NAMIC AHM, Jan 2008 Registration Helper Classes Stephen Aylward Matt Turek Luis Ibanez

NAMIC AHM, Jan 2008 Goals 1.Increase the speed of image registration in ITK 2.Provide Slicer modules for image registration 3.Provide Slicer modules for batch image registration 4.Reduce the effort and expertise required for ITK image registration

NAMIC AHM, Jan 2008 Outline ITK Image Registration Helper class Features Slicer Modules Status and Future Work

NAMIC AHM, Jan 2008 Image Registration Helper Class Multi-threaded Implicitly handles oriented images Options (via enumerations): –Transforms VersorRigid3D, Affine, BSplines –Metrics MattesMI, NormalizedCorrelation, MeanSquaredError –Interpolators Linear, BSpline, Windowed Sinc –Optimizers Gradient –FRPR for Rigid/Affine and LBFSGB for BSpline Multi-resolution –3-levels, Gradient at each level Evolutionary –OnePlusOne followed-by Gradient –Initialization Centers of Images, Centers of Mass, Second Moments

NAMIC AHM, Jan 2008 Image Registration Helper Class Examples of member functions –LoadParameters( std::string filename ) “T1-T2-BrainRegistration.prm”, “CT-CT-LiverRegistration.prm”, “MyProjectsRegistration.prm” Simplifies batch processing –SetExpectedOffsetMagnitude( double expectedOffset ) Used to calculate scales for rigid/affine optimization –SetBSplineControlPointPixelSpacing( double controlPointSpacing ) Used to calculate number of control points for BSplines –Update( void ) Load transform and resample moving image Initial registration Rigid registration Affine registration BSpline registration

NAMIC AHM, Jan 2008 Image Registration Helper Class Default behavior of Update() –Initial Centers of mass –Rigid Versor3D + MattesMI + LinearInterpolation + SamplingRatio= EvolutionaryOptimization + MaxIterations=100 + … –Affine Affine + MattesMI + LinearInterpolation + SamplingRatio= Gradient + MaxIterations=100 + … –BSpline BSpline + MattesMI + BSplineInterpolation + SamplingRatio=0.2 + Gradient + MaxIterations=50 + ControlPointPixelSpacing=20

NAMIC AHM, Jan 2008 Usage #include “itkImageToImageRegistrationHelper.h” Int main(int argc, char *argv[]) { typedef itk::OrientedImage ImageType typedef itk::ImageToImageRegistrationHelper RegType; RegType::Pointer reg = RegType::New(); reg->LoadFixedImage( argv[1] ); reg->LoadMovingImage( argv[2] ); reg->LoadParameters( argv[3] ); reg->SetRigidOptimizationMethodEnum( RegType::MULTIRESOLUTION_OPTIMIZATION ); reg->Update(); reg->SaveImage( argv[4], reg->GetFinalMovingImage() ); }

NAMIC AHM, Jan 2008 Internal Class Hierarchy itkImageToImageRegistrationMethod itkInitialImageToImage RegistrationMethod itkOptimizedImageToImage RegistrationMethod itkRigidImageToImage RegistrationMethod itkAffineImageToImage RegistrationMethod itkBSplineImageToImage RegistrationMethod = Derives from itkProcessObject

NAMIC AHM, Jan 2008 Multi-threaded

NAMIC AHM, Jan 2008 New Slicer Modules Status: –Requires CVS ITK –CMake enable: ITK_USE_REVIEW ITK_USE_OPTIMIZED_REGISTRATION_METHODS –Bug in Optimized Linear Interpolation –Parameter tweaking –Testing modules: oriented images, etc. RegisterImages BatchRegisterImages

NAMIC AHM, Jan 2008

NAMIC DTI Atlas Registration Atlas = FixedImage = Red Channel = ICBM DTI Atlas: ICBM_T2.nhdr Subject = MovingImage = Green Channel = t2w.nrrd

NAMIC AHM, Jan 2008 More Information IJ article on multi-threaded registration Article on modifications to ITK pending –Matt Turek et al. Thanks Matt Turek and Luis Ibanez!!!

NAMIC AHM, Jan 2008 Future Work Fix linear interpolation Testing and tweaking –Oriented images Manage memory requirements –itkOptimization.h: typedef Array ParametersType; Speed –BSplines: Only process control points that contain samples