JPH06242026A - X-ray tomographic method and system - Google Patents

Abstract

PURPOSE:To obtain a tomographic image only of a specified substance by substantially eliminating various complicated image processings for extracting an image of specified substance from a tomographic image containing a plurality of types of substance image. CONSTITUTION:An objective member containing a plurality (n) of types of object made of known materials is irradiated with (n) types of characteristic X-ray individually to obtain (n) types of transmission intensity data. (n) simultaneous equations representative of relationship between irradiation intensity and transmission intensity are then solved to obtain the transmission distance of a required object and then a tomographic image of the required object is configured again based on the transmission distance data. This method simplifies data processing and enhances processing speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a specific structure of an object (hereinafter referred to as a measurement object or an object) containing a plurality of kinds of objects (hereinafter referred to as constituent materials) whose material is known and whose shape and distribution are unknown. The present invention relates to position detection of a material (hereinafter referred to as a target material), and particularly to formation of a cross-sectional image of the target material by X-ray CT.

[0002]

2. Description of the Related Art This type of technology is described, for example, in "Measurement and Control", June 1978 issue (Vol.17, No.6), Nos. 451-459.
Kazumi Murata and Naoshi Baba explain in “Image Reproduction from Projection” on page. Using this kind of technology, conventionally, X-rays suitable for see-through of the target material are irradiated,
While the X-ray is scanned around the object by the rotational drive of the X-ray source or the rotational drive of the object or the linear drive of the X-ray source or the object, the X-ray sensor corresponds to the scanning position and the X-ray sensor The detected transmitted X-ray intensity is written in the memory, and when one rotation scanning or one linear drive in each of the x and y directions is completed, a cross-sectional image (tomographic image) of the object is obtained based on the transmitted X-ray intensity data of the memory. Is generated (generally called reconstruction). Then, image processing technology is used to separate or clarify the target material image in the tomographic image.

[0003]

In the separation or clarification of the target material image from the tomographic image (image) by the image processing technique, the calculation is complicated and the processing time is long. In particular, when separating multiple types of target material images from the same tomographic image, various sophisticated and complex image processing techniques must be used for accurate separation, and each target material image is separated from the tomographic image. Processing time is extremely long.

An object of the present invention is to simplify the separation of each target material image.

[0005]

According to the X-ray tomography method of the present invention, A. The transmission intensity of the i-th type characteristic X-ray in the direction along the surface of the virtually same cross section of the measurement target material is measured at a plurality of points, and the transmission intensity I _ip is stored in the i-th memory means at the measurement position p. ,
i = 1, ..., N, n is an integer of 2 or more; B. I-type characteristic X-ray absorption coefficient μ _ji of the substance of material m _j ,
The relationship between the irradiation X-ray intensity I _oi , the transmission intensity I _ip and the X-ray transmission distance χ _jp I _ip = I _oi exp (−Σ _j (μ _ji · χ _jp )) j = 1, ... An integer less than or equal to n, Σ _j , j = 1
From j = sigma up to m, X-ray transmission distance required material m _j based on the _{χ jp = -Σ i (ν ji} · ln (I ip / I oi)) Σ i from i = 1 i = sigma up to n, ν _ji is μ _ji
C., and C. Based on the obtained X-ray transmission distance χ _jp , a cross-sectional image of the required material m _{j in} the cross section is formed.

[0006]

The X-ray absorption coefficient μ differs depending on the substance, and this absorption coefficient μ also differs depending on the X-ray quality (type of characteristic X-ray). An example of this number is shown in FIG. Therefore, the material m _j (j = 1, ..., m) is provided between the i-th type characteristic X-ray source and the X-ray sensor.
Is placed, the transmission intensity in the direction along the surface of the virtually same cross section of the measurement target material is measured at a plurality of points, and the transmission intensity I _ip is stored in the i-th memory means at the measurement position p. , I = 1, ... N, n is an integer of 2 or more, j = 1, ... M, m is an integer of n or less, μ _ji : Characteristic X-ray absorption of the i-th kind of the substance of material m _j factor, I _oi: X-ray intensity, I _ip: transmission intensity, chi _uk: X-ray transmission distance material m _j (material m _j, the measurement position p
In the case of characteristic X-rays, when one kind of characteristic X-rays is irradiated to one substance, I _p = I _o exp (−μ) between the irradiation X-ray intensity I _o and the transmission intensity I _p. · χ _p) ··· (1) since there is a relationship, n species of characteristic X-ray i (i = 1, ··
・ Individually, i = n), and m kinds of substances m _j (j = 1, ...
(j = m) When a series of substances is irradiated, I _ip = I _oi exp (−Σμ _ji · χ _jp ) (2) However, Σ is a sigma from j = 1 to j = m.

