What is the output factor of a 60 Cobalt unit for a 6 cm x 6 cm field if the air kerma rate is 100 cGy/min?

The output factor is a crucial parameter in radiotherapy, particularly for cobalt-60 units, as it represents the ratio of the radiation dose delivered to the patient in a specific field size compared to a reference field size. In the case of cobalt-60, the output factors are influenced by various aspects including the energy of the radiation, the geometry of the treatment field, and the physical properties of the tissue being irradiated.

When dealing with a 6 cm x 6 cm field size, the output factor will often be less than the standard air kerma rate value, which is measured at a reference condition. Given the scenario where the air kerma rate is 100 cGy/min, it indicates the dose rate for a standard or reference output.

The choice reflecting 92 cGy/min as the output factor suggests that under the specified conditions, the dose rate is slightly less (92% of the air kerma rate) due to geometric and tissue interaction factors inherent to a smaller field size. This output factor accounts for the decreased efficiency of dose delivery for smaller treatment areas, which is a common occurrence due to scattering and other physical interactions. Thus, the output factor of 92 cGy/min for the 6 cm x 6 cm field correctly