Visualizing the alveolar compartment in ILD patients by Optical Coherence Tomography

Background: Transbronchial (cryo)lungbiopsies in ILD are frequently inconclusive due to sampling-error and come with a significant complication risk (bleeding/pneumothorax). Optical coherence tomography (OCT) is a high-resolution, minimally invasive laser-based imaging technique. Objective: To test the feasibility of endobronchial OCT, identify OCT characteristics of ILD and compare this to histology. Methods: In 11 ILD patients, the alveolar compartment was imaged by advancing the OCT probe (St.Jude Medical) to peripheral lung areas and obtain 5.4cm pull-backs (539 images). Subsequent cryobiopsies were taken at the same location. OCT alveolar characteristics were identified and compared to histopathology. Results: OCT alveolar compartment characteristics included; Normal alveolar network (normal)(1A) Thickening of alveolar septa/loss of alveolar structure (fibrosis)(2B) Dark, round-shaped structures (honeycombing)(3C) Widened bronchial-structures in peripheral lung tissue (bronchiectasis)(4D) Alveolar structures and its border (diaphragm, thoracic wall)(5E) No adverse events occurred related to OCT-imaging. Conclusions: OCT-imaging of the alveolar compartment was feasible and safe. OCT seems capable of visualizing different subsets of (ab)normal alveolar/lungtissue and its borders (diaphragm/ thoracic wall). Implications: OCT might qualify as a diagnosis- and guidance-tool for transbronchial lung (cryo)biopsies in ILD.