Electrical Impedance Imaging Laboratory
EIT reconstruction algorithms and hardware systems for clinical applications
We are an applied mathematics group focused on the research and development of novel medical imaging techniques.
To learn more, meet our team, or inquire about collaboration opportunities, please explore the options below:
Electrical impedance tomography reveals ventilation and perfusion heterogeneity in infants with bronchopulmonary dysplasia
Katelyn G. Enzer, Nilton Barbosa Da Rosa Jr, Allison Keck, Ella Hagopian, John T. Brinton, Omid Rajabi Shishvan, Gary Saulnier, David Isaacson, Jennifer L. Mueller & Christopher D. Baker.
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Objective
Preterm infants have pulmonary ventilation and perfusion abnormalities, yet few imaging modalities can inform clinicians about this ventilation/perfusion (V/Q) relationship. Electrical impedance tomography (EIT) is an imaging technique with V/Q imaging capabilities that has not been well described in infants with BPD.
Study design
EIT was performed every 4 weeks in preterm infants for a maximum of 5 visits per infant. Term infants with healthy lungs had one EIT imaging visit as controls.
Results
Data were collected from a total of 51 EIT visits. Novel V/Q maps were generated from each visit. Ventilation heterogeneity (measured by the global inhomogeneity index) and V/Q heterogeneity (measured by coefficient of variation of V/Q maps) were significantly higher in preterm infants at the visit closest to 36 weeks post-menstrual age than controls (p = 0.002 and p = 0.039, respectively).
Conclusions:
Pulmonary ventilation, perfusion, and V/Q relationship can be quantified by EIT, and may be indicators of chronic lung disease.
CT scans without X-rays: Parallel-beam imaging from nonlinear current flows
Melody Alsaker, Siiri Rautio, Fernando Moura, Juan Pablo Agnelli, Rashmi Murthy, Matti Lassas, Jennifer L. Mueller, and Samuli Siltanen.
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Parallel-beam X-ray computed tomography (CT) and electrical impedance tomography (EIT) are two imaging modalities that stem from completely different underlying physics, and for decades have been thought to have little in common either practically or mathematically. CT is only mildly ill-posed and uses straight X-rays as measurement energy, which admits simple linear mathematics. However, CT relies on exposing targets to ionizing radiation and requires cumbersome setups with expensive equipment. In contrast, EIT uses harmless electrical currents as measurement energy and can be implemented using simple low-cost portable setups. But EIT is burdened by nonlinearity stemming from the curved paths of electrical currents, as well as extreme ill-posedness that causes characteristic low spatial resolution. In practical EIT reconstruction methods, nonlinearity and ill-posedness have been considered intertwined in a complicated fashion. In this work, we demonstrate a surprising connection between CT and EIT, first announced in the theoretical work by Greenleaf et al., 2018, which partly unravels the main problems of EIT and leads directly to a proposed reconstruction technique that we call virtual hybrid parallel-beam tomography (VHPT). We show that hidden deep within EIT data is information that possesses the same linear geometry as parallel-beam CT data. This admits a fundamental restructuring of EIT, separating ill-posedness and nonlinearity into simple modular sub-problems, and yields “virtual radiographs” and CT-like images that reveal previously concealed information. Furthermore, as proof of concept, we present VHPT images of simulated and experimentally collected data
Use of an anatomical atlas in real-time EIT reconstructions of ventilation and pulsatile perfusion in preterm infants
Christopher J. Rocheleau, Trevor D. Overton, Nilton Barbosa da Rosa Jr., Gary J. Saulnier, Omid Rajabi Shishvan, Christopher D. Baker, Katelyn G. Enzer & Jennifer L. Mueller.
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Electrical impedance tomography (EIT) is a bedside imaging technique in which voltage data arising from current applied on electrodes is used to compute images of admittivity in real time. Due to the severe ill-posedness of the inverse problem, good spatial resolution poses a challenge in EIT. Conversely, the temporal resolution is high, facilitating dynamic bedside imaging. In this work, we propose a real-time linearized reconstruction algorithm that makes use of an anatomical atlas to provide prior spatial information at two stages of the reconstruction with the goal of improving the spatial resolution. The algorithm updates a non-constant initial estimate of an anatomically relevant distribution of conductivity and susceptivity obtained from the mean of the atlas, and using the Schur complement method as a post-processing technique. Two atlases are constructed from a database of CT scans of 89 infants; one for the reconstruction of ventilation and one for the reconstruction of pulsatile perfusion. The algorithm is applied to data collected on 16 premature infants with lung disease of prematurity and 5 healthy control infants to reconstruct conductivity and susceptivity images of both ventilation and pulsatile perfusion in real time using the ACT 5 EIT system. EIT parameters describing homogeneity of ventilation distribution throughout the lung and the distribution anterior/posterior and in the left versus right lung were computed for each infant. The left/right ventilation distribution was found to distinguish between the healthy and the preterm infants with statistical significance (p-value< 0.05). The reconstructions demonstrate qualitatively improved resolution when compared to the NOSER algorithm currently used on the ACT 5 system for real-time bedside imaging, and the ability to image changes due to ventilation and pulsatile perfusion, as well as regional inhomogeneity. Since CT scans were not available for these infants, there is no gold standard for validation. In conclusion, we present a novel real-time algorithm with the goal of improving spatial resolution for bedside imaging with EIT for conductivity and susceptivity imaging of ventilation and pulsatile perfusion, with the potential to aid in the evaluation of lung function in infants at the bedside.
Feasibility of Electric Impedance Tomography in the Assessment of Lung Perfusion and Ventilation in Congenital Pulmonary Vein Stenosis
Jenny E. Zablah, Catalina Vargas-Acevedo, Nilton Barbosa da Rosa Jr., Omid Rajabi Shishvan, Gary Saulnier, David Isaacson, Gareth J. Morgan & Jennifer L. Mueller.
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Pulmonary vein stenosis (PVS) is a complex disease that requires repeated percutaneous interventions. Electrical impedance tomography (EIT) is a functional imaging technique that provides real-time images of pulmonary perfusion and ventilation. We aimed to determine the feasibility of EIT to evaluate ventilation/perfusion in PVS before and after catheter-based interventions. EIT was conducted in patients with PVS using the ACT5 EIT system. Lung regions were segmented from the perfusion images, and time-dependent blood volume curves were computed voxel-wise and by lung region. The distribution of pulmonary blood flow (PBF) was computed from EIT images and compared pre and post intervention. Finally, a blinded interventional cardiologist reviewed the results to evaluate three findings: (1) side and extent of PVS, (2) perfusion, and (3) ventilation. During the study period, twelve patients were included. Of these, seven were female (58.3%) with a median age of 3.5 years. Six patients had history of prematurity, and four had history of previous surgical PVS intervention. Three patients (25%) had an episode of pulmonary hemorrhage during the current intervention. In general, ventilation/perfusion data were successfully obtained in all cases. EIT correctly depicted all 12 cases of PVS correlating with angiography performed on the same day. EIT is a non-invasive, radiation-free technique that estimates lung perfusion/ventilation and percent distribution of PBF. The subject-based evaluation of EIT correlates to the severity and sidedness of the veins involved. This technology has the potential of providing perfusion/ventilation information in-PVS patients without the need of contrast or radiation
Albert C. Yates Endowed Chair in Mathematics
Professor
Department of Mathematics
Professor (Joint Appointment)
School of Biomedical Engineering, Department of Electrical and Computer Engineering
Courses: MATH 535, MATH 633