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Spin–spin relaxation
About: Spin–spin relaxation is a research topic. Over the lifetime, 2186 publications have been published within this topic receiving 50330 citations.
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1,740 citations
TL;DR: In this article, it was shown that the distortion of the hydrated complex by collisions with other water molecules is responsible for the decrease in T2 in Mn++ (and other) solutions in very high magnetic fields.
Abstract: The proton relaxation time in solutions of paramagnetic ions depends, among other factors, on the relaxation time of the electron spins, τs. It is shown that the latter, for ions of the iron group, is determined mostly by the distortion of the hydrated complex by collisions with other water molecules. The theory provides a quantitative explanation for the decrease in T2 in Mn++ (and other) solutions in very high magnetic fields. The experimentally observed field and temperature dependence of the proton relaxation times, T1 and T2, for ions of the iron group is compared with theory and the features which depend on τs are stressed.
1,192 citations
1,158 citations
TL;DR: By producing a train of absorption or dispersion signals (continuous wave magnetic resonance) or free induction decays (pulsed magnetic resonance), it is possible to save time in spin-lattice relaxation measurements as mentioned in this paper.
Abstract: By producing a train of absorption or dispersion signals (continuous‐wave magnetic resonance) or free induction decays (pulsed magnetic resonance) it is possible to save time in spin‐lattice relaxation measurements due to the fact that it is not necessary to wait for equilibrium magnetization before initiating the train. The relaxation time may be calculated from the train according to a simple rapidly converging iteration.
795 citations
TL;DR: Comparisons between Monte Carlo simulations and experiments with polystyrene microspheres to demonstrate that enhanced relaxation can be explained quantitatively for both spin echo and gradient echo imaging experiments and show that several regimes of behavior exist, and that contrast dependence is quite different in these regimes.
Abstract: Microscopic susceptibility variations invariably increase apparent transverse relaxation rates. In this paper, we present comparisons between Monte Carlo simulations and experiments with polystyrene microspheres to demonstrate that this enhanced relaxation can be explained quantitatively for both spin echo and gradient echo imaging experiments. The spheres used (1 to 30 microms), and degree of susceptibility variation (caused by 0-12 mM Dy-DTPA) covered a wide range of biologically relevant compartment sizes and contrast agent concentrations. These results show that several regimes of behavior exist, and that contrast dependence is quite different in these regimes. For a given susceptibility, delta chi, a small range of particle sizes show peak transverse relaxation. For the range of susceptibilities found in the first pass of a clinical IV contrast agent bolus, this size range is 5 to 10 microns, or roughly capillary sized compartments. In both our simulations and experiments, smaller spheres showed quadratic relaxation versus concentration curves, and larger particles showed sublinear behavior. For particles corresponding to the peak relaxivity, the relaxation-concentration curves were linear. In addition, we demonstrated that increasing the diffusion coefficient can increase, decrease, or, paradoxically, leave unaffected the apparent relaxation rate. The regime for which the diffusion coefficient is relatively unimportant corresponds to the region of peak relaxivity. By using the Bloch-Torrey equation to produce scaling rules, the specific Monte Carlo simulations were extended to more general cases. We use these scaling rules to demonstrate why we often find that susceptibility-induced relaxation rates vary approximately linearly with concentration of injected agent.
679 citations