Using 7.5 frames per second reduces radiation exposure in lower extremity peripheral vascular interventions

Radiation Awareness for Endovascular Abdominal Aortic Aneurysm Repair in the Hybrid Operating Room. An Instant Patient Risk Chart for Daily Practice

Purpose: To determine which patient and C-arm characteristics are the strongest predictors of intraoperative patient radiation dose rates (DRs) during endovascular aneurysm repair (EVAR) procedures and create a patient risk chart. Methods: A retrospective analysis was performed of 74 EVAR procedures, including 16,889 X-ray runs using fixed C-arm imaging equipment. Four multivariate log-linear mixed models (with patient as a random effect) were constructed. Mean air kerma DR (DR_AK, mGy/s) and the mean dose area product DR (DR_DAP, mGycm²/s) were the outcome variables utilized for fluoroscopy as differentiated from digital subtraction angiography (DSA). These models were used to predict the maximum radiation duration allowed before a 2-Gy skin threshold (for DR_AK) or a 500-Gycm² threshold (for DR_DAP) was reached. Results: The strongest predictor of DR_AK and DR_DAP for fluoroscopy imaging was the radiation protocol, with an increase of 200% when changing from “low” to “medium” and 410% from “low” to “normal.” The strongest predictors of DR_AK and DR_DAP for DSA were C-arm angulation, with an increase of 47% per 30° of angulation, and body mass index (BMI), with an increase of 58% for every 5-point increase in BMI. Based on these models, a patient with a BMI of 30 kg/m², combined with 45° of rotation and a field size of 800 cm² in the medium fluoroscopy protocol has a predicted DR_AK of 0.39 mGy/s (or 85.5 minutes until the 2-Gy skin threshold is reached). While using comparable settings but switching the acquisition to a DSA with a “2 frames per second” protocol, the predicted DR_AK will be 6.6 mGy/s (or 5.0 minutes until the 2-Gy threshold is reached). Conclusion: X-ray radiation DRs are constantly fluctuating during and between patients based on BMI, the protocols, C-arm position, and the image acquisitions that are used. An instant patient risk chart visualizes these radiation dose fluctuations and provides an overview of the expected duration of X-ray radiation, which can be used to predict when follow-up dose thresholds are reached during abdominal endovascular procedures.