Design and Implementation of a Constant Tension Mid-Upper Arm Circumference (CT-MUAC) device for improved detection of malnutrition in children

Mid-upper arm circumference (MUAC) is an important indicator of the nutritional index, particularly of children in low resource countries of the world. It is a significant anthropometric tool with simple cut-off values which is easy to implement in large scale screening measurements. A conventional MUAC device is essentially an insertion strap and has many merits over other anthropometric measurements techniques, but a lack of reproducibility in measurements is its leading problem since the measurement depends on how strongly a person pulls the strap around an arm of the subject. The aim of the present study is to minimize this reproducibility problem. For this the existing MUAC device has been modified using a short length of an elastic band to provide a constant tension while measuring, making it a Constant Tension MUAC device. Using both the MUAC devices (conventional and CT-MUAC), data were collected from seven subjects by 70 observers (10 observers measuring one subject). Statistical analyses showed that the CT-MUAC device gives a significant improvement with less variability over the conventional device. Thus, the new CT-MUAC device has the potential for improved detection of malnutrition throughout the world. Bangladesh Journal of Medical Physics Vol.11 No.1 2018 P 26-37

A new mechanism controlling conduction in stretched myelinated nerves and a comprehensive nerve conduction model

Analysing published experimental findings this paper revealed that for myelinated nerves the conduction velocity (CV) increases on stretching out of the nerve, which has not been pointed out by anyone before. This apparently contradicts existing concepts since stretching out of a nerve fibre reduces its diameter which is expected to reduce the CV. Besides, the change is reversible and immediate, which cannot be explained with existing knowledge either. In order to explain this anomaly, the present work invoked a new resistance to ion flow between the nerve axon and the extracellular fluid created by interdigitated fingerlike processes of myelin sheaths coming from two sides of a node of Ranvier, analyzing published electron microscopic images. When stretched out, the gaps between the processes increase, decreasing the resistance to ion flow and thereby hastening depolarization, increasing CV in turn. The gaps close immediately on the release of the stretching force because of the pull of the elastic endoneurium, thus retrieving the original CV. To represent this new mechanism, a new resistive element has been added to the existing electrical model of a myelinated nerve, which is being claimed to be the dominant component that determines the conduction delay. Stretching also affects other nerve parameters and this paper developed a mathematical formulation involving all these parameters to show satisfactorily that CV indeed increases with stretching, in which the contribution of the proposed resistance dominates. The paper also proposed an appropriate modification of the representative schematic model commonly used to depict propagation of action potential in a myelinated nerve fibre. The suggested new mechanism and the resistance model is a breakthrough in the explanation of neural conduction and opens up the door for new study as well as for reviewing all previous experiments on myelinated nerves afresh. Bangladesh Journal of Medical Physics Vol.11 No.1 2018 P 38-56

Epileptic Seizure Prediction and Source Localization using Entropy Analysis of Scalp EEG

Epilepsy is one of most common neurological disorders that affects people of all ages and can cause unpredictable seizures which may even cause death. The prediction of epileptic activities thus can have a great impact in avoiding fatal injuries through early preparation with medicines and also in improving the efficacy of medicines. A technique for early prediction of epileptic seizure from EEG signal is proposed in this paper. The pre-ictal period of epileptic seizure clearly depicts a start of seizure and comparing the changes in entropy of EEG signals in different brain regions during the pre-seizure period, the proposed technique could successfully predict the seizure using entropy analysis. Moreover, the region of the epileptic activities was also localized by dividing the total brain into four topographic regions and by calculating the entropy from this four zones separately. Thus, this proposed technique has the potential to help the clinical neurologists to investigate seizure detection and treat the patient in a better way with less supervision and better accuracy. Bangladesh Journal of Medical Physics Vol.11 No.1 2018 P 16-25

Simple electrode configurations for probing deep organs using Electrical Bio-Impedance techniques

