IMRT Planning Using 5, 7 and 9 Radiation Field Directions for Nasopharyngeal Cancer Cases Lira Senja Alfitra (a), Suwandi (b), Idam Arif (a*)
a. FMIPA, Institut Teknologi Bandung, Jalan Ganesha 10, Bandung 40132, Indonesia
* idam[at]itb.ac.id
b. Instalasi Radioterapi, Rumah Sakit Hasan Sadikin, Jalan Pasteur No.38 Bandung, Indonesia
Abstract
Nasopharyngeal carcinoma (NPC) is one of the deadliest cancers in the world, including Indonesia. One of the methods to treat NPC is the Intensity Modulated Radiation Therapy (IMRT) technique that uses radiation fields from several directions to kill cancer cells and shrink tumors. With many organs at risk (OAR) around the nasopharyngeal cavity, the technique requires accurate planning using the Treatment Planning System (TPS). The purpose of this study is to analyze the results of treatment planning for nasopharyngeal cancer using IMRT techniques related to the use of different radiation field directions. The study focuses on the distribution of dose in the target tumor and organs at risk around the target. The treatment planning parameters are Dose Volume Histogram (DVH), Conformity Index (CI), and Homogeneity Index (HI). The TPS used was TPS Monaco with the Monte Carlo algorithm and the inverse planning method. Based on DVH, CI and HI parameters, the results of this study indicate that for cases of nasopharyngeal cancer, the most optimal number of radiation field directions to give prescribed doses was in the planning with 9 radiation field directions. It is also indicated that, there was no significant difference in the average dose received by OARs in planning with 7 fields and 9 radiation field directions. In the planning using 5 field directions it appears that most of the OARs received doses above the tolerance limit, while in the planning using 7 and 9 field directions, OARs received doses below the tolerated doses so that they met the permitted treatment requirements.
