Label-free quantitative measurement of cardiovascular dynamics in a zebrafish embryo using frequency-comb-referenced-quantitative phase imaging.

Significance: Real-time monitoring of the heart rate and blood flow is crucial for studying cardiovascular dysfunction, which leads to cardiovascular diseases.

Aim: This study aims at in-depth understanding of high-speed cardiovascular dynamics in a zebrafish embryo model for various biomedical applications via frequency-comb-referenced quantitative phase imaging (FCR-QPI).

Approach: Quantitative phase imaging (QPI) has emerged as a powerful technique in the field of biomedicine but has not been actively applied to the monitoring of circulatory/cardiovascular parameters, due to dynamic speckles and low frame rates.

High-brightness laser imaging with tunable speckle reduction enabled by electroactive micro-optic diffusers.

High coherence of lasers is desirable in high-speed, high-resolution, and wide-field imaging. However, it also causes unavoidable background speckle noise thus degrades the image quality in traditional microscopy and more significantly in interferometric quantitative phase imaging (QPI). QPI utilizes optical interference for high-precision measurement of the optical properties where the speckle can severely distort the information.

Speckle reduction in quantitative phase imaging by generating spatially incoherent laser field at electroactive optical diffusers.

We studied quantitative phase imaging (QPI) using coherent laser illumination coupled with static and moving optical diffusers. The spatial coherence of a continuous-wave laser was controlled by tuning the particle size and the diffusion angle of optical diffusers for speckle-reduced 3D phase imaging of transparent objects. We used a common-path QPI configuration to investigate the coherent phase mapping of polystyrene micro-beads and breast cancer cells (MCF-7) under different degrees of coherent speckles.