itkMIRegistrationFunction.txx

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/*=========================================================================

Program:   Insight Segmentation & Registration Toolkit
Module:    $RCSfile: itkMIRegistrationFunction.txx,v $
Language:  C++
Date:      $Date: 2009-01-26 21:45:50 $
Version:   $Revision: 1.22 $

Copyright (c) Insight Software Consortium. All rights reserved.
See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.

This software is distributed WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE.  See the above copyright notices for more information.

=========================================================================*/
#ifndef __itkMIRegistrationFunction_txx
#define __itkMIRegistrationFunction_txx

#include "itkMIRegistrationFunction.h"
#include "itkImageRandomIteratorWithIndex.h"
#include "itkExceptionObject.h"
#include "vnl/vnl_math.h"
#include "itkNeighborhoodIterator.h"

#include <vnl/vnl_matrix.h>

namespace itk {

template <class TFixedImage, class TMovingImage, class TDeformationField>
MIRegistrationFunction<TFixedImage,TMovingImage,TDeformationField>
::MIRegistrationFunction()
{

  RadiusType r;
  unsigned int j;
  m_NumberOfSamples=1;
  m_NumberOfBins=4;

  for( j = 0; j < ImageDimension; j++ )
    {
    r[j] = 2;
    m_NumberOfSamples *= (r[j]*2+1);
    }
  this->SetRadius(r);

  m_MetricTotal=0.0;

  m_TimeStep = 1.0;
  m_Minnorm=1.0;
  m_DenominatorThreshold = 1e-9;
  m_IntensityDifferenceThreshold = 0.001;
  this->SetMovingImage(NULL);
  this->SetFixedImage(NULL);
  m_FixedImageGradientCalculator = GradientCalculatorType::New();

  m_DoInverse = true;
  m_DoInverse = false;

  if (m_DoInverse)
    {
    m_MovingImageGradientCalculator = GradientCalculatorType::New();
    }
  typename DefaultInterpolatorType::Pointer interp =
    DefaultInterpolatorType::New();

  m_MovingImageInterpolator = static_cast<InterpolatorType*>(
    interp.GetPointer() );
}


/*
 * Standard "PrintSelf" method.
 */
template <class TFixedImage, class TMovingImage, class TDeformationField>
void
MIRegistrationFunction<TFixedImage,TMovingImage,TDeformationField>
::PrintSelf(std::ostream& os, Indent indent) const
{

  Superclass::PrintSelf(os, indent);
/*
  os << indent << "MovingImageIterpolator: ";
  os << m_MovingImageInterpolator.GetPointer() << std::endl;
  os << indent << "FixedImageGradientCalculator: ";
  os << m_FixedImageGradientCalculator.GetPointer() << std::endl;
  os << indent << "DenominatorThreshold: ";
  os << m_DenominatorThreshold << std::endl;
  os << indent << "IntensityDifferenceThreshold: ";
  os << m_IntensityDifferenceThreshold << std::endl;
*/
}


/*
 * Set the function state values before each iteration
 */
template <class TFixedImage, class TMovingImage, class TDeformationField>
void
MIRegistrationFunction<TFixedImage,TMovingImage,TDeformationField>
::InitializeIteration()
{
  if( !this->m_MovingImage || !this->m_FixedImage || !m_MovingImageInterpolator )
    {
    itkExceptionMacro( << "MovingImage, FixedImage and/or Interpolator not set" );
    }

  // setup gradient calculator
  m_FixedImageGradientCalculator->SetInputImage( this->m_FixedImage );

  if (m_DoInverse)
    {
    // setup gradient calculator
    m_MovingImageGradientCalculator->SetInputImage( this->m_MovingImage );
    }
  // setup moving image interpolator
  m_MovingImageInterpolator->SetInputImage( this->m_MovingImage );

  m_MetricTotal=0.0;

}

template <class TFixedImage, class TMovingImage, class TDeformationField>
typename MIRegistrationFunction<TFixedImage,TMovingImage,TDeformationField>
::PixelType
MIRegistrationFunction<TFixedImage,TMovingImage,TDeformationField>
::ComputeUpdate(const NeighborhoodType &it, void * itkNotUsed(globalData),
                const FloatOffsetType& itkNotUsed(offset))
{
  // we compute the derivative of MI w.r.t. the infinitesimal
  // displacement, following viola and wells.

