Cargando…

Investigation of the Saturation Pulse Artifact in Non-Enhanced MR Angiography of the Lower Extremity Arteries at 7 Tesla

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 arti...

Descripción completa

Detalles Bibliográficos
Autores principales: Johst, Sören, Maderwald, Stefan, Fischer, Anja, Quick, Harald H., Ladd, Mark E., Orzada, Stephan
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4364710/
https://www.ncbi.nlm.nih.gov/pubmed/25785837
http://dx.doi.org/10.1371/journal.pone.0119845
_version_ 1782362112384827392
author Johst, Sören
Maderwald, Stefan
Fischer, Anja
Quick, Harald H.
Ladd, Mark E.
Orzada, Stephan
author_facet Johst, Sören
Maderwald, Stefan
Fischer, Anja
Quick, Harald H.
Ladd, Mark E.
Orzada, Stephan
author_sort Johst, Sören
collection PubMed
description 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.
format Online
Article
Text
id pubmed-4364710
institution National Center for Biotechnology Information
language English
publishDate 2015
publisher Public Library of Science
record_format MEDLINE/PubMed
spelling pubmed-43647102015-03-23 Investigation of the Saturation Pulse Artifact in Non-Enhanced MR Angiography of the Lower Extremity Arteries at 7 Tesla Johst, Sören Maderwald, Stefan Fischer, Anja Quick, Harald H. Ladd, Mark E. Orzada, Stephan PLoS One Research Article 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. Public Library of Science 2015-03-18 /pmc/articles/PMC4364710/ /pubmed/25785837 http://dx.doi.org/10.1371/journal.pone.0119845 Text en © 2015 Johst et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Johst, Sören
Maderwald, Stefan
Fischer, Anja
Quick, Harald H.
Ladd, Mark E.
Orzada, Stephan
Investigation of the Saturation Pulse Artifact in Non-Enhanced MR Angiography of the Lower Extremity Arteries at 7 Tesla
title Investigation of the Saturation Pulse Artifact in Non-Enhanced MR Angiography of the Lower Extremity Arteries at 7 Tesla
title_full Investigation of the Saturation Pulse Artifact in Non-Enhanced MR Angiography of the Lower Extremity Arteries at 7 Tesla
title_fullStr Investigation of the Saturation Pulse Artifact in Non-Enhanced MR Angiography of the Lower Extremity Arteries at 7 Tesla
title_full_unstemmed Investigation of the Saturation Pulse Artifact in Non-Enhanced MR Angiography of the Lower Extremity Arteries at 7 Tesla
title_short Investigation of the Saturation Pulse Artifact in Non-Enhanced MR Angiography of the Lower Extremity Arteries at 7 Tesla
title_sort investigation of the saturation pulse artifact in non-enhanced mr angiography of the lower extremity arteries at 7 tesla
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4364710/
https://www.ncbi.nlm.nih.gov/pubmed/25785837
http://dx.doi.org/10.1371/journal.pone.0119845
work_keys_str_mv AT johstsoren investigationofthesaturationpulseartifactinnonenhancedmrangiographyofthelowerextremityarteriesat7tesla
AT maderwaldstefan investigationofthesaturationpulseartifactinnonenhancedmrangiographyofthelowerextremityarteriesat7tesla
AT fischeranja investigationofthesaturationpulseartifactinnonenhancedmrangiographyofthelowerextremityarteriesat7tesla
AT quickharaldh investigationofthesaturationpulseartifactinnonenhancedmrangiographyofthelowerextremityarteriesat7tesla
AT laddmarke investigationofthesaturationpulseartifactinnonenhancedmrangiographyofthelowerextremityarteriesat7tesla
AT orzadastephan investigationofthesaturationpulseartifactinnonenhancedmrangiographyofthelowerextremityarteriesat7tesla