MODEL STUDIES OF BLOOD FLOW IN BASILAR ARTERY WITH 3D LASER DOPPLER ANEMOMETER

MODEL STUDIES OF BLOOD FLOW IN BASILAR ARTERY WITH 3D LASER DOPPLER ANEMOMETER

Biomedical Engineering

Sergey Frolov, Tambov State Technical University, RussiaSergey Sindeev, Tambov State Technical University, Russia

Dieter Liepsch, Munich University of Applied Sciences, GermanyAndrea Balasso, Technical University of Munich, Germany

Sergey Proskurin, Tambov State Technical University, RussiaAnton Potlov, Tambov State Technical University, Russia

Актуальность

Brain aneurysm suffers 3-5 % of adult population

Topicality

More then 60 % die from ruptured aneurysm (stroke)


Aneurysm

Кафедра «Биомедицинская техника»

Protrusion of the arterial wall due to its stretching or thinning


Current stateCauses of aneurysm development and growth are not fully studied

Researchers suggest that key role in aneurysm development play violation of local and global hemodynamics


Flow-diverters

Problem of choice


Morphology

«classic»≈ 35-40 % cases

deviations


Multiscale model of basilar artery hemodynamics

)(),( tPtu ),(),,( txPtxu ),,,(

),,,,(

tzyxP

tzyxu




Compartments of cardiovascular systemCardiovascular system is a set of compartments (elastic chambers)

Every chamber is characterized by blood volume in it and pressure

Link between chambers is characterized by blood flow


0D model• 14 chamber model• Pulsating heart• Heart as a source of

pressure• Valves with backflow• Flow inertia


System of global hemodynamics simulation (bmt.tstu.ru/cvs)


Link «Left ventricle – aorta»




1D model№ Artery № Artery

1 Ascending aorta 25 Left carotid2 Aortic arch 1 26 Right carotid3 Aortic arch 2 27 Left external carotid4 Thoracic aorta 1 28 Right external carotid5 Thoracic aorta 2 29 Right vertebral6 Abdominal aorta A 30 Left vertebral7 Intercostals 31 Right internal carotid 18 Coelic 32 Left internal carotid9 Gastric 33 Basilar10 Splenic 34 Right posterior cerebral artery111 Hepatic 35 Left posterior cerebral artery 112 Left subclavian 1 36 Right posterior cerebral artery 213 Left subclavian 2 37 Right posterior communicating artery14 Left radius 1 38 Right internal carotid 215 Left ulnar 1 39 Right middle cerebral artery16 Left ulnar 2 40 Right anterior cerebral artery 117 Left interosseous 41 Right anterior cerebral artery 218 Brachiocephalicus 42 Anterior communicating artery19 Right subclavian 1 43 Right brachial20 Right subclavian 2 44 Left anterior cerebral artery 121 Right radius 45 Left middle cerebral artery22 Right ulnar 1 46 Left internal carotid 223 Right interosseous 47 Left posterior communicating artery24 Right ulnar 2 48 Left posterior cerebral artery 2


ApproachArterial tree is a set of elementary regions

Number of elementary regions may be N>48

Number of equations is 3*N


Festdaten

12

i-2 i-1

i

i+1 i+2

)(2 tqi

)(tqi

)(3 tqi )(2 tqi)(1 tqi

)(1 tqi

i – elementary region;

ie

i

i

i

U

R

L

Elasticity;

Inertia;

Resistance;

Unstrained volume;

Stiffness [mmHg/ sm3 ]; ii eС /1

[mmHg*s2 / sm2];

[Тоrr *s / sm2];

[sm3];

iiii URLe ,,,

i

i

iii

S

l

SlL

;/

Conductivity;

Length;

Cross sectional area

);(tVi

)(tPi)(tVi

)(tPi

)(tqiVolume; [sm3 ]; Pressure; [mmHg]; Blood flow; [sm3 /s];

Parameters

Functions

ie ii eС /1

Approach




3D modelNavier-Stokes

equations

Continuity equation

Boundary conditions

Initial conditions


Parallel computing

8 parts

Domain Decomposition

Computational mesh spits on N parts.Every part is computed by it’s own thread

Technology: MPI + OpenMPProgramming language: С++Libraries: Intel MKL, Trilinos, LifeVSolver: GMRESPreconditioner: Domain DecompositionTimestep: 0.0001 s.Precision: 1e-10

Problem of choice of number N*, that T min


3D model of bifurcations

Geometrical model

Pressure Velocity fieldVelocity profile Velocity


Experimental setup3D Laser Doppler Anemometer measure blood velocity in elastic vessel model. It gives opportunity to estimate stent influence on blood flow


Principle of LDA


Signalconditioner

Flow

Signal Processing unit:

Laser HeNe Photomultiplier

PC

Measurements


The flow velocity is measured with a 1-component laser Doppler anemometer system equipped with a 5mW He-Ne laser with a wavelength of 632.8nm. The laser Doppler anemometer does not disturb the flow and is not affected by temperature, pressure or fluid density. It offers a high spatial (focus point less than 70 µm) and temporal (1ms) resolution. Velocity measurements are performed in the model at different cross sections allowing a 2D or a 3D-flow-reconstruction.

Measurements


Blood cannot be used as a fluid for LDA measurements, because the laser light is absorbed by the red cells. The model fluid have a similar flow behavior as blood, a refraction index of n =1.41 to match the refraction index of the silicon rubber model wall. The fluid and the model wall have to be transparent so that the laser beam can pass undisturbed the medium.

A 58% aqueous glycerol mixture with Separan AP45 and Separan AP302 (a macromolecular polyacrylamide) with a dynamic viscosity of 8mPas is used. The mixture shows viscoelastic flow behavior similar to the non-Newtonian characteristics of blood.

Realistic vessel model


Scheme of experimental setupAn overflow chamber (3) filled with the perfusion mixture gives the constant inflow pressure to the model (10). A computer-controlled piston pump (1) superimposes a dynamic pressure gradient needed to obtain systolic and diastolic pressures in the inflow section of 80 mmHg and 145 mmHg respectively. Pressure transducers (9) monitor the amplitude and frequency of the pulse wave. The outflow of the model is connected to a reservoir of variable height (11) to allow control of the flow volume.


Thanks for attention


Documents

MODEL STUDIES OF BLOOD FLOW IN BASILAR ARTERY WITH 3D LASER DOPPLER ANEMOMETER