In bone tissue, osteocytes are embedded within a microfluid-filled network which expose them to high levels of fluid shear stress (FSS). The osteocytes’ sensitivity to different levels of FSS has demonstrated. However, there are few attempts to image 3D cellular deformation under FSS by label-free and quantitative microscopy. Digital holographic (DH) microscopy is a powerful imaging technique that can provide rich intracellular information based on the refractive index (RI) contrast, without exogenous contrast agents. However, in DH image recording process, the recorded wave-front contains not only the object’s information but also the aberrations caused by the microscope objective (MO) and the imperfections of optical components of the system. The fitting-based numerical method removes total aberrations by detecting object-free background as reference surfaces. In this paper, we proposed a convolutional neural network (CNN) for multivariate regression to cope with the phase aberration compensation problem automatically thus allows performing long-term monitoring of bone cells morphological response under FSS. We transformed the problem of estimating the coefficients for fitting a phase aberration map to a regression problem. The aberrated phase images are put into this model which can automatically learns the internal features of phase aberrations. Then the optimal coefficients are estimated as an output of the network. Based on these coefficients, the phase aberration map is built by the polynomial fitting, and the phase aberrations are removed by subtracting the aberration phase image with the phase map. The trainning and validation set contain thousands of phase image of cells. The mean square error (MSE) is used as the loss function. Then, the trained model was used for aberrations compensation in the FFS experiment of osteocytes. The results show that the proposed approach can predict the optimal coefficients and automatically compensating the phase aberrations without detecting background regions and knowing any physical parameters.
Endometrial cancer is one of the most common gynecological malignancies. In endometrial cancer treatment, drug resistance test plays the vital role since different patients have different reactions to chemotherapy. Traditional methods of drug resistance test usually take a few days to obtain results, which will be quite a long time for patients waiting for cancer treatment. In this research, in order to quickly quantify the drug resistance of cancer cells, we managed to find some relationships between the dynamic changing processes and drug resistance of endometrial cancer cells. To accurately obtain and quantitatively analyze the dynamic processes, we utilized digital holographic microscopy (DHM) to retrieve phase maps of living cancer cells. Based on the real-time reconstructed phase maps, we reestablished the dynamic process of both the cisplatin-resistant cell (Ishikawa, ISK) and non-cisplatin-resistant cell (Ishikawa/CisR, ISKC). ISK and ISK-C were separately treated with cisplatin (0ug/ml, control; 5ug/ml, low concentration, LC; and 100ug/ml, high concentration, HC), and holograms of cells in each group were recorded by a DHM setup for 30min before and 150min after cisplatin treatment with a frame rate of one record every five second. Several morphological parameters, including cell height, cell projected area, and cell volume, were calculated from the retrieved phase maps and membrane fluctuations were analyzed both in temporal and spatial domains. Statistically significant differences in the changing processes were found between the two kinds of cells.
Living cells as phase objects require not only non-invasive measurement but also quantitative phase information during dynamic biopsy. Digital Holographic Microscopy (DHM), measuring three-dimensional morphology without changing the active condition of cells and in situ inspection, is becoming excellent tools for biology research. We have described a DHM method for quantitative, unlabeled observation of living cell subjected to fluid shear stress (FSS) in flowing fluid. The holographic recording system combined with the fluid shear system is improved. The numerical reconstruction technique firstly employed deep learning Convolutional Neural Network model filter, which achieved automatically processing large scale the spectrum of holograms immediately. Osteocytes as the experimental samples were observed and their morphological changes under the stimulation of FSS was successfully measured.
In the development and production process of laser gyros, reflective mirrors have always been a core component, as they are directly related to the performance of laser gyros. Besides, surface profile deviation and surface defects of mirrors may lead to irreversible serious damages to gyros. In order to achieve effective three-dimensional (3D) quantitative measurements of their surface profiles and defects, we adopt digital holographic microscopy (DHM). Using a DHM system with multiple magnifications and the aberration compensation method, we obtained 3D profile images and estimated the precise quantitative sizes of not only a profile with an aperture of 6.41 mm and a curvature radius of 8.39 m, but also a scratch with a line-equivalent width of 0.45μm and an equivalent depth of 137.28 nm and a pit with an equivalent diameter of 0.86μm and an equivalent depth of 42.95 nm. These results demonstrate that the method is feasible and effective to meet the requirements of engineering practice.
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