diff --git a/Modules/PhotoacousticsAlgorithms/Resources/DMAS.cl b/Modules/PhotoacousticsAlgorithms/Resources/DMAS.cl
index 46dfdb1ff2..20886fa3d8 100644
--- a/Modules/PhotoacousticsAlgorithms/Resources/DMAS.cl
+++ b/Modules/PhotoacousticsAlgorithms/Resources/DMAS.cl
@@ -1,76 +1,85 @@
 /*===================================================================
 
 The Medical Imaging Interaction Toolkit (MITK)
 
 Copyright (c) German Cancer Research Center,
 Division of Medical and Biological Informatics.
 All rights reserved.
 
 This software is distributed WITHOUT ANY WARRANTY; without
 even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.
 
 See LICENSE.txt or http://www.mitk.org for details.
 
 ===================================================================*/
 
 __kernel void ckDMAS(
   __global float* dSource, // input image
   __global float* dDest, // output buffer
   __global unsigned short* usedLines,
   __global unsigned short* AddSamples,
   __constant float* apodArray,
   unsigned short apodArraySize,
   unsigned int inputL,
   unsigned int inputS,
   unsigned int Slices,
   unsigned int outputL,
   unsigned int outputS  // parameters
 )
 {
   // get thread identifier
   unsigned int globalPosX = get_global_id(0);
   unsigned int globalPosY = get_global_id(1);
   unsigned int globalPosZ = get_global_id(2);
 
   // terminate non-valid threads
   if ( globalPosX < outputL && globalPosY < outputS && globalPosZ < Slices )
   {	
     float l_i = (float)globalPosX / (float)outputL * (float)inputL;
 
     unsigned short curUsedLines = usedLines[globalPosY * 3 * outputL + 3 * globalPosX];
     unsigned short minLine = usedLines[globalPosY * 3 * outputL + 3 * globalPosX + 1];
     unsigned short maxLine = usedLines[globalPosY * 3 *outputL + 3 * globalPosX + 2];
 
     float apod_mult = (float)apodArraySize / (float)curUsedLines;
 
     unsigned short Delay1 = 0;
     unsigned short Delay2 = 0;
 
     float output = 0;
     float mult = 0;
+    
+    float s_1 = 0;
+    float s_2 = 0;
+    float sign = 0;
 
     for (short l_s1 = minLine; l_s1 < maxLine; ++l_s1)
     {
-      Delay1 = AddSamples[globalPosY * inputL + (int)fabs(l_s1 - l_i)];
+      Delay1 = AddSamples[globalPosY * inputL + (int)(fabs(l_s1 - l_i))];
       if (Delay1 < inputS && Delay1 >= 0) {
+        s_1 = dSource[(int)(globalPosZ * inputL * inputS + Delay1 * inputL + l_s1)];
+        sign += s_1;
+        
         for (short l_s2 = l_s1 + 1; l_s2 < maxLine; ++l_s2)
         {
-          Delay2 = AddSamples[globalPosY * inputL + (int)fabs(l_s2 - l_i)];
+          Delay2 = AddSamples[globalPosY * inputL + (int)(fabs(l_s2 - l_i))];
           if (Delay2 < inputS && Delay2 >= 0) {
+            s_2 = dSource[(int)(globalPosZ * inputL * inputS + Delay2 * inputL + l_s2)];
+            
             mult = apodArray[(int)((l_s2 - minLine)*apod_mult)] *
-              dSource[(int)(globalPosZ * inputL * inputS + Delay2 * inputL + l_s2)]
+              s_2
               * apodArray[(int)((l_s1 - minLine)*apod_mult)] *
-              dSource[(int)(globalPosZ * inputL * inputS + Delay1 * inputL + l_s1)];
+              s_1;
               
-            output += sqrt(mult * ((float)(mult>0)-(float)(mult<0))) * ((mult > 0) - (mult < 0));
+            output += sqrt(fabs(mult)) * ((mult > 0) - (mult < 0));
           }
         }
       }
       else
         --curUsedLines;
     }
 
