Abstract
Although autofluorescence bronchoscopy improves the detection rate of high grade dysplasia and carcinoma in‐situ compares to white‐light examination, the natural history of preneoplastic bronchial lesions is still poorly understood because the biopsy procedure for histological confirmation can mechanically remove these small lesions. The lack of accurate information regarding the spontaneous progression and regression rates of preneoplastic lesions make if difficult to assess the effect of chemoprevention agents. It is therefore important to develop non‐biopsy methods that can characterize preneoplastic lesions in the bronchial epithelium.
Optical coherence tomography (OCT) is an optical imaging method that can visualize cellular and extra‐cellular structures at and below tissue surface. In principle, it is similar to B‐type ultrasound. Instead of using sound waves, a low coherence near infra‐red light such as from a broadband 1300 nm superluminescent diode source is passed into the tissue. By detecting the reflected light as it interacts with tissue structures as a function of depth, a cross sectional image is created through optical interferometry. Its contrast is the backscattered light from interfaces at different depths in the tissue, due to the heterogeneity of optical refractive indices from different tissue compositions and densities. Changes in the extracellular matrix can be readily seen due to the strong back‐scattering properties of collagen and elastin. OCT provides cross‐sectional tomographic images about anatomic layered structures of tissues with a large field‐of‐view, a spatial resolution of 3 to 16 microns and a depth penetration of 2 – 3 mm to provide near‐histological images. The imaging procedure is performed using fiber optic probes that can be miniaturized to enable imaging of airways down to the terminal bronchiole. Unlike ultrasound, light waves do not require liquid based coupling medium and thus are more compatible with airway imaging. There are no associated risks from the weak near infrared light. OCT has distinct advantages over CT and MRI for imaging small airways in‐vivo in that it has superior resolution approaching near‐microscopic resolution and requires no ionizing radiation. It has advantages over confocal microscopy in that it can penetrate tissue three times deeper, does not require contact with the tissue surface and is less susceptible to motion artifacts due to real‐time image acquisition. In addition to morphometric information, functional OCT, such as Doppler OCT, can also provide quantitative information on blood flow of blood vessels and micro‐vasculature. OCT imaging has been applied to study bronchial and lung tissues and has been shown to be promising in the detection and characterization of preneoplastic lesions tumor in central and peripheral airways.
Citation Information: Cancer Prev Res 2010;3(1 Suppl):CN06-04.
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