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Relaxometry

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https://www.readbyqxmd.com/read/28317922/optical-imaging-of-localized-chemical-events-using-programmable-diamond-quantum-nanosensors
#1
Torsten Rendler, Jitka Neburkova, Ondrej Zemek, Jan Kotek, Andrea Zappe, Zhiqin Chu, Petr Cigler, Jörg Wrachtrup
Development of multifunctional nanoscale sensors working under physiological conditions enables monitoring of intracellular processes that are important for various biological and medical applications. By attaching paramagnetic gadolinium complexes to nanodiamonds (NDs) with nitrogen-vacancy (NV) centres through surface engineering, we developed a hybrid nanoscale sensor that can be adjusted to directly monitor physiological species through a proposed sensing scheme based on NV spin relaxometry. We adopt a single-step method to measure spin relaxation rates enabling time-dependent measurements on changes in pH or redox potential at a submicrometre-length scale in a microfluidic channel that mimics cellular environments...
March 20, 2017: Nature Communications
https://www.readbyqxmd.com/read/28303617/joint-system-relaxometry-jsr-and-cr%C3%A3-mer-rao-lower-bound-optimization-of-sequence-parameters-a-framework-for-enhanced-precision-of-despot-t1-and-t2-estimation
#2
Rui Pedro A G Teixeira, Shaihan J Malik, Joseph V Hajnal
PURPOSE: This study aims to increase the precision of single-compartment DESPOT relaxometry by two means: (i) a joint system relaxometry (JSR) approach that estimates parameters in a single step using all available data; and (ii) optimizing acquisition parameters by deploying a robust design tool based on the Crámer-Rao lower bound (CRLB). METHODS: Following the development of the analysis and design capabilities, phantom and four in vivo subject experiments were performed to compare directly the precision achieved with DESPOT and JSR estimation using published protocols and protocols designed using a proposed CRLB framework...
March 16, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28281697/measurement-and-visualization-of-tight-rock-exposed-to-co2-using-nmr-relaxometry-and-mri
#3
Haitao Wang, Zengmin Lun, Chengyuan Lv, Dongjiang Lang, Bingyu Ji, Ming Luo, Weiyi Pan, Rui Wang, Kai Gong
Understanding mechanisms of oil mobilization of tight matrix during CO2 injection is crucial for CO2 enhanced oil recovery (EOR) and sequestration engineering design. In this study exposure behavior between CO2 and tight rock of the Ordos Basin has been studied experimentally by using nuclear magnetic resonance transverse relaxation time (NMR T2) spectrum and magnetic resonance imaging (MRI) under the reservoir pressure and temperature. Quantitative analysis of recovery at the pore scale and visualization of oil mobilization are achieved...
March 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28276684/ultrasound-induced-magnetic-imaging-of-tumors-targeted-by-biofunctional-magnetic-nanoparticles
#4
Kai-Wen Huang, Jen-Jie Chieh, Chih-Kuang Yeh, Shu-Hsien Liao, Yi-Yan Lee, Pei-Yi Hsiao, Wen-Chun Wei, Hong-Chang Yang, Herng-Er Horng
Biofunctional magnetic nanoparticles (MNPs) have been widely applied in biomedical engineering. MNPs are used as a contrast medium in magnetic imaging. Current methods of magnetic imaging, such as magnetic particle imaging and magnetic relaxometry, use small amounts of MNPs at target points far from the surface of the patient's body; these methods always consume considerable power to produce magnetic fields of high uniformity or gradient excitations. Some drawbacks, such as a limited imaging region, imaging system shielding, and complex algorithms based on assumptions of MNP properties or environmental factors, also limit the application of MNP methods in clinics...
March 9, 2017: ACS Nano
https://www.readbyqxmd.com/read/28267532/r2-relaxometry-of-the-pancreas-in-patients-with-human-hemochromatosis-protein-associated-hereditary-hemochromatosis
#5
B Henninger, S Rauch, H Zoller, M Plaikner, W Jaschke, C Kremser
PURPOSE: To evaluate pancreatic iron in patients with human hemochromatosis protein associated hereditary hemochromatosis (HHC) using R2* relaxometry. MATERIALS AND METHODS: 81 patients (58 male, 23 female; median age 49.5, range 10-81 years) with HHC were retrospectively studied. All underwent 1.5T magnetic resonance imaging (MRI) of the abdomen. A fat-saturated multi-gradient echo sequence with 12 echoes (TR=200ms; TE-initial 0.99ms; Delta-TE 1.41ms; 12 echoes; flip-angle: 20°) was used for the R2* quantification of the liver and the pancreas...
