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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Immersed Boundary Method Halo Exchange in a Hemodynamics Application

In recent years, highly parallelized simulations of blood flow resolving individual blood cells have been demonstrated. Simulating such dense suspensions of deformable particles in flow often involves a partitioned fluid-structure interaction (FSI) algorithm, with separate solvers for Eulerian fluid and Lagrangian cell grids, plus a solver - e.g., immersed boundary method - for their interaction. Managing data motion in parallel FSI implementations is increasingly important, particularly for inhomogeneous systems like vascular geometries. In this study, we evaluate the influence of Eulerian and Lagrangian halo exchanges on efficiency and scalability of a partitioned FSI algorithm for blood flow. We describe an MPI+OpenMP implementation of the immersed boundary method coupled with lattice Boltzmann and finite element methods. We consider how communication and recomputation costs influence the optimization of halo exchanges with respect to three factors: immersed boundary interaction distance, cell suspension density, and relative fluid/cell solver costs.

Gounley, John↗
DOE OSTI2022

Evaluation of intracoronary hemodynamics identifies perturbations in vorticity

Coronary artery disease (CAD) is highly prevalent and associated with adverse events. Challenges have emerged in the treatment of intermediate coronary artery stenoses. These lesions are often interrogated with fractional flow reserve (FFR) testing to determine if a stenosis is likely to be causative for ischemia in a cardiac territory. This invasive test requires insertion of a pressure wire into a coronary vessel. Recently computational fluid dynamics (CFD) has been used to noninvasively assess fractional flow reserve in vessels reconstructed from medical imaging data. However, many of these simulations are unable to provide additional information about intravascular hemodynamics, including velocity, endothelial shear stress (ESS), and vorticity. We hypothesized that vorticity, which has demonstrated utility in the assessment of ventricular and aortic diseases, would also be an important hemodynamic factor in CAD. Three-dimensional (3D), patient-specific coronary artery geometries that included all vessels >1 mm in diameter were created from angiography data obtained from 10 patients who underwent diagnostic angiography and FFR testing (n = 9). A massively parallel CFD solver (HARVEY) was used to calculate coronary hemodynamic parameters including pressure, velocity, ESS, and vorticity. These simulations were validated by comparing velocity flow fields from simulation to both velocities derived from in vitro particle image velocimetry and to invasively acquired pressure wire-based data from clinical testing. There was strong agreement between findings from CFD simulations and particle image velocimetry experimental testing (p < 0.01). CFD-FFR was also highly correlated with invasively measured FFR (ρ = 0.77, p = 0.01) with an average error of 5.9 ± 0.1%. CFD-FFR also had a strong inverse correlation with the vorticity (ρ = -0.86, p = 0.001). Simulations to determine the effect of the coronary stenosis on intravascular hemodynamics demonstrated significant differences in velocity and vorticity (both p < 0.05). Further evaluation of an angiographically normal appearing non-FFR coronary vessel in patients with CAD also demonstrated differences in vorticity when compared with FFR vessels (p < 0.05). The use of highly accurate 3D CFD-derived intravascular hemodynamics provides additional information beyond pressure measurements that can be used to calculate FFR. Vorticity is one parameter that is modified by a coronary stenosis and appears to be abnormal in angiographically normal vessels in patients with CAD, highlighting a possible use-case in preventative screening for early coronary disease.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Collagen Turnover in Relation to Risk Factors and Hemodynamics in Human Intracranial Aneurysms