-    dDest[ globalPosZ * outputL * outputS + globalPosY * outputL + globalPosX ] = output / (float)(curUsedLines * curUsedLines - (curUsedLines - 1));
+    dDest[ globalPosZ * outputL * outputS + globalPosY * outputL + globalPosX ] = output / (float)(curUsedLines * curUsedLines - (curUsedLines - 1)) * ((sign > 0) - (sign < 0));
   }
 }
diff --git a/Modules/PhotoacousticsAlgorithms/source/mitkPhotoacousticBeamformingFilter.cpp b/Modules/PhotoacousticsAlgorithms/source/mitkPhotoacousticBeamformingFilter.cpp
index 3ca60f63df..ffa15eebf1 100644
--- a/Modules/PhotoacousticsAlgorithms/source/mitkPhotoacousticBeamformingFilter.cpp
+++ b/Modules/PhotoacousticsAlgorithms/source/mitkPhotoacousticBeamformingFilter.cpp
@@ -1,557 +1,577 @@
 /*===================================================================
 mitkPhotoacousticBeamformingFilter
 The Medical Imaging Interaction Toolkit (MITK)
 
 Copyright (c) German Cancer Research Center,
 Division of Medical and Biological Informatics.
 All rights reserved.
 
 This software is distributed WITHOUT ANY WARRANTY; without
 even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.
 
 See LICENSE.txt or http://www.mitk.org for details.
 
 ===================================================================*/
 
 #define _USE_MATH_DEFINES
 
 #include "mitkProperties.h"
 #include "mitkImageReadAccessor.h"
 #include <algorithm>
 #include <itkImageIOBase.h>
 #include <chrono>
 #include <cmath>
 #include <thread>
 #include <itkImageIOBase.h>
 #include "mitkImageCast.h"
 #include "mitkPhotoacousticBeamformingFilter.h"
 
 mitk::BeamformingFilter::BeamformingFilter() : m_OutputData(nullptr), m_InputData(nullptr), m_Message("noMessage")
 {
   this->SetNumberOfIndexedInputs(1);
   this->SetNumberOfRequiredInputs(1);
 
   m_ProgressHandle = [](int, std::string) {};
 
   m_BeamformingOclFilter = mitk::PhotoacousticOCLBeamformingFilter::New();
 
   m_VonHannFunction = VonHannFunction(m_Conf.apodizationArraySize);
   m_HammFunction = HammFunction(m_Conf.apodizationArraySize);
   m_BoxFunction = BoxFunction(m_Conf.apodizationArraySize);
 }
 
 void mitk::BeamformingFilter::SetProgressHandle(std::function<void(int, std::string)> progressHandle)
 {
   m_ProgressHandle = progressHandle;
 }
 
 mitk::BeamformingFilter::~BeamformingFilter()
 {
   delete[] m_VonHannFunction;
   delete[] m_HammFunction;
   delete[] m_BoxFunction;
 }
 
 void mitk::BeamformingFilter::GenerateInputRequestedRegion()
 {
   Superclass::GenerateInputRequestedRegion();
 
   mitk::Image* output = this->GetOutput();
   mitk::Image* input = const_cast<mitk::Image *> (this->GetInput());
   if (!output->IsInitialized())
   {
     return;
   }
 
   input->SetRequestedRegionToLargestPossibleRegion();
   //GenerateTimeInInputRegion(output, input);
 }
 
 void mitk::BeamformingFilter::GenerateOutputInformation()
 {
   mitk::Image::ConstPointer input = this->GetInput();
   mitk::Image::Pointer output = this->GetOutput();
 
   if ((output->IsInitialized()) && (this->GetMTime() <= m_TimeOfHeaderInitialization.GetMTime()))
     return;
 
   itkDebugMacro(<< "GenerateOutputInformation()");
 
   unsigned int dim[] = { m_Conf.ReconstructionLines, m_Conf.SamplesPerLine, input->GetDimension(2) };
   output->Initialize(mitk::MakeScalarPixelType<float>(), 3, dim);
 
   mitk::Vector3D spacing;
   spacing[0] = m_Conf.Pitch * m_Conf.TransducerElements * 1000 / m_Conf.ReconstructionLines;
   spacing[1] = (m_Conf.TimeSpacing * m_Conf.inputDim[1]) / 2 * m_Conf.SpeedOfSound * 1000 / m_Conf.SamplesPerLine;
   spacing[2] = 1;
 
