Advances in gradient echo myelin water imaging at 3T and 7T

Shin, Hyeong-Geol; Oh, Se Hong; Fukunaga, Masaki; Nam, Yoonho; Lee, Doo-Hee; Jung, Woojin; Jo, Minju; Ji, Soo-Yeon; Choi, Joon Yul; Lee, Jong-Ho

doi:10.1016/j.neuroimage.2018.11.040

Cited by 18 publications

(41 citation statements)

References 41 publications

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“…The multicompartment analysis of

T_{2}^{*}

decays based on MGRE acquisitions has the advantage over T 2 decays that more echoes can be acquired before the myelin signal decays. Moreover, energy deposition restrictions are less limiting, and acquisitions can be performed at high magnetic field strengths 77 . The MWF estimations from the MGRE sequence were compared and found to be in agreement with MET 2 analysis 78 .…”

Section: Discussionmentioning

confidence: 74%

Probing myelin content of the human brain with MRI: A review

Piredda

Hilbert

Thiran

et al. 2020

Magnetic Resonance in Med

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Rapid and efficient transmission of electric signals among neurons of vertebrates is ensured by myelin‐insulating sheaths surrounding axons. Human cognition, sensation, and motor functions rely on the integrity of these layers, and demyelinating diseases often entail serious cognitive and physical impairments. Magnetic resonance imaging radically transformed the way these disorders are monitored, offering an irreplaceable tool to noninvasively examine the brain structure. Several advanced techniques based on MRI have been developed to provide myelin‐specific contrasts and a quantitative estimation of myelin density in vivo. Here, the vast offer of acquisition strategies developed to date for this task is reviewed. Advantages and pitfalls of the different approaches are compared and discussed.

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“…The multicompartment analysis of

T_{2}^{*}

Section: Discussionmentioning

confidence: 74%

Probing myelin content of the human brain with MRI: A review

Piredda

Hilbert

Thiran

et al. 2020

Magnetic Resonance in Med

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“…However, the reduced number of T 2 contrasts acquired in T 2 prep experiments to keep the TA short 52 may affect MWF quantification, especially in the presence of pathological tissues 21,53 . Multi‐compartment analysis of

T_{2}^{*}

decays acquired with a multi‐gradient echo (MGRE) sequence has also been investigated for MWF computation 54 and found to be in agreement with multi‐echo T 2 based analysis 55 . While allowing the sampling of a larger number of echoes before the complete decay of the myelin water signal, constrained models assuming only three water pools are required to correct for contaminations due to B 0 field inhomogeneities 56 and they might fail to generalize in the presence of pathological tissues 57 .…”

Section: Discussionmentioning

confidence: 99%

Fast and high‐resolution myelin water imaging: Accelerating multi‐echo GRASE with CAIPIRINHA

Piredda

Hilbert

Canales-Rodríguez

et al. 2020

Magnetic Resonance in Med

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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. 210 | PIREDDA Et Al. F I G U R E 8 Comparison of MWF maps derived from the multi-echo GRASE in a scan-rescan scenario. A, MWF maps acquired from the same subject after repositioning. Correlation (B) and Bland-Altman (C) analysis considering average values from extracted brain ROIs 220 | PIREDDA Et Al. Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement no. 754462 (EuroTech-Postdoc). CONFLICT OF INTEREST This research is a part G.F. Piredda's Ph.D. thesis funded by Siemens Healthcare AG, Switzerland; T. Hilbert, C. von Deuster and T. Kober are employees of the same company.

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“…One of the main drawbacks is the ambiguity of the origin of the aT2* signal. The previous studies have shown that T2* is sensitive both to collagen [25,27] and myelin [41]. A multi-echo approach would have allowed to estimate the multiple T2* components of T2* relaxation; however, our sequence was originally designed to highlight the short T2* species with the subtraction technique, and only two echoes were acquired.…”

Section: Discussionmentioning

confidence: 99%

Variable echo time imaging for detecting the short T2* components of the sciatic nerve: a validation study

Felisaz¹,

Belatti²,

Deligianni

et al. 2020

Magn Reson Mater Phy

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Objective The aim of this study was to develop and validate an MRI protocol based on a variable echo time (vTE) sensitive to the short T2* components of the sciatic nerve. Materials and methods 15 healthy subjects (M/F: 9/6; age: 21–62) were scanned at 3T targeting the sciatic nerve at the thigh bilaterally, using a dual echo variable echo time (vTE) sequence (based on a spoiled gradient echo acquisition) with echo times of 0.98/5.37 ms. Apparent T2* (aT2*) values of the sciatic nerves were calculated with a mono-exponential fit and used for data comparison. Results There were no significant differences in aT2* related to side, sex, age, and BMI, even though small differences for side were reported. Good-to-excellent repeatability and reproducibility were found for geometry of ROIs (Dice indices: intra-rater 0.68–0.7; inter-rater 0.70–0.72) and the related aT2* measures (intra-inter reader ICC 0.95–0.97; 0.66–0.85) from two different operators. Side-related signal-to-noise-ratio non-significant differences were reported, while contrast-to-noise-ratio measures were excellent both for side and echo. Discussion Our study introduces a novel MR sequence sensitive to the short T2* components of the sciatic nerve and may be used for the study of peripheral nerve disorders.

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Advances in gradient echo myelin water imaging at 3T and 7T

Cited by 18 publications

References 41 publications

Probing myelin content of the human brain with MRI: A review

Probing myelin content of the human brain with MRI: A review

Fast and high‐resolution myelin water imaging: Accelerating multi‐echo GRASE with CAIPIRINHA

Variable echo time imaging for detecting the short T2* components of the sciatic nerve: a validation study

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