Picker International, Inc.

William Sattin

Wayne R Dannels

Kenneth S Denison

Larry Kasuboski

Eric E Gatchalian

A radio frequency pulse (32), a gradient pulse (34), and a first frequency offset pulse (38a) are applied to cause the presaturation region (36a) adjacent one face of an imaging volume (30) such that material flowing into the imaging volume from that face is saturated. An imaging sequence is applied which generates magnetic resonance image data that has non-saturated flow in the imaging volume identified by a characteristic phase modulated intensity. The saturation and gradient pulses are applied again with a second frequency offset pulse (38b) to position the saturation region (36b) adjacent the opposite face of the image volume. The exact same imaging sequence is applied to generate a second set of image data in which non-saturated flowing material is identified by a characteristic phase modulated intensity. Magnitude values from these two data sets are reconstructed (72, 74) into image representations that are subtractively combined (76), to form a difference image representation. In the difference image representation, the static material has essentially a zero value, flowing material that entered from one face is strictly positive, and flowing material that entered from the other face is strictly negative. In this manner, two different flowing materials, such as venous and arterial blood, are separately encoded in only two imaging sequences.

Minimum basis set MR angiography

A magnetic resonance excitation pulse (50, 150, 250) is applied to excite resonance in selected dipoles in an examination region. A second radio frequency pulse (60, 160, 260) induces a primary echo which is phase encoded by a phase encode gradient (56, 156, 256) with a first phase encode angle. Optionally, an additional phase encode gradient (356) may be applied after the primary echo to remove the first phase encoding. A third radio frequency pulse (70, 170, 270) rotates the magnetization, typically 90.degree., to cause a stimulated echo (72, 172, 272) which is phase encoded in accordance with a second phase encode gradient (78, 178, 278). Optionally, another phase encode gradient pulse (378) may be applied after the stimulated echo to remove the second phase encoding. In the preferred embodiment, the first phase encoding is varied in steps from central phase encoding to a first preselected maximum phase encoding and the second phase encoding varies from about the central phase encoding to a second maximum of about the same magnitude as the first maximum but of the opposite polarity. In this manner, an interface between primary and secondary echo data is defined adjacent the central phase encode angle. The primary and stimulated echo data are corrected for discontinuities and reconstructed into an image representation. Redundant primary and stimulated echo data are collected adjacent the interface for comparison during the alignment.

Quick imaging scheme utilizing differently phase encoded primary and

In a magnetic resonance imaging or spectroscopy apparatus, radio frequency pulses of a selected size are applied to cause a corresponding tip angle. However, the actual tip angle which results varies with, for example, coil loading and patient geometry. For accuracy of the resultant image or data, the RF pulse size is adjusted or calibrated to produce a selected tip angle precisely - most commonly 90.degree. and 180.degree. tip angles. To calibrate the 90.degree. tip angle, a sequence of three like pulses (.alpha.-.alpha.-.alpha.) is applied. In each repetition, the pulses are varied in magnitude to produce tip angles around 90.degree. and the actual resulting tip angles are determined. The RF pulse size that produces or is projected by a least-squares fit to produce the exact 90.degree. tip angle is determined. To calibrate the 180.degree. tip angle, the pulse sequence includes the RF pulse (.alpha.) determined to produce the 90.degree. tip followed by two additional RF pulses (.beta.). The sequence (.alpha.-.beta.-.beta.) is repeated a plurality of times with the second and third RF pulses varied to produce tip angles around 180.degree.. From the zero frequency terms of Fourier transforms of the induced primary and stimulated echoes, the actual tip angle is determined. The RF pulse for producing a 180.degree. tip angle is calibrated to the size which produces or is projected to produce the 180.degree. tip angle.

High signal-to-noise, rapid calibration of RF pulses

Radio frequency pulses (40, 50, 60) having tip angles in the range of 5.degree. to 15.degree. are applied concurrently with slice select gradient pulses (42, 52, 62) to tip a component of the magnetization into a transverse plane. Phase encode gradients (44, 54, 64) phase encode magnetic resonance echoes (48, 58, 68) which are collected in the presence of read gradients (46, 56, 66). The magnitude of components of the slice select , read, and phase encode gradients along three system axes (grad1, grad2, grad3) are different in conjunction with each echo such that each echo represents a view of data along a different slice through a region of interest. The tip angle (.alpha.) and duration (t) between RF pulses are selected such that the magnetization of dipoles within the most recently selected slice regrows along the magnetic field axis until it is indistinguishable over integrated noise from the magnetization corresponding to other dipoles in the image region.

Simultaneous multislice-multiangle images without saturation bands

A scanner (A) generates electronic data which is indicative of characteristics of an interior region of a subject in an examination region. A computer generator (B) generates corresponding pixel values of first and second electronic image representations which are stored in first and second image memories (12, 22). A video processor 14 retrieves pixel values from one of the memories and converts them into a video signal for generating a visual display on a video monitor (16). An audio processor 24 retrieves values from the other image memory and utilizes them to control the frequencies and amplitudes or other characteristcs with which modulators (52, 54, 56, 58) modulate an audio icon signal. In this manner, the audio icon signal is modulated in accordance with the selected characteristics of the interior region. An electroacoustic transducer (66) converts the modulated audio signal into an audible display of the selected characteristic. The audio displayed selected characteristic might include flow rate, intensity, phase, relaxation values, diffusion coefficients, attenuation coefficients, acoustic impedance, flow velocities, photon counts, and a myriad of other parameters, both general and specific to the selected imaging modality.

Audio coded imaging

In a magnetic resonance imaging system, a plurality of RF pulses (24) are applied in bundles (62). The pulses in each bundle have an interpulse spacing (66) which is shorter than the T1 and T2 relaxation time of an imaged sample. The next pulse of the bundle is applied before the magnetic resonance response can build to a steady state echo. After a steady state resonance condition is reached, the application of radio frequency pulses is interrupted for an interbundle duration (72) which is sufficiently long for the steady state echo (96) to occur. Magnetic resonance imaging data is sampled during the steady state echo. Slice select gradients (34) are applied concurrently with each radio frequency pulse. In the interbundle interval, a phase encode gradient (42) and a read gradient (38) are applied. The sequence is repeated a plurality of times each with a different phase encode gradient to generate the appropriate data lines or views for transformation into an image representation.

Steady-state echo magnetic resonance imaging

A magnetic resonance excitation RF pulse (50) is applied to excite resonance in selected dipoles in an image region. A first phase encode gradient (56) phase encodes the resonating dipoles with one of a plurality of preselected phase angles. A magnetization rotation RF pulse (60), typically 90.degree., causes a primary echo (62) which is phase encoded with the preselected phase angle. A second magnetization rotation RF pulse (70) rotates the magnetization, typically 90.degree., to cause a stimulated echo (72). A second phase encode gradient pulse (78) is supplied subsequent to the second magnetization rotation pulse to alter the phase angle with which the stimulated echo is phase encoded. In this manner, data collected during the primary and stimulated echoes have different phase encoding such that more than one phase encoded view of data is generated following each excitation pulse.

An MRI or other scanner (A) generates medical diagnostic data d(x,y) which has a Gaussian noise distribution for reconstruction by an imager (B) into an electronic image representation P(i,j) which may have a Gaussian or Rayleigh noise distribution. An image improving circuit (C) replaces each image pixel value P(i,j) from an image reconstruction means (32) with an improved pixel value P*(i,j) defined as follows:

Growing community of inventors

Cleveland Hts., OH, United States of America

William Sattin