diff --git a/Isodose/Logic/vtkMRMLIsodoseNode.cxx b/Isodose/Logic/vtkMRMLIsodoseNode.cxx
index 3e8844e62..d0365377f 100644
--- a/Isodose/Logic/vtkMRMLIsodoseNode.cxx
+++ b/Isodose/Logic/vtkMRMLIsodoseNode.cxx
@@ -50,6 +50,9 @@ vtkMRMLIsodoseNode::vtkMRMLIsodoseNode()
   this->ShowScalarBar = false;
   this->ShowScalarBar2D = false;
   this->ShowDoseVolumesOnly = true;
+  this->DoseUnits = DoseUnitsType::Unknown;
+  this->ReferenceDoseValue = -1.;
+  this->RelativeRepresentationFlag = false;
 
   this->HideFromEditors = false;
 }
@@ -69,6 +72,10 @@ void vtkMRMLIsodoseNode::WriteXML(ostream& of, int nIndent)
   vtkMRMLWriteXMLBooleanMacro(ShowScalarBar, ShowScalarBar);
   vtkMRMLWriteXMLBooleanMacro(ShowScalarBar2D, ShowScalarBar2D);
   vtkMRMLWriteXMLBooleanMacro(ShowDoseVolumesOnly, ShowDoseVolumesOnly);
+  vtkMRMLWriteXMLIntMacro(DoseUnits, DoseUnits);
+  vtkMRMLWriteXMLFloatMacro(ReferenceDoseValue, ReferenceDoseValue);
+  vtkMRMLWriteXMLBooleanMacro(RelativeRepresentationFlag, RelativeRepresentationFlag);
+
   vtkMRMLWriteXMLEndMacro(); 
 }
 
@@ -84,6 +91,9 @@ void vtkMRMLIsodoseNode::ReadXMLAttributes(const char** atts)
   vtkMRMLReadXMLBooleanMacro(ShowScalarBar, ShowScalarBar);
   vtkMRMLReadXMLBooleanMacro(ShowScalarBar2D, ShowScalarBar2D);
   vtkMRMLReadXMLBooleanMacro(ShowDoseVolumesOnly, ShowDoseVolumesOnly);
+  vtkMRMLReadXMLIntMacro(DoseUnits, DoseUnits);
+  vtkMRMLReadXMLFloatMacro(ReferenceDoseValue, ReferenceDoseValue);
+  vtkMRMLReadXMLBooleanMacro(RelativeRepresentationFlag, RelativeRepresentationFlag);
   vtkMRMLReadXMLEndMacro();
 
   this->EndModify(disabledModify);
@@ -104,6 +114,9 @@ void vtkMRMLIsodoseNode::Copy(vtkMRMLNode *anode)
   vtkMRMLCopyBooleanMacro(ShowScalarBar);
   vtkMRMLCopyBooleanMacro(ShowScalarBar2D);
   vtkMRMLCopyBooleanMacro(ShowDoseVolumesOnly);
+  vtkMRMLCopyIntMacro(DoseUnits);
+  vtkMRMLCopyFloatMacro(ReferenceDoseValue);
+  vtkMRMLCopyBooleanMacro(RelativeRepresentationFlag);
   vtkMRMLCopyEndMacro();
 
   this->EndModify(disabledModify);
@@ -120,6 +133,9 @@ void vtkMRMLIsodoseNode::PrintSelf(ostream& os, vtkIndent indent)
   vtkMRMLPrintBooleanMacro(ShowScalarBar);
   vtkMRMLPrintBooleanMacro(ShowScalarBar2D);
   vtkMRMLPrintBooleanMacro(ShowDoseVolumesOnly);
+  vtkMRMLPrintIntMacro(DoseUnits);
+  vtkMRMLPrintFloatMacro(ReferenceDoseValue);
+  vtkMRMLPrintBooleanMacro(RelativeRepresentationFlag);
   vtkMRMLPrintEndMacro();
 }
 
@@ -172,3 +188,21 @@ void vtkMRMLIsodoseNode::SetAndObserveColorTableNode(vtkMRMLColorTableNode* node
 
   doseVolumeNode->SetNodeReferenceID(COLOR_TABLE_REFERENCE_ROLE, (node ? node->GetID() : nullptr));
 }
+
+//----------------------------------------------------------------------------
+void vtkMRMLIsodoseNode::SetDoseUnits(int doseUnits)
+{
+  switch (doseUnits)
+  {
+    case 0:
+      SetDoseUnits(DoseUnitsType::Gy);
+      break;
+    case 1:
+      SetDoseUnits(DoseUnitsType::Relative);
+      break;
+    case -1:
+    default:
+      SetDoseUnits(DoseUnitsType::Unknown);
+      break;
+  }
+}
diff --git a/Isodose/Logic/vtkMRMLIsodoseNode.h b/Isodose/Logic/vtkMRMLIsodoseNode.h
index 4d3c79096..6bf5d4723 100644
--- a/Isodose/Logic/vtkMRMLIsodoseNode.h
+++ b/Isodose/Logic/vtkMRMLIsodoseNode.h
@@ -37,6 +37,7 @@ class vtkMRMLColorTableNode;
 class VTK_SLICER_ISODOSE_LOGIC_EXPORT vtkMRMLIsodoseNode : public vtkMRMLNode
 {
 public:
+  enum DoseUnitsType { Unknown = -1, Gy = 0, Relative = 1 };
   static const char* COLOR_TABLE_REFERENCE_ROLE;
 
   static vtkMRMLIsodoseNode *New();
@@ -94,12 +95,27 @@ class VTK_SLICER_ISODOSE_LOGIC_EXPORT vtkMRMLIsodoseNode : public vtkMRMLNode
   vtkSetMacro(ShowDoseVolumesOnly, bool);
   vtkBooleanMacro(ShowDoseVolumesOnly, bool);
 
+  /// Get/Set reference dose value
+  vtkGetMacro(ReferenceDoseValue, double);
+  vtkSetMacro(ReferenceDoseValue, double);
+
+  /// Get/Set dose units type
+  vtkGetMacro(DoseUnits, DoseUnitsType);
+  vtkSetMacro(DoseUnits, DoseUnitsType);
+
+  /// Get/Set relative representation flag
+  vtkGetMacro(RelativeRepresentationFlag, bool);
+  vtkSetMacro(RelativeRepresentationFlag, bool);
+  vtkBooleanMacro(RelativeRepresentationFlag, bool);
+
 protected:
   vtkMRMLIsodoseNode();
   ~vtkMRMLIsodoseNode();
   vtkMRMLIsodoseNode(const vtkMRMLIsodoseNode&);
   void operator=(const vtkMRMLIsodoseNode&);
 
+  void SetDoseUnits(int doseUnits);
+
 protected:
   /// State of Show isodose lines checkbox
   bool ShowIsodoseLines;
@@ -115,6 +131,16 @@ class VTK_SLICER_ISODOSE_LOGIC_EXPORT vtkMRMLIsodoseNode : public vtkMRMLNode
 
   /// State of Show dose volumes only checkbox
   bool ShowDoseVolumesOnly;
+
+  /// Type of dose units
+  DoseUnitsType DoseUnits;
+
+  /// Reference dose value
+  double ReferenceDoseValue;
+
+  /// Whether use relative isolevels representation
+  /// for absolute dose (Gy) and unknown units or not
+  bool RelativeRepresentationFlag;
 };
 
