JPH03209120A - X-ray ct apparatus - Google Patents

Abstract

PURPOSE:To enhance a space resolving power by collecting the X-ray transmission data on a specimen by 2n+1 time (n=1, 2,...) by the translational movement of a specimen moving means to prescribed distances and the rotation at prescribed angles thereof. CONSTITUTION:An X-ray generator 1, the specimen A and an X-ray detector 3 are respectively disposed in such positional relations that a X-ray spot light source, the center of rotation of the specimen A and the detecting center of the detector 3 exist respectively on the same straight line. The X-ray beam transmitted through the specimen A is, therefore, macroprojected in the position of the detector 3 at the magnification corresponding to the distance between the generator 1 and the specimen A and the distance between the generator 1 and the detector 3. Moving stages 2, 5 are constituted movable along a straight line (X-axis). The stage 2 is translated and the data is connected 2n+1(n=1, 2,...) times by combining the translational motion and the angular rotation, by which the data for one scanning covering the entire range of the specimen A of an arbitrary size is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an X*CT apparatus that is mainly used for industrial purposes and is suitable for nondestructively inspecting the inside of a microstructure.

[Conventional technology]

The medical XiJCT device is now widely used because of its excellent feature of being able to observe internal tissues of a living body from the outside. In addition, industrial X@CT equipment is made of metal,
Since it is also possible to non-destructively inspect minute defects inside ceramics, composite materials, etc., it has been increasingly used in recent years to evaluate the quality of materials. For medical X-ray CT equipment, the required spatial resolution is at most several hundred micrometers, but for industrial CT equipment, the spatial resolution is an order of magnitude higher than this (several tens of micrometers). is required.

As a method of increasing the spatial resolution of the XWICT device, there is a method of increasing the number of individual x-ray detection elements constituting the X-ray detector and reducing their dimensions, thereby increasing the number of samplings, and a method of increasing the number of samplings, and adding a point light source to the X'lAB. There is a method of relatively improving the resolution of the X#llA detector by enlarging and projecting the object onto the x&I detector using something close to .

[Problem to be solved by the invention]

However, the former method has a problem in that the detection circuit becomes complicated as the number of X-ray detection elements increases, and the costs of the X-ray detector and the detection circuit increase. Also, in the latter method,
When the size of the object to be examined is large or to increase the magnification
When bringing a subject close to a radiation source, the range through which the X-ray beam passes through the subject is geometrically limited, and it may not be possible to obtain transmission data for the entire range of the subject. In this case, only a partial OCT image of the object can be obtained, but an entire OCT image of the object cannot be obtained.

Furthermore, if the distance between the X-ray source and the X-ray detector is increased, the projection magnification increases, but there is a problem in that the efficiency of using X-rays decreases.

The present invention has been made based on the above circumstances, and can be achieved without increasing the number of detection elements of the X-ray detector or changing the distance between the X'4lA source and the subject or the X-ray detector. It is an object of the present invention to provide an X-ray imaging device that can increase the number of samplings of transmission data and improve the magnification of a projected image.

[Means to solve the problem]

In order to achieve the above object, an X-ray CT apparatus according to the present invention irradiates a fan-shaped XvA beam from an X-ray generator toward a subject, and has an X-ray CT system in which a large number of X-ray detection elements are arranged one-dimensionally. x′4lAi3 for reconsidering the CT image by detecting the X-rays after passing through the object with a ray detector
in an X-ray CT apparatus that obtains excessive data, disposed between the X-ray generator and the X-ray detector,
The X-ray generator is rotatable in a plane parallel to a plane containing the Xwa source and the X-ray detection element, and the
A subject moving means capable of translational movement by an arbitrary distance in parallel to the arrangement direction of the radiation detection elements is provided, and by translationally moving a predetermined distance and rotating a predetermined angle of the subject moving means, the X-rays are detected with respect to the subject. XwAi3 passing data with the beam partially transmitted 2n+1 times (n=
1.2, ...) by collecting X & 91i! over the entire range of the cross section of the object to be transversely This method is characterized by obtaining excessive data.

[Effect]

an operation of moving the subject by a distance determined by the distance between the rotation center of the subject and the XvA generator and the irradiation angle of the X-ray beam in the arrangement direction of the X-ray detection elements by the subject moving means; By combining this with the rotating motion of the subject, when the X-ray beam is partially transmitted through the subject, it is possible to prevent the portions of the X-ray beam that pass through the subject from being overlapped.

