A REVIEW OF MRI PULSE SEQUENCES AND TECHNIQUES IN NEUROIMAGING

BACKGROUND The unmatched soft tissue contrast provided by magnetic res onance imaging (MRI) has made it the modality of choice for many neuro imaging examinations. The fact that signal intensity in MRI depends on many parameters, including spin-lattice and spin-spin relaxation time s, proton density, and velocity, makes it possible to highlight variou s pathologies by appropriate choice of pulse sequences and pulse seque nce parameters. It is somewhat overwhelming, however, to filter throug h various pulse sequences and parameters in order to understand how th eir selection affects image contrast. This brief review is intended to highlight common pulse sequences and parameters as well as introduce new techniques currently being released for clinical use. MATERIALS Ba sic pulse sequences are described and the influence of the acquisition parameters on image contrast are illustrated. Such basic sequences in clude the ubiquitous spin echo, fast spin echo, and gradient echo sequ ences. Specialized techniques for fat suppression and magnetic resonan ce angiography are also presented. Currently approved contrast agents for use in MRI are briefly reviewed, and various advanced pulse sequen ces, such as those for diffusion and magnetization transfer contrast i maging, are briefly outlined. RESULTS The utility of basic and advance d pulse sequences are demonstrated by clinical examples and images of normal brain and spine. New sequences and techniques are briefly outli ned with regard to their potential for improving neuroimaging examinat ions. CONCLUSIONS This brief review outlines how the choice of pulse s equence and acquisition parameters influences the resulting image cont rast for a variety of basic and advanced imaging techniques. (C) 1997 by Elsevier Science Inc.