Picker International, Inc.

Kabushiki Kaisha Toshiba

Toshiba Medical Systems Corporation

Technicare Corporation

James B Murdoch

Andrew James Wheaton

Mark J Loncar

David A Lampman

Rao P Gullapalli

James M McNally

Russell A Compton

Moriel S NessAiver

David M Kramer

Martyn N Paley

Lawrence M Strenk

An MRI multi-echo data acquisition sequence (REFUSAL=REFocusing Used to Selectively Attenuate Lipids) includes a spectrally-selective re-focusing RF pulse. The REFUSAL pulse can be non-spatially selective or spatially-selective. The REFUSAL pulse selectively refocuses water spins and avoids refocusing lipid spins. The REFUSAL pulse ideally maximizes refocusing for water and minimizes any lipid refocusing, with built-in robustness to B0-inhomogeneity and B1-inhomogeneity. Following the REFUSAL pulse, the remainder of the echo train continues in a conventional fashion. Only those spins that were refocused with the spectrally selective REFUSAL pulse continue to evolve coherently and generate a train of echoes. Those spins that were minimally refocused are spoiled and thus do not contribute signal to the final image. To incorporate a longer duration REFUSAL pulse, the echo spacing can be made non-uniform such that the first echo spacing is longer than the remainder of the echo spacings in the echo train.

B1-robust and T1-robust species suppression in MRI

Magnets (12) create a temporally constant magnetic field through an examination region (14). Radio frequency coils (26, 34) and a transmitter (24) transmit radio frequency saturation pulses (52) and the resonance excitation and manipulation pulses of a magnetic resonance imaging sequence (72) into the examination region. Gradient amplifiers (20) and gradient coils (22, 32) create magnetic field gradients across the examination region for spatially focusing the saturation, for spoiling (62, 66, 70) residual transverse magnetization and for frequency and phase encoding in the magnetic resonance imaging sequence. A sequence controller (40) includes a saturation pulse controller (44) for generating the saturation pulse (52) and slice select gradients (58) and a steady state sequence controller (48) for generating the imaging sequence (72). The saturation is spectrally focused by limiting the frequency of the saturation pulse to selected frequencies. The saturation is spatially focused by applying the slice or other spatially limiting gradient pulses concurrently with the radio frequency saturation pulse. A phase shift controller (76) increments the phase of the RF saturation pulse by a preselected phase increment, e.g., 105.degree.. Preferably, the phase shift increment increases linearly in each cyclic repetition, i.e., increases 105.degree. in the first repetition, 210.degree. in the next repetition, 315.degree. in the next repetition, etc. A reconstruction processor (80) reconstructs resonance signals generated during the imaging sequences into an image representation for storage in a memory (82) and display on a video monitor (86).

Phase rotated spoiling for spatial and spectral saturation techniques

During a cardiac cine examination, a multiplicity of imaging sequences, each about 20 msec long, are applied following the R-wave. Each imaging sequence includes a saturation portion in which a bi-modal pre-saturation pulse (38) and a spoiler gradient (56) are applied. The bi-modal RF pulse has a relatively low tip angle, about 50.degree., but is repeated sufficiently often that blood in regions (30a, 30b) parallel to a selected slice (32) are driven toward saturation. Each imaging sequence further includes a gradient echo or other conventional imaging sequence during an imaging portion to generate magnetic resonance data (60). Each imaging sequence is repeated twice for each temporal interval with the same phase encoding, but once with the relative phase of the signal in the slice and the relative phase of the signals from within the pair of regions (30a, 30b) reversed. These two signals are combined such that the signals from within the slice add and the signals from with the pair of regions subtract. Signals corresponding to the same temporal interval after the R-wave with each of a multiplicity of phase encodings are reconstructed (82) into an image representations (84) for display on a video monitor (96).

High temporal resolution black blood cine imaging

RF and gradient pulse combinations (30, 32, 36, 38) are applied to limit or define a region of interest in two dimensions (42) by pre-saturating surrounding regions (34a, 34b, 40a, 40b). A 90.degree. RF pulse (50) is applied in the presence of a slice select gradient (60) to excite selected dipoles in a slice or slab, defining the region of interest or voxel in the third dimension. Phase encoding gradients (62) and (64) are applied to encode spatial position in two dimensions of the slice. A binomial refocusing pulse (52) suppresses the water and refocuses the metabolite resonance into an echo which is acquired (68) by a receiver (26). A Fourier transform means (72, 74) transforms the received magnetic resonance signals to create a two dimensional array (76) or matrix of spectra (78) corresponding to a two dimensional array of spatial positions within the slice. A third phase encode gradient (66) may be applied to encode the regionof interest in three dimensions for generating a three dimensional array of the spectra.

Multi-axis pre-saturated spin echo phase encoded spectroscopy

A technique for producing multiple spin echo signals following an initial excitation pulse is provided. A first inverting pulse is applied a given time interval following the initial excitation pulse, resulting in the formation of the usual first spin echo signal after passage of the given time interval. At a later point in time, a second inverting pulse is applied. The time interval between the initial excitation pulse and this second inverting pulse is not required to be harmonically related to the first given time interval. This results in the production of at least a second, later occurring spin echo signal which does not contain harmonically-related artifact components of the earlier pulses and spin echo signals.

Non harmonic NMR spin echo imaging

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Solon, OH, United States of America

James B Murdoch