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Prostate RegistrationUseful Concepts and toolsC. Antonio SnchezDept of Elec & Comp EngUniversity of British ColumbiaVancouver, BC, Canadaantonios@ece.ubc.ca
Siavash KhallaghiDept of Elec & Comp EngUniversity of British ColumbiaVancouver, BC, Canadasiavashk@ece.ubc.caMy name is Antonio, Im a PhD student at UBC, I work in the area of volumetric muscle modelling
Today I am presenting our Finite Element Muscle Modelling Cookbook; how we assemble these models of muscles from various data sources.1Prostate Biopsy
Prostate BiopsyQ: Can we determine where the biopsy came from?Target suspicious regionsGuarantee adequate coverageWe may want to Relies on doctor intuitionTake a large number of samples to increase likelihood of adequate coverage Patients often asked to undergo repeat biopsies if high levels of Prostate-specific antigen (PSA)Current practice:Prostate MRI
Prostate Ultrasound
Ultrasound Sweep
3D MR-TRUS Registration
MRIUS
Point-Set RegistrationSet up an error (objective) functionMinimize w.r.t. transform parametersDifferentiate, set derivatives to zero, solve
Affine transform + translationx1y1x2y2
Point-Set RegistrationSet up an error (objective) functionMinimize w.r.t. transform parametersDifferentiate, set derivatives to zero, solve
x1y1x2y2Point-Set RegistrationCorrespondences unknown? Missing data?
Point-Set RegistrationGaussian Mixture ModelTreat complete set as a probability density of GaussiansMaximize likelihood of observation
Probability yj belongs to Gaussian xi(adds fuzziness)In practice: iterate between computing probabilities / updating transformPoint-Set RegistrationGaussian Mixture ModelTreat complete set as a probability density of GaussiansMaximize likelihood of observationIn practice: iterate between computing probabilities / updating transformPoint-Set Registration
Transformations
RIGID:AFFINE:INTERPOLATION:
Finite Element Method BasicsDivide volume into building blocks ('elements')Define interpolation functions inside elements ('shape functions')n1n2n3xInterpolation matrix
Finite Element Method BasicsDivide volume into building blocks ('elements')Define interpolation functions inside elements ('shape functions')Assign material propertiesn1n2n3x
strain energy:
3D Surface-Based Reg.3D FEM representation from MRIGaussian Mixture Model for prostate surfacePartial segmentation from US
FEM-transformed Gauss centreslimits deformationadds 'fuzziness'yjxi3D Surface-Based Reg.
MRIUSMRIRegisteredLocating a 2D Slice
Intensity-Based Reg.
3D volume imagemaps 2D3D2D slice image
Trajectory-Based Constraint
Probe is tracked!!Tracking alone not sufficientTrajectory-Based ConstraintProbe is tracked!!Tracking alone not sufficient
Trajectory-Based ConstraintProbe is tracked!!Tracking alone not sufficientTrajectory traces rectal wallNew image lies on rectal wallTrajectory-Based ConstraintProbe is tracked!!Tracking alone not sufficientTrajectory traces rectal wallNew image lies on rectal wallTrajectory-Based ConstraintProbe is tracked!!Tracking alone not sufficientTrajectory traces rectal wallNew image lies on rectal walls = 0s = 1
slides along trajectory, rotate x3FEM-Based DeformationStill need to account for:Non-rigid deformationOff-trajectory translation
maps 2D slice to 3D volumelimits deformationloops over all 2D slice pixelsLocating a 2D slice
TargetProjectionTrajectoryFEM
Summary3D MRI 3D TRUSs = 0s = 12D TRUS 3D TRUS
USFIN
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