Sharif Digital Repository

Radiation therapy is a treatment modality that is used in treatment of most newly diagnosed cancer patients. In this method the interaction of radiation with matter and their biological effects is used for cancer treatment. The energy and intensity of the radiation in radiotherapy should be considered in order to have a lethal effect on tumors. Linear accelerators are substitutes for previous methods of radiotherapy in all over the world. These machines can work in both electron and photon mode. The Monte Carlo technique has become ubiquitous in medical physics in the last 50 years. The range of applications is very broad in medical physics. The increased use of Monte Carlo techniques is... 

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... 

As a method of cancer treatment or improvement of cancer-related complications, external radiation therapy is prescribed by physicians, in case of detection of a tumor in a region of patient’s body. Over time, various techniques have been developed for external beam radiation therapy. Among which, Intensity Modulated Radiation Therapy (IMRT), due to its ability to adjust the intensity of radiation beams, has a higher capacity to generate appropriate dose distribution based on tumor size and volume and it is one of the most widely used techniques in cancer treatment centers.The core process in treatment planning is using appropriate computer algorithms which results in posing enough damage to... 

It is necessary to evaluate dosimetry accuracy in the framework of advanced methods for radiation therapy such as Intensity Modulated Radiation Therapy (IMRT) to ensure reliability of a proposed treatment. The ability of the Monte Carlo codes to model linear accelerator (LINAC) and to calculate the exact dose distribution in clinical radiation therapy is one of the reasons to use such codes. The purpose of this project is to validate a treatment planning system with BEAMnrc and DOSXYZnrc Monte Carlo codes. In this study, the dose distribution obtained from DOSXYZnrc in considered to be thr main criterion with which the dose distribution obtained from treatment planning system is assessed and... 

Intensity Modulated Radiation Therapy is one of the most commonly used procedures of delivering radiation to cancerous tissues, with the aim of reaching the prescripted dose in the target volume while minimizing damage to nearby healthy organs. Two decisions are of fundamental importance: to select the beam angles and calculate the beam intensities. Beam Angle selection (Beam Angle Optimization) is an important problem. Due to the large amounts of computational time, beam angles are often selected manually based on human experience and intuition. In this study, three optimization methods –Simulated Annealing, Branch & Prune and Local Neighborhood Search- that are selected among known methods... 

Cancer is one of the main causes of death among all people around the world. This shows that more and more attention should be paid to cure cancer. One of the most common cancer treatments is radiation therapy. Among all radiation therapy treatments, Intensity-Modulated Radiation Therapy is a very effective and flexible ways to treat cancer. There are numerous mathematical problems to find the perfect treatment plan. One of these mathematical problems is Fluence Map Optimization in which we try to find the best dose intensity for each tumor and surrounding organs. The main purpose in this problem is to minimize the number of cancerous cells which are being destroyed while minimizing the... 

Intensity Modulated Radiation Therapy is one of the common methods for treating cancer patients because of the ability to transfer high doses of radiation to the tumor and minimize damage to surrounding healthy organs. In this method, the patient is placed in a special bed, while a linear accelerator directs the beams to radiation to the target's size. Patient treatment requires a unique treatment plan, and optimization of the treatment plan involves two basic decisions: (1) selecting the beam angles; (2) calculating the beams intensity. In the radiation therapy process, there are various uncertainty factors, such as patient setup, tumor volume definition, tumor growth or movement, and the... 

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... 

Validation of dosimetry accuracy in the context of advanced methods for radiotherapy, including proton therapy for ensure the accuracy of treatment plan is nessecory. One of the reasons for using MC code is the modeling of PT systems and the support of more accurate computation of dose distribution in clinical tarin. The purpose of this project is to validate the modeling of a spot scanning proton therapy system using a GATE MC code. In this study, the dose distribution calculated in the calibration process of the device and syno TPS is used as a criterion and the dose distribution obtained from the GATE MC code is calculated and validated with it. For this purpose, a water phantom was used... 

Over the past few decades, computed tomography (CT) has been introduced as one of the leading cross-sectional imaging techniques in a wide range of clinical applications in diagnostic radiology, oncology, and multimodal molecular imaging. Despite the recognized value of this imaging technique, the quality and accuracy of CT images can be compromised by a number of physical destructive factors. The presence of metal objects such as dental fillings, hip or knee prostheses, heart pacemakers, war fragments and spinal cages can cause and intensify image artifacts. These types of artifacts appear as black and white lines in the image, obscuring the structures and textures around the metal implant... 

In radiation therapy, different radiation were used to cancer treatment. The use of hadrons is more common than gamma rays for cancer treatment. Hadron therapy is appropriate to treat cancers that are close to organs at risk and can be severely damaged by X-rays during treatment. The survival fraction of cells was irradiated is important during treatment. In this study, using Geant code, simulation of choroidal melanoma tumor in the phantom of the eye was performed. The linear energy transfer and dose data of proton beam radiation were calculated, in addition, the cell survival fraction were calculated using Survival codeand the Geant simulation data such as number of inputs and dose with... 

Cancer is one of the leading causes of death around the world according to WHO. Scientists’ tried different approaches for treating this illness and from about 100 years ago one of the leading approaches to treat cancer is radiotherapy. With advancement of technology possibility of using different kinds of radiation for this purpose became available and one of the most interesting ones is high energy charged ions. But using high energy charged ions for treatment planning needs deep understanding of its nature and factors that affects the human body cells response to it. This thesis briefly reviewed the working principles of radiation therapy and then investigated two of the most used... 

One of the common methods for cancer treatment is radiotherapy, which is used in combination with other treatment methods, such as surgery and chemotherapy, as one of the fundamental strategies in treating many cancer patients. This approach not only helps achieve more effective results in cancer treatment, but also enables patients to experience fewer side effects compared to other treatment methods and improves their quality of life. Optimization in radiotherapy is the primary step in the process of determining the optimal radiation doses for each patient. This process involves adjusting the intensity and direction of the beams in such a way that provides significant therapeutic benefits...