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Disorders Affecting White and Gray Matter:
Published in Swati Goyal, Neuroradiology, 2020
“Dawson’s fingers” refer to initial finger-like thin and linear hyperintensities along the medullary veins, followed by ovoid/elliptical configuration, arranged perpendicularly to the lateral ventricles, extending radially outward and best visualized on sagittal images. CE-MRI − incomplete peripheral enhancement around active lesions (“open ring” sign − open component represents the GM side of the lesion, and the enhancing component represents the WM side of the lesion).Double inversion recovery (DIR) sequences use two inversion times and better delineate cortical lesions by suppressing both WM and CSF signals.Magnetization transfer imaging calculates the ratio (MTR), which is a marker of myelin disorder, a reduction in which favors the diagnosis of multiple sclerosis.DTI − increased fractional anisotropy (FA) and diffusivity values.
The diagnosis of Alzheimer’s disease and dementia
Published in Howard H. Feldman, Atlas of Alzheimer's Disease, 2007
Najeeb Qadi, Howard H. Feldman
Magnetization transfer imaging (MTI) maps the density of macromolecules in tissue. It has been shown in inflammatory white matter diseases to be a strong predictor of the severity of neuropsychologic deficits.52 MTI requires extensive post-processing to generate clinically useful data and has uncertain benefit in AD.
Physicochemical Principles of MR Contrast Agents
Published in Michel M. J. Modo, Jeff W. M. Bulte, Molecular and Cellular MR Imaging, 2007
A more recent approach to providing contrast is a magnetization transfer technique termed chemical exchange saturation transfer (CEST) (Chapters 5 and 6). The magnetization transfer (MT) effect that is used clinically exploits a pool of hidden water in some tissues. Water protons associated with macromolecules (e.g., hydrogen bonded to protein and membrane surfaces) have restricted mobility and, because of this, have short T2. This short T2 results in a very broad line width of several kilohertz. Mobile water, which makes up most of the tissue, has a relatively long T2 and a narrow line width. This is illustrated in Figure 2.9a, where magnetization is plotted as a function of frequency. If an rf pulse is applied at a frequency significantly different from the liquid water resonance (e.g., >1 kHz), then the hidden water can become saturated. This hidden water exchanges magnetization with the mobile water via chemical exchange and dipolar coupling. As a result, part of this saturation is transferred to the mobile water peak. This loss of magnetization results in signal loss, as shown in Figure 2.9b. The MT effect can provide contrast since different tissues exhibit MT effects of different magnitudes.
Imaging-based internal body temperature measurements: The journal Temperature toolbox
Published in Temperature, 2020
Juho Raiko, Kalle Koskensalo, Teija Sainio
Magnetization transfer method is an MRI technique that can be utilized in tissues with protons in three different states: protons in free water, protons bound to macromolecules, and protons in water molecules in the hydration layer between free water and macromolecules [23]. Magnetization transfer method uses selective radiofrequency pulses to saturate protons in macromolecules and water molecules bound to macromolecules. These saturated protons may then enter either the free pool of protons or transfer the magnetization to free water protons during the pulse sequence resulting in decreased magnetic resonance (MR) signal in areas with macromolecules affected by the magnetization transfer [23]. Magnetization transfer is not only temperature-dependent but also low in sensitivity and tissue-dependent [24] therefore limiting its use in research.
Magnetic resonance enterography in Crohn’s disease patients: current state of the art and future perspectives
Published in Expert Review of Medical Devices, 2021
Hila Bufman, Rami Eliakim, Noam Tau, Michal Marianne Amitai
Magnetization transfer (MT) in a newly proposed MRI sequence, in which macromolecules, such as collagen, are evaluated by using on-off sequences of mobile and immobile protons that are bound to the macromolecules. Thus, it may assist in evaluating bowel wall fibrosis. The first major study on CD patients by Li et al. compared the use of MT in order to characterize fibrosis as opposed to inflammation, using histopathological analysis as the reference. Results showed that normalized MT ratio correlated with fibrosis, yet no correlation was shown to inflammation. There was also a significant difference in the degree of wall fibrosis. Thus, this experimental method showed promising results in assessing bowel wall fibrosis but needs further studying [26].
Advances in imaging techniques to assess kidney fibrosis
Published in Renal Failure, 2023
Buchun Jiang, Fei Liu, Haidong Fu, Jianhua Mao
Magnetization transfer imaging (MTI) is aimed principally at detecting increases in macromolecules in renal fibrosis. According to the different magnetization between free water molecules and water molecules combined with ECM, MTI can reflect the macromolecule content in the renal parenchyma, which indicates renal fibrosis indirectly. The index of MTI is the MT ratio (MTR), which can indicate the macromolecule content in the renal parenchyma. Several animal studies confirmed that MTR is positively associated with renal fibrosis [122–124]. Additionally, an animal experiment found that MTR was little influenced by renal perfusion, indicating the reliability of MTR in assessing renal fibrosis [125].