Determinants for molecular and structural instability, that is, impending growth or rupture, of intracranial aneurysms (IAs) remain uncertain. To elucidate this, we endeavored to estimate the actual turnover rates of the main molecular constituent in human IA (collagen) on the basis of radiocarbon ( 14 C) birth dating in relation to IA hemodynamics. Collagen turnover rates in excised human IA samples were calculated using mathematical modeling of 14 C birth dating data of collagen in relation to risk factors and histological markers for collagen maturity/turnover in selected IA. Hemodynamics were simulated using image-based computational fluid dynamics. Correlation, logistic regression, and receiver operating characteristic analyses were performed. Collagen turnover rates were estimated in 46 IA (43 patients); computational fluid dynamics could be performed in 20 IA (20 patients). The mean collagen turnover rate (γ) constituted 126% (±1% error) per year. For patients with arterial hypertension, γ was greater than 2600% annually, whereas γ was distinctly lower with 32% (±1% error) per year for patients without risk factors, such as smoking and hypertension. There was a distinct association between histological presence of rather immature collagen in human IA and the presence of modifiable risk factors. Spatial-temporal averaged wall shear stress predicted rapid collagen turnover (odds ratio, 1.6 [95% CI, 1.0–2.7]). Receiver operating characteristic analysis demonstrated a good test accuracy (area under the curve, 0.798 [95% CI, 0.598–0.998]) for average wall shear stress with a threshold ≥4.9 Pa for rapid collagen turnover. Our data indicate that turnover rates and stability of collagen in human IA are strongly associated with the presence of modifiable risk factors and aneurysmal hemodynamics. Finally, these findings underline the importance of strict risk factor modification in patients with unruptured IA. Future should include more detailed risk factor data to establish a more causal understanding of hemodynamics and the rupture risk of individual IA.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Inferior Vena Cava Filters in Hemodynamically Unstable Patients with Acute Pulmonary Embolism: How Often are They Used? Data from Multicenter Prospective Registries on Acute Pulmonary Embolism

The use of inferior vena cava (IVC) filters is recommended in patients with acute pulmonary embolism (PE) who have absolute contraindications to anticoagulant drugs and/or in those subjects with recurrent PE despite treated with an adequate anticoagulant regimen. During the last 2 decades, some investigations have demonstrated that the use of IVC filters in high-risk PE patients, treated or not with systemic thrombolysis, was able to reduce the short-term mortality rate if inserted early after the acute event. The aim of the present review is to analyze the use of IVC filters in high-risk PE patients enrolled in prospective multicenter registries between 1990 and 2018. After screening 3542 article in PubMed, Scopus, Cochrane library and Goggle Scholar databases, we identified four registry studies meeting the inclusion criteria. In a prospective cohort of 39,056 patients, 1387 (3.5%) were hemodynamically unstable at admission. Among them, IVC filters were used only in 2.7% of cases. Conversely, IVC filters were inserted in 3.8% of hemodynamically stable patients. Over the years, a fluctuating trend in the use of IVC filters was observed. In the absence of randomized controlled trial on this issue, which would be difficult, if not impossible to realize, data obtained from the medical literature seem to suggest that IVC filters could represent a valid adjunctive therapy in hemodynamically unstable PE patients, able to prevent further hemodynamic deterioration. Further and larger subgroup analyses, obtained both by prospective and retrospective studies, are necessary to clarify this therapeutic approach.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Effects of a human recombinant alkaline phosphatase on renal hemodynamics, oxygenation and inflammation in two models of acute kidney injury

Two small clinical trials indicated that administration of bovine intestinal alkaline phosphatase (AP) improves renal function in critically ill patients with sepsis-associated acute kidney injury (AKI), for which the mechanism of action is not completely understood. Here, we investigated the effects of a newly developed human recombinant AP (recAP) on renal oxygenation and hemodynamics and prevention of kidney damage and inflammation in two in vivo AKI models. To induce AKI, male Wistar rats (n = 18) were subjected to renal ischemia (30 min) and reperfusion (I/R), or sham-operated. In a second model, rats (n = 18) received a 30 min infusion of lipopolysaccharide (LPS; 2.5 mg/kg), or saline, and fluid resuscitation. In both models, recAP (1000 U/kg) was administered intravenously (15 min before reperfusion, or 90 min after LPS). Following recAP treatment, I/R-induced changes in renal blood flow, renal vascular resistance and oxygen delivery at early, and cortical microvascular oxygen tension at late reperfusion were no longer significantly affected. RecAP did not influence I/R-induced effects on mean arterial pressure. During endotoxemia, recAP treatment did not modulate the LPS-induced changes in systemic hemodynamics and renal oxygenation. In both models, recAP did exert a clear renal protective anti-inflammatory effect, demonstrated by attenuated immunostaining of inflammatory, tubular injury and pro-apoptosis markers. Whether this renal protective effect is sufficient to improve outcome of patients suffering from sepsis-associated AKI is being investigated in a large clinical trial. - Highlights: • Human recombinant alkaline phosphatase (recAP) is a potential new therapy for sepsis-associated acute kidney injury (AKI). • RecAP can modulate renal oxygenation and hemodynamics immediately following I/R-induced AKI. • RecAP did not modulate endotoxemia-induced changes in systemic hemodynamics and renal oxygenation. • RecAP did exert a clear renal protective anti-inflammatory effect in both models.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Use of Cardiac Imaging to Evaluate Cardiac Function and Pulmonary Hemodynamics in Patients with Heart Failure

