Conventional photoacoustic computed tomography (PACT) images the spatial distribution of optical absorption, which is approximated as an isotropic optical property. The optical absorption of many biological tissues, however, is anisotropic. This anisotropy, known as dichroism or diattenuation, encodes rich information about molecular conformation and structural alignment. Here we report a novel imaging method called dichroism-sensitive PACT (DS-PACT). Using a lock-detection strategy, our method can measure the amplitude of tissue’s dichroism and the orientation of the optic axis of uniaxial dichroic tissue, even at a depth of 3.25 transport mean free paths. We experimentally demonstrated DS-PACT by imaging plastic polarizers and ex vivo bovine tendons deep inside scattering media. Our method extends the functionality of PACT to include a new capability, imaging tissue absorption anisotropy.
Yuan Qu, Lei Li, Yuecheng Shen, Junjie Yao, Terence T. W. Wong, and Lihong V. Wang, "Imaging dichroism by photoacoustic computed tomography (Conference Presentation)," Proc. SPIE 10494, Photons Plus Ultrasound: Imaging and Sensing 2018, 104941U (Presented at SPIE BiOS: January 30, 2018; Published: 15 March 2018); https://doi.org/10.1117/12.2287432.5752215457001.
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