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Littérature scientifique sur le sujet « High resolution 7T MRI »

Auteur : Grafiati

Publié le 9 mars 2023

Mis à jour le 10 mars 2023

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Articles de revues sur le sujet "High resolution 7T MRI"

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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Thèses sur le sujet "High resolution 7T MRI"

MILESI, GLORIA. « Temporal lobe epilepsy : a combined study with high field (7T) Magnetic Resonance Imaging and optical and ultrastructural histopathology ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2014. http://hdl.handle.net/10281/80943.

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Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy with 60-75% of cases reported in surgical series. The hippocampus is involved in the genesis of the seizures and hippocampal sclerosis (HS) is the most frequent neuropathological finding observed in surgical samples. However extra-hippocampal neocortical structures may also be involved and the focal cortical dysplasia (FCD) is the most common second alteration frequently associated with HS. Aim of this project was to clarify, both at radiological and neuropathological level, the abnormalities frequently observed in the temporal pole of many TLE patients as the focal cortical dysplasia, the hippocampal sclerosis and the radiological alteration of grey/white matter boundary called “blurring”. The study was performed on surgical specimens of human temporal cortices and hippocampi from TLE patients and autoptic hippocampi at different stage of development submitted first to high resolution (7T) MRI and then processed for histological analysis. Comparison between 7T MRI data with corresponding histological and immunohistochemical features was done. The first part of this study demonstrates that thanks to differences in MRI signal intensities, depending on different density and distribution of cells and myelin fibres, high-resolution ex-vivo MRI enables to visualize the intracortical organization in normal and pathological areas and can detect the subtle architectural alterations in samples presenting dysplastic cortex. The temporo-polar blurring has demonstrated to be due to a great degeneration of fibre bundles in the white matter and, since the age at epilepsy onset is earlier in patients with blurring in comparison to those without blurring, these data suggest that it consists in a slowly evolving chronic degeneration process with the redistribution of the remaining fibres. The comparative imaging-histology investigation on healthy hippocampal specimens shows that 7T MRI can identify the main anatomical structures and the sublayers of the normal hippocampus along its anterior-posterior axis. In sclerotic surgical hippocampi high resolution MRI reveals areas of anomalous hyperintensity of signal associated to marked loss of neurons and intense gliosis as visualized by histological analysis for neuronal and glial cells. Moreover the investigation of intrahippocampal projections performed using fractional anisotropy and fiber tracking, demonstrates a disorganization of fibers in sclerotic samples in comparison to normal hippocampi. The same experimental protocol applied to healthy autoptic hippocampi at different stage of development reveals that during fetal period the MRI signal is related to the cellular density, in fact the regions characterized by densely packed neurons are easily recognizable on ex vivo high field MRI as hypointense areas, while in post-natal specimens the MRI signal is still linked to the cell density but, with the appearance and the progressive increase of the myelin fibers content, this correlation becomes less obvious and the myelin represent the histological component which mainly contributes on MRI signal intensity. This study shows the potential utility of ex-vivo high-field MRI in the understanding of temporal cortical and hippocampal abnormalities, included developmental hippocampal changes, and suggests its possible application in vivo in the near future for the study of several disorders.

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d'Arcy, James Andrew. « High resolution and rapid MRI ». Thesis, Institute of Cancer Research (University Of London), 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544181.

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Manivannan, Niranchana. « Super Resolution in Ultra High Field MRI - A Comparison ». The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1293632071.

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Ohno, Ayami. « The comparison of high-resolution diffusion weighted imaging (DWI) with high-resolution contrast-enhanced MRI in the evaluation of breast cancers ». Kyoto University, 2020. http://hdl.handle.net/2433/259003.

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Sahebjavaher, Ramin. « Development of a desktop high-resolution MRI for microflow visualization ». Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2613.

