The American college of radiology diagnostic fluoroscopy dose index registry pilot: Dosimetric performance and benchmarking challenges.

BACKGROUND: The ACR Diagnostic Fluoroscopy Dose Index Registry (DIR-Fluoro) is expanding to include diagnostic fluoroscopy. Variations in dose reference points and overhead radiography events may introduce unique challenges for benchmarking. PURPOSE: To survey the technological status and dosimetric performance of fluoroscopes participating in the DIR-Fluoro pilot project, focusing on longitudinal stability and variability of fluoroscopic dose reporting accuracy across multiple institutions and vendors. METHODS: Sixty-six fluoroscopic systems from nine institutions (24 facilities) were surveyed for facility type, fluoroscope type, image receptor type, age, dose reporting capabilities, and other key features. Of these, 56 were evaluable. Semi-annual measurements assessed reference air kerma (Ka,r) and air kerma area product (PKA) accuracy. Linear mixed-effects models evaluated changes in dose accuracy over time, incorporating system-specific random effects; models were compared using likelihood ratio testing. Radiation Dose Structured Reports (RDSR) contents were investigated to understand the challenges in benchmarking diagnostic fluoroscopy dose indices. RESULTS: Nearly 80% of units were tube-under-table fluoroscopes. Average age was 9.6 ± 5.2 years. Sixty-four percent of the units produced RDSRs. Median deviations for Ka,r and PKA were 1%-4%. Accuracy of PKA and Ka,r remained stable, with no significant time-dependent drift for RDSR-capable systems (p > 0.05). Incorporating detector type significantly improved performance for PKA measurements (p < 0.05 for all datasets); Ka,r models were generally best fit by simpler models (p > 0.05 for 3 of 4 datasets). Major discrepancies in RDSRs were observed, including differences in Ka,r reference point definitions and in event-level data. Overhead radiography exposures were not well distinguished from fluoroscope exposures. These issues resulted in inconsistencies in reported Ka,r values. CONCLUSION: Fluoroscopic dose indices were accurate and stable over time. Differences in RDSR availability result in data biased to newer systems with flat panel detectors. Discrepancies in RDSR content and inconsistent reference point definitions necessitate use of PKA as the primary benchmark metric.