Assessment of Human Arm Bioelectrical Impedance using Microcontroller Based System

Background and aims: In a wide field of research, the devices available based on long-established methods for measurement of bioelectrical impedance are large in size, expensive and low in accuracy. In this research, a system is developed for the measurement of the segmental bioelectrical impedance of the human body with high accuracy and small of a size. Methods: Developed method uses multi-frequency to measure segmental bioelectrical impedance that follows four electrodes segmental measurement technique and is equipped with an impedance analyzer with a touch screen. Multi-frequency signals flow to the human body to measure bioelectrical impedance and also compare data measured by developing a device to standard device. Results: Data have been collected through a developed device and is being analyzed. The outcomes show that the relative error of measured amplitude at multi-frequency is less than 1.50% while the absolute error of phase is up to 10. Comparison between two devices shows that the accuracy parameter of the developed device is more than 98% with the standard device. A compatible correlation (~ 0.9993) can be seen between both devices that they measure a nearly equal impedance of left and right arm at the same frequency. Conclusions: Use of the developed device for the measurement of segmental bioelectrical impedance using multi-frequency, adequately enhances all trait of measurement as state-of-the-art facilities, small size and liberated to use due to simplicity

ELECTRICAL IMPEDANCE SPECTROSCOPY AND TOMOGRAPHY: APPLICATIONS ON PLANT CHARACTERIZATION

World population will grow to 9.6 billion by 2050 and global food production needs to be increased by 70% to feed the increased population. Hence, better insight into plant physiology can impart better quality in fruits, vegetables, and crops, and eventually contribute to food security and sustainability. In this direction, this thesis utilizes electrical sensing technology, electrical impedance spectroscopy (EIS) and tomography (EIT), for better understanding and characterization of a number of physiological and structural aspects of the plant. It investigates the dehydration process in onion and ripening process in avocado by EIS, and perform 3D structural imaging of root by EIT. The thesis tracks and analyzes the dynamics of natural dehydration in onion and also assesses its moisture content using EIS. The work develops an equivalent electrical circuit that simulates the response of the onion undergoing natural drying for a duration of three weeks. The developed electrical model shows better congruence with the experimental data when compared to other conventional models for plant tissue with a mean absolute error of 0.42% and root mean squared error of 0.55%. Moreover, the study attempts to find a correlation between the measured impedance data and the actual moisture content of the onions under test (measured by weighing) and develops a simple mathematical model. This model provides an alternative tool for assessing the moisture content of onion nondestructively. The model shows excellent correlation with the ground truth data with a deterministic coefficient of 0.977, root mean square error of 0.030 and sum of squared error of 0.013. Next, the thesis presents an approach that will integrate EIS and machine learning technique that allows us to monitor ripening degree of avocado. It is evident from this study that the impedance absolute magnitude of avocado gradually decreases as the ripening stages (firm, breaking, ripe and overripe) proceed at a particular frequency. In addition, Principal component analysis shows that impedance magnitude (two principal components combined explain 99.95% variation) has better discrimination capabilities for ripening degrees compared to impedance phase angle, impedance real part, and impedance imaginary part. The developed classifier utilizes two principal component features over 100 EIS responses and demonstrate classification over firm, breaking, ripe and overripe stages with an accuracy of 90%, precision of 93%, recall of 90%, f1-score of 90% and an area under ROC curve (AUC) of 88%. Later on, this thesis presents the design, development, and implementation of a low-cost EIT system and analyzes root imaging as well. The designed prototype consists of an electrode array system, an Impedance analyzer board, 2 multiplexer units, and an Arduino. The Eval-Ad5933-EBZ is used for measuring the bio-impedance of the root, and two CD74HC4067 Multiplexers are used as electrode switching unit. Measuring and data collecting are controlled by the Arduino, and data storage is performed in a PC. By performing Finite Element Analysis and solving forward and inverse problem, the tomographic image of the root is reconstructed. The system is able to localize and build 2D and 3D tomographic image of root in a liquid medium. This proposed low-cost and easy-to-access system enables the users to capture the repetitive, noninvasive and non-destructive image of a plant root. Furthermore, the study proposes a simple mathematical model, based on ridge regression, which can predict root biomass from EIT data nondestructively with an accuracy of more than 93%. Thus, this study offers plant scientists and crop consultants the ability to better understand plant physiology nondestructively and noninvasively