  // 1)  collect samples from  M (Moving) and F (Fixed)
  // 2)  compute minimum and maximum values of M and F
  // 3)  discretized M and F into N bins
  // 4)  estimate joint probability P(M,F) and P(F)
  // 5)  derivatives is given as :
  //
  //  $$ \nabla MI = \frac{1}{N} \sum_i \sum_j (F_i-F_j)
  //    ( W(F_i,F_j) \frac{1}{\sigma_v} -
  //                W((F_i,M_i),(F_j,M_j)) \frac{1}{\sigma_vv} ) \nabla F
  //
  // NOTE : must estimate sigma for each pdf

  typedef vnl_matrix<double>               matrixType;
  typedef std::vector<double>              sampleContainerType;
  typedef std::vector<CovariantVectorType> gradContainerType;
  typedef std::vector<double>              gradMagContainerType;
  typedef std::vector<unsigned int>        inImageIndexContainerType;


  PixelType update;
  PixelType derivative;
  unsigned int j;

  const IndexType oindex = it.GetIndex();

  unsigned int indct;

  for (indct=0;indct<ImageDimension;indct++)
    {
    update[indct]=0.0;
    derivative[indct]=0.0;
    }


  float thresh2=1.0/255.;//  FIX ME : FOR PET LUNG ONLY !!
  float thresh1=1.0/255.;
  if ( this->m_MovingImage->GetPixel(oindex) <= thresh1 &&
       this->m_FixedImage->GetPixel(oindex) <= thresh2 ) return update;

  typename FixedImageType::SizeType hradius=this->GetRadius();

  FixedImageType* img =const_cast<FixedImageType *>(this->m_FixedImage.GetPointer());
  typename FixedImageType::SizeType imagesize=img->GetLargestPossibleRegion().GetSize();


  bool inimage;

// now collect the samples
  sampleContainerType fixedSamplesA;
  sampleContainerType movingSamplesA;
  sampleContainerType fixedSamplesB;
  sampleContainerType movingSamplesB;
  inImageIndexContainerType inImageIndicesA;
  gradContainerType  fixedGradientsA;
  gradMagContainerType fixedGradMagsA;
  inImageIndexContainerType inImageIndicesB;
  gradContainerType  fixedGradientsB;
  gradMagContainerType fixedGradMagsB;

  unsigned int samplestep=2; //m_Radius[0];

  double minf=1.e9,minm=1.e9,maxf=0.0,maxm=0.0;
  double movingMean=0.0;
  double fixedMean=0.0;
  double fixedValue=0,movingValue=0;

  unsigned int sampct=0;


  ConstNeighborhoodIterator<DeformationFieldType>
    asamIt( hradius,
            this->GetDeformationField(),
            this->GetDeformationField()->GetRequestedRegion());
  asamIt.SetLocation(oindex);
  unsigned int hoodlen=asamIt.Size();

// first get the density-related sample
  for(indct=0; indct<hoodlen; indct=indct+samplestep)
    {
    IndexType index=asamIt.GetIndex(indct);
    inimage=true;
    for (unsigned int dd=0; dd<ImageDimension; dd++)
      {
      if ( index[dd] < 0 || index[dd] > static_cast<typename IndexType::IndexValueType>(imagesize[dd]-1) ) inimage=false;
      }
    if (inimage)
      {

      fixedValue=0.;
      movingValue=0.0;
      CovariantVectorType fixedGradient;

      // Get fixed image related information
      fixedValue = (double) this->m_FixedImage->GetPixel( index );


      fixedGradient = m_FixedImageGradientCalculator->EvaluateAtIndex( index );

      // Get moving image related information
      typedef typename DeformationFieldType::PixelType DeformationPixelType;
      const DeformationPixelType itvec = this->GetDeformationField()->GetPixel(index);

