Endoscopic Optical Coherence Tomography imaging of the airway

A narrowing, either of the nasal airway or the large airways, causes impaired airflow and results in respiratory insufficiency. Imaging the airways is important for the diagnostic evaluation of airway disorders. Existing approaches, such as bronchoscopy/ endoscopy or Computed Tomography (CT), are either qualitative or are impractical to use for routine assessments. Endoscopic Optical coherence Tomography (OCT) can be used to obtain quantitative images of the dynamic airway in real-time and to reconstruct airway volumes.In order to image the large airways, an OCT system with a long imaging range and high sensitivity is necessary. The data acquisition scheme for an endoscopic OCT system with a wavelength swept laser source was developed and refined to enable imaging in the large airways. A pressure acquisition system was also integrated to allow synchronous, invasive, pressure measurements to be made in conjunction with OCT scans. Experiments were performed in mechanically ventilated pigs to demonstrate the airway imaging capabilities of the OCT system. The results obtained from OCT were validated against CT scans acquired during the same exam. The combined pressure and OCT-derived cross sectional area plots, measured in vivo over a respiratory cycle, exhibited hysteresis loops, indicating the viscoelastic nature of the airway deformation. Endoscopic OCT imaging was also performed in the nasal cavities of cadaver heads to assess the outcomes of functional rhinoplasty procedures. OCT-derived volumes of the nasal airway were compared against CT volumes and found to depict the nasal vault faithfully.A fiber-optic probe with a low numerical aperture lens at its tip is better suited for imaging large luminal organs, as the distance between the probe and the tissue surface is unknown and variable. A novel, multi-segment, all-fiber lens, that can produce nearly collimated beams with working distances larger than 14 mm, was designed, fabricated, and tested. Finally, the non-unform rotation distortion produced by a super-elastic Nitinol tube drive-shaft was compared against the performance of a torque coil drive-shaft. It is hoped that the results presented will help advance the adoption of endoscopic OCT in routine clinical practice for the assessment of airway disorders.Doctor of Philosoph