Magnetic proton density

Figure 1.1. Nuclear precession nuclear charge and nuclear spin give rise to a magnetic moment of nuclei such as protons and carbon-13. The vector n of the magnetic moment precesses in a static magnetic field with the Larmor frequency vo about the direction of the magnetic flux density vector Bo...

Abbreviations D, self-diffusion coefficient ge, gradient-echo IR, inversion recovery IRFT, inversion recovery fourier transform MRS, magnetic resonance spectroscopy PD, proton density PFGSE, pulsed field gradient spin echo se, spin-echo. 

It is difficult to make an exhaustive list of the applications of quantitative imaging, because a large number of parameters are quantifiable proton density, relaxation time T, T2, T2 or T 2, T p), data qualifying interaction of pools by magnetization transfer, apparent diffusion coefficients, indices characterizing diffusion phenomena from tensor estimation or a (/-space approach, temperature difference, static magnetic field, B1 field amplitude, current density or values related to dynamic MRI contrast agent uptake. 

In CT, contrast occurs solely because of the attenuation of the X-ray beam by its interaction with tissue. Contrast in MRI depends on how the image is acquired. Proton density images reflect the different amounts of water content in different tissues. Chemical shift imaging can distinguish water from fat, based on the different chemical shifts of these protons. Contrast also can be altered in other ways by the exploitation of differences in water diffusion in tissue, by chemical exchange, and by magnetization transfer effects, to name a few. The majority of scans used clinically derive contrast from differences in the relaxation times Ti, T2, and T2. ... 

For determination of the energy of a particles and for identification of a-emitting radionuclides, a. spectrometers are usually applied, having been calibrated by use of a emitters of known energy. Relatively exact determination of the energy of a particles, protons and deuterons can be made by means of a magnetic spectrometer. The relation between the velocity r of the particles, the magnetic flux density B and the radius r of the particles is... 

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