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Optimization of the Dose Distribution in the Brachytherapy Using the Genetic Algorithm in Order to Increase the Absorbed Dose in the Cancer Tumor and to Reduce It in the Healthy Tissues

Naderi, Hossein | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54573 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Hosseini, Abolfazl
  7. Abstract:
  8. Prostate cancer is the second most common cancer in men and the fourth most common cancer in all cancers. Cancer treatment is done according to the type of cancer and its diagnosis stage with different treatment methods and plans. Brachytherapy is one of the most common methods of cancer treatment along with teletherapy, surgery and chemotherapy. In this method, the source of radiation is located near or inside the tumor, and its advantage is to achieve a lower dose ratio of healthy tissue to the tumor is lower compared to teletherapy. One of the challenges in brachytherapy is to prescribe the appropriate treatment plan for the patient, so that the maximum dose of sources reaches the cancerous tissue uniformly and the minimum dose reaches the healthy tissues. To achieve this goal, we must perform optimization, which can be done on various parameters of this treatment, such as the number of seeds, seeds activity and others, to ultimately optimize the dose distribution in the patient. But an important factor that has a great impact on the dose distribution of brachytherapy is choosing the right place for source seeds. In this study, we intend to optimize the location or distance of I-125 seeds in brachytherapy treatment with the help of MCNP simulation tool and non-dominant sorting genetic algorithm (NSGAII), to have an optimal and uniform dose distribution. First, with the help of MCNP tool and considering the effect of distance on dose uniformity in target tissue and dose deposition in healthy tissues, two target functions for these two factors are fitted. then the non-dominant sorting genetic algorithm is applied to the target functions obtained from the MCNP and a Pareto front is obtained. According to the Pareto curve, the optimal distance is obtained to achieve a uniform dose while the dose of healthy organs is also minimal. This value was 4.1 mm for our problem. After performing dosimetric calculations using MCNP, the prostate dose was 147.7751 Gy, which is an acceptable value according to the available references and is higher than the minimum dose we considered. Also, the dose of healthy organs of bladder, colon and testes were 3.4033, 0.2282 and 0.5215 Gy, respectively. According to the studied references, the dose in the organs at risk should be below 60%, In addition, these values have been improved compared to another reference
  9. Keywords:
  10. Brachytherapy ; Monte Carlo Simulation ; Optimization ; Monte Carlo N-Particle (MCNP)Code ; Prostate Cancer ; Non-Dominate Sorting Genetic Algorithm (NSGAII) Method ; Cancer Treatment ; Absorption Dose

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