Picker International, Inc.

Koninklijke Philips Corporation N.v.

Picker Corporation

Other

Theodore A Resnick

Walter A Dupuis

Rodney Arnold Mattson

Mark Douglas Herold

William E Szabo

Lester Donald Miller

Carl J Brunnett

James E Burke

Anthony M Palermo, Jr

Donald A Hescht

John Kociecki

David A Wilcox

Richard J Elliott

A dose-modulated irradiating system includes an x-ray tube () with at least a filament () for generating electrons, a cathode () and an anode () for accelerating and collimating the generated electrons into an electron beam (), and an electrostatic grid with grid electrodes () for steering the electron beam () on the anode (). The anode () generates an x-ray beam () responsive to the electron beam (). Grid biasing is provided for applying a time-varying electrical bias to the grid electrodes () that produces a first time-varying intensity modulation of the electron beam (). A current of the filament () is modulated to produce a second time-varying intensity modulation of the electron beam (). A controller () controls cooperatively combining the first and second time-varying intensity modulations to produce a combined time-varying intensity modulation.

High speed modulation of switched-focus x-ray tube

A computerized tomography system includes a stationary section (A) and a rotating section electrically linked by at least one interconnecting slip ring (D). On one side the slip ring (D) is configured as a series of electrically conductive segments ( A- H) separated by non-conductive interruptions ( A- H). On the other side a like number of transmitters ( A- H) is in selective electrical contact with the conductive segments ( ) depending on a position of the rotating frame. Also included is a de-multiplexer ( ) which takes image data from the plurality of receivers (RxA-RxH) and rearranges the image data in a determined sequence. Also shown is an angular encoder ( ) for providing angular displacement signals ( ) to the de-multiplexer ( ) for assistance in reconstructing the data channels ( ) in the determined sequence.

Multi-channel segmented slip ring

A computerized tomography system includes a stationary section (A) and a rotating section electrically linked by at least one interconnecting slip ring (D). On one side the slip ring (D) is configured as a series of electrically conductive segments (,A-,H) separated by non-conductive interruptions (,A-,H). On the other side a like number of transmitters (,A-,H) is in selective electrical contact with the conductive segments (,) depending on a position of the rotating frame. Also included is a de-multiplexer (,) which takes image data from the plurality of receivers (RxA-RxH) and rearranges the image data in a determined sequence. Also shown is an angular encoder (,) for providing angular displacement signals (,) to the de-multiplexer (,) for assistance in reconstructing the data channels (,) in the determined sequence.

An x-ray radiation stabilization system is provided including an x-ray tube (,) which emits x-ray radiation (,). The x-ray tube (,) has an anode (,), a cathode (,), and a vacuum envelope (,) which houses the anode (,) and the cathode (,). A high-voltage generator (,) is connected to the x-ray tube (,). It supplies a high-voltage electric potential between the cathode (,) and anode (,) such that an electron beam flows therebetween. The electron beam strikes the anode (,) producing the x-ray radiation (,). A reference radiation detector (,) samples a representative portion of the x-ray radiation (,) emitted by the x-ray tube (,) and generates an error signal in response to an intensity of the sampled x-ray radiation (,). A feedback circuit (,) is connected between the reference radiation detector (,) and the high-voltage generator (,). The feedback circuit (,) processes the error signal and in response thereto directs the high-voltage generator (,) to adjust the high-voltage electric potential supplied to the x-ray tube (,) so that in the x-ray radiation (,) ripple having a predetermined frequency range is substantially canceled.

Reduction of temporal variations in X-ray radiation

A high voltage power supply includes a high voltage high frequency generator (10) having outputs (12, 14). An arc limiting device (20) is connected in series to the outputs (12, 14) of the generator (10). The arc limiting device (20) includes two coils (22, 24) of a wound length of wire (50) that exhibit a skin effect. The skin effect forces higher frequency current components to flow at a surface of the wire (50) through a limited skin layer portion (62) of a cross section of the wire (50). In one preferred embodiment, the arc limiting device (20) is connected via high voltage cables (32, 34) with an x-ray tube (40). Suitable material for the wire (50) includes those materials with high permeability to resistivity ratios, for example iron, purified iron, 78 permalloy, 4-97 permalloy, mu metal, or supermalloy.

