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Dual‐energy digital mammography: Calibration and inverse‐mapping techniques to estimate calcification thickness and glandular‐tissue ratio
Author(s) -
Kappadath S. Cheenu,
Shaw Chris C.
Publication year - 2003
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1576394
Subject(s) - mammography , calibration , materials science , inverse , microcalcification , breast cancer , optics , biomedical engineering , mathematics , geometry , physics , medicine , cancer , statistics
Breast cancer may manifest as microcalcifications in x‐ray mammography. Small microcalcifications, essential to the early detection of breast cancer, are often obscured by overlapping tissue structures. Dual‐energy imaging, where separate low‐ and high‐energy images are acquired and synthesized to cancel the tissue structures, may improve the ability to detect and visualize microcalcifications. Transmission measurements at two different kVp values were made on breast‐tissue‐equivalent materials under narrow‐beam geometry using an indirect flat‐panel mammographic imager. The imaging scenario consisted of variable aluminum thickness (to simulate calcifications) and variable glandular ratio (defined as the ratio of the glandular‐tissue thickness to the total tissue thickness) for a fixed total tissue thickness—the clinical situation of microcalcification imaging with varying tissue composition under breast compression. The coefficients of the inverse‐mapping functions used to determine material composition from dual‐energy measurements were calculated by a least‐squares analysis. The linear function poorly modeled both the aluminum thickness and the glandular ratio. The inverse‐mapping functions were found to vary as analytic functions of second (conic) or third (cubic) order. By comparing the model predictions with the calibration values, the root‐mean‐square residuals for both the cubic and the conic functions were ∼50 μm for the aluminum thickness and ∼0.05 for the glandular ratio.