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Fast and high‐resolution myelin water imaging: Accelerating multi‐echo GRASE with CAIPIRINHA
Author(s) -
Piredda Gian Franco,
Hilbert Tom,
CanalesRodríguez Erick Jorge,
Pizzolato Marco,
Deuster Constantin,
Meuli Reto,
Pfeuffer Josef,
Daducci Alessandro,
Thiran JeanPhilippe,
Kober Tobias
Publication year - 2021
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.28427
Subject(s) - echo (communications protocol) , repeatability , nuclear magnetic resonance , sampling (signal processing) , spin echo , undersampling , nuclear medicine , magnetic resonance imaging , mathematics , physics , computer science , medicine , artificial intelligence , statistics , radiology , optics , computer network , detector
Purpose Although several MRI methods have been explored to achieve in vivo myelin quantification, imaging the whole brain in clinically acceptable times and sufficiently high resolution remains challenging. To address this problem, this work investigates the acceleration of multi‐echo T 2 acquisitions based on the multi‐echo gradient and spin echo (GRASE) sequence using CAIPIRINHA undersampling and adapted k‐space reordering patterns. Methods A prototype multi‐echo GRASE sequence supporting CAIPIRINHA parallel imaging was implemented. Multi‐echo T 2 data were acquired from 12 volunteers using the implemented sequence (1.6 × 1.6 × 1.6 mm 3 , 84 slices, acquisition time [TA] = 10:30 min) and a multi‐echo spin echo (MESE) sequence as reference (1.6 × 1.6 × 3.2 mm 3 , single‐slice, TA = 5:41 min). Myelin water fraction (MWF) maps derived from both acquisitions were compared via correlation and Bland‐Altman analyses. In addition, scan‐rescan datasets were acquired to evaluate the repeatability of the derived maps. Results Resulting maps from the MESE and multi‐echo GRASE sequences were found to be correlated (r = 0.83). The Bland‐Altman analysis revealed a mean bias of −0.2% ( P = .24) with the limits of agreement ranging from −3.7% to 3.3%. The Pearson’s correlation coefficient among MWF values obtained from the scan‐rescan datasets was found to be 0.95 and the mean bias equal to 0.11% ( P = .32), indicating good repeatability of the retrieved maps. Conclusion By combining a 3D multi‐echo GRASE sequence with CAIPIRINHA sampling, whole‐brain MWF maps were obtained in 10:30 min with 1.6 mm isotropic resolution. The good correlation with conventional MESE‐based maps demonstrates that the implemented sequence may be a promising alternative to time‐consuming MESE acquisitions.