Measures of Ventilation Heterogeneity Mapped with Hyperpolarized
Helium-3 (HHe-3) MRI Demonstrate a T2-High Phenotype in Asthma
Abstract
Background: HHe-3 MR is a non-invasive imaging method which maps and
quantifies regions of ventilation heterogeneity (VH) in the lung. VH is
an important feature of asthma, but little is known as to how VH informs
patient phenotypes. Purpose: To determine if VH indicators quantified by
HHe-3 MRI predict phenotypic characteristics and map to regions of
inflammation in children with problematic wheeze/asthma. Methods. Sixty
children with poorly-controlled asthma underwent HHe-3 MRI, including 22
with bronchoalveolar lavage (BAL). The HHe-3 signal intensity defined
four ventilation compartments. The non-ventilated and hypoventilated
compartments divided by the total lung volume defined a VH index (VHI
%). Results: Children with VHI % in the upper quartile had
significantly greater airflow limitation, bronchodilator responsiveness,
blood eosinophils, expired nitric oxide (FeNO), and BAL eosinophilic/
neutrophilic granulocyte patterns compared to children with VHI % in
the lower quartile. Lavage return from hypoventilated bronchial segments
had greater eosinophil % than from ventilated segments. Conclusion: In
children with asthma, greater VHI % as measured by HHe-3 MRI identifies
a severe phenotype with higher type 2 inflammatory markers, and maps to
regions of lung eosinophilia. Listed on ClinicalTrials.gov
(NCT02577497).