**Figure 3.**

*Depth dose distribution in aluminum (Al, Zeff = 13), graphite (C, Zeff = 6), water (H2O, Zeff = 7.4), and polypropylene (C2H4, Zeff = 5.4) irradiated with 10 MeV electrons.*

Electrons with the energies up to 10 MeV, which is the maximum energy used in radiation treatment of biological objects, lose their energy due to ionization losses. It can be seen from **Figure 3**, the higher its effective charge *Zeff* and density, the more energy is lost by an electron penetrating an equal depth in different materials, according to the Bethe-Bloch formula [46]. Moreover, with an increase in the effective charge *Zeff* the maximum penetration depth of electrons throughout the object decreases, at the same time causing the surface absorbed dose to decrease compared to the maximum value. Therefore, the material with a higher electron density tends to have a lower irradiation uniformity compared with the material with a lower electron density, as **Table 2** shows.
