scholarly journals Effective Computational Framework for Pre-Interventional Planning of Peripheral Arteriovenous Malformations with In Vivo and In Vitro Validation

2021 ◽  
Author(s):  
Gaia Franzetti ◽  
Mirko Bonfanti ◽  
Cyrus Tanade ◽  
Chung Sim Lim ◽  
Janice Tsui ◽  
...  
Keyword(s):  
Blood Flow ◽  
Computational Model ◽  
Arteriovenous Malformations ◽  
Clinical Decision Making ◽  
Patient Specific ◽  
Post Intervention ◽  
Computational Framework ◽  
Mock Circulatory System ◽  
Flow Through

Purpose: Peripheral arteriovenous malformations (pAVMs) are congenital lesions characterised by abnormal high-flow, low-resistance vascular connections - constituting the so-called nidus - between arteries and veins. The mainstay treatment typically involves the embolisation of the nidus with embolic and sclerosant agents, however the complexity of AVMs often leads to uncertain outcomes. This study aims at developing a simple, yet effective computational framework to aid the clinical decision making around the treatment of pAVMs. Methods: A computational model was developed to simulate the pre-, intra-, and post-intervention haemodynamics of an AVM. A porous medium of varying permeability was used to simulate the effect that the sclerosant has on the blood flow through the nidus. The computational model was informed by computed tomography (CT) scans and digital subtraction angiography (DSA) images, and the results were compared against clinical data and experimental results. Results: The computational model was able to simulate the blood flow through the AVM throughout the intervention and predict (direct and indirect) haemodynamic changes due to the embolisation. The simulated transport of the dye in the AVM was compared against DSA time-series obtained at different intervention stages, providing confidence in the results. Moreover, experimental data obtained via a mock circulatory system involving a patient specific 3D printed phantom of the same AVM provided further validation of the simulation results. Conclusion: We developed a simple computational framework to simulate AVM haemodynamics and predict the effects of the embolisation procedure. The developed model lays the foundation of a new, computationally driven treatment planning tool for AVM embolisation procedures.

scholarly journals A Computational Framework for Pre-Interventional Planning of Peripheral Arteriovenous Malformations

2021 ◽  
Author(s):  
Gaia Franzetti ◽  
Mirko Bonfanti ◽  
Cyrus Tanade ◽  
Chung Sim Lim ◽  
Janice Tsui ◽  
...  
Keyword(s):  
Porous Medium ◽  
Computational Model ◽  
Clinical Data ◽  
Flow Rate ◽  
Arteriovenous Malformations ◽  
Patient Specific ◽  
Post Intervention ◽  
Computational Framework ◽  
Inlet Flow ◽  
Numerical Predictions

Abstract Purpose Peripheral arteriovenous malformations (pAVMs) are congenital lesions characterised by abnormal high-flow, low-resistance vascular connections—the so-called nidus—between arteries and veins. The mainstay treatment typically involves the embolisation of the nidus, however the complexity of pAVMs often leads to uncertain outcomes. This study aims at developing a simple, yet effective computational framework to aid the clinical decision making around the treatment of pAVMs using routinely acquired clinical data. Methods A computational model was developed to simulate the pre-, intra-, and post-intervention haemodynamics of a patient-specific pAVM. A porous medium of varying permeability was employed to simulate the sclerosant effect on the nidus haemodynamics. Results were compared against clinical data (digital subtraction angiography, DSA, images) and experimental flow-visualization results in a 3D-printed phantom of the same pAVM. Results The computational model allowed the simulation of the pAVM haemodynamics and the sclerotherapy-induced changes at different interventional stages. The predicted inlet flow rates closely matched the DSA-derived data, although the post-intervention one was overestimated, probably due to vascular system adaptations not accounted for numerically. The nidus embolization was successfully captured by varying the nidus permeability and increasing its hydraulic resistance from 0.330 to 3970 mmHg s ml−1. The nidus flow rate decreased from 71% of the inlet flow rate pre-intervention to 1%: the flow completely bypassed the nidus post-intervention confirming the success of the procedure. Conclusion The study demonstrates that the haemodynamic effects of the embolisation procedure can be simulated from routinely acquired clinical data via a porous medium with varying permeability as evidenced by the good qualitative agreement between numerical predictions and both in vivo and in vitro data. It provides a fundamental building block towards a computational treatment-planning framework for AVM embolisation.

