We report the development and application of a knowledge-based coherent anti-Stokes Raman scattering (CARS) microscopy system for label-free imaging, pattern recognition, and classification of cells and tissue structures for differentiating lung cancer from non-neoplastic lung tissues and identifying lung cancer subtypes. A total of 1014 CARS images were acquired from 92 fresh frozen lung tissue samples. The established pathological workup and diagnostic cellular were used as prior knowledge for establishment of a knowledge-based CARS system using a machine learning approach. This system functions to separate normal, non-neoplastic, and subtypes of lung cancer tissues based on extracted quantitative features describing fibrils and cell morphology. The knowledge-based CARS system showed the ability to distinguish lung cancer from normal and non-neoplastic lung tissue with 91% sensitivity and 92% specificity. Small cell carcinomas were distinguished from nonsmall cell carcinomas with 100% sensitivity and specificity. As an adjunct to submitting tissue samples to routine pathology, our novel system recognizes the patterns of fibril and cell morphology, enabling medical practitioners to perform differential diagnosis of lung lesions in mere minutes. The demonstration of the strategy is also a necessary step toward in vivo point-of-care diagnosis of precancerous and cancerous lung lesions with a fiber-based CARS microendoscope.
Lung carcinoma is the most prevalent type of cancer in the world, and it is responsible for more deaths than other types
of cancer. During diagnosis, a pathologist primarily aims to differentiate small cell carcinoma from non-small cell
carcinoma on biopsy and cytology specimens, which is time consuming due to the time required for tissue processing
and staining. To speed up the diagnostic process, we investigated the feasibility of using coherent anti-Stokes Raman
scattering (CARS) microscopy as a label-free strategy to image lung lesions and differentiate subtypes of lung cancers.
Different mouse lung cancer models were developed by injecting human lung cancer cell lines, including
adenocarcinoma, squamous cell carcinoma, and small cell carcinoma, into lungs of the nude mice. CARS images were
acquired from normal lung tissues and different subtypes of cancer lesions ex vivo using intrinsic contrasts from
symmetric CH2 bonds. These images showed good correlation with the hematoxylin and eosin (H&E) stained sections
from the same tissue samples with regard to cell size, density, and cell-cell distance. These features are routinely used in
diagnosing lung lesions. Our results showed that the CARS technique is capable of providing a visualizable platform to
differentiate different kinds of lung cancers using the same pathological features without histological staining and thus
has the potential to serve as a more efficient examination tool for diagnostic pathology. In addition, incorporating with
suitable fiber-optic probes would render the CARS technique as a promising approach for in vivo diagnosis of lung
cancer.
Breast cancer is a common disease in women. Current imaging and diagnostic methods for breast cancer confront several
limitations, like time-consuming, invasive and with a high cost. Alternative strategies are in high demand to alleviate
patients' trauma and lower medical expenses. Coherent anti-Stokes Raman scattering (CARS) imaging technique offers
many advantages, including label-free, sub-wavelength spatial resolution and video-rate imaging speed. Therefore, it has
been demonstrated as a powerful tool for various biomedical applications. In this study, we present a label-free fast
imaging method to identify breast cancer and its subtypes using CARS microscopy. Human breast tissues, including
normal, benign and invasive carcinomas, were imaged ex vivo using a custom-built CARS microscope. Compared with
results from corresponding hematoxylin and eosin (H&E) stains, the CARS technique has demonstrated its capability in
identifying morphological features in a similar way as in H&E stain. These features can be used to distinguish breast
cancer from normal and benign tissues, and further separate cancer subtypes from each other. Our pilot study suggests
that CARS microscopy could be used as a routine examination tool to characterize breast cancer ex vivo. Moreover, its
label-free and fast imaging properties render this technique as a promising approach for in vivo and real-time imaging
and diagnosis of breast cancer.
Endoscopic optical coherence tomography (OCT) allowing high-resolution imaging of internal tissue is attractive for
medical imaging. Fibre, fibre bundle or GRIN lens rod acting as endoscopic probe is placed in the sample arm of a
Michelson interferometer in current endoscopic OCT systems, this arrangement has to be carefully configured to avoid
dispersion and polarization fading. In this study, a common path OCT system with outside path length compensation is
presented. The system based on Fizeau configuration requires a Michelson interferometer to compensate the optical path
difference between the reference and signal light in the Fizeau sensing interferometer. Experiments of path length
compensation and vibration are conducted, and the results demonstrate that this outside compensation method is feasible
and the system is immune to the vibration which occurs at the Fizeau sensing interferometer. This OCT imaging
approach is very suitable for endoscopic imaging and detailed endoscopic OCT system is also presented. Several
samples were imaged to demonstrate the performance of the proposed OCT system.
Projected index computed tomography (PICT) is an emerging noninvasive imaging technique that can provide
tomographic mapping of sample's refractive index. In this paper, we report a PICT system developed on the basis of a
fiber-optic OCT system. The tomographic mapping is reconstructed with convolution back projection algorithm using a
series of angular projection data collected by optical coherence tomography (OCT) at sequential orientations.
Measurement of refractive index distribution of a glass tube is carried out. The result shows that the developed system
has high resolution and sensitivity to discriminate tube boundaries. With index information involved, the reconstructed
PICT image is free of distortions, which are inherent artifacts of conventional OCT image.
In optical coherence tomography (OCT), broad-bandwidth optical sources are required to achieve high axial resolution.
Introducing a variable phase shift achromatically between the probe and reference beams is required for phase-shifting
algorithms implemented to extract the coherence signal. We propose a full-field OCT using an achromatic phase shifter
based on wave plates. The phase shifter that is almost independent of the wavelength over a range of 240 nm, can
provide a phase shift of eight times the rotating angle of the half-wave plate. The system is based on a Michelson
interferometer, illuminated by a white light source, and has several advantages compared with previous implementation
of full-field OCT based an achromatic phase shifter. Numerical simulation on phase shift error and amplitude ratio
between orthogonal polarization components at nominal phase shifts required for two typical phase-stepping algorithms
is conducted. Approach for extracting OCT signal by the revised Carre algorithm is presented.
Fluorescence Correlation Spectroscopy (FCS) is one of the most popular techniques in the studying of intramolecular dynamics as well as molecular interactions of biomolecules in the local microenvironments of cells or tissues. In FCS, fluorescence intensity fluctuations due to Brown movement are measured in a microscopic detection volume defined by a tightly focused laser beam. By fluorescence correlation analysis, a multitude of parameters such as local concentrations & diffuse coefficients are assessed. Combined with high sensitive photoelectric detector, processing circuit and high performance computer, the applications has been reported includes combination of antigen and antibody, micro PH measuring, pharmaceutical drug screening and so on. Particle in light field will be applied a radiation force, especially in two-photon excitation FCS due to its high intensity focused laser beam. This radiation force can be described by two components, i.e. scattering force and gradient force. In this paper, we simulate the two forces of the particle applied in Rayleigh scattering regime, and analyze the radiation force influenced by different radius of the particle.
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