Field Effects

E.i. Dupont De Nemours and Company

Robert L Gluckstern

Ronald F Holsinger

Robert R Lown

John C Fisher

NMR bias magnet apparatus employing permanent magnets and methods therefor are provided in accordance with the teachings of the present invention. According to the present invention a plurality of insulating sleeves which may be rotated are disposed about the periphery of a structure having a curvilinear cross section such as a cylinder. Each of the plurality of insulating sleeves are filled with stacks of slabs of permanent magnet material forming slugs and having an anisotropic axis of magnetic orientation aligned at an azimuth corresponding to a=2.phi.. The length of slug sections or even of individual slabs within each sleeve may be varied for purposes of introducing desired harmonics, as may the manner in which each sleeve is filled, so long as quadrature symmetry is maintained.

Cylindrical NMR bias magnet apparatus employing permanent magnets and

An NMR imaging apparatus is described having a desired imaging volume for imaging of biological tissue, said apparatus comprising bias means for generating a bias field, means for generating gradient fields, and radio frequency means for applying a pulse of electromagnetic radiation to the biological tissue and for detecting the resultant signals emitted from said tissue; wherein said bias means comprises a plurality of dipole ring magnets, each dipole ring magnet comprising a plurality of segments, each segment comprising an oriented, anisotropic permanent magnet material arranged in a ring so that there is a substantially continuous ring of permanent magnet material.

Permanent magnet NMR imaging apparatus

A segmented permanent ring magnet which is tunable to provide a preselected transverse magnetic field within the magnet interior is disclosed. The permanent magnet is constructed of material which has essentially linear behavior in the second quadrant of the B-H curve. The invention includes a method of tuning a segmented permanent ring magnet and a method of manufacture for the blocks of magnetic material which make up the magnet. The magnets of the present invention are particularly adapted for use as bias magnets in NMR imaging systems.

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College Park, MD, United States of America

Robert L Gluckstern