Quantification of in vitro and in vivo energy metabolism of the gastrointestinal tract of fed or fasted sheep

1993 ◽  
Vol 73 (4) ◽  
pp. 855-868 ◽  
Author(s):  
J. M. Kelly ◽  
B. G. Southorn ◽  
C. E. Kelly ◽  
L. P. Milligan ◽  
B. W. McBride
Keyword(s):  
Blood Flow ◽  
Gastrointestinal Tract ◽  
Portal Blood Flow ◽  
Whole Body ◽  
Hepatic Portal Vein ◽  
Flow Through ◽  
Hepatic Portal ◽  
Ouabain Inhibition

The effect of level of nutrition on in vitro and in vivo O2 consumption by the gastrointestinal tract in four nonlactating, nonpregnant ewes catheterized in the anterior mesenteric vein, hepatic portal vein and mesenteric artery with duodenal cannulae was investigated. Animals were fed a pelleted ration at maintenance (M) or twice maintenance (2M) or fasted (F) subsequent to the M measurement. Duodenal in vitro O2, ouabain-sensitive O2 (OSO2) and cycloheximide-sensitive O2 (CSO2) consumption was determined polarographically using a YSI O2 monitor; whole-gut O2 consumption was determined as (arterio-venous difference of O2 concentration) × (blood flow through the PV). Whole-body O2 consumption was determined using indirect calorimetry. Ewes fed 2M exhibited higher (P < 0.10) whole-body O2 consumption than either M or F ewes. Ewes fed M and 2M had higher (P < 0.10) duodenal in vitro O2 and ouabain-insensitive O2 (OIO2) consumption than F ewes. Hepatic portal blood flow was directly proportional to level of intake (P < 0.10): it was lowest for F ewes (81.0 L h−1), intermediate for M ewes (97.7 L h−1) and highest for 2M ewes (122.5 L h−1). Ouabain inhibition of O2 consumption by portal-drained viscera (PDV) was highest in M ewes and lowest in 2M ewes (P < 0.10). CSO2 consumption by the entire PDV was not affected by level of intake, corresponding to no change in OIO2 consumption by the PDV. As a proportion of whole-body O2 consumption, total O2, OSO2 and cycloheximide-insensitive O2 consumption by the PDV was higher in F ewes than in 2M ewes (P < 0.10). Fasted ewes expended a greater proportion of whole-body O2 consumption on gastrointestinal energetics than did 2M ewes. Key words: Sheep, gastrointestinal oxygen consumption, sodium–potassium ATPase, protein synthesis

NUMERICAL INVESTIGATION OF THE EFFECTS OF BED SHAPE ON THE END-TO-SIDE CABG HEMODYNAMICS

2019 ◽  
Vol 19 (04) ◽  
pp. 1950019
Author(s):  
MEHDI RAMEZANPOUR ◽  
MEHDI MAEREFAT ◽  
NAHID RAMEZANPOUR ◽  
MANIJHE MOKHTARI-DIZAJI ◽  
FARIDEH ROSHANALI ◽  
...  
Keyword(s):  
Artery Bypass ◽  
Stress Gradient ◽  
Patient Specific ◽  
Post Intervention ◽  
Simple Modification ◽  
Design Engineers ◽  
Structural Environment ◽  
Relative Residence Time ◽  
Clinical Experiments