Tetrapolar Impedance Method (TPIM) and Focused Impedance Method (FIM) are two simple modalities of electrical bio-impedance measurement that could be employed to give useful physiological and diagnostic information of the human body. FIM is based on TPIM but uses a combination of two sets of TPIM, producing a focusing effect, which is useful to localize specific target organs. Most non-invasive electrical bio-impedance measurements based on TPIM and FIM use electrodes on one side of the body, outside the skin surface, which gives a shallow depth sensitivity. The sensitivity decreases with depth so that deep organs like lungs, heart, liver, stomach and bladder are not fully assessed through such measurements. Based on a long experience of studying electrical impedance methods, several qualitative ideas are presented in this article for probing deep organs using a few modified TPIM and FIM configurations. The suggestions are based on visualisations of both equipotentials and a popular sensitivity equation for transfer impedance, but not based on any quantitative analysis. Simulation and phantom studies based on these ideas may produce some practically useful electrode configurations for real life bio-impedance measurements. Bangladesh Journal of Medical Physics Vol.11 No.1 2018 P 1-15

Development of Low Cost Miniature USB Based Data Acquisition System for Biomedical Instrumentation

In biomedical instrumentation, computer based data acquisition system is required for recording of physiological parameters and bioelectric signals, which allows signal processing, display, analysis and storage in digital media. However, Most of the commercially available PC based Data Acquisition systems are of very high cost and requires specific commercial software, again at a very high cost. Moreover, if the data is not stored in raw binary or known format, it is not possible for the user to use the data in other system or software of their own choice. Therefore, a low cost, simple and open source PC based data acquisition system for biomedical application would be very useful for biomedical instrument developers and researchers in the low resource countries. In this work, we present such development of data acquisition system. The developed system utilizes an 8-bit ordinary low cost microcontroller and some electronic circuit component to develop the data acquisition system and implementation of USB 1.1 (Universal Serial Bus) interface to PC. The onboard 10-bit ADC of the microcontroller was used for analog data sampling. Two sampling and data transfer mode is implemented, (i) Continuous mode with low sampling rate (800 sample/sec) and practically real time plotting and (ii) Batch mode, with high sampling rate (76.9 k sample/sec) but with batch type plotting. To evaluate the system, PC side GUI (Graphical User Interface) software was also developed. The GUI of system shows that a test sinusoidal signal is reproduced very nicely without any amplitude and phase distortion within the frequency band of 1 to 10 KHz. The system is suitable for low frequency bioelectric signals like ECG, EEG etc. and as well as high frequency signal like EMG, NCV etc. The system is low cost, miniature, simple, and efficient and being used in several indigenously developed medical devices like ECG, EMG, NCV and FIM [Rabbani et al, 1999] at the authors’ department with excellent satisfactory results.Bangladesh Journal of Medical Physics Vol.10 No.1 2017 1-11

Effect of top cover tilt angle with ground surface on productivity of basin type solar distillation unit

Basin type solar stills were made with two types of top cover, transparent PVC sheet and another with glass sheet. A soaked black towel was at the base which was heated through green-house effect and contributed to the water for distillation. Productivity of these two basin type solar stills were studied at different tilt angles of the top transparent cover with ground surface (13o, 23o and 35o). The average amount of distilled water produced increased with the tilt angles for both types of cover materials, that for glass being much higher than that for PVC cover.Bangladesh Journal of Medical Physics Vol.10 No.1 2017 40-46

Real-Time Classification of Multi-Channel Forearm EMG to Recognize Hand Movements using Effective Feature Combination and LDA Classifier

Electromyography (EMG) signals acquired from surface of arms can be crucial in recognizing nature of hand gestures. The concept is used in current highly demanding fields such as controlling prosthetic limbs, diagnosing neuromuscular disorders, manipulation of robotic arm etc. The purpose of the work was to classify a set of hand motions from corresponding multi-channel surface EMG signals by developing MATLAB tools. The research focused on extracting multiple signal features and finding the appropriate combination of extracted intelligible features to get the best classification accuracy for the specific set of hand gestures. For dynamic and fast classification purpose, linear discriminant analysis (LDA) classifier was employed. Effect of feature dimensionality reduction on classification accuracy was also investigated via Principal Component Analysis (PCA) in this research. Finally, the research analyzed different electrode placements by comparing classification accuracy for each of the set of motions and proposed a simple and compact data acquisition instrumentation having less number of electrodes while maintaining high classification accuracy.Bangladesh Journal of Medical Physics Vol.10 No.1 2017 25-39

