Optical Coherence Tomography For Tissue Engineering Imaging

With the development of tissue engineering,visualization and tracking of the dynamic changes of cells,scaffolds and tissues occurring in three-dimensional structures become more and more important.Compared with traditional histological sections,Optical coherence tomography(OCT)technology provides a real-time non-invasive function of evaluating and monitoring engineering tissues.Compared with other imaging technologies such as CT,MRI,ultrasound,etc.,the imaging accuracy is low and cannot meet the accuracy requirements of three-dimensional cell imaging.Fourther,CT can cause irreversible cell damage.The imaging depth of traditional optical imaging technologies such as laser confocal and the like can only reach micron level and cannot perform overall imaging on cells in the stent.OCT technology provides high resolution(1?15?m)and appropriate imaging depth(1?10mm)and is a good tissue engineering detection tool.The main contents of this paper are as follows:(1)The significance of tissue engineering 3D detection and existing 3D detection technologies are briefly introduced.The application of OCT technology in tissue engineering is described,including quantitative visualization of internal structure,influence of cells/materials on tissue formation,growth and development of tissue engineering,dynamic tracking of cells,monitoring of fluid flow field in three-dimensional culture,and detection of biomechanical properties of tissue engineering.(2)The construction,signal processing method and key technical parameters of the swept OCT system used in this paper are introduced,and the key to the optimization of system resolution and signal-to-noise ratio is the need for K-domain equal interval sampling is pointed out.(3)Aiming at the K-domain equal interval sampling requirement of swept OCT system.In this paper,a K-domain phase numerical compensation method is proposed.Compensation data are obtained through the phase difference between the original unwrapped phase and the linear fitting phase at different imaging depths in the average wavenumber domain(K-domain),thus realizing the imperfect numerical compensation for sampling at equal wavenumber intervals in swept-frequency OCT systems.The research results show that the axial resolution of the K-domain phase compensation method proposed in this paper is stable between 12.67-16.63?m in the range of 5mm imaging depth,which is close to the ideal resolution of the system,and the SNR increase rate of the system is up to 7.4%.(4)In order to realize the aseptic detection of OCT and ensure the imaging effect,the relationship between the volume of added cell culture medium and the imaging quality of OCT was preliminarily explored,and the optimal volume of culture medium was determined.The growth of cell-loaded hydrogel scaffolds on the 2nd,4th,6th,8th,12th and 15th days and the growth of cells inoculated into ?-TCP scaffolds on the 1st,3rd,5th and 7th days were investigated.The imaging differences between high-water content scaffolds and low-water content scaffolds were compared by OCT.The growth trend of cells could be predicted through the comparative analysis of OCT sequence diagrams at different time points,and the feasibility of OCT to observe the growth and development of tissue engineering cells was verified.Although the research in this paper shows that OCT has the feasibility of observing the cell growth in tissue engineering scaffolds,the existing OCT system has limited resolution and cannot detect the growth of individual cells.Moreover,the contrast of cells/materials in the image is poor due to the contrast method presented by OCT according to the refractive index difference of materials.Therefore,new methods for improving the contrast of cells/materials need to be further explored.