   output->GetGeometry()->SetSpacing(spacing);
   output->GetGeometry()->Modified();
   output->SetPropertyList(input->GetPropertyList()->Clone());
 
   m_TimeOfHeaderInitialization.Modified();
 }
 
 
 void mitk::BeamformingFilter::GenerateData()
 {
   GenerateOutputInformation();
   mitk::Image::Pointer input = this->GetInput();
   mitk::Image::Pointer output = this->GetOutput();
 
   if (!output->IsInitialized())
     return;
 
   float* ApodWindow;
   if (m_ConfOld.apodizationArraySize != m_Conf.apodizationArraySize)
   {
     delete[] m_VonHannFunction;
     delete[] m_HammFunction;
     delete[] m_BoxFunction;
     m_VonHannFunction = VonHannFunction(m_Conf.apodizationArraySize);
     m_HammFunction = HammFunction(m_Conf.apodizationArraySize);
     m_BoxFunction = BoxFunction(m_Conf.apodizationArraySize);
 
     m_ConfOld = m_Conf;
   }
 
   // set the appropiate apodization window
   switch (m_Conf.Apod)
   {
   case BeamformingSettings::Apodization::Hann:
     ApodWindow = m_VonHannFunction;
     break;
   case BeamformingSettings::Apodization::Hamm:
     ApodWindow = m_HammFunction;
     break;
   case BeamformingSettings::Apodization::Box:
     ApodWindow = m_BoxFunction;
     break;
   default:
     ApodWindow = m_BoxFunction;
     break;
   }
 
   auto begin = std::chrono::high_resolution_clock::now(); // debbuging the performance...
 
   if (!m_Conf.UseGPU)
   {
     int progInterval = output->GetDimension(2) / 20 > 1 ? output->GetDimension(2) / 20 : 1;
     // the interval at which we update the gui progress bar
 
     float inputDim[2] = { (float)input->GetDimension(0), (float)input->GetDimension(1) };
     float outputDim[2] = { (float)output->GetDimension(0), (float)output->GetDimension(1) };
 
     for (unsigned int i = 0; i < output->GetDimension(2); ++i) // seperate Slices should get Beamforming seperately applied
     {
       mitk::ImageReadAccessor inputReadAccessor(input, input->GetSliceData(i));
 
       // first, we check whether the dara is float, other formats are unsupported
       if (input->GetPixelType().GetTypeAsString() == "scalar (float)" || input->GetPixelType().GetTypeAsString() == " (float)")
       {
         m_InputData = (float*)inputReadAccessor.GetData();
       }
       else
       {
         MITK_INFO << "Pixel type is not float, abort";
         return;
       }
 
       m_OutputData = new float[m_Conf.ReconstructionLines*m_Conf.SamplesPerLine];
 
       // fill the image with zeros
       for (int l = 0; l < outputDim[0]; ++l)
       {
         for (int s = 0; s < outputDim[1]; ++s)
         {
           m_OutputData[l*(short)outputDim[1] + s] = 0;
         }
       }
 
       std::thread *threads = new std::thread[(short)outputDim[0]];
 
       // every line will be beamformed in a seperate thread
       if (m_Conf.Algorithm == BeamformingSettings::BeamformingAlgorithm::DAS)
       {
         if (m_Conf.DelayCalculationMethod == BeamformingSettings::DelayCalc::QuadApprox)
         {
           for (short line = 0; line < outputDim[0]; ++line)
           {
             threads[line] = std::thread(&BeamformingFilter::DASQuadraticLine, this, m_InputData, m_OutputData, inputDim, outputDim, line, ApodWindow, m_Conf.apodizationArraySize);
           }
         }
         else if (m_Conf.DelayCalculationMethod == BeamformingSettings::DelayCalc::Spherical)
         {
           for (short line = 0; line < outputDim[0]; ++line)
           {
             threads[line] = std::thread(&BeamformingFilter::DASSphericalLine, this, m_InputData, m_OutputData, inputDim, outputDim, line, ApodWindow, m_Conf.apodizationArraySize);
           }
         }
       }
       else if (m_Conf.Algorithm == BeamformingSettings::BeamformingAlgorithm::DMAS)
       {
         if (m_Conf.DelayCalculationMethod == BeamformingSettings::DelayCalc::QuadApprox)
         {
           for (short line = 0; line < outputDim[0]; ++line)
           {
             threads[line] = std::thread(&BeamformingFilter::DMASQuadraticLine, this, m_InputData, m_OutputData, inputDim, outputDim, line, ApodWindow, m_Conf.apodizationArraySize);
           }
         }
         else if (m_Conf.DelayCalculationMethod == BeamformingSettings::DelayCalc::Spherical)
         {
           for (short line = 0; line < outputDim[0]; ++line)
           {
             threads[line] = std::thread(&BeamformingFilter::DMASSphericalLine, this, m_InputData, m_OutputData, inputDim, outputDim, line, ApodWindow, m_Conf.apodizationArraySize);
           }
         }
       }
       // wait for all lines to finish
       for (short line = 0; line < outputDim[0]; ++line)
       {
         threads[line].join();
       }
 
