Room: Exhibit Hall | Forum 8
Purpose: The purpose of this work was to assess the contribution of scatter emitting from the exit window of the angiography collimator assembly to operator occupational radiation dose. In addition, the potential for a modified collimator assembly cover to mitigate tube scatter was evaluated.
Methods: Scatter dose emitting from a 30x30x25cmÂ³ PMMA stack and that arising directly from the X-ray tube exit window was measured for three angiography systems (A, B, and C). System A was also modified to include 0.5 mm Pb inside the collimator assembly cover. Scatter dose was measured with a 1800 cmÂ³ ionization chamber positioned 150 cm above the floor and 40-200 cm from the central axis. In addition, the influence of patient positioning on tube and patient scatter reaching the operator was measured with transverse table translation. The X-ray technique was set to 81 kV with beam filtration fixed at 0.2 mm Cu. Scatter dose measurements were normalized by the system reported dose area product(DAP).
Results: Scatter dose from the phantom was the same for all X-ray systems. Considering all systems, X-ray tube scatter accounted for 20-60% of total scatter. The lead lined cover installed on System A provided ~50% protection from tube scatter.
Conclusion: X-ray tube scatter described herein was due to interaction of the primary x-ray beam with components of the collimator assembly and was found to contribute substantially to scatter dose at the location of an X-ray operator. For System A, the presence of a physical DAP meter was associated with increased tube scatter and the addition of 0.5 mm Pb to the collimator assembly cover substantially reduced X-ray tube scatter. For all X-ray angiography systems, radiation protection practices should be revised to recognize and mitigate for scatter originating from within the X-ray tube collimator assembly and emitting from the exit port.