Articles de revues : « High resolution 7T MRI »

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Soldati, Enrico, Martine Pithioux, Daphne Guenoun, David Bendahan et Jerome Vicente. « Assessment of Bone Microarchitecture in Fresh Cadaveric Human Femurs : What Could Be the Clinical Relevance of Ultra-High Field MRI ». Diagnostics 12, n^o 2 (8 février 2022) : 439. http://dx.doi.org/10.3390/diagnostics12020439.

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MRI could be applied for bone microarchitecture assessment; however, this technique is still suffering from low resolution compared to the trabecular dimension. A clear comparative analysis between MRI and X-ray microcomputed tomography (μCT) regarding microarchitecture metrics is still lacking. In this study, we performed a comparative analysis between μCT and 7T MRI with the aim of assessing the image resolution effect on the accuracy of microarchitecture metrics. We also addressed the issue of air bubble artifacts in cadaveric bones. Three fresh cadaveric femur heads were scanned using 7T MRI and µCT at high resolution (0.051 mm). Samples were submitted to a vacuum procedure combined with vibration to reduce the volume of air bubbles. Trabecular interconnectivity, a new metric, and conventional histomorphometric parameters were quantified using MR images and compared to those derived from µCT at full resolution and downsized resolutions (0.102 and 0.153 mm). Correlations between bone morphology and mineral density (BMD) were evaluated. Air bubbles were reduced by 99.8% in 30 min, leaving partial volume effects as the only source of bias. Morphological parameters quantified with 7T MRI were not statistically different (p > 0.01) to those computed from μCT images, with error up to 8% for both bone volume fraction and trabecular spacing. No linear correlation was found between BMD and all morphological parameters except trabecular interconnectivity (R2 = 0.69 for 7T MRI-BMD). These results strongly suggest that 7T MRI could be of interest for in vivo bone microarchitecture assessment, providing additional information about bone health and quality.

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Salehi, F., BY Kwan, SM Mirsattari, DH Lee, JG Burneo, D. Steven, R. Hammond, TM Peters et AR Khan. « P.127 Ultra-high field 7-Tesla magnetic resonance imaging and electroencephalography findings in epilepsy ». Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 48, s3 (novembre 2021) : S55—S56. http://dx.doi.org/10.1017/cjn.2021.403.

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Background: Assessment of patients for temporal lobe epilepsy (TLE) surgery requires multimodality input, including EEG to ensure optimal surgical planning. Often EEG demonstrates abnormal foci not detected on clinical MRI. 7T MRI provides improved resolution and we investigated its utility to detect potential abnormalities associated with EEG. Methods: Images were acquired on 7T MRI scanner (N=13) in oatients with TLE. Evaluation of 7T imaging for focal abnormalities was performed. Correlation of 7T MRI findings with EEG of focal slowing or interictal epileptic spikes (IEDs) and seizures was performed. Results: Assessment of 7T MRI demonstrated concordance with TLE in 8/13 cases. Three cases exhibited abnormal 7T MRI abnormalities not detected by 1.5 T MRI. Eleven out of 13 cases had EEG findings without anatomic correlates on MRI, with IEDs localizing to contralateral temporal, frontal, and parieto-occipital lobes. 7T images did not reveal focal anatomical abnormalities to account for the EEG findings in these patients. Conclusions: To our knowledge, this is the first study to investigate the role of 7T MRI in relation to EEG abnormalities. 7T RI findings show concordance with clinical data. 7T MRI did not reveal anatomical findings to account for EEG abnormalities, suggesting that such changes may be functional rather than anatomical.

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Willemink, Martin J., Bram F. Coolen, Hadrien Dyvorne, Philip M. Robson, Ilda Bander, Seigo Ishino, Alison Pruzan et al. « Ultra-high resolution, 3-dimensional magnetic resonance imaging of the atherosclerotic vessel wall at clinical 7T ». PLOS ONE 15, n^o 12 (14 décembre 2020) : e0241779. http://dx.doi.org/10.1371/journal.pone.0241779.

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Accurate quantification and characterization of atherosclerotic plaques with MRI requires high spatial resolution acquisitions with excellent image quality. The intrinsically better signal-to-noise ratio (SNR) at high-field clinical 7T compared to the widely employed lower field strengths of 1.5 and 3T may yield significant improvements to vascular MRI. However, 7T atherosclerosis imaging also presents specific challenges, related to local transmit coils and B1 field inhomogeneities, which may overshadow these theoretical gains. We present the development and evaluation of 3D, black-blood, ultra-high resolution vascular MRI on clinical high-field 7T in comparison lower-field 3T. These protocols were applied for in vivo imaging of atherosclerotic rabbits, which are often used for development, testing, and validation of translatable cardiovascular MR protocols. Eight atherosclerotic New Zealand White rabbits were imaged on clinical 7T and 3T MRI scanners using 3D, isotropic, high (0.63 mm3) and ultra-high (0.43 mm3) spatial resolution, black-blood MR sequences with extensive spatial coverage. Following imaging, rabbits were sacrificed for validation using fluorescence imaging and histology. Image quality parameters such as SNR and contrast-to-noise ratio (CNR), as well as morphological and functional plaque measurements (plaque area and permeability) were evaluated at both field strengths. Using the same or comparable imaging parameters, SNR and CNR were in general higher at 7T compared to 3T, with a median (interquartiles) SNR gain of +40.3 (35.3–80.1)%, and a median CNR gain of +68.1 (38.5–95.2)%. Morphological and functional parameters, such as vessel wall area and permeability, were reliably acquired at 7T and correlated significantly with corresponding, widely validated 3T vessel wall MRI measurements. In conclusion, we successfully developed 3D, black-blood, ultra-high spatial resolution vessel wall MRI protocols on a 7T clinical scanner. 7T imaging was in general superior to 3T with respect to image quality, and comparable in terms of plaque area and permeability measurements.

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Jarraya, Mohamed, Rafael Heiss, Jeffrey Duryea, Armin M. Nagel, John A. Lynch, Ali Guermazi, Marc-André Weber et al. « Bone Structure Analysis of the Radius Using Ultrahigh Field (7T) MRI : Relevance of Technical Parameters and Comparison with 3T MRI and Radiography ». Diagnostics 11, n^o 1 (12 janvier 2021) : 110. http://dx.doi.org/10.3390/diagnostics11010110.

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Bone fractal signature analysis (FSA—also termed bone texture analysis) is a tool that assesses structural changes that may relate to clinical outcomes and functions. Our aim was to compare bone texture analysis of the distal radius in patients and volunteers using radiography and 3T and 7T magnetic resonance imaging (MRI)—a patient group (n = 25) and a volunteer group (n = 25) were included. Participants in the patient group had a history of chronic wrist pain with suspected or confirmed osteoarthritis and/or ligament instability. All participants had 3T and 7T MRI including T1-weighted turbo spin echo (TSE) sequences. The 7T MRI examination included an additional high-resolution (HR) T1 TSE sequence. Radiographs of the wrist were acquired for the patient group. When comparing patients and volunteers (unadjusted for gender and age), we found a statistically significant difference of horizontal and vertical fractal dimensions (FDs) using 7T T1 TSE-HR images in low-resolution mode (horizontal: p = 0.04, vertical: p = 0.01). When comparing radiography to the different MRI sequences, we found a statistically significant difference for low- and high-resolution horizontal FDs between radiography and 3T T1 TSE and 7T T1 TSE-HR. Vertical FDs were significantly different only between radiographs and 3T T1 TSE in the high-resolution mode; FSA measures obtained from 3T and 7T MRI are highly dependent on the sequence and reconstruction resolution used, and thus are not easily comparable between MRI systems and applied sequences.

