diff --git a/Modules/ImageStatistics/mitkPointSetDifferenceStatisticsCalculator.cpp b/Modules/ImageStatistics/mitkPointSetDifferenceStatisticsCalculator.cpp
index 14defc16d6..0cce31d3eb 100644
--- a/Modules/ImageStatistics/mitkPointSetDifferenceStatisticsCalculator.cpp
+++ b/Modules/ImageStatistics/mitkPointSetDifferenceStatisticsCalculator.cpp
@@ -1,208 +1,208 @@
 /*=========================================================================
 
 Program:   Medical Imaging & Interaction Toolkit
 Language:  C++
 Date:      $Date: 2009-05-12 19:56:03 +0200 (Di, 12 Mai 2009) $
 Version:   $Revision: 17179 $
 
 Copyright (c) German Cancer Research Center, Division of Medical and
 Biological Informatics. All rights reserved.
 See MITKCopyright.txt or http://www.mitk.org/copyright.html 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.
 
 =========================================================================*/
 
 
 #include "mitkPointSetDifferenceStatisticsCalculator.h"
 
 mitk::PointSetDifferenceStatisticsCalculator::PointSetDifferenceStatisticsCalculator() :
   m_StatisticsCalculated(false)
 {
   m_PointSet1 = mitk::PointSet::New();
   m_PointSet2 = mitk::PointSet::New();
   m_Statistics.Reset();
 }
 
 mitk::PointSetDifferenceStatisticsCalculator::PointSetDifferenceStatisticsCalculator(mitk::PointSet::Pointer pSet1, mitk::PointSet::Pointer pSet2)
 {
   m_PointSet1 = pSet1;
   m_PointSet2 = pSet2;
   m_StatisticsCalculated = false;
   m_Statistics.Reset();
 }
 
 mitk::PointSetDifferenceStatisticsCalculator::~PointSetDifferenceStatisticsCalculator()
 {
 }
 
 void mitk::PointSetDifferenceStatisticsCalculator::SetPointSets(mitk::PointSet::Pointer pSet1, mitk::PointSet::Pointer pSet2)
 {
   if (pSet1.IsNotNull())
   {
     m_PointSet1 = pSet1;
   }
   if (pSet2.IsNotNull())
   {
     m_PointSet2 = pSet2;
   }
   m_StatisticsCalculated = false;
   m_Statistics.Reset();
 }
 
 std::vector<double> mitk::PointSetDifferenceStatisticsCalculator::GetDifferences()
 {
   if (!m_StatisticsCalculated)
   {
     this->ComputeStatistics();
   }
   return m_DifferencesVector;
 }
 
 std::vector<double> mitk::PointSetDifferenceStatisticsCalculator::GetSquaredDifferences()
 {
   if (!m_StatisticsCalculated)
   {
     this->ComputeStatistics();
   }
   return m_SquaredDifferencesVector;
 }
 
 double mitk::PointSetDifferenceStatisticsCalculator::GetMean()
 {
   if (!m_StatisticsCalculated)
   {
     this->ComputeStatistics();
   }
   return m_Statistics.Mean;
 }
 
 double mitk::PointSetDifferenceStatisticsCalculator::GetSD()
 {
   if (!m_StatisticsCalculated)
   {
     this->ComputeStatistics();
   }
   return m_Statistics.Sigma;
 }
 
 double mitk::PointSetDifferenceStatisticsCalculator::GetVariance()
 {
   if (!m_StatisticsCalculated)
   {
     this->ComputeStatistics();
   }
   return m_Statistics.Variance;
 }
 
 double mitk::PointSetDifferenceStatisticsCalculator::GetRMS()
 {
   if (!m_StatisticsCalculated)
   {
     this->ComputeStatistics();
   }
   return m_Statistics.RMS;
 }
 
 double mitk::PointSetDifferenceStatisticsCalculator::GetMedian()
 {
   if (!m_StatisticsCalculated)
   {
     this->ComputeStatistics();
   }
   return m_Statistics.Median;
 }
 
 double mitk::PointSetDifferenceStatisticsCalculator::GetMax()
 {
   if (!m_StatisticsCalculated)
   {
     this->ComputeStatistics();
   }
   return m_Statistics.Max;
 }
 
 double mitk::PointSetDifferenceStatisticsCalculator::GetMin()
 {
   if (!m_StatisticsCalculated)
   {
     this->ComputeStatistics();
   }
   return m_Statistics.Min;
 }
 
 double mitk::PointSetDifferenceStatisticsCalculator::GetNumberOfPoints()
 {
   if (!m_StatisticsCalculated)
   {
     this->ComputeStatistics();
   }
   return m_Statistics.N;
 }
 
 void mitk::PointSetDifferenceStatisticsCalculator::ComputeStatistics()
 {
-  if ((m_PointSet1==NULL)||(m_PointSet2==NULL))
+  if ((m_PointSet1.IsNull())||(m_PointSet2.IsNull()))
   {
     itkExceptionMacro("Point sets specified are not valid. Please specify correct Point sets");
   }
   else if (m_PointSet1->GetSize()!=m_PointSet2->GetSize())
   {
     itkExceptionMacro("PointSets are not equal. Please make sure that your PointSets have the same size and hold corresponding points.");
   }
   else if (m_PointSet1->GetSize()==0)
   {
     itkExceptionMacro("There are no points in the PointSets. Please make sure that the PointSets contain points");
   }
   else
   {
     double mean, sd, rms= 0.0;
     std::vector<double> differencesVector;
     mitk::Point3D point1;
     mitk::Point3D point2;
     int numberOfPoints = m_PointSet1->GetSize();
     for (int i=0; i<numberOfPoints; i++)
     {
       point1 = m_PointSet1->GetPoint(i);
       point2 = m_PointSet2->GetPoint(i);
       double squaredDistance = point1.SquaredEuclideanDistanceTo(point2);
       mean+=sqrt(squaredDistance);
       rms+=squaredDistance;
       this->m_SquaredDifferencesVector.push_back(squaredDistance);
       differencesVector.push_back(sqrt(squaredDistance));
     }
     m_DifferencesVector = differencesVector;
     mean = mean/numberOfPoints;
     rms = sqrt(rms/numberOfPoints);
     for (int i=0; i<differencesVector.size(); i++)
     {
       sd+=(differencesVector.at(i)-mean)*(differencesVector.at(i)-mean);
     }
     double variance = sd/numberOfPoints;
     sd = sqrt(variance);
     std::sort(differencesVector.begin(),differencesVector.end());
     double min = differencesVector.at(0);
     double max = differencesVector.at(numberOfPoints-1);
     double median = 0.0;
     if (numberOfPoints%2 == 0)
     {
       median = (differencesVector.at(numberOfPoints/2)+differencesVector.at(numberOfPoints/2-1))/2;
     }
     else
     {
       median = differencesVector.at((numberOfPoints-1)/2+1);
     }
     m_Statistics.Mean = mean;
     m_Statistics.Sigma = sd;
     m_Statistics.Variance = variance;
     m_Statistics.RMS = rms;
     m_Statistics.Min = differencesVector.at(0);
     m_Statistics.Max = differencesVector.at(numberOfPoints-1);
     m_Statistics.Median = median;
     m_Statistics.N = numberOfPoints;
 
     m_StatisticsCalculated = true;
   }
 }