 #endif
diff --git a/Isodose/Logic/vtkSlicerIsodoseModuleLogic.cxx b/Isodose/Logic/vtkSlicerIsodoseModuleLogic.cxx
index 0a44b4670..6852fe047 100644
--- a/Isodose/Logic/vtkSlicerIsodoseModuleLogic.cxx
+++ b/Isodose/Logic/vtkSlicerIsodoseModuleLogic.cxx
@@ -64,9 +64,11 @@
 //----------------------------------------------------------------------------
 const char* DEFAULT_ISODOSE_COLOR_TABLE_FILE_NAME = "Isodose_ColorTable.ctbl";
 const char* DEFAULT_ISODOSE_COLOR_TABLE_NODE_NAME = "Isodose_ColorTable_Default";
+const char* RELATIVE_ISODOSE_COLOR_TABLE_NODE_NAME = "Isodose_ColorTable_Relative";
 const std::string vtkSlicerIsodoseModuleLogic::ISODOSE_MODEL_NODE_NAME_PREFIX = "IsodoseLevel_";
 const std::string vtkSlicerIsodoseModuleLogic::ISODOSE_PARAMETER_SET_BASE_NAME_PREFIX = "IsodoseParameterSet_";
 const std::string vtkSlicerIsodoseModuleLogic::ISODOSE_ROOT_HIERARCHY_NAME_POSTFIX = "_IsodoseSurfaces";
+const std::string vtkSlicerIsodoseModuleLogic::ISODOSE_RELATIVE_ROOT_HIERARCHY_NAME_POSTFIX = "_RelativeIsodoseSurfaces";
 const std::string vtkSlicerIsodoseModuleLogic::ISODOSE_COLOR_TABLE_NODE_NAME_POSTFIX = "_IsodoseColorTable";
 
 //----------------------------------------------------------------------------
@@ -104,6 +106,7 @@ void vtkSlicerIsodoseModuleLogic::SetMRMLSceneInternal(vtkMRMLScene* newScene)
   if (isodoseColorTableNode)
   {
     vtkSlicerIsodoseModuleLogic::CreateDefaultDoseColorTable(newScene);
+    vtkSlicerIsodoseModuleLogic::CreateRelativeDoseColorTable(newScene);
   }
   else
   {
@@ -238,10 +241,8 @@ vtkIdType vtkSlicerIsodoseModuleLogic::GetIsodoseFolderItemID(vtkMRMLNode* node)
 
   std::vector<vtkIdType> doseChildItemIDs;
   shNode->GetItemChildren(doseShItemID, doseChildItemIDs, false);
-  std::vector<vtkIdType>::iterator childIt;
-  for (childIt=doseChildItemIDs.begin(); childIt!=doseChildItemIDs.end(); ++childIt)
+  for (vtkIdType childItemID : doseChildItemIDs)
   {
-    vtkIdType childItemID = (*childIt);
     std::string childItemName = shNode->GetItemName(childItemID);
     std::string childItemNamePostfix = childItemName.substr(childItemName.size() - ISODOSE_ROOT_HIERARCHY_NAME_POSTFIX.size());
     if (!childItemNamePostfix.compare(ISODOSE_ROOT_HIERARCHY_NAME_POSTFIX))
@@ -284,14 +285,60 @@ vtkMRMLColorTableNode* vtkSlicerIsodoseModuleLogic::GetDefaultIsodoseColorTable(
   //colorTableNode->SetAttribute("Category", vtkSlicerRtCommon::SLICERRT_EXTENSION_NAME);
 
   colorTableNode->NamesInitialisedOn();
-  colorTableNode->SetNumberOfColors(6);
-  colorTableNode->GetLookupTable()->SetTableRange(0,5);
+  colorTableNode->SetNumberOfColors(7);
+  colorTableNode->GetLookupTable()->SetTableRange(0,6);
   colorTableNode->AddColor("5", 0, 1, 0, 0.2);
   colorTableNode->AddColor("10", 0.5, 1, 0, 0.2);
   colorTableNode->AddColor("15", 1, 1, 0, 0.2);
   colorTableNode->AddColor("20", 1, 0.66, 0, 0.2);
   colorTableNode->AddColor("25", 1, 0.33, 0, 0.2);
   colorTableNode->AddColor("30", 1, 0, 0, 0.2);
+  colorTableNode->AddColor("35", 221./255., 18./255., 123./255., 0.2);
+  colorTableNode->SaveWithSceneOff();
+  
+  scene->AddNode(colorTableNode);
+  return colorTableNode;
+}
+
+//------------------------------------------------------------------------------
+vtkMRMLColorTableNode* vtkSlicerIsodoseModuleLogic::GetRelativeIsodoseColorTable(vtkMRMLScene* scene)
+{
+  if (!scene)
+  {
+    vtkGenericWarningMacro("vtkSlicerIsodoseModuleLogic::GetRelativeIsodoseColorTable: Invalid MRML scene");
+    return nullptr;
+  }
+
+  // Check if default color table node already exists
+  vtkSmartPointer<vtkCollection> relativeIsodoseColorTableNodes = vtkSmartPointer<vtkCollection>::Take(
+    scene->GetNodesByName(RELATIVE_ISODOSE_COLOR_TABLE_NODE_NAME) );
+  if (relativeIsodoseColorTableNodes->GetNumberOfItems() > 0)
+  {
+    if (relativeIsodoseColorTableNodes->GetNumberOfItems() != 1)
+    {
+      vtkWarningWithObjectMacro(scene, "GetRelativeIsodoseColorTable: Multiple default isodose color table nodes found");
+    }
+
+    vtkMRMLColorTableNode* isodoseColorTableNode = vtkMRMLColorTableNode::SafeDownCast(relativeIsodoseColorTableNodes->GetItemAsObject(0));
+    return isodoseColorTableNode;
+  }
+
+  // Create default isodose color table if does not yet exist
+  vtkNew<vtkMRMLColorTableNode> colorTableNode;
+  colorTableNode->SetName(RELATIVE_ISODOSE_COLOR_TABLE_NODE_NAME);
+  colorTableNode->SetTypeToUser();
+  colorTableNode->SetSingletonTag(RELATIVE_ISODOSE_COLOR_TABLE_NODE_NAME);
+  //colorTableNode->SetAttribute("Category", vtkSlicerRtCommon::SLICERRT_EXTENSION_NAME);
+
+  colorTableNode->NamesInitialisedOn();
+  colorTableNode->SetNumberOfColors(5);
+  colorTableNode->GetLookupTable()->SetTableRange(0,4);
+
+  colorTableNode->AddColor("80", 108./255., 0., 208./255., 0.2);
+  colorTableNode->AddColor("90", 0., 147./255., 221./255., 0.2);
+  colorTableNode->AddColor("100", 1., 1., 0., 0.2);
+  colorTableNode->AddColor("105", 1., 0.5, 0., 0.2);
+  colorTableNode->AddColor("110", 1., 0., 0., 0.2);
   colorTableNode->SaveWithSceneOff();
   
   scene->AddNode(colorTableNode);
@@ -390,6 +437,52 @@ vtkMRMLColorTableNode* vtkSlicerIsodoseModuleLogic::CreateDefaultDoseColorTable(
   return defaultDoseColorTable;
 }
 