Purpose of Review: Noninvasive hemodynamic assessments in patients with heart failure (HF) are essential for appropriate diagnosis and establishment of the best treatment strategies. Recently, the impact of pulmonary circulation and right ventricular function on prognosis in HF patients has drawn increasing attention. In this article, we explore the usefulness of cardiac imaging for hemodynamic assessments, mainly focusing on echocardiographic evaluation. Recent Findings: The reliability of Doppler echocardiography as a noninvasive alternative to Swan-Ganz catheterization has been well investigated with higher than 80% accuracy for estimating pulmonary artery pressure. Strain measurement and three-dimensional echocardiography are useful for evaluating right ventricular function together with pulmonary circulation. The accuracy of analyzing left and right ventricular functions by cardiac computed tomography and cardiac magnetic resonate imaging has also been established. These modalities can provide myocardial tissue information and allow calculation of the extracellular volume fraction as well. Summary: According to the rapid improvement of technologies, cardiac imaging has become an essential tool for hemodynamic evaluation in HF management.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Accelerating massively parallel hemodynamic models of coarctation of the aorta using neural networks

Comorbidities such as anemia or hypertension and physiological factors related to exertion can influence a patient’s hemodynamics and increase the severity of many cardiovascular diseases. Observing and quantifying associations between these factors and hemodynamics can be difficult due to the multitude of co-existing conditions and blood flow parameters in real patient data. Machine learning-driven, physics-based simulations provide a means to understand how potentially correlated conditions may affect a particular patient. Here, we use a combination of machine learning and massively parallel computing to predict the effects of physiological factors on hemodynamics in patients with coarctation of the aorta. We first validated blood flow simulations against in vitro measurements in 3D-printed phantoms representing the patient’s vasculature. We then investigated the effects of varying the degree of stenosis, blood flow rate, and viscosity on two diagnostic metrics – pressure gradient across the stenosis (ΔP) and wall shear stress (WSS) - by performing the largest simulation study to date of coarctation of the aorta (over 70 million compute hours). Using machine learning models trained on data from the simulations and validated on two independent datasets, we developed a framework to identify the minimal training set required to build a predictive model on a per-patient basis. We then used this model to accurately predict ΔP (mean absolute error within 1.18 mmHg) and WSS (mean absolute error within 0.99 Pa) for patients with this disease.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Model-based approach to investigate equipment-induced error in pressure-waveform derived hemodynamic measurements

