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Low field MRI

Karin Markenroth Bloch, Johannes Töger, Freddy Ståhlberg
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...
January 1, 2017: Acta Radiologica
Sergej Schneider, Rasmus Irming Jølck, Esther Gera Cornelia Troost, Aswin Louis Hoffmann
PURPOSE: X-ray based position verification of the target volume in image-guided radiation therapy (IGRT) of patients with pancreatic ductal adenocarcinoma (PDAC) is currently performed on solid fiducial markers that are implanted under endoscopic ultrasonography. A new biodegradable liquid fiducial marker has recently been introduced. To assess its potential use for magnetic resonance imaging (MRI) guided photon or proton radiotherapy of PDAC, the MRI visibility and artefacts of this marker were quantified and compared against solid gold markers...
November 14, 2017: Medical Physics
Henk M De Feyter, Raimund I Herzog, Bart R Steensma, Dennis W J Klomp, Peter B Brown, Graeme F Mason, Douglas L Rothman, Robin A de Graaf
PURPOSE: (13) C magnetic resonance spectroscopy (MRS) in combination with infusion of (13) C-labeled substrates has led to unique insights into human brain metabolism and neurotransmitter cycling. However, the low sensitivity of direct (13) C MRS and high radiofrequency power requirements has limited (13) C MRS studies to predominantly data acquisition in large volumes of the occipital cortex. The purpose of this study is to develop an MRS technique for localized detection of (13) C-labeling of glutamate and glutamine in the human frontal lobe...
November 13, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Michael Loecher, Daniel B Ennis
PURPOSE: To introduce and demonstrate a nonconvex optimization method for reconstructing velocity data from low-velocity-encoding (Venc ) phase-contrast MRI data. THEORY AND METHODS: Solving for velocity values from phase-contrast MRI data was formulated as a nonconvex optimization problem. Weighting was added to account for intravoxel dephasing, and a Laplacian-based regularization was used to account for residual velocity aliasing. The reconstruction was tested with two low-Venc schemes: dual-Venc and a multidirectional high-moment encoding...
November 11, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Shun Kishimoto, Ken-Ichiro Matsumoto, Keita Saito, Ayano Enomoto, Shingo Matsumoto, James Mitchell, Nallathamby Devasahayam, Murali C Krishna
SIGNIFICANCE: Electron Paramagnetic Resonance imaging (EPRI) is a powerful technique capable of generating images of tissue oxygenation using exogenous paramagnetic probes such as trityl radicals or nitroxyl radicals. Using principles similar to Magnetic Resonance Imaging (MRI) with field gradients, the spatial distribution of the paramagnetic probecan be generatedand,from its spectral features, spatial maps of oxygen can be obtained from live objects. In this review, two methods of signal acquisition, image formation/reconstruction will be described...
November 12, 2017: Antioxidants & Redox Signaling
Anja Wacker, Fabio Carniato, Carlos Platas-Iglesias, David Esteban-Gomez, Hans-Jürgen Wester, Lorenzo Tei, Johannes Notni
Gadolinium(iii) complexes with pH-dependent relaxivities have been proposed as responsive magnetic resonance imaging (MRI) contrast agents (CA) for mapping of pH value in living subjects. The latter is clinically relevant because hypoxia-induced reduction of interstitial pH (acidosis) is a hallmark of tumor progression and resistance against chemotherapy. In order to obtain versatile building blocks for integration of a pH-responsive MRI-CA functionality into larger molecular assemblies, such as bioconjugates, micelles or nanoparticles, we equipped the structural motif GdDO3A-ethylene(arylsulfonic acid) with additional carboxylic acid moieties in the aromatic para-position...
November 10, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Andrej Babic, Vassily Vorobiev, Celine Xayaphoummine, Gaelle Lapicorey, Anne-Sophie Chauvin, Lothar Helm, Eric Allémann
Gadolinium-loaded nanomicelles show promise as future magnetic resonance imaging (MRI) contrast agents (CAs). Their increased size and high gadolinium (Gd) loading gives them an edge in proton relaxivity over smaller molecular Gd-complexes. Their size and stealth properties are fundamental for their long blood residence time opening the possibility for use as blood-pool contrast agents. Using L-tyrosine as a three-functional scaffold we synthesized a nanostructure building block 8. The double C18 aliphatic chain on one side, Gd-DO3A with access to bulk water in the center and 2 kDa PEG on the hydrophilic side gave the amphiphilic properties required for the core-shell nanomicellar architecture...
