IMPT plans with various multi-angle beams were planned by the Varian Eclipse\ntreatment planning system for one case of brain cancer. Dose distributions\nfor each plan, along with the associated linear energy transfer distributions,\nwere recomputed using an in-house fast Monte Carlo dose calculator\nwith a FRBE of 1.1 or with a previously published VRBE model. We then\ncompared dosimetric parameters obtained by the VRBE with those obtained\nby the FRBE. Biological doses obtained by the VRBE for the clinical target\nvolume in all plans were 1% - 2% larger than those obtained by the FRBE.\nThe minimum dose obtained by the VRBE for the right optic nerve in the\nMFO IMPT with 4 fields was 70% larger than that obtained by the FRBE, but\nthe difference was only 18.1 cGy (RBE). The difference in maximum dose for\nthe right optic nerve in the MFO IMPT with 5 fields was less than 10.4%, but\nthe difference was 131.8 cGy (RBE). The mean difference in maximum dose\nwas less than 2% for all other organs at risk. We found that biological dose\nwith the FRBE had any dose errors in IMPT with various multi-angle beams.
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