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1
Takeda, Y., H. Maeda, K. Ohki e Y. Yanagisawa. "Review of the temporal stability of the magnetic field for ultra-high field superconducting magnets with a particular focus on superconducting joints between HTS conductors". Superconductor Science and Technology 35, n. 4 (25 febbraio 2022): 043002. http://dx.doi.org/10.1088/1361-6668/ac5645.
Abstract (sommario):
Abstract Superconducting magnets used in applications such as magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) require significant temporal magnetic field stability, which can be achieved when the MRI and NMR magnets are operated in the persistent current mode (persistent-mode) using superconducting joints. However, the ultra-high field MRI and NMR magnets are sometimes operated in the driven mode. Herein, we present an analysis of the temporal magnetic field drift and fluctuations observed for MRI and NMR magnets operating in the driven mode and an exploration of effective methods for stabilizing the temporal magnetic field fluctuations. In the last decade, substantial improvements have been achieved in superconducting joints between high-temperature superconductors (HTSs). These superconducting joints enable the development of persistent-mode ultra-high field magnets using HTS coils. Therefore, we herein review the superconducting joint technology for HTS conductors and describe the results of the persistent-mode operation achieved by a medium-field NMR magnet using an HTS coil. Particularly, the cutting-edge progress achieved concerning HTS superconducting joints, including joining methods, superconducting properties, and future prospects, is highlighted along with the issues that need to be addressed.
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Ullah, Ubaid, Safia Bano e Shoaib Saleem. "Evaluation of Central Nervous System Tuberculomas by Using Modern Diagnostic Techniques". Pakistan Journal of Medical and Health Sciences 16, n. 6 (22 giugno 2022): 16–18. http://dx.doi.org/10.53350/pjmhs2216616.
Abstract (sommario):
Aim: To assess central nervous system tuberculomas by using modern MRI techniques such as Diffusion MRI (dMRI), Nuclear magnetic resonance spectroscopy (NMR spectroscopy) and BOLD venographic imaging. Study design: A retrospective study design Study setting: From 5th Feb 2021 to 5th Feb 2022 at the department of Neurology of Ibe-e-Siena Hospital, Multan. Methods: A retrospective study was conducted in the neurology department of Ibe-e-Siena Hospital & Research Institute Multan from 5th February 2021 to 5th February 2022. A total of 100 patients with suspected intracranial tuberculomas were included in the study. Advanced MRI techniques, including Diffusion MRI (dMRI), Nuclear magnetic resonance spectroscopy (NMR spectroscopy) and BOLD venographic imaging and conventional MRI, was performed on the patients. The study was approved by the ethical committee of the hospital, and all the patients provided their written consent for inclusion in the study Results: NMR spectroscopy evaluation showed that N-acetylaspartate /Creatine and N-acetylaspartate /Choline ratios of tuberculomas did not differ significantly from malignant brain lesions (p>0.04). But the malignant brain lesion (2.59) were significantly higher than the Choline/Creatine ratio of tuberculomas(1.29). BOLD venographic imaging evaluation showed no hypointense peripheral ring in malignant brain lesions but showed complete and regular rings in 36 (58.1%) of tuberculomas. Conclusion: Diffusion MRI did not help distinguish tuberculomas from metastasis and gliomas. However, NMR spectroscopy did offer this advantage by evaluating their unique metabolite pattern. BOLD venographic imaging showed the presence of a complete peripheral hypointense ring helping in diagnosing tuberculomas Keywords: Intracranial tuberculomas, Nuclear magnetic resonance spectroscopy, diffusion MRI,
3
Banko, B. A., J. P. Milovanovic e R. M. Maksimovic. "NMR diagnostic vallue inassessing laryngeal tumor". Acta chirurgica Iugoslavica 56, n. 3 (2009): 55–59. http://dx.doi.org/10.2298/aci0903055b.
Abstract (sommario):
Aims: To evaluate diagnostic accuracy of pretreatment surgical magnetic resonance images (MRI) in assessment of patients with tumors of the larynx. Materials and methods: The study included 12 patients, 11 men and 1 women, age 614 years. All patients underwent laryngeal endoscopy and biopsy followed by MRI. The biopsy confirmed that all patient had squamous-cell carcinoma. The MRI images were evaluated for presence in supraglottic, glottic or subglottic region, invasion of submucosal space, cartilage, extension to extralaryngeal tissue, presence of regional lymph nodes in regions I to VII. Imaging data were compared to surgical findings. Results: In 11 patients (92%) the tumor was supraglottic and glotic region and in 1 (8%) subglottic. None of them had tumor only in one region. Paraglottic ivasion was seen in 9 (75%) and preepiglottic in 2 (50%) patients. Paraglottic and preepiglotic invasion in the same time was seen in 3(25%) patients. 7 (58%) patients had normal vocal cord mobility, 3 (25%) mobility was unilateral and 2 (17%) had no vocal cord mobility. Cartilage invasion has not been seen in present study. All patients had billateral limphadenopathy region II-IV. Extension to extralaryngeal tissue was absent. These findings were confirmed on surgery with high diagnostic accuracy. Conclusion: MRI has been shown to be a reliable method for presurgical assessment of patients with tumor of the larynx.
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Sharma, Uma, e Naranamangalam R. Jagannathan. "Magnetic Resonance Imaging (MRI) and MR Spectroscopic Methods in Understanding Breast Cancer Biology and Metabolism". Metabolites 12, n. 4 (27 marzo 2022): 295. http://dx.doi.org/10.3390/metabo12040295.
Abstract (sommario):
A common malignancy that affects women is breast cancer. It is the second leading cause of cancer-related death among women. Metabolic reprogramming occurs during cancer growth, invasion, and metastases. Functional magnetic resonance (MR) methods comprising an array of techniques have shown potential for illustrating physiological and molecular processes changes before anatomical manifestations on conventional MR imaging. Among these, in vivo proton (1H) MR spectroscopy (MRS) is widely used for differentiating breast malignancy from benign diseases by measuring elevated choline-containing compounds. Further, the use of hyperpolarized 13C and 31P MRS enhanced the understanding of glucose and phospholipid metabolism. The metabolic profiling of an array of biological specimens (intact tissues, tissue extracts, and various biofluids such as blood, urine, nipple aspirates, and fine needle aspirates) can also be investigated through in vitro high-resolution NMR spectroscopy and high-resolution magic angle spectroscopy (HRMAS). Such studies can provide information on more metabolites than what is seen by in vivo MRS, thus providing a deeper insight into cancer biology and metabolism. The analysis of a large number of NMR spectral data sets through multivariate statistical methods classified the tumor sub-types. It showed enormous potential in the development of new therapeutic approaches. Recently, multiparametric MRI approaches were found to be helpful in elucidating the pathophysiology of cancer by quantifying structural, vasculature, diffusion, perfusion, and metabolic abnormalities in vivo. This review focuses on the applications of NMR, MRS, and MRI methods in understanding breast cancer biology and in the diagnosis and therapeutic monitoring of breast cancer.
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Tse, T. Y., R. M. Spanswick e L. W. Jelinski. "Quantitative evaluation of NMR and MRI methods to measure sucrose concentrations in plants". Protoplasma 194, n. 1-2 (marzo 1996): 54–62. http://dx.doi.org/10.1007/bf01273167.
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Prichard, James W., e Bruce R. Rosen. "Functional Study of the Brain by NMR". Journal of Cerebral Blood Flow & Metabolism 14, n. 3 (maggio 1994): 365–72. http://dx.doi.org/10.1038/jcbfm.1994.47.
Abstract (sommario):
Nuclear magnetic resonance (NMR) methods allow a wide variety of noninvasive measurements to be made on living animals and humans. The most extensively developed application of such methods is magnetic resonance imaging (MRI) of the brain and other organs, which has already come to the attention of most biomedical scholars, many physicians, and even much of the lay public because of its widespread use in neurological research and medical diagnosis.
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Hiltunen, Sami, Arttu Mankinen, Muhammad Asadullah Javed, Susanna Ahola, Martti Venäläinen e Ville-Veikko Telkki. "Characterization of the decay process of Scots pine caused by Coniophora puteana using NMR and MRI". Holzforschung 74, n. 11 (26 novembre 2020): 1021–32. http://dx.doi.org/10.1515/hf-2019-0246.
Abstract (sommario):
AbstractWood decay is an economically significant process, as it is one of the major causes of wood deterioration in buildings. In this study, the decay process of Scots pine (Pinus sylvestris) samples caused by cellar fungus (Coniophora puteana) was followed by nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) methods. Altogether, 30 wood sample pieces were exposed to fungus for 10 weeks. Based on the decrease of the dry mass, the samples were categorized into three classes: decomposed (mass decrease 50–70%), slightly decomposed (10–50%), and nondecomposed (<10%). MRI made it possible to identify the active regions of fungus inside the wood samples based on the signal of free water brought by the fungus and arisen from the decomposition of wood carbohydrates. MRI implies that free water is not only created by the decay process, but fungal hyphae also transports a significant amount of water into the sample. Two-dimensional 1H T1-T2 relaxation correlation NMR measurements provided detailed information about the changes in the microstructure of wood due to fungal decomposition. Overall, this study paves the way for noninvasive NMR and MRI detection of fungal decay at early stages as well as the related structural changes.
