Author: Caroline Cheney, Nicole M. Lafata, Zaiyang Long, Dustin W. Lynch, Erin B. Macdonald, Andy Madore, Douglas E. Pfeiffer, Colin Schaeffer, Alexander W. Scott 👨🔬
Affiliation: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, UVA Health, Duke University Health System, Mayo Clinic, Henry Ford Health, Boulder Community Health, Varian, Cedars-Sinai Medical Center 🌍
Purpose: This work evaluates the significance of performing established radiography automatic exposure control (AEC) tests by comparing testing methodology, outcomes, and failure rates across multiple institutions.
Methods: AEC performance testing data were retrospectively collected by physicists from six institutions utilizing physics survey results spanning three to five years. Tests performed and their methodologies were compared, and survey outcomes were analyzed to determine test failure rates. For institutions regularly performing AEC sensitivity tests, percent errors were reviewed.
Results: A total of 724 unique physics reports comprising 8,394 AEC tests were reviewed. These included 656 annual, 48 acceptance, 17 post-service, and 3 other reports. Testing set up (grid use, technique, attenuator type, etc.) and pass-fail criteria varied between institutions for the majority of tests. Data from six different manufacturers were represented. The tests most frequently performed across institutions were exposure reproducibility, cell balance, and AEC sensitivity. Tests with failure rates exceeding 2% included combination thickness and kV tracking (16.6%), sensitivity (9.0%), density selector (5.4%), and cell balance (5.1%). The overall test failure rates varied significantly across institutions, ranging from 0.2% - 8.3%. Notably, the institution with the smallest fail rate performed fewer of the high fail rate tests than other institutions. Three institutions submitted AEC sensitivity data, the percent error from the target sensitivity was evaluated. The median absolute value for sensitivity percent error was 8.1% ± 20.4%, the kurtosis of this data distribution was 14.7, suggesting extreme outliers are more likely.
Conclusion: The relatively high failure rates for tests such as tracking and sensitivity, which directly impact AEC consistency and exposure level performance, demonstrate regular testing of AEC functionality is essential for maintaining optimal system performance.