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Investigating the Use of Gold Nanoparticle in Increasing Dose of Tumor and Reducing the Dose of Normal Tissue in Brachytherapy

Mahmoodi, Monireh | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54183 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Hosseini, Abolfazl
  7. Abstract:
  8. Over the past few decades, brachytherapy has been used as one of the leading methods in the treatment of a wide range of cancers, including breast cancer. Due to the high dose gradient of brachytherapy radiation sources, this method is used to treat such tumors that are grown at the vicinity of sensitive points or tissues of the body. Therefore, as irradiation get started by implanting radiation sources in the desired position, at the same time healthy tissue are also receiving the same dose as tumor tissues do Reducing healthy tissue dose along with increasing the dose of tumor tissue is one of the challenging topics that researchers are always looking for a solution. In the left breast tissue, after surgery and removal of the tumor, in order to ensure the destruction of cancer cell remnants, it is necessary to radiate an area about one centimeter thick around the empty cavity caused by the operated tumor. The aim of this study was to use the benefits of gold nanoparticles and apply a direct current electric field in increasing the dose of tumor cells in the process of tissue irradiation by permanent breast brachytherapy while at the same time lower dose reaches to healthy tissues. Accordingly, after simulating the left breast tissue using Monte Carlo code Geant4.10.7, iodine-125 brachytherapy seeds were placed in the tissue. In order to increase the dose of tumor cells, it is used gold nanoparticles with 50 nm diameter and the amount of 105 nanoparticles and also direct electric field under intensities of 2, 5, 10, 30, 50 and 2000 V/Cm in two different direction are applied to the tissue. Dosimetric measurements were performed in four stages. In the first step, the simulated breast tissue including the empty cavity with 50 implanted brachytherapy seeds was gone through the Dosimetric measurements. In the second step, dosimetric measurements were performed when the gold nanoparticles were injected to the one centimeter margine of the simulated tissue around the empty cavity. In the third step, the simulated breast tissue was subjected under the electric field with diferent intensities and different directions of the applied electric field, and then the dosimetric results were presented. In the last step, the effect of gold nanoparticles and the application of electric fields with different intensities were investigated simultaneously. Finally, the achieved results were compared together and then, the obtained data were discussed. Dosimetric measurements showed that the application of an electric field to the tissue led to an increase in the dose received in other organs, while gold nanoparticles amounted to 105 nanoparticles and with a nonuniform distribution led to an increase in dose by very small amounts. Also, the presence of an electric field led to a uniform distribution of the dose with Gaussian distribution, the dose reaching the center of the tumor had the highest possible value
  9. Keywords:
  10. Breast Cancer ; Dosimeters ; Brachytherapy ; Electrical Field ; Gold Nanoparticle ; Radiotherapy

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