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Journal of Biomedical Optics

Photoacoustic thermal flowmetry with a single light source
Author(s): Wei Liu; Bangxin Lan; Leo Hu; Ruimin Chen; Qifa Zhou; Junjie Yao
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Paper Abstract

We report a photoacoustic thermal flowmetry based on optical-resolution photoacoustic microscopy (OR-PAM) using a single laser source for both thermal tagging and photoacoustic excitation. When an optically absorbing medium is flowing across the optical focal zone of OR-PAM, a small volume of the medium within the optical focus is repeatedly illuminated and heated by a train of laser pulses with a high repetition rate. The average temperature of the heated volume at each laser pulse is indicated by the photoacoustic signal excited by the same laser pulse due to the well-established linear relationship between the Grueneisen coefficient and the local temperature. The thermal dynamics of the heated medium volume, which are closely related to the flow speed, can therefore be measured from the time course of the detected photoacoustic signals. Here, we have developed a lumped mathematical model to describe the time course of the photoacoustic signals as a function of the medium’s flow speed. We conclude that the rising time constant of the photoacoustic signals is linearly dependent on the flow speed. Thus, the flow speed can be quantified by fitting the measured photoacoustic signals using the derived mathematical model. We first performed proof-of-concept experiments using defibrinated bovine blood flowing in a plastic tube. The experiment results have demonstrated that the proposed method has high accuracy (∼±6%) and a wide range of measurable flow speeds. We further validated the method by measuring the blood flow speeds of the microvasculature in a mouse ear in vivo.

Paper Details

Date Published: 5 September 2017
PDF: 6 pages
J. Biomed. Opt. 22(9) 096001 doi: 10.1117/1.JBO.22.9.096001
Published in: Journal of Biomedical Optics Volume 22, Issue 9
Show Author Affiliations
Wei Liu, Duke Univ. (United States)
Bangxin Lan, Duke Univ. (United States)
Leo Hu, Duke Univ. (United States)
Ruimin Chen, The Univ. of Southern California (United States)
Qifa Zhou, The Univ. of Southern California (United States)
Junjie Yao, Duke Univ. (United States)

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