      PointType mappedPoint;
      this->GetFixedImage()->TransformIndexToPhysicalPoint(index, mappedPoint);
      for( j = 0; j < ImageDimension; j++ )
        {
        mappedPoint[j] += itvec[j];
        }
      if( m_MovingImageInterpolator->IsInsideBuffer( mappedPoint ) )
        {
        movingValue = m_MovingImageInterpolator->Evaluate( mappedPoint );
        }
      else
        {
        movingValue = 0.0;
        }

      if (fixedValue > maxf) maxf=fixedValue;
      else if (fixedValue < minf) minf=fixedValue;
      if (movingValue > maxm) maxm=movingValue;
      else if (movingValue < minm) minm=movingValue;

      fixedMean += fixedValue;
      movingMean += movingValue;

      fixedSamplesA.insert(fixedSamplesA.begin(),(double)fixedValue);
      fixedGradientsA.insert(fixedGradientsA.begin(),fixedGradient);
      movingSamplesA.insert(movingSamplesA.begin(),(double)movingValue);


//        fixedSamplesB.insert(fixedSamplesB.begin(),(double)fixedValue);
//        fixedGradientsB.insert(fixedGradientsB.begin(),fixedGradient);
//        movingSamplesB.insert(movingSamplesB.begin(),(double)movingValue);

      sampct++;
      }

    }


// BEGIN RANDOM A SAMPLES
  bool getrandasamples=true;
  if (getrandasamples)
    {

    typename FixedImageType::RegionType region=img->GetLargestPossibleRegion();

    ImageRandomIteratorWithIndex<FixedImageType> randasamit(img,region);
//     unsigned int numberOfSamples=20;
    unsigned int numberOfSamples=10;
    randasamit.SetNumberOfSamples( numberOfSamples );
//  numberOfSamples=100;

    indct=0;

    randasamit.ReinitializeSeed(0);
    randasamit.GoToBegin();
    while( !randasamit.IsAtEnd() &&  indct < numberOfSamples )
      {
      IndexType index=randasamit.GetIndex();
      inimage=true;

      float d=0.0;
      for (unsigned int dd=0; dd<ImageDimension; dd++)
        {
        if ( index[dd] < 0 || index[dd] > static_cast<typename IndexType::IndexValueType>(imagesize[dd]-1) ) inimage=false;
        d += (index[dd]-oindex[dd])*(index[dd]-oindex[dd]);
        }

      if (inimage )
        {
        fixedValue=0.;
        movingValue=0.0;
        CovariantVectorType fixedGradient;
        double fgm=0;
        // Get fixed image related information
        fixedValue = (double) this->m_FixedImage->GetPixel( index );
        fixedGradient = m_FixedImageGradientCalculator->EvaluateAtIndex( index );

        for( j = 0; j < ImageDimension; j++ )
          {
          fgm += fixedGradient[j] *fixedGradient[j];
          }
        // Get moving image related information
        typedef typename DeformationFieldType::PixelType DeformationPixelType;
        const DeformationPixelType itvec=this->GetDeformationField()->GetPixel(index);
        PointType mappedPoint;
        this->GetFixedImage()->TransformIndexToPhysicalPoint(index, mappedPoint);
        for( j = 0; j < ImageDimension; j++ )
          {
          mappedPoint[j] += itvec[j];
          }
        if( m_MovingImageInterpolator->IsInsideBuffer( mappedPoint ) )
          {
          movingValue = m_MovingImageInterpolator->Evaluate( mappedPoint );
          }
        else
          {
          movingValue = 0.0;
          }

        //      if ( (fixedValue > 0 || movingValue > 0 || fgm > 0) || !filtersamples)

        if ( fixedValue > 0 || movingValue > 0 || fgm > 0 )
          {
          fixedMean += fixedValue;
          movingMean += movingValue;

          fixedSamplesA.insert(fixedSamplesA.begin(),(double)fixedValue);
          fixedGradientsA.insert(fixedGradientsA.begin(),fixedGradient);
          movingSamplesA.insert(movingSamplesA.begin(),(double)movingValue);
          sampct++;
          indct++;
          }

