Project

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Subject-adapted 3D dynamic bio-impedance models: application to blood pressure monitoring

Applicant Thiran Jean-Philippe
Number 153364
Funding scheme Project funding (Div. I-III)
Research institution Laboratoire de traitement des signaux 5 EPFL - STI - IEL - LTS5
Institution of higher education EPF Lausanne - EPFL
Main discipline Information Technology
Start/End 01.04.2014 - 31.03.2017
Approved amount 225'721.00
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Keywords (6)

numerical simulations ; non-invasive blood pressure; electrical impedance tomography (EIT); continuous monitoring; physiological sensors; medical image segmentation

Lay Summary (French)

Lead
La pression artérielle (PA) est définie comme la pression exercée par le sang sur les parois des artères. Lorsque la PA augmente trop, ces parois peuvent subir des dommages irréversibles ; on parle alors d’hypertension. Les artères se raidissent, s’épaississent, compliquant ainsi l’action de pompage du cœur. Ce dernier se fatigue alors davantage et le risque cardiovasculaire augmente. Prévenir l’hypertension en en détectant les signes précurseurs est donc d’une importance primordiale, d’autant plus que 40% de la population mondiale en est atteinte. Ceci requiert un monitorage continu et sur le long terme (par ex. 24 h). Malheureusement, les standards actuels pour le monitorage non-invasif de la PA sur une longue durée nécessitent l’utilisation d’un brassard encombrant au haut du bras. La mesure est non seulement non-continue, mais aussi souvent douloureuse et parfois peu fiable, en particulier de nuit.
Lay summary

Ce projet propose d’évaluer la possibilité de mesurer la PA via la tomographie d’impédance électrique (TIE), une technologie sûre, non-invasive, bon marché, et dont la mesure est continue et indolore. La TIE permet de reconstruire des  images représentant les changements d’impédance intra-thoracique au moyen de mesures d’impédance faites à la périphérie du thorax. De nombreux paramètres cardio-respiratoires peuvent ainsi être estimés via leur analyse, car les phénomènes cardiaques et respiratoires génèrent – par les variations de volumes de sang et d’air qu’ils induisent – des changements d’impédance intra-thoracique. En particulier, l’information temporelle portée par les changements d’impédance dans les poumons et l’aorte sont supposés corréler avec la PA. C’est précisément l’hypothèse que ce projet propose d’investiguer. La TIE pourrait ainsi potentiellement combler les lacunes actuelles du monitorage non-invasif et continu de la PA.

 

Direct link to Lay Summary Last update: 16.05.2014

Lay Summary (English)

Lead
Arterial blood pressure (BP) is defined as the pressure exerted by blood upon the walls of the arteries. When BP gets too high - a condition called hypertension - irreparable damage to the arteries occurs. Their stiffness and thickness increase, and pumping blood through them becomes harder. The heart’s workload thus increases drastically with hypertension and with it the cardiovascular risk. This is the reason why - with 40% of the world’s population affected by hypertension - being able to easily detect early signs of increasing BP is of paramount importance for worldwide health. This requires continuous and long-term (e.g. 24 hours) monitoring. Unfortunately, today’s standards for non-invasively monitoring BP over a long period of time necessitate the use of cumbersome cuffs at the upper arm. This way of measuring BP is non-continuous, often painful and even unreliable at night, because of its tendency to induce awakening reactions, and thus abnormal BP changes.
Lay summary
The present project proposes to investigate the possibility of measuring BP with electrical impedance tomography (EIT), a perfectly safe, non-invasive, continuous, low-cost and painless technology. Through electrical impedance measurements at the periphery of the thorax, images depicting intra-thoracic impedance changes can be reconstructed with EIT. Because respiration- and cardiac-related physiological events produce intra-thoracic impedance changes, many cardio-respiratory parameters can be estimated from the analysis of such images. In particular, the timing information of cardiac-related impedance changes in the lungs and the aorta are hypothesized to correlate with BP. This is precisely the hypothesis the present project aims at investigating. EIT could thus potentially fill the so-far unresolved loopholes of continuous long-term non-invasive BP monitoring.
Direct link to Lay Summary Last update: 16.05.2014

