Quantifying tracheobronchial tree dimensions: methods, limitations and emerging techniques

Abstract

The ability to measure airway dimensions is important for clinicians, interventional bronchoscopists and researchers in order to accurately quantify structural abnormalities and track their changes over time or in response to treatment.Most quantitative airway measurements are based on X-ray computed tomography and, more recently, on multidetector computed tomography. Quantitative bronchoscopic techniques have also been developed, although these are less widely employed. Emerging techniques, including magnetic resonance imaging, endoscopic optical coherence tomography, endobronchial ultrasound and confocal endomicroscopy, provide new research tools with potential clinical applications.An understanding of issues related to the acquisition, processing and analysis of images, and how such issues impact on imaging the tracheobronchial tree, is essential in order to assess measurement accuracy and to make effective use of the newer methods. This article contributes to this understanding by providing a comprehensive review of current and emerging techniques for quantifying airway dimensions.KEYWORDS: Airway dimensions, confocal endomicroscopy, multidetector computed tomography, optical coherence tomography, videobronchoscopy A dvances over the past 20 yrs in medical imaging and bronchoscopy have heralded an era of unprecedented access to quantitative information on tracheobronchial structure and, increasingly, function. The expanding scope of technical advances challenges the ability of clinicians and researchers to keep abreast of recent developments and emerging techniques. Computed tomography (CT) and, to a lesser extent, bronchoscopy are the two imaging tools that have contributed most to our understanding of the airway in vivo and are used on a daily basis by clinicians in the management of airway diseases. Newer techniques, such as magnetic resonance imaging, optical coherence tomography, fibreoptic confocal endomicroscopy and endobronchial ultrasound, offer fresh insights into the way we view and quantify the airway.Over the coming years, the clinical applications of these newer techniques will be defined. As with endobronchial ultrasound, which has been adopted by interventional bronchoscopists in a little over a decade from its first reported use [1], it is likely that smoking-related lung diseases, such as bronchogenic cancer and chronic obstructive pulmonary disease (COPD), will drive the rapid development of new endoscopic imaging modalities and maintain the current pace of technical improvements of existing techniques, in particular CT. Initial applications of these techniques may focus on screening and surveillance of endobronchial malignancies and the use of real-time airway measurements during interventional procedures to deploy endobronchial stents. In these settings, accurate real-time quantitative imaging is advantageous.

Elastic Properties of the Central Airways in Obstructive Lung Diseases Measured Using Anatomical Optical Coherence Tomography

“…The light-based imaging technique used in this study confers several advantages in measuring airways over existing direct imaging modalities, such as CT (10,25,26), or indirect techniques, such as measurement of anatomical dead space (2-4) or Pitot tubes (9,11). These include: the ability to perform airway measurements at specific sites within the tracheobronchial tree, allowing localized rather than global mechanical measurements without exposure to ionizing radiation; and the capacity to precisely, directly, and repeatedly measure airway dimensions.…”

Tomografia de coerência óptica broncoscópica

“…be promising in the study of airway changes in patients with COPD. Two groups of authors (12,24) also compared the use of OCT + bronchoscopy with that of CT in the measurement of the airways and obtained accurate results, suggesting that OCT be used in the study of airway remodeling in asthma patients.…”

“…The movements should be smooth and coordinated in order not to compromise the quality of the image. The similarity between OCT images and those produced evaluation of smoke-induced airway injury, (2) evaluation of anastomosis and small airways in lung transplantation, performance of endobronchial biopsies, (21) and measurement of tracheobronchial stenosis, (20) as well as evaluation of normal microanatomy and small airway and smooth muscle thickening in asthma patients, (22) COPD patients, (23) cystic fibrosis patients, and smokers, (24,25) together with pre-and post-bronchial thermoplasty evaluation. (26) In addition, OCT can aid in determining the size of the bronchi in the endoscopic treatment of emphysema with one-way valves.…”

Spirometer-controlled cine magnetic resonance imaging used to diagnose tracheobronchomalacia in paediatric patients

“…However, this technique in children is, in general, not feasible due to a lack of cooperation [4]. Finally, bronchoscopy does not provide exact measurements of airway dimensions comparable to that provided by imaging techniques [3][4][5].…”