Advanced hemodynamic monitoring systems have provided less invasive methods for estimating pressure-derived measurements such as pressure-derived cardiac output (CO) measurements. These devices apply algorithms to arterial pressure waveforms recorded via pressure recording components that transmit the pressure signal to a pressure monitor. While standards have been developed for pressure monitoring equipment, it is unclear how the equipment-induced error can affect secondary measurements from pressure waveforms. We propose an approach for modelling different components of a pressure monitoring system and use this model-based approach to investigate the effect of different pressure recording configurations on pressure-derived hemodynamic measurements. The proposed model-based approach is a three-step process. (1) Modelling the response of pressure recording components using bench tests; (2) verifying the identified models through nonparametric equivalence tests; and (3) assessing the effects of pressure recording components on pressure-derived measurements. To delineate the application of this approach, we performed a series of model-based analyses to quantify the combined effect of a wide range of tubing configurations with various damping ratios and natural frequencies and monitors with different bandwidths on pressure waveforms and CO measurements by six pulse contour algorithms. Model-based results show the error in pressure-derived CO measurements because of tubing configurations with different natural frequencies and damping ratios. Tubing configurations with low natural frequencies (<23 Hz) altered characteristics of pressure waveforms in a way that affected the CO measurement, some by as much as 20%. Our method can serve as a tool to quantify the performance of pressure recording systems with different dynamic properties. In conclusion, this approach can be applied to investigate the effects of physiologic signal recording configurations on various pressure-derived hemodynamic measurements.

42 ENGINEERING↗
DOE OSTI2016

Novel Software-Assisted Hemodynamic Evaluation of Pelvic Flow During Chemoperfusion of Pelvic Arteries for Bladder Cancer: Double- Versus Single-Balloon Technique

PurposeApproximately 83 % of patients with bladder cancer have achieved a complete response after undergoing a novel bladder preservation therapy involving balloon-occluded intra-arterial infusion chemotherapy (BOAI) using a four-lumen double-balloon catheter, known as the Osaka Medical College regimen. This study aimed to show the quantitative difference in hemodynamics of the bladder arteries using syngo iFlow (Siemens Healthcare, Erlangen, Germany), which provides an automatic tool for quantitative blood flow analysis between double BOAI (D-BOAI) and conventional single BOAI (S-BOAI).Materials and MethodsFifty patients were included. The catheters were introduced into both posterior trunks of the internal iliac arteries via contralateral femoral artery access. A side hole between the distal and proximal balloons was placed at the origin of each bladder artery to allow clear visualization of angiographic flow of the injected agent into the urinary bladder. Digital subtraction angiography was used during analysis with the syngo iFlow to evaluate the hemodynamics of the contrast medium in the pelvic arteries during BOAI. The comparative change in the amount of contrast medium in the bladder arteries between D-BOAI and S-BOAI was assessed using syngo iFlow.ResultsOne-hundred pelvic sides were analyzed. The amount of contrast medium in the bladder arteries using D-BOAI was more than twice that using S-BOAI (right, 3.03-fold; left, 2.81-fold).ConclusionThe amount of contrast medium in the bladder arteries using D-BOAI was higher than that using conventional S-BOAI. This may increase the anticancer drug concentration in the affected bladder, leading to a good clinical response.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

The Potential of Computational Fluid Dynamics Simulation on Serial Monitoring of Hemodynamic Change in Type B Aortic Dissection

PurposeWe aimed to assess the potential of computational fluid dynamics simulation (CFD) in detecting changes in pressure and flow velocity in response to morphological changes in type B aortic dissection.Materials and MethodsPressure and velocity in four morphological models of type B aortic dissection before and after closure of the entry tear were calculated with CFD and analyzed for changes among the different scenarios. The control model (Model 1) was patient specific and built from the DICOM data of CTA, which bore one entry tear and three re-entry tears. Models 2–4 were modifications of Model 1, with two re-entry tears less in Model 2, one re-entry tear more in Model 3, and a larger entry tear in Model 4.ResultsThe pressure and velocity pertaining to each of the morphological models were unique. Changes in pressure and velocity findings were accountable by the changes in morphological features of the different models. There was no blood flow in the false lumen across the entry tear after its closure, the blood flow direction across the re-entry tears was reversed after closure of the entry tear.ConclusionCFD simulation is probably useful to detect hemodynamic changes in the true and false lumens of type B aortic dissection in response to morphological changes, it may potentially be developed into a non-invasive and patient-specific tool for serial monitoring of hemodynamic changes of type B aortic dissection before and after treatment.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

An assessment of the safety, hemodynamic response, and diagnostic accuracy of commonly used vasodilator stressors in patients with severe aortic stenosis