November 9, 2017: Chemistry: a European Journal
Mizuki Nakamura, Sayaka Shibata, Toshihide Yamasaki, Megumi Ueno, Ikuo Nakanishi, Ken-Ichiro Matsumoto, Tadashi Kamada, Ken-Ichi Yamada, Ichio Aoki
The effect of different static magnetic field strengths, 1 T or 7 T, on the quality of nitroxyl radical-based magnetic resonance redox imaging (MRRI) was examined. A stable nitroxyl radical, 3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl (MC-PROXYL), was used as a T1 contrast agent. Phantoms and animals were scanned at 1 T and 7 T using a similar gradient echo sequence. The quality of T1-weighted images and susceptibility of T1-weighted signals were compared. The nitroxyl radical-based T1-weighted signal enhancement ratio was higher at 1 T compared with at 7 T when the identical phantom was scanned using a similar gradient echo sequence...
2017: American Journal of Translational Research
Dan Xiao, Bruce J Balcom
MRI image resolution is proportional to the maximum k-space value, i.e. the temporal integral of the magnetic field gradient. High resolution imaging usually requires high gradient amplitudes and/or long spatial encoding times. Special gradient hardware is often required for high amplitudes and fast switching. We propose a high resolution imaging sequence that employs low amplitude gradients. This method was inspired by the previously proposed PEPI (π Echo Planar Imaging) sequence, which replaced EPI gradient reversals with multiple RF refocusing pulses...
October 31, 2017: Journal of Magnetic Resonance
Rianne Stam, Sachiko Yamaguchi-Sekino
High exposures to electromagnetic fields (EMF) can occur near certain medical devices in the hospital environment. A systematic assessment of medical occupational EMF exposure could help to clarify where more attention to occupational safety may be needed. This paper seeks to identify sources of high exposure for hospital workers and compare the published exposure data to occupational limits in the European Union. A systematic search for peer-reviewed publications was conducted via PubMed and Scopus databases...
November 3, 2017: Industrial Health
Gordon E Sarty, Logi Vidarsson
While the idea of using spatial encoding fields (SEM) for image formation has been proven, conventional wisdom still holds that a magnetic resonance imaging (MRI) system begins with a highly uniform magnetic field. In particular, radio frequency (RF) encoding MRIs designed and tested to date have largely used uniform magnetic fields. Here we demonstrate magnetic resonance imaging in a magnetic field with a built-in gradient that gives non-planar slices - curved surfaces - when the nuclear spins are excited with narrow band RF pulses...
November 4, 2017: Magnetic Resonance Imaging
Kotoe Kamata, Takashi Maruyama, Hiroshi Iseki, Minoru Nomura, Yoshihiro Muragaki, Makoto Ozaki
BACKGROUND: Awake craniotomy paired with intraoperative magnetic resonance imaging (iMRI) is now the established technique for maximizing surgical resection, while preserving neurological function. However, leaving an unsecured airway patient in the iMRI gantry represents considerable risk. Our study aimed at identifying the incidence of critical adverse events in unsecured airway patients during iMRI as part of awake craniotomy. MATERIALS AND METHODS: We conducted a clinical chart review of consecutive awake craniotomies performed between November 1999 and December 2015...
October 25, 2017: Journal of Neurosurgical Anesthesiology
Rustem Zairov, Gulshat Khakimullina, Sergey Podyachev, Irek Nizameev, Georgy Safiullin, Rustem Amirov, Alberto Vomiero, Asiya Mustafina
Today, nanostructure-based contrast agents (CA) are emerging in the field of magnetic resonance imaging (MRI). Their sensitivity is reported as greatly improved in comparison to commercially used chelate-based ones. The present work is aimed at revealing the factors governing the efficiency of longitudinal magnetic relaxivity (r1) in aqueous colloids of core-shell Gd(III)-based nanoparticles. We report for the first time on hydration number (q) of gadolinium(III) as a substantial factor in controlling r1 values of polyelectrolyte-stabilized nanoparticles built from water insoluble complexes of Gd(III)...
