Fluid-Structure Interaction in Biological Media / FSI
Bahman Vahidi; Nasser Fatouraee
Volume 2, Issue 4 , June 2008, , Pages 285-296
Abstract
Arterial embolism is one of the major killers of the people who have heart diseases. In cerebral arteries, the danger of embolism is that the ruptured particles are carried into the brain, provoking neurological symptoms or a stroke. In this research, for the first time, we have presented a numerical ...
Read More
Arterial embolism is one of the major killers of the people who have heart diseases. In cerebral arteries, the danger of embolism is that the ruptured particles are carried into the brain, provoking neurological symptoms or a stroke. In this research, for the first time, we have presented a numerical model to study the complete blockage of the human common carotid artery resulted from the physical motion of a blood clot bulk with spherical geometry in it. In the numerical model, a transient flow was assumed in an axisymmetric finite length tube. The incompressible Navier-Stokes equations were used as the governing equations for the fluid and a linear elastic model was utilized for the blood clot bulk. In order to model the contact conditions between the blood clot and arterial wall, an axisymmetric rigid contact model was used. The arbitrary Lagrangian-Eulerian formulation (ALE) was applied to analyze the solid large displacements inside fluid flow. The results indicated that during contact between stenosis and the clot, separation and reattachment regions were occurred on the stenosis extensively which are susceptible to thrombosis onset and growth. By abruption of the clot from the arterial wall during its passage through the stenosis, an extensive recirculation zone occurred downstream of the stenosis and beneath the moving clot bulk. Analysis of the clot motion and deformation have showed that when the clot passed the stenosis completely, the areas near the clot peak had a large tendency to expand which indicated the propensity of these areas to disperse.
Fluid-Structure Interaction in Biological Media / FSI
Bahman Vahidi; Nasser Fatouraee; Ali Imanparast
Volume 2, Issue 1 , June 2008, , Pages 29-37
Abstract
Ureter reflux is one of the prevalent factors that causes pyelonefrit and sistit syndromes. Dilatation of ureter, renal pelves and calyx are detectable with reflux. In this paper, in order to analyze this phenomenon, an axisymmetric model was introduced. We utilized a rigid body, which is in contact ...
Read More
Ureter reflux is one of the prevalent factors that causes pyelonefrit and sistit syndromes. Dilatation of ureter, renal pelves and calyx are detectable with reflux. In this paper, in order to analyze this phenomenon, an axisymmetric model was introduced. We utilized a rigid body, which is in contact with the outer ureter wall to model ureter contraction. The Navier-Stokes equations are solved for the fluid and a linear elastic model is used for ureter wall structure. The finite element equations for both the structure and the fluid were solved by the Newton-Raphson iterative method. The effect of ureter wall elasticity, pressure difference between the ureter inlet and outlet and the effect of the average velocity of peristaltic wave along the length of the ureter on the ureter outlet flow rate were analyzed. Moreover, the effect of the number of contraction waves on the pressure and flow relations in the ureter was analyzed. Increase in the number of contraction waves reduced the flow passing through the ureter. The results of investigating about the contraction wave velocity variations indicated that if average velocity the contraction wave was lower than a limited magnitude, its existence did not have any considerable effect on the ureter outlet flow rate. Finally improper function of urinary tubes junctions results in the passage of a part of back flow even in the case of low velocity beginning of the contraction wave.
Biomedical Image Processing / Medical Image Processing
Mehdi Marsousi; Javad Alirezaie; Armen Kocharian
Volume 2, Issue 3 , June 2008, , Pages 203-214
Abstract
In this paper, a new method for boundary detection of left ventricle in echocardiography images is proposed. We have modified B-Spline Snake algorithm to achieve much faster convergence and more reliability toward noises in echocardiography images. A novel approach for inserting new node points during ...
Read More
In this paper, a new method for boundary detection of left ventricle in echocardiography images is proposed. We have modified B-Spline Snake algorithm to achieve much faster convergence and more reliability toward noises in echocardiography images. A novel approach for inserting new node points during iterations is applied to maintain a maximum distance between two adjacent nodes. This strategy is applied in order to simultaneously increase the smoothness of the contour and optimize the computational time. A multi-resolution strategy is also adapted to provide further robustness toward noises in the images. In addition, morphological operators are utilized to specify the initial contour automatically within the left ventricle chamber in echocardiography images. The parameters of node points are determined during each transition from coarser to finer resolution according to the average intensity of the sample points on the contour near each node point. The volumes of left ventricle in the end of both systolic and diastolic frames are calculated using modified Simpson method. The ejection fraction ratio is also calculated; this is frequently used by specialist before each surgery. Moreover, a method is introduced to draw the 3D model of left ventricle with the aid of basis function of B-Spline. The proposed method is assessed by comparison between the obtained results and clinical observations by expert radiologists and demonstrates a high accuracy.
