Quantitative Evaluation of Subglottic Stenosis Using Ultrashort Echo Time MRI in a Rabbit Model

Abstract

Objective/Hypothesis To assess the ability of ultra‐short echo time (UTE)‐MRI to detect subglottic stenosis (SGS) and evaluate response to balloon dilation. To correlate measurements from UTE‐MRI with endotracheal‐tube (ETT)‐sizing and to investigate whether SGS causes change in airway dynamics. Study Design Animal research study. Methods Eight adult New‐Zealand white rabbits were used as they approximate neonatal airway‐size. The airways were measured using ETT‐sizing and 3D UTE‐MRI at baseline, 2 weeks post‐cauterization induced SGS injury, and post‐balloon dilation treatment. UTE‐MR images were acquired to determine airway anatomy and motion. Airways were segmented from MR images. Cross‐sectional area (CSA), major and minor diameters (D_major and D_minor), and eccentricity were measured. Results Post‐injury CSA at SGS was significantly reduced (mean 38%) compared to baseline (P = .003) using UTE‐MRI. ETT‐sizing correlated significantly with MRI‐measured CSA at the SGS location (r = 0.6; P < .01), particularly at the post‐injury timepoint (r = 0.93; P < .01). Outer diameter from ETT‐sizing (OD) correlated significantly with D_major (r = 0.63; P < .01) from UTE‐MRI at the SGS location, especially for the post‐injury timepoint (r = 0.91; P < .01). Mean CSA of upper trachea did not change significantly between end‐expiration and end‐inspiration at any timepoint (all P > .05). Eccentricity of the upper trachea increased significantly post‐balloon dilation (P < .05). Conclusions UTE‐MRI successfully detected SGS and treatment response in the rabbit model, with good correlation to ETT‐sizing. Balloon dilation increased CSA at SGS, but not to baseline values. SGS did not alter dynamic motion for the trachea in this rabbit model; however, tracheas were significantly eccentric post‐balloon dilation. UTE‐MRI can detect SGS without sedation or ionizing radiation and may be a non‐invasive alternative to ETT‐sizing. Level of Evidence Not Applicable Laryngoscope, 2020