Abstract: Radio frequency pulses (40, 50, 60) having tip angles in the range of 5.degree. to 15.degree. are applied concurrently with slice select gradient pulses (42, 52, 62) to tip a component of the magnetization into a transverse plane. Phase encode gradients (44, 54, 64) phase encode magnetic resonance echoes (48, 58, 68) which are collected in the presence of read gradients (46, 56, 66). The magnitude of components of the slice select , read, and phase encode gradients along three system axes (grad1, grad2, grad3) are different in conjunction with each echo such that each echo represents a view of data along a different slice through a region of interest. The tip angle (.alpha.) and duration (t) between RF pulses are selected such that the magnetization of dipoles within the most recently selected slice regrows along the magnetic field axis until it is indistinguishable over integrated noise from the magnetization corresponding to other dipoles in the image region.

Abstract: A system and method for monitoring progress of a radiographic exposure is disclosed. The system samples the cumulative radiation as an exposure progresses, and aborts the exposure if the rate of rise in cumulative radiation is insufficiently low to cause a good exposure. Similarly, the system will terminate an exposure early, at a properly timed out interval, even if the radiation accumulation rises excessively fast due to an erroneous system set up.

Abstract: A radiation imaging system is disclosed. A radiation source directs a thin spread beam of radiation toward a detector assembly which is aligned with the radiation beam. The detector assembly includes a printed circuit board having a bowed configuration and bearing board circuitry. An array of photodiode detector elements are attached to the board. The detector includes a front and a rear array of elements arranged one behind the other. The circuit board defines a slot between the front and rear arrays in which a radiation filter can be removably and slidably interposed. The detector elements are buried or recessed in outer surfaces of the circuit board to a depth sufficient to position contact fingers of the elements substantially flush with the unrecessed surface of the board. Radiation sensitive phosphor material is removably positioned over each of the respective front and rear detector element arrays.

Abstract: Magnets (12) create a main magnetic field along a z-axis through an image region. A localized coil (D) is disposed in the image region at least to receive magnetic resonance signals from nuclei of the subject which have been induced to resonance. The localized coil includes an inner conductor (30), preferably a plate, which defines a current path extending along the z-axis. The inner conductor is mounted closely adjacent and parallel to a surface of the subject. An outer conductor (32), preferably also a plate, is mounted parallel to but further from the subject than the first conductor. A connecting member (34) interconnects a first end of the inner and outer conductors and is disposed perpendicular to the z-axis. A matching circuit (36) including capacitors (50) which define the resonant frequency of the coil are connected adjacent second ends of the inner and outer conductors.

Abstract: Magnet (12) creates a main magnetic field along a z-axis through an image region. A localized coil (D) is disposed in the image region at least to receive magnetic resonance signals from nuclei of the subject which have been induced to resonance. The localized coil includes an inner conductor (30), an outer conductor (32), and a dielectric material (52) therebetween. The outer conductor defines a gap (50) midway between its ends. One end of the inner conductor is connected with a gate of an FET transistor (66) and the outer conductor is connected with its source. The transistor source and drain are connected by a coaxial transmission cable (38) with a DC power supply (70) which provides a DC bias across the transistor source and drain. The cable also connects the transistor with a radio frequency receiver (40) to convey preamplified magnetic resonance signals thereto.

Abstract: A system and method is disclosed for utilizing image pixel value information generated by a digital radiographic system for quantifying the amount of calcium in a particular object of interest within a subject, wherein the subject also contains additional quantities of calcium located at positions such that the additional calcium interfers with the acquisition of data describing the object of interest. A cursor configured as a parallelogram is described and pixel values are summed along lines parallel to the sides of the parallelogram. A profile is generated from these summations. A portion of the profile corresponding to pixel lines not intersecting the object of interest is used to estimate the contribution of background and other calcium to the profile as a whole, and this estimated value is subtracted from the total profile. Integration of the remainder of the profile provides a scalar value corresponding to the amount of calcium in the object of interest.

Abstract: A magnetic resonance or other diagnostic imaging scanner (A) is connected with an image reconstruction module (B) for reconstructing diagnostic images. An integrated expert system (C) selects scan parameter settings for conducting the scan such that utility of the image is optimized for the intended diagnosis. A keyboard (12) receives subject and intended diagnostic application data such as the age of the patient, the region of the patient to be imaged, the anticipated size of the lesion, and the like. A first expert system (10) derives appropriate constraints on values for each performance index and priorities for each performance index from the subject and intended application data. The performance indices include contrast, resolution, scan suration, and the like. A scan parameter estimator look-up table (14) is addressed by the performance index constraints and priorities and retrieves corresponding estimated scan parameters.

