Biomedical Image Processing / Medical Image Processing
Mahdie Ghasemi; Ali Mahloojifar; Mehdi Omidi
Volume 8, Issue 3 , September 2014, , Pages 261-275
Abstract
Functional changes in the brain motor network are responsible for the major clinical features of Parkinson’s disease (PD). Recent studies on investigation of the brain function show that there are spontaneous fluctuations between regions at rest as resting state network affected in various disorders. ...
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Functional changes in the brain motor network are responsible for the major clinical features of Parkinson’s disease (PD). Recent studies on investigation of the brain function show that there are spontaneous fluctuations between regions at rest as resting state network affected in various disorders. In this paper, we examine changes of functional dependency between brain regions of interest associated with known anatomical pathology in Parkinson Disease (PD) using copula theory on resting state fMRI. Five types of copulas were tested: Gaussian and t (Euclidean), Clayton, Gumbel and Frank (Archimedean). We used an efficient maximum likelihood procedure for estimating copula parameters. Goodness of fits was tested using root mean square error (RMSE) and kulback-leibler divergence between each copula function and joint empirical cumulative distribution. Control vs PD group comparison was also done on dependency parameter using parametric and nonparametric tests. The results show that functional dependency between cerebellum and basal ganglia is much stronger in PD than in control. In this paper, we proposed for the first time that joint distribution characteristics could potentially provide information on discriminative features for functional connectivity analysis between healthy and patients.
Nano-Biomaterials
Sahar Rezaei; Nader Riahi Alam
Volume 8, Issue 2 , June 2014, , Pages 151-158
Abstract
Detection of tumors at an early stage is important for the diagnosis of cancer. Therefore, to detect cancer cells it is necessary to distinguish between metastases from normal cells at an early stage. Due to the large size and coverage necessary to prevent chemical reactions of the current contrast agents ...
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Detection of tumors at an early stage is important for the diagnosis of cancer. Therefore, to detect cancer cells it is necessary to distinguish between metastases from normal cells at an early stage. Due to the large size and coverage necessary to prevent chemical reactions of the current contrast agents in the body, they are just applicable to the extracellular space. Due to the small size of nanoparticles in comparison to cells, it is possible for them to enter the cells. Therefore, these materials are used for molecular imaging. In this paper, variations in the external magnetic field (Tesla) due to magnetic nanoparticles in homogeneous tissue were studied by the finite element method. For this purpose, a simulation was performed in the presence of magnetic nanoparticles and without it. By the finite element method, conversion of differential and integral governing equations to simple and solvable equations that are numerically stable was made possible. The results obtained indicate that the external magnetic field is intensified by the presence of magnetic nanoparticles.
Bioelectromagnetics
Somayye Mohamadalikhani; Faeze Ghanati; Maryam Soleimani; Hasan Zare Maivan; Abazar Hajnorouzi
Volume 8, Issue 2 , June 2014, , Pages 173-181
Abstract
Water molecules can be affected by magnetic fields due to their bipolar characteristics. In the present study an experimental maize field was irrigated with magnetically treated water. Tap water was passed through a locally designed alternative magnetic field generating apparatus (110 mT). The maize ...
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Water molecules can be affected by magnetic fields due to their bipolar characteristics. In the present study an experimental maize field was irrigated with magnetically treated water. Tap water was passed through a locally designed alternative magnetic field generating apparatus (110 mT). The maize plants were irrigated by the magnetically treated water from sowing to the seedling stage. Treatment with magnetically treated waterincreased the shoot and root lengths, fresh and dry weight of seedling (30%, 19.1%, 22% and 22%, respectively), compared with the control groups. The contents of photosynthetic pigments, total sugar and total protein of the leaves did not show significant differences between the treated plants and the control group. The ratio of Fv/Fm of seedling and growth parameters of second family were increased, compared to those of non-treated ones. The combined results suggested that the treatment of water a magnetic field with represents a plausible candidate for the mediation of MF effects on plant cells.
