Abstract
Stroke is a severe cerebrovascular disease and is the second greatest cause of death worldwide. Because diagnostic tools (CT and MRI) to detect acute stroke cannot be used until the patient reaches the hospital setting, a portable diagnostic tool is urgently needed. Because biological tissues have different impedance spectra under normal physiological conditions and different pathological states, multi-frequency electrical impedance tomography (MFEIT) can potentially detect stroke. Accurate impedance spectra of normal brain tissue (gray and white matter) and stroke lesions (ischemic and hemorrhagic tissue) are important elements when studying stroke detection with MFEIT. To our knowledge, no study has comprehensively measured the impedance spectra of normal brain tissue and stroke lesions for the whole frequency range of 1 MHz within as short as possible an ex vivo time and using the same animal model. In this study, we established intracerebral hemorrhage and ischemic models in rabbits, then measured and analyzed the impedance spectra of normal brain tissue and stroke lesions ex vivo within 15 min after animal death at 10 Hz to 1 MHz. The results showed that the impedance spectra of stroke lesions significantly differed from those of normal brain tissue; the ratio of change in impedance of ischemic and hemorrhagic tissue with regard to frequency was distinct; and tissue type could be discriminated according to its impedance spectra. These findings further confirm the feasibility of detecting stroke with MFEIT and provide data supporting further study of MFEIT to detect stroke.
Highlights
Acute stroke is a severe cerebrovascular disease. It can be broadly divided into ischemic stroke caused by cerebral venous thrombosis and hemorrhagic stroke caused by intracerebral hemorrhage or subarachnoid hemorrhage [1]
The black arrow indicates the location of the stroke lesion
In the case of normal brain tissue, white matter impedance was greater than gray matter impedance over the whole frequency range (Figure 4), which largely agrees with previous studies [6,26]
Summary
Acute stroke is a severe cerebrovascular disease. It can be broadly divided into ischemic stroke caused by cerebral venous thrombosis and hemorrhagic stroke caused by intracerebral hemorrhage or subarachnoid hemorrhage [1]. Stroke is characterized by high morbidity and mortality and is the second greatest cause of death worldwide after ischemic heart disease [2]. The prognosis of stroke patients can be significantly improved if prompt intervention by clinical staff is given. Two different types of stroke patients require distinct treatment. Ischemic patients are given tissue plasminogen activator, a thrombolytic agent, within 3–4.5 h [3], while hemorrhagic stroke patients are treated with timely surgery. Because thrombolytic therapy makes hemorrhagic stroke worse, before treatment, prompt brain imaging is needed to discriminate ischemic from hemorrhagic stroke
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