scholarly journals Computational and Phantom-Based Feasibility Study of 3D dcNCI With Ultra-Low-Field MRI

2021 ◽  
Vol 9 ◽  
Author(s):  
Nora Höfner ◽  
Jan-Hendrik Storm ◽  
Peter Hömmen ◽  
Antonino Mario Cassarà ◽  
Rainer Körber
Keyword(s):  
Low Noise ◽  
Current Dipole ◽  
3 Dimensional ◽  
Low Field ◽  
Single Dipole ◽  
Source Models ◽  
Low Field Mri ◽  
Magnetic Resonance Imaging Mri ◽  
Neuronal Current ◽  
Phantom Experiments

The possibility to directly and non-invasively localize neuronal activities in the human brain, as for instance by performing neuronal current imaging (NCI) via magnetic resonance imaging (MRI), would be a breakthrough in neuroscience. In order to assess the feasibility of 3-dimensional (3D) NCI, comprehensive computational and physical phantom experiments using low-noise ultra-low-field (ULF) MRI technology were performed using two different source models within spherical phantoms. The source models, consisting of a single dipole and an extended dipole grid, were calibrated enabling the quantitative emulation of a long-lasting neuronal activity by the application of known current waveforms. The dcNCI experiments were also simulated by solving the Bloch equations using the calculated internal magnetic field distributions of the phantoms and idealized MRI fields. The simulations were then validated by physical phantom experiments using a moderate polarization field of 17 mT. A focal activity with an equivalent current dipole of about 150 nAm and a physiologically relevant depth of 35 mm could be resolved with an isotropic voxel size of 25 mm. The simulation tool enabled the optimization of the imaging parameters for sustained neuronal activities in order to predict maximum sensitivity.

Improved Contrast in Ultra-Low-Field MRI with Time-Dependent Bipolar Prepolarizing Fields: Theory and NMR Demonstrations

2013 ◽  
Vol 20 (3) ◽  
pp. 327-336 ◽  
Author(s):  
Jaakko O. Nieminen ◽  
Jens Voigt ◽  
Stefan Hartwig ◽  
Hans Jürgen Scheer ◽  
Martin Burghoff ◽  
...  
Keyword(s):  
Field Strength ◽  
Time Course ◽  
Signal Strength ◽  
Relaxation Rates ◽  
Resonance Imaging ◽  
New Approach ◽  
Spin Lattice ◽  
Low Field ◽  
Low Field Mri ◽  
Magnetic Resonance Imaging Mri

Abstract The spin-lattice (T1) relaxation rates of materials depend on the strength of the external magnetic field in which the relaxation occurs. This T1 dispersion has been suggested to offer a means to discriminate between healthy and cancerous tissue by performing magnetic resonance imaging (MRI) at low magnetic fields. In prepolarized ultra-low-field (ULF) MRI, spin precession is detected in fields of the order of 10-100 μT. To increase the signal strength, the sample is first magnetized with a relatively strong polarizing field. Typically, the polarizing field is kept constant during the polarization period. However, in ULF MRI, the polarizing-field strength can be easily varied to produce a desired time course. This paper describes how a novel variation of the polarizing-field strength and duration can optimize the contrast between two types of tissue having different T1 relaxation dispersions. In addition, NMR experiments showing that the principle works in practice are presented. The described procedure may become a key component for a promising new approach of MRI at ultra-low fields

scholarly journals Arthroscopic and Low-Field MRI (0.25 T) Evaluation of Meniscus and Ligaments of Painful Knee

2012 ◽  
Vol 2 ◽  
pp. 24 ◽  
Author(s):  
Harish S Lokannavar ◽  
Xiaochun Yang ◽  
Harsha Guduru
Keyword(s):  
Negative Predictive Value ◽  
Predictive Value ◽  
Imaging Study ◽  
Cost Effective ◽  
Non Invasive ◽  
Low Field ◽  
Cost Effective Technique ◽  
Low Field Mri ◽  
Magnetic Resonance Imaging Mri ◽  
Sensitivity Specificity

