scholarly journals Computational Modeling of the Liver Arterial Blood Flow for Microsphere Therapy: Effect of Boundary Conditions

2020 ◽  
Vol 7 (3) ◽  
pp. 64
Author(s):  
Amirtahà Taebi ◽  
Rex M. Pillai ◽  
Bahman S. Roudsari ◽  
Catherine T. Vu ◽  
Emilie Roncali
Keyword(s):  
Blood Flow ◽  
Boundary Conditions ◽  
Hepatic Artery ◽  
Transarterial Embolization ◽  
Arterial Blood Flow ◽  
Patient Specific ◽  
Computational Domain ◽  
Arterial Tree ◽  
Arterial Blood ◽  
Therapy Effect

Transarterial embolization is a minimally invasive treatment for advanced liver cancer using microspheres loaded with a chemotherapeutic drug or radioactive yttrium-90 (90Y) that are injected into the hepatic arterial tree through a catheter. For personalized treatment, the microsphere distribution in the liver should be optimized through the injection volume and location. Computational fluid dynamics (CFD) simulations of the blood flow in the hepatic artery can help estimate this distribution if carefully parameterized. An important aspect is the choice of the boundary conditions imposed at the inlet and outlets of the computational domain. In this study, the effect of boundary conditions on the hepatic arterial tree hemodynamics was investigated. The outlet boundary conditions were modeled with three-element Windkessel circuits, representative of the downstream vasculature resistance. Results demonstrated that the downstream vasculature resistance affected the hepatic artery hemodynamics such as the velocity field, the pressure field and the blood flow streamline trajectories. Moreover, the number of microspheres received by the tumor significantly changed (more than 10% of the total injected microspheres) with downstream resistance variations. These findings suggest that patient-specific boundary conditions should be used in order to achieve a more accurate drug distribution estimation with CFD in transarterial embolization treatment planning.

Spiral Laminar Flow in Vivo

1996 ◽  
Vol 91 (1) ◽  
pp. 17-21 ◽  
Author(s):  
P. A. Stonebridge ◽  
P. R. Hoskins ◽  
P.L. Allan ◽  
J. F. F. Belch
Keyword(s):  
Blood Flow ◽  
Reverse Flow ◽  
Arterial Disease ◽  
Flow Patterns ◽  
Endothelial Damage ◽  
Arterial Blood Flow ◽  
Arterial Tree ◽  
Arterial Blood ◽  
Blood Flow Patterns

1. Blood flow patterns are poorly understood despite their impact on arterial disease. There have been few measurements in vivo of the three-dimensional blood flow patterns; we present the results of such studies using a new non-invasive in-vivo method of examining biplanar arterial blood flow patterns. 2. Multiple colour Doppler ultrasound directional velocity images were obtained at two different beam target angles from the artery in the plane perpendicular to its axis. Ensemble average images were constructed; the absolute velocity and direction were calculated by compounding the left and right averaged images. Simple directional, non-directional velocity and vector maps were constructed. 3. Flow patterns were sampled in 11 healthy male volunteers at four points of the pulse cycle; peak systole, systolic downswing, diastolic reverse flow and diastolic forward flow and at three sites; the right common and distal superficial femoral and the left common femoral arteries. 4. Stable rotational flow was observed in all subjects, the direction of rotation varying between sides and individuals. 5. There are theoretical advantages to spiral laminar blood flow; the forward-directed, rotationally induced stability and reduction of laterally directed forces may reduce turbulence in the tapering branching arterial tree and at stenoses and have a beneficial effect on mechanisms of endothelial damage and repair.

