TITLE:
Dose Comparison between Eclipse Dose Calculation and Fast Dose Calculator in Single- and Multi-Field Optimization Intensity-Modulated Proton Therapy Plans with Various Multi-Beams for Brain Cancer
AUTHORS:
Ryosuke Kohno, Wenhua Cao, Pablo Yepes, Xuemin Bai, Falk Poenisch, David R. Grosshans, Tetsuo Akimoto, Radhe Mohan
KEYWORDS:
Fast Dose Calculator, Monte Carlo, Intensity-Modulated Proton Therapy, Single-Field Optimization (SFO), Multi-Field Optimization (MFO)
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.6 No.4,
November
23,
2017
ABSTRACT: The purpose of this study
was to grasp current potential problems of dose error in intensity-modulated
proton therapy (IMPT) plans. We were interested in dose differences of the
Varian Eclipse treatment planning system (TPS) and the fast dose calculation method (FDC) for single-field optimization
(SFO) and multi-field optimization
(MFO) IMPT plans. In addition, because some authors have reported dosimetric benefit of a proton arc
therapy with ultimate multi-fields in recent years, we wanted to
evaluate how the number of fields and beam angles affect the differences for IMPT plans. Therefore, for one brain cancer patient with a large
heterogeneity, SFO and MFO IMPT plans with various multi-angle beams were
planned by the TPS. Dose
distributions for each IMPT plan were calculated by both the TPS’s conventional
pencil beam algorithm and the FDC. The dosimetric parameters were compared
between the two algorithms. The TPS
overestimated 400 - 500 cGy (RBE) for minimum dose to the CTV relative to the
dose calculated by the FDC. These differences indicate clinically relevant effect on clinical results. In addition, we observed
that the maximum difference in dose calculated between the TPS and the
FDC was about 900 cGy (RBE)
for the right optic nerve, and this quantity also has a possibility to have a
clinical effect. The major difference was not seen in calculations for SFO IMPT
planning and those for MFO IMPT planning. Differences between the TPS and the FDC in SFO and
MFO IMPT plans depend strongly on beam arrangement and the presence of a
heterogeneous body. We advocate use of a Monte Carlo method in proton treatment
planning to deliver the most precise proton dose in IMPT.