2,745 research outputs found
Design of a CMOS active electrode IC for wearable electrical impedance tomography systems
This paper describes the design of an active electrode integrated circuit (IC) for a wearable electrical impedance tomography (EIT) system required for real time monitoring of neonatal lung function. The IC comprises a wideband high power current driver (up to 6 mAp-p output current), a low noise voltage amplifier and two shape sensor buffers. The IC has been designed in a 0.35-μm CMOS technology. It operates from ±9 V power supplies and occupies a total die area of 5 mm2. Post-layout simulations are presented
Design of a CMOS active electrode IC for wearable electrical impedance tomography systems
This paper describes the design of an active electrode integrated circuit (IC) for a wearable electrical impedance tomography (EIT) system required for real time monitoring of neonatal lung function. The IC comprises a wideband high power current driver (up to 6 mAp-p output current), a low noise voltage amplifier and two shape sensor buffers. The IC has been designed in a 0.35-μm CMOS technology. It operates from ±9 V power supplies and occupies a total die area of 5 mm2. Post-layout simulations are presented
A CMOS current driver with built-in common-mode signal reduction capability for EIT
This paper presents an integrated fully differential
current driver for wearable multi-frequency electrical impedance
tomography (EIT). The integrated circuit (IC) comprises a
wideband current driver (up to 500 kHz) functioning as the
master for current sourcing, and a differential voltage receiver
with common-mode feedback configuration as the slave for
current sinking. The IC is fabricated in a 0.18-µm CMOS
technology. It operates from ±1.65 V power supplies and occupies
a total die area of less than 0.05 mm2
. The current driver has a
measured output impedance of 750 kΩ at 500 kHz and provides a
common-mode signal reduction of 32 dB at 500 kHz. The
application of the IC in a wearable EIT lung monitoring system
is presented
Towards Bio-impedance Based Labs: A Review
In this article, some of the main contributions to BI (Bio-Impedance) parameter-based systems for medical, biological and
industrial fields, oriented to develop micro laboratory systems are summarized. These small systems are enabled by the development
of new measurement techniques and systems (labs), based on the impedance as biomarker. The electrical properties of the life mater
allow the straightforward, low cost and usually non-invasive measurement methods to define its status or value, with the possibility
to know its time evolution. This work proposes a review of bio-impedance based methods being employed to develop new LoC
(Lab-on-a-Chips) systems, and some open problems identified as main research challenges, such as, the accuracy limits of
measurements techniques, the role of the microelectrode-biological impedance modeling in measurements and system portability
specifications demanded for many applications.Spanish founded Project: TEC 2013-46242-C3-1-P: Integrated Microsystem for Cell Culture AssaysFEDE
A high frame rate wearable EIT system using active electrode ASICs for lung respiration and heart rate monitoring
A high specification, wearable, electrical impedance tomography (EIT) system with 32 active electrodes is presented. Each electrode has an application specific integrated circuit (ASIC) mounted on a flexible printed circuit board, which is then wrapped inside a disposable fabric cover containing silver-coated electrodes to form the wearable belt. It is connected to a central hub that operates all the 32 ASICs. Each ASIC comprises a high- performance current driver capable of up to 6 mAp−p output, a voltage buffer for EIT and heart rate signal recording as well as contact impedance monitoring, and a sensor buffer that provides multi-parameter sensing. The ASIC was designed in a CMOS 0.35-μm high-voltage process technology. It operates from ±9-V power supplies and occupies a total die area of 3.9 mm2. The EIT system has a bandwidth of 500 kHz and employs two parallel data acquisition channels to achieve a frame rate of 107 frames/s, the fastest wearable EIT system reported to date. Measured results show that the system has a measurement accuracy of 98.88% and a minimum EIT detectability of 0.86 Q/frame. Its successful operation in capturing EIT lung respiration and heart rate biosignals from a volunteer is demonstrated
A high frame rate wearable EIT system using active electrode ASICs for lung respiration and heart rate monitoring
