Simultaneous Optimization of MP2RAGE T1-weighted (UNI) and FLuid And White matter Suppression (FLAWS) brain images at 7T using Extended Phase Graph (EPG) Simulations

Ayse Sila Dokumaci; Fraser R. Aitken; Jan Sedlacik; Pip Bridgen; Raphael Tomi-Tricot; Ronald Mooiweer; Katy Vecchiato; Tom Wilkinson; Chiara Casella; Sharon Giles; Joseph V. Hajnal; Shaihan Malik; Jonathan O'Muircheartaigh; David W. Carmichael

doi:10.1002/mrm.29479

Ayse Sila Dokumaci, Fraser R. Aitken, Jan Sedlacik, Pip Bridgen, Raphael Tomi-Tricot, Ronald Mooiweer, Katy Vecchiato, Tom Wilkinson, Chiara Casella, Sharon Giles, Joseph V. Hajnal, Shaihan Malik, Jonathan O'Muircheartaigh, David W. Carmichael

Original language	English
Journal	Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine
Early online date	9 Nov 2022
DOIs	https://doi.org/10.1002/mrm.29479
Accepted/In press	16 Sep 2022
E-pub ahead of print	9 Nov 2022
Additional links	Link to publication in Scopus

Funding Information: Great Ormond Street Hospital Children's Charity (GOSHCC), Grant/Award Number: Sparks Grant V4419; Innovate UK, Grant/Award Number: 68539; King's Health Partners, Medical Research Council (UK), Grant/Award Numbers: MR/ K006355/1; MR/LO11530/1; Medical Research Council Center for Neurodevelopmental Disorders, King's College London, Grant/Award Number: MR/N026063/1; National Institute for Health Research Mental Health Biomedical Research Centre at Guy's and St Thomas' Hospitals NHS Foundation Trust, National Institute for Health Research Mental Health Biomedical Research Centre at South London, Maudsley NHS Foundation Trust, King's College London, Sir Henry Dale Fellowship jointly funded by the Wellcome Trust and the Royal Society, Grant/Award Number: 206675/Z/17/Z; Wellcome Engineering and Physical Sciences Research Council for Medical Engineering at King's College London, Grant/Award Number: WT203148/Z/16/Z Funding information Funding Information: This research was supported by Great Ormond Street Hospital Children's Charity (GOSHCC) Sparks Grant V4419, King's Health Partners, in part by the Medical Research Council (UK) (grants MR/K006355/1 and MR/LO11530/1) and Medical Research Council Center for Neurodevelopmental Disorders, King's College London (MR/N026063/1), and by core funding from the Wellcome Engineering and Physical Sciences Research Council Centre for Medical Engineering at King's College London [WT203148/Z/16/Z]. j.o.m., k.v. , and c.c. were funded by a Sir Henry Dale Fellowship jointly by the Wellcome Trust and the Royal Society (206675/Z/17/Z). c.c. was also funded by a grant from GOSHCC (VC1421). R.M. was funded by the Innovate UK grant (68539). Infrastructure support was provided by the National Institute for Health Research Mental Health Biomedical Research Centre at South London, Maudsley NHS Foundation Trust, King's College London and the National Institute for Health Research Mental Health Biomedical Research Centre at Guy's and St Thomas' Hospitals NHS Foundation Trust. This research was funded in whole, or in part, by the Wellcome Trust [WT203148/Z/16/Z and 206675/Z/17/Z]. For the purpose of open access, the author has applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission. Publisher Copyright: © 2022 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.

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Simultaneous Optimization of MP2RAGE_DOKUMACI_Publishedonline9November2022_GOLD VoR (CC BY)
Simultaneous_Optimization_of_MP2RAGE_DOKUMACI_Publishedonline9November2022_GOLD_VoR_CC_BY_.pdf, 4.77 MB, application/pdf
Uploaded date:11 Nov 2022
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Purpose: The MP2RAGE sequence is typically optimized for either T₁-weighted uniform image (UNI) or gray matter–dominant fluid and white matter suppression (FLAWS) contrast images. Here, the purpose was to optimize an MP2RAGE protocol at 7 Tesla to provide UNI and FLAWS images simultaneously in a clinically applicable acquisition time at <0.7 mm isotropic resolution. Methods: Using the extended phase graph formalism, the signal evolution of the MP2RAGE sequence was simulated incorporating T₂ relaxation, diffusion, RF spoiling, and B₁⁺ variability. Flip angles and TI were optimized at different TRs (TR_MP2RAGE) to produce an optimal contrast-to-noise ratio for UNI and FLAWS images. Simulation results were validated by comparison to MP2RAGE brain scans of 5 healthy subjects, and a final protocol at TR_MP2RAGE = 4000 ms was applied in 19 subjects aged 8–62 years with and without epilepsy. Results: FLAWS contrast images could be obtained while maintaining >85% of the optimal UNI contrast-to-noise ratio. Using TI₁/TI₂/TR_MP2RAGE of 650/2280/4000 ms, 6/8 partial Fourier in the inner phase-encoding direction, and GRAPPA factor = 4 in the other, images with 0.65 mm isotropic resolution were produced in <7.5 min. The contrast-to-noise ratio was around 20% smaller at TR_MP2RAGE = 4000 ms compared to that at TR_MP2RAGE = 5000 ms; however, the 20% shorter duration makes TR_MP2RAGE = 4000 ms a good candidate for clinical applications example, pediatrics. Conclusion: FLAWS and UNI images could be obtained in a single scan with 0.65 mm isotropic resolution, providing a set of high-contrast images and full brain coverage in a clinically applicable scan time. Images with excellent anatomical detail were demonstrated over a wide age range using the optimized parameter set.

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