## 3 Results
### Percentual Depth Dose and Dose Profiles
Titanium and steel exhibit a mild attenuation, with inline doses of 77.36% and 53.09%, respectively. The tabulated data indicate that the Co-Cr-Mo alloy significantly influences dose attenuation at 100 MeV VHEE. In contrast, titanium and steel demonstrate a very low attenuation relative to water. Figure 7 presents simulations of the dose distributions for 150 MeV VHEE in addition to their analysis. At a depth of 1 cm in water, the dose attains 82.89%, which is analogous to the values for Co-Cr-Mo alloy (82.95%), titanium (82.96%), and steel (82.80%). At increasing depths, the disparities become more evident; at a depth of 5 cm, water attains 90.95%, whilst Co-Cr-Mo declines to 81.54%. Titanium shows higher values (81.66%), but steel attains 82.1%, signifying a marginal reduction relative to Co-Cr-Mo alloy. At a depth of 15 cm, the dose in water is 99.85%, whereas Co-Cr-Mo diminishes to 80.59%, further demonstrating its considerable attenuation. Crossline profiles exhibit the same behavior, with the dose attaining 100% in water but decreasing to 61.12% for Co-Cr-Mo. Titanium exhibits a high value of 93.76%, whereas steel attains 75.51%. The inline profiles exhibit a consistent pattern, indicating that water maintains a value of 100%, while Co-Cr-Mo substantially decreases to 60.67%, titanium registers at 93.5%, and steel at 74.16%. The results indicate that the Co-Cr-Mo alloy significantly influences dose attenuation at 150 MeV VHEE. However, titanium and steel exhibit a mild attenuation relative to water, as evidenced by the lower discrepancies among values at all depths and profiles. Figure 6: (**a**) PDDs for 100 MeV (VHEE) with metal box; (**b**) dose profiles for 100 MeV (VHEE) with metal box. In the case of 170 MeV protons (Figure 8), the range of the Bragg peak in water is a benchmark for comparing the effect of different metallic materials on the shift and dose reduction. In the simulations, the Bragg peak for water was set to a depth of 19.4 cm, with metallic materials inducing significant shifts of this peak towards the surface, characteristic of protons' interaction with dense materials. The Co-Cr-Mo alloy caused the most significant shift of the Bragg peak, namely to 9.9 cm, which implies a shortening of the rank by almost 9.5 cm relative to water. This shift is directly related to the high density of Co-Cr-Mo, which causes intense proton energy loss in the surface layers. This phenomenon is significant in treating patients with Co-Cr-Mo implants, as there is a sharp reduction in the depth near the implant where the maximum dose is achieved. For the titanium alloy, the Bragg peak shifted to 15 cm, representing a more moderate shift of approximately 4.4 cm relative to water. As a lower-density material compared to Co-Cr-Mo, titanium causes less of a shift, meaning its effect on proton therapy is less  
Figure 8: (**a**) PDD for 170 MeV (protons) with metal box; (**b**) dose distribution for 170 MeV (protons) with metal box. Figure 7: (**a**) PDDs for 150 MeV (VHEE) with metal box; (**b**) dose profiles for 150 MeV (VHEE) with metal box. dramatic but still significant. Stainless steel caused a shift of the Bragg peak to 12.4 cm, which is intermediate between Co-Cr-Mo and titanium, with a shift of 7 cm from the reference value for water. The steel also exhibits a high interaction with protons, leading to a significant shortening of the rank.