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

Abstract

Optical coherence tomography (OCT) is an emerging technology for non-invasive cross-sectional imaging of biological tissue and material with um resolution. In the field of pulmonary medicine, non-invasive high resolution cross-sectional imaging is desired for investigation of diseases in lung. So far, a few works have been reported about OCT imaging of lung. Since the lung consists of alveoli separated by thin wall, ultrahigh resolution (UHR) OCT is supposed to be effective for the imaging of fine structure in lung tissue. In this work, ex vivo cross-sectional imaging of isolated rat and hamster lungs was demonstrated using UHR-OCT. A 120 nm-wide, high-power, Gaussian-like supercontinuum (SC) was generated at wavelength of 0.8 um region. The generated SC was used in a time-domain OCT system, and UHR-OCT imaging was demonstrated. An ultrahigh resolution of 2.9 um in air and 2.1 um in tissue was obtained. The achieved sensitivity was 105 dB. Using this system, ex vivo UHR-OCT imaging of isolated rat and hamster lungs was demonstrated for the first time. The structures of the trachea, visceral pleura, and alveoli were observed clearly. When saline was instilled into the lung, the penetration depth was improved, and clear images of the fine structure of the lung, including alveoli, were observed owing to the index matching effect. We have also demonstrated the UHR-OCT imaging of lung tissue using 1.3 um and 1.7 um SC sources. As the results, owing to the precise structures of lung tissues and index matching by saline, the finest images were observed with 0.8 um UHR-OCT system.