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Relaxometry

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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
#1
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
#2
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
#3
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
#4
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
#5
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/a-novel-experimental-modeling-approach-to-characterize-perfluorinated-surfactants-in-soils
#6
Denis Courtier-Murias, Eric Michel, Stéphane Rodts, François Lafolie
Soil contamination is still poorly understood and modeled in part due to the difficulties of looking inside the "black box" constituted by soils. Here, we investigated the application of a recently developed 1H NMR technique to 19F NMR relaxometry experiments and utilized the results as inputs for an existing model. This novel approach yields 19F T2 NMR relaxation values of any fluorinated contaminant, which are among the most dangerous ones, allowing us to non-invasively and directly monitor their fate in soils...
February 6, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28138975/direct-diffusion-tensor-estimation-using-a-model-based-method-with-spatial-and-parametric-constraints
#7
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...
December 10, 2016: Medical Physics
https://www.readbyqxmd.com/read/28128291/gd-eob-dtpa-enhanced-mr-relaxometry-for-the-detection-and-staging-of-liver-fibrosis
#8
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
#9
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
#10
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
#11
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
#12
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
#13
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...
January 17, 2017: Colloids and Surfaces. B, Biointerfaces
https://www.readbyqxmd.com/read/28109242/local-spin-dynamics-of-iron-oxide-magnetic-nanoparticles-dispersed-in-different-solvents-with-variable-size-and-shape-a-1-h-nmr-study
#14
M Basini, T Orlando, P Arosio, M F Casula, D Espa, S Murgia, C Sangregorio, C Innocenti, A Lascialfari
Colloidal magnetic nanoparticles (MNPs) based on a nearly monodisperse iron oxide core and capped by oleic acid have been used as model systems for investigating the superparamagnetic spin dynamics by means of magnetometry measurements and nuclear magnetic resonance ((1)H NMR) relaxometry. The key magnetic properties (saturation magnetization, coercive field, and frequency dependent "blocking" temperature) of MNPs with different core size (3.5 nm, 8.5 nm, and 17.5 nm), shape (spherical and cubic), and dispersant (hexane and water-based formulation) have been determined...
January 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28090441/principal-component-analysis-t1%C3%AF-voxel-based-relaxometry-of-the-articular-cartilage-a-comparison-of-biochemical-patterns-in-osteoarthritis-and-anterior-cruciate-ligament-subjects
#15
Valentina Pedoia, Colin Russell, Allison Randolph, Xiaojuan Li, Sharmila Majumdar
BACKGROUND: Quantitative MR, including T1ρ mapping, has been extensively used to probe early biochemical changes in knee articular cartilage of subjects with osteoarthritis (OA) and others at risk for cartilage degeneration, such as those with anterior cruciate ligament (ACL) injury and reconstruction. However, limited studies have been performed aimed to assess the spatial location and patterns of T1ρ. In this study we used a novel voxel-based relaxometry (VBR) technique coupled with principal component analysis (PCA) to extract relevant features so as to describe regional patterns and to investigate their similarities and differences in T1ρ maps in subjects with OA and subjects six months after ACL reconstruction (ACLR)...
December 2016: Quantitative Imaging in Medicine and Surgery
https://www.readbyqxmd.com/read/28074498/imaging-and-t2-relaxometry-of-short-t2-connective-tissues-in-the-knee-using-ultrashort-echo-time-double-echo-steady-state-utedess
#16
Akshay S Chaudhari, Bragi Sveinsson, Catherine J Moran, Emily J McWalter, Ethan M Johnson, Tao Zhang, Garry E Gold, Brian A Hargreaves
PURPOSE: To develop a radial, double-echo steady-state (DESS) sequence with ultra-short echo-time (UTE) capabilities for T2 measurement of short-T2 tissues along with simultaneous rapid, signal-to-noise ratio (SNR)-efficient, and high-isotropic-resolution morphological knee imaging. METHODS: THe 3D radial UTE readouts were incorporated into DESS, termed UTEDESS. Multiple-echo-time UTEDESS was used for performing T2 relaxometry for short-T2 tendons, ligaments, and menisci; and for Dixon water-fat imaging...
