We developed full-range, ultrahigh-resolution (UHR) spectral-domain optical coherence tomography (SD-OCT) in 1.7 um wavelength region for high-resolution and deep-penetration OCT imaging of turbid tissues. To realize an ultrahigh axial resolution, the ultra-broadband supercontinuum source at 1.7 um wavelength with a spectral width of 0.4 um at FWHM and home-built spectrometer with a detection range from 1.4 to 2.0 um were employed. Consequently, we achieved the axial resolution of 3.6 um in tissue (a refractive index n = 1.38). To observe deep regions of turbid tissues while keeping the ultrahigh axial resolution, a full-range OCT method to eliminate a coherent ghost image was utilized for our UHR-SD-OCT. Because the full-range method allows us to avoid the formation of a coherent ghost image when the zero delay position is in the inside of specimens, we set the zero delay position to the laser focus position in this study, and then, a region of interest in specimens was moved to the laser focus position where the highest signal intensity is achieved, resulting in the improvement of the observation depth. Thanks to the deep-penetration property of the 1.7 um light and elimination of a ghost image, we successfully demonstrated the visualization of the mouse brain structures at a depth over 1.5 mm from the surface with the 1.7 um UHR-SD-OCT. In this experiment, we confirmed that the brain specific structures, such as corpus callosum, pyramidal cell layer, and hippocampus, were clearly observed.
Hiroyuki Kawagoe, Masahito Yamanaka, Shuichi Makita, Yoshiaki Yasuno, and Norihiko Nishizawa, "High-resolution and deep-tissue imaging with full-range, ultrahigh-resolution spectral-domain optical coherence tomography in 1.7 um wavelength region (Conference Presentation)," Proc. SPIE 10053, Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XXI, 100531V (Presented at SPIE BiOS: February 01, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2254740.5371723170001.
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