With this procedure, you can get X for one scan! By obtaining i3 transmission data by collecting X-ray transmission data multiple times, accurate X-rays can be obtained over the entire cross-sectional area of the object without overlapping the area where the fan-shaped X-ray beam passes through the object. Transmission data is obtained.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of an X-ray CT apparatus according to an embodiment of the present invention. The device consists of an X-ray generator 1 that emits a fan-shaped X-ray beam from a point light source, a moving stage 2 that holds and moves the subject A, and an X&I detector that has a number of X&I detection elements arranged one-dimensionally. 3. A collimating plate 4 having a gap parallel to the CT tomographic plane and defining the slice width of the subject; a moving stage 5 on which the X-ray detector 3 and the collimating plate 4 are placed.

The X-ray generator 1, the object A, and the
It is also the center of rotation. ), and the detection center of the X-ray detector 3 are arranged in a positional relationship such that they are on the same straight line.

Therefore, the X-ray beam transmitted through the subject A is determined by the distance between the X-ray generator 1 and the subject A, and the
The image is enlarged and projected onto the X-ray detector 3 at a magnification corresponding to the distance from the ray detector 3 . Furthermore, the moving stages 2 and 5 are movable along the above-mentioned vertical axis vA (this is taken as the X-axis). Therefore, the magnification of the enlarged and projected X-ray beam is It can be changed by moving.

Further, the moving stage 2 is rotated at an arbitrary angle and moved in a direction (this is referred to as the Y-axis direction) approximately parallel to the arrangement direction of the X-ray detection elements (hereinafter referred to as translation).
is also considered possible.

Next, the geometrical relationship between the fan-shaped X-ray beam and the cross section of the subject in the above apparatus, the operation of the moving stage 2, etc. will be explained. Figures 2 to 5 show an X-ray beam 1 emitted from an X-ray generator 1 and detected by an X-ray detector 3.
1 is a diagram showing the relationship between 0 and the cross section of the subject A, and corresponds to the arrangement shown in FIG. 1 viewed from above. In these figures, the center of rotation of the subject 6 in its initial state is the origin, and the trajectory of the translation operation of this center of rotation is the Y-axis. Also, the position of the X-ray source was changed to F. Both ends of the X-ray detector 3 are A I and A, and the point where the edge of the X-ray beam 10 intersects with the Y axis is 81
and Bz, and the points where the periphery of the subject A intersects with the Y axis are C and C2.

In the case shown in FIG. 2, the subject A cannot fully enter the X-ray beam 10, so the entire subject A cannot be covered by collecting transmission data only once. Of course, if the subject A is moved to the left side of the figure until the entire subject A enters the X-ray beam 10, the entire range of the subject can be covered in one data collection, but in this case the projection magnification will be reduced. and the spatial resolution decreases. In addition, simply collecting data multiple times by simply moving parallel
The areas exposed to X-rays overlap, making it impossible to accumulate accurate data. First, the moving stage 2 is translated to move the center of the subject 8 to 01 on the Y axis as shown in FIG. This 01 is parallel to the X axis and the straight line passing through this point is the straight line FA! When the point where it intersects is D1, 10+D+l
Does it satisfy =lOFl? It is located at At this time l OB. t
> l QC,l, so if the X-ray transmission data is collected at this position, the enlarged and projected X-ray transmission data of the area e in the cross-sectional view of the subject A shown in Fig. 6 will be obtained. .

Next, translate the moving stage 2 again and move to the fourth stage.
As shown in the figure, the center position of the subject A is moved to point 02. This 02 is located at a position that satisfies the relationship tool l=l○O. Therefore, if we use point 02 and let D be the point where a straight line parallel to the X-axis intersects straight line FA, the relationship 0■Dz -l0+D+ l=l○F holds true. When the X-ray transmission data is collected at this position, the enlarged and projected X-ray transmission data of the area f in FIG. 6 is obtained.

Subsequently, as shown in FIG. 5, the moving stage 2 is translated so that the center of the subject A coincides with the origin again, and the moving stage 2 is further rotated by an angle π. When collecting X-ray transmission data at this position, area g in Figure 6
Enlarged and projected X-ray transmission data of the portion is obtained.

