title: Measurement of breast-tissue x-ray attenuation by spectral mammography: solid lesions.
abstract: Knowledge of x-ray attenuation is essential for developing and evaluating x-ray imaging technologies. For instance, techniques to distinguish between cysts and solid tumours at mammography screening would be highly desirable to reduce recalls, but the development requires knowledge of the x-ray attenuation for cysts and tumours. We have previously measured the attenuation of cyst fluid using photon-counting spectral mammography. Data on x-ray attenuation for solid breast lesions are available in the literature, but cover a relatively wide range, likely caused by natural spread between samples, random measurement errors, and different experimental conditions. In this study, we have adapted a previously developed spectral method to measure the linear attenuation of solid breast lesions. A total of 56 malignant and 5 benign lesions were included in the study. The samples were placed in a holder that allowed for thickness measurement. Spectral (energy-resolved) images of the samples were acquired and the image signal was mapped to equivalent thicknesses of two known reference materials, which can be used to derive the x-ray attenuation as a function of energy. The spread in equivalent material thicknesses was relatively large between samples, which is likely to be caused mainly by natural variation and only to a minor extent by random measurement errors and sample inhomogeneity. No significant difference in attenuation was found between benign and malignant solid lesions. The separation between cyst-fluid and tumour attenuation was, however, significant, which suggests it may be possible to distinguish cystic from solid breast lesions, and the results lay the groundwork for a clinical trial. In addition, the study adds a relatively large sample set to the published data and may contribute to a reduction in the overall uncertainty in the literature.
authors.affiliation: Philips Health Systems, Mammography Solutions, Smidesvägen 5, 171 41 Solna, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Fredenberg
authors.forename: Fleur
authors.initials: F
authors.lastname: Kilburn-Toppin
authors.forename: Paula
authors.initials: P
authors.lastname: Willsher
authors.forename: Elin
authors.initials: E
authors.lastname: Moa
authors.forename: Mats
authors.initials: M
authors.lastname: Danielsson
authors.forename: David R
authors.initials: DR
authors.lastname: Dance
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Young
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Wallis
mesh_terms: D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008327:Mammography / Q000379:methods*; D017785:Photons; D014965:X-Rays