Studies of in vivo speckle contrast imaging based on an improved laser speckle imaging method.

Significance: Laser speckle contrast imaging (LSCI) is widely used for intraoperative blood flow monitoring, but traditional methods have limitations in imaging low blood flow velocities and small vessels. An improved LSCI method, termed the fluent imaging technique, is proposed to enhance imaging sensitivity and accuracy, providing real-time and high-resolution blood flow assessment for neurosurgical applications.

Aim: We aim to validate the performance of the fluent imaging technique in imaging small vessels with low blood flow velocities and assess its application in cerebrovascular surgical procedures, including carotid artery clamping, reperfusion, and ferric chloride ${(\mathrm{FeCl}}_3)$ -induced thrombosis.

Approach: The fluent imaging technique was validated in vivo using male Sprague-Dawley rats, with three types of experiments: (1) ear vein vessel imaging, (2) proximal common carotid artery blood flow intervention (stenosis and clamping), and (3) ${\mathrm{FeCl}}_3$ -induced thrombosis. Blood flow changes were monitored in real time using an LSCI system, and signal-to-background ratio (SBR) analysis was conducted to assess image quality improvements.

Results: The fluent imaging technique improved image quality, particularly for small vessels and low-velocity blood flow, compared with traditional LSCI methods. In capillary regions, it achieved up to 189% improvement in SBR over spatial contrast (SK) and 37% over AWSDK. In a selected region of interest, the SBR increased from 0.53 (SK) and 1.12 (AWSDK) to 1.53 with the fluent imaging method. In carotid artery interventions, the method effectively captured dynamic blood flow changes, including early Relative Blood Flow Index (RBFI) recovery after clamp release. In ${\mathrm{FeCl}}_3$ -induced thrombosis experiments, it detected vascular occlusion and collateral perfusion.

Conclusions: The fluent imaging technique enhances the accuracy and sensitivity of LSCI for blood flow monitoring in neurosurgery. It provides reliable real-time intraoperative assessment of vascular conditions, improving surgical safety and efficacy. We establish a foundation for its broader clinical application and further optimization.