Background: Increasing numbers of patients are undergoing transcatheter aortic valve replacement, which often involves assessment of coronary artery disease ischemic burden. The safety and diagnostic accuracy of vasodilator stress agents in patients with severe aortic stenosis (AS) undergoing SPECT myocardial perfusion imaging (MPI) has not been established. Methods: Patients with severe AS (valve area <1 cm{sup 2}) on echocardiography who underwent vasodilator stress SPECT MPI at two centers were identified. Patients with aortic valve intervention prior to MPI or who underwent concurrent exercise during stress testing were excluded. AS patients were matched to controls without AS based on age, gender, BMI, ejection fraction, and stress agent. Symptoms, serious adverse events, hemodynamic response, and correlation to invasive angiography were assessed. Results: A total of 95 cases were identified with 45% undergoing regadenoson, 31% dipyridamole, and 24% adenosine stress. A significant change in systolic blood pressure (BP), cases vs controls, was observed with adenosine [−17.9 ± 20.1 vs −2.6 ± 24.9 P = .03)], with a trend toward significance with regadenoson [−16.8 ± 20.3 vs −9.4 ± 17.9 (P = .08)] and dipyridamole [−17.8 ± 20.6 vs -9.0 ± 12.1 (P = .05)]. The change in heart rate was significantly different only for adenosine [5.3 ± 16.8 vs 14.2 ± 10.8 (P = .04)]. Overall, 45% of cases vs 24% of controls (P = .004) had a >20 mmHg decrease in systolic BP. Age, BMI, and resting systolic BP were related to a >20 mmHg decrease in systolic BP on univariate analysis, although only higher resting systolic BP was a predictor on multivariate analysis. In 33 patients who underwent angiography, the sensitivity, specificity, and diagnostic accuracy of vasodilator stress MPI was 77%, 69%, and 73%, respectively. No serious adverse events occurred in the severe AS patients. Conclusion: Severe AS patients are more likely to have a hemodynamically significant decrease in systolic BP with vasodilator stress. There were no serious adverse events in this severe AS cohort with good diagnostic performance of MPI compared to angiography.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Adenosine stress myocardial perfusion imaging in octogenarians: Safety, tolerability, and long-term prognostic implications of hemodynamic response and SPECT-related variables

Background: Evaluation of tolerability, safety, and prognostic implications of adenosine stress myocardial perfusion imaging (MPI) in octogenarians. Methods: 370 octogenarians (49% known coronary artery disease) were studied. Hemodynamic response, MPI-related data, and rest-left ventricular ejection fraction (LVEF) based on echocardiography were registered per patient, and prospective follow-up was performed to document all-cause death (ACD), cardiac death (CD), myocardial infarction (MI), and late revascularization. Results: No deaths or MIs were observed during adenosine infusion or the short-term post-infusion period. 86% of patients were able to tolerate a 6-minute infusion. All side effects terminated spontaneously after infusion cessation, except for one case of pulmonary oedema. After 9.3 years, there were 124 ACDs, 62 CDs, 16 MIs, and 35 revascularizations. Differences between survival curves of summed stress score (SSS)-based risk groups were significant for all end points (P < .001). SSS and LVEF were independent predictors of all end points (P ≤ .01) and lung uptake of cardiac end points. ΔHR <10 bpm (OR = 1.78, P = .004) and inability to increase HR by >10 bpm and decrease systolic blood pressure by >10 mmHg (OR = 2, P = .02) during adenosine infusion were independent predictors of ACD and CD, respectively. Hemodynamic response variables, SSS, and lung uptake provided incremental prognostic value over pre-test data for ACD and CD. Conclusions: In octogenarians, adenosine stress MPI is well tolerated and provides effective long-term risk stratification.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Multilevel and multifidelity uncertainty quantification for cardiovascular hemodynamics

