Purpose: Optical coherence tomography (OCT) can obtain high-resolution, cross-sectional microscopic images of tissue, potentially enabling optical biopsy to substitute for conventional excisional biopsy. We sought to investigate the capability of OCT to image the microstructure of normal and abnormal bronchial tissue.
Equipment: The OCT system was produced by Light Lab Imaging (Boston, U.S.A.) and Pentax. (Tokyo, Japan). Preliminary examination: the OCT system was used to image-resected lung specimens from patients who had given written informed consent for this study. We inserted the OCT catheter via the working channel of the bronchoscope to evaluate the bronchial lumen. The catheter delivers a radial OCT beam and scans circumferentially to generate a transluminal image. We collected OCT images of normal bronchus, primary tumors and alveoli. All images were saved and labeled according to the patient and type of tissue imaged for later correlation with histologic studies. Clinical examination: five other patients, all of whom had given written informed consent, were examined with the OCT system under local anesthesia. The OCT catheter was inserted into the working channel of the bronchoscope for evaluation of the bronchial lumen. We collected OCT images of the normal bronchus and tumors in vivo.
Results: (1) Normal bronchus: the bronchial mucosal and submucosal layers appear homogeneous in OCT images. The submucosal layer is relatively reflective due to the presence of an extracellular matrix. A membrane can be seen between the submucosal and the smooth muscle layer, and areas of cartilage show high levels of scattering. (2) Alveoli: OCT images show the uniform appearance of the bronchial wall and the structure of air-containing alveoli. (3) Central type lung cancers: in preliminary and clinical examinations, the tumors showed unevenly distributed high backscattering areas and resultant loss of the normal layer structure.
Conclusions: This study was the first report of the endobronchial OCT for lung cancer in clinical practice. Layers of the bronchial wall were distinctly observed in the normal bronchus on the OCT images, as opposed to bronchial tumors which lacked a layered structure. The ability of OCT to identify abnormal areas may well revise present methods for early diagnosis endoscopically.