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Low field MRI

Oleksandr Zelyak, B Gino Fallone, Joel St-Aubin
Modern effort in radiotherapy to address the challenges of tumor localization and motion has led to the development of MRI guided radiotherapy technologies. Accurate dose calculations must properly account for the effects of the MRI magnetic fields. Previous work has investigated the accuracy of a deterministic linear Boltzmann transport equation (LBTE) solver that includes magnetic field, but not the stability of the iterative solution method. In this work, we perform a stability analysis of this deterministic algorithm including an investigation of the convergence rate dependencies on the magnetic field, material density, energy, and anisotropy expansion...
March 12, 2018: Physics in Medicine and Biology
Björn Friebe, Martin Richter, Susanne Penzlin, Christian Stärke, Siegfried Kropf, Christoph Lohmann, Frank Fischbach, Oliver Speck
OBJECTIVES: The aim of this study was to compare the assessment of low-grade meniscal tears and cartilage damage in ultrahigh-field magnetic resonance imaging (MRI) at 7 T to routine clinical MRI at 3 T. MATERIALS AND METHODS: This study was approved by the local ethics committee, and written informed consent was obtained from each patient. Forty-one patients with suspected meniscal damage or mild osteoarthritis (Kellgren-Lawrence score, 0-2) received 7 T as well as routine clinical 3 T consecutively...
March 8, 2018: Investigative Radiology
Jesper D Nielsen, Kristoffer H Madsen, Oula Puonti, Hartwig R Siebner, Christian Bauer, Camilla Gøbel Madsen, Guilherme B Saturnino, Axel Thielscher
Anatomically realistic volume conductor models of the human head are important for accurate forward modeling of the electric field during transcranial brain stimulation (TBS), electro- (EEG) and magnetoencephalography (MEG). In particular, the skull compartment exerts a strong influence on the field distribution due to its low conductivity, suggesting the need to represent its geometry accurately. However, automatic skull reconstruction from structural magnetic resonance (MR) images is difficult, as compact bone has a very low signal in magnetic resonance imaging (MRI)...
March 5, 2018: NeuroImage
Wencheng Shao, Xiaobin Tang, Yanling Bai, Diyun Shu, Changran Geng, Chunhui Gong, Fada Guan
Background: Magnetic resonance imaging (MRI)-guided radiotherapy is a promising image-guided cancer radiotherapy method. For MRI-guided radiotherapy, the proper energy of a therapeutic beam is important for beam-designing processes, and the magnetic-induced dose perturbation would be mainly influenced, especially the perturbation surrounding the tissue-air or air-tissue interfaces. Thus, it was necessary to investigate the impact of beam energy from photon, proton, and carbon ion beams on the magnetic-induced dose perturbations...
January 2018: Journal of Cancer Research and Therapeutics
Georg Hille, Sylvia Saalfeld, Steffen Serowy, Klaus Tönnies
BACKGROUND AND OBJECTIVE: In this work we propose a 3D vertebral body segmentation approach for clinical magnetic resonance (MR) spine imaging. So far, vertebrae segmentation approaches in MR spine imaging are either limited to particular MR imaging sequences or require minutes to compute, which can be hindering in clinical routine. The major contribution of our work is a reasonably precise segmentation result, within seconds and with minimal user interaction, for spine MR imaging commonly used in clinical routine...
March 2018: Computer Methods and Programs in Biomedicine
Ulrik Nikolaj Ascanius Felding
Isolated fractures of the orbital floor or medial wall are often referred to as blowout fractures (BOFs). Debilitating double vision and aesthetic deformity may affect the patients' quality of life and daily living skills, for instance, working or driving a car. The management of blowout fractures is, however, challenging, since not all fractures demand surgery. Some patients may have symptoms which subside, or may never develop symptoms. Due to a lack of evidence, there are still considerable differences in opinion on the criteria for surgery...
March 2018: Danish Medical Journal
Roberto Guidotti, Raffaele Sinibaldi, Cinzia De Luca, Allegra Conti, Risto J Ilmoniemi, Koos C J Zevenhoven, Per E Magnelind, Vittorio Pizzella, Cosimo Del Gratta, Gian Luca Romani, Stefania Della Penna
The prototypes of ultra-low-field (ULF) MRI scanners developed in recent years represent new, innovative, cost-effective and safer systems, which are suitable to be integrated in multi-modal (Magnetoencephalography and MRI) devices. Integrated ULF-MRI and MEG scanners could represent an ideal solution to obtain functional (MEG) and anatomical (ULF MRI) information in the same environment, without errors that may limit source reconstruction accuracy. However, the low resolution and signal-to-noise ratio (SNR) of ULF images, as well as their limited coverage, do not generally allow for the construction of an accurate individual volume conductor model suitable for MEG localization...
