Optimized laser speckle-based imaging system and methods for deep tissue cerebral blood flow imaging in small rodents.

Significance: The imaging of cerebral blood flow in small rodents is crucial for a better understanding of brain functions in healthy and diseased conditions. Existing methods often struggle to provide both superficial and deep tissue blood flow measurements in a non-invasive, flexible, and reliable manner, creating a need for an integrated platform that addresses these limitations.

Aim: We aim to design and develop a multi-modal laser speckle-based imaging platform and associated algorithms to image superficial and deep tissue cerebral blood flow in small rodents.

Approach: A modular design has been adopted to integrate laser speckle contrast imaging and multi-speckle diffuse correlation tomography to a single cerebral blood flow imaging platform for small rodents with an independent module for animal holding and handling. A topographic imaging method, equipped with a filter to remove surface artifacts, was incorporated to image cerebral blood flow changes in response to forepaw and olfactory stimuli activations, with the skull and scalp kept intact.

Results: A significant increase in blood flow was found in the olfactory bulbs of mice post-stimulation by various odors ( $p<0.01$ ). Similarly, forepaw stimulation resulted in a significant increase in blood flow in the contralateral side of the somatosensory cortex with the application of the filter for skull and scalp intact, skull intact, and skull removed cases ( $p<0.01$ ).

Conclusions: We have validated our system through functional studies, demonstrating its capability to detect enhanced blood flow changes across the olfactory bulbs and somatosensory cortex in rodents with potential for broad applications in preclinical research.