A non-invasive real-time monitoring system for cytotoxic brain edema in postischemic stroke based on near-field coupling

BACKGROUND: As a common secondary pathophysiological process in postischemic stroke (IS), cytotoxic brain edema (CBE) is an independent factor leading to poor prognosis of patients. Near-field coupling (NFC) technology has some advantages such as non-invasive, non-contact, and unimpeded penetration of the skull. In theory, it can reflect the difference between normal and edema tissues through the near-field coupling phase shift (NFCPS) in the electromagnetic wave transmission trait. METHODS: Combining NFC detection principle and computer programming, we established a high-performance real-time monitoring system with functions such as automatic setting of measurement parameters, data acquisition, real-time filtering and dynamic waveform display. To investigate the feasibility of this system to detect CBE, a saline simulation experiment and a 24-hour real-time monitoring experiment after middle cerebral artery occlusion (MCAO) in rats were carried out. RESULTS: The results of the saline simulation experiment showed that the change of NFCPS was proportional to the increase of the simulated edema solution, and the variation range of NFCPS was more than 9∘ after 5 ml injection. In the 24-hour monitoring after MCAO, the NFCPS of the experimental group showed an overall downward trend over time an average change of -17.7868 ± 1.6325∘ and the change rate gradually decreased. The 24-hour NFCPS in the control group fluctuates slightly around the initial value, which has no obvious upward or downward trend. CONCLUSION: The intragroup and intergroup difference statistical analysis shows that NFCPS can effectively distinguish different intracranial pathophysiological states after IS. This work provides sufficient evidence and a technical basis for using NFCPS to monitor CBE in the future.