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Li, Jingyu, e Erni Ma. "Characterization of Water in Wood by Time-Domain Nuclear Magnetic Resonance Spectroscopy (TD-NMR): A Review". Forests 12, n. 7 (7 luglio 2021): 886. http://dx.doi.org/10.3390/f12070886.
Abstract (sommario):
This review summarizes the development of the experimental technique and analytical method for using TD-NMR to study wood-water interactions in recent years. We briefly introduce the general concept of TD-NMR and magnetic resonance imaging (MRI), and demonstrate their applications for characterizing the following aspects of wood-water interactions: water state, fiber saturation state, water distribution at the cellular scale, and water migration in wood. The aim of this review is to provide an overview of the utilizations and future research opportunities of TD-NMR in wood-water relations. It should be noted that this review does not cover the NMR methods that provide chemical resolution of wood macromolecules, such as solid-state NMR.
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Li, Na, Yong Shen, Wenru Liu, Jun Mei e Jing Xie. "Low-Field NMR and MRI to Analyze the Effect of Edible Coating Incorporated with MAP on Qualities of Half-Smooth Tongue Sole (Cynoglossus Semilaevis Günther) Fillets during Refrigerated Storage". Applied Sciences 8, n. 8 (17 agosto 2018): 1391. http://dx.doi.org/10.3390/app8081391.
Abstract (sommario):
Nondestructive and fast measurement and characterization of fish is highly desired during various processing treatments. This research investigated the effectiveness of low field LF-NMR and MRI as fast monitoring techniques to estimate the qualities of half-smooth tongue sole fillets treated with edible coating combined with modified atmosphere packaging during refrigeration. T2 relaxation spectra showed three peaks representing bound water (T21), immobile water (T22), and free water (T23), respectively. pT22 accounted for the largest proportion of three types of water, followed by pT23. The weighted MRI provided the internal structure information associated with different samples, indicting the combination of edible coating and MAP (70% CO2 + 30% N2) is the best performance in the maintenance of qualities and freshness of HTS fillets. All results demonstrated that the combination of LF-NMR and MRI as fast and nondestructive methods have great potential to monitor qualities deterioration and predict shelf life in of HTS fillets during refrigerated storage.
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Prichard, James W. "Neurorehabilitation: Three New NMR Tools". Neuroscientist 4, n. 4 (luglio 1998): 231–35. http://dx.doi.org/10.1177/107385849800400411.
Abstract (sommario):
NMR methods suitable for neurological diagnosis and research have proliferated since the biomedical NMR era began with the introduction of MRI in the late 1970s. The versatility and noninvasive nature of NMR present special opportunities for the study of tissue repair in the nervous system. Longitudinal observations of anatomical, functional, and biochemical aspects of repair processes through well-established NMR techniques are already feasible. Three newly developed techniques that promise to extend the range and depth of NMR work on neurorehabilitation are discussed in this article. These new techniques allow for the detection of 1) nerve fiber bundle orientation through the diffusional anisotropy of axoplasmic and interstitial water, 2) signs of neural activation within the first few hundred milliseconds after task onset, and 3) two-dimensional mapping of biochemical changes associated with tissue damage and repair. NEUROSCIENTIST 4: 231–235, 1998
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Gervits, Natalia E., Andrey A. Gippius, Alexey V. Tkachev, Evgeniy I. Demikhov, Sergey S. Starchikov, Igor S. Lyubutin, Alexander L. Vasiliev et al. "Magnetic properties of biofunctionalized iron oxide nanoparticles as magnetic resonance imaging contrast agents". Beilstein Journal of Nanotechnology 10 (2 ottobre 2019): 1964–72. http://dx.doi.org/10.3762/bjnano.10.193.
Abstract (sommario):
Background: One of the future applications of magnetic nanoparticles is the development of new iron-oxide-based magnetic resonance imaging (MRI) negative contrast agents, which are intended to improve the results of diagnostics and complement existing Gd-based contrast media. Results: Iron oxide nanoparticles designed for use as MRI contrast media are precisely examined by a variety of methods: powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, Mössbauer spectroscopy and zero-field nuclear magnetic resonance (ZF-NMR) spectroscopy. TEM and XRD measurements reveal a spherical shape of the nanoparticles with an average diameter of 5–8 nm and a cubic spinel-type crystal structure of space group Fd−3m. Raman, Mössbauer and NMR spectroscopy clearly indicate the presence of the maghemite γ-Fe2O3 phase. Moreover, a difference in the magnetic behavior of uncoated and human serum albumin coated iron oxide nanoparticles was observed by Mössbauer spectroscopy. Conclusion: This difference in magnetic behavior is explained by the influence of biofunctionalization on the magnetic and electronic properties of the iron oxide nanoparticles. The ZF-NMR spectra analysis allowed us to determine the relative amount of iron located in the core and the surface layer of the nanoparticles. The obtained results are important for understanding the structural and magnetic properties of iron oxide nanoparticles used as T 2 contrast agents for MRI.
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Keenan, Kathryn E., Zydrunas Gimbutas, Andrew Dienstfrey, Karl F. Stupic, Michael A. Boss, Stephen E. Russek, Thomas L. Chenevert et al. "Multi-site, multi-platform comparison of MRI T1 measurement using the system phantom". PLOS ONE 16, n. 6 (30 giugno 2021): e0252966. http://dx.doi.org/10.1371/journal.pone.0252966.
Abstract (sommario):
Recent innovations in quantitative magnetic resonance imaging (MRI) measurement methods have led to improvements in accuracy, repeatability, and acquisition speed, and have prompted renewed interest to reevaluate the medical value of quantitative T1. The purpose of this study was to determine the bias and reproducibility of T1 measurements in a variety of MRI systems with an eye toward assessing the feasibility of applying diagnostic threshold T1 measurement across multiple clinical sites. We used the International Society of Magnetic Resonance in Medicine/National Institute of Standards and Technology (ISMRM/NIST) system phantom to assess variations of T1 measurements, using a slow, reference standard inversion recovery sequence and a rapid, commonly-available variable flip angle sequence, across MRI systems at 1.5 tesla (T) (two vendors, with number of MRI systems n = 9) and 3 T (three vendors, n = 18). We compared the T1 measurements from inversion recovery and variable flip angle scans to ISMRM/NIST phantom reference values using Analysis of Variance (ANOVA) to test for statistical differences between T1 measurements grouped according to MRI scanner manufacturers and/or static field strengths. The inversion recovery method had minor over- and under-estimations compared to the NMR-measured T1 values at both 1.5 T and 3 T. Variable flip angle measurements had substantially greater deviations from the NMR-measured T1 values than the inversion recovery measurements. At 3 T, the measured variable flip angle T1 for one vendor is significantly different than the other two vendors for most of the samples throughout the clinically relevant range of T1. There was no consistent pattern of discrepancy between vendors. We suggest establishing rigorous quality control procedures for validating quantitative MRI methods to promote confidence and stability in associated measurement techniques and to enable translation of diagnostic threshold from the research center to the entire clinical community.
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Dhenain, Marc. "Preclinical MRI and NMR Biomarkers of Alzheimer's Disease: Concepts and Applications". Magnetic Resonance Insights 2 (gennaio 2008): MRI.S971. http://dx.doi.org/10.4137/mri.s971.
Abstract (sommario):
Alzheimer's disease is an important social and economic issue for our societies. The development of therapeutics against this severe dementia requires assessing the effects of new drugs in animal models thanks to dedicated biomarkers. This review first overviews Alzheimer's disease and its models as well as the concept of biomarkers. It then focuses on MRI and NMR biomarkers of Alzheimer's disease in animals. Anatomical markers such as atrophy and angiography are useful to phenotype newly developed models of Alzheimer's disease, even if the alterations in these animals are not as severe as in humans. Amyloid plaques imaging is a promising marker of the pathology in animals, and is a rapidly evolving field of MRI. Functional methods such as perfusion and diffusion imaging or spectroscopy are able to detect alterations in transgenic mice mimicking Alzheimer and also to show similar alterations than in humans. They can thus be good translational markers of the disease. Manganese-Enhanced MRI shows a reduction of neuronal transportation in transgenic models of Alzheimer and it allows monitoring improvements induced by treatments of the disease. It is thus a promising biomarker of the pathology in animals.
