Ebook Advanced MR neuroimaging: Part 2
➤ Gửi thông báo lỗi ⚠️ Báo cáo tài liệu vi phạmNội dung chi tiết: Ebook Advanced MR neuroimaging: Part 2
Ebook Advanced MR neuroimaging: Part 2
Magnetic Resonance Spectroscopy5.1 IntroductionFocus Point•MRS can be considered as a bridge between the anatomic and physiological information and th Ebook Advanced MR neuroimaging: Part 2he metabolic characteristics of tissue in vivo.•The principal phenomenon of MRS is the “chemical shift.” which is directly related to the biochemical environment of every nucleus.•The proton nucleus is the most useful nucleus for MRS, due to its high natural abundance (>99.9%) and intrinsic sensitiv Ebook Advanced MR neuroimaging: Part 2ity (high gyromagnetic ratio y).Magnetic resonance spectroscopy (MRS) is a technique which provides a non-invasive method for characterizing the celluEbook Advanced MR neuroimaging: Part 2
lar biochemistry of brain pathologies, as well as for monitoring the biochemical changes after treatment in vivo. In that sense, it can be considered Magnetic Resonance Spectroscopy5.1 IntroductionFocus Point•MRS can be considered as a bridge between the anatomic and physiological information and th Ebook Advanced MR neuroimaging: Part 2 phenomenon is the so-called “chemical shift,” which is caused by the unique (for every nucleus) shielding from the external magnetic field (Bp) by the electrons surrounding them. Hence, this chemical shift effect is directly related to the biochemical environment of the nuclei. The electron magneti Ebook Advanced MR neuroimaging: Part 2c moment opposes the primary applied magnetic field Bo; therefore, the more the electrons the less the magnetic field the nuclei will “feel.” This “feEbook Advanced MR neuroimaging: Part 2
eling" can be expressed as the effective magnetic field Bp of the nucleus:Bp = Bo(l-c)-5.1where Ơ, is the screening constant, which is proportional toMagnetic Resonance Spectroscopy5.1 IntroductionFocus Point•MRS can be considered as a bridge between the anatomic and physiological information and th Ebook Advanced MR neuroimaging: Part 2ectrum of resonant peaks is produced.Due to the chemical shift phenomenon, it is evident that MRS is feasible on any nucleus possessing a magnetic moment, such as a proton CH), carbon-13 C'C), phosphorus f *P), and sodium (BNa).Early MRS studies were focused on the phosphorus nucleus (3IP) since thi Ebook Advanced MR neuroimaging: Part 2s was the most technically feasible at the early 1980s when in vivo MRS became possible (Luyten et al., 1989). In recent years, though, proton MRS CH-Ebook Advanced MR neuroimaging: Part 2
MRS) has become much more popular as it is possible to obtain high resolution spectra in reasonably short scan times (Frahm et al., 1989; Soares and LMagnetic Resonance Spectroscopy5.1 IntroductionFocus Point•MRS can be considered as a bridge between the anatomic and physiological information and th Ebook Advanced MR neuroimaging: Part 2egyromagnetic ratio y). Until now, 'H-MRS has been used both as a research as well as a clinical tool for detecting abnormalities, visible or not yet visible, on conventional MRI. Suggestively, Moller-Hartman et al. reported that when only the MR images were used for radiological diagnosis of focal Ebook Advanced MR neuroimaging: Part 2intracranial mass lesions, their type and grade were correctly identified in 55% of the cases. Hie addition of MR spectroscopic information significanEbook Advanced MR neuroimaging: Part 2
tly increased the proportion of correctly diagnosed cases to 71% (Moller-Hartmann et al., 2002).Figure 5.1 illustrates typical examples of magnetic reMagnetic Resonance Spectroscopy5.1 IntroductionFocus Point•MRS can be considered as a bridge between the anatomic and physiological information and th Ebook Advanced MR neuroimaging: Part 2__________Pf_______________________(a)(b)FIGU RE 5.1 Typical example of single voxel magnetic resonance spectroscopy of a 62-year-old male with a glioma, (a) Spectrum from the lesion, (b) Spectrum from the contralateral normal parenchyma.Magnetic Resonance Spectroscopy93of spatial or signal abnormal Ebook Advanced MR neuroimaging: Part 2ities as a result of the disease conditions is evident by pure visual evaluation of the spectra.The application of‘H-MRS has been always challenging iEbook Advanced MR neuroimaging: Part 2
n terms of its technical requisites (held homogeneity, gradients, coils and software), as well as the accurate metabolic interpretation with regard toMagnetic Resonance Spectroscopy5.1 IntroductionFocus Point•MRS can be considered as a bridge between the anatomic and physiological information and th Ebook Advanced MR neuroimaging: Part 2ore robust and user-friendly along with improved data analysis, spectra post-processing techniques and metabolite interpretation confidence.I he success of MRS as a valuable clinical tool depends on the accuracy of the acquired data as well as correct post-process and analyses. I he purpose of this Ebook Advanced MR neuroimaging: Part 2chapter is to elaborately introduce the current status of‘H-MRS in terms of the metabolites delected in the brain with their clinical usefulness, inclEbook Advanced MR neuroimaging: Part 2
uding the technical considerations, the acquisition, and postprocessing methods.5.2 MRS Basic Principles ExplainedFocus Point•The position of the peakMagnetic Resonance Spectroscopy5.1 IntroductionFocus Point•MRS can be considered as a bridge between the anatomic and physiological information and th Ebook Advanced MR neuroimaging: Part 2oncentration of metabolites.•The ppm unit represents frequencies as a fraction of their absolute resonance frequency, and is independent of field strength.Proton, derived from the Greek word Ttpwrov (meaning “first”) is a subatomic particle with a positive electric charge and one-half spin, and exhi Ebook Advanced MR neuroimaging: Part 2bits the electromagnetic properties of a dipole magnet. This name was given to the hydrogen nucleus by Ernest Rutherford in 1920.When protons are placEbook Advanced MR neuroimaging: Part 2
ed in an external magnetic field Bo, they align themselves along the direction of the field (either parallel or anti-parallel) and demonstrate a circuMagnetic Resonance Spectroscopy5.1 IntroductionFocus Point•MRS can be considered as a bridge between the anatomic and physiological information and th Ebook Advanced MR neuroimaging: Part 2cular structures to which protons belong. Ulis can be expressed by the Larmor equation:w0 = yBo-5.2where O)0 is the Larmor frequency, Y is the gyromagnetic ratio specific for the nucleus, and Bo is the strength of the external magnetic field. Ebook Advanced MR neuroimaging: Part 2Magnetic Resonance Spectroscopy5.1 IntroductionFocus Point•MRS can be considered as a bridge between the anatomic and physiological information and thGọi ngay
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