       output->SetSlice(m_OutputData, i);
 
       if (i % progInterval == 0)
         m_ProgressHandle((int)((i + 1) / (float)output->GetDimension(2) * 100), "performing reconstruction");
 
       delete[] m_OutputData;
       m_OutputData = nullptr;
       m_InputData = nullptr;
     }
   }
   #if defined(PHOTOACOUSTICS_USE_GPU) || DOXYGEN
   else
   {
     try
     {
       // first, we check whether the data is float, other formats are unsupported
       if (!(input->GetPixelType().GetTypeAsString() == "scalar (float)" || input->GetPixelType().GetTypeAsString() == " (float)"))
       {
         MITK_ERROR << "Pixel type is not float, abort";
         return;
       }
 
       m_ProgressHandle(50, "performing reconstruction");
 
       m_BeamformingOclFilter->SetApodisation(ApodWindow, m_Conf.apodizationArraySize);
       m_BeamformingOclFilter->SetConfig(m_Conf);
       m_BeamformingOclFilter->SetInput(input);
       m_BeamformingOclFilter->Update();
 
       void* out = m_BeamformingOclFilter->GetOutput();
       output->SetImportVolume(out, 0, 0, mitk::Image::ImportMemoryManagementType::ManageMemory);
     }
     catch (mitk::Exception &e)
     {
       std::string errorMessage = "Caught unexpected exception ";
       errorMessage.append(e.what());
       MITK_ERROR << errorMessage;
 
       float* dummyData = new float[m_Conf.ReconstructionLines * m_Conf.SamplesPerLine * m_Conf.inputDim[2]];
       output->SetImportVolume(dummyData, 0, 0, mitk::Image::ImportMemoryManagementType::ManageMemory);
 
       m_Message = "An openCL error occurred; all GPU operations in this and the next session may be corrupted.";
     }
   }
   #endif
   m_TimeOfHeaderInitialization.Modified();
 
   auto end = std::chrono::high_resolution_clock::now();
   MITK_INFO << "Beamforming of " << output->GetDimension(2) << " Images completed in " << ((float)std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin).count()) / 1000000 << "ms" << std::endl;
 }
 
 float* mitk::BeamformingFilter::VonHannFunction(int samples)
 {
   float* ApodWindow = new float[samples];
 
   for (int n = 0; n < samples; ++n)
   {
     ApodWindow[n] = (1 - cos(2 * M_PI * n / (samples - 1))) / 2;
   }
 
   return ApodWindow;
 }
 
 float* mitk::BeamformingFilter::HammFunction(int samples)
 {
   float* ApodWindow = new float[samples];
 
   for (int n = 0; n < samples; ++n)
   {
     ApodWindow[n] = 0.54 - 0.46*cos(2 * M_PI*n / (samples - 1));
   }
 
   return ApodWindow;
 }
 
 float* mitk::BeamformingFilter::BoxFunction(int samples)
 {
   float* ApodWindow = new float[samples];
 
   for (int n = 0; n < samples; ++n)
   {
     ApodWindow[n] = 1;
   }
 
   return ApodWindow;
 }
 
 void mitk::BeamformingFilter::DASQuadraticLine(float* input, float* output, float inputDim[2], float outputDim[2], const short& line, float* apodisation, const short& apodArraySize)
 {
   float& inputS = inputDim[1];
   float& inputL = inputDim[0];
 
