Can 7T MPRAGE match MP2RAGE for gray-white matter contrast?

Oliveira, Ícaro A.F.; Roos, Thomas; Dumoulin, Serge O.; Siero, Jeroen C.W.; Zwaag, Wietske van der

doi:10.1016/j.neuroimage.2021.118384

Cited by 21 publications

(19 citation statements)

References 32 publications

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“…Thus, if the learning-related structural changes observed in similar experimental designs based on MPRAGE sequences were predominantly of vascular origin, they would have been mostly cancelled out had MP2RAGE been used instead. Remarkably, even though the MP2RAGE sequence has been available for over 10 years (Marques et al 2010) and it is becoming the recommended sequence for gray-white matter segmentation (Droby et al 2021; Oliveira et al 2021), no published studies have, to the best of our knowledge, shown longitudinal training-related structural changes on a similar time-scale using this MR sequence, which may be a symptom of its lower sensitivity to vascular alterations. Nevertheless, this interpretation remains speculative, and more research will be needed to elucidate this question.…”

Section: Discussionmentioning

confidence: 99%

Cortical changes during the learning of sequences of simultaneous finger presses

Garzón

Helms

Olsson

et al. 2023

Preprint

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The cortical alterations underpinning the acquisition of motor skills remain debated. In this longitudinal study in younger adults, we acquired performance and neuroimaging (7T MRI) measures weekly over the course of 6 weeks to investigate neural changes associated with learning sequences of simultaneous finger presses executed with the non-dominant hand. Both the intervention group (n = 33) and the control group (n = 30) showed general performance improvements, but performance improved more and became more consistent for sequences that were intensively trained by the intervention group, relative to those that were not. Brain activity for trained sequences decreased compared with untrained sequences in the bilateral parietal and premotor cortices. No training-related changes in the primary sensorimotor areas were detected. The similarity of activation patterns between trained and untrained sequences decreased in secondary, but not primary, sensorimotor areas, while the similarity of the activation patterns between different trained sequences did not show reliable changes. Neither the variability of activation patterns across trials, nor the estimates of brain structure displayed practice-related changes that reached statistical significance. Overall, the main correlate of learning configural sequences was a reduction in brain activity in secondary motor areas.

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Section: Discussionmentioning

confidence: 99%

Cortical changes during the learning of sequences of simultaneous finger presses

Garzón

Helms

Olsson

et al. 2023

Preprint

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“…The small difference in in-plane acceleration used here is not expected to lead to different amounts of g-factor noise across the ROIs for the current 32-channel coil (Hendriks, Luijten, Klomp, & Petridou, 2019;Wiggins et al, 2006). Third, RFpower optimization was done over the whole brain, which leads to overtipping in the center and undertipping in the temporal poles and cerebellum (Oliveira, Roos, Dumoulin, Siero, & van der Zwaag, 2021).…”

Section: Discussionmentioning

confidence: 99%

Functional magnetic resonance imaging responses during perceptual decision‐making at 3 and 7 T in human cortex, striatum, and brainstem

Colizoli

Gee

Zwaag

et al. 2021

Human Brain Mapping

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While functional magnetic resonance imaging (fMRI) at ultra-high field (7 T) promises a general increase in sensitivity compared to lower field strengths, the benefits may be most pronounced for specific applications. The current study aimed to evaluate the relative benefit of 7 over 3 T fMRI for the assessment of responses evoked in different brain regions by a well-controlled cognitive task. At 3 and 7 T, the same participants made challenging perceptual decisions about visual motion combined with monetary rewards for correct choices. Previous work on this task has extensively characterized the underlying cognitive computations and single-cell responses in cortical and subcortical structures. We quantified the evoked fMRI responses in extrastriate visual cortical areas, the striatum, and the brainstem during the decision interval and the post-feedback interval of the task. The dependence of response amplitudes on field strength during the decision interval differed between cortical, striatal, and brainstem regions, with a generally bigger 7 versus 3 T benefit in subcortical structures. We also found stronger responses during relatively easier than harder decisions at 7 T for dopaminergic midbrain nuclei, in line with reward expectation.Our results demonstrate the potential of 7 T fMRI for illuminating the contribution of small brainstem nuclei to the orchestration of cognitive computations in the human brain.

