scholarly journals Experimental and numerical investigations of a small animal coil for ultra-high field magnetic resonance imaging (7T)

2019 ◽  
Vol 5 (1) ◽  
pp. 525-528 ◽  
Author(s):  
Maíra M. Garcia ◽  
Tiago R. Oliveira ◽  
Daniel Papoti ◽  
Khallil T. Chaim ◽  
Maria C. G. Otaduy ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Small Animal ◽  
Small Animals ◽  
Rf Coil ◽  
Resonance Imaging ◽  
Ultra High Field ◽  
Good Image Quality ◽  
Magnetic Resonance Imaging Mri ◽  
The University

AbstractThe purpose of this work was to develop and investigate a radiofrequency (RF) coil to perform image studies on small animals using the 7T magnetic resonance imaging (MRI) system, installed in the imaging platform in the autopsy room (Portuguese acronym PISA), at the University of Sao Paulo, Brazil, which is the unique 7T MRI scanner installed in South America. Due to a high demand to create new specific coils for this 7T system, it is necessary to carefully assess the distribution of electromagnetic (EM) fields generated by the coils and evaluate the patient/object safety during MRI procedures. To achieve this goal 3D numerical methods were used to design and analyse a 8-rungs transmit/receive linearly driven birdcage coil for small animals. Calculated magnetic field (B1) distributions generated by the coil were crosschecked with measured results, indicating good confidence in the simulated results. Electric field results were post-processed and predictions of local specific absorption rate (SAR) values were achieved for a spherical phantom filled with muscle-like tissue, indicating that the sample would not suffer any unsafe deposition of energy. Post mortem abdomen images obtained from a rat presented good image quality and no artifacts related to field non-homogeneity were observed.

scholarly journals Numerical Analysis of a Flexible Dual Loop Coil and its Experimental Validation for pre-Clinical Magnetic Resonance Imaging of Rodents at 7 T

2016 ◽  
Vol 16 (6) ◽  
pp. 294-299 ◽  
Author(s):  
S. Solis-Najera ◽  
F. Vazquez ◽  
R. Hernandez ◽  
O. Marrufo ◽  
A.O. Rodriguez
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Imaging System ◽  
Ex Vivo ◽  
Small Animal ◽  
Magnetic Resonance Imaging System ◽  
External Diameter ◽  
Rf Coil ◽  
Resonance Imaging ◽  
Clinical Magnetic Resonance Imaging

Abstract A surface radio frequency coil was developed for small animal image acquisition in a pre-clinical magnetic resonance imaging system at 7 T. A flexible coil composed of two circular loops was developed to closely cover the object to be imaged. Electromagnetic numerical simulations were performed to evaluate its performance before the coil construction. An analytical expression of the mutual inductance for the two circular loops as a function of the separation between them was derived and used to validate the simulations. The RF coil is composed of two circular loops with a 5 cm external diameter and was tuned to 300 MHz and 50 Ohms matched. The angle between the loops was varied and the Q factor was obtained from the S11 simulations for each angle. B1 homogeneity was also evaluated using the electromagnetic simulations. The coil prototype was designed and built considering the numerical simulation results. To show the feasibility of the coil and its performance, saline-solution phantom images were acquired. A correlation of the simulations and imaging experimental results was conducted showing a concordance of 0.88 for the B1 field. The best coil performance was obtained at the 90° aperture angle. A more realistic phantom was also built using a formaldehyde-fixed rat phantom for ex vivo imaging experiments. All images showed a good image quality revealing clearly defined anatomical details of an ex vivo rat.

Radial magnetic resonance imaging (MRI) using a rotating radiofrequency (RF) coil at 9.4 T

2017 ◽  
Vol 31 (2) ◽  
pp. e3860 ◽  
Author(s):  
Mingyan Li ◽  
Ewald Weber ◽  
Jin Jin ◽  
Thimo Hugger ◽  
Yasvir Tesiram ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Rf Coil ◽  
Resonance Imaging ◽  
Magnetic Resonance Imaging Mri

scholarly journals Magnetic Resonance Imaging (MRI) for the Horse

EDIS ◽  
2013 ◽  
Vol 2013 (6) ◽  
Author(s):  
Alison Morton
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Poor Performance ◽  
Resonance Imaging ◽  
University Of Florida ◽  
Full Color ◽  
Imaging Service ◽  
Magnetic Resonance Imaging Mri ◽  
The University

The veterinarians of the University of Florida Equine Lameness & Imaging Service specialize in the treatment and rehabilitation of poor performance in sport horses. This series of one-page full color fact sheets describes various diagnostic and imaging services available for diagnosing and treating lameness issues in horses. http://edis.ifas.ufl.edu/topic_series_equine_lameness_and_imaging_service

scholarly journals Magnetic Resonance Imaging in Animal Models of Alzheimer’s Disease Amyloidosis

2021 ◽  
Author(s):  
Ruiqing Ni
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Animal Models ◽  
Amyloid Beta ◽  
High Field ◽  
Diffusion Tensor ◽  
Small Animal ◽  
Resonance Imaging ◽  
Magnetic Resonance Imaging Mri

