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electrical impedance tomography

James Hope, Frederique Vanholsbeeck, A J McDaid
In neural interfaces for peripheral nerve a trade-off exists between the level of invasiveness and the selectivity of neural recordings. In this study, we implement electrical impedance tomography (EIT) in a nerve cuff with the aim to investigate the achievable level of selectivity.
 Approach: Established modelling approaches in neural-EIT are expanded on to be used, for the first time, on myelinated fibres which are abundant in mammalian peripheral nerves and transmit motor commands. The model is then used to evaluate the viability of using EIT with a nerve cuff to record neural activity in peripheral nerves...
March 16, 2018: Physiological Measurement
Barry James McDermott, Emily Porter, Marggie Jones, Brian McGinley, Martin O'Halloran
OBJECTIVE: The theoretical basis, experimental implementation, and proof of concept of a novel Electrical Impedance Tomography (EIT) imaging technique, called Symmetry Difference EIT, is described. This technique is applicable in situations where there is inherent symmetry in the region being imaged. METHODS: The sample scenario of the human head is used to describe the technique. The head is largely symmetrical across the sagittal plane. A unilateral lesion such as a haemorrhage or region of ischaemia distorts that symmetry...
March 13, 2018: Physiological Measurement
Nick Polydorides
We propose a numerical framework to simulate the Lorentz Force Electrical Impedance Tomography (LFEIT) measurements on accurate electrode models and an image reconstruction scheme for which data on two pairs of electrodes are sufficient. The adopted finite element-based complete electrode model encompasses the electrode's geometry and contact impedance, accounting for the power losses at the contact interface. The results of our simulation study suggest that electrode modelling has a significant impact on the measurements and electrode model inaccuracies may be detrimental to the image reconstruction...
March 13, 2018: Physiological Measurement
Tingting Zhang, Rihui Li, Thomas Potter, Jin Keun Seo, Guanglin Li, Yingchun Zhang
Electrical properties of human tissues are usually linked with structure of thin insulating membranes and thereby reflect physiological function of the tissues or organs. It is clinically important to characterize electrical properties of tissues in vivo. Electrical impedance tomography (EIT) is a recently developed medical imaging technique which has been exploited to characterize electrical properties (conductivity and permittivity) of human tissues by injecting currents and measuring the resulting voltages at boundary electrodes...
March 8, 2018: International Journal for Numerical Methods in Biomedical Engineering
Louiza Sophocleous, Inez Frerichs, Martijn Miedema, Merja Kallio, Thalia Papadouri, Christina Karaoli, Tobias Becher, David G Tingay, Anton van Kaam, Richard H Bayford, Andreas Daniel Waldmann
OBJECTIVE: Critically ill neonates and infants might particularly benefit from continuous chest electrical impedance tomography (EIT) monitoring at the bedside. In this study a textile 32-electrode interface for neonatal EIT examination has been developed and tested to validate its clinical performance. The objectives were to assess ease of use in a clinical setting, stability of contact impedance at the electrode-skin interface and possible adverse effects. APPROACH: Thirty preterm infants (gestational age: 30...
March 8, 2018: Physiological Measurement
Anna Witkowska-Wrobel, Kirill Aristovich, Mayo Faulkner, James Avery, David Holder
Imaging ictal and interictal activity with Electrical Impedance Tomography (EIT) using intracranial electrode mats has been demonstrated in animal models of epilepsy. In human epilepsy subjects undergoing presurgical evaluation, depth electrodes are often preferred. The purpose of this work was to evaluate the feasibility of using EIT to localise epileptogenic areas with intracranial electrodes in humans. The accuracy of localisation of the ictal onset zone was evaluated in computer simulations using 9M element FEM models derived from three subjects...
February 27, 2018: NeuroImage
Gregory Reychler, Valeska Uribe Rodriguez, Cheryl Elizabeth Hickmann, Bertrand Tombal, Pierre-François Laterre, Axel Feyaerts, Jean Roeseler
INTRODUCTION: Impairment of global and regional pulmonary ventilations is a well-known consequence of general anesthesia. Positive expiratory pressure (PEP) or incentive spirometry (IS) is commonly prescribed, albeit their efficacy is poorly demonstrated. The aim of this study was to assess the effects of PEP and IS on lung ventilation and recruitment in patients after surgery involving anesthesia using electrical impedance tomography (EIT). METHOD: Ten male subjects (age = 61...