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Babuka, David, Kristyna Kolouchova, Ondrej Groborz, Zdenek Tosner, Alexander Zhigunov, Petr Stepanek e Martin Hruby. "Internal Structure of Thermoresponsive Physically Crosslinked Nanogel of Poly[N-(2-hydroxypropyl)methacrylamide]-Block-Poly[N-(2,2-difluoroethyl)acrylamide], Prominent 19F MRI Tracer". Nanomaterials 10, n. 11 (10 novembre 2020): 2231. http://dx.doi.org/10.3390/nano10112231.
Abstract (sommario):
Fluorine-19 MRI is a promising noninvasive diagnostic method. However, the absence of a nontoxic fluorine-19 MRI tracer that does not suffer from poor biodistribution as a result of its strong fluorophilicity is a constant hurdle in the widespread applicability of this otherwise versatile diagnostic technique. The poly[N-(2-hydroxypropyl)methacrylamide]-block-poly[N-(2,2-difluoroethyl)acrylamide] thermoresponsive copolymer was proposed as an alternative fluorine-19 MRI tracer capable of overcoming such shortcomings. In this paper, the internal structure of self-assembled particles of this copolymer was investigated by various methods including 1D and 2D NMR, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS). The elucidated structure appears to be that of a nanogel with greatly swollen hydrophilic chains and tightly packed thermoresponsive chains forming a network within the nanogel particles, which become more hydrophobic with increasing temperature. Its capacity to provide a measurable fluorine-19 NMR signal in its aggregated state at human body temperature was also investigated and confirmed. This capacity stems from the different fluorine-19 nuclei relaxation properties compared to those of hydrogen-1 nuclei.
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Dominique, Georgina, Wayne G. Brisbane e Robert E. Reiter. "The utility of prostate MRI within active surveillance: description of the evidence". World Journal of Urology 40, n. 1 (3 dicembre 2021): 71–77. http://dx.doi.org/10.1007/s00345-021-03853-9.
Abstract (sommario):
Abstract Purpose We present an overview of the literature regarding the use of MRI in active surveillance of prostate cancer. Methods Both MEDLINE® and Cochrane Library were queried up to May 2020 for studies of men on active surveillance with MRI and later confirmatory biopsy. The terms studied were ‘prostate cancer’ as the anchor followed by two of the following: active surveillance, surveillance, active monitoring, MRI, NMR, magnetic resonance imaging, MRI, and multiparametric MRI. Studies were excluded if pathologic reclassification (GG1 → ≥ GG2) and PI-RADS or equivalent was not reported. Results Within active surveillance, baseline MRI is effective for identifying clinically significant prostate cancer and thus associated with fewer reclassification events. A positive initial MRI (≥ PI-RADS 3) with GG1 identified at biopsy has a positive predictive value (PPV) of 35–40% for reclassification by 3 years. MRI possessed a stronger negative predictive value, with a negative MRI (≤ PI-RADS 2) yielding a negative predictive value of up to 85% at 3 years. Surveillance MRI, obtained after initial biopsy, yielded a PPV of 11–65% and NPV of 85–95% for reclassification. Conclusion MRI is useful for initial risk stratification of prostate cancer in men on active surveillance, especially if MRI is negative when imaging is obtained during surveillance. While useful, MRI cannot replace biopsy and further research is necessary to fully integrate MRI into active surveillance.
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Shkilnyuk, Galina G., Andrey A. Bogdan, Elena V. Kryukova, Andrey M. Petrov, Tatyana N. Trofimova e Igor D. Stolyarov. "Spectroscopic analysis of metabolic profile in patients with relapsed multiple sclerosis". Annals of Clinical and Experimental Neurology 16, n. 4 (23 dicembre 2022): 12–17. http://dx.doi.org/10.54101/acen.2022.4.2.
Abstract (sommario):
Introduction. Managing patients with relapsing-remitting multiple sclerosis (RMS) remains a pressing issue.
Objective. To detect the reversible metabolic changes of the brain matter in patients with clinically exacerbated RMS and to follow them up after intravenous glucocorticoid (IVGC) treatment.
Materials and methods. Neurological examination and neuroimaging in the RMS patients included expanded disability status scale (EDSS) scoring, conventional brain magnetic resonance imaging (MRI), and proton nuclear magnetic resonance spectroscopy (1H-NMR spectroscopy) before and after IVGC treatment. Multivoxel 1H-NMR spectroscopy was used to assess metabolism in the centra semiovale and cingulate gyri.
Results. Based on the multivoxel 1H-NMR spectroscopy, relative metabolite concentrations in the grey and white matter statistically differed within the study cohort before and after the IVGC treatment. The N-acetylaspartate/choline ratio significantly recovered and the choline/creatine ratio decreased in the anterior cingulate gyri in 27% of patients. The brainstem function score significantly improved in the metabolic response group as compared to the non-metabolic response group.
Conclusion. We should study the potential predictors of RMS activity and the IVGC response to select the RMS relapses when pulse-therapy with IVGCs is definitely indicated. Spectroscopy may reveal RMS pathogenesis variability earlier than conventional MRI.
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Guiheneuf, Thierry M., Jean-Joseph Tessier, Nicholas J. Herrod e Laurance D. Hall. "Magnetic Resonance Imaging of Meat Products: Automated Quantitation of the NMR Relaxation Parameters of Cured Pork, by Both ‘bulk’ NMR and MRI Methods". Journal of the Science of Food and Agriculture 71, n. 2 (giugno 1996): 163–73. http://dx.doi.org/10.1002/(sici)1097-0010(199606)71:2<163::aid-jsfa565>3.0.co;2-j.
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de Almeida Martins, João P., Chantal M. W. Tax, Filip Szczepankiewicz, Derek K. Jones, Carl-Fredrik Westin e Daniel Topgaard. "Transferring principles of solid-state and Laplace NMR to the field of in vivo brain MRI". Magnetic Resonance 1, n. 1 (28 febbraio 2020): 27–43. http://dx.doi.org/10.5194/mr-1-27-2020.
Abstract (sommario):
Abstract. Magnetic resonance imaging (MRI) is the primary method for noninvasive investigations of the human brain in health, disease, and development but yields data that are difficult to interpret whenever the millimeter-scale voxels contain multiple microscopic tissue environments with different chemical and structural properties. We propose a novel MRI framework to quantify the microscopic heterogeneity of the living human brain as spatially resolved five-dimensional relaxation–diffusion distributions by augmenting a conventional diffusion-weighted imaging sequence with signal encoding principles from multidimensional solid-state nuclear magnetic resonance (NMR) spectroscopy, relaxation–diffusion correlation methods from Laplace NMR of porous media, and Monte Carlo data inversion. The high dimensionality of the distribution space allows resolution of multiple microscopic environments within each heterogeneous voxel as well as their individual characterization with novel statistical measures that combine the chemical sensitivity of the relaxation rates with the link between microstructure and the anisotropic diffusivity of tissue water. The proposed framework is demonstrated on a healthy volunteer using both exhaustive and clinically viable acquisition protocols.
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Kennedy, Christopher B., Bruce J. Balcom e Igor V. Mastikhin. "Article". Canadian Journal of Chemistry 76, n. 11 (1 novembre 1998): 1753–65. http://dx.doi.org/10.1139/v98-226.
Abstract (sommario):
A new MRI method, recently employed in porous-media studies, is introduced for the imaging of rigid polymeric materials. The method, Single-Point Ramped Imaging with T1 Enhancement (SPRITE), is designed to spatially encode short lifetime, T2*, signals characteristic of rigid materials. We investigate the advantages of the SPRITE technique over conventional imaging methods by comparing a 2D SPRITE image of four common polymers to a 2D spin-echo image of the same substances. We demonstrate the general applicability of SPRITE by imaging two commercial products, a stop-valve made of chlorinated polyvinyl chloride and a solid-core, multilayer golf ball, both containing synthetic materials with effective 1H spin-spin relaxation times, T2*, well under 300 µs. Three-dimensional images of millimeter resolution reveal internal physical differentiation and chemical inhomogeneities that cannot be observed using conventional MRI methods. We also consider the incorporation of active spoiler gradients in SPRITE for visualization of samples with long spin-spin relaxation times, T2.Key words: MRI, NMR, SPI, SPRITE, polymers, imaging.
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De Deene, Yves. "Radiation Dosimetry by Use of Radiosensitive Hydrogels and Polymers: Mechanisms, State-of-the-Art and Perspective from 3D to 4D". Gels 8, n. 9 (19 settembre 2022): 599. http://dx.doi.org/10.3390/gels8090599.
