Abstract: A 3D MRI image is acquired as a series of spherical shells of increasing radius. Each shell is sampled by one or more interleaved spiral sampling trajectories and to shorten the scan time one or more spiral sampling trajectories are skipped in the larger shells that sample the periphery of k-space. Motion correction of the acquired k-space data is accomplished by reconstructing tracking images from each of the shells and locating markers therein which indicate object movement from a reference position. The k-space data is corrected using this movement information.

Abstract: A CE-MIRA image is acquired using a centric view order. The acquired k-space data set is motion corrected by reconstructing tracking images from successive annular segments of k-space data and detecting the location of a point spread object therein. Each k-space data segment is phase corrected to align the point spread object with a reference position.

Abstract: A CE-MRA image is acquired using a centric view order. The acquired k-space data set is motion corrected by reconstructing tracking images from successive annular segments of k-space data and detecting the location of a point spread object therein. Each k-space data segment is phase corrected to align the point spread object with a reference position.

Abstract: An MRI system performs a pulse sequence to acquire image data from a subject. The RF power applied to the subject is monitored and the acquisition is altered if any one of three trip levels is exceeded. Each trip level is different and is associated with a different time interval over which applied RF power is measured.

Abstract: An MRI system performs a pulse sequence to acquire image data from a subject. The RF power applied to the subject is monitored and the acquisition is altered if any one of three trip levels is exceeded. Each trip level is different and is associated with a different time interval over which applied RF power is measured.

Abstract: An MRI system acquires NMR signals and digitizes them at a fixed sample rate. A lower, prescribed sample rate is obtained by fractionally decimating the sampled NMR signals. Fractional decimation is achieved by a combination of zeropadding the sampled NMR signal in the frequency domain and decimating the sampled NMR signal in the time domain.

Abstract: An MRI system acquires MRA data from two overlapping thin slabs using a 3DTOF pulse sequence. Motion artifacts are reduced by using a reverse centric phase encode order during the first thin slab acquisition and a centric phase encode order during the second thin slab acquisition. Patient movement is reduced by producing a uniform sound with gradient pulse sequences during the interval between thin slab acquisitions and during a preparation period prior to the first thin slab acquisition.

Abstract: In an MRI system using high-performance gradient hardware, a method includes de-rating selected lobes in a 2DTOF imaging pulse sequence; employing images from the two-dimensional imagery to detect the presence of disease; and performing three-dimensional contrast-enhanced MRA if disease was detected at a sufficiently high level to make three-dimensional imaging useful. By de-rating selected lobes of the 2DTOF imaging pulse sequence, sensitivity to carotid stenosis at or above the clinically important range of 60-70% is achieved.

Abstract: A method of peripheral MR angiography is provided for imaging an artery or other vessel, wherein the vessel is of such length that MR data must be acquired at each of a plurality of scan stations spaced along the vessel. In accordance with the method, a contrast agent is intravenously injected, in order to provide a bolus which successively flows to each of the scan stations. After acquiring an initial subset of the MR data associated with a given scan station, the bolus is tracked to determine whether it has arrived at the next-following scan station. If so, at least some of the MR data associated with the next scan station are then acquired. However, if it is found that the bolus has not yet arrived at the next scan station, acquisition of further data at the given scan station is continued.

Abstract: An MRI system acquires MRA data from two overlapping thin slabs using a 3DTOF pulse sequence. Motion artifacts are reduced by using a reverse centric phase encode order during the first thin slab acquisition and a centric phase encode order during the second thin slab acquisition. Patient movement is reduced by producing a uniform sound with gradient pulse sequences during the interval between thin slab acquisitions and during a preparation period prior to the first thin slab acquisition.

Abstract: A method for acquiring spatially and spectrally selective MR images by means of an MR imaging system includes the step of selecting an SPSP pulse sequence, comprising a succession of RF sub-pulses and an oscillatory gradient magnetic field, which is disposed to select a slice through a subject. The method further includes measuring specified parameters of a perturbation magnetic field associated with the imaging system, and deriving an expression for the perturbation field from respective measured parameters and from the oscillatory gradient magnetic field. A specified ideal frequency modulation function, associated with the SPSP sequence, is disposed to offset the slice to a particular spatially localized region of the subject. The SPSP pulse sequence is modified by adjusting the frequency modulation function in specified corresponding relationship with the expression.

