Positive Airway Pressure to Enhance Computed Tomography Imaging for Airway Segmentation for Virtual Bronchoscopic Navigation

Abstract

Rationale: Virtual bronchoscopic navigation (VBN) guidance to peripheral pulmonary lesions is often limited by insufficient segmentation of the peripheral airways. Objectives: To test the effect of applying positive airway pressure (PAP) during CT acquisition to improve segmentation, particularly at end-expiration. Methods: CT acquisitions in inspiration and expiration with 4 PAP protocols were recorded prospectively and compared to baseline inspiratory acquisitions in 20 patients. The 4 protocols explored differences between devices (flow vs. turbine), exposures (within seconds vs. 15-min) and pressure levels (10 vs. 14 cmH₂O). Segmentation quality was evaluated with the number of airways and number of endpoints reached. A generalized mixed-effects model explored the estimated effect of each protocol. Measurements and Main Results: Patient characteristics and lung function did not significantly differ between protocols. Compared to baseline inspiratory acquisitions, expiratory acquisitions after 15 min of 14 cmH₂O PAP segmented 1.63-fold more airways (95% CI 1.07–2.48; p = 0.018) and reached 1.34-fold more endpoints (95% CI 1.08–1.66; p = 0.004). Inspiratory acquisitions performed immediately under 10 cmH₂O PAP reached 1.20-fold (95% CI 1.09–1.33; p < 0.001) more endpoints; after 15 min the increase was 1.14-fold (95% CI 1.05–1.24; p < 0.001). Conclusions: CT acquisitions with PAP segment more airways and reach more endpoints than baseline inspiratory acquisitions. The improvement is particularly evident at end-expiration after 15 min of 14 cmH₂O PAP. Further studies must confirm that the improvement increases diagnostic yield when using VBN to evaluate peripheral pulmonary lesions.

Ultrathin Bronchoscopy with and without Virtual Bronchoscopic Navigation: Influence of Segmentation on Diagnostic Yield

“…Although mini-cryobiopsy probes are not commercially available yet, it is thought that they can potentially obtain tissue surrounding distal bronchi [27]. Finally, we have recently obtained promising results when attempting to improve VBN segmentation by using PAP-enhanced CT [28]. …”

Segmentation of distal airways using structural analysis

“…Main analysis was performed using generalized mixed models in logarithmic scale. In particular, we followed the model that was used in the CPAP study [25] with an extra variable for the segmentation method. The CPAP model was designed by the Statistical Service of Hospital Universitari de Bellvitge.…”