In vivo flow mapping in complex vessel networks by single image correlation

Area of Science:

• Biophysics
• Microscopy
• Fluid Dynamics

Background:

• Accurate measurement of flow speed in microcirculation is crucial for understanding physiological and pathological processes.
• Existing techniques often require multiple images or specialized setups, limiting their applicability in vivo.
• Complex vessel networks present challenges for traditional flow velocimetry methods.

Purpose of the Study:

• To introduce a novel method, Flow Image Correlation Spectroscopy (FLICS), for determining flow speeds in complex vascular networks.
• To validate the theoretical framework of FLICS using systems of increasing complexity.
• To demonstrate the application of FLICS in mapping blood flow in the murine hepatic microcirculatory system.

Main Methods:

• FLICS utilizes a single raster-scanned optical xy-image acquired in vivo via confocal or two-photon microscopy.
• The method analyzes intensity fluctuations in image columns to compute the Cross Correlation Function (CCF).
• The analytical expression of the CCF is derived from scanning fluorescence correlation concepts applied to drifting objects.

Main Results:

• FLICS successfully extracts flow speeds from complex vessel networks using a single microscopy image.
• The theoretical framework was validated across systems of increasing complexity.
• High-resolution mapping of blood flow speed in multiple murine hepatic capillaries was achieved simultaneously from one image.

Conclusions:

• FLICS offers a powerful, non-invasive tool for in vivo velocimetry in complex microcirculatory systems.
• The technique provides high spatial and temporal resolution for dynamic flow monitoring.
• FLICS has significant potential for research in vascular biology and disease.