JPH0678913A - Ct scanner - Google Patents

Abstract

PURPOSE:To provide a CT scanner which can obtain a correct tomographic image without a false image even if the characteristic of a detecting element varies. CONSTITUTION:A CT scanner comprises a multi-channel radiation detector 2 to which an extra detecting element capable of detecting radiation in an angle range wider than a fan angle theta is added, a radiation detector oscillating mechanism 4 for oscillating the multi-channel radiation detector 2 in the circumferential direction, and a data collecting processor 7 for processing the output data of the multi-channel radiation detector 2. Thus, a tomographic image can be analyzed and diagnosed correctly and quickly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CT scanner for non-destructive imaging of tomographic images of various materials, industrial products, animals and plants.

[0002]

2. Description of the Related Art Generally, in this type of CT scanner, transmitted radiation data is collected from a direction in which all directions are discretized into several 100 points on the same cross section of an object to be inspected. Further, in order to improve the resolution of the tomographic image, it is necessary to subdivide the cross section of the object to be inspected for measurement, and therefore, a number of detectors are arranged to make an efficient measurement.

Hereinafter, industrial C using an X-ray source as a radiation source
An example of the T scanner will be described. FIG. 6A shows a so-called second generation CT scanner, which includes an X-ray generator 10
The intensity of the fan-beam-shaped X-rays having a fan angle θ emitted from 1 is measured by the opposing multi-channel X-ray detector 102. At this time, the X-ray generator 101 and the multi-channel X-ray detector 102 are integrally linearly moved in the direction of the arrow (hereinafter referred to as traverse) to irradiate the inside of the circle S (hereinafter referred to as scan area) with X-rays. To do.
In one measurement, the inspection object 10 in the scan area
Since 3 is irradiated only from the direction of the fan angle θ,
Next, the inspection object 103 is rotated by θ to traverse the X-ray generator 101 and the multi-channel X-ray detector 102 again, and the adjacent θ range is irradiated. In this way, 18
By repeating a series of operations 0 / θ times, data obtained by irradiating all the points in the scan area from the direction of 0 ° to 180 ° can be obtained. FIG. 3B shows a so-called third-generation CT scanner. Since the fan angle θ is wider than the former and the number of detection elements of the multi-channel X-ray detector 102 is increased, the fan angle θ is not traversed. It can cover the scan area inscribed in. The inspection object 103 is rotated 360 degrees around the center of the scan area, or the inspection object 103 is fixed and X
The line generator 101 and the multi-channel X-ray detector 102 are simultaneously rotated 360 degrees about the center of the scan area while maintaining their relative positional relationship, so that all the points in the scan area are rotated from 0 degrees to 360 degrees. Irradiation data is obtained from the direction of the range.

[0004]

However, in the above-mentioned conventional third-generation CT scanner, the traverse as in the second-generation is not required, and the measurement time is shortened, while the multi-channel X-ray detector There is a drawback that a ring-shaped false image is generated due to variation in characteristics between the detection elements. The reason why the false image occurs will be described with reference to FIG. Now, the point P0 in the figure (a) is the center of the scan area S, and the point P1 is X.
A point P2, which is the center of the line generator 101, indicates the center of a specific detection element of the multi-channel X-ray detector 102 arranged on an arc centered at the point P1. Straight line P1P2
Indicates a path of X-rays emitted from the X-ray generator 101 from the point P1, transmitted through the scan area and irradiated to the point P2 of the multi-channel X-ray detector 102. When the contact point of the circle R inscribed in the straight line P1P2 with the center at the point P0 is P3, the object to be inspected in the scan area is the point P0.
The locus of the contact point P3 when rotating 360 degrees around the circle coincides with the circle R. FIG. 2B shows a path Q of transmitted X-rays when the inscribed circle R is fixed and the X-ray generator 101 and the multi-channel X-ray detector 102 are integrally rotated around the point P0.
1, Q2, ... Therefore, from the above description, the multi-channel X-ray detector 10 located at the point P2
If the characteristics of the second detection element differ from the characteristics of the other elements, a circle R
It can be seen that a ring-shaped false image corresponding to When the characteristics of the plurality of detection elements are different, the same number of concentric false images as the number of elements are generated.

