Abstract: An imaging scanner (10) acquires imaging data. A reconstruction processor (30) reconstructs the imaging data into an unfiltered reconstructed image. A local noise mapping processor (64, 120, 136, 140, 142, 152) generates a noise map (68, 68?, 68?) representative of spatially varying noise characteristics in the unfiltered reconstructed image. A locally adaptive non linear noise filter (60) differently filters different regions of the unfiltered reconstructed image in accordance with the noise map (68, 68?, 68?) to produce a filtered reconstructed image.

Abstract: In a magnetic resonance imaging method, inner radial readout lines (100, 200, 300, 400) in an inner portion (102, 202, 302, 402) of k-space are acquired using a first readout magnetic field gradient profile (120, 220, 320, 420). Outer radial readout lines (104, 204, 304, 404) in an outer portion (106, 206, 306, 406) of k-space disposed substantially outside of the inner portion of k-space are acquired using a second readout magnetic field gradient profile (124, 224, 324, 424) different from the first readout magnetic field gradient profile. The acquired inner and outer radial readout lines are reconstructed to produce a reconstructed image.

Abstract: When scanning a patient to generate an image thereof, radio frequency (RF) coil modules are scalably coupled to each other using a plurality of clips to form flat or polygonal coil arrays that are placed on or around the patient or a portion thereof. A user assesses the volume to be imaged, identifies a coil array configuration of suitable size and shape and employs clips of one or more pre-determined angles to construct the identified coil array configuration, which is placed on or about the volume. Coil modules are coupled to a preamplifier interface box (PIB), which provides preamplified coil signal(s) to a patient imaging device, such as an MRI scanner. Small arrays are constructible to accommodate pediatric patients and/or smaller animals. Modules are hermetically sealed, can be sanitized between uses, and discarded at end-of-life. In one aspect, the modular coil array, clips, and PIB are maintained in an isolated contamination zone, separate from the patient imaging device.

Abstract: A dose of a contrast agent (44) is administered to the patient (42). A magnetic resonance is excited by an RF pulse (200) in a region of interest of the patient (42). An echo-planar imaging (EPI) readout waveform is implemented a preselected duration after the excitation to generate T2 or T2* weighted data. During the preselected duration, another echo planar readout waveform is implemented to generate T1 or proton density weighted data. The data is reconstructed (56) to generate a T2 or T2* weighted image and a T1 weighted image. The T1 and T2 or T2* weighted images are combined (62) to generate a contrast enhanced image.

Abstract: A method of magnetic resonance imaging is provided. It includes supporting a subject in an examination region of an MRI scanner (A), and applying an EPI pulse sequence with the MRI scanner (A) to induce a detectable magnetic resonance signal from a selected region of the subject. The magnetic resonance signal are received and demodulated to generate raw data. Applied to the raw data are a pair of ghost reducing correction factors (&thgr;,&Dgr;). The pair of corrections factors (&thgr;,&Dgr;) included a phase correction (&thgr;) and a read delay (&Dgr;). The phase correction (&thgr;) compensates for phase errors in the raw data, and the read delay (&Dgr;) effectively shifts a data acquisition window (120) under which the raw data was collected to thereby align the raw data in k-space. The correction factors affect how data is loaded into k-space to generate k-space data, and the k-space data is subjected to a reconstruction algorithm to generate image data.

Abstract: A main magnet assembly (12) creates a main magnetic field (Bo) through an imaging region (10). An operator selects sizes and locations of at least two intersecting slabs (72, 74) in a region of interest. A sequence controller (42) includes a gradient synthesizer (44) and an RF pulse synthesizer (46) that synthesize slab select gradient field pulses (80, 82) and magnetization tipping RF pulses (&agr;, &bgr;) to tip or rotate the magnetization in the slabs and an intersection region (70). A first RF pulse (&agr;) and slab select gradient tip the magnetization in the first slab and the intersection region out of alignment with the (Bo) field (FIGS. 5A, 7A). A second RF pulse (&bgr;) and slab select gradient tip the magnetization in the second slab out of alignment with the (Bo) field (FIG. 6B) and further manipulate the magnetization in the intersection region (FIG. 7B).

Abstract: A magnetic resonance imaging system includes a gradient hardware subsystem (36), a radio frequency transmission hardware subsystem (30), and a data sampling and digitization hardware subsystem (40) A sequence control processor (20) applies control signals or pulses to the hardware subsystems to cause the implementation of a selected EPI imaging sequence. Due to inductive loads, analog filters, and other circuit constructions within the hardware subsystems, each of the hardware subsystems has a different inherent delay between receipt of a control signal and actually achieving the controlled function such as applying a gradient or RF pulse or sampling data. Due to these different inherent delays, the imaging sequence occurs with timing variations from the intended sequence. Echo planar imaging sequences are very sensitive to phase errors caused by these relative delays, which phase errors manifest themselves in the form of Nyquist ghosts.

