Enhancement and validation of Geant4 Brachytherapy application on clinical HDR super(192)Ir source

The Geant4 Monte Carlo MC associated Brachytherapy example was adapted, enhanced and several analysis techniques have been developed. The simulation studies the isodose distribution of the total, primary and scattered doses around a Nudetron microSelectron super(192)Ir source. Different phantom materials were used (water, tissue and bone) and the calculation was conducted at various depths and planes. The work provides an early estimate of the required number of primary events to ultimately achieve a given uncertainty at a given distance, in the otherwise CPU and time consuming clinical MC calculation. The adaptation of the Geant4 toolkit and the enhancements introduced to the code are all validated including the comprehensive decay of the super(192)lr source, the materials used to build the geometry, the geometry itself and the calculated scatter to primary dose ratio. The simulation quantitatively illustrates that the scattered dose in the bone medium is larger than its value in water and tissue. As the distance away from the source increases, scatter contribution to dose becomes more significant as the primary dose decreases. The developed code could be viewed as a platform that contains detailed dose calculation model for clinical application of HDR super(192)Ir in Brachytherapy.