The present invention has been made to solve such a conventional problem, and an object thereof is to provide a CT scanner which does not generate a false image.

[0006]

In order to achieve the above object, in a CT scanner according to a first aspect, a tomographic image of an object to be inspected is non-destructively imaged by using a radiation generator that emits fan-beam-shaped radiation. In a CT scanner to be realized, a multi-channel radiation detector including a detection element capable of detecting radiation in a wider angle range than a fan angle θ of a fan beam, and the multi-channel radiation detector in the same plane as the fan beam, and The gist of the present invention is to provide a radiation detector swinging mechanism that swings in a circumferential direction of a circle around the apex of the fan beam.

According to the CT scanner of claim 2,
In a CT scanner that non-destructively forms a tomographic image of a test object by using a radiation generator that emits fan-beam-shaped radiation, a detection element that can detect radiation in a wider angle range than the fan angle θ of the fan beam. And a radiation detector oscillating mechanism for oscillating the multi-channel radiation detector in the same plane as the fan beam and in the circumferential direction of a circle centered on the apex of the fan beam. A data collection processing device for rearranging the data from the multi-channel radiation detector according to the movement of the arrival area of the radiation due to the rocking.

[0008]

According to the invention described in claim 1, the multi-channel radiation detector is oscillated while rotating the object to be inspected by taking such means, so that the radiation emitted from the radiation generator in a specific direction. Are not always detected by the same detection element. Therefore, it is possible to obtain a correct tomographic image having no false image even if there is a difference in characteristics between the detection elements.

According to the second aspect of the present invention, the data from the detectors are rearranged and arranged in accordance with the movement of the radiation arrival region due to the swing of the multi-channel radiation detector, so that the data can be accurately arranged. It contributes to the formation of tomographic images.

[0010]

EXAMPLES Industrial X will be described below as a representative example of the present invention.
A line CT scanner will be taken up and described. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is an X-ray generator that radiates fan-beam-shaped X-rays with a fan angle θ, and 2 is a plurality of X-ray detection elements on the circumference of the same plane as the fan beam centered at a point P1. A multi-channel X-ray detector integrally arranged by arranging at equal intervals and determining the number of detection elements such that the angle formed by the intersections of two straight lines connecting the detection elements at both ends and the point P1 is larger than the fan angle θ. Reference numeral 3 denotes an object to be inspected, 4 denotes an X-ray detector swinging mechanism for swinging the multi-channel X-ray detector 2 on the circumference of the same plane as the fan beam centered on the point P1, and 5 denotes X-ray detection. A rocking mechanism control device for controlling the device rocking mechanism 4 and rotating the inspection object 3 in a scan area described later, 6 is a rotation angle output device for outputting the rotation angle of the inspection object 3, and 7 is a multi-channel X Output signals from all detection elements of the line detector 2, output from the swing mechanism control device 5 The data collection processing device that rearranges the data of the detection elements by inputting the swing angle and the rotation angle obtained from the rotation angle output device 6, and 8 reconstructs the tomographic image based on the data from the data collection processing device 7. Image reconstructing device,
Reference numeral 9 is an operator console and 10 is an image display device. S indicates a scan area bounded by a circle inscribed in two straight lines intersecting with each other at a fan angle θ.

