Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session R05: Medical Flow and Devices I |
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Chair: Iman Borazjani, Texas A&M University, College Station Room: Ballroom E |
Monday, November 25, 2024 1:50PM - 2:03PM |
R05.00001: Abbas-Borazjani’s comprehensive model for simulating the coagulation kinetics in medical devices Syed Samar Abbas, Iman Borazjani We develop a generalizable, comprehensive model for simulating the coagulation cascade in Blood Contacting Medical Devices (BCMDs). Coagulation is a platelet-surface mediated process, requiring activated platelets for the binding and conversion of inactive zymogens to active enzymes. Thrombin, the main product of the coagulation cascade, not only converts soluble Fibrinogen to insoluble Fibrin, but also promotes the activation of further platelets. For the numerical methods to precisely predict the coagulation kinetics, therefore, the accurate estimation of platelet activation is critically significant. We propose a novel coagulation model that comprehensively incorporates the shear-, contact-, and enzyme-induced platelet activation caused by BCMDs in general, with application to Mechanical Heart Valves (MHVs) in specific. The surface-adhesion of platelets, and platelet-platelet cohesion is also modelled by tracking several platelet species, both mobile and bound, by solving a system of partial and ordinary differential equations. The model is extended to characterize the dominant mechanism of platelet activation (shear stresses versus foreign contact) in two designs of MHVs, being a Trileaflet MHV (TMHV) and a Bileaflet MHV (BMHV). |
Monday, November 25, 2024 2:03PM - 2:16PM |
R05.00002: Development of a Physiologically Realistic, 3D-Printed, Configurable Coronary Artery Mock Circulatory Loop Ian A Carr, Sailahari V Ponnaluri, Andreu Badal, Jackson Hair, P. F. Adrian Magee, Brent A Craven, Brent A Craven, Prasanna Hariharan Modern medical imaging techniques and numerical modeling have paved the way for less invasive diagnostic procedures for coronary artery disease. One of the most prominent applications is the estimation of fractional flow reserve through a coronary stenosis using a computed tomography scan. While these techniques are commonly used in clinical practice, the methods used for experimental validation vary widely, and thus the quality of the validation evidence included in regulatory evaluation also varies. To help address this, we are developing a standardized end-to-end validation dataset using a baseline coronary artery lumen geometry which is based on a survey of patient geometric parameters in the literature. As part of this study, we have developed a 3D-printed coronary artery test section using this geometry with configurable coronary artery branches and integrated it into a mock circulatory loop. This mock circulatory loop has optical access sufficient for laser-based flow measurement techniques like particle image velocimetry and particle tracking velocimetry. Herein we will present the current state of development of our experimental setup and present our development plan and expected challenges. Once completed, this validation dataset will be made available to the public via the FDA Office of Science and Engineering Laboratories (OSEL) Regulatory Science Tool Catalog. |
Monday, November 25, 2024 2:16PM - 2:29PM |
R05.00003: In vitro and in silico studies of Flow Diverting Stents for Intracranial Aneurysms Fanette Chassagne, Duilio M La Rocca, Michael Barbour, Alberto Aliseda Flow Diverting Stents (FDS) are high porosity (~70%) tubular meshes that are deployed in cerebral arteries for the treatment of intracranial aneurysms. They aim at lowering both the inflow and the blood velocity in the aneurysmal sac, promoting thrombus formation to isolate the wall from mechanical stresses and prevent rupture. Previous experimental work has demonstrated the negative effect of parent vessel curvature on treatment effectiveness, as it both impacts the inflow and the porosity of the FDS. Numerical simulations are widely used for patient-specific analysis of aneurysm treatment, but they require the use of a model for the FDS, which is very often modelled as a porous surface. We aim at validating the porous media models commonly used in CFD with our previous experimental PIV work in idealized geometries treated with FDS. We use FDS geometries from Synchrotron micro-tomography of the deployed stents to build "high-fidelity" CFD simulations. Simpler simulations were run using a porous surface, whose properties were first taken from the literature. The resulting flow topologies were compared to the experimental observations and the porous model parameters were adjusted, based on the curvature of the parent vessel, to improve the accuracy of the modeled stent in the aneurysm hemodynamics. |
