Optical imaging of hemoglobin oxygen saturation using a small number of spectral images for endoscopic application

Tissue hypoxia is associated with tumor and inflammatory diseases, and detection of hypoxia is potentially useful for their detailed diagnosis. An endoscope system that can optically observe hemoglobin oxygen saturation (StO(2)) would enable minimally invasive, real-time detection of lesion hypoxia in vivo. Currently, point measurement of tissue StO(2) via endoscopy is possible using the commercial fiber-optic oximeter T-Stat, which is based on visible light spectroscopy at many wavelengths. For clinical use, however, imaging of StO(2) is desirable to assess the distribution of tissue oxygenation around a lesion. Here, we describe our StO(2) imaging technique based on a small number of wavelength ranges in the visible range. By assuming a homogeneous tissue, we demonstrated that tissue StO(2) can be obtained independently from the scattering property and blood concentration of tissue using four spectral bands. We developed a prototype endoscope system and used it to observe tissue-simulating phantoms. The StO(2) (%) values obtained using our technique agreed with those from the T-Stat within 10%. We also showed that tissue StO(2) can be derived using three spectral band if the scattering property is fixed at preliminarily measured values. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.