From this, the thickness χ _jp of the substance m _j at the measurement position p is obtained as χ _jp = -Σ [ν _ip · ln (I _ip / I _oi )] (3). However, Σ is a sigma from i = 1 to i = n, and ν _ji is an inverse matrix of μ _ji .

For example, i = 1, 2, and 3, j = 1, 2.
And 3, that is, the characteristic X-ray of the first type (i =
1), characteristic X-rays of the second kind (i = 2) and characteristic X-rays of the third kind (i = 3) individually and in this order, the substance m of the first kind m
_When a series of ₁ (j = 1), the second type substance m ₂ (j = 2) and the third type substance m ₃ (j = 3) is irradiated, the equation (2) is expressed as I _1p = I _o1 exp [-(Μ ₁₁・ χ _1p ＋ μ ₂₁・ χ _2p ＋ μ ₃₁・ χ _3p ) ・ ・ ・ (2-1) I _2p ＝ I _o2 exp 〔－ (μ ₁₂・ χ _1p ＋ μ ₂₂・ χ _2p ＋ μ ₃₂・ χ _3p ) ・ ・ ・ (2-2) I _3p = I _o3 exp [− (μ ₁₃ · χ _1p + μ ₂₃ · χ _2p + μ ₃₃ · χ _3p ) ・ ・ ・ (2-3) If the type is known and there are m types,
Since the irradiation intensity I _o and the absorption coefficient μ _ji are known, m
By sequentially irradiating the characteristic X-rays i or more of the species and detecting the transmission intensity I _ip , the equation (2) is solved, that is, the equation (3) is used to calculate the transmission distance (thickness) χ _jp of each of the m types of substances. sell.

According to the present invention, n-type (n ≧ m) characteristic X-rays are individually radiated to the material to be measured, which is a known type and consists of m-type substances, to detect the transmission intensity I _ip. , The detection data I _ip is stored in the memory means, and the transmission distance χ _jp of the required material m _j is calculated according to the equation (3), and a tomographic image is formed based on the transmission distance χ _jp . This tomographic image shows only a sectional image of the required material m _j . Therefore, the extraction process of the specific image by the image processing technique, which is conventionally required, can be omitted.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the outline of the configuration of an embodiment of the present invention. On the gantry 1 that supports the object 6, a double-opening chuck mechanism (not shown) for holding each of the ends of the object and a chuck center rotation axis (horizontal axis; immovable) are driven to rotate. The rotary mechanism (not shown) is provided, and a rotary encoder (not shown) is coupled to the rotary mechanism. The electric motor of the rotating mechanism is rotationally energized by the driver 7, and the rotation synchronizing pulse generated by the rotary encoder is given to the controller 8. The X-ray source 2 and the X-ray sensor 3 are located on a vertical axis orthogonal to the chuck central axis, and the X-ray source 2 is located above the chuck central axis.
The X-ray sensor 3 is on the lower side. The X-ray source 2 and the X-ray sensor 3 are supported by a vertical base (not shown). A filter scanner 4 is fixed to the vertical base. The filter scanner 4 is equipped with three filters 5a, 5b, 5c and is equipped with a filter positioning mechanism (not shown). The three filters are integrally connected so that they can be simultaneously moved by the positioning mechanism. Driven in the direction, one filter is always positioned in the X-ray path between the X-ray source 2 and the X-ray sensor 3. The electric motor of the filter positioning mechanism is the driver 1
It is driven in the forward and reverse directions at 3. The positioning mechanism has a plurality of switches for detecting a filter (filter number) in the X-ray path between the X-ray source 2 and the X-ray sensor 3.
The open / close signals of these switches are given to the controller 14.

The X-ray sensor 3 includes a fluorescent plate for converting X-rays into light and a line image for converting the brightness of the fluorescent light into an electric signal.
Including CCD sensor (line CCD), CCD driver 11
Supplies the electric signal of the image sensor to the signal processing circuit 12. The signal processing circuit 12 converts the electric signal representing the brightness of the fluorescent light into digital data, stores the data for one line in a buffer memory, and transfers the data to the CT processing device 15 line by line.

The controller 10 sets the filament current and the positive / negative voltage of the X-ray tube. These values are
C corresponding to the filter (one of 5a, 5b and 5c) for positioning in the X-ray path between the X-ray source 2 and the X-ray sensor 3
The T processor 15 supplies the controller 10.