Biological Computer Modeling / Biological Computer Simulation
Pejman Ghassemi; Mohammad Hossein Miranbaygi
Volume 2, Issue 4 , June 2008, , Pages 305-315
Abstract
In this research we present a new method to evaluate changes in size and refractive index of Titanium dioxide (TiO2) nanoparticles which are the main component of anti-UV creams. The main objective of this research is assessing the impact of changing in size and refractive index of TiO2 on the polarization ...
Read More
In this research we present a new method to evaluate changes in size and refractive index of Titanium dioxide (TiO2) nanoparticles which are the main component of anti-UV creams. The main objective of this research is assessing the impact of changing in size and refractive index of TiO2 on the polarization state of backscattered light. The proposed technique is based on modeling the propagated polarized laser beam inside a phantom and evaluating the change in the polarization of backscattered light. The phantom is simulated by software to have the polarization properties of anti-UV creams. As scattering particles (TiO2) in these creams configure polarization properties, then through modeling we have simulated the phantom with matrix of resin epoxy that has unit refractive index including Titanium dioxide nanoparticles. It will be shown that size parameter and relative refractive index of these particles influence cream's properties like purity, quality, coating power and degree of filtration and directly affect its polarization properties. The measurement technique which is presented here is based on scattering polarimetry. To assess the scattering phenomenon, the polarization state of incident and backscattered light is analyzed by simulating a laboratory polarimeter. Then polarization information of the simulated phantom is extracted as Mueller matrix and degree of polarization index. All modeling and simulations are performed in MATLAB 2006 and the results are presented towards the end part of the paper. The main outcome of this research is the ability of extracting and the recognition of those elements of the Mueller matrix which are very sensitive to changes in size parameter and relative refractive index of TiO2. That will define the main markers for quality assessment of anti-UV creams.
Fluid-Structure Interaction in Biological Media / FSI
Hamed Avari; Farzan Ghalichi; Majid Ahmadlouy Darab
Volume 2, Issue 1 , June 2008, , Pages 39-46
Abstract
Adjusting the rhythm of breath is one of the important parameters that a successful athlete must consider. In this paper, the relationship between man's activity and respiration rhythm is studied. A numerical simulation is carried out on a 2D axi-symmetric model using computational fluid dynamics (CFD) ...
Read More
Adjusting the rhythm of breath is one of the important parameters that a successful athlete must consider. In this paper, the relationship between man's activity and respiration rhythm is studied. A numerical simulation is carried out on a 2D axi-symmetric model using computational fluid dynamics (CFD) method. The model considers the oxygen uptake in the pulmonary capillaries in alveolar microcirculation system. The geometry consists of three main parts: a stationary capillary membrane, a moving plasma region and four semi-circular-shaped RBCs. Results show an inverse relationship between saturation time of RBCs and respiration rhythm. Using an inversion factor, a relationship is presented to assess the proper respiration rhythm for different exercise states.
Biomedical Image Processing / Medical Image Processing
Saeed Kermani; Hamid Abrishami Moghaddam; Mohammad Hasan Moradi
Volume 2, Issue 3 , June 2008, , Pages 215-231
Abstract
This paper presents a new method for quantification analysis of left ventricular performance from the sequences of cardiac magnetic resonance imaging using the three-dimension active mesh model (3DAMM). AMM is composed of topology and geometry of L V and associated elastic material properties. The ...
Read More
This paper presents a new method for quantification analysis of left ventricular performance from the sequences of cardiac magnetic resonance imaging using the three-dimension active mesh model (3DAMM). AMM is composed of topology and geometry of L V and associated elastic material properties. The LV deformation is estimated by fitting the model to the initial sparse displacements which is measured by a new establishing point correspondence procedure. To improve the model, a new shape-based interpolation algorithm was proposed for reconstruction of the intermediate slices. The proposed approach is capable of estimating the displacement field for every desired point of the myocardial wall. Then it leads to measure dense motion field and the local dynamic parameters such as Lagrangian strain. To evaluate the performance of the proposed algorithm, eight image sequences (six real and two synthetic sets) were used and the findings were compared with those reported by other researchers. For synthetic image sequence sets, the mean square error between the length of motion field estimated by the Algorithm and the analytical values was less than 0.5 mm. The results showed that the strain measurements of the normal cases were generally consistent with the previously published values. The results of analysis on a patient data set were also consistent with his clinical evidence. In conclusion, the results demonstrated the superiority of the novel strategy with respect to our formerly presented algorithm. Furthermore, the results are comparable to the current state-of-the-art methods.
