Ribbonators in magnetic resonance imaging of the hand and wrist, a dynamical approach to NMR of macromolecule bound nuclei of half-integer spin greater than 1/2, and cross-polarization NMR in polymers at liquid helium temperatures.

摘要

he optimization of single-turn solenoids for use in magnetic resonance imaging of the hand and wrist was studied. A "ribbonator" is a device that is electrically similar to a loop-gap resonator but is of rectangular geometry. These resonators exhibited radio-frequency magnetic field homogeneity superior to commonly used surface coils, and eliminated artifacts caused by inhomogeneous transmission and detection field distributions. These devices allowed reorientation of the hand to radial and ulnar deviations, with the hand in place within the resonator. Images are presented that show excellent anatomical detail and no significant artifacts from field inhomogeneity.;Decreasing the temperature of a sample increases its thermal equilibrium nuclear magnetization, and, if the temperature of a sample is decreased from room temperature to near liquid helium temperatures, a net increase in NMR signal of nearly 70 fold is expected. However, decreasing the sample temperature also increases longitudinal relaxation rates in the solid and, because of changes in the spin dynamics of the system at low temperatures, can possibly introduce spectral artifacts. The combination of decreasing sample temperature along with the ;The effect on linewidth of manipulating the rotational correlation time of a macromolecule to which a quadrupolar nucleus is bound was explored. A dynamical regime is sought in which the molecule rotates quickly enough such that second order quadrupolar interaction contributions are averaged, but still slowly enough that transverse relaxation times are long and first order quadrupolar interactions are not averaged away. Bovine serum albumen and ethylenediaminetetraacetic acid complexes with aluminum were studied as well as aluminum in various clays. No dynamical regime was found that yields aluminum resonance line-widths smaller than