Objective: Magnetic resonance imaging (MRI) is an accurate, non-invasive, cost-effective technique for examination of the soft tissue and osseous structures of the knee. The purpose of this study was to evaluate the accuracy of low-field MRI by comparing the results with subsequent arthroscopy. Materials and Methods: MR imaging study of 146 patients was done using 0.25 T ESTOATE G-SCAN and the sequence used were SE, FSE and GRE in all the three planes. The comparison was based on five parameters: accuracy, sensitivity, specificity, positive predictive value, and negative predictive value. Result: Our study showed high accuracy (98.08%) and negative predictive value (98.62%) for MRI in comparison with arthroscopy. Conclusion: Low-field MRI alleviates the need of arthroscopy for detection of meniscus tears and ligament tears.

Evaluation of Magnetic Resonance Imaging Responsiveness in Active Psoriatic Arthritis at Multiple Timepoints during the First 12 Weeks of Antitumor Necrosis Factor Therapy

2015 ◽  
Vol 43 (1) ◽  
pp. 75-80 ◽  
Author(s):  
Marie Feletar ◽  
Stephen Hall ◽  
Paul Bird
Keyword(s):  
Magnetic Resonance Imaging ◽  
Psoriatic Arthritis ◽  
Magnetic Resonance ◽  
High Field ◽  
Early Response ◽  
Resonance Imaging ◽  
Low Field ◽  
Low Field Mri ◽  
Magnetic Resonance Imaging Mri ◽  
Necrosis Factor

Objective.To assess the responsiveness of high- and low-field extremity magnetic resonance imaging (MRI) variables at multiple timepoints in the first 12 weeks post-antitumor necrosis factor (anti-TNF) therapy initiation in patients with psoriatic arthritis (PsA) and active dactylitis.Methods.Twelve patients with active PsA and clinical evidence of dactylitis involving at least 1 digit were recruited. Patients underwent sequential high-field conventional (1.5 Tesla) and extremity low-field MRI (0.2 Tesla) of the affected hand or foot, pre- and postgadolinium at baseline (pre-TNF), 2 weeks (post-TNF), 6 weeks, and 12 weeks. A blinded observer scored all images on 2 occasions using the PsA MRI scoring system.Results.Eleven patients completed the study, but only 6 patients completed all high-field and low-field MRI assessments. MRI scores demonstrated rapid response to TNF inhibition with score reduction in tenosynovitis, synovitis, and osteitis at 2 weeks. Intraobserver reliability was good to excellent for all variables. High-field MRI demonstrated greater sensitivity to tenosynovitis, synovitis, and osteitis and greater responsiveness to change posttreatment. Treatment responses were maintained to 12 weeks.Conclusion.This study demonstrates the use of MRI in detecting early response to biologic therapy. MRI variables of tenosynovitis, synovitis, and osteitis demonstrated responsiveness posttherapy with high-field scores more responsive to change than low-field scores.

scholarly journals Inflammatory and post-inflammatory lesions in the sacroiliac joints and lumbar spine according to magnetic resonance imaging in patients with early axial spondyloarthritis

2019 ◽  
Vol 57 (1) ◽  
pp. 28-32 ◽  
Author(s):  
D. G. Rumyantseva ◽  
Sh. Erdes ◽  
A. V. Smirnov
Keyword(s):  
Magnetic Resonance Imaging ◽  
Lumbar Spine ◽  
Magnetic Resonance ◽  
Disease Duration ◽  
Resonance Imaging ◽  
Sacroiliac Joints ◽  
Low Field ◽  
Low Field Mri ◽  
Magnetic Resonance Imaging Mri ◽  
Inflammatory Changes

