JPS6274337A - Ct scanner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a CT scanner that takes a tomographic image of a specific cross section of an object to be inspected, and particularly relates to an improvement in a correction means for correcting positional deviation of a scanning mechanism.

[Technical front of the invention and its problems] A CT scanner irradiates a specific cross section of an object to be inspected with radiation from all directions, obtains projection data by measuring the transmission line history of these radiations, and uses this projection data. A tomographic image of a specific cross section of the object to be inspected is obtained from the data, and from the image data of each slice position obtained by this tomography, information regarding the measurement of the object to be inspected, such as information about the object to be inspected. size.

Information such as the cross-sectional shape, presence or absence of defects, and tissue distribution of the human body can be obtained. Therefore, the above CT scanner is widely used for industrial or medical purposes.

Incidentally, in recent years, there has been a desire for further improvement in the resolution of CT scanners, and efforts are being made to subdivide the sampling pitch and reduce the pixel size. The accuracy of scanning operations for data collection is an important point. However, the operational accuracy of the scanning mechanism section is limited by the guide mechanism, and thus has its own limitations.

FIG. 5 is a system diagram showing the configuration of a conventional first generation CT scanner. In FIG. 5, a radiation beam 2 emitted from radiation 8!1 is focused into a pencil-shaped beam by a collimator 3, passes through an object to be inspected 4, and is detected by an M-ray detector 5.

The object to be inspected 4 is moved by the traverse mechanism 6 as shown by the arrow A in the figure.
It performs a traverse operation as shown in
While the inspected object 4 performs one traverse operation, the data collection system 7 collects one piece of projection data in response to the detection signal S of the radiation detector 5. When one traverse operation is completed, the object to be inspected 4 is rotated by a predetermined pitch angle as shown by arrow B in the figure by the rotation mechanism 8 provided above the traverse machine 116, and the object to be inspected is 4
When it has rotated by one pitch angle, the traverse operation is performed again and data collection is continued by the data collection system 7. The projection data from the entire circumferential direction of the specific cross section of the object to be inspected 4 collected by the data collection system 7 in this way is as follows:
After being converted into integral data into linear absorption coefficients as input data for the reconstruction algorithm in the preprocessing section 9, the data is sent to the image reconstruction calculation section 10, where the 117i layer image is reconstructed by the reconstruction algorithm. This tomographic image is then displayed on a display 11 such as a CRT. Note that drive control of the traverse mechanism 6 and the rotation mechanism 8 as a scanning mechanism is performed by a mechanism control section 12.

Here, for example, if runout occurs at the center of rotation due to radial runout of the bearing in the rotating mechanism 8, the projection data (solid line in Figure 6) when the runout occurs will be blurred, as shown in Figure 6. Projection data when not available (dashed line in Figure 6)
A deviation ΔC occurs in the traverse direction compared to the above. As a result, blurring and artifacts ((a
i) could occur. Such blurring and artifacts in tomographic images can occur not only in first generation CT scanners but also in second and third generation CT scanners due to backlash or disturbance in the scanning mechanism.

For this reason, we currently offer high-precision scanning BJI using robot technology and IC technology. Horizontal systems have been developed, but they are all expensive, susceptible to environmental changes such as temperature changes, and have poor reliability. In addition, it was difficult to manufacture a large-sized, high-load scanning mechanism.

On the other hand, the third generation CT Suki A! In this case, rotation 111
1, data with a shifted slice position will be collected, resulting in a decrease in the resolution of the tomographic image. This surface runout of the rotating mechanism is mainly due to the axial deviation of the bearings, and to prevent this, it is possible to use special bearings such as air bearings.
These special bearings were still very expensive and were easily affected by environmental changes. Furthermore, in first-generation and second-generation CT scanners, when an error occurs in the rotation pitch angle due to axial vibration of the rotation mechanism, the resolution of tomographic images decreases (B).

