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Published November 30, 2023 | in press
Journal Article Open

Photoacoustic vector tomography for deep haemodynamic imaging

  • 1. ROR icon California Institute of Technology


Imaging deep haemodynamics non-invasively remains a quest. Although optical imaging techniques can be used to measure blood flow, they are generally limited to imaging within ∼1 mm below the skin's surface. Here we show that such optical diffusion limit can be broken through by leveraging the spatial heterogeneity of blood and its photoacoustic contrast. Specifically, successive single-shot wide-field photoacoustic images of blood vessels can be used to visualize the frame-to-frame propagation of blood and to estimate blood flow speed and direction pixel-wise. The method, which we named photoacoustic vector tomography (PAVT), allows for the quantification of haemodynamics in veins more than 5 mm deep, as we show for regions in the hands and arms of healthy volunteers. PAVT may offer advantages for the diagnosis and monitoring of vascular diseases and for the mapping of the function of the circulatory system.

Copyright and License

© The Author(s), under exclusive licence to Springer Nature Limited 2023.


We thank K. Maslov, L. Li and R. Cao for discussions about the flow mechanism; S. L. Spitalnik and P. Buehler for discussions about blood physiology; S. Davis and B. Park for discussion on the potential improvement of flow visualization; and L. Li for the suggestion about fibre coupling and assistance in light alignment. This work was sponsored by the United States National Institutes of Health (NIH) grants U01 EB029823 (BRAIN Initiative) and R35 CA220436 (Outstanding Investigator Award).


These authors contributed equally: Yang Zhang, Joshua Olick-Gibson.

L.V.W., Y.Z. and J.O.-G. designed the study. Y.Z. and J.O.-G. built the system, analysed the data and wrote the paper with input from all authors. Y.Z., J.O.-G. and A.K. performed the experiments. L.V.W., Y.Z., J.O.-G. and A.K. interpreted the data. L.V.W. supervised the study and revised the paper.

Data Availability

The data supporting the findings of this study are provided within the paper and its Supplementary Information. The raw and analysed datasets generated during the study are available for research purposes from the corresponding author on reasonable request.

Code Availability

The reconstruction codes based on the universal back-projection algorithm are proprietary and used in licensed technologies, yet they are available from the corresponding author on reasonable request.

Conflict of Interest

L.V.W. has a financial interest in Microphotoacoustics Inc., CalPACT LLC and Union Photoacoustic Technologies Ltd. These companies did not provide support for this work. All other authors declare no competing interests.


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Additional details

December 1, 2023
December 1, 2023