Monday, November 25, 2024 2:29PM - 2:42PM |
R05.00004: Flow Field Dynamics of a Wide-Neck Intracranial Aneurysm With and Without the Presence of Double-Wall Vascular Stent Josue Fonseca, Eunseo Yang, Xiaoqian Fang, Robert Freeman, Isaac Choutapallli An experimental study is performed to investigate the flow dynamics of a wide-neck intracranial aneurysm with and without the presence of a double-wall vascular stent. A laboratory model of a lateral side-wall aneurysm 3 cm in length and with a 10 mm wide-neck was fabricated using clear plexiglass. The aneurysm model was placed in a circuit driven by a peristaltic pump that delivered water cycling at the rate of one pulse per second. The fluid flow rate was measured using a Honeywell vortex shedding flow meter and was kept constant at 200 mL/min. The flow field was captured by means of stereoscopic Particle Image Velocimetry. The illumination is provided by a dual-oscillator Nd:YAG laser with 30 mJ/pulse at 532nm wavelength with a maximum repetition rate of 10kHz. A light sheet of 1 mm thickness is created by suitable combination of spherical and cylindrical lenses. The images are recorded by two CMOS cameras (Phantom VEO 410L) with a resolution 1280(H) x 800(V) pixels of a size of 20 microns. A total of 2500 image pairs per second were acquired. The results show that the double-wall vascular stent greatly reduced flow recirculation and wall shear stress. The study provides a basis for the future feasibility of double-wall vascular stents in preventing aneurysm rupture. |
Monday, November 25, 2024 2:42PM - 2:55PM |
R05.00005: Enhancing size-based leukocyte enrichment in a passive viscoelastic microfluidic separation device Dhiren Mohapatra, Amit Agrawal, Rahul Purwar In this work, we have analyzed the combined effect of cell concentration and viscosity on the margination of leukocytes in a bifurcated rectangular channel inertial flow. This study will help enhance the leukocyte separation efficiency of inertial microfluidic devices, as it depends on the margination of leukocytes while separating from blood. Several studies have reported the effects of various individual parameters like channel geometry, shear rate, hematocrit, sample composition, and red blood cell (RBC) geometry on the margination of leukocytes. Here, we focus on the physical phenomenon due to the variation of the bio-physical properties, like the behavior of cells and viscosity and their correlation, instead of the individual parametric study. PBS and viscoelastic fluid were used to vary the viscosity and cell concentration. Leukocyte margination was analyzed in terms of enrichment with viscosities and dilution factors. The output sample analysis was done based on the leukocyte enrichment factor. The viscosity of the PVP diluted sample was the same as that of blood by maintaining the PVP solution viscosity. All the experiments demonstrate that viscoelastic fluid improves the leukocyte margination compared to a PBS-diluted sample. However, using a higher PVP concentration decreases the margination of leukocytes. This study found that enhancing any parameter solely, like viscosity, Reynolds number, or Hydraulic diameter, is insufficient for higher margination. The combined effect of the parameters discussed here is responsible for higher margination. It can be hypothesized that the leukocyte margination mainly depends on cell-cell interaction in the focusing zone. The margination tends to be barely affected at lower and higher viscosities. Maintaining the viscosity of the blood sample, optimizing the width of the cell-free layers, and ensuring more cell-cell interaction in the focusing zone of the channel can enhance the leukocyte margination collectively. |
Monday, November 25, 2024 2:55PM - 3:08PM |
R05.00006: Novel technique for estimating urethral tissue compliance for stricture detection Noah D Roselli, Emily Ji, Sourav Halder, Ziho Lee, Neelesh A Patankar Urethral strictures are a pathologic condition that predominantly impacts the male population following trauma. Voiding efficacy is decreased as a result of spongiofibrosis and scar tissue formation, increasing the stiffness of the urethra and narrowing the urethral diameter. The current gold standard study used to diagnose urethral stricture disease is a retrograde urethrogram (RUG), an x-ray imaging technique that illuminates the urethra by injecting contrast through the tip of the penis. However, there is a large variability in the length and location of a stricture determined by different physicians. Furthermore, there is no indication of tissue quality from the static RUGs. As such, patients are counseled regarding the potential for multiple surgical techniques and possible need to harvest buccal mucosa graft from the oral cavity, depending on the severity and length of the fibrosis. A novel technique was developed to locate the stricture by estimating the compliance of the tissue along the length of the urethra using a sequence of RUGs showing urethral distension. The urethra was considered to be an elastic cylindrical tube; one-dimensional conservation of mass and momentum equations with a constitutive relation were used to model the flow through it. By considering the patient-specific length and location of the stricture and the compliance of the tissue, patients can be better counseled on the most appropriate surgical intervention preoperatively. |