Abstract (sommario):
Gel dosimetry was developed in the 1990s in response to a growing need for methods to validate the radiation dose distribution delivered to cancer patients receiving high-precision radiotherapy. Three different classes of gel dosimeters were developed and extensively studied. The first class of gel dosimeters is the Fricke gel dosimeters, which consist of a hydrogel with dissolved ferrous ions that oxidize upon exposure to ionizing radiation. The oxidation results in a change in the nuclear magnetic resonance (NMR) relaxation, which makes it possible to read out Fricke gel dosimeters by use of quantitative magnetic resonance imaging (MRI). The radiation-induced oxidation in Fricke gel dosimeters can also be visualized by adding an indicator such as xylenol orange. The second class of gel dosimeters is the radiochromic gel dosimeters, which also exhibit a color change upon irradiation but do not use a metal ion. These radiochromic gel dosimeters do not demonstrate a significant radiation-induced change in NMR properties. The third class is the polymer gel dosimeters, which contain vinyl monomers that polymerize upon irradiation. Polymer gel dosimeters are predominantly read out by quantitative MRI or X-ray CT. The accuracy of the dosimeters depends on both the physico-chemical properties of the gel dosimeters and on the readout technique. Many different gel formulations have been proposed and discussed in the scientific literature in the last three decades, and scanning methods have been optimized to achieve an acceptable accuracy for clinical dosimetry. More recently, with the introduction of the MR-Linac, which combines an MRI-scanner and a clinical linear accelerator in one, it was shown possible to acquire dose maps during radiation, but new challenges arise.
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López-Cebral, Rita, Manuel Martín-Pastor, Begoña Seijo e Alejandro Sanchez. "Progress in the characterization of bio-functionalized nanoparticles using NMR methods and their applications as MRI contrast agents". Progress in Nuclear Magnetic Resonance Spectroscopy 79 (maggio 2014): 1–13. http://dx.doi.org/10.1016/j.pnmrs.2014.01.002.
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BAUMGARTNER, S., G. LAHAJNAR, A. SEPE e J. KRISTL. "Quantitative evaluation of polymer concentration profile during swelling of hydrophilic matrix tablets using H NMR and MRI methods". European Journal of Pharmaceutics and Biopharmaceutics 59, n. 2 (febbraio 2005): 299–306. http://dx.doi.org/10.1016/j.ejpb.2004.08.010.
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Hillel, Inbar, Itzhak Binderman, Yifat Sarda e Uri Nevo. "Monitoring of Cellular Changes in the Bone Marrow following PTH(1-34) Treatment of OVX Rats Using a Portable Stray-Field NMR Scanner". Journal of Osteoporosis 2017 (2017): 1–10. http://dx.doi.org/10.1155/2017/7910432.
Abstract (sommario):
Osteoporosis is characterized by reduction in trabecular bone in conjunction with increased marrow cell adiposity. While these changes occur within weeks, monitoring of treatment efficacy as performed by DEXA is sensitive only to long-term changes. MRI is sensitive to bone marrow changes but is less affordable. In a recent study, we have shown that a stray-field NMR can monitor bone marrow cellular changes that are related to osteoporosis. Objectives. To demonstrate sensitivity of a low-field tabletop NMR scanner to bone marrow dynamics following hormonal treatment in rats. Methods. Two-month-old female rats (n=36) were ovariectomized (OVX) and dosed for the ensuing 3 or 5 weeks with 20 mg/kg of PTH(1-34). Hind limbs femurs and tibiae were isolated and underwent ex vivo microradiography and histology and NMR relaxometry at 6 weeks (preventive experiment) and 11 weeks (therapeutic treatment experiment) after OVX. Results. OVX rats developed osteoporotic changes including adipogenic marrow compared to Sham and PTH treated rats. T2 and ADC NMR relaxation coefficients were found to correlate with marrow composition. Conclusions. This study suggests that stray-field NMR, an affordable method that is sensitive to the rapid cellular changes in bone marrow, may have a clinical value in monitoring hormonal treatment for osteoporosis.
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Sun, Shan, Siqi Wang, Rong Lin, Shasha Cheng, Biao Yuan, Zhixiang Wang e Mingqian Tan. "Effect of Different Cooking Methods on Proton Dynamics and Physicochemical Attributes in Spanish Mackerel Assessed by Low-Field NMR". Foods 9, n. 3 (21 marzo 2020): 364. http://dx.doi.org/10.3390/foods9030364.
Abstract (sommario):
The states of protons within food items are highly related to their physical attributes. In this study, the effect of cooking methods including boiling, steaming, roasting and frying on proton dynamics, physicochemical parameters and microstructure of Spanish mackerel was assessed by low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) techniques. The treatment of cooking resulted in a significant reduction of proton mobility and declined freedom of protons. The state changes of protons can be monitored easily in an intuitive and non-destructive manner during various cooking process. The treatments of boiling, steaming, roasting and frying resulted in different cooking loss and similar water-holding capability. A significant increase of total carbonyl content and thiobarbituric acid reactive substances was found, while a decrease of the values for free thiols and surface hydrophobicity was observed. The analysis of circular dichroism spectroscopy and cryo-scanning electron microscopy showed significant structural change. The correlation coefficients of Rcal2 and Rcv2 from partial least squares (PLS) regression models were more than 0.980, suggesting good correlation between LF-NMR data and hardness, resilience, springiness, chewiness, gumminess, and adhesiveness. Good recoveries and a relatively small coefficient of variation (CV) were obtained from the PLS regression models, indicating good reliability and accuracy in predicting texture parameters for mackerel samples.
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Rhodes, Christopher J. "Magnetic Resonance Spectroscopy". Science Progress 100, n. 3 (settembre 2017): 241–92. http://dx.doi.org/10.3184/003685017x14993478654307.
Abstract (sommario):
Since the original observation by Zeeman, that spectral lines can be affected by magnetic fields, ‘magnetic spectroscopy’ has evolved into the broad arsenal of techniques known as ‘magnetic resonance’. This review focuses on nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and muon spin resonance (μSR): methods which have provided unparalleled insight into the structures, reactivity and dynamics of molecules, and thereby contributed to a detailed understanding of important aspects of chemistry, and the materials, biomedical, and environmental sciences. Magnetic resonance imaging (MRI), in vivo magnetic resonance spectroscopy (MRS) and functional magnetic resonance spectroscopy (fMRS) are also described. EPR is outlined as a principal method for investigating free radicals, along with biomedical applications, and mention is given to the more recent innovation of pulsed EPR techniques. In the final section of the article, the various methods known as μSR are collected under the heading ‘muon spin resonance’, in order to emphasise their complementarity with the more familiar NMR and EPR.
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Buyse, Chloé, Nicolas Joudiou, Cyril Corbet, Olivier Feron, Lionel Mignion, Julien Flament e Bernard Gallez. "Impact of Inhibition of the Mitochondrial Pyruvate Carrier on the Tumor Extracellular pH as Measured by CEST-MRI". Cancers 13, n. 17 (25 agosto 2021): 4278. http://dx.doi.org/10.3390/cancers13174278.
Abstract (sommario):
(1) Background: The acidosis of the tumor micro-environment may have profound impact on cancer progression and on the efficacy of treatments. In the present study, we evaluated the impact of a treatment with UK-5099, a mitochondrial pyruvate carrier (MPC) inhibitor on tumor extracellular pH (pHe); (2) Methods: glucose consumption, lactate secretion and extracellular acidification rate (ECAR) were measured in vitro after exposure of cervix cancer SiHa cells and breast cancer 4T1 cells to UK-5099 (10 µM). Mice bearing the 4T1 tumor model were treated daily during four days with UK-5099 (3 mg/kg). The pHe was evaluated in vivo using either chemical exchange saturation transfer (CEST)-MRI with iopamidol as pHe reporter probe or 31P-NMR spectroscopy with 3-aminopropylphosphonate (3-APP). MR protocols were applied before and after 4 days of treatment; (3) Results: glucose consumption, lactate release and ECAR were increased in both cell lines after UK-5099 exposure. CEST-MRI showed a significant decrease in tumor pHe of 0.22 units in UK-5099-treated mice while there was no change over time for mice treated with the vehicle. Parametric images showed a large heterogeneity in response with 16% of voxels shifting to pHe values under 7.0. In contrast, 31P-NMR spectroscopy was unable to detect any significant variation in pHe; (4) Conclusions: MPC inhibition led to a moderate acidification of the extracellular medium in vivo. CEST-MRI provided high resolution parametric images (0.44 µL/voxel) of pHe highlighting the heterogeneity of response within the tumor when exposed to UK-5099.
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Chen, Haiyan, e Yongbao Shen. "Investigation of Water Distribution and Mobility Dynamics in Recalcitrant Quercus acutissima Seeds during Desiccation Using Magnetic Resonance Methods". Forests 14, n. 4 (4 aprile 2023): 738. http://dx.doi.org/10.3390/f14040738.