Bioelectromagnetics
Mohammad Reza Yousefi; Reza Jafari; Hamid Abrishami Moghaddam
Volume 8, Issue 1 , March 2014, , Pages 69-86
Abstract
In this paper, a combined wavelet based mesh free method has been presented to solve the forward problem in magnetic induction tomography (MIT). Being a non-contact safe imaging technique, MIT has been an appropriate method for noninvasive industrial and medical imaging. In this imaging method, a primary ...
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In this paper, a combined wavelet based mesh free method has been presented to solve the forward problem in magnetic induction tomography (MIT). Being a non-contact safe imaging technique, MIT has been an appropriate method for noninvasive industrial and medical imaging. In this imaging method, a primary magnetic field is applied by one or more excitation coils to induce eddy currents in the material to be studied, and then the secondary magnetic field from these eddy currents is detected in sensing coils. Image reconstruction is obtained from estimated electric conductivity coefficients by using measurement data and solutions of forward and inverse problems. In general, the forward problem is solved using finite element method (FEM) with acceptable accuracy but in problems involving moving objects or objects with changing geometrical appearance, mesh distortion is inevitable and susceptible to producing error in numerical results. Since the solution of the FEM depends on the mesh shape and boundary condition constraints are difficult to be applied to the mesh free method, in this paper, the combined wavelet based mesh free approach is suggested to resolve the disadvantages of both methods in the MIT forward problem. In order to apply interface conditions between the two finite element and mesh free sub-domains, slope jump functions are entered to the set of basis functions. The simulation results obtained by the proposed method are compared with the FEM in terms of accuracy and computational cost.
Biomedical Image Processing / Medical Image Processing
Mohammad Reza Rezaeian; Gholam Ali Hossein-Zadeh; Hamid Soltanian Zadeh
Volume 8, Issue 1 , March 2014, , Pages 87-99
Abstract
Chemical exchange saturation transfer (CEST) is a new mechanism of contrast generation in magnetic resonance imaging (MRI) which differentiates molecule biomarkers via chemical shift. CEST MRI contrast mechanism is very complex and depends on radio frequency (RF) power and RF pulse shape. Two approaches ...
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Chemical exchange saturation transfer (CEST) is a new mechanism of contrast generation in magnetic resonance imaging (MRI) which differentiates molecule biomarkers via chemical shift. CEST MRI contrast mechanism is very complex and depends on radio frequency (RF) power and RF pulse shape. Two approaches have been used to saturate contrast agent (CA) protons: continuous wave CEST (CW-CEST) and pulsed CEST. To find the optimal RF pulse, numerical solution of Bloch-McConnell equations (BME) may be used. In this paperwe find the optimum values of RF pulse parameters that maximize the CEST contrast. Discrete pulses have lower specific absorption ratio (SAR) than CW RF pulses. However, since discretization is performed on continuous RF pulses, optimizing the continuous RF pulses leads to the optimization of discrete RF pulses. Therefore, in this paper, Rectangular, Gaussian and Fermi pulses are investigated as CW RF pulses. In this investigation, in addition to considering the SAR limitation, 60 dB approximation for the RF pulse amplitude is used. To compare the efficiency of pulses, their resultant flip angles (FA) are assumed equal. Efficiency of CW-CEST is investigated using two parameters, CEST ratio and SAR. According to these parametres, rectangular, Fermi and Gaussian RF pulses have the best performance respectively. Since implementation of rectangular RF is harder than Gaussian and Fermi RF pulses, Fermi and Gaussian RF pulses are desired. Our results suggest that it is possible to maximize CEST ratio by optimizing parameters of rectangular (with an amplitude of 5.7μT), Gaussian (σ about 0.7s) and Fermi (a-value about 0.3s) pulses. Results are verified by empirical formulation of CEST ratio.
