Abstract
INTRODUCTION: Diffuse Correlation Spectroscopy (DCS) is a non‐invasive optical technique that measures cerebral blood flow (CBF) based on dynamic scattering of coherent light from moving red blood cells. It remains largely untested in the pre‐hospital phase, despite this window being critical for patients with acute neurological emergencies such as stroke.We aimed to determine whether DCS can provide accurate, robust, and continuous CBF measurements during emergency transport, establishing its role as a practical frontline tool in acute stroke care. METHODS: Cerebral blood flow was non‐invasively monitored using diffuse correlation spectroscopy (DCS). The DCS system (built at MGH) used a fiber optical probe placed on the left side of the subject's forehead with a 25 mm source‐detector separation. A blood flow index (BFi) was derived from the autocorrelation of detected light intensity fluctuations. The probe was secured using Tegaderm and covered with dark silicone material for light shielding. A head band was also used in some subjects. Simultaneous continuous arterial blood pressure was collected using a Finometer device (Finapres Medical Systems, Enschede, Netherlands) and a three‐axis accelerometer was used to record any motion of the probe.18 healthy subjects were monitored in a mobile stroke unit (MSU) in Fowler's position, first with the vehicle at rest, then while driving on city streets near the Texas Tech University Health Sciences Center in El Paso. A 20 second breath‐hold (BH) and an 8 second carotid compression (transient hyperemic response test ‐ THRT) were done both at rest, and during motion. DCS BFi time courses were averaged over 3 second intervals to increase the signal to noise ratio (SNR). Subjects were excluded from the group average if they were unable to properly perform the maneuver, if there was missing data or if the stationary measurement SNR was too low. RESULTS: Figure 1 shows normalized group‐averaged responses (vs. a 9‐second baseline period). The maneuver responses agreed well with and without MSU motion. Absolute DCS BFi values at rest were the same when the MSU was stationary or in motion in 75% of the subjects where only Tegadem was used, with mild elevations in others. Nevertheless, even in these cases the maneuver responses remained consistent. CONCLUSIONS: These findings demonstrate the feasibility of employing DCS in emergency pre‐hospital settings. We obtained repeatable, physiologically plausible CBF measurements when compared to published in‐lab studies, supporting the robustness of DCS against motion artifacts for real‐time cerebral perfusion monitoring in acute stroke care. [Image: see text]