ELECTRICAL IMPEDANCE SPECTROSCOPY AND TOMOGRAPHY: APPLICATIONS ON PLANT CHARACTERIZATION

World population will grow to 9.6 billion by 2050 and global food production needs to be increased by 70% to feed the increased population. Hence, better insight into plant physiology can impart better quality in fruits, vegetables, and crops, and eventually contribute to food security and sustainability. In this direction, this thesis utilizes electrical sensing technology, electrical impedance spectroscopy (EIS) and tomography (EIT), for better understanding and characterization of a number of physiological and structural aspects of the plant. It investigates the dehydration process in onion and ripening process in avocado by EIS, and perform 3D structural imaging of root by EIT. The thesis tracks and analyzes the dynamics of natural dehydration in onion and also assesses its moisture content using EIS. The work develops an equivalent electrical circuit that simulates the response of the onion undergoing natural drying for a duration of three weeks. The developed electrical model shows better congruence with the experimental data when compared to other conventional models for plant tissue with a mean absolute error of 0.42% and root mean squared error of 0.55%. Moreover, the study attempts to find a correlation between the measured impedance data and the actual moisture content of the onions under test (measured by weighing) and develops a simple mathematical model. This model provides an alternative tool for assessing the moisture content of onion nondestructively. The model shows excellent correlation with the ground truth data with a deterministic coefficient of 0.977, root mean square error of 0.030 and sum of squared error of 0.013. Next, the thesis presents an approach that will integrate EIS and machine learning technique that allows us to monitor ripening degree of avocado. It is evident from this study that the impedance absolute magnitude of avocado gradually decreases as the ripening stages (firm, breaking, ripe and overripe) proceed at a particular frequency. In addition, Principal component analysis shows that impedance magnitude (two principal components combined explain 99.95% variation) has better discrimination capabilities for ripening degrees compared to impedance phase angle, impedance real part, and impedance imaginary part. The developed classifier utilizes two principal component features over 100 EIS responses and demonstrate classification over firm, breaking, ripe and overripe stages with an accuracy of 90%, precision of 93%, recall of 90%, f1-score of 90% and an area under ROC curve (AUC) of 88%. Later on, this thesis presents the design, development, and implementation of a low-cost EIT system and analyzes root imaging as well. The designed prototype consists of an electrode array system, an Impedance analyzer board, 2 multiplexer units, and an Arduino. The Eval-Ad5933-EBZ is used for measuring the bio-impedance of the root, and two CD74HC4067 Multiplexers are used as electrode switching unit. Measuring and data collecting are controlled by the Arduino, and data storage is performed in a PC. By performing Finite Element Analysis and solving forward and inverse problem, the tomographic image of the root is reconstructed. The system is able to localize and build 2D and 3D tomographic image of root in a liquid medium. This proposed low-cost and easy-to-access system enables the users to capture the repetitive, noninvasive and non-destructive image of a plant root. Furthermore, the study proposes a simple mathematical model, based on ridge regression, which can predict root biomass from EIT data nondestructively with an accuracy of more than 93%. Thus, this study offers plant scientists and crop consultants the ability to better understand plant physiology nondestructively and noninvasively

Designing of a variable frequency standalone impedance analyzer for in vitro biological applications

Maximum biological samples have some electrical property, which gave us a new dimension in the field of biomedical engineering. Now-a-days measurement of impedance by applying an electrical voltage/current, has a broader application for analyzing different biological samples. Most of the devices used for the measurement of bio-impedance are bulky and much costlier. This approach will help us to design a portable, standalone, multi frequency (10Hz – 10kHz) bio-impedance monitoring device with acceptable accuracy and resolution for in-vitro studies of biological cells and tissue

A novel approach to bioelectrical impedance plethysmography for the assessment of arterial and venous circulatory problems in the forearm

