Plum Pudding Random Medium Model of Biological Tissue and Optical Biomedical Imaging in NIR and SWIR Spectral Windows

Abstract Biological tissue has a complex structure and exhibits rich spectroscopic behavior. Light of longer wavelength is less scattered by typical tissue, yet it is unexpectedly scattered more into the forward directions (the anisotropy of light scattering increases) within the visible and near-infrared (NIR) spectral range as revealed by some thorough measurements. We present a plum pudding random medium (PPRM) model for biological tissue to account, for the first time , for the observed spectroscopy of tissue light scattering and its anisotropy. PPRM succinctly describes tissue as a superposition of distinctive scattering structures (plum) embedded inside a fractal continuous medium of background refractive index fluctuation (pudding). PPRM faithfully reproduces the power law wavelength dependence of tissue light scattering and attributes the “anomalous” trend in the anisotropy to the plum. As light scattering is the key factor hampering the depth and resolution of optical biomedical imaging, PPRM provides much needed quantitative model of light scattering by biological tissue to gauge the merits of biomedical imaging with light of varying wavelengths. Optical breast and brain imaging are used as two examples to compare the performance of imaging in NIR and shortwave infrared (SWIR) spectral windows.