Abstract (sommario):
Recalcitrant seed vigor is closely related to seed moisture, so how do the water distribution and status change during seed drying? In this study, we investigated the association between water content (WC) and germination of Quercus acutissima seeds and used nuclear magnetic resonance (NMR) to monitor the water dynamics during seed drying. Results showed that freshly dispersed seeds had 38.8% WC, but drying to 14.8% WC resulted in a complete loss of vigor. Magnetic resonance images (MRI) reveal that the embryonic axis had the highest WC and the fastest rate of water loss, and seeds lost water from the embryonic axis to the apex and from the center to the end of cotyledons during desiccation. According to low-field NMR results, the proportion of free water in fresh seeds was the highest at 55%, followed by bound water at 10% and immobile water at 35%. During drying, the bound water and free water of seeds were lost simultaneously, and free water was lost most when the seeds died. Our results revealed that Q. acutissima seeds are highly sensitive to desiccation and that the water loss sites of the seeds were at the micropyle and scar. During desiccation, the bound water could not be retained, and the water balance in the seeds was broken, eventually leading to seed death.
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Grey, Clare P. "Following Function in Real Time: New NMR and MRI Methods for Studying Structure and Dynamics in Batteries and Supercapacitors". Zeitschrift für anorganische und allgemeine Chemie 638, n. 10 (agosto 2012): 1551. http://dx.doi.org/10.1002/zaac.201202005.
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Bagheri, Khashayar, Michael Deschamps e Elodie Salager. "Novel Operando Nuclear Magnetic Resonance Approach for Tracking the Electrode State of Charge in Li/Na-Ion Batteries". ECS Meeting Abstracts MA2023-02, n. 1 (22 dicembre 2023): 87. http://dx.doi.org/10.1149/ma2023-02187mtgabs.
Abstract (sommario):
Lithium and sodium-ion batteries have become the focal point of interest for the energy transition due to their promising applications for electric cars and energy grid storage. Operando characterization of batteries is critical to understand the degradation processes and increasing their electrochemical performance, especially in abusive conditions like during fast charges. Knowledge of the redox state of each electrode is essential to identify the origins of capacity loss in full batteries. Among the methods used for these investigations, operando Nuclear Magnetic Resonance (NMR) methods are promising since, without destroying the battery, they enable monitoring in real-time the electrochemical processes and the formation of short-lived metastable or reactive phases [1,2]. Up to now, most operando NMR studies have focused on 7Li NMR spectroscopy to follow the lithiation and degradation processes in the solid electrodes of lithium-ion batteries. However, the large shifts and broadenings of the NMR spectra, which result from the redox-active paramagnetic ions (Ni2/3+, Co4+, Mn3/4+) or from the metallicity of the electrodes [3], complicate operando NMR spectra acquisition and interpretation for full batteries. Herein, we demonstrate that the 1H operando NMR signal of the liquid electrolyte solvent can be used to spy on the positive electrode evolution while benefitting from the high sensitivity of 1H liquid-state NMR compared to 7Li NMR. So far, operando NMR using the liquid electrolyte signal was mainly exploited to follow electrolyte decomposition [4] or to image indirectly dendrite formation [5]. Contrary to the lithium or sodium atoms composing the electrodes, hydrogen atoms in the electrolyte solvent are not a direct probe of the state of charge of the electrode. We demonstrate that the 1H NMR signal of the electrolyte molecules in the battery is, however, highly sensitive to the magnetic susceptibility (and therefore the redox state) of the neighboring particles of positive electrode active material. The state-of-charge (SOC) of the positive electrodes in the charging battery can be tracked indirectly through distortion in the spectrum of the dimethyl carbonate (DMC) solvent near the positive electrode. The effect of the other battery components such as current collectors, separators, or even negative electrodes is shown to be negligible compared to the perturbations induced by the positive electrode. We define specific descriptors to track the changes in the distorted 1H NMR spectrum of the battery and we correlate these changes with the state-of-charge of the positive electrode inside the battery as it is charged and discharged. This approach will enable measuring, operando, the redox state of positive electrodes in batteries, even when their 7Li signals cannot be detected by NMR. Exact knowledge of the redox state will contribute to a better exploitation of the electrochemical curves in full batteries. [1] Bagheri, K.; Deschamps, M.; Salager, E. Nuclear Magnetic Resonance for Interfaces in Rechargeable Batteries. Current Opinion in Colloid & Interface Science 2023, 64, 101675. https://doi.org/10.1016/j.cocis.2022.101675. [2] Liu, X.; Liang, Z.; Xiang, Y.; Lin, M.; Li, Q.; Liu, Z.; Zhong, G.; Fu, R.; Yang, Y. Solid‐State NMR and MRI Spectroscopy for Li/Na Batteries: Materials, Interface, and in Situ Characterization. Advanced Materials 2021, 33 (50), 2005878. https://doi.org/10.1002/adma.202005878. [3] Grey, C. P.; Dupré, N. NMR Studies of Cathode Materials for Lithium-Ion Rechargeable Batteries. Chemical Reviews 2004, 104 (10), 4493–4512. https://doi.org/10.1021/cr020734p. [4] Wiemers-Meyer, S.; Winter, M.; Nowak, S. NMR as a Powerful Tool to Study Lithium Ion Battery Electrolytes. Annual Reports on NMR Spectroscopy 2019, 121–162. https://doi.org/10.1016/bs.arnmr.2018.12.003. [5] Ilott, A. J.; Mohammadi, M.; Chang, H. J.; Grey, C. P.; Jerschow, A. Real-Time 3D Imaging of Microstructure Growth in Battery Cells Using Indirect MRI. Proceedings of the National Academy of Sciences 2016, 113 (39), 10779–10784. https://doi.org/10.1073/pnas.1607903113.
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Vidmar, Jernej, Franci Bajd, Zoran V. Milosevic, Igor J. Kocijancic, Miran Jeromel e Igor Sersa. "Retrieved cerebral thrombi studied by T2 and ADC mapping: preliminary results". Radiology and Oncology 53, n. 4 (20 novembre 2019): 427–33. http://dx.doi.org/10.2478/raon-2019-0056.
Abstract (sommario):
Abstract Background Recent advances in MRI technology makes it increasingly more competitive to CT also in the field of interventions. Multi-parametric MRI offers a significant amount of data relevant for characterization of human cerebral thrombi. Patients and methods Cerebral thrombi of 17 patients diagnosed with acute stroke were acquired by mechanical thrombectomy. The thrombi were subsequently scanned using a high spatial-resolution 3D T1-weighted MRI to obtain morphological characteristics of the thrombi and also by apparent diffusion coefficient (ADC) and transversal nuclear magnetic resonance (NMR) relaxation time (T2) mapping. The MRI results were analysed for possible correlations between thrombectomy procedure parameters (recanalization time and number of passes) and MR-measurable parameters (sample-mean ADC and T2, within-sample coefficient of variation of ADC and T2, and thrombus length). Results Both MRI mapping techniques enabled a good discrimination among thrombi regions of different water mobility and compaction. Within-sample coefficient of variation of ADC was found most sensitive for discrimination between the thrombi where thrombectomy procedure was performed in a single pass and those where is was performed in two or more passes (p = 0.03). Interestingly, negative correlation was found between the recanalization time and thrombus length (ρ = -0.22). Conclusions Preliminary results of presented study shows that pretreatment MRI assessment of thrombi in stroke patients could potentially ease stroke treatment planning. In this study it is shown that within-sample coefficient of variation of ADC could serve for prediction of possible complications during thrombectomy procedures.
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Schiepers, Christiaan, Paul Van Hecke, Rik Vandenberghe, Sylvie Van Oostende, Patrick Dupont, Philippe Demaerel, Guy Bormans e Herwig Carton. "Positron emission tomography, magnetic resonance imaging and proton NMR spectroscopy of white matter in multiple sclerosis". Multiple Sclerosis Journal 3, n. 1 (febbraio 1997): 8–17. http://dx.doi.org/10.1177/135245859700300102.
Abstract (sommario):
Objective: To assess characteristics of MS lesions and normal appearing white matter (NAWM) with various imaging modalities. Glucose metabolism was investigated with FDG - PET, metabolite concentration with proton NMR spectroscopy, and lesion detection with routine brain MRI. Methods: Thirteen patients were studied in a stable phase of their disease, and two during an acute episode. Nine healthy volunteers served as controls. Results: Three patients had a normal brain MRI, 12 had typical lesions. MR images were registered to the PET planes. Lesions and contra-lateral control areas were analyzed, 10/15 lesions showed relative hyper-metabolism and 2 hypo-metabolism. NAA concentration was significantly decreased in both lesions and NAWM. Conclusion: In stable MS, most large lesions have a relatively increased glucose utilization and decreased NAA concentration. NAWM showed a significantly decreased NAA concentration compared to healthy subjects, but no difference in glucose metabolism. Active lesions in acute MS are also hyper-metabolic. This finding opens a new window on the classification of white matter lesions based on glucose utilization.
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Boesch, Chris. "Magic angle spinning magnetic resonance: a novel method opening up translational research into NAFLD?" Clinical Science 116, n. 5 (2 febbraio 2009): 401–2. http://dx.doi.org/10.1042/cs20080621.
