Accelerated B1+$$ {\mathrm{B}}_1^{+} $$ mapping and robust parallel transmit pulse design for heart and prostate imaging at 7 T

Magnetic Resonance in Medicine, vol. 92, pp. 1933–1951

Abstract

Abstract Purpose To investigate the impact of reduced k‐space sampling on mapping and the resulting impact on phase shimming and dynamic/universal parallel transmit (pTx) RF pulse design. Methods Channel‐wise 3D maps were measured at 7 T in 35 and 23 healthy subjects for the heart and prostate region, respectively. With these maps, universal phase shims optimizing homogeneity and efficiency were designed for heart and prostate imaging. In addition, universal 4kT‐point pulses were designed for the heart. Subsequently, individual phase shims and individual 4kT‐pulses were designed based on maps with different acceleration factors and tested on the original maps. The performance of the pulses was compared by evaluating their coefficients of variation (CoV), efficiencies and specific energy doses (SED). Furthermore, validation measurements were carried out for one heart and one prostate subject. Results For both organs, the universal phase shims showed significantly higher efficiencies and lower CoVs compared to the vendor provided default shim, but could still be improved with individual phase shims based on accelerated maps (acquisition time = 30 s). In the heart, the universal 4kT‐pulse achieved significantly lower CoVs than tailored phase shims. Tailored 4kT‐pulses based on accelerated maps resulted in even further reduced CoVs or a 2.5‐fold reduction in SED at the same CoVs as the universal 4kT‐pulse. Conclusion Accelerated maps can be used for the design of tailored pTx pulses for prostate and cardiac imaging at 7 T, which further improve homogeneity, efficiency, or SED compared to universal pulses.

Authors 12

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. 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

3. Saskia Wildenberg Aachen

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

   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

4. Andreas K. Bitz Aachen

   FH Aachen

   Affiliation as printed

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

5. 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

6. Jürgen Herrler

   Siemens Healthineers (Germany)

   Affiliation as printed

   Siemens Healthcare Erlangen Bavaria Germany

   Siemens Healthcare, Erlangen, Bavaria, Germany

7. Christian R. Meixner

   Siemens Healthineers (Germany)

   Affiliation as printed

   Siemens Healthcare Erlangen Bavaria Germany

   Siemens Healthcare, Erlangen, Bavaria, Germany

8. Ralph Kimmlingen

   Siemens Healthineers (Germany)

   Affiliation as printed

   Siemens Healthcare Erlangen Bavaria Germany

   Siemens Healthcare, Erlangen, Bavaria, Germany

9. Titus E. Lanz

   RAPID Biomedical (Germany)

   Affiliation as printed

   Rapid Biomedical Rimpar Germany

   Rapid Biomedical, Rimpar, Germany

10. Sebastian Schmitter

    Physikalisch-Technische Bundesanstalt

    Affiliation as printed

    Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany

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

11. 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

12. Armin Michael Nagel

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