Parametric response map registered CT feature and small airway physiology analysis in asthma

Asthma is a disease characterized by spatiotemporal ventilation heterogeneity (VH). We hypothesized that imaging biomarkers of VH, extracted from parametric response map (PRM) registered inspiratory and expiratory CT scans in asthma, would be associated with asthma severity and small airway physiology. We aimed to evaluate PRM based CT features including a novel spatially regionalized approach, stratified axial analysis (SAA), in a cohort of asthma patients and healthy volunteers. We hypothesized that SAA biomarkers would associate with VH small airway biomarkers Sacin and R5-R20. 41 patients with asthma and 11 healthy age-matched volunteers underwent inspiratory (expiratory) volumetric CT scanning at TLC (FRC). CT biomarkers, notably SAA based inferior-superior ventilation slope (SAAz), were calculated. Linear discriminant analysis (LDA) was utilized to understand how spirometry, clinical and CT feature sets could discriminate Sacin and R5-R20. SAAz was found to provide the best single feature discriminator for both Sacin and R5-R20. LDA demonstrated that CT based feature sets can contribute significantly to VH discrimination. Polar analysis of SAAz revealed statistically significant (p < 0.05) ventilation gradient reversal [Figure 1]. We developed a novel stratified axial based CT imaging biomarker of inferior-superior ventilation gradient in asthma, which associates with small airway biomarkers of VH.