Biomechanics
Adel Maghsoudpour; Ali Dorostghol; Ali Ghaffari; Mansour NikkhahBahrami
Abstract
To quickly detect sudden Cardiac Death (SCD), it's decisive to gather suitable information and enhance the accuracy of the diagnosis algorithms. Consequently, In the present study the heart rate variability (HRV) signal of subjects who experienced sudden cardiac death (SCD) was studied. We looked at ...
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To quickly detect sudden Cardiac Death (SCD), it's decisive to gather suitable information and enhance the accuracy of the diagnosis algorithms. Consequently, In the present study the heart rate variability (HRV) signal of subjects who experienced sudden cardiac death (SCD) was studied. We looked at people's heart signals for one hour before something happened to see if there were any noticeable changes. The patients' HRV signals are segregated into 5-minute parts in the suggested approach. Each section is divided into four shorter signals. Thereupon, The energy and instant amplitude of each sub-signal are examined. The information flows between signal strengths and measuring the complexity of energy sub-signals would be checked. A significant change from its former section is identified. A support vector machine (SVM) classifier benefits from detecting individuals exposed to SCD by considering significant changes as indicators of the SCD process. It can anticipate SCD 15 minutes before it happens. Not restricted to any special subclass of cardiac diseases, this technique has priority. To evaluate the algorithm's specificity, it has been used not only with patients having SCD but also with individuals who are healthy, as well as those with coronary artery disease (CAD) and congestive heart failure (CHF), analyzing their HRV signals. The specificity values for normal, CHF, and CAD patients are 100%, 93.3%, and 95.6%, respectively, in the results.
Biomechanics
Puria Talebi Barmi; Bahman Vahidi
Abstract
Arterial embolism is one of the major causes of brain infarction. Investigating the hemodynamic factors of this phenomenon can help us to get a better understanding of this complication. The carotid artery is one of the primary tracts that emboli can go toward the brain through it. In this study, we ...
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Arterial embolism is one of the major causes of brain infarction. Investigating the hemodynamic factors of this phenomenon can help us to get a better understanding of this complication. The carotid artery is one of the primary tracts that emboli can go toward the brain through it. In this study, we used a 3D model of the carotid bifurcation, and two geometries, elliptical and spherical, were considered for the clots. Hyperelastic and visco-hyperelastic models were used for the mechanical properties of clots. The governing equations of the fluid are Navier-Stokes and continuity equations and have been solved in an Arbitrary Lagrangian-Eulerian (ALE) formulation through the fluid-structure interaction method. The hemodynamic parameters of fluid and shear stress on the wall of the carotid artery were calculated. Besides, by using ADINA software, the effective stress (Von Mises stress) of the clots and the shear stress created on them were evaluated as well. Results revealed that the elliptical clot has more effects on the hemodynamic parameters of the fluid, and the mechanical property of clots has significant effects on the amount of stress created on the clots. Also, clot fracture will not occur due to the point that the maximum effective stress in this study was 1819 Pa but the creation of crack in clots is more probable, and this probability is more for the elliptical clot.
Biomechanics
Diana Martins; Rui Couto; Elza M M Fonseca; Ana Rita Carreiras
Abstract
This work presents a numerical approach to predict the influence of material stiffness in a dental implant using different thread profile shapes, always with a constant number of threads, thread width and thread pitch. Dental implant affects bone tissue, in response to various mechanical stimuli where ...
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This work presents a numerical approach to predict the influence of material stiffness in a dental implant using different thread profile shapes, always with a constant number of threads, thread width and thread pitch. Dental implant affects bone tissue, in response to various mechanical stimuli where the biomechanical behavior plays a significant role in the study of stress and strain calculation. In this work, four different thread profile shapes were considered (Model1 - Plateau typeA, Model2 - Plateau typeB, Model3 - Triangular, Model4 - Rectangular) with two different inner diameters equal to 4 and 6 mm, using three different implant materials (titanium, an iso-elastic titanium and zirconium alloys). Two dimensional computational axisymmetric models of a bone-implant were constructed using the finite element method. This study presents the numerical results about the mechanical stimuli on dental implant according to the chosen material and profile shape. The main contribution of this work is giving additional information about the stability and implant loosening with the application on surgical techniques in dental science.
Biomechanics
Safoora Karimi; Mitra Dadvar; Bahram Dabir
Abstract
One of the critical limitations of studies on cardiovascular blood flow simulation is to determine outlet boundary conditions accurately. In the present study, for the first time, pore network model is proposed as a useful technique to take into account interaction between blood flow and other body organs. ...
