Assessment and visualization of hemodynamic loading in aneurysm sac and neck: Effect of foam insertion

Shape memory polymer (SMP) foam is often proposed as the future alternative of coils in aneurysm treatment devices. Present work numerically investigates the unsteady, three-dimensional simulation of blood flow in a cerebral aneurysm filled with SMP foam. Simulations are conducted on patient-specific geometries with realistic blood velocity waveform imposed at the inlet while SMP foam is treated as a porous medium. The present study introduces a “loading risk map” that helps to visualize the hemodynamic effect of foam insertion on the aneurysm sac and neck. The loading risk maps suggest that while the SMP foam subdues the flow and wall shear pulsations in the aneurysm sac, the pressure distribution is minimally affected. The maps suggest that while the downstream lip is the most risk-prone site for both geometries, downstream vascular anatomy significantly influences foam efficiency in reducing pressure and wall shear stress loading.

Download Full-text

Computational Fluid Dynamics Characterization of Two Patient-Specific Systemic-to-Pulmonary Shunts before and after Operation

Computational and Mathematical Methods in Medicine ◽

10.1155/2019/1502318 ◽

2019 ◽

Vol 2019 ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

Neichuan Zhang ◽

Haiyun Yuan ◽

Xiangyu Chen ◽

Jiawei Liu ◽

Qifei Jian ◽

...

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Pulmonary Artery ◽

Energy Loss ◽

Three Dimensional ◽

Left Pulmonary Artery ◽

Postoperative Recovery ◽

Patient Specific ◽

Wall Shear ◽

Ct Data

Studying the haemodynamics of the central shunt (CS) and modified Blalock–Taussig shunt (MBTS) benefits the improvement of postoperative recovery for patients with an aorta-pulmonary shunt. Shunt configurations, including CS and MBTS, are virtually reconstructed for infants A and B based on preoperative CT data, and three-dimensional models of A, 11 months after CS, and B, 8 months after MBTS, are reconstructed based on postoperative CT data. A series of parameters including energy loss, wall shear stress, and shunt ratio are computed from simulation to analyse the haemodynamics of CS and MBTS. Our results showed that the shunt ratio of the CS is approximately 30% higher than the MBTS and velocity distribution in the left pulmonary artery (LPA) and right pulmonary artery (RPA) was closer to a natural development in the CS than the MBTS. However, energy loss of the MBTS is lower, and the MBTS can provide more symmetric pulmonary artery (PA) flow than the CS. With the growth of infants A and B, the shunt ratio of infants was decreased, but maximum wall shear stress and the distribution region of high wall shear stress (WSS) were increased, which raises the probability of thrombosis. For infant A, the preoperative abnormal PA structure directly resulted in asymmetric growth of PA after operation, and the LPA/RPA ratio decreased from 0.49 to 0.25. Insufficient reserved length of the MBTS led to traction phenomena with the growth of infant B; on the one hand, it increased the eddy current, and on the other hand, it increased the flow resistance of anastomosis, promoting asymmetric PA flow.

Download Full-text

Application of A Microstructural Constitutive Model of the Pulmonary Artery to Patient-Specific Studies: Validation and Effect of Orthotropy

Journal of Biomechanical Engineering ◽

10.1115/1.2485780 ◽

2006 ◽

Vol 129 (2) ◽

pp. 193-201 ◽

Cited By ~ 12

Author(s):

Yanhang Zhang ◽

Martin L. Dunn ◽

Kendall S. Hunter ◽

Craig Lanning ◽

D. Dunbar Ivy ◽

...

Keyword(s):

Pulmonary Artery ◽

Animal Studies ◽

Three Dimensional ◽

Vascular Anatomy ◽

Initial Study ◽

Patient Specific ◽

Pulmonary Vasculature ◽

Cross Linking ◽

Microstructural Model ◽

Pulmonary Arterial

We applied a statistical mechanics based microstructural model of pulmonary artery mechanics, developed from our previous studies of rats with pulmonary arterial hypertension (PAH), to patient-specific clinical studies of children with PAH. Our previous animal studies provoked the hypothesis that increased cross-linking density of the molecular chains may be one biological remodeling mechanism by which the PA stiffens in PAH. This study appears to further confirm this hypothesis since varying molecular cross-linking density in the model allows us to simulate the changes in the P‐D loops between normotensive and hypertensive conditions reasonably well. The model was combined with patient-specific three-dimensional vascular anatomy to obtain detailed information on the topography of stresses and strains within the proximal branches of the pulmonary vasculature. The effect of orthotropy on stress∕strain within the main and branch PAs obtained from a patient was explored. This initial study also puts forward important questions that need to be considered before combining the microstructural model with complex patient-specific vascular geometries.