Abstract: A system and method is disclosed to combine both a fractional echo (k.sub.x) and a fractional NEX (k.sub.y) to reduce acquisition times and echo times in MR imaging. The method uses both zero-filling and homodyne reconstruction to construct concurrent fractional NEX and fractional echo data in a single image while minimizing any blurring effects. The system includes acquiring partial MRI data in the k.sub.x direction and acquiring partial MRI data in the k.sub.y direction. Once a partial echo and a partial NEX are acquired, the missing data is first zero-filled in the k.sub.x direction and Fourier transformed to acquire a full x direction data set. Next, the data is synthesized in the k.sub.y direction using a homodyne reconstruction technique to acquire a full data set in the k.sub.y direction. The full x,y data set can then be used to reconstruct an MR image with reduced acquisition and echo times.

Abstract: A system and method for correcting systematic errors that occur in MR images due to magnetic gradient non-uniformity is disclosed for use with parametric analysis. A GradWarp geometric correction operation is applied in reconstructing quantitative parametric analysis images in regions of gradient non-uniformity. The method includes generating an error map of magnetic gradient strength as a function of distance for an MR image scan and acquiring MR data that contain such systematic errors. The method next includes either calculating a measured diffusion image, a phase difference image, or similar image, based on the acquired MR data, and then calculating a corrected parametric image using the error map and the measured diffusion image, the phase difference image, or other similar parametric image. The method is incorporated into a system having a computer programmed to perform the aforementioned steps and functions.

Abstract: A method of peripheral MR angiography is provided for imaging an artery or other vessel, wherein the vessel is of such length that MR data must be acquired at each of a plurality of scan stations spaced along the vessel. In accordance with the method, a contrast agent is intravenously injected, in order to provide a bolus which successively flows to each of the scan stations. After acquiring an initial subset of the MR data associated with a given scan station, the bolus is tracked to determine whether it has arrived at the next-following scan station. If so, at least some of the MR data associated with the next scan station are then acquired. However, if it is found that the bolus has not yet arrived at the next scan station, acquisition of further data at the given scan station is continued.

Abstract: A fast spin echo (FSE) pulse sequence is employed to perform a multi-slice, multi-angle MRI scan. The slices are scanned in groups, with all the slices in each group being oriented at the same angle and sampled in an interleaved manner. Total scan time is reduced by acquiring multiple, separately phase encoded echo signals during each FSE pulse sequence. Presaturation bands may be produced for each group of slices to reduce flow artifacts in the reconstructed slice images.

Abstract: Two methods are disclosed to remove the image artifacts produced by Maxwell terms arising from the imaging gradients in an echo planar imaging pulse sequence. In the first method, the frequency and phase errors caused by the Maxwell terms are calculated on an individual slice basis and subsequently compensated during data acquisition by dynamically adjusting the receiver frequency and phase. In the second method, two linear phase errors, one in the readout direction and the other in the phase-encoding direction, both of which arise from the Maxwell terms, are calculated on an individual-slice basis. These errors are compensated for in the k-space data after data acquisition.

Abstract: A method is provided for measuring the weight of a medical imaging scanner patient. The scanner has a bore portion for receiving and housing the patient during a scan. Initially, a reclining apparatus associated with the scanner is provided, on which the patient can recline during the scan. A hydraulic lift mechanism is then used to position the reclining apparatus and the patient at bore level. The pressure within the hydraulic lift mechanism can then be measured as a function of downward force exerted by the reclining apparatus and the patient surface. Alternatively, the automatic measuring of patient mass, associated with the movement of the reclining apparatus and patient into the bore, can be determined by calculating instantaneous acceleration of the reclining apparatus and patient as the reclining apparatus and patient are slid into the bore.

Abstract: Fast spin echo pulse sequences are adjusted to reduce, or eliminate image artifacts caused by Maxwell terms arising from the linear imaging gradients. The waveforms of the slice selection, phase encoding and readout gradients are adjusted in shape, size or position to eliminate or reduce the phase error caused by the spatially quadratic Maxwell terms.

Abstract: Fast spin echo pulse sequences are adjusted to reduce, or eliminate image artifacts caused by Maxwell terms arising from the linear imaging gradients. The waveforms of the slice selection, phase encoding and readout gradients are adjusted in shape, size or position to eliminate or reduce the phase error caused by the spatially quadratic Maxwell terms.

Abstract: A method and apparatus is provided for generating an MR image of a structural portion of a subject, the portion lying within a hypothetical imaging volume. A specified level of hyperpolarized magnetization is provided within the imaging volume, and a series of MR pulse sequences are applied to the imaging volume to generate respective corresponding MR data signals, each pulse sequence comprising a number of magnetic field gradient pulses and an excitation pulse, and having an associated flip angle determined by the excitation pulse. The associated flip angles of successive pulse sequences are progressively increased to maintain the signal strength of the corresponding MR data signals at a substantially constant level. Acquired MR data signals are cumulatively processed to provide an image of the structural portion.