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Do, Huy, Pascal Bourdon, David Helbert, Mathieu Naudin et Remy Guillevin. « 7T MRI super-resolution with Generative Adversarial Network ». Electronic Imaging 2021, n^o 18 (18 janvier 2021) : 106–1. http://dx.doi.org/10.2352/issn.2470-1173.2021.18.3dia-106.

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The high-resolution magnetic resonance image (MRI) provides detailed anatomical information critical for clinical application diagnosis. However, high-resolution MRI typically comes at the cost of long scan time, small spatial coverage, and low signal-to-noise ratio. The benefits of the convolutional neural network (CNN) can be applied to solve the super-resolution task to recover high-resolution generic images from low-resolution inputs. Additionally, recent studies have shown the potential to use the generative advertising network (GAN) to generate high-quality super-resolution MRIs using learned image priors. Moreover, existing approaches require paired MRI images as training data, which is difficult to obtain with existing datasets when the alignment between high and low-resolution images has to be implemented manually.This paper implements two different GAN-based models to handle the super-resolution: Enhanced super-resolution GAN (ESRGAN) and CycleGAN. Different from the generic model, the architecture of CycleGAN is modified to solve the super-resolution on unpaired MRI data, and the ESRGAN is implemented as a reference to compare GAN-based methods performance. The results of GAN-based models provide generated high-resolution images with rich textures compared to the ground-truth. Moreover, results from experiments are performed on both 3T and 7T MRI images in recovering different scales of resolution.

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van Veluw, Susanne J., Jaco JM Zwanenburg, JooYeon Engelen-Lee, Wim GM Spliet, Jeroen Hendrikse, Peter R. Luijten et Geert Jan Biessels. « In Vivo Detection of Cerebral Cortical Microinfarcts with High-Resolution 7T MRI ». Journal of Cerebral Blood Flow & ; Metabolism 33, n^o 3 (19 décembre 2012) : 322–29. http://dx.doi.org/10.1038/jcbfm.2012.196.

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Cerebrovascular disease has an important role in cognitive decline and dementia. In this context, cerebral microinfarcts are attracting increasing attention, but these lesions could thus far not be detected in vivo. The aim of this study was to try to identify possible cortical microinfarcts on high-resolution 7T in vivo magnetic resonance imaging (MRI) and to perform a histopathologic validation study on similar appearing lesions on 7T ex vivo MRI of postmortem brain tissue. The study population consisted of 22 elderly subjects, who underwent 7T MRI. The fluid attenuated inversion recovery, T2, and T1 weighted scans of these subjects were examined for possible cortical microinfarcts. In the ex vivo MRI study, 15 formalin-fixed coronal brain slices of 6 subjects with Alzheimer and vascular pathology were examined and subjected to histopathologic verification. On the in vivo scans, 15 cortical lesions could be identified that were likely to be microinfarcts in 6 subjects. In the postmortem tissue, 6 similar appearing lesions were identified of which 5 were verified as cortical microinfarcts on histopathology. This study provides strong evidence that cortical microinfarcts can be detected in vivo, which will be of great value in further studies into the role of vascular disease in cognitive decline and dementia.

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Markenroth Bloch, Karin, Johannes Töger et Freddy Ståhlberg. « Investigation of cerebrospinal fluid flow in the cerebral aqueduct using high-resolution phase contrast measurements at 7T MRI ». Acta Radiologica 59, n^o 8 (15 novembre 2017) : 988–96. http://dx.doi.org/10.1177/0284185117740762.

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Background The cerebral aqueduct is a central conduit for cerebrospinal fluid (CSF), and non-invasive quantification of CSF flow in the aqueduct may be an important tool for diagnosis and follow-up of treatment. Magnetic resonance (MR) methods at clinical field strengths are limited by low spatial resolution. Purpose To investigate the feasibility of high-resolution through-plane MR flow measurements (2D-PC) in the cerebral aqueduct at high field strength (7T). Material and Methods 2D-PC measurements in the aqueduct were performed in nine healthy individuals at 7T. Measurement accuracy was determined using a phantom. Aqueduct area, mean velocity, maximum velocity, minimum velocity, net flow, and mean flow were determined using in-plane resolutions 0.8 × 0.8, 0.5 × 0.5, 0.3 × 0.3, and 0.2 × 0.2 mm2. Feasibility criteria were defined based on scan time and spatial and temporal resolution. Results Phantom validation of 2D-PC MR showed good accuracy. In vivo, stroke volume was −8.2 ± 4.4, −4.7 ± 2.8, −6.0 ± 3.8, and −3.7 ± 2.1 µL for 0.8 × 0.8, 0.5 × 0.5, 0.3 × 0.3, and 0.2 × 0.2 mm2, respectively. The scan with 0.3 × 0.3 mm2 resolution fulfilled the feasibility criteria for a wide range of heart rates and aqueduct diameters. Conclusion 7T MR enables non-invasive quantification of CSF flow and velocity in the cerebral aqueduct with high spatial resolution.

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Thomas, Bradley P., E. Brian Welch, Blake D. Niederhauser, William O. Whetsell, Adam W. Anderson, John C. Gore, Malcolm J. Avison et Jeffrey L. Creasy. « High-resolution 7T MRI of the human hippocampus in vivo ». Journal of Magnetic Resonance Imaging 28, n^o 5 (novembre 2008) : 1266–72. http://dx.doi.org/10.1002/jmri.21576.

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Sladky, Ronald, Pia Baldinger, Georg S. Kranz, Jasmin Tröstl, Anna Höflich, Rupert Lanzenberger, Ewald Moser et Christian Windischberger. « High-resolution functional MRI of the human amygdala at 7T ». European Journal of Radiology 82, n^o 5 (mai 2013) : 728–33. http://dx.doi.org/10.1016/j.ejrad.2011.09.025.

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van der Land, Veronica, Jaco J. M. Zwanenburg, Karin Fijnvandraat, Bart J. Biemond, Jeroen Hendrikse, Henri J. M. M. Mutsaerts, Fredy Visser et al. « Cerebral Lesions on 7 Tesla MRI in Patients with Sickle Cell Anemia ». Cerebrovascular Diseases 39, n^o 3-4 (2015) : 181–89. http://dx.doi.org/10.1159/000373917.

