SIMULASI PEMBENTUKAN KURVA ISODOSIS BERKAS FOTON 6 MV UNTUK TEKNIK RADIOTERAPI VMAT DENGAN MENGGUNAKAN EGSNRC
Abstract
Radioterapi merupakan salah satu modalitas utama dalam pengobatan kanker. VMAT (Volumetric Modulated Arc Therapy) merupakan salah satu teknik radioterapi yang memberikan seluruh fraksi dosis secara kontinyu pada saat gantry terus menerus berotasi dengan mengatur kecepatan rotasi gantry, bentuk penampang berkas (MLC leaf position), dan fraksi dosis yang diberikan. Dalam penelitian ini dilakukan simulasi Monte Carlo VMAT dengan menggunakan EGSnrc code system untuk mengetahui distribusi dosis radiasi berkas foton 6 MV pada kasus kanker paru dengan data parameter berasal dari rtplan. Phantom yang digunakan berasal dari data CT scan thorax yang dibaca dengan ctcreate. Simulasi dilakukan dengan membagi jumlah control point VMAT ke dalam 38 kali simulasi dengan setiap simulasi terdiri dari 3 buah control point. Sebagai perbandingan dilakukan pula simulasi VMAT dengan seluruh control point sekaligus. Hasil menunjukkan bahwa distribusi dosis yang terbentuk dari kedua simulasi cenderung memiliki pola kurva isodosis yang hampir serupa, namun perbandingan jumlah history partikel yang digunakan untuk membentuk kurva isodosis yang sama antara kedua simulasi belum dapat diketahui secara pasti.
Radiotherapy is one of major modalities in cancer treatment. VMAT (Volumetric Modulated Arc Therapy) is a radiotherapy technique, which provides a continuous full dose radiation as the gantry rotates (dynamic beam delivery) that manages gantry rotation speed, beam cross-sectional shape arranged by MLC leaf position, and fraction of the given dose simultaneously as the treatments take place. The aim of this study was to conduct Monte Carlo VMAT simulation using EGSnrc code system to determine dose distribution of radiation in lung cancer using parameters data deriving from the rtplan. The phantom used comes from data CT scans of thorax, which was then read by ctcreate. Simulation was done by dividing the number of control points of VMAT into 38 simulations in which each simulation consists of three pieces of control point. As a comparison, a VMAT simulation with all of control points was done simultaneously at a time. The results suggest that the dose distributions formed from the sum of data from all simulations with 3 control points tend to have a similar pattern to the dose distribution form of simulations involving all control points, but the comparison of the number of particles history used to form the same isodose curve between the two simulations can not be known for certain.
Key words: Radioteraphy; VMAT; Monte Carlo; Control point; Isodose Curve
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DOI: https://doi.org/10.17509/wafi.v3i1.11082
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