Sains Malaysiana 46(9)(2017): 1407–1411

http://dx.doi.org/10.17576/jsm-2017-4609-08

Monte Carlo Simulation of 6 MV Flattening Filter Free Photon Beam of TrueBeam STx LINAC at Songklanagarind Hospital

(Simulasi Monte Carlo 6 MV Perataan Tanpa Penurasan Alur Foton TrueBeam STx LINAC di Hospital Songklanagarind)

M. ARIF EFENDI^{1 2} , AMPORN FUNSIAN², THAWAT CHITTRAKARN¹ & TRIPOB BHONGSUWAN¹*

¹Department of Physics, Faculty of Science, Prince of Songkla University, 90110 Hatyai City, Songkla, Thailand

²Department of Radiology, Faculty of Medicine, Prince of Songkla University

90110 Hatyai City, Songkla, Thailand

Diserahkan: 31 Ogos 2016/ Diterima: 17 Januari 2017

ABSTRACT

In this study, 6 MV photon beam of TrueBeam STx Varian LINAC with Flattening Filter Free (FFF) was simulated using PRIMO code. The depth dose profiles for various jaws open fields and cross beam profiles for various depths inside water phantom were determined using Monte Carlo (MC) simulation technique and validated with experimental result. The experiments were performed using the Source to Surface Distance (SSD) technique with a 100 cm distance from target to the surface of water. Simulation used 10⁹ histories with the same configurations with experiments. The depth dose profiles and cross beam profiles of 6 MV FFF photon beam was determined using MC simulations and compared with experimental results. The results showed that depth dose profiles and cross beam profiles by MC simulation accurately matched with experimental results. The best result of depth dose profile was obtained at 10×10 cm2 jaws open field with 98.53% passing criterion whereas cross beam profile was obtained at 10 cm depth inside water phantom with 88.96% passing criterion. The discrepancies were caused by scatter of particle and incompatibility of primary beam in PRIMO with experiment.

Keywords: Flattening Filter Free (FFF); Linear Accelerator (LINAC); Monte Carlo simulation; PRIMO Code

ABSTRAK

Dalam kajian ini, 6 MV alur foton daripada TrueBeam STx Varian LINAC dengan perataan tanpa penurasan (FFF) disimulasikan menggunakan kod PRIMO. Profil kedalaman dos untuk pelbagai ukuran rahang dan profil melintang alur untuk pelbagai kedalaman dalam fantom air telah ditentukan dengan menggunakan teknik simulasi Monte Carlo (MC) dan disahkan secara eksperimen. Uji kaji telah dijalankan dengan menggunakan teknik jarak sumber kepada permukaan (SSD) dengan jarak 100 cm dari sasaran ke permukaan air. Simulasi menggunakan 10⁹ peristiwa, konfigurasi yang sama dengan uji kaji. Profil kedalaman dos dan profil melintang alur daripada 6 MV FFF alur foton ditentukan dengan menggunakan simulasi MC dan dibandingkan dengan keputusan uji kaji. Hasil kajian menunjukkan bahawa hasil simulasi MC daripada profil kedalaman dos dan profil melintang alur adalah sepadan tepat dengan keputusan uji kaji. Keputusan terbaik profil kedalaman dos adalah pada 10×10 cm2 dengan kriteria lulus 98.53%. Keputusan terbaik profil melintang alur adalah pada kedalaman 10 cm dalam fantom air dengan kriteria lulus 88.96%. Percanggahan adalah disebabkan oleh serakan zarah dan ketidaksesuaian alur utama dalam PRIMO berbanding dengan uji kaji.

Kata kunci: Kod PRIMO; pemecut linear (LINAC); perataan tanpa penurasan (FFF); simulasi Monte Carlo

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*Pengarang untuk surat-menyurat; email: tripop.b@psu.ac.th