Sharif Digital Repository

Proton beam therapy (PBT) is a modern external beam radiation therapy characterized by superior dose distribution. Small field PBT refers to the treatment of tumor sizes less than 7 cm in diameter. In this study, a fast and accurate GATE model was developed and then validated for a small field scattering PBT delivery. To this aim, a fixed single scattering nozzle was modeled in the GATE platform. To accelerate the GATE simulations, a variance reduction technique (VRT) was also incorporated by ignoring the tracking of the secondary particles having a range below a predefined cutoff. In addition, the influence of collimator material on the model performance was evaluated. Beam uniformity,... 

Proton therapy (PT) is an emerging external beam radiation therapy characterized by superior dose distribution compared to conventional modalities. In the present study, an optimal GATE model was developed and then validated for a double scattering proton nozzle based on the previously constructed model. To this aim, a double scattering treatment nozzle was modeled in the GATE platform. To accelerate the GATE simulations, a virtual range modulation wheel (vRMW) and a variance reduction technique (VRT) were implemented. Proton beam flatness, symmetry, and delivery efficiency, secondary neutron dose, and dosimetric performance were characterized through a set of GATE simulations. The findings... 

Purpose: Proton Beam Therapy (PBT) is an emerging radiotherapy technique using beams of proton to treat cancer. As the first report addressing the topic, the principal aim is to highlight the present status of PBT research and development in Iran as a developing country. Materials and Methods: To do so, the demand for PBT in Iran and Iran National Ion Therapy Center (IRNitc) was investigated and introduced. Then, Scopus and PubMed were searched for studies that dealt with PBT research in Iran and subsequently 6 major subfields of interest were identified. Furthermore, international collaborations were extracted from the bibliographic data. To combine both research and development sides, a... 

The effect of pulse shaping on the intense laser-driven proton beam produced through radiation pressure acceleration as a highly efficient mechanism is investigated. In this regard, the interaction of pulses with modified frequencies, including positive and negative chirped pulses with plasma, is simulated using particle-in-cell code. The simulation results indicate that the proton acceleration could be significantly enhanced for both negative and positive chirped pulses. As a consequence of the acceleration time extension as well as the electron heating suppression, a sharper and narrower proton beam could be achieved for negative chirped pulses. The same trend is observed for all negative... 

Based on the determination of protons fluence at the phantom's surface, a 3D dose distribution is calculated inside a water phantom using a fast method. The dose contribution of secondary particles, originating from inelastic nuclear interactions, is also taken into account. This is achieved by assuming that 60% of the energy transferred to secondary particles is locally absorbed. Secondary radiation delivers approximately 16.8% of the total dose in the plateau region of the Bragg curve for monoenergetic protons of energy 190 MeV. The physical dose beyond the Bragg peak is obtained for a proton beam of 190 MeV using a Geant4 simulation. It is found that the dose beyond the Bragg peak is <... 

Background: in this study, two proton beam delivery designs, i.e. passive scattering proton therapy (PSPT) and pencil beam scanning (PBS), were quantitatively compared in terms of dosimetric indices. The GATE Monte Carlo (MC) particle transport code was used to simulate the proton beam system; and the developed simulation engines were benchmarked with respect to the experimental measurements. Method: A water phantom was used to simulate system energy parameters using a set of depth-dose data in the energy range of 120-235 MeV. To compare the performance of PSPT against PBS, multiple dosimetric parameters including Bragg peak width (BP W50), peak position, range, peak-To-entrance dose ratio,... 

The selection of a suitable duty factor (DF) remains a major challenge in respiratory-gated treatments. Therefore, this study aims at presenting a new methodology for fast optimizing the gating window width (duty factor (DF)) in respiratory-gated proton partial breast irradiation (PBI). To do so, GATE Monte Carlo simulations were performed for various target sizes and locations in supine and prone positions. Three different duty factors of 20, 25, and 33% were considered. Sparing factors (SF) for four organs-at-risk (OARs) were then assessed. The weighted-sum method was employed to search for an optimal DF. The results indicate that an SF higher than unity was obtained for all plans. The SF...