In this study, a detection system based on Polarization-Sensitive Optical Coherence Tomography (PS-OCT) using Mueller Matrix Optical Coherence Tomography (MM-OCT) was developed. By employing PS-OCT technology, the system was able to fully detect all sixteen elements of the Mueller matrix. By comparing the intensity element M00 among the sixteen elements of the Mueller matrix, the texture structure of the pearl layers could be observed. This allowed for differentiation between freshwater and saltwater pearls, identification of genuine and fake pearls, detection of internal flaws in pearls, and differentiation between nucleated and non-nucleated pearls. The study also involved the labeling of connected regions in binary images, where pixels within the same connected region were assigned the same label. The labeled images were displayed to facilitate more intuitive qualitative analysis, and quantitative analysis was performed using gray-level co-occurrence matrices. Subsequently, pearl layer pixels were extracted from multiple angles in the images, and the thickness of the pearl layer was calculated using the extracted pixels and axial resolution. Finally, detection and classification of unknown pearls were conducted, yielding results consistent with the actual outcomes. The measured thickness results after sectioning matched the calculated results, providing evidence for the feasibility of the experimental method proposed in this study.
Photoacoustic Imaging (PAI) is a non-invasive imaging technology. It breaks through the limitation of shallow imaging depth of traditional optical imaging and low imaging contrast of acoustic imaging. It has a potential wide application in early cancer detection. PAI combined with endoscopy has great significance in the early diagnosis of gastric tumors. However, imaging just obtains the local location information. It cannot obtain the information of any location visually, especially in the process of photothermal therapy. In this paper, COMSOL was employed to simulate the visual model of photoacoustic photothermal imaging of gastric tissue and tumor. The physical processes of photoacoustic imaging such as photothermal strain-ultrasound generated by pulsed laser in stomach were simulated. A complete photoacoustic model was established through the coupling of each physical field. Firstly, a simplified gastric tissue model was constructed, and physical parameters were set for grid division. Then several physical field modules in COMSOL were coupled. The light distribution, temperature change and photoacoustic signal generated by thermal expansion during the propagation of light in biological tissues were obtained by simulation. The simulation results showed that the distribution of light in gastric tumor was significantly lower than that around the stomach. The tumor absorbs more light energy, resulting in a significantly higher temperature than surrounding stomach tissue. The photoacoustic signal of thermal expansion caused by laser irradiation of biological tissue was obtained. This study is helpful to understand the propagation and interaction of light in normal tissues and gastric tumors. It also provides a certain reference for the research and application of photoacoustic imaging in gastric cancer.
In this study, the modified spectral domain polarization-sensitive optical coherence tomography (SD PS-OCT) is proposed for determining the birefringence of the myocardial tissue. In this modified SD PS-OCT, the circular polarization state of light was generated before entering the beam splitter. Thus, the polarization states in the reference and sample arms are both circular, and the symmetry between them is good without using additional Quarter-Wave Plate (QWP), which reduce the dispersion effect. The results demonstrated that theoretical analysis for determination of birefringence including the phase retardance and the fast axis orientation based on Stokes parameters of backscattered from biological tissue, which is different from the traditional SD PS-OCT. In addition, the phase retardance and the fast axis orientation was used to differentiate the myocaridal tissue in the diastole of the cardiac cycle the from that in the systole of the cardiac cycle. The findings suggest that the SD PS-OCT be a potential tool for the real-time monitoring the change of the myocardial wall during the cardiac cycle.
Due to the advantages of high sensitivity, high resolution and nondestructive in vivo three-dimensional detection, optical coherence tomography has been widely studied in various fields such as biology, genetics and medicine. Zebrafish is a kind of freshwater fish, whose embryos are easy to reproduce in large numbers and have high transparency for observation. In particular, the genetic homology between zebrafish and human is as high as 70%, which makes zebrafish gradually become an excellent model for studying human development or various serious diseases. In this study, a method for continuous observation of zebrafish embryos using OCT was proposed. In this experiment, the development of zebrafish embryos before hatching (0dpf-3dpf) was continuous observed by OCT, and the proportion of yolk sac to embryo volume was extracted and quantified. The proportion of embryos collected by OCT was compared with the proportion of zebrafish embryos observed by microscope. All experiments were repeated three times. The results show that the method of quantification of zebrafish embryo development by OCT can not only observe the internal development structure of the embryo, but also calculate the volume proportion of embryo development more accurately than microscope. This method provides a more rapid and precise important means for early clinical judgment of embryo development.
Terahertz waves are increasingly used in fields such as information and communication technology, homeland security, and biomedical engineering. Optical Coherence Tomography (OCT) is a non-invasive, high-resolution imaging technique that can image within a depth of 1mm under the skin, and it has the characteristics of fast imaging speed and high detection sensitivity. Using OCT technology to study human skin, it was found that the human skin sweat ducts are helical structures. When the sweat ducts of the helical structure are filled with sweat composed of conductive electrolytes, combined with the morphological and dielectric properties of the skin, the sweat ducts can act as low Q-factor helical antennas and have electromagnetic effects in the Sub-Terahertz band. In this study, based on the morphological structure of sweat ducts in the skin, we established a basic sweat duct equivalent model, which consists of spiral sweat ducts and three skin layers (stratum corneum, epidermis, and dermis). In this work, we investigate the frequency points of the stronger radiation of the sweat duct model at different frequencies and compare the effects of the turning direction of the helical sweat duct and changing the length of the sweat duct on its radiation variation at specific frequencies. The results show that there are significant differences in the magnitude and direction of planar radiation for different lengths of sweat ducts, and the differences in the turning direction of the helical sweat ducts also affect the angle of sweat duct radiation. The research on the electromagnetic radiation characteristics of sweat tubes in this study is of great guidance to the IC design research of human skin sweat tubes.
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