How to choose the right MR sequence for your research question at 7 T and above?

Marques, José P.; Norris, David G.

doi:10.1016/j.neuroimage.2017.04.044

Cited by 46 publications

(44 citation statements)

References 259 publications

(261 reference statements)

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“…b, Nonremitter exhibited significantly increased activity between fMRI-1 and fMRI-2 in the no pain contrast (**represents p = 0.034, FWE voxel-level). Activation represents t-tests between remitter and nonremitter between fMRI-2 and fMRI-1 others show that advantages in group discrimination over lower field strengths might be negligable [19]. For response-prediction markers research, multimodal approaches [20] and machine learning analyses [21] might be more valuable than higher field strengths.…”

Section: Discussionmentioning

confidence: 99%

The pulvinar nucleus and antidepressant treatment: dynamic modeling of antidepressant response and remission with ultra-high field functional MRI

et al. 2018

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Functional magnetic resonance imaging (fMRI) successfully disentangled neuronal pathophysiology of major depression (MD), but only a few fMRI studies have investigated correlates and predictors of remission. Moreover, most studies have used clinical outcome parameters from two time points, which do not optimally depict differential response times. Therefore, we aimed to detect neuronal correlates of response and remission in an antidepressant treatment study with 7 T fMRI, potentially harnessing advances in detection power and spatial specificity. Moreover, we modeled outcome parameters from multiple study visits during a 12-week antidepressant fMRI study in 26 acute (aMD) patients compared to 36 stable remitted (rMD) patients and 33 healthy control subjects (HC). During an electrical painful stimulation task, significantly higher baseline activity in aMD compared to HC and rMD in the medial thalamic nuclei of the pulvinar was detected (p = 0.004, FWE-corrected), which was reduced by treatment. Moreover, clinical response followed a sigmoid function with a plateau phase in the beginning, a rapid decline and a further plateau at treatment end. By modeling the dynamic speed of response with fMRI-data, perigenual anterior cingulate activity after treatment was significantly associated with antidepressant response (p < 0.001, FWE-corrected). Temporoparietal junction (TPJ) baseline activity significantly predicted non-remission after 2 antidepressant trials (p = 0.005, FWE-corrected). The results underline the importance of the medial thalamus, attention networks in MD and antidepressant treatment. Moreover, by using a sigmoid model, this study provides a novel method to analyze the dynamic nature of response and remission for future trials.

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Section: Discussionmentioning

confidence: 99%

The pulvinar nucleus and antidepressant treatment: dynamic modeling of antidepressant response and remission with ultra-high field functional MRI

et al. 2018

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“…One approach to accelerate 2D MRI sequences is to simultaneously acquire multiple slices (simultaneous multislice [SMS]) instead of only one . This is particularly useful from an SNR perspective when the 2D acquisitions have TRs significantly greater than the T 1 of the tissues of interest . The SMS excitation pulses, in particular multiband (MB) pulses, are created by multiplexing sinc pulses, resulting in RF pulses that may be clipped due to higher RF amplitudes.…”

Section: Introductionmentioning

confidence: 99%

“…24,25 This is particularly useful from an SNR perspective when the 2D acquisitions have TRs significantly greater than the T 1 of the tissues of interest. 26 The SMS excitation pulses, in particular multiband (MB) pulses, are created by multiplexing sinc pulses, resulting in RF pulses that may be clipped due to higher RF amplitudes. Additionally, multiplexing results in a larger power deposition and hence restrictions due to specific absorption rate (SAR) safety constraints.…”

Section: Introductionmentioning

confidence: 99%

Fast model‐based T₂ mapping using SAR‐reduced simultaneous multislice excitation

Hilbert

Schulz

Marques

et al. 2019

Magnetic Resonance in Med

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Purpose To obtain whole‐brain high‐resolution T2 maps in 2 minutes by combining simultaneous multislice excitation and low‐power PINS (power independent of number of slices) refocusing pulses with undersampling and a model‐based reconstruction. Methods A multi‐echo spin‐echo sequence was modified to acquire multiple slices simultaneously, ensuring low specific absorption rate requirements. In addition, the acquisition was undersampled to achieve further acceleration. Data were reconstructed by subsequently applying parallel imaging to separate signals from different slices, and a model‐based reconstruction to estimate quantitative T2 from the undersampled data. The signal model used is based on extended phase graph simulations that also account for nonideal slice profiles and B1 inhomogeneity. In vivo experiments with 3 healthy subjects were performed to compare accelerated T2 maps to fully sampled single‐slice acquisitions. The accuracy of the T2 values was assessed with phantom experiments by comparing the T2 values to single‐echo spin‐echo measurements. Results In vivo results showed that conventional multi‐echo spin‐echo, simultaneous multislice, and undersampling result in similar mean T2 values within regions of interest. However, combining simultaneous multislice and undersampling results in higher SDs (about 7 ms) in comparison to a conventional sequence (about 3 ms). The T2 values were reproducible between scan and rescan (SD < 1.2 ms) within subjects and were in similar ranges across subjects (SD < 4.5 ms). Conclusion The proposed method is a fast T2 mapping technique that enables whole‐brain acquisitions at 0.7‐mm in‐plane resolution, 3‐mm slice thickness, and low specific absorption rate in 2 minutes.