Download Full-text

Experimental and Numerical Investigation of the Flow Behavior in a Tapered Rectangular Sprue

Materials: Processing, Characterization and Modeling of Novel Nano-Engineered and Surface Engineered Materials ◽

10.1115/imece2002-32660 ◽

2002 ◽

Author(s):

Abdessalem Derdouri ◽

Florin Ilinca ◽

Kalonji Kabanemi ◽

Jean-Franc¸ois He´tu

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Flow Behavior ◽

Three Dimensional ◽

Pressure Sensors ◽

Reinforced Polymers ◽

Volumetric Rate ◽

Wall Shear ◽

Dimensional Simulation ◽

Large Width

The present study is part of a continuing effort to obtain a better understanding of the rheological behavior during the injection molding of unfilled and reinforced polymers and help improve the prediction by numerical three dimensional simulation of the process. The slightly tapered rectangular sprue of a centrally gated plaque mold was equipped with flush mounted pressure sensors to monitor the time evolution of the wall shear stress prior to entering the cavity. Two Polycarbonate with different zero-shear rate viscosities were tested at various injection speeds. Atter an initial rise, the wall shear stress in the sprue remains constant during the filling stage of the mold. The transient shear viscosity was determined from the known volumetric rate using a simplified one-dimensional flow approach and compared to the viscosity measured by traditional off-line rheometers. A finite element three-dimensional code is used to simulate the flow in the sprue with small and large width over thickness ratios. The pressures predicted are used in combination with the simplified theory to calculate the viscosity and compare the results from the experiments.

Download Full-text

Dynamic Patient-Specific Three-Dimensional Simulation of Mitral Repair

Innovations Technology and Techniques in Cardiothoracic and Vascular Surgery ◽

10.1177/155698451801300103 ◽

2018 ◽

Vol 13 (1) ◽

pp. 11-22 ◽

Cited By ~ 3

Author(s):

Olivia K. Ginty ◽

John M. Moore ◽

Yuanwei Xu ◽

Wenyao Xia ◽

Satoru Fujii ◽

...

Keyword(s):

Three Dimensional ◽

Patient Specific ◽

Mitral Repair ◽

Dimensional Simulation

Download Full-text

Hemodynamics in growing and stable cerebral aneurysms

Journal of NeuroInterventional Surgery ◽

10.1136/neurintsurg-2014-011339 ◽

2015 ◽

Vol 8 (4) ◽

pp. 407-412 ◽

Cited By ~ 29

Author(s):

Daniel M Sforza ◽

Kenichi Kono ◽

Satoshi Tateshima ◽

Fernando Viñuela ◽

Christopher Putman ◽

...

Keyword(s):

Shear Stress ◽

Logistic Regression ◽

Wall Shear Stress ◽

Statistical Models ◽

Three Dimensional ◽

Cerebral Aneurysms ◽

Patient Specific ◽

Unruptured Aneurysms ◽

Aspect Ratios ◽

Wall Shear

ObjectiveThe detailed mechanisms of cerebral aneurysm evolution are poorly understood but are important for objective aneurysm evaluation and improved patient management. The purpose of this study was to identify hemodynamic conditions that may predispose aneurysms to growth.MethodsA total of 33 intracranial unruptured aneurysms longitudinally followed with three-dimensional imaging were studied. Patient-specific computational fluid dynamics models were constructed and used to quantitatively characterize the hemodynamic environments of these aneurysms. Hemodynamic characteristics of growing (n=16) and stable (n=17) aneurysms were compared. Logistic regression statistical models were constructed to test the predictability of aneurysm growth by hemodynamic features.ResultsGrowing aneurysms had significantly smaller shear rate ratios (p=0.01), higher concentration of wall shear stress (p=0.03), smaller vorticity ratios (p=0.01), and smaller viscous dissipation ratios (p=0.01) than stable aneurysms. They also tended to have larger areas under low wall shear stress (p=0.06) and larger aspect ratios (p=0.18), but these trends were not significant. Mean wall shear stress was not significantly different between growing and stable aneurysms. Logistic regression models based on hemodynamic variables were able to discriminate between growing and stable aneurysms with a high degree of accuracy (94–100%).ConclusionsGrowing aneurysms tend to have complex intrasaccular flow patterns that induce non-uniform wall shear stress distributions with areas of concentrated high wall shear stress and large areas of low wall shear stress. Statistical models based on hemodynamic features seem capable of discriminating between growing and stable aneurysms.