Amyloid-beta plays an important role in the pathogenesis of Alzheimer’s disease. Aberrant amyloid-beta and tau accumulation induce neuroinflammation, cerebrovascular alterations, synaptic deficits, functional deficits, and neurodegeneration, leading to cognitive impairment. Animal models recapitulating the amyloid-beta pathology such as transgenic, knock-in mouse and rat models have facilitated the understanding of disease mechanisms and development of therapeutics targeting at amyloid-beta. There is a rapid advance in high-field MR in small animals. Versatile high-field magnetic resonance imaging (MRI) sequences such as diffusion tensor imaging, arterial spin labelling, resting-state functional MRI, anatomical MRI, MR spectroscopy as well as contrast agents have been developed for the applications in animal models. These tools have enabled high-resolution in vivo structural, functional, and molecular readouts with a whole brain field-of-view. MRI have been utilized to visualize non-invasively the amyloid-beta deposits, synaptic deficits, regional brain atrophy, impairment in white matter integrity, functional connectivity, cerebrovascular and glymphatic system in animal models of amyloidosis. Many of the readouts are translational in clinical MRI in the brain of patients with Alzheimer’s disease. In this review, we summarize the recent advance of using MRI for visualizing the pathophysiology in amyloidosis animal model. We discuss the outstanding challenges in brain imaging using MRI in small animal and propose future outlook in visualizing amyloid-beta-related alterations in brain of animal models.

scholarly journals Medullar Kock without Pott: 13 cases observed at the university hospital center of Conakry, Guinea

2019 ◽  
Author(s):  
Fode Abass Cisse ◽  
Foksouna Sakadi ◽  
Nana Rahamatou Aminou Tassiou ◽  
Amadou Talibe Balde ◽  
Arcel Steven Nitcheu Woga ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
University Hospital ◽  
Resonance Imaging ◽  
Neurological Signs ◽  
Diagnostic Certainty ◽  
Magnetic Resonance Imaging Mri ◽  
Compressive Myelopathy ◽  
The University ◽  
Hospital Center

Background: The diagnostic certainty of medullar tuberculosis (TB) without Pott disease is difficult to establish in a tropical environment with the large group of infectious, parasitic, and systemic myelopathies, despite the increasing availability of magnetic resonance imaging (MRI) data and improvement of biological exploration platforms. Methods: We retrospectively analyzed the files of 186 patients hospitalized in the Department of Neurology and Neurosurgery of the University Hospital Center of Conakry, Guinea, between 2008 and 2016 for the management of non-compressive and compressive myelopathy. Biological evidence of TB infection was demonstrated for 13 (6.9%) patients.  Results: Infectious clinical picture prior to the development of neurological signs was reported in 11 patients (84.6%). The neurological signs were summed up by the existence of a sensitivo-motor semiology of progressive evolution (100% of cases) with sphincter disorders in 11 patients (84.6%) and a medullary compression symptomatology with a lesion and under lesion syndrome from the outset in 4 patients (30.8%). Medullary MRI revealed an extensive intramedullary hypersignal in 9 patients with non-compressive myelopathy and in 4 cases, the lesions appeared in T1 hypersignal and T2 isosignal were localized. Lumbar puncture (LP) revealed lymphocytic pleocytosis, hypoglucorrhage (0.3 to 0.5 g/l), and leukocytosis. Conclusion: This study reveals a classic clinical, biological, neuroradiological, and evolutionary profile of compressive and non-compressive myelopathies. These results are important for the  therapeutic and evolutionary discussion of TB myelopathies for good management.

Magnetic Resonance Imaging Assessment of Cerebral Arteriovenous Malformation Obliteration After Stereotactic Radiosurgery

Neurosurgery ◽  
2013 ◽  
Vol 73 (5) ◽  
pp. 761-766 ◽  
Author(s):  
Timothy E. O'Connor ◽  
William A. Friedman
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Stereotactic Radiosurgery ◽  
Diagnostic System ◽  
Resonance Imaging ◽  
University Of Florida ◽  
Magnetic Resonance Imaging Assessment ◽  
Magnetic Resonance Imaging Mri ◽  
Complete Thrombosis ◽  
The University

