Quantification of airway compliance can aid in the diagnosis and treatment of obstructive airway disorders by detecting regions vulnerable to collapse. Here we evaluate the ability of a swept-source anatomic optical coherence tomography (SSaOCT) system to quantify airway cross-sectional compliance (CC) by measuring changes in the luminal crosssectional area (CSA) under physiologically relevant pressures of 10-40 cmH 2 O. The accuracy and precision of CC measurements are determined using simulations of non-uniform rotation distortion (NURD) endemic to endoscopic scanning, and experiments performed in a simplified tube phantom and ex vivo porcine tracheas. NURD simulations show that CC measurements are typically more accurate than that of the CSAs from which they are derived. Phantom measurements of CSA versus pressure exhibit high linearity (R 2 >0.99), validating the dynamic range of the SSaOCT system. Tracheas also exhibited high linearity (R 2 = 0.98) suggestive of linear elasticity, while CC measurements were obtained with typically ± 12% standard error.
Objective measurement of the nasal valve region is valuable for the assessment of functional rhinoplasty surgical outcomes. Anatomical optical coherence tomography (aOCT) is an imaging modality that may be used to obtain real-time, quantitative, and volumetric scans of the nasal airway. We aim to evaluate if volumetric aOCT imaging is useful for the examination of the nasal valve region before and after functional rhinoplasty procedures. aOCT scans of the nasal valves were performed on four cadaveric heads before and after spreader graft and butterfly graft procedures. The resulting aOCT images were compared against video endoscopy images, and the segmented volumes of the nasal airway obtained from aOCT scans were compared with computed tomography (CT) derived volumes acquired under the same conditions. The aOCT-derived volumes match the CT volumes closely, with a mean Dice similarity coefficient of 0.88 and a mean Hausdorff distance of 2.3 mm. Furthermore, the aOCT images were found to represent the shape of the nasal cavity accurately. Due to its ability to perform realtime, quantitative, and accurate evaluation of the nasal airway, aOCT imaging is a promising modality for the objective assessment of the nasal valves before and after functional rhinoplasty procedures.
. It is hypothesized that the local, viscoelastic (time-dependent) properties of the airway are important to accurately model and ultimately predict dynamic airway collapse in airway obstruction. Toward this end, we present a portable, endoscopic, swept-source anatomical optical coherence tomography (aOCT) system combined with a pressure catheter to capture local airway dynamics in vivo during respiration. aOCT scans were performed in the airways of a mechanically ventilated pig under paralysis with dynamic and static ventilation protocols. Validation of dynamic aOCT luminal cross-sectional area (CSA) measurements against Cine CT, obtained during the same exam, showed an aggregate difference of . aOCT-derived CSA obtained in the in vivo trachea also exhibited hysteresis as a function of pressure, depicting the viscoelastic nature of the airway wall. The volumetric imaging capabilities were validated by comparing aOCT- and CT-derived geometries of the porcine airway spanning nine generations from the trachea to the bronchioles. The ability to delineate regional differences in airway viscoelastic properties, by measuring airway deformation using aOCT combined with intraluminal pressure, paves the way to patient-specific models of dynamic airway collapse.
Quantitative endoscopic imaging is at the vanguard of novel techniques in the assessment upper airway obstruction. Anatomic optical coherence tomography (aOCT) has the potential to provide the geometry of the airway lumen with high-resolution and in 4 dimensions. By coupling aOCT with measurements of pressure, optical coherence elastography (OCE) can be performed to characterize airway wall stiffness. This can aid in identifying regions of dynamic collapse as well as informing computational fluid dynamics modeling to aid in surgical decision-making. Toward this end, here we report on an anatomic optical coherence tomography (aOCT) system powered by a wavelength-swept laser source. The system employs a fiber-optic catheter with outer diameter of 0.82 mm deployed via the bore of a commercial, flexible bronchoscope. Helical scans are performed to measure the airway geometry and to quantify the cross-sectional-area (CSA) of the airway. We report on a preliminary validation of aOCT for elastography, in which aOCT-derived CSA was obtained as a function of pressure to estimate airway wall compliance. Experiments performed on a Latex rubber tube resulted in a compliance measurement of 0.68±0.02 mm2/cmH2O, with R2=0.98 over the pressure range from 10 to 40 cmH2O. Next, ex vivo porcine trachea was studied, resulting in a measured compliance from 1.06±0.12 to 3.34±0.44 mm2/cmH2O, (R2>0.81). The linearity of the data confirms the elastic nature of the airway. The compliance values are within the same order-of-magnitude as previous measurements of human upper airways, suggesting that this system is capable of assessing airway wall compliance in future human studies.
We describe an elastographic method to circumferentially-resolve airway wall compliance using endoscopic, anatomic optical coherence tomography (aOCT) combined with an intraluminal pressure catheter. The method was first demonstrated on notched silicone phantoms of known elastic modulus under respiratory ventilation, where localized compliance measurements were validated against those predicted by finite element modeling. Then, ex vivo porcine tracheas were scanned, and the pattern of compliance was found to be consistent with histological identification of the locations of (stiff) cartilage and (soft) muscle. This quantitative method may aid in diagnosis and monitoring of collapsible airway wall tissues in obstructive respiratory disorders.
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