Relevant bibliographies by topics / Longitudinal relaxation enhancement

Academic literature on the topic 'Longitudinal relaxation enhancement'

Author: Grafiati
Published: 10 March 2023

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Journal articles on the topic "Longitudinal relaxation enhancement"

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Shemesh, Noam, Jean-Nicolas Dumez, and Lucio Frydman. "Longitudinal Relaxation Enhancement in1H NMR Spectroscopy of Tissue Metabolites via Spectrally Selective Excitation." Chemistry - A European Journal 19, no. 39 (September 3, 2013): 13002–8. http://dx.doi.org/10.1002/chem.201300955.

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Shmyreva, Anna A., Majid Safdari, István Furó, and Sergey V. Dvinskikh. "NMR longitudinal relaxation enhancement in metal halides by heteronuclear polarization exchange during magic-angle spinning." Journal of Chemical Physics 144, no. 22 (June 14, 2016): 224201. http://dx.doi.org/10.1063/1.4953540.

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Shemesh, Noam, Jens T. Rosenberg, Jean-Nicolas Dumez, Samuel C. Grant, and Lucio Frydman. "Metabolic T1 Dynamics and Longitudinal Relaxation Enhancement In Vivo at Ultrahigh Magnetic Fields on Ischemia." Journal of Cerebral Blood Flow & Metabolism 34, no. 11 (September 10, 2014): 1810–17. http://dx.doi.org/10.1038/jcbfm.2014.149.

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Interruptions in cerebral blood flow may lead to devastating neural outcomes. Magnetic resonance has a central role in diagnosing and monitoring these insufficiencies, as well as in understanding their underlying metabolic consequences. Magnetic resonance spectroscopy (MRS) in particular can probe ischemia via the signatures of endogenous metabolites including lactic acid (Lac), N-acetylaspartate, creatine (Cre), and cholines. Typically, MRS reports on these metabolites' concentrations. This study focuses on establishing the potential occurrence of in vivo longitudinal relaxation enhancement (LRE) effects—a phenomenon involving a reduction of the apparent T1 with selective bandwidth excitations— in a rat stroke model at 21.1 T. Statistically significant reductions in Cre's apparent T1s were observed at all the examined post-ischemia time points for both ipsi- and contralateral hemispheres, thereby establishing the existence of LREs for this metabolite in vivo. Ischemia-dependent LRE trends were also noted for Lac in the ipsilateral hemisphere only 24 hours after ischemia. Metabolic T1s were also found to vary significantly as a function of post-stroke recovery time, with the most remarkable and rapid changes observed for Lac T1s. The potential of such measurements to understand stroke at a molecular level and assist in its diagnosis, is discussed.
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Bing, Shen, Hou Bo, and Zhang Shibin. "Diagnostic Value of Gadolinium Delayed Enhancement Combined with Longitudinal Relaxation Time Quantitative Imaging for Myocardial Amyloidosis." Journal of Medical Imaging and Health Informatics 11, no. 7 (July 1, 2021): 1929–38. http://dx.doi.org/10.1166/jmihi.2021.3588.

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This article is based on the use of GE combined with longitudinal lag time to quantify cardiac MRI screening for amyloidosis autologous thousand-cell transplantation, combined with clinical routine risk stratification, method for risk assessment of patients with amyloidosis and monitor the patient’s evaluation of the efficacy after treatment. Cardiac involvement with systemic amyloidosis is of great significance for both treatment and prognosis assessment, and is essential for quantitative and qualitative diagnosis or objectively providing prognostic value. In summary, myocardial amyloidosis needs to be studied before heart failure. It is recommended that patients undergo routine cardiac MRI examination to comprehensively evaluate cardiac morphology, function, risk stratification, prognosis, and treatment guidance. Diagnosis based on a single modality has been replaced by a comprehensive multi-modality method, and there is sufficient evidence to show the potential value of cardiac. However, with the continuous improvement of quality and value in the medical field, the field of cardiac will inevitably develop. The predicted and baseline indexes of myocardial strain predicted cardiac remission were 0.96 and 0.79, respectively. When the predictive value of clinical routine indicators and cardiac indicators is analyzed using blood response as the evaluation standard, the reduction in end-diastolic volume/body surface area (P = 0.031) can predict complete haematological remission. Folded cross-validation test shows that the end-diastolic volume/body surface area reduction and the baseline index IgG combined with myocardial strain predict AUC of complete blood remission of 0.78 and 0.76, respectively. This study will also continue to follow up and increase the sample size to verify the current conclusions.
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Razanahoera, Aiky, Anna Sonnefeld, Geoffrey Bodenhausen, and Kirill Sheberstov. "Paramagnetic relaxivity of delocalized long-lived states of protons in chains of CH2 groups." Magnetic Resonance 4, no. 1 (February 16, 2023): 47–56. http://dx.doi.org/10.5194/mr-4-47-2023.

