When using cutouts to shape electron fields, what must be ensured about the cutout area for accurate dosimetry?

Ensuring that the open or cutout area is large enough for lateral electronic equilibrium is crucial when shaping electron fields in radiation therapy. In electron beam dosimetry, for accurate dose delivery, it is important that the region where the electron beam exits the cutout maintains the characteristics of the dose distribution expected from a uniform field.

Lateral electronic equilibrium occurs when the number of electrons entering a volume equals the number of electrons exiting it, which usually requires that the cutout be sufficiently large. If the cutout area is too small, there will be insufficient electron scattering and buildup in that region, leading to inaccuracies in the dose delivery and potential underdosage or overdosage at the treatment site.

Effective cutout design, which maintains lateral electronic equilibrium, directly impacts the effectiveness of the treatment plan, ensuring that the maximum dose is deposited in the target area while minimizing exposure to surrounding healthy tissues. Thus, for precise dosimetry when using cutouts in electron beam therapy, maintaining a cutout area that supports lateral electronic equilibrium is essential.