As the field of view (FOV) decreases during fluoroscopy, what happens to the patient dose?

As the field of view (FOV) decreases during fluoroscopy, the patient dose increases because the system concentrates the radiation to a smaller area. When the FOV is reduced, the tube output is typically adjusted to maintain image quality, meaning that the same amount of radiation is delivered over a smaller area. This results in a higher dose of radiation to the patient per unit area, increasing the overall dose.

Additionally, a smaller FOV also means that any increase in image noise is counteracted by increasing the radiation exposure to ensure the image remains diagnostically useful. Therefore, although the area being imaged is smaller, the amount of radiation delivered to that area increases, resulting in a higher patient dose compared to a larger FOV where the radiation is more evenly distributed and averaged over a greater area.