacements and Von Mises stress distribution (for structural analysis), as well as shear stress and pressure distribution (for CFD analysis) were quantified concerning anatomical patient's structures. The regions of abnormal stresses on the aortic leaflets and annulus, with asymmetrically open bicuspid valve, were related to the increased pressures and shear stresses and analyzed for this patient-specific case. Due to the difficulties in obtaining such characteristics in vitro or in vivo, the performed computational analysis gave better insight into the biomechanics of the aortic root with BAV that is needed to achieve improvements in surgical repair techniques and presurgical planning.

One of the most common clinical treatments of arterial stenosis is the implantation of an endovascular prosthesis called a stent. Computer modeling represents a useful tool that enables the analysis of the complex behavior of the stent during implantation within a patient specific artery. The numerical model presented in this paper can simulate the expansion of multiple stents, as well as the interaction of the stents with the arterial wall and the behavior of the arterial wall due to the forces caused by the stents. Also, GPU principles are used during implementation, to enable the execution of simulations in real time. In this paper, two stents are deployed within patient-specific artery and the results of this simulation are presented. The numerical models that are originally applied in engineering are used in the presented numerical model, in order to create a useful tool that can be used in bio-medicine. This software can be used for a more detailed prediction of the shape of the stents and artery after implantation and thus this software can improve the techniques used for treatment of the arterial stenosis and pre-operative patient-specific planning.

Atherosclerosis is characterized by dysfunction of endothelium, vasculitis and accumulation of lipid, cholesterol and cell elements inside blood vessel wall. Determination of plaque location and plaque volume for a specific patient is very important for prediction of atherosclerotic disease progression. In this study coupled computer modeling of atherosclerosis progression is analysed. Continuum approach assumed mass transport of LDL through the wall and the simplified inflammatory process coupled with three additional reaction-diffusion equations and lesion growth model in the intima. Discrete modeling used dissipative particle dynamics method which individual blood constituents (e.g., platelets, RBCs, white blood cells) treated as particle interaction. Coupled continuum and discrete model was investigated with real patient baseline and follow up study for right and left coronary arteries.

Benign paroxysmal positional vertigo (BPPV) is the most commonly diagnosed vertigo syndrome that affects 15% of older persons. BPPV is characterized by sudden attacks of dizziness and nausea triggered by changes in head orientation, and primarily afflicts the posterior canal. We are modeling human semicircular canals (SSC) which considers the morphology of the organs and the composition of the biological tissues and their viscoelastic and mechanical properties. The Navier-Stokes equations of balance of linear momentum and the continuity equation with application of Penalty method are used. For fluid-structure interaction problem we use loose coupling methodology with ALE (Arbitrary Lagrangian Eulerian) formulation. The tissue of SSC has nonlinear constitutive laws, leading to materially-nonlinear finite element formulation. The incremental-iterative equation is using for nonlinear wall tissue problem. Our results simulate many dynamics position of head and dynamic fluid parameters, shear stress, effective wall stress of membrane. This could help in better diagnostic and therapy process for BPPV disease.

Human hearing system in general, and particularly the cochlea, is very interesting for investigation. The most important reason for it is hearing loss - a health problem that affects a large part of the world's human population. The highest percentage of people with hearing problems are older people, but the problem also occurs in newborns. Experimental research in this area provides some information about the level of hearing loss. Therefore, it is very useful to have a numerical model of the hearing system that can significantly contribute to the understanding of the origin of the mentioned health problem. Two numerical models are developed to investigate hearing problems: passive 3D cochlea model and 2D cochlea cross-section model. Those models are weakly coupled in order to make an active cochlea model [1].

Atherosclerosis is a medical condition becoming the number one cause of death worldwide. For this reason, any developement that may help physicians in early diagnostic and selection of the most appropriate treatment strategy is of great importance. In this paper we describe three-dimensional computer model of plaque formation and development for human coronary artery. In order to validate proposed model we used ten specific patients from CT study belonging to one of the following groups: (1) de-novo group - patients with new formed plaques, (2) old-lesions group - patients with plaques with progression and (3) control group - patients with plaques without progression. Plaque volume progression is fitted by using two time points for baseline and follow up. Results obtained within this study indicate high potential of this model to be used in clinical practice, thus assisting physicians by providing them valuable information about future disease progression.

The finite element method is increasingly used in the analysis of blood flow through blood vessels. Our work represents the research of blood flow through a cerebral aneurysm. The current work describes the blood flow in 4 patient-specific models of saccular aneurysms. They are located in the region of the anterior and posterior circulation of the circle of Willis. The unstructed grids are constructed from segmented images. Using three-dimensional continuity and momentum equations for unsteady laminar flow and realistic pulsatile flow conditions, we determined the wall shear stress (WSS), pressure and drag forces that acting on the wall of the blood vessel. It is known that wall shear stress (WSS) play an important role in initiation, growth and rupture of cerebral aneurysm, so, determination of the forces that acting in this region helps with understanding aneurysms better.

In this study we investigated the hot caloric test response in the three semicircular canals using coupled fluid flow, natural convection and fluid-structure interaction with the finite element method. We demonstrated that the temperature distribution of the horizontal canal duct is more dominant and a longer period of irrigation time is required in order to stimulate the two other vertical canals. Our results also show shear stress and force distribution from end lymph flow during natural convection. Future studies are necessary for validation of the presented computer model with clinical measurements.

The cochlea is a very interesting part of the body. There are several investigations of experiments on the real cochlea and mathematical models. The cochlea works on the basis of a vibrating system. SIFEM project focuses on the development the multi-scale modelling of the inner-ear with regard to the sensorineural hearing loss. In this study we focused on the finite element model of the cochlea. The first approximation is straight box model where both domain basilar membrane and surrounding fluid are modeled. Fluid-structure interaction problem was implemented. The basilar membrane was modeled as structural plate with 3D brick finite element and fluid domain around the basilar membrane was modeled as full 3D Navier-Stokes equations. ALE formulation was employed for fluid domain and mesh moving algorithm for motion of the membrane and fluid mesh. The results for different frequencies for 3D box and spiral model are presented. It can be observed that viscous fluid allow a sharper response of the membrane, because the viscous fluid would quickly damp out the vibratory motion.