Robustness of focused and global impedance estimates of bladder volumes against uncertainty of urine conductivity

Bioimpedance measurements are currently used to monitor various biological processes and are potentially useful for studies of urodynamics. Global impedance (GI) and focused impedance measurements (FIM) can be used to monitor bladder volumes, but these are subject to varying conductivity of urine. To address this, we emulated a human bladder using an agar phantom filled with saline solutions of varying conductivities and estimated volumes using a modified FIM-based approach. Using this novel strategy, electrical potentials did not change significantly with constant liquid volumes, even when the conductivity of the saline solutions was varied between 1.027 to 1.877 and 2.610 S/m. Conversely, GI and classic FIM measurements of constant liquid volumes varied with conductivity. These observations suggest that the proposed FIM approach is suitable for bladder volume estimation due to its robustness against uncertainties of conductivity. The bioimpedance hardware used in our experiments comprised 8 electrodes and a a small and low cost impedance measurement system based on an AFE4300 direct impedance measurement device.Peer ReviewedPostprint (author's final draft

Tomografía de impedancia eléctrica: fundamentos de hardware y aplicaciones médicas

Introduction: The following article shows a systematic review of publications on hardware topologies used to capture and process electrical signals used in Electrical Impedance Tomography (EIT) in medical applications, as well topicality of the EIT in the field of biomedicine. This work is the product of the research project “Electrical impedance tomography based on mixed signal devices”, which took place at the University of Cauca during the period 2017-2019. Objective: This review describes the operation, topicality and clinical use of Electrical Impedance Tomography systems. Methodology: A systematic review was carried out in the IEEE-Xplore, ScienceDirect and Scopus databases. After the classification, 106 relevant articles were obtained on scientific studies of EIT systems; applications dedicated to the analysis of medical images. Conclusions: Impedance-based methods have a variety of medical applications as they allow for the reconstruction of a body region, by estimating the conductivity distribution inside the human body; this is without exposing the patient to the damaging effects of radiation and contrast elements. Impedance-based methods are therefore a very useful and versatile tool in the treatment of diseases such as: monitoring blood pressure, detection of atherosclerosis, localization of intracranial hemorrhages, determining bone density, among others. Originality: It describes the necessary components to design an EIT system, as well as the design characteristics depending on the pathology to be visualized.  Introducción: En el siguiente artículo se muestra una revisión sistemática de publicaciones sobre topologías hardware utilizadas para capturar y procesar señales eléctricas utilizadas en tomografía por impedancia eléctrica (TIE) en aplicaciones médicas, así como la actualidad del TIE en el campo de la biomedicina. Este trabajo es producto del proyecto de investigación “Tomografía de impedancia eléctrica basada en dispositivo de señal mixta”, que tiene lugar en la Universidad del Cauca durante el período 2017-2019.   Objetivo: Esta revisión describe la estructura hardware de los sistemas de TIE, además de sus características, como frecuencia y magnitud de señales de corriente, patrones de inyección y medición de señales y número de electrodos orientado a, uso clínico.   Metodología: Se realizó una revisión sistemática, en las bases de datos IEEE-Xplore, ScienceDirect y Scopus. Tras la clasificación se obtuvo 106 artículos relevantes sobre estudios científicos de sistemas, aplicaciones dedicadas al análisis de imágenes médicas.   Conclusión: Los métodos basados en impedancia, tienen una variedad de aplicaciones médicas, puesto que permite la reconstrucción de una región corporal, mediante la estimación de la distribución de conductividad al interior del cuerpo humano, sin radiación y elementos de contraste, tan perjudiciales para la salud de los pacientes; convirtiéndola en una herramienta muy útil y versátil en el tratamiento de enfermedades como: monitorear la presión arterial, detección de arterosclerosis, localización de hemorragias intracraneales, determinar la densidad ósea, entre otras.     &nbsp

Application of machine learning algorithms to the discretization problem in wearable electrical tomography imaging for bladder tracking

The article presents the implementation of artificial intelligence algorithms for the problem of discretization in Electrical Impedance Tomography (EIT) adapted for urinary tract monitoring. The primary objective of discretization is to create a finite element mesh (FEM) classifier that will separate the inclusion elements from the background. In general, the classifier is designed to detect the area of elements belonging to an inclusion revealing the shape of that object. We show the adaptation of supervised learning methods such as logistic regression, decision trees, linear and quadratic discriminant analysis to the problem of tracking the urinary bladder using EIT. Our study focuses on developing and comparing various algorithms for discretization, which perfectly supplement methods for an inverse problem. The innovation of the presented solutions lies in the originally adapted algorithms for EIT allowing for the tracking of the bladder. We claim that a robust measurement solution with sensors and statistical methods can track the placement and shape change of the bladder, leading to effective information about the studied object. This article also shows the developed device, its functions and working principle. The development of such a device and accompanying information technology came about in response to particularly strong market demand for modern technical solutions for urinary tract rehabilitation

Thorax measurement and analysis using electrical impedance tomography

The article deals with a novel method of visualizing interior of an object based on the measurements made on the boundary. Although an electrical impedance tomography is well established in areas where reference measurement can be easily made (difference method), it is still rather a theoretical approach for areas where reference cannot be taken (mainly in medicine). We have made a thorax measurement using difference method. The results show that electrical impedance tomography can provide valuable information for thorax visualization

Thermal dosimetry for bladder hyperthermia treatment. An overview.

The urinary bladder is a fluid-filled organ. This makes, on the one hand, the internal surface of the bladder wall relatively easy to heat and ensures in most cases a relatively homogeneous temperature distribution; on the other hand the variable volume, organ motion, and moving fluid cause artefacts for most non-invasive thermometry methods, and require additional efforts in planning accurate thermal treatment of bladder cancer. We give an overview of the thermometry methods currently used and investigated for hyperthermia treatments of bladder cancer, and discuss their advantages and disadvantages within the context of the specific disease (muscle-invasive or non-muscle-invasive bladder cancer) and the heating technique used. The role of treatment simulation to determine the thermal dose delivered is also discussed. Generally speaking, invasive measurement methods are more accurate than non-invasive methods, but provide more limited spatial information; therefore, a combination of both is desirable, preferably supplemented by simulations. Current efforts at research and clinical centres continue to improve non-invasive thermometry methods and the reliability of treatment planning and control software. Due to the challenges in measuring temperature across the non-stationary bladder wall and surrounding tissues, more research is needed to increase our knowledge about the penetration depth and typical heating pattern of the various hyperthermia devices, in order to further improve treatments. The ability to better determine the delivered thermal dose will enable clinicians to investigate the optimal treatment parameters, and consequentially, to give better controlled, thus even more reliable and effective, thermal treatments

Noninvasive Bladder Volume Monitoring Using Bioimpedance

Due to the electrical conductivity of the urine, several bioimpedance techniques have been considered for bladder volume monitoring. This chapter shows several approaches for bladder volume estimation; among these, Global Impedance (GI), presents a high accuracy in volume estimation. Other proposed approaches are Voltage Change Ratios (VCR), Impedance Ratio Method (IRM), and Focused Impedance Method (FIM), which presents highly sensitive to changes in the conductivity, just like GI. Therefore, these approaches are not suitable for long-term monitoring of the bladder, because the conductivity of urine varies with health status and diet. The proposal FIM-IE presents a low sensibility to the conductivity uncertainty; being a promising technique for long-term monitoring of the bladder and would support the assisted bladder emptying process

Focus on advances in electrical impedance tomography

Editoria