Program Information
Improved Patient Entrance DAP Estimates for Fluoroscopically-Guided Lumbosacral Epidural Injections
S Mann*, A Joshi , M Elliott , J Hoye , J Wells , G Agasthya , R Reiman , E Samei , Duke University Medical Center, Durham, NC
Presentations
TU-C3-GePD-I-2 (Tuesday, August 1, 2017) 10:30 AM - 11:00 AM Room: Imaging ePoster Lounge
Purpose: Lumbosacral epidural injections are commonly performed for pain management, often with multiple procedures performed per year. Fluoroscopy is routinely used for needle guidance during these procedures thus subjecting patients to ionizing radiation. Typically used mobile fluoroscopes provide limited dosimetry information. Current methods utilize dose area product (DAP) for determining radiation burden to the patient population and are subject to errors related to acquisition geometry and dose reporting accuracy. This work aims to better estimate patient entrance DAP by accounting for acquisition geometry, table and support attenuation, and system-reported dose accuracy.
Methods: Following IRB approval and patient consent, data from lumbosacral epidural injections were acquired over four weeks. Exam data such as patient BMI, AP/LAT abdominal dimensions, and injection location were recorded for each patient. For each image series acquired, gantry position, source-to-surface distance, x-ray technique factors, field size, beam-on time, and air kerma (AK) were also recorded. Series-specific DAP values (DAPₓ) were estimated as a fraction of the total reported DAP using the field size and AK from each image series. DAPₓ were then corrected as a function of kVp for system accuracy and table attenuation and grouped by gantry position into AP and LAT effective views.
Results: A total of 46 patients participated in the study. The reported DAP (1530 ± 1100 mGy-cm²) was found to be 58% higher and 12% more variable than corrected values (970 ± 580 mGy-cm²). By comparison, the mean (uncorrected) DAP value of 2100 mGy-cm² has been reported elsewhere in literature.
Conclusion: This work demonstrates improved methods for estimating patient entrance DAP for fluoroscopic procedures with limited dosimetry information. The corrections should provide improved accuracy and a more realistic dose distribution for risk estimates. Further work is underway to compute organ doses using Monte Carlo techniques informed by data acquired in this study.
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