Effects of diffusion on magnetic resonance imaging of laser-polarized xenon gas

Abstract

Articles you may be interested inTheoretical signal-to-noise ratio and spatial resolution dependence on the magnetic field strength for hyperpolarized noble gas magnetic resonance imaging of human lungs Med.Molecular diffusion during the application of magnetic field gradients can distort magnetic resonance images. A systematic characterization of these distortions in one dimension was performed using highly spin-polarized xenon gas. By varying the strength of the applied gradient and the geometric dimension of the sample, the evolution of these image distortions between the regimes of strong and weak diffusion was observed. These results are compared with numerical simulations. By directly measuring the displacement distribution of the polarized xenon atoms, it is shown that in the weak-diffusion regime the image distortions originate from the restricted diffusive motion near the sample boundaries, in agreement with previous theoretical work. Additionally, it is shown that the effects of diffusion can be utilized to enhance the contrast between the boundaries and bulk in the images of polarized gas samples, and thus may be exploited as a means of boundary detection in such systems.

Nuclear Magnetic Resonance of Laser-Polarized Noble Gases in Molecules, Materials, and Organisms

“…More precisely, theoretical work [197] has shown that this distance is equal to -a~ig, where al is the first zero of the derivative of the first Airy function, and a! s -1.0188; This value is consistent with the results presented here [201] and with those of Saam et al [200]. It ii important to remember, however,…”

“…In a more recent study, the effects of diffusion on MRI were examined in greater detail using 1-D samples of laser-polarized xenon gas [201]. In these experiments, the strength of the applied gradient and the geometric dimension of the 1-D sample could be varied, permitting the evolution of diffusion-mediated image distortions between…”

Achieving high spatial resolution and high SNR in low-field MRI of hyperpolarised gases with Slow Low Angle SHot

“…The presence of container walls (that locally enforce null perpendicular components for the magnetisation currents) may induce strong edge enhancement distortions, that have been observed with hyperpolarised gases in 1D situations [30,31]. This has been discussed by several authors in various contexts (see, e.g., [32,33,34,35] and references therein).…”

Some Pleasures in Chemical Physics

“…When Andy Freedman excited it near 300 nm, in one dissociation channel two Re(CO) 5 fragments separated with a strongly parallel distribution (31). Evidently the absorption is localized on the ReRe bond and is a simple σ → σ * transition.…”

“…(CO) 5 Re-Re(CO) 5 Dirhenium decacarbonyl has two rhenium atoms bonded together, each with a surrounding cluster of five CO ligands. When Andy Freedman excited it near 300 nm, in one dissociation channel two Re(CO) 5 fragments separated with a strongly parallel distribution (31).…”