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Background: Patients with sickle cell anemia (SCA) are at a high risk to develop cerebral damage. Most common are silent cerebral infarctions (SCIs), visible as white matter hyperintensities (WMHs) on MRI in a patient without neurological deficits. The etiology of SCIs remains largely unclear. In addition, patients are at an increased risk for overt stroke, which is associated with large vessel disease. This classification based on the presence or absence of neurological deficits may not be the most fitting for research purposes, as it does not match the different underlying pathology. A classification based on imaging findings may therefore be a more straightforward approach for research purposes. We explored the feasibility to identify imaging features of SCIs in young, asymptomatic patients with SCA using ultra high-field 7 Tesla (7T) MRI. 7T MRI has a high resolution, which offers a unique chance to investigate small subclinical brain lesions in detail. To explore the superiority of 7T in identifying imaging abnormalities, we compared our results with 3T MRI. Methods: Ten young, neurologically asymptomatic patients with SCA underwent 7T and 3T MRI; 10 healthy, age-matched controls underwent 7T MRI. We used existing neuroimaging standards to classify the brain lesions. We scored 7T and 3T scans separately, blinded for all other results. Results: Using 7T MRI, we identified more patients with intracerebral lesions (9/10 vs. 5/10), a higher total count of WMHs (203 vs. 190, p = 0.016) and more lacunes (5 vs. 4) compared to 3T MRI. Abnormalities seen on 7T, which could not be identified on 3T, were cortical hyperintensities (in 3/10) and a different aspect of irregular WMHs, closely associated with cortical hyperintensities in a patient with large vessel stenosis. In 7 controls, a total of 13 WMHs were present. Conclusion: Using 7T MRI, we identified more intracerebral lesions compared to 3T, and found several abnormalities not visible on 3T. 7T MRI in SCA seems of particular interest to study the cortical involvement and the relation between WMHs and the cortex. We found some imaging features that are thought to be representative for small vessel disease, including WMHs, lacunes and prominent perivascular spaces; to understand whether small vessel disease plays a role in SCA requires further research.

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Santyr, B., JC Lau et AR Khan. « P.175 Direct Visualization of Thalamic Nuclei using 7 Tesla MRI and quantification in patients with temporal lobe epilepsy. » Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 48, s3 (novembre 2021) : S70. http://dx.doi.org/10.1017/cjn.2021.451.

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Background: Most individual thalamic nuclei cannot be directly visualized on routine clinical MRI. Stereotactic targeting techniques are indirect, relying on histological atlases and electrophysiological recording. We investigate whether high-field MRI can directly visualize the thalamic nuclei in vivo and allow for analysis of disease-related changes. Methods: Thirty-two healthy individuals were imaged with 7T MRI at a resolution of 0.7mm3. To obtain a high-resolution composite image, these were registered across subjects and averaged together. Three thalamic structures closely integrated in seizure propagation, the anterior thalamic nucleus (ATN), mammillothalamic tract (MTT), and centromedian nucleus (CM) were manually segmented in a subset of healthy subjects and patients with temporal lobe epilepsy (TLE). Results: There is sufficient resolution within the thalamus at 7T for visualization of the ATN, CM, and MTT. In the small subset of 5 controls and 5 TLE patients examined, there was no significant difference (p>0.05) in volume or mean T1map for the three thalamic sturctures of interest. Conclusions: MRI at 7T provides a method of direct visualization of thalamic nuclei, uncovering substructures not previously identifiable in vivo. These advances will enable quantitative analysis of disease-related changes to these structures and improved clinical targeting as demonstrated in this initial ‘proof-of-concept’ subset analysis.

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Da Costa, Sandra, Jérémie Clément, Rolf Gruetter et Özlem Ipek. « Evaluation of the whole auditory pathway using high-resolution and functional MRI at 7T parallel-transmit ». PLOS ONE 16, n^o 9 (7 septembre 2021) : e0254378. http://dx.doi.org/10.1371/journal.pone.0254378.

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Purpose The aim of the present study is to show a MR procedure for the evaluation of simultaneous left and right auditory functions with functional MRI, and high-resolution acquisition of anatomical auditory pathway using parallel-transmit (pTx) methods at 7T. Methods The time-efficient MR acquisition included two steps: RF weights were optimized for the regions-of-interest and high-resolution MR images of the inner-ear were acquired for the first 30 min (400 μm-iso resolution) followed by functional MRI acquisitions along the whole auditory pathway during the next 20 minutes. Data was processed with a linear cross-correlation analysis to define frequency preferences for each voxel in the auditory relays. Results Tonotopic maps revealed ordered bilateral frequency gradients in the auditory relays whereas at the level of the cochlear nuclei and superior olivary complexes the frequency gradients were less evident. A 21% increase in transmit-field efficiency was achieved over the left/right inner-ear regions and thus its main structures were clearly discernible using the pTx methods, compared to a single transmit RF coil. Conclusion Using 7T pTx allows a fast (less than 60 min in total) and qualitative evaluation of the simultaneous left and right auditory response along the entire auditory pathway, together with high-resolution anatomical images of the inner-ear. This could be further used for patient examination at 7T.

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Lenglet, C., E. Yacoub, G. Ghose, G. Adriany, G. Krüger, G. Sapiro, K. Ugurbil et N. Harel. « High Resolution Diffusion MRI on in-vivo Monkey Brains at 7T ». NeuroImage 47 (juillet 2009) : S74. http://dx.doi.org/10.1016/s1053-8119(09)70467-7.

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Rivera, Debra. « Emerging Role for 7T MRI and Metabolic Imaging for Pancreatic and Liver Cancer ». Metabolites 12, n^o 5 (30 avril 2022) : 409. http://dx.doi.org/10.3390/metabo12050409.

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Advances in magnet technologies have led to next generation 7T magnetic resonance scanners which can fit in the footprint and price point of conventional hospital scanners (1.5–3T). It is therefore worth asking if there is a role for 7T magnetic resonance imaging and spectroscopy for the treatment of solid tumor cancers. Herein, we survey the medical literature to evaluate the unmet clinical needs for patients with pancreatic and hepatic cancer, and the potential of ultra-high field proton imaging and phosphorus spectroscopy to fulfil those needs. We draw on clinical literature, preclinical data, nuclear magnetic resonance spectroscopic data of human derived samples, and the efforts to date with 7T imaging and phosphorus spectroscopy. At 7T, the imaging capabilities approach histological resolution. The spectral and spatial resolution enhancements at high field for phospholipid spectroscopy have the potential to reduce the number of exploratory surgeries due to tumor boundaries undefined at conventional field strengths. Phosphorus metabolic imaging at 7T magnetic field strength, is already a mainstay in preclinical models for molecular phenotyping, energetic status evaluation, dosimetry, and assessing treatment response for both pancreatic and liver cancers. Metabolic imaging of primary tumors and lymph nodes may provide powerful metrics to aid staging and treatment response. As tumor tissues contain extreme levels of phospholipid metabolites compared to the background signal, even spectroscopic volumes containing less than 50% tumor can be detected and/or monitored. Phosphorus spectroscopy allows non-invasive pH measurements, indicating hypoxia, as a predictor of patients likely to recur. We conclude that 7T multiparametric approaches that include metabolic imaging with phosphorus spectroscopy have the potential to meet the unmet needs of non-invasive location-specific treatment monitoring, lymph node staging, and the reduction in unnecessary surgeries for patients undergoing resections for pancreatic cancer. There is also potential for the use of 7T phosphorous spectra for the phenotyping of tumor subtypes and even early diagnosis (<2 mL). Whether or not 7T can be used for all patients within the next decade, the technology is likely to speed up the translation of new therapeutics.

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Lau, JC, J. DeKraker, KW MacDougall, H. Joswig, AG Parrent, JG Burneo, DA Steven, TM Peters et AR Khan. « P.063 Stereotactic targeting of hippocampal substructures using ultra-high field magnetic resonance imaging : Feasibility study in patients with epilepsy ». Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 45, s2 (juin 2018) : S32—S33. http://dx.doi.org/10.1017/cjn.2018.165.

