Dataset Information

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

ABSTRACT:

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.

SUBMITTER: Dokumacı AS

PROVIDER: S-EPMC10100108 | biostudies-literature | 2023 Mar

REPOSITORIES: biostudies-literature

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Publications

Simultaneous Optimization of MP2RAGE T<sub>1</sub> -weighted (UNI) and FLuid And White matter Suppression (FLAWS) brain images at 7T using Extended Phase Graph (EPG) Simulations.

Dokumacı Ayşe Sıla AS Aitken Fraser R FR Sedlacik Jan J Bridgen Pip P Tomi-Tricot Raphael R Mooiweer Ronald R Vecchiato Katy K Wilkinson Tom T Casella Chiara C Giles Sharon S Hajnal Joseph V JV Malik Shaihan J SJ O'Muircheartaigh Jonathan J Carmichael David W DW

Magnetic resonance in medicine 20221109 3

<h4>Purpose</h4>The MP2RAGE sequence is typically optimized for either T<sub>1</sub> -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.<h4>Methods</h4>Using the extended phase graph formalism, the signal evolution of the MP2RAGE sequence was simula ...[more]

PMID: 36352772

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Project description:In the recent MRI scanning, ultra-high-field (7T) MR imaging provides higher resolution and better tissue contrast compared to routine 3T MRI, which may help in more accurate and early brain diseases diagnosis. However, currently, 7T MRI scanners are more expensive and less available at clinical and research centers. These motivate us to propose a method for the reconstruction of images close to the quality of 7T MRI, called 7T-like images, from 3T MRI, to improve the quality in terms of resolution and contrast. By doing so, the post-processing tasks, such as tissue segmentation, can be done more accurately and brain tissues details can be seen with higher resolution and contrast. To do this, we have acquired a unique dataset which includes paired 3T and 7T images scanned from same subjects, and then propose a hierarchical reconstruction based on group sparsity in a novel multi-level Canonical Correlation Analysis (CCA) space, to improve the quality of 3T MR image to be 7T-like MRI. First, overlapping patches are extracted from the input 3T MR image. Then, by extracting the most similar patches from all the aligned 3T and 7T images in the training set, the paired 3T and 7T dictionaries are constructed for each patch. It is worth noting that, for the training, we use pairs of 3T and 7T MR images from each training subject. Then, we propose multi-level CCA to map the paired 3T and 7T patch sets to a common space to increase their correlations. In such space, each input 3T MRI patch is sparsely represented by the 3T dictionary and then the obtained sparse coefficients are used together with the corresponding 7T dictionary to reconstruct the 7T-like patch. Also, to have the structural consistency between adjacent patches, the group sparsity is employed. This reconstruction is performed with changing patch sizes in a hierarchical framework. Experiments have been done using 13 subjects with both 3T and 7T MR images. The results show that our method outperforms previous methods and is able to recover better structural details. Also, to place our proposed method in a medical application context, we evaluated the influence of post-processing methods such as brain tissue segmentation on the reconstructed 7T-like MR images. Results show that our 7T-like images lead to higher accuracy in segmentation of white matter (WM), gray matter (GM), cerebrospinal fluid (CSF), and skull, compared to segmentation of 3T MR images.

Dataset Information

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

Purpose

Methods

Results

Conclusion

Publications

Simultaneous Optimization of MP2RAGE T<sub>1</sub> -weighted (UNI) and FLuid And White matter Suppression (FLAWS) brain images at 7T using Extended Phase Graph (EPG) Simulations.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Dataset Information

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

Purpose

Methods

Results

Conclusion

Publications

Simultaneous Optimization of MP2RAGE T&lt;sub&gt;1&lt;/sub&gt; -weighted (UNI) and FLuid And White matter Suppression (FLAWS) brain images at 7T using Extended Phase Graph (EPG) Simulations.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

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

Simultaneous Optimization of MP2RAGE T<sub>1</sub> -weighted (UNI) and FLuid And White matter Suppression (FLAWS) brain images at 7T using Extended Phase Graph (EPG) Simulations.