Tissue Engineering
Mohammad Haghpanahi; Mohammad Nikkhoo; Habibollah Peirovi
Volume 2, Issue 1 , June 2008, , Pages 47-56
Abstract
According to mechanobilogical studies as an infrastructure for tissue engineering researches, this paper presents a triphasic finite element modeling of intervertebral discs such a hydrated porous soft tissue. First, the governmental equations were derived on the basis of the laws of continuum mechanics. ...
Read More
According to mechanobilogical studies as an infrastructure for tissue engineering researches, this paper presents a triphasic finite element modeling of intervertebral discs such a hydrated porous soft tissue. First, the governmental equations were derived on the basis of the laws of continuum mechanics. Then the standard Galerkin weighted residual method was used to form the finite element model. The implicit time integration schemes were applied to solve the nonlinear equations. The formulation accuracy and convergence for one dimensional case were examined with Simon's and Sun's analytical solutions and also Drost's experimental Data. It was shown that the mathematical model is in excellent agreement and has the capability to simulate the intervertebral disc response under different types of mechanical and electrochemical loading conditions. Finally, to have a short review of the capability of the model, a homogenous two dimensional version of the model was applied to simulate the response of a simple sagittal slice of the intervertebral disc.
Bioheat Transfer
Farzan Ghalichi; Sohrab Behnia
Volume 1, Issue 1 , June 2007, , Pages 1-8
Abstract
The methods of focusing ultrasonic waves in order to apply hyperthermia cancer therapy have studied and a transducer capable of focusing waves on cancerous tissues with the aid of its piezoelectricelements has introduced. The amount of absorbed energy was computed by solving numerically the acoustic ...
Read More
The methods of focusing ultrasonic waves in order to apply hyperthermia cancer therapy have studied and a transducer capable of focusing waves on cancerous tissues with the aid of its piezoelectricelements has introduced. The amount of absorbed energy was computed by solving numerically the acoustic pressure equation using Rayleigh-Summerfield Integral, with the intention to determine the optimum spatial array of piezoelectric elements for energy concentration. In order to control the treatment procedure, the numerical solution of Bio-heat Transfer Equation (BHTE), along with the finite-element simulation of thermal energy distribution in a cervix cancerous tissue is considered.
Biomedical Image Processing / Medical Image Processing
Nader Riahi Alam; Reza Aghaeizade Zoroofi; Masoume Giti; Arian Deldari; Alireza Ahmadian
Volume 1, Issue 3 , June 2007, , Pages 157-165
Abstract
In this study, the need of a CAD system and its capabilities has been investigated and then a sample program for a mammographic CAD system proper to Iranian tropical patients was designed. In the first step, the analog mammographic images were digitized by 56 and 112 mm spatial resolution and then were ...
Read More
In this study, the need of a CAD system and its capabilities has been investigated and then a sample program for a mammographic CAD system proper to Iranian tropical patients was designed. In the first step, the analog mammographic images were digitized by 56 and 112 mm spatial resolution and then were processed by the designed sample program. Analysis and technical details for designing and implementing the program included for following steps: The capability of the program image displayer consisting of viewing four mammographic images from four breast views (RCC, RMLO, LCC, LMLO) in one window, determining breast region by background removing and other conventional preprocessing application tools; Software processing tools including theresholding, histogram, ROI determination; Patient information fields such as clinical information, conventional reporting section as used in radiological department in Iran; Computer-aided diagnostic section including proper diagnostic processing algorithm to automatic detection of breast abnormality. For instance the application of wavelet and fuzzy logic for detecting malignant clusters of microcalcification. The introduced mammographic CAD system can provide the collection, organizing and the availability of the patient local information. Therefore by using the prepared database the evaluation of the sensitivity and specifity of the detecting algorithm for comparison of different research methods would be possible.