April 2017: European Journal of Radiology
https://www.readbyqxmd.com/read/28267494/aggregation-and-gelation-of-oat-%C3%AE-glucan-in-aqueous-solution-probed-by-nmr-relaxometry
#6
Jia Wu, Lan Zhao, Jian Li, Shanshan Jin, Shanshan Wu
Nuclear magnetic resonance was used to study water proton transverse relaxation in oat β-glucan aqueous solutions during storage. The molecular weights of the samples ranged from 112 to 494kDa. The polysaccharide structure was identified by IR, GC-MS, NMR spectroscopy, and high performance anion exchange chromatography. In 1% solutions, 494kDa β-glucan formed stable solution phase. Aggregates were generated in the solution of low molecular weight polysaccharide. The transverse relaxation time of water associated with the aggregate microphase was about 15ms...
May 1, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28266528/gd-eob-dtpa-enhanced-mri-for-evaluation-of-liver-function-comparison-between-signal-intensity-based-indices-and-t1-relaxometry
#7
Michael Haimerl, Niklas Verloh, Florian Zeman, Claudia Fellner, Dominik Nickel, Sven A Lang, Andreas Teufel, Christian Stroszczynski, Philipp Wiggermann
Gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) is a paramagnetic hepatobiliary magnetic resonance (MR) contrast agent. Due to its OATP1B1/B3-dependent hepatocyte-specific uptake and paramagnetic properties increasing evidence has emerged to suggest that Gd-EOB-DTPA-enhanced MRI can be potentially used for evaluation of liver function. In this paper we compare the diagnostic performance of Gd-EOB-DTPA-enhanced relaxometry-based and commonly used signal-intensity (SI)-based indices, including the hepatocellular uptake index (HUI) and SI-based indices corrected by spleen or muscle, for evaluation of liver function, determined using the Indocyanin green clearance (ICG) test...
March 7, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28222197/generalized-min-max-bound-based-mri-pulse-sequence-design-framework-for-wide-range-t1-relaxometry-a-case-study-on-the-tissue-specific-imaging-sequence
#8
Yang Liu, John R Buck, Vasiliki N Ikonomidou
This paper proposes a new design strategy for optimizing MRI pulse sequences for T1 relaxometry. The design strategy optimizes the pulse sequence parameters to minimize the maximum variance of unbiased T1 estimates over a range of T1 values using the Cramér-Rao bound. In contrast to prior sequences optimized for a single nominal T1 value, the optimized sequence using our bound-based strategy achieves improved precision and accuracy for a broad range of T1 estimates within a clinically feasible scan time. The optimization combines the downhill simplex method with a simulated annealing process...
2017: PloS One
https://www.readbyqxmd.com/read/28213048/low-field-single-sided-nmr-for-one-shot-1d-mapping-application-to-membranes
#9
Patrick Judeinstein, Filippo Ferdeghini, Rodrigo Oliveira-Silva, Jean-Marc Zanotti, Dimitrios Sakellariou
Many single-sided permanent magnet NMR systems have been proposed over the years allowing for 1D proton-density profiling, diffusion measurements and relaxometry. In this manuscript we make use of a recently published unilateral magnet for low-field NMR exhibiting an extremely uniform magnetic field gradient with moderate strength and cylindrical symmetry, allowing for a well-defined sweet spot. Combined with a goniometer, our system is used to characterize precisely the uniformity of its gradient and to achieve micrometric precision 1D profiling, as well as spatially localized relaxometry and diffusometry on thick (∼150μm) membrane samples...
February 8, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28194423/effects-of-liver-fibrosis-progression-on-tissue-relaxation-times-in-different-mouse-models-assessed-by-ultrahigh-field-magnetic-resonance-imaging
#10
Andreas Müller, Katrin Hochrath, Jonas Stroeder, Kanishka Hittatiya, Günther Schneider, Frank Lammert, Arno Buecker, Peter Fries
Recently, clinical studies demonstrated that magnetic resonance relaxometry with determination of relaxation times T1 and T2(⁎) may aid in staging and management of liver fibrosis in patients suffering from viral hepatitis and steatohepatitis. In the present study we investigated T1 and T2(⁎) in different models of liver fibrosis to compare alternate pathophysiologies in their effects on relaxation times and to further develop noninvasive quantification methods of liver fibrosis. MRI was performed with a fast spin echo sequence for measurement of T1 and a multigradient echo sequence for determination of T2(⁎)...
