What is the required field size for lateral scatter equilibrium for a 10 MeV clinical electron beam?

For lateral scatter equilibrium in clinical electron beams, especially in the context of a 10 MeV beam, the field size must be sufficiently large to allow for adequate scattering to occur. Generally, lateral scatter equilibrium is achieved when the width of the treatment field is large enough to minimize the influence of any border effects from the edges of the beam.

In the case of a 10 MeV electron beam, a field size of 10 cm x 10 cm is typically considered the minimum to ensure that lateral scatter contributions are significant enough to maintain dose uniformity across the beam. Smaller field sizes may not allow the scattered particles to achieve equilibrium, leading to a drop-off in dose at the periphery.

Field sizes larger than 10 cm x 10 cm can further enhance scatter and improve dose uniformity, but the given context of the question focuses on the minimum requirement. لذا, the indicated choice reflects the standard practices for achieving proper treatment planning and ensuring a consistent dose distribution necessary for effective clinical outcomes in radiation therapy.