X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
1998-12-02
2001-04-03
Bruce, David V. (Department: 2876)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S004000, C378S017000, C378S195000
Reexamination Certificate
active
06212251
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a helical-scanning type of X-ray CT apparatus which scans an object to be scanned in a helical manner and, more particularly, to a helical-scanning type of X-ray CT apparatus which carries out the helical scanning for the object to be scanned by means of a movable gantry, without moving the object to be scanned.
2. Description of the Related Art
In the conventional helical-scanning type of CT apparatus, a table top of a patient couch mounting the object to be scanned thereon is continuously moved at a regular speed in a X-ray CT gantry dome including, for example, a X-ray tube and a detector both rotating continuously, so that a helical movement of a scanning section relative to the object to be scanned can be accomplished.
Recently, with the broad field of medical treatments with the application of the X-ray CT apparatus, there are demands for executing the X-ray CT scanning during a surgical operation for brain and inspecting while taking an angiography unit and the X-ray CT apparatus together in the interventional radiology (IVR) technique where a puncturing, an exploratory excision and a catheter handling are carried out with reference to the radiographic image of the object to be scanned.
However, it should be noted that there is raised the following problem in the application of the conventional X-ray CT apparatus to the field of medical treatment.
For example, in case of executing such an X-ray CT scanning during the brain surgical operation, it should be recognized a patient couch mounting the patient thereon is a table for surgical operation. It is general that the table for surgical operation is required to have a function of allowing the patient to be fixed into a desirable posture for the operation.
For example, in the brain surgical operation, the table is required to have a function of maintaining the patient's semi-sitting posture (i.e. Fowler position) where the only upper body of the patient is raised by 40 to 50 cm. Therefore, it is difficult in technique to allow the table for operation to have a function of feeding a tabletop for helical scanning.
Note, although there has been provided a patient couch which is commonly usable for the angiography unit and X-ray CT apparatus in the interventional radiology (IVR) technique, the patient couch has a problem of making a free manipulation for a tabletop heavier since the angiography unit is required to have a function of allowing the tabletop to be moved back, forth, right and left freely, while the X-ray CT apparatus is required to have a function of feeding the tabletop precisely for the helical scanning,
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a helical-scanning type of X-ray CT apparatus which is capable of scanning the object to be scanned without moving the object.
Another object of the present invention is to provide a helical-scanning type of X-ray CT apparatus which is capable of scanning the object mounted on a tabletop or a surgical table etc. each of which has no function of feeding the tabletop.
To achieve the objects described above, there is provided a helical-scanning type of X-ray CT apparatus comprising:
a CT gantry having an X-ray source for irradiating an X-ray while rotating about an object to be scanned and an X-ray detector for detecting the X-ray penetrating through the object to be scanned;
a moving unit for continuously moving the CT gantry with respect to the object to be scanned; and
a detector for detecting a moving distance of the CT gantry.
According to the invention, the helical scanning for the object to be scanned can be accomplished by moving the CT gantry in succession while rotating the X-ray source about the object to be scanned.
In the above-mentioned constitution, preferably, the moving unit comprises a dolly which mounts the CT gantry thereon and is capable of moving in a horizontal direction, while a rotating plane of the X-ray source is generally vertical. In this case, the helical scanning operation of the X-ray CT apparatus is carried out by combining a translation (horizontal movement) of the dolly with the rotation of the X-ray source.
Alternatively, it is also preferable that the moving unit comprises
a dolly which is movable together with the CT gantry and a sliding table which mounts the CT gantry thereon and is capable of moving continuously with respect to the dolly. In this case, the helical scanning operation of the X-ray CT apparatus is carried out by combining the continuous movement of the sliding table with the rotation of the X-ray source.
In the above-mentioned present invention, preferably, the moving unit comprises:
a first driving unit for positioning the CT gantry in a rough-and-ready manner;
a second driving unit for moving the CT gantry strictly for helical-scanning; and
a switching unit which switches the operations of the first and second driving units so that either one of the first and second driving units does operate solely.
With the above-mentioned arrangement, it is possible to rapidly bring the X-ray CT apparatus near the object to be scanned by the first driving unit and precisely move the CT gantry for helical scanning by the second driving unit.
Alternatively, for the same purpose, the moving unit may comprise:
a single drive motor; and
a changing unit which is capable of changing a rotating speed of the single drive motor by changing any one of voltages, currents, frequency, pulse frequency all supplied for the single drive motor and motor windings to which power is applied.
In the X-ray CT apparatus, more preferably, the dolly is provided with at least one safety switch for detecting that the dolly comes into contact with an external object which is not a constituent of the X-ray CT apparatus.
In this case, owing to the provision of the safety switch, it is expected to prevent the dolly and the external object from being damaged seriously.
Similarly, it is also preferable that the CT gantry is provided, on a front side thereof close to the object to be scanned, with at least one safety switch for detecting that the CT gantry comes into contact with an external object which is not a constituent of the X-ray CT apparatus.
Also in this case, owing to the provision of the safety switch, it is expected to prevent the CT gantry and the external object from being damaged seriously.
Similarly, it is also preferable that the CT gantry is provided, on an inner wall defining a radiographic port thereof, with a safety switch which can detect that the CT gantry comes into contact with the object to be scanned.
In such a case, owing to the provision of the safety switch, it is expected to prevent the object to be scanned from taking contact with the CT gantry intensely.
In the above arrangement, more preferably, the safety switch is in form of a mat switch of which sensitive part includes material for cushioning the object to be scanned against a contact thereof with the CT gantry.
In this case, it is possible to soften the shock of the object to be scanned and the external object with the CT gantry furthermore.
Alternatively, in place of the above safety switches, the moving unit may includes a control unit which controls the dolly in such a manner that once the positioning of the dolly prior to the helical scanning is completed, thereafter the dolly can be only traveled in one direction receding from the object to be scanned. In this case, since the dolly after being positioned does not approach the object any more, it is possible to exclude the possibility of contact of the dolly with the object.
These and other objects and features of the present invention will become more fully apparent from the following description and appended claims taken in conjunction with the accompany drawing.
REFERENCES:
patent: 5448607 (1995-09-01), McKenna
patent: 5740222 (1998-04-01), Fujita et al.
patent: 5748696 (1998-05-01), Fujita et al.
Phillips Catalog, Tomoscan M, CT System, 10 pages.
Kodaira Yasuo
Seki Yasuhiro
Tomura Masatoshi
Watanabe Naofumi
Bruce David V.
Felten Daniel S
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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