2017: BioMed Research International
https://www.readbyqxmd.com/read/28191646/non-invasive-evaluation-of-blood-oxygen-saturation-and-hematocrit-from-t1-and-t2-relaxation-times-in-vitro-validation-in-fetal-blood
#11
Sharon Portnoy, Mike Seed, John G Sled, Christopher K Macgowan
PURPOSE: We propose an analytical method for calculating blood hematocrit (Hct) and oxygen saturation (sO2 ) from measurements of its T1 and T2 relaxation times. THEORY: Through algebraic substitution, established two-compartment relationships describing R1=T1-1 and R2=T2-1 as a function of hematocrit and oxygen saturation were rearranged to solve for Hct and sO2 in terms of R1 and R2 . Resulting solutions for Hct and sO2 are the roots of cubic polynomials. METHODS: Feasibility of the method was established by comparison of Hct and sO2 estimates obtained from relaxometry measurements (at 1...
February 12, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28183023/molecular-dynamics-based-selectivity-for-fast-field-cycling-relaxometry-by-overhauser-and-solid-effect-dynamic-nuclear-polarization
#12
Oliver Neudert, Carlos Mattea, Siegfried Stapf
In the last decade nuclear spin hyperpolarization methods, especially Dynamic Nuclear Polarization (DNP), have provided unprecedented possibilities for various NMR techniques by increasing the sensitivity by several orders of magnitude. Recently, in-situ DNP-enhanced Fast Field Cycling (FFC) relaxometry was shown to provide appreciable NMR signal enhancements in liquids and viscous systems. In this work, a measurement protocol for DNP-enhanced NMR studies is introduced which enables the selective detection of nuclear spin hyperpolarized by either Overhauser effect or solid effect DNP...
January 21, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28165731/novel-experimental-modeling-approach-for-characterizing-perfluorinated-surfactants-in-soils
#13
Denis Courtier-Murias, Eric Michel, Stéphane Rodts, François Lafolie
Soil contamination is still poorly understood and modeled in part because of the difficulties of looking inside the "black box" constituted by soils. Here, we investigated the application of a recently developed (1)H NMR technique to (19)F NMR relaxometry experiments and utilized the results as inputs for an existing model. This novel approach yields (19)F T2 NMR relaxation values of any fluorinated contaminant, which are among the most dangerous contaminants, allowing us to noninvasively and directly monitor their fate in soils...
February 16, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28138975/direct-diffusion-tensor-estimation-using-a-model-based-method-with-spatial-and-parametric-constraints
#14
Yanjie Zhu, Xi Peng, Yin Wu, Ed X Wu, Leslie Ying, Xin Liu, Hairong Zheng, Dong Liang
PURPOSE: To develop a new model-based method with spatial and parametric constraints (MB-SPC) aimed at accelerating diffusion tensor imaging (DTI) by directly estimating the diffusion tensor from highly undersampled k-space data. METHODS: The MB-SPC method effectively incorporates the prior information on the joint sparsity of different diffusion-weighted images using an L1-L2 norm and the smoothness of the diffusion tensor using a total variation seminorm. The undersampled k-space datasets were obtained from fully sampled DTI datasets of a simulated phantom and an ex-vivo experimental rat heart with acceleration factors ranging from 2 to 4...
February 2017: Medical Physics
https://www.readbyqxmd.com/read/28128291/gd-eob-dtpa-enhanced-mr-relaxometry-for-the-detection-and-staging-of-liver-fibrosis
#15
Michael Haimerl, Kirsten Utpatel, Niklas Verloh, Florian Zeman, Claudia Fellner, Dominik Nickel, Andreas Teufel, Stefan Fichtner-Feigl, Matthias Evert, Christian Stroszczynski, Philipp Wiggermann
Gd-EOB-DTPA, a liver-specific contrast agent with T1-shortening effects, is routinely used in clinical routine for detection and characterization of focal liver lesions and has recently received increasing attention as a tool for the quantitative analyses of liver function. We report the relationship between the extent of Gd-EOB-DTPA- induced T1 relaxation and the degree of liver fibrosis, which was assessed according to the METAVIR score. For the T1 relaxometry, a transverse 3D VIBE sequence with inline T1 calculation was acquired prior to and 20 minutes after Gd-EOB-DTPA administration...
