Paediatric lung imaging: the times they are a-changin'

Abstract

Until recently, functional tests were the most important tools for the diagnosis and monitoring of lung diseases in the paediatric population. Chest imaging has gained considerable importance for paediatric pulmonology as a diagnostic and monitoring tool to evaluate lung structure over the past decade. Since January 2016, a large number of papers have been published on innovations in chest computed tomography (CT) and/or magnetic resonance imaging (MRI) technology, acquisition techniques, image analysis strategies and their application in different disease areas. Together, these papers underline the importance and potential of chest imaging and image analysis for today's paediatric pulmonology practice. The focus of this review is chest CT and MRI, as these are, and will be, the modalities that will be increasingly used by most practices. Special attention is given to standardisation of image acquisition, image analysis and novel applications in chest MRI. The publications discussed underline the need for the paediatric pulmonology community to implement and integrate state-of-the-art imaging and image analysis modalities into their structure-function laboratory for the benefit of their patients.

FIGURE 1

A method for the objective assessment of airway artery dimensions (the AA method) to diagnose bronchiectasis. Boxplots show the ratio between the outer edge of the airway (A_out) and the adjacent artery (A). A_out/A ratios are shown for four consecutive groups: control (n=23); first and second cystic fibrosis-computed tomography (CF-CT₁ (n=12) and CF-CT₂ (n=12), respectively); and CT scans in a cross sectional cohort including patients aged 6–16 years (CF 6–16) (n=11). In total, 11 262 AA pairs were measured. A_out/A ratios are plotted against segmental generation (1 is the first segmental bronchus up to the 12th airway generation peripheral from the segmental bronchus). Control subjects were age-matched for CF patients. Median ages are 2 years, 3.9 years and 11 years for CF-CT₁, CF-CT₂ and CF 6–16, respectively. Boxes show median (horizontal line), interquartile range (box) and 1.5× interquartile range (whiskers). Outliers are shown as points. Note that for controls, A_out/A ratios were constant, whereas for each of the three CF groups an increasing and significant difference could be found in A_out/A ratio between the CF and control group from generation 2 to generation 5 (all p≤0.02). Furthermore, the difference between CF and controls was bigger for the oldest CF patients. Note that for generation 9 and higher, no more airway artery pairs were visible on the scans for control subjects, while airway artery pairs were still visible on the CT scans of CF patients [34, 35]. Reproduced and modified from [34].

FIGURE 2

Chest magnetic resonance images of a 15-year-old boy with asthma. Comparison between 3D spoiled gradient echo (SPGR) and 3D ultra-short echo time (UTE) at 3 T (Dicovery MR750; GE Healthcare, Chicago, IL, USA). a) 2×2×2 mm end-expiratory breath-hold axial 3D SGPR (TE=0.748 ms); b) 2×2×2 mm end-expiratory respiratory-triggered 3D UTE (TE=0.032 ms). Note the higher resolution and signal-to-noise ratio of UTE with better definition of the airways and air wall (arrow).