5185576 Local gradient coil

XL11

New Patents steering of a rotating magnetic field signal used to induce magnetic resonance. The response signals issued by the excited volume element are then collected by focusing of these response signals, using a phased array of antennae for this purpose. Use of the invention with well known nuclear magnetic resonance excitation procedures, such as spin echo, echo planar, gradient recalled and backprojection, are discussed.

5185576 LOCAL

GRADIENT

COIL

Robert M Vavrek, Daniel Schaefer, Christopher C Myers, Thomas G McFarland, Robert Turner assigned to General Electric Company; The United States of America as represented by the Secretary of the Department of Health and Human Servic

5185574 NMR MEASUREMENTS USING RECURSIVE RF EXCITATION Richard L Ehman, Mayo Foundation Research

ient field system signal is substantially unaffected by the multipole system in the region of interest.

James Greenleaf assigned to for Medical Education and

An NMR echo signal is produced in a recursive process in which one or more pulse sequences are executed and the NMR echo signal produced by each pulse sequence is employed to shape the RF excitation pulse employed in the subsequent pulse sequence. The series of NMR echo signals produced by this recursive process are progressively modified to enhance the signals produced by prominent features in the subject.

A compact local gradient coil is combined with a local RF coil to provide lower powered, higher strength gradient fields and faster gradient response as is useful in magnetic resonance imaging. Interference between the RF coil and gradient coil is minimized by placement of the gradient coil external to the RF coil and by gradient coils that are axially symmetric and/or have conductors substantially orthogonal to the RF coil conductors. Acoustic noise in these smaller, stronger coils is reduced with ports cut into the coil forms.

5185577 5185575

RECEIVER COIL FOR NUCLEAR MAGNETIC RESONANCE IMAGING APPARATUS

MAGNETIC RESONANCE IMAGING APPARATUS WITH ARTEFACT REDUCTION Johannes Overweg, Eindhoven, signed to U S Philips Corp

Netherlands

Takashi Minemura, Ootawara, to Kabushiki Kaisha Toshiba

Japan

assigned

as-

A high order multipole gradient field generating system in a magnetic resonant imaging apparatus comprises spaced quadrants of windings, the windings of each quadrant generating adjacent fields in each quadrant in opposing relation. The multipole system is located adjacent to a lower order conventional gradient field coil system to shield the region of interest from field aberrations, the multipole system generating a relatively strong local magnetic field adjacent to the coils of the gradient field coil system and a negligible change in field in the region of interest. The multipole system causes a frequency shift of the aberrations in the region of interest which are outside the detection frequency range such that the conventional grad-

A receiver coil for a nuclear magnetic resonance imaging apparatus, capable of fulfilling the condition for a satisfactory signal reception completely for the imaging of a region of interest that cannot be placed symmetrically with respect to the central axis of the receiver coil. The receiver coil includes coil element for defining an opening section into which a region of interest is to be inserted, and for receiving a nuclear magnetic resonance signal from the region of interest; and a coil support member for supporting the coil elements in a configuration in which a sensitivity central axis of a region of uniform signal reception sensitivity for the coil elements is located away from a central axis of the opening section. The coil elements are preferably supported in a configuration corresponding to a shape of the region of interest.