THE CORRELATION BETWEEN VOXEL SIZE WITH THE AMOUNT AND POSITION OF BREAST CANCER BRACHYTHERAPY SEED

• Main Author: Diana, Lani
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/49170
• Institution: Institut Teknologi Bandung

Breast cancer is the most common cancer found in Indonesian women. Brachytherapy, which is a therapy that uses seed containing radioactive source and is placed inside or near the tumor, is one of the most common methods that is used to treat early-stage breast cancer or to be post-surgery treatment. Seeds is placed inside or near the tumor, so it can effectively kill the tumor by give maximum dose to the target and minimum dose to the OAR (Organ At Risk, organ near the target). Simulation needs to be done in order to determine the right amount and position of seed. Organ that contain tumor is called as Phantom which usually will be divided into small 3D cubes called voxels. Voxels are used to determine the distribution dose based on dose profile, isodose curve, and DVH (Dose Volume Histogram) which are the results from simulation. The size of a voxel will affect the amount of voxels which indirectly will have an effect to the amount and position of seed. But no research has been conducted regarding the correlation of the two. The purpose of this research is to determine the correlation between voxel size with the amount and position of brachytherapy seed for early-stage breast cancer case. The research is done using DOSXYZnrc which is a software that runs monte carlo simulation for dose distribution. The size of breast phantom for this research is 16 x 16 x 16 cm3 that contains 4 tissue which is normal tissue, target, lung, and bone. There are 3 variation for voxel size, first is 0,125 x 0,125 x 0,125 cm3, then 0,2 x 0,2 x 0,2 cm3, and 0,5 x 0,5 x 0,5 cm3. There are 2 variation for the amount of seed, the first one is 8 seeds with 1 cm distance between each seeds, and the other is 16 seeds (with the addition of 8 seeds that have 2 cm distance between each seeds). The radioactive used for this research is microselectronIr-192 as one of the most common radioactive used for early-stage breast cancer case. The data from DOSXYZnrc will be transformed using MATLAB code, so the results will be in form of dose profile, isodose curves, and DVH. The results obtained indicate that the difference in voxel size makes the dose distribution or the percentage of dose absorbed by each tissue are different. The percentage of the absorbed dose will affect the position of the seed and when the dose accumulation is still not as desired, it is necessary to change the amount of the seed. The size of the voxel affects the number and position of the seed as seen from the percentage of dose absorbed by each tissue.