Velocity measurements in whole blood using acoustic resolution photoacoustic Doppler

Abstract

Acoustic resolution photoacoustic Doppler velocimetry promises to overcome the spatial resolution and depth penetration limitations of current blood flow measuring methods. Despite successful implementation using blood-mimicking fluids, measurements in blood have proved challenging, thus preventing in vivo application. A common explanation for this difficulty is that whole blood is insufficiently heterogeneous relative to detector frequencies of tens of MHz compatible with deep tissue photoacoustic measurements. Through rigorous experimental measurements we provide new insight that refutes this assertion. We show for the first time that, by careful choice of the detector frequency and field-of-view, and by employing novel signal processing methods, it is possible to make velocity measurements in whole blood using transducers with frequencies in the tens of MHz range. These findings have important implications for the prospects of making deep tissue measurements of blood flow relevant to the study of microcirculatory abnormalities associated with cancer, diabetes, atherosclerosis and other conditions. A comparison of Doppler optical coherence tomography methods, " Biomed. Opt. Express 3(10), 2669–2680 (2012). 6. P. Vennemann, R. Lindken, and J. Westerweel, " In vivo whole-field blood velocity measurement techniques, " Exp. Fluids 42(4), 495–511 (2007). 7. J. Brunker and P. Beard, " Pulsed photoacoustic Doppler flowmetry using time-domain cross-correlation: accuracy, resolution and scalability, " J. Acoust. Soc. Am. 132(3), 1780–1791 (2012). 8. S. L. Chen, T. Ling, S. W. Huang, H. Won Baac, and L. J. Guo, " Photoacoustic correlation spectroscopy and its application to low-speed flow measurement, " Opt. Lett. 35(8), 1200–1202 (2010). 9. A. Sheinfeld, S. Gilead, and A. Eyal, " Photoacoustic Doppler measurement of flow using tone burst excitation, " Opt. Express 18(5), 4212–4221 (2010). 10. A. Sheinfeld, S. Gilead, and A. Eyal, " Simultaneous spatial and spectral mapping of flow using photoacoustic Doppler measurement, " J. Biomed. Opt. 15(6), 066010 (2010). 11. P. J. van den Berg, K. Daoudi, and W. Steenbergen, " Review of photoacoustic flow imaging: its current state and its promises, " Photoacoustics 3(3), 89–99 (2015). Transverse flow imaging based on photoacoustic Doppler bandwidth broadening, " J. Biomed. Opt. 15(2), 021304 (2010). 13. S.-L. Chen, Z. Xie, P. L. Carson, X. Wang, and L. J. Guo, " In vivo flow speed measurement of capillaries by photoacoustic correlation spectroscopy, " Opt. Lett. 36(20), 4017–4019 (2011).