JPS61154645A - Tomographic apparatus - 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 an improvement in a tomography apparatus that creates a tomographic image of a subject using radiation.

[Technical background of the invention and its problems]

In principle, a conventional tomography apparatus of this type has a configuration as shown in FIG. 7. That is, subject 1
The approximate center line of is assumed to be a fixed axis 2, and the X-ray tube 3 and film 4 are rotated around this fixed axis with a phase shift of 180 degrees and facing each other with the subject 1 sandwiched between them. Transmitted X transmitted through the X-ray tube 3 and the object 1 during rotation and output
A film 4 is exposed to the ray 5 to obtain an X-ray transmission image of the subject 1. At this time, the film surface is held perpendicular to the fixed axis 2, and its rotation is controlled only by revolution without rotation.

Therefore, when the above-mentioned exposure operation is performed, the X-ray transmitted image forms a sharp image on the film surface in only one plane 6 geometrically, and the other parts are blurred in a circular shape, essentially making it difficult to see the object being examined. This means that a tomographic image by one plane 6 of 1 is created. 7 indicates a film trajectory, and 8 indicates an X-ray tube trajectory.

However, in practice, the tomography apparatus described above can only create a tomographic image of one plane 6 of the subject 1 when the X-ray tube 3 and film 4 take one revolution along the trajectory 7.8. The data obtained by photographing one rotation includes data of all cross sections of the subject 1, but there is a problem in that it is not effectively utilized.

[Purpose of the invention]

The present invention has been made with attention to the above points, and an object of the present invention is to provide a tomography apparatus that can create a tomographic image of an arbitrary cross section of a subject using a scanning method similar to conventional tomography. be.

[Summary of the Invention] The present invention allows a radiation generator and a radiation detector to perform, for example, a circular motion while maintaining parallelism with respect to a certain origin fixed to a subject, and during this motion, multiple This is a tomography apparatus that creates a tomographic image of an arbitrary cross section by shifting the images of a plurality of radiation detectors obtained by emitting radiation at certain positions by an amount of deviation determined according to the cross section of the subject, and superimposing them.

[Embodiments of the invention]

An embodiment of the present invention will be described below.

FIG. 1 is a diagram showing a schematic configuration of the device.

In the same figure, 11 and 1z indicate a radiation generator such as an X-ray tube and a two-dimensional radiation detector, which rotate the virtual common axis 13 by 180 degrees as shown in the scanning diagram of FIG.
They are supported by the mechanism section 15 so that they can be rotated stepwise (see Fig. 3) with a phase shift of 100 degrees, and are opposed to each other with the subject 14 in between. The two-dimensional radiation detector 1
2 is composed of, for example, a fluorescent screen + If (image intensifier) + a television camera, and is a so-called X
It is collectively referred to as a line television display system or an imaging device. Therefore, the two-dimensional radiation detector 12 outputs a scanning signal and sequentially reads out the images captured by the television camera and sends them to the subsequent data collection unit 16. The data collection unit 16 amplifies the analog radiation transmission data outputted from the two-dimensional radiation detector 12 to a required table level using an amplifier, and then extracts the diisotal radiation transmission data.
Convert and output. 11 is a central processing unit (
(hereinafter referred to as CPU), the control console 1
It outputs an operation start signal based on the operation command from the data collection section 16, stores the data from the data collection section 16 as an image file in its own image memory, and correlates the N pieces of radiographic data to obtain information about the subject 14. It has the function of creating a tomographic image of a certain plane. 19 is a mechanism control section, 20 is a radiation control section, and 21 is a display section such as a CRT display that displays images processed by the CPU 17. 22 is a support base that supports the subject 14 in an appropriate state.

Next, the operation of the device configured as described above will be explained.

When an operation command to start operation is generated from the control console 18 manually or based on a sequence program, in response to this command, the CPU f 7 mechanically controls the command signal for initial position setting based on its own program etc. 19. Here, the mechanism control unit 19 sets the radiation generator 11 and the two-dimensional radiation detector 12 to initial positions in step A1. In this state, the radiation generator 11
It is assumed that the radiation generation point S exists at 81 shown in Figure WC3, and the radiation generator 11 and the two-dimensional radiation detector 12 are 180 degrees out of phase with respect to the rotation direction about the common axis 13 as shown in Figure 2. It is set in a state where the subject 14 is sandwiched with a deviation.

