Seguimento de células e cálculo da sua deformação em microcanais: um método automático

A deformação dos glóbulos vermelhos ao longo do escoamento sanguíneo tem sido cada vez mais estudada, uma vez que o seu conhecimento abre caminhos para diagnosticar diversas patologias. Assim, têm surgido vários métodos para medir este fenómeno, bem como técnicas de fabricação de microcanais transparentes que permitem estudar em detalhe a deformabilidade das células sanguíneas. Os métodos manuais existentes para calcular a deformação dos glóbulos vermelhos são exaustivos, demorados e propícios à ocorrência de erros por parte dos utilizadores. Assim, existe a necessidade de desenvolver métodos automáticos de forma a eliminar estes problemas. Neste trabalho, utilizando técnicas de processamento de imagem desenvolveu-se um método automático (MKHtrackCells) para o seguimento de células ao longo de microcanais e cálculo do seu índice de deformação. O método proposto foi utilizado para estudar o comportamento de glóbulos vermelhos humanos ao longo de um microcanal com uma microestenose e de uma contração hiperbólica. Ambos os microcanais foram fabricados usando a técnica de litografia suave. Os resultados obtidos demostram que o método proposto é uma técnica promissora para o seguimento de células, bem como para a determinação do seu comportamento fisiológico ao longo de microcanais.The deformation of red blood cells along the blood flow has been increasingly studied, since its knowledge may demonstrate the ability to diagnose several pathologies. Thus, many methods for measuring this phenomenon have been proposed, as well as transparent microchannels manufacturing techniques allows to study blood cells deformability in detail. Current manual methods to calculate red blood cells deformability are labor intensive, time consuming and may introduce user errors into the data. Hence, it is crucial to develop automatic methods in order to eliminate those problems. In this work, by using image processing technique, an automatic method was developed (MKHtrackCells) not only to track cells along microchannels and but also to calculate their deformability. The proposed method was used to study the behavior of human red blood cells along a microchannel with a microstenosis and with a hyperbolic contraction. Both microchannels were fabricated using a soft lithography technique. The results have shown that the proposed method is a promising technique for cells tracking and to determine their dynamical behavior along the microchannel.Apoio financeiro do Global COE Program 2007 “Global Nano-Biomedical Engineering Education and Research Network”, Japão, ajuda concedida pela Fundação para a Ciência e Tecnologia no âmbito dos projetos PTDC/SAU-BEB/108728/2008, PTDC/SAU-BEB/105650/2008, PTDC/EME-MFE/ 099109/2008 e PTDC/SAU-ENB/116929/2010, COMPETE, QREN e União Europeia (FEDER)

Automatic tracking and deformation measurements of red blood cells flowing through a microchannel with a microstenosis: the keyhole model

This study aimed to assess the motion and its deformation index (DI) of red blood cells (RBCs) flowing through a microchannel with a microstenosis using an image analysis-based method. For this purpose, a microchannel having a smooth contraction was used and the images were captured by a standard high-speed microscopy system. An automatic image-processing and analysing method was developed in a MATLAB environment to not only track the motion of RBCs but also measure the DI along the microchannel. The keyhole model, tested in this study, proved to be a promising technique to automatically track individual RBCs in microchannels.This study was financially supported by the Science and Technology Foundation (FCT), COMPETE, QREN and the European Union (FEDER) [grant numbers PTDC/SAU-BEB/ 105650/2008, PTDC/SAU-ENB/116929/2010, EXPL/EMS-SIS/ 2215/2013]info:eu-repo/semantics/publishedVersio

Erythrocytes tracking through a microchannel using an automatic method of image analysis

In this study, an image processing and analyzing method has been developed in the MATLAB environment, to characterize the motion of RBCs flowing through a microchannel with a smooth contraction shape

Visualization of red blood cells flowing through a PDMS microchannel with a microstenosis: an image analysis assessment