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Research in lab-on-a-chip (LOC) technology involving microfluidics is a growing field aiming at the development of miniaturized biomedical systems with rich functionality. In order to design effective LOC microfluidic systems, the flow fields and the fluids inside LOC devices need to be carefully characterized. High-resolution magnetic resonance imaging (MRI) offers a powerful non-intrusive technology for this application. In this thesis, the design and implementation of a prototype for a desktop high-resolution MRI instrument, consisting of a magnet, gradient coils, gradient amplifiers, and radio frequency (RF) electronics, is presented. To reduce the size and cost of this MRI instrument, a permanent magnetic configuration with a magnetic flux density of 0.6 T is designed with off-the-shelf NdFeB permanent magnets. The coils of the triaxial gradient module are developed using a novel lithography technique. This gradient module is capable of generating gradient fields as high as 2.83 T/m with custom made current amplifiers. The radio frequency (RF) probe is integrated with the gradient module and is connected to the RF electronics which are made using off-the-shelf components. Pulse sequences and signal processing for acquiring static images and velocity profiles are described. The performance of this instrument in terms of static and dynamic image resolution are presented. As a preliminary test, the velocity profile of water flowing inside a small tube was measured with a nominal resolution of 40 μm. The instrument is designed for a static resolution of better than 30 μm and a velocity resolution better than 50 μm/s. Improvements to the current instrument in addition to theoretical limitations are also detailed.

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Al, Mohamad Zakriya Ali E. « Quantitative assessment of the biochemical composition of equine cartilage using 7T ultra-high field magnetic resonance imaging (MRI) techniques ». Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/8227/.

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Equine fetlock region disease is responsible for significant morbidity and mortality. Diagnosis of sesamoidean ligament, cartilage and subchondral bone injury has been obtained by clinical MRI. Low-field MRI provides images helpful in the investigation of MCPJ/MTPJ region pathology in horses in the clinical setting but the greater resolution of high and ultra-field MR images has the potential to aid interpretation through a better understanding of MRI anatomy. Quantitative MRI could provide a non-invasive technique to determine tissue biochemical properties associated with the early onset of articular cartilage degenerative conditions such as osteoarthritis. So far, ultra-high field MRI has not been used in equine research and practice. However, recently 3T MRI has been introduced in equine hospitals in Europe and the US. The general objectives of this project, which utilised cadaver limbs, was to improve understanding of the MRI anatomy of the equine MCPJ/MTPJ region and to evaluate the use of MRI for the non-invasive, quantitative assessment of articular cartilage from the same region. The first specific objective was to describe the appearance of the normal anatomy of the equine MCPJ/MTPJ region, especially the SDFT & DDFT and DSLs, using high field (1.5T) and ultra high field (7T) MRI and to compare the images obtained with the two systems. The second objective was to determine the accuracy and precision of articular cartilage thickness measurements using 1.5T and 7T MRI and comparing the measurements with those made from histological sections of the MCPJ/MTPJ. The third objective was to measure T1 & T2 MRI sequence relaxation times for normal horse articular cartilage pre and post gadolinium contrast (dGEMRIC) administration and to determine their correlation with GAG concentration, including a description of topographical variation. The fourth objective was to compare sodium concentration in normal equine MCPJ/MTPJ articular cartilage measured using 7T MR imaging with a dual tuned quadrature 23Na/1H coil with the biochemical properties (sodium concentration determined by flame photometry and GAG concentration). The final objective was to evaluate MR sodium imaging for the assessment of enzymatically degraded equine cartilage. The findings demonstrated that 7T MRI produces high resolution images, which enable better evaluation of the hard and soft tissues of the equine MCPJ/MTPJ region than images from lower field MR systems and which permit accurate and precise articular cartilage thickness measurements to be made. Moreover, it was found that the dGEMRIC technique appears to provide a feasible quantitative tool for evaluating the articular cartilage properties. However, the quantitative parameters determined by the dGEMRIC method cannot fully characterise the biochemical properties of the cartilage. Moreover, delayed gadolinium-enhanced (dGEMRIC) techniques are time consuming, requiring relatively long incubation and scanning times. The measurement of T2 time is a very complex method. The work described in the last chapters demonstrated that sodium MRI was significantly correlated with the biochemical properties of the equine articular cartilage. Therefore the sodium MRI technique showed promise in imaging articular cartilage and providing useful information on the biochemical properties of the cartilage.