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Background: The hippocampus can be divided longitudinally into the head, body, and tail; and unfolded medial-to-laterally into the subiculum, cornu ammonis (CA) sectors, and the dentate gyrus. Ultra-high field (≥ 7 Tesla; 7T) magnetic resonance imaging (MRI) enables submillimetric visualization of these hippocampal substructures which could be valuable for surgical targeting. Here, we assess the feasibility of using 7T MRI in conjunction with a novel computational unfolding method for image-based stereotactic targeting of hippocampal substructures. Methods: 53 patients with drug-resistant epilepsy were identified undergoing first-time implantation of the hippocampus. An image processing pipeline was created for computationally transforming post-operative electrode contact locations into our hippocampal coordinate system. Results: Of 178 implanted hippocampal electrodes (88 left; 49.4%), 25 (14.0%) were predominantly in the subiculum, 85 (47.8%) were in CA1, 23 (12.9%) were in CA2, 18 (10.1%) were in CA3/CA4, and 27 (15.2%) were in dentate gyrus. Along the longitudinal axis, hippocampal electrodes were most commonly implanted in the body (92; 51.7%) followed by the head (86; 48.3%). Conclusions: 7T MRI enables high-resolution anatomical imaging on the submillimeter scale in in vivo subjects. Here, we demonstrate the utility of 7T imaging for identifying the relative location of SEEG electrode implantations within hippocampal substructures for the invasive investigation of epilepsy.

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Hamilton-Craig, Christian, Daniel Stäeb, Aiman Al Najjar, Kieran O’Brien, William Crawford, Sabine Fletcher, Markus Barth et Graham Galloway. « 7-Tesla Functional Cardiovascular MR Using Vectorcardiographic Triggering—Overcoming the Magnetohydrodynamic Effect ». Tomography 7, n^o 3 (4 août 2021) : 323–32. http://dx.doi.org/10.3390/tomography7030029.

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Objective: Ultra-high-field B0 ≥ 7 tesla (7T) cardiovascular magnetic resonance (CMR) offers increased resolution. However, electrocardiogram (ECG) gating is impacted by the magneto-hydrodynamic effect distorting the ECG trace. We explored the technical feasibility of a 7T magnetic resonance scanner using an ECG trigger learning algorithm to quantitatively assess cardiac volumes and vascular flow. Methods: 7T scans were performed on 10 healthy volunteers on a whole-body research MRI MR scanner (Siemens Healthineers, Erlangen, Germany) with 8 channel Tx/32 channels Rx cardiac coils (MRI Tools GmbH, Berlin, Germany). Vectorcardiogram ECG was performed using a learning phase outside of the magnetic field, with a trigger algorithm overcoming severe ECG signal distortions. Vectorcardiograms were quantitatively analyzed for false negative and false positive events. Cine CMR was performed after 3rd-order B0 shimming using a high-resolution breath-held ECG-retro-gated segmented spoiled gradient echo, and 2D phase contrast flow imaging. Artefacts were assessed using a semi-quantitative scale. Results: 7T CMR scans were acquired in all patients (100%) using the vectorcardiogram learning method. 3,142 R-waves were quantitatively analyzed, yielding sensitivity of 97.6% and specificity of 98.7%. Mean image quality score was 0.9, sufficient to quantitate both cardiac volumes, ejection fraction, and aortic and pulmonary blood flow. Mean left ventricular ejection fraction was 56.4%, right ventricular ejection fraction was 51.4%. Conclusion: Reliable cardiac ECG triggering is feasible in healthy volunteers at 7T utilizing a state-of-the-art three-lead trigger device despite signal distortion from the magnetohydrodynamic effect. This provides sufficient image quality for quantitative analysis. Other ultra-high-field imaging applications such as human brain functional MRI with physiologic noise correction may benefit from this method of ECG triggering.

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Wu, Xiaoping, Edward J. Auerbach, An T. Vu, Steen Moeller, Christophe Lenglet, Sebastian Schmitter, Pierre‐François Van de Moortele, Essa Yacoub et Kâmil Uğurbil. « High‐resolution whole‐brain diffusion MRI at 7T using radiofrequency parallel transmission ». Magnetic Resonance in Medicine 80, n^o 5 (30 mars 2018) : 1857–70. http://dx.doi.org/10.1002/mrm.27189.

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van Veluw, Susanne J., Jaco JM Zwanenburg, Annemieke JM Rozemuller, Peter R. Luijten, Wim GM Spliet et Geert Jan Biessels. « The Spectrum of MR Detectable Cortical Microinfarcts : A Classification Study with 7-Tesla Postmortem MRI and Histopathology ». Journal of Cerebral Blood Flow & ; Metabolism 35, n^o 4 (21 janvier 2015) : 676–83. http://dx.doi.org/10.1038/jcbfm.2014.258.

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Cerebral microinfarcts (CMIs) are common neuropathologic findings in aging and dementia. We explored the spectrum of cortical CMIs that can be visualized with 7T magnetic resonance imaging (MRI). Thirty-three coronal brain slices of 11 individuals with neuropathologically confirmed dementia were subjected to a high-resolution postmortem 7T MRI protocol. First, we identified all visible small (5 mm) intracortical and juxtacortical lesions on postmortem MRI. Lesions were classified as CMI or nonCMI based on histology, and their MR features were recorded. Thirty lesions were identified on the initial MRI evaluation, of which twenty-three could be matched with histology. Histopathology classified 12 lesions as CMIs, all of which were located intracortically. On the basis of their MR features, they could be classified as chronic gliotic CMIs—with or without cavitation or hemorrhagic components—and acute CMIs. Eleven MRI identified lesions were not of ischemic nature and most commonly enlarged or atypically shaped perivascular spaces. Their MRI features were similar to gliotic CMIs with or without cavitation, but these ‘CMI mimics’ were always located juxtacortically. 7T postmortem MRI distinguishes different histopathologic types of cortical CMIs, with distinctive MR characteristics. On the basis of our findings, we propose in vivo rating criteria for the detection of intracortical CMIs.

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Weiss, Alessandro, Paolo Perrini, Matteo De Notaris, Guadalupe Soria, Alarcon Carlos, Maura Castagna, Lodovico Lutzemberger et al. « Endoscopic Endonasal Transclival Approach to the Ventral Brainstem : Anatomic Study of the Safe Entry Zones Combining Fiber Dissection Technique with 7 Tesla Magnetic Resonance Guided Neuronavigation ». Operative Neurosurgery 16, n^o 2 (10 mai 2018) : 239–49. http://dx.doi.org/10.1093/ons/opy080.

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Abstract BACKGROUND Treatment of intrinsic lesions of the ventral brainstem is a surgical challenge that requires complex skull base antero- and posterolateral approaches. More recently, endoscopic endonasal transclival approach (EETA) has been reported in the treatment of selected ventral brainstem lesions. OBJECTIVE In this study we explored the endoscopic ventral brainstem anatomy with the aim to describe the degree of exposure of the ventral safe entry zones. In addition, we used a newly developed method combining traditional white matter dissection with high-resolution 7T magnetic resonance imaging (MRI) of the same specimen coregistered using a neuronavigation system. METHODS Eight fresh-frozen latex-injected cadaver heads underwent EETA. Additional 8 formalin-fixed brainstems were dissected using Klingler technique guided by ultra-high resolution MRI. RESULTS The EETA allows a wide exposure of different safe entry zones located on the ventral brainstem: the exposure of perioculomotor zone requires pituitary transposition and can be hindered by superior cerebellar artery. The peritrigeminal zone was barely visible and its exposure required an extradural anterior petrosectomy. The anterolateral sulcus of the medulla was visible in most of specimens, although its close relationship with the corticospinal tract makes it suboptimal as an entry point for intrinsic lesions. In all cases, the use of 7T-MRI allowed the identification of tiny fiber bundles, improving the quality of the dissection. CONCLUSION Exposure of the ventral brainstem with EETA requires mastering surgical maneuvers, including pituitary transposition and extradural petrosectomy. The correlation of fiber dissection with 7T-MRI neuronavigation significantly improves the understanding of the brainstem anatomy.

