Biomedical Image Processing / Medical Image Processing
Elahe Moghimirad; Ali Mahloojifar; Babak Mohammadzadeh Asl
Volume 8, Issue 3 , September 2014, , Pages 277-291
Abstract
A new implementation of a synthetic aperture focusing technique is presented in the paper. Standard medical ultrasound imaging is done using line-by-line transmission with classical Delay-and-Sum (DAS) image reconstruction. Synthetic aperture imaging, however, has a better resolution and frame rate in ...
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A new implementation of a synthetic aperture focusing technique is presented in the paper. Standard medical ultrasound imaging is done using line-by-line transmission with classical Delay-and-Sum (DAS) image reconstruction. Synthetic aperture imaging, however, has a better resolution and frame rate in cost of more computational load. To overcome this problem, block processing algorithms are used in radar and sonar which are relatively unknown in medical. To extend the methods to medical field, one should concern the parameters difference such as carrier frequency, signal band width, beam width and depth of imaging. In this paper, we extended one of these methods called wavenumber to medical ultrasound imaging with a simple model of synthetic aperture focus. We have also used chirp pulse excitation followed by matched filtering, windowing and spotlighting algorithm to compensate the effect of differences in parameters between radar and medical imaging. Computational complexity of the two reconstruction methods, wavenumber and DAS, have been calculated. Field II simulated point data has been used to evaluate the results in terms of resolution and contrast. Evaluations with simulated data show that for typical phantoms, reconstruction by wavenumber algorithm is almost 20 times faster than classical DAS while retaining the resolution.
Tissue Engineering
Sara Zadegan; Bahman Vahidi; Nooshin Haghighipour
Volume 16, Issue 3 , December 2022, , Pages 289-299
Abstract
Repairing osteochondral defects (OCD) remains a formidable challenge due to the high complexity of native osteochondral tissue and the limited self-repair capability of cartilage. In this regard, the development of osteochondral tissue engineering with scaffolds seeded with stem cells along with mechanical ...
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Repairing osteochondral defects (OCD) remains a formidable challenge due to the high complexity of native osteochondral tissue and the limited self-repair capability of cartilage. In this regard, the development of osteochondral tissue engineering with scaffolds seeded with stem cells along with mechanical stimulation has been considered by the researchers as a new proposed technique for the repair of this tissue. In this study, at first we fabricated an integrated and biomimetic trilayered Silk Fibroin (SF) scaffold containing SF nano fibers in each layer. Then fluid wall shear stress in different areas of the scaffold was predicted in dynamic cell culture condition under the inlet velocity of 0.4 ml/min in a perfusion bioreactor using finite elements and fluid-structure interactions methods. Finally, using the simulation results, osteogenesis and chondrogenesis of rabbit adipose derived stem cells (RADSCs) were analyzed. The results showed that this novel osteochondral graft has a seamlessly integrated layer structure and a high degree of pore interconnectivity. The average size of the pores in the bone layer, middle layer, and cartilage were 76, 152, and 102 microns, respectively. In addition, this biomimetic scaffold presented compressive moduli of 0.4 MPa and uitimate tensile strength of 10 MPa in the wet state. Also, based on the simulation analyses, the shear stress distribution is more uniform if the bone layer is exposed to the fluid inlet path which facilitates bone differentiation. Good adhesion and infiltration of cells were observed after 14 days dynamic culture. The results of expression analysis of differentiated genes in bone and cartilage layer containing RADSc after 21 days of culture under static and dynamic conditions showed that perfusion flow significantly upregulated the expression of bone and cartilage genes in the respective layers and downregulated the hypertrophy gene expression in intermediate layer of scaffold.
Cardiovascular Biomechanics
Saeed Bahrami; Faramarz Firouzi
Volume 9, Issue 3 , December 2015, , Pages 293-303
Abstract
It is accepted that wall shear stress (WSS) and Oscillatory Shear index (OSI) are strong hemodynamic factors to development of atherosclerotic (AS) plaque. Sometimes, OSI has an important effect on AS plaque formation, because WSSdoesn't make it happenalone. Most computational fluid dynamic (CFD) simulations ...
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It is accepted that wall shear stress (WSS) and Oscillatory Shear index (OSI) are strong hemodynamic factors to development of atherosclerotic (AS) plaque. Sometimes, OSI has an important effect on AS plaque formation, because WSSdoesn't make it happenalone. Most computational fluid dynamic (CFD) simulations were performed on left main coronary bifurcation geometry, and whole left coronary artery tree has not been investigated by now. In this paper, a thorough three-dimensional model of left coronary artery tree was considered, including left main coronary, left anterior descending and its branches, left circumflex artery and its branches. Effects of cardiac motions on vessel wall of left coronary were considered. The governingNavier–Stokes equations for pulsatile flow and incompressible non-Newtonian blood was analyzed with finite element method. The study concentrates on shear stress distribution and OSI distribution on the vessel wall. Comparing the results of this study with previous clinical investigations shows that the regions with low wall shear stress (equal to and less than 1.5[Pa]) along with high OSI value (equal to and more than 0.3) have potential to development of AS plaque.So it can be predicted that the LAD region after D3 and the bifurcation of LCxA-OM have high potential to development of AS, in addition to the bifurcation of LCxA-LMCA which had been specified before.
