The recent development of multidetector CT has enabled rapid examination and diagnosis, resulting in its frequent use in clinical medicine. Furthermore, as the application of MRI is being expanded to include its use in children, certain CT imaging techniques can be replaced by MRI to reduce radiation exposure. In this article, we describe the recent use of MRI in pediatric radiology.

　Gradient echo sequences (GRE sequences) might look simple on the sequence diagram, but understanding their principles is more difficult. In this review, the four main types of GRE sequences are explained. Since GRE sequences rely on spin echoes as well as stimulated echoes, coherence pathways and echo formation are also explained. Moreover, the history of the development of GRE sequences is briefly described.