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 15 % ± 3 % . 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.
To aid in diagnosis and treatment of upper airway obstructive disorders (UAOD), we propose anatomic Optical Coherence Tomography (aOCT) for endoscopic imaging of the upper airway lumen with high speed and resolution. aOCT and CT scans are performed sequentially on in vivo swine to compare dynamic airway imaging data. The aOCT system is capable of capturing the dynamic deformation of the airway during respiration. This may lead to methods for airway elastography and aid in our understanding of dynamic collapse in UAOD.
We describe a novel, multi-modal imaging protocol for validating quantitative dynamic airway imaging performed using anatomical Optical Coherence Tomography (aOCT). The aOCT system consists of a catheter-based aOCT probe that is deployed via a bronchoscope, while a programmable ventilator is used to control airway pressure. This setup is employed on the bed of a Siemens Biograph CT system capable of performing respiratory-gated acquisitions. In this arrangement the position of the aOCT catheter may be visualized with CT to aid in co-registration. Utilizing this setup we investigate multiple respiratory pressure parameters with aOCT, and respiratory-gated CT, on both ex vivo porcine trachea and live, anesthetized pigs. This acquisition protocol has enabled real-time measurement of airway deformation with simultaneous measurement of pressure under physiologically relevant static and dynamic conditions- inspiratory peak or peak positive airway pressures of 10-40 cm H2O, and 20-30 breaths per minute for dynamic studies. We subsequently compare the airway cross sectional areas (CSA) obtained from aOCT and CT, including the change in CSA at different stages of the breathing cycle for dynamic studies, and the CSA at different peak positive airway pressures for static studies. This approach has allowed us to improve our acquisition methodology and to validate aOCT measurements of the dynamic airway for the first time. We believe that this protocol will prove invaluable for aOCT system development and greatly facilitate translation of OCT systems for airway imaging into the clinical setting.
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