        }
      ++randasamit;
      }

    }
  // END RANDOM A SAMPLES

  const DeformationFieldType * const field = this->GetDeformationField();

  for (j=0;j<ImageDimension; j++)
    {
    hradius[j]=0;
    }
  ConstNeighborhoodIterator<DeformationFieldType>
    hoodIt( hradius, field, field->GetRequestedRegion());
  hoodIt.SetLocation(oindex);

  // then get the entropy ( and MI derivative ) related sample
  for(indct=0; indct<hoodIt.Size(); indct=indct+1)
    {
    const IndexType index=hoodIt.GetIndex(indct);
    inimage=true;
    float d=0.0;
    for (unsigned int dd=0; dd<ImageDimension; dd++)
      {
      if ( index[dd] < 0 || index[dd] > static_cast<typename IndexType::IndexValueType>(imagesize[dd]-1) ) inimage=false;
      d += (index[dd]-oindex[dd])*(index[dd]-oindex[dd]);
      }
    if (inimage  && vcl_sqrt(d) <= 1.0)
      {
      fixedValue=0.;
      movingValue=0.0;
      CovariantVectorType fixedGradient;

      // Get fixed image related information
      fixedValue = (double) this->m_FixedImage->GetPixel( index );
      fixedGradient = m_FixedImageGradientCalculator->EvaluateAtIndex( index );

      // Get moving image related information
      // Get moving image related information
      const typename DeformationFieldType::PixelType hooditvec=this->m_DeformationField->GetPixel(index);
      PointType mappedPoint;
      this->GetFixedImage()->TransformIndexToPhysicalPoint(index, mappedPoint);
      for(j = 0; j < ImageDimension; j++ )
        {
        mappedPoint[j] += hooditvec[j];
        }
      if( m_MovingImageInterpolator->IsInsideBuffer( mappedPoint ) )
        {
        movingValue = m_MovingImageInterpolator->Evaluate( mappedPoint );
        }
      else
        {
        movingValue = 0.0;
        }

      fixedSamplesB.insert(fixedSamplesB.begin(),(double)fixedValue);
      fixedGradientsB.insert(fixedGradientsB.begin(),fixedGradient);
      movingSamplesB.insert(movingSamplesB.begin(),(double)movingValue);
      }
    }

  double fsigma=0.0;
  double msigma=0.0;
  double jointsigma=0.0;

  const double numsamplesB= (double) fixedSamplesB.size();
  const double numsamplesA= (double) fixedSamplesA.size();
  double nsamp=numsamplesB;
//  if (maxf == minf && maxm == minm) return update;
//    else std::cout << " b samps " << fixedSamplesB.size()
//    << " a samps " <<  fixedSamplesA.size() <<
//    oindex  << hoodIt.Size() << it.Size() << std::endl;

  fixedMean /= (double)sampct;
  movingMean /= (double)sampct;

  bool mattes=false;

  for(indct=0; indct<(unsigned int)numsamplesA; indct++)
    {
// Get fixed image related information
    fixedValue=fixedSamplesA[indct];
    movingValue=movingSamplesA[indct];

    fsigma += (fixedValue-fixedMean)*(fixedValue-fixedMean);
    msigma += (movingValue-movingMean)*(movingValue-movingMean);
    jointsigma += fsigma+msigma;

    if (mattes)
      {
      fixedSamplesA[indct]=fixedSamplesA[indct]-minf;
      movingSamplesA[indct]=movingSamplesA[indct]-minm;
      if (indct < numsamplesB)
        {
        fixedSamplesB[indct]=fixedSamplesB[indct]-minf;
        movingSamplesB[indct]=movingSamplesB[indct]-minm;
        }
      }
    }


  fsigma=vcl_sqrt(fsigma/numsamplesA);
  float sigmaw=0.8;
  double m_FixedImageStandardDeviation=fsigma*sigmaw;
  msigma=vcl_sqrt(msigma/numsamplesA);
  double m_MovingImageStandardDeviation=msigma*sigmaw;
  jointsigma=vcl_sqrt(jointsigma/numsamplesA);

  if (fsigma < 1.e-7 || msigma < 1.e-7 ) return update;


  double m_MinProbability = 0.0001;
  double dLogSumFixed=0.,dLogSumMoving=0.,dLogSumJoint=0.0;
  unsigned int bsamples;
  unsigned int asamples;