A New Hexahedral Mesher for a Numerically Efficient Patient Specific Analysis of Arterial Blood Flow and Wall Shear Stress

2010 ◽  
Author(s):  
G. De Santis ◽  
P. Mortier ◽  
M. De Beule ◽  
P. Segers ◽  
P. Verdonck ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Imaging Techniques ◽  
Arterial Blood Flow ◽  
Patient Specific ◽  
Arterial Tree ◽  
Arterial Blood ◽  
Current Measuring ◽  
Wall Shear

Atherosclerosis depends on systemic risk factors but manifests itself as geometrically focal plaques, which appear in regions of the arterial tree experiencing low and/or oscillating Wall Shear Stress (WSS) such as outer edges of vessels bifurcations and highly curved vessels. Because direct measurements of WSS (differential quantity) in vivo are difficult due to limited spatial resolution offered by current measuring technologies (ultrasound, phase contrast MRI), an indirect approach is often taken, integrating medical imaging techniques (biplane angiography, CT, MRI) with Computational Fluid Dynamics (CFD) for patient specific WSS profiling.

scholarly journals Optimization of topological complexity for one-dimensional arterial blood flow models

2018 ◽  
Vol 15 (149) ◽  
pp. 20180546 ◽  
Author(s):  
Fredrik E. Fossan ◽  
Jorge Mariscal-Harana ◽  
Jordi Alastruey ◽  
Leif R. Hellevik
Keyword(s):  
Blood Flow ◽  
Pulse Pressure ◽  
Arterial System ◽  
Arterial Blood Flow ◽  
Patient Specific ◽  
Flow Measurements ◽  
One Dimensional ◽  
Flow Models ◽  
Arterial Blood ◽  
Blood Flow Models

As computational models of the cardiovascular system are applied in modern personalized medicine, maximizing certainty of model input becomes crucial. A model with a high number of arterial segments results in a more realistic description of the system, but also requires a high number of parameters with associated uncertainties. In this paper, we present a method to optimize/reduce the number of arterial segments included in one-dimensional blood flow models, while preserving key features of flow and pressure waveforms. We quantify the preservation of key flow features for the optimal network with respect to the baseline networks (a 96-artery and a patient-specific coronary network) by various metrics and quantities like average relative error, pulse pressure and augmentation pressure. Furthermore, various physiological and pathological states are considered. For the aortic root and larger systemic artery pressure waveforms a network with minimal description of lower and upper limb arteries and no cerebral arteries, sufficiently captures important features such as pressure augmentation and pulse pressure. Discrepancies in carotid and middle cerebral artery flow waveforms that are introduced by describing the arterial system in a minimalistic manner are small compared with errors related to uncertainties in blood flow measurements obtained by ultrasound.

Participation of adrenoceptors in liver blood flow regulation in anesthetized dogs

1987 ◽  
Vol 253 (5) ◽  
pp. H1053-H1058
Author(s):  
N. Terada ◽  
S. Koyama ◽  
J. Horiuchi ◽  
T. Takeuchi
Keyword(s):  
Blood Flow ◽  
Portal Vein ◽  
Hepatic Artery ◽  
Vascular Resistance ◽  
Adrenergic Receptors ◽  
Liver Blood Flow ◽  
Arterial Blood Flow ◽  
Tissue Blood Flow ◽  
Intact Group ◽  
Arterial Blood

We evaluated involvement of adrenergic receptors in the responses of the hepatic vasculature to reduction either of portal venous flow or hepatic arterial inflow. Portal vein occlusion caused an increase in hepatic arterial blood flow (HAF) and decreases in hepatic arterial pressure (HAP) and hepatic arterial vascular resistance (HAR) in the intact group. After pretreatment with either yohimbine or prazosin, but not propranolol, occlusion of the portal vein produced a greater decrease in HAP as compared with that in the intact group. No significant changes in HAF, HAR, or hepatic tissue blood flow (HTF) occurred after the treatment. These results indicate that the compensatory response of the hepatic arterial vasculature to altered portal blood flow (PVF) is regulated independently of the intrahepatic adrenergic receptors. Hepatic arterial occlusion caused a significant decrease in portal venous pressure, PVF, and HTF. Portal venous vascular resistance (PVR) was reduced slightly, but not significantly. After pretreatment with either yohimbine or prazosin, but not propranolol, occlusion of the hepatic artery produced an opposite effect: to increase PVF and significantly decrease PVR. These results indicate that intrahepatic alpha-adrenoceptors participate in the regulation of portal vascular tone to maintain portal vein pressure at a steady level, when inflow from the hepatic artery is reduced.

