Author(s)

Ryosuke Kohno^1,2,3, Wenhua Cao², Pablo Yepes², Xuemin Bai², Falk Poenisch², David R. Grosshans², Tetsuo Akimoto³, Radhe Mohan²

¹Medical Physics Section, National Institute of Radiological Sciences, Chiba, Japan.
²Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, USA.
³Division of Radiation Oncology and Particle Therapy, Exploratory Oncology Research & Clinical Trial Center, National Cancer Center Hospital East, Chiba, Japan.

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

IMPT, Monte Carlo, Biological Dose, Variable RBE

Kohno, R. , Cao, W. , Yepes, P. , Bai, X. , Poenisch, F. , Grosshans, D. , Akimoto, T. and Mohan, R. (2019) Biological Dose Comparison between a Fixed RBE and a Variable RBE in SFO and MFO IMPT with Various Multi-Beams for Brain Cancer. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 8, 32-45. doi: 10.4236/ijmpcero.2019.81004.