Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1998-02-05
2001-07-03
Smith, Ruth S. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C005S601000, C378S167000, C378S173000, C378S177000, C378S181000, C378S209000
Reexamination Certificate
active
06256528
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an X-ray scanner including a patient table having a table top for receiving a patient, first imaging means for obtaining an image of a patient placed on the table top by of computed tomography, the first imaging means comprising an X-ray source and an X-ray detector, which are driven together by a rotational driving mechanism and are mounted so as to be rotatable about an axis of rotation which is substantially parallel to the longitudinal direction of the table top and extends through an examination space, and second imaging means for obtaining an image of the patient on the table top by radiography, the second imaging means including detection means sensitive to X-rays.
2. Description of Related Art
An X-ray scanner of this type is known from the English-language abstract of JP-A-6-47040. The known device comprises a table top that is slidable on a table support. The table top comprises a first portion for cooperation with the first imaging means and a second portion for cooperation with the second imaging means. The second imaging means comprise a second X-ray source located at some distance from the first imaging means and a cassette for receiving a material that is sensitive to X-rays that is located in the table support, opposite the second X-ray source. In order to obtain images of a given part of a patient by means of CT and by means of conventional radiography, the patient has to be moved in the longitudinal direction of the table top so that the said part is first located on the first portion of the table top and then on the second portion. This moving is inconvenient and sometimes even dangerous, e.g. for patients in trauma. Moreover, the table top must be very long in order to enable the movement of the patient over a distance sufficient to image each part of the patient by means of CT and radiography.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an X-ray scanner of the kind set forth in which it is possible to obtain images by means of CT and conventional radiography without moving the patient relative to the table top. The X-ray scanner according to the invention is characterized in that the table top comprises a chamber for receiving the detection means, said chamber having a length that is substantially equal to the length of the table top.
It should be noted that the detection means can be designed in several forms which are well known per se. The detection means may be implemented as a digital detector having as many X-ray sensitive detection elements as there are image pixels to be stored. Such a digital detector is known, for example from the U.S. Pat. Nos. 5,132,541 or 5,276,329. The detection means may also be implemented as a conventional cassette for receiving a sheet that is sensitive to X-rays. Wherever the term “cassette” is used hereinafter, it should be understood to mean also a digital detector as indicated above.
For conventional radiography, the cassette or the digital detector can be placed inside the chamber at the location of the portion of the patient that has to be imaged and for CT the cassette or the digital detector can be removed from this location so that the table top is transparent to X-rays again as required for the proper operation of the first imaging means. As a result, it is only the cassette or the digital detector and not the patient that has to be moved.
It is possible to slide the cassette or the digital detector into and out of the chamber by hand. However, operation of the X-ray scanner is more convenient in an embodiment that is characterized in that the chamber contains a trolley for carrying the detection means, driving means being provided for moving said trolley in the longitudinal direction of the table top over substantially the full length of the chamber.
The driving means may comprise any known device, for example a belt drive as disclosed in DE-C-42 10 423, but a preferred embodiment is characterized in that the driving means comprise a telescopic tube extending parallel to the longitudinal direction of the table top and hydraulic means for varying the length of the telescopic tube. Such a device is simple to operate and it occupies very little space when the telescopic tube has its shortest length, i.e. when the trolley is at a position near the end of the table top where the cassette or the digital detector can be removed from the table top.
For some examinations it is sufficient to obtain a single image by means of conventional radiography. However, for other examinations it may be desirable to make a series of images. In that case, when using a cassette for receiving a sheet comprising a material that is sensitive to X-rays as a detection means, the cassette can be moved to the end of the table top after each exposure so as to replace the exposed sheet (which is e.g. a photographic film or a selenium plate) by a fresh one. This is rather inefficient and a much simpler procedure is made possible by a further embodiment of the device in accordance with the invention, which is characterized in that # the cassette comprises a sheet dispenser and a sheet holder, the sheet dispenser comprising at least a first compartment for receiving unexposed sheets and a second compartment for receiving exposed sheets, the cassette further comprising transport means for transporting unexposed sheets from the first compartment to the sheet holder and for transporting exposed sheets from the sheet holder to the second compartment. In this embodiment the sheets can be exchanged while the cassette remains in the position for making radiographic images.
In some cases it may be desirable to obtain radiographic images of the whole body (or a substantial portion of the body) of a patient. An embodiment which makes this possible is characterized in that the detection means has a length that is substantially equal to the length of the chamber, the X-ray source being shared by the first imaging means and the second imaging means. This embodiment has the further advantage that a second X-ray source for radiography can be dispensed with so that the device is less expensive and smaller.
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patent: 4942597 (1990-07-01), Van Acker et al.
patent: 5132541 (1992-07-01), Conrads et al.
patent: 5185777 (1993-02-01), Hasegawa
patent: 5276329 (1994-01-01), Hughes
patent: 5365565 (1994-11-01), Barbaric
patent: 5490508 (1996-02-01), Kato
patent: 5751781 (1998-05-01), Brown et al.
patent: 4210423C1 (1993-04-01), None
patent: 647040A (1994-02-01), None
Op de Beek Johannes C. A.
Zonneveld Frans W.
Smith Ruth S.
U.S. Philips Corporation
Vodopia John F.
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