What effect does hardening the beam from a physical wedge have?

The correct understanding of the effect of hardening the beam from a physical wedge relates to its ability to modify the energy distribution of the radiation reaching the patient. When a physical wedge is used in radiation therapy, it effectively changes the beam characteristics by filtering out lower-energy photons, leading to what is known as beam hardening.

This hardening process increases the average energy of the beam, which typically improves the tissue penetration capabilities of the radiation treatment. As a consequence, the higher-energy photons are less absorbed by superficial tissues, leading to an enhanced dose distribution that can be better tailored to spare healthy tissue while adequately targeting tumor tissues located deeper within the body.

Thus, while the overall dose delivered to the tumor is generally not reduced by the use of a wedge alone, the modification of the beam can optimize the dose distribution by decreasing the dose to the surface tissues (skin-sparing effect). Improved skin sparing is indeed a beneficial effect of beam hardening with wedges, as it can help reduce the unintended exposure of healthy tissues.

Thus, the concept of "reducing overall dose delivered" primarily needs to be understood in the context of the dose to specific tissues rather than the total dose of the treatment plan. Instead, the use of physical wedges primarily focuses on