JPH0229329B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention provides information on arbitrary curved tomographic trajectories.
It relates to a device that displays images as dimensional plane images, and is mainly used for dental diagnosis by photographing the dental arches of the human body.In addition, it is also used for measuring the degree of wear of automobile tires, tomography of trees, fatigue testing of metals, etc. , which provides equipment that can be applied to various types of industrial CT.

<Prior Art> A curved tomography apparatus using film reception that directly utilizes the photographic effect of X-rays has been known to achieve a similar purpose to that of the present invention. In this device, an X-ray source and a film, which are placed opposite to each other with the subject in between, are moved relative to each other at a fixed ratio, and the X-rays that pass through the subject are received on the film surface to obtain an X-ray photographic image. It has been put into practical use as a dental panoramic X-ray imaging device.

However, this type of equipment uses film that requires X-ray photographic action, that is, a long reaction time and strong X-ray energy, so the amount of X-rays that the subject is exposed to in one imaging session is considerable. This is not very desirable when the subject is a human body, such as in a panoramic X-ray imaging device. In addition, density unevenness is likely to occur in the resulting X-ray photographic images, and in order to obtain clear images, not only must the X-ray intensity and exposure time be appropriately controlled, but also the time and effort required to develop the film is required. However, there are problems such as not being able to know the actual results, and furthermore, problems during film development may result in unnecessary shooting. Furthermore, since a film feeding means is required in addition to moving the X-ray source, the apparatus itself tends to become larger and more complicated.

In order to solve these problems, devices have been proposed that convert transmitted X-ray images into electrical video signals and process them instead of taking photographs using film (for example, 157086, JP-A-57-25837, US Pat. No. 4,239,971, etc.).

<Problems to be Solved by the Invention> However, in the above-mentioned apparatus that electrically processes images of transmitted X-rays, images of objects other than the object that overlap in the depth direction are removed, and images on the target tomographic trajectory are removed. There are many points that lack practicality, such as not being able to detect just the image, or requiring special sweeping means or a display screen.

This invention focuses on such problems and
The purpose of this invention is to provide an apparatus that electrically processes a line image to obtain an image on a target tomographic trajectory as a clear two-dimensional plane image.

<Means for Solving the Problems> In order to achieve the above object, this invention has the following features:
Equipped with an X-ray source and an X-ray image sensor that convert and output the transmitted X-rays as X-ray image information, which are placed facing each other with the subject in between, these X-ray sources and the X-ray image sensor are integrally driven around the subject. A pivoting arm is provided for pivoting. Each time this swing arm turns by a predetermined minute angle, the X-ray image information output from the X-ray image sensor is taken into the calculation memory of the logical operation circuit, and this taken-in X-ray image information is X-rays on a desired tomographic trajectory are added by sequentially shifting and adding the addresses of positions where the same image information on the tomographic trajectory overlaps in the memory multiple times in accordance with the acquisition interval of the X-ray image information. A two-dimensional plane image in which only the image information is emphasized is formed, and the two-dimensional plane composite image thus obtained is displayed on a television monitor.

<Function> The X-ray image information output from the X-ray image sensor includes not only images on the target tomographic trajectory but also images other than the target object that overlap in the depth direction. However, the X-ray image information is transferred multiple times by sequentially shifting the X-ray image information at intervals corresponding to the acquisition interval of the X-ray image information so that the same image information on the desired tomographic trajectory overlaps in the memory. When added across, information on images that are not on the desired tomographic trajectory will not be overlapped in this addition process because the acquisition interval and shift interval in the memory do not correspond, and the X-ray images on the desired tomographic trajectory will not be overlapped. Only the information is emphasized through addition, and a clear two-dimensional plane composite image is obtained.

Next, the principle of obtaining X-ray image information on a desired tomographic trajectory using the above processing procedure will be explained with reference to FIGS. 4 and 5.

