Computed tomography

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== <span style="color:#000080"> Introduction </span> ==
== <span style="color:#000080"> Introduction </span> ==
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This tutorial will based on the DICOM GEANT4 example originally developed by Louis Archambault, Luc Beaulieu and Vincent Hubert-Tremblay. In this example a list of DICOM files (.dcm) are converted to ASCII files (.g4dcm) and binary (.g4bin) that can be read by GEANT4. Then, these files are used by GEANT4 to construct patient geometry. The geometry is constructed by voxelizing computed tomography data. Four navigation algorithms are available to create the voxel geometry: G4SmartVoxel, G4VNestedParameterisation, G4RegularNavigation and G4Replica. In this tutorial we investigate the different geometry implementations.   
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This tutorial will based on the DICOM GEANT4 example originally developed by Louis Archambault, Luc Beaulieu and Vincent Hubert-Tremblay. In this example a list of DICOM files (.dcm) are converted to ASCII files (.g4dcm) and binary (.g4bin) that can be read by GEANT4. Each of these files corresponds to a Z slice. Then, the .g4dcm (.g4bin) files are merged into one unique volume and used by GEANT4 to construct the patient geometry and materials.   
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The DICOM images pixel values represent Hounsfield numbers which are converted to density according to the [http://www.hep.ucl.ac.uk/pbt/RadiotherapyWorkbook/skins/common/images/DICOM/CT2Density.dat Hounsfield scale].  
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The geometry is constructed by voxelizing the volume. There are four navigation algorithms used to create the voxel geometry: G4SmartVoxel, G4VNestedParameterisation, G4RegularNavigation and G4Replica. In this tutorial we investigate the different geometry implementations. 
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Then, the densities are converted to material type according to the information in the [http://www.hep.ucl.ac.uk/pbt/RadiotherapyWorkbook/skins/common/images/DICOM/Materials.txt file].
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The material is constructed by converting the pixel values (Hounsfield numbers) from the DICOM images to densities using 
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the [http://www.hep.ucl.ac.uk/pbt/RadiotherapyWorkbook/skins/common/images/DICOM/CT2Density.dat Hounsfield scale]. Then, the densities are converted to material type according to this [http://www.hep.ucl.ac.uk/pbt/RadiotherapyWorkbook/skins/common/images/DICOM/Materials.txt table].
A simple monenergetic electron beam is simulated inside the patient. The output of the example is a text file with dose deposited in several voxels.
A simple monenergetic electron beam is simulated inside the patient. The output of the example is a text file with dose deposited in several voxels.
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http://www.hep.ucl.ac.uk/pbt/RadiotherapyWorkbook/skins/common/images/DICOM/dicom.png
http://www.hep.ucl.ac.uk/pbt/RadiotherapyWorkbook/skins/common/images/DICOM/dicom.png
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This is one of the DICOM files that will be used in this tutorial.
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This is one of the DICOM files that is used in the tutorial.
== <span style="color:#000080"> Setting up the environment </span> ==
== <span style="color:#000080"> Setting up the environment </span> ==

Revision as of 15:48, 28 August 2014

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