Highly accelerated submillimeter resolution 3D GRASE with controlled  blurring in ‐weighted functional MRI at 7 Tesla: A feasibility study

Park, Suhyung; Torrisi, Salvatore; Townsend, Jennifer; Beckett, Alexander; Feinberg, David

doi:10.1002/mrm.28589

Cited by 20 publications

(25 citation statements)

References 69 publications

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“…Further development and sequence parameter optimization of GRASE alone could have advantages to VASO, as it would eliminate the use of complex sequence timing with inversion pulses and the inefficiency of acquiring a double readout for BOLD

T_{2}^{*}

correction. A recent development of CS‐GRASE to increase slice coverage is a promising further development of the methods used here 85,86 …”

Section: Discussionmentioning

confidence: 99%

“…However, in this particular experiment, the larger PSF in the slice direction for GRASE will have less of an effect than it might otherwise, due to the nature of the neural anatomy under investigation, in which thicker slices were placed orthogonal to the central sulcus and laminar activity was resolved in‐plane. In more convoluted areas of the cortex, where resolutions closer to isotropic are required, methods to mitigate through plane blurring in GRASE such as VFA 48 or CS 85,86 may prove critical, although the curvature of cortex within an imaging volume may mitigate the effect of through‐plane blurring on cortical depth profiles 7 . The robust functional results obtained using GRASE, despite its larger PSF, indicate that larger through‐plane voxels can be used in cases in which the slice plane can be placed orthogonal to the area of interest.…”

Section: Discussionmentioning

confidence: 99%

“…A recent development of CS-GRASE to increase slice coverage is a promising further development of the methods used here. 85,86 Although the sensitivity and lower pial bias of GRASE demonstrated here make it a good candidate for mesoscopic imaging, it is not without drawbacks. As noted previously, the PSF in the slice direction is increased for GRASE ( Figure 9) due to the T 2 decay across the echo train, which can be mitigated to an extent using VFA on the refocusing pulses, 48 at the expense of some overall SNR.…”

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confidence: 92%

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Comparison of BOLD and CBV using 3D EPI and 3D GRASE for cortical layer functional MRI at 7 T

Beckett

Dadakova

Townsend

et al. 2020

Magnetic Resonance in Med

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Purpose Functional MRI (fMRI) at the mesoscale of cortical layers and columns requires both sensitivity and specificity, the latter of which can be compromised if the imaging method is affected by vascular artifacts, particularly cortical draining veins at the pial surface. Recent studies have shown that cerebral blood volume (CBV) imaging is more specific to the actual laminar locus of neural activity than BOLD imaging using standard gradient‐echo EPI sequences. Gradient and spin‐echo (GRASE) BOLD imaging has also shown greater specificity when compared with standard gradient‐echo EPI BOLD. Here we directly compare CBV and BOLD contrasts in high‐resolution imaging of the primary motor cortex for laminar functional MRI in four combinations of signal labeling, CBV using slice‐selective slab‐inversion vascular space occupancy (VASO) and BOLD, each with 3D gradient‐echo EPI and zoomed 3D‐GRASE image readouts. Methods Activations were measured using each sequence and contrast combination during a motor task. Activation profiles across cortical depth were measured to assess the sensitivity and specificity (pial bias) of each method. Results Both CBV imaging using gradient‐echo 3D‐EPI and BOLD imaging using 3D‐GRASE show similar specificity and sensitivity and are therefore useful tools for mesoscopic functional MRI in the human cortex. The combination of GRASE and VASO did not demonstrate high levels of sensitivity, nor show increased specificity. Conclusion Three‐dimensional EPI with VASO contrast and 3D‐GRASE with BOLD contrast both demonstrate sufficient sensitivity and specificity for laminar functional MRI to be used by neuroscientists in a wide range of investigations of depth‐dependent neural circuitry in the human brain.

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T_{2}^{*}

correction. A recent development of CS‐GRASE to increase slice coverage is a promising further development of the methods used here 85,86 …”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 92%

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Comparison of BOLD and CBV using 3D EPI and 3D GRASE for cortical layer functional MRI at 7 T

Beckett

Dadakova

Townsend

et al. 2020

Magnetic Resonance in Med

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“…Both imaging coverage and temporal resolution of the proposed technique can be further improved by utilizing accelerated image acquisition and constrained reconstructions (52,53). It is also feasible to perform perfusion based functional connectivity analysis of brain network dynamics with increased coverage and temporal resolution (54).…”

Section: Discussionmentioning

confidence: 99%

Laminar perfusion imaging with zoomed arterial spin labeling at 7 Tesla

Shao

Guo

Shou

et al. 2021

Preprint

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Laminar fMRI based on BOLD and CBV contrast at ultrahigh magnetic fields has been applied for studying the dynamics of mesoscopic brain networks. However, the quantitative interpretations of BOLD/CBV fMRI results are confounded by different baseline physiology across cortical layers. Here we introduce a novel 3D zoomed pseudo-continuous arterial spin labeling technique at 7T that offers the unique capability for quantitative measurements of laminar cerebral blood flow (CBF) both at rest and during task activation with high spatial specificity and sensitivity. We found arterial transit time in superficial layers is ~100 msec shorter than in middle/deep layers revealing the dynamics of labeled blood flowing from pial arteries to downstream microvasculature. Resting state CBF peaked in the middle layers which is highly consistent with microvascular density measured from human cortex specimens. Finger tapping induced a robust two-peak laminar profile of CBF increases in the superficial (somatosensory and premotor input) and deep (spinal output) layers of M1, while finger brushing task induced a weaker CBF increase in superficial layers (somatosensory input). We further demonstrated that top-down attention induced a predominant CBF increase in deep layers and a smaller CBF increase on top of the lower baseline CBF in superficial layers of V1 (feedback cortical input), while bottom-up stimulus driven activity peaked in the middle layers (feedforward thalamic input). These quantitative laminar profiles of perfusion activity suggest an important role of M1 superficial layers for the computation of finger movements, and that visual attention may amplify deep layer output to the subcortex.

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“…The plots in the left column were simulated with constant refocusing flip angles α of 20° and 40° with and without 90°+α/2 preparation, 23 and with α = 180° in bold. Signals shown in the middle column were calculated with variable refocusing flip angle schemes v1/v4/v7, as given in Park et al 24 for an ES of 38/24 ms, k2 according to Kemper et al 25 for an ES of 36 ms, and a refocusing flip angle scheme that produces constant echo amplitudes of 0.05‐0.07 M 0 (bottom middle) for ES of 15 ms. These flip angles were calculated with the algorithm given by Busse et al 15 According to experimental settings given in Ref.…”

Section: Resultsmentioning

confidence: 99%