October 25, 2017: Scientific Reports
Tian-Ran Li, Ming-Hui Yu, Xiao-Bin Huang, Zhi-Jie Yang, Guang-Ming Lu, Yan-Jun Li
BACKGROUND: Biotherapy based on human bone marrow-derived mesenchymal stem cells (BMSCs) is currently the focus of research, especially in the field of autologous stem cell transplantation. A novel type of metastasis-associated magnetic resonance (MR) molecular imaging probe was constructed, and the changes in metastasis and proliferation of hepatocellular carcinoma (HCC) before and after BMSC intervention were observed through MR imaging (MRI). METHODS: Metastasis-associated MR molecular imaging probe, integrin αvβ3ligand cRGD-PEG-DGL-DTPA-Gd (Gd-RGD), were constructed...
November 5, 2017: Chinese Medical Journal
Zeju Li, Yuanyuan Wang, Jinhua Yu, Zhifeng Shi, Yi Guo, Liang Chen, Ying Mao
This work proposed a novel automatic three-dimensional (3D) magnetic resonance imaging (MRI) segmentation method which would be widely used in the clinical diagnosis of the most common and aggressive brain tumor, namely, glioma. The method combined a multipathway convolutional neural network (CNN) and fully connected conditional random field (CRF). Firstly, 3D information was introduced into the CNN which makes more accurate recognition of glioma with low contrast. Then, fully connected CRF was added as a postprocessing step which purposed more delicate delineation of glioma boundary...
2017: Journal of Healthcare Engineering
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...
October 24, 2017: Physics in Medicine and Biology
Paolo Tini, Valerio Nardone, Pierpaolo Pastina, Giuseppe Battaglia, Clelia Miracco, Salvatore Francesco Carbone, Lucio Sebaste, Giovanni Rubino, Alfonso Cerase, Luigi Pirtoli
BACKGROUND: and Purpose: The aim is to investigate the potential role of EGFR protein expression in predicting the modality of treatment failure in Glioblastoma (GB). MATERIAL AND METHOD: Patients with unifocal GB undergoing surgery and postoperative radio-chemotherapy (RT-TMZ) from February 2008 to July 2015 were included into the study. The EGFR protein expression level was assessed by immunohistochemistry in GB tissues and classified into High (H-EGFR) and Low (L-EGFR) expression...
October 20, 2017: World Neurosurgery
Iksung Kang
In this paper, a portable, low-cost, 3D-printed system for main magnetic field is proposed to suggest a solution for accessibility problems of current magnetic imaging systems, e.g. MRI scanner, their size and cost. The system consists of twelve pairs of NdFeB N35 permanent magnets arranged in a Halbach array in a 3D-printed, cylindrical container based on FEM simulation results by COMSOL Multiphysics 4.4b. Its magnetic field homogeneity and field strength were measured by Hall sensors, WSH-135 XPAN2 by Wilson Semiconductor, and the container was printed by 3DISON H700 by Rokit...
July 2017: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Carlos Ros, Cristian de la Fuente, Sergio Rodenas, Rosa Novellas, Judit Viu, Sonia Añor
MRI is considered gold standard for the diagnosis of presumptive acute hydrated non-compressive nucleus pulposus extrusions (AHNCNPE). This retrospective study describes the myelographic findings in dogs with AHNCNPE diagnosed by low-field MRI and their association with neurological grade, need of surgical decompression and outcome. Forty-two myelographies (21 dogs with presumptive AHNCNPE, 21 dogs with Hansen type I disc disease herniation) were blindly evaluated. Site of herniation, compression pattern, ratio of length of the lesion to length of the second lumbar vertebra (LL:L2) and degree of spinal cord compression (SCC) were measured on the myelographies of dogs with presumptive AHNCNPE and were compared with the corresponding MRI features...
October 19, 2017: Veterinary Record
Min Li, Bin Li, Weijia Zhang
Method development for monitoring economically motivated food adulteration is pivotal for preventing health problems caused by illegal food additives. In this work, low-field nuclear magnetic resonance (LF-NMR) spectroscopy and magnetic resonance imaging (MRI) was applied for the detection and mapping of adulterated prawns injected with different hydrocolloids including gelatin, carrageenan, agar, amorophophallus konjac and xanthan gum. The characteristic T2 fitting curves were obtained which can be used to tell apart adulterated prawns from normal ones...
March 1, 2018: Food Chemistry
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