Browsing by Author "Takeda, Motohiro"
Now showing 1 - 10 of 14
Results Per Page
Sort Options
- Blood cell motions and interactions in microchannelsPublication . Lima, Rui A.; Ishikawa, Takuji; Fujiwara, Hiroki; Takeda, Motohiro; Imai, Yohsuke; Tsubota, Ken-ichi; Wada, Shigeo; Yamaguchi, TakamiDetailed knowledge on the motions and interactions of individual blood cells flowing in microchannels is essential to provide a better understanding on the blood rheological properties and disorders in microvessels. This paper presents the ability of a confocal micro-PTV system to track red blood cells (RBCs) through a 100 μm circular glass microchannel. The technique consists of a spinning disk confocal microscope, high speed camera and a diode-pumped solid state (DPSS) laser combined with a single particle tracking (SPT) software (MtrackJ). Detailed measurements on the motions of RBCs were measured at different haematocrits (Hct). Our results show clearly that this technique can provide detailed information about microscale disturbance effects caused by the blood cells.
- Determination of blood cells motions and interactions by a confocal micro-PIV systemPublication . Lima, Rui A.; Ishikawa, Takuji; Imai, Yohsuke; Takeda, Motohiro; Wada, Shigeo; Yamaguchi, TakamiThe development of optical experimental techniques has contributed to obtain explanations on the way the blood flows through microvessels. Although the past results have been encouraging, detailed studies on the flow properties of blood in the microcirculation has been limited by several technical factors such as poor spatial resolution and difficulty to obtain quantitative detailed measurements at such small scales. In recent years, due to advances in computers, confocal microscopy, and digital image processing techniques, it has become possible to combine a micro-particle tracking velocimetry (PTV) system with a confocal microscope. The present study shows for the first time confocal micro-PTV measurements of the dynamic flow behaviour of red blood cells (RBCs) in concentrated suspensions. The measurements were performed at several depths of a 100 um glass capillaries
- Dispersion of red blood cells in microchannels : a confocal micro-PTV assessmentPublication . Lima, Rui A.; Ishikawa, Takuji; Imai, Yohsuke; Fujiwara, Hiroki; Takeda, Motohiro; Matsuki, Noriaki; Wada, Shigeo; Yamaguchi, TakamiBlood in large arteries may be treated as a homogenous fluid from a macroscopic prospective. However, in reality blood is a suspension of deformable cells in viscous fluid plasma. In microcirculation, which comprises the smallest arteries and veins, the flow behavior of individual blood cells and their interactions provide the microrheological basis of flow properties of blood at a macroscopic level. Hence, in microcirculation it is fundamental to study the flow behavior of blood at cellular level. Several studies on both individual and concentrated RBCs have already been performed in the past. However, all studies used conventional microscopes and also ghost cells to obtain visible trace RBCs through the microchannel. The present study is concerned in providing further insights into the microscale blood flow behavior through microchannels by applying an emerging optical technique known as confocal micro-PIV/PTV. The technique consists of a spinning disk confocal microscope, high speed camera and a diode-pumped solid state (DPSS) laser combined with a single particle tracking (SPT) software (MtrackJ). Detailed measurements on the motions of RBCs were measured at different haematocrits (Hct) and the correspondent radial dispersion coefficient was determined.
- In vitro blood flow in a rectangular PDMS microchannel: experimental observations using a confocal micro-PIV systemPublication . Lima, Rui A.; Wada, Shigeo; Tanaka, Shuji; Takeda, Motohiro; Ishikawa, Takuji; Tsubota, Ken-ichi; Imai, Yohsuke; Yamaguchi, TakamiProgress in microfabricated technologies has attracted the attention of researchers in several areas, including microcirculation. Microfluidic devices are expected to provide powerful tools not only to better understand the biophysical behavior of blood flow in microvessels, but also for disease diagnosis. Such microfluidic devices for biomedical applications must be compatible with state-of-the-art flow measuring techniques, such as confocal microparticle image velocimetry (PIV). This confocal system has the ability to not only quantify flow patterns inside microchannels with high spatial and temporal resolution, but can also be used to obtain velocity measurements for several optically sectioned images along the depth of the microchannel. In this study, we investigated the ability to obtain velocity measurements using physiological saline (PS) and in vitro blood in a rectangular polydimethysiloxane (PDMS) microchannel (300 μm wide, 45 μm deep) using a confocal micro-PIV system. Applying this combination, measurements of trace particles seeded in the flow were performed for both fluids at a constant flow rate (Re = 0.02). Velocity profiles were acquired by successive measurements at different depth positions to obtain three-dimensional (3-D) information on the behavior of both fluid flows. Generally, the velocity profiles were found to be markedly blunt in the central region, mainly due to the low aspect ratio (h/w = 0.15) of the rectangular microchannel. Predictions using a theoretical model for the rectangular microchannel corresponded quite well with the experimental micro-PIV results for the PS fluid. However, for the in vitro blood with 20% hematocrit, small fluctuations were found in the velocity profiles. The present study clearly shows that confocal micro-PIV can be effectively integrated with a PDMS microchannel and used to obtain blood velocity profiles along the full depth of the microchannel because of its unique 3-D optical sectioning ability. Advantages and disadvantages of PDMS microchannels over glass capillaries are also discussed.