In the figure, A is the desired fault trajectory, a, b, c...
is the information on the orbit, B is the orbit of the image other than the target object, A, B, C... is the information on the orbit, C ₁ and
X ₁ is the X-ray image information detected by the X-ray image sensor at a certain turning position and the X-ray beam at that time, C ₂ and X ₂ are the X-ray image information when the arm turns by a predetermined minute angle θ ₁₂ The X-ray beam at that time is shown, and the X-ray image information C ₁ and C ₂ include information on orbits A and B, respectively, as shown. Please note that the figure is a schematic drawing.
In each row of X-ray image information _C1 and _C2 , the information is shown side by side as C and B, but in reality, these pieces of information are detected and stored in an overlapping state in which they cannot be distinguished. (same as below).

Fig. 5a shows the case where the X-ray image information _C1 and _C2 are added as they are, and the information on each orbit is added one unit at a time at the same level. However, as shown in figure b, if the information in each stage of the X-ray image information C ₁ is shifted to the lower address one step at a time to become C ₁ ', and then the X-ray image information C ₂ is added to this, the information in figure c is Thus, information a, b, c, etc. are added to become two units of information, whereas information a, b, c, etc. are not added and each remains one unit of information. Therefore, if this process is repeated multiple times, only the information a, b, c... on the desired fault trajectory A will be added one after another,
The level difference between information A, B, C, etc. is gradually expanded, and the S/N ratio is improved, so that image information on the desired tomographic trajectory A can be obtained in a clear state.

<Example> The illustrated example will be described below. FIG. 1 is a block diagram of an embodiment of the present invention in a dental panoramic X-ray imaging apparatus, and FIGS. 2 and 3 are operation explanatory diagrams.

[Schematic configuration of the device]

In the figure, reference numeral 1 denotes a rotating arm in which an X-ray head 110 equipped with an X-ray source 11 and an X-ray image sensor 12 are disposed facing each other, and is driven and rotated around a subject P as a unit. This arm 1 is driven by an arm drive motor 21 connected to the main shaft of the arm, and this drive motor 21 operates upon receiving a command signal from an arm drive controller 22.

23 is a means for detecting the rotational angle (rotational position) of the arm 1, and is realized by a photo encoder, a pulse counter for a pulse motor, etc., and this output is sent to the memory controller 34 of the logic operation circuit 3 and the X-ray head. It is sent to the shutter controller 13 at 110.

The X-ray head 110 is connected to the high-pressure generator 14 and is equipped with a shutter mechanism in the X-ray irradiation window.The shutter 15 is opened and closed in response to command signals from the shutter controller 13, and directs X-rays toward the subject P intermittently. It is configured to irradiate the target. 17
is a slit attached to the front of the shutter mechanism to narrow the X-ray flux by defining the field of X-rays emitted from the X-ray head, and at the same time to prevent unnecessary X-ray exposure and reduce the exposure dose. be.

The X-ray image sensor 12 detects the X-rays that have passed through the subject P, converts the image information from the X-rays into a video signal, and outputs it, and is typically a combination of an X-ray brightness multiplier tube and a television camera. However, any device that amplifies detected X-rays and converts them into electrical signals as X-ray image information may be used, and other devices such as an X-ray CCD may also be used. 16 is a second slit for avoiding the influence of scattering of transmitted X-rays.

Reference numerals 2A and 2B indicate control means for controlling the rotational drive of the rotating arm 1 and the irradiation of the X-ray source 11 so as to maintain a constant relationship.

The logic operation circuit 3 digitally encodes the video signal output from the X-ray image sensor 12 as density information with gradations for each pixel, and digitally processes this encoded image information. The processing necessary to reproduce the image is performed within this circuit. This arithmetic circuit 3 is an A/D conversion circuit 3
1. Arithmetic memory 32 with addition shift and division functions, frame memory 33, memory controller 34,
It is composed of a D/A conversion circuit 36 and the like.

The A/D conversion circuit 31 connects the X-ray image sensor 1
The video signal output from 2 is sampled and held for each pixel and code-converted into a digital signal with gradation.

In addition, the frame memory 33 stores information about the TV monitor 4.
It stores image information to be displayed on the CRT 41, and two types of frame memories are selected by a known switching means (not shown). Of these, the first memory has information stored in one-to-one correspondence with the image information displayed on the monitor 4 in units of one frame, and the second memory stores information stored in the memory. monitor 4
It is designed to store more information than the one-frame image information displayed above, and is used when displaying a flow video, which will be described later. The image information stored in each of these memories is reproduced as a video signal by the D/A conversion circuit 36,
It is displayed panoramicly on a CRT 41 as an X-ray tomographic image 42 of all the teeth along the dental arch.