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Abstract. Long-lived states (LLSs) have lifetimes TLLS that can be much longer than longitudinal relaxation times T1. In molecules containing several geminal pairs of protons in neighboring CH2 groups, it has been shown that delocalized LLSs can be excited by converting magnetization into imbalances between the populations of singlet and triplet states of each pair. Since the empirical yield of the conversion and reconversion of observable magnetization into LLSs and back is on the order of 10 % if one uses spin-lock induced crossing (SLIC), it would be desirable to boost the sensitivity by dissolution dynamic nuclear polarization (d-DNP). To enhance the magnetization of nuclear spins by d-DNP, the analytes must be mixed with radicals such as 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL). After dissolution, these radicals lead to an undesirable paramagnetic relaxation enhancement (PRE) which shortens not only the longitudinal relaxation times T1 but also the lifetimes TLLS of LLSs. It is shown in this work that PRE by TEMPOL is less deleterious for LLSs than for longitudinal magnetization for four different molecules: 2,2-dimethyl-2-silapentane-5-sulfonate (DSS), homotaurine, taurine, and acetylcholine. The relaxivities rLLS (i.e., the slopes of the relaxation rate constants RLLS as a function of the radical concentration) are 3 to 5 times smaller than the relaxivities r1 of longitudinal magnetization. Partial delocalization of the LLSs across neighboring CH2 groups may decrease this advantage, but in practice, this effect was observed to be small, for example, when comparing taurine containing two CH2 groups and homotaurine with three CH2 groups. Regardless of whether the LLSs are delocalized or not, it is shown that PRE should not be a major problem for experiments combining d-DNP and LLSs, provided the concentration of paramagnetic species after dissolution does not exceed 1 mM, a condition that is readily fulfilled in typical d-DNP experiments. In bullet d-DNP experiments however, it may be necessary to decrease the concentration of TEMPOL or to add ascorbate for chemical reduction.
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Zhang, Yapeng, Jingjing Cheng, and Wenzhong Liu. "Characterization and Relaxation Properties of a Series of Monodispersed Magnetic Nanoparticles." Sensors 19, no. 15 (August 2, 2019): 3396. http://dx.doi.org/10.3390/s19153396.

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Magnetic iron oxide nanoparticles are relatively advanced nanomaterials, and are widely used in biology, physics and medicine, especially as contrast agents for magnetic resonance imaging. Characterization of the properties of magnetic nanoparticles plays an important role in the application of magnetic particles. As a contrast agent, the relaxation rate directly affects image enhancement. We characterized a series of monodispersed magnetic nanoparticles using different methods and measured their relaxation rates using a 0.47 T low-field Nuclear Magnetic Resonance instrument. Generally speaking, the properties of magnetic nanoparticles are closely related to their particle sizes; however, neither longitudinal relaxation rate r 1 nor transverse relaxation rate r 2 changes monotonously with the particle size d . Therefore, size can affect the magnetism of magnetic nanoparticles, but it is not the only factor. Then, we defined the relaxation rates r i ′ (i = 1 or 2) using the induced magnetization of magnetic nanoparticles, and found that the correlation relationship between r 1 ′ relaxation rate and r 1 relaxation rate is slightly worse, with a correlation coefficient of R 2 = 0.8939, while the correlation relationship between r 2 ′ relaxation rate and r 2 relaxation rate is very obvious, with a correlation coefficient of R 2 = 0.9983. The main reason is that r 2 relaxation rate is related to the magnetic field inhomogeneity, produced by magnetic nanoparticles; however r 1 relaxation rate is mainly a result of the direct interaction of hydrogen nucleus in water molecules and the metal ions in magnetic nanoparticles to shorten the T 1 relaxation time, so it is not directly related to magnetic field inhomogeneity.
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Faas, Henryk M., James L. Krupa, Alexander J. Taylor, Francesco Zamberlan, Christopher J. Philp, Huw E. L. Williams, Simon R. Johnson, Galina E. Pavlovskaya, Neil R. Thomas, and Thomas Meersmann. "Accelerated 19F·MRI Detection of Matrix Metalloproteinase-2/-9 through Responsive Deactivation of Paramagnetic Relaxation Enhancement." Contrast Media & Molecular Imaging 2019 (February 28, 2019): 1–13. http://dx.doi.org/10.1155/2019/4826520.

