Relationships between radiation exposure dose, time, and projection in videofluoroscopic swallowing studies

Purpose: Clinicians are trained to rely on radiation exposure time as an indicator of patient radiation exposure in Videofluoroscopic Swallowing Studies (VFSSs). However, it has been shown in other medical uses of fluoroscopy that dose area product (DAP), the amount of radiation delivered to the patient, is a better indicator of overall patient radiation exposure than radiation exposure time. This study sought to understand the relationship of DAP in VFSSs with radiation exposure time and projection used (lateral vs. posterior-anterior [PA]). Method: DAP, radiation exposure time, and projection were recorded in 200 adults undergoing clinically indicated VFSSs conducted in accordance with the Modified Barium Swallow Impairment Profile guidelines. Data were analyzed using Spearman correlation and related sample Wilcoxon test. Results: DAP and radiation exposure time did not correlate significantly in the lateral or upper PA projections. DAP was significantly higher in the PA compared to lateral projection (p <.01); however, time was shorter in PA versus lateral (p <.01). The average mGy-cm² per second was 7 for lateral projections, 14 for upper PA projections, 17 for middle PA projections, and 34 for lower PA projections. Conclusions: Radiation exposure time and DAP do not strongly correlate across VFSSs. Specifically, this means that 1 patient can have a low radiation exposure time with a high DAP relative to another person with a higher radiation exposure time but a lower DAP. The results of this study question the common clinical practice of using time (specifically the 5-min indicator) as a threshold for radiation exposure during a VFSSs.