The logic operation circuit 3 converts the digital code signal outputted from the A/D conversion circuit 31 under the control of the memory controller 34 to the arm rotation angle detector 2.
By importing this digital code signal into the calculation memory 32 at time intervals synchronized with the arm rotation angle (rotational position) detection signal from 3, and adding this digital code signal while sequentially shifting it to another address at an interval corresponding to the import time interval, The emphasized X-ray image information on the desired tomographic trajectory is synthesized and reproduced. And this X
After the line image information is divided for each raster unit,
The image is subjected to XY conversion and sent to the frame memory 33 for storage.

[Information processing means]

Next, the processing procedure will be explained in more detail.

First, by the cooperation of the control means 2A and 2B and the arm rotation angle detector 23, the shutter is activated every time the swing arm 1 turns by a predetermined minute angle and reaches a predetermined rotation position (hereinafter referred to as a check point). 15 is opened, and the X-rays from the X-ray source 11 are focused on the irradiation field through the first slit and directed toward the subject P.
is irradiated towards. The X-rays transmitted through the subject P are detected by the X-ray image sensor 12 via the second slit 16 as X-ray image information modulated by the difference in absorption capacity of the internal tissues of the subject P, and converted into a video signal. After being output, it is converted into digital code by the A/D conversion circuit 31 and stored in the calculation memory 32.
taken within. This operation is performed every time the rotating arm 1 rotates by a predetermined minute angle and reaches the next check point, and the X-ray image information transmitted through the subject P is detected one after another by the X-ray image sensor 12. The image information is processed by the arithmetic circuit 3 and information on the desired tomographic trajectory is reproduced.

Note that instead of opening and closing the shutter 15 for each checkpoint to irradiate X-rays intermittently as described above, it is possible to capture the video signal output from the X-ray image sensor 12 for each checkpoint while continuously irradiating the X-rays. It can also be done.

Here, the X-ray image information detected by the X-ray image sensor 12 includes not only images on the target tomographic trajectory but also objects other than objects that overlap along the depth direction (X-ray irradiation direction). images are also included at the same time, and the positions where these images are incident on the X-ray image sensor 12 move little by little in response to the small angle of rotation of the rotating arm 1.

In conventional film-type devices, the desired curved tomographic trajectory plane to be imaged depends on the relative relationship between the moving speed of the X-ray source rotating around the subject and the feeding speed of the film that receives the transmitted X-rays. However, in this example, for the rotational speed of the arm,
The tomographic trajectory plane to be imaged is set by adjusting the transfer distance for shifting information in the memory (interval of data transfer or data acquisition time in the calculation memory 32, etc.). This setting can be easily performed using a microcomputer.

FIGS. 2 and 3 are explanatory diagrams of this moving situation. Reference numeral 120 in the figure indicates the primary fluorescent screen of the X-ray brightness intensifier tube that constitutes the X-ray image sensor 12.
The fluorescent screen 12 is arranged so that the scanning line is sequentially scanned from left to right from bottom to top perpendicular to the plane of rotation of the arm.
0 is arranged so that the transmitted X-rays are irradiated onto the m-th to n-th scanning lines corresponding to the width of the slit 16.

Therefore, when the memory controller 34 detects the first (m-1) horizontal synchronization signal after the swing arm 1 reaches a certain check point, it converts the image information on the m-th to n-th scanning lines from A/D. The circuit 31 digitally encodes the data and stores it in an arithmetic memory 32 at addresses corresponding to predetermined scanning lines. At this time, each scanning line carries, for example, information g, h, i, . . . as shown in FIG.

Figure 3 shows the state when the next check point is reached, and at this time each piece of information g, h, i... is at the position moved by α lines measured in scanning line units according to the rotation angle of the rotation arm 1. For example, information g is transferred to the m+αth scanning line.
It is moving onto m′. Therefore, each piece of information g, h, i... stored in the calculation memory 32 at the time of FIG.
correspond to the movement amount α measured in units of scanning lines on the X-ray image sensor 12, and the m'-th, m'+1-th, and
If you move it to the address corresponding to m'+2nd... scanning line, the next information g will be added to the first information g, and the same information will be added to h, i... It is. Note that this amount of movement is not the same in the case of a dental panoramic X-ray imaging device, but is changed between the anterior and molar regions in the same way as changing the film feeding speed in a film-type device. An image that matches the shape of the bow can be obtained.

