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US 4,361,902 AGranted
Collimator for x-ray diagnostic apparatus
AssigneeGeneral Electric Company
InventorsRichard T. Brandt, Robert B. Hauck
Life of this patent
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AssigneeGeneral Electric Company
InventorsRichard T. Brandt, Robert B. Hauck
Estimating the term…
A collimator assembly for defining an aperture for the passage of a diagnostic x-ray beam in an x-ray diagnostic apparatus which may, for example, be used in computer assisted tomography. The collimator assembly comprises a framework adapted to be secured to the x-ray apparatus contiguous the x-ray tube, and includes a first and a second blade subassembly lying in a common plane with each other in the path of x-rays emanating from the x-ray tube. Leaf spring means connect each of the blade subassemblies to the framework, the leaf spring means biasing the first and second blade subassemblies into abutting relation to each other whereby to define a zero aperture condition for the passage of a diagnostic x-ray beam through said collimator assembly to the patient. Cam follower means are carried by each of the respective first and second blade subassemblies, and movable cam means are mounted on the framework and engageable with the cam follower means of said first and said second blade subassemblies whereby movement of the cam means is effective to move the first and second blade subassemblies against the biasing force of the spring means to a controlled degree of opening between the first and second blade subassemblies whereby to define a collimating aperture of a predetermined size between said subassemblies for the passage of a diagnostic x-ray beam of a predetermined size to the patient. A further feature of the collimator assembly is the use of a direct acting sensing arrangement for sensing the collimating opening between the two blade subassemblies. This sensing arrangement is embodied in an electromagnetic transducer in the form of a linear variable differential transformer.
A collimator assembly for defining an elongated aperture for the passage of a diagnostic x-ray beam in an x-ray diagnostic apparatus, said assembly comprising a framework, said assembly comprising a first and a second blade subassembly mounted on said framework, each of said first and said second blade subassemblies respectively comprising a corresponding elongated aperture bounding means cooperating with and in confronting relation to the elongated aperture bounding means of the other of said blade subassemblies, said elongated aperture bounding means of said first and said second blade subassemblies lying in a common plane which is in the projected path of x-rays which the x-ray tube is adapted to emanate, spring means operatively associated with said subassemblies and with said framework, said spring means biasing said first and said second blade subassemblies to a position in which said elongated aperture bounding means of said respective subassemblies are in mutually abutting relation to define a zero aperture condition for the non-passage of a diagnostic x-ray beam through said collimator assembly to the patient, each of said blade subassemblies comprising a first and a second cam follower means at the respective opposite ends thereof, said assembly comprising a first cam means mounted on said framework and interposed between the respective first cam follower means of both of said blade subassemblies and contiguous one end of said blade subassemblies, and a second cam means mounted on said framework and interposed between the respective second cam follower means of both of said blade subassemblies and at the opposite end of said blade subassemblies, link means connecting said first and said second cam means to each other such that movement of one of said cam means is imparted to the other of said cam means, means for driving one of said cam means such that both said first and said second cam means move to cause movement of said first and said second blade subassemblies relative to each other against the biasing force of said spring means to provide a predetermined spacing between said elongated aperture bounding means of said first and said second subassemblies, and means for securing said collimator assembly to said x-ray diagnostic apparatus.