After the initial settings have been made as described above, the radiation control unit 20 supplies high voltage to the radiation generator 12 in response to a command from the CPU 17, so that the radiation control unit 20 supplies a high voltage to the radiation generator 12, so that a fan that covers the entire width area of the subject 14 from the generator 12 is generated. Radiation 23 at an angle is emitted (Stellaf "A2" in FIG. 4), and the radiation transmission data transmitted through the subject 14 and outputted at this time is detected by the two-dimensional radiation detector 12 and sent to the data collection section 16. This data collection unit 16 collects data from the detector 12, digitizes it, and sends it to the CPU 17, and the radiographic image from the first radiation exposure is stored in its own image memory (
Stella fA3).

After the transmission image is stored in the CPU 17, the Stellar 7
'A4 determines whether or not the N measurements shown in Figure 3 have been completed, and if the measurements have not yet been completed, the CPU continues to
17 outputs a rotation command signal and gives it to the mechanism control section 19. Here, the mechanism control unit 19 rotates the common shaft 13 of the radiation generator 11 and the two-dimensional radiation detector 12 by a minute angle (step A5). Therefore, the radiation generation point S in this case is the position S! shown in FIG. In this state, the process moves to step A2 as described above, and the radiation generator 11 irradiates the subject 14 with the radiation 23.
The radiographic image at that time is stored in the image memory of the CPU 17.

As described above, the radiation generation point S is rotated by a minute angle as shown in FIG. and,
After the radiographic images at the N positions S1 to sN are stored, the image of the subject 1 shown in FIG.
4, the correlation between the radiographic images measured N times is created based on the arbitrary cross-sectional position dK of the object 14, and a cross-sectional image for the cross-sectional position d of the subject 14 is created and displayed on the display unit 21 (Stella Fa
ll).

Next, a tomographic profile creation algorithm for creating a tomographic profile at an arbitrary cross-sectional position d from a radiographic image will be described with reference to FIG. FIG. 5 is a diagram showing the geometrical relationship seen from the y-axis direction. Now, when the radiation generation point S moves in a circle with a radius R, the detector center point C moves along the detection surface 12 d (
A circular motion of radius RO is performed on the plane of Z=-Dl. O in the figure is a point that is symmetrical when viewed from the radiation generation point S side to the detector 12 side.

By the way, the injection pattern on the cross section 14h of the subject represented by Z=d in two directions from the 0 point performs a circular motion with a radius R on the detection surface 12a. Note that in the figure, the point A on the two axes is taken as an example, but the same applies to each point of the subject on the line connecting points s-pA excluding points that are not on the z-axis, that is, point A.

On the other hand, considering the movement of the two-dimensional radiation detector 12, the projection of any point on the cross section d of the object is on the detection surface 12h with a radius r
(=R-R6) circular motion. Therefore, by calculating the relationship between d and r by simple geometric calculation, it can be expressed as follows.

On the other hand, the vector of circular motion of the detector 12 corresponding to the positions 81 to SN of the radiation generation point S is.

Let's call this a shift vector. However, θY is the phase angle of the radiation generator 11, and iJ is the unit vector in each of the X-axis and y-axis directions. This means that N transmission images of radius rn are obtained by the positions 5l-SN of the radiation generation point S, but these transmission images are located at each position 81-SN.
This means that each SN appears different by a certain amount.

Therefore, in the CPU J 7, when the transmission images corresponding to each position S1 to SN are shifted by -r and the N transmission images are superimposed (added), the tomographic plane 14a is emphasized, so-called out of focus. You can create a tomographic image that matches your needs.

Furthermore, when creating tomographic images of different cross-sections d' of the subject 14, the radius Bi corresponding to cross-section ♂ is determined by equation (1), and the radius Bi corresponding to cross-section ♂ is determined by applying equation (2) to this bi to determine the two-dimensional plane. When the amount of deviation in the x and y directions is calculated, and the transmitted images at each position 81 to SN are shifted and superimposed by the amount of deviation, the cross section d' of the object 14 is emphasized. can create tomographic images.

Note that the present invention is not limited to the above embodiments.