Disrupted flow initiates and aggravates intimal thickening in the end-to-side (ETS) coronary artery bypass grafting (CABG), which may lead to failure. To enhance the post-intervention hemodynamics, the geometry is either optimized or totally reconfigured. Majority of configurations proposed by researchers have not suited CABG surgery, for they entailed rigorous manipulation on conventional grafts in situ, which was neither swift nor straightforward. The aim of the present study is, thus, to introduce a slight, yet effective, modification to a conventional ETS CABG configuration, and numerically investigate its effects on updated hemodynamic and structural environment, anticipating the longevity of proposed configuration and CABG success. This fairly simple modification may easily be made positioning a pre-designed anastomotic device between the bed of host artery in the conventional ETS CABG and its surrounding tissues. Conducting comprehensive numerical simulations, performance of the proposed configuration was assessed using idealized and patient-specific geometries of the conventional ETS CABG. Blood flow was simulated in a conventional and an updated CABG configuration considering 2-way fluid–structure interaction. Results revealed that, although the proposed configuration may induce higher structural stresses in vessels walls, it may improve important hemodynamic metrics such as wall shear stress gradient, oscillatory shear index, and relative residence time on host artery bed reducing disruption of flow. This study may also set the stage for design engineers and regulatory officials to evolve ETS CABG toward more hemodynamics-friendly approaches. Further in vitro, preclinical, and clinical experiments are, yet, entailed to accomplish ideal designs of procedural guidelines/grafts.

Application of a locally conservative Galerkin (LCG) method for modelling blood flow through a patient-specific carotid bifurcation

2010 ◽  
Vol 64 (10-12) ◽  
pp. 1274-1295 ◽  
Author(s):  
R. L. T. Bevan ◽  
P. Nithiarasu ◽  
R. Van Loon ◽  
I. Sazonov ◽  
H. Luckraz ◽  
...  
Keyword(s):  
Blood Flow ◽  
Carotid Bifurcation ◽  
Patient Specific ◽  
Flow Through ◽  
Locally Conservative

The Effect of Flow on Lysis of Plasma Clots in a Plasma Environment

2000 ◽  
Vol 83 (03) ◽  
pp. 469-474 ◽  
Author(s):  
Dingeman Rijken ◽  
Dmitry Sakharov
Keyword(s):  
Blood Flow ◽  
Shear Rate ◽  
High Concentration ◽  
Specific Lysis ◽  
Plasma Environment ◽  
Thrombolytic Agents ◽  
Flow Through ◽  
The Impact

SummaryFibrinolysis initially generates channels in an occluding thombus which results in blood flow through the thrombus. Since the impact of flow along the surface of a thrombus on thrombolysis has not been investigated in detail, we studied in vitro how such a flow affects lysis. Compacted and noncompacted plasma clots were used as model thrombi. With compacted clots, fibrin-specific lysis induced by alteplase in the outer plasma was accelerated about 2-fold by strong flow (arterial shear rate). Non-fibrin-specific lysis induced either by a high concentration of alteplase or by streptokinase was slow, was accompanied by rapid depletion of plasminogen in the outer plasma, and was only slightly accelerated by flow. With noncompacted clots, similar acceleration factors were documented, when mild flow (venous shear rate) was applied. Strong flow further accelerated fibrin-specific lysis, up to 10-fold as compared to lysis without flow, but paradoxically retarded non-fibrin-specific lysis. The data suggest that flow accelerates lysis by enhancing transport of plasminogen from the outer plasma to the surface of the clot. Both opposite effects of the strong flow were mediated by forceful intrusion of the outer plasma into the noncompacted clot due to flow irregularities. In the case of non-fibrin-specific lysis this resulted in the replacement of the plasminogen-containing milieu by plasminogen-depleted outer plasma in certain areas of the clot turning them into virtually unlysable fragments. This flow-enforced “plasminogen steal” may contribute to the relatively high percentage of incomplete thrombolysis (TIMI-2 grade flow) documented in a number of trials for non-fibrin-specific thrombolytic agents. In the case of fibrin-specific lysis, the effect of flow on the speed of fibrinolysis is always beneficial.

scholarly journals 517 In vitro study of blood flow through a modeled aortic valve and in a modeled Valsalva sinus

2005 ◽  
Vol 2004.17 (0) ◽  
pp. 209-210
Author(s):  
Shinichi IIDA ◽  
Kenkichi OHBA ◽  
Tsutomu TAJIKAWA ◽  
Masataka YOSHIDA ◽  
Fuyo TSUKIYAMA
Keyword(s):  
Blood Flow ◽  
Aortic Valve ◽  
In Vitro Study ◽  
Vitro Study ◽  
Flow Through
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