February 27, 2018: Physiotherapy Theory and Practice
Kristyna Buzkova, Martin Muller, Ales Rara, Karel Roubik, Tomas Tyll
BACKGROUND AND AIMS: During laparoscopic surgery, a capnoperitoneum is created to optimize the operating space for surgeons. One effect of this is abdominal pressure which alters the physiological thoraco-abdominal configuration and pushes the diaphragm and lungs cranially. Since the lung image acquired by electrical impedance tomography (EIT) depends on the conditions within the thorax and abdomen, it is crucial to know the diaphragm position to determine the effect of diaphragm shift on EIT thorax image...
February 21, 2018: Biomedical Papers of the Medical Faculty of the University Palacký, Olomouc, Czechoslovakia
Mayo Faulkner, Sana Hannan, Kirill Y Aristovich, James Avery, David S Holder
<i>Objective</i>. Electrical Impedance Tomography (EIT) can image impedance changes associated with evoked physiological activity in the cerebral cortex using an array of epicortical electrodes. An impedance change is observed as the externally applied current, normally confined to the extracellular space is admitted into the conducting intracellular space during neuronal depolarisation. The response is largest at DC and decreases at higher frequencies due to capacitative transfer of current across the membrane...
February 16, 2018: Physiological Measurement
Zhanqi Zhao, Wei Wang, Zuojing Zhang, Meiying Xu, Inez Frerichs, Jing-Xiang Wu, Knut Moeller
The aim of the study was to explore the feasibility of titrating tidal volume (VT) and positive end-expiratory pressure (PEEP) during one-lung ventilation (OLV) based on ventilation distribution and oxygenation. Approach: Twenty four consecutive patients requiring intubation with a double-lumen tube and subsequent OLV for thoracic surgical procedures were examined prospectively in lateral posture. Electrical impedance tomography (EIT), blood gases, respiratory mechanics were successfully measured in 21 patients at various combinations of VT (4 ml/kg, 6 ml/kg, 8 ml/kg body weight) and PEEP (0 cmH2O, 4 cmH2O, 8 cmH2O) during OLV...
February 12, 2018: Physiological Measurement
Beatriz Lobo, Cecilia Hermosa, Ana Abella, Federico Gordo
Continuous assessment of respiratory status is one of the cornerstones of modern intensive care unit (ICU) monitoring systems. Electrical impedance tomography (EIT), although with some constraints, may play the lead as a new diagnostic and guiding tool for an adequate optimization of mechanical ventilation in critically ill patients. EIT may assist in defining mechanical ventilation settings, assess distribution of tidal volume and of end-expiratory lung volume (EELV) and contribute to titrate positive end-expiratory pressure (PEEP)/tidal volume combinations...
January 2018: Annals of Translational Medicine
Gunther Hempel, Philipp Simon, Peter Salz, Hermann Wrigge
Acute and chronic respiratory failures require immediate diagnosis and preferably individualized ventilation therapy. If possible, non-invasive ventilation should be considered to avoid complications of invasive mechanical ventilation. Especially in patients with ARDS and moderate to severe cases, non-invasive ventilation may not be suitable and should not be used uncritically.Invasive mechanical ventilation parameters should be adjusted individually. In the future, additional parameters such as transpulmonary pressure, monitoring of regional ventilation using electrical impedance tomography could help to individualize ventilator settings...
February 2018: Anästhesiologie, Intensivmedizin, Notfallmedizin, Schmerztherapie: AINS
Carolina Meira, Fabiola B Joerger, Annette P N Kutter, Andreas Waldmann, Simone K Ringer, Stephan H Böehm, Samuel Iff, Martina Mosing
OBJECTIVE: To compare the efficacy of three continuous positive airway pressure (CPAP) interfaces in dogs on gas exchange, lung volumes, amount of leak during CPAP and rebreathing in case of equipment failure or disconnection. STUDY DESIGN: Randomized, prospective, crossover, experimental trial. ANIMALS: Ten purpose-bred Beagle dogs. METHODS: Dogs were in dorsal recumbency during medetomidine-propofol constant rate infusions, breathing room air...
December 5, 2017: Veterinary Anaesthesia and Analgesia
Jakob Orschulik, Nadine Hochhausen, Michael Czaplik, Daniel Teichmann, Steffen Leonhardt, Marian Walter
Bioimpedance measurements are used in many biomedical applications, such as Bioimpedance Spectroscopy (BIS) or Electrical Impedance Tomography (EIT). While BIS measures and analyzes the impedance in a frequency range at constant electrode positions, EIT aims to reconstruct images of the conductivity distribution from multiple measurements at different electrode positions. Our aim is to add spatial information to BIS measurements by using electrode positions focus measurements on desired regions of interest...