Biomedical Signal Processing / Medical Signal Processing / Biosignal Processing
Adib Keikhosravi; Edmond Zahedi
Volume 6, Issue 4 , June 2012, , Pages 307-317
Abstract
The photoplethysmogram (PPG) is a low cost and ubiquitous signal and has always had a great significance in cardiovascular parameter identification such as arterial dilation due to a stimulus. The PPG is generally recorded from the fingertip which is affected by the auto-regulation mechanism (ARM), preventing ...
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The photoplethysmogram (PPG) is a low cost and ubiquitous signal and has always had a great significance in cardiovascular parameter identification such as arterial dilation due to a stimulus. The PPG is generally recorded from the fingertip which is affected by the auto-regulation mechanism (ARM), preventing the results to be well correlated with standard methods based on imaging the brachial or radial artery. Based on the fact that the ARM has no effect on conduit arteries, the correlation between fingertip and radial artery PPG is investigated in this work. A custom made probe is fabricated using an array of photodiodes and a 960 nm LED for recording the wrist photoplethysmogram (PPG). The design is based on Monte-Carlo simulation of light propagation in tissues. Two series of experiments were carried-out: normal breathing and deep breathing. In both experiments, index finger and wrist PPG were simultaneously recorded. In the first series of experiments, signals from 9 subjects were recorded and the correlation coefficient for the raw signals (AC+DC), the AC and DC components of wrist and finger PPG were 62.5% ± 12.1%, 91.2% ± 6.9% and 61% ± 13.4% respectively. In the second series of experiment (deep breathing), signals from 6 subjects were recorded and the correlation coefficient for the raw signals (AC+DC), the AC and DC components were 89.7% ± 5.9%, 93.7% ± 3.3% and 89.9% ± 5.9% respectively. These results show that under normal breathing conditions, only the AC components of the PPG signals are highly correlated. When respiration becomes the dominant effect, both AC and DC parts become highly correlated.
Tissue Engineering
Rana Imani; Parisa Rahnama Moshtaq; Shahriar Hojati Emami; Sasan Jalili; Ali Mohammad Sharifi
Volume 3, Issue 4 , June 2009, , Pages 315-324
Abstract
Cell therapy based on cell encapsulation technology holds out the promise of the treatment of many diseases. The technology of cell encapsulation represents a strategy in which cells that secrete therapeutic products are immobilized and immunoprotected within polymeric and biocompatible carriers. Hydrogels ...
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Cell therapy based on cell encapsulation technology holds out the promise of the treatment of many diseases. The technology of cell encapsulation represents a strategy in which cells that secrete therapeutic products are immobilized and immunoprotected within polymeric and biocompatible carriers. Hydrogels - highly hydrated polymer networks- have ideal characteristics for this application because of good biocompatibility and mimicking natural ECM properties. They can homogeneously incorporate and suspend cells, growth factors, and other bioactive compounds. Temperature-sensitive hydrogels, which can form implants in situ in response to temperature change, from ambient to body temperature, have been extensively used in various cell encapsulation, and tissue repair. The objective of this study was preparation, Characterization and selection the optimum composition of agarose-gelatin blend hydrogel, for cell encapsulation application. In order to obtain hydrogel with appropriate properties, rheological, mechanical, and structural characteristics of obtained hydrogels were examined. Furthermore, the stability of samples was characterized by degradation and gelatin release measurements under physiological condition. Cell attachment and cytotoxicity analysis were also performed. Based on the results, hydrogel containing a 1:1 mixture of gelatin and agarose exhibited sol-to-gel transition near body temperature. Samples contain 50% agarose and more, exhibited mechanical integrity under physiological condition. Indentation test of the mechanical properties demonstrated viscoelastic behavior of the blend gelatin-agarose hydrogels under static load; however by increasing the agarose portion, hydrogel behaved more elastically. In vitro biocompatibility experiments showed undetectable cytotoxicity of the hydrogels. Also adding gelatin to agarose modified cell attachment behavior. The results of this study indicate the possibility of the potential use of prepared thermo-responsive agarose/gelatin conjugate with nearly same portion of two components as cell encapsulation carrier.