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Balu, Niranjan. « Quantitative characterization of carotid arterial remodeling by high-resolution serial MRI / ». Thesis, Connect to this title online ; UW restricted, 2007. http://hdl.handle.net/1773/8112.

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Macnair, Andrew. « A targetted system for high resolution in vivo broad-line MRI ». Thesis, University of Kent, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294314.

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Hurley, Christopher Anthony. « The development of normoxic polymer gel dosimetry using high resolution MRI ». Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16442/1/Christopher_Hurley_Thesis.pdf.

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Dosimetry is a vital component of treatment planning in radiation therapy. Methods of radiation dosimetry currently include the use of: ionization chambers, thermoluminescent dosimeters (TLDs), solid-state detectors and radiographic film. However, these methods are inherently either 1D or 2D and their use involves the perturbation of the radiation beam. Although the dose distribution within tissues following radiation therapy treatments can be modeled using computerized treatment planning systems, a need exists for a dosimeter that can accurately measure dose distributions directly and produce 3D dose maps. Some radiation therapy and brachytherapy treatments require mapping the dose distributions in high-resolution (typically < 1 mm). A dosimetry technique that is capable of producing high resolution 3D dose maps of the absorbed dose distribution within tissues is required. Gel dosimetry is inherently a 3D integrating dosimeter that offers high spatial resolution, precision and accuracy. Polymer gel dosimetry is founded on the basis that monomers dissolved in the gel matrix polymerize due to the presence of free radicals produced by the radiolysis of water molecules. The amount of polymerization that occurs within a polymer gel dosimeter can be correlated to the absorbed dose. The gel matrix maintains the spatial integrity of the polymers and hence a dose distribution can be determined by imaging the irradiated polymer gel dosimeter using an imaging modality such as MRI, x-ray computed tomography (CT), ultrasound, optical CT or vibrational spectroscopy. Polymer gel dosimeters, however, suffer from oxygen contamination. Oxygen inhibits the polymerization reaction and hence polymer gel dosimeters must be manufactured, irradiated and scanned in hypoxic environments. Normoxic polymer gel dosimeters incorporate an anti-oxidant into the formulation that binds the oxygen present in the gel and allows the dosimeter to be made under normal atmospheric conditions. The first part of this study was to provide a comprehensive investigation into various formulations of polymer and normoxic polymer gel dosimeters. Several parameters were used to characterize and assess the performance of each formulation of polymer gel dosimeter including: spatial resolution and stability, temporal stability of the R2-dose response, optimal R2-dose response for changes in concentration of constituents and the effects of oxygen infiltration. This work enabled optimal formulations to be determined that would provide greater dose sensitivity. Further work was done to investigate the chemical kinetics that take place within normoxic polymer gel dosimeters from manufacture to post-irradiation. This study explored the functions that each of the constituent chemicals plays in a polymer gel dosimeter. Although normoxic polymer gel dosimeters exhibit very similar characteristics to polyacrylamide polymer gel dosimeters, one important difference between them was found to be a decrease in R2-dose sensitivity over time in the normoxic polymer gel dosimeter compared to an increase in the polyacrylamide polymer gel dosimeters. From an investigation into the function of anti-oxidants in normoxic polymer gel dosimeters, alternatives were proposed. Several alternative anti-oxidants were explored in this study that found that whilst some were reasonably effective, tetrakis (hydroxymethyl) phosphonium chloride (THPC) had the highest reaction rate. THPC was found not only to be an aggressive scavenger of oxygen, but also to increase the dose sensitivity of the gel. Hence, a formulation of normoxic polymer gel dosimeter was proposed, called MAGAT, that comprised: methacrylic acid, gelatin, hydroquinone and THPC. This formulation was examined in a similar fashion to the studies of the other formulations of polymer and normoxic polymer gel dosiemeters. The gel was found to exhibit spatial and temporal stability and an optimal formulation was proposed based on the R2-dose response. Applications such as IVBT require high-resolution dosimetry. Combined with high-resolution MRI, polymer gel dosimetry has potential as a high-resolution 3D integrated dosimeter. Thus, the second component of this study was to commission a micro-imaging MR spectrometer for use with normoxic polymer gel dosimeters and investigate artifacts related to imaging in high-resolutions. Using high-resolution MRI requires high gradient strengths that, combined with the Brownian motion of water molecules, was found to produce an attenuation of the MR signal and hence lead to a variation in the measured R2. The variation in measured R2 was found to be dependent on both the timing and amplitude of pulses in the pulse sequence used during scanning. Software was designed and coded that could accurately determine the amount of variation in measured R2 based on the pulse sequence applied to a phantom. Using this software, it is possible to correct for differences between scans using different imaging parameters or pulse sequences. A normoxic polymer gel dosimeter was irradiated using typical brachytherapy delivery and the resulting dose distributions compared with dose points predicted by the computerized treatment planning system.The R2-dose response was determined and used to convert the R2 maps of the phantoms to dose maps. The phantoms and calibration vials were imaged with an in-plane resolution of 0.1055 mm/pixel and a slice thickness of 2 mm. With such a relatively large slice thickness compared to the in-plane resolution, partial volume effects were significant, especially in the region immediately adjacent the source where high dose gradients typically exist. Estimates of the partial volume effects at various distances within the phantom were determined using a mathematical model based on dose points from the treatment planning system. The normalized and adjusted dose profiles showed very good agreement with the dose points predicted by the treatment planning system.

