title: Investigation of the saturation pulse artifact in non-enhanced MR angiography of the lower extremity arteries at 7 Tesla.
abstract: When performing non-enhanced time-of-flight MR angiography of the lower extremity arteries at 7 T with cardiac triggering, the acquisition time is a crucial consideration. Therefore, in previous studies, saturation RF pulses were applied only every second TR. In the axial source images a slight artifact with an appearance similar to aliasing could be observed. The purpose of this study was to investigate the origin of this artifact. The reason for the artifact is supposed to be related to the two effective TRs during acquisition caused by the sparsely applied saturation RF pulse. Several sequence variants were simulated and implemented within the sequence source code to examine this hypothesis. An adaptation of the excitation flip angles for each TR as well as a correction factor for the k-space data was calculated. Additionally, a different ordering of the k-space data during acquisition was implemented as well as the combination of the latter with the k-space correction factor. The observations from the simulations were verified using both a static and a flow phantom and, finally, in a healthy volunteer using the same measurement setup as in previous volunteer and patient studies. Of all implemented techniques, only the reordering of the k-space was capable of suppressing the artifact almost completely at the cost of creating a ringing artifact. The phantom measurements showed the same results as the simulations and could thus confirm the hypothesis regarding the origin of the artifact. This was additionally verified in the healthy volunteer. The origin of the artifact could be confirmed to be the periodic signal variation caused by two effective TRs during acquisition.
authors.affiliation: Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany.
authors.forename: Sören
authors.initials: S
authors.lastname: Johst
authors.affiliation: Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Maderwald
authors.affiliation: Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany; Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, University Duisburg-Essen, Essen, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Fischer
authors.affiliation: Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany; High Field and Hybrid MR Imaging, University Hospital Essen, University Duisburg-Essen, Essen, Germany.
authors.forename: Harald H
authors.initials: HH
authors.lastname: Quick
authors.affiliation: Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany; Medical Physics in Radiology, German Cancer Research Center (dkfz), Heidelberg, Germany.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Ladd
authors.affiliation: Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Orzada
mesh_terms: D001158:Arteries / Q000033:anatomy & histology*; D016477:Artifacts; D003198:Computer Simulation; D006801:Humans; D035002:Lower Extremity / Q000098:blood supply*; D018810:Magnetic Resonance Angiography / Q000379:methods*