Cardiovascular Biomechanics
Nasser Fatouraee; Mojtaba Gholipour Samarghaveh
Volume 1, Issue 1 , June 2007, , Pages 9-17
Abstract
Blood is one of the vital fluids of the human body. Measurement of its viscosity and other properties is very important in detecting and understanding different cardiovascular diseases. In this study, the blood flow in a concentric cylinder viscometer was simulated numerically. The blood flow patterns ...
Read More
Blood is one of the vital fluids of the human body. Measurement of its viscosity and other properties is very important in detecting and understanding different cardiovascular diseases. In this study, the blood flow in a concentric cylinder viscometer was simulated numerically. The blood flow patterns were analyzed by applying different rotational speed of inner cylinder. Creation of a Couette flow, end effects and suitable rotational speed limit were analyzed. The amount of the torque applied to the inner cylinder which prevents the generation of the Taylor vortices was also predicted. From the obtained results, one can conclude that these vortices were not as important as the end effects were. In order to keep the blood sample temperature within a constant and acceptable range a thermal bath was used. Heat removal rate with different inflow rates of coolant was also predicted numerically.
Cardiovascular Biomechanics
Mehdi Maerefat; Asghar Khoushkar Shalmani; Manije Mokhtari Dizaji
Volume 1, Issue 2 , June 2007, , Pages 95-104
Abstract
Modeling of blood flow and arterial wall in large arteries such as carotid artery, using ultrasonic measurements, allows non-invasive evaluation of clinically interesting homodynamic variables. In this study, a nonlinear mathematical model for the pulsatile arterial flow is proposed using the approximation ...
Read More
Modeling of blood flow and arterial wall in large arteries such as carotid artery, using ultrasonic measurements, allows non-invasive evaluation of clinically interesting homodynamic variables. In this study, a nonlinear mathematical model for the pulsatile arterial flow is proposed using the approximation of “local flow” theory. The blood velocity profile, the pressure gradient and the elastic modulus can be calculated using the model by measuring instantaneous radius and center-line blood velocity. An original mathematical model of pressure gradient in a tapered and elastic tube, using center-line blood velocity, is presented. A Newtonian incompressible Navier-Stokes solver coupled with elastic or visco-elastic arterial wall model is developed to solve the equations of model. The results of modeling and simulation indicate that the approach can estimate the elastic modulus of arterial wall from ultrasonic data. There is a good agreement between the computed arterial wall elasticity and the measured one. The method presented is relatively simple to implement clinically and can be taken as a new diagnostic tool for detecting local vascular change.
Biomechanics of Bone / Bone Biomechanics
Ahmad Raeisi Najafi; Ahmad Reza Arshi; Mohammad Reza Eslami; Shahriar Fariborz; Mansour Moeinzadeh
Volume 1, Issue 3 , June 2007, , Pages 177-188
Abstract
A two dimensional finite element model for the human Haversian cortical bone is represented. The interstitial bone tissue, the osteons and the cement line were modeled as the matrix, the fibers and the interface, respectively. This was due to similarities between fiber-ceramic composite materials and ...
Read More
A two dimensional finite element model for the human Haversian cortical bone is represented. The interstitial bone tissue, the osteons and the cement line were modeled as the matrix, the fibers and the interface, respectively. This was due to similarities between fiber-ceramic composite materials and the human Haversian cortical bone. The stress intensity factor in the microcrack tips vicinity was computed using the linear elastic fracture mechanics theory and assuming a plane strain condition. It was therefore possible to study the effect of microstructure and mechanical properties of Haversian cortical bone on microcrack propagation trajectory. The results indicated that this effect was limited to the vicinity of the osteon. If both osteon and cement line were assumed to be softer than the interstitial tissue, the stress intensity factor was increased when the crack distance to the osteon reduced. The stress intensity factor decreased if both osteon and cement line were assumed to be stiffer than the interstitial tissue. The resulting simulation indicated that the effect of existence of osteon on the stress intensity factor was no significance, if both the interstitial tissue and cement line were assumed either stiffer or softer than the osteon. Microcrack trajectory was observed to deviate from the osteon under tensile loading; indicating an independence from the mechanical properties of various tissues. In fact, the microcrack adopts a trajectory between the osteons, thereby increasing the necessary absorbed energy for fracture. This results in an increase in the human Haversian cortical bone toughness. The result of this finite element modeling has been confirmed by through evaluation and comparison made with experimental results.