  // the B samples estimate the entropy
  for(bsamples=0; bsamples<(unsigned int)numsamplesB; bsamples++)
    {
    double dDenominatorMoving = m_MinProbability;
    double dDenominatorJoint = m_MinProbability;
    double dDenominatorFixed = m_MinProbability;
    double dSumFixed = m_MinProbability;

    // this loop estimates the density
    for(asamples=0; asamples<(unsigned int)numsamplesA; asamples++)
      {
      double valueFixed = ( fixedSamplesB[bsamples] - fixedSamplesA[asamples] )
        / m_FixedImageStandardDeviation;
      valueFixed = vcl_exp(-0.5*valueFixed*valueFixed);

      double valueMoving = ( movingSamplesB[bsamples] - movingSamplesA[asamples] )
        / m_MovingImageStandardDeviation;
      valueMoving = vcl_exp(-0.5*valueMoving*valueMoving);

      dDenominatorMoving += valueMoving;
      dDenominatorFixed += valueFixed;
      dSumFixed += valueFixed;

// everything above here can be pre-computed only once and stored,
//  assuming const v.f. in small n-hood
      dDenominatorJoint += valueMoving * valueFixed;
      } // end of sample A loop

    dLogSumFixed -= vcl_log(dSumFixed );
    dLogSumMoving -= vcl_log(dDenominatorMoving );
    dLogSumJoint -= vcl_log(dDenominatorJoint );

    // this loop estimates the density
    for(asamples=0; asamples<(unsigned int)numsamplesA; asamples++)
      {
      double valueFixed = ( fixedSamplesB[bsamples] - fixedSamplesA[asamples] )
        / m_FixedImageStandardDeviation;
      valueFixed = vcl_exp(-0.5*valueFixed*valueFixed);

      double valueMoving = ( movingSamplesB[bsamples] - movingSamplesA[asamples] )
        / m_MovingImageStandardDeviation;
      valueMoving = vcl_exp(-0.5*valueMoving*valueMoving);
      const double weightFixed = valueFixed / dDenominatorFixed;
// dDenominatorJoint and weightJoint are what need to be computed each time
      const double weightJoint = valueMoving * valueFixed / dDenominatorJoint;

// begin where we may switch fixed and moving
      double weight = ( weightFixed - weightJoint );
      weight *= ( fixedSamplesB[bsamples] - fixedSamplesA[asamples] );
// end where we may switch fixed and moving

// this can also be stored away
      for (unsigned int i=0; i<ImageDimension;i++)
        {
        derivative[i] += ( fixedGradientsB[bsamples][i] - fixedGradientsA[asamples][i] ) * weight;
        }
      } // end of sample A loop
    } // end of sample B loop

  const double threshold = -0.1 * nsamp * vcl_log(m_MinProbability );
  if( dLogSumMoving > threshold || dLogSumFixed > threshold ||
      dLogSumJoint > threshold  )
    {
    // at least half the samples in B did not occur within
    // the Parzen window width of samples in A
    return update;
    }

  double value=0.0;
  value  = dLogSumFixed + dLogSumMoving - dLogSumJoint;
  value /= nsamp;
  value += vcl_log(nsamp );

  m_MetricTotal += value;
  this->m_Energy += value;

  derivative /= nsamp;
  derivative /= vnl_math_sqr( m_FixedImageStandardDeviation );

  double updatenorm=0.0;
  for (unsigned int tt=0; tt<ImageDimension; tt++)
    {
    updatenorm += derivative[tt]*derivative[tt];
    }
  updatenorm=vcl_sqrt(updatenorm);

  if (updatenorm > 1.e-20 && this->GetNormalizeGradient())
    {
    derivative=derivative/updatenorm;
    }

  return derivative*this->GetGradientStep();
}

} // end namespace itk

#endif