When the state shown in FIG. 3 is reached, the arm drive controller 22 sends a shutter open signal to the shutter controller 13 and at the same time sends a strobe signal to the memory controller 34 to control reading, addition, writing, etc. I do. At this time, as in the previous writing, the signal on the m+αth scanning line m′ is added to the information at the address corresponding to the m+αth scanning line in the calculation memory 32, and then the added data is the same again. It is written to the address. Third
In the figure, information g is superimposed on the m+αth scanning line m', and the address in the arithmetic memory 32 corresponding to this scanning line m' is on the mth scanning line m in FIG. Since the information g has already been shifted and written, the information g will be emphasized.

Such data addition and rewriting processing is performed by separating the horizontal synchronization signal from the video output signal of the X-ray image sensor 12 and addressing the vertical address counter with this horizontal synchronization signal. This is possible by finding the line, sequentially adding the information on this scanning line and the information at the m-th address of the calculation memory 32, and sequentially writing the sum to the m-th address of the calculation memory 32. .

Until the memory controller 34 detects the n-th horizontal synchronization signal in this way, the memory controller 34 writes to the address of the calculation memory 32 corresponding to the position on the scanning line,
When the n-th horizontal synchronization signal is detected, it stops outputting the address signal of the calculation memory 32, and at the same time sends a close operation command signal to the shutter controller 13, and starts X-ray radiation. stop. When the shutter 15 is closed and the arm 1 is rotating, information is moved in the calculation memory 32 in order to extract only image information on a preset tomographic trajectory.

Here, the information on the addresses corresponding to the n-αth to nth scanning lines is displayed appropriately on the monitor 4 after division corresponding to the number of additions because there is no address to move within the calculation memory 32. The addresses are subjected to XY conversion and transferred to the frame memory 33 in order to compose an image. The information corresponding to the n-αth to nth scanning lines is written into the frame memory 33 at the address output from the memory controller 34, but the address at this time is on each raster on the monitor 4. It is defined corresponding to the pixel. The writing and reading addresses of the frame memory 33 are output from different controllers (not shown), and images are synthesized.

In this way, by matching the change α in the position of the information on the tomographic trajectory on the primary photosensitive surface of the X-ray image sensor 12 due to the rotation of the arm with the amount of movement within the calculation memory 32, the desired tomographic Information on the orbit is recorded in the memory in an emphasized form, but other information is stored in a manner that corresponds to the movement of the X-ray image sensor 12 on the primary photosensitive surface and the movement of data within the calculation memory 32. Because it is not calculated, it becomes the sum of different data, and it becomes saturated, or even if it is not saturated, it loses its characteristics.

These series of operations are performed in response to a command signal from the memory controller 34 when the shutter 15 is closed and the arm 1 is rotating, and this process continues until the swing arm 1 finishes rotating within a predetermined range necessary for photographing. is repeated. Then, the data after the addition is divided and averaged in accordance with the number of additions, and then XY converted and sequentially recorded in the frame memory 33. The image information thus recorded in the frame memory 33 is read out sequentially in synchronization with raster scanning in response to the output signal of the synchronization signal generation circuit 35, and is reproduced as a video signal via the D/A conversion circuit 36.
The information is displayed on the monitor 4 as bright spot information corresponding to each pixel of the CRT 41.

In this way, in the logic operation circuit 3, the memory is divided into two groups, one of which is dedicated to calculations, so that the capacity of the frame memory is reduced. Furthermore, the circuit configuration can be simplified by performing division in the arithmetic memory by transferring information with lower bits discarded.

