Comparison and calculation of absorbed dose rate in the brain by the Mammosite and Mammosite-ML (Contura) applicator in breast cancerbrachytherapy with MCNP

1. BackgroundBrachytherapy is one of the ways to treat breast cancer. In brachytherapy treatments, high-dose sources are used in interstitial placement. Here, Iridium-192 is used. In this project, breast cancer treatment applicators called Mammosite and Mammosite-ML (Contura) are modeled by the Monte Carlo simulation code. The absorbed dose is calculated by the brain. An application that can produce asymmetric doses and providesless doses to the brain is introduced. 2. Method MCNPX: is the based on the Monte Carlo method. The code, with input file information, solves the problem and produces results in an output file. MIRD phantom: To calculate the dose, a model of the human body is required as a phantom. Mammosite applicator: This device has a catheter that can be attached to the high dose rate afterloading machine that connects to the source. Mammosite-ML applicator: is almost identical to Mammosite, The difference is that the Mammosite has a central duct But the Mammosite-ML model has 3, 4 or 5 additional ducts around the central duct, in this project we use model that has 5 lumens. 3. ResultsIn Mammosite applicator: when the breast is treated right or left, When the tumor is in the right breast and the right breast is being treated the absorbed dose by the brain is constant, dose rate of: Brain= 7/98 x 10−4 Gy/min, But when the breast is treated left, the absorbed dose in brain =7/95x10−4 Gy/min. In Mammosite- ML applicator: when the breast is treated right, the absorbed dose in Brain=5/91 x 10−4 Gy/min, when thebreast is treated left, the absorbed dose in Brain=5/88 x 10−4 Gy/min. 4. ConclusionsThe amount of absorbed dose in the brain when used with a Mammosite-ML applicator is much less than that used by the Mammosite applicator. So, it can be concluded that the multivariate applicator is capable of producing asymmetric doses and the brain is exposed to less radiation exposure and can provide a better quality and safe treatment.5. References 1. Peter Hoskin, DR Catherine Coyle, 2011,Radiotherapy in Practice Brachytherapy