We are developing optical imaging techniques and probes toward clinical imaging of diseases of the airway including chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, and sleep apnoea.
Section 1. Lung disease
Diseases such as emphysema and pulmonary fibrosis damage the alveoli in a patient’s lungs. Emphysema, predominantly caused by long-term exposure to cigarette smoke, results in destruction of the alveoli walls. Pulmonary fibrosis causes a thickening of the alveoli walls with scar tissue. Emphysema and pulmonary fibrosis combined account for over three quarters of all lung transplants. We are working with physiologists at the University of Western Australia to find new ways to image the lung, and detect the damage caused by disease.
We have acquired the world’s first scans of lung tissue using OCT needle probes. The figure below shows images taken from a rat lung, allowing physiologist to visualize individual alveoli and small airways called bronchioles. The image on the left shows an image from the point of view of the needle probe. The black hole in the centre (n) corresponds to the needle. The centre image shows a longitudinal view taken as the needle is retracted. The image on the right shows hematoxylin and eosin-stained histology of the same sample of tissue, highlighting the individual bronchioles and vessels that were identified in the OCT image.
Using a 30-gauge needle probe (outer diameter: 310 μm), it is possible to acquire a 3D volume scan of a section of tissue. The video below shows a 3D visualization of a sample of sheep lung, showing the complex relationship between airways.
0.1. Download movie: 3D visualization of sheep lung, showing alveoli and bifurcation of bronchioles. The field of view of this image is approximately 2mm
We have also developed fast-scanning needle probes, able to rapidly acquire images of dynamic processes in the body. The animation shows a section of ex vivo pig lung as it is inflated and deflated, allowing visualization of individual alveoli opening and expanding.
0.2. Download movie: Dynamic OCT needle scan of a pig lung during simulated breathing
Section 2. Sleep apnoea
In obstructive sleep apnoea, the patient suffers repeated interruptions to breathing due to a temporary collapse of part of the airway. It affects 2-4% of middle-aged adults and has been linked to hypertension and cardiovascular disease. We have developed an anatomical OCT (aOCT) system to assess changes in the airways in patients with obstructive sleep apnoea.
The aOCT probe is placed inside a catheter, which is then inserted through the nares (nostrils) to the level of the mid-oesophagus. The probe is rotated to obtain a profile of the upper airway, with a maximum imaging diameter of approximately 72mm. A controlled pullback of the probe through the airway allows the acquisition of a 3D image of the airway.
For the upper airway, OCT has allowed high-resolution structural imaging during sleep studies without the radiation exposure of CT or fluoroscopy, or the noise and logistical considerations of MRI.
A typical acquisition is shown below. The bright yellow outline is the air-tissue interface of the upper airway, showing the shape of the airway. This represents one cross-sectional image as the probe is pulled back through the airway. A 3D reconstruction of a different airway is shown below.
Section 3. Airway disease: quick links
1) Key techniques
2) Key Publications
- A. McLaughlin, X. Yang, B.C. Quirk, D. Lorenser, R.W. Kirk, P.B. Noble, D.D. Sampson, Static and dynamic imaging of alveoli using optical coherence tomography needle probes, Journal of Applied Physiology, 113, 2012.
- C. Quirk, R.A. McLaughlin, A. Curatolo, R.W. Kirk, P.B. Noble, D.D. Sampson, In situ imaging of lung alveoli with an optical coherence tomography needle probe, Journal of Biomedical Optics, 16(3):036009, 2011.
- J. Armstrong, M. S. Leigh, D. D. Sampson, J. H. Walsh, D. R. Hillman, and P. R. Eastwood, Quantitative upper airway imaging with anatomic optical coherence tomography, American Journal of Respiratory and Critical Care Medicine, vol. 173, pp. 226-233, 2006.