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

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 Effectiveness of low-field magnetic resonance imaging in diagnosing brachial plexus tumours in dogs – short communication

2015 ◽  
Vol 59 (2) ◽  
pp. 317-319
Author(s):  
Zbigniew Adamiak ◽  
Yauheni Zhalniarovich ◽  
Paulina Przyborowska ◽  
Joanna Głodek ◽  
Adam Przeworski
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Brachial Plexus ◽  
Resonance Imaging ◽  
Gadolinium Contrast ◽  
Gadolinium Contrast Agent ◽  
Low Field ◽  
Mri Sequences ◽  
Magnetic Resonance Imaging Mri ◽  
Brachial Plexus Tumours

AbstractThe aim of the study was to identify magnetic resonance imaging (MRI) sequences that contribute to a quick and reliable diagnosis of brachial plexus tumours in dogs. The tumours were successfully diagnosed in 6 dogs by the MRI with the use of SE, FSE, STIR, Turbo 3 D, 3D HYCE, and GE sequences and the gadolinium contrast agent

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.

Magnetic Resonance Microscopy of Chemically-Induced Liver Foci

1989 ◽  
Vol 17 (4_part_1) ◽  
pp. 613-616 ◽  
Author(s):  
G. Allan Johnson ◽  
Robert R. Maronpot
Keyword(s):  
Magnetic Resonance ◽  
Imaging Technique ◽  
Relaxation Times ◽  
Basic Research ◽  
Resonance Imaging ◽  
T2 Relaxation ◽  
Spin Lattice ◽  
Chemically Induced ◽  
Magnetic Resonance Imaging Mri

Magnetic resonance imaging (MRI) is a new imaging technique used in clinical diagnosis. This paper describes extension of the technique to basic research applications–specifically detecting and characterizing chemically-induced liver neoplasms and foci of cellular alteration. Two systems have been built that allow spatial microscopic resolution–more than 100,000 x greater than that of earlier efforts. Use of spin-lattice (T1) and spin-spin (T2) relaxation times permits detailed characterization of the tissue.

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