Peripheral vascular disease (PVD) and/or peripheral arterial disease (PAD) are sicknesses known to inadequate delivery of either arterial or venous blood towards the extremities. Such sickness may trigger complications owing to the lack of transport of oxygen and nutrients, thus causing hypoxic events that may eventually prompt to ischaemic tissue or even the loss of the compromised limb. One of the most prominent indicators of prosperous health is blood volume and flow. The basic information within these health parameters may show cardiovascular problems or the advance of further complications related to other diseases like diabetes. In clinical setting, there effective methods to measure these parameters like Doppler ultrasound, photoplethysmography or venous occlusion plethysmography. These methods take measurements from either single vessels and/or small volume of tissue. However, it is difficult to establish a relation between the obstruction of arterial and/or venous circulation and the amount of blood received by the tissue. Bioelectrical impedance plethysmography (iPG) measures blood changes by driving a small amount of AC current into the body and after measuring the potential created by fluids flowing through tissue. This technique apart from taking measures within defined volumes of tissue, it is easy to use as only needs four electrodes on the skin. Hence, a bespoken bioelectrical impedance device including hardware and software was built ready to measure changes in blood volume/flow in the upper limbs. The system was assessed in an in-vivo controlled environment with 8 participants. The blood flow towards their left arms was altered by constricting the upper arm with a cuff at three levels: 1) below venous pressure 2) amongst venous and arterial pressure and 3) during total occlusion. Simultaneously, measurements from various instruments like ECG, Doppler ultrasound, laser Doppler flowmetry and PPG were taken and compared to the measurements obtained from the iPG instrument and defining its correlation with the impedimetric signal. The results from the experiments showed that the bioelectrical impedance signal changed in basal and arterial pulses showing specific characteristics for each kind of occlusion. The data indicated that it is possible to differentiate between a venous and arterial occlusion by examining both components of the impedance signal. The impedance during venous occlusion dropped in average 0.658±0.230% from the baseline. On the other hand, during arterial occlusion the base impedance dropped in a higher rate approximately 1.13±04.82%, indicating a differentiator during both type of blood flow disruption. Furthermore, the impedance plethysmography waveform morphology also reshaped during these occlusive periods. The whole waveform during artificial venous obstruction increased in magnitude, the systolic peak rose 31.80%, the dicrotic notch 47.73% and the diastolic point 31.92%, where the value of the latter was higher than the dicrotic notch point. In contrast, in the time of partial arterial occlusion the waveform also increased in size at all these points, but its shape was altered. The impedance magnitude at the diastolic point went below the ones at the dicrotic notch. These fluctuations provided additional further information that it might be possible to differentiate amongst venous and arterial occlusions. By consolidating the data obtained by the iPG device, it is possible to produce an index ratio between the basal impedance and these three reference points which may help to identify early circulatory problems in the arterial and/or venous systems

Multimodal Wearable Sensors for Human-Machine Interfaces

Certain areas of the body, such as the hands, eyes and organs of speech production, provide high-bandwidth information channels from the conscious mind to the outside world. The objective of this research was to develop an innovative wearable sensor device that records signals from these areas more conveniently than has previously been possible, so that they can be harnessed for communication. A novel bioelectrical and biomechanical sensing device, the wearable endogenous biosignal sensor (WEBS), was developed and tested in various communication and clinical measurement applications. One ground-breaking feature of the WEBS system is that it digitises biopotentials almost at the point of measurement. Its electrode connects directly to a high-resolution analog-to-digital converter. A second major advance is that, unlike previous active biopotential electrodes, the WEBS electrode connects to a shared data bus, allowing a large or small number of them to work together with relatively few physical interconnections. Another unique feature is its ability to switch dynamically between recording and signal source modes. An accelerometer within the device captures real-time information about its physical movement, not only facilitating the measurement of biomechanical signals of interest, but also allowing motion artefacts in the bioelectrical signal to be detected. Each of these innovative features has potentially far-reaching implications in biopotential measurement, both in clinical recording and in other applications. Weighing under 0.45 g and being remarkably low-cost, the WEBS is ideally suited for integration into disposable electrodes. Several such devices can be combined to form an inexpensive digital body sensor network, with shorter set-up time than conventional equipment, more flexible topology, and fewer physical interconnections. One phase of this study evaluated areas of the body as communication channels. The throat was selected for detailed study since it yields a range of voluntarily controllable signals, including laryngeal vibrations and gross movements associated with vocal tract articulation. A WEBS device recorded these signals and several novel methods of human-to-machine communication were demonstrated. To evaluate the performance of the WEBS system, recordings were validated against a high-end biopotential recording system for a number of biopotential signal types. To demonstrate an application for use by a clinician, the WEBS system was used to record 12‑lead electrocardiogram with augmented mechanical movement information

Development of a Digital Body Mass Index (BMI) measuring device for low-resource settings

The global burden of nutrition-related diseases majorly: diabetes, obesity, and cardiovascular diseases have been on a geometrical increase. One way of knowing the risk factor of these is by accurately measuring the Body Mass Index (BMI) of an individual. The design  of a digital BMI device, which measures and displays a subject's BMI, was executed. Materials used include an ultrasonic sensor  for height measurement, load cells for weight measurement and an Arduino UNO microprocessor which receives the output from  measuring devices, calculates the BMI and sends it for display on a liquid crystal display (LCD) screen. This device depicts a low-cost  solution for accurate measurement of a subject’s BMI. The results of the tests performed on the data obtained from the anthropometric  measurements of eight subjects using the digital BMI device, a stadiometer and a weighing scale proved the equipment is reliable in BMI  measurement, with 0.32 root mean square error (RMSE) compared to the 1.19 RMSE gotten from the BMI measurement calculated  from a wall-mounted height measurement meter rule against the stadiometer measurement

