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. 2025 Aug;35(8):4846-4860.
doi: 10.1007/s00330-025-11367-w. Epub 2025 Feb 1.

Normative values for lung, bronchial sizes, and bronchus-artery ratios in chest CT scans: from infancy into young adulthood

Qianting Lv  1   2 , Yuxin Chen  1   2 , Daan Caudri  1   2 , Eleni-Rosalina Andrinopoulou  3   4 , Wieying Kuo  5 , Jean-Paul Charbonnier  6 , Robert J Fleck  7 , Luis Riera Soler  8 , Matteo Paoletti  9 , Francois Vermeulen  10 , Giovanni Morana  11 , Edward Y Lee  12 , Marleen de Bruijne  2   13 , Harm A W M Tiddens  1   2   6 , Pierluigi Ciet  14   15 ; Normal Chest CT Study Group
Collaborators, Affiliations

Normative values for lung, bronchial sizes, and bronchus-artery ratios in chest CT scans: from infancy into young adulthood

Qianting Lv et al. Eur Radiol. 2025 Aug.

Abstract

Objective: To estimate the developmental trends of quantitative parameters obtained from chest computed tomography (CT) and to provide normative values on dimensions of bronchi and arteries, as well as bronchus-artery (BA) ratios from preschool age to young adulthood.

Materials and methods: Two independent radiologists screened a dataset of 1160 chest CT scans, initially reported as normal, from participants aged 0 to 24 years. Using an automated deep learning-based algorithm, we computed the following bronchus and artery parameters: bronchial outer diameter (Bout), bronchial inner diameter (Bin), adjacent pulmonary artery diameter (A), bronchial wall thickness (Bwt), bronchial wall area (BWA), and bronchial outer area (BOA). From these parameters, we computed the following ratios: Bout/A, Bin/A, Bwt/A, Bwt/Bout, and BWA/BOA. Furthermore, mean lung density, total lung volume, and the square root of wall area of bronchi with a 10-mm lumen perimeter (Pi10) were obtained. The effects on CT parameters of age, sex, and iodine contrast were investigated using mixed-effects or regression model analyses.

Results: 375 normal inspiratory chest CT scans (females / males = 156 / 219; mean age [SD] 12.7 [5.0] years) met the inclusion criteria. Bout and Bin progressively increased with age (all p < 0.05), but Bwt, Bout/A, Bin/A, Bwt/A, Bwt/Bout, or BWA/BOA did not. Total lung volume and mean lung density continuously increased with age (both p < 0.001), while Pi10 did not exhibit such a trend. Bout, total lung volume, and mean lung density were the only parameters that differed between males and females, all higher in males than females (all p < 0.03). The presence of iodinated contrast led to greater values for Bwt, Bwt/Bout, and BWA/BOA, but lower values for Bin, Bout/A, Bin/A, and Bwt/A (all p < 0.01).

Conclusion: Quantitative CT parameters of both lung parenchyma and bronchi exhibit growth-related changes, but from 6 to 24 years ratios between bronchus and artery dimensions remain constant. Contrast-enhanced CT scans affect the assessment of lung parenchyma and bronchial size. We propose age and technique-dependent normative values for bronchial dimensions and wall thickness.

Key points: Question What are the developmental trends of quantitative lung CT parameters in patients from childhood into young adulthood? Findings The ratio between bronchus and pulmonary artery dimensions demonstrates consistent values across age groups, indicating synchronized growth between bronchi and paired pulmonary arteries. Clinical relevance Our findings highlight the importance of standardized CT protocol and volume acquisition, and emphasize the need for ongoing collection of normal chest CT scans to refine the proposed reference values.

Keywords: Adolescents; Bronchi; Computer-assisted diagnosis; Reference values.

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Conflict of interest statement