Myocardial Ischemia Detection from Slope of ECG ST Segment

Myocardial ischemia occurs when blood flow to heart is reduced preventing it from receiving enough oxygen. It is a possible indication of partial or complete blockage of coronary arteries. Though ischemia is accompanied by symptoms (fatigue, chest pain, shortness of breath etc.) sometimes it can be silent. If not treated, it can lead to various heart diseases. Most importantly it can progress to myocardial infarction (heart attack), which can be fatal. Thus detecting ischemia at an early stage is important to prevent serious implications. Nowadays personal healthcare monitoring systems are used which provide vital physiological information. In future ECG measurement devices would also be common in homes. So, the proposed work intends to develop an algorithm in detecting myocardial ischemia from ECG, which would be computationally less complex and easy to implement in homecare ECG devices. One way to do it is through continuous or long term monitoring of ECG. The ST segment elevation (or depression) indicates presence of ischemia. The proposed method measures slope of ST segment which must vary in case of ST changes. The algorithm is tested on selected records of the European ST-T database and returns an accuracy of 83.33%.Bangladesh Journal of Medical Physics Vol.10 No.1 2017 12-24

A Feasibility Study of Employing EOG Signal in Combination with EEG Based BCI System for Improved Control of a Wheelchair

For a fully paralysed person, EEG (Electroencephalogram) based Brain Computer Interface (BCI) has a great promise for controlling electromechanical equipment such as a wheelchair. Again EOG (Electrooculography) based Human Machine Interface system also provides a possibility. Individually, none of these methods is capable of giving a fully error free reliable and safe control, but an appropriate combination may provide a better reliability, which is the aim of the present work. Here we intend to use EEG data to classify two classes, corresponding to left and right hand movement, and EOG data to classify two classes corresponding to left and right sided eyeball movement. We will use these classifications independently first and then combine these with different weightage to find if a better and reliable control is possible. For this purpose offline classification of motor imaginary EEG data of a subject was carried out extracting features using Common Spatial Pattern (CSP) and classifying using Linear Discriminative Analysis. The independent EEG motor imaginary data classification resulted in 89.8% of accuracy in 10 fold one leave out cross validation. The EOG eyeball movement produces distinctive signals of opposite polarities and is classified using a simple discriminant type classification resulting in 100% accuracy. However, using EOG solely is not acceptable as there always will be unintentional eye movement giving false commands. Combining both EEG and EOG with different weightage to the two classifications produced varied degrees of improvement. For 50% weightage to both resulted in 100% accuracy, without any error, and this may be accepted as a practical solution because the chances of unintentional false commands will be very rare. Therefore, a combination of EOG and BCI may lead to a greater reliability in terms of avoidance of undesired control signals.Bangladesh Journal of Medical Physics Vol.10 No.1 2017 47-58

Development of an electrical impedance based spirometer

Spirometry, or measurement of respiration conventionally involves measurement of the time variation of volume or flow of air breathed in or out through the mouth using an air-flow sensor. Electrical impedance of thorax changes during breathing and conceptually this modality should be applicable in spirometry, but no attempts have been made so far. This paper describes the development of an electrical impedance based spirometer placing electrodes on four limbs so that the whole lung volume may contribute to the measurement. An impedance based measurement system (IBS) consisting of a constant current drive at 11 kHz and necessary voltage measurement circuitry was designed and developed for this purpose. A portable oscilloscope (PicoScope 2208A) was used for acquisition of the measured voltage signal to a PC and an algorithm in Matlab software was used to demodulate the time varying impedance from a carrier signal. The variation of impedance with time during forced expiration as measured by the implemented impedance measurement system was compared with that obtained using a standard bellows type commercial spirometer (Vitalograph) on eight volunteers, between 22 and 32 years of age. The subjects included smokers, non-smokers, and asthma patients. Repeatability of the measurements were satisfactory. The correlation coefficient between the spirogram obtained using the IBS and that obtained using standard spirometer varied from 0.81 to 0.99 indicating preliminary success of the proposed technique. However, a possible source of error is the bending of the body during forced expiration which, if prevented, may give a better outcome.Bangladesh Journal of Medical Physics Vol.9 No.1 2016 17-27