Structured-illumination photoacoustic Doppler flowmetry of axial flow in homogeneous scattering media
We propose a method for photoacoustic flow measurement based on the Doppler effect from a flowing homogeneous medium. Excited by spatially modulated laser pulses, the flowing medium induces a Doppler frequency shift in the received photoacoustic signals. The frequency shift is proportional to the component of the flow speed projected onto the acoustic beam axis, and the sign of the shift reflects the flow direction. Unlike conventional flowmetry, this method does not rely on particle heterogeneity in the medium; thus, it can tolerate extremely high particle density. A red-ink phantom flowing in a tube immersed in water was used to validate the method in both the frequency and time domains. The phantom flow immersed in an intralipid solution was also measured.
Additional Information© 2013 AIP Publishing LLC. Received 3 July 2013; accepted 15 August 2013; published online 28 August 2013. The authors would like to thank Professor James Ballard for his close reading of the manuscript. We also appreciate technical assistance from and useful discussions with Lidai Wang, Yong Zhou, Jinyang Liang, Wenxin Xing, Arie Krumholz, and Yan Liu. This research was supported by the National Institutes of Health Grants DP1 EB016986 (NIH Director's Pioneer Award), R01 EB008085, R01 CA134539, U54 CA136398, R01 CA157277, R01 CA159959. L.V.W. has a financial interest in Microphotoacoustics, Inc. and Endra, Inc., which, however, did not support this work. K.M. has a financial interest in Microphotoacoustics, Inc., which, however, did not support this work.
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