Published Online: October 29, 2015
Magnetic Resonance (MR) images of the lung with inhaled hyperpolarized noble gases such as helium or xenon yield significant information about the distribution of gas in the lung. The method does not expose the patient to ionizing radiation hence it offers significant advantages over standard chest computed tomography (CT) especially in young children. Hyperpolarized gas MRI studies in patients with asthma have shown large ventilation defects or areas of the lung, which do not receive any inspired gas. The clinical relevance of such ventilation defects to the care of patients with asthma is not well established.
In an original report published recently in The Journal of Allergy and Clinical Immunology (JACI), Altes and colleagues performed a detailed characterization of the phenotypic features of 31 children, between ages 3 and 17 (with a median age of 10), with severe and mild to moderate asthma who underwent MR image studies with inhaled hyperpolarized Helium-3. An automated scoring system transformed the Helium-3 signal intensity to four lung ventilation volumes ranging from well ventilated to non-ventilated.
The authors report that hyperpolarized gas lung MRI can be used to precisely measure a range of ventilation volumes in the lungs of children with asthma, and that the lung defect volume is highly relevant to many standard outcomes used to manage asthma. Altes et al found that the ventilation defect volume fraction is greatest in children with severe asthma and those with airflow limitation, most notably in the small airways. Furthermore they found that the ventilation defect volume correlated with a number of clinical indicators including the level of asthma control, number of controller medications taken, and selected inflammatory markers including blood eosinophilia.
Lung imaging of children, even those who are small, is safe and feasible with inhaled hyperpolarized Helium-3 gas. In children with asthma the volume of the non-ventilated lung regions informs many clinically relevant features including severity, symptom control, lung function, and inflammatory markers.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.