Biomedical Image Processing / Medical Image Processing
Neda Behzadfar; Hamid Soltanian Zadeh
Volume 7, Issue 3 , June 2013, , Pages 219-236
Abstract
Segmentation of tumors in magnetic resonance images is an important task. However, it is quite time consuming and has low accuracy and reproducibility when performed manually. Automating the process is challenging, due to high diversity in appearance of tumor tissue in different patients and in many ...
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Segmentation of tumors in magnetic resonance images is an important task. However, it is quite time consuming and has low accuracy and reproducibility when performed manually. Automating the process is challenging, due to high diversity in appearance of tumor tissue in different patients and in many cases, similarity between tumor and normal tissues. This paper presents semi-automatic approach for analysis of multi-parametric magnetic resonance images (MRI) to segment a highly malignant brain tumor called Glioblastoma multiform (GBM). MRI studies of 12 patients with GBM tumors are used. To show that the proposed method identifies Gd-enhanced tumor pixels from T1-post contrast images minimal user interactions. They are also used to illustrate that the segmentation results obtained by the proposed approach are close to those of an expert, by showing excellent correlations among them (R2=0.97). In order to evaluate the proposed method in practical applications, effects of treatment of GBM brain tumors using Bevacizumab are predicted. Bevacizumab is a recent therapy for stopping tumor growth and even shrinking tumor through inhibition of vascular development (angiogenesis). To this end, two image series of 12 patients before and after treatment and relative changes in the volumes of the Gd-enhanced regions in T1-post contrast images are used as measure of response. The proposed method applies signal decomposition with KNN classifier to minimize user interactions and increase reproducibility of the results. Then histogram analysis is applied to extract statistical features from Gd-enhanced regions of tumor and quantify its micro structural characteristics. Predictive models developed in this work have large regression coefficients (maximum R2=0.91) indicating their capability to predict response to therapy. The results obtained by the proposed approach are compared with those of previous work where excellent correlations are obtained.
Biomedical Image Processing / Medical Image Processing
Maryam Afzali; Emadoddin Fatemizadeh; Hamid Soltanian Zadeh
Volume 7, Issue 1 , June 2013, , Pages 57-64
Abstract
Diffusion tensor magnetic resonance imaging (DTMRI) is a non-invasive method for investigating the brain white matter structure. It can be used to evaluate fiber bundles in the brain but in the regions with crossing fibers, it fails. To resolve this problem, high angular resolution diffusion imaging ...
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Diffusion tensor magnetic resonance imaging (DTMRI) is a non-invasive method for investigating the brain white matter structure. It can be used to evaluate fiber bundles in the brain but in the regions with crossing fibers, it fails. To resolve this problem, high angular resolution diffusion imaging (HARDI) with a large number of diffusion encoding directions is used and for reconstruction, the Q-ball method is applied. In this method, orientation distribution function (ODF) of fibers can be calculated. Mathematical models play a crucial role in the field of ODF. For instance, in registering Q-ball images for applications like group analysis or atlas construction, one needs to interpolate ODFs. To this end, principal diffusion directions (PDDs) of each ODF are needed. In this paper, PDDs are defined as vectors that connect the corresponding local maxima of ODF values. Then, ODFs are interpolated using PDDs.We find the principal direction of ODF of the dataset to be interpolated and then rotate it to lie in the direction of the reference dataset. Now that ODFs are parallel, we apply linear interpolation to generate interpolated data. The proposed method is evaluated and compared with previous protocols. Experimental results show that the proposed interpolation algorithm preserves the principal direction of fiber tracts without producing any deviations in the tracts. It is shown that changes in the entropy of the interpolated ODFs are almost linear and the bloating effect (blurring of the principal directions) can be removed.
Bioelectromagnetics
Maryam Sadri; Parviz Abdolmaleki; Saeed Abroun; Bahare Beiki; Fazel Samani
Volume 6, Issue 2 , June 2012, , Pages 91-98
Abstract
The Mesenchymal Stem cells derived from human newborn cords were cultured and exposed to a 24mT Static magnetic field for 24 hours. The viability percentage and the cell cycle progression was then investigated in exposed samples and the obtained results was compared with the control samples. The results ...
