Current Advances in COPD Imaging

Abstract

Objective: To review the recent advances in available technologies for imaging COPD and present the novel optical coherence tomography (OCT) airway imaging technology.

Materials and methods: This is an unstructured review of published evidence of available pulmonary imaging technologies along with a demonstration of state-of-the-art OCT imaging technology of in vivo human and animal airways.

Results: Advanced imaging techniques such as Magnetic Resonance (MR) imaging using hyperoloarized noble gases, micro-Computed Tomography (micro-CT), and OCT aim to further our understanding of COPD. Lung densitometry can aid in identifying an exacerbation prone phenotype which may have implications for targeting specific therapies to these individuals. MR ventilation scans have the ability to provide a functional and regional distribution of airflow obstruction offering insight into the airway and parenchymal changes induced by COPD. Micro-CT gives a near microscopic view of the terminal bronchioles and alveoli permitting study of the microarchitecture of the lung ex vivo. Optical coherence tomography can visualize the microstructure of the airway walls (epithelium, smooth muscle, blood vessels, cartilage) permitting real time in vivo as well as longitudinal evaluation of airway changes in patients with COPD.

Conclusion: Advanced imaging techniques play a vital role in expanding our current understanding of COPD.

Keywords: COPD; Optical coherence tomography.

Fig. 1.

Visualization of emphysema distribution in a patient with COPD by chest CT density masks. Representative examples of morphologic images from nonenhanced multidetector computed tomography of the chest (left) are complemented by density maps generated by dedicated software highlighting low attenuation areas less than −950 Hounsfield units (right, each color signifies a lobe). Total emphysema was calculated to be 34%. COPD, chronic obstructive lung disease; CT, computed tomography. (Color version of figure is available online.)

Fig. 2.

Static 3-He MR ventilation scan in a patient with apical emphysema [Adapted with permission (31)]. MR, magnetic resonance. (Color version of figure is available online.)

Fig. 3.

(a) Full grey-scale synchrotron-based micro-Computed tomography image showing a branching conductive airways (red asterisks). (b) The slices were binarized so that the branching acinus could be segmented [Adapted with permission (50)]. (Color version of figure is available online.)

Fig. 4.

(a) Representative in vivo 2D image of canine airway acquired with an OCT system operating at 1300 nm. The white circle in the center of the airway lumen is the OCT catheter and plastic sheath. The concentric circles radiating out from the OCT catheter in the lumen are artifacts. (b) Corresponding H&E histology. BV, blood vessel, E, epithelium; H&E, Hematoxylin & Eosin; OCT, optical coherence tomography; SM, smooth muscle. (Color version of figure is available online.)

Fig. 5.

Changes in (a) airway wall thickness, (b) luminal diameter and (c) WA ratio along a 50 mm human airway measured in vivo by OCT. The middle panel (b) also shows three 2D OCT images of the airway taken at three points along the airway branch. WA, wall area; OCT, optical coherence tomography. (Color version of figure is available online.)

Fig. 6.

3D OCT reconstructed image of a fifth generation sheep airway. Note the appearance of luminal (bronchial) blood vessels in the airway wall. [Adapted with permission (63)]. OCT, optical coherence tomography. (Color version of figure is available online.)

Fig. 7.

2D OCT image corresponding to a proximal cross-section indicated by the blue dashed line in Fig. 6. [Adapted with permission (63)]. (Color version of figure is available online.). OCT, optical coherence tomography. (Color version of figure is available online.)

Fig. 8.

On the left is a 3X-magnified section of airway wall from Fig. 7. The tissue components of the airway wall are identified including epithelium (E), smooth muscle (SM), cartilage (C), and alveoli (A). There was a high degree of correlation between the fine microstructures on OCT (left) and tissue components on the H&E histology slide (right). The black bars represent 1 mm in distance. [Adapted with permission (63)]. H&E, Hematoxylin & Eosin; OCT, optical coherence tomography. (Color version of figure is available online.)