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Haines, K.; Smith, Nadine B.; Webb, Andrew

doi:10.1016/j.jmr.2010.01.003

Cited by 94 publications

(128 citation statements)

References 38 publications

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“…Dielectric padding was used for improved image homogeneity. 13 Scanning parameters are listed in Table 1. Images were acquired prior to the administration of contrast and again after the intravenous administration of 0.1 mmol/kg gadoteridol (ProHance, Bracco Imaging, Milan, Italy).…”

Section: Methodsmentioning

confidence: 99%

Longitudinal Persistence of Meningeal Enhancement on Postcontrast 7T 3D-FLAIR MRI in Multiple Sclerosis

Jonas

Izbudak

Frazier

et al. 2018

AJNR Am J Neuroradiol

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Background and Purpose: Preliminary research has demonstrated that post-gadolinium 3D FLAIR MRI at 7T may be a valuable tool for detecting abnormal meningeal enhancement and inflammation in MS; however, researchers have not systematically investigated its longitudinal persistence. We hypothesize that persistence of meningeal enhancement in MS varies based on pattern of enhancement as well as demographic and clinical factors such as treatment status, disease phenotype, and disability score. Materials and Methods: Thirty-one subjects with MS were prospectively scanned before and after intravenous contrast administration at 2 time points, approximately 1 year apart. Fifteen subjects in the cohort were scanned another time approximately 1 year later. Foci of enhancement were categorized into four subtypes: subarachnoid spread/fill, subarachnoid nodular, vessel wall, and dural foci. We reviewed follow-up scans to determine whether foci changed between time points and then compared persistence to demographic and clinical variables. Results: Persistence ranged from 71–100% at 1 year, and 73–100% at 2 years depending on enhancement pattern. Subarachnoid spread/fill and subarachnoid nodular subtypes persisted less often than vessel wall and dural foci. Persistence was not significantly different between those on/off treatment and those with progressive/non-progressive diseases phenotypes. Number of persisting foci was significantly different in subjects with/without increasing Expanded Disability Status Scale scores (median 12 v 7.5, p=0.04). Conclusion: Longitudinal persistence of meningeal enhancement on 3D FLAIR at 7T in MS varies by pattern of enhancement and correlates with worsening disability; however, it is not significantly different in those on/off treatment or those with progressive/non-progressive disease phenotypes.

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Section: Methodsmentioning

confidence: 99%

Longitudinal Persistence of Meningeal Enhancement on Postcontrast 7T 3D-FLAIR MRI in Multiple Sclerosis

Jonas

Izbudak

Frazier

et al. 2018

AJNR Am J Neuroradiol

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“…However, this technology is still in development and at the time was not sufficiently mature in implementation for routine and repeated use as demanded by the HCP. We therefore opted for an alternative, passive B 1 + shimming approach, which has been shown to locally improve B 1 + transmit efficiency, with practically no detrimental impact on SAR or image quality (Haines et al, 2010; Teeuwisse et al, 2012; Vu et al, 2015). Our approach involved careful placement of 5 mm thick, high permittivity dielectric pads under the neck and on both sides of the head to improve the generally poor B 1 + in the cerebellum and temporal lobes by upwards of a factor of two in flip angle.…”

Section: Methodsmentioning

confidence: 99%

Tradeoffs in pushing the spatial resolution of fMRI for the 7T Human Connectome Project

et al. 2017

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Whole-brain functional magnetic resonance imaging (fMRI), in conjunction with multiband acceleration, has played an important role in mapping the functional connectivity throughout the entire brain with both high temporal and spatial resolution. Ultrahigh magnetic field strengths (7 T and above) allow functional imaging with even higher functional contrast-to-noise ratios for improved spatial resolution and specificity compared to traditional field strengths (1.5 T and 3 T). High-resolution 7 T fMRI, however, has primarily been constrained to smaller brain regions given the amount of time it takes to acquire the number of slices necessary for high resolution whole brain imaging. Here we evaluate a range of whole-brain high-resolution resting state fMRI protocols (0.9, 1.25, 1.5, 1.6 and 2 mm isotropic voxels) at 7 T, obtained with both in-plane and slice acceleration parallel imaging techniques to maintain the temporal resolution and brain coverage typically acquired at 3 T. Using the processing pipeline developed by the Human Connectome Project, we demonstrate that high resolution images acquired at 7 T provide increased functional contrast to noise ratios with significantly less partial volume effects and more distinct spatial features, potentially allowing for robust individual subject parcellations and descriptions of fine-scaled patterns, such as visuotopic organization.

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“…A head-only quadrature coil and a 32-channel phased-array head coil (Nova Medical, Wilmington, MA) were used for RF transmit and reception, respectively. A pair of pads filled with high dielectric constant materials (39) were placed on the lateral sides of the subjects’ head inside the coil to mitigate B1 field inhomogeneity (40). T1-weighted anatomical images were acquired with a 3D MPRAGE sequence (TR/TI/TE = 4500/563/2 ms, voxel = 1 mm isotropic, 180 slices).…”

Section: Methodsmentioning

confidence: 99%

Measurement of arteriolar blood volume in brain tumors using MRI without exogenous contrast agent administration at 7T

Agarwal

Jones

et al. 2016

Magnetic Resonance Imaging

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Purpose Arteriolar cerebral-blood-volume (CBVa) is an important perfusion parameter that can be measured using inflow-based vascular-space-occupancy (iVASO) MRI without exogenous contrast agent administration. The purpose of this study is to assess the potential diagnostic value of CBVa in brain tumor patients by comparing it with total-CBV (including arterial, capillary and venous vessels) measured by dynamic-susceptibility-contrast (DSC) MRI. Methods Twelve brain tumor patients were scanned using iVASO (on 7T as part of a research project) and DSC (on 3T as part of routine clinical protocols) MRI. Region-of-interest analysis was performed to compare the resulting perfusion measures between tumoral and contralateral regions, and to evaluate their associations with tumor grades. Results CBVa measured by iVASO-MRI significantly correlated with WHO grade (ρ=0.37, P=0.04). Total-CBV measured by DSC-MRI showed a trend of correlation with WHO grade (ρ=0.28, P=0.5). Signal-to-noise ratio was comparable (P>0.1) between the two methods, while contrast-to-noise ratio between tumoral and contralateral regions was higher in iVASO-CBVa than DSC-CBV in WHO II/III patients (P<0.05) but comparable in WHO IV patients (P>0.1). A trend of positive correlation between DSC-CBV and iVASO-CBVa was observed (R2=0.28, P=0.07). Conclusion In this initial patient study, CBVa demonstrated a stronger correlation with WHO grade than total-CBV. Further investigation with a larger cohort is warranted to validate whether CBVa can be a better classifier than total-CBV for the stratification of brain tumors, and whether iVASO-MRI can be a useful alternative method for the assessment of tumor perfusion, especially when exogenous contrast agent administration is difficult in certain patient populations.

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New high dielectric constant materials for tailoring theB1+distribution at high magnetic fields

Cited by 94 publications

References 38 publications

Longitudinal Persistence of Meningeal Enhancement on Postcontrast 7T 3D-FLAIR MRI in Multiple Sclerosis

Longitudinal Persistence of Meningeal Enhancement on Postcontrast 7T 3D-FLAIR MRI in Multiple Sclerosis

Tradeoffs in pushing the spatial resolution of fMRI for the 7T Human Connectome Project

Measurement of arteriolar blood volume in brain tumors using MRI without exogenous contrast agent administration at 7T

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