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Hurley, Christopher Anthony. « The development of normoxic polymer gel dosimetry using high resolution MRI ». Queensland University of Technology, 2006. http://eprints.qut.edu.au/16442/.

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Livres sur le sujet "High resolution 7T MRI"

Practical MR mammography : High-resolution MRI of the breast. 2^e éd. Stuttgart : Thieme, 2012.

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Fischer, Uwe. Practical MR Mammography : High-Resolution MRI of the Breast. Thieme Medical Publishers, Incorporated, 2012.

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Slegte, R. G. M. Cisternographic Anatomy of the Posterior Cranial Fossa : High Resolution Ct and Mri Study. Van Gorcum Ltd, 1986.

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McGonagle, Dennis, et Iris Eshed. MRI. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198737582.003.0018.

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The features of psoriatic arthritis (PsA) are disparate—from peripheral synovitis to axial inflammation, from bone destruction to bone formation or both, and nail disease. Fat suppression magnetic resonance imaging (MRI) has had a major impact on understanding PsA. MRI suggests a unifying anatomical basis for PsA with the common denominator of disease localization to entheses and adjacent bone and other sites of high biomechanical stress. MRI has also shown that entheseal changes are not uncommon in generalized osteoarthritis and occasionally in normals, making careful clinical correlation essential for imaging interpretation. MRI is useful in predicting the course of axial spondyloarthritis but there are no specific studies in axial PsA; most data comes from ankylosing spondylitis. Additionally MRI has been used for monitoring therapeutic response in PsA where good resolution of enthesitis/osteitis has been reported. Further studies are needed to define the role of MRI in measuring biological remission of PsA.

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Kastler, Bruno, et Adrian Kastler. Lumbar Sympathetic Block and Neurolysis : Computed Tomography. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199908004.003.0031.

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Lumbar sympathetic block and neurolysis are accepted treatment procedures in patients with sympathetic mediated lower limb pain and patients with advanced peripheral arterial disease. The use of imaging guidance is highly recommended in order to achieve best possible results and to avoid complications. The high image resolution (as opposed to fluoroscopy) and high availability (as opposed to MRI) offered by CT makes it the imaging guidance technique preferred. This chapter reviews the indications of lumbar sympathetic chain blockade and neurolysis and the basic anatomical background. Then it demonstrates how CT guidance allows a step-by-step control of positioning the needle tip at the target for either lumbar blockade or alcohol neurolysis and the advantages and disadvantages of each technique are summarized.