Although the radiation detector 12 needs to revolve without rotating, the radiation generator 11 may rotate as well as revolve. Further, in the above embodiment, the radiation generator 1
The radiation detector 1 and the radiation detector 12 are moved in a circular motion while keeping parallel to each other, but the point is that as long as the origin 0 is point symmetrical and the radiation detector 12 is kept parallel to each other, the two move in a circular arc or in parallel. As a specific example, FIG. 6 shows an example in which a raster scan movement is performed. In the figure, 3 indicates the radiation generation point trajectory, 32 the detector trajectory, and 33 the detector center point. That is, in this example,
Both devices 11 are kept constant while maintaining the ratio of the distance between point 0 and the radiation generator 11 and the distance between point 0 and the radiation detector 12.
．． The radiation beam 23 is irradiated by raster scanning the object 12 in a rectangular shape while moving the objects 12 in opposite directions.
A plurality of transmission images are obtained. In this case, the shift vector r does not change circularly, but instead changes n in a raster scan pattern.
If the vector of the radiation generation point S considered on the xy plane at this time is R8n, the center vector R0n of the detector 12 considered on the X7 plane changes in a shirasta shape, and the absolute It becomes a shift pattern and changes in a raster pattern. Therefore, the shift vector r changes in a raster pattern as follows. Therefore, as above, (4)
By calculating the amount of deviation in the cross section d of the object based on the formula and equation (5), shifting the images by the amount of the deviation, and superimposing them, it is possible to create a tomographic image in which a certain cross section d of the object 14 is emphasized. . Other 1 The present invention can be implemented with various modifications without departing from the gist thereof.

〔Effect of the invention〕

As described in detail above, according to the present invention, a plurality of transmitted images obtained by - times of tomographic imaging are superimposed by performing image shifting based on a shift vector corresponding to the cross-sectional position of the object. , it is possible to create a tomographic image of an arbitrary cross section of the subject using the same amount of radiation exposure to the subject as in one conventional tomographic imaging, and the information can be used effectively.
It is possible to provide a tomography device that greatly contributes to improving inspection efficiency.

[Brief explanation of drawings]