Standard approaches for uncertainty quantification in cardiovascular modeling pose challenges due to the large number of uncertain inputs and the significant computational cost of realistic three-dimensional simulations. Here, we propose an efficient uncertainty quantification framework utilizing a multilevel multifidelity Monte Carlo (MLMF) estimator to improve the accuracy of hemodynamic quantities of interest while maintaining reasonable computational cost. This is achieved by leveraging three cardiovascular model fidelities, each with varying spatial resolution to rigorously quantify the variability in hemodynamic outputs. We employ two low-fidelity models (zero- and one-dimensional) to construct several different estimators. Our goal is to investigate and compare the efficiency of estimators built from combinations of these two low-fidelity model alternatives and our high-fidelity three-dimensional models. We demonstrate this framework on healthy and diseased models of aortic and coronary anatomy, including uncertainties in material property and boundary condition parameters. Our goal is to demonstrate that for this application it is possible to accelerate the convergence of the estimators by utilizing a MLMF paradigm. Therefore, we compare our approach to single fidelity Monte Carlo estimators and to a multilevel Monte Carlo approach based only on three-dimensional simulations, but leveraging multiple spatial resolutions. We demonstrate significant, on the order of 10 to 100 times, reduction in total computational cost with the MLMF estimators. We also examine the differing properties of the MLMF estimators in healthy versus diseased models, as well as global versus local quantities of interest. As expected, global quantities such as outlet pressure and flow show larger reductions than local quantities, such as those relating to wall shear stress, as the latter rely more heavily on the highest fidelity model evaluations. Similarly, healthy models show larger reductions than diseased models. In all cases, our workflow coupling Dakota’s MLMF estimators with the SimVascular cardiovascular modeling framework makes uncertainty quantification feasible for constrained computational budgets.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Personalized and uncertainty-aware coronary hemodynamics simulations: From Bayesian estimation to improved multi-fidelity uncertainty quantification

Non-invasive simulations of coronary hemodynamics have improved clinical risk stratification and treatment outcomes for coronary artery disease, compared to relying on anatomical imaging alone. However, simulations typically use empirical approaches to distribute total coronary flow amongst the arteries in the coronary tree, which ignores patient variability, the presence of disease, and other clinical factors. Further, uncertainty in the clinical data often remains unaccounted for in the modeling pipeline. We present an end-to-end uncertainty-aware pipeline to (1) personalize coronary flow simulations by incorporating vessel-specific coronary flows as well as cardiac function; and (2) predict clinical and biomechanical quantities of interest with improved precision, while accounting for uncertainty in the clinical data. We assimilate patient-specific measurements of myocardial blood flow from clinical CT myocardial perfusion imaging to estimate branch-specific coronary artery flows. Simulated noise in the clinical data is used to estimate the joint posterior distributions of the model parameters using adaptive Markov Chain Monte Carlo sampling. Additionally, the posterior predictive distribution for the relevant quantities of interest is determined using a new approach combining multi-fidelity Monte Carlo estimation with non-linear, data-driven dimensionality reduction. This leads to improved correlations between high- and low-fidelity model outputs. Our framework accurately recapitulates clinically measured cardiac function as well as branch-specific coronary flows under measurement noise uncertainty. We observe substantial reductions in confidence intervals for estimated quantities of interest compared to single-fidelity Monte Carlo estimation and state-of-the-art multi-fidelity Monte Carlo methods. This holds especially true for quantities of interest that showed limited correlation between the low- and high-fidelity model predictions. In addition, the proposed multi-fidelity Monte Carlo estimators are significantly cheaper to compute than traditional estimators, under a specified confidence level or variance. The proposed pipeline for personalized and uncertainty-aware predictions of coronary hemodynamics is based on routine clinical measurements and recently developed techniques for CT myocardial perfusion imaging. The proposed pipeline offers significant improvements in precision and reduction in computational cost.