   float& outputS = outputDim[1];
   float& outputL = outputDim[0];
 
   short AddSample = 0;
   short maxLine = 0;
   short minLine = 0;
   float delayMultiplicator = 0;
   float l_i = 0;
   float s_i = 0;
 
   float part = 0.07 * inputL;
   float tan_phi = std::tan(m_Conf.Angle / 360 * 2 * M_PI);
   float part_multiplicator = tan_phi * m_Conf.TimeSpacing * m_Conf.SpeedOfSound / m_Conf.Pitch * inputL / m_Conf.TransducerElements;
   float apod_mult = 1;
 
   short usedLines = (maxLine - minLine);
 
   //quadratic delay
   l_i = line / outputL * inputL;
 
   for (short sample = 0; sample < outputS; ++sample)
   {
     s_i = (float)sample / outputS * inputS / 2;
 
     part = part_multiplicator*s_i;
 
     if (part < 1)
       part = 1;
 
     maxLine = (short)std::min((l_i + part) + 1, inputL);
     minLine = (short)std::max((l_i - part), 0.0f);
     usedLines = (maxLine - minLine);
 
     apod_mult = (float)apodArraySize / (float)usedLines;
 
     delayMultiplicator = pow((1 / (m_Conf.TimeSpacing*m_Conf.SpeedOfSound) * (m_Conf.Pitch*m_Conf.TransducerElements) / inputL), 2) / s_i / 2;
 
     for (short l_s = minLine; l_s < maxLine; ++l_s)
     {
       AddSample = delayMultiplicator * pow((l_s - l_i), 2) + s_i + (1 - m_Conf.isPhotoacousticImage)*s_i;
       if (AddSample < inputS && AddSample >= 0) 
         output[sample*(short)outputL + line] += input[l_s + AddSample*(short)inputL] * apodisation[(short)((l_s - minLine)*apod_mult)];
       else
         --usedLines;
     }
     output[sample*(short)outputL + line] = output[sample*(short)outputL + line] / usedLines;
   }
 }
 
 void mitk::BeamformingFilter::DASSphericalLine(float* input, float* output, float inputDim[2], float outputDim[2], const short& line, float* apodisation, const short& apodArraySize)
 {
   float& inputS = inputDim[1];
   float& inputL = inputDim[0];
 
   float& outputS = outputDim[1];
   float& outputL = outputDim[0];
 
   short AddSample = 0;
   short maxLine = 0;
   short minLine = 0;
   float l_i = 0;
   float s_i = 0;
 
   float part = 0.07 * inputL;
   float tan_phi = std::tan(m_Conf.Angle / 360 * 2 * M_PI);
   float part_multiplicator = tan_phi * m_Conf.TimeSpacing * m_Conf.SpeedOfSound / m_Conf.Pitch * inputL / (float)m_Conf.TransducerElements;
   float apod_mult = 1;
 
   short usedLines = (maxLine - minLine);
 
   //exact delay
 
   l_i = (float)line / outputL * inputL;
 
   for (short sample = 0; sample < outputS; ++sample)
   {
     s_i = (float)sample / outputS * inputS / 2;
 
     part = part_multiplicator*s_i;
 
     if (part < 1)
       part = 1;
 
     maxLine = (short)std::min((l_i + part) + 1, inputL);
     minLine = (short)std::max((l_i - part), 0.0f);
     usedLines = (maxLine - minLine);
 
     apod_mult = (float)apodArraySize / (float)usedLines;
 
     for (short l_s = minLine; l_s < maxLine; ++l_s)
     {
       AddSample = (int)sqrt(
         pow(s_i, 2)
         +
         pow((1 / (m_Conf.TimeSpacing*m_Conf.SpeedOfSound) * (((float)l_s - l_i)*m_Conf.Pitch*(float)m_Conf.TransducerElements) / inputL), 2)
       ) + (1 - m_Conf.isPhotoacousticImage)*s_i;
       if (AddSample < inputS && AddSample >= 0) 
         output[sample*(short)outputL + line] += input[l_s + AddSample*(short)inputL] * apodisation[(short)((l_s - minLine)*apod_mult)];
       else
         --usedLines;
     }
     output[sample*(short)outputL + line] = output[sample*(short)outputL + line] / usedLines;
   }
 }
 