A high specification, wearable, electrical impedance tomography (EIT) system with 32 active electrodes is presented. Each electrode has an application specific integrated circuit (ASIC) mounted on a flexible printed circuit board, which is then wrapped inside a disposable fabric cover containing silver-coated electrodes to form the wearable belt. It is connected to a central hub that operates all the 32 ASICs. Each ASIC comprises a high- performance current driver capable of up to 6 mAp−p output, a voltage buffer for EIT and heart rate signal recording as well as contact impedance monitoring, and a sensor buffer that provides multi-parameter sensing. The ASIC was designed in a CMOS 0.35-μm high-voltage process technology. It operates from ±9-V power supplies and occupies a total die area of 3.9 mm2. The EIT system has a bandwidth of 500 kHz and employs two parallel data acquisition channels to achieve a frame rate of 107 frames/s, the fastest wearable EIT system reported to date. Measured results show that the system has a measurement accuracy of 98.88% and a minimum EIT detectability of 0.86 Q/frame. Its successful operation in capturing EIT lung respiration and heart rate biosignals from a volunteer is demonstrated
Techniques for imaging small impedance changes in the human head due to neuronal depolarisation
A new imaging modality is being developed, which may be capable of imaging small impedance changes in the human head due to neuronal depolarization. One way to do this would be by imaging the impedance changes associated with ion channels opening in neuronal membranes in the brain
during activity. The results of previous modelling and experimental studies indicated that impedance changes between 0.6%and 1.7% locally in brain grey matter when recorded at DC. This reduces by a further of 10% if measured at the surface of the head, due to distance and the effect of the resistive skull. In principle, this could be measured using Electrical Impedance Tomography (ElT) but it is close to its threshold of detectability.
With the inherent limitation in the use of electrodes, this work proposed two new schemes. The first is
a magnetic measurement scheme based on recording the magnetic field with Superconducting
Quantum Interference Devices (SQUIDs), used in Magnetoencephalography (MEG) as a result of a
non-invasive injection of current into the head. This scheme assumes that the skull does not attenuate
the magnetic field. The second scheme takes into consideration that the human skull is irregular in
shape, with less and varying conductivity as compared to other head tissues. Therefore, a key issue is to
know through which electrodes current can be injected in order to obtain high percentage changes in surface potential when there is local conductivity change in the head. This model will enable the prediction of the current density distribution at specific regions in the brain with respect to the varying skull and local conductivities.
In the magnetic study, the head was modelled as concentric spheres, and realistic head shapes to mimic
the scalp, skull, Cerebrospinal Auid (CSF) and brain using the Finite Element Method (FEM). An
impedance change of 1 % in a 2cm-radius spherical volume depicting the physiological change in the
brain was modelled as the region of depolarisation. The magnetic field, 1 cm away from the scalp, was
estimated on injecting a constant current of 100 µA into the head from diametrically opposed
electrodes. However, in the second scheme, only the realistic FEM of the head was used, which
included a specific region of interest; the primary visual cortex (V1). The simulated physiological
change was the variation in conductivity of V1 when neurons were assumed to be firing during a visual
evoked response. A near DC current of 100 µA was driven through possible pairs of 31 electrodes
using ElT techniques. For a fixed skull conductivity, the resulting surface potentials were calculated
when the whole head remained unperturbed, or when the conductivity of V1 changed by 0.6%, 1 %,
and 1.6%.
The results of the magnetic measurement predicted that standing magnetic field was about 10pT and
the field changed by about 3fT (0.03%) on depolarization. For the second scheme, the greatest mean
current density through V1 was 0.020 ± 0.005 µAmm-2, and occurred with injection through two electrodes positioned near the occipital cortex. The corresponding maximum change in potential from baseline was 0.02%. Saline tank experiments confirmed the accuracy of the estimated standing
potentials. As the noise density in a typical MEG system in the frequency band is about 7fT/√Hz, it
places the change at the limit of detectability due to low signal to noise ratio. This is therefore similar
to electrical recording, as in conventional ElT systems, but there may be advantages to MEG in that
the magnetic field direcdy traverses the skull and instrumentation errors from the electrode-skin
interface will be obviated. This has enabled the estimation of electrode positions most likely to permit
recording of changes in human experiments and suggests that the changes, although tiny, may just be
discernible from noise
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.
 
DICOM for EIT
With EIT starting to be used in routine clinical practice [1], it important that the clinically relevant information is portable between hospital data management systems. DICOM formats are widely used clinically and cover many imaging modalities, though not specifically EIT. We describe how existing DICOM specifications, can be repurposed as an interim solution, and basis from which a consensus EIT DICOM ‘Supplement’ (an extension to the standard) can be writte
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