Abstract
Visualization of deep blood vessels in speckle images is an important task as it is used to analyze the dynamics of the blood flow and the health status of biological tissue. Laser speckle imaging is a wide-field optical technique to measure relative blood flow speed based on the local speckle contrast analysis. However, it has been reported that this technique is limited to certain deep blood vessels (about ? = 300 ?? ? m ) because of the high scattering of the sample; beyond this depth, the quality of the vessel’s image decreases. The use of a representation based on homogeneity values, computed from the co-occurrence matrix, is proposed as it provides an improved vessel definition and its corresponding diameter. Moreover, a methodology is proposed for automatic blood vessel location based on the kurtosis analysis. Results were obtained from the different skin phantoms, showing that it is possible to identify the vessel region for different morphologies, even up to 900 ?? ? m in depth.
Highlights
The visualization of blood vessels is of fundamental importance for a wide variety of biological and biomedical applications, such as obstruction, stiffness, and response to an external stimulus
Photothermal-Laser speckle imaging (LSI) is a recently developed technique that combines the photoinduced heating of Pulsed photothermal radiometry (PPTR) and the contrast of integrated intensity of LSI to improve the visualization of the deep blood vessels.[7]
The gray level co-occurrence matrix (CM) is one of the standard methods to analyze texture in digital image processing[13] and can be used for describing the information of raw speckle images (RSI), as we report in an initial approach.[15]
Summary
The visualization of blood vessels is of fundamental importance for a wide variety of biological and biomedical applications, such as obstruction, stiffness, and response to an external stimulus. Laser speckle imaging (LSI) is a technique based on the spatial–temporal integration of the light scattered from a biological sample when illuminated with coherent light and imaged by an optical detector (i.e., CCD camera).[1,2] Particle motion (i.e., blood cells) in the illuminated area causes a decrease in contrast, seen as a blurring effect in the image, which is related to the speed of the particles in the illuminated sample. Under the influence of an external magnetic field, the mobility of those particles increases, allowing their visualization through the contrast of integrated speckle.[8] Physicochemical tissue optical clearing (PCTOC) uses a topical substance that matches the refractive index of the skin.[9] these techniques may increase the visualization of the deep blood vessels up to a few hundred micrometers, all of them require an external agent or stimulus.
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