When a field size different from 10 x 10 cm is used in treatment planning, what factor is applied?

When using a field size different from the standard 10 x 10 cm in treatment planning, the field size correction factor is applied to ensure accurate dosimetry. This factor accounts for the changes in dose distribution and scatter that occur when the treatment field dimensions vary from the reference field size.

In radiation therapy, the 10 x 10 cm field is often used as a baseline because it represents a standard condition where the dose can be reliably calculated. When a different field size is used, the arrangement of the beam and the amount of tissue irradiated change, impacting the dose received by the patient. The field size correction factor is specifically designed to adjust the calculated dose to reflect these variances, enhancing the precision of the treatment planning process.

Therefore, the application of the field size correction factor ensures that the prescribed dose delivered to the tumor remains accurate, taking into account the different scattering patterns and the increased or decreased surface area being treated.