A New Method For Selective Stimulation In Cochlear Implant Using Non-Simultaneous Multi Electrode Stimulation
Hamed
Sajedi
Electrical Engineering Department, AmirKabir University of Technology
author
Seyed Ahmad
Motamedi
Electrical Engineering Department, AmirKabir University of Technology
author
Seyed Mohammad
Firouzabadi
Medical Science Department, Tarbiat Modarres University
author
text
article
2004
per
Auditory nerve fibers stimulating using electrical current with implanted electrodes are the basis of cochlear implant system. Therefore, expansion of current spread in volume conductor will change the electrical potential in a larger region. This expansion causes larger region stimulation and decreases the accuracy and resolution of the stimulation in both the possibility of investigation of a particular region at Neural Response Telemetry (NRT) tests and also in hearing stimulation. Therefore, narrowing the width of stimulated region is the main goal in the selective stimulation. The conventional multi polar stimulation methods use lateral inhibitory electrode to form the spatial pattern of the electrical potential distribution for narrowing the stimulated region, but it needs to simultaneous stimulation of the electrodes, which is not available in implanted systems. In this paper, a new non-simultaneous multi-electrode stimulation method has been presented, which is based on applying the inhibitory pre-pulses by lateral electrodes. Inhibitory effect of the lateral electrodes pulses changes the initial conditions of the fibers and their thresholds. The results of simulations show that this method will solve the problem of simultaneous stimulation in conventional tri-polar stimulation methods and also is effective at controlling of stimulation area, comparing with tri-polar stimulation area, qualitatively and quantitatively.
Iranian Journal of Biomedical Engineering
Iranian Society for Biomedical Engineering
5869-2008
-1
v.
1
no.
2004
3
14
https://www.ijbme.org/article_13512_9432ff669de4487b363db2ab9633dc23.pdf
dx.doi.org/10.22041/ijbme.2004.13512
Sensitivity Analysis Of Muscle Activation-Joint Position Using Computer Simulation Of A Model For The Thumb And Index Finger
Ali
Esteki
Department of Medical Physics and Engineering, Shahid Beheshti University of Medical Sciences
author
text
article
2004
per
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.
Iranian Journal of Biomedical Engineering
Iranian Society for Biomedical Engineering
5869-2008
-1
v.
1
no.
2004
15
23
https://www.ijbme.org/article_13513_d708e8d7fdedec0b8ad8b7a92d780961.pdf
dx.doi.org/10.22041/ijbme.2004.13513
Detection Of The Cognitive Components Of Brain Potentials Using Wavelet Coefficients
Vahid
Abootalebi
Department of Biomedical Engineering, AmirKabir University of Technology
Research Center of Intelligent Signal Processing
author
Mohammad Hasan
Moradi
Department of Biomedical Engineering, AmirKabir University of Technology
author
Mohammad Ali
Khalilzadeh
Research Center of Intelligent Signal Processing
Department of Biomedical Engineering, Azad University of Mashhad
author
text
article
2004
per
P300 is the most predominant cognitive component of the brain signals. In this study, the single trial event related potentials recorded from the scalp, were decomposed to their time-frequency components using discrete wavelet transform. These quantities were later analyzed as the features related to the cognitive activities of brain. Study on these features showed that cognitive processes of the brain of ten reflected in the feature of δ and θ bands. The aim of this study, as a primary step for "lie detection using brain signals (EEG - Polygraphy)", was to design a system for discriminating between single trials involved P300 and those without it. In the first approach, an optimal discriminant function based on 9 features was designed using "Stepwise Linear Discriminant Analysis". Detection accuracy was 75% in training data and 71% in test data. More study on this method showed that almost similar accuracy could be obtained from the features of Pz channel alone. In the second approach, the modular learning strategy - based on principal component analysis and neural networks - was used. After training the systems, the maximum classification accuracy was 76% in train data and 72% in test data.
Iranian Journal of Biomedical Engineering
Iranian Society for Biomedical Engineering
5869-2008
-1
v.
1
no.
