(Saturday, 4/7/2018) 10:30 AM - 12:30 PM
Room: Marquis Ballroom 5-8
Purpose: Occupational radiation protection procedures for angiographic procedures have been developed assuming nearly all scatter originates from the patient. The purpose of this work is to assess the contribution of scatter originating from the x-ray tube on occupational radiation dose.
Methods: Scatter from a 30x30x25 cm^3 PMMA phantom and that originating directly from the x-ray tube was measured with an 1800 cm^3 ionization chamber at an elevation of 150 cm. Scatter was measured as a function of lateral distance from the central ray (40-200 cm) for three angiography systems (A1, A2 and B). Also, system A1 was modified to include 0.5 mm Pb inside the collimator cover to surround the X-ray beam exit window. The X-ray technique was set to 81-85 kV with beam filtration fixed at 0.2 mm Cu and dose was normalized to system dose area product. No accessory radio-protective shields were used.
Results: Scatter dose from the phantom was the same for all X-ray systems. X-ray tube scatter was 2-4 times greater from Systems A1 and A2 than System B due in part to scatter originating within a physical DAP meter. The relative contribution of tube scatter ranged from 23% (System B) to 48% (System A1) at a lateral distance of 80 cm. The modified collimator cover reduced X-ray tube scatter of System A1 from 48% to 27%.
Conclusion: Scatter emitted from the X-ray tube exit window was found to contribute significantly to overall scatter dose. The presence of a physical DAP meter was associated with increased tube scatter and the addition of 0.5 mm Pb to the collimator cover of System A1 reduced tube scatter to levels similar to System B. These finding demonstrate that radiation protection practices should be revised to recognize and mitigate for scatter originating within the X-ray tubes of X-ray angiography systems.
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