Peripheral lung nodules found by CT-scans are difficult to localize and biopsy bronchoscopically particularly for those ≤ 2 cm in diameter. In this work, we present the results of endoscopic co-registered optical coherence tomography and autofluorescence imaging (OCT-AFI) of normal and abnormal peripheral airways from 40 patients using 0.9 mm diameter fiber optic rotary pullback catheter. Optical coherence tomography (OCT) can visualize detailed airway morphology endoscopically in the lung periphery. Autofluorescence imaging (AFI) can visualize fluorescing tissue components such as collagen and elastin, enabling the detection of airway lesions with high sensitivity. Results indicate that AFI of abnormal airways is different from that of normal airways, suggesting that AFI can provide a sensitive visual presentation for rapidly identifying possible sites of pulmonary nodules. AFI can also rapidly visualize in vivo vascular networks using fast scanning parameters resulting in vascular-sensitive imaging with less breathing/cardiac motion artifacts compared to Doppler OCT imaging. It is known that tumor vasculature is structurally and functionally different from normal vessels. Thus, AFI can be potentially used for differentiating normal and abnormal lung vasculature for studying vascular remodeling.
In this work, we present multimodal imaging of peripheral airways in vivo using an endoscopic imaging system capable of co-registered optical coherence tomography and autofluorescence imaging (OCT-AFI). This system employs a 0.9 mm diameter double-clad fiber optic-based catheter for endoscopic imaging of small peripheral airways. Optical coherence tomography (OCT) can visualize detailed airway morphology in the lung periphery and autofluorescence imaging (AFI) can visualize fluorescent tissue components such as collagen and elastin, improving the detection of airway lesions. Results from in vivo imaging of 40 patients indicate that OCT and AFI offer complementary information that may increase the ability to identify pulmonary nodules in the lung periphery and improve the safety of biopsy collection by identifying large blood vessels. AFI can rapidly visualize in vivo vascular networks using fast scanning parameters resulting in vascular-sensitive imaging with less breathing/cardiac motion artifacts compared to Doppler OCT imaging. By providing complementary information about structure and function of tissue, OCT-AFI may improve site selection during biopsy collection in the lung periphery.
Diagnosis of peripheral lung nodules is challenging because they are rarely visualized endobronchially. Imaging
techniques such as endobronchial ultrasound (EBUS) are employed to improve tumor localization. The current EBUS
probe provides limited nodule characterization and has an outer diameter of 1.4 mm that restricts access to small
peripheral airways. We report a novel co-registered autofluoresence Doppler optical coherence tomography (AF/DOCT)
system with a 0.9 mm diameter probe to characterize peripheral lung nodules prior to biopsy in vivo.
Method: Patients referred for evaluation of peripheral lung nodules underwent bronchoscopy with examination of
standard EBUS and the novel AF/DOCT system. The lesion of interest was first identified with EBUS and then imaged
with the AF/DOCT system. The abnormal area was biopsied. AF/DOCT images of pathology proved lung malignancies
were reviewed by a panel of a pathologist, respirologists, and AF/DOCT experts.
Results: Eleven patients with biopsy proven lung cancer underwent examination with AF/DOCT. The majority of the
cancers were adenocarcinoma. AF/DOCT images were obtained in all patients. There were no complications to the
procedures. Lung abnormalities visualized in AF/ OCT images were observed in 11 cases. In one case large blood
vessels were identified and biopsy was avoided.
Conclusion: In this pilot study, AF/DOCT obtained high quality images of peripheral pulmonary nodules. The present
study supports the safety and feasibility of AF/DOCT for the evaluation of lung cancer. The addition of Doppler
information may improve biopsy site selection and reduce hemorrhage.
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