To evaluate the development stage of skin cancer accurately is very important for prompt treatment and clinical prognosis. In this paper, we used the FLIM system based on time-correlated single-photon counting (TCSPC) to acquire fluorescence lifetime images of skin tissues. In the cases of full sample data, three kinds of sample set partitioning methods, including bootstrapping method, hold-out method and K-fold cross-validation method, were used to divide the samples into calibration set and prediction set, respectively. Then the binary classification models for skin cancer were established based on random forest (RF), K-nearest neighbor (KNN)，support vector machine (SVM) and linear discriminant analysis (LDA) respectively. The results showed that FLIM combining with appropriate machine learning algorithms can achieve early and advanced canceration classification of skin cancer, which could provide reference for the multi-classification, clinical staging and diagnosis of skin cancer.
This paper presents DMD-addressing based ptychographic phase microscopy (DA-PPM) and phase/fluorescence dual-modality imaging in DA-PPM. Compared with conventional ptychographic approaches, the imaging speed of DA-PPM is significantly enhanced by DMD based illumination selection, and is further enhanced by parallel illumination, i.e., lighting up parallelly multiple sub-areas in one shot. Furthermore, two-folds spatial resolution enhancement can be achieved in DA-PPM by incorporating structured illumination generated by DMD. Last but not least, phase/fluorescence dual-modality imaging will be performed in DA-PPM, providing for the same sample complementary information, including structural and functional information.
Conventional optical microscopy provides only intensity images, for which the contrast is induced by fluorescence or the absorption of the sample on the illumination light. Yet, the phase, polarization, and spectrum information of the sample is lost. Meanwhile, limited by design, conventional optical microscopy suffers from the conflict between spatial resolution and field of view (FOV). Modulated illuminations based computational microscopy (CM), which joints front-end optics and post-detection signal processing can, in general, extend the capability of conventional microscopy; for example, it allows the acquisition of the intensity, phase, polarization information, and enhance the spatial resolution within a large FOV. In this paper, modulated illumination based CM was exploited for implementation of phase imaging, resolution enhancement, dual-modality imaging. First, modulated illumination based CM provides quantitative amplitude and phase images, revealing the 3D shape and the inner structure of transparent or translucent samples in the absence of fluorescent labeling. Second, pupil-segmentation based CM measures the aberration of focus modulation microscopy (FMM). Hence, the resolution and SNR of FMM was enhanced after the aberration compensation. Third, phase and fluorescence dualmodality imaging was implemented in confocal laser scanning microscopy (CLSM) by extending the depth of field (DOF) of the CLSM system with a tunable acoustic gradient index of refraction (TAG) lens, providing complementary information (structural/functional) with pixel-to-pixel correspondence for the same sample. Furthermore, the combination of the two imaging modalities enables standalone determination of the refractive index of live cells.
Structured illumination microscopy (SIM) is a well-known super-resolution imaging technique, which exploits moiré patterns created when a sample is illuminated with periodic stripes. Conventional SIM often applies to fluorescent samples, or the samples which have absorption on illumination light. Here we report quantitative phase imaging of transparent samples with a SIM apparatus in transmittance-mode. For this purpose, two sets of fringe patterns, which have two orthogonal orientations and five phase-shifts for each orientation, were generated by a digital micro-mirror device (DMD) and projected on a sample. Under different fringe illuminations slightly-defocused images of the sample were recorded sequentially by a CCD camera, where the object waves along the ±1st orders of the illumination interfere with each other with a lateral shear in-between. The phase derivatives of the sample along the shear direction can be reconstructed from the phase-shifted intensity patterns. Eventually, the quantitative phase distribution of the sample was obtained by integrating the two phase derivatives. Furthermore, an iterative algorithm was used to enhance the resolution of the phase image, considering the structured illumination synthesizes a larger spectrum in the Fourier domain, similar to oblique illuminations in digital holography. This apparatus can also work in the conventional SIM mode, which images fluorescent samples in an in-focus manner. We believe such simple and versatile apparatus will be widely applied to biological imaging or industrial inspection.