Objective: We sought to assess the effectiveness of a novel CT radiation dose reduction strategy in which filtration was added at the x-ray tube output port between the x-ray beam and the breast area of three sizes of anthropomorphic phantoms.
Materials and methods: To evaluate the dose-reduction potential of partial arc x-ray beam filtration, copper foil filtration or lead foil filtration was placed over CT scanners' covers when scanning anthropomorphic phantoms representative of a 5-year-old child, a 10-year-old child, and an adult female. Dose reduction was calculated as the percentage difference between the mean entrance radiation dose (on the phantoms' surfaces at locations representing the sternum and left breast) in unshielded scans compared with the mean dose in scans shielded by copper or lead foil. We also compared the CT numbers and noise sampled in regions representing the lung and the soft tissues near the sternum, left breast, and spine in CT images of the phantoms during unshielded scans relative to acquisitions shielded by copper or lead foil.
Results: Entrance dose at the sternum and left breast in the three anthropomorphic phantoms was reduced by 28-66% and 54-79% when using copper or lead foil filtration, respectively. However, copper foil filtration affected the CT numbers and noise in the CT images less than the lead foil filtration did (8.2% vs 32% mean increase in noise).
Conclusion: By incorporating partial arc beam filtration into CT scanners, substantial dose reductions may be achieved with a minimal increase in image noise.