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Federau, Christian, et Daniel Gallichan. « Motion-Correction Enabled Ultra-High Resolution In-Vivo 7T-MRI of the Brain ». PLOS ONE 11, n^o 5 (9 mai 2016) : e0154974. http://dx.doi.org/10.1371/journal.pone.0154974.

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Wu, Wenchuan, Benedikt A. Poser, Gwenaëlle Douaud, Robert Frost, Myung-Ho In, Oliver Speck, Peter J. Koopmans et Karla L. Miller. « High-resolution diffusion MRI at 7T using a three-dimensional multi-slab acquisition ». NeuroImage 143 (décembre 2016) : 1–14. http://dx.doi.org/10.1016/j.neuroimage.2016.08.054.

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Samaniego, Edgar A., Jorge A. Roa et David Hasan. « Vessel wall imaging in intracranial aneurysms ». Journal of NeuroInterventional Surgery 11, n^o 11 (23 juillet 2019) : 1105–12. http://dx.doi.org/10.1136/neurintsurg-2019-014938.

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High-resolution vessel wall imaging (HR-VWI) is becoming a useful tool in the characterization and identification of unstable unruptured brain aneurysms. However, it has not been validated for clinical use. The current evidence on HR-VWI techniques for characterization of brain aneurysms is described in this review. Specific imaging approaches such as aneurysm wall contrast enhancement, MRI-quantitative susceptibility mapping, and 7T MRI are described in detail.

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Dong, William, Kanchna Ramchandran, Adam Galloy, Marco A. Nino, Marla Kleingartner, Madhavan L. Raghavan, Sneha Phadke et Vincent A. Magnotta. « Abstract P3-04-07 : Safety and artifact testing of a nitinol breast biopsy clip in an ultra-high resolution magnetic resonance imaging (MRI) environment ». Cancer Research 83, n^o 5_Supplement (1 mars 2023) : P3–04–07—P3–04–07. http://dx.doi.org/10.1158/1538-7445.sabcs22-p3-04-07.

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Abstract Background: The lack of safety clearance of several metallic breast implants in 7T(Tesla) poses a significant hurdle to standard clinical breast cancer care and research from reaping the benefits of ultra-high resolution MR imaging. A breast biopsy clip (Ultracor Twirl, Becton, Dickinson and Company, Vernon Hills, IL) composed of nitinol, was tested for safety and artifact susceptibility clearance in a 7T MRI scanner, using standardized procedures. This clearance is significant in henceforth allowing patients with this implant to be scanned in now FDA approved ultra-high-field MRI scanners of 7T or less for clinical and research purposes. Methods: Tests for magnetic susceptibility (torque and translational attraction), MRI-related heating, and artifacts were conducted as per standardized protocols. The torque and translational attraction tests evaluated the effects of magnetic force by the MRI to cause the clip to move and twist respectively. The heating test was conducted with customized MR parameters of short TR (repetition time) and maximum echo-train length, designed to induce temperature change. The artifact test using T1 weighted spin and gradient echo imaging sequences, evaluated potential localized signal loss that may result in misrepresentation of the imaged area. This may occur due to the presence of the metallic clip in the MR environment. Results: The torque and translational attraction tests respectively indicated that the MR environment did not induce any movement in the clip in eight orientations, with a deflection angle of 0 degrees. Results of the heating test indicated no significant temperature change of the clip. A temperature change of less than 0.45C° was observed in the phantom gel in both the absence and presence of the clip, which is well within the safety threshold (< 1°C). Results of the artifact test indicated a very small artifact, with the largest artifact cross-sectional area appearing on gradient echo images. Conclusion: These cumulative results indicate that the Ultracor Twirl breast biopsy clip is safe for imaging patients at 7T. Citation Format: William Dong, Kanchna Ramchandran, Adam Galloy, Marco A. Nino, Marla Kleingartner, Madhavan L. Raghavan, Sneha Phadke, Vincent A. Magnotta. Safety and artifact testing of a nitinol breast biopsy clip in an ultra-high resolution magnetic resonance imaging (MRI) environment [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-04-07.

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Sanchez-Panchuelo, R. M., S. Francis, R. Bowtell et D. Schluppeck. « Mapping Human Somatosensory Cortex in Individual Subjects With 7T Functional MRI ». Journal of Neurophysiology 103, n^o 5 (mai 2010) : 2544–56. http://dx.doi.org/10.1152/jn.01017.2009.

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Functional magnetic resonance imaging (fMRI) is now routinely used to map the topographic organization of human visual cortex. Mapping the detailed topography of somatosensory cortex, however, has proven to be more difficult. Here we used the increased blood-oxygen-level-dependent contrast-to-noise ratio at ultra-high field (7 Tesla) to measure the topographic representation of the digits in human somatosensory cortex at 1 mm isotropic resolution in individual subjects. A “traveling wave” paradigm was used to locate regions of cortex responding to periodic tactile stimulation of each distal phalangeal digit. Tactile stimulation was applied sequentially to each digit of the left hand from thumb to little finger (and in the reverse order). In all subjects, we found an orderly map of the digits on the posterior bank of the central sulcus (postcentral gyrus). Additionally, we measured event-related responses to brief stimuli for comparison with the topographic mapping data and related the fMRI responses to anatomical images obtained with an inversion-recovery sequence. Our results have important implications for the study of human somatosensory cortex and underscore the practical utility of ultra-high field functional imaging with 1 mm isotropic resolution for neuroscience experiments. First, topographic mapping of somatosensory cortex can be achieved in 20 min, allowing time for further experiments in the same session. Second, the maps are of sufficiently high resolution to resolve the representations of all five digits and third, the measurements are robust and can be made in an individual subject. These combined advantages will allow somatotopic fMRI to be used to measure the representation of digits in patients undergoing rehabilitation or plastic changes after peripheral nerve damage as well as tracking changes in normal subjects undergoing perceptual learning.

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Gottwald, L. M., J. Töger, K. Markenroth Bloch, E. S. Peper, B. F. Coolen, G. J. Strijkers, P. van Ooij et A. J. Nederveen. « High Spatiotemporal Resolution 4D Flow MRI of Intracranial Aneurysms at 7T in 10 Minutes ». American Journal of Neuroradiology 41, n^o 7 (25 juin 2020) : 1201–8. http://dx.doi.org/10.3174/ajnr.a6603.

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Kleinnijenhuis, Michiel, Tim van Mourik, David G. Norris, Dirk J. Ruiter, Anne-Marie van Cappellen van Walsum et Markus Barth. « Diffusion tensor characteristics of gyrencephaly using high resolution diffusion MRI in vivo at 7T ». NeuroImage 109 (avril 2015) : 378–87. http://dx.doi.org/10.1016/j.neuroimage.2015.01.001.

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Soldati, Enrico, Jerome Vicente, Daphne Guenoun, David Bendahan et Martine Pithioux. « Validation and Optimization of Proximal Femurs Microstructure Analysis Using High Field and Ultra-High Field MRI ». Diagnostics 11, n^o 9 (2 septembre 2021) : 1603. http://dx.doi.org/10.3390/diagnostics11091603.