January 11, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28072579/development-of-advanced-signal-processing-and-source-imaging-methods-for-superparamagnetic-relaxometry
#17
Ming-Xiong Huang, Bill Anderson, Charles W Huang, Gerd J Kunde, Erika C Vreeland, Jeffrey W Huang, Andrei N Matlashov, Todor Karaulanov, Christopher P Nettles, Andrew Gomez, Kayla Minser, Caroline Weldon, Giulio Paciotti, Michael Harsh, Roland R Lee, Edward R Flynn
Superparamagnetic relaxometry (SPMR) is a highly sensitive technique for the in vivo detection of tumor cells and may improve early stage detection of cancers. SPMR employs superparamagnetic iron oxide nanoparticles (SPION). After a brief magnetizing pulse is used to align the SPION, SPMR measures the time decay of SPION using super-conducting quantum interference device (SQUID) sensors. Substantial research has been carried out in developing the SQUID hardware and in improving the properties of the SPION. However, little research has been done in the pre-processing of sensor signals and post-processing source modeling in SPMR...
February 7, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28069115/metabolism-variation-and-better-storability-of-dark-versus-light-coloured-soybean-glycine-max-l-merr-seeds
#18
Jiang Liu, Wen-Ting Qin, Hai-Jun Wu, Cai-Qiong Yang, Jun-Cai Deng, Nasir Iqbal, Wei-Guo Liu, Jun-Bo Du, Kai Shu, Feng Yang, Xiao-Chun Wang, Tai-Wen Yong, Wen-Yu Yang
The effects of storage duration on the seed germination and metabolite profiling of soybean seeds with five different coloured coats were studied. Their germination, constituents and transcript expressions of isoflavones and free fatty acids (FFAs) were compared using chromatographic metabolomic profiling and transcriptome sequencing. The seed water content was characterized using nuclear magnetic resonance (NMR) relaxometry. Results showed that dark-coloured seeds were less inactivated than light-coloured seeds...
May 15, 2017: Food Chemistry
https://www.readbyqxmd.com/read/28040654/verification-of-the-authenticity-of-drugs-by-means-of-nmr-relaxometry-viagra-%C3%A2-as-an-example
#19
S Wilczyńki, M Petelenz, M Florek-Wojciechowska, S Kulesza, Sz Brym, B Błońska-Fajfrowska, D Kruk
(1)H spin-lattice Nuclear Magnetic Resonance (NMR) relaxometry, vibrational spectroscopy and Atomic Force Microscopy (AFM) have been applied to differentiate between original and counterfeit Viagra(®). The relaxation studies have been performed in a frequency range covering four orders of magnitude, from 4kHz to 40MHz. It has been shown that for the counterfeit product the relaxation is bi-exponential in the whole frequency range, while for the original Viagra(®) the relaxation process is always single exponential...
December 23, 2016: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/28040490/biological-effects-of-iron-oxide-protamine-sulfate-complex-on-mesenchymal-stem-cells-and-its-relaxometry-based-labeling-optimization-for-cellular-mri
#20
Sushanta Kumar Mishra, Subash Khushu, Gurudutta Gangenahalli
Mesenchymal stem cells (MSCs) are frequently used as a therapeutic, but reliable imaging technique to longitudinally evaluate the engraftment of transplanted cells is inadequate. For magnetic resonance imaging (MRI), it is essential to understand the technical competence of in vitro stem cells labeling with iron oxide with regard to its relaxation behavior and significance of its biological expressions. The purpose of the study was to optimize the effective labeling of MSCs with high transverse relaxivity iron oxide contrast agent with protamine sulfate and also evaluate the biological effects (phenotype and function) of labeled MSCs...
December 28, 2016: Experimental Cell Research
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