Comparison of diffusion coefficient measurement through Coherent or Incoherent Backscattering measurement, for the characterization of complex media

This study compares methods to calculate the diffusion coefficient (D) in complex media using Coherent or Incoherent Backscattering (CBS and IBS). In heterogeneous media like lung or bone tissue, conventional ultrasound imaging is inadequate for diagnostics. Quantitative Ultrasound (QUS), including D measurement, offers insights into the “randomness” of such media. Changes in D reflect multiple scattering effects and are associated with an increased intensity of IBS and a reduced intensity of CBS over time. The study evaluates D measurement methods with varying air inclusion proportions in soft tissues, both numerically and experimentally. The three approaches include: (1) traditional CBS with plane wave beamforming for emission and reception, (2) enhanced CBS (eCBS), which leverages phase coherence between backscattered waves in different directions to improve CBS measurements through amplitude and phase data, and (3) IBS analysis through matrix treatment to separate the incoherent intensity from the CBS peak using a virtual antireciprocity. Numerical simulations demonstrate that eCBS provides more stable and accurate diffusion measurements compared to CBS or IBS. Pending experiments on water-filled sponge phantoms and rat lungs with fibrosis seem to confirm the reliability of eCBS. This method holds promise for improved diagnostics in complex media, particularly where conventional imaging is insufficient.