Cell Biomechanics / Cell Mechanics / Mechanobiology
Hamid Khaloozadeh; Pedram Yazdanbakhsh; Fateme Homaei Shandiz
Volume 1, Issue 4 , June 2007, , Pages 319-334
Abstract
The optimal doses of Doxorubicin and Cyclophosphamide (AC) regimen in pre-operation Neoadjuvant chemotherapy for the patients suffering from stage III breast cancer were investigated. The major benefit of Neoadjuvant chemotherapy is that it can shrink large cancers so that they are small enough to be ...
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The optimal doses of Doxorubicin and Cyclophosphamide (AC) regimen in pre-operation Neoadjuvant chemotherapy for the patients suffering from stage III breast cancer were investigated. The major benefit of Neoadjuvant chemotherapy is that it can shrink large cancers so that they are small enough to be removed by lumpectomy instead of mastectomy. The optimal regimen designed in this paper was based on the special conditions that every patient had been treated by her/his own physician and the resistance of tumor cells. With respect to these regimen that can achieve non equivalent doses of drug in treatment times for neoadjuvant chemotherapy. The purpose of treating the patients with cancer in neoadjuvant chemotherapy could be either destroying the cancer cells or preserving the normal cell populations in the best way, or different cases between these two situations. In this article, by solving a cost function involved with the dynamics of both cancer cells and normal cells - using the appropriate weighting coefficients suggested by the treating physician- the optimal doses of AC drugs for the patients suffering from breast cancer at stage III were computed by the proposed optimal controller.
Neuro-Muscular Engineering
Hamid Reza Kobravi; Abbas Erfanian Omidvar
Volume 2, Issue 4 , June 2008, , Pages 335-349
Abstract
In this paper an adaptive robust fuzzy controller based on sliding mode control (SMC) approach is proposed to control the knee joint position using quadriceps electrical stimulation and it has been tested on three subjects. The proposed method is based on SMC. The main advantage of SMC derives from the ...
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In this paper an adaptive robust fuzzy controller based on sliding mode control (SMC) approach is proposed to control the knee joint position using quadriceps electrical stimulation and it has been tested on three subjects. The proposed method is based on SMC. The main advantage of SMC derives from the property of robustness to system uncertainties and external disturbances. However, a large value has to be applied to the control gain when the boundary of uncertainties is unknown. Unfortunately, this large control gain may cause chattering on the sliding surface and therefore deteriorate the system performance. In this paper a robust control strategy proposed which is based on the combination of sliding mode, fuzzy logic systems, and an adaptive compensator to reduce the system uncertainties while alleviating the effects of chattering. The fuzzy logic system is used to identify the muscle-joint dynamics. The parameters of this fuzzy system were estimated using another fuzzy system. The controller is evaluated through the simulation studies on a virtual patient and experimental studies on intact subjects. The results show that the adaptive robust controller provides an accurate tracking of desired knee-joint angle for different subjects and different days and can generate control signals to compensate the muscle fatigue and reject the external disturbance.
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.
Biomedical Image Processing / Medical Image Processing
Amir Sezavar; Hassan Farsi; Farima Farsi
Volume 12, Issue 4 , January 2019, , Pages 341-355
Abstract
Prostate cancer is one of the most important diseases of men whose growth can be disrupted by early diagnosis of it. In order to determine the grade of prostate cancer, the biopsy is used and structure of tissue is examined under microscopes. According to new grading system, the prostate tissues are ...
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Prostate cancer is one of the most important diseases of men whose growth can be disrupted by early diagnosis of it. In order to determine the grade of prostate cancer, the biopsy is used and structure of tissue is examined under microscopes. According to new grading system, the prostate tissues are grading to five categories, between 1 to 5, where the highest grade shows the worst condition. Since human grading is time consuming, automatic grading systems have been used since recent years. Although some efficient algorithms have been introduced for image classification, the semantic gap between low-level features and human visual concept is still an important reason not to achieve high precision. In this paper, a new method for prostate cancer grading is presented which uses a combination of deep features, extracted by convolional neural network (CNN), and stochastic tissue features, extracted using multi-level gray level co-occurrence matrixes (ML-GLCM). Therefore, high-level features are achieved by using CNN and by combining with stochastic tissue features, the grading precision is increased. In order to evaluate the proposed method, it is examined on the pathology prostate image database which is generated by international society of urological pathology (ISUP). Experimental results demonstrate that the proposed method achieves more accuracy than state-of-the-art methods on prostate cancer grading.
Biofluid Mechanics / Biofluids
Milad Mahdinezhad Asiyabi; Bahman Vahidi
Volume 14, Issue 4 , February 2021, , Pages 345-355
Abstract
It is possible to replace or repair damaged tissue with regenerative medicine. Most tissues in the body rely on blood vessels to supply oxygen and nutrients to individual cells. New blood vessels are essential to grow tissue longer than 100-200 mm due to limited oxygen delivery; This restriction also ...
