Research and development of polarized photoacoustic imaging technology
Authors: Liu Jie , Chen Wei , Yang Qiu-Lin , Mu Gen , Gao Hao , Shen Tao , Yang Si-Hua , Zhang Zhen-Hui ,   School of Information Optoelectronics Technology, South China Normal University, Guangzhou 510006, China,   Key Laboratory of Laser Life Sciences, Ministry of Education, Institute of Biological Photonics, South China Normal University, Guangzhou 510631, China
Published: August 2023

Life is a highly ordered combination, and the basic biological processes of cells and tissues are essentially controlled by the structural order of biomolecular assembly, in which the conformational characteristics of biomolecule arrangement, orientation, helix, and folding are closely related to the physiological functions of biological tissues. In the skin, muscle, and nerve tissues of living animals, for instance, fibrous proteins, collagen, nerve fibers, and DNA frequently exhibit molecular spatial conformation properties such as particular alignment or helical structure, and such tissues have distinct optical polarization responses. The fundamental structural foundation for tissues to carry out certain activities is provided by molecular conformational characteristics. Early illness diagnosis will be aided by the accurate detection and efficient revelation of molecular conformational characteristics and their changes. The microscopic organization, structure, orientation, chirality, and other structural details of living things or materials can be obtained by using polarization imaging. The analysis of the imaging depth and polarization data is challenging, despite its widespread usage in the fields of material detection and biological imaging. Photoacoustic imaging preserves both the great contrast of optical imaging and the deep penetration of ultrasonic imaging by using light as an excitation source and ultrasound as the carrier for information transmission. While keeping the benefits of non-invasiveness, it is capable of high-resolution imaging, deep penetration, and functional imaging. A polarized photoacoustic imaging technology has recently been developed to complement polarization optical imaging and allow the collection of three-dimensional polarization data from deeper layers of the medium. This provides a straightforward and efficient method of measuring the polarimetry of tissues, suggesting substantial promise for both biological imaging and substance detection. The evolution of polarized photoacoustic imaging technology is outlined in this paper. First, the technical underpinnings of polarized photoacoustic imaging are described. Then, from the two applications of biological tissue imaging and nanomaterial detection, the related research progress of polarized photoacoustic microscopic imaging, polarized photoacoustic computational tomography, and polarized photoacoustic nanoparticles' molecular imaging is presented. We briefly explain the depolarization that results from particle size, density, and organization as polarized light travels through tissue. In an anisotropic medium, the change in the mid-incident polarization state of such a sample is caused by tissue birefringence and scattering because of the inherent birefringence effect of molecules, whereas in the isotropic medium, depolarization is largely determined by the density and size of the scatter. The potential applications of polarized photoacoustic imaging are then discussed.