Compliance with ethical standards. Guarantor: The scientific guarantor of this publication is Dr. Pierluigi Ciet. Conflict of interest: The author of this manuscript, Harm Tiddens, declares relationships with the following companies: Insmed, TBIO, Thirona, Neupharma and Boehringer. The author of this manuscript, Jean-Paul Charbonnier, declares relationships with Thirona. Daan Caudri is director of the Erasmus MC-LungAnalysis laboratory. The author of this manuscript, Pierluigi Ciet, declares relationships with the following companies: Vertex Pharmaceutical, Chiesi Pharmaceuticals, and Siemens Healthineers. Wieying Kuo is affiliated with Voiant Clinical. The rest of the authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article. Statistics and biometry: One of the authors, Eleni-Rosalina Andrinopoulou, has significant statistical expertise. Informed consent: Written informed consent was not required for this study because this is a retrospective study. Ethical approval: Institutional Review Board approval was obtained. Study subjects or cohorts overlap: The cohort has been previously reported in Kuo et al [6]. In the previous study, the dataset consisted of 294 out of 1160 chest CT scans of children and adolescents were collected retrospectively by the international multicenter Normal Chest CT Study Group. The previous study aimed to define normative data on central airway dimensions, in particular trachea, right main bronchi, and left main bronchi, in chest CT of children. On these 294 inspiratory CT scans, central airways were semi-automatically analyzed using Myrian XP-Lung software (version 1.19.1, Intrasense). The intrathoracic tracheal length was measured from the carina to the thorax inlet manually. In the recent study, the dataset consisted of 375 out of 1160 chest CT scans of children and young adults. The primary aim of the current study is to establish normative data for the dimensions of peripheral airways extending down to the 6th bronchial generation, in chest CT of children. On these 375 inspiratory CT scans, bronchi and adjacent pulmonary arteries were automatically analyzed using LungQ (version 2.0.1, Thirona). Using this algorithm, we computed the following bronchus and artery parameters from segmental bronchi to the most peripheral detectable bronchi: bronchial outer diameter (Bout), bronchial inner diameter (Bin), adjacent pulmonary artery diameter (A), bronchial wall thickness (Bwt), bronchial wall area (BWA), and bronchial outer area (BOA). From these parameters, we computed the following ratios: Bout/A, Bin/A, Bwt/A, Bwt/Bout, and BWA/BOA. Furthermore, mean lung density, total lung volume, and the square root of wall area of bronchi with a 10-mm lumen perimeter (Pi10) were obtained by using another module from the same software package. Methodology: Retrospective Observational Multicenter study

Figures

Fig. 1
Fig. 1
Schematic view of the bronchial tree and of a bronchus-artery (BA) pair in cross-section, showing measurements for each bronchus [5]. The bronchial tree (blue) with its accompanying pulmonary artery system (pink) is shown on the left. The segmental bronchi are defined as G0 and the sub-segmental bronchi as G1. When a bronchus splits into two or more branches, the generation number increases by one. On the right, a bronchus-artery (BA)-pair is shown, the bronchus in blue and the adjacent pulmonary artery in pink, which is drawn by pretending they are perfect circles. The arrows depict the bronchus and pulmonary artery dimensions that can be measured by the automatic BA method: Bronchial outer diameter (Bout); Bronchial inner diameter (Bin), Bronchial wall thickness (Bwt), and adjacent pulmonary Artery diameter (A)
Fig. 2
Fig. 2
Flowchart of Normal Chest CT Group dataset
Fig. 3
Fig. 3
Relationship between branching and age. BA pair, bronchus-artery pair; CT, computed tomography. a Representative three-dimensional volume rendering of the bronchial tree for each age group. b Plot of the average BA-pair count compared to the segmental generations. In the horizontal axis of Fig. 2b, segmental generation 0 indicates the segmental bronchi and 1 indicates consecutive sub-segmental bronchi and so forth. The number of BA pairs represents the number of detectable bronchial branches. Note that according participant’s group, bronchi located more distally from segmental generation 4 are present in lower numbers or not visible, especially in the younger age groups, due to the resolution of the CT scanner. Some adjacent arteries originating from G0 were challenging to detect due to their clustered anatomical structure. Thus unpaired bronchial measurements (lacking paired arteries) were excluded from the dataset. As a result, the average number of branching artery pairs from G0 ranged between 7 to 10
Fig. 4
Fig. 4
Bronchial dimensions of non-iodine contrast CT scans in each segmental generation grouped by age. Plots (a–c) show trends of Bout (a), Bin (b), and Bwt (c) (vertical axis) in each age group against segmental generation (horizontal axis). Note that 1 indicates the sub-segmental bronchi and Gn+1 the consecutive higher generations. Each line represents a different age group. The point on each line shows the median of the bronchial dimensions in each segmental generation. The variability of the median of bronchial dimensions after segmental generation 6 is caused by the limited number of detected BA pairs related to the resolution limitation of commonly used CT scanners
Fig. 5
Fig. 5
The BA ratios of non-iodine contrast CT scans in each age group. Panel a shows the ratios of bronchial diameters, while Panel b represents the ratios of bronchial wall thickness. Bout/A: ratio of bronchial outer diameter and adjacent pulmonary artery; Bin/A: ratio of bronchial inner diameter and adjacent pulmonary artery; Bwt/A: ratio of bronchial wall thickness and adjacent pulmonary artery; Bwt/Bout: ratio of bronchial wall thickness and bronchial outer diameter; Bwa/Boa: ratio of bronchial wall area and bronchial outer wall area. Each box shows median (horizontal line), interquartile range (solid box), 1.5*quartile range (whiskers), and outliers (circles). Plots show stable ratios of Bout/A, Bin/A, Bwt/A, Bwt/Bout, and Bwa/Boa across the age groups
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