Improving Electrical Impedance Tomography Imaging of the Brain

Hemorrhagic transformation (HT) is an ischemic stroke complication occurring in 10% of ischemic stroke patients with infarcts. HT is detected by symptom and CT monitoring, though exposes patients to repeated radiation doses. Symptom monitoring for detecting perioperative ischemia is ineffective in anesthetized patients. A non-ionizing modality for continuous monitoring of cerebral blood volume (CBV) would therefore be valuable. Electrical impedance tomography (EIT) is an imaging technique that reconstructs the internal conductivity distribution of a body non-invasively. EIT can detect changes in CBV, but only hemorrhage, not ischemia, has been detected with EIT. A novel EIT processing method was developed that depicted arterial blood pressure related CBV changes and successfully detected ischemia in swine, as verified by MRI. Software tools and EIT electrode hardware were developed to apply this method to functional imaging studies in humans. Finally, an automated electrode quality and data rejection tool, which simplifies EIT preprocessing, was developed.