Papers by Marianne Fenech
International Journal of Molecular Sciences
Patients with sickle cell disease (SCD) have poorly deformable red blood cells (RBC) that may imp... more Patients with sickle cell disease (SCD) have poorly deformable red blood cells (RBC) that may impede blood flow into microcirculation. Very few studies have been able to directly visualize microcirculation in humans with SCD. Sublingual video microscopy was performed in eight healthy (HbAA genotype) and four sickle cell individuals (HbSS genotype). Their hematocrit, blood viscosity, red blood cell deformability, and aggregation were individually determined through blood sample collections. Their microcirculation morphology (vessel density and diameter) and microcirculation hemodynamics (local velocity, local viscosity, and local red blood cell deformability) were investigated. The De Backer score was higher (15.9 mm−1) in HbSS individuals compared to HbAA individuals (11.1 mm−1). RBC deformability, derived from their local hemodynamic condition, was lower in HbSS individuals compared to HbAA individuals for vessels < 20 μm. Despite the presence of more rigid RBCs in HbSS individu...
Frontiers in Physiology
Predicting blood microflow in both simple and complex geometries is challenging because of the co... more Predicting blood microflow in both simple and complex geometries is challenging because of the composition and behavior of the blood at microscale. However, characterization of the velocity in microchannels is the key for gaining insights into cellular interactions at the microscale, mechanisms of diseases, and efficacy of therapeutic solutions. Image-based measurement techniques are a subset of methods for measuring the local flow velocity that typically utilize tracer particles for flow visualization. In the most basic form, a high-speed camera and microscope setup are the only requirements for data acquisition; however, the development of image processing algorithms and equipment has made current image-based techniques more sophisticated. This mini review aims to provide a succinct and accessible overview of image-based experimental measurement techniques to characterize the velocity field of blood microflow. The following techniques are introduced: cell tracking velocimetry, kym...
Red Blood Cells (RBCs) or erythrocytes tend to form chain-like aggregates under low shear rate ca... more Red Blood Cells (RBCs) or erythrocytes tend to form chain-like aggregates under low shear rate called rouleaux. This is a reversible process and rouleaux disaggregate in high shear rates. Therefore, RBCs aggregation occurs in the microcirculation where low shear rates are present but does not occur under normal physiological conditions in large arteries. Numerical modeling of RBCs interactions is fundamental in analytical models of a blood flow in microcirculation. Population Balance Modeling (PBM) is particularly useful for studying problems where particles agglomerate and break in a two phase flow systems to find flow characteristics. In this method, the elementary particles lose their individual identity due to continuous destructions and recreations by break-up and agglomeration. The aim of this study is to find RBCs aggregation in a dynamic situation. Simplified PBM was used previously to find the aggregation rate on a static observation of the RBCs aggregation in a drop of blo...
Stenosis or incompetence at severe levels reduce the performance of the heart and place additiona... more Stenosis or incompetence at severe levels reduce the performance of the heart and place additional stress and strain upon it. Therefore, in many cases, surgical replacement of the diseased valve with a Bioprosthetic or Mechanical Heart Valves (MHV) is necessary to restore valve function. Although the lifelong anticoagulant medication and the possible clinical complications (e.g. blood elements damage and/or thrombus formation), Bileaflet MHV are the most implanted valves with over 170,000 implants worldwide each year as a result of high durability and appropriate characteristics for blood hemodynamics (in terms of low pressure gradient and low shear stress level)[1]. Unfortunately, in some cases, Thromboembolic complications and/or pannus formation are possible after Bileaflet valve implantation. The mortality percentage for the reoperation might be as high as 69%. By the way, even though the low percentage of the deficiency in one or both leaflets(0.2%-6% per patient-year), the dan...
This work describes the development of a two- dimensional CFD model for Red Blood Cells (RBC) sed... more This work describes the development of a two- dimensional CFD model for Red Blood Cells (RBC) sedimentation. Population balance dynamic equation is solved for RBCs including RBCs aggregation. Rate of RBCs aggregation is obtained from literature and time of sedimentation is compared to what is on literature. Using this model cell free zone formation and RBC’s network formation could be modeled and be seen. Link between aggregation rate and sedimentation time is an important matter which is been described in this paper.