[Purpose of the invention]

The present invention was made based on these circumstances,
The purpose of this is to create a CT scanner that can improve the scanning accuracy of the scanning mechanism and the resolution of tomographic images with a simple and inexpensive configuration, and that can prevent blurring of tomographic images and artifacts. It is about providing.

[Summary of the invention]

According to the present invention, the scanning mechanism is provided with a position detector that detects a shift in the scan operation position, and when the position detector detects a shift in the scan operation position in the vertical direction, correction is performed according to the amount of shift. This is what I did.

Further, in the present invention, the scanning mechanism is provided with a position detector that detects a shift in the scan operation position, and when a horizontal shift in the scan operation position is detected by this position detector, correction is performed according to this shift S. This is how it was done.

[Embodiments of the invention]

Figure 1 shows a first example in which the present invention is applied to a second generation C-cho scanner.
FIG. 2 is a system diagram showing the configuration of an embodiment. Note that the same parts as in FIG. 5 are given the same reference numerals, and detailed explanations will be omitted. In FIG. 1, an emitted fA radiation beam 2 emitted from a radiation source 1 is transmitted through an object to be inspected 4 as a fan-shaped beam, and is detected by a multi-channel radiation detector 5.

Reference numeral 21 denotes a traverse table, and on both sides of the traverse table 21 are provided a plurality of (four in this case) first proximity switches 22a, 22b, 22c each consisting of a magnetic detector or a photodetector.

22d is fixed. The first proximity switch 22
Guide plates 23a a to 22d are installed on both sides of the traverse mechanism 6 parallel to the traverse axis and serve as a reference for the linearity of the traverse motion.

The guide brake 1-23a detects the position of the guide brake 1-23b, and the linearity of the traverse movement is impaired due to backlash or disturbance in the traverse mechanism 6.

23b, a detection signal S1 is generated according to the amount of approach.
It is supposed to output. 24 is the traverse mechanism 6
This is a fixed correction table, and it is a table driver! 111
1125, it is movable in the direction perpendicular to the traverse axis (arrow D in the figure).

Further, on the traverse table 21, second proximity switches 26a and 26b, which are composed of magnetic detectors, photodetectors, etc., are arranged opposite to each other across the rotating shaft 8a of the rotating mechanism 8 in which the object to be inspected 4 is placed on the table. is set up. These second
The proximity switches 26a and 26b are for detecting the deflection of the rotating shaft 8a, and when the rotating shaft 8a swings due to backlash in the rotating mechanism 8, a detection signal S is output according to the amount of deflection.
2 is output.

On the other hand, 27 is a data correction sieve unit, and a detection signal S2 outputted from the second proximity switches 26a and 26b.
Based on this, the projection data collected by the data collection system 7 is corrected electrically or through arithmetic processing. Further, 28 is a mechanism correction m calculation unit, which is applied to the first proximity switch 2 through the table control unit 29.
Based on the detection signals S1 from 2a to 22d, the function outputs the operation control signal $3 to the mechanism control unit 12, calculates the correction movement amount of the correction table 24, and performs table control according to this movement amount. It has a function of outputting a movement command signal S4 to the section 29. The table control section 29 receives a movement command signal S4 fy output from the mechanism correction amount calculation section 28.
Accordingly, the controller @$5 is output to the table drive mechanism 25 to control the movement of the correction table 24 in the D direction.

Next, the operation of this embodiment configured as described above is illustrated in FIG.
This will be explained with reference to the flowcharts shown in a) and (b).

A fan-shaped radiation beam 2 is emitted from the radiation II#i1, and this radiation beam 2 is detected by the radiation detector 5. In this state, the object to be inspected 4 placed on the rotary table of the rotation mechanism 8 is traversed in the direction of the arrow in FIG. 1 by the rubber mechanism 6 (step (hereinafter abbreviated as ST) 1). At this time, the traverse table 21 is displaced due to play in the traverse mechanism 6 or disturbance, for example, the proximity switch 22a.

22b approaches the guide plate 23a.

