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 method for approximating X-ray detector data from malfunctioning computed tomography detectors. A view of data is gathered for each of a plurality of detectors in a stationary detector scanner. Data for each malfunctioning detectors is approximated by interpolating data from detectors closely positioned with respect to the malfunctioning detectors after regions of high contrast within a cross-section of interest have been identified.

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 digital radiography system is disclosed having a multi-element curved detector assembly. The system includes an X-ray tube having a focal spot from which its X-ray energy primarily emanates, and which is spaced from the detector assembly to define a subject examination space. The detector assembly includes a number of individual detector elements each having a radiation sensitive face, the element faces collectively defining a concave curved surface oriented toward the focal spot. The assembly of elements can embody forms including a single curved line of elements, multiple similarly curved lines defining collectively a portion of a cylinder, or a three-dimensional curved array defining a portion of a sphere. Multiple layer stacked arrays can also be used. Each element responds to incident X-rays to produce an electrical charge signal indicative of the radiation.

Abstract: An electronic module for generating gradient energization signals in magnetic resonance imaging to correct for eddy current effects. An energization profile is modified by an amount related to the magnitude of eddy current fields generated in the vicinity of a gradient coil. This modification produces an energization profile resulting in a gradient magnetic field corresponding to the magnetic field the unmodified energization profile would have produced but for the presence of induced eddy currents.

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: A multi-pulse radio frequency signal sequence includes a 90.degree. excitation pulse (50) and at least a first 180.degree. refocusing pulse (52) and a second 180.degree. refocusing pulse (54). The excitation pulse and first refocusing pulse are separated by a duration A and the first and second refocusing pulses are separated by A+B. A free induction decay (60) follows the excitation pulse, a first spin echo (62) occurs a duration A after the first refocusing pulse and a second spin echo (64) occurs the duration B after the second refocusing pulse. A first read gradient (90) is applied between the excitation and first refocusing pulses; a second read gradient (92) is applied between the first refocusing pulse and the first spin echo; a third read gradient (94) is applied between the first spin echo and the second refocusing pulse; and a fourth read gradient (96) is applied between the second refocusing pulse and the second spin echo. Because the 90.degree. and 180.degree.

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: 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 magnetic resonance imaging apparatus (A) generates a uniform main magnetic field, gradient fields transversely thereacross, excites resonance in nuclei within an image region, receives radio frequency signals from the resonating nuclei, and reconstructs images representative thereof. Electrodes (30) monitor the cardiac cycle of a patient (B) being imaged and an expansible belt (32) monitors the respiratory cycle. A carrier signal from a generator (52) is modulated with the respiratory signals. The modulated carrier signals are combined (60) with the cardiac signals and converted to a light signal by a light source (62). A fiber optic cable (36) conducts the light signals to a light receiver (70). Band pass filters (72, 100) separate the received cardiac and respiratory encoded carrier signals. A zero detector (80) provides a scan initiation signal in response to a preselected portion of the cardiac cycle.

Abstract: A main magnetic field coil (10) and control (12) cause a generally uniform main magnetic field through an image region. A resonance excitation control (22) causes an R.F. coil (20) to generate excitation pulses (100). A slice gradient control (32) and a read gradient control (34) cause a gradient coil (30) to generate complementary slice selection gradient profiles (112, 114) and complementary read gradient profiles (122, 124) in such a manner that the effective first moment in time is substantially zero. By time shifting a pulse in one or both of the slice selection and read gradient sequences (FIGS. 3 and 4), resonating nuclei in the selected slice can be phase encoded. A transform algorithm (40) transforms field echo signals (102) received by the R.F. coil into image representations.

Abstract: A high speed data transfer method and apparatus. A high speed data bus includes separate data transfer and master control bus portions. A system host computer loads a sequence of source and destination addresses corresponding to communications units coupled to the bus into memory in a bus master controller. The bus controller sequences through these address pairs at an aggregate rate greater than at least some of the devices' ability to transfer data to enhance data transmission speed on the bus. Bus cycles are allocated to devices on the bus according to a scheme dependent on those devices ability to utilize the bus. High speed devices are allocated a greater number of bus cycles per unit time than slower devices.

Abstract: Method and apparatus for a computed tomography patient localization scan. A source of radiation that orbits a patient during a normal computed tomography scan is fixed relative an array of radiation detectors. The patient is then moved in a direction generally perpendicular to the plane of the radiating source and array to obtain a first shadowgraph data set. The source is orbited a small amount and the patient is again moved relative the source and detector array to obtain a second shadowgraph set of data. The two sets of data are then interleaved to obtain a shadowgraph image having higher resolution than either the first or second shadowgraph.

Abstract: In a magnetic resonance imager or other spectrometer, an interface (D) selectively connects quadrature probe coils (E) with a transmitter (C) and with a receiver (F). The interface includes a first RF switch (10), such as a first PIN diode (12) which has a low radio frequency impedance state for passing transmitted radio frequency signals to the probe coils and a high radio frequency impedance state for blocking the passage of radio frequency signals to the probe coils. A quarter wave length cable (20) or the equivalent is connected between the probe coils to shift the phase of the radio frequency signals 90 degrees. A second radio frequency switch (40) includes a second quarter wave length cable (42) and a second pin diode (44) which selectively pass and block radio frequency signals from passing between the probe coils and the receiver.

Abstract: An X-ray tube having a capability to produce multiple anode spots. The X-ray tube can produce three or more different size anode focal spots without modification of the connectors, cabling, or high voltage supply for routing high voltage signals to the X-ray tube. An isolating fiber optic control input connects an external light emitting diode to a controller inside the tube housing. The controller responds to light signals from the light emitting diode to control the size of focus spots on the tube anode. In a preferred embodiment each of three filaments are individually energized to produce three different size focal spots and a cathode cup to which the filaments are mounted is also biased to add a four spot capability. In an alternate embodiment a split or segmented cathode cup has its segments biased to different electrical potentials by tapping power from a conventional high voltage filament supply used in energizing a cathode filament.

Abstract: A main magnetic field coil and control cause a generally uniform main magnetic field through an image region. A resonance excitation control causes an R.F. coil to generate excitation pulses. An inversion pulse control causes the R.F. coil to generate a first 180 degree inversion pulse after the excitation pulse and a second 180 degree inversion pulse immediately preceding the excitation pulse. A slice gradient control and a read gradient control cause a gradient coil to generate complimentary slice selection gradients and complimentary read gradient profiles on either side of the first inversion pulse in such a manner that the effective first moment in time is substantially zero. By time shifting one or both of the slice selection and read gradients, resonating nuclei in the selected slice can be phase encoded. A transform algorithm transforms resonance signals received by the R.F. coil into image representations.

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: 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.

Abstract: Improved apparatus, circuitry and method is disclosed for control of a television camera in a radiographic imaging system. The system includes a radiation source, an image intensifier tube and several associated components for acquiring analog radiation representing images in one or more of several prime analog study modes. The analog acquisition components include any one or a combination of a cine camera, a spot film camera and a spot film device. Radiation is directed from the source through a subject to the intensifier tube input and to selected analog acquisition components. As the analog images are acquired, a television camera views the image tube output to produce another image, by way of a monitor, in verification that the radiation exposure is of a character suitable for the selected analog image acquisition mode. Sets of representations of camera operating parameter value decisions are stored in non-volatile random access memory circuitry coupled to the camera.

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.