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One of the critical limitations of studies on cardiovascular blood flow simulation is to determine outlet boundary conditions accurately. In the present study, for the first time, pore network model is proposed as a useful technique to take into account interaction between blood flow and other body organs. Thus body organs are simulated by pore network model. Thanks to the method, pressure distribution among the porous medium of organ is determined and consequently the required boundary conditions are obtained for the simulation of arterial blood flow. The comparison between permeability resulted from developed model and experimental results shows that the difference is about 3% for the assumption of non-Newtonian blood flow through organ. This indicates the pore network model can accurately simulate velocity and pressure in the organs. Afterwards, a 3D patient-specific abdominal aorta was simulated under the proposed outlet boundary condition. The maximum deviation of predicted pressure from physiological data is 11.14% near the systole instant. Generally, the predicted pressure and velocity profiles are evident that the model can adequately simulate the blood flow through the arteries which feed main organs.
Biomechanics
Faramarz Talati; AliAsghar Asghar Taheri
Abstract
Hyperthermia is one of the first applications of nanotechnology in medicine by using micro/nano magnetic particles that act based on the heat of ferric oxide nanoparticles or quantum dots in an external alternating magnetic field. In this study, a two-dimensional model of body and tumor tissues embedded ...
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Hyperthermia is one of the first applications of nanotechnology in medicine by using micro/nano magnetic particles that act based on the heat of ferric oxide nanoparticles or quantum dots in an external alternating magnetic field. In this study, a two-dimensional model of body and tumor tissues embedded is considered. Initially, the temperature distribution is obtained with respect to tumor properties and without the presence of an electromagnetic field. Then, the effect of the electromagnetic field on the temperature distribution is studied. The results are compared with those of other papers. The results indicate that the use of the electromagnetic field causes a significant rise in the tumor temperature; however, the risk of damage to the healthy tissues surrounding the cancerous tissue seems to be high. Then, the micro/nanoparticles are injected into the tumor tissue to focus energy on cancerous tissue and maximally transfer the heat onto the tissue. The temperature distribution in the state is compared with the case with no nanoparticles and other numerical works. The results demonstrate that with the injection of nanoparticles into the tumor, the maximum temperature location is transferred to the center of the tumor and also increases to 6°C. After determining the temperature distribution in the presence of nanoparticles, the effects of different variables of the problem are studied. According to the obtained results, the increase in the concentration and radius of nanoparticles have a positive effect on the temperature distribution in the tissue; on the other hand, the increase in the frequency and size of the electrodes have a negative effect. The relevant equations are solved numerically using the finite difference method.
Biomechanics
Mehdi Jahangiri; Mohsen Saghafian; Mahmood Reza Sadeghi
Abstract
A numerical study of hemodynamic parameters of pulsatile blood flow is presented in a stenotic artery with A numerical study of hemodynamic parameters of pulsatile blood flow is presented in a stenotic artery with non-Newtonian models using ADINA. Blood flow was considered laminar, and the arterial ...
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A numerical study of hemodynamic parameters of pulsatile blood flow is presented in a stenotic artery with A numerical study of hemodynamic parameters of pulsatile blood flow is presented in a stenotic artery with non-Newtonian models using ADINA. Blood flow was considered laminar, and the arterial wall was considered rigid. Studied stenosis severities were 30, 50, and 70% of the cross-sectional area of the artery. Six non-Newtonian models were used to model the non-Newtonian behavior of blood, and their results were compared with the Newtonian model. The results showed that in Power-law and Walburn-Schneck models, unlike other models, shear stress values before and after the stenosis were smaller than Newtonian models. Also, in maximum flow rate, the Carreua, generalized Power-law, Casson, and Carreua-Yasuda models showed a reduction in global importance factor of non-Newtonian behavior, and subsequently, the results approached Newtonian model. In minimum flow rate, the global importance factor of Newtonian behavior increased, which highlighted the importance of Newtonian model. In minimum flow rate, Carreua-Yasuda model was more sensitive to the non-Newtonian behavior of blood compared to Carreua, Casson, and Power-law models. Also, in that time period, Walburn-Schneck was less sensitive to the non-Newtonian behavior of blood. On the other hand, this model did not show sensitivity when the flow rate was at its peak. Power-law model overestimated the global importance factor values. Therefore, Power-law model was not suitable, because it showed extreme sensitivity to dimension. Walburn-Schneck model was not suitable too because it lacked sensitivity.