The CT processing device 15 includes an input / read of the operation / display board 15a, a process corresponding to the input, a controller 8,
A system control computer unit centered on the CPU 1, which outputs commands to the signals 10 and 14 and the signal processing circuit 12 and controls the system in the device 15, CPU
In response to the command 1, the reading and writing of data to the memory and the calculation of the transmission distance based on the memory data are performed.
An arithmetic processing computer unit centered on the CPU 2,
In addition, in response to a command from the CPU 1, generation of tomographic image information based on transmission distance data on the memory, storage in the memory, display of the tomographic image on the color CRT 15b, printout of the tomographic image, etc. are performed. , An image processing computer unit centered on the CPU 3. The device 15
Is equipped with a floppy disk device, and transfer of tomographic image data from the tomographic image memory to the floppy disk device, CRT 15b or printer 15c is performed by C
The CPU 3 performs the command in response to the instruction from the PU 1.

2 and 3 show the CT processing control operation of the CPU 1 related to the implementation of the present invention. In the standby state in which the tomographic image generation process of the object can be executed, the CPU 1 waits for the input operation of the operation / display board 15a (step 1 in FIG. 2; hereinafter, the term step in parentheses). Is omitted and only the step number is shown). Here, the operator can specify any of the filters A, B and C. When the operator designates "filter A" on the operation / display board 15a, the CPU 1 causes the filter A
The controller 14 is instructed to set (5a in FIG. 1).
The controller 14 positions the filter 5a in the X-ray path between the X-ray source 2 and the X-ray sensor 3 (2). When the controller 14 sends information indicating the end of positioning, C
PU1 waits for data input or start input (3). If there is data input, the corresponding processing is performed. For example, when the X-ray tube applied voltage and current are input, the data of the registers assigned to them are rewritten to the input data. The planned data is, in addition, data that specifies the level at which the CCD electric signal is converted into digital data.
Data, target object rotation speed (instruction value), calculation formula specification data,
There are calculation coefficient data and the like.

When the operator gives an instruction to start the operation / display board 15a, the CPU 1 transfers the X-ray tube applied voltage and current value to the controller 10 and gives an instruction for the X-ray irradiation to control the controller. The rotation speed data is given to the rotor 8 to instruct the rotation, and the signal processing circuit 12 receives the parameters related to the signal processing.
When data is given to instruct CCD reading, and the rotary encoder of the rotating mechanism that rotationally drives the chuck mechanism generates a base point pulse (start point for counting 360 degrees), rotation angle counting (rotation synchronization) is performed. Pulse count-up), and every time a predetermined number of rotation synchronization pulses are generated,
The CPU 2 is instructed to read the data. The CPU 2 transfers the data I _1p for one line transferred from the signal processing circuit 12 to the memory area A1 assigned to the filter 5a.
Address corresponding to the rotation angle (line address: rotation angle)
Write in (4). The position of each data on one line is the position of the transmission X-ray in the horizontal direction (line CCD line direction).

When the rotary encoder of the rotating mechanism regenerates the base point pulse (when the rotation of 360 degrees is completed), C
The PU 1 instructs the controller 10 to stop the X-ray irradiation, the controller 8 to stop the rotation drive, the controller signal processing circuit 12 to stop the reading, and the CPU 2 to stop the data reading. To do. Then, it waits for the next instruction from the operation / display board 15a (5, 6).

Here, the operator can specify either of filters B and C. When the operator designates "filter B" on the operation / display board 15a, the CPU 1
Sets the filter B (5b in FIG. 1) to the controller 1
Command 4 The controller 14 sets the filter 5b to X
The X-ray path between the radiation source 2 and the X-ray sensor 3 is positioned (7). When the controller 14 sends the information indicating the end of positioning, the CPU 1 waits for the data input or the start input (8). If there is data input, the corresponding processing is performed.

When the operator gives an instruction to start the operation / display board 15a, the CPU 1 transfers the X-ray tube applied voltage and current values to the controller 10 and gives an instruction to the X-ray irradiation to make a control. The rotation speed data is given to the rotor 8 to instruct the rotation, and the signal processing circuit 12 receives the parameters related to the signal processing.
When data is given to instruct CCD reading, and the rotary encoder of the rotating mechanism that rotationally drives the chuck mechanism generates a base point pulse, rotation angle counting is started,
Every time a predetermined number of rotation synchronizing pulses are generated, the CPU 2 is instructed to read the data. The CPU 2 writes the data I _2p for one line transferred by the signal processing circuit 12 into the memory area B1 assigned to the filter 5b at the address corresponding to the rotation angle (9). The position of each data on one line is the horizontal position of the transmitted X-ray.

