An optical method to detect tissue scattering: Theory, experiments and biomedical applications

In vivo physiological sensing is typically done either by imaging thin tissues or by examining changes in the attenuation coefficient. One known technique for thin tissue in vivo applications is the optical coherence tomography (OCT). However, deep tissue methods are usually based on diffusion reflection (DR), which correlates the optical properties to the reflected light intensity. The attenuation coefficient is composed of tissue absorption and scattering. We present a noninvasive nanophotonics technique, the iterative multi-plane optical property extraction (IMOPE) for extracting the scattering properties from a turbid medium. The reflectance-based IMOPE is most relevant for in vivo applications, hence, in this research we suggest a new theoretical description of phase accumulation in deep tissue, which is rarely mentioned in the literature, using a modified DR theory that represents the phase based on the effective pathlength. The IMOPE records multiple intensity images, reconstructs the phase using Gerchberg-Saxton (GS) algorithm. This algorithm is usually being used for beam shaping or phase reconstruction. We propose to calculate the phase second order moment to estimate the scattering. IMOPE experiments were conducted with tissue-like phantoms for calibration purposes, as well as ex vivo and in vivo measurement. The suggested technique was applied both in transmission and reflection mode. The transmission based IMOPE detected organic nanoparticles within tissues and the quantitative signature of milk components. The reflectance-based IMOPE was applied for tissue viability test and in vivo gold nanorods and blood flow detection.