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Impact of gradient imperfections on bone water quantification with UTE MRI
Author(s) -
Zhao Xia,
Lee Hyunyeol,
Song Hee Kwon,
Cheng ChengChieh,
Wehrli Felix W.
Publication year - 2020
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.28272
Subject(s) - scanner , offset (computer science) , imaging phantom , gradient echo , flip angle , compensation (psychology) , physics , nuclear magnetic resonance , nuclear medicine , biomedical engineering , materials science , optics , computer science , magnetic resonance imaging , radiology , medicine , psychology , psychoanalysis , programming language
Purpose The impact of gradient imperfections on UTE images and UTE image‐derived bone water quantification was investigated at 3 T field strength. Methods The effects of simple gradient time delays and eddy currents on UTE images, as well as the effects of gradient error corrections, were studied with simulation and phantom experiments. The k‐space trajectory was mapped with a 2D sequence with phase encoding on both spatial axes by measuring the phase of the signal in small time increments during ramp‐up of the read gradient. In vivo 3D UTE images were reconstructed with and without gradient error compensation to determine the bias in bone water quantification. Finally, imaging was performed on 2 equally configured Siemens TIM Trio systems (Siemens Medical Solutions, Erlangen, Germany) to investigate the impact of such gradient imperfections on inter‐scanner measurement bias. Results Compared to values derived from UTE images with full gradient error compensation, total bone water was found to deviate substantially with no (up to 17%) or partial (delay‐only) compensation (up to 10.8%). Bound water, obtained with inversion recovery‐prepared UTE, was somewhat less susceptible to gradient errors (up to 2.2% for both correction strategies). Inter‐scanner comparison indicated a statistically significant bias between measurements from the 2 MR systems for both total and bound water, which either vanished or was substantially reduced following gradient error correction. Conclusion Gradient imperfections impose spatially dependent artifacts on UTE images, which compromise not only bone water quantification accuracy but also inter‐scanner measurement agreement if left uncompensated.