Detection of intraventricular hemorrhage in neonates using electrical impedance tomography

Electrical impedance tomography (EIT) is a medical imaging technique in which images of conductivity within a body can be inferred from surface electrode measurements. EIT has been studied in different clinical areas such as brain imaging, thorax imaging and breast imaging. The focus of this thesis is to investigate the feasibility of EIT on the detection of intraventricular hemorrhage in premature neonates.;Cerebral intraventricular hemorrhage (IVH) in neonatal human infants is a common consequence of pre-term delivery. It is currently assessed using ultrasound, MRI or CT scan. These modalities are not suitable for continuous monitoring of infants and involve large personnel or equipment costs. Because blood has a high electrical conductivity contrast relative to other cranial tissue, its appearance can be detected and monitored using electrical impedance methods. EIT is a non-invasive, low-cost monitoring alternative to these imaging modalities, and has the potential to measure bleeding rate and approximately localize the bleeding site.;The first part of this work aimed to find a robust current pattern for the detection of IVH. We proposed three different electrode layouts and current patterns (RING, EEG and Cz-RING patterns), and compared their performance using a homogeneous spherical head model. Sensitivity analysis shows that the EEG current pattern has larger absolute selectivities than the RING and Cz-RING patterns in all the regions of interest. Numerical simulation and saline phantom experiments also show that the reconstructed images using the EEG pattern have better image qualities and quantification accuracies in general.;The second part of this study involved numerical simulations and phantom experiments using models with realistic boundary geometry. We investigated the advantage and disadvantage of using a sensitivity matrix calculated from a homogeneous realistic geometry model (the RG matrix). We found that the RG matrix does not always produce better image quality than the spherical matrix when there is a model mismatch in boundary geometry. In addition to that, the RG matrix does not show any advantage in terms of quantification accuracy. Therefore, we decided that using the spherical sensitivity matrix would be a better choice for applications on real subjects.;Finally, post mortem and in vivo experiments were conducted on piglets to validate our method. We were able to detect 0.2 ml saline injections in post mortem piglets and quantify the accumulative blood volumes with consistent accuracy. We successfully detected 0.5 ml blood injections in live animals. The quantification results are consistent for all the in vivo experiments. The reconstructed images of blood volumes are confirmed by the brain slices after each experiment. All the results indicate that EIT will be an effective method for monitoring intraventricular bleeding in neonates.