In fluoroscopy, which technique reduces patient exposure by delivering the dose in short pulses?

• A. Use pulsed fluoroscopy
• B. Increase frame rate
• C. Use continuous fluoroscopy
• D. Increase exposure time

Answer: (A)

The main idea is that patient dose in fluoroscopy is driven by how long the x-ray beam is on. Delivering exposure in short pulses cuts the average beam-on time, so the cumulative dose is reduced while still providing real-time imaging. In pulsed fluoroscopy, the beam is on only briefly during each pulse and off in between, lowering the overall exposure over a procedure.

Increasing frame rate, using continuous fluoroscopy, or simply increasing exposure time would increase the amount of time the beam is on (and often the number of frames acquired), which raises the patient dose instead of reducing it. Pulsed fluoroscopy achieves dose reduction by decreasing the duty cycle—the fraction of time the beam is active—without necessarily sacrificing diagnostic usefulness.