The purpose of this study is to determine if Electrical Impedance Tomography (EIT) can produce reproducible and accurate images in people with stroke or head injury compared to existing standards such as MRI, CT.

Electrical Impedance Tomography is a relatively new medical imaging method, which has the potential to provide novel images of brain function. It is fast, portable, safe and inexpensive, but currently has a relatively poor spatial resolution. It produces images of the internal electrical impedance of a subject with stroke or head injury using rings of ECG like electrodes on the skin. EIT recording will take place as early as possible, usually within 24 hours of admission. Following completion of the recording, the EIT images will subsequently be analysed and compared to other imaging data for accuracy.

Electrical Impedance Tomography (EIT) is a novel medical imaging method in which tomographic images are rapidly produced using electrodes placed around the body. The principal applicant's group has demonstrated that EIT can rapidly image functional brain activity in stroke, epilepsy and normal activity in animal models and has developed instrumentation and image reconstruction algorithms which work well in head-shaped tanks.

The principal aim of this research is to optimise and assess accuracy of Electrical Impedance Tomography (EIT) using scalp electrodes in imaging stroke/head injury in human participants. EIT could provide a unique new imaging modality which could provide continuous monitoring at the bedside after head injury or diagnosis in the back of an ambulance or GP surgery and so permit rapid deployment of thrombolytic therapy. If successful, EIT would become a standard imaging technique available in all ambulances and A&E departments for this purpose. It would be used in all cases of suspected stroke which present except to dedicated acute stroke centres. Imaging could be undertaken at presentation by paramedical staff if in an ambulance, or nurses or radiographers if in A&E. Images would be reported by radiologists remotely who could then sanction administration of thrombolytic agents by physicians, nurses or paramedical staff. EIT would allow neuroimaging to be undertaken significantly earlier in all situations where a dedicated stroke centre with available urgent CT was not available. This would benefit clinical staff who could provide an improved service and patients, who would enjoy improved outcome and greater access to thrombolytic therapy.

The recording will take place with scalp electrodes while the patient sits comfortably in a chair or lies on a bed. Recording takes for 10 minutes to 1 hour. In some subjects, EIT can be used to image changes in the brain over hours following head injury. In this case, recording will take place over hours or days with scalp electrodes according to the clinical situation. Stroke patients could also be recorded in this study, as similar changes in the injured brain could also occur after stroke. Following completion of the recording, scalp electrodes and any paste will be removed. Collected data will be analysed and compared to other imaging data.

Inclusion Criteria:

• Patient with MRI or CT evidence of a stroke
• Ability to give informed consent or have a consultee able to provide informed consent (for stroke group)
• Any subject admitted for observation following a head injury (for head injury group)

Exclusion Criteria:

• non (for stroke group)
• Any skull fractures or other injury which precludes the safe application of scalp electrodes (for head injury group)

Stroke patients or patients under hospital observation after a head injury at the University College Hospital