Investigation of the evolution of early axial spondylitis (axSP) is now of great importance especially before the appearance of reliable radiological signs of ankylosing spondylitis (AS). Of particular interest is the assessment of inflammatory and post-inflammatory changes in the sacroiliac joints (SJ) and in the spine using magnetic resonance imaging (MRI).The aimof the study was to analyze inflammatory foci in bone according to MRI in the area of SJ and lumbar spine (LS) in patients with early axSP.Material and methods.The study involved the patients of the Moscow cohort CORSAIR (Early Spondyloarthritis Cohort), which was formed in V.A. Nasonova Research Institute of Rheumatology. Low field MRI of SJ and LS was carried out in all patients at inclusion in the study in the T1 and STIR modes.Results and discussion.SJ MRI most often (34.1%) revealed combined foci of inflammation (active and chronic sacroiliitis – SI), 32.9% of patients showed signs of only chronic, rarely – only active SI (19.5%). In a few cases, MRI showed inflammatory changes in LS, which were regarded as active and chronic spondylitis. In patients with a disease duration of up to 1 year, signs of active SI were more common according to MRI than in patients with a longer duration of the disease (30.0 and 14.4%, respectively; p<0.05). All active foci of inflammation (with or without signs of chronic SI) were significantly more frequently detected in patients with AS than in non-radiological axSP (NR-axSP; 61.6% and 44.2%, respectively; p<0.05). The overall incidence of chronic spondylitis (in combination with or without active spondylitis) in patients with AS was higher than in NR-axSP(13.9% and 5.8%, respectively; p<0.05).Conclusion.Patients with AS more often have active lesions at MRI of SJ and chronic ones at MRI of LS than patients with NR-axSP

scholarly journals Magnetic Resonance Imaging of Surgical Implants Made from Weak Magnetic Materials

2013 ◽  
Vol 13 (4) ◽  
pp. 165-168 ◽  
Author(s):  
D. Gogola ◽  
A. Krafčík ◽  
O. Štrbák ◽  
I. Frollo
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Inhomogeneous Field ◽  
Resonance Imaging ◽  
Low Field ◽  
Surgical Implants ◽  
Low Field Mri ◽  
Magnetic Resonance Imaging Mri ◽  
Processing Techniques ◽  
High Magnetic Susceptibility

Materials with high magnetic susceptibility cause local inhomogeneities in the main field of the magnetic resonance (MR) tomograph. These inhomogeneities lead to loss of phase coherence, and thus to a rapid loss of signal in the image. In our research we investigated inhomogeneous field of magnetic implants such as magnetic fibers, designed for inner suture during surgery. The magnetic field inhomogeneities were studied at low magnetic planar phantom, which was made from four thin strips of magnetic tape, arranged grid-wise. We optimized the properties of imaging sequences with the aim to find the best setup for magnetic fiber visualization. These fibers can be potentially exploited in surgery for internal stitches. Stitches can be visualized by the magnetic resonance imaging (MRI) method after surgery. This study shows that the imaging of magnetic implants is possible by using the low field MRI systems, without the use of complicated post processing techniques (e.g., IDEAL).

scholarly journals Approaches for Image Reconstruction in Low-Field Magnetic Resonance Imaging

2021 ◽  
Author(s):  
Johnes Obungoloch ◽  
Emmanuel Ahishakiye
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Image Reconstruction ◽  
Data Driven ◽  
Resonance Imaging ◽  
Learning Methods ◽  
Image Reconstruction Techniques ◽  
Low Field ◽  
Low Field Mri ◽  
Magnetic Resonance Imaging Mri

Abstract Background: Magnetic Resonance Imaging (MRI) and spectroscopic techniques are frequently employed for clinical diagnostics as well as basic research in areas like cognitive neuroimaging. MRI is a widely used imaging modality for intracranial diseases. However, conventional MRI is expensive to purchase, maintain and sustain, limiting their use in low-income countries. Low field MRI can provide an economical, long-term, and safe imaging option to high-field MRI and computed tomography (CT) for brain imaging. This paper offers a review of the image reconstruction techniques used in low field magnetic resonance imaging (MRI). It is aimed at familiarizing the readers with the relevant knowledge, literature, and the latest updates on the state-of-art image reconstruction techniques that have been used in low field MRI citing their strengths, and areas for improvement. Methods: An in-depth keyword-based search was undertaken for publications on image reconstruction approaches in low-field MRI in the top scientific databases such as Google Scholar, Wiley, Science Direct, Springer, IEEE, Scopus, Nature, Elsevier, and PubMed throughout this study. This research also contained relevant postgraduate theses. For the selection of relevant research publications, the PRISMA flow diagram and protocol were also used.Results: Studies revealed that Inhomogeneities are present in low field MRI, implying that the traditional method of acquiring the image, using the inverse Fourier Transform, is no longer viable. The image reconstruction techniques reviewed include iterative methods, dictionary learning methods, and deep learning methods. Experimental results from the literature revealed improved image quality of the reconstructed images using data driven and learning based methods (deep learning and dictionary learning methods). Conclusion: The study revealed that there is limited literature on the image reconstruction approaches in low field MRI even if though there are sufficient studies on the subject in high field MRI. Data driven and learning based methods improves image reconstruction quality when compared to analytic and iterative approaches.

