Overview of MR imaging pulse sequences.

This article reviews general pulse-sequence properties and the pulse-sequence techniques most commonly used for clinical MR imaging. The techniques are divided into three major categories: spin echo, gradient echo, and hybrids. The description of each technique emphasizes the basic structure of the pulse sequence, the manner in which transverse magnetization is generated and encoded, and the typical forms of image contrast. In addition, specific advantages or disadvantages of each method are discussed. The techniques described include only a few of the literally thousands of MR imaging pulse sequences that have been developed over the past 20 years. As this brief survey indicates, pulse sequences have been developed that furnish a great range of image contrast behaviors, acquisition speeds, and sensitivities to artifacts. The key to choosing clinically relevant techniques is the appropriate combination of these properties. Undoubtedly, many new MR imaging pulse sequences will join the ranks of the clinically relevant techniques during the next several years.