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It is possible to replace or repair damaged tissue with regenerative medicine. Most tissues in the body rely on blood vessels to supply oxygen and nutrients to individual cells. New blood vessels are essential to grow tissue longer than 100-200 mm due to limited oxygen delivery; This restriction also applies to engineered tissues. Therefore, one of the prerequisites for tissue survival and growth is the presence of vasculature. One way to overcome this limitation is to use microfluidic channels that are created by planting a layer of endothelial cells on the channel wall and applying in vitro flow. In this study, the channels were placed inside a type 1 collagen scaffold with 81% porosity, and a drainage channel was considered for the scaffold with lymphatic function. The geometry of the perfusion channel was based on Murray’s law. The effect of parameters such as drainage channel radius, perfusion channel pressure difference, scaffold hydraulic conductivity, and vascular hydraulic conductivity on transmural pressure and shear stress was investigated. The effect of the bifurcation angle on shear stress was also studied. The finite element method was used to solve the problem. In the simulation on a vessel with a diameter of 100 mm, the maximum interstitial velocity was 50E-9 m/s, the maximum interstitial pressure was 1.34E+3 Pa, and the minimum transmural pressure was 1.49E+3 Pa. The average shear stress on the vessel walls was 10 dyn/cm2. It was noted that reducing the pressure at the drainage channel outlet, the internal insulation of the scaffold from the pressure difference within the perfusion channel, reducing the vascular hydraulic conductivity, increasing the scaffold hydraulic conductivity, and increasing the radius of the drainage channel will create and maintain positive transmural pressure. The results of this study can be used in creating implantable tissue consisting of vascular network and drainage.
Biomedical Signal Processing / Medical Signal Processing / Biosignal Processing
Alireza Talesh Jafadideh; Babak Mohammadzadeh Asl
Volume 10, Issue 4 , January 2017, , Pages 347-359
Abstract
Minimum variance beamformer (MVB) and its extensions are most widely used techniques in brain source localization due to their high spatial resolution. Unfortunately, beacause of using data covariance matrix, these methods often fail when the number of samples of the recorded data sequences is ...
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Minimum variance beamformer (MVB) and its extensions are most widely used techniques in brain source localization due to their high spatial resolution. Unfortunately, beacause of using data covariance matrix, these methods often fail when the number of samples of the recorded data sequences is small in comparison to the number of electrodes. This condition is particularly relevant when measuring evoked potentials. For solving this problem, Fast Fully Adaptive (FFA) algorithm was developed a few years ago. This method is a multistage adaptive processing technique drawing its inspiration from the butterfly structure of the Fast Fourier Transform (FFT) and decreasing the data requirement significantly. Unfortunately, the high sensitivity of FFA to data partitioning sequences and also its low performance in low SNRs pose a doubt on using it as a reliable localizer for short time brain activities. In this paper, a preprocessing step is proposed to enhance the FFA method. In this step, the brain is divided into separate areas, the components of each area are determined, the data is projected to each area using components of that area. After that, FFA is applied to the projected data. The performance of the enhanced FFA is compared with FFA method by using simulated ERP and real ERF data. In all simulations, enhanced FFA shows the better performance in terms of localization error (enhancement about 2-10 mm) and spread radius (enhancement about 4-9 mm). In addition, the proposed method for real ERF data shows accurate localization result with the most concentrated power spectrum, compared to FFA approach. It is noteworthy that enhanced FFA offers less sensitivity to data partitioning sequences. Emprical results illustrate that enhanced FFA can be implemented as a reliable method for localizing brain short time activities.
Targeted Drug Delivery / Smart Drug Delivery / Drug Targeting
Seyed Ali Naghi Ahmadi; Tahere Fanaei Sheykhol-Eslami; Mehri Mehrjoo; Morteza Maleki
Volume 7, Issue 4 , June 2013, , Pages 351-360
Abstract
A secure self-biased remote controller for a drug delivery system, working at 956 MHz, is designed using piezoelectric substrate containing an implantable micropump. For this purpose, the effect of Lithium Niobate substrate on the actuation voltage, signal to noise ratio, insertion loss, bandwidth, and ...
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A secure self-biased remote controller for a drug delivery system, working at 956 MHz, is designed using piezoelectric substrate containing an implantable micropump. For this purpose, the effect of Lithium Niobate substrate on the actuation voltage, signal to noise ratio, insertion loss, bandwidth, and real and imaginary part of the admittance are investigated. The results of analytical calculation and numerical simulation show that the actuation voltage of the Lithium Niobate substrate is about 5.8 V, and the calculated bandwidth is 160 MHz with the signal to noise ratio of 26.52 dB. The security for actuation of the device is assured with Barker code. The insertion loss is equal to 2.1 dB which is adequate for maximum power transfer. Numerical simulation indicates that the generated voltage could create a displacement about 9.3353 nm in the conductive diaphragm, which is enough to ascertain the correct drug delivery by the micropomp. According to the analytical calculations and numerical simulations, the performance of the designed controller is qualified to correctly stimulate the drug delivery device.
