Ultrahigh resolution optical coherence tomography imaging of diseased rat lung using Gaussian shaped super continuum sources

We have been investigating ultrahigh resolution optical coherence tomography (UHR-OCT) imaging of lung tissues using fiber super continuum sources. The high power, low-noise, Gaussian shaped supercontinuum generated with ultrashort pulses and optical fibers at several wavelengths were used as the broadband light sources for UHR-OCT. For the 800 nm wavelength region, the axial resolution was 3.0 um in air and 2.0 um in tissue. Since the lung consists of tiny alveoli which are separated by thin wall, the UHR-OCT is supposed to be effective for lung imaging. The clear images of alveoli of rat were observed with and without index matching effects by saline. In this work, we investigated the UHR-OCT imaging of lung disease model. The lipopolysaccharide (LPS) induced acute lung injury / acute respiratory distress syndrome (ALI/ARDS) model of rat was prepared as the sample with disease and the UHR-OCT imaging of the disease part was demonstrated. The increment of signal intensity by pleural thickening was observed. The accumulation of exudative fluid in alveoli was also observed for two samples. By the comparison with normal lung images, we can obviously show the difference in the ALI/ARDS models. Since the lung consists of alveolar surrounded by capillary vessels, the effect of red-blood cells (RBC) is considered to be important. In this work, ex-vivo UHR-OCT imaging of RBC was demonstrated. Each RBC was able to be observed individually using UHR-OCT. The effect of RBC was estimated with the rat lung perfused with PBS.