7 Tesla MR Imaging: Opportunities and Challenges

Umutlu, Lale; Ladd, Mark E.; Forsting, M.; Lauenstein, Thomas C.

doi:10.1055/s-0033-1350406

Cited by 17 publications

(25 citation statements)

References 50 publications

(92 reference statements)

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“…The 29% detection rate of epileptogenic lesions we found comparing 7T to conventional MRI could in the first instance be attributed to inherent advances related to 7T imaging; 7T offers higher SNR, enabling higher spatial resolution with better depiction of anatomical structures. [21][22][23] An additional factor contributing to the diagnostic gain of 7T MRI might derive from the use of a dedicated protocol, in particular the GRE and FLAIR images. Due to the high spatial resolution and sensitivity to the magnetic susceptibility properties of tissues, GRE imaging allows better evaluation of the different components within the cortex, which are otherwise uniform using other sequences.…”

Section: Discussionmentioning

confidence: 99%

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7TMRIin focal epilepsy with unrevealing conventional field strength imaging

Ciantis

Barba

Tassi³

et al. 2016

Epilepsia

134

127

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SUMMARYObjective: To assess the diagnostic yield of 7T magnetic resonance imaging (MRI) in detecting and characterizing structural lesions in patients with intractable focal epilepsy and unrevealing conventional (1.5 or 3T) MRI. Methods: We conducted an observational clinical imaging study on 21 patients (17 adults and 4 children) with intractable focal epilepsy, exhibiting clinical and electroencephalographic features consistent with a single seizure-onset zone (SOZ) and unrevealing conventional MRI. Patients were enrolled at two tertiary epilepsy surgery centers and imaged at 7T, including whole brain (three-dimensional [3D] T 1 -weighted [T1W] fast-spoiled gradient echo (FSPGR), 3D susceptibility-weighted angiography [SWAN], 3D fluid-attenuated inversion recovery [FLAIR]) and targeted imaging (2D T 2 *-weighted dual-echo gradient-recalled echo [GRE] and 2D gray-white matter tissue border enhancement [TBE] fast spin echo inversion recovery [FSE-IR]). MRI studies at 1.5 or 3T deemed unrevealing at the referral center were reviewed by three experts in epilepsy imaging. Reviewers were provided information regarding the suspected localization of the SOZ. The same team subsequently reviewed 7T images. Agreement in imaging interpretation was reached through consensus-based discussions based on visual identification of structural abnormalities and their likely correlation with clinical and electrographic data. Results: 7T MRI revealed structural lesions in 6 (29%) of 21 patients. The diagnostic gain in detection was obtained using GRE and FLAIR images. Four of the six patients with abnormal 7T underwent epilepsy surgery. Histopathology revealed focal cortical dysplasia (FCD) in all. In the remaining 15 patients (71%), 7T MRI remained unrevealing; 4 of the patients underwent epilepsy surgery and histopathologic evaluation revealed gliosis. Significance: 7T MRI improves detection of epileptogenic FCD that is not visible at conventional field strengths. A dedicated protocol including whole brain FLAIR and GRE images at 7T targeted at the suspected SOZ increases the diagnostic yield.

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Section: Discussionmentioning

confidence: 99%

“…[21][22][23] Compared to conventional field strengths (1.5-3T), 7T MRI offers higher signal-to-noise ratio (SNR), which enables higher spatial resolution. As a result, 7T can provide better depiction of anatomic structures and enhance both detection and characterization of brain lesions, increasing diagnostic confidence.…”

Section: Gre and Flair Imagesmentioning

confidence: 99%

7TMRIin focal epilepsy with unrevealing conventional field strength imaging

Ciantis

Barba

Tassi³

et al. 2016

Epilepsia

134

127

View full text Add to dashboard Cite

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“…(a) Single slice body image reported from early 4 T experiments from the research laboratories of Siemens [1], [2]. (b) A contemporary 7 T image of a slice in the human torso, targeting imaging of the heart, obtained with a 16-channel transmit and receive array coil [48], [49], using B 1 “shimming” (image provided by C. J. Synder, L. DeLaBarre, and T. Vaughan) (c) and (d) The transmit B 1 magnitude map (normalized intensity, color coded) before (c) and after (d) optimization over the heart, demonstrating that the B 1 is normally highly inhomogeneous and weak over this organ of interest (c), but can be improved significantly by multichannel transmit methods (d) [48], [49].…”

Section: Figmentioning

confidence: 99%

Magnetic Resonance Imaging at Ultrahigh Fields

Uğurbil

2014

IEEE Trans. Biomed. Eng.

