Abstract: A multistage, proximity type, radiation image intensifier tube having improved performance characteristics and more rugged construction is provided. A scintillator assembly is comprised of a first ceramic, cellular substrate defining an array of hexagonally shaped cells. The cell walls taper to an edge and are coated with a conductive material such as aluminum. The cells are filled with a scintillation material such as cesium iodide. A first flat photocathode is provided adjacent the first substrate. An intermediate assembly spaced from the scintillator assembly is provided comprised of a second ceramic, cellular substrate similar to the first. The cell walls are coated with a conductive material such as aluminum. A support layer is mounted to the substrate on an end opposite the scintillator assembly. A first flat phosphor display screen is mounted to the support layer on a side internal the second substrate. A second photocathode is provided adjacent the second substrate.

Abstract: A method and apparatus for calibrating the detector gain of a dual energy digital radiography system is provided. A basis material calibration object is scanned to create low and high energy pixel data. A regression is performed on the pixel data to derive at least one high energy calibration vector and at least one low energy calibration vector. The calibration vectors are transformed into high and low energy gain functions represented by a Taylor series expansion. An examination object is scanned to create low and high energy image data. The image data is combined with the gain function to create corrected low and high energy image data.

Abstract: A multistage, proximity type, radiation image intensifier tube having improved performance characteristics and more rugged construction is provided. A scintillator assembly is comprised of a first ceramic, cellular substrate defining an array of hexagonally shaped cells. The cell walls taper to an edge and are coated with a conductive material such as aluminum. The cells are filled with a scintillation material such as cesium iodide. A first flat photocathode is provided adjacent the first substrate. An intermediate assembly spaced from the scintillator assembly is provided comprised of a second ceramic, cellular substrate similar to the first. The cell walls are coated with a conductive material such as aluminum. A support layer is mounted to the substrate on an end opposite the scintillator assembly. A first flat phosphor display screen is mounted to the support layer on a side internal the second substrate. A second photocathode is provided adjacent the second substrate.

Abstract: A method of nuclear magnetic resonance imaging wherein motion artifacts in the image are reduced by compensating for variations in the coupling between the RF transmitter and/or detector coils (9A, 9B and/or 10A, 10B) and the body (43) being imaged due to movement of the body. Compensation is suitably effected by measuring the position of the body (43) with respect to a datum immediately prior to each excitation of nuclear spins in the body and setting the amplitude of the applied RF excitation pulse B (90.degree.) and the detector sensitivity in dependence on the measured position.

Abstract: An improved phototimer control and compensation scheme is provided. The control monitors electrical signals produced by a plurality of photomultiplier tubes. PMT dark current is sampled prior to exposure and is compensated for as exposure begins. Each PMT produces a signal proportional to incident radiation which is integrated by separate integrator means to produce first ramp signals. Switching means are provided for selecting any one or combination of first ramp signals. Mixing means combines selected first ramp signals. Amplifier means amplifies mixed signals as a function signals selected to produce a second ramp signal. Gain selection means compensates the gain of the second ramp signal to the speed with the film-screen combination chosen. An exposure compensation scheme produces an exposure reference signal defining the net effect of system variables. Equations defining kV reference curves are stored in a first storage means.

Abstract: A method of operating an electromagnet arrangement comprising a main electromagnet and a number of correction coils for applying correction fields to the field produced by the main electromagnet to produce a resultant desired homogeneous magnetic field in a given volume. The method comprises obtaining the least squares fit values for the correction coil currents and, if the required current in any coil lies outside a range of permissible values for that coil current, following a special procedure to find the best selection of coil currents consistent with the permissible currents in the coils.

Abstract: A method, and an apparatus for performing the method, are described, for imaging a region of a body using NMR in which part of the region is moving with a motion such that its displacement with respect to time is a nonmonotonic function during the time period over which NMR data signals are collected. The data signals are collected in an order dependent on the motion such that motion artifacts are reduced.

Abstract: A multistage, proximity type, radiation image intensifier tube having improved performance characteristics and more rugged construction is provided. A scintillator assembly is comprised of a first ceramic, cellular substrate defining an array of hexagonally shaped cells. The cell walls taper to an edge and are coated with a conductive material such as aluminum. The cells are filled with a scintillation material such as cesium iodide. A first flat photocathode is provided adjacent the first substrate. An intermediate assembly spaced from the scintillator assembly is provided comprised of a second ceramic, cellular substrate similar to the first. The cell walls are coated with a conductive material such as aluminum. A support layer is mounted to the substrate on an end opposite the scintillator assembly. A first flat phosphor display screen is mounted to the support layer on a side internal the second substrate. A second photocathode is provided adjacent the second substrate.

Abstract: An NMR spectroscopy method monitors a component of a sample, the component having two resonances in coupled together different spectral regions. The first resonance lies in a region including a resonance of a second component of a sample while the second resonance lies in a spectral region including a resonance of a third component of the sample. Two spin-echo pulse sequences each consisting of pulses of a predetermined frequency are applied, the spin-echo resonance spectra together being used to obtain the second resonance of the first component with the resonance of the third component suppressed.

