Confocal Fluorescence Endomicroscopy of the Human Airways

Abstract

Confocal endomicroscopes aim at providing to the clinician microscopic imaging of a living tissue. The currently available microendoscopic devices use the principle of confocal fluorescent microscopy, in which the objective is replaced by an optical fiber and a miniaturized scanhead at the distal end of the endoscope or by a retractable bundle of optical fibers. Such systems have recently been applied to the explorations of several organs, including the gastrointestinal tract, and more recently to the proximal and distal airways in vivo. Respiratory fluorescence microendoscopes use 488 nm or 660 nm excitation laser light and thin flexible miniprobes that are introduced into the working channel of the bronchoscope. The devices have a lateral resolution of 3 microm, a field of view of 600 microm, and produce real-time imaging at 9 frames per second. For in vivo imaging, the miniprobe is applied onto the bronchial wall surface or advanced into a distal bronchiole down to the acinus. In nonsmokers, the 488-nm excitation device images the autofluorescence of the elastin that is contained in the basement membrane of the proximal airways and that participates to the axial backbone of the peripheral interstitial respiratory system. In smokers, a specific tobacco tar-induced fluorescence allows in vivo macrophage and alveolar wall imaging. Using 660 nm excitation and topical methylene blue, the technique enables cellular imaging of both bronchial epithelial layer and peripheral lung nodules. This article reviews the capabilities and possible limitations of confocal microendoscopy for in vivo proximal and distal lung explorations.

In vivoprobe-based confocal laser endomicroscopy in amiodarone-related pneumonia

“…Briefly, a 4.4-mm bronchoscope (MP60 model; Olympus, Tokyo, Japan) was inserted into the airways down to the smallest reachable bronchi. The pCLE miniprobe was then introduced into the working channel of the bronchoscope, and was pushed smoothly beyond the bronchoscope view into the successive divisions of the bronchial tree until it penetrated into a pulmonary lobule, as previously described [15][16][17]22]. pCLE sequences were recorded and stored for subsequent analysis.…”

“…The procedure enables the exploration of proximal bronchus and alveolar regions during bronchoscopy in real time [15][16][17][18]. Studies have demonstrated that the main endogenous fluorophore, observed with pCLE at 488 nm excitation wavelength, is the elastin, which is a major component of the distal lung interstitial network, present in the axial backbone of the alveolar ducts and alveolar entrances [19,20].…”

A View on Imaging in Drug Research and Development for Respiratory Diseases

“…An exploratory method worth mentioning is human in vivo fluorescence microimaging. It provides tremendous detail of the airways up to alveolar ducts and sacs (Thiberville et al, 2009). However, the technique requires bronchoscopy and minute tissue puncture, but without any reported adverse effects.…”

Needle-based confocal laser endomicroscopy in the diagnosis of peripheral pulmonary nodule: a preliminary report

“…Elastin accounts for 50% of connective tissue fibers in peripheral pulmonary (4), possesses the autofluorescent properties with an excitation wavelength of 488 nm (5), which makes it the major visible structure under the exploration of confocal endomicroscopy (6,7). Previous studies reported that confocal endomicroscopy with pCLE probes could detect the changes of elastin composition in the airway and alveolar in the lung cancer tissues (8).…”