- In vitro confocal micro-PIV measurements of blood flow in a square microchannel: the effect of the haematocrit on instantaneous velocity profilesPublication . Lima, Rui A.; Wada, Shigeo; Takeda, Motohiro; Tsubota, Ken-ichi; Yamaguchi, TakamiA confocal microparticle image velocimetry (micro-PIV) system was used to obtain detailed information on the velocity profiles for the flow of pure water (PW) and in vitro blood (haematocrit up to 17%) in a 100-μm-square microchannel. All the measurements were made in the middle plane of the microchannel at a constant flow rate and low Reynolds number (Re=0.025). The averaged ensemble velocity profiles were found to be markedly parabolic for all the working fluids studied. When comparing the instantaneous velocity profiles of the three fluids, our results indicated that the profile shape depended on the haematocrit. Our confocal micro-PIV measurements demonstrate that the root mean square (RMS) values increase with the haematocrit implying that it is important to consider the information provided by the instantaneous velocity fields, even at low Re. The present study also examines the potential effect of the RBCs on the accuracy of the instantaneous velocity measurements.
- Measurement of erythrocyte motions in microchannels by using a confocal micro-PTV systemPublication . Lima, Rui A.; Ishikawa, Takuji; Takeda, Motohiro; Tanaka, Shuji; Imai, Yohsuke; Tsubota, Ken-ichi; Wada, Shigeo; Yamaguchi, TakamiDetailed knowledge on the motion of individual red blood cells (RBCs) flowing in microchannels is essential to provide a better understanding on the blood rheological properties and disorders in microvessels. Several studies on both individual and concentrated RBCs have already been performed in the past. However, all studies used conventional microscopes and also ghost cells to obtain visible trace RBCs through the microchannel. Recently, considerable progress in the development of confocal microscopy and consequent advantages of this microscope over the conventional microscopes have led to a new technique known as confocal micro-PIV. This technique combines the conventional PIV system with a spinning disk confocal microscope (SDCM). Due to its outstanding spatial filtering technique together with the multiple point light illumination system, this kind of microscope has the ability to obtain in-focus images with optical thickness less than 1 μm, a task extremely difficult to be achieved by using a conventional microscope. The main purpose of this paper is to investigate the ability of our confocal micro-PTV system to measure the motion of individual RBCs at different haematocrit (Hct) through microchannels.
- Measurement of individual red blood cell motions under high hematocrit conditions using a confocal micro-PTV systemPublication . Lima, Rui A.; Ishikawa, Takuji; Imai, Yohsuke; Takeda, Motohiro; Wada, Shigeo; Yamaguchi, TakamiDevelopments in optical experimental techniques have helped in elucidating how blood flows through microvessels. Although initial developments were encouraging, studies on the flow properties of blood in microcirculation have been limited by several technical factors, such as poor spatial resolution and difficulty obtaining quantitative detailed measurements at such small scales. Recent advances in computing, microscopy, and digital image processing techniques have made it possible to combine a particle tracking velocimetry (PTV) system with a confocal microscope. We document the development of a confocal micro-PTV measurement system for capturing the dynamic flow behavior of red blood cells (RBCs) in concentrated suspensions. Measurements were performed at several depths through 100-mm glass capillaries. The confocal micro-PTV system was able to detect both translational and rotational motions of individual RBCs flowing in concentrated suspensions. Our results provide evidence that RBCs in dilute suspensions (3% hematocrit) tended to follow approximately linear trajectories, whereas RBCs in concentrated suspensions (20% hematocrit) exhibited transversal displacements of about 2% from the original path. Direct and quantitative measurements indicated that the plasma layer appeared to enhance the fluctuations in RBC trajectories owing to decreased obstruction in transversal movements caused by other RBCs. Using optical sectioning and subsequent image contrast and resolution enhancement, the system provides previously unobtainable information on the motion of RBCs, including the trajectories of two or more RBCs interacting in the same focal plane and RBC dispersion coefficients in different focal planes.
