The benefit of high-performance gradients on echo planar imaging for BOLD-based resting-state functional MRI

Kang, Daehun; Jo, Hang Joon; In, Myung Ho; Yarach, Uten; Meyer, Nolan; Speltz, Lydia J. Bardwell; Gray, Erin M.; Trzasko, Joshua D.; Huston, John; Bernstein, Matt A.; Shu, Yunhong

doi:10.1088/1361-6560/abb2ec

Cited by 7 publications

(11 citation statements)

References 53 publications

(44 reference statements)

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“…The increase in the slew rate allowed notably shorter echo times (TEs) in DWI and fast spin echo (FSE) sequences, and echo spacing reduction in echo‐planar imaging (EPI). These reductions in acquisition achieved images with better SNR, sharpness, and geometric fidelity than images acquired in a whole‐body 3 T scanner 75,76 . Nonetheless, C3T images required higher‐order gradient nonlinearity correction and experienced similar amounts of motion artifacts.…”

Section: Accessible Magnet Configurationsmentioning

confidence: 99%

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Superconducting magnet designs and MRI accessibility: A review

2023

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Presently, magnetic resonance imaging (MRI) magnets must deliver excellent magnetic field (B0) uniformity to achieve optimum image quality. Long magnets can satisfy the homogeneity requirements but require considerable superconducting material. These designs result in large, heavy, and costly systems that aggravate as field strength increases. Furthermore, the tight temperature tolerance of niobium titanium magnets adds instability to the system and requires operation at liquid helium temperature. These issues are crucial factors in the disparity of MR density and field strength use across the globe. Low‐income settings show reduced access to MRI, especially to high field strengths. This article summarizes the proposed modifications to MRI superconducting magnet design and their impact on accessibility, including compact, reduced liquid helium, and specialty systems. Reducing the amount of superconductor inevitably entails shrinking the magnet size, resulting in higher field inhomogeneity. This work also reviews the state‐of‐the‐art imaging and reconstruction methods to overcome this issue. Finally, we summarize the current and future challenges and opportunities in the design of accessible MRI.

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Section: Accessible Magnet Configurationsmentioning

confidence: 99%

“…These reductions in acquisition achieved images with better SNR, sharpness, and geometric fidelity than images acquired in a whole-body 3 T scanner. 75,76 Nonetheless, C3T images required higher-order gradient nonlinearity correction and experienced similar amounts of motion artifacts.…”

Section: Specialty Mrimentioning

confidence: 99%

Superconducting magnet designs and MRI accessibility: A review

2023

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“…the Sorensen-Dice index) were calculated using AFNI. After labelling brain regions based on anatomical image using FreeSurfer software (Reuter et al 2012), the cortical coverage ratio between EPI and anatomical volume were calculated and evaluated, as performed in a previous study (Kang et al 2020).…”

Section: Spatial and Temporal Resolutions For Multi-band Rg-fmrimentioning

confidence: 99%

Minimizing susceptibility-induced BOLD sensitivity loss in multi-band accelerated fMRI using point spread function mapping and gradient reversal

In¹,

Kang²,

Jo³

et al. 2023

Phys. Med. Biol.

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Objective: Interleaved reverse-gradient fMRI (RG-fMRI) with a point-spread-function (PSF) mapping-based distortion correction scheme has the potential to minimize signal loss in echo-planar-imaging (EPI). In this work, the RG-fMRI is further improved by imaging protocol optimization and application of reverse Fourier acquisition. Approach: Multi-band imaging was adapted for RG-fMRI to improve the temporal and spatial resolution. To better understand signal dropouts in forward and reverse EPIs, a simple theoretical relationship between echo shift and geometric distortion was derived and validated by the reliable measurements using PSF mapping method. After examining practical imaging protocols for RG-fMRI in three subjects on both a conventional whole-body and a high-performance compact 3T, the results were compared and the feasibility to further improve the RG-fMRI scheme were explored. High-resolution breath-holding RG-fMRI was conducted with nine subjects on the compact 3T and the fMRI reliability improvement in high susceptibility brain regions was demonstrated. Finally, reverse Fourier acquisition was applied to RG-fMRI, and its benefit was assessed by a simulation study based on the breath-holding RG-fMRI data. Main Results: The temporal and spatial resolution of the multi-band RG-fMRI became feasible for whole-brain fMRI. Echo shift measurements from PSF mapping well estimated signal dropout effects in the EPI pair and were useful to further improve the RG-fMRI scheme. Breath-holding RG-fMRI demonstrated improved fMRI reliability in high susceptibility brain regions. Reverse partial Fourier acquisition omitting the late echoes could further improve the temporal or spatial resolution for RG-fMRI without noticeable signal degradation and spatial resolution loss. Significance: With the improved imaging scheme, RG-fMRI could reliably investigate the functional mechanisms of the human brain in the temporal and frontal areas suffering from susceptibility-induced functional sensitivity loss.

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“…On the contrary, the whole-body scanner could only obtain a third echo at 81.5 ms, with the echo signal too weak to be useful. Additional benefits of reduced echo spacing includes greatly improved magneticsusceptibility-induced geometric distortion [33][34][35]. Additionally, the shortened readout improves SNR obliviating the need for a partial Fourier sampling [36].…”

Section: Introductionmentioning

confidence: 99%

Improved Resting-State Functional MRI Using Multi-Echo Echo-Planar Imaging on a Compact 3T MRI Scanner with High-Performance Gradients

Kang

et al. 2023

Sensors

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In blood-oxygen-level-dependent (BOLD)-based resting-state functional (RS-fMRI) studies, usage of multi-echo echo-planar-imaging (ME-EPI) is limited due to unacceptable late echo times when high spatial resolution is used. Equipped with high-performance gradients, the compact 3T MRI system (C3T) enables a three-echo whole-brain ME-EPI protocol with smaller than 2.5 mm isotropic voxel and shorter than 1 s repetition time, as required in landmark fMRI studies. The performance of the ME-EPI was comprehensively evaluated with signal variance reduction and region-of-interest-, seed- and independent-component-analysis-based functional connectivity analyses and compared with a counterpart of single-echo EPI with the shortest TR possible. Through the multi-echo combination, the thermal noise level is reduced. Functional connectivity, as well as signal intensity, are recovered in the medial orbital sulcus and anterior transverse collateral sulcus in ME-EPI. It is demonstrated that ME-EPI provides superior sensitivity and accuracy for detecting functional connectivity and/or brain networks in comparison with single-echo EPI. In conclusion, the high-performance gradient enabled high-spatial-temporal resolution ME-EPI would be the method of choice for RS-fMRI study on the C3T.

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The benefit of high-performance gradients on echo planar imaging for BOLD-based resting-state functional MRI

Cited by 7 publications

References 53 publications

Superconducting magnet designs and MRI accessibility: A review

Superconducting magnet designs and MRI accessibility: A review

Minimizing susceptibility-induced BOLD sensitivity loss in multi-band accelerated fMRI using point spread function mapping and gradient reversal

Improved Resting-State Functional MRI Using Multi-Echo Echo-Planar Imaging on a Compact 3T MRI Scanner with High-Performance Gradients

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