Abstract BACKGROUND: Stereotactic radiosurgery is ideal for treating small cerebral arteriovenous malformations (AVMs) that are surgically inaccessible. However, given the inherent delay of AVM obliteration and the potential for radiosurgical failure, detailed evaluation of the neurovascular architecture is necessary to monitor persistence of residual flow. Modern imaging systems such as magnetic resonance imaging (MRI) and angiography allow clinicians to assess transnidus flow after radiosurgical intervention. OBJECTIVE: To determine the accuracy of an MRI diagnosis of complete thrombosis and to identify variables that affect the precision of MRI assessment. METHODS: One hundred twenty patients were reviewed after receiving radiosurgery at the University of Florida from 1990 to 2010. Each patient had an MRI demonstrating AVM obliteration and an angiogram either confirming or denying AVM thrombosis. RESULTS: MRI correctly predicted complete AVM obliteration in 82% of patients. There was a significant correlation between AVM volume and MRI accuracy in 2 separate models. In the first model, logistic regression analysis revealed a significant linear relationship between the natural log of AVM volume and MRI accuracy. The second model showed significant evidence of a cutoff point in MRI accuracy near an AVM volume of 2.80 cm3, above which MRI agreement with angiography is 90% and below which MRI agreement falls off sharply to remain constant at 70%. CONCLUSION: MRI is a useful diagnostic system for assessing AVM obliteration, but its accuracy is inherently linked to the nidus volume it is measuring. These results suggest that MRI may be able to take on an increasingly independent role in the evaluation of AVM regression.

scholarly journals Identification of hippocampal cortical microinfarcts on postmortem 3-T magnetic resonance imaging

2021 ◽  
Author(s):  
Max Scheffler ◽  
Rares Salomir ◽  
Enrique Maturana ◽  
Marie-Louise Montandon ◽  
Enikö V. Kövari ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Cognitive Impairment ◽  
Magnetic Resonance ◽  
High Field ◽  
Correlation Study ◽  
Post Mortem ◽  
Resonance Imaging ◽  
Ultra High Field ◽  
Magnetic Resonance Imaging Mri ◽  
Double Blinded

AbstractCortical microinfarcts (CMI) are increasingly recognized in the neurological community as a biomarker related to cognitive impairment and dementia. If their radiological depiction has been largely described in experimental settings using ultra-high-field magnetic resonance imaging (MRI), less is known about their visibility on routinely used 3-T MRI. In this radiologic-pathologic correlation study, using 3-T post-mortem MRI, we searched for hippocampal CMI, in a double-blinded fashion, and found that only 4/36, or 11%, were clearly demonstrated on both radiological and histopathological exams.

scholarly journals Investigating the influence of dielectric pads in 7T magnetic resonance imaging – simulated and experimental assessment

2020 ◽  
Vol 6 (3) ◽  
pp. 24-27
Author(s):  
Maíra M. Garcia ◽  
Khallil T. Chaim ◽  
Maria C. G. Otaduy ◽  
Andreas Rennings ◽  
Daniel Erni ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Electric Fields ◽  
Dielectric Constants ◽  
Rf Coil ◽  
Resonance Imaging ◽  
Magnetic Components ◽  
Magnetic Resonance Imaging Mri ◽  
High Dielectric ◽  
Ultrahigh Fields

AbstractDipole radiofrequency (RF) elements have been successfully used to compose multi-channel RF coils for ultrahigh fields (UHF) magnetic resonance imaging (MRI). As magnetic components of RF fields (B1) can be very inhomogeneous at UHF (B0≥7T), dielectric pads with high dielectric constants were proposed to improve the B1 efficiency and homogeneity [1]. Dielectric pads can be used as a passive B1 shimmimg technique thanks to inducing a strong secondary magnetic field in their vicinity. The use of such dielectric pads affect not only the B1 field but also the electric field. This in turn affects the specific absorption rate (SAR) and consequently the temperature distribution inside the patient’s body. To study these effects, a 29 cm-long transmission dipole RF coil element terminated by two meander was used for 7T MRI [2]. Using a cylindrical agarose-gel phantom, numerical and experimental results were analyzed with respect to homogeneity and amplitude of the magnetic and electric fields generated by the RF element in various configurations with and without dielectric pads. Calculated and measured B1 results were cross-checked and found to be in good agreement. When using dielectric pads B1 homogeneity and magnitude increase in regions where it was previously weak or insufficient. Calculations suggest that SAR distribution will change when using the pads.

scholarly journals Magnetic resonance imaging with a multi-tunable metamaterial-inspired radiofrequency coil

2021 ◽  
Vol 2015 (1) ◽  
pp. 012171
Author(s):  
V Puchnin ◽  
V Ivanov ◽  
M Gulyaev ◽  
M Zubkov
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Wide Frequency Range ◽  
Small Animals ◽  
Coil Design ◽  
Rf Coil ◽  
Resonance Imaging ◽  
Frequency Range ◽  
Radiofrequency Coil ◽  
Tunable Metamaterial

Abstract We present the initial experimental results obtained using a two-part receive/transmit (Rx/Tx) radiofrequency (RF) coil design for small animals magnetic resonance imaging at 7 T. The assembly uses a butterfly-type coil tuned to 300 MHz for scanning the 1H nuclei and a non-resonant antenna with a metamaterial-inspired resonator tunable over wide frequency range for X-nuclei. 1H, 31P, 23Na and 13C are selected as test nuclei in this work. Coil simulations show the two parts of the RF-assembly to be efficiently operating at the required frequencies. Simulations and phantom imaging show sufficiently homogeneous transverse transmit RF fields and tuning capabilities for the pilot heteronuclear experiments.

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