2004
25
45
https://www.ijbme.org/article_13514_879affa45c42a4bd98b857c8b863020d.pdf
dx.doi.org/10.22041/ijbme.2004.13514
Synthesis Of Amorphous Calcium Phosphate And Its Solubility Behavior In Simulated Osteoclastic Activity Conditions
Abdorreza
Sheikh Mehdi Mesgar
Bioceramics Lab, Department of Biomedical Engineering, AmirKabir University of Technology
author
Zahra
Mohammadi
School of Mechanical Engineering, Iran University of Science & Technology
author
text
article
2004
per
The conditions for synthesis of amorphous calcium phosphates (ACPs) according to the crystallization principles were described. By selecting reaction parameters correctly (low temperature, high pH, immediate removing of water and using solutions containing calcium cations and phosphate anions at low concentrations), full ACPs can be reproducibly synthesized. The X-ray diffraction patterns of synthesized amorphous specimens were showed a characteristic broad peak. The Ca/P ratio of the resulting precipitates was weakly dependent on the initial Ca/P ratio. Solubility of synthesized specimens in simulated osteoclastic activity conditions was showed that the rate of dissolution would be decreased with increasing crystallinity level. The synthesized amorphous calcium phosphates showed the highest dissolution rate in the simulated solution, and can be a suitable candidate for using in the field of hard tissue engineering applications.
Iranian Journal of Biomedical Engineering
Iranian Society for Biomedical Engineering
5869-2008
-1
v.
1
no.
2004
47
55
https://www.ijbme.org/article_13515_e5a7f89456bbe2084d55e6ad413c575d.pdf
dx.doi.org/10.22041/ijbme.2004.13515
Fabrication Of A Porous Composite Scaffold For Bone Tissue Engineering Based On Gelatin And Hydroxyapatite, Part I: Cell Culture Results
Karim
Asgarzadeh Tabrizi
Department of Biomedical Engineering, AmirKabir University of Technology
author
Fariba
Ourang
Biomaterials Group, Department of Biomedical Engineering, Amir Kabir University of Technology
author
text
article
2004
per
Gelatin is a protein which is derived from the organic constituent of bone (collagen). Combination of this protein with the inorganic constituent of bone (hydroxyapatite) may provide closer properties to the natural bone. In this study, a biodegradable composite scaffold based on gelatin and hydroxyapatite was prepared as a substitute for bone tissue. To increase the biocompatibility of this, composite, its fabrication was carried out without using any organic solvent. Porosities obtained were spontaneously achieved without any porogen. The pore morphology indicated a high interconnectivity with diameters ranging from 50 to 200 micrometers, which seems appropriate for bone tissue engineering applications. In order to study the biocompatibility of the scaffolds, mouse fibroblastic cells were used. After 24-hour cell culture period in vitro, suitable cell attachment was observed showing high biocompatibility for all the samples. Further examinations demonstrated that the best biocompatibility is obtained for the composite of 50 wt% hydroxyapatite and 50 wt% gelatin.
Iranian Journal of Biomedical Engineering
Iranian Society for Biomedical Engineering
5869-2008
-1
v.
1
no.
2004
57
64
https://www.ijbme.org/article_13516_55a03d6d9338770f268d8912ce53fc46.pdf
dx.doi.org/10.22041/ijbme.2004.13516
Effects Of Depolarizing Prepulses With Different Parameters On The Selective Stimulation Of Myelinated Fibers And Suggestion Of A New Prepulse Waveform With Superior Performance Based On Simulation Of
Amin
Mahnam
Bioelectrics Division, Department of Biomedical Engineering, AmirKabir University of Technology
author
Seyed Mohammad
Firouzabadi
Medical Physics Department, Faculty of Medicine, Tarbiat Modarres University
author
Seyed Mohammad Reza
Hashemi Golpayegani
Bioelectrics Division, Department of Biomedical Engineering, AmirKabir University of Technology
author
text
article
2004
per
In recent years, various methods have been suggested to improve selectivity in electrical stimulation of neural fibers or cells. One of these methods is the use of depolarizing under-threshold prepulse to selectively stimulate fibers far from the electrode, without excitation of nearer fibers. In this paper, by implementing a nonlinear model of neural fiber and simulating electrical stimulation of the model, the effect of changes in various parameters of rectangular and stepwise prepulses on the range of applicability of this technique in selective stimulation of fibers in different distances from the electrode and with different diameters has been studied. This study has led to suggest a new waveform for the prepulse; ramp prepulse. The applicability of this prepulse has been studied also. The superiority of this prepulse in comparison with previous suggested ones has been shown. Using this prepulse, it is possible to stimulate selectively fibers in broader range of distances and diameters. Therefore in stimulating neural fibers in spinal cord or peripheral fibers or even neural fibers of special senses, the use of this prepulse can improve distinguishability of fibers in their stimulation.
