Patient-specific Cardiovascular Modeling System using Immersed Boundary TechniqueWee-Beng Taya, Yu-Heng Tsenga, Liang-Yu Linb, Wen-Yih TsengcaHigh Performance Computing & Environmental Fluid Dynamic Laboratory, Department of Atmospheric Sciences, National Taiwan University, Taipei, Taiwan (yhtseng@as.ntu.edu.tw)bNational Taiwan University Hospital, Taipei, TaiwancCenter for Optoelectronic Biomedicine, National Taiwan University College of Medicine, Taipei, Taiwan* Special thanks to Peskin and Mcqueen for providing the CFD code

**OutlinesIntroductionPatient-specific Cardiovascular Modeling System4-D MRI systemNumerical methods Results and discussions Conclusion and future work

**IntroductionDevelop a CFD based, patient-specific cardiovascular modeling systemFacilitate physicians diagnosis at early stage through hybrid CFD simulation and 4-D MRIUse Immersed boundary method (IBM) to simulate fluid-elastic interaction of heartInvestigate the vortex dynamic and effects of reservoir pressure boundary condition (RPBC) on the flows in Left Ventricle (LV)

**Patient-specific Cardiovascular Modeling SystemMethodology

**Patient-specific Cardiovascular Modeling System4-D phase contract magnetic resonance imaging (PC-MRI) system

Currently at the National Taiwan University HospitalImages acquired using an eight-channel phased-array body coilTime-resolved 3D hemodynamicvelocity fieldsAllows one to reconstruct the 3Dimages of the heart over a cardiac cycleData comprises of both healthyvolunteer as well as patients withcardiac problems for comparison

**Patient-specific Cardiovascular Modeling SystemImage resolution at 192x256x8Extracted slice at z=3, T*=0.2

1T=1 heart cycle

**Numerical Method IBMIncompressible Navier-Stokes equations (f represents force density)

Interaction between immersed boundary, fluid and boundary forces

(Lai and Peskin, 2000)

**Numerical Method - IBM

**Sensitivity of the pressure inflow conditionsReservoir pressure boundary condition (RPBC)5 sources of RPBC at (a) superior (b) inferior vena cava (c) pulmonary vein (d) artery (e) aorta

**Sensitivity of the pressure inflow conditionsInfluence of reservoir pressure boundary condition (RPBC)Investigate the effects/impacts of different pressure BC on the simulation resultsStudy vortex dynamics of left ventricle (LV)

**Sensitivity of the pressure inflow conditionsRPBC vs. T (Run 1 to 4)

**Sensitivity of the pressure inflow conditionsPV and Aorta RPBC vs. T (Run 1 to 4)

**Results and DiscussionsHigher pressure BC gives higher blood inflow at the PVFlow rates decrease and even reverse for all cases except Run 4 Decrease and reverse in flow rate for Run 1 to 3 despite mitral valve closureHemodynamic comparison for PV

**Results and DiscussionsMinimal difference in flow rate of aorta for different data sets during initial filling of blood in the LVWhen systole phase begins , there is a large outflow to deliver oxygenated blood to other parts of the bodyHemodynamic comparison for aorta

**Results and DiscussionsMagnitude of the PV flow rate from Run 1 is generally twice as high as that of Fortini et al Current outflow is about 5 times that of Fortini et al.Comparison with Fortini et al. results

**Results and Discussions2-D Vorticity visualization and verification (Run 1)

2-D vorticity plots obtained by extracting a slice of the Z vorticity at z=0.56. A pair of opposing signs vortices can be seen for all data setsSimilar experimental results from Fortini et al. and Gharib et al.

**Results and Discussions3-D Iso-surface vorticity magnitude visualization

T=0.06 Flow entering LV, vortex rings start to get connectedT=0.37 Reached a more mature stage, vortices stabilized, showing connected vortex ringsT=0.56 Only left a small region of weak vorticity

**Results and DiscussionsVortex formation time TvA good indicator of the cardiac health of the patient

EDV = LV end-diastolic volume (LV filling), = time-averaged mitral (annulus) valve diameter, EF = ejection fraction, ESV = LV volume at the end of systole (LV ejection), SV = the stroke volume, difference between ESV and EDV (Gharib et al., 2006)

**Results and DiscussionsVortex formation time TvExpected value of Tv for healthy volunteer is 3.3< Tv

**Results and DiscussionsKinetic Energy (KE) of 4-D PC-MRI system

1st peak of KE (initial diastole), higher2nd peak of KE (atrial contraction), lower

**Results and DiscussionsKinetic Energy (KE) of Run 1 (z=0.56 slice)

2nd lower peak of KE (atrial contraction)1st higher peak of KE (LV filling)

Maximum KE vs. T for Run 1 to 4

**Results and Discussions

**Results and DiscussionsSurface pressure analysis

Significant reduction in surface pressure after systoleHigh surface pressure during systole, especially in the front

**Results and DiscussionsSurface shear stress analysis

High shear stress, now near apex of the heartHigh shear stress during systole, near the aorta

**Conclusions and future work

Patient specific cardiovascular modeling system Simulation of heart using IBM4-D PC-MRI systemInvestigate the effect of RPBC on different variables such as KE, vorticity etcVerified with experimental results from MRI and other means through KE, vorticityVisualization of pressure and shear stress distribution on heart surfaceFurther investigation of the realistic reservoir pressure BC is requiredFuture work to include input of patient specific data in CFD code

**The End

*Add motivation, objectives and what we are going to implement**Add a figure or something (rather than text description)*Enlarge right*Make fonts larger*Enlarge pic*20+fonts

*Graph font larger*Fonts larger, pic size change*Shift pic, enlargeShift pic, enlargeShift pic, enlargeAdd the comparison with the 4-D MRI data (I have one figure).*Add the comparison with the 4-D MRI data (I have one figure).*Enlarge font tableSame vortex observation, vortex formation time*