Autofluorescence spectro-endomicroscopy of alveoli: Comparative spectral analysis of healthy smocker volonteers and amiodarone-induced pneumonitis patients

Fluorescence endomicroscopy with spectroscopic analysis capability was used during bronchoscopy, at 488nm excitation, to record, simultaneously, autofluorescence (AF) images and associated emission spectra of the alveoli of healthy smoking volunteers (HS) and amiodarone treated non-smoker patients (ATNS). Alveolar fluorescent cellular infiltration was observed in both groups. Our objective was to assess the potential of spectroscopy in differentiating these two groups. Each normalized spectrum was modeled as a linear combination of several components: cellular flavins (FAD) and another cellular component, namely lipopigments, modelled by a Voigt profile, extracellular matrix (ECM) elastin and tobacco tar; HbO2 absorption was also taken into account. Besides the FAD and elastin contributions, the addition of a tobacco tar component is necessary to account for HS group spectral shape. The ATNS patients autofluorescence spectra result from the contribution of elastin, FAD and lipopigments, the tobacco tar component being found to zero. In conclusion, spectral analysis is able to differentiate between similar cellular infiltrated images from healthy smokers and ATNS patients.