Intra-individual variation of upper airway measurements based on computed tomography

Ning Zhou, Jean-Pierre T. F. Ho, Cornelis Klop, Ruud Schreurs, Ludo F. M. Beenen, GhizlaneAarab, Jan de Lange.

Abstract
The aims of this study were (1) to quantify the intra-individual variation in the upper airway measurements on supine computed tomography (CT) scans at two different time points; and (2) to identify the most stable parameters of the upper airway measurements over time. Ten subjects with paired CT datasets (3–6 months interval) were studied, using computer software to segment and measure the upper airway. The minimum cross-sectional area of the total airway and all its segments (velopharynx, oropharynx, tongue base, and epiglottis) generally had the largest variation, while the length of the total airway had the lowest variation.

Introduction
Over the past decades growing awareness of the detrimental effects of obstructive sleep apnea (OSA) has increasingly raised interest in morphometric evaluation of the upper airway [1–3]. Traditionally, upper airway morphology imaging consisted of a two-dimensional (2D) lateral cephalogram [4, 5]. However, due to the technical advancement of computed tomography (CT), this imaging modality has gained increasing popularity [5, 6]. Compared with a 2D lateral cephalogram, CT exhibits the capacity to analyze the upper airway three-dimensionally [7, 8]. Three-dimensional (3D) analysis has been widely used to assess the upper airway, which has given rise to the proposal and usage of multiple methods [3, 9, 10]. Volumetric, areal, and linear measurements, the parameters commonly used for upper airway evaluation, have been shown to have good to excellent inter-operator and intra-operator reliability in previous studies.

Materials and methods
The population consisted of 10 subjects selected from a patient database of the Department of Oral and Maxillofacial Surgery (5 males and 5 females; mean age 50.3 ± 10.3 years, range 34–68 years), which had two CT datasets (T0 and T1) of the head and neck region acquired in the Amsterdam UMC. They were scanned for various indications, viz., maxillary/mandibular granuloma and palatal fistula, with a 3–6 months’ time interval between scans (mean 4.8 ± 1.2 months).

Results
Descriptive statistics of all measurements, intra-individual variation estimated by relative difference, intra-individual repeatability estimated by ICC, inter-operator variation estimated by relative difference, and inter-operator reliability estimated by ICC are presented in Table 2. Of the 50 upper airway parameters, the ICC values of intra-individual repeatability were greater than 0.75 for 26, between 0.40 to 0.75 for 19, and less than 0.40 for 5. For the inter-operator reliability estimated by the ICC, all the parameters showed excellent reliability (ICC 0.832–0.999). As for the intra-individual variation in the total airway, the mean relative difference was maximum in MCA (35.5%) and minimum in length (4.9%).

Conclusion
Our study demonstrates that the dimensions and morphology of the upper airway in CT scans can vary considerably within an individual at different time points, even if the same patient instruction protocol for image acquisition is used. The MCA of the total airway and all its segments generally had the largest intra-individual variation, with relative differences of approximately 30%. The length of the total airway had the lowest intra-individual variation, with relative difference of 4.9%. The relative differences of the sphericity between two scans in the total airway and each segment were all below 15%. The length of the total upper airway, and the sphericity of the total airway and each segment were stable over time.

Citation: Zhou N, Ho J-PTF, Klop C, Schreurs R, Beenen LFM, Aarab G, et al. (2021) Intra-individual variation of upper airway measurements based on computed tomography. PLoS ONE 16(11): e0259739. https://doi.org/10.1371/journal.pone.0259739

Editor: Claudia Trindade Mattos, Universidade Federal Fluminense, BRAZIL

Received: May 3, 2021; Accepted: October 25, 2021; Published: November 5, 2021

Copyright: © 2021 Zhou et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the manuscript and its Supporting information files.

Funding: The authors received no specific funding for this work.

Competing interests: The authors have declared that no competing interests exist.

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