Abstract (sommario):
NAFLD (non-alcoholic fatty liver disease) and NASH (non-alcoholic steatohepatitis) are of increasing importance, both in connection with insulin resistance and with the development of liver cirrhosis. Histological samples are still the ‘gold standard’ for diagnosis; however, because of the risks of a liver biopsy, non-invasive methods are needed. MAS (magic angle spinning) is a special type of NMR which allows characterization of intact excised tissue without need for additional extraction steps. Because clinical MRI (magnetic resonance imaging) and MRS (magnetic resonance spectroscopy) are based on the same physical principle as NMR, translational research is feasible from excised tissue to non-invasive examinations in humans. In the present issue of Clinical Science, Cobbold and co-workers report a study in three animal strains suffering from different degrees of NAFLD showing that MAS results are able to distinguish controls, fatty infiltration and steatohepatitis in cohorts. In vivo MRS methods in humans are not obtainable at the same spectral resolution; however, know-how from MAS studies may help to identify characteristic changes in crowded regions of the magnetic resonance spectrum.
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Wang, Wang, Jinyu Chen e Jinzhen Cao. "Using low-field NMR and MRI to characterize water status and distribution in modified wood during water absorption". Holzforschung 73, n. 11 (25 ottobre 2019): 997–1004. http://dx.doi.org/10.1515/hf-2018-0293.
Abstract (sommario):
Abstract In this study, synergism between two wood modification methods was investigated with the aim of providing insights into improving wood hydrophobicity. Loblolly pine (Pinus taeda) was modified using two variants of the same treatment procedure: in the first case, paraffin wax emulsion (PWE) impregnation was followed by thermal modification (TM); in the second case, the order was reversed, and TM was followed by PWE impregnation. The treated samples were then immersed in distilled water for 1, 6, 24, 48 or 96 h. Low-field nuclear magnetic resonance (LF-NMR) and nuclear magnetic resonance imaging (MRI) were employed to evaluate the concentration of different water components, as well as the water distribution. The results indicated that the combined treatment showed much better performance than either treatment individually, particularly when PWE impregnation was followed by TM. Moreover, through the use of MRI, we characterized the role of both methods in the synergistic relationship, which showed that the PWE impregnation increased the wood hydrophobicity through decreasing free water absorption, while the TM performed the same function through bound water absorption. In addition, paraffin wax penetrated the newly formed cracks caused by TM, which also contributed to the synergistic mechanism between PWE impregnation and TM.
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Hill-Casey, Sakho, Mohammed, Rossetto, Ahwal, Duckett, John, Richardson, Virgo e Halse. "In Situ SABRE Hyperpolarization with Earth’s Field NMR Detection". Molecules 24, n. 22 (14 novembre 2019): 4126. http://dx.doi.org/10.3390/molecules24224126.
Abstract (sommario):
Hyperpolarization methods, which increase the sensitivity of nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI), have the potential to expand the range of applications of these powerful analytical techniques and to enable the use of smaller and cheaper devices. The signal amplification by reversible exchange (SABRE) method is of particular interest because it is relatively low-cost, straight-forward to implement, produces high-levels of renewable signal enhancement, and can be interfaced with low-cost and portable NMR detectors. In this work, we demonstrate an in situ approach to SABRE hyperpolarization that can be achieved using a simple, commercially-available Earth’s field NMR detector to provide 1H polarization levels of up to 3.3%. This corresponds to a signal enhancement over the Earth’s magnetic field by a factor of ε > 2 × 108. The key benefit of our approach is that it can be used to directly probe the polarization transfer process at the heart of the SABRE technique. In particular, we demonstrate the use of in situ hyperpolarization to observe the activation of the SABRE catalyst, the build-up of signal in the polarization transfer field (PTF), the dependence of the hyperpolarization level on the strength of the PTF, and the rate of decay of the hyperpolarization in the ultra-low-field regime.
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Rayner, Peter J., Michael J. Burns, Alexandra M. Olaru, Philip Norcott, Marianna Fekete, Gary G. R. Green, Louise A. R. Highton, Ryan E. Mewis e Simon B. Duckett. "Delivering strong 1H nuclear hyperpolarization levels and long magnetic lifetimes through signal amplification by reversible exchange". Proceedings of the National Academy of Sciences 114, n. 16 (4 aprile 2017): E3188—E3194. http://dx.doi.org/10.1073/pnas.1620457114.
Abstract (sommario):
Hyperpolarization turns typically weak NMR and MRI responses into strong signals so that ordinarily impractical measurements become possible. The potential to revolutionize analytical NMR and clinical diagnosis through this approach reflect this area's most compelling outcomes. Methods to optimize the low-cost parahydrogen-based approach signal amplification by reversible exchange with studies on a series of biologically relevant nicotinamides and methyl nicotinates are detailed. These procedures involve specific 2H labeling in both the agent and catalyst and achieve polarization lifetimes of ca. 2 min with 50% polarization in the case of methyl-4,6-d2-nicotinate. Because a 1.5-T hospital scanner has an effective 1H polarization level of just 0.0005% this strategy should result in compressed detection times for chemically discerning measurements that probe disease. To demonstrate this technique’s generality, we exemplify further studies on a range of pyridazine, pyrimidine, pyrazine, and isonicotinamide analogs that feature as building blocks in biochemistry and many disease-treating drugs.
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ERIKSON, U., E. VELIYULIN, T. E. SINGSTAD e M. AURSAND. "Salting and Desalting of Fresh and Frozen-thawed Cod (Gadus morhua) Fillets: A Comparative Study Using 23Na NMR, 23Na MRI, Low-field 1H NMR, and Physicochemical Analytical Methods". Journal of Food Science 69, n. 3 (31 maggio 2006): FEP107—FEP114. http://dx.doi.org/10.1111/j.1365-2621.2004.tb13362.x.
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Chu, W. J., H. P. Hetherington, R. I. Kuzniecky, T. Simor, G. F. Mason e G. A. Elgavish. "Lateralization of human temporal lobe epilepsy by 31P NMR spectroscopic imaging at 4.1 T". Neurology 51, n. 2 (agosto 1998): 472–79. http://dx.doi.org/10.1212/wnl.51.2.472.
Abstract (sommario):
Objective: To compare the phosphorous metabolite ratios in the mesial temporal lobe of healthy volunteers (n = 20) with the corresponding ratios in patients with temporal lobe epilepsy (n = 30) using 31P NMR spectroscopic imaging and to lateralize the seizure focus in temporal lobe epilepsy patients using various phosphorous metabolite ratios-phosphocreatine to inorganic phosphate(PCr/Pi), PCr to adenosine triphosphate (PCr/γ-ATP), and(γ-ATP/Pi)-and to compare with clinical lateralization results.Methods: All 31P NMR spectroscopic imaging studies were performed on a high-field, 4.1 T, whole-body NMR spectroscopic imaging system using a31 P/1H double-tuned volume coil.Results: We found an average reduction of 15% in the PCr/Pi and γ-ATP/Pi ratios compared with the corresponding ratios in healthy volunteers in the entire mesial temporal lobe, and more than a 30% reduction in these two ratios in the anterior region of the epileptogenic mesial temporal lobe. These ratios were also reduced significantly in the ipsilateral lobe when compared with their corresponding values in the contralateral lobe. In patients we lateralized the seizure focus, based on these 31P NMR data, and compared the results with the clinical lateralization. The lateralization based on either the PCr/Pi or the γ-ATP/Pi ratio yielded a correspondence of 70 to 73% with the final clinical lateralization. In the subgroup of patients (n = 9) that needed intracranial EEG for the presurgical lateralization because of inconclusive results from the noninvasive methods, a 78% correspondence was found with the 31P NMR-based lateralization, whereas MRI provided a correspondence of only 33%, and scalp EEG provided a correspondence of only 56%.Conclusions: These results suggest the utility of adding the 31P NMR method to the group of noninvasive modalities used for presurgical decision making in temporal lobe epilepsy patients.
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Xu, Fangfang, Xin Jin, Lu Zhang e Xiao Dong Chen. "Investigation on water status and distribution in broccoli and the effects of drying on water status using NMR and MRI methods". Food Research International 96 (giugno 2017): 191–97. http://dx.doi.org/10.1016/j.foodres.2017.03.041.
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Jiang, Hong, Leo Svenningsson e Daniel Topgaard. "Multidimensional encoding of restricted and anisotropic diffusion by double rotation of the q vector". Magnetic Resonance 4, n. 1 (15 marzo 2023): 73–85. http://dx.doi.org/10.5194/mr-4-73-2023.
