Electrical Impedance Changes at Different Phases of Cerebral Edema in Rats with Ischemic Brain Injury

Abstract

Cerebral edema contributes significantly to the morbidity and mortality associated with many common neurologic conditions. Clinically, a diagnostic tool that can be used to monitor cerebral edema in real-time and differentiate between different types of cerebral edema is urgently needed. Because there are differences in electrical impedance between normal cortical tissue and cerebral edema tissue, electrical impedance tomography (EIT) can potentially be used to detect cerebral edema. Accurate recording of the electrical impedance properties of cerebral edema tissue at different time points is important when detecting cerebral edema with EIT. In this study, a rat cerebral edema model was established; then, following the onset of ischemic brain injury, variation in the electrical impedance of cerebral edema was measured at different time points within a 24-hour period and the corresponding morphologic variation was analyzed. After the first six hours, following the onset of ischemic brain injury, the resistivity of brain tissue increased (p < 0.05); during this period, brain cell volume increased (p < 0.05) and the intercellular space decreased (p < 0.05) (behaving like cytotoxic cerebral edema). From 6 to 24 hours, the resistivity of brain tissue decreased; during this time, brain cell volume unchanged (p > 0.05) while intercellular space increased (p < 0.05) (behaving like vasogenic cerebral edema). These findings support the notion that EIT can be used to monitor the development of cerebral edema in real-time and differentiate between different types of brain edema.

A Preliminary Study on the Feasibility of Detecting Global Acute Cerebral Ischemia by the MIPS Method

“…In 2018, Neeraja et al reported that the penetration depth of the sensor is inadequate to compensate for the increased distance between the sensor and brain tissue, thereby resulting in inaccurately high values (>80%) [21]. A shortcoming of EIT is that the highly resistant skull has a natural electrical isolation that limits current penetration and restricts deep imaging of the brain [22]. The main magnetic field created by a detection system can easily penetrate the skull although resistance is very high.…”

Twenty-four-hour real-time continuous monitoring of acute focal cerebral ischemia in rabbits based on magnetic inductive phase shift

“…The MIPS variation trend in the experimental group may be related to the occurrence of cytotoxic edema and vasogenic edema after cerebral ischemia. According to the measurement result of Song et al [27], the dielectric property presented a first increasing and then decreasing trend after focal cerebral ischemic injury in mice. As pointed out by Schafer et al [28], the impedance of skeletal muscle also first increased and then decreased due to ischemia.…”

“…As pointed out by Schafer et al [28], the impedance of skeletal muscle also first increased and then decreased due to ischemia. According to the pathological process analysis of cerebral ischemic stroke, cytotoxic edema and vasogenic edema after cerebral ischemia constituted a dynamic variation process, where they played a dominant role at the early and later stages, respectively [27,29].…”

A noninvasive flexible conformal sensor for accurate real-time monitoring of local cerebral edema based on electromagnetic induction

“…But continuous TCD is still under improvement. Electrical Impedance Tomography (EIT) has been proposed as a possible method to detect cerebral injuries (Song et al, 2018). Yet EIT requires current injection through a series of electrodes precisely placing on the corresponding position on the head, not mention that the current is ''blocked'' by the high resistivity skull which in turns may reduce the detection precision (Yan et al, 2017).…”