January 27, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28119190/time-domain-nmr-relaxometry-as-an-alternative-method-for-analysis-of-chitosan-paramagnetic-ion-interactions-in-solution
#16
Flávio Vinícius Crizóstomo Kock, Tatiana Monaretto, Luiz Alberto Colnago
Chitosan (CHI)-paramagnetic ion interactions in aqueous solution as affected by pH were studied using time-domain NMR (TD-NMR) relaxometry. Longitudinal (T1) and transverse (T2) relaxation times of CHI solutions with Fe(3+), Cu(2+), and Mn(2+) were measured using a single-shot pulse sequence named CP-CWFPx-x. The results indicate that CHI interacted with Fe(3+) ions or iron oxide nanoparticles, maintaining the metal ion in solution at pH ranging from 3 to 5. Above this pH, CHI coagulated and removed Fe ions or nanoparticles, resulting in a clear supernatant...
January 21, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28116233/longitudinal-changes-of-cortical-microstructure-in-parkinson-s-disease-assessed-with-t1-relaxometry
#17
Lucas Nürnberger, René-Maxime Gracien, Pavel Hok, Stephanie-Michelle Hof, Udo Rüb, Helmuth Steinmetz, Rüdiger Hilker, Johannes C Klein, Ralf Deichmann, Simon Baudrexel
BACKGROUND: Histological evidence suggests that pathology in Parkinson's disease (PD) goes beyond nigrostriatal degeneration and also affects the cerebral cortex. Quantitative MRI (qMRI) techniques allow the assessment of changes in brain tissue composition. However, the development and pattern of disease-related cortical changes have not yet been demonstrated in PD with qMRI methods. The aim of this study was to investigate longitudinal cortical microstructural changes in PD with quantitative T1 relaxometry...
2017: NeuroImage: Clinical
https://www.readbyqxmd.com/read/28113567/importance-of-multimodal-mri-in-characterizing-brain-tissue-and-its-potential-application-for-individual-age-prediction
#18
Andrea Cherubini, Maria Eugenia Caligiuri, Patrice Peran, Umberto Sabatini, Carlo Cosentino, Francesco Amato
This study presents a voxel-based multiple regression analysis of different magnetic resonance image modalities, including anatomical T1-weighted, T2* relaxometry, and diffusion tensor imaging. Quantitative parameters sensitive to complementary brain tissue alterations, including morphometric atrophy, mineralization, microstructural damage, and anisotropy loss, were compared in a linear physiological aging model in 140 healthy subjects (range 20-74 years). The performance of different predictors and the identification of the best biomarker of age-induced structural variation were compared without a priori anatomical knowledge...
April 27, 2016: IEEE Journal of Biomedical and Health Informatics
https://www.readbyqxmd.com/read/28113491/optimizing-mr-scan-design-for-model-based-i-t-i-sub-1-sub-i-t-i-sub-2-sub-estimation-from-steady-state-sequences
#19
Gopal Nataraj, Jon-Fredrick Nielsen, Jeffrey Fessler
Rapid, reliable quantification of MR relaxation parameters T1 and T2 is desirable for many clinical applications. Steady-state sequences such as Spoiled Gradient-Recalled Echo (SPGR) and Dual-Echo Steady-State (DESS) are fast and wellsuited for relaxometry because the signals they produce are quite sensitive to T1 and T2 variation. However, T1, T2 estimation with these sequences typically requires multiple scans with varied sets of acquisition parameters. This paper describes a systematic framework for selecting scan types (e...
October 4, 2016: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28113125/mechanism-of-drug-release-from-silica-gelatin-aerogel-relationship-between-matrix-structure-and-release-kinetics
#20
Péter Veres, Mónika Kéri, István Bányai, István Lázár, István Fábián, Concepción Domingo, József Kalmár
Specific features of a silica-gelatin aerogel (3 wt.% gelatin content) in relation to drug delivery has been studied. It was confirmed that the release of both ibuprofen (IBU) and ketoprofen (KET) is about tenfold faster from loaded silica-gelatin aerogel than from pure silica aerogel, although the two matrices are structurally very similar. The main goal of the study was to understand the mechanistic background of the striking difference between the delivery properties of these closely related porous materials...
April 1, 2017: Colloids and Surfaces. B, Biointerfaces
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