Tissue Engineering
Farhad Farmanzad; Siamak Najarian; Mohammad Reza Eslami; Amir Saeed Seddighi
Volume 1, Issue 4 , June 2007, , Pages 281-288
Abstract
Two different types of computer modeling, i.e., the elastic and hyperelastic plane strain models were employed and compared with each other. Using finite element analysis, we determined a suitable model for describing the biomechanical behavior of the brain, especially the deformation and displacement ...
Read More
Two different types of computer modeling, i.e., the elastic and hyperelastic plane strain models were employed and compared with each other. Using finite element analysis, we determined a suitable model for describing the biomechanical behavior of the brain, especially the deformation and displacement of the brain ventricles. The CT-Scan of an epidural hematoma patient was modeled using both approaches. Then, by varying the mechanical parameters of the tissue (i.e., C10, C01, E, and v) and the internal ventricular pressure, the displacement rate of the corresponding points in the ventricles was simulated. Finally, the results of the simulation were compared with those of the actual ventricles, and then, the data set with the least amount of error was identified. For various types of loadings and with different pressure gradients, the results of the simulation show that if the effect of an increase in the internal pressure of the ventricles is neglected, it will lead to unrealistic results. Particularly, in unidirectional strain loading with a pressure gradient of zero (AP= 0), the walls of the ventricle adjacent to the hematoma will collapse completely. The best results were obtained for the elastic model where ΔP = 9.4 mmHg (1.25 kPa) and for the hyperelastic model where ΔP = 7.5 mmHg (1.00 kPa). These findings are consistent with the clinical conditions of the patient. In the plane strain biomechanical modeling, for unidirectional strain loading (conditions which are similar to the application of navigation systems in surgeries), neglecting the geometry and the variation of the internal pressure of the ventricles will not lead to acceptable results. Taking into account the abovementioned parameters in describing the mechanical behavior of the brain (for epidural hematoma lesions), the elastic model (88.7% average relative accuracy) brings about better results compared with those of the hyperclastic model (86.9% average relative accuracy).
Biomedical Image Processing / Medical Image Processing
Seyed Mohammad Shams; Gholam Ali Hossein-Zadeh; Mohammad Mehdi Karimi
Volume 1, Issue 1 , June 2007, , Pages 29-37
Abstract
In order to analyze the functional Magnetic Resonance Imaging (fMRI) data, the parameters of a nonlinear model for the hemodynamic system, so called Balloon model, were characterized and estimated. Two different approaches were applied to estimate these parameters. In the first step of both approaches, ...
Read More
In order to analyze the functional Magnetic Resonance Imaging (fMRI) data, the parameters of a nonlinear model for the hemodynamic system, so called Balloon model, were characterized and estimated. Two different approaches were applied to estimate these parameters. In the first step of both approaches, the voxels which show neural activity were identified. Then, the parameters of the balloon model for these active voxels were estimated by both steepest descent algorithm, and through genetic algorithm. Proposed approaches were applied on experimental fMRI data and the parameters of nonlinear Balloon model were estimated for different brain voxels. Accuracy of these characterizations was assessed via comparing the measured time series at each voxel with the modeled time series. Also, it was shown that the results of the parameter-estimation are consistent with the results obtained from system characterization via Volterra Kernels (which were reported in previous studies). It was concluded that the suggested approaches could accomplish a nonlinear system characterization through numerical methods, whereas they avoid theoretical complexities and they have acceptable speed (especially steepest descent algorithm).
Fluid-Structure Interaction in Biological Media / FSI
Farzan Ghalichi; Majid Ahmadlouy Darab; Ahmad Ramezani Saadatabadi
Volume 1, Issue 2 , June 2007, , Pages 111-117
Abstract
In order to compare the aorta-coronary and coronary-coronary bypasses blood flow fields in the Endto-Side Anastomosis, we carried out numerical simulation of three dimensional pulsatile blood flow for 50% stenosis by using FLUENT 5.2.3 software. In this study, the blood was assumed to be as the Newtonian, ...
Read More
In order to compare the aorta-coronary and coronary-coronary bypasses blood flow fields in the Endto-Side Anastomosis, we carried out numerical simulation of three dimensional pulsatile blood flow for 50% stenosis by using FLUENT 5.2.3 software. In this study, the blood was assumed to be as the Newtonian, incompressible and homogeneous fluid. The arterial wall was also considered to be rigid. Non-existence of the secondary flows in the coronary-coronary bypass blood flow fields for various degrees of bypass grafting angles against the aorta-coronary-coronary bypass, return of total blood flow toward upstream in the coronary-coronary bypass three times over a heart cycle, high temporary oscillation in the wall shear stress magnitudes for the aorta-coronary bypass and low wall shear stress magnitudes for the coronary-coronary bypass were of the important results.
