Bronchoscopic applications of anatomical optical coherence tomography

Jonathan Williamson

    Research output: ThesisDoctoral Thesis

    229 Downloads (Pure)

    Abstract

    [Truncated abstract] Background. The ability to measure airway dimensions during bronchoscopy would provide information with which interventional bronchoscopists could base treatment decisions such as selection of stent size or balloon dilators for the treatment of central airway obstruction (CAO). Such measurements would also assist researchers investigating the physiological characteristics of airway pathology by providing regional and functional assessment of airway changes in vivo. However, current techniques for bronchoscopic airway measurements are limited by operator subjectivity and variable accuracy. Anatomical optical coherence tomography (aOCT), a light-based imaging technique, may overcome these limitations. The aims of this thesis are to validate aOCT for bronchoscopic use and investigate potential clinical and research applications. Methods. Three interrelated studies were undertaken. The first study sought to assess measurement validity of aOCT in phantom tubes, explanted porcine airways and in vivo human airways. (i) In an airway phantom constructed from 10 plastic tubes, the accuracy and repeatability of aOCT area and diameter measurements were assessed. (ii) Four explanted porcine airways were used to compare measurements of airway compliance and the shape factor K (derived from the pressure vs area curve) obtained using aOCT and endoscopic imaging. (iii) In four patients undergoing bronchoscopy and chest computed tomography (CT), measurements of airway calibre performed with CT and aOCT were compared using Bland-Altman analyses. In the second study, 14 patients undergoing bronchoscopy for symptomatic central airway obstruction were recruited. CT scans were reviewed prior to bronchoscopy and relevant airway dimensions, such as the length and calibre of stenosed airway segments, were recorded. During bronchoscopy, stenosis dimensions were re-measured using aOCT. Based on the combination of CT findings, bronchoscopic appearance and aOCT measurements, a treatment strategy, such as airway stenting or balloon dilatation, was formulated. Measured airway dimensions were used to guide stent selection (length and calibre) or the target size for airway dilatation. Treatment efficacy was assessed using pre- and post-procedure spirometry, dyspnoea score and Eastern Cooperative Oncology Group (ECOG) performance status. In the final study, the research applications of aOCT were explored. Post-bronchodilator measurements of regional airway compliance and elastic recoil were performed during bronchoscopy under general anaesthesia in healthy controls (n=10) and in cases of asthma (n=16), chronic obstructive pulmonary disease (COPD) (n=9) and bronchiectasis (n=8). While airway pressure was incrementally increased, airway area (Ai) was recorded to generate (transpulmonary) pressure-area curves. Airway elastic properties were measured from these curves and compared between groups using analysis of variance. Results. aOCT measurements of phantom tube cross-sectional area were highly accurate and reproducible (intra/inter-repeatability coefficients <2%). Porcine airway compliance and the compliance shape factor K were not significantly different when measured with the endoscopic or aOCT techniques...
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2010

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