Quantifying Radiation Doses in Common Endoscopic Retrograde Cholangiopancreatography Scenarios: An Evaluation of Radiation Safety Measures in a Real-World Environment

**Background:** Radiation safety training among gastroenterologists performing endoscopic retrograde cholangiopancreatography (ERCP) is highly variable, with over half of surveyed endoscopists lacking formal training in fluoroscopy system operation. Despite published guidelines, adherence to the ALARA (as low as reasonably achievable) principle is inconsistent. This study aimed to provide concrete, quantifiable dosimeter readings for common ERCP scenarios to support the three pillars of radiation safety: distance, time, and shielding.

**Methods:** The study was conducted in a fixed fluoroscopy unit (Philips Easy Diagnost Fluoro System) at Kaiser Permanente Los Angeles Medical Center. Two anthropomorphic phantoms were used: an "average" phantom (22-cm anterior/posterior diameter) and a "large" phantom (32-cm anterior/posterior diameter), positioned as for an actual ERCP with a blocking drape. Default settings for the average phantom were 70 kVp and 0.4 mA; for the large phantom, 107 kVp and 0.8 mA. Radiation scatter was measured with an ion survey meter in milliroentgen per hour (mR/h) at distances of 1.5 ft (operator position), 6 ft (nurse/anesthesiologist), and 9 ft (room border), both with and without a 0.5-mm lead apron, at thyroid (5 ft) and gonad (3 ft) levels. Frame rate effects were tested at 8, 4, and 2 frames per second (fps). Image quality was assessed using a TOR 18FG fluoroscopy phantom, counting visible line pairs at different air gaps (0 in. and 18 in.) and frame rates.

**Key Results:** - **Distance:** For the average phantom, unshielded scatter at thyroid level decreased from 0.75 mR/h at 1.5 ft to 0.28 mR/h at 6 ft (62.7% reduction) and to 0.15 mR/h at 9 ft (46.5% reduction from 6 ft). For the large phantom, scatter decreased from 50.00 mR/h at 1.5 ft to 9.20 mR/h at 6 ft (81.6% reduction) and to 3.06 mR/h at 9 ft (66.7% reduction from 6 ft). The reduction from 6 ft to 9 ft approximated the inverse-square law, but the reduction from 1.5 ft to 6 ft did not. - **Time (Frame Rate):** For the average phantom, scatter at thyroid level was 55.00 mR/h at 8 fps, 24.50 mR/h at 4 fps, and 13.60 mR/h at 2 fps—roughly a 2-fold decrease with each halving of frame rate. For the large phantom, scatter was 5400 mR/h at 8 fps, 2700 mR/h at 4 fps, and 1340 mR/h at 2 fps. Fluoroscopy pedal actuation showed a linear relationship with scatter (1.6 mR/h for average, 96 mR/h for large phantom). - **Shielding:** Using a 0.5-mm lead apron reduced scatter by 97.2% for both phantoms: from 4.10 to 0.11 mR/h (average) and from 15.30 to 0.43 mR/h (large). - **Image Quality:** Decreasing frame rate from 8 fps to 2 fps did not change the number of line pairs identified (11 line pairs at both rates). Increasing air gap from 0 in. to 18 in. increased line pairs from 4 to 8.

**Clinical Implications:** This study provides concrete evidence that implementing the three pillars of radiation safety—increasing distance, reducing fluoroscopy time (via lower frame rates or less pedal actuation), and using lead shielding—can dramatically reduce radiation scatter in ERCP. Notably, reducing frame rate from 8 to 2 fps did not degrade image resolution, suggesting that lower frame rates can be safely adopted. The findings support standardized radiation safety education for gastroenterologists, as current training is inconsistent. The authors advocate for mandatory documentation of fluoroscopy doses, time-limited fluoroscopy, and emerging AI-based collimation systems to further reduce exposure. These principles are applicable to other fluoroscopy-using specialties.