+//------------------------------------------------------------------------------
+vtkMRMLColorTableNode* vtkSlicerIsodoseModuleLogic::CreateRelativeDoseColorTable(vtkMRMLScene* scene)
+{
+  if (!scene)
+  {
+    vtkGenericWarningMacro("vtkSlicerIsodoseModuleLogic::CreateRelativeDoseColorTable: Invalid MRML scene");
+    return nullptr;
+  }
+
+  // Check if default color table node already exists
+  vtkSmartPointer<vtkCollection> relativeDoseColorTableNodes = vtkSmartPointer<vtkCollection>::Take(
+    scene->GetNodesByName(vtkSlicerRtCommon::RELATIVE_DOSE_COLOR_TABLE_NAME) );
+  if (relativeDoseColorTableNodes->GetNumberOfItems() > 0)
+  {
+    if (relativeDoseColorTableNodes->GetNumberOfItems() != 1)
+    {
+      vtkWarningWithObjectMacro(scene, "CreateRelativeDoseColorTable: Multiple relative dose color table nodes found");
+    }
+
+    vtkMRMLColorTableNode* doseColorTable = vtkMRMLColorTableNode::SafeDownCast(relativeDoseColorTableNodes->GetItemAsObject(0));
+    return doseColorTable;
+  }
+
+  // Create relative dose color table if does not yet exist
+  vtkMRMLColorTableNode* relativeIsodoseColorTable = vtkSlicerIsodoseModuleLogic::GetRelativeIsodoseColorTable(scene);
+  if (!relativeIsodoseColorTable)
+  {
+    vtkErrorWithObjectMacro(scene, "CreateRelativeDoseColorTable: Unable to access relative isodose color table");
+    return nullptr;
+  }
+
+  vtkSmartPointer<vtkMRMLColorTableNode> relativeDoseColorTable = vtkSmartPointer<vtkMRMLColorTableNode>::New();
+  relativeDoseColorTable->SetName(vtkSlicerRtCommon::RELATIVE_DOSE_COLOR_TABLE_NAME);
+  relativeDoseColorTable->SetTypeToFile();
+  relativeDoseColorTable->SetSingletonTag(vtkSlicerRtCommon::RELATIVE_DOSE_COLOR_TABLE_NAME);
+  //relativeDoseColorTable->SetAttribute("Category", vtkSlicerRtCommon::SLICERRT_EXTENSION_NAME);
+  relativeDoseColorTable->SetNumberOfColors(256);
+  relativeDoseColorTable->SaveWithSceneOff();
+
+  // Create dose color table by stretching the isodose color table
+  vtkSlicerRtCommon::StretchDiscreteColorTable(relativeIsodoseColorTable, relativeDoseColorTable);
+
+  scene->AddNode(relativeDoseColorTable);
+  return relativeDoseColorTable;
+}
+
 //------------------------------------------------------------------------------
 vtkMRMLColorTableNode* vtkSlicerIsodoseModuleLogic::SetupColorTableNodeForDoseVolumeNode(vtkMRMLScalarVolumeNode* doseVolumeNode)
 {
@@ -447,36 +540,86 @@ void vtkSlicerIsodoseModuleLogic::SetNumberOfIsodoseLevels(vtkMRMLIsodoseNode* p
   colorTableNode->SetNumberOfColors(newNumberOfColors);
   colorTableNode->GetLookupTable()->SetTableRange(0, newNumberOfColors-1);
 
-  // Set the default colors in case the number of colors was less than that in the default table
-  for (int colorIndex=currentNumberOfColors; colorIndex<newNumberOfColors; ++colorIndex)
+  vtkMRMLIsodoseNode::DoseUnitsType doseUnits = parameterNode->GetDoseUnits();
+
+  bool relativeFlag = false;
+  if (parameterNode->GetRelativeRepresentationFlag() 
+    && (doseUnits == vtkMRMLIsodoseNode::Gy
+    || doseUnits == vtkMRMLIsodoseNode::Unknown))
+  {
+    relativeFlag = true;
+  }
+  else if (doseUnits == vtkMRMLIsodoseNode::Relative)
   {
-    switch (colorIndex)
+    relativeFlag = true;
+  }
+
+  if (!relativeFlag) // absolute values
+  {
+    // Set the default colors in case the number of colors was less than that in the default table
+    for (int colorIndex=currentNumberOfColors; colorIndex<newNumberOfColors; ++colorIndex)
+    {
+      switch (colorIndex)
+      {
+      case 0:
+        colorTableNode->SetColor(colorIndex, "5", 0, 1, 0, 0.2);
+        break;
+      case 1:
+        colorTableNode->SetColor(colorIndex, "10", 0.5, 1, 0, 0.2);
+        break;
+      case 2:
+        colorTableNode->SetColor(colorIndex, "15", 1, 1, 0, 0.2);
+        break;
+      case 3:
+        colorTableNode->SetColor(colorIndex, "20", 1, 0.66, 0, 0.2);
+        break;
+      case 4:
+        colorTableNode->SetColor(colorIndex, "25", 1, 0.33, 0, 0.2);
+        break;
+      case 5:
+        colorTableNode->SetColor(colorIndex, "30", 1, 0, 0, 0.2);
+        break;
+      case 6:
+        colorTableNode->SetColor(colorIndex, "35", 221./255., 18./255., 123./255., 0.2);
+        break;
+      }
+    }
+    // Add colors with index 7 and higher with default gray color
+    for (int colorIndex=7; colorIndex<newNumberOfColors; ++colorIndex)
     {
-    case 0:
-      colorTableNode->SetColor(colorIndex, "5", 0, 1, 0, 0.2);
-      break;
-    case 1:
-      colorTableNode->SetColor(colorIndex, "10", 0.5, 1, 0, 0.2);
-      break;
-    case 2:
-      colorTableNode->SetColor(colorIndex, "15", 1, 1, 0, 0.2);
-      break;
-    case 3:
-      colorTableNode->SetColor(colorIndex, "20", 1, 0.66, 0, 0.2);
-      break;
-    case 4:
-      colorTableNode->SetColor(colorIndex, "25", 1, 0.33, 0, 0.2);
-      break;
-    case 5:
-      colorTableNode->SetColor(colorIndex, "30", 1, 0, 0, 0.2);
-      break;
+      colorTableNode->SetColor(colorIndex,
+        vtkSlicerRtCommon::COLOR_VALUE_INVALID[0], vtkSlicerRtCommon::COLOR_VALUE_INVALID[1], vtkSlicerRtCommon::COLOR_VALUE_INVALID[2], 0.2);
     }
   }
-  // Add colors with index 6 and higher with default gray color
-  for (int colorIndex=6; colorIndex<newNumberOfColors; ++colorIndex)
+  else // relative
   {
-    colorTableNode->SetColor(colorIndex,
-      vtkSlicerRtCommon::COLOR_VALUE_INVALID[0], vtkSlicerRtCommon::COLOR_VALUE_INVALID[1], vtkSlicerRtCommon::COLOR_VALUE_INVALID[2], 0.2);
+    for (int colorIndex=currentNumberOfColors; colorIndex<newNumberOfColors; ++colorIndex)
+    {
+      switch (colorIndex)
+      {
+      case 0:
+        colorTableNode->SetColor(colorIndex, "80", 108./255., 0., 208./255., 0.2);
+        break;
+      case 1:
+        colorTableNode->SetColor(colorIndex, "90", 0., 147./255., 221./255., 0.2);
+        break;
+      case 2:
+        colorTableNode->SetColor(colorIndex, "100", 1., 1., 0., 0.2);
+        break;
+      case 3:
+        colorTableNode->SetColor(colorIndex, "105", 1., 0.5, 0., 0.2);
+        break;
+      case 4:
+        colorTableNode->SetColor(colorIndex, "110", 1., 0., 0., 0.2);
+        break;
+      }
+    }
+    // Add colors with index 5 and higher with default gray color
+    for (int colorIndex=5; colorIndex<newNumberOfColors; ++colorIndex)
+    {
+      colorTableNode->SetColor(colorIndex,
+        vtkSlicerRtCommon::COLOR_VALUE_INVALID[0], vtkSlicerRtCommon::COLOR_VALUE_INVALID[1], vtkSlicerRtCommon::COLOR_VALUE_INVALID[2], 0.2);
+    }
   }
 
   // Something messes up the category, it needs to be set back to SlicerRT
@@ -523,8 +666,25 @@ void vtkSlicerIsodoseModuleLogic::CreateIsodoseSurfaces(vtkMRMLIsodoseNode* para
     shNode->RemoveItem(isodoseFolderItemID, true, true);
   }
 
+  // Check if that absolute of relative values
+  bool relativeFlag = false;
+  vtkMRMLIsodoseNode::DoseUnitsType doseUnits = parameterNode->GetDoseUnits();
+  if (parameterNode->GetRelativeRepresentationFlag() 
+    && (doseUnits == vtkMRMLIsodoseNode::Gy
+    || doseUnits == vtkMRMLIsodoseNode::Unknown))
+  {
+    relativeFlag = true;
+  }
+  else if (doseUnits == vtkMRMLIsodoseNode::Relative)
+  {
+    relativeFlag = true;
+  }
+  std::string isodoseName = relativeFlag ? 
+    vtkSlicerIsodoseModuleLogic::ISODOSE_RELATIVE_ROOT_HIERARCHY_NAME_POSTFIX :
+    vtkSlicerIsodoseModuleLogic::ISODOSE_ROOT_HIERARCHY_NAME_POSTFIX;
+
   // Setup isodose subject hierarchy folder
-  std::string isodoseFolderName = std::string(doseVolumeNode->GetName()) + vtkSlicerIsodoseModuleLogic::ISODOSE_ROOT_HIERARCHY_NAME_POSTFIX;
+  std::string isodoseFolderName = std::string(doseVolumeNode->GetName()) + isodoseName;
   isodoseFolderItemID = shNode->CreateFolderItem(doseShItemID, isodoseFolderName);
 