Iranian Journal of Biomedical Engineering
Iranian Society for Biomedical Engineering
5869-2008
-1
v.
1
no.
2004
65
76
https://www.ijbme.org/article_13517_81a6405b0c5c57c3c00b68a7aecca476.pdf
dx.doi.org/10.22041/ijbme.2004.13517
New Combined Electrochemical Path Modeling Of The Heart Based Membrane Ionic Channels
Farhad
Tabatabaei Ghomshe
Biomechanics Division, Department of Biomedical Engineering, AmirKabir University of Technology
author
Ahmad Reza
Arshi
Biomechanics Division, Department of Biomedical Engineering, AmirKabir University of Technology
author
Masoud
Mahmoudian
Faculty of Medicine, Department of Pharmacology, Iran Medical Sciences University
author
Mahyar
Janahmadi
Faculty of Medicine, Department of Physiology, Shaheid Beheshti Medical Sciences University
author
text
article
2004
per
Effective pharmacological analysis encompassing both the pharmacodynamics and the pharmacokinetics of the heart, dictates the necessity for responses made by the main channel receptors, to be appropriately modelled. This approach is of critical value when the pharmacological responses of the organ during pathological states are under investigation. To this effect, the electrochemical phenomenon in the heart was simulated using a specifically simplified three dimensional model based on the cellular physiological concepts. Various advanced models for different types of heart cells were combined to produce a three dimensional model capable of describing the electrophysiological, electrochemical and geometric characteristics of a heart in a non-pathological state. Various cell type models such as central and peripheral SA node, AV node, atrial myocyte, ventricular myocyte, and specialized cells for rapid conductance like purkinje fibres were included in the 3D model. The cellular architecture in the model follows the non-heterogeneity of the heart structure accompanied by gap junctions representing cellular interconnections. Here the transport of Na+, Ca++, K+ and CL- was primarily governed by such factors as electrical and chemical potential gradients along with other energetic mechanisms. The simplified heart geometry is introduced through 18 layers with 25 cells in each layer. Model equations were solved to simulate a one second using a 2.6 GHz Pentium IV PC. The simulation was performed utilizing MA TLAB programming language which provides effective visualization capabilities. The CEP model could be adopted as a preliminary basis towards individualizations in pharmacology and electrophysiology.
Iranian Journal of Biomedical Engineering
Iranian Society for Biomedical Engineering
5869-2008
-1
v.
1
no.
2004
77
92
https://www.ijbme.org/article_13518_62a1212be709c51316ec207219ba252b.pdf
dx.doi.org/10.22041/ijbme.2004.13518
Skin Response To Applied Pressure In Model Of Guinea Pig
Giti
Torkamaan
Physical Therapy Department, Tarbiat Modarres University
author
Ali Akbar
Sharafi
Department of Radiology, Iran University of Medical Sciences
author
Ali
Fallah
Department of Biomedical Engineering, AmirKabir University of Technology
author
Hamid Reza
Katouzian
Department of Biomedical Engineering, AmirKabir University of Technology
author
Mahmoud
Mofid
Department of Anatomy, Baghiyatollah University of Medical Sciences
author
text
article
2004
per
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.
Iranian Journal of Biomedical Engineering
Iranian Society for Biomedical Engineering
5869-2008
-1
v.
1
no.
2004
93
100
https://www.ijbme.org/article_13519_584329a6510591d1d3d822046aff3cbe.pdf
dx.doi.org/10.22041/ijbme.2004.13519