- Measurement of multi-red blood cells interactions in blood flow by confocal micro-PTVPublication . Lima, Rui A.; Ishikawa, Takuji; Fujiwara, Hiroki; Takeda, Motohiro; Imai, Yohsuke; Tsubota, Ken-ichi; Matsuki, Noriaki; Wada, Shigeo; Yamaguchi, TakamiIn microcirculation the flow behavior of red blood cells (RBCs) plays a crucial role in many physiological and pathological phenomena. For instance, the interaction of RBCs in shear flow is believed to play an important role to the thrombogenesis process. Despite the relevance of this phenomenon on the blood mass transport, very little studies have been performed during the years, partly due to the absence of adequate visualization techniques able to obtain both direct and quantitative measurements on multi-RBCs motions in concentrated suspensions. Past studies on both individual and concentrated RBCs used conventional microscopes and/or ghost cells to obtain visible trace RBCs at high concentration suspension of blood cells [1, 2]. Recently, advances of confocal microscopy and consequent advantages over conventional microscopes have led to an emerging technique known as confocal micro-PIV [3, 4]. This paper presents the application of a confocal micro- PTV system to measure RBC-RBC hydrodynamic interactions in flowing blood.
- Microscale flow dynamics of red blood cells in a circular microchannelPublication . Lima, Rui A.; Nakamura, M.; Ishikawa, Takuji; Tanaka, Shuji; Takeda, Motohiro; Imai, Yohsuke; Tsubota, Ken-ichi; Wada, Shigeo; Yamaguchi, TakamiThe blood flow dynamics in microcirculation depends strongly on the motion, deformation and interaction of RBCs within the microvessel. This paper presents the application of a confocal micro-PTV system to track RBCs through a circular polydimethysiloxane (PDMS) microchannel. This technique, consists of a spinning disk confocal microscope, high speed camera and a diode-pumped solid state (DPSS) laser combined with a single particle tracking (SPT) method. By using this system detailed motions of individual RBCs were measured at a microscale level. Our results showed that this technique can provide detailed information about microscale disturbance effects caused by RBCs in flowing blood.
- Radial dispersion of red blood cells in blood flowing through glass capillaries: the role of hematocrit and geometryPublication . Lima, Rui A.; Ishikawa, Takuji; Imai, Yohsuke; Takeda, Motohiro; Wada, Shigeo; Yamaguchi, TakamiThe flow properties of blood in the microcirculation depend strongly on the hematocrit (Hct), microvessel geometry, and cell properties. Previous in vitro studies have measured the radial displacement of red blood cells (RBCs) at concentrated suspensions using conventional microscopes. However, to measure the RBCs motion they used transparent suspensions of ghost red cells, which may have different physical properties than normal RBCs. The present study introduces a new approach (confocal micro-PTV) to measure the motion of labeled RBCs flowing in concentrated suspensions of normal RBCs. The ability of confocal systems to obtain thin infocus planes allowed us to measure the radial position of individual RBCs accurately and to consequently measure the interaction between multiple labeled RBCs. All the measurements were performed in the center plane of both 50 mm and 100 mm glass capillaries at Reynolds numbers (Re) from 0.003 to 0.005 using Hcts from 2 to 35%. To quantify the motion and interaction of multiple RBCs, we used the RBC radial dispersion (Dyy). Our results clearly demonstrate that Dyy strongly depends on the Hct. The RBCs exhibited higher Dyy at radial positions between 0.4 R and 0.8 R and lower Dyy at locations adjacent to the wall (0.8 R–1 R) and around the middle of the capillary (0 R–0.2 R). The present work also demonstrates that Dyy tends to decrease with a decrease in the diameter. The information provided by this study not only complements previous investigations on microhemorheology of both dilute and concentrated suspensions of RBCs, but also shows the influence of both Hct and geometry on the radial dispersion of RBCs. This information is important for a better understanding of blood mass transport mechanisms under both physiological and pathological conditions.