Abstract: A radiographic/fluoroscopic X-ray system is disclosed employing a new and improved apparatus for supporting a patient under examination. The system includes a table assembly comprising a main support structure and a patient support member. The patient support member is movably mounted to the main support structure while maintaining a clearance space therebetween. A guard means, mounted to one end of the patient support member is provided to discourage inadvertent placement of a patient's fingers in the clearance space. The guard means is comprised of rigid or semi-rigid material and extends above the clearance space and beyond the end of the patient support member. The guard means defines a space for finger placement which is remote from the clearance space.

Abstract: A coil arrangement for producing a magnetic field of high homogeneity, such as is required in magnetic resonance imaging, comprising a single pair of identical annular coils (17A, 17B) disposed coaxially in spaced relationship and a pair of annular members (19A, 19B) of ferromagnetic material disposed coaxially with the coils, symmetrically with respect to the plane which perpendicularly intersects the axis of the coils centrally between them. The coils and ferromagnetic members have dimensions and are relatively positioned so that, with the coils carrying equal energizing currents, the more significant spherical harmonic coefficients are eliminated.

Abstract: A nuclear magnetic resonance imaging method and apparatus using the Hahn spin echo technique wherein dephasing of spins due to selection field gradients (G1x, G2x, G3x) applied during the radio frequency excitation pulses (B1 (90.degree.), B2 (90.degree.), B3 (90.degree.) of the Hahn technique is corrected solely by magnetic field gradients (-G'x, -G2'x) applied before the last radio frequency excitation pulse.

Abstract: In a steady state free precession (SFP) magnetic resonance imaging method, after each pulse of an applied train of phase coherent RF pulses which excite magnetic resonance spins in a region of a body being examined, magnetic field gradients are applied to encode the excited spins and the encoded spins are detected, and at least one further magnetic field gradient is then applied to rephase the spins by the time the next RF pulse is applied.

Abstract: A nuclear magnetic resonance method and apparatus for examining a predetermined particular location (55) in a body wherein processed data obtained from four procedures are combined to extract processed data relating to the particular location. Each procedure comprises exciting spins in a region (45) of the body including the location (55) and acquiring and processing data in respect of the excited spins. In a first procedure the excited spins are of the same phase throughout the region (45). In a second procedure the excited spins are of a first phase in a first portion (49) of the region (45) of which portion the predetermined location (55) forms part, and are of the opposite phase in the rest of the region (45). In a third procedure the excited spins are of a first phase in a second portion (53) of the region which intersects the first portion (45) at the predetermined location (55) and are of the opposite phase in the rest of the region (45).

Abstract: A radiographic/fluoroscopic X-ray system is disclosed employing a new and improved method and apparatus for viewing an image of a subject under examination. The system includes a flat panel display screen integrally mounted to the spotfilmer/imaging system housing. The display screen is mounted to the spotfilmer/imaging system housing to provide pivotal movement in at least one direction. Where a tiltable X-ray table is used, apparatus and circuitry is provided to maintain correct viewing orientation of the image with respect to the operator while the table is tilted throughout its range.

Abstract: An off-focal radiation collimator is disclosed which includes a plurality of radiation absorbing elements supported in spaced relationship with respect to one another in a housing such that each element is aligned along radii extending from the focal spot of a radiation source. The off-focal collimator is preferably disposed between the radiation source and a primary beam collimator. The off-focal collimator also acts as a radiation beam compensator. By varying the spatial density of the radiation absorbing elements by a function of location within the housing, the radiation beam can be shaped to any desired profile.

Abstract: An NMR chemical shift imaging method and apparatus wherein a number of experiments are performed with different encoding gradients sufficient to obtain a desired spatial resolution in the image, and each of said number of experiments is repeated for each of a number of different delay times between excitation and the start of data collection sufficient to obtain a desired chemical shift resolution in the image.

Abstract: A phantom for use in assessing the performance of an NMR imaging apparatus which enables quantitative assessments of image slice width and spatial resolution under different conditions of contrast to be made, and which enables an assessment of overall performance of the apparatus to be made to facilitate comparison of the performance of the apparatus when operating in different modes. The structure and methods of use of the phantom are described.

Abstract: Tomographic images are obtained at a plane of interest by taking a series of x-ray exposures, producing a series of multiple images therefrom, arranging these multiple images so that points residing within a desired plane of interest are coincident to form a first order clarified image, repeating the step for a predetermined number of other planes which are parallel to the first plane of interest, to produce a first order clarified image for each of these planes, and then producing a smeared image for each of such planes, except one, by replicating the first order image for said plane a predetermined number of times and shifting each of the replicated images in the plane as a function of the distance between that particular plane and the x-ray source, the distance between that particular plane and the x-ray image device, the same distances but taken relative to a plane of interest, and the distance moved between exposures by the x-ray source.