 void mitk::BeamformingFilter::DMASQuadraticLine(float* input, float* output, float inputDim[2], float outputDim[2], const short& line, float* apodisation, const short& apodArraySize)
 {
   float& inputS = inputDim[1];
   float& inputL = inputDim[0];
 
   float& outputS = outputDim[1];
   float& outputL = outputDim[0];
 
   short maxLine = 0;
   short minLine = 0;
   float delayMultiplicator = 0;
   float l_i = 0;
   float s_i = 0;
 
   float part = 0.07 * inputL;
   float tan_phi = std::tan(m_Conf.Angle / 360 * 2 * M_PI);
   float part_multiplicator = tan_phi * m_Conf.TimeSpacing * m_Conf.SpeedOfSound / m_Conf.Pitch * inputL / (float)m_Conf.TransducerElements;
   float apod_mult = 1;
 
   float mult = 0;
   short usedLines = (maxLine - minLine);
 
   //quadratic delay
   l_i = line / outputL * inputL;
 
   for (short sample = 0; sample < outputS; ++sample)
   {
     s_i = sample / outputS * inputS / 2;
 
     part = part_multiplicator*s_i;
 
     if (part < 1)
       part = 1;
 
     maxLine = (short)std::min((l_i + part) + 1, inputL);
     minLine = (short)std::max((l_i - part), 0.0f);
     usedLines = (maxLine - minLine);
 
     apod_mult = (float)apodArraySize / (float)usedLines;
 
     delayMultiplicator = pow((1 / (m_Conf.TimeSpacing*m_Conf.SpeedOfSound) * (m_Conf.Pitch*m_Conf.TransducerElements) / inputL), 2) / s_i / 2;
 
     //calculate the AddSamples beforehand to save some time
     short* AddSample = new short[maxLine - minLine];
     for (short l_s = 0; l_s < maxLine - minLine; ++l_s)
     {
       AddSample[l_s] = (short)(delayMultiplicator * pow((minLine + l_s - l_i), 2) + s_i) + (1 - m_Conf.isPhotoacousticImage)*s_i;
     }
 
+    float s_1 = 0;
+    float s_2 = 0;
+    int sign = 0;
+
     for (short l_s1 = minLine; l_s1 < maxLine - 1; ++l_s1)
     {
-      if (AddSample[l_s1 - minLine] < (short)inputS && AddSample[l_s1 - minLine] >= 0)
+      if (AddSample[l_s1 - minLine] < inputS && AddSample[l_s1 - minLine] >= 0)
       {
         for (short l_s2 = l_s1 + 1; l_s2 < maxLine; ++l_s2)
         {
           if (AddSample[l_s2 - minLine] < inputS && AddSample[l_s2 - minLine] >= 0)
           {
-            mult = input[l_s2 + AddSample[l_s2 - minLine] * (short)inputL] * apodisation[(short)((l_s2 - minLine)*apod_mult)] * input[l_s1 + AddSample[l_s1 - minLine] * (short)inputL] * apodisation[(short)((l_s1 - minLine)*apod_mult)];
+            s_2 = input[l_s2 + AddSample[l_s2 - minLine] * (short)inputL];
+            s_1 = input[l_s1 + AddSample[l_s1 - minLine] * (short)inputL];
+
+            sign += ((s_1 > 0) - (s_1 < 0));
+            sign += ((s_2 > 0) - (s_2 < 0));
+
+            mult = s_2 * apodisation[(int)((l_s2 - minLine)*apod_mult)] * s_1 * apodisation[(int)((l_s1 - minLine)*apod_mult)];
             output[sample*(short)outputL + line] += sqrt(fabs(mult)) * ((mult > 0) - (mult < 0));
           }
         }
       }
       else
         --usedLines;
     }
 
