Program Information
Dedicated Breast CT: Numerical Evaluation of Improvement in X-Ray Fluence Uniformity Using 3D Beam-Shaping X-Ray Filter
S Vedantham*, A Karellas , The University of Arizona College of Medicine, Tucson, AZ
Presentations
TU-H-CAMPUS-IT-2 (Tuesday, August 1, 2017) 4:30 PM - 5:30 PM Room: Imaging ePoster Theater
Purpose: Current generation of commercially available dedicated breast CT systems do not use x-ray beam-shaping (bowtie) filter. In order to reduce the radiation dose to the breast, a 3-D beam-shaping x-ray filter (BSXF) can be beneficial. The improvement in x-ray beam equalization with a 3-D BSXF was numerically evaluated.
Methods: A total of 23,760 2-D projections from 132 clinical 3-D breast CT datasets were used to design the 3-D BSXF. Numerical simulations with semi-ellipsoidal breasts of 10 to 22 cm diameter at chest-wall (anterior-posterior extent = 0.75 x diameter) were performed to evaluate the x-ray beam equalization achieved in terms of the x-ray fluence incident on the detector. A conventional 2-D bowtie filter appropriate for each breast diameter was also numerically evaluated. Evaluations were performed for 60 kV, 3.68 mm Al HVL x-ray spectrum and for two (C and Al) elemental filter materials. The x-ray beam equalization achieved by the 3-D BSXF and 2-D bowtie filter were quantified by normalizing the cone/fan angle dependent x-ray fluence to that along the central-ray (zero degree cone/fan angles) incident on the detector.
Results: The maximum thicknesses of the 3-D BSXF were 31.6 mm for Al and 1.13 mm for Cu. Along the fan-angle (lateral) direction, the 3-D BSXF performed marginally better than the 2-D bowtie filter in equalizing the x-ray fluence with a 4% to 10% improvement. Along the cone-angle (anterior-posterior) direction, the 3-D BSXF demonstrated a significant improvement of 140% to 300% over the bowtie filter in equalizing the x-ray fluence.
Conclusion: The 3-D BSXF provides substantial improvement in equalizing the x-ray beam, particularly along the anterior-posterior (cone-angle) direction. This 3-D BSXF may lead to further reduction in radiation dose compared to bowtie filters and needs to be investigated.
Funding Support, Disclosures, and Conflict of Interest: This work was supported in part by NIH/NCI grants R01 CA195512 and R01 CA199044. The contents are solely the responsibility of the authors and do not represent the official views of the NIH/NCI
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