Technical note: Workload and transmission data for mobile C-arm fluoroscopy in gastrointestinal endoscopy.

Abstract

Mobile C-arms may be used in fixed locations, and it is recommended that qualified experts evaluate structural shielding. To assess clinical workload distributions for mobile C-arms used in gastrointestinal endoscopy and determine the Archer equation parameters for the C-arm beam spectra. Consecutive (30 months) gastrointestinal endoscopic procedures on two Cios Alpha systems (Siemens) were retrospectively analyzed. X-ray tube voltage, tube current-time product, reference point air kerma (Ka,r), air kerma-area product (PKA), and fluoroscopic time were examined. The primary beam half-value layer (HVL) was measured with an ionization chamber and aluminum 1100 plates. Stray radiation fraction at 1m from a scattering source (ACR R/F phantom) was directly measured. Monte Carlo (Geant4) simulation was performed to calculate the transmission of broad X-ray beams through lead, concrete, gypsum, and steel, with X-ray HVLs matching those of the C-arm X-ray beam. The transmission data were fitted to the Archer equation. The number of procedures (3509) was equivalent to 13.48 procedures per room per week. Dose quantities were 54.8 mGy (Ka,r), 18.3Gy∙cm2 (PKA), and 7.8 min (fluoroscopic time) per procedure. X-ray beam irradiation events were recorded for 2906 (82.8%) procedures with 160,009 events, whose mA-minute weighted tube voltage was 91.0kV and the workload was 0.68mA-minute per procedure. The two rooms had a significant difference in the number of procedures per week, 17.3 (29) [mean (maximum)] and 9.6 (16), respectively. The stray radiation fraction was 9.7×10-4 (80kV) and 1.25×10-3 (120kV). Transmission fitting parameters were provided for the tube voltage (on average, 90kV; high end, 120kV) of the C-arm. This work provides workload and transmission data for mobile C-arm fluoroscopy in gastrointestinal endoscopy, which indicates a need for structural shielding evaluation of the procedure rooms.