Quantitative CT emphysema subtypes and pulmonary blood volume on dual-energy CT: The MESA Lung Study

Abstract

Rationale: The pulmonary vasculature is critical for cardiopulmonary function. Perfused pulmonary blood volume (PBV) can be assessed using dual energy CT (DECT). Prior work has shown that PBV is reduced with age and former smoking, and that microvascular PBV (mPBV) is lower with greater percent emphysema (LAA-950HU). Unsupervised machine learning has identified six reproducible regional CT emphysema subtypes (CTES) with distinct characteristics. We investigate the relationship between CTES and PBV on DECT.

Methods: The Multi-Ethnic Study of Atherosclerosis (MESA) recruited adults from the community at six US sites. Participants without kidney disease or contrast allergy were asked to undergo iodine enhanced DECT at functional residual capacity. PBV was calculated by material decomposition and normalized with iodine concentration in the pulmonary trunk. mPBV was defined as PBV in peripheral 2cm of the lung. CTES were assessed on non-contrast CT at total lung capacity. Linear models included age, sex, race/ethnicity, height, weight, smoking status, site, and education.

Results: Of 2,445 eligible MESA participants, 560 had both PBV and CTES data (mean age 71± 7, 55% male, 40% White, 27% Black, 18% Hispanic, 15% Asian, 51% never smokers). In adjusted models, PBV and mPBV were inversely associated with the diffuse emphysema subtype (-0.25 mL PBV, p=0.008 and -0.22 mL mPBV per 10% increase in emphysema, p=0.002) but no other CTES.

Conclusion: Whole lung measures of PBV and mPBV are inversely associated with the diffuse emphysema subtype, similar to the ‘pink puffer’ clinical phenotype, but no other CTES, suggesting that pulmonary vascular changes in emphysema differ across subtypes.