2018: PloS One
Bahareh Behzadnezhad, Bruce D Collick, Nader Behdad, Alan B McMillan
Additive manufacturing provides a low-cost and rapid means to translate 3D designs into the construction of a prototype. For MRI, this type of manufacturing can be used to construct various components including the structure of RF coils. In this paper, we characterize the material properties (dielectric constant and loss tangent) of several common 3D-printed polymers in the MRI frequency range of 63-300 MHz (for MRI magnetic field strengths of 1.5-7 T), and utilize these material properties in full-wave electromagnetic simulations to design and construct a very low-cost subject/anatomy-specific 3D-printed receive-only RF coil that fits close to the body...
February 21, 2018: Journal of Magnetic Resonance
F Bünger, D Feierabend, P Storch, R Kalff, R Reichart
BACKGROUND: Subcutaneous peripheral nerve field stimulation (sPNFS) is an established procedure for the treatment of chronic localized neuropathic pain of peripheral origin. The treatment of nummular headache primarily focuses on conservative methods with limited prospects of success. The role of sPNFS in the treatment of nummular headache has not been investigated as yet. QUESTION: Is the sPNFS an option in the management of nummular headache? MATERIALS AND METHODS: In addition to a summary of established methods in the treatment of nummular headache, sPNFS as a possible form of therapy is discussed...
March 2, 2018: Der Schmerz
Zhiyong Zhang, Michael Lustig, Lucio Frydman
PURPOSE: To develop a rapid, non-CPMG high-resolution volumetric imaging approach, exhibiting a speed and in-plane resilience to field inhomogeneities comparable to RARE/turbo-spin-echo (TSE) while endowed with unique downsampling characteristics. METHODS: A multi-scan extension of cross-term spatiotemporal encoding (xSPEN) is introduced and analyzed. The method simultaneously yields ky /kz data containing low and high frequency components, as well as transposed, low-resolution z/y images...
March 1, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Elvis Dohmatob, Gael Varoquaux, Bertrand Thirion
In Echo-Planar Imaging (EPI)-based Magnetic Resonance Imaging (MRI), inter-subject registration typically uses the subject's T1-weighted (T1w) anatomical image to learn deformations of the subject's brain onto a template. The estimated deformation fields are then applied to the subject's EPI scans (functional or diffusion-weighted images) to warp the latter to a template space. Historically, such indirect T1w-based registration was motivated by the lack of clear anatomical details in low-resolution EPI images: a direct registration of the EPI scans to template space would be futile...
2018: Frontiers in Neuroscience
David E J Waddington, Mathieu Sarracanie, Najat Salameh, Fanny Herisson, Cenk Ayata, Matthew S Rosen
Overhauser-enhanced MRI (OMRI) is an electron-proton double-resonance imaging technique of interest for its ability to non-invasively measure the concentration and distribution of free radicals. In vivo OMRI experiments are typically undertaken at ultra-low magnetic field (ULF), as both RF power absorption and penetration issues-a consequence of the high resonance frequencies of electron spins-are mitigated. However, working at ULF causes a drastic reduction in MRI sensitivity. Here, we report on the design, construction and performance of an OMRI platform optimized for high NMR sensitivity and low RF power absorbance, exploring challenges unique to probe design in the ULF regime...
March 1, 2018: NMR in Biomedicine
Graham L Baum, David R Roalf, Philip A Cook, Rastko Ciric, Adon F G Rosen, Cedric Xia, Mark A Elliott, Kosha Ruparel, Ragini Verma, Birkan Tunc, Ruben C Gur, Raquel E Gur, Danielle S Bassett, Theodore D Satterthwaite
Multiple studies have shown that data quality is a critical confound in the construction of brain networks derived from functional MRI. This problem is particularly relevant for studies of human brain development where important variables (such as participant age) are correlated with data quality. Nevertheless, the impact of head motion on estimates of structural connectivity derived from diffusion tractography methods remains poorly characterized. Here, we evaluated the impact of in-scanner head motion on structural connectivity using a sample of 949 participants (ages 8-23 years old) who passed a rigorous quality assessment protocol for diffusion magnetic resonance imaging (dMRI) acquired as part of the Philadelphia Neurodevelopmental Cohort...
