diff --git a/Modules/PhotoacousticSimulation/src/ProbeDesign/mitkPhotoacousticProbe.cpp b/Modules/PhotoacousticSimulation/src/ProbeDesign/mitkPhotoacousticProbe.cpp
index e65b026001..23df49e71b 100644
--- a/Modules/PhotoacousticSimulation/src/ProbeDesign/mitkPhotoacousticProbe.cpp
+++ b/Modules/PhotoacousticSimulation/src/ProbeDesign/mitkPhotoacousticProbe.cpp
@@ -1,134 +1,134 @@
 /*===================================================================
 
 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.
 
 ===================================================================*/
 
 #include "mitkPhotoacousticProbe.h"
 
 mitk::PhotoacousticProbe::PhotoacousticProbe(std::string file, bool verbose) :
   m_TotalEnergy(0),
   m_Verbose(verbose)
 {
   TiXmlDocument xmlDoc(file);
   bool success = xmlDoc.LoadFile(TIXML_ENCODING_UTF8);
   if(m_Verbose)
   {
     std::cout << "reading of document was " << (success ? "" : "not ") << "successful" << std::endl;
     std::cout << "Content of the Xml file:" << std::endl;
     xmlDoc.Print();
   }
   if(success)
   {
     InitProbe(xmlDoc);
   }
   else
   {
     if(m_Verbose)
     {
       std::cerr << "Could not load xml file" << std::endl;
     }
   }
 }
 
 mitk::PhotoacousticProbe::PhotoacousticProbe(const char* fileStream, bool verbose) :
   m_TotalEnergy(0),
   m_Verbose(verbose)
 {
   TiXmlDocument xmlDoc;
   const char* success = xmlDoc.Parse(fileStream, 0, TIXML_ENCODING_UTF8);
   if(m_Verbose)
   {
     std::cout << "reading document was " << (success==nullptr ? "" : "not ")<< "successful (" << (success==nullptr ? "NULL" : success) << ")" << std::endl ;
     std::cout << "Content of the Xml file:" << std::endl;
     xmlDoc.Print();
   }
   if(success == nullptr || atoi(success)==0)
   {
     InitProbe(xmlDoc);
   }
   else
   {
     if(m_Verbose)
     {
       std::cerr << "Could not load xml file" << std::endl;
     }
   }
 }
 
 mitk::PhotoacousticProbe::~PhotoacousticProbe()
 {
 
 }
 
 mitk::PhotoacousticLightSource::PhotonInformation mitk::PhotoacousticProbe::GetNextPhoton(double rng1, double rnd2, double rnd3, double rnd4,
                                                                                           double rnd5, double rnd6, double rnd7, double rnd8)
 {
   rng1 = rng1*m_TotalEnergy;
   double currentEnergy = 0;
   for(mitk::PhotoacousticLightSource::Pointer lightSource : m_LightSources)
   {
     currentEnergy += lightSource->GetEnergy();
     if(currentEnergy>=rng1)
       return lightSource->GetNextPhoton(rnd2, rnd3, rnd4, rnd5, rnd6, rnd7, rnd8);
   }
 
   //Last resort: If something goes wrong, return a position from the first source.
   return m_LightSources[0]->GetNextPhoton(rnd2, rnd3, rnd4, rnd5, rnd6, rnd7, rnd8);
 }
 
 bool mitk::PhotoacousticProbe::IsValid()
 {
   return m_IsValid;
 }
 
 void mitk::PhotoacousticProbe::InitProbe(TiXmlDocument xmlDoc)
 {
 
   m_IsValid = true;
 
-  TiXmlElement* root= xmlDoc.FirstChildElement("Probe");
+  TiXmlElement* root= xmlDoc.FirstChildElement(XML_TAG_PROBE);
   if(root)
   {
-    for(TiXmlElement* element = root->FirstChildElement("LightSource");
-        element !=nullptr; element = element->NextSiblingElement("LightSource"))
+    for(TiXmlElement* element = root->FirstChildElement(XML_TAG_LIGHT_SOURCE);
+        element !=nullptr; element = element->NextSiblingElement(XML_TAG_LIGHT_SOURCE))
     {
       mitk::PhotoacousticLightSource::Pointer lightSource = mitk::PhotoacousticLightSource::New(element, m_Verbose);
       if(lightSource.IsNotNull() && lightSource->IsValid())
       {
         m_LightSources.push_back(lightSource);
         m_TotalEnergy += lightSource->GetEnergy();
       }
       else
       {
         m_IsValid = false;
       }
     }
   }
   else
   {
     m_IsValid = false;
   }
 
   if(!m_IsValid)
   {
     std::cerr << "Creation of a valid Photoacoustic Probe failed." << std::endl;
   }
   else
   {
     if(m_Verbose)
     {
       std::cout << "Successfully created Photoacoustic Probe." << std::endl;
     }
   }
 }
diff --git a/Modules/PhotoacousticSimulation/src/ProbeDesign/mitkPhotoacousticProbe.h b/Modules/PhotoacousticSimulation/src/ProbeDesign/mitkPhotoacousticProbe.h
index 03e8571352..005e5e3fae 100644
--- a/Modules/PhotoacousticSimulation/src/ProbeDesign/mitkPhotoacousticProbe.h
+++ b/Modules/PhotoacousticSimulation/src/ProbeDesign/mitkPhotoacousticProbe.h
@@ -1,68 +1,71 @@
 /*===================================================================
 
 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.
 
 ===================================================================*/
 
 #ifndef MITKPHOTOACOUSTICPROBE_H
 #define MITKPHOTOACOUSTICPROBE_H
 
 #include <MitkPhotoacousticSimulationExports.h>
 
 #include <mitkCommon.h>
 
 //Includes for smart pointer usage
 #include "mitkCommon.h"
 #include "itkLightObject.h"
 
 #include "mitkPhotoacousticLightSource.h"
 #include <vector>
 #include <tinyxml.h>
 
 namespace mitk {
 
 /**
  * @brief The PhotoacousticProbe class
  * The representation of a PhotoacousticProbe
  */
 class MITKPHOTOACOUSTICSIMULATION_EXPORT PhotoacousticProbe : public itk::LightObject
 {
 public:
 
   mitkClassMacroItkParent(mitk::PhotoacousticProbe, itk::LightObject)
   mitkNewMacro2Param(Self, std::string, bool)
   mitkNewMacro2Param(Self, const char*, bool)
 
+  const std::string XML_TAG_PROBE = "Probe";
+  const std::string XML_TAG_LIGHT_SOURCE = "LightSource";
+
   mitk::PhotoacousticLightSource::PhotonInformation GetNextPhoton(double rng1, double rnd2, double rnd3, double rnd4,
                                                                   double rnd5, double rnd6, double rnd7, double rnd8);
 
   bool IsValid();
 
   PhotoacousticProbe(std::string xmlFile, bool verbose);
   PhotoacousticProbe(const char* fileStream, bool verbose);
   virtual ~PhotoacousticProbe();
 
 protected:
 
   std::vector<mitk::PhotoacousticLightSource::Pointer> m_LightSources;
   bool m_IsValid;
   double m_TotalEnergy;
   bool m_Verbose;
 
   void InitProbe(TiXmlDocument document);
 
 };
 
 }
 
 #endif // MITKPHOTOACOUSTICPROBE_H