Introduction
Interventional endoscopic ultrasound (EUS) procedures are crucial for gastrointestinal disease management. Radiation safety is important for patients and medical staff. We identified determinants of radiation dose in interventional EUS procedures.

Methods
We performed univariate analysis on demographic, clinical and procedural factors of 62 consecutive patients who underwent interventional EUS procedures (cystgastrostomy, biliary drainage and gastroenterostomy) at our unit over 2 years.

Primary outcomes were procedure time, fluoroscopy time and radiation dose (Dose Area Product (DAP) (µGym²)). All procedures were performed by either one or both of the interventional endosonographers in our unit. Multivariable analysis was performed on factors with p<0.1 on univariate analysis to identify independent predictors.

Results
54.8% of patients were male, with a mean age of 63.2±16.2 years and BMI of 22.0±5.2kg/m². 29 patients (46.8%) underwent EUS cystgastrostomy, 23 (37.1%) EUS biliary drainage, and 10 (16.1%) EUS gastroenterostomy. 48.4% of procedures were performed under general anesthesia. Procedures were performed either in supine or prone position. 18 patients (29.0%) had ascites. 34 procedures (54.8%) were performed by both interventional endoscopists. The overall complication rate was 14.5%. Procedure DAP dose was 2291±3295µGym². Procedures lasted 50.1±29.4mins, with a fluoroscopy time of 665±537s.

On multivariable analysis: Procedures performed together by two attending interventional endosonographers was associated with significantly shorter procedure time (38.6 vs 64.2mins, p=0.001), shorter fluoroscopy time (444.9 vs 933.0s, p<0.001) and lower radiation dose (4020.5 vs 867.6 µGym², p=0.001) compared to procedures performed by one interventional endosonographer alone.

Fellow involvement was associated with significantly longer procedure time (52.2 vs 34.3mins, p=0.007), longer fluoroscopy time (702.1 vs 376.3s, p=0.001) and higher radiation dose (2502.8 vs 630.8µGym², p<0.001). Presence of intra-procedure complications had longer procedure time (87.1 vs 43.6mins (p=0.01), longer fluoroscopy time (1351.3 vs 548.8s, p=0.007) and higher radiation dose (4839.4 vs 1858.8µGym² , p=0.091) (Tables 1 and 2).

Higher radiation dose was required in patients with a higher Body Mass Index (BMI) (p<0.001). Neither depth of anesthesia nor presence of ascites significantly affected the study outcomes.

In a subgroup analysis, EUS cystgastrostomy using only plastic stents had longer fluoroscopy time compared to using lumen apposing metal stents (892.4 vs 389.3s, p=0.017).

Conclusion
Interventional EUS procedures are technically complex. Involvement of more than one interventional endosonographer significantly reduced radiation dose, fluoroscopy time and procedure time. Further studies are needed to establish its role as a radiation reduction strategy

Multivariable analysis of determinants of procedure time for interventional EUS procedures

Multivariable analysis of determinants of fluoroscopy time and radiation dose for interventional EUS procedures

Samuel Lim

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