Biomechanics of Bone / Bone Biomechanics
Mohammad Haghpanahi; Mehdi Pourdanial
Volume 1, Issue 4 , June 2007, , Pages 289-299
Abstract
A 3D anatomically accurate finite element model of the human first cervical vertebra (atlas), including cortical and cancellous bones, was developed in ANSYS 9 based on CT-scan images. The main objective was to investigate the effect of cancellous bone on the value and distribution of maximum and average ...
Read More
A 3D anatomically accurate finite element model of the human first cervical vertebra (atlas), including cortical and cancellous bones, was developed in ANSYS 9 based on CT-scan images. The main objective was to investigate the effect of cancellous bone on the value and distribution of maximum and average Von Mises stress in Atlas. The results showed that the material property of cancellous bone has no significant effect on the location of maximum stress and the pattern of average stress distribution in anterior arch, the junction of posterior arch and lateral mass and the groove of the posterior arch. Although the presence of cancellous bone in the model yielded higher values for the maximum and average stresses. The boundary condition had a considerable effect on this increase. Altering the material property of cancellous bone under neutral and hyperextension loading configurations, affected the average stress only in cancellous bone in the lateral mass, but change in the material property of cortical bone resulted in average stress change both in the cortical and cancellous bones, and in the lateral displacement of the lateral mass as well. The interconnected effects of changing the material properties of these two bone tissues were also studied.
Biomechanics of Bone / Bone Biomechanics
Mohammad Haghpanahi; Ali Gorginzadeh; Saba Sohrabi
Volume 1, Issue 2 , June 2007, , Pages 131-136
Abstract
Considering the life threatening consequences of the cervical spine injuries, the study of its biomechanical behavior has become important. The most common axis (second cervical vertebra) injury is called odontoid fracture, the majority of which is type II or dens fracture. In this study, an exact 3D ...
Read More
Considering the life threatening consequences of the cervical spine injuries, the study of its biomechanical behavior has become important. The most common axis (second cervical vertebra) injury is called odontoid fracture, the majority of which is type II or dens fracture. In this study, an exact 3D finite element model of axis was developed and analyzed. To evaluate the stress distributions in the odontoid process during type II injuries, pressure loads were applied on the dens at locations where it is likely to come into contact with the surrounding neck construct. Results indicate stress concentration in the odontoid junction with the vertebral body, which suggests that there is a possibility of occurring type II fracture in the case of impaction of odontoid with atlas anterior arch, lateral masses and transverse ligament.
Biological Computer Modeling / Biological Computer Simulation
Azade Ahouraei; Farzad Towhidkhah; Fateme Haji Ebrahim Tehrani; Rasoul Khayati
Volume 1, Issue 1 , June 2007, , Pages 63-69
Abstract
Jaundice (hyperbilirubinemia) is a common disease in newborn babies. Under certain circumstances, elevated bilirubin levels may have detrimental neurological effects. In some cases, phototherapy is needed to lower the level of total serum bilirubin, which indicates the presence and severity of jaundice. ...
Read More
Jaundice (hyperbilirubinemia) is a common disease in newborn babies. Under certain circumstances, elevated bilirubin levels may have detrimental neurological effects. In some cases, phototherapy is needed to lower the level of total serum bilirubin, which indicates the presence and severity of jaundice. Recently, diagnosis and treatment modeling of disease have been considered by many researchers. In this paper, we present two models for classification and prediction of neonatal jaundice. The models are based on recorded data of Iranian Neonates. This study is oriented on the basis of following procedures: a short review on physiology of Jaundice, and then description of the models. Two three-layer feed forward neural networks were used in the modeling. The neural network model for classification is able to specify the type of jaundice, and the model for prediction can evaluate the risk of jaundice for newborns. These models can be used to decrease the risk in the critical cases as well as the cost of treatment.
Biomechanics of Bone / Bone Biomechanics
Khalil Farhangdoust; Ali Banihashem; Ali Ghaneei
Volume -2, Issue 1 , July 2005, , Pages 1-8
Abstract
Using ceramic coatings has increased in popularity due to their compatibility with bone, absence of the fibrous layer at the coating-implant interface, and the stronger coating-bone bonding. Among these coatings, hydroxyapatite (HA) and fluoroapatite (FA) are more popular. For the first time in this ...
