Assessing Sensitivity of Brain-to-Scalp Blood Flows in Laser Speckle Imaging by Occluding the Superficial Temporal Artery

TL;DR

This study demonstrates that laser speckle imaging can differentiate between scalp and brain blood flow by occluding the superficial temporal artery, optimizing non-invasive cerebral blood flow measurement.

Contribution

We developed a multi-channel speckle contrast system and validated its ability to isolate brain signals from scalp blood flow during artery occlusion.

Findings

Scalp blood flow decreased significantly during occlusion.

Brain blood flow showed minimal change during occlusion.

Optimal channel configurations enhance brain signal detection.

Abstract

Cerebral blood flow is a critical metric for cerebrovascular monitoring, with applications in stroke detection, brain injury evaluation, aging, and neurological disorders. Non-invasively measuring cerebral blood dynamics is challenging due to the scalp and skull, which obstruct direct brain access and contain their own blood dynamics that must be isolated. We developed an aggregated seven-channel speckle contrast optical spectroscopy system to measure blood flow and blood volume non-invasively. Each channel, with distinct source-to-detector distance, targeted different depths to detect scalp and brain blood dynamics separately. By briefly occluding the superficial temporal artery, which supplies blood only to the scalp, we isolated surface blood dynamics from brain signals. Results on 20 subjects show that scalp-sensitive channels experienced significant reductions in blood dynamics during occlusion, while brain-sensitive channels experienced minimal changes. This provides experimental evidence of brain-to-scalp sensitivity in optical measurements, highlighting optimal configuration for preferentially probing brain signals non-invasively.