Blind-deconvolution optical-resolution photoacoustic microscopy for high-resolution imaging of compact capillary

Abstract

As the body's largest solid organ, the liver plays a very important role in the body's metabolism. More and more studies have shown that the liver may be an immune organ. A large amount of blood containing nutrients and pathogenic bacteria enters the liver. The liver is extremely rich in blood vessels, including the hepatic artery and portal vein. In the liver circulation, hepatic sinusoids have a unique structure and maintain normal immune homeostasis. More importantly, many liver diseases will directly affect liver sinusoids, such as hepatitis and liver fibrosis. Therefore, the ability to obtain high-resolution images of liver sinusoids of living livers is of great significance for the study of liver diseases. Photoacoustic imaging is becoming a very promising tool for the research of living organisms. It combines the high contrast of optical imaging and the high resolution of acoustic imaging to realize the imaging of absorption clusters in biological tissues. Since the scattering of ultrasound signals in biological tissues is 2-3 orders of magnitude weaker than the scattering of light in biological tissues, the endogenous absorption difference of tissues is directly used in the imaging process, so photoacoustic imaging has the advantages of deep imaging depth and non-destructive. As an important branch of photoacoustic imaging, photoacoustic microscopy can provide micron-level or even sub-micron-level imaging resolution, which is of great significance for biological research such as liver blood vessel detection. Since the lateral resolution of the photoacoustic microscopy imaging system depends on the focus of the laser, a higher resolution can be obtained by increasing the numerical aperture of the condenser objective. However, a large numerical aperture usually means a shorter working distance and makes the entire imaging system very sensitive to small optical defects. Therefore, the improvement of resolution through this method will be limited in practical applications. This paper implements a method of using iterative deconvolution to obtain a high-resolution photoacoustic image of the liver blood vessel. The focal spot of the photoacoustic microscopy is measured to obtain the lateral PSF (point spread function) of the system. Making the measured PSF as the initial system PSF to perform Lucy- Richardson (LR) deconvolution. The image resolution of liver lobules obtained by this method is higher. The full width at half maximum (FWHM) of the same liver sinusoid width before and after deconvolution are 9.52 μm and 6.65 μm, respectively, and the image definition is increased by about 1.4 times. Experiments show that this method can further improve the clarity of photoacoustic images of liver blood vessels, which lays the foundation for further research on liver diseases.