When treating the chest wall with an electron beam, what may be utilized to ensure a uniform dose to the target volume if part of the wall is of lesser thickness?

Using bolus material is an effective technique for ensuring a uniform dose when treating the chest wall with an electron beam, particularly in areas where the thickness of the tissue may be less than the necessary treatment depth. Bolus material, often made from a flexible polymer, is placed on the skin surface, effectively bringing the dose distribution closer to the surface. This compensatory measure helps overcome the issue of electron beams losing energy as they pass through tissue, ensuring that the target volume receives an adequate dose, especially in thicker regions.

The need for bolus arises because the dose from an electron beam is highest just beneath the surface, and as the beam penetrates deeper, the dose typically decreases. In regions where the chest wall is thinner, using bolus can help boost the surface dose to levels that ensure therapeutic effectiveness while still protecting surrounding healthy tissues. This technique is critical in treating conditions such as post-surgery breast cancer, where precision in dose distribution can significantly affect treatment outcomes.

The other options do not effectively address the issue of ensuring a uniform dose across varying thicknesses of tissue in the context of electron beam therapy for the chest wall.