Which factor has the least effect on the radiation dose received by a patient during a radiologic exam?

Filtration has the least effect on the radiation dose received by a patient during a radiologic exam, primarily because its primary role is to enhance the quality of the x-ray beam rather than to significantly reduce the quantity of radiation the patient receives. Filtration removes low-energy x-rays from the beam, which do not contribute to the formation of the diagnostic image but do increase the overall dose to the patient.

While it does play a role in dose optimization, the other factors—tube current, exposure time, and source-to-image distance—have a much more direct influence on the actual dose received. Tube current and exposure time directly correlate to the amount of ionizing radiation produced and, consequently, the dose delivered to the patient. The source-to-image distance affects the intensity of the x-ray beam at the patient's location, with closer proximity resulting in higher doses due to the inverse square law.

Therefore, while filtration is an important consideration in radiography for image quality and patient safety, its impact on the dose received is comparatively minor when placed alongside the other factors.