Multiple‐coil <i>k</i>‐space interpolation enhances resolution in single‐shot spatiotemporal MRI

Liberman, Gilad; Solomon, Eddy; Lustig, Michael; Frydman, Lucio

doi:10.1002/mrm.26731

Cited by 17 publications

(26 citation statements)

References 41 publications

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“…Figures and show the full pulse sequence and data processing flow chart used in this study. The sequence involved up to 4 nested loops (Figure ); from inner‐ to outer‐most these include an oscillating readout acquisition delivering the 2D SPEN image, an MSE loop encoding the T 2 information, a multislice loop extending this information into a third dimension, and an optional multishot loop used for eventual interleaving and thereby resolution improvement along the SPEN dimension . The corresponding data processing flow chart (Figure ) started with a Fourier transform along the readout dimension.…”

Section: Methodsmentioning

confidence: 99%

Dynamic T₂ mapping by multi‐spin‐echo spatiotemporal encoding

Bao

Liberman

et al. 2020

Magnetic Resonance in Med

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Purpose:To develop a pulse sequence for acquiring robust, quantitative T 2 relaxation maps in real time. Methods: The pulse scheme relies on fully refocused spatiotemporally encoded multi-spin-echo trains, which provide images that are significantly less distorted than spin-echo echo planar imaging-based counterparts. This enables single-shot T 2 mapping in inhomogeneity-prone regions. Another advantage of these schemes stems from their ability to interleave multiple scans in a reference-free manner, providing an option to increase sensitivity and spatial resolution with minimal motional artifacts. Results: The method was implemented in preclinical and clinical scanners, where single-shot acquisitions delivered reliable T 2 maps in ≤200 ms with ≈250 µm and ≈3 mm resolutions, respectively. Ca. 4 times higher spatial resolutions were achieved for the motion-compensated interleaved versions of these acquisitions, delivering T 2 maps in ca. 10 s per slice. These maps were nearly indistinguishable from multiscan relaxometric maps requiring orders-of-magnitude longer acquisitions; this was confirmed by mice head and real-time mice abdomen 7T scans performed following contrast-agent injections, as well as by 3T human brain and breast scans. Conclusion: This study introduced and demonstrated a new approach for acquiring rapid and quantitative T 2 data, which is particularly reliable when operating at high fields and/or targeting heterogeneous organs or regions. K E Y W O R D Sabdominal imaging, breast MRI, multi-spin-echo sequences, quantitative T2 mapping, spatiotemporal encoding

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Section: Methodsmentioning

confidence: 99%

Dynamic T₂ mapping by multi‐spin‐echo spatiotemporal encoding

Bao

Liberman

et al. 2020

Magnetic Resonance in Med

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“…Later, the characteristics of Chirp RF pulses in improving the incoherence between the sparsity and the sensing bases motivated the combination of SPEN with CS reconstruction in a hybrid framework. 14,15 Although energy is more spread out than in Fourier encoding, the hybrid SPEN framework is still less efficient than other non-Fourier encoding methods in providing incoherent characteristics. For wavelet encoding, spatially selective RF pulses are designed by wavelet functions to encode the signal, providing some spread of the energy in k-space.…”

Section: Introductionmentioning

confidence: 99%

Improved gradient‐echo 3D magnetic resonance imaging using compressed sensing and Toeplitz encoding with phase‐scrambled RF excitation

Wang

Liang

et al. 2020

Medical Physics

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Purpose: To develop a novel three-dimensional (3D) hybrid-encoding framework using compressed sensing (CS) and Toeplitz encoding with variable phase-scrambled radio-frequency (RF) excitation, which has the following advantages: low power deposition of RF pulses, reduction of the signal dynamic range, no additional hardware requirement, and signal-to-noise ratio (SNR) improvement. Methods: In light of the actual imaging framework of magnetic resonance imaging (MRI) scanners, we applied specially tailored RF pulses with phase-scrambled RF excitation to implement a 3D hybrid Fourier-Toeplitz encoding method based on 3D gradient-recalled echo pulse (GRASS) sequence. This method exploits Toeplitz encoding along the phase encoding direction, while keeping Fourier encoding along the readout and slice encoding directions. Phantom experiments were conducted to optimize the amplitude of specially tailored RF pulses in the 3D GRASS sequence. In vivo experiments were conducted to validate the feasibility of the proposed method, and simulations were conducted to compare the 3D hybrid-encoding method with Fourier encoding and other non-Fourier encoding methods. Results: An optimized low RF amplitude was obtained in the phantom experiments. Using the optimized specially tailored RF pulses, both the watermelon and knee experiments demonstrated that the proposed method was able to preserve more image details than the conventional 3D Fourier-encoded methods at acceleration factors of 3.1 and 2.0. Additionally, SNR was improved because of no additional gradients and 3D volume encoding, when compared with single-slice scanning without 3D encoding. Simulation results demonstrated that the proposed scheme was superior to the conventional Fourier encoding method, and obtained comparative performance with other non-Fourier encoding methods in preserving details. Conclusions: We developed a practical hybrid-encoding method for 3D MRI with specially tailored RF pulses of phase-scrambled RF excitation. The proposed method improves image SNR and detail preservation compared with the conventional Fourier encoding methods. Furthermore, our proposed method exhibits superior performance in terms of detail preservation, compared with the conventional Fourier encoding method.

