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. Author manuscript; available in PMC: 2012 Jul 15.
Published in final edited form as: Int J Radiat Oncol Biol Phys. 2010 Jul 7;80(4):1015–1022. doi: 10.1016/j.ijrobp.2010.03.012

Figure 5.

Figure 5

(a) and (b) Illustrations of the concept of using a range shifter (RS) to reduce the spots size: dose distributions of a single spot with energy 138.1 MeV (a) and 171.3 MeV (b). Both spots reached the same depth in the body but with different lateral profiles at the depth of the arrows (red for the lower energy spot without RS, blue for the higher energy beam with RS). (c). The higher energy spots going through the RS demonstrated a smaller full width half maximum compared with the lower energy spot without RS in the body, indicating possible penumbra margin reduction.