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Fully phase‐encoded MRI near metallic implants using ultrashort echo times and broadband excitation
Author(s) -
Wiens Curtis N.,
Artz Nathan S.,
Jang Hyungseok,
McMillan Alan B.,
Koch Kevin M.,
Reeder Scott B.
Publication year - 2018
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.26859
Subject(s) - imaging phantom , excitation , magnetic resonance imaging , materials science , bandwidth (computing) , phase (matter) , broadband , ultrashort pulse , optics , signal (programming language) , nuclear magnetic resonance , physics , biomedical engineering , computer science , laser , medicine , radiology , telecommunications , quantum mechanics , programming language
Purpose To develop a fully phase‐encoded MRI method for distortion‐free imaging near metallic implants, in clinically feasible acquisition times. Theory and Methods An accelerated 3D fully phase‐encoded acquisition with broadband excitation and ultrashort echo times is presented, which uses a broadband radiofrequency pulse to excite the entire off‐resonance induced by the metallic implant. Furthermore, fully phase‐encoded imaging is used to prevent distortions caused by frequency encoding, and to obtain ultrashort echo times for rapidly decaying signal. Results Phantom and in vivo acquisitions were used to describe the relationship among excitation bandwidth, signal loss near metallic implants, and T 1 weighting. Shorter radiofrequency pulses captured signal closer to the implant by improving spectral coverage and allowing shorter echo times, whereas longer pulses improved T 1 weighting through larger maximum attainable flip angles. Comparisons of fully phase‐encoded acquisition with broadband excitation and ultrashort echo times to T 1 ‐weighted multi‐acquisition with variable resonance image combination selective were performed in phantoms and subjects with metallic knee and hip prostheses. These acquisitions had similar contrast and acquisition efficiency. Conclusions Accelerated fully phase‐encoded acquisitions with ultrashort echo times and broadband excitation can generate distortion free images near metallic implants in clinically feasible acquisition times. Magn Reson Med 79:2156–2163, 2018. © 2017 International Society for Magnetic Resonance in Medicine.