scholarly journals A Multi-Frequency Focused Impedance Measurement System Based on Analogue Synchronous Peak Detection

2021 ◽  
Vol 2 ◽  
Author(s):  
Muhammad Abdul Kadir ◽  
Adrian J. Wilson ◽  
K. Siddique-e Rabbani
Keyword(s):  
Sampling Rate ◽  
Current Source ◽  
Impedance Measurement ◽  
Biological Tissues ◽  
Peak Detection ◽  
Impedance Method ◽  
Impedance Measurements ◽  
Enhanced Sensitivity ◽  
Physiological Processes ◽  
High Output Impedance

Monitoring of anatomical structures and physiological processes by electrical impedance has attracted scientists as it is noninvasive, nonionizing and the instrumentation is relatively simple. Focused Impedance Method (FIM) is attractive in this context, as it has enhanced sensitivity at the central region directly beneath the electrode configuration minimizing contribution from neighboring regions. FIM essentially adds or averages two concentric and orthogonal combinations of conventional Tetrapolar Impedance Measurements (TPIM) and has three versions with 4, 6, and 8 electrodes. This paper describes the design and testing of a multi-frequency FIM (MFFIM) system capable of measuring all three versions of FIM at 8 frequencies in the range 10 kHz—1 MHz. A microcontroller based multi-frequency signal generator and a balanced Howland current source with high output impedance (476 kΩ at 10 kHz and 58.3 kΩ at 1 MHz) were implemented for driving currents into biological tissues with an error <1%. The measurements were carried out at each frequency sequentially. The peak values of the amplified voltage signals were measured using a novel analogue synchronous peak detection technique from which the transfer impedances were obtained. The developed system was tested using TPIM measurements on a passive RC Cole network placed between two RC networks, the latter representing skin-electrode contact impedances. Overall accuracy of the measurement was very good (error <4% at all frequencies except 1 MHz, with error 6%) and the resolution was 0.1 Ω. The designed MFFIM system had a sampling rate of >45 frames per second which was deemed adequate for noninvasive real-time impedance measurements on biological tissues.

Design of a Current Source for Bioelectrical Impedance Measurement

2012 ◽  
Vol 239-240 ◽  
pp. 387-391
Author(s):  
Ke Ning Wang ◽  
Heng Zhao ◽  
Wei Wang
Keyword(s):  
Current Source ◽  
Impedance Measurement ◽  
Bioelectrical Impedance ◽  
Good Choice ◽  
Output Impedance ◽  
High Output Impedance ◽  
A Current ◽  
High Output

Current source with high output impedance is a key part in bioelectrical impedance measurement. In this paper, we presented a design of a current source based on the improved Howland current pump circuit. Then the performance of the proposed current source was simulated in Multisim software. The designed current source was implemented and its output impedance was tested. Both the simulated and tested results show that the proposed current source is a good choice for BI measurement.

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

2019 ◽  
Vol 11 (1) ◽  
pp. 1-15 ◽  
Author(s):  
K Siddique E Rabbani
Keyword(s):  
Medical Physics ◽  
Real Life ◽  
Impedance Measurement ◽  
Skin Surface ◽  
The Body ◽  
Impedance Method ◽  
Sensitivity Equation ◽  
Impedance Measurements ◽  
Focusing Effect ◽  
Phantom Studies

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

scholarly journals A computational framework for modeling cell–matrix interactions in soft biological tissues

2021 ◽  
Author(s):  
Jonas F. Eichinger ◽  
Maximilian J. Grill ◽  
Iman Davoodi Kermani ◽  
Roland C. Aydin ◽  
Wolfgang A. Wall ◽  
...  
Keyword(s):  
Soft Tissues ◽  
Three Dimensional ◽  
Biological Tissues ◽  
Computational Framework ◽  
Cell Matrix ◽  
Physiological Processes ◽  
Matrix Interactions ◽  
Mechanical Homeostasis ◽  
Cell Matrix Interactions ◽  
Short Time

AbstractLiving soft tissues appear to promote the development and maintenance of a preferred mechanical state within a defined tolerance around a so-called set point. This phenomenon is often referred to as mechanical homeostasis. In contradiction to the prominent role of mechanical homeostasis in various (patho)physiological processes, its underlying micromechanical mechanisms acting on the level of individual cells and fibers remain poorly understood, especially how these mechanisms on the microscale lead to what we macroscopically call mechanical homeostasis. Here, we present a novel computational framework based on the finite element method that is constructed bottom up, that is, it models key mechanobiological mechanisms such as actin cytoskeleton contraction and molecular clutch behavior of individual cells interacting with a reconstructed three-dimensional extracellular fiber matrix. The framework reproduces many experimental observations regarding mechanical homeostasis on short time scales (hours), in which the deposition and degradation of extracellular matrix can largely be neglected. This model can serve as a systematic tool for future in silico studies of the origin of the numerous still unexplained experimental observations about mechanical homeostasis.

