Dosimetric differences in flattened and flattening filter-free beam treatment plans

Abstract

This study investigated the dosimetric differences in treatment plans from flattened and flattening filter-free (FFF) beams from the TrueBeam System. A total of 104 treatment plans with static (sliding window) intensity-modulated radiotherapy beams and volumetric-modulated arc therapy (VMAT) beams were generated for 15 patients involving three cancer sites. In general, the FFF beam provides similar target coverage as the flattened beam with improved dose sparing to organ-at-risk (OAR). Among all three cancer sites, the head and neck showed more important differences between the flattened beam and FFF beam. The maximum reduction of the FFF beam in the mean dose reached up to 2.82 Gy for larynx in head and neck case. Compared to the 6 MV flattened beam, the 10 MV FFF beam provided improved dose sparing to certain OARs, especially for VMAT cases. Thus, 10 MV FFF beam could be used to improve the treatment plan.

Keywords: Flattening filter-free beam; intensity-modulated radiotherapy; treatment plan.

Figure 1

Normalized treatment plans comparison between the flattened and the flattening filter-free beams for the static intensity-modulated radiation therapy and the volumetric-modulated arc therapy plans for 6 MV beam. Head and neck, lung, and prostate cases are shown. The solid lines are the flattened beam plans and the dashed lines are the flattening filter-free beam plans

Figure 2

Normalized treatment plans comparison between the flattened and the flattening filter-free beams for the static intensity-modulated radiation therapy and the volumetric-modulated arc therapy plans for 10 MV beam. Head and neck, lung, and prostate cases are shown. The solid lines are the flattened beam plans and the dashed lines are the flattening filter-free beam plans