Objective assessment of computed tomographic pulmonary attenuation of inspiratory and expiratory series in dogs with and without bronchomalacia.

Objective: To document objective metrics of attenuation of the pulmonary parenchyma on inspiratory and expiratory breath-hold CT in dogs with bronchomalacia (BM) and dogs without BM (NoBM) using automated software analysis. Metrics included mean lung attenuation, percent low-attenuation area at -856 HU, percent high-attenuation area at -700 HU, and percent attenuation area between -600 and -250 HU.

Animals: Client-owned dogs with BM (n = 123) and NoBM (20).

Methods: This retrospective study utilized 3D Slicer software (Brigham and Women's Hospital) to assess pulmonary CT attenuation. Analysis used Spearman correlation and 2-way ANOVA with beta regression.

Results: Comparing the difference between inspiratory and expiratory phases, there was a significantly greater increase in mean lung attenuation (P = .001), a significant reduction in percent low-attenuation area at -856 HU (P = .016), and a significant increase in percent high-attenuation area at -700 HU and percent attenuation area between -600 and -250 HU (P < .001 and P < .0001, respectively) in BM versus NoBM dogs.

Conclusions: The higher inspiratory and expiratory difference in lung attenuation in BM compared to NoBM dogs supports the presence of impaired parenchymal aeration downstream of segmental and subsegmental airway collapse.

Clinical Relevance: Quantitative image analysis holds promise for objectively evaluating changes with BM.