MRI of diffuse lung and airway disease

Dedicated high end MRI techniques are capable to routinely provide diagnostic images of the lung either in diffuse or airway disease as well as other entities. MRI has overcome the difficulties associated with low spin density, susceptibility artefacts as well as cardiac and respiratory motion. A basic MRI protocol includes visualization of the morphology using fast T1- and T2-weighted sequences as well as post contrast scans. Reticular, nodular and cystic patterns as well as ground glass infiltrates and consolidations are easily visualized. The detection rate is comparable to CT although the images have a lower spatial resolution. Enhancement is a good indicator to assess active disease, such as alveolitis in diffuse lung disease or active inflammation and exacerbations in airway disease. Liquid-sensitive T2-weighted sequences are very helpful in the detection of mucus, especially mucus plugging in cystic fibrosis, or fluid collections and abscess formation. The morphological evaluation can be complemented by MR angiography to further assess the vascular involvement of the disease. The angiotropic distribution of abnormalities is nicely illustrated, collagen vascular lung disease can be differentiated and rarefication of the vasculature in severe airway disease is demonstrated. Time-resolved MR angiography can be applied to illustrate different vascular territories, especially the significance of systemic arteries supplying the lung. Their contribution can be increased in diffuse lung and airway disease. The real strength of MRI is its capability to provide additional functional information, such as on perfusion, blood flow or ventilation. Perfusion defects due to destruction of the normal lung parenchyma or hypoxic vasoconstriction are easily depicted. Flow measurements can be applied in order to estimate the amount of left to right shunt volume. Several techniques are available for ventilation imaging. MRI using hyperpolarized 3He gas generates images with high signal intensity whereas oxygen-enhanced proton MRI is easier to implement, but the signal increase is much lower and interpretation of areas showing signal abnormalities is difficult. In general, diffuse lung disease only leads to small defects on ventilation MRI whereas obstructive airway disease is associated with larger defects.

Lernziele:

To learn about MRI techniques to examine structure and function in lung diseases.

To review typical MRI findings in diffuse lung and airway disease.

Korrespondierender Autor: Kauczor HU

DKFZ, Radiologie, Im Neuenheimer Feld 280, 69120 Heidelberg

E-Mail: [e-mail]