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Paramagnetic gadolinium ions (GdIII), complexed within DOTA-based chelates, have become useful tools to increase the magnetic resonance imaging (MRI) contrast in tissues of interest. Recently, “on/off” probes serving as 19F·MRI biosensors for target enzymes have emerged that utilize the increase in transverse (T2∗ or T2) relaxation times upon cleavage of the paramagnetic GdIII centre. Molecular 19F·MRI has the advantage of high specificity due to the lack of background signal but suffers from low signal intensity that leads to low spatial resolution and long recording times. In this work, an “on/off” probe concept is introduced that utilizes responsive deactivation of paramagnetic relaxation enhancement (PRE) to generate 19F longitudinal (T1) relaxation contrast for accelerated molecular MRI. The probe concept is applied to matrix metalloproteinases (MMPs), a class of enzymes linked with many inflammatory diseases and cancer that modify bioactive extracellular substrates. The presence of these biomarkers in extracellular space makes MMPs an accessible target for responsive PRE deactivation probes. Responsive PRE deactivation in a 19F biosensor probe, selective for MMP-2 and MMP-9, is shown to enable molecular MRI contrast at significantly reduced experimental times compared to previous methods. PRE deactivation was caused by MMP through cleavage of a protease substrate that served as a linker between the fluorine-containing moiety and a paramagnetic GdIII-bound DOTA complex. Ultrashort echo time (UTE) MRI and, alternatively, short echo times in standard gradient echo (GE) MRI were employed to cope with the fast 19F transverse relaxation of the PRE active probe in its “on-state.” Upon responsive PRE deactivation, the 19F·MRI signal from the “off-state” probe diminished, thereby indicating the presence of the target enzyme through the associated negative MRI contrast. Null point 1H·MRI, obtainable within a short time course, was employed to identify false-positive 19F·MRI responses caused by dilution of the contrast agent.
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Baggiano, Andrea, Alberico Del Torto, Marco Guglielmo, Giuseppe Muscogiuri, Laura Fusini, Mario Babbaro, Ada Collevecchio, et al. "Role of CMR Mapping Techniques in Cardiac Hypertrophic Phenotype." Diagnostics 10, no. 10 (September 29, 2020): 770. http://dx.doi.org/10.3390/diagnostics10100770.

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Non-ischemic cardiomyopathies represent a heterogeneous group of myocardial diseases potentially leading to heart failure, life-threatening arrhythmias, and eventually death. Myocardial dysfunction is associated with different underlying pathological processes, ultimately inducing changes in morphological appearance. Thus, classification based on presenting morphological phenotypes has been proposed, i.e., dilated, hypertrophic, restrictive, and right ventricular cardiomyopathies. In light of the key diagnostic and prognostic role of morphological and functional features, cardiovascular imaging has emerged as key element in the clinical workflow of suspected cardiomyopathies, and above all, cardiovascular magnetic resonance (CMR) represents the ideal technique to be used: thanks to its physical principles, besides optimal spatial and temporal resolutions, incomparable contrast resolution allows to assess myocardial tissue abnormalities in detail. Traditionally, weighted images and late enhancement images after gadolinium-based contrast agent administration have been used to perform tissue characterization, but in the last decade quantitative assessment of pre-contrast longitudinal relaxation time (native T1), post-contrast longitudinal relaxation time (post-contrast T1) and transversal relaxation time (T2), all displayed with dedicated pixel-wise color-coded maps (mapping), has contributed to give precious knowledge insight, with positive influence of diagnostic accuracy and prognosis assessment, mostly in the setting of the hypertrophic phenotype. This review aims to describe the available evidence of the role of mapping techniques in the assessment of hypertrophic phenotype, and to suggest their integration in the routine CMR evaluation of newly diagnosed cardiomyopathies with increased wall thickness.
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Rastrelli, Federico, Diego Frezzato, Ronald G. Lawler, Yongjun Li, Nicholas J. Turro, and Alessandro Bagno. "Predicting the paramagnet-enhanced NMR relaxation of H 2 encapsulated in endofullerene nitroxides by density-functional theory calculations." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, no. 1998 (September 13, 2013): 20110634. http://dx.doi.org/10.1098/rsta.2011.0634.

