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Phase relaxed localized excitation pulses for inner volume fast spin echo imaging
Author(s) -
Malik Shaihan J.,
Hajnal Joseph V.
Publication year - 2016
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.25996
Subject(s) - excitation , magnetic resonance imaging , nuclear magnetic resonance , spin echo , imaging phantom , pulse (music) , amplitude , physics , phase (matter) , fast spin echo , radio frequency , flip angle , signal (programming language) , optics , echo (communications protocol) , computer science , medicine , radiology , programming language , computer network , telecommunications , quantum mechanics , detector
Purpose To design multidimensional spatially selective radiofrequency (RF) pulses for inner volume imaging (IVI) with three‐dimensional (3D) fast spin echo (FSE) sequences. Enhanced background suppression is achieved by exploiting particular signal properties of FSE sequences. Theory and Methods The CPMG condition dictates that echo amplitudes will rapidly decrease if a 90° phase difference between excitation and refocusing pulses is not present, and refocusing flip angles are not precisely 180°. This mechanism is proposed as a means for generating additional background suppression for spatially selective excitation, by biasing residual excitation errors toward violating the CPMG condition. 3D RF pulses were designed using this method with a 3D spherical spiral trajectory, under‐sampled by factor 5.6 for an eight‐channel PTx system, at 3 Tesla. Results 3D‐FSE IVI with pulse durations of approximately 12 ms was demonstrated in phantoms and for T 2 ‐weighted brain imaging in vivo. Good image quality was obtained, with mean background suppression factors of 103 and 82 ± 6 in phantoms and in vivo, respectively. Conclusion Inner Volume Imaging with 3D‐FSE has been demonstrated in vivo with tailored 3D‐RF pulses. The proposed design methods are also applicable to 2D pulses. Magn Reson Med 76:848–861, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine