PowerPoint Presentation
Prostate RegistrationUseful Concepts and toolsC. Antonio
SnchezDept of Elec & Comp EngUniversity of British
ColumbiaVancouver, BC, [email protected]
Siavash KhallaghiDept of Elec & Comp EngUniversity of
British ColumbiaVancouver, BC, [email protected] 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
