China
Africa
Explore chapters and articles related to this topic
Magnetic Resonance Imaging
Published in Shoogo Ueno, Bioimaging, 2020
Magnetic resonance imaging (MRI) is a technique to obtain images based on nuclear magnetic resonance (NMR) signals generated by nuclei under a strong magnetic field. The MRI technique was demonstrated by Paul Lauterbur in 1973 [1]. The method later progressed through the development of magnets that stably generate strong magnetic fields, developments of diverse imaging techniques and increases in scan speed, the application of diagnosing various diseases, and the development of image processing methods, until it became an essential technology for imaging diagnosis. Features of MRI that distinguish it from other diagnostic imaging methods include the high contrast between soft tissues and the acquisition of functional information such as metabolic processes and brain activity in addition to morphological information. Furthermore, it involves no radiation exposure and is noninvasive. This chapter introduces the basic principles of MRI and the mechanism of imaging methods such as functional MRI and diffusion MRI.
Introduction
Published in Bertil R. R. Persson, Freddy Ståhlberg, Health and Safety of Clinical NMR Examinations, 2019
Bertil R. R. Persson, Freddy Ståhlberg
NMR imaging offers some special advantages over other diagnostic imaging methods used in medicine. First of all, NMR imaging does not use ionizing radiation and would therefore be less hazardous than imaging modalities using X-rays, γ-rays, positrons, neutrons, or heavy ions. In contrast to ultrasound, the Rf radiation used in NMR imaging penetrates bony structures without attenuation. Moreover, besides giving morphological information, NMR imaging gives additional diagnostic insight through the relaxation parameters, which are not available from other imaging modalities. Damadian et al. in 1971 had already made the important observation that the relaxation times Tl and T2 were significantly higher in cancerous tissue than in corresponding normal tissue.10 Finally, in contrast to CT X-ray scanning, NMR imaging can directly provide 3-D images or images of arbitrarily orientated slices such as transverse, coronal, or sagittal.
Thermal Dosimetry
Published in Leopold J. Anghileri, Jacques Robert, Hyperthermia in Cancer Treatment, 2019
Nuclear magnetic resonance (NMR), a new diagnostic imaging modality, recently has emerged from the physics laboratory and is now diffusing into the medical research environment amid much excitement and far-reaching potential applications. Images are produced through the use of radio waves that stimulate transitions between “spin states” of nuclei in a magnetic field. The relaxation time (time required for the nucleus to return to equilibrium) gives information on the environment of that nucleus.
Laterality in functional and metabolic state of the bulbectomised rat brain detected by ASL and 1H MRS: A pilot study
Published in The World Journal of Biological Psychiatry, 2023
Iveta Pavlova, Eva Drazanova, Lucie Kratka, Petra Amchova, Ondrej Macicek, Jana Starcukova, Zenon Starcuk, Jana Ruda-Kucerova
In preclinical studies, several animal models of depression have already been examined by structural and functional NMR methods (McIntosh et al. 2017). The forced swimming test result suggested membrane turnover with no neuronal degeneration (Hong et al. 2006). A later study of this model agrees with ours: lower Cho/tCr and lower Cho/NAA in the model group than in the control group, but in contrast, the region of this difference does not concur with ours. They showed the metabolite ratio levels difference in the left hippocampus, while our data showed it in the right hippocampus. This disagreement may be a consequence of a technical issue related to experimental small animal magnet systems where the position of the measuring subject is crucial. It is necessary to be aware of often mirror rotated NMR images. Our study reported the left side as the animal’s left side and the right side as the animal’s right side. However, the metabolite ratio differences between the model and the control group in the hippocampus may reflect a probable metabolic dysfunction in the pathology of MDD and the animal models of depression. This finding does not match the metabolite alterations observed in other models of depression described in the introduction, which may mean that these ratios are depression model-specific.
Therapeutic Nuclear Magnetic Resonance affects the core clock mechanism and associated Hypoxia-inducible factor-1
Published in Chronobiology International, 2021
Viktoria Thöni, Regina Oliva, David Mauracher, Margit Egg
Nuclear Magnetic Resonance (NMR) forms the basis for Magnetic Resonance Imaging (MRI), Magnetic Resonance Spectroscopy (MRS), as well as for the therapeutic tool of NMR therapy (tNMR or MBST®-NMR). tNMR is used for the treatment of osteoarthritis and osteoporosis and regeneration of bone and soft tissue. Its basis, and that of the other above listed techniques, is the so-called spin effect, as a quantum mechanical property of atomic nuclei with an odd number of protons or neutrons . When such spinning nuclei, for example, hydrogen protons, are exposed to an external magnetic field, they align in parallel or antiparallel to the field lines. The application of an additional corresponding radio frequency pulse forces the nuclear spins to deviate from the spin direction, thereby gaining energy. Once the radio frequency pulse ceases, the increase in energy is released to the close environment of the nuclei. In MRI, this release of energy is used for the generation of images, while in MRS it is used to determine the concentrations of chemical compounds. In tNMR, the release of energy is supposed to affect a yet unspecified cellular signaling, which consequently leads to regeneration and healing of the irradiated tissue. While MRI and MRS require strong magnetic fields, typically in the range of several Tesla, the MBST® therapy device generates a magnetic field of only 0.4 mT, and the used radio frequencies, therefore, are much lower as well (MBST®-NMR: 17 kHz-130 kHz compared to MRI: 10 MHz–200 MHz).
Use of omic technologies in early life gastrointestinal health and disease: from bench to bedside
Published in Expert Review of Proteomics, 2021
Lauren C Beck, Claire L Granger, Andrea C Masi, Christopher J Stewart
Metabolomics studies typically utilize MS or nuclear magnetic resonance (NMR) based techniques. For MS-based techniques, metabolites are first separated using one of a variety of methods, including but not limited to gas chromatography (GC) and ultra-performance liquid chromatography (UPLC) [53]. The choice of chromatography will impact which metabolites are retained and subsequently detected by MS. The choice of column used is therefore important and should reflect the study hypotheses or multiple different columns could be used, such as combining reverse-phase liquid chromatography (RPLC) and hydrophilic interaction liquid chromatography (HILIC) [54]. Recent efforts have also focused on combining different chromatography to maximize the number of metabolites detected. NMR spectroscopy, on the other hand, exploits the local magnetic field that exists around atomic nuclei, allowing the molecular structure of metabolites to be elucidated. MS-based techniques are more sensitive than NMR, but require known standards to be run alongside samples in order to identify metabolites of interest [55]. Without doing so, any identification can only be putative and therefore most features in an LC-MS experiment will remain unidentified.