Responsible applicant and co-applicants

Employees

Publications

Publication
Non-invasive monitoring of pulmonary artery pressure from timing information by EIT: experimental evaluation during induced hypoxia
Proença Martin, Braun Fabian, Solà Josep, Adler Andy, Lemay Mathieu, Thiran Jean-Philippe, Rimoldi Stefano F (2016), Non-invasive monitoring of pulmonary artery pressure from timing information by EIT: experimental evaluation during induced hypoxia, in Physiological Measurement, 37(6), 713-726.
Noninvasive pulmonary artery pressure monitoring by EIT: a model-based feasibility study
Proença Martin, Braun Fabian, Solà Josep, Thiran Jean-Philippe, Lemay Mathieu (2016), Noninvasive pulmonary artery pressure monitoring by EIT: a model-based feasibility study, in Proc. of the 2017 SSC and SSCC Joint Conference, SSC & SSCC, Baden, Switzerland.
4D Heart Model Helps Unveiling Contributors to Cardiac EIT Signal
Braun Fabian, Proença Martin, Rapin Michael, Alba Xenia, Lekadir Karim, Lemay Mathieu, Solà Josep, Frangi Alejandro F, Thiran Jean-Philippe (2015), 4D Heart Model Helps Unveiling Contributors to Cardiac EIT Signal, in Proc. of the 2015 EIT Conference, 2015 EIT Conference, Neuchâtel, Switzerland.
Feasibility of EIT-based pulmonary arterial pressure monitoring
Proença M, Braun F, Rapin M, Solà J, Lemay M, Thiran J-Ph (2015), Feasibility of EIT-based pulmonary arterial pressure monitoring, in Proc. of the 2015 EIT Conference, 2015 EIT Conference, Neuchâtel, Switzerland.
Influence of heart motion on cardiac output estimation by means of electrical impedance tomography: a case study
Proença Martin, Braun Fabian, Rapin Michael, Solà Josep, Adler Andy, Grychtol Bartłomiej, Bohm Stephan H, Lemay Mathieu, Thiran Jean-Philippe (2015), Influence of heart motion on cardiac output estimation by means of electrical impedance tomography: a case study, in Physiological Measurement, 36(6), 1075-1091.
Noninvasive pulmonary artery pressure monitoring by EIT: a model-based feasibility study
Proença Martin, Braun Fabian, Solà Josep, Thiran Jean-Philippe, Lemay Mathieu, Noninvasive pulmonary artery pressure monitoring by EIT: a model-based feasibility study, in Medical & Biological Engineering & Computing.

Associated projects

Number Title Start Funding scheme
157063 Towards micro-structure-based tractography for quantitative brain connectivity analysis 01.10.2014 Project funding (Div. I-III)
124840 Stroke Volume determination through Electrical Impedance Tomography: research on the influence of cardiac and respiratory organ motion 01.07.2009 Project funding (Div. I-III)
103837 Contours actifs avec information a priori 01.04.2004 Project funding (Div. I-III)
115971 Segmentation et classification conjointes de scènes dynamiques 01.04.2007 Project funding (Div. I-III)

Abstract

Arterial blood pressure (BP) acts as a major risk factor for numerous cardiovascular, cerebrovascular, renal and neurological diseases. While in the normotensive population one out of two deaths is of cardiovascular nature, among hypertensive patients it reaches a two out of three ratio. Systemic hypertension is thus strongly correlated with morbidity and mortality and afflicts more than two billion individuals nowadays at a worldwide scale. However, to this day the accurate diagnosis of a systemic hypertensive condition remains limited by the obtrusive and intermittent aspects of its gold standard measurement modality. The clinical demand for a technology providing a non-occlusive, ambulatory-compliant, continuous and unsupervised means of monitoring systemic BP has not been met yet.With lesser prevalence and mortality than its left heart counterpart, pulmonary hypertension is characterized by its difficult early diagnosis. With symptoms severely lacking of specificity and strongly invasive or limiting measurement modalities, pulmonary hypertension is usually diagnosed at a late stage, when right heart failure has already begun. Providing the medical community with a beat-by-beat non-invasive technique that could detect early signs of pulmonary hypertension is a challenge that remains to be overcome. Electrical impedance tomography (EIT) has shown promising results in that matter. Allowing the visualization of cardiorespiratory phenomena such as ventilation and pulmonary perfusion, this technology has lead recent works to show that it could be exploited to assess central BP in a fully non-occlusive, ambulatory-compliant, continuous and unsupervised way. Because of its non-invasive, non-ionizing and low-cost nature, EIT provides an interesting modality for portable BP monitors to be investigated. However, numerous research questions regarding the influence of cardiac motion in EIT signals need to be addressed first. The goals of this research are thus multiple: in a first phase, it aims at identifying and quantifying - through numerical simulation - the various factors affecting EIT impedance changes. To that end, methods and tools allowing the automated generation of subject-adapted 3D dynamic bio-impedance models need to be developed. In a second phase, enhanced EIT images - where cardiac motion has minimal influence - will be reconstructed. Finally, these model-improved EIT images will be validated through the estimation of systemic BP and pulmonary artery pressure in humans and animals.The precise research objectives of the herein proposed research are thus the following:1.Investigate and implement methods for the automated segmentation of 4D MR images of the thorax.2.Use these segmentations for the creation of dynamic 3D bio-impedance models.3.Exploit said models to study those factors affecting the EIT cardiac signals through numerical simulation.4.Create a novel EIT image reconstruction strategy where the influence of cardiac motion is minimized.5.Validate our model-improved EIT images through the estimation of hemodynamic parameters such as systemic BP and pulmonary artery pressure.This research aims at meeting the clinical demand for non-obtrusive and continuous means of monitoring systemic and pulmonary artery pressure. The research is largely interdisciplinary going from MR image processing, EIT reconstruction and simulation to biomedical signal analysis. The expected outcome is a leap forward in the understanding of cardiac EIT signal genesis, and an opening wedge towards new techniques for the portable and non-obtrusive measurement of BP.
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