Bayesian parameter estimation↗
DOE OSTI2019

Propagating uncertainties in large-scale hemodynamics models via network uncertainty quantification and reduced-order modeling

Numerical simulations of the cardiovascular system are affected by uncertainties arising from a substantial lack of data related to the boundary conditions and the physical parameters of the mathematical models. Quantifying the impact of this uncertainty on the numerical results along the circulatory network is challenged by the complexity of both the morphology of the domain and the local dynamics. Here, we propose to integrate (i) the Transverse Enriched Pipe Element Methods (TEPEM) as a reduced-order model for effectively computing the 3D local hemodynamics; and (ii) a combination of uncertainty quantification via Polynomial Chaos Expansion and classical relaxation methods – called network uncertainty quantification (NetUQ) – for effectively propagating random variables that encode uncertainties throughout the networks. The findings demonstrate the computational effectiveness of computing the propagation of uncertainties in networks with nontrivial topology, including portions of the cerebral and the coronary systems.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

Perioperative Hemodynamic Monitoring of Common Hepatic Artery for Endovascular Embolization of a Pancreaticoduodenal Arcade Aneurysm with Celiac Stenosis

This report describes perioperative hemodynamic monitoring of the common hepatic artery (CHA) during endovascular treatment of a pancreaticoduodenal arcade aneurysm, in a patient with celiac artery stenosis caused by the median arcuate ligament. Pressure monitoring was performed as a safety measure against critical complications such as liver ischemia. As the aneurysm was located in the anterior pancreaticoduodenal artery (APDA) and the posterior pancreaticoduodenal artery (PPDA) was small in caliber, the patient was considered to be at a high risk of liver ischemia. No significant change in pressure was observed in the CHA on balloon occlusion test in the APDA. Immediately after embolization, the PPDA enlarged and the pressure in the CHA was well maintained. Pressure monitoring appears to improve patient safety during endovascular treatment of visceral aneurysms.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Multi-GPU immersed boundary method hemodynamics simulations

Large-scale simulations of blood flow that resolve the 3D deformation of each comprising cell are increasingly popular owing to algorithmic developments in conjunction with advances in compute capability. Among different approaches for modeling cell-resolved hemodynamics, fluid structure interaction (FSI) algorithms based on the immersed boundary method are frequently employed for coupling separate solvers for the background fluid and the cells within one framework. GPUs can accelerate these simulations; however, both current pre-exascale and future exascale CPU-GPU heterogeneous systems face communication challenges critical to performance and scalability. In this paper, we describe, to our knowledge, the largest distributed GPU-accelerated FSI simulations of high hematocrit cell-resolved flows with over 17 million red blood cells. We compare scaling on a fat node system with six GPUs per node and on a system with a single GPU per node. Through comparison between the CPU- and GPU-based implementations, we identify the costs of data movement in multiscale multi-grid FSI simulations on heterogeneous systems and show it to be the greatest performance bottleneck on the GPU.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Data-driven Modeling of Hemodynamics and its Role on Thrombus Size and Shape in Aortic Dissections

Aortic dissection is a pathology that manifests due to microstructural defects in the aortic wall. Blood enters the damaged wall through an intimal tear, thereby creating a so-called false lumen and exposing the blood to thrombogenic intramural constituents such as collagen. The natural history of this acute vascular injury thus depends, in part, on thrombus formation, maturation, and possible healing within the false lumen. A key question is: Why do some false lumens thrombose completely while others thrombose partially or little at all? An ability to predict the location and extent of thrombus in subjects with dissection could contribute significantly to clinical decision-making, including interventional design. We develop, for the first time, a data-driven particle-continuum model for thrombus formation in a murine model of aortic dissection. In the proposed model, we simulate a final-value problem in lieu of the original initial-value problem with significantly fewer particles that may grow in size upon activation, thus representing the local concentration of blood-borne species. Numerical results confirm that geometry and local hemodynamics play significant roles in the acute progression of thrombus. Despite geometrical differences between murine and human dissections, mouse models can provide considerable insight and have gained popularity owing to their reproducibility. Our results for three classes of geometrically different false lumens show that thrombus forms and extends to a greater extent in regions with lower bulk shear rates. Dense thrombi are less likely to form in high-shear zones and in the presence of strong vortices. Here, the present data-driven study suggests that the proposed model is robust and can be employed to assess thrombus formation in human aortic dissections.

60 APPLIED LIFE SCIENCES↗