Adiabatic RF pulse design for Bloch‐Siegert B mapping |
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| Authors: | Mohammad Mehdi Khalighi Brian K Rutt Adam B Kerr |
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| Institution: | 1. Global Applied Science Laboratory, GE Healthcare, , Menlo Park, California, USA;2. Department of Radiology, Stanford University, , Stanford, California, USA;3. Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, , Stanford, California, USA |
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| Abstract: | The Bloch–Siegert (B–S)  mapping method has been shown to be fast and accurate, yet it suffers from high Specific Absorption Rate (SAR) and moderately long echo time. An adiabatic RF pulse design is introduced here for optimizing the off‐resonant B–S RF pulse to achieve more B–S  measurement sensitivity for a given pulse width. The extra sensitivity can be used for higher angle‐to‐noise ratio  maps or traded off for faster scans. Using numerical simulations and phantom experiments, it is shown that a numerically optimized 2‐ms adiabatic B‐S pulse is 2.5 times more efficient than a conventional 6‐ms Fermi‐shaped B–S pulse. The adiabatic B–S pulse performance is validated in a phantom, and in vivo brain  mapping at 3T and 7T are shown. Magn Reson Med 70:829–835, 2013. © 2012 Wiley Periodicals, Inc. |
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| Keywords: | B mapping flip angle Bloch‐Siegert shift off resonance parallel transmit adiabatic RF pulse design |
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