U.S. Philips Corporation

North American Philips Corporation

Johannes M Van Eggermond

Cornelis M Van Uijen

Johannes H Den Boef

Russell Whitman, Ii

Abraham Naparstek

Stamatis M Rombotis

An MR imaging method and apparatus especially adapted for invivo cardiac MR imaging, rejects data acquired during periods of arrhythmia while maintaining the magnetic fields and pulsing of the RF coils during such periods. Data acquisition is resumed after M cycles of regular period, and after remeasuring the data acquired during N cycles prior to the occurrence of the arrhythmia, where M and N are integers preferably from 1 to 5. The average timing can periodically be recalculated in order to compensate for slow changes in cardiac rate.

Method and apparatus for MR imaging

The invention relates to a method and system for determining an image of a nuclear magnetization distribution in a body. In known methods, particularly in nuclear spin echo techniques, a resonance signal is generated which has high dynamics. In the method according to the invention dephasing is effected which is non-linear place-dependent or which is frequency-dependent within a spectroscopy distribution, as a result of which the generated resonance signal will have a much smaller amplitude. Since the non-linear dephasing applied within the distribution is known, a correction can be made for this after the determination of the measuring signals. The non-linear dephasing can be effected by means of excitation pulses and/or with subsequent nuclear spin echo pulses (also termed refocusing pulses) which have a frequency spectrum with a non-linear phase characteristic (possibly in the presence of a gradient magnetic field), or by means of a non-linear, place-dependent extra magnetic field, which can, for example, be applied during the preparation period. The non-linear extra magnetic field will preferably have higher order components, such as quadratic components. The reduction in signal dynamics to be achieved depends on the (frequency or) place-dependence of non-linear dephasing. If, for example, in an image of n.times.n pixels a non-linear, place-dependent extra magnetic field is used, which is dependent on two coordinates, then it is possible to achieve a maximum reduction in signal dynamics equal to .sqroot.n.times.n.

Method and arrangement for determining a nuclear magnetization

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Bridgeport, CT, United States of America

Johannes M Van Eggermond