Payvand Taherparvar; Ali AziziGanjgah
Abstract
Low energy I-125- seeds are considered as a common source in different brachytherapy techniques for treatment of different cancers. In this study, at first, we simulated and validated I-125 (model 6711) seed according to the TG-43U1 recommendation, by GEANT4 Monte Carlo toolkit. Moreover, we simulated ...
Read More
Low energy I-125- seeds are considered as a common source in different brachytherapy techniques for treatment of different cancers. In this study, at first, we simulated and validated I-125 (model 6711) seed according to the TG-43U1 recommendation, by GEANT4 Monte Carlo toolkit. Moreover, we simulated new seeds containing cylindrical Ag+Al2O3 markers with different ratio of Ag and Al2O3 in the final composition of the marker and compared the radial dose functions and anisotropy functions of the sources. For validation and evaluation purposes, the radial dose function and anisotropy function were calculated at various distances from the center of the different simulated sources. The source validation results show that GEANT4 Monte Carlo toolkit produces accurate results for dosimetric parameters of the I-125 seed by choosing the appropriate physics list. On the other hand, results show a similarity between calculated dosimetric parameters of the I-125 seed (6711) and other sources, with a percentage difference of about 5%.
Milad Payandeh; Mahdi Sadeghi; Dylan Richeson; Somayeh Gholami
Abstract
It is important to have accurate information regarding the dose distribution for treatment planning and to accurately deposit that dose in the tissue surrounding the brachytherapy source. However, the practical measurement of dose distribution for various reasons is associated with several problems. ...
Read More
It is important to have accurate information regarding the dose distribution for treatment planning and to accurately deposit that dose in the tissue surrounding the brachytherapy source. However, the practical measurement of dose distribution for various reasons is associated with several problems. In this study, 6711 I-125, Micro Selectron mHDR-v2r Ir-192, and Flexisource Co-60 sources were simulated using the MCNP5 Monte Carlo method. To simulate the sources, the exact geometric characteristics of each source, the material used in them, and the energy spectrum of each source were entered as input to the program, and finally, the dosimetric parameters including dose rate constant, radial dose function, and anisotropy function were calculated for considered seeds according to AAPM, TG-43 protocol recommendation. Results obtained for dosimetric parameters of dose rate constant, radial dose function, and anisotropy function for I-125, Ir-192, and Co-60 sources agreed with other studies. According to the good agreement obtained between the parameters of TG43 and other studies, now these datasets can be used as input in the treatment planning systems and to validate their calculations.
Payman Rafiepour; Shahab Sheibani; Daryiush Rezaey Uchbelagh; Hossein Poorbaygi
Abstract
Radioactive stents loaded with I-125 seeds have been widely used for the treatment of advanced esophageal cancer. Understanding the dose distribution of such stents before the clinical use is essential. This study provides a dosimetric investigation of I-125 seed-loaded stents based on the seed's arrangement ...
Read More
Radioactive stents loaded with I-125 seeds have been widely used for the treatment of advanced esophageal cancer. Understanding the dose distribution of such stents before the clinical use is essential. This study provides a dosimetric investigation of I-125 seed-loaded stents based on the seed's arrangement and activity. A cylindrical water equivalent phantom with an esophageal stent loaded with I-125 seeds, were employed. The seeds arrangements were determined based on the distance between the centers of two adjacent seeds (z) along the stent length. EBT3 films as well as Geant4 Monte Carlo toolkit were used to obtain the dose distribution around the stent. By modeling the MIRD phantom, the dose delivered to the related organs at risk was calculated. The appropriate dose distribution is achieved for z=15 mm, in which the absorbed dose at a depth of 5 mm reaches about 45% of the absorbed dose near the stent surface, thereby the therapeutic dose is delivered to the reference points. Both arrangements (z=15 and 20 mm) seemed to be clinically eligible and their utilization depends on the patient and the hospital facilities. Using esophageal stents with z>20 mm is not recommended due to the presence of cold spots in the dose distribution.
