Fluoroscopic Procedure-Room Scatter-Dose Reduction Using a Region-of-Interest (ROI) Attenuator

During fluoroscopically-guided interventional (FGI) procedures, dose to the patient as well as the scatter dose to staff can be high. However, a significant dose reduction can be possible by using a region-of-interest (ROI) attenuator that reduces the x-ray intensity in the peripheral x-ray field while providing full field of view imaging. In this work, we investigated the magnitude of scatter dose reduction to staff made possible by using an ROI attenuator composed of 0.7 mm Cu with a central circular hole that projected a 5.4 cm ROI onto a Kyoto anthropomorphic phantom in the head, chest, and abdomen regions. A 150-cc ionization chamber was placed on a stand at a height of 150 cm (eye level) from the floor and 25 cm and 50 cm lateral distance from the gantry isocenter in a direction perpendicular to the table centerline to measure scatter dose at different positions along the length of the table. Scatter dose per entrance air kerma (mGy/Gy) was measured with and without the ROI attenuator and the percent scatter reduction for the ROI attenuator was determined as a function of staff positions, beam energy and gantry angulation. For head imaging, the measured percent dose reduction was 50%-65% and, for chest and abdomen imaging, the scatter dose reduction was 63%-72% at 50 cm lateral distance when using this ROI attenuator with about 20% beam transmission at 80 kVp. Overall, a considerable reduction of scattered radiation in the interventional room can be realized using an ROI attenuator.