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Hayashi, Daichi, Ali Guermazi et Frank W. Roemer. Radiography and computed tomography imaging of osteoarthritis. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199668847.003.0016.

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Osteoarthritis (OA) is the most prevalent joint disorder in the elderly worldwide and there is still no effective treatment, other than joint arthroplasty for end-stage OA, despite ongoing research efforts. Imaging is essential for assessing structural joint damage and disease progression. Radiography is the most widely used first-line imaging modality for structural OA evaluation. Its inherent limitations should be noted including lack of ability to directly visualize most OA-related pathological features in and around the joint, lack of sensitivity to longitudinal change and missing specificity of joint space narrowing, and technical difficulties regarding reproducibility of positioning of the joints in longitudinal studies. Magnetic resonance imaging (MRI) is widely applied in epidemiological studies and clinical trials. Computed tomography (CT) is an important additional tool that offers insight into high-resolution bony anatomical details and allows three-dimensional post-processing of imaging data, which is of particular importance for orthopaedic surgery planning. However, its major disadvantage is limitations in the assessment of soft tissue structures compared to MRI. CT arthrography can be useful in evaluation of focal cartilage defects or meniscal tears; however, its applicability may be limited due to its invasive nature. This chapter describes the roles and limitations of both conventional radiography and CT, including CT arthrography, in clinical practice and OA research. The emphasis is on OA of the knee, but other joints are also mentioned where appropriate.

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Kaufmann, Philipp A., et Oliver Gaemperli. Hybrid Cardiac Imaging. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199392094.003.0028.

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Assessment of both coronary anatomy and myocardial perfusion are equally important for the appropriate treatment of patients with stable coronary artery disease. Cardiac hybrid imaging allows integration of coronary anatomy and perfusion in one all-in-one image, thereby avoiding mental integration of findings. In selected subgroups of patients, cardiac hybrid imaging has demonstrated superior diagnostic accuracy compared to single modalities. The combination of coronary anatomy and function provides incremental prognostic information and improves risk stratification of patients with suspected or known CAD. Aside from CT coronary angiography, coronary artery calcium score (CACS) scans obtained from native ECG-triggered CT are used for hybrid imaging. They are used either for attenuation correction, or can be combined with radionuclide information to improve CAD detection and risk stratification. A large number of integrated hybrid scanners are commercially available and offer advantages for cardiac hybrid imaging. However, these devices are not mandatory, and hybrid imaging is perfectly feasible from two separate datasets using appropriate image fusion software. Cardiac magnetic resonance has entered the arena of hybrid imaging and several integrated PET/MRI devices are already commercially available. Its advantages include the lack of ionizing radiation and a high spatial resolution, particularly for soft tissue structures. In research, hybrid imaging moves beyond its conventional borders of perfusion imaging to target specific molecular or biological pathways that underlie cardiac disease, a concept known as molecular imaging. The combination of radionuclide imaging with CT or MRI offers attractive features to co-localize biological signals from radiolabeled targeted compounds with microanatomical structures.

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Kaeley, Gurjit S. Use of ultrasound in psoriatic arthritis. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198737582.003.0017.

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Psoriatic arthritis (PsA) is much more than just joint disease. Although previous clinical classifications have categorized by pattern of joint involvement and axial disease, imaging techniques such as MRI and ultrasound have demonstrated that not only are many more joints involved but also a wide variety of adjoining tissues. The concept of enthesitis is evolving and high resolution imaging studies are demonstrating involvement of tissues beyond just the enthesis. Many investigators have chosen to use sonographic entheseal systems designed for Spondyloarthritis in general which may not be appropriate and may lead to excess confounding by obesity. Inclusion of entheses that seem more relevant to PsA may improve the validity and specificity of the sonographic outcome tool. Nail affliction is associated with PsA, as well as enthesitis. Sonography is able to demonstrate the nail apparatus. More recent pathoanatomic findings may help explain the close link with enthesitis. Synovitis in PsA is often involved with inflammation and alteration of neighbouring structures such as the extensor tendons, palmar or plantar plates. Some investigators have proposed that inflammation in PsA may start at the entheseal sites and then spread to the joint. Dactylitis epitomizes the concept of multiple tissues involved in the digit giving rise to the clinical appearance of a uniformly swollen digit. Sonography can image many of these tissues in high resolution and offer insights into the pathophysiology of dactylitis.

