The imaging depth and contrast of optical imaging are restricted as a result of high optical scattering of biological tissue. The optical clearing techniques can be used to reduce the optical scattering thus improve the imaging depth and contrast. However, the mechanism of optical clearing is still in controversy. The monitoring of changes of structure and parameters during optical clearing is critical to understand the mechanism. And it would be a good measure in selection and application of optical clearing agent.
The research teams led by Prof. Qingming Luo combined the photoacoustic microscopy and ultrasonography to monitor the changes of ultrasonic and optical parameters during optical clearing for the first time. The ultrasonography revealed the structural changes of collagen fibers and also the water content in skin. The photoacoustic microscopy showed the signal enhancement of subcutaneous blood vessels. The results verified the hypothesis of mechanism, and more significantly, the results could be used to estimate the potential of penetration and optical clearing in vivo. This work was published in Optics Express (Vol. 22, No. 1, pp. 1094-1104, 2014).
The work was supported by National Major Scientific Research Program of China (Grant No. 2011CB910401), Science Fund for Creative Research Group of China (Grant No. 61121004), and National Natural Science Foundation of China (Grants No. 81201067, 81171376).
The figures showed the photoacoustic images, ultrasonic echo images and fused images before and after the optical clearing. The photoacoustic signal of subcutaneous blood vessels was enhanced, the echoheterogenity was elevated and also obvious dehydration could be seen.