Abstract (sommario):
Abstract. Diffusion NMR and MRI methods building on the classic pulsed gradient spin-echo sequence are sensitive to many aspects of translational motion, including time and frequency dependence (“restriction”), anisotropy, and flow, leading to ambiguities when interpreting experimental data from complex heterogeneous materials such as living biological tissues. While the oscillating gradient technique specifically targets frequency dependence and permits control of the sensitivity to flow, tensor-valued encoding enables investigations of anisotropy in orientationally disordered materials. Here, we propose a simple scheme derived from the “double-rotation” technique in solid-state NMR to generate a family of modulated gradient waveforms allowing for comprehensive exploration of the 2D frequency–anisotropy space and convenient investigation of both restricted and anisotropic diffusion with a single multidimensional acquisition protocol, thereby combining the desirable characteristics of the oscillating gradient and tensor-valued encoding techniques. The method is demonstrated by measuring multicomponent isotropic Gaussian diffusion in simple liquids, anisotropic Gaussian diffusion in a polydomain lyotropic liquid crystal, and restricted diffusion in a yeast cell sediment.
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Gudjónsdóttir, María, Amidou Traoré, Ásbjörn Jónsson, Magnea Gudrún Karlsdóttir e Sigurjón Arason. "The effects of pre-salting methods on salt and water distribution of heavily salted cod, as analyzed by 1H and 23Na MRI, 23Na NMR, low-field NMR and physicochemical analysis". Food Chemistry 188 (dicembre 2015): 664–72. http://dx.doi.org/10.1016/j.foodchem.2015.05.060.
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Htun, Khin Thandar, Jie Pan, Duanghathai Pasanta, Montree Tungjai, Chatchanok Udomtanakunchai, Thanaporn Petcharoen, Nattacha Chamta et al. "Advanced Molecular Imaging (MRI/MRS/1H NMR) for Metabolic Information in Young Adults with Health Risk Obesity". Life 11, n. 10 (1 ottobre 2021): 1035. http://dx.doi.org/10.3390/life11101035.
Abstract (sommario):
Background: Obesity or being overweight is a medical condition of abnormal body fat accumulation which is associated with a higher risk of developing metabolic syndrome. The distinct body fat depots on specific parts of the anatomy have unique metabolic properties and different types of regional excessive fat distribution can be a disease hazard. The aim of this study was to identify the metabolome and molecular imaging phenotypes among a young adult population. Methods: The amount and distribution of fat and lipid metabolites profile in the abdomen, liver, and calf muscles of 46 normal weight, 17 overweight, and 13 obese participants were acquired using MRI and MR spectroscopy (MRS), respectively. The serum metabolic profile was obtained using proton NMR spectroscopy. NMR spectra were integrated into seven integration regions, which reflect relative metabolites. Results: A significant metabolic disorder symptom appeared in the overweight and obese group, and increased lipid deposition occurred in the abdomen, hepatocytes, and muscles that were statistically significant. Overall, the visceral fat depots had a marked influence on dyslipidemia biomarkers, blood triglyceride (r = 0.592, p < 0.001), and high-density lipoprotein cholesterol (r = −0.484, p < 0.001). Intrahepatocellular lipid was associated with diabetes predictors for hemoglobin (HbA1c%; r = 0.379, p < 0.001) and for fasting blood sugar (r = 0.333, p < 0.05). The lipid signals in serum triglyceride and glucose signals gave similar correspondence to biochemical lipid profiles. Conclusions: This study proves the association between alteration in metabolome in young adults, which is the key population for early prevention of obesity and metabolic syndrome. This study suggests that dyslipidemia prevalence is influenced mainly by the visceral fat depot, and liver fat depot is a key determinant for glucose metabolism and hyperglycemia. Moreover, noninvasive advanced molecular imaging completely elucidated the impact of fat distribution on the anthropometric and laboratory parameters, especially indices of the metabolic syndrome biomarkers in young adults.
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Mikac, Urša, Maks Merela, Primož Oven, Ana Sepe e Igor Serša. "MR Study of Water Distribution in a Beech (Fagus sylvatica) Branch Using Relaxometry Methods". Molecules 26, n. 14 (16 luglio 2021): 4305. http://dx.doi.org/10.3390/molecules26144305.
Abstract (sommario):
Wood is a widely used material because it is environmentally sustainable, renewable and relatively inexpensive. Due to the hygroscopic nature of wood, its physical and mechanical properties as well as the susceptibility to fungal decay are strongly influenced by its moisture content, constantly changing in the course of everyday use. Therefore, the understanding of the water state (free or bound) and its distribution at different moisture contents is of great importance. In this study, changes of the water state and its distribution in a beech sample while drying from the green (fresh cut) to the absolutely dry state were monitored by 1D and 2D 1H NMR relaxometry as well as by spatial mapping of the relaxation times T1 and T2. The relaxometry results are consistent with the model of homogeneously emptying pores in the bioporous system with connected pores. This was also confirmed by the relaxation time mapping results which revealed the moisture transport in the course of drying from an axially oriented early- and latewood system to radial rays through which it evaporates from the branch. The results of this study confirmed that MRI is an efficient tool to study the pathways of water transport in wood in the course of drying and is capable of determining the state of water and its distribution in wood.
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Maria-Andreea, Micu, e Emese Orban. "Nuclear magnetic resonance: actualities and perspectives". Medic.ro 4, n. 1 (30 settembre 2021): 29–34. http://dx.doi.org/10.26416/med.142.4.2021.5416.
Abstract (sommario):
Nuclear magnetic resonance (NMR) is a complex physical process based on the interaction of protons in an electromagnetic field, the most well-known and widespread application in medical-clinical and medical-surgical field being nuclear magnetic resonance imaging. Considering the interdependent relationship between research in scientific fields that are closely related to medicine and the medical world, it is particularly important to be aware of the existence of other applications of the physical process mentioned before: diffusionometry, relaxometry and MRI spectroscopy. These are well-known and studied research entities, but their applicability in the clinical diagnostic process is still limited, despite the huge potential to provide a much broader and more detailed perspective on various biological tissues in vitro, but even in vivo. We want to review the evolution of nuclear magnetic resonance tomography or imaging, which has gone from being a Nobel Prize-winning idea to one of the most widespread and useful methods of non-invasive and non-irradiating medical imaging, but especially an example of the feasibility of diffusionometry, relaxometry, respectively MRI spectroscopy in a medical setting, through global studies on their potential diagnosis in areas such as oncology, neurology, endocrinology and others.
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Chi, Lu, Kai Cheng e Zoya Heidari. "Improved Assessment of Interconnected Porosity in Multiple-Porosity Rocks by Use of Nanoparticle Contrast Agents and Nuclear-Magnetic-Resonance Relaxation Measurements". SPE Reservoir Evaluation & Engineering 19, n. 01 (29 dicembre 2015): 095–107. http://dx.doi.org/10.2118/170792-pa.
Abstract (sommario):
Summary Nuclear-magnetic-resonance (NMR) measurements are considered among the most-reliable methods to evaluate porosity and pore-size distribution in fluid-bearing rocks. However, in reservoirs with complex pore geometry, there is still a challenge to interpret accurately NMR relaxometry data to evaluate petrophysical properties of these reservoirs such as interconnected porosity. In this paper, we introduce the application of nanoparticle contrast agents to improve assessment of interconnected porosity with NMR measurements. The comparison of NMR relaxometry data before and after nanoparticle injection enables distinguishing connected and isolated pore volumes (PVs), which might not be possible in the absence of contrast agents. The use of these contrast agents was demonstrated successfully in the magnetic-resonance-imaging (MRI) technique for clinical diagnosis. We used superparamagnetic iron oxide nanoparticles (SPION) as contrast agents injected into rock samples with a multiple-porosity system (including intra-/intergranular pores and natural fractures) and then quantified their impact on NMR measurements with laboratory experiments and numerical simulations. We injected contrast agents in sandstone and organic-rich mudrock samples, and measured NMR T2 (spin-spin relaxation time) distributions before and after contrast-agent injection. We simulated the NMR responses in sandstone and organic-rich mudrock samples before and after injection of contrast agent with a random-walk algorithm. The simulated NMR T2 distribution was cross validated by experimental results. We also documented the simulation results in a carbonates sample before and after injection of contrast agents, and characterized the pore-network connectivity with the simulation T2 distribution. The results show that the comparison of NMR relaxometry data before and after SPION injection improves characterization of interconnected porosity and connectivity of natural fractures in rock samples with complex pore geometry such as those from carbonate and organic-rich mudrock formations. We observed that the long-relaxation-time peaks in NMR T2 distribution significantly shift to short relaxation time after SPION injection, indicating that interconnected large pores/fractures are most easily invaded by SPION. However, the original short-relaxation-time peaks remained at the same position with almost the same amplitude and shape, indicating that small pores are not invaded by SPION. The accumulative porosity of the rock remains almost the same before and after SPION injection, indicating that SPION invasion in the rock only results in the downshifting of T2 relaxation time, but does not affect the NMR estimates of total porosity. We conclude from the experimental and numerical-simulation results that interconnected large pores/fractures, isolated large pores, and small pores can be differentiated in NMR T2 distribution with the aid of contrast agents. The outcomes of this paper are promising for the successful application of the introduced technique for pore characterization in heterogeneous multiple-porosity systems containing natural fractures.