Then, this first proximity switch 22a.

22b outputs the detection signal S1, and the table controller 2
(Sr2
). In the mechanism correction amount calculating section 28, a signal level TO is set in advance based on the allowable shift rotation of the traverse mechanism 6, and this signal level TO is compared with the signal level T1 of the detection signal $1. (Sr3).Here, if the signal level T1 of the detection signal s1 is smaller than the set signal level TO, the detection signal s1 is ignored and the traverse mechanism 6 performs the 1 to 1 rubber movement of the object 4 to be inspected. Then, when one traverse operation is completed (Sr4), the projection data collected by the data acquisition system 7 is transferred to the preprocessing section 9 (Sr1).Then, the object 4 to be inspected rotates 1ffl18. The object to be inspected 4 is rotated by a predetermined pitch angle, the traverse operation is performed again, and projection data is collected.The above operations are performed until the rotation pitch angle of the object to be inspected 4 is 3600 (Sr1). Projection data from all circumferential angles in a specific section of the body 4 are collected, and after reconstruction calculation is performed by the image reconstruction calculation unit 10 (S T 7'), the data is displayed as a tomographic image on the display 11 ( Sr1),.

On the other hand, in ST3, if the signal level T1 of the detection signal $1 is higher than the set signal level T0, an operation stop command signal is sent from the mechanism correction amount calculation section 28 to the mechanism control section 12 as an operation control signal S3. is output and the mechanism il
Traverse 8 due to control of l tII part 12! The drive of the lateral 6 is stopped (Sr9).

At the same time, the mechanism correction amount calculation section 28 calculates the correction movement amount of the correction table 24 and outputs it to the table control section 29 . Then, from this table control unit 29, the table drive 411I! A control signal S5 is output to 25,
The correction table 24 is moved in the direction indicated by the arrow in the figure (in this case, the first proximity switch 22a).

22b moves away from the guide plate 23a (ST10). And the first proximity switch 22a
, 22b when the signal level T1 of the detection signal s1 becomes lower than the set signal level To (ST11) la! Groove correction correction m calculation section 28 operation start command signal is sent to mechanism control section 1
2, and the traverse mechanism 6 is activated under the control of the structure control section 12 (ST12). The subsequent operations are the same as those from Sr4 described above, and will be omitted here.

Furthermore, when the inspected object 4 rotates at a predetermined pitch angle,
Assume that the rotation axis 8a of the rotation mechanism 8 is displaced due to backlash or disturbance. At this time, the second proximity switch 26a,
26b outputs the detection signal s2 to the data correction calculation section 27 (ST13).

Then, in the data correction sieve section 27, 1
Each time the traverse operation is completed, the projection data transferred from the data collection system 7 is corrected electrically or by arithmetic processing based on the detection signal S2 (ST14). Then, this corrected projection data is transferred to the preprocessing section 9 (Sr
1). Then, when the collection of projection data from the entire circumferential direction on a specific cross section of the object to be inspected 4 is completed (Sr1),
Image reconstruction 'a Reconstruction calculation is performed in the sieve unit 10 (S
r7), displayed as a tomographic image on the display 11 (
Sr1).

As described above, according to this embodiment, even if the traverse mechanism 6 shifts due to backlash or disturbance, this shift is detected in a non-contact and highly accurate manner by the first proximity switches 22a to 22d, and the amount of rock formation correction is adjusted. Arithmetic unit 28. Table control section 2
9, the position of the traverse mechanism 6 is quickly corrected by the amount of deviation. Therefore, stable traverse operation is possible at all times, eliminating blurring and artifacts in tomographic images.
There is no possibility that ~ will occur. In addition, if the rotation axis of the rotation mechanism 8 deviates, the amount of deviation can be controlled by the second proximity switch 26.
a and 26b, and the projection data collected by the data collection system 7 is corrected according to the amount of deviation. Therefore, the same result as when rotating with high precision can be obtained, so I! There is no risk of blurring or artifacts occurring in the l'i layer image, and there is also no risk of reducing the resolution of section Ill.