Download Full-text

Three-dimensional simulation of thrombus formation in Fontan circulation using patient-specific models of blood flow channel

The Proceedings of the JSME Conference on Frontiers in Bioengineering ◽

10.1299/jsmebiofro.2016.27.c216 ◽

2016 ◽

Vol 2016.27 (0) ◽

pp. C216

Author(s):

Takuya TAKEUCHI ◽

Koichi SUGHIMOTO ◽

Ken-ichi TSUBOTA

Keyword(s):

Blood Flow ◽

Thrombus Formation ◽

Three Dimensional ◽

Fontan Circulation ◽

Flow Channel ◽

Patient Specific ◽

Dimensional Simulation

Download Full-text

Patient-Specific Augmentation Rhinoplasty Using a Three-Dimensional Simulation Program and Three-Dimensional Printing

Aesthetic Surgery Journal ◽

10.1093/asj/sjx046 ◽

2017 ◽

Vol 37 (9) ◽

pp. 988-998 ◽

Cited By ~ 10

Author(s):

Yim Don Choi ◽

Youngjun Kim ◽

EunSoo Park

Keyword(s):

Three Dimensional ◽

Simulation Program ◽

Patient Specific ◽

Augmentation Rhinoplasty ◽

Three Dimensional Printing ◽

Dimensional Simulation ◽

Dimensional Printing

Download Full-text

In-Vitro Blood Flow and Wall Shear Stress Measurements in Idealised and Patient Specific Models of the Carotid Artery Bifurcation

ASME 2008 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2008-193263 ◽

2008 ◽

Cited By ~ 1

Author(s):

Nicolas A. Buchmann ◽

Mark C. Jermy

Keyword(s):

Shear Stress ◽

Carotid Artery ◽

Wall Shear Stress ◽

Three Dimensional ◽

Patient Specific ◽

Specific Geometry ◽

Wall Shear ◽

Magnetic Resonance Imaging Mri ◽

Vitro Model

This work presents Particle Image Velocimetry (PIV) measurements in idealised and patient specific human carotid artery bifurcations (CAB) under steady and pulsatile flow. The geometry and corresponding boundary conditions were obtained by Magnetic Resonance Imaging (MRI) and replicated in an in-vitro model. A complex three-dimensional flow structure exists inside the CAB and vorticity and wall shear stress data are used to quantify the differences between the idealised and patient specific geometry.

Download Full-text

Stent design properties and deployment ratio influence indexes of wall shear stress: a three-dimensional computational fluid dynamics investigation within a normal artery

Journal of Applied Physiology ◽

10.1152/japplphysiol.01329.2003 ◽

2004 ◽

Vol 97 (1) ◽

pp. 424-430 ◽

Cited By ~ 100

Author(s):

John F. LaDisa ◽

Lars E. Olson ◽

Ismail Guler ◽

Douglas A. Hettrick ◽

Said H. Audi ◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Shear Stress ◽

Wall Shear Stress ◽

Neointimal Hyperplasia ◽

Three Dimensional ◽

Vascular Anatomy ◽

Fold Increase ◽

Stent Strut ◽

Wall Shear

Restenosis limits the effectiveness of stents, but the mechanisms responsible for this phenomenon remain incompletely described. Stent geometry and expansion during deployment produce alterations in vascular anatomy that may adversely affect wall shear stress (WSS) and correlate with neointimal hyperplasia. These considerations have been neglected in previous computational fluid dynamics models of stent hemodynamics. Thus we tested the hypothesis that deployment diameter and stent strut properties (e.g., number, width, and thickness) influence indexes of WSS predicted with three-dimensional computational fluid dynamics. Simulations were based on canine coronary artery diameter measurements. Stent-to-artery ratios of 1.1 or 1.2:1 were modeled, and computational vessels containing four or eight struts of two widths (0.197 or 0.329 mm) and two thicknesses (0.096 or 0.056 mm) subjected to an inlet velocity of 0.105 m/s were examined. WSS and spatial WSS gradients were calculated and expressed as a percentage of the stent and vessel area. Reducing strut thickness caused regions subjected to low WSS (<5 dyn/cm2) to decrease by ∼87%. Increasing the number of struts produced a 2.75-fold increase in exposure to low WSS. Reducing strut width also caused a modest increase in the area of the vessel experiencing low WSS. Use of a 1.2:1 deployment ratio increased exposure to low WSS by 12-fold compared with stents implanted in a 1.1:1 stent-to-vessel ratio. Thinner struts caused a modest reduction in the area of the vessel subjected to elevated WSS gradients, but values were similar for the other simulations. The results suggest that stent designs that reduce strut number and thickness are less likely to subject the vessel to distributions of WSS associated with neointimal hyperplasia.

Download Full-text