Quantitative photoacoustic elastography of Young's modulus in humans
Elastography can noninvasively map the elasticity distribution of biological tissue, which is often altered in pathological states. In this work, we report quantitative photoacoustic elastography (QPAE), capable of measuring Young's modulus of human tissue in vivo. By combining photoacoustic elastography with a stress sensor having known stress-strain behavior, QPAE can simultaneously measure strain and stress, from which Young's modulus is calculated. We first applied QPAE to quantify the Young's modulus of tissue-mimicking agar phantoms with different concentrations. The measured values fitted well with both the empirical expectations based on the agar concentrations and those measured in independent standard compression tests. We then demonstrated the feasibility of QPAE by measuring the Young's modulus of human skeletal muscle in vivo. The data showed a linear relationship between muscle stiffness and loading. The results proved that QPAE can noninvasively quantify the absolute elasticity of biological tissue, thus enabling longitudinal imaging of tissue elasticity. QPAE can be exploited for both preclinical biomechanics studies and clinical applications.
Additional Information© 2017 SPIE. We thank Alejandro Garcia-Uribe, Chiye Li, and Guo Li for their help in the project. We also thank Professor James Ballard for a close reading of this paper. This work was sponsored by the March of Dimes Foundation Grant No. 22FY14486 and the US National Institutes of Health grant Nos. DP1 EB016986 (NIH Director's Pioneer Award), R01 CA186567 (NIH Director's Transformative Research Award), and S10 RR026922. L. V. Wang has a financial interest in Microphotoacoustics, Inc., which, however, did not support this work.
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