Abstract
We present the real-time single snapshot multiple frequency demodulation - spatial frequency domain imaging (SSMD-SFDI) platform implemented with a visible digital mirror device that is capable of imaging and monitoring dynamic turbid medium and processes over a large field of view. One challenge in quantitative imaging of biological tissue such as the skin is the complex structure rendering techniques based on homogeneous medium models to fail. To address this difficulty we have also developed a novel method that maps the layered structure to a homogeneous medium for spatial frequency domain imaging. The varying penetration depth of spatially modulated light on its wavelength and modulation frequency is used to resolve the layered structure. The efficacy of the real-time SSMD-SFDI platform and this two-layer model is demonstrated by imaging forearms of 6 healthy subjects under the reactive hyperemia protocol. The results show that our approach not only successfully decouples light absorption by melanin from that by hemoglobin and yields accurate determination of cutaneous hemoglobin concentration and oxygen saturation, but also provides reliable estimation of the scattering properties, the melanin content and the epidermal thickness in real time. Potential applications of our system in imaging skin physiological and functional states, cancer screening, and microcirculation monitoring are discussed at the end.
Highlights
The skin is the largest organ of the body, accounting for about 15% of the total adult body weight
We present a real-time Single Snapshot Multiple Frequency Demodulation Spatial Frequency Domain Imaging (SSMD-spatial frequency domain imaging (SFDI)) platform implemented with a visible digital mirror device to map the optical properties of the subsurface of the skin continuously
We have presented a noncontact imaging technique snapshot multiple frequency demodulation (SSMD)-SFDI, which is capable of mapping optical properties and physiological parameters including hemoglobin concentration, oxygen saturation, melanin content and epidermal thickness over a large field of view for skin in real time
Summary
The skin is the largest organ of the body, accounting for about 15% of the total adult body weight. Optical methods for characterizing skin structure and hemodynamics have been long pursued due to some important advantages including non-invasiveness, high sensitivity to hemoglobin, and low cost [1]. Optical coherence tomography (OCT) [2], and multi-photon microscopy (MPM) [3] provide high-resolution (e.g., 1–10 μm) structural images of skin with optical sectioning capability and limited penetration depth (e.g., 100 μm–1mm). These techniques, are limited to mainly morphology and are unable to assess hemodynamics or provide useful physiological information on microcirculation. As a point detection method, NIRS will require scanning to form an image
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