This work aims to develop a method to quantitatively analyze red blood cell (RBC) aggregates unde... more This work aims to develop a method to quantitatively analyze red blood cell (RBC) aggregates under controlled flow conditions, based on image processing. The set up consists of RBC suspensions entrained by a second fluid in a 150x33 μm microchannel. The experiments are performed by varying the hematocrit (10, 15 & 20%) and the flow rate (Q=5 & 10 μl/hr). The flow is visualized using a high speed camera coupled to a micro Particle Image Velocimetry (μPIV) system. Videos obtained with the high speed camera are processed using a MATLAB program to detect RBC aggregates based on the images intensities. An average aggregate size has been determined for each of the shear rates and hematocrits. The aggregates are shown to be larger at low flow rates and high hematocrits.
Advances in Engineering Software, 2019
Over the past several decades, image processing and automated tracking of particles has emerged a... more Over the past several decades, image processing and automated tracking of particles has emerged as a useful tool for the study of biological particles behaviour. This article describes an open-source computational implementation of a method for determining particle velocity and size distributions of large groups of particles by analyzing video sequences acquired using a video-microscopic systems. Although, in this study, red blood cells are used as a subject, this implementation can be used for any particle-laden flow where particles present a range of sizes and details of the velocity distribution of each size is of interest. From each single image, the current program detects particles and classifies them according to their size. It uses sequential images to track particles and compute the instantaneous velocity distribution of the particles. The tool can also assign an ellipse to each particle and report the major axis, the minor axis and the orientation of particles in each image. Use of the program improves repeatability of image processing and is suitable for studies related to particle dynamics, colloids, and microfluidic flow measurement. The size distribution and the velocity distribution of particles is often useful in the study of effect of parameters like shear stress on particle collision rate, agglomeration and breakage rate.
Lab on a Chip, 2019
A one-mask microfabrication process to build artificial vascular networks for the analysis of blo... more A one-mask microfabrication process to build artificial vascular networks for the analysis of blood flows and hemophysics.
International Journal of Heat and Mass Transfer, 2016
The focus of this work is the characterization of the thermal and hydraulic performance of pin fi... more The focus of this work is the characterization of the thermal and hydraulic performance of pin fin arrays produced using the cold spray additive manufacturing process. The heat transfer and the pressure losses of 1 mm high round base, square base and diamond base tapered pin fin arrays were assessed in both the inline and staggered configurations for fin densities of 8 fpi and 12 fpi. These performances were correlated to the turbulence intensity and the turbulent kinetic energy values at various locations in the flow, measured by micro-particle image velocimetry. It was inferred that the form drag is the main contributor to the pressure loss and was found to correlate with the flow turbulent kinetic energy in the fin wake. In contrast, the convective heat transfer coefficient correlated better with the turbulence intensity, leading to the conclusion that heat transfer is not dictated solely by the turbulent kinetic energy, but by the relative strength of the velocity fluctuations with respect to the average flow velocity at the same location. Furthermore, the flow structures for the different fin array samples were visualized and are discussed. Finally, it was found that although the samples had very varied thermal and hydrodynamic performances as a function of Reynolds number, the different samples at a given fin density had similar thermal conductances at a given pumping power.
