Process and apparatus to remove stimulated echo artifacts caused by interactions of a preparation sequence with a gradient echo sequence in MR imaging

摘要

The present invention is directed to a process and system for removing artifacts resulting from the interactions of a preparation sequence and a gradient echo sequence. A process for suppressing stimulated echoes for spatial preparation sequences without affecting sequence timing or image contrast is disclosed. Stimulated echoes often form when gradient crushers of a preparation sequence are constant in magnitude and direction throughout the imaging sequence. Changing the direction or effective areas of these gradient crushers throughout imaging acquisition prevents stimulated echoes from forming, thereby eliminating ghosting and blurring artifacts. By applying unbalanced gradients or sets of unbalanced gradients between selective RF pulses of an RF pulse sequence, signals attributable to spin transverse magnetization are suppressed resulting in reduced ghosting and/or artifacts. Additionally, the process varies the phase of each RF pulse with each application of the RF pulse to minimize any artifacts generated by stimulated echoes.