Arc limiting device using the skin effect in ferro-magnetic materials

A radiographic scanner (10) has a stationary gantry portion (12) defining a subject receiving region (16) and a rotating gantry portion (20) on which an imaging x-ray tube (22) is mounted. The rotating gantry portion (20) is rotatably mounted to the stationary gantry portion (12) for rotation about the subject receiving region (16). A slip ring assembly extending around the subject receiving region (16) connected with the stationary and rotating gantry portions, includes a scintillating optical fiber (44) mounted around the patient receiving region (16) to one of the rotating and stationary gantry portions. A communication x-ray tube (40) is mounted to the other gantry portion and directed such that radiation therefrom enters the scintillating optical fiber (44) from a lateral direction. The scintillating optical fiber (44) converts the incident x-rays (52) to light (58) and transmits the light (58) along its longitudinal axis. The scintillating optical fiber (44) is enclosed in a protective sheathing (50) that is opaque to optical radiation which protects the fiber from damage and eliminates noise, inaccuracy, and false signals caused by ambient and stray light entering the fiber.

Wideband non-contact data link using X-ray sources to excite

An x-ray tube of a CT scanner is powered by a high-voltage power supply (26). The high-voltage power supply includes a plurality of sections (102) each having three straight-up transformers (48) which receive three 120.degree. phase shifted alternating current components as inputs. The straight-up transformers perform a direct voltage transformation with single or multiple transformers and with no capacitive multipliers. Each straight-up transformer has a primary winding (T1) and two secondary windings (T1-A, T1-B). The secondary windings are connected together in delta and wye configurations (84). The alternating current components have their voltage boosted and are rectified and summed to form a high-voltage output that is substantially ripple-free. A pulse-width modulated converter (34) generates a conditioned output current from an inputted direct current. Resonant inverters (36) receive the conditioned output current and convert the conditioned, direct current into alternating current received by each of the straight-up transformers (48) in the stack. The resonant inverters (36) operate at or near resonance. The power supply (26) has no added capacitance and stores a minimum of energy. It provides rise and fall times which enable the x-ray tube to perform sub-second exposures with very short rise and fall times.

High-voltage power supply for x-ray tubes

A toroidal x-ray tube (I) is supported and selectively positioned by a gantry (II). The x-ray tube includes a toroidal housing (A) in which a rotor (30) is rotatably mounted. One or more cathodes (C) are mounted on the rotor for generating an electron beam which strikes an anode (B) to generate a beam of x-rays which passes through a window (20) and strikes an annular ring of detectors (160). A grid bias control circuit (100) selectively applies a continuously adjustable bias to a grid (36) for regulating the electron current, hence the intensity of the x-ray beam. A scintillating optical fiber (110) extends around the exterior of the window. The scintillation optical fiber includes fluorescent dopant (116) which convert a very small fraction of the x-rays into optical light which is transmitted along the fibers to an opto-electric transducer (118). The opto-electric transducer is connected with the grid bias control circuit. The opto-electrical transducer (118) can also be connected with an intensity compensator (162) for adjusting the signals from the detector ring before they are reconstructed (164 ) into an image representation.

X-ray reference channel and x-ray control circuit for ring tube CT

A toroidal x-ray tube (I) is supported (II) for rotation about a horizontal axis (170), translation along a vertical axis (172), and translation along a horizontal axis (174). The x-ray tube includes a toroidal housing (A), an annular anode (B), and a cathode (0) which rotates a beam of electrons around the annular anode. A plurality of parallel connected voltage sources (90.sub.1, 90.sub.2, . . . , 90.sub.n) provide a sufficiently high bias voltage between the electron source and the anode that x-rays are generated. The x-ray beam passes through a compensator crystal (62), an annular window (20), a collimator (132), through a subject received in a central bore (26) of the x-ray tube, and impacts an arc segment of radiation detectors (130). The x-ray detectors are stationarily mounted outside of the plane of the annular window (FIGS. 2 and 7), nutate into the plane of the windows opposite of the origin of the x-ray beam (FIG. 6 ), rotate in part (FIG. 9 ) or rotate in full (FIG. 8 ) Angular position monitors (58, 154) determine the angular position of the cathode assembly, hence the x-ray beam, and the angular position of the detectors in the rotating detector embodiment.

