Introduction to magnetic resonance imaging.

Magnetic resonance imaging (MRI) has become an important diagnostic tool with a wide variety of clinical applications. This article provides a qualitative description of physical principles of MRI fundamental to an appreciation of the capabilities and limitations of this complex technology. The same physical principles are used to explain the appearance of the images and the ability of MRI to provide spectroscopic data. Contrast agents, types of MRI equipment, and the safety of MRI in carrying out patient population goals are discussed. This article provides background knowledge for two subsequent articles which cover clinical application of MRI in greater detail.