A micro approach to quantitative dehydration sensor development

Thesis (MEng)--Stellenbosch University, 2015.ENGLISH ABSTRACT: The assessment of dehydration is an ever elusive golden standard, even given the plethora of hydration markers that exist to date. Many literature sources acknowledge the need for a portable device that can be used as an indicative tool for hydration. This project sought to find a solution for assessing dehydration on a micro level looking for an indication of hydration by investigating the levels of water concentration in the skin and water compartments of the body using bioelectrical impedance, stratum corneum impedance and infrared spectrometry. Two studies were conducted to evaluate the efficacy of these devices: an infield study to assess the efficacy of the devices for measuring dehydration brought on by exercise in adults and an infant study where the devices where used to assess its ability to measure dehydration in infants who have succumbed to diarrhoea. The studies showed that the devices are not applicable in measuring real time hydration in exercising subjects as sweat was a perturbing factor in the measurements. The infant study provided promising results with regards to the usage of the infrared device. It is believed that these results could spur further investigation into the field of using infrared spectrometry as a dehydration marker. Dehydration still remains to be an ever elusive standard but the importance of finding a solution to quantitatively assess hydration is a field which could benefit the general population and its importance should not be underestimated.AFRIKAANSE OPSOMMING: Die assessering van dehidrasie is steeds 'n ontwykende goue standaard selfs gegewe die oorvloed van hidrasiemerkers wat bestaan tot op datum. Baie literatuurbronne erken egter die behoefte aan 'n draagbare toestel wat as 'n hulpmiddel kan dien vir die evaluering van die vlakke van dehidrasie. Hierdie projek streef daarna om ondersoek in te stel tot die assessering van dehidrasie op 'n mikrovlak deur die waterkonsentrasies te meet in die vel en die verskeie waterkompartemente in die liggaam via die gebruik van bio-elektriese impedansie analise, stratum corneum impedansie analise en infrarooi-spektrometrie. Twee studies is gedoen om die doeltreffendheid van die toestelle te evalueer: 'n inveldstudie wat die hidrasievlakke van volwassenes meet wat ly aan dehidrasie weens oefening en 'n studie wat dehidrasie meet in neonate wat ly aan dehidrasie weens diarree. Die studies het bewyse gelewer dat die toestelle nie effektief is met betrekking tot die meet van dehidrasie in aktiewe volwassenes nie, weens die rede dat sweet 'n verstorende faktor is. Die neonate studie het belowende resultate verskaf met betrekking tot die gebruik van die infrarooi toestel. Daar word geglo dat hierdie resultate verdere ondersoek in die veld met betrekking tot infrarooi spektrometrie as 'n hidrasie merker kan motiveer. Finale bevindinge wys dat die kwantifisering van dehidrasie steeds 'n ontwykende standaard is, maar die belangrikheid van 'n moontlike oplossing sal voordelig wees vir die wêreld se volke en moet dus nie onderskat word nie

A Feedback-Based Pneumatic Compression System for Effective Lymphedema Management

Bioimpedance analysis (BIA) is a method of detecting lymphedema- a debilitating medical condition involving swelling of the extremities. Pneumatic compression devices are frequently used in the compression treatment of lymphedema. Although existing compression technology provides relief of symptoms, it has limitations in terms of ease-of-use, portability, and monitoring of treatment progress. Currently, there are no BIA analyzers in the market that run on a low-power microcontroller and a rechargeable battery. Moreover, no such device currently exists that integrate the BIA analysis with pneumatic compression system to offer a feedback-based solution for lymphedema treatment. This work represents the first steps towards a complete system and describes the pneumatic compression and circuit designs for a portable BIA analyzer. The study proposes a lightweight, battery operated pneumatic compression device that can apply a pressure of 50 mmHg in a four-chamber compression garment. A microcontroller-based BIA system that can provide accurate indication of swelling based on a Nyquist plot was introduced. The envisioned mechatronic system features programmable compression sequences and operates with the human-in-the-loop using bioimpedance spectroscopy as control feedback. Performance of the compression system is verified by measurement of applied pressures and the BIA circuits are validated for single frequency and multi frequency impedance analysis of a phantom test load. With further development in the future, the system has the potential to serve as a quantitative source of valuable diagnostic information for clinicians, and in the long run may enable the smart management of lymphedema with the device essentially prescribing the course of treatment in response to measured conditions. This kind of human-in-the-loop control system may be a breakthrough in treatment of chronic conditions