confOrganiser.com - Work: COMPARISON OF DOSIMETRIC LEAF GAP FOR TWO VARIAN TRUEBEAM LINEAR ACCELERATORS

COMPARISON OF DOSIMETRIC LEAF GAP FOR TWO VARIAN TRUEBEAM LINEAR ACCELERATORS

1. Dražan Jaroš, Centar za radioterapiju, Republic of Srpska, Bosnia and Herzegovina
2. Goran Kolarević, Republic of Srpska, Bosnia and Herzegovina
3. Dragoljub Mirjanić, Akademija nauka i umjetnosti Republike Srpske, Bana Lazarevića 1, Banja Luka, Republic of Srpska, Bosnia and Herzegovina

The aim of this study was to compare dosimetric leaf gap (DLG) for two Varian TrueBeam linear accelerators. The Eclipse treatment planning system (TPS) (Varian Medical Systems, Palo Alto, CA) must model complex motions of the Multileaf colimator (MLC) to deliver the intended dose according to the prescribed dose constraints. It is important to model accurately the MLC characteristics defined in the TPS, such as the dosimetric leaf gap (DLG), in order to deliver the correct dose to patients. The DLG values for all photon beam were measured on two Varian TrueBeam linear accelerators (Varian Medical Systems, Palo Alto, CA) equipped with Millennium 120 MLC. Measurements were performed with a Farmer-type ion chamber. DLG parameters for TrueBeam 1 and TrueBeam 2 are presented in the table 1.
Table 1. Dosimetric leaf gap (DLG) for two TrueBeam linear accelerators
DLG [cm]
Beam energy 6MV 10MV 16MV 6FFF 10FFF
TrueBeam 1 1.45 1.61 1.62 1.33 1.57
TrueBeam 2 1.5 1.64 1.61 1.366 1.56
The DLG is used in the Varian Eclipse treatment planning system as an approximation factor to reduce the dosimetric calculation uncertainty arising from the use of a simple MLC model with straight leaf ends. Results of the DLG in this study are showing that the difference in the calculation uncertainty will be less than 3% for two machines.

Key words: Dosimetric leaf gap; TrueBeam.

Thematic field: SIMPOZIJUM B - Biomaterijali i nanomedicina

Date: 03.08.2020.

Contemporary Materials 2020 - Savremeni Materijali

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