Dynamic lung water MRI during exercise stress

Abstract

PurposeExercise‐induced dyspnea caused by lung water is an early heart failure symptom. Dynamic lung water quantification during exercise is therefore of interest to detect early stage disease. This study developed a time‐resolved 3D MRI method to quantify transient lung water dynamics during rest and exercise stress.MethodsThe method was evaluated in 15 healthy subjects and 2 patients with heart failure imaged in transitions between rest and exercise, and in a porcine model of dynamic extravascular lung water accumulation through mitral regurgitation (n = 5). Time‐resolved images were acquired at 0.55T using a continuous 3D stack‐of‐spirals proton density weighted sequence with 3.5 mm isotropic resolution, and derived using a motion corrected sliding‐window reconstruction with 90‐s temporal resolution in 20‐s increments. A supine MRI‐compatible pedal ergometer was used for exercise. Global and regional lung water density (LWD) and percent change in LWD (ΔLWD) were automatically quantified.ResultsA ΔLWD increase of 3.3 ± 1.5% was achieved in the animals. Healthy subjects developed a ΔLWD of 7.8 ± 5.0% during moderate exercise, peaked at 16 ± 6.8% during vigorous exercise, and remained unchanged over 10 min at rest (−1.4 ± 3.5%, p = 0.18). Regional LWD were higher posteriorly compared the anterior lungs (rest: 33 ± 3.7% vs 20 ± 3.1%, p < 0.0001; peak exercise: 36 ± 5.5% vs 25 ± 4.6%, p < 0.0001). Accumulation rates were slower in patients than healthy subjects (2.0 ± 0.1%/min vs 2.6 ± 0.9%/min, respectively), whereas LWD were similar at rest (28 ± 10% and 28 ± 2.9%) and peak exercise (ΔLWD 17 ± 10% vs 16 ± 6.8%).ConclusionLung water dynamics can be quantified during exercise using continuous 3D MRI and a sliding‐window image reconstruction.