The Effect of Prestress on Vibration Behavior of Structures in Impedance Method Damage Detection

2008 ◽  
Vol 41-42 ◽  
pp. 401-406 ◽  
Author(s):  
Xian Hua Liu ◽  
Roshun Paurobally ◽  
Jie Pan
Keyword(s):  
Damage Detection ◽  
Temperature Change ◽  
Impedance Measurement ◽  
Economic Benefits ◽  
Structural Vibration ◽  
Impedance Method ◽  
Local Vibration ◽  
Vibration Behavior ◽  
Excited Vibration ◽  
Measurement Results

Structural health monitoring or damage detection has long been a research interest for its great potential for life safety and economic benefits to the industrialized world. Structural vibration behavior is an essential signature of the integrity of structures and hence has been used for damage detection. Structural vibration impedance by way of piezoceramic patch excitation offers a local damage detection technique. It has been known that temperature change has adverse effects on the measured impedance result and can complicate the damage analysis. It is believed that one way of temperature influence on vibration is through adding thermal prestress to the structure. Prestress affects vibration in different ways on different structures and application problems. For the impedance method, prestress comes not only from temperature change but also from other sources such as wind, gravity and working load. This paper deals with prestress effects in the context of local vibration behavior of structures. A theoretical analysis is given on how prestress affects the vibration. Experimental impedance measurement results for piezoceramic patch excited vibration of simple structures such as plates under prestress are presented.

scholarly journals Design of a Microcontroller Based System to Implement 4-Electode Focused Impedance Method (FIM)

2013 ◽  
Vol 4 (1) ◽  
pp. 75-79
Author(s):  
Dr Aktharuzzaman ◽  
Tanvir N Baig ◽  
K Siddique-e Rabbani
Keyword(s):  
Measurement System ◽  
Medical Physics ◽  
Impedance Measurement ◽  
Simulation Software ◽  
Signal Generator ◽  
Constant Current ◽  
Impedance Method ◽  
Electronic Circuitry ◽  
Measuring Unit

Designing of electronic circuitry and development of necessary software has been performed in the present work for a microcontroller based 4-electrode Focused Impedance measurement system. This needs a complex sequential analog switching of constant current ac signal generator and a potential measuring unit to 4 electrodes on the object under study. The performances of the designed system and the developed microcontroller software have been studied using a commercially available simulation software, ‘Proteus-7’, and the results are very satisfactory. DOI: http://dx.doi.org/10.3329/bjmp.v4i1.14690 Bangladesh Journal of Medical Physics Vol.4 No.1 2011 75-79

scholarly journals Low Cost Instrumentation for Electrical Impedance Tomography in Biomedical Applications

2015 ◽  
Author(s):  
Stewart Smith ◽  
Hancong Wu ◽  
Jiabin Jia
Keyword(s):  
Electrical Impedance Tomography ◽  
Integrated Circuit ◽  
Biomedical Applications ◽  
Electrical Impedance ◽  
Low Cost ◽  
Impedance Measurement ◽  
Impedance Tomography ◽  
Impedance Measurements ◽  
Additional Circuitry ◽  
Initial Results

This poster reports the design, implementation and testing of a portable and inexpensive bio-impedance measurement system intended for electrical impedance tomography (EIT) in cell cultures. The system is based on the AD5933 impedance analyser integrated circuit with additional circuitry to enable four-terminal measurement. Initial results of impedance measurements are reported along with an EIT image reconstructed using the open source EIDORS package.