Biomedical Image Processing / Medical Image Processing
Fateme Nazem; Alireza Ahmadian; Mohammad Javad Abolhasani; Nasim Dadashi; Masoume Gity; Mohammad Bagher Shiran
Volume 5, Issue 4 , June 2011, , Pages 351-358
Abstract
Abstract: Image guided liver surgery based on intra-operative ultrasound images has received much attention in recent years. Using an efficient point-based registration method to improve both the accuracy and computational time for registration of pre-deformation CT liver images to post-deformation Ultrasound ...
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Abstract: Image guided liver surgery based on intra-operative ultrasound images has received much attention in recent years. Using an efficient point-based registration method to improve both the accuracy and computational time for registration of pre-deformation CT liver images to post-deformation Ultrasound images is of great concern during surgical procedure. Although, Iterative Closest Point (ICP) algorithm is widely used in surface-based registration, its performance is strongly dependent on existence of noise and initial alignment. The registration technique based on the Unscented Kalman Filter (UKF) proposed recently can be a solution to overcome to noise and outliers on an incremental registration basis but it suffers from computational complexity. To overcome the limitations of ICP and UKF algorithms we proposed an incremental two-stage registration algorithm based on the combination of ICP and UKF algorithm to update the registration process based on arrival of intra-operative images. The two-stage algorithm is examined on phantom data sets. The results of phantom study confirm that the two-stage algorithm outperforms the accuracy of ICP and UKF by 23% and 13%, respectively and reduces the running time of UKF by 60%.
Spinal Biomechanics
Yousef Mohammadi; Rasoul Abedi; Navid Arjmand; Gholamreza Ataei; Nasser Fatouraee
Volume 11, Issue 4 , February 2018, , Pages 351-363
Abstract
The growth of low back pain and disoreders are increasing in different societies. Furthermore,the direct in vivo measurement of spinal and muscle forces is so difficult. Hence, the use of musculoskeletal biomechanical models has been emerged applicably as a tool for calculating and estimating spinal ...
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The growth of low back pain and disoreders are increasing in different societies. Furthermore,the direct in vivo measurement of spinal and muscle forces is so difficult. Hence, the use of musculoskeletal biomechanical models has been emerged applicably as a tool for calculating and estimating spinal forces under various activities. Thus, the purpose of this study is to estimate the mentioned forces with different methods especially in lifting tasks. To this end, a six-joint model with eighteen degrees of freedom and 76 trunk muscle fascicles has been developed. Due to more number of unknowns (muscle forces) than equilibrium equations, the system is redundant and the problem is indeterminate to be solved. So the electromyography assisted optimization (EMGAO) approach is used for estimating muscle forces. Since foregoing EMG muscle forces do not satisfy equilibrium equations, correction coefficients have been used for satisfying equilibrium at all lumbar joint levels. According to results in an identical task, all of the approaches indicated substantial differences in correction coefficients for each muscle. Although the stability and muscle forces are different in various EMGAO methods, spinal compression and shear forces are closer to each other in these methods. For validation of results, the intradiscal pressure (IDP) at L4-L5 in various methods are in agreement with in vivo IDP value of an experimental test measurement so that both of them reported this quantity in the range of 0.3-1.8 (MPa).
Cardiovascular Biomechanics
Sara Barati; Nasser Fatouraee; Malikeh Nabaei
Volume 15, Issue 4 , March 2022, , Pages 355-366
Abstract
Transcatheter aortic valves have become the standard procedure for high-risk patients with severe aortic valve stenosis. This minimally invasive procedure can expand to a wider range of patients with a lower risk of surgery. The complications after the implantation and the structural malfunction of these ...
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Transcatheter aortic valves have become the standard procedure for high-risk patients with severe aortic valve stenosis. This minimally invasive procedure can expand to a wider range of patients with a lower risk of surgery. The complications after the implantation and the structural malfunction of these prostheses are the obstacles of this transition. Design optimization of the stents of these prostheses can improve their performance and reduce the post-operative complications associated with them. Since all prostheses are crimped before implantation, the designs should guarantee an acceptable structural performance after expansion, especially self-expandable stents for which the fatigue behavior strongly depends on the strain. This study applies a simple, cost-effective optimization framework to optimize the geometric parameters of these stents regarding the maximum strain during the crimping process. The design parameters include diameter profile, cell size, number of repeating components, and strut cross-section. The simplified models are evaluated and verified by the 3D simulations. The results show that the middle cells' height, number of cells, and strut width have the most prominent effect on the maximum crimping strain of the stent. The maximum strain of the optimized stent in the selected design space was 0.52. This stent had a width of 0.2 mm, thickness of 0.3 mm, the number of cells and patterns of 3 and 15, respectively, and the diameter profile associated with the diameter ratio of 1.05. This framework can be applied to a wide range of stent designs and tremendously reduce the cost of stent design and optimization.