Figures 1 to 5 are for explaining an embodiment of the tomography apparatus according to the present invention. Figure 1 shows the overall configuration of the apparatus, and Figure 2 shows a radiation generator and a radiation detector. Figure 3 is a diagram showing the position of each radiation generation point of the radiation generator, Figure 4 is a flowchart showing the overall operation of the device, and Figure 5 is a diagram showing the generator in a cross section of the subject. FIG. 6 is a diagram showing another embodiment of the apparatus of the present invention, and FIG. 7 is a diagram of the geometric relationship of a conventional apparatus using photography. DESCRIPTION OF SYMBOLS 11... Radiation generator, 12... Two-dimensional radiation detector, 13... Common axis, 14... Subject, 15...
Mechanism section, 16 - data collection section, 17... CPU, 2
9... Mechanism control unit, 20... Radiation control unit, d...
・Example cross section. Applicant's representative Patent attorney Suzue Takehiko ivA 2nd figure 7) -, 2 Procedural amendment Showa No. 00, 15B Commissioner of the Patent Office Uga Michibe 1, Patent application for indication of the case Showa No. 59-276197 No. 2, Name of the invention Tomography device 3, Relationship with the person making the amendment Patent applicant (307) Toshiba Corporation 4, Agent 6, Specification to be amended 7, Contents of the amendment (1) "2. Scope of Claims" of the specification is amended as shown in the attached sheet. (2) The sentence "Then, the center point of the detector...can be modified and implemented" in the first line of page 9 to the first line of page 13 of the specification has been changed to the following: correct. Then, the center point C of the detector performs a circular motion with a radius R8 on the detection surface 12d (plane where Z=-D). O in the figure is a point at which the radiation generation point S and the detector 12 move in a point-similar manner with respect to this point. Incidentally, the projection of a point on the cross section 14a of the subject represented by z=d in two directions from the 0 point causes a circular motion with a radius R on the detection surface 12m. Although the figure takes point A on two axes as an example, the projection of any point on the surface 74a onto the surface 12m similarly performs a circular motion with a radius R. On the other hand, considering the movement of the two-dimensional radiation detector 12, the projection of any point on the cross section d of the object is on the detection surface 12a with a radius r
(=R-Ro) circular motion. Therefore, by calculating the relationship between υd and r by simple geometric calculation, it can be expressed as D+(Dt-d). On the other hand, the circular motion vector of the detector 12 corresponding to the positions s, to sH of the radiation generation point S will be referred to as a shift vector. However, θ. represents the phase angle of the radiation generator II, and ij represents the unit vectors in the X-axis and y-axis directions, respectively. This means that the position 8 of the radiation generation point S
N transmitted images are obtained from 1 to SN, but when focusing on the surface 14B, this means that these transmitted images appear shifted by rn for each position 81 to SM. Therefore, C.P.
In U17, the transmitted images corresponding to each position 81 to s14 are -
By shifting the image by rn and superimposing (adding) the N transmitted images, a so-called in-focus tomographic image in which the tomographic plane 24M is emphasized can be created. Furthermore, when creating a tomographic image of a different cross section d' of the subject 14, the radius r corresponding to the cross section d' is calculated using equation (1).
′, and apply equation (2) to this r′ to calculate the amount of deviation in the +1 direction, which is a two-dimensional plane.
By shifting the 1%8N transmission image by the shift amount and superimposing N transmission images, a tomographic image in which the cross section d' of the subject 14 is emphasized can be created. Note that the present invention is not limited to the above embodiments. The radiation detector 12 needs to revolve only without rotating or tilting, but the radiation generator 1 may not only revolve but also rotate or tilt. Further, in the above embodiment, the radiation generator 1 and the radiation detector 12 are each moved in a circular motion within a plane parallel to each other, but the point is that the radiation generator 1 and the radiation detector 12 are moved in a circular motion within a plane parallel to each other while maintaining point similarity with respect to the origin OK. As long as they move, they may move in any manner, and as a specific example, FIG. 6 shows an example in which a raster scan movement is performed. In the figure, 3 indicates the radiation generation point trajectory, 32 the detector trajectory, and 33 the detector center point. That is, in this embodiment, while keeping the ratio of the distance between the point ○ and the radiation generator 11 and the distance between the point ○ and the radiation detector 12 constant, the two devices 11 and 12 are moved in mutually opposite directions. The radiation beam 23 is irradiated by raster scanning in a rectangular shape to obtain a plurality of transmitted images of the subject 14. Shift vector r in this case
n is considered to change n times in a raster scan pattern without changing circularly, and if the vector of the radiation generation point S considered on the xy plane at this time is "an," then the detector 12 considered on the xy plane The central vector R0n changes like a shirasta, and the absolute shift vector Rn
Changes to the original shirasta shape. Therefore, the shift vector rn changes in a raster fashion as follows. Therefore, as above, (5)
By determining the amount of shift in the cross section d of the subject based on the formula, shifting the images by the amount of shift, and superimposing the images, it is possible to create a tomographic image in which a certain cross section d of the subject 14 is emphasized. In addition, the present invention can be implemented with various modifications without departing from the gist thereof. In the above example, setting the 0 point within the detector plane is (
nz=o), it will be easily understood that the detector does not have to be moved. Furthermore, in the above embodiments, the radiation generation point and the detector were moved within a plane, but movement outside the plane, for example, within a spherical or cylindrical surface, is possible as long as image errors can be tolerated. . 2. Claims (1) A radiation generator and a radiation detector that perform a predetermined movement while maintaining point-similar positions with respect to a certain origin fixed with respect to the subject, and during the movement of both these devices. a transmission image acquisition means for emitting radiation at a plurality of positions and acquiring and storing a plurality of radiation transmission images of the subject obtained by the exposure; and a tomographic image creating means for creating a tomographic image of a cross section of the object by shifting and superimposing the images by an amount of deviation determined according to the cross section of the object, and creating a tomographic image of an arbitrary cross section of the object. A tomography device that uses (2) A cross section according to claim (1), wherein the radiation generation point and the radiation detector each move in substantially parallel planes, and the orientation of the detector is kept unchanged during the movement. Photography equipment. (3) The tomography apparatus according to claim (1), wherein the radiation detector has a detection portion formed in a substantially two-dimensional planar shape.

Claims (3)

[Claims] (1) A radiation generator and a radiation detector that move in a predetermined manner while maintaining a parallel state with respect to a fixed origin relative to the subject, and emit radiation at multiple positions during the movement of both devices. a transmission image acquisition means for acquiring and storing a plurality of radiographic images of the subject obtained by the exposure; 1. A tomographic imaging apparatus, comprising a tomographic image creating means for creating a tomographic image of a cross section of the subject by shifting the images by a predetermined amount of deviation and superimposing the images, and creating a tomographic image of an arbitrary cross section of the subject. (2) The radiation generator and the radiation detector perform any one of circular motion, circular arc motion, and rectangular raster motion while maintaining a relative phase angle or distance. The tomography apparatus according to item (1). (3) The tomography apparatus according to claim (1), wherein the radiation detector is formed in a two-dimensional planar shape.