We have previously demonstrated multimodal optical coherence tomography and autofluorescence imaging (OCT-AFI) in the distal airways of the lung. To combine the two modalities into a single-fiber endoscope, we use double-clad fibers, which causes additional blurred OCT images from the fibers' higher-order modes. Recently, we established multipath contrast imaging (MCI) which leverages these higher-order images to elucidate angular backscattering of tissue. MCI can be generated retroactively; we seek to re-evaluate images from our in vivo OCT-AFI lung cancer study. Early MCI results demonstrate high contrast in healthy tissue compared to blood, and for a histologically confirmed adenocarcinoma.
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.
For the first time, the use of fiber-optic color Doppler optical coherence tomography (CDOCT) to map in vivo the three-dimensional (3-D) vascular network of airway segments in human lungs is demonstrated. Visualizing the 3-D vascular network in the lungs may provide new opportunities for detecting and monitoring lung diseases such as asthma, chronic obstructive pulmonary disease, and lung cancer. Our CDOCT instrument employs a rotary fiber-optic probe that provides simultaneous two-dimensional (2-D) real-time structural optical coherence tomography (OCT) and CDOCT imaging at frame rates up to 12.5 frames per second. Controlled pullback of the probe allows 3-D vascular mapping in airway segments up to 50 mm in length in a single acquisition. We demonstrate the ability of CDOCT to map both small and large vessels. In one example, CDOCT imaging allows assignment of a feature in the structural OCT image as a large (∼1 mm diameter) blood vessel. In a second example, a smaller vessel (∼80 μm diameter) that is indistinguishable in the structural OCT image is fully visualized in 3-D using CDOCT.
Introduction: A recent ex-vivo study using micro-CT in patients with chronic obstructive pulmonary disease (COPD) showed that narrowing and disappearance of small conducting airways precedes the onset of emphysematous destruction in COPD. Until recently, the airway remodeling process could not be studied in detail in-vivo. In this study, we investigated the repeatability of navigating an Optical Coherence Tomography (OCT) catheter to image the same airways in smokers with and without COPD. Method: OCT imaging was performed by inserting the catheter through a sub-segmental airway to a small bronchiole. Three-dimensional OCT imaging of 5 cm of airway segments was obtained. The catheter was removed and reinsertion into the same airway was attempted. The number of airway generations and quantitative measurements of the airway wall area were investigated. Results: Sixty-three airways in 30 subjects were analyzed. Repeated insertion into the same airway was observed at 53.8 %, 92.3% and 70.8% of the time in the upper, middle and lower lobes respectively. The percentage differences of paired measurements of airway wall area between matched and unmatched airways in bronchioles were 5.8 ± 4.6 % and 7.3 ± 5.4 % respectively Conclusions: Repeated OCT imaging of airways is possible in the majority of cases except in the upper lobes. For airways that are not completely matched, some of the airway segments can still be used for comparison by careful alignment of the airway. OCT may be a useful method to study the remodeling process in small airways and the effect of therapeutic intervention.
Architectural changes in and remodeling of the bronchial and pulmonary vasculature are important pathways in diseases
such as asthma, chronic obstructive pulmonary disease (COPD), and lung cancer. However, there is a lack of methods
that can find and examine small bronchial vasculature in vivo. Structural lung airway imaging using optical coherence
tomography (OCT) has previously been shown to be of great utility in examining bronchial lesions during lung cancer
screening under the guidance of autofluorescence bronchoscopy. Using a fiber optic endoscopic OCT probe, we acquire
OCT images from in vivo human subjects. The side-looking, circumferentially-scanning probe is inserted down the
instrument channel of a standard bronchoscope and manually guided to the imaging location. Multiple images are
collected with the probe spinning proximally at 100Hz. Due to friction, the distal end of the probe does not spin
perfectly synchronous with the proximal end, resulting in non-uniform rotational distortion (NURD) of the images. First,
we apply a correction algorithm to remove NURD. We then use a speckle variance algorithm to identify vasculature.
The initial data show a vascaulture density in small human airways similar to what would be expected.
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