Imaging parenchymal lung diseases with confocal endomicroscopy.

BACKGROUND: "Optical biopsy" using bronchoscopic probe-based confocal endomicrosocopy (pCLE) provides real time images of the autofluorescent elastin scaffold of the healthy acinus.
OBJECTIVES: To establish how different parenchymal lung diseases (PLDs) alter the pCLE image, if intravenous fluorescein provides additional diagnostic information, and to assess pCLE's safety for investigating PLDs (UK REC: 09/H0708/18).
METHODS: 116 bronchopulmonary segments were examined in 38 patients and 4 healthy non-smoker volunteers. pCLE images were correlated with consensus multidisciplinary diagnosis from HRCT, bronchoalveolar lavage, and transbronchial/CT guided biopsies.
RESULTS: Severe emphysema is evident on pCLE imaging, with increased spacing between septal walls, sudden loss of fluorescence from bullae and a subsequent reticular pleural image. Other PLDs demonstrated marked loss of lobular autofluorescence and distinctiveness. In all diseases imaged, differentiation between septal wall and microvessel elastin is more difficult in diseased versus healthy acini. Smokers displayed a hyperfluorescent 15-30 micron cellular alveolar infiltrate - alveolar macrophages on in vitro BAL analysis. Varied intravenous fluorescein doses only create a hyperfluorescent foreground with bubbles. pCLE can cause pleuritic discomfort but there were no pneumothoraces. 3 patients had transient bleeding, and in vivo tearing of septal walls and microvessels abutting the probe was observed.
CONCLUSIONS: Marked emphysema is demonstrable from loss of elastic walls. The detail of high-resolution pCLE images is attenuated in other PLDs without further clarity from intravenous fluorescein. Nevertheless, pCLE is safe for PLD investigation. These findings form a basis for future work to harness pCLE's potential utility as part of a multiassessment modality for PLD diagnosis.