Multimodal imaging guidance for laser ablation in tracheal stenosis

Septimiu D Murgu,Matt Brenner,Henri G Colt,David Mukai

doi:10.1002/lary.21047

Abstract

Laser-induced damage of tracheal wall microstructures might contribute to recurrence after bronchoscopic treatment of tracheal strictures. The purpose of this study was to demonstrate how multimodal imaging using white light bronchoscopy (WLB), endobronchial ultrasound (EBUS), and optical coherence tomography (OCT) might identify in vivo airway wall changes before and resulting from Nd:YAG laser ablation and dilation of tracheal stenosis. Case study. Commercially available WLB, high frequency EBUS using a 20-MHz radial probe and time-domain, frontal imaging OCT systems were used to characterize the extent, morphology, and airway wall microstructures at the area of hypertrophic fibrotic tissue formation before, during and after treatment of postintubation tracheal stenosis. WLB revealed the location of a complex, extensive, severe stricture. EBUS showed a homogeneous layer overlying a hyperechogenic layer corresponding to disrupted cartilage. OCT showed a homogeneous light backscattering layer and absence of layered microstructures, confirming absence in close proximity of normal airway wall. After laser ablation, OCT of charred tissue showed high backscattering and shadowing artifacts. OCT of noncharred tissue showed a thinner, homogeneous, light backscattering layer. EBUS showed thinner but persistent hypertrophic tissue suggesting incomplete treatment. WLB revealed improved airway patency postprocedure and recurrence 3 weeks later. EBUS identified cartilage disruption and residual hypertrophic tissue, the evidence of which might contribute to recurrence. OCT revealed homogeneous light backscaterring representing persistent noncharred hypertrophic tissues but it did not visualize cartilage disruption. Future studies are warranted to confirm whether these technologies can help guide bronchoscopic treatments.

Highlights

Bronchoscopic treatment of complex postintubation tracheal stenosis is offered when open surgical resection is not indicated either because of stricture length, severe comorbidities, desire to attempt minimally invasive treatments, or when impending death warrants urgent restoration of airway patency.[1]
In vivo optical coherence tomography (OCT) imaging of hypertrophic tissues showed a “bland” image consisting of homogeneous light backscattering and absence of layered microstructure, confirming the absence in close proximity of normal airway wall, which would be characterized by ordered layered microstructures (Figs. 2 and 3)
The results from this study show how the addition of radial probe endobronchial ultrasound (EBUS) and OCT to standard white light bronchoscopy (WLB) might help identify in vivo real-time changes in airway wall structures and hypertrophic stenotic tissues

Summary

Introduction

Bronchoscopic treatment of complex postintubation tracheal stenosis is offered when open surgical resection is not indicated either because of stricture length, severe comorbidities, desire to attempt minimally invasive treatments, or when impending death warrants urgent restoration of airway patency.[1] Stricture recurrence after bronchoscopic treatment is frequent, suggesting that the nature of the treatment itself, which often includes laser resection and mechanical dilation, might induce or exacerbate airway wall injury.[1] Histologic examination of excised specimens has confirmed that mucosal and submucosal hypertrophy accompanied by exuberant fibrosis, and, at later stages, fragmentation of cartilage and replacement by fibrotic tissue, characterizes complex strictures.[2,3] Results from experimental studies in canine tracheas demonstrate how cartilage injury might cause tracheal stenosis, and reveal the potential for laser-induced collateral damage to chondrocytes even at a distance from the laser induced mucosal lesion.[4]. The potential for collateral damage of surrounding tissues warrants appropriate control of laser–tissue interactions, much of which currently depends on subjective visual and tactile feedback from the surface ablation site.[5]

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Results

Conclusion