What happens to patient radiation dose when the image intensifier is moved away from the patient in a fluoroscopic system with ABC mechanism?

In a fluoroscopic system equipped with Automatic Brightness Control (ABC), moving the image intensifier further away from the patient increases the patient’s radiation dose primarily due to the inverse square law. This law states that the intensity of radiation is inversely proportional to the square of the distance from the source.

As the distance between the x-ray source and the image intensifier increases, the amount of radiation that reaches the patient must be increased to maintain the same image quality. This increase in radiation exposure happens because the ABC system automatically compensates for the reduced amount of radiation reaching the image detector by increasing the exposure rate, which, in turn, raises the dose to the patient.

The other options are based on misunderstandings of how distance affects radiation dose. Improved image quality does not necessarily correlate with decreased radiation dose when distance increases; in fact, maintaining image quality requires more radiation. The dose remaining unchanged regardless of distance does not align with the principles of radiation physics. Additionally, better x-ray absorption as a reason for decreased dose when increasing distance does not hold, as absorption is not directly influenced by the distance to the image intensifier; it is primarily related to tissue composition and thickness.