By collecting the X-ray transmission data in the manner described above, it is possible to cover the entire range of the cross section of the subject A, and the regions where the respective X-ray transmission data are collected do not overlap with each other. That is, 3 translation operations and 3
By collecting XMA transmission data twice, XvA transmission data for one scan can be obtained. The series of X&Ii3 data thus obtained is stored in a control computer (not shown) as data for one scan.

Therefore, in order to obtain a subject OCT image, a scanning operation similar to that described above is performed over a predetermined angular range of the subject A. In addition, in this example, the number of actual X-ray detection elements is 3.
The same number of data samplings as in the case where xl transmission data is collected using an X-ray detector consisting of twice the number of X-ray detection elements can be obtained.

If the object to be examined is larger than that shown in FIG. 2, as shown in FIG. 7, the entire object cannot be covered even if X-ray transmission data is collected three times. In this case, for example, first, the center of the subject at J in FIG. 8 is translated to the position 02 as in FIG. 4, and XvA transmission data is collected.

From this point onwards, data collection is performed for area i in FIG. Then, by translating the four centers of the subject to symmetrical positions about the
Data collection is performed in area j in Figure 0. Next, the moving stage is rotated by an angle π, and the center of the subject is translated to the 0.
2100z l=loOi 1) Collect X-ray transmission data. As a result, data collection for area k in FIG. 10 is performed. Furthermore, data can be collected for areas m and n in FIG. 10 by performing a suitable combination of rotation by an angle π and translation.

The entire range of the object can be covered by collecting X-ray transmission data three times in the case of Figure 6 and five times in the case of Figure 10, but if this is generalized, the translation Combining motion and rotation of angle π, 2n+I
By collecting data (n=1.2, . . . ) times, it is possible to obtain data for one scan covering the entire range of a subject of arbitrary size. The basic distance of this translation is the distance corresponding to l 00 II I 00z l, and as is clear from the above explanation, this distance is the distance between the rotation center of the subject and the X-ray source, and the distance between the fan-shaped It is determined by the irradiation angle of the line beam. In the examples so far, we have considered only the case where the cross section of the object is a circle, but if we consider the object to have a cross section of a circle whose radius is the maximum distance from the center of the object, it can be any shape. A CT image of the entire cross section of the subject can be obtained in the same manner as described above.

〔Effect of the invention〕

As explained above, according to the present invention, even for a large object in which the fan-shaped X-ray beam cannot penetrate the entire range of the object's cross section, Since X-ray transmission data can be collected without overlapping transmission areas, it is possible to move the X-ray detector away from the X-ray generator to reduce the efficiency of X-ray utilization, or It is possible to increase the spatial resolution without increasing the cost of the X-ray detection circuit by increasing the number of X-ray detection elements, and furthermore, it is possible to obtain a larger number of data samples than the actual number of X-ray detection elements. 4lJ.CT
equipment can be provided.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an X-ray CT apparatus according to an embodiment of the present invention, and Figs. 2 to 5 show an X-ray beam irradiated from the XvA generator and detected by an Figure 6 shows the area of the subject where X-ray transmission data is collected by the operations shown in Figures 2 to 5, and Figures 7 to 9 show the relationship with the cross section. A diagram showing the relationship between the X-ray beam irradiated from the device and detected by the X-ray detector and a cross section of a different object than the above. FIG. 2 is a diagram illustrating a region of a subject where collection of images is performed. 1... X-ray generator, 2.5.・．． Moving stage, 3
... X4i! Detector, 4... Collimating plate, 10... X-ray beam.

Claims (1)

[Claims] A fan-shaped X-ray beam is irradiated from an X-ray generator toward a subject, and an X-ray detector in which a large number of X-ray detection elements are arranged one-dimensionally detects the In an X-ray CT apparatus that obtains X-ray transmission data for reconstructing a CT image by detecting rays, the X-ray CT apparatus is arranged between the X-ray generator and the X-ray detector,
It is rotatable in a plane parallel to a plane containing the X-ray source of the X-ray generator and the X-ray detection element, and can be translated by an arbitrary distance parallel to the arrangement direction of the X-ray detection element. A subject moving means is provided, and the subject moving means is translated by a predetermined distance and rotated by a predetermined angle to transmit X-ray transmission data of the subject through which the X-ray beam is partially transmitted 2_n+1 times (n =1
, 2, ...) to obtain X-ray transmission data covering the entire range of the cross section of the subject.