Publication: Sistema medidor de impedancia para su incorporación en un sistema de audiometría objetivo por microfónicos cocleares
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2019-10
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2019-10-17
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Abstract
La audiometría objetiva es una técnica muy útil en el diagnóstico de pacientes con disfunción auditiva, ya que no requiere de la colaboración del paciente, como puede ser un recién nacido o una persona con discapacidad cognitiva. Con esta técnica, se pueden registrar los microfónicos cocleares producidos en la cóclea humana y compararlos con la respuesta que tendría ésta en un paciente sano. Este método inocuo registra las señales eléctricas producidas en el órgano de Corti mediante la disposición de dos electrodos superficiales ubicados en la apófisis mastoidea del hueso temporal del cráneo y una referencia en la frente para la eliminación del modo común.
El resultado de estas mediciones es un audiograma completo del rango de audición del paciente según la potencia de las señales eléctricas producidas. Debido a la atenuación al paso por los tejidos que componen la zona temporal del encéfalo, las señales registradas en la superficie de la piel se ven atenuadas de una manera significativa, lo que puede generar una mala interpretación del audiograma y que conlleve a problemas en el ajuste de aparatos de audición y agravar la disfunción auditiva de los pacientes.
Para poder solucionar este problema, en este trabajo se toma como objetivo específico modelar un sistema eléctrico que calcule la atenuación de la señal que se mide en los electrodos proveniente del órgano auditivo mediante la recreación de un fantoma. La caracterización de cada uno de los tejidos que atraviesan las señales microfónicas cocleares, como son la piel, el hueso y la médula ósea será un paso importante para estimar la atenuación en pacientes según su fisionomía.
El diseño se realizó con la preparación de un fantoma de piel compuesta de un gel salino, un fantoma de la médula ósea mediante una solución salina y un fantoma del hueso temporal con la recreación de un modelo 3D real de filamento conductivo. Todos los modelos fueron caracterizados según datos de conductividad y resistividad documentadas en la bibliografía y se agruparon para un registro de medidas completo en el laboratorio de Bioinstrumentación y Nanotecnología del Centro de Tecnología Biomédica de la UPM, donde se dispone del equipamiento adecuado para realizarlas.
La conclusión general del estudio es que se ha conseguido modelar la anatomía deseada y se ha obtenido un modelo eléctrico que caracteriza casi al completo la atenuación de una persona sana a pesar del desajuste de uno de sus tejidos. Además, en el trabajo se han incluido las distintas líneas de trabajo futuras para la obtención de una mejora del sistema de modelado y de la recreación de un fantoma más exacto y desarrollado.
Objective audiometry is a very useful technique in the diagnosis of patients with auditory dysfunction, as it doesn’t require the collaboration of the patient, such as a newborn or a person with cognitive disability or impairment. With this technique, the cochlear microphones produced in the human cochlea can be recorded and compared with the response of the human cochlea in a healthy patient. This harmless or innocuous method records the electrical signals produced in the Corti organ through the arrangement of two surface electrodes located in the mastoid process of the temporal bone of the skull and a reference on the forehead for the elimination of the common mode. The result of these measurements is a complete audiogram of the patient's hearing range according to the power of the electrical signals produced, due to the attenuation to the passage through the tissues that compose the temporal zone of the brain, the signals registered on the surface of the skin are attenuated in a significant way, which can generate a bad interpretation of the audiogram and that entails problems in the adjustment of hearing devices and aggravate the hearing dysfunction of the patients. In order to solve this problem, the specific objective of this work is to model an electrical system that calculates the attenuation of the signal is measured in the electrodes coming from the auditory organ through the recreation of a phantom. The characterization of each of the tissues that cross or pass the cochlear microphonic signals, such as skin, bone and bone marrow, will be an important step to estimate attenuation in patients according to their physiognomy. The design was done by preparing a skin phantom composed of a saline jelly or gel, a bone marrow phantom using a saline solution and a temporal bone phantom by recreating a real 3D modelo of conductive filament. All models were characterized according to conductivity and resistivity data documented in the bibliography and were grouped for a complete measurement record in the Bioinstrumentation and Nanotechnology laboratory of the UPM Biomedical Technology Center, where the appropiate equipment is available to perform them. The general conclusion of the study is that the desired anatomy has been modelled and an electrical model has been obtained that almost completely characterizes the attenuation of a healthy person despite the mismatch of one of its tissues. In addition, the different lines of future work have been included in the work in order to obtain an improvement in the modeling system and the recreation of a more accurate and developed phantom.
Objective audiometry is a very useful technique in the diagnosis of patients with auditory dysfunction, as it doesn’t require the collaboration of the patient, such as a newborn or a person with cognitive disability or impairment. With this technique, the cochlear microphones produced in the human cochlea can be recorded and compared with the response of the human cochlea in a healthy patient. This harmless or innocuous method records the electrical signals produced in the Corti organ through the arrangement of two surface electrodes located in the mastoid process of the temporal bone of the skull and a reference on the forehead for the elimination of the common mode. The result of these measurements is a complete audiogram of the patient's hearing range according to the power of the electrical signals produced, due to the attenuation to the passage through the tissues that compose the temporal zone of the brain, the signals registered on the surface of the skin are attenuated in a significant way, which can generate a bad interpretation of the audiogram and that entails problems in the adjustment of hearing devices and aggravate the hearing dysfunction of the patients. In order to solve this problem, the specific objective of this work is to model an electrical system that calculates the attenuation of the signal is measured in the electrodes coming from the auditory organ through the recreation of a phantom. The characterization of each of the tissues that cross or pass the cochlear microphonic signals, such as skin, bone and bone marrow, will be an important step to estimate attenuation in patients according to their physiognomy. The design was done by preparing a skin phantom composed of a saline jelly or gel, a bone marrow phantom using a saline solution and a temporal bone phantom by recreating a real 3D modelo of conductive filament. All models were characterized according to conductivity and resistivity data documented in the bibliography and were grouped for a complete measurement record in the Bioinstrumentation and Nanotechnology laboratory of the UPM Biomedical Technology Center, where the appropiate equipment is available to perform them. The general conclusion of the study is that the desired anatomy has been modelled and an electrical model has been obtained that almost completely characterizes the attenuation of a healthy person despite the mismatch of one of its tissues. In addition, the different lines of future work have been included in the work in order to obtain an improvement in the modeling system and the recreation of a more accurate and developed phantom.
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Keywords
Bioimpedancia, Bioseñal, Audiometría objetiva, Microfónicos cocleares, Fantoma