Author: Brendon J. Villegas 👨🔬
Affiliation: University of Alabama Birmingham 🌍
Purpose: The Cumulative Air Kerma (CAK) has traditionally been a surrogate metric for patient exposure to ionizing radiation during clinical esophagrams. Recently, UAB technologists observed that a newer fluoroscopy unit was delivering higher radiation doses than the other units. While esophagram doses are generally low, there is no standardized method to compare dose characteristics between units to help optimize patient dose. While esophagram radiation doses can be compared between exams, patient size significantly impacts radiation dose and CAK does not account for this variability.
Methods: The x-ray tech recorded the Cumulative Air Kerma (CAK), total fluoroscopy time, and fluoroscopic operator after each esophagram. CAK was normalized to fluoroscopy time (CAK/Fluoro Time) and further normalized to patient BMI using weight and height data from Cerner's “Powerchart.” Imaging data from the “Double Contrast” and “Modified Barium Swallow” esophagrams were collected across three fluoroscopic units (Siemens, Phillips, Shimadzu) in both the outpatient and inpatient clinical settings.
Results: The Double Contrast Esophagrams had an average of 0.434, 0.327, and 0.771 mGy/(min*kg/m2) for the Siemens, Phillips and Shimadzu units, respectively. The Modified Barium Swallow (MBS) Esophagrams had an average of 0.174, 0.163 and 1.148 mGy/(min*kg/m2) for the Siemens, Phillips and Shimadzu units, respectively. The Shimadzu fluoroscopy unit consistently produces larger patient doses as confirmed for both the double contrast and MBS esophagrams.
Conclusion: This work confirms that the Shimadzu fluoroscopy unit consistently delivers higher patient radiation doses compared to Siemens and Phillips units for both Double Contrast and Modified Barium Swallow esophagrams. The significant variability in dose across different units, as demonstrated by a one-way ANOVA (p < 0.0001), highlights the need for a standardized method to compare fluoroscopy dose characteristics. Normalizing CAK to fluoroscopy time and patient BMI provides a quick and robust assessment of patient radiation exposure during the esophagram.