Rüdiger Stirnberg1,2, Daniel Brenner3,4, Tony Stöcker4,5, N Jon Shah3,6. 1. Institute of Neuroscience and Medicine 4, Medical Imaging Physics, Research Centre Jülich GmbH, Jülich, Germany. ruediger.stirnberg@dzne.de. 2. German Centre for Neurodegenerative Diseases (DZNE), Bonn, Germany. ruediger.stirnberg@dzne.de. 3. Institute of Neuroscience and Medicine 4, Medical Imaging Physics, Research Centre Jülich GmbH, Jülich, Germany. 4. German Centre for Neurodegenerative Diseases (DZNE), Bonn, Germany. 5. Department of Physics and Astronomy, University of Bonn, Bonn, Germany. 6. Department of Neurology, Faculty of Medicine, RWTH Aachen University, JARA, Aachen, Germany.
Abstract
PURPOSE: To investigate a method for rapid water excitation with minimal radiofrequency power deposition for efficient functional MRI at ultrahigh fields. THEORY AND METHODS: The suitability of the spectral response of a single rectangular radiofrequency pulse (rect) as a replacement of conventional fat saturation in segmented three-dimensional (3D) echo planar imaging (EPI) is explored. A pulse duration formula for lipid signal nulling independent of the small-tip-angle approximation is derived and tested by means of simulations and experiments at 3 and 7 Tesla (T). RESULTS: Compared with conventional binomial-11 water excitation, the single rect method is more selective and less sensitive to shim imperfections. In functional MRI, a significant measurement speedup (25%) and specific absorption rate reduction (from 44% to 1% at 7T) compared with conventional fat saturation are achieved. Furthermore, magnetization transfer effects are reduced resulting in up to 25% higher brain tissue signal-to-noise ratio. CONCLUSION: The proposed method is well suited for whole-brain functional MRI, not only at ultra-high fields, as it maximizes the sensitivity per unit time and at the same time minimizes radiofrequency power deposition. It requires little implementation effort and may thus be used in other spatially nonselective imaging methods that require fat suppression at minimal specific absorption rate and time requirements. Magn Reson Med 76:1517-1523, 2016.
PURPOSE: To investigate a method for rapid water excitation with minimal radiofrequency power deposition for efficient functional MRI at ultrahigh fields. THEORY AND METHODS: The suitability of the spectral response of a single rectangular radiofrequency pulse (rect) as a replacement of conventional fat saturation in segmented three-dimensional (3D) echo planar imaging (EPI) is explored. A pulse duration formula for lipid signal nulling independent of the small-tip-angle approximation is derived and tested by means of simulations and experiments at 3 and 7 Tesla (T). RESULTS: Compared with conventional binomial-11 water excitation, the single rect method is more selective and less sensitive to shim imperfections. In functional MRI, a significant measurement speedup (25%) and specific absorption rate reduction (from 44% to 1% at 7T) compared with conventional fat saturation are achieved. Furthermore, magnetization transfer effects are reduced resulting in up to 25% higher brain tissue signal-to-noise ratio. CONCLUSION: The proposed method is well suited for whole-brain functional MRI, not only at ultra-high fields, as it maximizes the sensitivity per unit time and at the same time minimizes radiofrequency power deposition. It requires little implementation effort and may thus be used in other spatially nonselective imaging methods that require fat suppression at minimal specific absorption rate and time requirements. Magn Reson Med 76:1517-1523, 2016.
Authors: Ann-Kathrin Kreuder; Dirk Scheele; Johannes Schultz; Juergen Hennig; Nina Marsh; Torge Dellert; Ulrich Ettinger; Alexandra Philipsen; Mari Babasiz; Angela Herscheid; Laura Remmersmann; Ruediger Stirnberg; Tony Stöcker; René Hurlemann Journal: Proc Natl Acad Sci U S A Date: 2020-05-08 Impact factor: 11.205
Authors: N A da Silva; P Lohmann; J Fairney; A W Magill; A-M Oros Peusquens; C-H Choi; R Stirnberg; G Stoffels; N Galldiks; X Golay; K-J Langen; N Jon Shah Journal: Eur J Nucl Med Mol Imaging Date: 2018-02-24 Impact factor: 9.236