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The Mesenchymal Stem cells derived from human newborn cords were cultured and exposed to a 24mT Static magnetic field for 24 hours. The viability percentage and the cell cycle progression was then investigated in exposed samples and the obtained results was compared with the control samples. The results clearly demonstrated a significant reduction of cell viability due to the exposure of 24 hours of SMF and post-exposure cultures within the time frames of 36,48,60 hours. The cell development through the cell-cycle, also verified this finding, however, 72 hours of post-exposure culture, significantly leveled off the drop in viable stem cell rates.
Bioelectromagnetics
Samane Sedighi; Keyvan Keramati; Ali Safari-Varyani; Ahmad Nikpey
Volume 6, Issue 2 , June 2012, , Pages 99-106
Abstract
Exposure to magnetic fields can effect on the learning and memory. The protective effect of saffron extract on memory consolidation disorders in rats exposed to magnetic fields was investigated. 120 male Wistar rats in 12 groups exposed to magnetic field For 5 days with intensity 2.5 tesla for 1, 3 and ...
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Exposure to magnetic fields can effect on the learning and memory. The protective effect of saffron extract on memory consolidation disorders in rats exposed to magnetic fields was investigated. 120 male Wistar rats in 12 groups exposed to magnetic field For 5 days with intensity 2.5 tesla for 1, 3 and 5 hour and protective effects of saffron extract with doses of 125 mg, 200 mg and 300 mg (P ≤0.05) compared to the control group by passive avoidance learning method in shuttle box. One hour exposure with magnetic field had no effect on the rats’ memory consolidation (P ≤0.05). Increase exposure time to 3 and 5 hours had a memory consolidation Impairment compared to the control group (P ≤0.05). Administered rats with 300 mg Inter peritoneal saffron extract improved memory consolidation (P ≤0.05) compared to the control group. Exposure to magnetic fields 2.5 mT, 50 Hz impair memory consolidation. Saffron aqueous extract at a dose of 300 mg per kg may have a protective effect and be improvement consolidation impairments.
Bioelectromagnetics
Susan Kohzad; Bahram Bolouri; Farnaz Nikbakht; Zahra Kohzad
Volume 6, Issue 2 , June 2012, , Pages 107-111
Abstract
There is a growing public concern that the extremely low frequency (ELF) range of the environmental electromagnetic fields may have adverse biological effects. In this frequency range, 217Hz is the modulating signal being used in Global System of Mobile. This study investigated the possible effects of ...
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There is a growing public concern that the extremely low frequency (ELF) range of the environmental electromagnetic fields may have adverse biological effects. In this frequency range, 217Hz is the modulating signal being used in Global System of Mobile. This study investigated the possible effects of 217 Hz pulsed electromagnetic field on the anxiety and the cortisol level in rats. Twenty four male Wistar rat (200 - 250 g) were randomly grouped into test, sham and control. Using a pair of Helmholtz coil system, the test group was exposed to a uniform pulsed EMF of 200µT intensity for 4 h/day for 21 days. A similar procedure with no field was repeated for the sham group. All groups were tested in an `Elevated- plus` maze system. Then via the heart puncture scheme, the blood samples were collected. The serum cortisol levels were evaluated using ELISA method.The ANOVA test revealed no significant differences for the Elevated- plus maze test. Serum cortisol level was significantly higher in test group compared to the control group.These findings were in consistent with the work of others indicating that low frequency band of EMF might not have any effect on the anxiety but it increases the cortisol levels as a stress marker.
Genetic Engineering / Genetic Modification / Genetic Manioulation
Ayatollah Rezaei; Faeze Ghanati; Mehrdad Behmanesh
Volume 6, Issue 2 , June 2012, , Pages 113-122
Abstract
In this study cell growth, some physiological parameters, production of Taxol and gene expression in cell culture of hazel under effect of the magnetic field were investigated. Cells in suspension culture were treated by a 30 mT static magnetic field on days 8-11 after subculture and 4 hours each day. ...
