Identification of specific vascular patterns in skin formations is important for non-invasive differential diagnosis of benign and malignant tissues. Accurate blood vessel mapping and quantitative analysis of the vessels morphology may increase the diagnostic efficiency significantly in comparison to conventional dermatoscopy methods. In this paper, we propose videocapillaroscopy technique for non-invasive visualization of microvascular architecture right in the nevi area. It includes acquisition of skin lesion images by exoscope-based imaging system and their digital processing including non-uniformity correction, local and global stabilization, detection and quantification of vessels, comparison of the obtained vessel maps with the reference data. We have demonstrated the efficiency of microvascular network visualization in various melanocytic skin formations. Proposed technique may complement conventional dermatoscopy for diagnosing skin lesions and become especially effective in the early stages of diseases.
An approach to visualization of the vascular bed with the possibility of assessing changes in blood filling and identifying diagnostically significant periodic changes in the signal by analyzing speckle images is proposed. The effect of singlet oxygen by direct excitation of an oxygen molecule by 1267 nm laser radiation on changes in the vascular bed parameters was studied using this approach.
The paper deals with processing data obtained using nailfold high-speed videocapillaroscopy. To detect the red blood cells velocity two approaches are used. The deterministic approach is based on pixel intensities analysis for object detection and calculation of the displacement and velocity of red blood cells in a capillary. The obtained data formulate targets for the second approach. The stochastic approach is based on a sequence of artificial neural networks. The semantic segmentation network UNet is used for capillary detection. Then, the classification network GoogLeNet or ResNet is used as a feature extractor to convert masked video frames to a sequence of feature vectors. And finally, the long short-term memory network is used to approximate the red blood cells velocity. The results demonstrated that the accuracy of the mean velocity approximation in the time range of several seconds is up to 0.96. But the accuracy at each specific time moment is less accurate. So, the proposed algorithm allows the determination of the RBCs mean velocity but it doesn't allow determination of the RBCs pulsations accurate enough.
Videocapillaroscopy (VCS) and laser Doppler flowmetry (LDF) are non-invasive methods for evaluating microcirculation parameters. The VCS method is based on a high-speed video recording of capillaries in the nailfold. The recorded video frames are processed using a specialized algorithm to determine the red blood cells velocity. The LDF technique is based on the analysis of the Doppler shift of back-scattered laser radiation from moving red blood cells. In this work, simultaneous measurements of VCS and LDF have been performed in healthy volunteers and rheumatic patient. The study was conducted using a cold pressor test. Changes were recorded in response to cold exposure in rheumatic diseases.
Advanced processing of high-speed video-capillaroscopy data revealed that
erythrocytes speed follows variations of arterial blood pressure, whereas intensity of light returned
from a single capillary is almost unmodulated at the heartbeat frequency.
An optical instrument for nailfold fluorescence capillaroscopy and image registration has been developed. With this
instrument, an effect of increasing fluorescence intensity in the spectral range of NADH fluorescence during ischemia
was detected.
Several problems of spectral photometry analysis of handwritten documents have been studied like combined reflection from the both ink and paper material impregnated by ink, the illumination spatial non-uniformity with small light intensity, flexibility and instability of paper sheets. The images acquired at different wavelengths were spatially matched using developed computer algorithm and then regions of interests, i.e. ink lines were extracted. Then reflection spectra obtained at all pixels of ink lines were composed in vector representation, and comparison of the vectors was conducted. As the result, degree of correspondence between different fragments of text has been evaluated. The optical setup and its calibration procedures are considered in detail as well as results of image processing, matching, segmentation and spectral photometry evaluation of ink. Experimental results of different text fragments matching and estimates of text fragments spectral correspondence degree are presented and discussed.
A multi-view scanning method is suggested to assess a complicated surface relief by white light interferometer.
Peculiarities of the method are demonstrated on a special object in the form of quadrangular pyramid cavity, which is
formed at measurement of micro-hardness of materials using a hardness gauge. An algorithm of the joint processing of
multi-view scanning results is developed that allows recovering correct relief values. Laser ablation craters were studied
experimentally, and their relief was recovered using the developed method. It is shown that the multi-view scanning
reduces ambiguity when determining the local depth of the laser ablation craters micro relief. Results of experimental
studies of the multi-view scanning method and data processing algorithm are presented.
