An Exploratory Study to Characterize Noncontrast CT Derived Lung Perfusion in Patients with COPD
American Journal of Respiratory and Critical Care Medicine
Rationale: Loss of pulmonary blood vessel volume and perfusion often occur early in COPD. We have previously shown that pulmonary blood mass dynamics induced by tidal breathing can be quantified from non-contrast CT scans. We have extended this concept to develop a novel CT-Perfusion (CT-P) method for computing the magnitude blood mass changes apparent on dynamic non-contrast CT as a surrogate for pulmonary perfusion. We hypothesize decremental loss in CT-P measured mean magnitude blood mass change (BMC) with increasing COPD severity. Methods: The CT-P method applies image processing and physical modeling to an Inhale/Exhale CT image pair to generate a CT-P image. CT-P characterizes the change in spatial blood mass distribution from inhale to exhale and therefore provides a map of blood flow throughout the lungs. We analyzed 50 random patients from COPDGene study according to Global Initiative on Obstructive Lung Disease (GOLD) staging (10 from each stage). For each patient, BMC scores were calculated as the mean CT-P voxel value taken over the full lung volume. Results: BMC values significantly dropped with increasing GOLD stages (Figure-1). On univariate analysis, Log-BMC scores were significantly lower in self-reported African-American population compared to and Non-Hispanic Whites (95% CI: -0.571, -0.070,p 0.01), and with decreased lung function(FEV1%pred - 95%CI: 0.004, 0.009, p <0.001; FVC% pred - 95%CI: 0.003, 0.009, p 0.001). Log-BMC was lower in those with higher St. George's Respiratory Questionnaire (95%CI: -0.009, - 0.002, p 0.003) and higher in those with increasing BMI (95% CI: 0.022, 0.056, p <0.001). On multivariate analysis, Log-BMC scores were significantly lower in patients with COPD GOLD class II-IV even after adjusting for age, BMI, race and SGRQ. Conclusion: BMC computed from CT-P is a promising method for assessing perfusion in patients with COPD. It has wide potential implication for assessment of progression, early detection and therapeutic effects of medications in patients with COPD. Figure 1: (Left) Box plots of the BMC scores for each GOLD score category. BMC, which is a surrogate for pulmonary perfusion, decreases as GOLD score increases. (Right) CT-P images for a patient with GOLD score 1 (top) and a patient with GOLD score 4 (bottom), shown with consistent color scale. As indicated by the color bar, the GOLD 1 patient has some regions of decreased perfusion whereas the GOLD 4 patient has low perfusion throughout the lungs.
Nair GB, Lynch DA, Hatt C, Han MK, Galban CJ, Stevens C, et al. An Exploratory Study to Characterize Noncontrast CT Derived Lung Perfusion in Patients with COPD [Internet]. American Thoracic Society; 2021. (TP121. TP121 COPD: FROM CELLS TO THE CLINIC). Available from: https://doi.org/10.1164/ajrccm-conference.2021.203.1_MeetingAbstracts.A4576