X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
1999-01-22
2001-03-06
Bruce, David V. (Department: 2876)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S092000, C378S004000
Reexamination Certificate
active
06198790
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an X-ray diagnostic apparatus with a computed tomography device of the type having an X-ray tube, which is fastened to a gantry ring and which emits a fan-shaped effective beam, and an opposed radiation receiver, which consists of a row of single detectors, each of which forms an electrical signal corresponding to the received radiation intensity.
2. Description of the Prior Art
German Utility Model 295 21 308 discloses an X-ray examination system with a computed tomography device and other receiving devices relevant to X-ray technology in which components of the system can be used jointly in connection with the computed tomography device and the other receiving devices.
In a computed tomography device of this type, an image of the irradiated slice of the examination subject is reconstructed from the output signals of the individual detectors obtained at various irradiation directions. Digital radiographs can also be generated in a shadow-image mode by the additionally provided X-ray device. To do this, however, the gantry of the computed tomography device must be pushed to the side so that the image pick-up by the additional X-ray device can proceed undisturbed.
U.S. Pat. No. 5,293,416 describes a computed tomography device with a curved CT detector in which an additional, stationary detector array for the creation of X-ray shadow images is provided. This additional detector array is arranged perpendicularly to the plane formed by the curved CT detector, i.e., it is arranged in the direction of the axis of rotation of the X-ray tube. A diaphragm which directs a fan-shaped X-ray onto the detector array for every position of the X-ray tube is provided in the beam path. CT exposures and X-ray shadow images can not occur simultaneously in this apparatus either, since at least the diaphragm must be pushed into the beam path of the X-ray tube.
U.S. Pat. No. 5,604,778 teaches a computed tomography device for spiral scanning which has a number of X-ray tubes, which are attached to the gantry ring, and a stationary annular CT detector row, or a number of CT detector rows which are fastened to the gantry ring, so that an improved and faster spiral scanning can occur. X-ray shadow images can not be produced with this apparatus.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a computed tomography apparatus of the abovementioned type wherein X-ray images can be easily created together with CT slice exposures.
This object is achieved in an X-ray diagnostic apparatus according to the invention wherein a second X-ray tube is fastened to the gantry ring, opposite which a matrix-shaped X-ray detector is arranged at the gantry ring, the second X-ray tube being activated in specific positions in a pulse-like fashion. It is thus possible that low-power X-ray exposures can be created simultaneously with the acquisition of the measurement values for the production of the slice exposures.
It has proven advantageous to fasten the second X-ray tube to the gantry ring at a right angle to the first X-ray tube.
In order to register topograms, the second X-ray tube is activated when it is a uppermost point (top dead center) during a rotation of the gantry ring.
Biplanar exposures can be created when the second X-ray tube is activated, in pulse-like fashion, not only at the uppermost point, but also at a point which is rotationally shifted 90° relative to top dead center.
Image pairs can be inventively picked up in an X-ray stereo made wherein the second X-ray tube is activated in pulse-like fashion at a specific angle of rotation before the uppermost point and at the same angle of rotation after the uppermost point. This angle of rotation can be 30°, for example.
A phase shifter can be connected upstream to the high-voltage generator for the second X-ray tube, this phase shifter being constructed to shift the activation point of the second X-ray tube with respect to the uppermost point.
A precise triggering of the X-ray pulse is accomplished in an embodiment wherein a position detector is allocated to the gantry ring, this position detector being connected to a control unit which effects the pulsed activation of the high-voltage generator for the second X-ray tube.
REFERENCES:
patent: 5068882 (1991-11-01), Eberhard
patent: 5293416 (1994-03-01), Pfeiler
patent: 5485494 (1996-01-01), Williams et al.
patent: 5604778 (1997-02-01), Polacin et al.
patent: 5966422 (1999-10-01), Dafni et al.
patent: 295 21 308 U (1997-02-01), None
Bruce David V.
Hobden Pamela R.
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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