What principle explains why less hardening occurs with dynamic wedges compared to traditional wedges?

The principle that justifies why less hardening occurs with dynamic wedges compared to traditional wedges is that less material is present in the beam path. Dynamic wedges employ movable components in the linear accelerator that allow for variable beam shaping without the need for a physical wedge that remains in the path of the beam. Because traditional wedges are solid pieces of material placed in the beam, they add to the effective attenuation of the beam, leading to greater hardening due to increased interactions with the material.

In contrast, since dynamic wedges manipulate the shape and angle of the beam using mechanical means rather than additional physical material, there is a reduced opportunity for beam hardening effects that are a result of photon interactions with dense materials. By ensuring a more direct path with less obstruction, dynamic wedges maintain the energy characteristics of the beam more effectively, leading to less hardening than seen with traditional wedges that inherently modify the beam quality through their material composition.