Thoracic magnetic resonance imaging: physics and pulse sequences.

The article summarizes the basic concepts of magnetic resonance (MR) physics so that radiologists can optimize the images obtained in MR imaging of the chest. The specification of thoracic MR scan protocols is more complex than for other body regions because of cardiac and respiratory motion and blood flow. Various motion suppressing techniques such as motion compensation, respiratory compensation, and spatial presaturation have been developed, but their appropriate application is facilitated by a thorough understanding of the imaging process. Magnetic susceptibility and low proton density limit the usefulness of MR imaging in the assessment of the lung parenchyma. Nevertheless, recent studies have shown considerable improvement in image quality with the use of short echo times. Suggested imaging protocols for the evaluation of chest wall, mediastinum, hilum, heart, and great vessels are discussed.