131

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Since the introduction of 4 T human systems in three academic laboratories circa 1990, rapid progress in imaging and spectroscopy studies in humans at 4 T and animal model systems at 9.4 T have led to the introduction of 7 T and higher magnetic fields for human investigation at about the turn of the century. Work conducted on these platforms has demonstrated the existence of significant advantages in SNR and biological information content at these ultrahigh fields, as well as the presence of numerous challenges. Primary difference from lower fields is the deviation from the near field regime; at the frequencies corresponding to hydrogen resonance conditions at ultrahigh fields, the RF is characterized by attenuated traveling waves in the human body, which leads to image nonuniformities for a given sample-coil configuration because of interferences. These nonuniformities were considered detrimental to the progress of imaging at high field strengths. However, they are advantageous for parallel imaging for signal reception and parallel transmission, two critical technologies that account, to a large extend, for the success of ultrahigh fields. With these technologies, and improvements in instrumentation and imaging methods, ultra-high fields have provided unprecedented gains in imaging of brain function and anatomy, and started to make inroads into investigation of the human torso and extremities. As extensive as they are, these gains still constitute a prelude to what is to come given the increasingly larger effort committed to ultrahigh field research and development of ever better instrumentation and techniques.

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“…For most experiments, use a baseline of 200 msec prior to stimulus onset and a post stimulus interval of 600 msec to cover the time interval of interest ( Table 1). 4. Remove epochs that contain movement or blink artifacts: mark channels with a peak to peak amplitude higher than 150 mV -adjust this threshold depending on the participant group and data quality.…”

Section: Discussionmentioning

confidence: 99%

“…In addition to structural images, MRI also provides the possibility to measure changes in blood oxygenation to investigate brain function (fMRI). In summary, MRI offers relatively high spatial resolution of up to 0.5 mm 3 with modern high fields scanners and optimized parameters 4 . In contrast, the temporal resolution of fMRI is limited to the slow kinetics of the BOLD response, which only indirectly reflects the high temporal dynamics of neural activity 5,6 .…”

Section: Introductionmentioning

confidence: 99%

Cortical Source Analysis of High-Density EEG Recordings in Children

Bathelt

O’Reilly

Haan

2014

JoVE

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EEG is traditionally described as a neuroimaging technique with high temporal and low spatial resolution. Recent advances in biophysical modelling and signal processing make it possible to exploit information from other imaging modalities like structural MRI that provide high spatial resolution to overcome this constraint 1 . This is especially useful for investigations that require high resolution in the temporal as well as spatial domain. In addition, due to the easy application and low cost of EEG recordings, EEG is often the method of choice when working with populations, such as young children, that do not tolerate functional MRI scans well. However, in order to investigate which neural substrates are involved, anatomical information from structural MRI is still needed. Most EEG analysis packages work with standard head models that are based on adult anatomy. The accuracy of these models when used for children is limited 2 , because the composition and spatial configuration of head tissues changes dramatically over development 3 .In the present paper, we provide an overview of our recent work in utilizing head models based on individual structural MRI scans or age specific head models to reconstruct the cortical generators of high density EEG. This article describes how EEG recordings are acquired, processed, and analyzed with pediatric populations at the London Baby Lab, including laboratory setup, task design, EEG preprocessing, MRI processing, and EEG channel level and source analysis. Video LinkThe video component of this article can be found at

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7 Tesla MR Imaging: Opportunities and Challenges

Cited by 17 publications

References 50 publications

7TMRIin focal epilepsy with unrevealing conventional field strength imaging

7TMRIin focal epilepsy with unrevealing conventional field strength imaging

Magnetic Resonance Imaging at Ultrahigh Fields

Cortical Source Analysis of High-Density EEG Recordings in Children

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