ANALYSIS OF THE EFFECT OF DISTANCE BETWEEN IRIDIUM-192 SOURCES AND INHOMOGENEOUS MATERIALS ON ABSORBED DOSE DISTRIBUTION IN BRACHYTHERAPY SIMULATION

• Main Author: Jaza Aufa, Fatihah
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/83388
• Institution: Institut Teknologi Bandung

Brachytherapy absorbed dose distribution is influenced by the source arrangement and the materials surrounding the sources. This research aims to analyze the effect of distance between Iridium-192 sources and the presence of inhomogeneous materials to brachytherapy absorbed dose distribution. DOSXYZnrc simulation was used for data retrieval. The brachytherapy source was modeled as cuboid with the dimension of 0.09 x 0.45 x 0.09 cm with VariSource energy spectrum. The distance between source was varied by varying the distance between source’s center along X axis. The first variation used 4 source with a distance of 0.5 cm. The second variation used 8 sources with a distance of 0.25 cm. The number of histories for the first and second variation are 109 and 5 x 108 particles, respectively. Two phantoms were used in this study. The first phantom has dimension of 10 x 10 x 10 cm with water material, while the second is distinguished by the presence of inhomogeneous material in the form of tissue with dimension of 4 x 1 x 1 cm and density of 1,04 g/cm3 . There was no change in the shape of isodose curve due to variation of distance between sources in both phantoms. In both variations, the presence of tissue material also did not change the shape of the isodose curve. Furthermore, global and local gamma index calculations were carried out in the XY, XZ, and YZ planes with a criterion or tolerance limit of 3%/3mm and 95% Gamma Passing Rate (GPR). Gamma index calculations were carried out for the first and second variation in the water phantom, the first and second variation in the water-tissue phantom, the first variation in the water and water-tissue phantom, and the second variation in the water and water-tissue phantom. A GPR value of 100% was obtained for all calculations. It is concluded that with the carried out source arrangement, the difference in absorbed dose distribution due to the distance between sources and the presence of inhomogeneous materials is still below the specified criterion.