U.S. Philips Corporation

Dietrich J Holz

Volker Rasche

Michael Harald Kuhn

Johannes J Van Vaals

Hermann Schomberg

Bernd E Aldefeld

Johannes C Van Driel

The invention enables the temporal variation of the magnetic field generated by a gradient coil to be derived from the measured temporal variation of the current through this gradient coil and from a pulse response which has been determined once and stored for the relevant coil. In this case an inexpensive non-linear amplifier may be used in the gradient channel, and also a gradient coil with eddy current effects, without the reconstruction or the pulse design being degraded.

Magnetic resonance method

MR imaging apparatus includes a magnet (1) for generating in an examination zone (3) a uniform, steady magnetic field having substantially parallel lines of force extending in a first direction (Z), a gradient coil system (5) for generating a magnetic gradient field, and an RF coil system for generating RF pulses and for receiving MR signals. The apparatus also includes devices (25,27,31) for generating data from the MR signals, and a reconstruction unit (39) for reconstructing an MR image of the examination zone (3) from a set of the data. A patient support system includes a table top (7) drive means (11) configured for displacement of the table top in the first direction (Z), and a connection (43) for coupling the drive means and the control unit (29). The magnet (1) has a generally toroidal-shaped housing (15) surrounding a bore (17) and has a longitudinal axis (19) extending substantially parallel to the first direction (Z). The housing (15) has a radial thickness (r) in a direction transverse to said axis (19) and a longitudinal thickness (1) in a direction substantially parallel to said axis, the radial thickness being greater than the longitudinal thickness.

MR imaging apparatus

An MR imaging method and device in which an object to be examined is displaced at a defined speed relative to an examination zone and a plurality of sequences act on the examination zone in the presence of a steady, uniform magnetic field, each of the sequences including at least one RF pulse and possibly a phase encoding gradient, and a MR signal arising in the examination zone, after transposition to another frequency range by means of an oscillator signal, is used to produce an MR image. The method aims to enhance the quality of the MR image produced by preventing movement artefacts. This is achieved in that from one sequence to another, one or more of the frequency of the RF pulses, the frequency of the oscillator signal, and the phase position of the oscillator signal is adjusted in conformity with the position of the object to be examined relative to the examination zone so that a part of the object which is imaged in the MR image moves relative to the examination zone in synchronism with the object.

Growing community of inventors

Hamburg, Germany

Dietrich J Holz