A collimator assembly for defining an elongated aperture for the passage of a diagnostic x-ray beam in an x-ray diagnostic apparatus, said assembly comprising a framework, said assembly comprising a first and a second blade subassembly mounted on said framework, each of said first and said second blade subassemblies respectively comprising a corresponding elongated aperture bounding means cooperating with and in confronting relation to the elongated aperture bounding means of the other of said blade subassemblies, said elongated aperture bounding means of said first and said second blade subassemblies lying in a common plane which is in the projected path of x-rays which the x-ray tube is adapted to emanate, spring means operatively associated with said subassemblies and with said framework, said spring means biasing said first and said second blade subassemblies to a position in which said elongated aperture bounding means of said respective subassemblies are in mutually abutting relation to define a zero aperture condition for the non-passage of a diagnostic x-ray beam through said collimator assembly to the patient, each of said blade subassemblies comprising a first and a second cam follower means at the respective opposite ends thereof, said collimator assembly comprising a first cam means mounted on said framework and interposed between the respective first cam follower means of both of said blade subassemblies and contiguous one end of said blade subassemblies, and a second cam means mounted on said framework and interposed between the respective second cam follower means of both of said blade subassemblies and at the opposite end of said blade subassemblies, link means connecting said first and said second cam means to each other such that movement of one of said cam means is imparted to the other of said cam means, means for driving one of said cam means such that both said first and said second cam means move to cause movement of said first and second blade subassemblies relative to each other against the biasing force of said spring means to provide said predetermined spacing between said subassemblies, sensing means for sensing the size of the beam-defining aperture between said elongated aperture bounding means of said first and said second blade subassemblies, said sensing means comprising an electromagnetic transducer, said electromagnetic transducer comprising a first element mounted on and movable with one of said blade subassemblies, and a second element mounted on and movable with the other of said blade subassemblies, such that movement of said two blade subassemblies relative to each other produces a corresponding movement of said first and second elements relative to each other to produce a signal which is indicative of said relative movement of said two blade subassemblies, and means for securing said collimator assembly to an x-ray diagnostic apparatus.
A collimator assembly for defining an elongated aperture for the passage of a diagnostic x-ray beam in an x-ray diagnostic apparatus, said assembly comprising a framework, said assembly comprising a first and a second blade subassembly mounted on said framework, each of said first and said second blade subassemblies respectively comprising a bladeholder and an elongated collimating blade secured to the respective bladeholder, the respective collimating blades of said first and said second blade subassemblies lying in a common plane which is in the projected path of x-rays which the x-ray tube is adapted to emanate, separate leaf spring means operatively associated with each of said subassemblies and with said framework, said separate leaf spring means biasing said first and said second blade subassemblies to a position in which the collimating blades of said respective subassemblies are in mutually abutting relation to define a zero aperture condition for the non-passage of a diagnostic x-ray beam through said collimator assembly to the patient, each of said blade subassemblies comprising first and a second cam follower means at the respective opposite ends thereof, said collimator assembly comprising a first cam means mounted on said framework and interposed between the respective first cam follower means of both of said blade subassemblies and contiguous one end of said blade subassemblies, and a second cam means mounted on said framework and interposed between the respective second cam follower means of both of said blade subassemblies and at the opposite end of said blade subassemblies, link means connecting said first and said second cam means to each other such that movement of one of said cam means is imparted to the other of said cam means, means for driving one of said cam means such that both said first and said second cam means move to cause movement of said first and second blade subassemblies relative to each other against the biasing force of spring means to provide said predetermined spacing between said subassemblies, a linear variable differential transformer sensing means for sensing the size of the beam-defining aperture between said collimating blades of said first and said second blade subassemblies, said linear variable differential transformer comprising a first element mounted on and movable with one of said blade subassemblies, and a second element mounted on and movable with the other of said blade subassemblies, such that movement of said two blade subassemblies relative to each other produces a corresponding movement of said first and second elements relative to each other to produce a signal which is indicative of said relative movement of said two blade subassemblies, and means for securing said collimator assembly to an x-ray diagnostic apparatus.
Dependencies are inferred from the claim text.
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No related US applications are recorded in the indexed filing history.
Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment: diaphragms
Using diaphragms, collimators: using variable diaphragms, shutters, choppers
Medical diagnosis and surgery
Handling of particles or ionising radiation not otherwise provided for
Term ended 7 Jul 2000 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
This invention relates to x-ray diagnostic apparatus and to a collimator for defining an aperture which directs a diagnostic beam of x-rays in a predetermined manner toward the patient's body, and more particularly to a collimator which, while not restricted thereto, has particular utility in connection with computer assisted tomography.
It has been known in the prior x-ray technology to move an x-ray tube circumferentially to successive angularly spaced points along an arc drawn from an isocenter which corresponds substantially to the center of the patient's body, transmitting a beam of x-rays toward the patient at each of the successive positions of the x-ray tube, and superimposing onto a common sheet of film a plurality of images resulting from the x-ray beams transmitted in the plurality of angularly spaced positions of the x-ray tube. The plurality of superimposed x-ray images obtained in this manner and superimposed upon each other on the same sheet of film results in a composite x-ray picture in which only one plane is in focus, namely, a plane passing through the isocenter. The technique just described is conventional x-ray tomography.
