General Electric Company

Herbert E Daniels

Harold E Stehman

Norbert Joseph Pelc

Thomas W Lambert

Paul C Schanen

Paul M Stivender

Brian P Moran

Harvey G Randall

Robert V King

Vern R Petersen

Frank Bernstein

A power supply is switchable to apply a low kilovoltage and a relatively higher kilovoltage alternately to the anode of an X-ray tube that includes a filament and a control grid. A grid bias voltage generator uses an inverter driven in the kilohertz frequency range to feed the primary winding of a first transformer whose parasitic capacitance and inductance are used to produce a peak ac output voltage from the secondary of the first transformer at resonant frequency. The secondary output voltage is rectified and the resulting negative bias voltage is applied to the control grid synchronously with the high kilovoltage being applied to the anode so the X-ray tube current is then relatively low. A less negative or zero bias voltage is applied to the grid synchronously with the lower kilovoltage being applied to the anode so the X-ray tube current is then relatively high and substantially limited by the temperature and emissivity of the filament. A second transformer identical to the first one is used to sense the ac output voltage of the first one. A voltage-to-frequency converter switches the inverter. The resonant circuit ac output voltage sensed by the second transformer is rectified and compared with a selectable dc control signal and any resulting error signal is used to adjust the converter frequency and, hence, the inverter frequency so the bias on the X-ray tube grid voltage is proportional to the dc control signal level.

X-Ray tube bias supply

X-ray pulses at two different photon energy levels are produced with an x-ray tube that has an adjustable resistor element in a circuit that connects the anode and filament of the tube to a high voltage supply. Two bias voltage supplies are connected in additive fashion between a control grid element of the tube and its filament to enable control of voltage drop and current through the tube. Switch means are provided to selectively shunt either or both bias voltage supplies in a repeatable order to thereby alter the bias voltage on the control grid and enable producing x-ray pulses having energies corresponding with the voltage drop and current through the tube at a selected bias voltage in accordance with the load line on the anode characteristic curve plot of the tube as determined by the value of the adjustable resistor element.

Multiple voltage x-ray switching system

A system for supplying a selected voltage between the anode and cathode of an x-ray tube independent of power source voltage variations couples the x-ray tube power supply to the source with a transformer whose output voltages are selectable with tap switches. Prevailing source voltage and selected applied voltage are sensed and represented by analog signals which are converted to binary digital codes that form addresses for a read-only memory. The read-only memory is programmed with data representative of the pattern in which the tap switches should be set for the transformer to supply the selected voltage at the prevailing source voltage. When addressed by combinations of code words representative of the selected and source voltages, the memory outputs a code word that is used to set the switches in the corresponding pattern.

X-ray tube anode voltage compensator

An adjustable focus x-ray tube has its cathode connected to the negative side of a dc power supply which is below ground by half of the total voltage applied to the tube and its anode connected to the positive side of the supply which is above ground by half of the applied voltage. A voltage divider is connected between the negative side or cathode and ground and an intermediate point on the divider is connected to a focusing electrode in the x-ray tube for providing a focusing bias voltage. Since the bias voltage is derived from the cathode-to-ground voltage it will always track or remain proportional to the cathode voltage so the effect of variations in the latter on focusing will be negated.

X-Ray tube grid bias supply

An x-ray tube mA regulator has an SCR phase shift voltage regulator supplying the primary winding of a transformer whose secondary is coupled to the x-ray tube filament. Prior to initiation of an x-ray exposure, the filament is preheated to a temperature corresponding substantially to the electron emissivity needed for obtaining the desired tube mA during an exposure. During the preexposure interval, the phase shift regulator is controlled by a signal corresponding to the sum of signals representative of the voltage applied to the filament transformer, the desired filament voltage and the space charge compensation needed for the selected x-ray tube anode to cathode voltage. When an exposure is initiated, control of the voltage regulator is switched to a circuit that responds to the tube current by controlling the amount of phase shift and, hence, the voltage supplied to the transformer. Transformer leakage current compensation is provided during the exposure interval with a circuit that includes an element whose impedance is varied in accordance with the anode-to-cathode voltage setting so the element drains off tube current as required to cancel the effect of leakage current variations.

Electron emission regulator for an x-ray tube filament

A control console has a small and compact array of twenty-seven illuminable push buttons arranged in three continuous groups of nine each. The buttons in the upper group relate to anatomical areas in upper parts of the body, and the buttons in the lower group relate to areas in the lower parts of the body and the extremities. The middle group are control and x-ray technic variation buttons. Different anatomical regions are indicated by pictographs on the push buttons in an organized array in the upper and lower groups. Pressing at least one push button in the middle group and one in the other groups sets up and displays the x-ray exposure parameters corresponding with the equivalent of the user's priority technic, including safe patient exposure and safe x-ray tube operating time, which has been stored in a memory, for the particular anatomical region. The programmed values for tube kV, mA, mAs and time are displayed. Controls are provided for enabling the user to dominate the programmed settings by overriding the stored values when professional judgement indicates. The principal stored technic data values may be altered easily when and if experience with stored values shows need for override within the normal range of patients of one or more of the principal technic parameters to accommodate an abnormal patient or medical condition.

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Brown Deer, WI, United States of America

Herbert E Daniels