Monday, November 25, 2024 3:08PM - 3:21PM |
R05.00007: Flow dynamics of biolistic drug-delivery and therapeutic microparticles Ahmed Atef Abdelsatar Ahmed Hamada, Thomas S Howlett, Jeremiah J Gassensmith, Kianoosh Yousefi The needle- and syringe-based delivery of vaccines and other therapeutics have been of great benefit to human health but there are some critical issues, including the shortage of medical personnel, increasing biohazard waste, and cross-contamination risks. As such, alternate skin-based delivery routes are of significant interest, with biolistic delivery emerging as a promising option. In this study, we focus on the flow dynamic aspects of a novel biolistic delivery method, called "MOF-Jet"[TH1] , which uses a carrier gas to deliver a payload of drug-loaded metal-organic frameworks, as an alternative to needle-based administration methods. The process is modeled with a coupled Lagrangian-Eulerian framework, in which the drug particles are injected into a porous medium using a high-speed flow. This four-way coupling method models flow-particle interactions, including particle collisions. The MOF-Jet is a jet-crafted tube that accelerates drug particles at the nozzle throat and directs them into the porous medium. The numerical results showed excellent agreement with measurements and revealed intricate flow structures that can enhance drug delivery efficiency. The interactions between particles and porous skin are also explored through instantaneous flow dynamics. This study lays the milestone for future research on optimizing the biolistic design, offering a promising alternative to conventional techniques. |
Monday, November 25, 2024 3:21PM - 3:34PM |
R05.00008: Flow Evaluation of a Multifaceted Urine Analyzer Through Ansys Simulations and Experimental Photometry Piyush Hota, Peter Wiktor, Leslie Thomas, Marylaura Lind Thomas, Erica Forzani This study presents the development and validation of the Physical, Chemical, and Biological Dynamics Analyzer (PCODA), a multiscale, multimodal urine analyzer designed for point-of-care diagnostics. The PCODA device integrates a fluidic manifold that precisely mixes urine and reagent solutions to facilitate biomarker detection. Computational fluid dynamics (CFD) models using ANSYS Fluent® were developed to simulate fluid flow and mixing dynamics within the manifold, focusing on optimizing reagent injection and mixing efficiency. The simulations employed a multiphase Volume of Fluid (VOF) model and species transport to predict the diffusion and interaction of urine and reagent. Experimental validation was performed using a custom-built photometry system that monitors mixing dynamics in real-time by measuring the absorbance of a dyed reagent solution. The experimental results showed good agreement with the CFD simulations, confirming the accuracy of the model in predicting flow rates and mixing behavior. This combined computational and experimental approach provides valuable insights for design optimization and operational parameter refinement of the PCODA device. The work demonstrates a systematic process for integrating CFD modeling with experimental testing to advance the development of biomedical diagnostic devices. |
Monday, November 25, 2024 3:34PM - 3:47PM |
R05.00009: Flow Characterization and Parametric Analysis for Mechanical Kidney Stone Removal. Claire MacDougall, Jasmine Vallejo, Yilong Chang, Renee Zhao, Beverley J McKeon Kidney stones affect approximately 14% of individuals and are associated with significant morbidity, including severe pain due to urinary tract obstruction, renal injury, and potentially life-threatening infections (Khan et al., 2016). For larger and symptomatic stones, surgical intervention is often necessary. The most frequently employed surgical technique is ureteroscopy (URS), an endoscopic procedure wherein a small, flexible endoscope is inserted through the urethra into the bladder and subsequently advanced into the ureter to facilitate stone removal (Ho et al., 2017). |
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