Digital anthropomorphic breast phantoms have emerged in the past decade because of recent advances in 3D breast x-ray imaging techniques. Computer phantoms in the literature have incorporated power-law noise to represent glandular tissue and branching structures to represent linear components such as ducts. When power-law noise is added to those phantoms in one piece, the simulated fibroglandular tissue is distributed randomly throughout the breast, resulting in dense tissue placement that may not be observed in a real breast. The authors describe a method for enhancing an existing digital anthropomorphic breast phantom by adding binarized power-law noise to a limited area of the breast.Methods:
Phantoms with (0.5 mm)3 voxel size were generated using software developed by Bakic et al. Between 0% and 40% of adipose compartments in each phantom were replaced with binarized power-law noise (β = 3.0) ranging from 0.1 to 0.6 volumetric glandular fraction. The phantoms were compressed to 7.5 cm thickness, then blurred using a 3 × 3 boxcar kernel and up-sampled to (0.1 mm)3 voxel size using trilinear interpolation. Following interpolation, the phantoms were adjusted for volumetric glandular fraction using global thresholding. Monoenergetic phantom projections were created, including quantum noise and simulated detector blur. Texture was quantified in the simulated projections using power-spectrum analysis to estimate the power-law exponent β from 25.6 × 25.6 mm2 regions of interest.Results:
Phantoms were generated with total volumetric glandular fraction ranging from 3% to 24%. Values for β (averaged per projection view) were found to be between 2.67 and 3.73. Thus, the range of textures of the simulated breasts covers the textures observed in clinical images.Conclusions:
Using these new techniques, digital anthropomorphic breast phantoms can be generated with a variety of glandular fractions and patterns. β values for this new phantom are comparable with published values for breast tissue in x-ray projection modalities. The combination of conspicuous linear structures and binarized power-law noise added to a limited area of the phantom qualitatively improves its realism.
This work was funded in part by grants: DOD W81XWH-08-1-0353, NIH R21 EB008801, S10 RR021039, S10 RR029030, and P30 CA14599. The contents of this paper are solely the responsibility of the authors and do not necessarily represent the official views of any of the supporting organizations. The authors thank Andrew Maidment and Robert Schmidt for helpful discussions, and Lorenzo Pesce for assistance in running our code on the supercomputer. RM Nishikawa is a shareholder in and receives royalties from Hologic, Inc.
II. MATERIALS AND METHODS
II.A. Base phantom creation
II.B. Power-law noise addition
II.D. Resolution adjustment
II.E. Volumetric glandular fraction adjustment
II.F. Volumetric glandular fraction determination
II.H. β calculation
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