Magnetic resonance imaging of the normal and abnormal pulmonary hila.

Magnetic resonance (MR) images of the hila were reviewed in 25 normal subjects and 12 patients with unilateral or bilateral hilar masses. On spin echo MR images in normal patients, collections of soft tissue large enough to be confused with an abnormally enlarged lymph node were seen in three locations. In patients with a hilar mass, the mass was differentiated from hilar vasculature more easily using MR than contrast-enhanced CT. In five of these patients, hilar lymph nodes approximately 1 cm in diameter were easily seen using MR, but were difficult or impossible to appreciate prospectively on CT. However, because the spatial resolution of MR is inferior to that of CT, bronchi were difficult to evaluate using MR. In general, images obtained with a short TR (0.5 sec) provided the best definition of mediastinal extension of the hilar mass, and images with a longer TR (1.5 to 2.0 sec) provided a better signal-to-noise ratio and showed increased signal strength from hilar masses. Electrocardiographic-gated images showed better resolution of hilar structures but may not be necessary for large masses.