The above is an explanation of the case where the first frame memory 33 having an address corresponding to one frame unit on the monitor 4 is used. If you use the second frame memory 33' which has a frame in the horizontal direction and specify the address so that the starting point of the read address in the horizontal direction of this memory is shifted little by little each time one frame is read out, the monitor 4, rows of teeth are displayed one after another, flowing from right to left, for example. And if you use this method,
Since the tomographic photograph of the dentition is horizontally elongated compared to the screen of the monitor 4, the screen of the monitor 4 can be used efficiently and the details can be observed in detail. Furthermore, in this case, since the subject P is shifted in the direction of the X-ray source 11, it is also possible to project an enlarged image. Specifically, when displaying on the monitor 4, the frame memory 33
Each time a horizontal synchronization signal is detected, a certain initial value is given to the counter that determines the horizontal address of Movement speed increases. Furthermore, by keeping the initial value at a certain constant value, it becomes possible to display a desired location as a still image.

The above embodiment is an example in which the present invention is applied to curved tomography of a dental arch with a human body as the subject.
In addition to this, the present invention can be applied to various types of industrial CT imaging, such as measuring the degree of wear of automobile tires, tomography for inspecting tree rings, and fatigue testing of metal products with curved surfaces. is also possible, and in either case, the same effects as in the above embodiment can be obtained.

<Effects of the Invention> As is clear from the description of the above-mentioned embodiments, the present invention provides an X
The X-ray image information is converted into an electrical video signal, and image processing is performed so that only the X-ray image information on a desired tomographic trajectory is emphasized, and has the following advantages.

(a) A clear two-dimensional plane image with images other than the target object removed can be obtained.

(b) X-ray images are extracted by detecting transmitted X-rays with an X-ray image sensor using an X-ray brightness multiplier tube that reacts with an extremely small amount of radiation and has a short reaction time. Compared to conventional film-type devices that take photographs by directly utilizing the photographic effect of X-rays, the amount of X-rays to which the subject is exposed can be significantly reduced.

(c) X-rays can be irradiated intermittently, which also reduces the amount of X-rays the subject is exposed to. Also, X
If you irradiate X-rays by turning them on and off using a mechanical shutter mechanism while continuously emitting rays,
When applied to a dental arch imaging device for dental diagnosis,
It is possible to prevent the generation of soft X-rays that are harmful to the human body.

(d) Less density unevenness that tends to occur in X-ray images;
Since the gradation of an image is defined by the number of additions in the arithmetic memory, if the writing speed is set so that the number of additions is constant for all imaged parts, density unevenness will not occur at all.

(e) Since there is no need to develop the film and the results can be obtained immediately, it is possible to perform tests and diagnoses accurately.

(f) Since no mechanical film feeding means is required, it is possible to avoid increasing the size and complexity of the device.

(g) By specifying the writing speed of the calculation memory with respect to the moving speed of the X-ray source, the tomographic trajectory plane on which the image should be displayed can be arbitrarily defined, so that the setting of the tomographic trajectory plane can be easily changed. Furthermore, since image processing including operation of the arithmetic memory can be controlled using a microcomputer, the number of parts constituting the logical arithmetic circuit can be reduced, making it possible to reduce costs.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.
Figures 2 and 3 show the X-rays receiving transmitted X-rays, respectively.
FIGS. 4 and 5, which show the primary fluorescent screen of the line image sensor, are explanatory diagrams of the principle of the present invention. P...Subject, 1...Swivel arm, 3...Logic operation circuit, 4...TV monitor, 11...X-ray source, 12...X
Line image sensor, 32... calculation memory, 33... frame memory.

Claims (1)

[Claims] 1. X-ray sources 11 placed opposite to each other with the subject P in between
and an X that converts and outputs transmitted X-rays as X-ray image information.
ray image sensor 12, these X-ray sources 1
1 and an X-ray image sensor 12 integrally driven and rotated around a subject P; While taking in the image information into the calculation memory 32, the X-ray image information is sequentially shifted to the address of the position where the same image information on the desired tomographic trajectory overlaps in the memory in correspondence with the taking interval of the X-ray image information. By adding multiple times,
A two-dimensional planar image in which only the X-ray image information on the desired tomographic trajectory is emphasized is formed and stored in the frame memory 33.
a logical operation circuit 3 for storing information on an arbitrary curved tomographic trajectory on a two-dimensional plane; and a television monitor 4 for displaying a two-dimensional plane image stored in the frame memory 33. A device that displays images as images.