International Journal of Heat and Mass Transfer, 2016
Abstract The focus of this work is the identification and analysis of the flow structures found i... more Abstract The focus of this work is the identification and analysis of the flow structures found in pyramidal pin fin arrays produced using the Masked Cold Gas Dynamic Spraying (MCGDS) additive manufacturing process. The observed flow structures are described, with classic double recirculation patterns being identified. The turbulence intensity levels of the flow in the axial flow channels was measured and it was found that although the flow rates considered in this work correspond to low Reynolds numbers (500–3000), significant turbulence intensity levels are found. Furthermore, these levels increase as the flow progresses downstream, even though the large scale flow structures are well established after a few rows (as little as two in this case). A slight misalignment of the axial and transverse flow channels resulting from imperfections in the masks caused a bypass flow structure to arise in the wake of the pin fins, replacing the double recirculation pattern observed when there is no such misalignment. A CFD model was used to investigate the effect of these misalignments on heat transfer efficiency and predicted that there would be no significant effect in the configurations studied. Finally, this work shows the importance of not only considering the flow structures in the fin’s wake, but also the effect of these structures on the turbulence levels of the axial flow channels, which could significantly affect the thermal and hydrodynamic performance.
Ultrasonics, IEEE Symposium, 2007
Ultrasonic backscattered signals from blood contain frequency-dependent information that can be u... more Ultrasonic backscattered signals from blood contain frequency-dependent information that can be used to obtain quantitative parameters reflecting the aggregation state of red blood cells (RBCs). Recently, the structure factor size estimator (SFSE) was developed to solve for two parameters: the packing factor W and mean gyration radius of aggregates Rg, expressed in number of RBCs (Yu and Cloutier 2007, J.
Journal of Physics: Conference Series, 2013
ABSTRACT Electrical bioimpedance is an effective measuring tool to provide quick, non-invasive, r... more ABSTRACT Electrical bioimpedance is an effective measuring tool to provide quick, non-invasive, real-time results which will be applied to the detection of internal haemorrhaging. Experiments were performed on female Fancy Rats weighing 333±44g, and 10mL of porcine blood was injected abdominally over 3 minutes. Data was collected using an 8×8 needle electrode array at 5 kHz, and 95 kHz and sent to the BioParHom Z-Flow. A strong correlation was found between the electrode paths crossing directly through the blood injection site, showing a decrease of about -0.17±0.1Ω/mL for the 5 kHz frequency. This correlation allows us to quickly detect internal haemorrhaging and also localize it with the current path set-up in the electrode array.
ITBM-RBM, 2004
We have measured extracellular (VE) and total water (VT) volumes in 17 dialysed patients for a to... more We have measured extracellular (VE) and total water (VT) volumes in 17 dialysed patients for a total of 46 runs by impedance using a Xitron Hydra 4200 device and the bio-impedance spectroscopy method (BIS). These volumes were used to test two methods of patient dry weight determination by impedance, that of Chamney et al., based on Ve/W ratio and that of Lopot et al. Based on VE/VT ratio where W denotes body weight. We recommend the 2nd method, but using a new equation that we have proposed for calculating VT, which is ...
The Journal of the Acoustical Society of America, 2021
Chinchilla et al. Although quantitative ultrasound techniques based on the parameterization of th... more Chinchilla et al. Although quantitative ultrasound techniques based on the parameterization of the backscatter coefficient (BSC) have been successfully applied to blood characterization, theoretical scattering models assume blood as an isotropic scattering medium. However, the red blood cell (RBC) aggregates form anisotropic structures such as rouleaux. The present study proposes an anisotropic formulation of the Effective Medium Theory combined with the Local Monodisperse Approximation (EMTLMA) that considers perfectly aligned prolate-shaped aggregates. Theoretical BSC predictions were first compared with computer simulations of BSCs in a forward problem framework. Computer simulations were conducted for perfectly aligned prolate-shaped aggregates and more complex configurations with partially aligned prolate-shaped aggregates for which the size and orientation of RBC aggregates were obtained from blood optical observations. The isotropic and anisotropic EMTLMA models were then compared in an inverse problem framework to estimate blindly the structural parameters of RBC aggregates from the simulated BSCs. When considering the isotropic EMTLMA, the use of averaged BSCs over different insonification directions significantly improves the estimation of aggregate structural parameters. Overall, the anisotropic EMTLMA was found to be superior to the isotropic EMTLMA in estimating the scatterer volume distribution. These results contribute to a better interpretation of scatterer size estimates for blood characterization.