Abstract: A magnetic resonance imaging apparatus and method employ a magnet system (12) creating a temporally constant magnetic field through an examination region (14) in which at least a portion of an object to be imaged is placed. A radio frequency (RF) excitation system (24, 26) applies an RF excitation to a volume of interest of the object to be imaged, and a receiver system (32) detects and demodulates magnetic resonance data from the volume of interest. A magnetic field encoding system (20, 22, 40) applies encoding magnetic fields to provide spatial discrimination of magnetic resonance data from the volume of interest within a single radio frequency excitation period. The spatial encoding of the magnetic resonance signal data is performed and collected along a preselected k-space trajectory, the k-space trajectory covering a plurality of intersecting. planes or partial planes of k-space data.

Abstract: A method of calibrating pre-emphasis gradient pulse conditioning for long term eddy current compensation in an MRI system is provided. It includes positioning an object in the MRI system for imaging therewith. A long term eddy current generating pre-scan gradient pulse is applied, and after a delay, an EPI sequence is run such that a resulting image of the object is acquired. This process of applying the pre-scan gradient pulse followed by the EPI sequence is repeated while varying the delay therebetween. Size variations in the resulting images of the object are observed, and these size variations are fit to an exponential curve to obtain one or more time constants for the long term eddy currents. Next, a reference EPI sequence is run without applying the long term eddy current generating pre-scan gradient pulse such that a reference image of the object is acquired.

Abstract: Within a selected slice or slab, diffusion sensitizing gradients (54, 56) and read gradients (66, 68) are induced along each of a pair of orthogonal axes (G.sub.x, G.sub.y). The motion sensitizing gradient pulses sensitize excited magnetic resonance to diffusion in a preselected diffusion direction (D) which is orthogonal to a selected read gradient direction. The diffusion sensitizing gradients are rotated by sin(.theta.+.pi./2) and cos(.theta.+.pi./2) and the read gradients are rotated by sin.theta. and cos.theta. to generate a plurality of angularly displaced data lines. The diffusion sensitivity direction remains perpendicular to the read direction in each of the angularly displaced data lines. The phase of each data line is determined (90) and shifted (94) to compensate for linear translations. The data values within each data line are shifted (86) to center the peak amplitude of the data line at a preselected position to compensate for higher order motion.

Abstract: A magnetic resonance imaging magnet, gradient coil, and RF coil assembly is controlled by a workstation (40). The workstation (40) includes an operator input (46, 48) and a display system (58) including a video monitor (44) for displaying human-readable images reconstructed from magnetic resonance data. A scan/reconstruction rack (50) includes a scan processor (60) which controls scan parameters and a reconstruction processor (64) and associated hardware for reconstructing received magnetic resonance signals into the image representation. A scan sequencer (52) includes a master microcode board (90) which controls the scan sequencer in accordance with instructions received from the scan processor (60). The scan processor loads a series of codes describing gradient and RF waveform profiles into memories (130) of each of a plurality of profile channels (100, 102, 104, 106, 110, 112, 114).

Abstract: In a fast scanning technique in which the repeat time TR is less than the T2 relaxation time, a first generation component (34), a second generation component (52), and a third generation component (62) are each phase encoded by a phase encode gradient (36). The persisting second and third generation components are encoded with the sum of the phases with which they have been encoded in the present and prior repetitions. A composite data line is sampled during each echo and includes a first component (44), a second component (54), and a third component (64), each component having an independent phase encoding. The data lines are each stored in a first data set memory (80) in accordance with the phase encoding of the first generation component, in a second data set memory (82) in accordance with the phase encoding of the second component and in a third data set memory means (84) in accordance with the phase encoding of the third generation component.

Abstract: 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.

Abstract: A gradient field controller (30) generates current pulses with a preselected profile. Eddy current compensation circuits (42) alter the current pulse profile by adding additional components of selectable frequencies with selectable amplitudes or gains. A power amplifier (32) amplifies the modified current pulse and applies them to gradient field coils (34) of a magnetic resonance imager. A probe or coil (50) monitors the induced gradient response which is integrated (52) to provide an electronic representation of the induced gradient profile. A least squares analysis routine (72) determines the time constant and amplitude of a component attributable to a first eddy current which degrades the induced gradient profile. A filter frequency correction factor calculating routine (76) calculates appropriate filter frequency settings and a gain calibration factor calculating routine (78) calculates the gain settings for the compensation circuits (42).