فصلنامه مهندسی پزشکی زیستی
سال پنجم شماره 2 (تابستان 1390)

in this paper, a novel and effective algorithm for classification of important heart arrhythmia is presented. The proposed algorithm uses heart rate variation (HRV) signal which has better chaotic characteristics. In addition to commonly used linear time domain and frequency domain features, nonlinear (chaotic) features are examined, too. To increase classification accuracy and facilitate learning, two techniques are used: a) extracted features are reduced by generalized discriminant analysis (GDA) and b) by a self organizing map (SOM), the most informant data are selected. Chaotic features help to improve diagnosis accuracy from 92% up to 97%. The results indicate the importance of GDA and SOM in efficiency of proposed algorithm. MLP, SVM and PNN classifiers are examined and compared. The proposed algorithm was able to diagnose 7 arrhythmias PVC, AFL, AF, CHB, LBBB, VF, VT and normal sinus rhythm (NSR) with 97.4% accuracy.

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.

In this study we evaluate parameter of nonlinearity and parameter of h by measuring of the amplitude of the second harmonic component and the fundamental component.This method is a variation of the finiteamplitude that has been adopted for pulse echo measurements. We used normal and cooked pork muscle in-vitro. For B/A the result is showed as image and for h the result obtain as absolute mean.The result showed that these parameters can distinguish between normal and cooked tissue.This method was considered to be usable for control and monitoring HIFU.

Based on previous studies, human motor control system may apply two control strategies, impedance control and model based control, for learning motor skills and counteracting environmental instabilities. Since interaction among these controllers is not fully studied, the investigation of impedance and model based controllers function during learning period seems desirable. In this study a supervisory controller was used to coordinate the model based and impedance controllers. Coordinating model based controller and impedance controller by using supervisory unit will result in simultaneously adjustment of forward motor command and joint stiffness. In order to evaluate performance of the suggested model, it was applied to arm reaching movements in the presence of external force fields. Results showed that both suitable impedance values and a proper internal model are required to fulfill movements similar to those of humans under different circumstances. Research has shown that central nervous system is able to purposefully modulate arm impedance to counteract environmental disturbances. This study showed that beside this modulation, the maximum motor learning may occur in direction with the least impedance and the most kinematic error. It also concluded that confronting abrupt changes in disturbance, the system managed to decrease error without learning the new dynamic using previous knowledge by supervisory system. A part of this compensation is due to stiffness variations and another part is due to decreasing the influence of model based controller.

Prediction of the relationship between different types of mechanical loading and the failure of the intervertebral disc is so important to identify the risk factors which are difficult to study in vivo and in vitro. On the basis of finite element methods some of these issues may be overcome enabling more detailed assessment of the biomechanical behavior of the intervertebral disc. The objective of this paper is to develop a nonlinear axisymmetric poroelastic finite element model of lumbar motion segment and show its capability for studying the time-dependent response of disc. After comparison of the response of different models in quasi-static analysis, the poroelastic model of intervertebral disc is presented and the results of short-term, long-term creep tests and cyclic loading were investigated. The results of the poroelastic model are in agreement with experimental ones reported in the literature. Hence, this model can be used to study how different dynamic loading regimes are important as risk factors for initiation of intervertebral disc degeneration.

Silk fibroin is fibrous proteins with excellent mechanical properties which are produced by wide group of animals such as Bombyx Mori. Silk fibroin with specific molecular structure can be processed into a diverse set of morphologies. Additionally, biotechnologically produced silk proteins will allow the preparation of a new generation of protein-based bio-polymeric materials with programmed properties for a wide variety of exciting medical applications. In this study, silk protein was extracted from Bombyx Mori’s cocoons and evaluated by FTIR and XRD methods. Results showed sharp amide peaks in 1655 cm-1 and 1530 cm-1 wavelength in FTIR spectrum pattern confirming existence of fibroin. SEM images of the fibers showed continuous fibers with cross-section between 14 to 24 μm. Biocompatibility tests were carried out through seeding osteoblasts cell line G292 on 2D film as well as fibers. Adhesion and proliferation of osteoblasts were investigated by MTT assay which showed no cytotoxicity. Therefore, fibroin appears to be remarkable material for prospect application in biomedicine.

Ergonomic factors have a direct influence on the quality of spine support during sleep. Previous studies have shown that a mattress with a homogeneous stiffness can not necessarily maintain the natural spinal alignment. Using mattresses with components of different stiffness could be considered as a possible solution instead. In this research a new mattress system having elements with different stiffness has been designed. The springs used in this mattress has been combined with a special slice of polyurethane foam, and each of them has its own specific spring constant. After acquiring the anthropometrical data of 25 male volunteers, they were asked to lie in a lateral position on soft and very stiff surfaces according to predefined conditions. Then the coordinates of the markers mounted on their spinous processes were registered through the optical tracking methods. In the next step the arrangement of the foam-spring elements were changed for each subject several times, in order to spinal alignment in a frontal plane was close to his normal alignment corresponding to the upright position. The post-processing of acquired data was considered off line.In order to qualify our experiments the BRG.LifeMod was used to model body position when lying on a mattress. The anthropometrical data of 4 subjects were used for the dimensional indexes of model. Several numerical models were built with several surfaces corresponding to the experimental essays. Once again the spinal alignment extracted. Results of both experimental and numerical modeling showed that the mattress with custom-made arrangement of the elements is an appropriate solution for the optimal support of the spine during sleep. The numerical modeling was able to predict the spinal alignment. The results of this research can be very useful in designing the custom-made sleep systems according to the ergonomic factors.