   // Get color table
@@ -535,6 +695,28 @@ void vtkSlicerIsodoseModuleLogic::CreateIsodoseSurfaces(vtkMRMLIsodoseNode* para
     return;
   }
 
+  // Check that range is valid for dose and relative dose
+  // Set dose unit name
+  std::string doseUnitName = "Gy";
+  switch (doseUnits)
+  {
+  case vtkMRMLIsodoseNode::Gy:
+    break;
+  case vtkMRMLIsodoseNode::Relative:
+    doseUnitName = "%";
+    break;
+  case vtkMRMLIsodoseNode::Unknown:
+  default:
+    doseUnitName = "MU";
+    break;
+  }
+
+  // force percentage dose units for relative isodose representation
+  if (relativeFlag)
+  {
+    doseUnitName = "%";
+  }
+  
   // Progress
   int progressStepCount = colorTableNode->GetNumberOfColors() + 1 /* reslice step */;
   int currentProgressStep = 0;
@@ -577,12 +759,23 @@ void vtkSlicerIsodoseModuleLogic::CreateIsodoseSurfaces(vtkMRMLIsodoseNode* para
   double progress = (double)(currentProgressStep) / (double)progressStepCount;
   this->InvokeEvent(vtkSlicerRtCommon::ProgressUpdated, (void*)&progress);
 
+  // reference value for relative representation
+  double referenceValue = parameterNode->GetReferenceDoseValue();
+
   // Create isodose surfaces
   for (int i = 0; i < colorTableNode->GetNumberOfColors(); i++)
   {
     double val[6] = {0.0, 0.0, 0.0, 0.0, 0.0, 0.0};
     const char* strIsoLevel = colorTableNode->GetColorName(i);
     double isoLevel = vtkVariant(strIsoLevel).ToDouble();
+    // change isoLevel value for relative representation
+    if (relativeFlag)
+    {
+      if (doseUnits != vtkMRMLIsodoseNode::Relative)
+      {
+        isoLevel = isoLevel * referenceValue / 100.;
+      }
+    }
     colorTableNode->GetColor(i, val);
 
     vtkSmartPointer<vtkImageMarchingCubes> marchingCubes = vtkSmartPointer<vtkImageMarchingCubes>::New();
@@ -643,10 +836,6 @@ void vtkSlicerIsodoseModuleLogic::CreateIsodoseSurfaces(vtkMRMLIsodoseNode* para
       // Disable backface culling to make the back side of the model visible as well
       displayNode->SetBackfaceCulling(0);
 
-      // Get dose unit name
-      std::string doseUnitName = shNode->GetAttributeFromItemAncestor(
-        doseShItemID, vtkSlicerRtCommon::DICOMRTIMPORT_DOSE_UNIT_NAME_ATTRIBUTE_NAME, vtkMRMLSubjectHierarchyConstants::GetDICOMLevelStudy());
-
       vtkSmartPointer<vtkMRMLModelNode> isodoseModelNode = vtkSmartPointer<vtkMRMLModelNode>::New();
       std::string isodoseModelNodeName = vtkSlicerIsodoseModuleLogic::ISODOSE_MODEL_NODE_NAME_PREFIX + strIsoLevel + doseUnitName;
       isodoseModelNode->SetName(isodoseModelNodeName.c_str());
@@ -736,8 +925,8 @@ void vtkSlicerIsodoseModuleLogic::UpdateDoseColorTableFromIsodose(vtkMRMLIsodose
   int minDoseInDefaultIsodoseLevels = vtkVariant(isodoseColorTableNode->GetColorName(0)).ToInt();
   int maxDoseInDefaultIsodoseLevels = vtkVariant(isodoseColorTableNode->GetColorName(isodoseColorTableNode->GetNumberOfColors()-1)).ToInt();
 
-  doseVolumeDisplayNode->AutoWindowLevelOff();
   doseVolumeDisplayNode->SetWindowLevelMinMax(minDoseInDefaultIsodoseLevels, maxDoseInDefaultIsodoseLevels);
+  doseVolumeDisplayNode->AutoWindowLevelOn();
 
   // Get dose grid scaling
   vtkMRMLSubjectHierarchyNode* shNode = vtkMRMLSubjectHierarchyNode::GetSubjectHierarchyNode(scene);
diff --git a/Isodose/Logic/vtkSlicerIsodoseModuleLogic.h b/Isodose/Logic/vtkSlicerIsodoseModuleLogic.h
index 0ed2e34c3..bd9b035af 100644
--- a/Isodose/Logic/vtkSlicerIsodoseModuleLogic.h
+++ b/Isodose/Logic/vtkSlicerIsodoseModuleLogic.h
@@ -47,6 +47,7 @@ class VTK_SLICER_ISODOSE_LOGIC_EXPORT vtkSlicerIsodoseModuleLogic : public vtkSl
   static const std::string ISODOSE_MODEL_NODE_NAME_PREFIX;
   static const std::string ISODOSE_PARAMETER_SET_BASE_NAME_PREFIX;
   static const std::string ISODOSE_ROOT_HIERARCHY_NAME_POSTFIX;
+  static const std::string ISODOSE_RELATIVE_ROOT_HIERARCHY_NAME_POSTFIX;
   static const std::string ISODOSE_COLOR_TABLE_NODE_NAME_POSTFIX;
 
 public:
@@ -75,10 +76,16 @@ class VTK_SLICER_ISODOSE_LOGIC_EXPORT vtkSlicerIsodoseModuleLogic : public vtkSl
   /// Creates default isodose color table. Gets and returns if already exists
   static vtkMRMLColorTableNode* GetDefaultIsodoseColorTable(vtkMRMLScene* scene);
 
-  /// Creates default dose color table (which is the default isodose color table stretched.
+  /// Creates relative isodose color table. Gets and returns if already exists
+  static vtkMRMLColorTableNode* GetRelativeIsodoseColorTable(vtkMRMLScene *scene);
+
+  /// Creates default dose color table (which is the default isodose color table stretched).
   /// Gets and returns if already exists
   static vtkMRMLColorTableNode* CreateDefaultDoseColorTable(vtkMRMLScene *scene);
 
