Where should the x-ray tube be positioned during C-arm fluoroscopy to reduce dose to the patient?

Where should the x-ray tube be positioned during C-arm fluoroscopy to reduce dose to the patient?

• A. to the left of the patient
• B. over the patient
• C. to the right of the patient
• D. under the patient

Answer: (D)

In fluoroscopy, how the x-ray beam is introduced relative to the patient changes where the skin receives the highest dose and how scatter is distributed. Placing the x-ray tube under the patient means the beam enters from beneath the table and travels up through the body to the detector above. This geometry tends to spread the exposure over a larger skin area and lets the table/shielding contribute to reducing the peak entrance dose on the surface facing the beam. As a result, the maximum skin dose is lower than it would be if the tube were positioned over the patient, where the beam would more directly irradiate a single surface area. In short, under-table tube positioning uses the geometry and shielding to help minimize the patient’s skin dose during fluoroscopy.

In fluoroscopy, how the x-ray beam is introduced relative to the patient changes where the skin receives the highest dose and how scatter is distributed. Placing the x-ray tube under the patient means the beam enters from beneath the table and travels up through the body to the detector above. This geometry tends to spread the exposure over a larger skin area and lets the table/shielding contribute to reducing the peak entrance dose on the surface facing the beam. As a result, the maximum skin dose is lower than it would be if the tube were positioned over the patient, where the beam would more directly irradiate a single surface area. In short, under-table tube positioning uses the geometry and shielding to help minimize the patient’s skin dose during fluoroscopy.