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Thybo, Anette K., Piotr M. Szczypiński, Anders H. Karlsson, Sune Dønstrup, Hans S. Stødkilde-Jørgensen e Henrik J. Andersen. "Prediction of sensory texture quality attributes of cooked potatoes by NMR-imaging (MRI) of raw potatoes in combination with different image analysis methods". Journal of Food Engineering 61, n. 1 (gennaio 2004): 91–100. http://dx.doi.org/10.1016/s0260-8774(03)00190-0.
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Bustos, Damian, César Orellana Ugarte, Iván Bitar, Lucas Marangoni, Pablo Bertiche, Cristian Robles e Bernardo Murillo. "The Knee Magnetic Resonance Order: Can It Be Reduced by Specialists?" Orthopaedic Journal of Sports Medicine 6, n. 12_suppl5 (1 dicembre 2018): 2325967118S0021. http://dx.doi.org/10.1177/2325967118s00210.
Abstract (sommario):
Introduction: Knee pain is one of the most common complications in the trauma clinic. It is common to find patients who come to the office with a Nuclear Magnetic Resonance (MRI) who have a broken meniscus and who are looking for a lathe in the operating room. The majority of these patients are feasible for orthopedic treatment and it is sufficient to perform correct semiological maneuvers to determine it. Although there is a growing demand for knee MRI by members of the health team. The hypothesis of this work postulates that the NMR requested by the specialists in orthopedics and traumatology offer positive results both for the diagnoses and for the treatment plans. Objectives: The aim of this study is to compare the usefulness in diagnosis and in the therapeutic definition of knee MRIs requested by medical specialists. Materials and Methods: We retrospectively reviewed 1,186 knee MRI reports from January 1, 2015 to July 31, 2015, using the computerized clinical history system. These were classified according to the origin of the request for the images (specialists in orthopedics and traumatology, residents of traumatology and other medical specialties). This information was explored for its characterization. Retrospective study. Level of evidence IV Results: We obtained 33% (389) normal report of knee, significantly lower (p <0.001) to 67% reporting injuries. The proportion of studies requested was mostly by specialists in orthopedics and traumatology (59%), followed by the proportion required by different medical specialties (27%) and by those prescribed by traumatology residents (13%). The percentages of normal reports of those studies requested were different (p <0.05) 29, 42 and 32%, respectively. Conclusions: In primary care by physicians and residents of traumatology, the request for knee MRI reports a high percentage of normal reports. Specialists in orthopedics and traumatology request this exam with greater demand and present greater findings of injuries.
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Sultana, Mariam, Uroosa Arshad, Muhammad Khalid, Ali Akgül, Wedad Albalawi e Heba Y. Zahran. "A New Iterative Predictor-Corrector Algorithm for Solving a System of Nuclear Magnetic Resonance Flow Equations of Fractional Order". Fractal and Fractional 6, n. 2 (6 febbraio 2022): 91. http://dx.doi.org/10.3390/fractalfract6020091.
Abstract (sommario):
Nuclear magnetic resonance flow equations, also known as the Bloch system, are said to be at the heart of both magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) spectroscopy. The main aim of this research was to solve fractional nuclear magnetic resonance flow equations (FNMRFEs) through a numerical approach that is very easy to handle. We present a New Iterative Predictor-Corrector Algorithm (NIPCA) based on the New Iterative Algorithm and Predictor-Corrector Algorithm to solve nonlinear nuclear magnetic resonance flow equations of fractional order involving Caputo derivatives. Graphical representation of the solutions with detailed error analysis shows the higher accuracy of the new technique. This New Iterative Predictor-Corrector Algorithm requires less computational time than previously published numerical methods. The results achieved in this article indicate that the algorithm is fit to use for other chaotic systems of fractional differential equations.
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Wang, Xin-Yun, Jing Xie e Yun-Fang Qian. "A non-invasive method for quantitative monitoring of quality changes and water migration in bigeye tuna (Thunnus obesus) during simulated cold chain logistics using low-field nuclear magnetic resonance coupled with PCA". Food Science and Technology International 26, n. 6 (18 febbraio 2020): 475–84. http://dx.doi.org/10.1177/1082013220903148.
Abstract (sommario):
Bigeye tuna ( Thunnus obesus) is an important fish species worldwide due to its desirable flavour and rich nutrition. Cold chain logistics is one of the most common methods to store and sell bigeye tuna ( Thunnus obesus). The purpose of this study was to investigate how bigeye tuna ( T. obesus) deteriorate during simulated cold chain logistics with fluctuating temperatures by monitoring the quality changes and water distribution. The physical and chemical results showed that the sensory score, texture profile analysis (TPA), and water holding capacity (WHC) decreased, while total volatile basic nitrogen (TVB-N), K value, aerobic plate counts (APC), and psychrotrophic bacterial counts increased with fluctuating temperatures during 132 h. Low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) detection showed that the T21 (trapped water) and proton density decreased, while T22 (free water) decreased initially and then increased, indicating continuous water loss and water migration during storage. Principal component analysis (PCA) revealed that springiness, hardness, chewiness, T21, and sensory score were correlated with each other ( p < 0.05) and the linear combination of quality indicators and T2transverse relaxation time was established. Besides, temperature fluctuation (batch 3) accelerated the deterioration of bigeye tuna according to the comprehensive score of PCA. Results were based on LF-NMR which can be used to monitor quality changes in a fast non-invasive manner.
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Cicolari, Davide, Domenico Lizio, Patrizia Pedrotti, Riccardo Sironi, Monica Teresa Moioli, Alessandro Lascialfari e Alberto Torresin. "[P077] T1, T2 Relaxation times measurements methods: A comparison between standard sequences performed by an NMR spectrometer and MRI devices from different vendors at 1.5T". Physica Medica 52 (agosto 2018): 123. http://dx.doi.org/10.1016/j.ejmp.2018.06.399.
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Wood, John C., Michelle I. Aguilar, Maya Otto-Duessel, Hanspeter Nick, Marvin D. Nelson e Rex Moats. "Influence of Iron Chelation Therapy on R1 and R2 Calibration Curves in Gerbil Liver and Heart." Blood 108, n. 11 (16 novembre 2006): 1775. http://dx.doi.org/10.1182/blood.v108.11.1775.1775.
Abstract (sommario):
Abstract Introduction: MRI is gaining increasing importance for the noninvasive quantification of organ iron burden. To date, MRI validation studies have not systematically examined the effects of different iron chelators. Since transverse relaxation rates depend on iron distribution as well as iron concentration, physiologic and pharmacologic processes that alter iron distribution could change MRI calibration curves. This paper compares the effect of three iron chelators, deferoxamine, deferiprone, and deferasirox on R1 and R2 calibration curves according to two loading and chelation strategies. Methods: 33 Mongolian gerbils underwent iron dextran 500 mg/kg/wk for 4 weeks followed by 4 weeks of chelation therapy using deferoxamine, deferiprone and defersirox. An additional 32 animals received less aggressive iron loading (200 mg/kg/week) for 10 weeks, followed by 12 weeks of chelation therapy. R1 and R2 measurements were obtained immediately post euthanasia using an NMR relaxometer. Calibration curves from 28 unchelated animals loaded with 200 mg/kg/week from 2 to 48 weeks were used as the reference standard for both chelated groups, using Bland-Altman analysis. Results: In the liver, R2-iron calibration became more variable over time regardless of whether chelation was performed or not (mean COV 28% versus 12%); no significant changes were observed in the heart R2-iron relationship. Variability in R1 measurements did not change for either heart or liver. Two systematic chelator-specific changes in liver iron calibration curves were noted:deferiprone treated animals exhibited signficantly higher R1 values (Figure 1) anddeferasirox treated animals demonstrated lower R2 values for given iron concentration (Figure 2). Both changes were associated with obvious changes in water content or iron distribution. Discussion: The acuity of the iron loading process affects the variability but not the bias of MRI-iron calibration curves. In contrast, iron chelation can produce systematic shifts in MRI calibration curves compared with the unchelated state, reflecting gross changes in tissue hydration and iron distribution. Since the rate of iron-loading and extraction performed in animals is more extreme than occurs in humans, limiting tissue requilibration, it is possible that the present studies overestimate the potential for chelator-specific calibration bias. Nonetheless, caution should be used in extrapolating calibration curves derived from patients using deferoxamine therapy to others being treated with deferiprone and deferasirox. Careful, longitudinal assessment of MRI calibration curves of patients receiving oral chelation therapies is warranted. Figure Figure Figure Figure