Cerebral Blood Flow Monitoring with a Portable Radio Frequency Sensing System

Cerebral blood flow (CBF) represents the rate at which blood circulates through the blood vessels in the brain. CBF is a crucial physiological parameter and is a precursor to diagnosing neurodegenerative diseases. CBF irregularities can contribute to an inadequate blood supply to the brain, which affects cerebral metabolism. This leads to a progressive loss of neurons and may result in cognitive impairment, vascular dysfunction, stroke or dementia. Regular monitoring of CBF is critical for proactive assessment of underlying anomalies in the neurovascular system. An innovative Radio Frequency (RF) based sensing system is proposed, which can effectively detect blood flow variations through backscattered RF signal strength. The portable RF sensing system includes a novel miniaturized U-shaped antenna sensor, which is designed to integrate with glasses for live monitoring. The sensor design is validated through microwave computational software and the fabricated sensing system is experimentally validated using artificial blood flow variation within a fabricated brain model. Results are measured on both static and variable flow, and the system can detect blood flow variations (10-90 mL/min) within the fabricated arterial network. The CBF variability is examined through standard deviation in reflected power (max: 7.12 dB, min: 3.10 dB) and analysis of variance test (F-value: 5.76, p-value: 0.038). The safety of the portable sensing system is confirmed through Specific Absorption Rate analysis (SAR < 0.94 W/kg at 100 mW) and thermal transient analysis (increase in tissue temperature < 0.14 °C). The promising results indicate the effectiveness of low-cost, portable systems in non-invasive CBF monitoring.