+  /// Creates relative dose color table. Gets and returns if already exists
+  static vtkMRMLColorTableNode* CreateRelativeDoseColorTable(vtkMRMLScene *scene);
+
 protected:
   /// Loads default isodose color table from the supplied color table file
   /// \return The loaded color table node if loading succeeded, nullptr otherwise
diff --git a/Isodose/Resources/UI/qSlicerIsodoseModule.ui b/Isodose/Resources/UI/qSlicerIsodoseModule.ui
index 214ffee4c..ccd20758d 100644
--- a/Isodose/Resources/UI/qSlicerIsodoseModule.ui
+++ b/Isodose/Resources/UI/qSlicerIsodoseModule.ui
@@ -6,29 +6,14 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>402</width>
-    <height>528</height>
+    <width>373</width>
+    <height>604</height>
    </rect>
   </property>
   <property name="windowTitle">
    <string>Isodose</string>
   </property>
-  <layout class="QGridLayout" name="gridLayout">
-   <property name="leftMargin">
-    <number>4</number>
-   </property>
-   <property name="topMargin">
-    <number>4</number>
-   </property>
-   <property name="rightMargin">
-    <number>4</number>
-   </property>
-   <property name="bottomMargin">
-    <number>4</number>
-   </property>
-   <property name="spacing">
-    <number>4</number>
-   </property>
+  <layout class="QGridLayout" name="gridLayout_6">
    <item row="0" column="0">
     <layout class="QHBoxLayout" name="horizontalLayout">
      <property name="spacing">
@@ -63,41 +48,8 @@
      <property name="text">
       <string>Input</string>
      </property>
-     <layout class="QGridLayout" name="gridLayout_2">
-      <property name="leftMargin">
-       <number>4</number>
-      </property>
-      <property name="topMargin">
-       <number>4</number>
-      </property>
-      <property name="rightMargin">
-       <number>4</number>
-      </property>
-      <property name="bottomMargin">
-       <number>4</number>
-      </property>
-      <property name="spacing">
-       <number>4</number>
-      </property>
-      <item row="0" column="2">
-       <widget class="qMRMLNodeComboBox" name="MRMLNodeComboBox_DoseVolume">
-        <property name="enabled">
-         <bool>false</bool>
-        </property>
-        <property name="nodeTypes">
-         <stringlist>
-          <string>vtkMRMLScalarVolumeNode</string>
-         </stringlist>
-        </property>
-        <property name="addEnabled">
-         <bool>false</bool>
-        </property>
-        <property name="renameEnabled">
-         <bool>true</bool>
-        </property>
-       </widget>
-      </item>
-      <item row="1" column="2">
+     <layout class="QGridLayout" name="gridLayout_5">
+      <item row="1" column="1">
        <widget class="QLabel" name="label_NotDoseVolumeWarning">
         <property name="palette">
          <palette>
@@ -237,6 +189,15 @@
              </color>
             </brush>
            </colorrole>
+           <colorrole role="PlaceholderText">
+            <brush brushstyle="NoBrush">
+             <color alpha="128">
+              <red>0</red>
+              <green>0</green>
+              <blue>0</blue>
+             </color>
+            </brush>
+           </colorrole>
           </active>
           <inactive>
            <colorrole role="WindowText">
@@ -374,6 +335,15 @@
              </color>
             </brush>
            </colorrole>
+           <colorrole role="PlaceholderText">
+            <brush brushstyle="NoBrush">
+             <color alpha="128">
+              <red>0</red>
+              <green>0</green>
+              <blue>0</blue>
+             </color>
+            </brush>
+           </colorrole>
           </inactive>
           <disabled>
            <colorrole role="WindowText">
@@ -511,11 +481,21 @@
              </color>
             </brush>
            </colorrole>
+           <colorrole role="PlaceholderText">
+            <brush brushstyle="NoBrush">
+             <color alpha="128">
+              <red>0</red>
+              <green>0</green>
+              <blue>0</blue>
+             </color>
+            </brush>
+           </colorrole>
           </disabled>
          </palette>
         </property>
         <property name="font">
          <font>
+          <family>Liberation Sans</family>
           <pointsize>8</pointsize>
           <weight>75</weight>
           <bold>true</bold>
@@ -526,21 +506,25 @@
         </property>
        </widget>
       </item>
-      <item row="3" column="0" colspan="3">
-       <widget class="qMRMLColorTableView" name="tableView_IsodoseLevels">
-        <attribute name="horizontalHeaderVisible">
-         <bool>true</bool>
-        </attribute>
-       </widget>
-      </item>
       <item row="0" column="1">
-       <widget class="QLabel" name="label_2">
-        <property name="text">
-         <string>Dose volume:</string>
+       <widget class="qMRMLNodeComboBox" name="MRMLNodeComboBox_DoseVolume">
+        <property name="enabled">
+         <bool>false</bool>
+        </property>
+        <property name="nodeTypes">
+         <stringlist>
+          <string>vtkMRMLScalarVolumeNode</string>
+         </stringlist>
+        </property>
+        <property name="addEnabled">
+         <bool>false</bool>
+        </property>
+        <property name="renameEnabled">
+         <bool>true</bool>
         </property>
        </widget>
       </item>
-      <item row="2" column="2">
+      <item row="3" column="1">
        <widget class="QSpinBox" name="spinBox_NumberOfLevels">
         <property name="alignment">
          <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
@@ -553,14 +537,14 @@
         </property>
        </widget>
       </item>
-      <item row="2" column="1">
-       <widget class="QLabel" name="label_4">
+      <item row="0" column="0">
+       <widget class="QLabel" name="label_2">
         <property name="text">
-         <string>Number of iso levels:</string>
+         <string>Dose volume:</string>
         </property>
        </widget>
       </item>
-      <item row="1" column="1">
+      <item row="1" column="0">
        <widget class="QCheckBox" name="checkBox_ShowDoseVolumesOnly">
         <property name="text">
          <string>Show dose volumes only</string>
@@ -570,9 +554,132 @@
         </property>
        </widget>
       </item>
+      <item row="4" column="0" colspan="2">
+       <widget class="qMRMLColorTableView" name="tableView_IsodoseLevels">
+        <attribute name="horizontalHeaderVisible">
+         <bool>true</bool>
+        </attribute>
+       </widget>
+      </item>
+      <item row="3" column="0">
+       <widget class="QLabel" name="label_4">
+        <property name="text">
+         <string>Number of iso levels:</string>
+        </property>
+       </widget>
+      </item>
+      <item row="2" column="0" colspan="2">
+       <widget class="QGroupBox" name="groupBox_RelativeIsolevels">
+        <property name="enabled">
+         <bool>true</bool>
+        </property>
+        <property name="toolTip">
+         <string>Show isolevels as a percentage from the prescribed dose</string>
+        </property>
+        <property name="title">
+         <string>Relative isolevels of dose</string>
+        </property>
+        <property name="checkable">
+         <bool>true</bool>
+        </property>
+        <property name="checked">
+         <bool>true</bool>
+        </property>
+        <layout class="QGridLayout" name="gridLayout_2">
+         <item row="0" column="0">
+          <layout class="QHBoxLayout" name="horizontalLayout_4">
+           <item>
+            <widget class="QLabel" name="label_DoseValue">
+             <property name="enabled">
+              <bool>true</bool>
+             </property>
+             <property name="toolTip">
+              <string>Prescribed or reference dose value</string>
+             </property>
+             <property name="text">
+              <string>Dose value:</string>
+             </property>
+            </widget>
+           </item>
+           <item>
+            <widget class="ctkSliderWidget" name="sliderWidget_ReferenceDose">
+             <property name="enabled">
+              <bool>true</bool>
+             </property>
+            </widget>
+           </item>
+          </layout>
+         </item>
+         <item row="1" column="0">
+          <layout class="QHBoxLayout" name="horizontalLayout_2">
+           <item>
+            <widget class="QLabel" name="label_PercentageOfMaximumVolumeDose">
+             <property name="text">
+              <string>Percentage of maximum volume dose:</string>
+             </property>
+            </widget>
+           </item>
+           <item>
+            <widget class="QLabel" name="label_PercentageOfMaxVolumeDose">
+             <property name="text">
+              <string/>
+             </property>
+            </widget>
+           </item>
+          </layout>
+         </item>
+        </layout>
+       </widget>
+      </item>
      </layout>
     </widget>
    </item>
+   <item row="2" column="0">
+    <layout class="QHBoxLayout" name="horizontalLayout_3">
+     <item>
+      <spacer name="horizontalSpacer_2">
+       <property name="orientation">
+        <enum>Qt::Horizontal</enum>
+       </property>
+       <property name="sizeHint" stdset="0">
+        <size>
+         <width>40</width>
+         <height>20</height>
+        </size>
+       </property>
+      </spacer>
+     </item>
+     <item>
+      <widget class="QPushButton" name="pushButton_Apply">
+       <property name="enabled">
+        <bool>false</bool>
+       </property>
+       <property name="font">
+        <font>
+         <weight>75</weight>
+         <bold>true</bold>
+        </font>
+       </property>
+       <property name="text">
+        <string>Generate isodose</string>
+       </property>
+      </widget>
+     </item>
+     <item>
+      <spacer name="horizontalSpacer">
+       <property name="orientation">
+        <enum>Qt::Horizontal</enum>
+       </property>
+       <property name="sizeHint" stdset="0">
+        <size>
+         <width>40</width>
+         <height>20</height>
+        </size>
+       </property>
+      </spacer>
+     </item>
+    </layout>
+   </item>
    <item row="3" column="0">
     <widget class="ctkCollapsibleButton" name="CollapsibleButton_DisplayOptions">
      <property name="text">
@@ -655,55 +762,20 @@
      </layout>
     </widget>
    </item>
-   <item row="2" column="0">
-    <layout class="QHBoxLayout" name="horizontalLayout_3">
-     <item>
-      <spacer name="horizontalSpacer_2">
-       <property name="orientation">
-        <enum>Qt::Horizontal</enum>
-       </property>
-       <property name="sizeHint" stdset="0">
-        <size>
-         <width>40</width>
-         <height>20</height>
-        </size>
-       </property>
-      </spacer>
-     </item>
-     <item>
-      <widget class="QPushButton" name="pushButton_Apply">
-       <property name="enabled">
-        <bool>false</bool>
-       </property>
-       <property name="font">
-        <font>
-         <weight>75</weight>
-         <bold>true</bold>
-        </font>
-       </property>
-       <property name="text">
-        <string>Generate isodose</string>
-       </property>
-      </widget>
-     </item>
-     <item>
-      <spacer name="horizontalSpacer">
-       <property name="orientation">
-        <enum>Qt::Horizontal</enum>
-       </property>
-       <property name="sizeHint" stdset="0">
-        <size>
-         <width>40</width>
-         <height>20</height>
-        </size>
-       </property>
-      </spacer>
-     </item>
-    </layout>
-   </item>
   </layout>
  </widget>
  <customwidgets>
+  <customwidget>
+   <class>ctkCollapsibleButton</class>
+   <extends>QWidget</extends>
+   <header>ctkCollapsibleButton.h</header>
+   <container>1</container>
+  </customwidget>
+  <customwidget>
+   <class>ctkSliderWidget</class>
+   <extends>QWidget</extends>
+   <header>ctkSliderWidget.h</header>
+  </customwidget>
   <customwidget>
    <class>qMRMLColorTableView</class>
    <extends>QTableView</extends>
@@ -721,12 +793,6 @@
    <header>qSlicerWidget.h</header>
    <container>1</container>
   </customwidget>
-  <customwidget>
-   <class>ctkCollapsibleButton</class>
-   <extends>QWidget</extends>
-   <header>ctkCollapsibleButton.h</header>
-   <container>1</container>
-  </customwidget>
  </customwidgets>
  <resources/>
  <connections>
@@ -762,5 +828,69 @@
     </hint>
    </hints>
   </connection>
+  <connection>
+   <sender>groupBox_RelativeIsolevels</sender>
+   <signal>toggled(bool)</signal>
+   <receiver>label_DoseValue</receiver>
+   <slot>setEnabled(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>186</x>
+     <y>173</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>65</x>
+     <y>170</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>groupBox_RelativeIsolevels</sender>
+   <signal>toggled(bool)</signal>
+   <receiver>sliderWidget_ReferenceDose</receiver>
+   <slot>setEnabled(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>186</x>
+     <y>173</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>223</x>
+     <y>170</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>groupBox_RelativeIsolevels</sender>
+   <signal>toggled(bool)</signal>
+   <receiver>label_PercentageOfMaximumVolumeDose</receiver>
+   <slot>setEnabled(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>186</x>
+     <y>173</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>142</x>
+     <y>198</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>groupBox_RelativeIsolevels</sender>
+   <signal>toggled(bool)</signal>
+   <receiver>label_PercentageOfMaxVolumeDose</receiver>
+   <slot>setEnabled(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>186</x>
+     <y>173</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>301</x>
+     <y>198</y>
+    </hint>
+   </hints>
+  </connection>
  </connections>
 </ui>
diff --git a/Isodose/qSlicerIsodoseModuleWidget.cxx b/Isodose/qSlicerIsodoseModuleWidget.cxx
index 459bef266..1cb0af74d 100644
--- a/Isodose/qSlicerIsodoseModuleWidget.cxx
+++ b/Isodose/qSlicerIsodoseModuleWidget.cxx
@@ -115,11 +115,9 @@ qSlicerIsodoseModuleWidgetPrivate::qSlicerIsodoseModuleWidgetPrivate(qSlicerIsod
   this->ScalarBarWidget2DGreen->SetScalarBarActor(this->ScalarBarActor2DGreen);
   this->ScalarBarWidgets.push_back(this->ScalarBarWidget2DGreen);
 
