2220 RADIATION EXPOSURE DURING CONTINUOUS VERSUS PULSED FLUOROSCOPY

Abstract

INTRODUCTION AND OBJECTIVES: There are multiple modalities to produce and capture fluoroscopic images, including continuous and pulsed modes. Continuous fluoroscopy allows for real-time imaging but could deliver larger radiation doses to the patient. Pulsed fluoroscopy delivers bursts of radiation at set intervals, reducing fluoroscopy times. Despite this reduction in times, studies have shown no difference in effective dose when comparing pulsed fluoroscopy to continuous fluoroscopy due to the “ramp and trail effect”. Newer X-ray tubes can now deliver a more uniform current in a pulsed fashion while reducing unwanted radiation by minimizing this effect. The purpose of this study is to directly compare the amount of radiation delivered under pulsed fluoroscopy against continuous fluoroscopy in a modern C-arm system. METHODS: Thermoluminescent dosimeters (TLDs) were implanted at 3 sites in a female human cadaver to directly measure radiation dose, including the left kidney, posterior skin, and anterior skin. While in the supine position, the cadaver received 30 pedal activations either in the continuous or pulsed mode (1 pulse/sec) using a modern C-arm at 69 kVp and 1.51 mAs to visualize an implanted guide wire and a radio-opaque stone. The amount of radiation absorbed by the TLDs was recorded. Data was analyzed using a paired two-tailed Student’s t-test ( 0.05), Wilcoxon Signed Ranks procedure, and least-squares analysis. RESULTS: Pulsed fluoroscopy delivered lower doses of radiation compared to continuous fluoroscopy at each site examined: anterior skin (0.10 vs 0.26 mGy, p 0.001), kidney (0.15 vs 0.40 mGy, p 0.001), and posterior skin (0.92 vs 2.62 mGy, p 0.001). Mean fluoroscopy time differed significantly between continuous (12.5 s, range 12.2–13.7 s) and pulsed (3.0 s, range 2.9–3.0 s; p 0.001). Fluoroscopy time positively correlated with radiation exposure at all sites: anterior skin (0.017 mGy/sec, R 0.90), left kidney (0.026 mGy/ sec, R 0.96), and posterior skin (0.18 mGy/sec, R 0.98). However, pulsed mode delivered more radiation per second of fluoroscopy time compared to continuous mode overall and at all sites (p 0.001). CONCLUSIONS: When using fluoroscopy, pulsed images significantly reduce radiation exposure compared to continuous fluoroscopy. Using the same pedal activation time, continuous mode resulted in significantly longer fluoroscopy times compared to pulsed mode. These longer fluoroscopy times outweighed the higher dose per second delivered by the pulsed fluoroscopy mode. Thus, pulsed fluoroscopy could be used to minimize radiation exposure to patients whenever appropriate.