A method for measuring of blood velocity in the native vasculature of a chick embryo by the method of micro anemometry from particle images (μPIV) is improved. A method for interrogation regions sorting by the mask of the vasculature is proposed. A method for sorting of the velocity field of capillary blood flow is implemented. The in vitro method was evaluated for accuracy in a glass phantom of a blood vessel with a diameter of 50 μm and in vivo on the bloodstream of a chicken embryo, by comparing the transverse profile of the blood velocity obtained by the PIV method with the theoretical Poiseuille laminar flow profile.
The assessment of functioning microcirculatory network implies usage of adequate tools for testing the network responses on local changes of vessels state. While there are well-developed and widely used methods, such as focal application of vasoactive substances, or electric stimulation, there is a need for a non-destructive (and ideally – non-contact) and local method of impact a single vessel in order to trigger the network responce.
In this paper, we investigate the possibility of applying the effect of a reversible change in the diameter of a blood vessel caused by laser radiation as a functional test of a microcirculatory system. For this purpose, we combine this effect with the method of micro-PIV (particle image velocimetry), which provides information on both the dynamics of blood flow in neighboring segments and the changes in their diameters.
A manual measurement of blood vessels diameter is a conventional component of routine visual assessment of microcirculation, say, during optical capillaroscopy. However, many modern optical methods for blood flow measurements demand the reliable procedure for a fully automated detection of vessels and estimation of their diameter that is a challenging task. Specifically, if one measure the velocity of red blood cells by means of laser speckle imaging, then visual measurements become impossible, while the velocity-based estimation has their own limitations. One of promising approaches is based on fast switching of illumination type, but it drastically reduces the observation time, and hence, the achievable quality of images. In the present work we address this problem proposing an alternative method for the processing of noisy images of vascular structure, which extracts the mask denoting locations of vessels, based on the application of the continuous wavelet transform with the Morlet wavelet having small central frequencies. Such a method combines a reasonable accuracy with the possibility of fast direct implementation to images. Discussing the latter, we describe in details a new MATLAB program code realization for the CWT with the Morlet wavelet, which does not use loops completely replaced with element-by-element operations that drastically reduces the computation time.
We present adaptive micro-scale Particle Image Velocimetry (μPIV) technique for visualization of the capillary network blood flow microcirculation. The main idea of our method is a centering of the interrogation regions (IR) of the μPIV technique via capillary network masks. These masks were obtained by the algorithm of Niblack local binarization of the capillary network images for the each frame. Due to the inhomogeneous of red blood cells (RBCs) distribution, we have summarized the masks across a whole series of masks. The blood flow velocity map was measured within the limits of the resulting the mask. We illustrate step-by-step the blood flow velocity measurement method and we reconstruct velocity map for chorioallantoic membrane (CAM) of chicken embryo.
We propose μPIV-based technique for quantitative assessment of blood flow redistribution in microcirculatory networks. Our approach is based on per-segment averaging of measured quantities so we can avoid most of problems that are typical for point-wise measurements. The key point of our technique is the digital processing algorithms of recorded data that include: capillary network axial line construction; interrogation regions centering; blood flow velocity local estimate using PIV approach; blood flow velocity calculation by means of averaging over entire vessel segment; the calculation of blood volume flow rate map. We illustrate the application of developed technique with in vivo measurements and blood flow velocity map reconstruction for chorioallantoic membrane (CAM) of chicken embryo, in which the local vascular occlusion was produced using continuous wave laser light irradiation..
A digital optical system focused on work with laboratory animals for intravital capillaroscopy has been developed. It implements the particle image velocimetry (PIV) based approach for measurements of red blood cells velocity in laboratory rat stomach capillaries. We propose a method of involuntary displacement compensation of the capillary network images. Image stabilization algorithm is based on correlation of feature tracking. The efficiency of designed image stabilization algorithm was experimentally demonstrated. The results of capillary blood flow analysis are demonstrated.
A method is presented to obtain information on tissue perfusability from capillary velocimetry experiments coupled with venous occlusion probe. The method based on data fitting to developed mathematical model describing the blood flow redistribution caused by the introduced occlusion. Using mathematical modeling, we identify the segment of velocity time courses that corresponds to tissue swelling process and thus allows ones quantify it. We also compared the results of direct measurement of red blood cells (RBCs) velocity with time courses obtained from finger-placed sensors of two types: (i) photoplethysmographic sensor used in pulsometry and (ii) piezoelectric sensor for sphygmography. The obtained results suggest the measurable contribution of RBCs aggregation process in optical pulse signal formation.
A digital optical system for intravital capillaroscopy has been developed. It implements the particle image velocimetry
(PIV) based approach for measurements of red blood cells velocity in individual capillary of human nailfold. We propose
to use a digital real time stabilization technique for compensation of impact of involuntary movements of a finger on
results of measurements. Image stabilization algorithm is based on correlation of feature tracking. The efficiency of
designed image stabilization algorithm was experimentally demonstrated.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.