Next, the operation of the apparatus configured as described above will be described. When a scan start command is given to the operator console 9 by the operator, fan beam-shaped X-ray irradiation with a fan angle θ is started from the X-ray generator 1, and the swing mechanism controller 5 is preset. The inspection object 3 is rotated at a predetermined direction and speed based on the sequence, and at the same time, the multi-channel X-ray detector 2 is swung at a predetermined direction and speed in synchronization with the rotation of the inspection object 3. An example of the relationship between the rotation of the inspection object 3 and the swing of the multi-channel X-ray detector 2 will be described with reference to FIG. FIG. 1A shows a state at the time of starting data acquisition, in which the tip of the wedge-shaped inspection object 3 faces upward and the detection element 2-1 and the X-ray at the right end of the multi-channel X-ray detector 2 are shown. A straight line L-1 connecting the focal point P1 of the generator 1 indicates a circle S indicating a scan area.
Is in contact with, that is, the multi-channel X-ray detector 2 is swung to the leftmost direction. FIG. 2B shows a state in which the inspection object 3 is rotated 90 degrees clockwise as indicated by arrow A, and the multi-channel X-ray detector 2 is swinging rightward as indicated by arrow B. The figure (c) shows a state in which the inspection object 3 is rotated 90 degrees further clockwise than the figure (b), and the multi-channel X-ray detector 2 is also further right than the figure (b). Is swinging in the direction. The same figure (d)
Is also the same. FIG. 6E shows a state at the end of data collection, which is rotated 360 degrees from the initial state. At this time, the multi-channel X-ray detector 2 swings to the rightmost direction, and a straight line L-N connecting the detection element 2-N at the left end in the figure and the focal point P1 of the X-ray generator 1 indicates a scan area circle S. It is in contact with. As described above, the rotation of the inspection object 3 and the swing of the multi-channel X-ray detector 2 are controlled by the swing mechanism control device 5 in synchronization with each other. Through this series of operations, the rocking mechanism control device 5 rocks the data acquisition signal and the multi-channel X-ray detector 2 each time the rotation angle of the DUT 3 read from the rotation angle output device 6 reaches a predetermined value. The angle is output to the data collection processing device 7. The data acquisition processing device 7 reads the output data from all the detection elements within the fan angle of the multi-channel X-ray detector 2, the swing angle of the multi-channel X-ray detector 2, and the rotation angle of the inspection object 3, and digitally reads them. It is stored in the buffer memory as data. Inspection object 3
The above-described operation is continued until the object rotates one revolution, and when the rotation angle of the inspection object 3 reaches 360 degrees, the swing mechanism control device 5
Stops the rotation of the inspection object 3, the swing of the multi-channel X-ray detector 2 and the X-ray irradiation, and outputs a data acquisition end signal to the data acquisition processing device 7. Upon receiving the data collection end signal, the data collection processing device 7 rearranges the data stored in the buffer memory as follows.

In the conventional CT scanner shown in FIG. 6 (b), the position of the multi-channel X-ray detector 2 with respect to the X-ray generator 1 is fixed, and an arbitrary detection element of the multi-channel X-ray detector 2 detects it. Since the irradiation angle of the X-rays formed was unique to the detection element, the difference in the characteristics of the detection element produced a ring-shaped false image. In the embodiment of the present invention, since the relationship between the X-ray and the detection element at a certain irradiation angle is not fixed,
Although no false image is generated due to the difference in the characteristics of the detection element, the detection data is rearranged so as to correspond to the data at the irradiation angle that should be detected when there is no fluctuation. The data rearrangement process will be described with reference to FIG.
Detection elements 2-1 and 2- at both ends of the multi-channel X-ray detector 2.
Straight lines L-1, L connecting N and the focal point P1 of the X-ray generator 1
-The angle at which N intersects is θo (θo> θ), and multi-channel X
The number of detection elements of the line detector 2 is N, and a straight line L-1 connecting the detection element 2-1 at the right end in the figure of the multi-channel X-ray detector 2 and the focal point P1 of the X-ray generator 1 is a circle showing a scan area. The multi-channel X-ray from the state in contact with S, that is, the multi-channel X-ray detector 2 is swung to the leftmost direction.
Assuming that the swing angle of the line detector 2 is α _i , the number n _{i of} detection elements for which data should be shifted is given by the equation (1).

[0013] _{n i = INT [α i ·} N / θo] -1 (1) However, INT [] is an integer function. Therefore, the data obtained from the kth detector element is originally k−n.
By assuming that the data should be obtained from the th detection element, it is possible to correct the positional deviation of the data due to the swing.