Read More
Using ceramic coatings has increased in popularity due to their compatibility with bone, absence of the fibrous layer at the coating-implant interface, and the stronger coating-bone bonding. Among these coatings, hydroxyapatite (HA) and fluoroapatite (FA) are more popular. For the first time in this paper, modeling and stress analysis have been carried out for 24 implants in an axisymetric form using the finite element technique. Twelve of these samples belong to IMZ and the rest are from Dyna system. All implants had HA and FA coatings with thicknesses between 10 to 100 microns. The stress analysis results show that the stress concentration at the implant-coating and bone-coating bonding surfaces decreases with the increase of coating thickness. In addition, stress concentrations for implants with FA coatings are always more than those with HA coatings. In all implants, stress concentration has been observed around the bone crest.
Neuro-Muscular Engineering
Mehrak Mahmoudi; Mohammad Jafar Abd Khodaei; Saeide Khatibirad
Volume -2, Issue 1 , July 2005, , Pages 9-16
Abstract
A mathematical model is presented for simulation of neurotransmitter release in the synaptic cleft of a neuromuscular junction. Chaudhuri's model is improved by adding calcium diffusion effect on the neurotransmitter release. When an action potential occurs, the calcium channels on presynaptic membrane ...
Read More
A mathematical model is presented for simulation of neurotransmitter release in the synaptic cleft of a neuromuscular junction. Chaudhuri's model is improved by adding calcium diffusion effect on the neurotransmitter release. When an action potential occurs, the calcium channels on presynaptic membrane will open and allow calcium ions to enter in presynaptic terminal. Then, these ions diffuse between calcium channels and release sites, where clearance mechanisms remove some of them. The model is defined by some partial differential equations which are solved by numerical methods. Solving these equations, the temporal changes of calcium concentration in the release sites and the amount of neurotransmitter release at each time are obtained. Finally, the effect of two consecutive action potential pulses on the above mechanisms is studied.
Neuro-Muscular Engineering
Abbas Erfanian Omidvar
Volume -2, Issue 1 , July 2005, , Pages 81-92
Abstract
This paper is concerned with developing a force-generating model of electrically stimulated muscle under non-isometric condition. Hill-based muscle models have been the most popular structure. This type of muscle model was constructed as a combination of different independent blocks (i.e., activation ...
Read More
This paper is concerned with developing a force-generating model of electrically stimulated muscle under non-isometric condition. Hill-based muscle models have been the most popular structure. This type of muscle model was constructed as a combination of different independent blocks (i.e., activation dynamics, force-length and force-velocity relations, and series elastic element). The model assumes that the force-length and the force-velocity relations are uncoupled from the activation dynamics. However, some studies suggest that the shapes of the active force-length and the active force-velocity curves change with the level of the activation. Moreover, the "active state" block of the Hill-type model has no physical interpretation. To overcome the limitation of the Hill-type model, we used the multilayer perceptron (MLP) with back-propagation learning algorithm and Radial Basis Function (RBF) network with stochastic gradient learning rule for muscle modeling, where the stimulation signal, muscle length, velocity of length perturbation, and past measured or predicted force constitute the input of the neural model, and the predicted force is the output. Two modes of network operation are of interest: a time-varying network which allows updating the parameters of network to continue after convergence, and a time-invariant neural network with parameters fixed after convergence. The results show that time-varying and time-invariant neural networks would be able to track the muscle force with accuracy up to 99.5% and 95%, respectively. In addition, the results show that the accuracy of muscle force prediction depends on the structure of neural network. The prediction accuracy of RBF network after 1000 training epochs is higher than that of MLP network after 5000 training epochs.
Biological Computer Modeling / Biological Computer Simulation
Zohre Barani; Mohammad Haghpanahi; Hamid Reza Katouzian; Hasan Saeidi
Volume -1, Issue 2 , June 2005, , Pages 111-116
Abstract
Current research in foot biomechanics includes studies on prevention of recurrence of neuropathic foot ulcers. This prescribes accommodative insoles, which reduce plantar pressure levels particularly under the hallux. There is little quantitative information available regarding the effects of insole ...