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Chapitres de livres sur le sujet "High resolution 7T MRI"

Raitsimring, Arnold M., Andrei V. Astashkin et Peter Caravan. « High-Frequency EPR and ENDOR Characterization of MRI Contrast Agents ». Dans High Resolution EPR, 581–621. New York, NY : Springer New York, 2009. http://dx.doi.org/10.1007/978-0-387-84856-3_14.

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Anctil-Robitaille, Benoit, Christian Desrosiers et Herve Lombaert. « Manifold-Aware CycleGAN for High-Resolution Structural-to-DTI Synthesis ». Dans Computational Diffusion MRI, 213–24. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-73018-5_17.

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Nath, Vishwesh, Prasanna Parvathaneni, Colin B. Hansen, Allison E. Hainline, Camilo Bermudez, Samuel Remedios, Justin A. Blaber et al. « Inter-Scanner Harmonization of High Angular Resolution DW-MRI Using Null Space Deep Learning ». Dans Computational Diffusion MRI, 193–201. Cham : Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05831-9_16.

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Young, I. R., J. V. Hajnal, A. Oatridge, J. A. Wilson et G. M. Bydder. « High Resolution Studies of Oxygen, Carbogen and Carbon Dioxide in the Brain — with Supporting Findings from Peripheral Muscle ». Dans Functional MRI, 36–40. Milano : Springer Milan, 1996. http://dx.doi.org/10.1007/978-88-470-2194-5_8.

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Odille, Freddy, Aurélien Bustin, Bailiang Chen, Pierre-André Vuissoz et Jacques Felblinger. « Motion-Corrected, Super-Resolution Reconstruction for High-Resolution 3D Cardiac Cine MRI ». Dans Lecture Notes in Computer Science, 435–42. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-24574-4_52.

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Fernández, Elsa, Manuel Graña et Jorge Villanúa. « High Resolution Segmentation of CSF on Phase Contrast MRI ». Dans New Challenges on Bioinspired Applications, 96–103. Berlin, Heidelberg : Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-21326-7_11.

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Speck, Oliver. « What to do with All that Signal ? Issues of High-resolution MRI ». Dans High-Field MR Imaging, 127–34. Berlin, Heidelberg : Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/174_2010_102.

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Latt, L. Daniel, Gokhan Kuyumcu et Mihra S. Taljanovic. « High-Resolution Ultrasound and MRI Imaging of Peroneal Tendon Injuries ». Dans The Peroneal Tendons, 97–123. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-46646-6_5.

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Kim, Seong-Gi, et Sung-Hong Park. « High-Resolution Venographic BOLD MRI of Animal Brain at 9.4 T : Implications for BOLD fMRI ». Dans Susceptibility Weighted Imaging in MRI, 637–47. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9780470905203.ch34.

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Moore, John, Maria Drangova, Marcin Wierzbicki, John Barron et Terry Peters. « A High Resolution Dynamic Heart Model Based on Averaged MRI Data ». Dans Lecture Notes in Computer Science, 549–55. Berlin, Heidelberg : Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-540-39899-8_68.

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Actes de conférences sur le sujet "High resolution 7T MRI"

Ramadass, Karthik, Francois Rheault, Leon Y. Cai, Lucas W. Remedios, Micah D'Archangel, Ilwoo Lyu, Laura A. Barquero et al. « Ultra-high-resolution mapping of cortical layers 3T-guided 7T MRI ». Dans Image Processing, sous la direction de Ivana Išgum et Olivier Colliot. SPIE, 2022. http://dx.doi.org/10.1117/12.2611857.