-    output[sample*(short)outputL + line] = output[sample*(short)outputL + line] / (pow(usedLines, 2) - (usedLines - 1));
+    output[sample*(short)outputL + line] = output[sample*(short)outputL + line] / (float)(pow(usedLines, 2) - (usedLines - 1)) * ((sign > 0) - (sign < 0));
 
     delete[] AddSample;
   }
 }
 
 void mitk::BeamformingFilter::DMASSphericalLine(float* input, float* output, float inputDim[2], float outputDim[2], const short& line, float* apodisation, const short& apodArraySize)
 {
   float& inputS = inputDim[1];
   float& inputL = inputDim[0];
 
   float& outputS = outputDim[1];
   float& outputL = outputDim[0];
 
   short maxLine = 0;
   short minLine = 0;
   float l_i = 0;
   float s_i = 0;
 
   float part = 0.07 * inputL;
   float tan_phi = std::tan(m_Conf.Angle / 360 * 2 * M_PI);
   float part_multiplicator = tan_phi * m_Conf.TimeSpacing * m_Conf.SpeedOfSound / m_Conf.Pitch * inputL / (float)m_Conf.TransducerElements;
   float apod_mult = 1;
 
   float mult = 0;
 
   short usedLines = (maxLine - minLine);
 
   //exact delay
 
   l_i = (float)line / outputL * inputL;
 
   for (short sample = 0; sample < outputS; ++sample)
   {
     s_i = (float)sample / outputS * inputS / 2;
 
     part = part_multiplicator*s_i;
 
     if (part < 1)
       part = 1;
 
     maxLine = (short)std::min((l_i + part) + 1, inputL);
     minLine = (short)std::max((l_i - part), 0.0f);
     usedLines = (maxLine - minLine);
 
     apod_mult = (float)apodArraySize / (float)usedLines;
 
     //calculate the AddSamples beforehand to save some time
     short* AddSample = new short[maxLine - minLine];
     for (short l_s = 0; l_s < maxLine - minLine; ++l_s)
     {
       AddSample[l_s] = (short)sqrt(
         pow(s_i, 2)
         +
         pow((1 / (m_Conf.TimeSpacing*m_Conf.SpeedOfSound) * (((float)minLine + (float)l_s - l_i)*m_Conf.Pitch*(float)m_Conf.TransducerElements) / inputL), 2)
       ) + (1 - m_Conf.isPhotoacousticImage)*s_i;
     }
 
+    float s_1 = 0;
+    float s_2 = 0;
+    int sign = 0;
+
     for (short l_s1 = minLine; l_s1 < maxLine - 1; ++l_s1)
     {
       if (AddSample[l_s1 - minLine] < inputS && AddSample[l_s1 - minLine] >= 0)
       {
         for (short l_s2 = l_s1 + 1; l_s2 < maxLine; ++l_s2)
         {
           if (AddSample[l_s2 - minLine] < inputS && AddSample[l_s2 - minLine] >= 0)
           {
-            mult = input[l_s2 + AddSample[l_s2 - minLine] * (short)inputL] * apodisation[(int)((l_s2 - minLine)*apod_mult)] * input[l_s1 + AddSample[l_s1 - minLine] * (short)inputL] * apodisation[(int)((l_s1 - minLine)*apod_mult)];
+            s_2 = input[l_s2 + AddSample[l_s2 - minLine] * (short)inputL];
+            s_1 = input[l_s1 + AddSample[l_s1 - minLine] * (short)inputL];
+
+            sign += ((s_1 > 0) - (s_1 < 0));
+            sign += ((s_2 > 0) - (s_2 < 0));
+
+            mult = s_2 * apodisation[(int)((l_s2 - minLine)*apod_mult)] * s_1 * apodisation[(int)((l_s1 - minLine)*apod_mult)];
             output[sample*(short)outputL + line] += sqrt(fabs(mult)) * ((mult > 0) - (mult < 0));
           }
         }
       }
       else
         --usedLines;
     }
 
-    output[sample*(short)outputL + line] = output[sample*(short)outputL + line] / (float)(pow(usedLines, 2) - (usedLines - 1));
+    output[sample*(short)outputL + line] = output[sample*(short)outputL + line] / (float)(pow(usedLines, 2) - (usedLines - 1)) * ((sign > 0) - (sign < 0));
 
     delete[] AddSample;
   }
 }