February 6, 2018: Physiological Measurement
Chuong Ngo, Falk Dippel, Klaus Tenbrock, Steffen Leonhardt, Sylvia Lehmann
BACKGROUND: Electrical impedance tomography (EIT) provides information on global and regional ventilation during tidal breathing and mechanical ventilation. During forced expiration maneuvers, the linearity of EIT and spirometric data has been documented in healthy persons. The present study investigates the potential diagnostic use of EIT in pediatric patients with asthma. METHODS: EIT and spirometry were performed in 58 children with asthma (average age ± SD: 11...
February 6, 2018: Pediatric Pulmonology
Zhishen Sun, Guoqiang Liu, Hui Xia, Stefan Catheline
Lorentz force electrical-impedance tomography (LFEIT) combines ultrasound stimulation and electromagnetic field detection with the goal of creating a high-contrast and high-resolution hybrid imaging modality. To reduce the peak stimulation power to the ultrasound transducer in LFEIT, linearly frequency-modulated (LFM) ultrasound pulse was investigated in this paper. First, the coherency between LFM ultrasound excitation and the resulting local current density was established theoretically. Then, experiments were done using different agar phantoms of conductivity ranging from 0...
February 2018: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Savino Spadaro, Tommaso Mauri, Stephan H Böhm, Gaetano Scaramuzzo, Cecilia Turrini, Andreas D Waldmann, Riccardo Ragazzi, Antonio Pesenti, Carlo Alberto Volta
BACKGROUND: Assessing alveolar recruitment at different positive end-expiratory pressure (PEEP) levels is a major clinical and research interest because protective ventilation implies opening the lung without inducing overdistention. The pressure-volume (P-V) curve is a validated method of assessing recruitment but reflects global characteristics, and changes at the regional level may remain undetected. The aim of the present study was to compare, in intubated patients with acute hypoxemic respiratory failure (AHRF) and acute respiratory distress syndrome (ARDS), lung recruitment measured by P-V curve analysis, with dynamic changes in poorly ventilated units of the dorsal lung (dependent silent spaces [DSSs]) assessed by electrical impedance tomography (EIT)...
January 31, 2018: Critical Care: the Official Journal of the Critical Care Forum
Mohammad Takhti, Yueh-Ching Teng, Kofi Odame
This paper presents the design and implementation of a read-out chain for electrical impedance tomography (EIT) imaging. The EIT imaging approach can be incorporated to take spectral images of the tissue under study, offering an affordable, portable device for home health monitoring. A fast read-out channel covering a wide range of frequencies is a must for such applications. The proposed read-out channel comprising a programmable gain instrumentation amplifier, an analog-to-digital converter (ADC), and an ADC driver is designed and fabricated in a 0...
February 2018: IEEE Transactions on Biomedical Circuits and Systems
Fabian Braun, Martin Proença, Andy Adler, Thomas Riedel, Jean-Philippe Thiran, Josep Solà
Cardiac output (CO) and stroke volume (SV) are parameters of key clinical interest. Many techniques exist to measure CO and SV, but are either invasive or insufficiently accurate in clinical settings. Electrical impedance tomography (EIT) has been suggested as a noninvasive measure of SV, but inconsistent results have been reported. Our goal is to determine the accuracy and reliability of EIT-based SV measurements, and whether advanced image reconstruction approaches can help to improve the estimates. Data were collected on ten healthy volunteers undergoing postural changes and exercise...
2018: PloS One
K H Wodack, S Buehler, S A Nishimoto, M F Graessler, C R Behem, A D Waldmann, B Mueller, S H Böhm, E Kaniusas, F Thürk, A Maerz, C J C Trepte, D A Reuter
OBJECTIVE: Electrical impedance tomography (EIT) is a non-invasive and radiation-free bedside monitoring technology, primarily used to monitor lung function. First experimental data shows that the descending aorta can be detected at different thoracic heights and might allow the assessment of central hemodynamics, i.e. stroke volume and pulse transit time. APPROACH: First, the feasibility of localizing small non-conductive objects within a saline phantom model was evaluated...
February 28, 2018: Physiological Measurement
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