Evaluation of an interleaved acquisition scheme for improved robustness of channel‐wise relative B 1 + mapping at 7 T

Magnetic Resonance in Medicine, vol. 95, pp. 1157–1168

Abstract

Abstract Purpose The purpose was to evaluate, whether an interleaved acquisition scheme for a fast relative mapping method at 7 T reduces the likelihood of errors from exceeding the linear flip angle (FA) regime compared to a conventional sequential acquisition. Methods Simulations of a channel‐wise relative mapping sequence were performed for sequential and interleaved acquisition schemes at different reference voltages (≙ different FAs). The simulations were performed for a phantom, the heart and the prostate and were based on 7 T ground‐truth (GT) data acquired with an actual FA imaging sequence (phantom) or obtained from electromagnetic field simulations (heart/prostate). Acquisition schemes were evaluated based on their signal linearity by calculating a normalized mean FA error between simulated signal intensities and GT data. Additionally, validation measurements of relative maps with the sequential and interleaved acquisition schemes were acquired for the phantom. Results Validation measurements showed a good agreement with the simulation results for both acquisition schemes and displayed stronger deviations to the GT data for the sequential scheme. The quantitative evaluation yielded higher FA errors for the sequential acquisition scheme for all three regions and all simulated reference voltages. At the same level of error, mean signals were higher for the interleaved acquisition scheme in all cases. Differences between interleaved and sequential acquisition schemes were most pronounced in the steady‐state. Conclusion An interleaved acquisition of channel‐wise relative maps extends the range of the linear FA regime, reducing the likelihood of errors and increasing the robustness of the approach.

Authors 10

1. Nico Egger corresponding

   Friedrich-Alexander-Universität Erlangen-Nürnberg · Universitätsklinikum Erlangen

   Affiliation as printed

   Institute of Radiology University Hospital Erlangen, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg (FAU) Erlangen Germany

2. Laurent Ruck

   Friedrich-Alexander-Universität Erlangen-Nürnberg · Universitätsklinikum Erlangen

   Affiliation as printed

   Institute of Radiology University Hospital Erlangen, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg (FAU) Erlangen Germany

3. Sophia Nagelstraßer

   Friedrich-Alexander-Universität Erlangen-Nürnberg · Universitätsklinikum Erlangen

   Affiliation as printed

   Institute of Radiology University Hospital Erlangen, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg (FAU) Erlangen Germany

4. Judith Schirmer

   Friedrich-Alexander-Universität Erlangen-Nürnberg · Universitätsklinikum Erlangen

   Affiliation as printed

   Institute of Radiology University Hospital Erlangen, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg (FAU) Erlangen Germany

5. Saskia Wildenberg Aachen

   FH Aachen · Friedrich-Alexander-Universität Erlangen-Nürnberg · Universitätsklinikum Erlangen

   Affiliation as printed

   Electrical Engineering and Information Technology University of Applied Sciences ‐ FH Aachen Aachen Germany

   Institute of Radiology University Hospital Erlangen, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg (FAU) Erlangen Germany

   Institute of Radiology University Hospital Erlangen, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg (FAU) Erlangen Germany

6. Andreas K. Bitz Aachen Electrical Engineering and Information Technology

   FH Aachen

   Affiliation as printed

   Electrical Engineering and Information Technology University of Applied Sciences ‐ FH Aachen Aachen Germany

   Electrical Engineering and Information Technology, University of Applied Sciences - FH Aachen, Aachen, Germany

7. Jürgen Herrler

   Siemens Healthineers (Germany)

   Affiliation as printed

   Siemens Healthcare Erlangen Germany

   Siemens Healthcare, Erlangen, Germany

8. Sebastian Schmitter

   University of Minnesota · German Cancer Research Center · Physikalisch-Technische Bundesanstalt

   Affiliation as printed

   Center for Magnetic Resonance Research University of Minnesota Minneapolis Minnesota USA

   Division of Medical Physics in Radiology German Cancer Research Centre (DKFZ) Heidelberg Germany

   Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany

   Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA

   Division of Medical Physics in Radiology, German Cancer Research Centre (DKFZ), Heidelberg, Germany

   Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany

9. Michael Uder

   Friedrich-Alexander-Universität Erlangen-Nürnberg · Universitätsklinikum Erlangen

   Affiliation as printed

   Institute of Radiology University Hospital Erlangen, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg (FAU) Erlangen Germany

10. Armin Michael Nagel

    Friedrich-Alexander-Universität Erlangen-Nürnberg · German Cancer Research Center · Universitätsklinikum Erlangen

    Affiliation as printed

    Division of Medical Physics in Radiology German Cancer Research Centre (DKFZ) Heidelberg Germany

    Institute of Radiology University Hospital Erlangen, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg (FAU) Erlangen Germany

    Institute of Radiology University Hospital Erlangen, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg (FAU) Erlangen Germany