PURPOSE: To tailor and optimize the Dual Refocusing Echo Acquisition Mode (DREAM) approach for volumetric B1 (+) mapping of the brain at 7T. THEORY AND METHODS: A new DREAM echo timing scheme based on the virtual stimulated echo was derived to minimize potential effects of transverse relaxation. Furthermore, the DREAM B1 (+) mapping performance was investigated in simulations and experimentally in phantoms and volunteers for volumetric applications, studying and optimizing the accuracy of the sequence with respect to saturation effects, slice profile imperfections, and T1 and T2 relaxation. Volumetric brain protocols were compiled for different isotropic resolutions (5-2.5 mm) and SENSE factors, and were studied in vivo for different RF drive modes (circular/linear polarization) and the application of dielectric pads. RESULTS: Volumetric B1 (+) maps with good SNR at 2.5 mm isotropic resolution were acquired in about 20 s or less. The specific absorption rate was well below the safety limits for all scans. Mild flow artefacts were observed in the large vessels. Moreover, a slight contrast in the ventricle was observed in the B1 (+) maps, which could be attributed to T1 and T2 relaxation effects. CONCLUSION: DREAM enables safe, very fast, and robust volumetric B1 (+) mapping of the brain at ultrahigh fields.
PURPOSE: To tailor and optimize the Dual Refocusing Echo Acquisition Mode (DREAM) approach for volumetric B1 (+) mapping of the brain at 7T. THEORY AND METHODS: A new DREAM echo timing scheme based on the virtual stimulated echo was derived to minimize potential effects of transverse relaxation. Furthermore, the DREAM B1 (+) mapping performance was investigated in simulations and experimentally in phantoms and volunteers for volumetric applications, studying and optimizing the accuracy of the sequence with respect to saturation effects, slice profile imperfections, and T1 and T2 relaxation. Volumetric brain protocols were compiled for different isotropic resolutions (5-2.5 mm) and SENSE factors, and were studied in vivo for different RF drive modes (circular/linear polarization) and the application of dielectric pads. RESULTS: Volumetric B1 (+) maps with good SNR at 2.5 mm isotropic resolution were acquired in about 20 s or less. The specific absorption rate was well below the safety limits for all scans. Mild flow artefacts were observed in the large vessels. Moreover, a slight contrast in the ventricle was observed in the B1 (+) maps, which could be attributed to T1 and T2 relaxation effects. CONCLUSION: DREAM enables safe, very fast, and robust volumetric B1 (+) mapping of the brain at ultrahigh fields.
Authors: Maximilian N Voelker; Oliver Kraff; Daniel Brenner; Astrid Wollrab; Oliver Weinberger; Moritz C Berger; Simon Robinson; Wolfgang Bogner; Christopher Wiggins; Robert Trampel; Tony Stöcker; Thoralf Niendorf; Harald H Quick; David G Norris; Mark E Ladd; Oliver Speck Journal: MAGMA Date: 2016-04-20 Impact factor: 2.310
Authors: Mads S Vinding; Daniel Brenner; Desmond H Y Tse; Sebastian Vellmer; Thomas Vosegaard; Dieter Suter; Tony Stöcker; Ivan I Maximov Journal: MAGMA Date: 2016-08-02 Impact factor: 2.310
Authors: Christopher T Sica; Sebastian Rupprecht; Ryan J Hou; Matthew T Lanagan; Navid P Gandji; Michael T Lanagan; Qing X Yang Journal: Magn Reson Med Date: 2019-09-10 Impact factor: 4.668
Authors: Ronald Mooiweer; Alessandro Sbrizzi; Alexander J E Raaijmakers; Cornelis A T van den Berg; Peter R Luijten; Hans Hoogduin Journal: Magn Reson Med Date: 2016-09-16 Impact factor: 4.668
Authors: Desmond H Y Tse; Christopher J Wiggins; Dimo Ivanov; Daniel Brenner; Jens Hoffmann; Christian Mirkes; Gunamony Shajan; Klaus Scheffler; Kâmil Uludağ; Benedikt A Poser Journal: MAGMA Date: 2016-03-19 Impact factor: 2.310