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

Clinical Applications of Electrical Impedance Tomography in Stroke and Traumatic Brain Injury

Electrical Impedance Tomography (EIT) is a medical imaging technology which uses voltage measurements on the boundaries to reconstruct internal conductivity changes. When applied to imaging brain function, EIT is challenged by the unique geometry of the head and the high variability in the conductivities of brain tissue. Stroke and Trau-matic Brain Injury (TBI) are two of the leading causes of death and long-term disability worldwide. It has been suggested that EIT, which is already in clinical use primarily as a means of assessing lung function, could be used as a pre-hospital diagnostic tool for stroke and TBI, and for bedside monitoring for brain injury patients. The main aim of this PhD thesis is to bring the application of EIT in brain injury closer to regular clinical use. Chapter 1 introduces the concepts of EIT, stroke and TBI, and provides a comprehensive review of clinically relevant neuroimaging techniques and the current state of brain EIT. Chapter 2 presents the results of a series of lab experiments designed to investigate the characteristics and mechanisms of drift in measured boundary voltages, which is the key technical barrier to brain monitoring with EIT. Ex-periments were conducted on lab phantoms, vegetable skin, and healthy human subjects. Chapter 3 describes a feasibility study of monitoring for brain injury with EIT over several hours, using noise recorded on real healthy volunteers. This study also compares the performance of different electrode types. Chapter 4 presents a clinical pilot study performed on acute stroke patients. Multi-frequency (MF) EIT data were record-ed on patients and healthy controls to create the first of its kind clinical EIT dataset to be used as a resource for future research for the EIT community. Finally, the ability to identify stroke patients is demonstrated on the clinical EIT dataset