Mahdie Termeh; Afshin Ghanbarzadeh; Mohammad Hadi Honarvar; Kourosh Heidari Shirazi
Volume 13, Issue 4 , December 2019, , Pages 361-372
Abstract
A primary objective in many human upright state movements is control of balance and monitoring, analysis, and intervention to improve it, has become a part of human biomechanics research. In studies with a quantitative approach to human balance, it is necessary to know the numerical quantity of balance ...
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A primary objective in many human upright state movements is control of balance and monitoring, analysis, and intervention to improve it, has become a part of human biomechanics research. In studies with a quantitative approach to human balance, it is necessary to know the numerical quantity of balance in a body state or at any moment during a path. This study proposes a new quantitative Criterion to express stable state during walking cycle. The basis of this quantitative criterion is the Probability of dynamic success in completing the swing phase without losing balance and the initiation of a fall. The probability of motion realization has been calculated and simulated on a seven-link model with a distributed mass. In this study by taking into consideration the kinematic constraints, energy consumption, muscle stimulation level and changes in stimulation beside maximizing balance, the movement in stance phase is calculated as an optimal movement. The optimal step length has been calculated considering a weight for probability of motion realization and energy consumption. In this method both the maximum balance and minimum energy consumption have been considered. For instance, the optimal step length considering the maximum balance constraint in the specific path for an individual with the height of 187 cm and mass of 92 kg was calculated about 27 cm with this probabilistic approach. One of the factors in maintaining balance is cadence rate. By increasing the center of mass average velocity, the probability of balance maintenance decreases, thus also with considering center of mass average velocity beside maximum balance constraint, the optimal step length is calculated 46 cm.
Biomedical Signal Processing / Medical Signal Processing / Biosignal Processing
Fereshte Salimian Rizi; Vahid Abootalebi; Mohammad Taghi Sadeghi
Volume 9, Issue 4 , February 2015, , Pages 387-397
Abstract
Detection of Event Related Potentials (ERP) is an important prerequisite in the ERP-based Brain-Computer Interface (BCI) systems. In order to increase the classification accuracy in these systems, different filtering methods are used for improving the signal to noise ratio. This improvement facilitates ...
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Detection of Event Related Potentials (ERP) is an important prerequisite in the ERP-based Brain-Computer Interface (BCI) systems. In order to increase the classification accuracy in these systems, different filtering methods are used for improving the signal to noise ratio. This improvement facilitates the diagnosis and classification of the ERPs. In a number of studies, the performance of P300 detection systems which are based on common spatial pattern (CSP) and common temporal pattern (CTP) has been investigated. The former uses spatial filters while the latter is based on temporal filters. In these methods the filters are trained such that they maximize variance of one class and simultaneously minimize the other class variance. The associated results show that in P300 speller systems, the temporal filters outperform the spatial filters. In this study, in order to improve the performance of the CTP based systems, a Weighted Common Temporal Pattern (WCTP) algorithm which is a combined method is proposed. In this algorithm, each category of features has a weight based on the importance of its eigenvalues. In fact, the features produced by the initial and final CTP filters have more weight in the decision making process. In the combined method used in this algorithm, the LDA classifiers are used. It is shown that the set of features obtained by the WCTP method leads to an average classification accuracy of 90.2 percent which is about 4 percent better than the CTP method. The experiments are performed considering two different subjects on 5 trials.
Tissue Engineering
Farnaz Ghorbani; Ali Zamanian; Hanie Noje Dehian
Volume 8, Issue 4 , February 2015, , Pages 399-409
Abstract
In this study, we fabricated 3-dimentional PLGA-gelatin scaffolds with aligned-oriented pores by freeze casting technique which is similar to Extra Cellular Matrix (ECM), and evaluated its effect on both physical and mechanical features. Dissolving synthetic (PLGA) and natural (Gelatin) polymers in common ...
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In this study, we fabricated 3-dimentional PLGA-gelatin scaffolds with aligned-oriented pores by freeze casting technique which is similar to Extra Cellular Matrix (ECM), and evaluated its effect on both physical and mechanical features. Dissolving synthetic (PLGA) and natural (Gelatin) polymers in common solvent was one of the strengths of this investigation. Scanning electron microscopy (SEM) micrographs indicated that scaffolds contained 95% interconnected pores with diameter about 50-400 µm in horizontal direction and 50-200 µm in vertical direction. Moreover, the results of mercury intrusion porosimetry represented diameter of pores in range of 100–300 µm. According to fourieres transform infrared (FTIR) spectrum there was no inappropriate interactions during processing. Additionally, mechanical analysis (3.2 MPa) of PLGA-gelatin constructs illustrated that polymeric scaffolds can withstand mechanical loads in freezing direction. Based on the water absorption (950%) and biodegradation results, samples can support cellular interactions and prevent their integrity during tissue regeneration. In brief, freeze casted PLGA-gelatin scaffolds can provide unidirectional matrix with desired physical and mechanical characters to regenerate lesions.