When the rotary encoder of the rotating mechanism regenerates the base point pulse, the CPU 1 causes the controller 10 to generate an X signal.
Instructing the controller 8 to stop the line irradiation, the controller 8 to stop the rotation drive, and the controller signal processing circuit 12 to stop the reading.
PU2 is instructed to stop reading data. Then, it waits for the next instruction from the operation / display board 15a (1
0, 11).

Here, the operator can instruct any of the designation of the filter C, the tomographic image A generation instruction, the tomographic image B generation instruction, and the composite tomographic image generation instruction. When the operator inputs the "composite tomographic image generation instruction", the CPU 1 checks the type of imaging up to this point and has already executed the transmission imaging through the filter A and the transmission imaging through the filter B up to this point. Therefore, the CPU 1 instructs the CPU 2 to calculate the transmission distances χ _1p and χ _2p of the two substances m ₁ (j = 1) and m ₂ (j = 2) by the two kinds of filters A and B. The CPU 2 receives the transmission intensity data of the memory area A1.
Based on I _1p and I _2p and other known quantities, χ _jp = −Σ [ν _ip · ln (I _ip / I _oi )] (3-2) However, both i and j are filters A And two types corresponding to B (i, j = 1 and i, j = 2, Σ is i = 1 to i = 2).
Ν _ji is the inverse matrix of μ _ji , and the transmission distances χ _1p and χ _2p are calculated and stored in memory areas A2 and B2, respectively (12). In this case, C
PU2 is transmitted based on the relation of I _1p = I _o1 exp [-(μ ₁₁ · χ _1p + μ ₂₁ · χ _2p ) I _2p = I _{o 2} exp [-(μ ₁₂ · χ _1p + μ ₂₂ · χ _2p ). The distances χ _1p and χ _2p will be calculated.

When the CPU 2 notifies the end of this calculation, the CPU 1 informs the CPU 3 of the tomographic image A based on the transmission distance data of the memory area A2 and the tomographic image based on the transmission distance data of the memory area B2. The generation of the image B and the synthesis of the tomographic images A and B are instructed. The CPU 3 generates a tomographic image A (image data) by the back projection method, which is a known reconstruction method in this embodiment, writes the tomographic image A in the memory A3, and then the tomographic image B.
Is generated and written in the memory B3 (13), and the tomographic image A is used as the R (red) component, and the tomographic image B is G (green).
The tomographic images A and B are combined as components, and the combined image data is written in the memory area α (14). Next, the CPU 3 gives a composite image (image data in the memory area .alpha.) To the color display, displays it on the color CRT 15b, and notifies the CPU 1 of the end of the composition (15). Upon receiving this notification, the CPU 1 waits for an instruction to be input to the operation / display board 15a (16). Here, the operator can input printout, image registration, and end. When the operator inputs "end", the CPU 1 returns to "input reading" (1) shown in FIG. When "print out" is input, the CPU 1 prints the image data in the memory area .alpha.
Transfer to c and instruct to print out. When "Tomographic image registration" is input, the CPU 1 instructs the floppy disk device to register the image data in the memory area .alpha. On the floppy disk.

In the above-mentioned operation routine, if the operator inputs a "tomographic image A generation instruction" in "input reading" in step 11 of FIG. 2, in step 12 (FIG. 3) described above. Calculates only the transmission distance χ _1p ,
Only the tomographic image A is generated in step 13, the step 14 is skipped (not executed), and only the tomographic image A is output in step 15. If the operator inputs a "tomographic image B generation instruction" in "input reading" in step 11 of FIG. 2, only the transmission distance χ _2p is calculated and only the tomographic image B is output.

Further, if the operator designates the filter C in the step "input reading" of FIG. 2, the CPU 1 similarly executes the same processing as that of steps 7 to 10 with respect to the filter C. As a result, the transmission intensity I _3p through the filter C is stored in the memory area C1. Then, when this is finished, "input reading" corresponding to step 11
Then, the operator can designate and input a tomographic image A generation instruction, a tomographic image B generation instruction, a tomographic image C generation instruction, and a composite tomographic image generation instruction. When the synthetic tomographic image generation instruction is input, the tomographic image A is the R (red) component and the tomographic image B is the G component.
A composite image of the tomographic images A, B and C having the (green) component and the tomographic image C as the B (blu-) component is written in the memory area α and color-displayed on the CRT 15b. In this case, χ _jp = −Σ [ν _ip · ln (I _ip / I _oi )] (3-3) However, both i and j correspond to filters A, B, and C.
Is a species (i, j = 1, i, j = 2 and i, j = 3), Σ is a sigma from i = 1 to i = 3, and ν _ji is μ _ji
Then, the transmission distances χ _1p , χ _2p and χ _3p are calculated by the inverse matrix of, and stored in the memory areas A2, B2 and C2, respectively. In this case, the CPU 2 will calculate the transmission distances χ _1p , χ _2p and χ _3p based on the relationships expressed by the equations (2-1) to (2-3).

