Optical coherence tomography (OCT) is an emerging technology for non-invasive cross-sectional imaging of
biological tissue and material with um resolution. Recently, non-invasive high resolution cross-sectional imaging is
desired for investigation of diseases in lung in the field of pulmonary medicine. 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 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 and it was used as the
light source in time domain UHR-OCT. An ultrahigh resolution of 2.1 um in tissue was obtained and the achieved
sensitivity was 105 dB.
For the UHR-OCT imaging of trachea, the detailed structures of the tracheal cartilage and tracheal mucosa overlying
the cartilage were observed clearly. The epithelium and lamina propria were also distinguishable.
For the imaging of visceral pleura and alveoli, 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. The clear images of up to about 4 alveoli were observed below the visceral pleura. The shape of the
alveolar septum was clearly observed, and the alveolar sac was clearly visible.