X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
1999-06-25
2001-12-04
Church, Craig E. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S020000
Reexamination Certificate
active
06327328
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to computerized tomography systems and more particularly, to a computerized tomography system and method which can suitably take a tomographic image in a transversal plane of an object to be inspected with use of X ray.
A computerized tomography system (X-ray computed tomography (CT) system or X ray CT system) using X ray, which takes a tomographic image in a transversal plane of an object to be inspected, includes an X ray source for emitting an X ray, a detection device for detecting the X ray and a computer for creating a tomographic image. In particular, the detection device comprises, in many cases, an array detection device made up of a multiplicity of X ray detectors arrayed in a row. The X ray detectors of the array detection device are arranged to detect the X ray emitted from the single X ray source. In such an X ray CT system, especially employing a tomography called a third generation system, in order to increase the spatial resolution of a tomographic image, it is necessary to narrow an array interval or pitch between the X ray detectors of the array detection device.
However, the array detection device has its limitation on making narrow the array pitch between the X ray detectors of the array detection device, because the X ray detectors have a limited size. For example, when each X ray detector has a transverse width of 1 mm, it is impossible to make the pitch between the X ray detectors of the array detection device to be 1 mm or smaller. Accordingly, there has been demanded such a tomography system which can increase the spatial resolution of a tomographic image while eliminating the need for narrowing the array pitch between the X ray detectors of the array detection device.
In such an X ray CT system disclosed in JP-A-62-116238, a relative positional relationship between an X ray source and an array detection device is made variable in a range of interval or pitch between X ray detectors of the array detection device, thus enabling increase of a spatial resolution of an tomographic image while eliminating the need for physically narrowing the array pitch of the X ray detectors.
In the case of an X ray CT system wherein a collimator having slits for passage of an X ray is provided in front of the X ray detectors of the array detection device (on a side of an X ray source), however, it is impossible to employ such a technique as disclosed in the above JP-A. This is because the slits provided in front of the X ray detectors are positioned to face the single X ray source, so that a shift in the relative positional relationship between the X ray source and X ray detectors causes the X ray not to be directed on the X ray detectors.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a computerized tomography system which can realize an increase in the spatial resolution of a tomographic image.
In accordance with a first aspect of the present invention, the above object is attained by providing a computerized tomography system which includes a radiation source for emitting a radiation onto an object to be inspected, a rotary table for carrying the object to be inspected thereon to rotate the object to be inspected, a collimator having a plurality of through-holes for passage of the radiation passed through the object to be inspected, a plurality of radiation detectors disposed as opposed to the associated through-holes for detecting the radiation passed through the through-holes, a unit for setting the rotary center of the rotary table at positions different for every one rotation of the object to be inspected, and a unit for reconstructing a tomographic image in one transversal plane on the basis of detection signals of the plurality of radiation detectors obtained by irradiating the radiation on the object to be inspected while rotating the object to be inspected.
In the first aspect, a plurality of rotary center positions of the rotary table are set for one transversal plane of the object to be inspected, and the unit for reconstructing the tomographic image for one transversal plane of the object to be inspected is provided with use of the detection signals of the radiation detectors obtained by rotating the rotary table with the respective rotary center positions. Therefore, for the reconstruction of the tomographic image for one transversal plane of the object to be inspected, the detection signals of the radiation detectors detected with the interval substantially narrower than the array pitch of the radiation detectors can be used. This can lead to an improvement in the spatial resolution of the tomographic image.
In accordance with a second aspect of the present invention, the above object is attained by a computerized tomography system which includes a pivoting truck, a radiation source provided to said pivoting truck for emitting radiation toward an object to be inspected, a table disposed inside of the pivoting truck for mounting the object to be inspected thereon, a collimator having a plurality of through-holes for passage of the radiation passed through the object to be inspected and provided to the pivoting truck, a plurality of radiation detectors disposed to the pivoting truck as opposed to the through-holes for detecting the radiation passed through the through-holes, a unit for setting the radiation source and radiation detectors at different positions in an array direction of the radiation detectors for each turn according to the number of turns of the pivoting truck which is necessary for obtaining a tomographic image of a transversal plane of the object to be inspected, and a unit for reconstructing a tomographic image of the transversal plane by using digital signals of the plurality of radiation detectors obtained by irradiating the radiation on the object to be inspected during rotation of the pivoting truck for a plurality of set positions of the radiation source and radiation detectors.
Even in this case, for the reconstruction of the tomographic image for one transversal plane of the object to be inspected, the detection signals of the radiation detectors detected with the interval substantially narrower than the array pitch of the radiation detectors can be used. Thus this can lead to an improvement in the spatial resolution of the tomographic image.
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Izumi Shigeru
Satoh Katsutoshi
Antonelli Terry Stout & Kraus LLP
Church Craig E.
Hitachi , Ltd.
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