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We have investigated the structure and nuclear magnetic resonance (NMR) spectroscopic properties of some dihydrogen endofullerene nitroxides by means of density-functional theory (DFT) calculations. Quantum versus classical roto-translational dynamics of H 2 have been characterized and compared. Geometrical parameters and hyperfine couplings calculated by DFT have been input to the Solomon–Bloembergen equations to predict the enhancement of the NMR longitudinal relaxation of H 2 due to coupling with the unpaired electron. Estimating the rotational correlation time via computed molecular volumes leads to a fair agreement with experiment for the simplest derivative; the estimate is considerably improved by recourse to the calculation of the diffusion tensor. For the other more flexible congeners, the agreement is less good, which may be due to an insufficient sampling of the conformational space. In all cases, relaxation by Fermi contact and Curie mechanisms is predicted to be negligible.
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Surányi, Pál, Pál Kiss, Balazs Ruzsics, Brigitta C. Brott, Tamás Simor, and Gabriel A. Elgavish. "Equilibrium signal intensity mapping, an MRI method for fast mapping of longitudinal relaxation rates and for image enhancement." Magnetic Resonance Imaging 25, no. 5 (June 2007): 641–51. http://dx.doi.org/10.1016/j.mri.2006.10.008.

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Dissertations / Theses on the topic "Longitudinal relaxation enhancement"

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HOSEK, TOMAS. "Development of new NMR methods to study intrinsically disordered proteins." Doctoral thesis, 2015. http://hdl.handle.net/2158/969485.

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PIAI, ALESSANDRO. "Characterizing structural disorder through NMR: new methods and applications." Doctoral thesis, 2015. http://hdl.handle.net/2158/1015862.

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Intrinsically Disordered Proteins (IDPs) are flexible proteins that challenge structural biology due to the fact that they cannot be studied with the standard methods developed to characterize well-folded proteins. In the last decades, the discovery of their widespread presence and involvement in many biological functions, despite their deviation from the structure-function paradigm, has pushed the scientific community towards a growing acceptance of the importance of IDPs and to the development of new tools for studying their structure, dynamics and functions. In this context, Nuclear Magnetic Resonance (NMR) spectroscopy plays the leading role of most suitable technique to characterize IDPs. In this doctoral thesis, my contribution to the advancement of NMR spectroscopy, achieved by developing new experiments to study IDPs, is described. The new methods enable the characterization of structural disorder and allow to address topics of general interest such as the study of protein linkers and low-complexity regions, two areas of high biological relevance for which only very limited atomic resolution information is available so far. The methodological progress in NMR and the findings on the studied IDPs reported here give a contribution to the discovery of new roles for structural disorder and prompt towards an unified understanding of structure-dynamicsdisorder/function relationships.
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Book chapters on the topic "Longitudinal relaxation enhancement"

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"Relaxation and the NOE." In Essential Mathematics for NMR and MRI Spectroscopists, 636–69. The Royal Society of Chemistry, 2016. http://dx.doi.org/10.1039/bk9781782627975-00636.

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The relaxation of spins to an equilibrium state makes itself apparent the first time one encounters a free induction decay (FID). The two major types of relaxation in magnetic resonance spectroscopy, T1 and T2 relaxation, are examined. Spin temperature is discussed to emphasise the flow of energy to and from spin systems during an experiment. Longitudinal (T1) relaxation is presented visually as the movement of the transverse magnetisation vector towards the equilibrium z-axis position and is modelled as an exponential process. Transverse relaxation (T2) is also shown visually as a de-coherence of the phases of the many transverse vectors representing the many spin magnetic moments in the sample and is also modelled as an exponential process. The spectral density function is derived from the Fourier transform of the autocorrelation function for stochastic molecular motions and its properties are examined. The dipolar relaxation mechanism that is dominant in solution NMR spectroscopy is discussed in detail using material from earlier chapters. The Nuclear Overhauser Enhancement (NOE) is then introduced, using the results from the dipolar relaxation section.
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