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In this study cell growth, some physiological parameters, production of Taxol and gene expression in cell culture of hazel under effect of the magnetic field were investigated. Cells in suspension culture were treated by a 30 mT static magnetic field on days 8-11 after subculture and 4 hours each day. The results showed that while the growth rate and viability of cells weren’t affected by the magnetic field but membrane lipid peroxidation rate and H2O2 production increased. Activity of phenylalanine ammonia lyase, polyphenol oxidase and peroxidase enzymes was increased by the magnetic field compared with control. Production of phenolic compounds and Taxolin treated cells showed an increase compared to those of control cells. Magnetic field increased intracellular Taxol more than extracellurTaxol, and in treated cultures total taxol production was 2.9-fold compared to control culture. Gene expression of 1- deoxy -D- xylulose -5 - phosphate reductoisomerase involved in producing Taxol precursors and in its biosynthesis was also increased in treated cells compared to control. It appears that magnetic field by stimulating cell defense responses and inducing gene expression involved in Taxol biosynthesis has resulted in improved its production.
Bioelectromagnetics
Hadi Tavakoli; Ali Motie Nasrabadi; Seyed Mohammad Firouzabadi; Mehri Kaviyani Moghaddam
Volume 6, Issue 2 , June 2012, , Pages 123-131
Abstract
During recent years, the environment has been enormously changed by the wide range of magnetic fields. Therefore, comprehensive studies are being done for investigating their biological effects. The effects such as inhibition of bioelectric activity of neurons which is shown by evidence, like decreasing ...
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During recent years, the environment has been enormously changed by the wide range of magnetic fields. Therefore, comprehensive studies are being done for investigating their biological effects. The effects such as inhibition of bioelectric activity of neurons which is shown by evidence, like decreasing in the firing frequency or decreasing in the amplitude of action potential, have been shown. To notify and investigate these effects, the theory of “biological windows” have been proposed and considered. The effects of amplitude and/or frequency of magnetic field have been pointed in some research. In this study, regarding the behavior of nervous system, which has non-linear dynamic behavior, we study the behavior of nervous system under exposure to magnetic field. We investigate whether the low frequency field is able to affect the dynamic of nerve cells and to have influence on non-linear features of signal. We used 6 environmental intensities and 6 cells have been used in each intensity, and by calculating some of non-linear features of action potential such as Higuchi Dimension and Return map of signal, during the time and in some different intensities of magnetic fields, It was observed that all intensities magnetic fields lead to increasing in Higuchi Dimension and increasing in the scattering of the Return map of signal. Of course these effects has been more observed in the middle band of frequency which has been confirmed by the theory of ‘frequency window’ effect of magnetic fields, which it has been noticed and discussed in last two decades.
Bioelectromagnetics
Mehrdad Saviz; Sina Shirinpour; Ashkan Abedi; Reza Faraji-Dana
Volume 6, Issue 2 , June 2012, , Pages 133-140
Abstract
We introduce a new computational approach which is capable of providing estimations of the electric field strength induced in biological bodies at large to ultra-fine scales. The method is theoretically based on multi-scale analysis and excitation of the smaller-scale models by the computed fields at ...
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We introduce a new computational approach which is capable of providing estimations of the electric field strength induced in biological bodies at large to ultra-fine scales. The method is theoretically based on multi-scale analysis and excitation of the smaller-scale models by the computed fields at the larger-scale model. The method and its implementation are shown, and as a practical example, the electric field induced inside the plasma membrane has been successfully computed for cells residing at different locations in the human body-model. Also discussed are the origins of the frequency-dependent behavior of the induced field strength and the significance of its practical consequences for bioelectromagnetics.
