As the distance from the x-ray source increases, how must the dose be adjusted to maintain the same brightness?

To maintain the same brightness as the distance from the x-ray source increases, the dose must be increased. This is rooted in the inverse square law of radiation, which states that the intensity of radiation is inversely proportional to the square of the distance from the source.

As the distance from the x-ray source doubles, the intensity of the radiation reaching the target decreases by a factor of four (2 squared). Therefore, to achieve the same level of brightness or intensity at a greater distance, the dose applied must be increased to compensate for this reduction in intensity. This necessity to adjust the dose emphasizes the importance of understanding the relationship between distance and radiation exposure, particularly in the context of maintaining image quality in fluoroscopy.

Consequently, if you intend for the image to appear equally bright at varying distances, you must increase the radiation dose.