2021 IEEE International Symposium on Medical Measurements and Applications (MeMeA), 2021
Microfluidics is a prominent field used to analyze small amounts of biological fluids. Co-Flow mi... more Microfluidics is a prominent field used to analyze small amounts of biological fluids. Co-Flow microfluidic devices can be used to study red blood cell aggregation in blood samples under a controlled shear rate. The purpose of this paper is to optimize the parameters of a co-flow device in order to produce a linear velocity profile in blood samples which would provide a constant shear rate. This is desired as the eventual goal is to use an ultrasonic measurement sensor with the co-flow microfluidic device to analyze red blood cell aggregates. Computational fluid dynamic simulations were performed to model a microfluidic device. The simulation results were verified by µPIV of the experimental microfluidic device. Modifications were made to the geometry and flow rate ratio of the microfluidic device to produce a more linear velocity profile. By using a flow rate ratio of 50:1 of shearing fluid to sheared fluid, we were able to achieve a velocity profile in the blood layer that is approximately linear.
PLOS ONE, 2018
Red blood cells (RBCs) are the most abundant cells in human blood. Remarkably RBCs deform and bri... more Red blood cells (RBCs) are the most abundant cells in human blood. Remarkably RBCs deform and bridge together to form aggregates under very low shear rates. The theory and mechanics behind aggregation are, however, not yet completely understood. The main objective of this work is to quantify and characterize RBC aggregates in order to enhance the current understanding of the non-Newtonian behaviour of blood in microcirculation. Suspensions of human blood were flowed and observed in vitro in poly-di-methyl-siloxane (PDMS) microchannels to characterize RBC aggregates. These microchannels were fabricated using standard photolithography methods. Experiments were performed using a micro particle image velocimetry (μPIV) system for shear rate measurements, coupled with a high-speed camera for flow visualization. RBC aggregate sizes were quantified in controlled and measurable shear rate environments for 5, 10 and 15% hematocrit. Aggregate sizes were determined using image processing techniques, while apparent viscosity was measured using optical viscometry. For the samples suspended at 5% H, aggregate size was not strongly correlated with shear rate. For the 10% H suspensions, in contrast, lowering the shear rate below 10 s-1 resulted in a significant increase of RBC aggregate sizes. The viscosity was found to increase with decreasing shear rate and increasing hematocrit, exemplifying the established non-Newtonian shear-thinning behaviour of blood. Increase in aggregation size did not translate into a linear increase of the blood viscosity. Temperature was shown to affect blood viscosity as expected, however, no correlation for aggregate size with temperature was observed. Non-Newtonian parameters associated with power law and Carreau models were determined by fitting the experimental data and can be used towards the simple modeling of blood's non-Newtonian behaviour in microcirculation. This work establishes a relationship between RBC aggregate sizes and corresponding shear rates and one between RBC aggregate sizes and apparent blood viscosity at body and room temperatures, in a microfluidic environment for low hematocrit. Effects of hematocrit, shear rate, viscosity and temperature on RBC aggregate sizes have been quantified.
The purpose of the work presented this paper is to design a model to study experimentally and num... more The purpose of the work presented this paper is to design a model to study experimentally and numerically a micro-Couette blood flow to obtain a constant and controlled shear rate that is a suitable environment for analysis of Red Blood Cell (RBC) aggregation. Due to the simplicity of the flow conditions, aggregate size can be related to the constant shear rate applied. This Couette flow is created by the motion of a second fluid that entrains the blood. The experimental work is coupled with 3D numerical simulations performed using a research computational fluid dynamics solver, Nek5000, based on the spectral element method, while the experiments are conducted using a micro-particle image velocimetry system. Two models of microchannels, with different dimensions, 150 × 33μm and 170 × 64μm, are fabricated in the laboratory using standard photolithography methods. The design of the channel is based on several parameters determined by the simulations. A Newtonian model is tested numeri...
Journal of Visualized Experiments, 2015
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Papers by Marianne Fenech