Near-infrared diffuse transmittance imaging for localization of pulmonary nodules

Near-infrared diffuse transmittance imaging was investigated as a non-radiative real-time imaging technique for localizing solitary pulmonary nodules during pulmonary endoscopy and thoracoscopy combined. Ex vivo experiments on porcine lungs tissue were performed to examine near-infrared light propagation and to assess detectability of embedded optical phantoms. Transmittance measurements at 632.5 nm and 850 nm showed markedly higher signal levels and improved spatial information at 850 nm, consistent with the first NIR window. Tissue optical clearing with commercially available e-cigarettes liquids was used to increase transmitted signal levels and its applicability for the diagnostic method was examined. NIR imaging of tissue samples showed that the bronchial wall causes strong scattering and broadens the illumination spot. Nevertheless, small artificial nodules placed beneath the bronchial wall still produce detectable changes in the recorded images. The results confirm the feasibility of the method for detecting scattering local structures within heterogenous lung tissue. This study’s findings provide a technical basis for further optimization of near-infrared diffuse transmittance imaging as a minimally invasive, radiation-free real-time diagnostic imaging method for solitary pulmonary nodules localization.