Which size exposure field results in the least gonadal dose to the patient?

The size of the exposure field directly influences the radiation dose received by the patient, particularly to sensitive areas like the gonads. The smaller the exposure field, the more localized the radiation is, which reduces the amount of radiation that reaches surrounding tissues, including the gonads.

In this case, an 8 x 10 exposure field is the smallest relative to the others presented. This reduced size means that less area is exposed to radiation, effectively minimizing the patient's overall exposure and, particularly, the gonadal dose. Hence, using a field size of 8 x 10 leads to the least gonadal dose among the other options, which are larger in size and would therefore encompass more tissue and potentially deliver a higher dose to the gonadal region.

The other field sizes, while suitable for specific imaging requirements, increase the irradiated area and thereby the potential dose to the gonads, making them less advantageous in terms of minimizing patient exposure.