Electrical Impedance Measurements of PZT Nanofiber Sensors

2016 ◽  
Author(s):  
Richard Galos ◽  
Xin Li
Keyword(s):  
Dielectric Constant ◽  
Material Properties ◽  
Electrical Impedance ◽  
Impedance Measurement ◽  
Low Frequencies ◽  
Impedance Measurements ◽  
Conductive Afm ◽  
Electrical Impedance Measurement ◽  
Microfabrication Techniques

Electrical Impedance Measurement of PZT Nanofiber sensors are performed and material properties including resistivity and dielectric constant are derived from the measurements. Nanofibers formed by electro-spinning with diameters ranging from 10 to 150 nm were collected and integrated into sensors using microfabrication techniques. The nanosensor impedance was extremely high at low frequencies and special matching circuitry was fabricated to detect output. The resulting impedance measurements are also compared with those of individual nanofibers that were tested using Scanning Conductive Microscopy (SCM) and Conductive AFM.

A high output impedance current source

1994 ◽  
Vol 15 (2A) ◽  
pp. A79-A82 ◽  
Author(s):  
C W Denyer ◽  
F J Lidgey ◽  
Q S Zhu ◽  
C N McLeod
Keyword(s):  
Current Source ◽  
Output Impedance ◽  
High Output Impedance ◽  
High Output

Part Authentication Using Indirect Electromechanical Impedance Measurements

2020 ◽  
Author(s):  
Mohammad I. Albakri ◽  
Pablo A. Tarazaga
Keyword(s):  
Numerical Solutions ◽  
Numerical Models ◽  
Impedance Measurement ◽  
Piezoelectric Transducers ◽  
Frequency Range ◽  
Impedance Measurements ◽  
Manufacturing Defects ◽  
Electromechanical Impedance ◽  
Non Destructive Evaluation ◽  
Non Destructive

Abstract Motivated by its success as a structural health monitoring solution, electromechanical impedance measurements have been utilized as a means for non-destructive evaluation of conventionally and additively manufactured parts. In this process, piezoelectric transducers are either directly embedded in the part under test or bonded to its surface. While this approach has proven to be capable of detecting manufacturing anomalies, instrumentation requirements of the parts under test have hindered its wide adoption. To address this limitation, indirect electromechanical impedance measurement, through instrumented fixtures or testbeds, has recently been investigated for part authentication and non-destructive evaluation applications. In this work, electromechanical impedance signatures obtained with piezoelectric transducers indirectly attached to the part under test, via an instrumented fixture, are numerically investigated. This aims to better understand the coupling between the instrumented fixture and the part under test and its effects ON sensitivity to manufacturing defects. For this purpose, numerical models are developed for the instrumented fixture, the part under test, and the fixture/part assembly. The frequency-domain spectral element method is used to obtain numerical solutions and simulate the electromechanical impedance signatures over the frequency range of 10–50 kHz. Criteria for selecting the frequency range that is most sensitive to defects in the part under test are proposed and evaluated using standard damage metric definitions. It was found that optimal frequency ranges can be preselected based on the fixture design and its dynamic response.

scholarly journals Dual-Modal In Vivo Fluorescence/Photoacoustic Microscopy Imaging of Inflammation Induced by GFP-Expressing Bacteria

Sensors ◽  
2019 ◽  
Vol 19 (2) ◽  
pp. 238 ◽  
Author(s):  
Yubin Liu ◽  
Lei Fu ◽  
Mengze Xu ◽  
Jun Zheng ◽  
Zhen Yuan
Keyword(s):  
Multimodal Imaging ◽  
Fluorescent Protein ◽  
Biological Tissues ◽  
Photoacoustic Microscopy ◽  
Microscopy Imaging ◽  
Enhanced Sensitivity ◽  
Imaging Results ◽  
Molecular Specificity ◽  
Green Fluorescent

In this study, dual-modal fluorescence and photoacoustic microscopy was performed for noninvasive and functional in vivo imaging of inflammation induced by green fluorescent protein (GFP) transfected bacteria in mice ear. Our imaging results demonstrated that the multimodal imaging technique is able to monitor the tissue immunovascular responses to infections with molecular specificity. Our study also indicated that the combination of photoacoustic and fluorescence microscopy imaging can simultaneously track the biochemical changes including the bacterial distribution and morphological change of blood vessels in the biological tissues with high resolution and enhanced sensitivity. Consequently, the developed method paves a new avenue for improving the understanding of the pathology mechanism of inflammation.

Sign in / Sign up

Export Citation Format

Share Document