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“…Despite tremendous improvements, UHF data still suffers from image imperfections related-among other sources-to B 1 inhomogeneities leading to various errors in MRI-based cortical thickness measurements and/or relaxometry (Collins, Li, & Smith, 1998;Marques & Norris, 2017;Padormo, Beqiri, Hajnal, & Malik, 2016;Ugurbil, 2017;Vaughan et al, 2001). In particular, quantitative T 1 mapping approaches ideally allow acquisition of unbiased anatomical data with any influence of scanner imperfections removed, in contrast to conventional T 1 w images.…”

Section: Discussionmentioning

confidence: 99%

“…Although the majority of, in particular clinical, neuroimaging data is acquired at 1.5T or 3T magnetic field strengths, technical developments and increased availability have led to increased usage of ultra-high-field scanners (UHF, !7T) for neuroanatomical and functional studies (as recently reviewed by De Martino et al, 2017;Marques & Norris, 2017;and Ugurbil, 2017, and references herein). Compared to conventional field strengths, imaging at higher fields enables acquisition of higher signal-to-noise ratio (SNR; Pohmann, Speck, & Scheffler, 2016) data and increases in various contrasts with no or little acquisition duration penalty.…”

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confidence: 99%

The impact of correction on MP2RAGE cortical T₁ and apparent cortical thickness at 7T

Haast

Ivanov

Uludağ

2018

Human Brain Mapping

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Determination of cortical thickness using MRI has often been criticized due to the presence of various error sources. Specifically, anatomical MRI relying on T1 contrast may be unreliable due to spatially variable image contrast between gray matter (GM), white matter (WM) and cerebrospinal fluid (CSF). Especially at ultra‐high field (≥ 7T) MRI, transmit and receive B1‐related image inhomogeneities can hamper correct classification of tissue types. In the current paper, we demonstrate that residual normalB1+ (transmit) inhomogeneities in the T1‐weighted and quantitative T1 images using the MP2RAGE sequence at 7T lead to biases in cortical thickness measurements. As expected, post‐hoc correction for the spatially varying normalB1+ profile reduced the apparent T1 values across the cortex in regions with low normalB1+, and slightly increased apparent T1 in regions with high normalB1+. As a result, improved contrast‐to‐noise ratio both at the GM‐CSF and GM‐WM boundaries can be observed leading to more accurate surface reconstructions and cortical thickness estimates. Overall, the changes in cortical thickness ranged between a 5% decrease to a 70% increase after normalB1+ correction, reducing the variance of cortical thickness values across the brain dramatically and increasing the comparability with normative data. More specifically, the cortical thickness estimates increased in regions characterized by a strong decrease of apparent T1 after normalB1+ correction in regions with low normalB1+ due to improved detection of the pial surface. The current results suggest that cortical thickness can be more accurately determined using MP2RAGE data at 7T if normalB1+ inhomogeneities are accounted for.

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How to choose the right MR sequence for your research question at 7 T and above?

Cited by 46 publications

References 259 publications

The pulvinar nucleus and antidepressant treatment: dynamic modeling of antidepressant response and remission with ultra-high field functional MRI

The pulvinar nucleus and antidepressant treatment: dynamic modeling of antidepressant response and remission with ultra-high field functional MRI

Fast model‐based T₂ mapping using SAR‐reduced simultaneous multislice excitation

The impact of correction on MP2RAGE cortical T₁ and apparent cortical thickness at 7T

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How to choose the right MR sequence for your research question at 7 T and above?

Cited by 46 publications

References 259 publications

The pulvinar nucleus and antidepressant treatment: dynamic modeling of antidepressant response and remission with ultra-high field functional MRI

The pulvinar nucleus and antidepressant treatment: dynamic modeling of antidepressant response and remission with ultra-high field functional MRI

Fast model‐based T2 mapping using SAR‐reduced simultaneous multislice excitation

The impact of correction on MP2RAGE cortical T1 and apparent cortical thickness at 7T

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Fast model‐based T₂ mapping using SAR‐reduced simultaneous multislice excitation

The impact of correction on MP2RAGE cortical T₁ and apparent cortical thickness at 7T