The present study aims to assess the motion of red blood cells (RBCs) under both shear and extensional flow using an image based technique. For this purpose, a microchannel having a smooth contraction was used and the images were captured by a standard high-speed microscopy system. An image processing and analyzing method has been developed in the MATLAB environment, to track the RBCs motion. The keyhole model, tested in this study, proved to be a promising technique to track individual RBCs in microchannels.The authors acknowledge the financial support provided by 2007 Global COE Program “Global Nano-Biomedical Engineering Education and Research Network”, Japan and grant-in-Aid for Science and Technology PTDC/SAU-BEB/108728/2008, PTDC/SAU-BEB/105650/2008, PTDC/EME-MFE/099109/2008 and PTDC/SAU-ENB/116929/2010 from FCT (Science and Technology Foundation), COMPETE, QREN and European Union (FEDER).info:eu-repo/semantics/publishedVersio

Cell-free layer measurements in bifurcating microchannels: a global approach

In the present work, in vitro blood flowing through bifurcating microchannels was studied, with the aim of characterizing the cell-free layer (CFL). The original images were obtained by means of a high-speed video microscopy system and then processed in MatLab using the Image Processing Toolbox. The numerical data was obtained automatically and analyzed by optimization techniques using the genetic algorithm approach. The results suggest that the CFL were formed in a similar way at the upper and lower regions in all bifurcations, and the measurements can be approximated through a sum of trigonometric functions

Separation and deformation of red blood cells in PDMS microchannels

Over the years, several experimental techniques were performed in in vitro environments, in an attempt to understand the flow behaviour of blood in microcirculation. Several of these studies were performed in glass capillaries, and have produced significant results with respect to rheological properties of blood [1, 2]. Another way to perform in vitro blood studies is to use microchannels fabricated by soft- lithography [3, 4] and xurography [5]. With these techniques several studies have focused in the formation of the cell-free layer (CFL) that is caused by the tendency of red blood cells (RBCs) to migrate toward the centre of the microchannel, in that the physical reason is known as the Fahraeus Lindqvist. The presence of this CFL at the regions adjacent to the wall is affected by the geometry of the microchannel [4] and the physiological conditions of the working fluid, such as the hematocrit (Hct) [6], and the RBC deformability [7]. The formation of CFL can be used for separation of diseased cells from healthy blood cells [8]. The aim of this paper is to show briefly the importance of the microfluidic devices to study several physiological phenomena that happens in vivo environments with special focus on the CFL behaviour and RBC deformability

Blood flow in microchannels manufactured by a low cost technique: xurography

The xurography is a technique that has been used to make molds to produce microchannels. In contrast to soft lithography [1, 2], xurography uses equipments and materials commonly used in the printing industry, such as cutting plotters, vinyl and other materials. The main advantage of this technique is to fabricate microchannels at a reduced cost [3, 4]. The Fahraeus-Lindqvist effect is a well know phenomenon that happens in microcirculation, where red blood cells (RBCs) have tendency to migrate toward the centre of the microtube resulting in a marginal cell-free layer (CFL) at regions adjacent to the wall [5]. Recently several studies showed strong evidence that the formation of the CFL is affected by the geometry of the microchannel [1, 6, 7] and the physiological conditions of the working fluid, such as the hematocrit (Hct) [2, 8]. The main objective of the present work is to fabricate polydimethysiloxane (PDMS) microchannels by using a soft xurography technique in order perform blood flow studies. Additionally, a high-speed video microscopy system is used to measure the CFL thickness in two different geometries, i. e., bifurcations and confluences

Tracking red blood cells flowing through a microchannel with a hyperbolic contraction: an automatic method

The present chapter aims to assess the motion and deformation index of red blood cells (RBCs) flowing through a microchannel with a hyperbolic contraction using an image analysis based method. For this purpose, a microchannel containing a hyperbolic contraction was fabricated in polydimethylsiloxane by using a soft-lithography technique and the images were captured by a standard high-speed microscopy system. An automatic image processing and analyzing method has been developed in a MATLAB environment, not only to track both healthy and exposed RBCs motion but also to measure the deformation index along the microchannel. The keyhole model has proved to be a promising technique to track automatically healthy and exposed RBCs flowing in this kind of microchannels.info:eu-repo/semantics/publishedVersio