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Trabecular bone could be assessed non-invasively using MRI. However, MRI does not yet provide resolutions lower than trabecular thickness and a comparative analysis between different MRI sequences at different field strengths and X-ray microtomography (μCT) is still missing. In this study, we compared bone microstructure parameters and bone mineral density (BMD) computed using various MRI approaches, i.e., turbo spin echo (TSE) and gradient recalled echo (GRE) images used at different magnetic fields, i.e., 7T and 3T. The corresponding parameters computed from μCT images and BMD derived from dual-energy X-ray absorptiometry (DXA) were used as the ground truth. The correlation between morphological parameters, BMD and fracture load assessed by mechanical compression tests was evaluated. Histomorphometric parameters showed a good agreement between 7T TSE and μCT, with 8% error for trabecular thickness with no significative statistical difference and a good intraclass correlation coefficient (ICC > 0.5) for all the extrapolated parameters. No correlation was found between DXA-BMD and all morphological parameters, except for trabecular interconnectivity (R2 > 0.69). Good correlation (p-value < 0.05) was found between failure load and trabecular interconnectivity (R2 > 0.79). These results suggest that MRI could be of interest for bone microstructure assessment. Moreover, the combination of morphological parameters and BMD could provide a more comprehensive view of bone quality.

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Lau, JC, TM Peters, Y. Xiao, G. Gilmore, KW MacDougall, C. Currie, AR Khan et AG Parrent. « C.05 Direct visualization of the human zona incerta region using ultra-high field imaging : implications for stereotactic neurosurgery ». Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 46, s1 (juin 2019) : S13. http://dx.doi.org/10.1017/cjn.2019.100.

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Background: The zona incerta (ZI) is a small structure in the deep brain first identified by Auguste Forel for which robust in vivo visualization has remained elusive. The increased inherent signal from ultra-high field (7-Tesla or greater; 7T) magnetic resonance imaging (MRI) presents an opportunity to see structures not previously visible. In this study, we investigated the possibility of using quantitative T1 mapping at 7T to visualize the ZI region. Methods: We recruited healthy participants (N=32) and patients being considered for deep brain stimulation therapy as part of a prospective imaging study at 7T. Computational methods were used to process and fuse images to produce a high-resolution group average from which ZI anatomy could be delineated. Results: We pooled 7T data using image fusion methods and found that the contrast from quantitative T1 mapping was strikingly similar to classic histological staining, permitting facile identification of the ZI and nearby structures in reference to conventional stereotactic atlases. Conclusions: Using computational neuroimaging techniques, we demonstrate for the first time that the ZI is visible in vivo. Furthermore, we determined that this nuclear region can be decoupled from surrounding fibre pathways. This work paves the way for more accurate patient-specific optimization of deep brain targets for neuromodulation.

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Lüsebrink, Falk, Astrid Wollrab et Oliver Speck. « Cortical thickness determination of the human brain using high resolution 3T and 7T MRI data ». NeuroImage 70 (avril 2013) : 122–31. http://dx.doi.org/10.1016/j.neuroimage.2012.12.016.

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Glarin, Rebecca K., Bao N. Nguyen, Jon O. Cleary, Scott C. Kolbe, Roger J. Ordidge, Bang V. Bui, Allison M. McKendrick et Bradford A. Moffat. « MR-EYE : High-Resolution MRI of the Human Eye and Orbit at Ultrahigh Field (7T) ». Magnetic Resonance Imaging Clinics of North America 29, n^o 1 (février 2021) : 103–16. http://dx.doi.org/10.1016/j.mric.2020.09.004.

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Ding, Xuanfeng, John Olsen, Ryan Best, Marcus Bennett, Inna McGowin, Jennifer Dorand, Kerry Link et J. Daniel Bourland. « High resolution polymer gel dosimetry for small beam irradiation using a 7T micro-MRI scanner ». Journal of Physics : Conference Series 250 (1 novembre 2010) : 012094. http://dx.doi.org/10.1088/1742-6596/250/1/012094.

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Krithika alias Anbu Devi, M., et K. Suganthi. « Review of Medical Image Synthesis using GAN Techniques ». ITM Web of Conferences 37 (2021) : 01005. http://dx.doi.org/10.1051/itmconf/20213701005.

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Generative Adversarial Networks (GANs) is one of the vital efficient methods for generating a massive, high-quality artificial picture. For diagnosing particular diseases in a medical image, a general problem is that it is expensive, usage of high radiation dosage, and time-consuming to collect data. Hence GAN is a deep learning method that has been developed for the image to image translation, i.e. from low-resolution to highresolution image, for example generating Magnetic resonance image (MRI) from computed tomography image (CT) and 7T from 3T MRI which can be used to obtain multimodal datasets from single modality. In this review paper, different GAN architectures were discussed for medical image analysis.

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Mattern, Hendrik, Alessandro Sciarra, Falk Lüsebrink, Julio Acosta‐Cabronero et Oliver Speck. « Prospective motion correction improves high‐resolution quantitative susceptibility mapping at 7T ». Magnetic Resonance in Medicine 81, n^o 3 (9 octobre 2018) : 1605–19. http://dx.doi.org/10.1002/mrm.27509.

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Reiter, Theresa, David Lohr, Michael Hock, Markus Johannes Ankenbrand, Maria Roxana Stefanescu, Aleksander Kosmala, Mathias Kaspar, Christoph Juchem, Maxim Terekhov et Laura Maria Schreiber. « On the way to routine cardiac MRI at 7 Tesla - a pilot study on consecutive 84 examinations ». PLOS ONE 16, n^o 7 (23 juillet 2021) : e0252797. http://dx.doi.org/10.1371/journal.pone.0252797.

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Introduction Cardiac magnetic resonance (CMR) at ultrahigh field (UHF) offers the potential of high resolution and fast image acquisition. Both technical and physiological challenges associated with CMR at 7T require specific hardware and pulse sequences. This study aimed to assess the current status and existing, publicly available technology regarding the potential of a clinical application of 7T CMR. Methods Using a 7T MRI scanner and a commercially available radiofrequency coil, a total of 84 CMR examinations on 72 healthy volunteers (32 males, age 19–70 years, weight 50–103 kg) were obtained. Both electrocardiographic and acoustic triggering were employed. The data were analyzed regarding the diagnostic image quality and the influence of patient and hardware dependent factors. 50 complete short axis stacks and 35 four chamber CINE views were used for left ventricular (LV) and right ventricular (RV), mono-planar LV function, and RV fractional area change (FAC). Twenty-seven data sets included aortic flow measurements that were used to calculate stroke volumes. Subjective acceptance was obtained from all volunteers with a standardized questionnaire. Results Functional analysis showed good functions of LV (mean EF 56%), RV (mean EF 59%) and RV FAC (mean FAC 52%). Flow measurements showed congruent results with both ECG and ACT triggering. No significant influence of experimental parameters on the image quality of the LV was detected. Small fractions of 5.4% of LV and 2.5% of RV segments showed a non-diagnostic image quality. The nominal flip angle significantly influenced the RV image quality. Conclusion The results demonstrate that already now a commercially available 7T MRI system, without major methods developments, allows for a solid morphological and functional analysis similar to the clinically established CMR routine approach. This opens the door towards combing routine CMR in patients with development of advanced 7T technology.