Furthermore, since this embodiment requires only simple modifications to the conventional configuration, it can be realized at low cost.

Next, a second embodiment of the present invention will be described.

Figure 3 shows a second model in which the present invention is applied to a third generation CT scanner.
FIG. 2 is a system diagram showing the configuration of an embodiment of the present invention, in which the same parts as in FIG. 1 are given the same reference numerals and detailed explanations are omitted. In the third generation CT scanner, if vibration occurs in the rotating table 8b of the rotating mechanism 8 on which the inspected object 4 is placed, the resolution of the tomographic image decreases, and it also causes blurring and artifacts. Therefore, in this embodiment, the rotary table 8b
Proximity switches 32a and 32b are provided on both sides of the rotary table 8b to detect and cover the surface runout of the rotary table 8b. Reference numeral 33 in FIG. 3 denotes a lifting mechanism control section, which controls the driving of the lifting mechanism motor 34 for positioning the slice plane of the object 4 to be inspected. The screw shaft 35 is rotated by the drive of the lifting mechanism motor 34, and the rotating mechanism 8 fixed to the screw bearing 36 is raised or lowered.

In this embodiment having such a configuration, when a vertical deflection occurs in the rotating table 8b of the rotating mechanism 8 during a rotational scan, the proximity switch 32a is activated.

32b outputs a detection signal S6 according to the amount of surface roughness. Then, this detection signal S6 is the elevating mechanism υ1!1
L”4 is sent to the groove correction calculation section 28 via the first section 33,
The level of this detection signal S6 is compared with a preset reference position signal level. Therefore, when the detection signal level is higher, the mechanism control unit 12 controls the rotation mechanism 8.
When the operation stops, the lifting mechanism motor 34 is activated by the lifting mechanism control unit 33 to move the rotating mechanism 8 upward or downward, and the rotating table 8b is corrected to be located at the reference position (within the allowable range). be done.

Thus, according to this embodiment, in the third generation CT scanner, even if shake occurs in the rotary table 8b, the vertical position of the rotary table 8b is quickly corrected, so that stable rotational scanning is always performed. . Therefore, it has a long effect compared to the first embodiment. In addition, in this case, a lifting mechanism for positioning the slice plane, which is conventionally provided, can be used as the vertical position correction mechanism of the rotary table 8b. Therefore, it can be easily configured and manufactured at a lower cost.

It should be noted that the present invention is not limited to the above embodiments. For example, in the first embodiment, an example is shown in which both the means for electrically or theoretically correcting the projection data and the means for correcting the position of the scanning mechanism are provided, but only one of the means is provided. It may be.

FIG. 4 is a system diagram showing the configuration of a first generation CT scanner equipped with means for electrically or computationally correcting projection data, and the same parts as in FIG. 1 are given the same reference numerals. It is. In this case, when the detection signal S2 is output from the proximity switches 26a and 26b for detecting the axis capture of the rotating shaft 8a in the rotating mechanism 8 to the data correction processing section 27,
Based on this detection signal S2, the projection data provided by the data acquisition system 7 is corrected. This corrected projection data is then transferred to the preprocessing section 92 and the land reconstruction calculation section 1.
0G is output, and after a predetermined +21 processing is applied thereto, the tomographic image is displayed on the display 11 as -C.

In addition, in the second embodiment, 11 third generation C1 ski A
・Although we have shown a case in which the scanner is equipped with a means for correcting the position iη of the scan gate structure, the means for correcting the projection data electrically or through arithmetic processing should be applied to the third generation CT scanner #)-6J It is Noh. Similarly, it goes without saying that the means for correcting the position of each scan can be applied to the first generation CT scanner. The present invention is not limited to the above, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

(Effects of the Invention) As detailed above, the present invention provides the scanning mechanism with a position detector that detects a shift in the scan operation position, and when the position detector detects a shift in the scan operation position in the vertical direction. The correction is made according to the amount of deviation.

