Abstract: Artifacts in MR images caused by signals emanating from outside the design spherical volume (DSV) of the system are suppressed using customized spatial saturation pulse sequences interleaved with imaging pulse sequences. The spatial saturation pulse sequences are each customized to a specific region and are stored in a library for selective use when needed to suppress artifact producing signals emanating from specific regions outside the DSV.

Abstract: A method for performing MRI, including imposing N sets of steady-state free precession (SSFP) sequences on an object to be imaged, the sequences including respective initial radio-frequency (RF) excitation pulses, each initial RF excitation pulse having a predetermined phase shift relative to the other initial RF excitation pulses. N is a whole number larger than one and less than six.

Abstract: A method of generating an adiabatic FM pulse, comprising: selecting a starting trajectory for the pulse; and determining a velocity profile along the trajectory by constraining at least a portion of the velocity profile only to fulfill an adiabatic condition other than a frequency frame adiabatic condition. Preferably, the other adiabatic condition is one defined in a double-rotating reference frame.

Abstract: A method of NMR (nuclear magnetic resonance) excitation of a sample having a magnetic moment, including, applying a longitudinal magnetic field to the sample; and changing the magnetic moment in a substantially continuous manner by moving an effective magnetic-field vector &ohgr;e more than 90°, wherein for all portions of the sample in which the moment is changed, the angular velocity of the effective field vector at at least one angle, 90°+&agr;, is different from the angular velocity at 90°−&agr;.

Abstract: A method of selective excitation of a first spectral band in the presence of a second spectral band whose magnetization vector is not to be affected, comprising: selecting a central synthesizer frequency of substantially the second spectral band; applying a spectral-spatial pulse, centered on the selected synthesizer frequency to selectively excite the first spectral band. Preferably, the spectral-spatial pulse is a type II spectral-spatial pulse having odd and even pulse trains.

Abstract: A method of compensating for an eddy field according to measurements of the field. The method includes fitting the measurements of the field to a plurality of candidate models of the field. A stability value indicative of the stability of the fitted model to changes, is assigned to each of the fitted candidate models. A model is selected from the candidate models responsive to the stability values of the candidate models and the eddy fields are compensated responsive to the selected model.

Abstract: New methods of generating optimal inversion pulses and adiabatic pulses in magnetic resonance imaging are disclosed. Trajectories, maximum sweep rates, and velocity profiles are used in defining an optimal pulse, over support regions. Adiabatic pulses are optimized by using the trajectory as a constraint of optimization, but selecting trajectories with velocity profiles, without using the adiabatic condition as a constraint for optimizing the velocity profile. A method or inverting MR spins substantially, independently of the pulse duration, by selecting a transition width between 1.4 and 1.9 and dividing that width by the pulse duration is disclosed; and A new method of inverting adiabatic, MR, amplitude modulated spins, with a trajectory defined by sin .alpha./cos .alpha., where .alpha.<0.9 and at least 50% of the trajectory is outside, in a z-x rotating frame of reference that rotates at the instantaneous frequency of the RF pulse is also taught.

Abstract: A magnetic resonance angiography method for acquiring angiographic images using any or all of three different types of selective presaturation pulses to the particular parts of the body for enhancing vascular imaging. The three types are:1) an inversion pulse applied prior to the application of a burst of RF pulses used for tipping the spins designed to eliminate signals from unwanted blood entering the field of view being imaged,2) inversion pulses applied between the first inversion pulse and the first of the Rf pulses used to suppress blood not properly suppressed by the first type of suppression pulses, such as fast flowing blood, and3) saturation pulses applied within the burst of RF pulses to suppress signals from slow flowing blood when in the 2D acquisition mode. Special heart and breath gating methods are also described that enable good compromises between image quality and scan time.

Abstract: A magnetic resonance imaging system that:applies gradient pulses in a sequence that elicits large amounts of data early in a scan to provide an evolving image; and reduces the Gibbs artifacts to increase the utility of the evolving images.

Abstract: Elimination of truncation artifacts in Magnetic Resonance Images is accomplished by analaytically optimizing controllable parameters; i.e., filter characteristic and assymetry ratio when asymetrically sampling arid time domain filtering followed by complex conjugating the filtered data to reduce the Gibbs artifact.

Abstract: A system corrects for phase angles degradation due, for example to eddy currents, and uses the corrected phase angles to determine flow. The system acquires flow compensated low resolution images and uncompensated low and normal resolution images of a flowing fluid. The images include phase angle data. The phase angle data of the low resolution images are subtracted from the corresponding phase angle data of the normal resolution images to obtain phase angle corrected compensated and uncompensated images. The phase angle corrected compensated images are subtracted from the phase angle corrected uncompensated images to obtain flow images with minimized phase angle distortion. Reliable and accurate flow velocity for each pixel is thereby obtained using the minimized phase angle distortion flow images.

Abstract: The Gibb's artifact in magnetic resonance images is reduced by asymmetrically sampling acquired F.I.D. signals to obtain data, time domain filtering the obtained data with a filter that reduces overshoot, degrades resolution but increases SNR. Then obtaining symmetrical data by complex conjugating the time domain filtered data which improves the resolution, compresses the overshoot, but decreases SNR. Processing the symmetrical data to obtain images with insignificant Gibb's artifacts.

Abstract: Motion insensitive magnetic resonance scanning is provided when generating a signal from spins of a selected portion of a subject by acquiring a truncated signal comprising most of the signal's central portion and one wing of the usual two wings. Full image data is obtained by conjugating the truncated signal. The image thus obtained is relatively motion insensitive.

Abstract: A Magnetic Resonance (MR) data acquisition system using driven equilibrium in a spin echo scan sequence wherein the dephased spins in the transverse plane are accurately refocused prior to being driven to the Z axis and the encoding gradient pulses are distributed and adjusted to keep the encoding gradient pulses from affecting the refocused magnetization.

Abstract: Improved T2 values and signal to noise ratio obtained by magnetic resonance image synthesization. Each measured echo signal intensity is divided by a correcting factor that is a function of the echo number to obtain corrected echo signal intensity. A characteristic curve is best fitted to the corrected intensity values and the intensity values of the curve are used.

Abstract: Reduces artifacts in fast imaging sequences used in magnetic resonance imaging by changing the phase of the radio frequency pulse output of a synthesizer in order to prevent the transverse magnetization caused by the radio frequency pulses used for "tipping" aligned spins into the transverse plane from reaching a steady state condition. Steady state conditions are known to cause artifacts in the final images.

Abstract: An automatic shimming system for correcting inhomogeneties in magnetic resonance magnetic fields. The static magnetic field is mapped using three dimensional phantoms that comprise a plurality of samples including at least an element having non-zero nuclear magnetic moments spatially distributed to enable uniquely locating each sample with only two locating gradients.