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Harteveld, Anita A., Anja G. van der Kolk, H. Bart van der Worp, Nikki Dieleman, Jeroen C. W. Siero, Hugo J. Kuijf, Catharina J. M. Frijns, Peter R. Luijten, Jaco J. M. Zwanenburg et Jeroen Hendrikse. « High-resolution intracranial vessel wall MRI in an elderly asymptomatic population : comparison of 3T and 7T ». European Radiology 27, n^o 4 (7 juillet 2016) : 1585–95. http://dx.doi.org/10.1007/s00330-016-4483-3.

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Chang, Gregory, Cem M. Deniz, Stephen Honig, Kenneth Egol, Ravinder R. Regatte, Yudong Zhu, Daniel K. Sodickson et Ryan Brown. « MRI of the hip at 7T : Feasibility of bone microarchitecture, high-resolution cartilage, and clinical imaging ». Journal of Magnetic Resonance Imaging 39, n^o 6 (23 septembre 2013) : 1384–93. http://dx.doi.org/10.1002/jmri.24305.

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Spitz, Lena, Mareen Allgaier, Anastasios Mpotsaris, Daniel Behme, Bernhard Preim et Sylvia Saalfeld. « Segmentation of Circle of Willis from 7T TOF-MRI data and immersive exploration using VR ». Current Directions in Biomedical Engineering 8, n^o 1 (1 juillet 2022) : 129–32. http://dx.doi.org/10.1515/cdbme-2022-0033.

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Abstract 7T TOF MRI scans provide high resolution images of intracranial vasculature. When segmented, the Circle of Willis is detailed and thus opens up new possibilities, in research but also in education. We propose a segmentation pipeline for the Circle ofWillis, and introduce a prototype that enables exploration of not just the entire Circle of Willis, but also of its centerline, in an immersive VR enviroment. In our prototype, the model can be freely rotated, placed and scaled. A qualitative evaluation was performed with two experienced neuroradiologists, who rated the prototype and its potential positively.

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Korzowski, Andreas, et Peter Bachert. « High-resolution 31 P echo-planar spectroscopic imaging in vivo at 7T ». Magnetic Resonance in Medicine 79, n^o 3 (21 juin 2017) : 1251–59. http://dx.doi.org/10.1002/mrm.26785.

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Doss, Kishore Krishnagiri Manoj, Pei En Mion, Yu-Chieh Jill Kao, Tsung-Ter Kuo et Jyh-Cheng Chen. « Performance Evaluation of a PET of 7T Bruker Micro-PET/MR Based on NEMA NU 4-2008 Standards ». Electronics 11, n^o 14 (13 juillet 2022) : 2194. http://dx.doi.org/10.3390/electronics11142194.

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Purpose: This study aimed to measure the performance evaluation of the Bruker sequential micro-positron emission tomography/magnetic resonance imaging (PET/MRI) scanner by following National Electrical Manufacturers Association (NEMA) NU 4-2008 standards’ protocol. The system consists of a high-performance silicon photomultiplier (SiPM) advanced technology detector and a continuous lutetium-yttrium oxyorthosilicate (LYSO) crystal. Methods: A 22Na (sodium-22) point source was utilized to assess the spatial resolution and system sensitivity, and the Micro-PET scatter phantom measurements were conducted to measure count rate measurements and scatter fractions (SF). A mouse-like Micro-PET image quality (IQ) phantom was utilized as a model to analyze the uniformity, recovery coefficient (RC), and spillover ratio (SOR). A small animal PET/MRI imaging study was performed in a rat. Results: We calculated the spatial resolutions of filtered back-projection (FBP), and used 3D-MLEM to reconstruct PET images at the axial center and ¼ of the axial field of view (FOV) in axial, radial, and tangential directions. The best observed spatial resolutions in both reconstructed images were obtained in the tangential direction, and the values were 0.80 mm in 3D-MLEM and 0.94 mm in FBP. The peak noise equivalent count rate (NECR) in the 358–664 keV energy window was 477.30 kcps at 95.83 MBq and 774.45 kcps at 103.6 MBq for rat and mouse-sized scatter phantoms, respectively. The rat and mouse-sized phantoms scatter fractions (SF) were 14.2% and 6.9%, respectively. Conclusions: According to our results, the performance characteristics of the scanner are high sensitivity, good spatial resolution, low scatter fraction, and good IQ, indicating that it is suitable for preclinical imaging studies.

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Kilsdonk, ID, MD Steenwijk, PJW Pouwels, JJM Zwanenburg, F. Visser, PR Luijten, JJG Geurts, F. Barkhof et MP Wattjes. « Perivascular spaces in MS patients at 7 Tesla MRI : A marker of neurodegeneration ? » Multiple Sclerosis Journal 21, n^o 2 (10 juillet 2014) : 155–62. http://dx.doi.org/10.1177/1352458514540358.

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Background: Virchow-Robin spaces (VRS) are associated with vascular and neurodegenerative disease. In multiple sclerosis (MS), VRS have been associated with neuroinflammation. Ultra-high field imaging may be used to gain insight in these contradictory findings. Objective: The objective of this paper is to analyze VRS in MS patients using high-resolution 7 Tesla (T) MRI. Additionally, we investigated whether the widening of VRS is related to inflammatory or neurodegenerative aspects of MS. Methods: Thirty-four MS patients and 11 healthy controls were examined at 7T. Number and size of VRS were measured on three-dimensional (3D) T1-weighted images, and 3D fluid-attenuated inversion recovery (FLAIR) images were used for MS lesion detection. Brain atrophy was quantified by computing supratentorial brain volume fraction (sBVF). VRS counts were correlated with clinical variables, lesion count and sBVF. Results: MS patients displayed more VRS (median 11) than healthy controls (median four), p = 0.001. VRS size did not differ between both groups. VRS count in MS patients was associated with sBVF (rho = −0.40, p = 0.02), but not with lesion count ( p = 0.22). Conclusions: The 7T MRI reveals increased numbers of VRS in MS. The finding that VRS are associated with supratentorial brain atrophy, but not with lesion count, suggests that VRS might rather serve as a neurodegenerative than an inflammatory marker in MS.

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Priovoulos, Nikos, Heidi I. L. Jacobs, Dimo Ivanov, Kâmil Uludağ, Frans R. J. Verhey et Benedikt A. Poser. « High-resolution in vivo imaging of human locus coeruleus by magnetization transfer MRI at 3T and 7T ». NeuroImage 168 (mars 2018) : 427–36. http://dx.doi.org/10.1016/j.neuroimage.2017.07.045.

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Schindler, S., J. Schreiber, P. L. Bazin, R. Trampel, A. Anwander, U. Hegerl, S. Geyer et P. Schönknecht. « REMOVED : PB 14 Color up your MRI ! – performance of intensity standardisation techniques with 7T high-resolution MRIs ». Clinical Neurophysiology 128, n^o 10 (octobre 2017) : e320-e322. http://dx.doi.org/10.1016/j.clinph.2017.06.070.

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Yamada, Kenichi, Junichi Yoshimura, Masaki Watanabe et Kiyotaka Suzuki. « Application of 7 tesla magnetic resonance imaging for pediatric neurological disorders : Early clinical experience ». Journal of Clinical Imaging Science 11 (2 décembre 2021) : 65. http://dx.doi.org/10.25259/jcis_185_2021.

