Quantitative dynamic contrast-enhanced MRI of the lung in asthma

Purpose: To assess the ability of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to quantify pulmonary capillary permeability, leakage space and blood volume in asthmatic patients. Methods: Consenting volunteers (10 healthy, 20 asthmatic) underwent pulmonary function tests and DCE-MRI at 1.5 Tesla within 7 days. The extended Kety model was fitted to the contrast agent concentration-time curves to extract transfer constant (K trans ), fractional leakage volume (v e ) and the fractional blood plasma volume (v p ). Parameters were summarized using median values over the lungs. Results: Median v e was significantly higher in asthmatics (0.30 ± 0.06 ml/ml tissue) than in healthy subjects (0.23 ± 0.02 ml/ml tissue, P = 0.001) but was not different between mild and severe asthmatics, indicating the increased extravascular leakage space in asthmatic lungs. While median K trans did not differ between patients and healthy subjects, there was a difference between mild and severe asthmatics (0.19 ± 0.07 vs 0.28 ± 0.07 ml/min/ml tissue, P = 0.040), implying increased vascular permeability and/or blood flow in more severe disease. Median v p was not different between groups. Conclusion: Quantitative DCE-MRI parameters are promising biomarkers of pulmonary inflammation in asthma, with v e sensitive to the presence of asthma and K trans sensitive to asthma severity. Acknowledgement: Dorothy Hodgkin Postgraduate Award from AstraZeneca and RCUK for funds.