Bioelectromagnetics
Reza Masoomi Jahandizi; Parviz Abdolmaleki; Seyed Javad Mowla
Volume 5, Issue 2 , June 2011, , Pages 105-115
Abstract
The effect of 15 and 30 mT of static magnetic field on the cell cycle of neural inductive rat BMSC was evaluated. The BMSC was inductived by neural inductive medium (NIM). Duration of inductive and Exposure time were 2, 4 and 6 hours. The cells induction to neural inductive medium associated with SMF ...
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The effect of 15 and 30 mT of static magnetic field on the cell cycle of neural inductive rat BMSC was evaluated. The BMSC was inductived by neural inductive medium (NIM). Duration of inductive and Exposure time were 2, 4 and 6 hours. The cells induction to neural inductive medium associated with SMF as exposed group, besides we have a control group. The apparatus we used to generate the SMF was a locally designed SMF generator in which there was an incubator instrument capable to maintain the humidity, temperature and CO2 concentration in predefined level. After exposing, the cells were fixed, stained and their percent of cell cycle phases; G1, S, G2/M were elucidated using flowcytometer instrument. The WinMdi 2.9 Software was used to process data from flowcytometer and elucidation of phase's percents. The results showed SMF with 15 mT intensity did not significantly alter the cell cycle in three different (2, 4 and 6 hours) exposing times. Exposing 2 hours with 30 mT increased the G2/M phases in neural inductive BMSC comparing to the corresponding control. Static magnetic field decreased the percent of S phase in BMSC, during 4 hours exposure.
Biomedical Image Processing / Medical Image Processing
Effat Yahaghi; Yashar Nohi; Amir Movafeghi; Hamid Soltanian Zadeh
Volume 4, Issue 1 , June 2010, , Pages 1-11
Abstract
Magnetic resonance imaging (MRI) is a non-ionizing method for identification and evaluation of soft tissue lesions. Perfusion MRI evaluates soft tissues by measuring changes in magnetization of water molecules due to a contrast agent. To this end, concentration curves in the plasma and tissue are estimated ...
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Magnetic resonance imaging (MRI) is a non-ionizing method for identification and evaluation of soft tissue lesions. Perfusion MRI evaluates soft tissues by measuring changes in magnetization of water molecules due to a contrast agent. To this end, concentration curves in the plasma and tissue are estimated by MRI and effective longitudinal relaxation time (T1eff) of the tissue was calculated. To interpret the results, the effects of water exchange on the effective longitudinal relaxation time should be studied. This work presents such a study in which the equations of two- and three-compartmental models of rat brain tissue are solved using Hion and Runge-Kutta numerical methods for different input functions and simulated by Monte Carlo method. Since the exchange of water and contrast agent among different tissue compartments is a diffusion phenomenon, Monte Carlo method is applicable. Results of the numerical methods were compared with those of Monte Carlo simulation. The results of the two methods were almost identical with a maximum relative difference of less than 1%. In this work, concentration of contrast agent in plasma is estimated from MRI of a rat brain tissue. This data is used in the Monte Carlo method to obtain T1eff and exchange rate constants. An advantage of our method is that T1eff is obtained from real data and not from the curve fitting method as commonly used. We derive concentration of contrast agent as a function of time in extravascular space for different constants (K). Then, the curves of simulated and real data were compared to obtain the exchange rate constant of each compartment. The results showed that K of an abnormal tissue was larger than that of the normal tissues. As such, this parameter may be used for diagnosis and treatment of the soft tissue diseases.
Tissue Engineering
Jafar Ai; Saeed Sarkar; Mohammad Ali Oghabian
Volume 4, Issue 2 , June 2010, , Pages 161-166
Abstract
Various reviews have shown that strong electromagnetic fields have negative effects on human health. This study focused on the effect of MRI radiation on liver functional test histometery of liver in adult male rats. For this purpose, we used an MRI device that could produce 1.5 T electromagnetic radiations, ...