scholarly journals Modelling Blood Pressure in Stenosed Coronary Arteries

2017 ◽  
Vol 61 (3) ◽  
pp. 242
Author(s):  
Viktor Szabó ◽  
Csaba Jenei ◽  
Gábor Halász
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Coronary Arteries ◽  
Flow Model ◽  
Measurement Data ◽  
Arterial Blood Flow ◽  
Patient Specific ◽  
Arterial Blood ◽  
1D Model ◽  
Good Agreement

In this paper a 1D model is presented for the simulation of blood flow in stenosed coronary arteries. The model was developed by implementing a special boundary counditions in a previously published arterial blood flow model. The stenosis as well as the arterioles were modelled as linear resistances. Using patient-specific parameters, blood flow can be calculated for different inlet flow rates. The model was used to simulate blood pressure waveforms of 5 patients diagnosed with coronary stenosis. Simulation results show good agreement with measurement data.

On the Use of In Vivo Measured Flow Rates as Boundary Conditions for Image-Based Hemodynamic Models of the Human Aorta

2011 ◽  
Author(s):  
Diego Gallo ◽  
Gianluca De Santis ◽  
Federica Negri ◽  
Daniele Tresoldi ◽  
Giovanna Rizzo ◽  
...  
Keyword(s):  
Blood Flow ◽  
Boundary Conditions ◽  
Rigid Wall ◽  
Patient Specific ◽  
Human Aorta ◽  
Computational Domain ◽  
Healthy Human ◽  
Flow Rates ◽  
Measured Flow

It has been demonstrated that computational fluid dynamics (CFD) have the potential to enhance the comprehension of the role played by hemodynamic factors involved in atherosclerosis. Recently, phase-contrast magnetic resonance imaging (PC-MRI) has emerged as an effective tool for providing accurate vascular geometries for CFD simulations and quantitative data on blood flow rates, which can be used to specify realistic boundary conditions (BCs). However, the application of acquired flow waveforms at boundaries is not straightforward, mainly (i) due to possible occurrences of phase shifts and attenuations of outflow with respect to inflow rate and (ii) due to the instantaneous mass conservation constraint, which is required in hemodynamic simulations with rigid wall models, but is not guaranteed in in vivo measurements. As an alternative, new boundary conditions schemes have been developed in an effort to consider the interaction between the computational domain and the upstream/downstream vasculature by coupling through-scale hemodynamic models [1]. However, the identification of the parameters of these simplified vascular models on a subject-specific base involves both pressure and flow rates measurements [2]. In this context, it is clear that the direct application of individual PC-MRI measured flow rates waveforms as BCs in patient-specific simulations should be preferred [3]. In order to overcome the limitations mentioned above, measured flow rates should be combined with stress-free conditions or fixed mass flow ratio (derived from the same set of PC-MRI data) between inlet and multiple outlet sections. However, prescribing different BCs at boundaries can affect the solutions of the equations governing blood flow [1]. For this reason, different strategies in combining outlet BCs could lead to different simulated hemodynamics. This work analyzes the influence of different possible strategies of applying PC-MRI measured flow rates on an image-based hemodynamic model of a healthy human aortic arch with supra-aortic vessels. A total of six flow simulations was carried out applying six different schemes for treating BCs at outlets. Three common wall shear stress (WSS)-based indicators of abnormal flow were considered and the sensitivity of these indicators to the outlet treatment strategy was evaluated.

H2S contributes to the hepatic arterial buffer response and mediates vasorelaxation of the hepatic artery via activation of KATP channels

2008 ◽  
Vol 295 (6) ◽  
pp. G1266-G1273 ◽  
Author(s):  
Nikolai Siebert ◽  
Daniel Cantré ◽  
Christian Eipel ◽  
Brigitte Vollmar
Keyword(s):  
Blood Flow ◽  
Portal Vein ◽  
Hepatic Artery ◽  
Buffer Capacity ◽  
Venous Blood ◽  
Control Level ◽  
Vena Cava ◽  
Arterial Blood Flow ◽  
Venous Blood Flow ◽  
Arterial Blood