-  for (std::vector<vtkScalarBarWidget*>::iterator it = this->ScalarBarWidgets.begin();
-    it != this->ScalarBarWidgets.end(); ++it)
+  for (vtkScalarBarWidget* scalarBarWidget : ScalarBarWidgets)
   {
-    vtkSlicerRTScalarBarActor* actor = vtkSlicerRTScalarBarActor::SafeDownCast(
-      (*it)->GetScalarBarActor() );
+    vtkSlicerRTScalarBarActor* actor = vtkSlicerRTScalarBarActor::SafeDownCast( scalarBarWidget->GetScalarBarActor() );
     actor->SetOrientationToVertical();
     actor->SetNumberOfLabels(0);
     actor->SetMaximumNumberOfColors(0);
@@ -206,6 +204,7 @@ void qSlicerIsodoseModuleWidget::setMRMLScene(vtkMRMLScene* scene)
   this->Superclass::setMRMLScene(scene);
 
   qvtkReconnect( d->logic(), scene, vtkMRMLScene::EndImportEvent, this, SLOT(onSceneImportedEvent()) );
+  qvtkReconnect( d->logic(), scene, vtkMRMLScene::EndCloseEvent, this, SLOT(onSceneClosedEvent()) );
 
   // Find parameters node or create it if there is no one in the scene
   if (scene && d->MRMLNodeComboBox_ParameterSet->currentNode() == nullptr)
@@ -217,7 +216,7 @@ void qSlicerIsodoseModuleWidget::setMRMLScene(vtkMRMLScene* scene)
     }
     else 
     {
-      vtkSmartPointer<vtkMRMLIsodoseNode> newNode = vtkSmartPointer<vtkMRMLIsodoseNode>::New();
+      vtkNew<vtkMRMLIsodoseNode> newNode;
       this->mrmlScene()->AddNode(newNode);
       this->setParameterNode(newNode);
     }
@@ -230,6 +229,12 @@ void qSlicerIsodoseModuleWidget::onSceneImportedEvent()
   this->onEnter();
 }
 
+//-----------------------------------------------------------------------------
+void qSlicerIsodoseModuleWidget::onSceneClosedEvent()
+{
+  //TODO: Hide colorbars if they are shown on slices and 3D.
+}
+
 //-----------------------------------------------------------------------------
 void qSlicerIsodoseModuleWidget::enter()
 {
@@ -296,7 +301,10 @@ void qSlicerIsodoseModuleWidget::updateWidgetFromMRML()
       this->setDoseVolumeNode(d->MRMLNodeComboBox_DoseVolume->currentNode());
     }
 
-    this->updateScalarBarsFromSelectedColorTable();
+    d->groupBox_RelativeIsolevels->setChecked(paramNode->GetRelativeRepresentationFlag());
+
+    //TODO: It causes a crash when switch from Volumes module to Isodose module
+//    this->updateScalarBarsFromSelectedColorTable();
 
     d->checkBox_Isoline->setChecked(paramNode->GetShowIsodoseLines());
     d->checkBox_Isosurface->setChecked(paramNode->GetShowIsodoseSurfaces());
@@ -336,6 +344,8 @@ void qSlicerIsodoseModuleWidget::setup()
   connect( d->checkBox_ScalarBar2D, SIGNAL(toggled(bool)), this, SLOT( setScalarBar2DVisibility(bool) ) );
 
   connect( d->pushButton_Apply, SIGNAL(clicked()), this, SLOT(applyClicked()) );
+  connect( d->groupBox_RelativeIsolevels, SIGNAL(toggled(bool)), this, SLOT(setRelativeIsolevelsFlag(bool)));
+  connect( d->sliderWidget_ReferenceDose, SIGNAL(valueChanged(double)), this, SLOT(setReferenceDoseValue(double)));
 
   d->pushButton_Apply->setMinimumSize(d->pushButton_Apply->sizeHint().width() + 8, d->pushButton_Apply->sizeHint().height() + 4);
 
