Manchester system brachytherapy simulation using EGSnrc Monte Carlo simulation

Indonesian Physics Communication Vol. 21 | No. 3 November 2024 Department of Physics, Universitas Riau, Pekanbaru, Indonesia p-ISSN 1412-2960 | e-ISSN 2579-521X Web: https://kfi.ejournal.unri.ac.id E-mail: Manchester system brachytherapy simulation using EGSnrc Monte Carlo simulation Shella Salsa Octavia, Tony Sumaryada, Sitti Yani* Department of Physics, IPB University, Bogor 16680, Indonesia *Corresponding author: ABSTRACT One type of cervical cancer treatment is brachytherapy using the Manchester system. In this study, isodose curves were analyzed on tissue phantoms irradiated using several types of radioactive sources with the Manchester system using Monte Carlo simulation, EGSnrc. This study used a homogeneous tissue phantom with dimension 10 × 10 × 10 m3. The Manchester system uses 2 ovoid and 3 tandem containing radioactive sources placed inside the phantom. The resulting isodose curves were combined and analyzed using MATLAB-based VDOSE GUI. The results showed that the dose distribution for each type of radioactive source at the reference point had different values, namely Cobalt-60 had a dose distribution at reference point A of 15.08% with a dose distribution at reference point B of 0%, Cesium-137 was 13.37% and 0%, Iridium-192 was 13.27% and 0%. The use of radioactive source types can be adjusted to the actual location of cervical cancer. Keywords: Brachytherapy; EGSnrc; isodose curve; Monte Carlo; Manchester system Received 18-10-2024 | Revised 09-11-2024 | Accepted 23-11-2024 | Published 30-11-2024 INTRODUCTION Based on the mode of radiation delivery, radiotherapy is divided into two, namely teletherapy (the source is outside the body) and brachytherapy (the source is inside the body). Brachytherapy refers to a therapeutic technique with the placement of a radioactive source into or very close to the target tissue [1]. The most commonly used radioactive sources for brachytherapy treatment are Iridium-192 [2], Cobalt-60 [3], Cesium-137, and Radium [4]. Each radioactive source has different characteristics [3]. Brachytherapy is commonly used as a therapy for breast, prostate, cervical, and several other types of cancer [5]. Brachytherapy method by inserting a closed radioactive source in the cavity of the cancer cell site or intracavitary brachytherapy is often used in the treatment of cervical cancer [6]. Cervical cancer is an abnormal growth of cervical epithelial tissue in the neck of the ©Author(s) | DOI: 10.31258/jkfi.21.3.281-288 uterus [7]. The Manchester system is one of the systems used in the treatment of cervical cancer through the brachytherapy method. The Manchester system is a type of brachytherapy system by implanting radioactive substances into the body through uniform dose distribution. It uses two intravaginal applicators and a rubber tandem tube. This system distributes the dose to several points [8-10]. Dose calculation in the Manchester system can be done through the Monte Carlo (MC) method [11]. Several Monte Carlo codes have been used to calculate dose distributions in several cancers with brachytherapy techniques such as MCNP [12], Geant4 [13], and EGSnrc [11]. EGSnrc is a program to simulate the transport of photon and electron particles using the MC algorithm. In this study, modelling and analysis of the effect of the type of radioactive source on the distribution of radiation dose received by the target and its surroundings through the isodose curve are carried out. This 281 research will use the Manchester system as a method of placing radioactive sources using three radioactive sources, namely Ir-192, Cs137, and Co-60. The results of the isodose curves of the two types of radioactivity will be compared and analyzed to determine the dose distribution. Therefore, the purpose of this study is to compare and analyze isodose curves on tissue phantoms irradiated using several different types of radioactive sources with the Manchester system through Monte Carlo simulation. tube containing 3 radioactive seeds inside and two ovoids (intravaginal applicators) each containing a radioactive seed. In direct clinical use, points A and B are located on the right and left sides. Point A is located 2 cm to the right, left of the tandem and 2 cm above the ovoids. Point B is located 5 cm and 2 cm to the right, left of the tandem and above the ovoids. This point is 3 cm lateral to point A. Point B is used to deliver the dose to the distal parametrium [3]. RESEARCH METHODS Simulation Design This study uses EGSnrc with the user code DOSXYZnrc as a simulation program. DOSXYZnrc is used to design and simulate absorbed dose with various mediums and phantom sizes [14]. A phantom is a modeling of a human object used in the field of radiology for radiodiagnostics and radiotherapy. DOSXYZnrc has several types of sources as sources used in simulations. The type of DOSXYZnrc source in this study is isource= 6: Uniform isotropically radiating parallelepiped within DOSXYZnrc. The use of this source allows the simulation of a radioactive source placed in a phantom that emits uniform radiation. The volume of the field size can be adjusted as long as it is within the DOSXYZnrc phantom (active volume is limited). The active volume of the radioactive source is bounded in the x direction by xinl, xinu (cm), bounded in the y direction by yinl, yinu (cm), and zinl, zinu, which is the z boundary of the active volume (cm). The simulation was carried out by placing the radioactive source on a 10×10×10 m3 homogeneous phantom which all voxel parts contained tissue material with the information of each voxel shown in Table 1. The radioactive sources used were Iridium-192, Cesium-137, and Cobalt-60. The Manchester system applicator was inserted into the phantom with one intrauterine rubber tandem 282 Figure 1. Set-up of the phantom simulation. Table 1. Virtual phantom information. Voxel Voxel Voxel size Axis Boundaries number (cm) (cm) x 100 0.1 -5 to + 5 y 100 0.1 -5 to +5 z 100 0.1 0 to 10 Dose Distribution Analysis Each simulation produces output files that are used in the data analysis process, namely .3ddose files and .egsphant files. The dose profile is a dose distribution curve in a certain direction in one dimension obtained by analyzing the .3ddose file through the STATDOSE program. Isodose curves can be obtained using dosxyz_show or VDOSE. The .3ddose and .egsphant files of each radioactive source applicator location (2 on ovoid and 3 on tandem) will be merged using the MATLAB- Manchester system brachytherapy simulation using EGSnrc … (Octavia et al.) based VDOSE GUI. The merged results will produce isodose curves. The isodose curve will be analyzed at point A and point B of the Manchester system. The results of the dose distribution analysis are compared between the three types of radioactive sources used in this study. RESULTS AND DISCUSSION Dose Profile Relative dose (%) The three-dimensional dose distribution data generated by the simulation (...truncated)