Next, the rearrangement process for correcting the data positional deviation will be described with reference to FIG. FIG. 6A is a list of irradiation data before processing, where δ _i (i = 1,
, M) is the rotation angle of the inspection object 3 during the i-th data scan, and α _i (i = 1, ..., m) is the oscillation of the multi-channel X-ray detector 2 during the i-th data scan. Corner, x _{i, j}
(I = 1, ..., M; j = 1, ..., N) indicates irradiation data obtained from the j-th detection element at the i-th data scan. The figure (b) is the positional deviation correction value n _i (i = 1, ..., m) of the irradiation data x _{i, j} given by the equation (1).
Is calculated to shift the irradiation data x _{i, k} of the k-th detection element obtained by the i-th data scan to the position of x _{i, kn} . As described above, m n _i (i
= 1, ..., M) and shifting for all x _{i, j} can correct the positional deviation of the data due to the swinging of the multi-channel X-ray detector 2. The image reconstructing device 8 performs a standard CT scanner filter process and a back projection process using the corrected data and displays it on the image display device 10.

Therefore, according to the configuration of the above-described embodiment, the X-rays emitted in a specific direction are not always detected by the same detection element, so that the characteristics of the detection elements vary. Can also obtain a correct tomographic image without false images.

In the above embodiment, the example of the industrial CT scanner in which the inspection object 3 rotates is explained. However, the inspection object 3 is fixed, and the X-ray generator 1 and the multi-channel X-ray detector 2 are integrated. The same can be applied to the CT scanner for a human body that rotates at.

FIG. 5 shows another embodiment of the present invention. Instead of oscillating the multi-channel X-ray detector 2, the inspection object 3 is rotated while being in the same plane as the fan beam, and A CT scanner having an object swinging mechanism 11 that swings within a fan angle θ in the circumferential direction of a circle centered on the apex of a fan beam, and the same effect as that of the embodiment of FIG. 1 can be obtained. .

It should be noted that effective measurement is performed by changing the rocking speed as a function of position, repeating rocking a plurality of times while collecting data for one section, and changing the rocking amplitude. be able to. Further, the accuracy of the tomographic image can be improved by performing linear interpolation or non-linear interpolation between adjacent data.

[0019]

As described above, according to the first aspect of the present invention, the X-rays emitted in a specific direction are not always detected by the same detection element, so that the characteristics of the detection elements vary. Even if there is, a correct tomographic image without false images can be obtained. According to the invention of claim 2,
The tomographic image analysis and diagnosis can be performed accurately and quickly.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the relationship between the rotation of the inspection object and the swing of the X-ray detector.

FIG. 3 is an explanatory diagram of X-ray detector output data when there is a swing.

FIG. 4 is an explanatory diagram of a data rearrangement process in the data collection processing device.

FIG. 5 is a block diagram showing another embodiment of the present invention.

FIG. 6 is a block diagram of a conventional example.

FIG. 7 is an explanatory diagram showing generation of a false image.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 X-ray generator 2 Multi-channel X-ray detector 3 Object to be inspected 4 X-ray detector Swing mechanism 5 Swing mechanism control device 6 Rotation angle output device 7 Data acquisition processor 8 Image reconstruction device 9 Operator console 10 image Display device 11 Inspected object rocking mechanism

Claims (3)

[Claims] 1. A CT scanner for non-destructively imaging a tomographic image of an object to be inspected by using a radiation generator that emits fan-beam-shaped radiation.
A multi-channel radiation detector equipped with a detection element capable of detecting radiation in a wider angle range, and the circumference of a circle with the multi-channel radiation detector in the same plane as the fan beam and with the apex of the fan beam as the center. And a radiation detector swinging mechanism that swings in a predetermined direction. 2. A CT scanner for non-destructively imaging a tomographic image of an object to be inspected by using a radiation generator that emits fan-beam-shaped radiation.
A multi-channel radiation detector equipped with a detection element capable of detecting radiation in a wider angle range, and the circumference of a circle with the multi-channel radiation detector in the same plane as the fan beam and with the apex of the fan beam as the center. A radiation detector swinging mechanism that swings in a direction, and a data collection processing device that sorts the data from the multi-channel radiation detector according to the movement of the arrival area of radiation accompanying the swinging. CT scanner characterized by. 3. The inspecting object oscillating mechanism in which the radiation detector oscillating mechanism oscillates the inspecting object in the same plane as the fan beam and in the circumferential direction of a circle centered on the apex of the fan beam. The CT scanner according to claim 1, wherein