@@ -430,6 +440,56 @@ void qSlicerIsodoseModuleWidget::setDoseVolumeNode(vtkMRMLNode* node)
   if (paramNode->GetDoseVolumeNode() && vtkSlicerRtCommon::IsDoseVolumeNode(paramNode->GetDoseVolumeNode()))
   {
     d->label_NotDoseVolumeWarning->setText("");
+
+    vtkMRMLSubjectHierarchyNode* shNode = vtkMRMLSubjectHierarchyNode::GetSubjectHierarchyNode(this->mrmlScene());
+    if (!shNode)
+    {
+      qCritical() << Q_FUNC_INFO << ": Failed to access subject hierarchy node";
+      return;
+    }
+
+    std::string doseUnitName("");
+    vtkIdType doseShItemID = shNode->GetItemByDataNode(paramNode->GetDoseVolumeNode());
+    if (doseShItemID != vtkMRMLSubjectHierarchyNode::INVALID_ITEM_ID)
+    {
+      doseUnitName = shNode->GetAttributeFromItemAncestor(
+        doseShItemID, vtkSlicerRtCommon::DICOMRTIMPORT_DOSE_UNIT_NAME_ATTRIBUTE_NAME, vtkMRMLSubjectHierarchyConstants::GetDICOMLevelStudy());
+    }
+
+    double valueRange[2];
+    vtkImageData* image = paramNode->GetDoseVolumeNode()->GetImageData();
+    image->GetScalarRange(valueRange);
+    if (!doseUnitName.compare("RELATIVE"))
+    {
+      paramNode->SetDoseUnits(vtkMRMLIsodoseNode::Relative);
+      paramNode->SetReferenceDoseValue(-1.);
+      d->sliderWidget_ReferenceDose->setEnabled(false);
+      d->groupBox_RelativeIsolevels->setEnabled(false);
+      d->sliderWidget_ReferenceDose->setSuffix("");
+    }
+    else if (!doseUnitName.compare("GY"))
+    {
+      paramNode->SetDoseUnits(vtkMRMLIsodoseNode::Gy);
+      paramNode->SetReferenceDoseValue(valueRange[1]);
+      d->groupBox_RelativeIsolevels->setEnabled(true);
+      d->sliderWidget_ReferenceDose->setEnabled(true);
+      d->sliderWidget_ReferenceDose->setMinimum(valueRange[0]);
+      d->sliderWidget_ReferenceDose->setMaximum(2. * valueRange[1]);
+      d->sliderWidget_ReferenceDose->setValue(0.87 * valueRange[1]);
+      d->sliderWidget_ReferenceDose->setSuffix(tr(" Gy"));
+    }
+    else
+    {
+      paramNode->SetDoseUnits(vtkMRMLIsodoseNode::Unknown);
+      paramNode->SetReferenceDoseValue(valueRange[1]);
+      d->groupBox_RelativeIsolevels->setEnabled(true);
+      d->sliderWidget_ReferenceDose->setEnabled(true);
+      d->sliderWidget_ReferenceDose->setMinimum(valueRange[0]);
+      d->sliderWidget_ReferenceDose->setMaximum(2. * valueRange[1]);
+      d->sliderWidget_ReferenceDose->setValue(0.87 * valueRange[1]);
+      d->sliderWidget_ReferenceDose->setSuffix("");
+      d->label_NotDoseVolumeWarning->setText(tr("Neither \"GY\" nor \"RELATIVE\""));
+    }
   }
   else
   {
@@ -525,6 +585,121 @@ void qSlicerIsodoseModuleWidget::showDoseVolumesOnlyCheckboxChanged(int aState)
   }
 }
 
+//-----------------------------------------------------------------------------
+void qSlicerIsodoseModuleWidget::setRelativeIsolevelsFlag(bool useRelativeIsolevels)
+{
+  Q_D(qSlicerIsodoseModuleWidget);
+
+  if (!this->mrmlScene())
+  {
+    qCritical() << Q_FUNC_INFO << ": Invalid scene";
+    return;
+  }
+
+  vtkMRMLIsodoseNode* paramNode = vtkMRMLIsodoseNode::SafeDownCast(d->MRMLNodeComboBox_ParameterSet->currentNode());
+  if (!paramNode)
+  {
+    return;
+  }
+
+  paramNode->DisableModifiedEventOn();
+  paramNode->SetRelativeRepresentationFlag(useRelativeIsolevels);
+  paramNode->DisableModifiedEventOff();
+
+  vtkMRMLIsodoseNode::DoseUnitsType doseUnits = paramNode->GetDoseUnits();
+  
+  // Get dose unit name and assemble scalar bar title
+  QString labelHeaderTitle = QObject::tr("Label");
+  switch (doseUnits)
+  {
+  case vtkMRMLIsodoseNode::Gy:
+  {
+    QString msg = useRelativeIsolevels ? QObject::tr("Relative Dose (%)") : QObject::tr("Dose (Gy)");
+    labelHeaderTitle = msg;
+  }
+    break;
+  case vtkMRMLIsodoseNode::Unknown:
+  {
+    QString msg = useRelativeIsolevels ? QObject::tr("Relative Units (%)") : QObject::tr("Units (MU)");
+    labelHeaderTitle = msg;
+  }
+    break;
+  case vtkMRMLIsodoseNode::Relative:
+    labelHeaderTitle = QObject::tr("Relative Dose (%)");
+    break;
+  default:
+    break;
+  }
+  d->tableView_IsodoseLevels->model()->setHeaderData( 1, Qt::Horizontal, labelHeaderTitle);
+
+  // Make sure the dose volume has an associated isodose color table node
+  vtkMRMLColorTableNode* selectedColorNode = (useRelativeIsolevels) ? 
+    d->logic()->GetRelativeIsodoseColorTable(this->mrmlScene())
+    :
+    d->logic()->GetDefaultIsodoseColorTable(this->mrmlScene());
+
+  // Show color table node associated to the dose volume
+  paramNode->DisableModifiedEventOn();
+  paramNode->SetAndObserveColorTableNode(selectedColorNode);
+  paramNode->DisableModifiedEventOff();
+
+  d->tableView_IsodoseLevels->setMRMLColorNode(selectedColorNode);
+  // Set current number of isodose levels
+  bool wasBlocked = d->spinBox_NumberOfLevels->blockSignals(true);
+  if (selectedColorNode)
+  {
+    d->spinBox_NumberOfLevels->setValue(selectedColorNode->GetNumberOfColors());
+
+    qvtkConnect(selectedColorNode, vtkCommand::ModifiedEvent,
+      this, SLOT(updateScalarBarsFromSelectedColorTable()));
+  }
+  else
+  {
+    d->spinBox_NumberOfLevels->setValue(0);
+  }
+  d->spinBox_NumberOfLevels->blockSignals(wasBlocked);
+  // Update scalar bars
+  this->updateScalarBarsFromSelectedColorTable();
+  // Update dose volume palette
+  d->logic()->UpdateDoseColorTableFromIsodose(paramNode);
+}
+
+//-----------------------------------------------------------------------------
+void qSlicerIsodoseModuleWidget::setReferenceDoseValue(double value)
+{
+  Q_D(qSlicerIsodoseModuleWidget);
+
+  vtkMRMLIsodoseNode* paramNode = vtkMRMLIsodoseNode::SafeDownCast(d->MRMLNodeComboBox_ParameterSet->currentNode());
+  if (!paramNode)
+  {
+    return;
+  }
+
+  if (d->sliderWidget_ReferenceDose->maximum() > 0.)
+  {
+    double percentage = 200. * value / d->sliderWidget_ReferenceDose->maximum();
+    d->label_PercentageOfMaxVolumeDose->setText(tr("%1 %").arg( percentage, 0, 'g', 4));
+  }
+  else
+  {
+    d->label_PercentageOfMaxVolumeDose->setText("");
+  }
+
+  paramNode->DisableModifiedEventOn();
+  switch (paramNode->GetDoseUnits())
+  {
+  case vtkMRMLIsodoseNode::Gy:
+  case vtkMRMLIsodoseNode::Unknown:
+    paramNode->SetReferenceDoseValue(value);
+    break;
+  case vtkMRMLIsodoseNode::Relative:
+  default:
+    paramNode->SetReferenceDoseValue(-1.);
+    break;
+  }
+  paramNode->DisableModifiedEventOff();
+}
+
 //-----------------------------------------------------------------------------
 QString qSlicerIsodoseModuleWidget::generateNewIsodoseLevel() const
 {
@@ -569,10 +744,8 @@ void qSlicerIsodoseModuleWidget::setIsolineVisibility(bool visible)
 
