Abstract: Segmented echo planar nuclear magnetic resonance imaging is performed using an iterative correction method that corrects or suppresses geometric distortion in the image domain caused by off-resonance phase discontinuities in the phase encoding direction. The iterative correction method can be performed in a single scan by providing extra gradients in the pulse sequence to generate an extra transverse magnetization echo from the pulse. Additionally, the iterative correction method can be performed using a separate non-segmented double-echo scan in combination with data obtained using a conventional segmented echo planar imaging pulse sequence.

Abstract: A computer system for sharing information among a plurality of users, the computer system comprising: (a) a database having content stored therein, the content comprising (1) a plurality of data objects and (2) a user-configurable tree structure comprising a plurality of selectable nodes that index the data objects; (b) at least one client computer in communication with a global computer network, each client computer having a display screen on which the client computer is configured to display data to a user; (c) an application server in communication with the database and the network, the application server being configured to (1) send at least a portion of the tree structure over the network to a client computer at least partially in response to an access request received over the network from a client computer, (2) cause the client computer to display the tree structure sent thereto in a viewing frame of the client computer's display screen, (3) receive node selection input from the client computer that co

Abstract: A method for magnetic resonance imaging is described.

Abstract: A method for magnetic resonance imaging is described.

Abstract: A method of complex image reconstruction from partially acquired data in two or more dimensions is presented. This method uses an iterative multidimensional transformation to reconstruct a magnetic resonance image. The method of this invention abandons the theory that complex conjugation is necessary to reconstruct a complex image from partially acquired data and, instead, utilizes a phase constraint to make the solution determinable using a multidimensional transformation technique. This method of image reconstruction allows magnetic resonance images to be reconstructed by acquiring only one-half of the k-space data.

Abstract: The echo time in an MR pulse sequence is optimized in accordance with the application desired. Advantageously, the echo time is selected to cause a partial volume signal cancellation from veins as compared with background tissue, and the MR pulse sequence is of a velocity-compensated type. MR data are acquired from gradient echoes. Multiple echoes may be used to extract information (such as volume content and susceptibility) about the material under investigation.

Abstract: An imaging apparatus and method which provides for reconstruction of images from sampled data with improved resolution, improved signal-to-noise, optimal edge detection, and pattern recognition. The apparatus and method are characterized by the use of a priori information (constraints) and a high pass filter on the data to obtain superresolution reconstruction of image data. An object function is approximated by a series of known model functions such as box car and polynomial functions. Solution of the object function depends on a finite number of unknowns whereupon the model parameters can be perfectly resolved to obtain infinite or superresolution. The apparatus and method have particular application in nuclear magnetic resonance imaging as well as other imaging modalities.

Abstract: A portion of a subject (22) which is undergoing respiratory or other motion is disposed in an image region (20) to be examined. A respiratory or other motion monitor (50) monitors the cyclic respiratory motion and provides output signals indicative of chest expansion. A phase encoding gradient selector (60) selects the phase encoding gradient that is to be applied by a gradient magnetic field controller (40) and coil (42). A central phase encoding gradient is selected corresponding to a chest relaxation extreme and minimum and maximum phase encoding gradients are selected corresponding to a chest expansion extreme (FIG. 2). Intermediate degrees of monitored physical movement cause the selection of corresponding intermediate phase encoding gradients. Resonance signals collected during each phase encoding gradient are Fourier or otherwise transformed (80) into a corresponding view.

Abstract: A shimming magnetic field control (22) causes shimming magnetic fields for improving uniformity of a main magnetic field generated by main magnets (10). A resonance excitation control (32) selectively applies a resonance excitation pulse (34) and inversion pulse (36) for inverting the spin magnetization of water and lipid dipoles. A phase sensitive detector (30) selectively receives resonance signal components which are transformed by a transform algorithm (70) into a real image (72) and an imaginary image (74). The inversion pulse (36) is shifted by a time such that the water and lipid spin magnetizations are out of phase by a predetermined amount. With a 90.degree. phase difference, the real image represents water and the imaginary represents lipid. A phase image (80) is derived from a reference image pair (76, 78). A phase unwrap circuit (82) removes ambiguities attributable to the spin magnetizations becoming dephased by multiples of 2.pi. to create a phase map (84).

Abstract: A reference object (24) is disposed in an image region (20) with a subject (22) to be examined. The reference object has known parameters such as relaxation time, spin density, dimensions, and position. Magnetic resonance signals in which the spatial position of resonating nuclei is encoded in the relative phase and frequency thereof are sampled and temporarily stored in a view memory (56). A Fourier transform (60) is performed to convert the stored signals view into a representation of at least the positions and spin density of the resonating magnetic dipoles of the subject and reference object. The parameters of the reference object measured from the image representation are compared or inverse transformed back to data space for comparison with actual parameters of the reference object or thresholds. Based on the comparison, the resonance signals or the image representation are adjusted.

Abstract: The resonance signals from a magnetic resonance imaging apparatus are discretely sampled. The sampled data are non-uniform in data space due to motion, eddy currents in the magnetic field, inaccurate timing in the application of the gradient magnetic fields, non-uniform sampling of the data, or the like. The discretely sampled data, s(k.sub.x, k.sub.y), is mapped from data space to image space by a generalized transform. The generalized transform, unlike a Fourier transform, concurrently corrects for the non-uniformity as it transforms the non-uniform data space data into image space data with a preselected distribution, e.g. uniform. For a given y position of non-uniformly sampled data s(k,y), the estimated spin density .rho.(x,y) is related to the actual spin density .rho.(x,y) by the equation: ##EQU1## where the matrix A describes the non-uniformity and can be calculated or determined experimentally. When the matrix B=A.sup.-1, the estimated and actual data match.

Abstract: Hybrid fast scan magnetic resonance imaging is performed by using, for example, both a two dimensional Fourier transform (2DFT) method using phase encoding prior to data collection and an echo planar technique which phase encodes by using an oscillating gradient during data collection. In this hybrid imaging, the amplitude of the oscillating gradient determines the time savings achieved in imaging. The hybrid scan has particular application for medical diagnostic imaging since it is advantageous that such imaging be conducted as rapidly as possible.