Computerized tomographic scanner having a toroidal x-ray tube with a

An x-ray tube (10) of a CT scanner has a rotating anode and rotor combination which is propelled by AC currents applied to run and phase windings (42, 46) by a starter (22). A monitor (24) includes Hall effect current detectors (40, 44) which detect the actual current flowing through the run and phase windings. The detected analog current values, voltage values, and the like are multiplexed (132) and digitized in a preselected order by an analog to digital converter (60) and stored in that order in a FIFO memory (62). A microprocessor (64) performs a Fourier transform (94, 96) to convert the digital run and phase signals into frequency spectra. The run and phase frequency spectra are compared (100, 102, 104, 106) with frequency spectra indicative of rotor speed, bearing wear, anode vibration, failure of the anode to rotate, and other conditions, analyzed for symmetry or other characteristics, or the like (FIG. 5 ) to generate digital run and phase reference signals. An error amplifier (54) controls a pulse width modulator ( 56) or other power amplifier controls in accordance with a deviation between analog reference signals converted from the digital signals by a reference digital to analog converter (66) and the actually sensed run and phase signals (40, 44) to adjust the starter. A direct coupled driver (122) adjusts DC offsets in the drive currents to maintain balance and drive efficiency.

High speed starter operations monitor

A plurality of medical electronic apparatae (A) including a CT scanner (B) or other medical imaging equipment are disposed at each of a plurality of remote locations. A diagnostic service system (C) monitors each CT scanner to create a malfunction history therefor. A central polling station (D) polls the diagnostic service system of each scanner to retrieve the diagnostic history thereof. The diagnostic service system includes a plurality of monitors (80, 82, 84, 86, 88) which monitor operating conditions and parameters of the scanner. The monitored operating conditions include the operating mode within the sequence of operating modes, operating parameters of an X-ray tube (12), and the operation of other scanner components. When a fault detection circuit (92) detects a malfunction, a latch array (90) immediately stores an indication of the condition monitored by the monitors. A read/write circuit (94) transfers the latched condition data to a malfunction history memory (96). Data from the malfunction history memory may be displayed on diagnostic service display (104) or transmitted by a modem (112) to the central polling station.

Diagonostic service system for CT scanners

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.

Biphase quadrature drive for an x-ray tube rotor

Between scans, a stand-by control (40) causes a filament current power supply (44) to supply a low level of power to a tube filament (46). When x-rays are to be generated, a non-linear digital to analog converter (50) supplies a filament current control signal which is estimated to provide a selected tube current. A space charge compensation circuit adds an offset to the selected filament signal to compensate for the selected voltage at which the tube is to be operated. A current boost circuit (70) adds an incremental current boost (26) of a magnitude in accordance with a function of the difference between the actual filament temperature and the normal operating temperature in order to bring the filament up to operating temperature more quickly. A feedback loop (90 to 98) adjusts the selected filament current signal in accordance with any difference between the selected tube current and the actual tube current. A damping circuit (110) reduces the rate of change of the error signal such that the filament current changes at a rate commensurate with the heating rate of the filament.

Closed loop x-ray tube current control

An x-ray tube voltage generator with automatic stabilization circuitry is disclosed. The generator includes a source of pulsating direct current voltage such as from a rectified 3 phase transformer. This pulsating voltage is supplied to the cathode and anode of an x-ray tube and forms an accelerating potential for electrons within that tube. The accelerating potential is stabilized with a feedback signal which is provided by a feedback network. The network includes an error signal generator which compares an instantaneous accelerating potential with a preferred reference accelerating potential and generates an error function. This error function is transmitted to a control tube grid which in turn causes the voltage difference between x-ray tube cathode and anode to stabilize and thereby reduce the error function. In this way stabilized accelerating potentials are realized and uniform x-ray energy distributions produced.

Constant potential H-V generator

A closed loop feedback system for controlling the current output of an x-ray tube. The system has circuitry for improving the transient response and stability of the x-ray tube current over a substantial nonlinear portion of the tube current production characteristic. The system includes a reference generator for applying adjustable step function reference signals representing desired tube currents. The system also includes means for instantaneous sensing of actual tube current. An error detector compares the value of actual and reference tube current and produces an error signal as a function of their difference. The system feedback loop includes amplification circuitry for controlling x-ray tube filament DC voltage to regulate tube current as a function of the error signal value. The system also includes compensation circuitry, between the reference generator and the amplification circuitry, to vary the loop gain of the feedback control system as a function of the reference magnitude.

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Beachwood, OH, United States of America

Theodore A Resnick