A more recent development in diagnostic x-ray technology has been the development of what is known as "computer assisted tomography." In x-ray diagnostic apparatus for use in computer assisted tomography, an x-ray tube, a collimator, a detector, and a data acquisition system are mounted for rotation as a unit interiorly of a gantry which houses the diagnostic imaging equipment. The gantry is provided with a hollow, centrally located, axially extending patient-receiving opening through which the patient may be moved linearly to predetermined desired positions relative to the x-ray apparatus. The x-ray tube and the collimator are mounted within the gantry on one side of the patient-receiving opening, and the detector and the data acquisition system are mounted within the gantry on an opposite side of the patient-receiving opening in diametrically opposed relation to the x-ray tube and collimator. The x-ray tube, collimator, and detector/data acquisition unit are all in fixed position relative to each other and define a diagnostic imaging assembly which rotates as a unit about the isocenter of the x-ray apparatus. As the diagnostic imaging assembly rotates through a single 360.degree. rotation at a predetermined constant speed, a multiplicity of x-ray views, such as 288 or 576 views, for example, are taken at a corresponding number of angular positions of the imaging assembly. This multiplicity of views defines the data which is digitized and sent to a computer where an image is reconstructed electronically.
Further objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a perspective view, partially diagrammatic, showing an x-ray diagnostic apparatus of the computed tomography type, and embodying an improved collimator assembly in accordance with the present invention;
FIG. 2 is a diagrammatic view taken transverse of the longitudinal axis of the apparatus of FIG. 1 showing the relative positions of the various components of the diagnostic imaging assembly, including the x-ray tube, the collimator, and the detector/data acquisition unit;
Referring now to the drawings and more particularly to FIGS. 1, 2, and 3, there is shown an x-ray diagnostic apparatus generally indicated at 10 of the computed tomography type. The apparatus 10 comprises a gantry generally indicated at 12 which houses diagnostic imaging equipment, including an x-ray tube 14, a collimator assembly generally indicated at 16, a detector unit 18, and a data acquisition unit 20. The gantry is provided with a centrally located, axially extending patient-receiving opening 22. X-ray tube 14 and collimator assembly 16 are mounted on one side of the patient-receiving opening 22, and detector 18 and data acquisition unit 20 are mounted on the opposite side of patient-receiving opening 22 in diametrically opposed relation to x-ray tube 14 and collimator assembly 16. X-ray tube 14, collimator assembly 16, detector unit 18, and data acquisition unit 20 are all fixed with respect to each other and together define what will be referred to as the "diagnostic imaging subassembly." Means which form no part of the present invention is provided for rotating the diagnostic imaging subassembly within the interior of gantry 12 and about the central horizontal axis X--X of gantry 12 which passes through the isocenter 24 of the apparatus. A table generally indicated at 26 is provided as part of the x-ray diagnostic apparatus 10 and provides a support for the patient. Table 26 includes a patient support portion or "cradle" 28 which is movable relative to the main portion of table 26 to permit the patient to be moved into the patient-receiving opening 22 of gantry 12 in order to be properly positioned for the diagnostic procedure.
Referring now to FIG. 4, the collimator assembly generally indicated at 16, and which defines the aperture for the diagnostic beam, comprises a framework 36 which is suitably supported interiorly of gantry 12 in such manner that collimator assembly 16 is positioned in fixed relation to x-ray tube 14, detector 18, and data acquisition system 20.
Collimator assembly 16 includes a plate 17 which extends parallel to and in substantially abutting relation to the radially outer surface of blade subassemblies 38A and 38B (relative to axis X--X of FIGS. 1-3, inclusive). Plate 17 has an elongated aperture 19 therein (FIGS. 4 and 6) through which the x-ray beams pass. The adjustably movable collimating blades 48A and 48B (to be described) which form part of collimator assembly 16 lie radially inwardly of aperture 19 (relative to axis X--X in FIGS. 1-3, inclusive), in overlying masking relation to aperture 19, with the spacing between collimating blades 48A and 48B being adjustable to control the axial thickness (relative to axis X--X in FIGS. 1-3, inclusive), of the x-ray beam which is directed toward the patient.