فصلنامه مهندسی پزشکی زیستی
سال نهم شماره 2 (تابستان 1394)

Due to teeth robustness, uniqueness and availability of medical records, today a new branch of research for human identification is ongoing based on dental radiograph images. This method of identification has particular importance especially in events such as wars, fires, tsunamis and other similar events with other biometrics features heavily damaged. In this article also a framework for human identification based on dental characteristics is proposed.
The proposed framework consists of two stages: the first stage is teeth classification and numbering, and the second stage is teeth recognition. In this study, a new feature has been proposed for each of these two stages: Crown mesiodistal neck and anatomic crown length for the first and weighted sampling of teeth contours for the second. The proposed method is capable to solve principally and automatically problems such as diagnosis of posterior teeth, posterior teeth classification, diagnosis of number and kind of pulled teeth, which are overlooked or have been left with the simple premises in previous works.
To evaluate the proposed method, experiments on a set of bitewings, periapical and panoramic images are done. The practical results show an improvement of 8% in accuracy of classification and numbering, and also 27% improvement in accuracy of teeth recognition, in comparison with the preceding works.

Myocardial diseases are on the rise all over the world and due to lack of sufficient donors, heart transplants are not the perfect solutions to treat all patients with heart failure. Therefore, in recent years, blood pumps have received a worldwide admissibility and have become the unrivalled tools for replacing a failed heart. In addition to biological needs such as sufficient head and flow rate, an assist blood pump should be in an acceptable margin of safety in terms of blood injuries such as hemolysis and thrombosis. Reducing blood damages, minimizing dimensions, reducing exposure time and simulating blood flow of natural heart are amongst the greatest challenges in designing assist blood pumps. One of the most important factors in determining the amount of blood injuries inside the pump is the blades’ shape of different parts of the pump. Studies have been conducted about heart pumps show that it is feasible to increase the efficiency of the pump and reduce the stagnation points that lead to thrombus formation by changing the type of blades of the impeller. The purpose of this study is to compare the performance of several airfoils for the blades of the impeller of an assist heart pump in order to optimize the performance and efficiency of the pump and reduce blood damages.

A tumor cannot grow more than a few millimeters without a blood supply (avascular tumor), and for further growth it must initiate angiogenesis process. A vascularized tumor, which is permeated with blood vessels, rapidly increases in mass because of the new source of oxygen. In this study, a discrete mathematical model of angiogenesis process with considering the penetration of blood flow through the vessels in the two-dimensional network is presented. This structure is coupled with an adaptive model of sprouts spacing along the parent blood vessel at the beginning of the angiogenesis process. Then, progression of these sprouts in the extracellular matrix and their penetration into the tumor as well as penetration of blood flow through the capillary structure is presented. This model incorporates three steps of adaptive sprout spacing along the parent blood vessel, sprout progression, and blood flow and network remodeling. Then, based on the simulated vasculature network, oxygen transmission and other vital chemicals needed for continuous tumor growth are simulated. In this model we assumed that the growth of the tumor is driven by cell division. The tumor growth and angiogenesis are coupled by the changes of micro environment including oxygen, tumor growth factor, and the extracellular matrix concentration. Also, we have tried to create space and time adaptations in parameters of the model.

The humans’ heart is a chaotic system so use of fractal dimension to identify cardiac arrhythmias has been considered. Cardiac arrhythmias are prevalent diseases that is very important to be diagnosed. Hurst index which is calculated using rescaled range analysis method, is used as a criterion to evaluate chaotic systems and to quantify the fractal dimensions. Previous studies have shown that classical Hurst index is not appropriate for classification of cardiac arrhythmias because not only selection of algorithm parameters affect the value of determined Hurst index, but also it significantly varies as the heart rate changes. In this paper, modified multiple Hurst index has been proposed to classify the cardiac arrhythmias. The presented index is resistant against changes in heart rate and can be used to identify appropriate features to classify the cardiac arrhythmias. 80 signal from four types of ECG beats (normal, left bundle branch block, right bundle branch block and atrial premature beats) obtained from the MIT-BIH Arrhythmia dataset has been used to validate the algorithm. Results show that this method is able to detect normal rhythm and right bundle branch block (RBBB), left bundle branch block (LBBB) and atrial premature complex (APC) arrhythmias with accuracy of 100%, 96.25% and 88.75% using artificial neural network, k nearest neighbor and LDA classifiers respectively.

Investigating the mechanical stimuli on stem cells under in vitro and in vivo conditions is a very important topic to achieve an ability to control the cellular responses like growth, proliferation and differentiation. Many investigations carried out about biomechanical factors involved in this phenomenon and nowadays, it is proved that some factors like as cell morphology, subcellular elements configuration, scaffold architecture, substrate stiffness and mechanical stimulation via substrate displacement or fluid flow, have got an important effect on cellular responses. In this study, we have tried to evaluate the responses of a stem cell to the stiffness and thickness of the substrate by the means of finite element method. For this purpose, we have used collagen-based scaffolds as the artificial ECM and a cell culture in a bioreactor with fluid flow was simulated.by use of fluid-structure interaction method and solving the equations in two-way coupling scheme, the results show that the increase in thickness and stiffness of the substrate will result in 15 percent change in cell-substrate stresses, respectively. Also, it was seen that the change of substrate stiffness only in the range of 0.1-100 KPa could affect the cell response to an external stimulation.These results, along with other similar investigations, could be used as an instructor by the researchers to optimize the stem cell’s microenvironment in vitro, and finally get the most out of their stem cell related Investigations.

In the current study, a novel method for deriving the governing equations of the skeletal system of the human body has been presented. In this method, a novel approach for incorporating the kinematic characteristics of biological joints and also the effects of complex kinematic chains of the skeletal system has been proposed. The suggested method while utilizing the calculus of matrix-valued functions, derives the governing equations of the skeletal system in the form of ordinary differential equations. Moreover, since the formulations were presented in a recursive fashion, this paper suggests a computationally efficient algorithm to derive the differential equations of motion for the skeletal system. In order to examine the validity of the proposed formulations, a benchmark mechanism with three closed-loop kinematic constraints were considered. We compared the results obtained from our formulations with the outcomes presented in other studies and validated the proposed formulations. Besides, in order to investigate the application of the suggested method in simulation of the skeletal system of the human body, dynamical modeling of the shoulder rhythm was taken into consideration. Two models were employed for describing the shoulder rhythm: Original model and simplified model. The discrepancies observed between the outcomes of these two models delineate the necessity of using the original data for the shoulder rhythm. While the limitations of the available formulations have compelled the researchers to employ the simplified model for the shoulder rhythm, with the method we propose in this study this problem is obviated.