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Monte Carlo Simulation of Ir-192 Brachytherapy System for Intracavity Applicators and Benchmarking the Result with TLD and EDR2 Dosimeters

Babaei Bidmeshki, Nadia | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42153 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Sohrabpour, Mostafa; Mahdavi, Rabi
  7. Abstract:
  8. The main aim in radiotherapy is to destroy tumor while keeping the normal tissue in a safe condition. Brachytherapy is a method of radiotherapy in which sealed radioactive sources are used to deliver radiation at a short distance. With this mode of therapy, a high radiation dose can be delivered locally to the tumor with rapid dose fall-off in the surrounding normal tissue. Brachytherapy is usually used for cancer treatment such as breast, brain, liver, ovary, uterine cervix and prostate. In clinical application, the treatment plan is typically acquired from the planning softwares. Dose calculation in these softwares is based upon the published recommendations of AAPM TG-43 in which parameters such as radial dose function and anisotropy function are described. In this study, dosimetric characteristics of high dose rate iridium Flexisource is derived by means of thermoluminescent dosimetry and Monte Carlo simulation. Experimental and simulated data in this section were in good agreement and had a nominal error of 3%. Furthermore, the attenuation effect of the thickness of the titanium layers of the tandem and ovoid applicators were investigated. This was done to study this effect and comparison with the results of the Flexiplan which does not take this thickness into consideration. A Plexiglas pelvic phantom was designed and TLD- 100H dosimeters from Harshaw were used for dosimetry. Dosimeters were placed at four different slab positions in the phantom and a nominal error of 7.5% between dosimetry and the Flexiplan results were obtained. The experimental conditions were also simulated with the MCNP Monte Carlo code. The resulting errors between the experimental and the simulations showed pairwise results of TLDMCNP 6.2%; Flexiplan-MCNP 4.7%; TLD-Flexiplan 7.5%; and EDR2-Flexiplan 5.5%
  9. Keywords:
  10. Radiotherapy ; Monte Carlo Simulation ; Thermoluminesence Dosimetry ; Brachytherapy ; Iridium-192 Source (HDR) ; Tandem-Ovoid Applicators

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