Investigation of Occupational Dose to Interventional Radiologists
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AbstractProject 1: Measuring the Effects on Operator Dose of Changing Clinical Settings Purpose: This study was initiated as part of a multi-faceted investigation of occupational dose to Interventional Radiologists consequential to their role as operators of fluoroscopy equipment. This project aims to qualitatively evaluate general dose reduction techniques, including clinical protocol settings on different interventional fluoroscopes to determine the specific impact on operator dose at Duke University Hospital. Materials and Methods: For each unit, analogous baseline settings were selected with a general abdominal protocol. The patient table was set to a source-to-object distance (SOD) of 62.23 cm (24.5 in) and a patient phantom was placed in the beam as a scatter medium similar to a typical patient abdomen. An anthropomorphic “operator” phantom was draped with a lead apron and positioned to one side of the patient table with an ion chamber placed at collar level. The ion chamber was placed such that the center of the active volume was 38.1 cm (15 in) lateral to and 63.5 cm (25 in) inferior from the center of the flat-paneled detector. A series of scans was taken on each unit, with each one having a selected variable changed, and the exposure readings from the ion chamber were recorded for comparison. Results: The effects on operator exposure rate of personnel height, contour shield use, cine mode, magnification, low dose mode, and source-to-image distance (SID) were analyzed. Operator height was found to have a larger effect on exposure rate reduction with distance than anticipated. Use of the contour shield reduced the operator exposure rate by over 90% on each unit. Use of cine mode drastically increased the exposure rate to the operator, while magnification, low dose mode, and decreasing SID all resulted in lower exposure rates. Conclusions: Operators can utilize these results to contextualize the effects of their own dose reduction techniques. Knowledge and familiarity of the techniques which offer the best exposure rate reduction can guide radiation protection practices among staff and help to optimize occupational doses. Project 2: Developing a Conceptual Framework for Analyzing the Radiation Dose Structured Report Purpose: When investigating occupational dose to Interventional Radiologists, it is important to be able to accurately compare metrics related to dose from historical procedures. The Radiation Dose Structured Report (RDSR) provides characteristic data from historical procedures. With an appropriate framework for analyzing RDSR data, performance metrics between operators or units can be compared, and identified trends can be used to develop dose reduction techniques specific to the organization. Materials and Methods: RDSR data from five interventional fluoroscopy systems (K1 – K5) was extracted for a three-year period from July 2019 through August 2022, and multiple metrics of comparison were selected for analysis. To determine differences in machine output, air kerma rates of similar procedures were compared, as well as the overall machine utilization for each year. Differences in operator-selectable variable were compared through air kerma rate per procedure, fluoroscopy time per procedure (limited to central line procedures), and operator caseload makeup. Results: Machine comparison of air kerma rates showed a consistently higher median and variability on the Philips Allura systems compared to the other three units. The Philips AlluraClarity unit in suite K2 was noticeably under-utilized by Interventional Radiology staff due to it being the primary fluoroscope used by Neurosurgery staff who were outside the scope of this investigation. Operator air kerma rates were compared from August 2021 through August 2022 and largely showed similar median values and variability. Fluoroscopy time per procedure fit to lognormal distributions and compared through their distribution parameter μ showed a median value which dipped during the second year for most providers. One operater also had a consistently higher median time per procedure for all three years. Conclusions: The analysis described by this framework provides a means of utilizing RDSR data to compare performance of interventional procedures. Continual local analysis of these metrics can be used to guide operator training to ensure that occupational doses are optimized to be as low as reasonably achievable. This is an initial approach that can be expanded through investigation and further characterization of procedure data included in the RDSR.
Tysinger, Millicent P (2023). Investigation of Occupational Dose to Interventional Radiologists. Master's thesis, Duke University. Retrieved from https://hdl.handle.net/10161/27854.
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