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 ...
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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.
Biomedical Signal Processing / Medical Signal Processing / Biosignal Processing
Mina Amiri; Edmond Zahedi; Fereydoun Behnia
Volume 7, Issue 1 , June 2013, , Pages 85-95
Abstract
It is proved that the endothelial (artery inner lumen cells) function is associated with cardiovascular risk factors. Among all the common non-invasive methods employed in the research setting for assessing endothelial function, flow-mediated dilation is the most widely used one. This technique measures ...
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It is proved that the endothelial (artery inner lumen cells) function is associated with cardiovascular risk factors. Among all the common non-invasive methods employed in the research setting for assessing endothelial function, flow-mediated dilation is the most widely used one. This technique measures endothelial function by inducing reactive hyperemia using temporary arterial occlusion and measuring the resultant relative increase in blood vessel diameter via ultrasound. In this paper, the limitations associated with the ultrasound technique are overcome by using the photoplethysmogram (PPG) signal recorded during FMD. The correctness of this approach is investigated by modeling the AC changes of PPG after FMD by a 2nd order autoregressive model. A sensitivity of 78.6%, specificity of 81.6% and total accuracy of 80% were achieved in classification of 16 healthy and 14 diabetic subjects.
Hossein Banki-Koshki; Mohammad Tafazoli Shadpoor
Volume 10, Issue 1 , May 2016, , Pages 85-97
Abstract
Along with advancement in medical technologies, the academic field of Biomedical Engineering (BME) was developed. BME which was once considered as a subdivision of other disciplines, has gradually become an independent discipline with established departments. The extended medical and biological applications ...
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Along with advancement in medical technologies, the academic field of Biomedical Engineering (BME) was developed. BME which was once considered as a subdivision of other disciplines, has gradually become an independent discipline with established departments. The extended medical and biological applications of the new discipline resulted in itsrapid progress. It is essential for academic centers to examine novel education and research areas of biomedical engineering every few years. In this paper we presented educational and research status of biomedical engineering among world's 50 top universities from different continents. We used three world university rankings (Time, QS, CWUR) to select top universities in 2016. Overally we studied 17 universities from America, 19 universities from Europe and 14 universities from Asia and Oceania. The undergraduate and postgraduate educational programs were presented and the independency status of biomedical engineering departments were studied using four models and results were compared among universities from different continents. The foundation year and number of academic staff of BME departmentswere further shown.Moreover, the BME researchfiledswere shown and compared among top universities from different contients and the most prevalent research areas were presented.
Tissue Engineering
Giti Torkamaan; Ali Akbar Sharafi; Ali Fallah; Hamid Reza Katouzian; Mahmoud Mofid
Volume -1, Issue 1 , June 2004, , Pages 93-100
Abstract
Pressure ulcers are areas of tissue necrosis that tend to develop when tissue is compressed between a bony prominence and an external surface. Normal structure and physiological function of tissue viability are recognized but mechanism of tissue breakdown is unknown. In this study, an attempt has been ...
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Pressure ulcers are areas of tissue necrosis that tend to develop when tissue is compressed between a bony prominence and an external surface. Normal structure and physiological function of tissue viability are recognized but mechanism of tissue breakdown is unknown. In this study, an attempt has been made to recognize the tissue mechanical changes after pressure application using 61 male albino guinea pigs, 4-6 months old, weighing 300-450 g. A computer controlled indentor system was developed to induce pressure sore. This system is capable of monitoring and adjusting the applied pressure, friction and shearing force throughout the experiment. The applied force remained within ±10g of desired target force. The applied pressures were at 291 and 387 mmHg for 1,3 or 5 hours over the trochanter region of animal hind limb. The tissue was removed and blood was taken immediately, 2 and 7 days after pressure release. Uniaxial tensile test was performed using deformation rate of 20 mm/min. In this test, the contralateral site on the experimental animal served as intra-animal control. Full- thickness biopsy was taken and stained with H & E, trichrome and orcein for histological examination. Results of tensile tests showed that the maximum tensile strength (Fmax), stress and the area under load-deformation curve (work) have decreased significantly 7 days after pressure application (P<0.05). Histological study immediately and 2 days after force release, showed an increase in cellularity and inflammatory cells infiltration. Muscle necrosis and reduction of the skin fibers density were observed 7 days after load release. Serum CPK (2 days after) was increased. The amount of lactic acid as well as phosphorus immediately and 2 days after pressure also increased (P<0.05). Finally it was distinguished that pressure changed the biomechanical properties of skin and muscle. Decrease of tissue resistance was consistent with the histological findings as well as elevation of muscle specific enzymes in blood. It was also observed that pressure resulted in the tissue ischemia and breakdown.