Hepatic blood supply is uniquely regulated by the hepatic arterial buffer response (HABR), counteracting alterations of portal venous blood flow by flow changes of the hepatic artery. Hydrogen sulfide (H2S) has been recognized as a novel signaling molecule with vasoactive properties. However, the contribution of H2S in mediating the HABR is not yet studied. In pentobarbital-anesthetized and laparotomized rats, flow probes around the portal vein and hepatic artery allowed for assessment of the portal venous (PVBF) and hepatic arterial blood flow (HABF) under baseline conditions and stepwise reduction of PVBF for induction of HABR. Animals received either the H2S donor Na2S, DL-propargylglycine as inhibitor of the H2S synthesizing enzyme cystathionine-γ-lyase (CSE), or saline alone. Additionally, animals were treated with Na2S and the ATP-sensitive potassium channel (KATP) inhibitor glibenclamide or with glibenclamide alone. Na2S markedly increased the buffer capacity to 27.4 ± 3.0% ( P < 0.05 vs. controls: 15.5 ± 1.7%), whereas blockade of H2S formation by DL-propargylglycine significantly reduced the buffer capacity (8.5 ± 1.4%). Glibenclamide completely reversed the H2S-induced increase of buffer capacity to the control level. By means of RT-PCR, Western blot analysis, and immunohistochemistry, we observed the expression of both H2S synthesizing enzymes (CSE and cystathionine-β-synthase) in aorta, vena cava, hepatic artery, and portal vein, as well as in hepatic parenchymal tissue. Terminal branches of the hepatic afferent vessels expressed only CSE. We show for the first time that CSE-derived H2S contributes to HABR and partly mediates vasorelaxation of the hepatic artery via activation of KATP channels.

New method of hepatic artery reconstruction after its injury or resection.

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. e16221-e16221
Author(s):  
Oksana V. Katelnitskaya ◽  
Oleg I. Kit ◽  
Yuriy A. Gevorkyan ◽  
Aleksandr V. Snezhko ◽  
Oleg Yu. Kaymakchi ◽  
...  
Keyword(s):  
Blood Flow ◽  
Hepatic Artery ◽  
Left Gastric Artery ◽  
Common Hepatic Artery ◽  
Arterial Blood Flow ◽  
Gastric Artery ◽  
Arterial Blood ◽  
Iatrogenic Damage ◽  
The Common ◽  
Reduced Time

e16221 Background: Restoration the hepatic arterial blood flow is required in traumatic or iatrogenic damage to the hepatic artery and its branches, as well as in the planned resection of the hepatic artery with subsequent reconstruction. Various ways have been proposed to solve this problem: ligation of the hepatic artery and its branches, which is associated with an extremely high mortality rate, reaching 70%, and the need for extensive liver resections; portal vein arteriolization; transposition of the splenic artery with its severe complications (heart attack, abscess) or hepatic artery replacement sometimes are not available and imply aggressive anticoagulant therapy, which is often challenging after extensive oncological interventions. Prosthetic vascular grafts are associated with a high risk of infection. We propose replacement of the common hepatic artery defect by transposition of the left gastric artery and end-to-end anastomosis between the proximal end of the left gastric artery and the distal end of the hepatic artery. Methods: The proposed method was applied in 7 cancer patients - 4 cases of iatrogenic damage to the common hepatic artery in lymph node dissection of the hepatoduodenal ligament and 3 resection of the common hepatic artery with tumor infiltration. The mean age of patients was 53 years. 2 patients had surgery for gastric cancer, 5 - pancreatic cancer. Results: The vascular reconstruction lasted for 17 minutes. No thrombotic complications of the reconstruction area or liver necrosis in the postoperative period were registered. The main advantages of this method were the absence of synthetic materials or deficit blood supply to neighboring organs, and no need for extensive mobilization of the great vessels in other areas (renal artery, abdominal aorta). Conclusions: The proposed method for reconstruction of the hepatic artery allows performing a simple and adequate restoration of the hepatic arterial blood flow, reduced time of the vascular stage of the surgery and reduced incidence of postoperative complications associated with the vascular stage - reduced time of liver ischemia and reduced risk of thrombosis in the reconstruction area.

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