Optical CT Imaging of Hemoglobin Oxygen-Saturation Using Dual-Wavelength Time Gate Technique

Abstract

Several attempts have been made to measure hemoglobin oxygen-saturation level in various tissues in vivo by using near-infrared transmission or reflection spectroscopy (Jobsis, 1977, Chance et al. 1988, Delpy et al. 1988). This is based on the fact that oxyhemoglobin and deoxyhemoglobin have different absorption spectra in the near infrared region, where light absorption by other tissues is relatively weak. However, although tissues are quite transparent to near-infrared light, strong light scattering occurs, making it difficult to measure accurately the absorption due to hemoglobin contained in the tissue. Because of this multiple light scattering, oxygen-saturation imaging of tissues is very difficult, especially using the conventional filtered back-projection CT algorithm mainly employed in X-ray CT. We have already reported our method for in vivo visualization of the pattern of hemoglobin oxygen-saturation in the rat brain (Shinohara et al. 1991). The purpose of this presentation is to describe the results obtained with dual-wavelength time gate technique using different time gate widths for imaging of hemoglobin oxygen-saturation.