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Monitoring patients receiving mechanical ventilation is a leading application of electrical impedance tomography. Electrical impedance tomography has been shown to be a viable imaging modality for bedside lung monitoring, which can provide visual information about regional ventilation and pulmonary perfusion. However, a significant challenge in its use for patients receiving mechanical ventilation is efficient and safe electrode placement. The purpose of this paper is to present results from a case study in which a novel electrode solution is being used in a larger study to image patients with acute respiratory distress syndrome. Data was collected during a spontaneous breathing trial using the General Electric simultaneous multiple current source prototype electrical impedance tomography system, and 3-D conductivity difference images were computed using a linearization-based reconstruction algorithm. Regional lung volume estimates were computed from the images. The images show good agreement with the chest x-ray that showed suspected pleural fluid accumulation and atelectesis, and the dynamic global lung volume estimate was in good agreement with the volume range provided by the ventilator. [ABSTRACT FROM AUTHOR]

Objective: In electrical impedance tomography (EIT), we apply patterns of currents on a set of electrodes at the external boundary of an object, measure the resulting potentials at the electrodes, and, given the aggregate dataset, reconstruct the complex conductivity and permittivity within the object. It is possible to maximize sensitivity to internal conductivity changes by simultaneously applying currents and measuring potentials on all electrodes but this approach also maximizes sensitivity to changes in impedance at the interface. Methods: We have, therefore, developed algorithms to assess contact impedance changes at the interface as well as to efficiently and simultaneously reconstruct internal conductivity/permittivity changes within the body. We use simple linear algebraic manipulations, the generalized singular value decomposition, and a dual-mesh finite-element-based framework to reconstruct images in real time. We are also able to efficiently compute the linearized reconstruction for a wide range of regularization parameters and to compute both the generalized cross-validation parameter as well as the L-curve, objective approaches to determining the optimal regularization parameter, in a similarly efficient manner. Results: Results are shown using data from a normal subject and from a clinical intensive care unit patient, both acquired with the GE GENESIS prototype EIT system, demonstrating significantly reduced boundary artifacts due to electrode drift and motion artifact. [ABSTRACT FROM PUBLISHER]

Poor assessment of hydration status during hemodialysis can lead to under- or over-hydration in patients with consequences of increased morbidity and mortality. In current practice, fluid management is largely based on clinical assessments to estimate dry weight (normal hydration body weight). However, hemodialysis patients usually have co-morbidities that can make the signs of fluid status ambiguous. Therefore, achieving normal hydration status remains a major challenge for hemodialysis therapy. Electrical impedance technology has emerged as a promising method for hydration monitoring due to its non-invasive nature, low cost and ease-of-use. Conventional electrical impedance-based hydration monitoring systems employ single-channel current excitation (either 2-electrode or 4-electrode methods) to perturb and extract averaged impedance from bulk tissue and use generalized models from large populations to derive hydration estimates. In the present study, a prototype, single-frequency electrical impedance tomography (EIT) system with simultaneous multi-channel current excitation was used to enable regional hydration change detection. We demonstrated the capability to detect a difference in daily impedance change between left leg and right leg in healthy human subjects, who wore a compression sock only on one leg to reduce daily gravitational fluid accumulation. The impedance difference corresponded well with the difference of lower leg volume change between left leg and right leg measured by volumetry, which on average is ∼35 ml, accounting for 0.7% of the lower leg volume. We have demonstrated the feasibility of using multi-channel EIT to extract hydration information in different tissue layers with minimal skin interference. Our simultaneous, multi-channel current excitation approach provides an effective method to separate electrode contact impedance and skin condition artifacts from hydration signals. The prototype system has the potential to be used in clinical settings for helping optimize patient fluid management during hemodialysis as well as for home monitoring of patients with congestive heart failure, chronic kidney disease, diabetes and other diseases with peripheral edema symptoms. [ABSTRACT FROM AUTHOR]