   std::vector<vtkIdType> childItemIDs;
   shNode->GetItemChildren(isdoseFolderItemID, childItemIDs, false);
-  std::vector<vtkIdType>::iterator childIt;
-  for (childIt=childItemIDs.begin(); childIt!=childItemIDs.end(); ++childIt)
+  for (vtkIdType childItemID : childItemIDs)
   {
-    vtkIdType childItemID = (*childIt);
     vtkMRMLModelNode* modelNode = vtkMRMLModelNode::SafeDownCast(shNode->GetItemDataNode(childItemID));
     modelNode->GetDisplayNode()->SetVisibility2D(visible);
   }
@@ -614,10 +787,8 @@ void qSlicerIsodoseModuleWidget::setIsosurfaceVisibility(bool visible)
 
   std::vector<vtkIdType> childItemIDs;
   shNode->GetItemChildren(isdoseFolderItemID, childItemIDs, false);
-  std::vector<vtkIdType>::iterator childIt;
-  for (childIt=childItemIDs.begin(); childIt!=childItemIDs.end(); ++childIt)
+  for (vtkIdType childItemID : childItemIDs)
   {
-    vtkIdType childItemID = (*childIt);
     vtkMRMLModelNode* modelNode = vtkMRMLModelNode::SafeDownCast(shNode->GetItemDataNode(childItemID));
     modelNode->GetDisplayNode()->SetVisibility(visible);
   }
@@ -800,26 +971,35 @@ void qSlicerIsodoseModuleWidget::updateScalarBarsFromSelectedColorTable()
 
   int newNumberOfColors = selectedColorNode->GetNumberOfColors();
 
+  vtkMRMLIsodoseNode::DoseUnitsType doseUnits = paramNode->GetDoseUnits();
+  bool relativeRepresentation = paramNode->GetRelativeRepresentationFlag();
+  
   // Get dose unit name and assemble scalar bar title
-  std::string doseUnitName("");
-  vtkIdType doseShItemID = shNode->GetItemByDataNode(doseVolumeNode);
-  if (doseShItemID != vtkMRMLSubjectHierarchyNode::INVALID_ITEM_ID)
+  std::string scalarBarTitle("Isolevels");
+  switch (doseUnits)
+  {
+  case vtkMRMLIsodoseNode::Gy:
   {
-    doseUnitName = shNode->GetAttributeFromItemAncestor(
-      doseShItemID, vtkSlicerRtCommon::DICOMRTIMPORT_DOSE_UNIT_NAME_ATTRIBUTE_NAME, vtkMRMLSubjectHierarchyConstants::GetDICOMLevelStudy());
+    const char* str = relativeRepresentation ? " (%)" : " (Gy)";
+    scalarBarTitle += std::string(str);
   }
-  std::string scalarBarTitle("Dose");
-  if (!doseUnitName.empty())
+    break;
+  case vtkMRMLIsodoseNode::Relative:
+    scalarBarTitle += std::string(" (%)");
+    break;
+  case vtkMRMLIsodoseNode::Unknown:
+  default:
   {
-    scalarBarTitle += " (" + doseUnitName + ")";
+    const char* str = relativeRepresentation ? " (%)" : " (MU)";
+    scalarBarTitle += std::string(str);
+  }
+    break;
   }
 
   // Update all scalar bar actors
-  for (std::vector<vtkScalarBarWidget*>::iterator it = d->ScalarBarWidgets.begin();
-    it != d->ScalarBarWidgets.end(); ++it)
+  for (vtkScalarBarWidget* scalarBarWidget : d->ScalarBarWidgets)
   {
-    vtkSlicerRTScalarBarActor* actor = vtkSlicerRTScalarBarActor::SafeDownCast(
-      (*it)->GetScalarBarActor() );
+    vtkSlicerRTScalarBarActor* actor = vtkSlicerRTScalarBarActor::SafeDownCast( scalarBarWidget->GetScalarBarActor() );
 
     // Update actor
     actor->UseAnnotationAsLabelOn(); // Needed each time
@@ -832,6 +1012,6 @@ void qSlicerIsodoseModuleWidget::updateScalarBarsFromSelectedColorTable()
       actor->GetLookupTable()->SetAnnotation(colorIndex, vtkStdString(selectedColorNode->GetColorName(colorIndex)));
     }
     actor->SetTitle(scalarBarTitle.c_str());
-    (*it)->Render();
+    scalarBarWidget->Render();
   }
 }
diff --git a/Isodose/qSlicerIsodoseModuleWidget.h b/Isodose/qSlicerIsodoseModuleWidget.h
index de154b388..df80e80c9 100644
--- a/Isodose/qSlicerIsodoseModuleWidget.h
+++ b/Isodose/qSlicerIsodoseModuleWidget.h
@@ -59,6 +59,8 @@ public slots:
 
   /// Process loaded scene
   void onSceneImportedEvent();
+  /// Process is scene is closed
+  void onSceneClosedEvent();
 
   /// Set current parameter node
   void setParameterNode(vtkMRMLNode *node);
@@ -97,6 +99,12 @@ protected slots:
   /// Slot called on modify of the color table
   void updateScalarBarsFromSelectedColorTable();
 
+  /// Slot setting type of isolevels representation
+  void setRelativeIsolevelsFlag(bool useRelativeIsolevels);
+
+  /// Slot called to set reference dose value
+  void setReferenceDoseValue(double value);
+
 protected:
   // Generates a new isodose level name
   QString generateNewIsodoseLevel() const;
diff --git a/SlicerRtCommon/vtkSlicerRtCommon.cxx b/SlicerRtCommon/vtkSlicerRtCommon.cxx
index 9d3ea0ab1..cf16b0a5f 100644
--- a/SlicerRtCommon/vtkSlicerRtCommon.cxx
+++ b/SlicerRtCommon/vtkSlicerRtCommon.cxx
@@ -87,6 +87,7 @@ const std::string vtkSlicerRtCommon::DICOMRTIMPORT_SOURCE_HIERARCHY_NODE_NAME_PO
 const std::string vtkSlicerRtCommon::DICOMRTIMPORT_BEAMMODEL_HIERARCHY_NODE_NAME_POSTFIX = "_Beams";
 
 const char* vtkSlicerRtCommon::DEFAULT_DOSE_COLOR_TABLE_NAME = "Dose_ColorTable";
+const char* vtkSlicerRtCommon::RELATIVE_DOSE_COLOR_TABLE_NAME = "Dose_ColorTable_Relative";
 
 //----------------------------------------------------------------------------
 // Utility functions
diff --git a/SlicerRtCommon/vtkSlicerRtCommon.h b/SlicerRtCommon/vtkSlicerRtCommon.h
index 57505a79d..273330516 100644
--- a/SlicerRtCommon/vtkSlicerRtCommon.h
+++ b/SlicerRtCommon/vtkSlicerRtCommon.h
@@ -116,6 +116,7 @@ class VTK_SLICERRTCOMMON_EXPORT vtkSlicerRtCommon
   static const std::string DICOMRTIMPORT_BEAMMODEL_HIERARCHY_NODE_NAME_POSTFIX;
 
   static const char* DEFAULT_DOSE_COLOR_TABLE_NAME;
+  static const char* RELATIVE_DOSE_COLOR_TABLE_NAME;
 
   //----------------------------------------------------------------------------
   // Utility functions