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“…By contrast to what occurs in interleaved EPI, subsampling this axis during acquisition therefore does not bring about image folding effects; it only leads to lower resolution SPEN images. If available, resolution can then be improved by relying on multiple‐coil information, which then provides missing data in the spatial rather than in the usual k‐ domain . Alternatively, resolution can be improved by collecting multiple interleaved shots; each shot will then lead to full FOV images involving separate, slightly spatially shifted information.…”

Section: Introductionmentioning

confidence: 99%

“…If available, resolution can then be improved by relying on multiple-coil information, which then provides missing data in the spatial rather than in the usual k-domain. 26 Alternatively, resolution can be improved by collecting multiple interleaved shots; each shot will then lead to full FOV images involving separate, slightly spatially shifted information. An additional characteristic of these experiments rests in their ability to F I G U R E 1 Processing principles of the interleaved, multi-shot SPEN MRI approach here introduced, as pertaining to a multi-b-value DWI acquisition relying on multiple parallel receivers.…”

Section: Introductionmentioning

confidence: 99%

A regularized reconstruction pipeline for high‐definition diffusion MRI in challenging regions incorporating a per‐shot image correction

Cousin

Liberman

Solomon

et al. 2019

Magnetic Resonance in Med

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Purpose Diffusion MRI is of interest for clinical research and diagnosis. Whereas high‐ resolution DWI/DTI is hard to achieve by single‐shot methods, interleaved acquisitions can deliver these if motion and/or folding artefacts are overcome. Thanks to its ability to provide zoomed, folding‐free images, spatially encoded MRI can fulfill these requirements. This is here coupled with a regularized reconstruction and parallel receive methods, to deliver a robust scheme for human DWI/DTI at mm and sub‐mm resolutions. Methods Each shot along the spatially encoded dimension was reconstructed separately to retrieve per‐shot phase maps. These shots, together with coil sensitivities, were combined with spatially encoded quadratic phase‐encoding matrices associated to each shot, into single global operators. Their originating images were then iteratively computed aided by l1 and l2 regularization methods. When needed, motion‐corrupted shots were discarded and replaced by redundant information arising from parallel imaging. Results Full‐brain DTI experiments at 1 mm and restricted brain DTIs with 0.75 mm nominal in‐plane resolutions were acquired and reconstructed successfully by the new scheme. These 3 Tesla spetiotemporally encoded results compared favorably with EPI counterparts based on segmented and selective excitation schemes provided with the scanner. Conclusion A new procedure for achieving high‐definition diffusion‐based MRI was developed and demonstrated.

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Multiple‐coil k‐space interpolation enhances resolution in single‐shot spatiotemporal MRI

Cited by 17 publications

References 41 publications

Dynamic T₂ mapping by multi‐spin‐echo spatiotemporal encoding

Dynamic T₂ mapping by multi‐spin‐echo spatiotemporal encoding

Improved gradient‐echo 3D magnetic resonance imaging using compressed sensing and Toeplitz encoding with phase‐scrambled RF excitation

A regularized reconstruction pipeline for high‐definition diffusion MRI in challenging regions incorporating a per‐shot image correction

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Multiple‐coil k‐space interpolation enhances resolution in single‐shot spatiotemporal MRI

Cited by 17 publications

References 41 publications

Dynamic T2 mapping by multi‐spin‐echo spatiotemporal encoding

Dynamic T2 mapping by multi‐spin‐echo spatiotemporal encoding

Improved gradient‐echo 3D magnetic resonance imaging using compressed sensing and Toeplitz encoding with phase‐scrambled RF excitation

A regularized reconstruction pipeline for high‐definition diffusion MRI in challenging regions incorporating a per‐shot image correction

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Dynamic T₂ mapping by multi‐spin‐echo spatiotemporal encoding

Dynamic T₂ mapping by multi‐spin‐echo spatiotemporal encoding