Diagnostic Reference Levels for Fluoroscopy-guided Gastrointestinal Procedures in Japan from the REX-GI Study: A Nationwide Multicentre Prospective Observational Study

BACKGROUND: Diagnostic reference levels (DRLs) are required to optimize medical exposure. However, data on DRLs for interventional fluoroscopic procedures are lacking, especially in gastroenterology. This study aimed to prospectively collect currently used radiation doses and help establish national DRLs for fluoroscopy-guided gastrointestinal procedures in Japan. METHODS: This multicentre, prospective, observational study collected actual radiation dose data from endoscopic retrograde cholangiopancreatography (ERCP), interventional endoscopic ultrasound (EUS), balloon-assisted enteroscopy (BAE), enteral metallic stent placement, and enteral tube placement from May 2019 to December 2020. The study outcomes were fluoroscopy time (FT: min), air kerma at the patient entrance reference point (K(a,r): mGy), air kerma area product (P(KA): Gycm(2)), and radiation dose rate (RDR: mGy/min). Additionally, the basic settings of fluoroscopy equipment and the factors related to each procedure were investigated. This study was registered in the UMIN Clinical Trial Registry (UMIN 000036525). FINDINGS: Overall, 12959 fluoroscopy-guided gastrointestinal procedures were included from 23 hospitals in Japan. For 11162 ERCPs, the median/third quartile values of K(a,r) (mGy), P(KA) (Gycm(2)), and FT (min) were 69/145 mGy, 16/32 Gycm(2), and 11/20 min, respectively. Similarly, these values were 106/219 mGy, 23/41 Gycm(2) and 17/27 min for 374 interventional EUSs; 53/104 mGy, 16/32 Gycm(2) and 10/15 min for 523 metallic stents; 56/104 mGy, 28/47 Gycm(2), and 12/18 min for 599 tube placements; and 35/81 mGy, 16/43 Gycm(2) and 7/15 min for 301 BAEs, respectively. For the overall radiation dose rate, the median/third quartile values of RDR were 5.9/9.4 (mGy/min). The RDR values at each institution varied widely. INTERPRETATION: This study reports the current radiation doses of fluoroscopy-guided gastrointestinal procedures expressed as DRL quantities. This will serve as a valuable reference for national DRL values. FUNDING: This work was supported by a clinical research grant from the Japanese Society of Gastroenterology.