Biomedical Image Processing / Medical Image Processing
Somayeh Maleki Balajoo; Davoud Asemani; Hamid Soltanian-Zadeh
Volume 9, Issue 1 , April 2015, , Pages 99-111
Abstract
Although the cognitive deficits due to age-related brain differences have been largely analyzed, the altered connectivity of task related functional networks in aging requires more studies. As the brain of old adults experience some alterations in task performance during cognitive challenges, the related ...
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Although the cognitive deficits due to age-related brain differences have been largely analyzed, the altered connectivity of task related functional networks in aging requires more studies. As the brain of old adults experience some alterations in task performance during cognitive challenges, the related effects on connectivity of functional networks are here evaluated using event-related functional Magnetic Resonance Imaging (fMRI). The fMRI data have been acquired for simple visual and motor tasks. For each subject, several Functional Connectivity (FC) networks including, motor, visual and the default mode networks are firstly calculated using a conventional voxel-wise correlation analysis with predefined region of interest. Then, the strength of functional connectivity is assessed and compared for different age groups. The current study has evaluated three hypotheses on FC of aging brain: the frontal regions involved with motor network try to compensate for declines in the posterior regions, default-mode network is less suppressed and, the posterior regions involved with visual network exhibit less connectivity. The first two hypotheses are accepted by analysis results but visual network behaves differently. Also, results show that the task related functional connectivity is considerably altered in old adults compared to young adults. Old adults demonstrate higher connectivity strength on average with a slightly smaller variance than young adults.
Neuro-Muscular Engineering
Sohrab Barimani; Ali Maleki; Ali Fallah
Volume 8, Issue 1 , March 2014, , Pages 101-111
Abstract
FES based method used for rehabilitation of patients with spinal cord injury (SCI). One of these methods is FES cycling. FES cycling exercise has to be useful among SCI patients because of creating a periodic activity in the muscles of the lower extremities and stability of seating position. The major ...
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FES based method used for rehabilitation of patients with spinal cord injury (SCI). One of these methods is FES cycling. FES cycling exercise has to be useful among SCI patients because of creating a periodic activity in the muscles of the lower extremities and stability of seating position. The major challenge for application of FES in rehabilitation is early fatigue occurrence in electrically stimulated muscles. Motor control system selects a low-cost path among the infinite possible route to the body's movements. High efficiency and the minimum rate of muscle fatigue are main characteristics of the motor control system. This type of control system is called muscle synergy. In this study, the quantification of muscle synergy between the core muscles in cycling has been done by non-negative matrix factorization (NMF) method and considering the kinesiology basis. Four synergies were determined as appropriate and optimal synergies to describe the cycling in different mechanical terms. VAF criteria with regard to the four synergies to describe cycling in speeds of 40, 50 and 60 rpm are 92±4, 92±3 and 91±4% respectively and torques, 5, 7 and 9 Nm are 91±3, 92±5 and 92±4% respectively. Correlation between Synergies extracted at different mechanical terms is 98.4 percent in average.
Biomedical Image Processing / Medical Image Processing
Abbas Biniaz; Ataollah Abbasi; Mousa Shamsi
Volume 7, Issue 2 , June 2013, , Pages 175-186
Abstract
Segmentation divides an image to some subdivisions where which of ones has similar intensity gray levels. Among clustering methods fuzzy c-means (FCM) clustering has been frequently used for segmentation of medical images. However, this algorithm doesn’t incorporate spatial neighborhood information ...
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Segmentation divides an image to some subdivisions where which of ones has similar intensity gray levels. Among clustering methods fuzzy c-means (FCM) clustering has been frequently used for segmentation of medical images. However, this algorithm doesn’t incorporate spatial neighborhood information in segmentation. This approach is very susceptible to nuisance factors. Therefore this paper proposes a Gaussian spatial FCM (gsFCM) to MR image segmentation. Proposed method has less sensitivity to noise specially in tissue boundaries, angles, and borders than spatial FCM (sFCM). Furthermore by the suggested algorithm a pixel which is a separate tissue from structurally point of view for example a tumor in primary stages of its appearance, has more chance to be a unique cluster. Applying quantitative assessments using Jaccard similarity index, Dice coefficient, and other validation functions on FCM,sFCM and gsFCM approaches show efficient performance of the proposed method. In this research the ISBR data bank is used for simmulations.Moreover in medical applications getting patient condition and information with fast methods is very important especially in emergency circumstances. Therefore all effective agents in patient health must be fast even medical algorithms such as clustering ones . Hence in this paper to decrease the time of convergence considerably and decline the number of iterations significantly, cluster centroids are initialized by an algorithm.
