diff --git a/Modules/DiffusionImaging/Tractography/itkGibbsTrackingFilter.h b/Modules/DiffusionImaging/Tractography/itkGibbsTrackingFilter.h
index 8760c6fdf9..23405b88fb 100644
--- a/Modules/DiffusionImaging/Tractography/itkGibbsTrackingFilter.h
+++ b/Modules/DiffusionImaging/Tractography/itkGibbsTrackingFilter.h
@@ -1,164 +1,164 @@
 #ifndef itkGibbsTrackingFilter_h
 #define itkGibbsTrackingFilter_h
 
 #include "itkProcessObject.h"
 #include "itkVectorContainer.h"
 #include "itkImage.h"
 
 #include "GibbsTracking/pcRJMCMC.cpp"
 #include "GibbsTracking/auxilary_classes.cpp"
 
 #include <fstream>
 
 namespace itk{
 
   template< class TInputQBallImage, class TInputROIImage >
   class GibbsTrackingFilter :
   public ProcessObject{
   public:
     typedef GibbsTrackingFilter Self;
     typedef ProcessObject Superclass;
     typedef SmartPointer< Self > Pointer;
     typedef SmartPointer< const Self > ConstPointer;
 
     itkNewMacro(Self);
     itkTypeMacro( GibbsTrackingFilter, ProcessObject );
 
     /** Types for the DWI Input Image **/
     typedef TInputQBallImage InputQBallImageType;
 
     /** Types for the Mask Image **/
     typedef TInputROIImage MaskImageType;
     typedef typename MaskImageType::Pointer MaskImageTypePointer;
 
     typedef std::vector< itk::Point<float, 3> > FiberTractType;
     typedef std::vector< FiberTractType > FiberBundleType;
 
     itkSetMacro( TempStart, float );
     itkGetMacro( TempStart, float );
 
     itkSetMacro( TempEnd, float );
     itkGetMacro( TempEnd, float );
 
     itkSetMacro( NumIt, int );
     itkGetMacro( NumIt, int );
 
     itkSetMacro( ParticleWeight, float );
     itkGetMacro( ParticleWeight, float );
 
     /** width of particle sigma (std-dev of gaussian around center) **/
     itkSetMacro( ParticleWidth, float );
     itkGetMacro( ParticleWidth, float );
 
     /** length of particle from midpoint to ends **/
     itkSetMacro( ParticleLength, float );
     itkGetMacro( ParticleLength, float );
 
     itkSetMacro( ChempotConnection, float );
     itkGetMacro( ChempotConnection, float );
 
     itkSetMacro( ChempotParticle, float );
     itkGetMacro( ChempotParticle, float );
 
     itkSetMacro( InexBalance, float );
     itkGetMacro( InexBalance, float );
 
     itkSetMacro( Chempot2, float );
     itkGetMacro( Chempot2, float );
 
     itkSetMacro( FiberLength, int );
     itkGetMacro( FiberLength, int );
 
     itkGetMacro( Steps, int );
 
     itkSetMacro( AbortTracking, bool );
     itkGetMacro( AbortTracking, bool );
 
     itkSetMacro( CurrentStep, unsigned long );
     itkGetMacro( CurrentStep, unsigned long );
 
     itkSetMacro( SubtractMean, bool);
     itkGetMacro( SubtractMean, bool);
 
     /** Set/Get the Odf Input Image **/
     itkSetInputMacro(OdfImage, InputQBallImageType, 0);
     itkGetInputMacro(OdfImage, InputQBallImageType, 0);
 
     /** Set/Get the Input mask image **/
     itkSetMacro(MaskImage, MaskImageTypePointer);
     itkGetMacro(MaskImage, MaskImageTypePointer);
 
     itkGetMacro(NumParticles, unsigned long);
     itkGetMacro(NumConnections, unsigned long);
     itkGetMacro(NumAcceptedFibers, int);
     itkGetMacro(ProposalAcceptance, float);
 
     /** Entry Point For the Algorithm:  Is invoked when Update() is called
     either directly or through itk pipeline propagation
     **/
     void GenerateData();
 
     /** override the Process Object Update because we don't have a
     dataobject as an outpgnome themeut.  We can change this later by wrapping the
     tractcontainer in a dataobject decorator and letting the Superclass
     know about it.
     **/
     struct StochasticTractGenerationCallbackStruct{
       Pointer Filter;
     };
 
     virtual void Update(){
       this->GenerateData();
     }
 
     FiberBundleType* GetFiberBundle();
     float GetMemoryUsage();
 
   protected:
 
     GibbsTrackingFilter();
     virtual ~GibbsTrackingFilter();
 
     void ComputeFiberCorrelation();
 
     void BuildFibers(float* points, int numPoints);
 
     // Input Images
     typename InputQBallImageType::Pointer m_ItkQBallImage;
     typename MaskImageType::Pointer m_MaskImage;
 
     // Tracking parameters
     float   m_TempStart;  // Start temperature
     float   m_TempEnd;  // End temperature
     unsigned long m_NumIt;  // Total number of iterations
     unsigned long m_CurrentStep;  // current tracking step
     float   m_ParticleWeight; //w (unitless)
     float   m_ParticleWidth;  //sigma  (mm)
     float   m_ParticleLength; // ell (mm)
     float   m_ChempotConnection;  // gross L (chemisches potential)
     float   m_ChempotParticle;// unbenutzt (immer null, wenn groesser dann insgesamt weniger teilchen)
     float   m_InexBalance;    // gewichtung zwischen den lambdas
     // -5 ... 5 -> nur intern ... nur extern,default 0
     float   m_Chempot2;       // typischerweise 0,
     // korrektur fuer das geschaetzte integral
     int     m_FiberLength;
     bool    m_AbortTracking;
     bool    m_SubtractMean;
     int     m_NumAcceptedFibers;
-    bool    m_BuildFibers;
+    volatile bool    m_BuildFibers;
     int     m_Steps;
     float   m_Memory;
     float   m_ProposalAcceptance;
 
     RJMCMC* m_Sampler;
     FiberBundleType m_FiberBundle;
     unsigned long m_NumParticles;
     unsigned long m_NumConnections;
   };
 }
 
 #ifndef ITK_MANUAL_INSTANTIATION
 #include "itkGibbsTrackingFilter.cpp"
 #endif
 
 #endif