Abstract: A spin echo (52) and a gradient echo (60) are generated in each magnetic resonance sequence repetition. The spin echo is phase encoded by a phase encode gradient (44) in regular steps spanning about a quarter of k-space. More particularly, steps from -n to G.sub.max /2, where n is a small integer and G.sub.max is the maximum phase encode gradient. An off-set phase encode gradient (58) shifts the phase encoding of the gradient echo by G.sub.max /2 relative to the first phase encoding gradient. Data to fill the empty portions of k-space (142, 167) between -n and -G.sub.max are generated from the complex conjugate (140, 160), of the first echo data (74) and the second echo data (76). The first and second echo data and the complex conjugate data are transformed (122, 132, 146, 166) to generate parted image representations (124, 134, 148, 168).

Abstract: An x-ray tube (10) imaging system, such as a computed tomography scanner, includes a cathode (40) for generating a stream of electrons. A rotating anode (42) is placed in a path of the electron stream and generates x-rays as a result of collisions therewith. An induction rotor (44) causes rotation of the anode as a result of electromagnetic interaction with a stator (48) comprised of two windings: a run winding (50) and a phase winding (52). The run winding and the phase winding are connected to three nodes (54, 58, 60), one of which is common to both. The three nodes are actively driven with run, common, and phase signals, respectively. Actively driving the three nodes increases bus drive voltage over 40% over that achieved by half-bridge drives.

Abstract: A power supply line has two to four lead wires which are selectively connectable with terminals (10a-10d) of a transformerless AC-to-DC converter (A). The lead wire interconnection scheme is selected (FIGS. 1A-1D) in accordance with whether the line signal is single phase or three phase and whether the line voltage is 220 or 440 volts. The AC-to-DC converter produces a 620 volt DC, signal across its outputs (26, 28). A first inverter (B) converts to a pulsed AC signal and applies it across opposite phased primary windings (46a, 46b) of a step up transformer (C). Two pair of alternately phased secondary windings (48a-48d) and rectifier bridges (50, 52) provide a high voltage DC bias across a cathode (54) and an anode (56) of an x-ray tube (D). A summing junction (66) compares a voltage sensed across the x-ray tube with a reference voltage and generates a voltage deviation signal.

Abstract: A scanner (A) generates electronic data which is indicative of characteristics of an interior region of a subject in an examination region. A computer generator (B) generates corresponding pixel values of first and second electronic image representations which are stored in first and second image memories (12, 22). A video processor 14 retrieves pixel values from one of the memories and converts them into a video signal for generating a visual display on a video monitor (16). An audio processor 24 retrieves values from the other image memory and utilizes them to control the frequencies and amplitudes or other characteristcs with which modulators (52, 54, 56, 58) modulate an audio icon signal. In this manner, the audio icon signal is modulated in accordance with the selected characteristics of the interior region. An electroacoustic transducer (66) converts the modulated audio signal into an audible display of the selected characteristic.

Abstract: A digital radiographic system and method is disclosed having improved detector resolution. The system includes an X-ray source and a spaced detector assembly having several staggered columns of uniform square detector elements. The detector elements are thus arranged in interspersed rows with the center-to-center spacing between successive members of each row being about twice the lateral dimension of each square element. In response to incident X-radiation, each detector element produces an electrical charge signal indicative of the radiation. Power means actuates the source to propagate X-ray energy in a beam along a path toward the detector assembly, in which path a subject may be interposed for examination. Mechanism is provided for scanning the detector assembly, synchronously and in alignment with the X-ray beam, relative to a subject. The relative scanning motion is perpendicular to the columns of detector elements.

Abstract: A compact, lightweight, portable, versatile and modular field x-ray system is disclosed. A base member is provided and supports an x-ray table. Two vertical masts are also coupled to the base, for movement alongside the table in a direction parallel to its longitudinal dimension. The masts move independently of one another but can also be linked together for movement in unison. A tube head is attached to one mast by articulated structure, including a series of offset arms, which affords the tube head 6 degrees of freedom of movement, both above and below the x-ray table. A spot film device is movable coupled to the second mast. The second mast and spot film device are manually removable from the remainder of the system for operation in radiographic only mode.