Magnetic Resonance Imaging of Renal Masses at 0.02 Tesla

1988 ◽  
Vol 29 (1) ◽  
pp. 61-64
Author(s):  
L. Ekelund ◽  
S.-O. Hietala ◽  
B. Ljungberg ◽  
H. Lotz ◽  
G. Wickman
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Inferior Vena ◽  
Vena Cava ◽  
Resonance Imaging ◽  
Tumor Extension ◽  
Renal Masses ◽  
Low Field ◽  
Low Field Mri ◽  
Magnetic Resonance Imaging Mri

To determine the usefulness of extremely low field magnetic resonance imaging (MRI) in the evaluation of renal masses 19 patients with 15 tumors (13 renal and 2 renal pelvic carcinomas) and 8 cysts were examined in a 0.02 tesla MRI unit. The findings were compared with results of computed tomography (CT) and ultrasound. Cavography was performed in 6 patients. MRI enabled differentiation between cysts and solid tumors. Tumor extension into the inferior vena cava could be demonstrated in one case and liver metastases in two patients. The image quality was inferior to that reported at higher field strengths and the tumors were more precisely staged by CT and ultrasound. At present, it is unlikely that low field MRI will play any substantial role in the evaluation of renal masses.

scholarly journals Meyer’s Loop Anatomy Demonstrated Using Diffusion Tensor MR Imaging and Fiber Tractography at 3T

2014 ◽  
Vol 60 (5) ◽  
pp. 215-222 ◽  
Author(s):  
Cristina Goga ◽  
Zeynep Firat ◽  
Klara Brinzaniuc ◽  
Is Florian
Keyword(s):  
Diffusion Tensor Imaging ◽  
Diffusion Tensor ◽  
Region Of Interest ◽  
Fiber Tractography ◽  
Brain Images ◽  
3 Dimensional ◽  
Software Release ◽  
Magnetic Resonance Imaging Mri ◽  
Meyer’S Loop

Abstract Objective: The ultimate anatomy of the Meyer’s loop continues to elude us. Diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) may be able to demonstrate, in vivo, the anatomy of the complex network of white matter fibers surrounding the Meyer’s loop and the optic radiations. This study aims at exploring the anatomy of the Meyer’s loop by using DTI and fiber tractography. Methods: Ten healthy subjects underwent magnetic resonance imaging (MRI) with DTI at 3 T. Using a region-of-interest (ROI) based diffusion tensor imaging and fiber tracking software (Release 2.6, Achieva, Philips), sequential ROI were placed to reconstruct visual fibers and neighboring projection fibers involved in the formation of Meyer’s loop. The 3-dimensional (3D) reconstructed fibers were visualized by superimposition on 3-planar MRI brain images to enhance their precise anatomical localization and relationship with other anatomical structures. Results: Several projection fiber including the optic radiation, occipitopontine/parietopontine fibers and posterior thalamic peduncle participated in the formation of Meyer’s loop. Two patterns of angulation of the Meyer’s loop were found. Conclusions: DTI with DTT provides a complimentary, in vivo, method to study the details of the anatomy of the Meyer’s loop.

Improving Image Quality In Low-Field MRI With Deep Learning

2021 ◽  
Author(s):  
Armando Garcia Hernandez ◽  
Pierre Fau ◽  
Stanislas Rapacchi ◽  
Julien Wojak ◽  
Hugues Mailleux ◽  
...  
Keyword(s):  
Deep Learning ◽  
Image Quality ◽  
Low Field ◽  
Low Field Mri
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