Laser Doppler flowmetry (LDF) is widely used for diagnosing blood microcirculation diseases. It is well known that the Doppler shift of laser radiation scattered by moving red blood cells (RBC) can be assessed through analyzing photocurrent produced by a photodetector. LDF signal contains information about regulating blood flow rhythms: myogenic, cardiac, nervous and endothelial. The method of videocapillaroscopy (VCS) allows local capillary blood flow velocity evaluation and, using video data processing algorithms, is able to assess RBC velocity changes into capillary. We present the results of simultaneous investigations of changes in tissue perfusion of the distal phalanx of human finger by the LDF as well as changes in capillary blood flow velocity in the nail bed evaluated by the VCS method during arterial occlusion test. The experimental results confirmed the correspondence between blood perfusion and blood flow velocity.
The capillary blood flow parameters recovery is one of the videocapillaroscopy objectives. Capillaries position can vary at recorded video sequences due to the registration features of capillary blood flow. Stabilization algorithm of capillary blood flow video frames based on the advanced phase correlation is proposed and investigated. This algorithm is compared to the advanced version of known algorithms of video frames stabilization based on full-frame superposition and key points detection. Programs based on discussed algorithms are compared by processing of the experimentally recorded video sequences of human capillaries and by processing of computer-simulated video frames sequences with the specified offset. The full-frame superposition algorithm provides high quality of stabilization, however, the program based on this algorithm requires significant computational resources. Software implementation of the key points detection algorithm is characterized by good performance, but provides low quality of stabilization for capillary blood flow video sequences. Algorithm based on phase correlation method provides high quality of stabilization and program realization of this algorithm requires minimal computational resources. It is shown that the phase correlation algorithm is the most useful for stabilization of video sequences for capillaries blood flow. Obtained results can be used in software for biomedical diagnostics.
Fringe pattern analysis is widely used in moire, holographic and speckle interferometry for solving problems of nondestructive testing of objects. In the paper, the method of analysis of noisy fringe patterns and fringe phase retrieval is considered. The method is based on iterative evaluation of fringe amplitude, local fringe step (frequency) and local fringe orientation. High noise-immunity of the method proposed was verified experimentally when processing complicated fringe patterns with recovering full fringe phase.
Noisy interferometric signals and distorted interference fringe patterns analysis is very important for solving problems of metrology and nondestructive testing. In this paper the possibilities of the new nonlinear locally-adaptive filtering method were explored. This method can be used for preliminary noise suppression of fringe patterns at phase retrieval and for extreme lines location. It was verified experimentally high noise-immunity of the method proposed when processing real-obtained noisy distorted fringe patterns.
Image enhancement and evaluation play an important role in modern information and measurement technologies. An important image kind is obtained in coherent systems in holography and interferometry in the form of fringe patterns. Because of the physical and technical limitations fringe patterns are often distorted under the noise influence. It is proposed new noise-immune method for fringe pattern enhancement and evaluation. Unlike conventional filtering methods, in this method a filter impulse response is formed by the local empirical histogram modification with the spatial weighting function inside a dimensionally-varied area dependent on the local fringe intensity distribution. High efficiency of the method was verified experimentally when processing real noisy distorted fringe patterns.
Image enhancement and evaluation play an important role in modern information and measurement technologies. Because of the physical and technical limitations the obtained images are often distorted by noise influence and low resolution. Image enhancement provided by a conventional linear filtering and known standard smoothing methods can be not effective due to a contrast reduction. Image enhancement can be provided effectively by the adaptive nonlinear algorithms such as local gray-level histogram modification method recently investigated with application to images of special class like moire fringe patterns. This method was developed for noise suppression without decreasing the image contrast. It can be used for solving the image enhancement and restoration problems with application to different image kinds inherent in the remote sensing technologies.
Analysis of noisy interferometric signals and distorted interference fringe patterns with complicated structure is very important for solving problems of metrology and nondestructive testing. New nonlinear fringe processing method with spatially dependent filter impulse response is investigated. Unlike conventional filtering methods, in this method a filter impulse response is formed by the local empirical histogram modification with the spatial weighting function inside a dimensionally varied area dependent on the local fringe intensity distribution. High noise-immunity of the method proposed was verified experimentally when processing real noisy distorted fringe patterns.
A noise-immune method of phase retrieval of single moire interferometric fringe pattern is presented and discussed. The method is shown to provide accurate recovering of the phase information by combined method based on modification of local histogram of the fringe intensity and two dimensional Fourier transform of enhanced moire fringe pattern. The principle of the method is described and the experimental results of moire interferometric measurements with submicron sensitivity of the in-plane displacement fields of thick carbon fiber/PEEK composite laminates are presented as example of application of the technique.
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