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A Sketch-based Interface for Modeling Myocardial Fiber OrientationKenshi Takayama1 Takeo Igarashi1,2Ryo Haraguchi3 Kazuo Nakazawa3

1The University of Tokyo2JST SORST3National Cardiovascular Center Research Institute7th Symposium onSmart GraphicsSG 2007IntroductionBackgroundRelated workBasic ideaUser InterfaceAlgorithmUser ExperienceConclusionSG 200750,000 die from cardiac sudden deathAbnormal heart rhythm is its major causeIts mechanism is not clearBackground

SG 20073heart diseaseJapan, 2005second biggest cause of death90 thousand peoplesudden deathdie unexpectedly

mechanismvery unclear

2980~90%

Simulation approachElucidationPredictionEducationMathematical model

SG 20074300x300x3003 stages of processModeling

SimulationEvaluation

BottleneckSG 2007Various parameters

GeometryPurkinje fiber networkMyocardial fiber orientationOur targetSG 20076ShapePurkinje fiberMyocardial fiber orientation(APD)

Previous methodTake 2D slices from xyz directionSpecify vectors one-by-oneVery tediousSG 2007Vector field design on surfaces

Related work

[Praun et al,00][Turk,01][Zhang et al,06][Fisher et al,07]SG 20078vector field on surfaces is strongly related to texture synthesis on sufacesOur contributionPrevious work :Only vector field on surface

Ours :Design of volumetric vector fieldSG 2007Basic ideaObservationMyocardial fibers are parallel to the surface of the heart

Two-step algorithmStep 1:Construct tangent vector fieldStep 2:Construct volumetric vector fieldSG 200710Myocardial fiber orientation is represented by 3D directional unit vector.Simple sketching on the surface creates volumetric vector fields.IntroductionUser InterfaceStroke on the surfaceStroke crossing the modelStroke on the cross-sectionAlgorithmUser ExperienceConclusionSG 2007Stroke on the surfaceSpecify fiber orientations on the surface

SG 200712The user can draw as many strokes as he/she want.Stroke crossing the modelCuttingCreate cross-sectional surface

SG 2007Stroke on the cross-sectionSpecify fiber orientations inside the model

SG 2007DemoSG 2007IntroductionUser InterfaceAlgorithmTangent vector fieldVolumetric vector fieldLaplacian interpolationUser ExperienceConclusionSG 2007Tangent vector fieldSketchTangent vector fieldLaplacianinterpolationSG 200717On the mesh verticesVolumetric vector field Sketch Tangent vector fieldVolumetric vector fieldLaplacianinterpolationSG 200718On the voxelsLaplacian interpolationMinimize Laplacian

Satisfy constraint

xiLaplacianneighborneighborSG 2007Laplacian interpolationMatrix form

CLSG 2007Laplacian interpolationMatrix form

Least-square solution

SG 2007Laplacian interpolationSparse linear systemPrecomputable

SG 2007IntroductionUser InterfaceAlgorithmUser ExperiencePreliminary testInterviewConclusionSG 2007Preliminary testAsked a physician* to try our systemSample model by himIn about 8 minutesSample simulation result* T. Ashihara, MD, PhD, Shiga University of Medical Science

SG 2007InterviewPositive commentsWe need this tool!Interface is intuitive and quick.This can be a breakthrough.

SG 200725matches to the images of heart that physicians havebetter than working on each 2D slice

direct influence of myocardial fiber orientationcompare

important contribution to medial area

InterviewPoints to be improvedUse of MRI may be needed.

Cross-sectioning is not suitable for visualizing fiber orientation.

SG 200726In real heart, fibers areNot always continuoussometimes change suddenly

images of heart are mapped onto the model

IntroductionUser InterfaceAlgorithmUser ExperienceConclusionSG 2007ConclusionNovel method for modeling myocardial fiber orientation

2-step scheme (our contribution)Surface Volume

Preliminary user studywith a physicianSG 200728Come back to motivationFuture workTest other interpolation algorithmsMore formal user testUse of MRIPeeling UI

Other applicationsFibers in woodParticle animationThank you.

[Owada et al,04]SG 2007