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Various reviews have shown that strong electromagnetic fields have negative effects on human health. This study focused on the effect of MRI radiation on liver functional test histometery of liver in adult male rats. For this purpose, we used an MRI device that could produce 1.5 T electromagnetic radiations, and chose 22 Wistar rats as laboratory animal models. Rats were divided into two equal groups. The first group exposed to 1.5T electromagnetic radiation and RF radiation during a 30- minute MRI scan as experimental group. The control group experienced 1.5T electromagnetic radiation exposure without RF radiation by the same MRI device. The rats were anesthetized and blood samples were obtained from cardiac chambers to measure the serum levels of LDL, HDL, ALT, AST, ALP, total cholesterol, total protein, albumin, total billirobin, and direct bilirobin. Livers were then removed and the specimens fixed. Serial sections (5 μm thick) were prepared from livers and the diameter of hepatocytes and their nuclei were measured. The findings of the present study indicate that, there was a significant increase (P<0.5) in amount of HDL, ALT, AST, ALP, total billirobin, direct bilirobin and there was a significant decrease (P<0.5) in amount of total cholesterol, LDL, total protein, and albumin in experimental group by comparison with control group. But no significant differences were seen in the diameter of hepatocytes and their nuclei between both groups. The electromagnetic radiations of MRI device may influence the level of liver enzymes and liver function without any histomorphologically changes. Conducting clinical trial studies with human subjects is recommended.
Biomedical Image Processing / Medical Image Processing
Hamid Abrishami Moghaddam; Maryam Momeni; Kamran Kazemi; Reinhard Grebe; Fabrice Wallois
Volume 4, Issue 4 , June 2010, , Pages 337-360
Abstract
Diagnostic follow-up of the brain development during the neonatal period and childhood is an important clinical task. Any disturbance of this process can cause pathological deviations, especially if the baby is born premature. Recent advances in magnetic resonance imaging allow obtaining high-resolution ...
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Diagnostic follow-up of the brain development during the neonatal period and childhood is an important clinical task. Any disturbance of this process can cause pathological deviations, especially if the baby is born premature. Recent advances in magnetic resonance imaging allow obtaining high-resolution images of the neonatal brain. After segmenting the brains they can be used to reconstruct and model changes occurring during neonatal brain development. In addition such near-realistic model of the head, including the skin, skull and brain can be used to solve the inverse problem of determining the sources of registered signals from electrical brain activity. Although there exist numerous methods and various modeling schemes for adults, these cannot be used directly for neonates due to important differences in morphology. In this review article, neonatal brain atlases are divided into three categories: individual atlases, probabilistic atlases and stochastic atlases. In the following, existing neonatal brain atlases are placed in this classification and their methods of construction are presented. Furthermore, strengths and weaknesses of those neonatal brain atlases are analyzed and finally future research trends in this area are explained.
Tissue Engineering
Fateme Shamsi; Mohsen Janmaleki; Nasser Fatouraee
Volume 3, Issue 4 , June 2009, , Pages 265-274
Abstract
In this study a mechanism was modeled to control the jet path of nanofibers produced by electrospinning through inducing a magnetic field over the jet path. Firstly, a model was developed for the jet path in which the fibers composed of a series of viscoelastic segments. Considering the mass and momentum ...
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In this study a mechanism was modeled to control the jet path of nanofibers produced by electrospinning through inducing a magnetic field over the jet path. Firstly, a model was developed for the jet path in which the fibers composed of a series of viscoelastic segments. Considering the mass and momentum conservation and maxwellian model of stretching viscoelastic segments using three equations governing the jet dynamics of the jet model in electrospinning, a program was developed in MATLAB with Runge–Kutta method. After ensuring the accuracy of the model, its behavior was evaluated in the presence of a magnetic field. The field induced a uniform force distribution over the jet. As the intensity of the magnetic field increased; the instability and bending radius of the jet reduced. The results of the research showed that utilizing a suitable mechanism for applying magnetic field can provide help in controlling the jet path and alignment of the nanofibers.
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 ...
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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.
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, ...
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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).
