Real-time Monitoring System for Pulsatile Cerebral Blood Flow Based on Radio Frequency Coherent Sensing

Pulsatile cerebral blood flow (PCBF) measurement is essential for both clinical practice and research, as it offers critical insights into neurological conditions and directly reflects intracranial blood supply levels, with real-time continuous monitoring proving particularly valuable for enhancing stroke prognosis outcomes. PCBF is intricately linked to the levels of intracranial blood supply and can reflect various pathophysiological states. This study introduces a novel harmonic tag system based on Radio Frequency Coherent Sensing (RFCS) principles for the wireless and real-time monitoring of PCBF. RFCS capitalizes on the coherence between direct reflection signals and intracranial coupling signals to demodulate changes in brain tissue impedance, thereby acquiring crucial pathophysiological data from within the cranium. The system incorporates a harmonic tag, antennas, and the USRP B210 to facilitate this measurement. To validate the system, hypercapnia experiments were conducted involving five healthy volunteers, under three distinct states: normal breathing, hyperventilation, and post-hyperventilation. The measurement results were analyzed for key PCBF parameters: Time to the Peak (T), Systolic Wave Height (A), and Rapid Inflow Phase Area (S). The data revealed that during hyperventilation, T was significantly prolonged, while A and S were notably reduced. Following hyperventilation, T, A, and S values gradually returned to baseline levels. Statistical analysis indicated significant differences (p < 0.05) in the RFCS-derived PCBF parameters across the different states, confirming the sensitivity and accuracy of the experimental platform. These findings underscore the potential of the RFCS-based harmonic tag system for effectively monitoring and analyzing PCBF variations in real-time.