Further, in the present invention, the scanning mechanism is provided with a position detector that detects a shift in the scan operation position, and when a horizontal shift in the scan operation position is detected by this position detector, correction is performed according to this shift. This is how it was done.

Therefore, according to the present invention, it is possible to improve the scanning operation accuracy of the scanning mechanism and the resolution of tomographic images with a simple and inexpensive configuration, and to reduce blurring and artifacts in tomographic images.
- It is possible to provide a CT scanner that can prevent this.

[Brief explanation of drawings]

The first part is a system diagram showing the configuration of the first embodiment in which the present invention is applied to a second generation CT scanner, FIGS. 2(a) and (b) are flowcharts for explaining the operation of the same embodiment, and FIG. 4 is a system diagram showing a second embodiment in which the present invention is applied to a third generation CT scanner, and FIG. 4 is a system diagram showing the configuration of a third embodiment in which the present invention is applied to a first generation CT scanner. , Figure 5 shows the conventional first
FIG. 6 is a system diagram showing the configuration of the new generation CT scanner, and is a diagram for explaining the problems of the conventional technology. DESCRIPTION OF SYMBOLS 1... Radiation source, 2... Radiation, 4... Inspected object, 5... Radiation detector, 6... Traverse mechanism, 7
...Data collection system, 8...11 rotations, 9.
...3i[1 Science Department, 10...Image reconstruction calculation section, 11
...Display, 12... Mechanism control section, 21...
- Traverse table, 22a to 22d...first proximity switch, 23a. 23b...Guide plate, 24...Correction table, 26a, 26b...Second proximity switch, 27...
・Data correction calculation unit, 28... Authoritative correction amount calculation unit, 2
9... Table control unit, 32a, 32b... Proximity switch, 33... Lifting mechanism control unit, 34... Lifting mechanism motor. Applicant's agent Patent attorney Takehiko Suzue (a) (b) Figure 3

Claims (7)

[Claims] (1) In a CT scanner that performs image reconstruction processing on radiation absorption data obtained by irradiating a specific cross section of an object to be inspected with radiation from all around the circumference using a scanning mechanism to obtain image data regarding the specific cross section, the scanning mechanism a position detector that is provided and detects a shift in the scanning operation position;
A CT characterized by comprising: a correction means for performing correction according to the amount of deviation when at least a vertical deviation of the scanning operation position is detected by the position detector.
scanner. (2) The correction means is characterized in that the correction means corrects the position of the scanning mechanism by feeding back a position signal corresponding to the vertical deviation amount of the scanning operation position output from the position detector. Claim No. 1
CT scanner described in ). (3) The correction means corrects the radiation absorption data using a position signal corresponding to a vertical deviation amount of the scan operation position output from the position detector. CT described in scope item (1)
scanner. (4) In a CT scanner that performs image reconstruction processing on radiation absorption data obtained by irradiating a specific cross section of an object to be inspected with radiation from all around the circumference using a scanning mechanism to obtain image data regarding the specific cross section, the scanning mechanism a position detector that is provided and detects a shift in the scanning operation position;
A CT characterized by comprising: a correction means that performs correction according to the amount of deviation when at least a horizontal deviation of the scanning operation position is detected by the position detector.
scanner. (5) The correction means is characterized in that the correction means corrects the position of the scanning mechanism by feeding back a position signal corresponding to the amount of horizontal deviation of the scanning operation position output from the position detector. Claim No. 4
CT scanner described in ). (6) The correction means corrects the radiation absorption data using a position signal corresponding to a horizontal shift amount of the scanning operation position output from the position detector. CT described in scope item (4)
scanner. (7) The CT scanner is characterized in that the CT scanner is equipped with a correction means that performs correction according to the amount of deviation when a vertical deviation of the scanning operation position is detected by the position detector. CT as described in item (4)
scanner.