Role of MRI in Interstitial Lung Diseases

Interstitial lung diseases (ILDs) are a heterogeneous group of entities characterized by similar clinical, pathologic, and radiologic features. High-resolution CT scan is the first-line imaging modality; however, the use of ionizing radiation in patients requiring several follow-ups, the limitation in distinguishing active inflammation from fibrosis, as well as its poor tissular characterization properties have opened a scenario in which MRI may have a role in patients with ILD. The high prevalence of lung cancer in ILD and the frequently unrecognized ILD-related pulmonary hypertension (PH) have raised interest in the potential application of MRI in these patients.

Classical morphologic non-contrast-based MRI has moderate diagnostic performance for detection of parenchymal lung abnormalities. However, with the introduction of ultrashort echo time a "CT-like" appearance of MRI has become available, improving the characterization of tissue abnormalities in patients with ILD. Functional assessment of ventilation by oxygen-enhanced MRI or hyperpolarized MRI has become feasible. Noncontrast evaluation of ventilation and perfusion abnormalities is possible with Fourier decomposition and phase-resolved functional lung imaging. Advanced tissue characterization with diffusion-weighted imaging and perfusion-weighted imaging allows differentiation of malignant lesions as well as local staging. The addition of cardiac magnetic resonance sequences allows a comprehensive diagnosis of PH, with risk stratification and prognostic assessment.

Advanced MRI in ILD may provide a unique and holistic approach to patients with ILD, not only focusing on lung parenchymal abnormalities but also providing functional information about ventilation, perfusion, tissue characterization, diagnostic clues, and risk stratification of PH.