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Lerche, C., M. Lenz, W. Bi, J. Scheins, L. Tellmann, CH Choi, ER Kops et al. « Design and Simulation of a high-resolution and high-sensitivity BrainPET insert for 7T MRI ». Dans NuklearMedizin 2020. © Georg Thieme Verlag KG, 2020. http://dx.doi.org/10.1055/s-0040-1708248.

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Rengle, A., M. Armenean, R. Bolbos, J.-C. Goebel, A. Pinzano-Watrin, H. Saint-Jalmes, P. Gillet et O. Beuf. « A dedicated two-element phased array receiver coil for high resolution MRI of rat knee cartilage at 7T ». Dans 2007 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE, 2007. http://dx.doi.org/10.1109/iembs.2007.4353182.

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Haldar, Justin P., et Zhi-Pei Liang. « High-Resolution Diffusion MRI ». Dans 2007 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE, 2007. http://dx.doi.org/10.1109/iembs.2007.4352286.

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Derzhavskaya, T. A., S. B. Glybovski, A. A. Hurshkainen, I. V. Melchakova, A. J. E. Raaijmakers et C. A. T. van den Berg. « Decoupling capabilities of mushroom-type high-impedance metasurfaces in 7T MRI applications ». Dans 2015 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference (IMOC). IEEE, 2015. http://dx.doi.org/10.1109/imoc.2015.7369220.

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Lezhennikova, K., A. Raaijmakers, C. Simovski, R. Abdeddaim et S. Glybovski. « An extended birdcage coil for 7T MRI with a high-impedance shield ». Dans INTERNATIONAL CONFERENCE ON PHYSICS AND CHEMISTRY OF COMBUSTION AND PROCESSES IN EXTREME ENVIRONMENTS (COMPHYSCHEM’20-21) and VI INTERNATIONAL SUMMER SCHOOL “MODERN QUANTUM CHEMISTRY METHODS IN APPLICATIONS”. AIP Publishing, 2020. http://dx.doi.org/10.1063/5.0032571.

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Nakajima, Mitsuko, Martina Callaghan, Nicola Hobbs, Geraint Rees, Sarah J. Tabrizi et Peter McColgan. « E09 Quantitative MRI profiles across motor cortex cortical layers in premanifest Huntington’s disease using 7T MRI at 600μm resolution ». Dans EHDN 2022 Plenary Meeting, Bologna, Italy, Abstracts. BMJ Publishing Group Ltd, 2022. http://dx.doi.org/10.1136/jnnp-2022-ehdn.85.

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Almansour, Mohamed, Nagia M. Ghanem et Soheir Bassiouny. « High-Resolution MRI Brain Inpainting ». Dans 2021 IEEE EMBS International Conference on Biomedical and Health Informatics (BHI). IEEE, 2021. http://dx.doi.org/10.1109/bhi50953.2021.9508561.

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Attaran, Ali, Kyle M. Gilbert, Blaine A. Chronik et Ravi S. Menon. « Small footprint high gain and low noise figure preamplifier for 7T MRI scanner ». Dans 2017 IEEE 30th Canadian Conference on Electrical and Computer Engineering (CCECE). IEEE, 2017. http://dx.doi.org/10.1109/ccece.2017.7946614.

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Pearlman, Justin D., et Vivek V. Sukhatme. « High-resolution atheroma mixture-modeled MRI ». Dans Photonics West '98 Electronic Imaging, sous la direction de Robert F. Erbacher et Alex Pang. SPIE, 1998. http://dx.doi.org/10.1117/12.309545.

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Rapports d'organisations sur le sujet "High resolution 7T MRI"

Rosenkrantz, Andrew B. Prostate Cancer Detection Using High-Spatial Resolution MRI at 7.0 Tesla : Correlation with Histopathologic Findings at Radical Prostatectomy. Fort Belvoir, VA : Defense Technical Information Center, octobre 2012. http://dx.doi.org/10.21236/ada568025.

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