Which of the following factors influences operator dose the most during fluoroscopy?

The factor that influences operator dose the most during fluoroscopy is the distance from the primary beam. As the operator's distance from the radiation source increases, the intensity of the radiation exposure significantly decreases due to the inverse square law. This physical principle states that the intensity of radiation is inversely proportional to the square of the distance from the source. Therefore, maintaining a greater distance from the primary beam effectively reduces the radiation dose received by the operator.

While all options may impact overall operator dose in fluoroscopy, the distance from the primary beam has a particularly profound effect because even small increases in distance can lead to substantial decreases in dose. Other factors, such as procedure duration and type, can certainly influence total exposure, but they do not have the same fundamental impact as adjusting distance from the radiation source. Collimation, which is the process of restricting the beam to the area of interest, also reduces incidental exposure but to a lesser extent than the impact of distance.