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“…k T ‐point excitation pulses 39 were calculated based on the small‐flip‐angle interleaved greedy‐local optimization method, originally intended for spokes (code available for download at https://bitbucket.org/wgrissom/acptx/). 46–48 The following magnitude least‐squares 49 problem was solved:

\kern0.5em \underset{\mathbbm{K},\mathbf{b},\boldsymbol{\upphi}}{\arg\;\min}\left\{\frac{1}{2}{\left\Vert \sum \limits_{c=1}^8{\mathbf{\mathcal{S}}}_c\mathbf{A}\left(\mathbbm{K}\right){\mathbf{b}}_c-\mathbf{d}\left(\boldsymbol{\upphi} \right)\right\Vert}^2+\frac{\uplambda}{2}{\left\Vert \mathbf{b}\right\Vert}^2\right\}

where

{\mathbf{\mathcal{S}}}_c=\operatorname{diag}\left(\mathrm{vec}\left({\mathbf{S}}_c\left(\mathbf{x}\right)\right)\right)\in {\mathbb{C}}^{N_x\times {N}_x}

is the matrix with the complex

{\mathrm{B}}_1^{+}

maps

{\mathbf{S}}_c\left(\overrightarrow{r}\right)

from Eq. () at the

{N}_x

spatial locations

$$ ...

…”

Section: Methodsmentioning

confidence: 99%

“…k T -point excitation pulses 39 were calculated based on the small-flip-angle interleaved greedy-local optimization method, originally intended for spokes (code available for download at https://bitbucket.org/wgrissom/acptx/). [46][47][48] The following magnitude least-squares 49 problem was solved:…”

Section: K T -Point Excitationmentioning

confidence: 99%

Whole‐liver flip‐angle shimming at 7 T using parallel‐transmit k_T‐point pulses and Fourier phase‐encoded DREAMB1+ mapping

Runderkamp,

Roos,

van der Zwaag

et al. 2023

Magnetic Resonance in Med

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PurposeTo obtain homogeneous signal throughout the human liver at 7 T. Flip angle (FA) shimming in 7T whole‐liver imaging was performed through parallel‐transmit kT‐point pulses based on subject‐specific multichannel absolute maps from Fourier phase‐encoded dual refocusing echo acquisition mode (PE‐DREAM).MethodsThe optimal number of Fourier phase‐encoding steps for PE‐DREAM mapping was determined for a 7T eight‐channel parallel‐transmission system. FA shimming experiments were performed in the liver of 7 healthy subjects with varying body mass index. In these subjects, first shimming and Fourier PE‐DREAM mapping were performed. Subsequently, three small‐flip‐angle 3D gradient‐echo scans were acquired, comparing a circularly polarized (CP) mode, a phase shim, and a kT‐point pulse. Resulting homogeneity was assessed and compared with estimated FA maps and distributions.ResultsFourier PE‐DREAM with 13 phase‐encoding steps resulted in a good tradeoff between accuracy and scan time. Lower coefficient of variation values (average [min‐max] across subjects) of the estimated FA in the volume of interest were observed using kT‐points (7.4 [6.6%–8.0%]), compared with phase shimming (18.8 [12.9%–23.4%], p < 0.001) and CP (43.2 [39.4%–47.1%], p < 0.001). kT‐points delivered whole‐liver images with the nominal FA and the highest degree of homogeneity. CP and phase shimming resulted in either inaccurate or imprecise FA distributions. Here, locations having suboptimal FA in the estimated FA maps corresponded to liver areas suffering from inconsistent signal intensity and T1‐weighting in the gradient‐echo scans.ConclusionHomogeneous whole‐liver 3D gradient‐echo acquisitions at 7 T can be obtained with eight‐channel kT‐point pulses calculated based on subject‐specific multichannel absolute Fourier PE‐DREAM maps.

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Can 7T MPRAGE match MP2RAGE for gray-white matter contrast?

Cited by 21 publications

References 32 publications

Cortical changes during the learning of sequences of simultaneous finger presses

Cortical changes during the learning of sequences of simultaneous finger presses

Functional magnetic resonance imaging responses during perceptual decision‐making at 3 and 7 T in human cortex, striatum, and brainstem

Whole‐liver flip‐angle shimming at 7 T using parallel‐transmit k_T‐point pulses and Fourier phase‐encoded DREAMB1+ mapping

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Can 7T MPRAGE match MP2RAGE for gray-white matter contrast?

Cited by 21 publications

References 32 publications

Cortical changes during the learning of sequences of simultaneous finger presses

Cortical changes during the learning of sequences of simultaneous finger presses

Functional magnetic resonance imaging responses during perceptual decision‐making at 3 and 7 T in human cortex, striatum, and brainstem

Whole‐liver flip‐angle shimming at 7 T using parallel‐transmit kT‐point pulses and Fourier phase‐encoded DREAMB1+ mapping

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Product

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About

Whole‐liver flip‐angle shimming at 7 T using parallel‐transmit k_T‐point pulses and Fourier phase‐encoded DREAMB1+ mapping