Interferometric diffuse optics (iDO) enables non-invasive measurement of deep tissue blood flow without requiring photon-counting detectors. Due to hardware constraints, achieving both optical properties and depth-dependent dynamics within a single modality remains a challenge for iDO. We present a simple method based on frequency-modulated light scattering that overcomes this limitation.

In measuring cerebral blood flow (CBF) noninvasively using optical techniques, diffusing-wave spectroscopy is often combined with near-infrared spectroscopy to obtain a reliable blood flow index. Measuring the blood flow index at a determined depth remains the ultimate goal. In this study, we present a simple approach using dual-comb lasers where we simultaneously measure the absorption coefficient (μ_a), the reduced scattering coefficient (μ_s^′), and dynamic properties. This system can also effectively differentiate dynamics from various depths, which is crucial for analyzing multilayer dynamics. For CBF measurements, this capability is particularly valuable as it helps mitigate the influence of the scalp and skull, thereby enhancing the specificity of deep tissue.