ESTRO 2023 - Abstract Book

S1565

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ESTRO 2023

source to phantom distance (SPD) of 95 cm. The dose plane at 5 cm depth was scored at voxels of 0.5 x 0.5 x 2 mm ³ . The Geant4 physics list “QGSP_BIC_EMZ” with extended electromagnetic physics configuration “EM Opt4” was used. The production cuts for secondary particle generation were set to 0.1 mm. We have investigated fields limited by both MLC layers separately, as well as more interesting combo limited fields that use both layers. We have studied both static and modulated plans. Results As an example of the results, Figure 1 shows the MC simulated and measured dose profiles with static 4- and 2-mm openings. The 4 mm gaps shown on the left panel shown a perfect match of the MC simulations and measurements, there are no discrepancies found and the agreement is clearly within the MC error estimates. The more extreme combo case of tiny 2 mm gaps shows a small difference: MC dose peaks are somewhat higher than measured. The overall agreement even there is very good.

Figure 1: Monte Carlo and measured profiles with static 4 mm and 2 mm gap openings.