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. Author manuscript; available in PMC: 2021 Dec 2.
Published in final edited form as: Nat Rev Phys. 2021 Sep 17;3(12):777–790. doi: 10.1038/s42254-021-00368-5

Figure 2. Dose-averaged linear energy transfer versus depth in tissue for a single spread-out Bragg peak of protons, He, C and O providing a uniform physical dose (2 Gy) in the target volume.

Figure 2

a | The grey area represents the tumour region, a 2.5 × 2.5 × 2.5 cm3 volume centred at 8 cm in water. The yellow and orange lines are 100 and 20 keV μm-1 linear energy transfer (LET) levels, respectively. An ideal bullet should have LET < 20 keV μm-1 in the entrance channel and >100 keV μm-1 in the target volume7. b,c | Monte Carlo TRAX code simulation of C-ion tracks in the entrance channel (100 MeV/n; to the left of the grey tumour region in part a) and the Bragg peak (3 MeV/n), providing the same dose in a 1 × 1 × 0.5 μm3 volume. Figure modified from Tommasino et al.167, distributed under Creative Commons CC-BY. Part a is adapted from REF.167, CC BY 4.0.