February 24, 2018: NeuroImage
Alexander Kolb, Simon Robinson, David Stelzeneder, Markus Schreiner, Catharina Chiari, Reinhard Windhager, Siegfried Trattnig, Klaus Bohndorf
OBJECTIVES: To evaluate the clinical feasibility of ultrahigh field 7-T SWI to visualize vessels and assess their density in the immature epiphyseal cartilage of human knee joints. METHODS: 7-T SWI of 12 knees (six healthy volunteers, six patients with osteochondral abnormalities; mean age 10.7 years; 3 female, 9 male) were analysed by two readers, classifying intracartilaginous vessel densities (IVD) in three grades (no vessels, low IVD and high IVD) in defined femoral, tibial and patellar zones...
February 26, 2018: European Radiology
Marianna Biggi, Sue J Dyson
OBJECTIVE To use high-field and low-field MRI to describe the anatomy of the proximal portion of the tarsal region (proximal tarsal region) of nonlame horses. SAMPLE 25 cadaveric equine tarsi. PROCEDURES The proximal portion of 1 tarsus from each of 25 nonlame horses with no history of tarsal lameness underwent high-field (1.5-T) and low-field (0.27-T) MRI. Resulting images were used to subjectively describe the anatomy of that region and obtain measurements of the collateral ligaments of the tarsocrural joint...
March 2018: American Journal of Veterinary Research
Luigi Granato, Luce Vander Elst, Celine Henoumont, Robert N Muller, Sophie Laurent
Thanks to the understanding of the relationships between the residence lifetime τM of the coordinated water molecules to macrocyclic Gd-complexes and the rotational mobility τR of these structures, and according to the theory for paramagnetic relaxation, it is now possible to design macromolecular contrast agents with enhanced relaxivities by optimizing these two parameters through ligand structural modification. We succeeded in accelerating the water exchange rate by inducing steric compression around the water binding site, and by removing the amide function from the DOTA-AA ligand [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid mono(p-aminoanilide)] (L) previously designed...
December 16, 2017: Chemistry & Biodiversity
Roy A M Haast, Dimo Ivanov, Kâmil Uludağ
Determination of cortical thickness using MRI has often been criticized due to the presence of various error sources. Specifically, anatomical MRI relying on T1 contrast may be unreliable due to spatially variable image contrast between gray matter (GM), white matter (WM) and cerebrospinal fluid (CSF). Especially at ultra-high field (≥ 7T) MRI, transmit and receive B1 -related image inhomogeneities can hamper correct classification of tissue types. In the current paper, we demonstrate that residual B1+ (transmit) inhomogeneities in the T1 -weighted and quantitative T1 images using the MP2RAGE sequence at 7T lead to biases in cortical thickness measurements...
February 18, 2018: Human Brain Mapping
Lingling Song, Hongcai Zhang, Shunsheng Chen
The present study investigated the quantitative and non-destructive determination of Eriocheir sinensis' plumpness during four mature stages using low field-nuclear magnetic resonance (LF-1H NMR). Normalized lipid volume of live E. sinensis was calculated from Sept to Dec using 3D LF-1H nuclear magnetic imaging (MRI) and the validity of proposed technique was compared and verified with traditional Soxhlet extraction and live dissection method, respectively. The results showed the plumpness of female E. sinensis was higher than that of male ones from Sept to Dec and the highest plumpness of male and female E...
March 2018: Food Research International
Zhongliang Zu, Xiaoyu Jiang, Junzhong Xu, John C Gore
PURPOSE: To evaluate the ability of spin-lock imaging to detect the uptake of 3-o-methyl-D-glucose (3oMG) in normal brain and brain tumors in animals. METHODS: Measurements of the longitudinal relaxation rate in the rotating frame (R 1ρ ) were made over a range of spin-lock powers in rat brains bearing 9L tumors. The dispersion of R 1ρ values was quantified by ΔR 1ρ , the difference of R 1ρ values acquired with low and high locking powers. The glucose analogue 3oMG was administered intravenously and the differences of ΔR 1ρ values ( ΔR1ρdiff) before and as a function of time after administration were calculated to isolate the contribution of 3oMG to the dispersions, which at high fields primarily reflects chemical exchange effects...
February 9, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
QiaoRu Hou, Wei Gao, YuMin Zhong, AiMin Sun, Qian Wang, LiWei Hu, JingLei Wang
Tracheobronchial anomalies are common in congenital heart disease (CHD), including tracheobronchial stenosis, tracheal bronchus, cardiac bronchus, and bronchial isomerism, which can cause varying degrees of respiratory illness. It is necessary to assess tracheobronchial anomalies and make a preoperative airway evaluation. Multi-slice computed tomography (MSCT) and cardiac magnetic resonance imaging (MRI) are the most effective noninvasive modalities for the diagnosis of CHD and the associated tracheobronchial anomalies...
February 7, 2018: Scientific Reports
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