[0025]

As described above, according to the present invention, a plurality of types of characteristic X-rays are irradiated, and the transmission distance of at least one substance of a plurality of different substances to be measured is calculated based on their transmission intensities. However, since the tomographic image of the substance is generated based on the transmission distance, various complicated image processing for extracting the image of the specific substance from the tomographic image including the image of the different substance is substantially omitted, and the corresponding amount of data is reduced. -The processing becomes simple and the processing speed is improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of one device for carrying out the present invention, and a part thereof is a block diagram.

FIG. 2 is a flowchart showing a part of the outline of the system control operation of the CPU 1 shown in FIG.

3 is a flowchart showing a part of the outline of the system control operation of the CPU 1 shown in FIG.

FIG. 4 is a graph showing the relationship between the quality of X-rays irradiated on an object (horizontal axis) and the X-ray absorption coefficient of the object (vertical axis).

[Explanation of symbols]

1: Frame 2: X-ray source 3: X-ray sensor 4: Filter scanner 5a, 5b, 5c: Filter 6: Object to be measured 15: CT processing device 15a: Operation
Display board 15b: Color CRT 15c: Printer CPU 1-3: Microprocessor

Claims (3)

[Claims] 1. An X-ray tomography method comprising the steps of: A. The transmission intensity of the i-th type characteristic X-ray in the direction along the surface of the virtually same cross section of the measurement target material is measured at a plurality of points, and the transmission intensity I _ip is stored in the i-th memory means at the measurement position p. ，
i = 1, ..., N, n is an integer of 2 or more; B. I-type characteristic X-ray absorption coefficient μ _ji of the substance of material m _j ,
The relationship between the irradiation X-ray intensity I _oi , the transmission intensity I _ip and the X-ray transmission distance χ _jp I _ip = I _oi exp (−Σ _j (μ _ji · χ _jp )) j = 1, ... An integer less than or equal to n, Σ _j , j = 1
From j = sigma up to m, X-ray transmission distance required material m _j based on the _{χ jp = -Σ i (ν ji} · ln (I ip / I oi)) Σ i from i = 1 i = sigma up to n, ν _ji is μ _ji
C., and C. Based on the obtained X-ray transmission distance χ _jp , a cross-sectional image of the required material m _{j in} the cross section is formed. 2. An X-ray source; an X-ray sensor facing the X-ray source and converting the X-ray intensity into an electric signal level; X generated by the X-ray source.
A plurality of filters i, i = 1, ... Which substantially transmit the i-th characteristic X-ray of the line and substantially block other characteristic X-rays.
n and n are integers of 2 or more; filter selecting means for selectively setting the designated filter i on the X-ray path from the X-ray source to the X-ray sensor; on the X-ray path between the filter and the X-ray sensor. Supporting means for supporting the measurement target material to be placed; X-ray irradiation / detection system composed of an X-ray source, a filter and an X-ray sensor, and means for scanning and driving at least one of the measurement target materials relative to the other; A transmission intensity I _ip detected by the X-ray sensor when an X-ray is emitted by setting a filter i in the X-ray path from the X-ray source to the X-ray sensor is stored in the memory corresponding to the scanning position p by the scanning driving means. Data collecting means to be written in the means i; Correlation of the characteristic X-ray absorption coefficient μ _ji of the substance of the material m _j of the i-th type, the irradiation X-ray intensity I _oi , the transmission intensity I _ip and the X-ray transmission distance χ _jp X-ray transmission distance required material m _j based on the relationship _{χ jp = -Σ i (ν ji} · ln _{I ip / I oi)) Σ} i Sigma from i = 1 to i = n, [nu _ji is mu _ji
The inverse matrix of is calculated and written in the memory means j corresponding to the scanning position p, j = 1, ..., m, m is an integer of n or less; based on the X-ray transmission distance χ _jp of the memory means j. And an image forming means for forming a sectional image of the material m _j ; and a means for outputting the sectional image. 3. The image forming means forms a cross-sectional image of each material m _j based on the X-ray transmission distance χ _jp of each of the plurality of memory means j, and forms a cross-sectional image by combining these. Item 2. The X-ray tomography apparatus according to Item 2.