X-ray Attenuation Measurements of a Fibrous Breast Tissue Phantom

Conventional diagnostic x-ray imaging modalities exploit x-ray linear attenuation coefficient differences ( µ) of human tissues (i.e., tissues attenuate x-rays differently). The largest µ is between bone and so-called soft tissues. Clinical studies and µ measurements conducted over the past few decades indicated that dense (or fibrous) and cancerous human breast tissues have similar x-ray attenuation properties hindering accurate diagnosis and screening of breast cancer. Higher contrast was demonstrated by x-ray scattering experiments relying on histological differences between normal and malignant tissues and wave-like nature of x-rays. A silicon x-ray detector and an integrated x-ray tube (with tungsten target) and polycapillary x-ray lens unit were used to measure µ of a resin-based breast tissue phantom. Commercial fiberglass resin was mixed with salt (NaCl) (~98.2% resin and 1.8% NaCl mass concentrations) to increase its µ value and match reported mean values of fibrous/tumor breast tissues: 1.66 cm^-1, 1.19 cm^-1, and 0.92 cm^-1 for fibrous tissues and 1.61 cm^-1, 1.18 cm^-1, and 0.92 cm^-1 for breast tumor at 15, 17, and 19 keV photon energies, respectively. The resin-salt mixture µ values were measured at nine energies: 8.3, 9.6, 9.9, 11.3, and 11.6 keV (tungsten L-shell x-rays), and 12.5, 13.5, 14.5, 15.5 keV (bremsstrahlung). Measured µ values were in the 1.1 cm^-1 to 7.9 cm^-1 range for 15.5 keV down to 8.3 keV photon energies. Measured values of µ of 1.4, 1.1, and 1.0 cm^-1 at the 15, 17, and 19 keV photon energies were within the reported µ values for tumor and fibrous breast tissues at 17 keV and 19 keV energies, and ~11% lower than the minimum µ of breast tumor at 15 keV.