Read More
Current research in foot biomechanics includes studies on prevention of recurrence of neuropathic foot ulcers. This prescribes accommodative insoles, which reduce plantar pressure levels particularly under the hallux. There is little quantitative information available regarding the effects of insole materials. The insole models available in the literature are mostly two- dimensional (2-D). Hence, there is a need to develop a three-dimensional (3-D) model with actual geometry which includes sufficient details. In this study a 3-D model of the insole was constructed. A linear and non-linear static analysis using finite element method (FEM) was done. To construct the 3-D finite element model, 14736 nodes and 16170 elements were used. This research has shown that Silicone Gel is very effective in terms of reduction of stress concentrations. The techniques used in this research provide a promising approach to understand the behavior of insole material as well as a guideline in the design of therapeutic footwear and orthoses for insensate feet.
Cardiovascular Biomechanics
Faramarz Firouzi; Nasser Fatouraee; Siamak Najarian
Volume -1, Issue 2 , June 2005, , Pages 129-142
Abstract
Nowadays in the industrial world, because of increase of heart transplantation demand, long-term ventricular assist devices (VAD) are more needed. Implantable sac-type is one of the newest of them producing pulsatile flow. In this research, three different models of sac-type VAD are numerically simulated. ...
Read More
Nowadays in the industrial world, because of increase of heart transplantation demand, long-term ventricular assist devices (VAD) are more needed. Implantable sac-type is one of the newest of them producing pulsatile flow. In this research, three different models of sac-type VAD are numerically simulated. Simple motion is supposed for moving wall in model 1. In model 2, the motion of moving wall is assumed wavy form to study the effect of moving wall form on blood flow. In model 3, the pressure boundary condition is added to model 2. In this model, the effect of actual blood pressure on flow pattern is considered. Results of each model demonstrate the viscose term of blood flow stresses applied to the membrane is negligible, and only pressure term is effective. However, the motional pattern of membrane and also applied pressure on boundary are approximately ineffective on blood flow pattern.
Biomechanics of Bone / Bone Biomechanics
Seyed Hamed Hosseini Nasab; Farzam Farahmand; Mohammad Hossein Karegar Novin; Mohsen Karami
Volume -1, Issue 2 , June 2005, , Pages 159-172
Abstract
Several linear and nonlinear finite element models of intact and fixed lumbar spine were analyzed. The intact model was developed based on CT images, and following verification, was employed to simulate the spinal fixation procedure using two different commercial pedicle screw systems. The results including ...
Read More
Several linear and nonlinear finite element models of intact and fixed lumbar spine were analyzed. The intact model was developed based on CT images, and following verification, was employed to simulate the spinal fixation procedure using two different commercial pedicle screw systems. The results including the force-deformation behavior and the stress distribution within the structures were studied in detail. The effects of pedicle morphology, insertion errors and material properties of bone graft on the stress distribution pattern within the vertebrae and implant components were also studied. The results suggest superiority of titanium implants over steel implants, necessity of bone graft insertion, and a higher failure risk for screws due to osteoporosis. It has been recommended that surgeons use thicker screws when dealing with pedicels with larger anterior posterior length and avoid insertion errors to minimize the risk of screw fracture.
Neuro-Muscular Engineering
Ali Esteki
Volume -1, Issue 1 , June 2004, , Pages 15-23
Abstract
Computer simulation of a three dimensional model of the thumb and index finger was used to perform a sensitivity analysis of each joint position to individual muscle activation level. The results were used to study the effect of each muscle on hand posture and select specific muscles to get a desired ...
Read More
Computer simulation of a three dimensional model of the thumb and index finger was used to perform a sensitivity analysis of each joint position to individual muscle activation level. The results were used to study the effect of each muscle on hand posture and select specific muscles to get a desired posture of the hand to assist the implementation of FNS systems. The hand was treated as a multi-body system including rigid segments connected by joints. Each joint was subjected to a total moment including muscle active and joint passive components. The forward approach, in which the equilibrium equations are solved for joint positions as a function of muscle moments, was used. The results showed that at the base joint of the index finger, flexion effect of the extrinsic flexor muscles was about two times of that of the intrinsic muscles. It was also shown that each muscle of the extensor system is individually more effective than the extrinsic flexor muscles. At the more distal joints, intrinsic muscles acted as feeble extensors. At the base joint of the thumb, extensor muscles were much more powerful than the flexor and flexor effect of adductor muscles. Also, abductor muscles were much more effective than the adductors. It was revealed that flexor muscles of the more distal joints are as strong as the extensor muscles. The conclusions are that: the minimum required muscles for appropriate positioning of the hand and for grasp and applying force to objects are limited.