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Ultra-high field magnetic resonance imaging (MRI) has been introduced for use in pediatric developmental neurology. While higher magnetic fields have certain advantages, optimized techniques with specific considerations are required to ensure rational and safe use in children and those with pediatric neurological disorders (PNDs). Here, we summarize our initial experience with clinical translational studies that utilized 7 tesla (T)-MRI in the fields of developmental neurology. T2-reversed images and three-dimensional anisotropy contrast imaging enabled the depiction of targeted pathological brain structures with better spatial resolution. Diffusion imaging and susceptibility-weighted imaging enabled visualization of intracortical, subcortical, and intratumoral microstructures in vivo within highly limited scan times appropriate for patients with PNDs. 7T-MRI appears to have significant potential to enhance the depiction of the structural and functional properties of the brain, particularly those associated with atypical brain development.

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Schmitter, Sebastian, Susanne Schnell, Kâmil Uğurbil, Michael Markl et Pierre-François Van de Moortele. « Towards high-resolution 4D flow MRI in the human aorta using kt-GRAPPA and B1+ shimming at 7T ». Journal of Magnetic Resonance Imaging 44, n^o 2 (3 février 2016) : 486–99. http://dx.doi.org/10.1002/jmri.25164.

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Gallichan, Daniel, et José P. Marques. « Optimizing the acceleration and resolution of three-dimensional fat image navigators for high-resolution motion correction at 7T ». Magnetic Resonance in Medicine 77, n^o 2 (15 février 2016) : 547–58. http://dx.doi.org/10.1002/mrm.26127.

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Jorge, João, Frédéric Gretsch, Elena Najdenovska, Constantin Tuleasca, Marc Levivier, Philippe Maeder, Daniel Gallichan, José P. Marques et Meritxell Bach Cuadra. « Improved susceptibility‐weighted imaging for high contrast and resolution thalamic nuclei mapping at 7T ». Magnetic Resonance in Medicine 84, n^o 3 (12 février 2020) : 1218–34. http://dx.doi.org/10.1002/mrm.28197.

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Qian, Yongxian, Tiejun Zhao, Yik-Kiong Hue, Tamer S. Ibrahim et Fernando E. Boada. « High-resolution spiral imaging on a whole-body 7T scanner with minimized image blurring ». Magnetic Resonance in Medicine 63, n^o 3 (9 février 2010) : 543–52. http://dx.doi.org/10.1002/mrm.22215.

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Laule, Cornelia, Andrew Yung, Vlady Pavolva, Barry Bohnet, Piotr Kozlowski, Stanley A. Hashimoto, Stephen Yip, David KB Li et GR Wayne Moore. « High-resolution myelin water imaging in post-mortem multiple sclerosis spinal cord : A case report ». Multiple Sclerosis Journal 22, n^o 11 (11 juillet 2016) : 1485–89. http://dx.doi.org/10.1177/1352458515624559.

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Background: Loss of myelin in the spinal cord in multiple sclerosis (MS) is likely an important, and early, contributor to atrophy and associated disability. In vivo measurement of myelin is possible using myelin water fraction (MWF) imaging, but MWF has never been assessed in MS along the entire length of the spinal cord in vivo or in post-mortem tissue. Objective: To assess the feasibility of measuring the distribution of MWF along the entire length of the spinal cord in post-mortem MS tissue using high-field MRI. Methods: One formalin-fixed spinal cord from a female with secondary progressive MS (age: 78 years, disease duration: 25 years) was cut into 104 5-mm-thick cross sections along the entire length of the spinal cord from the cervico-medullary junction to the conus medullaris and imaged using a 64 echo T2 relaxation experiment at 7T. Results: Myelin water maps showed cord anatomy in superb detail, white matter demonstrating a higher MWF than the grey matter. Anatomical variation in myelin distribution along cervical, thoracic and lumbar regions was observed. Lesions demonstrated myelin loss. Conclusion: Post-mortem myelin water imaging of formalin-fixed MS spinal cord is feasible.

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Bebié, Pascal, Robert Becker, Volker Commichau, Jan Debus, Günther Dissertori, Lubomir Djambazov, Afroditi Eleftheriou et al. « SAFIR-I : Design and Performance of a High-Rate Preclinical PET Insert for MRI ». Sensors 21, n^o 21 (23 octobre 2021) : 7037. http://dx.doi.org/10.3390/s21217037.

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(1) Background: Small Animal Fast Insert for MRI detector I (SAFIR-I) is a preclinical Positron Emission Tomography (PET) insert for the Bruker BioSpec 70/30 Ultra Shield Refrigerated (USR) preclinical 7T Magnetic Resonance Imaging (MRI) system. It is designed explicitly for high-rate kinetic studies in mice and rats with injected activities reaching 500MBq, enabling truly simultaneous quantitative PET and Magnetic Resonance (MR) imaging with time frames of a few seconds in length. (2) Methods: SAFIR-I has an axial field of view of 54.2mm and an inner diameter of 114mm. It employs Lutetium Yttrium OxyorthoSilicate (LYSO) crystals and Multi Pixel Photon Counter (MPPC) arrays. The Position-Energy-Timing Application Specific Integrated Circuit, version 6, Single Ended (PETA6SE) digitizes the MPPC signals and provides time stamps and energy information. (3) Results: SAFIR-I is MR-compatible. The system’s Coincidence Resolving Time (CRT) and energy resolution are between separate-uncertainty 209.0(3)ps and separate-uncertainty 12.41(02) Full Width at Half Maximum (FWHM) at low activity and separate-uncertainty 326.89(12)ps and separate-uncertainty 20.630(011) FWHM at 550MBq, respectively. The peak sensitivity is ∼1.6. The excellent performance facilitated the successful execution of first in vivo rat studies beyond 300MBq. Based on features visible in the acquired images, we estimate the spatial resolution to be ∼2mm in the center of the Field Of View (FOV). (4) Conclusion: The SAFIR-I PET insert provides excellent performance, permitting simultaneous in vivo small animal PET/MR image acquisitions with time frames of a few seconds in length at activities of up to 500MBq.

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Movahedian Attar, Fakhereh, Evgeniya Kirilina, Daniel Haenelt, Kerrin J. Pine, Robert Trampel, Luke J. Edwards et Nikolaus Weiskopf. « Mapping Short Association Fibers in the Early Cortical Visual Processing Stream Using In Vivo Diffusion Tractography ». Cerebral Cortex 30, n^o 8 (8 avril 2020) : 4496–514. http://dx.doi.org/10.1093/cercor/bhaa049.

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Abstract Short association fibers (U-fibers) connect proximal cortical areas and constitute the majority of white matter connections in the human brain. U-fibers play an important role in brain development, function, and pathology but are underrepresented in current descriptions of the human brain connectome, primarily due to methodological challenges in diffusion magnetic resonance imaging (dMRI) of these fibers. High spatial resolution and dedicated fiber and tractography models are required to reliably map the U-fibers. Moreover, limited quantitative knowledge of their geometry and distribution makes validation of U-fiber tractography challenging. Submillimeter resolution diffusion MRI—facilitated by a cutting-edge MRI scanner with 300 mT/m maximum gradient amplitude—was used to map U-fiber connectivity between primary and secondary visual cortical areas (V1 and V2, respectively) in vivo. V1 and V2 retinotopic maps were obtained using functional MRI at 7T. The mapped V1–V2 connectivity was retinotopically organized, demonstrating higher connectivity for retinotopically corresponding areas in V1 and V2 as expected. The results were highly reproducible, as demonstrated by repeated measurements in the same participants and by an independent replication group study. This study demonstrates a robust U-fiber connectivity mapping in vivo and is an important step toward construction of a more complete human brain connectome.

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