Abstract: A medical diagnostic television imaging system is disclosed having an x-ray source, an image intensifier tube and a video camera positioned to view the output face of the image tube. A monitor is coupled to receive video and synchronization signals from the camera. Means is associated with the video camera for controlling the camera to scan at a selected one of a plurality of scan rate formats. Circuitry is provided for suppressing the delivery of video to the monitor in response to the selection of at least one of the plurality of scan rates. During video suppression, transmission of synchronization signals to the monitor continues.

Abstract: An X-ray tube having two individually energizable cathode filaments. If a primary filament is shorted to a cathode cup, a switch mounted inside the tube housing is thrown to couple a second filament to a filament energization signal. This avoids the necessity in replacing the X-ray tube if the primary filament is shorted and lengthens the effective life of the X-ray tube.

Abstract: A nuclear magnetic resonance radio frequency coil. The disclosed coil provides high frequency resonance signals for perturbing a magnetic field within the coil. The coil is impedance matched and tuned with adjustable capacitors. A balanced configuration is achieved with a co-axial cable chosen to phase shift an energization signal coupled to the coil. The preferred coil is a thin metallic foil having a shorting conductor, four wing conductors, and uniquely shaped parallel cross conductors connecting the shorting and wing conductors. When mounted to an rf transmissive plastic substrate and energized the coil produces a homogenous field within a region of interest the size of a patient head. A semicircular balanced feedbar arrangement is used to minimize undesired field contributions.

Abstract: A xenon gas system (B) introduces xenon gas into a patients's blood. The xenon gas concentration in the patient's blood is monitored and the characteristics of the patient's blood absorption curve are determined (34). A look-up table array (60) includes a plurality of look-up tables, each look-up table corresponding to one of a plurality of preselected blood absorption curves. A look-up table selection circuit (36) selects the look-up table which most closely corresponds to the projected blood absorption curve. A CT scanner (A) generates a plurality of image representations at preselected intervals after commencement of xenon gas interpolation, which images are stored in an image memory array (44). Xenon gas concentration values from corresponding pixels of each image representation are utilized to address the look-up table corresponding most closely to the patient's blood absorption curve in order to retrieve precalculated partition coefficient, blood flow rate, and confidence values.

Abstract: A resonance exciting coil (C) excites magnetic resonance in nuclei disposed in an image region in which a main magnetic field and transverse gradients have been produced. A flexible receiving coil (D) includes a flexible plastic sheet (40) on which one or more loops (20) are adhered to receive signals from the resonating nuclei. Velcro straps (46) strap the flexible sheet and the attached coil into close conformity with the surface of the portion of the patient to be imaged. An impedance matching or coil resonant frequency adjusting network (50) is mounted on the flexible sheet for selectively adjusting at least one of an impedance match and the peak sensitivity resonant frequency of the receiving coil. A preamplifier (52) amplifies the received signals prior to transmission on a cable (24). A selectively variable voltage source (70) applies a selectively adjustable DC bias voltage to the cable for selectively adjusting at least one of the impedance match and the LC resonant frequency of the receiving coil.

Abstract: In a magnetic resonance imaging system, a plurality of RF pulses (24) are applied in bundles (62). The pulses in each bundle have an interpulse spacing (66) which is shorter than the T1 and T2 relaxation time of an imaged sample. The next pulse of the bundle is applied before the magnetic resonance response can build to a steady state echo. After a steady state resonance condition is reached, the application of radio frequency pulses is interrupted for an interbundle duration (72) which is sufficiently long for the steady state echo (96) to occur. Magnetic resonance imaging data is sampled during the steady state echo. Slice select gradients (34) are applied concurrently with each radio frequency pulse. In the interbundle interval, a phase encode gradient (42) and a read gradient (38) are applied. The sequence is repeated a plurality of times each with a different phase encode gradient to generate the appropriate data lines or views for transformation into an image representation.

Abstract: A radiographic scanner (A) generates a high energy image representation which is stored in a high energy image matrix (V) and a low energy image representation which is stored in a low energy image memory (U). A pair of filter functions selecting circuits (C) select a first or soft tissue specific filter function and second or bone specific filter function, respectively. The soft tissue filter function selecting circuit selects and adjusts the soft tissue filter function in accordance with the pixel value of the low energy image representation for each corresponding pair of pixel values. Convolvers (44, 46) convolve pixel values from the high and low energy image representations with the selected and adjusted filter functions. A soft tissue transform function (48) transforms the filtered high and low energy image representations into a soft tissue or other material specific image representation (42).