Comparisons of diffuse optical imaging between direct-current and amplitude-modulation instrumentations

Breast tissues like fatty and fibroglandular ones are adipose mainly and possess high scattering nature, so that they diffuse and make the light approximately uniformly distribute over the measured cross-section besides absorbing to reduce the light intensity. Strong cause-and-effect relationships exist between absorption and intensity decay, and between scattering and phase delay as well. Thereby in a diffuse optical imaging system it is a general practice to estimate absorption coefficients from the measured intensity since it reflects most of the absorption property. This study aims to illustrate that both μ_a and μ_s ^′ images of breast can be reconstructed by only direct-current data reliably to a certain extent. Varied sets of phantom design with assigned absorption/scattering properties for inclusion and background were synthesized and image reconstructed to demonstrate this perspective. Moreover, we employed a slab-type diffuse optical imaging system with a dual-direction direct-current NIR measurement module, where reconstructed images were compared between with and without reflectance NIR data.