Diffuse Correlation Spectroscopy (DCS) is an established optical technique for noninvasive monitoring of cerebral blood flow (CBF). Conventional DCS implementations typically measure changes averaged across superficial cortical tissue volumes rather than within specific intracranial arteries. A vessel-targeted approach would extend DCS utility to continuous bedside assessment of vessel-specific cerebral perfusion, which could be valuable for cerebrovascular monitoring and acute stroke care.
The primary aim was to investigate the feasibility of targeted, noninvasive monitoring of blood flow in the Anterior Cerebral Artery (ACA) using DCS by optimizing probe geometry and placement to increase sensitivity to ACA-related flow changes.
The investigators used a custom-built DCS system operating at 785 nm to probe the ACA from the glabellar region. They systematically varied three probe parameters to maximize ACA sensitivity: source-detector (SD) separation, probe orientation, and exact probe location on the forehead. Optimization was guided by physiologic tasks that elicit ACA-territory hemodynamic changes: lower-limb motor activations and a mental arithmetic task were used as functional provocation to reveal which probe geometries best captured ACA-related flow changes.
The configuration that provided the highest sensitivity to ACA-related blood flow changes was an SD separation of 17 mm, a vertical probe orientation, and placement at the glabella. These parameters were selected based on task-evoked signal response during the optimization experiments.
To test the optimized configuration in a controlled setting, the team constructed an ACA-mimicking multilayer phantom. Phantom experiments evaluated sensitivity to flow changes in a simulated vessel located 45 mm beneath the scalp surface. The phantom studies showed measurable sensitivity to deep-vessel flow at this depth when probed through the glabellar window.
The authors note that the anatomical features beneath the glabella—specifically the presence of the frontal sinus, a cerebrospinal fluid layer, and relative absence of cortical tissue beneath the longitudinal fissure—create an optical window that favors probing of deeper ACA flow compared with other frontal locations.
The optimized probe configuration was validated in forty healthy volunteers. Physiologic perturbations intended to engage ACA territory perfusion included lower-limb activation tasks and postural changes. Two tasks explicitly reported in the results were standing leg marching and supine leg crunches, and responses to supine-to-stand postural transitions were also examined to assess the consistency of ACA-directed flow changes under dynamic conditions.
Phantom experiments demonstrated that the optimized DCS configuration could detect flow changes in a vessel positioned 45 mm below the scalp in a multilayer model that mimics the glabellar region.
In the cohort of forty healthy volunteers, the optimized DCS probe detected significant relative increases in cerebral blood flow during motor tasks: mean increases of 66.4 ± 38.6% during standing leg marching and 39.4 ± 32.2% during supine leg crunches. Task-evoked responses and supine-to-stand postural transitions produced consistent signals with statistical significance reported as p < 0.01 for the observed changes.
The reported results support the feasibility of a targeted DCS approach to measure blood flow within the ACA territory noninvasively. Key technical findings include the suitability of a 17 mm SD separation, vertical probe orientation, and glabellar placement for maximizing sensitivity to ACA flow, and the identification of the glabellar anatomical window (frontal sinus and CSF geometry) as advantageous for deep-vessel optical access.
Phantom validation confirms sensitivity to a vessel at approximately 45 mm depth, and human volunteer data show robust task-evoked increases in relative CBF using the optimized configuration. The authors propose that this technique provides a framework for continuous, bedside monitoring of ACA perfusion with potential applications in cerebrovascular monitoring and stroke care.
It should be noted that the article is a preprint and has not been peer reviewed. Details not reported in the available source text—such as full demographic breakdown of the volunteer cohort, complete statistical methodology, long-term reproducibility, and clinical performance in disease states—are not available here and would require consultation of the full manuscript or subsequent peer-reviewed publications.
Targeted DCS with the described probe geometry and glabellar placement appears feasible for noninvasive monitoring of Anterior Cerebral Artery blood flow. Phantom and healthy-volunteer data indicate sensitivity to deep-vessel flow and task-evoked CBF changes. The approach may enable continuous, vessel-specific perfusion monitoring at the bedside, warranting further validation and clinical testing.