Final answer:
The spacer device that limits the source-to-patient distance is attached to the x-ray tube.
Step-by-step explanation:
The spacer device that limits the source-to-patient distance to a prescribed minimum limit is attached to the x-ray tube on a portable c-arm fluoroscope.
On a mobile fluoroscopic unit, the spacer device is important for maintaining a safe distance between the x-ray source and the patient. By attaching it to the x-ray tube, the distance between the source and patient is controlled, reducing the risk of excessive radiation exposure to the patient.
This spacer device helps ensure that the patient receives the necessary diagnostic information while minimizing the potential harm from radiation.