JPH07308314A - Digital panorama x-ray photographing apparatus - Google Patents

Abstract

PURPOSE:To provide a digital panorama X-ray photographing apparatus wherein calculating time of a tomographic image can be remarkably shortened and, after X-ray photographing is performed, a required tomographic image can be rapidly displayed. CONSTITUTION:An X-ray source 2 and an X-ray image detector 3 are arranged in such a way that they are faced each other by placing a subject 1 to be photographed between them and are fixed on both ends of a revolving arm 4. An image storing part 6 continuously stores the image information of the subject 1 outputted from an X-ray image detector 3. In a frame memory M1, the first tomographic image of the first tomographic face calculated by an image processing part 7 is stored. In a frame memory M2, the second tomographic image of the second tomographic face calculated by the image processing part 7 is stored. In a frame memory M3, a converted image obtd. by converting the second tomographic image in the frame memory M2 along the first tomographic face by means of the image processing part 7 is stored. In a frame memory M4, a panorama image obtd. by reducing the converted image in the frame memory M3 from the first tomographic image in the frame memory M1 by means of the image of the image processing part 7 is stored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital panoramic X-ray photographing apparatus capable of obtaining information on an arbitrary curved surface tomographic trajectory as a two-dimensional panoramic image. It can be used in the field of dental medical care for panoramic imaging, medical field for performing tomographic imaging of other parts of the human body, and industrial field such as nondestructive inspection for examining internal tissues such as machines and structures.

[0002]

2. Description of the Related Art Conventionally, there has been known a dental panoramic X-ray photographing apparatus which obtains a panoramic image by comprehensively X-raying a dental arch or a jawbone using a silver salt film or the like. This device
The X-ray source and the film are arranged so as to face each other so as to sandwich the dental arch of the patient, and the X-ray source and the film are placed around the patient while generating a vertically long X-ray beam from the X-ray source through the primary slit. A tomographic image is formed on the film by rotating the film integrally and by relatively moving the film in synchronization with the rotating operation so that the X-ray image corresponding to the desired tomographic plane is stationary. The X-ray image corresponding to the area other than the tomographic plane does not appear as an image because the image is blurred due to the relative movement of the film and scattered over the entire area.

Further, instead of the X-ray film, an X-ray image sensor for converting X-ray intensity into an electric signal is used to store image information such as a dental arch, and then an arithmetic process is performed to correspond to an arbitrary tomographic plane. A digital panoramic X-ray imaging apparatus capable of calculating a tomographic image has been proposed (Japanese Patent Publication No. 2-29329). With this device, once the image information of the dental arch etc. is stored, it becomes possible to specify a desired tomographic plane thereafter and obtain an arbitrary tomographic image. A tomographic image will be obtained.

Further, by using a method for obtaining a tomographic image by such arithmetic processing, for example, a first tomographic image corresponding to the first tomographic plane along the dental arch to be diagnosed is calculated, and then image observation is performed. The second tomographic image corresponding to the second tomographic plane including the cervical spine and the corners of the mandible, which are obstructive to A digital panoramic X-ray imaging apparatus has been proposed which can obtain a tomographic image with few obstruction shadows by converting it into an obstruction shadow image on a tomographic plane and further subtracting the obstruction shadow image from the first tomographic image. (JP-A-4-144)
No. 548).

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the conventional digital panoramic X-ray imaging apparatus disclosed in Japanese Patent No. 44548, since only one frame memory required for image calculation processing is installed, it is necessary to share one frame memory for various calculation processing. Therefore, the content of the frame memory has to be rewritten every time one calculation is completed, which causes a problem that the calculation time for image calculation becomes long. Further, if it takes a long time to calculate an image, the image diagnosis after X-ray imaging will be delayed, and it becomes impossible to perform a prompt medical examination.

An object of the present invention is to provide a digital panoramic X-ray imaging apparatus capable of significantly shortening the calculation time of a tomographic image and rapidly displaying a desired tomographic image after X-ray imaging.

[0007]

According to the present invention, there is provided an X-ray source for irradiating a subject with X-rays, an X-ray image detecting means for detecting an X-ray image transmitted through the subject, and the X-ray source around the subject. And a rotating means for integrally rotating the X-ray image detecting means,
An image storage unit for storing the image information output from the X-ray image detection unit during the operation of the swivel unit and the image information stored in the image storage unit are used to detect a desired slice plane. Image processing means for forming a tomographic image and performing arithmetic processing on the tomographic image, a first frame memory for storing a first tomographic image along the first tomographic plane, and a second tomographic plane A second frame memory for storing the second tomographic image, and a third frame memory for converting the second tomographic image into a converted image along the first tomographic plane by the image processing means and storing the converted image. And a fourth step for storing the panoramic image, in which the image processing means subtracts the converted image stored in the third frame memory from the first tomographic image stored in the first frame memory to form a panoramic image. Frame memory and 4th frame A digital panoramic X-ray imaging apparatus characterized by comprising an image output unit for displaying the panoramic image stored in Mumemori.

Further, the present invention is characterized in that the second frame memory and the fourth frame memory are the same frame memory.

According to the present invention, the first fault plane is set so as to pass through the dentition and the jawbone, the second fault plane is set so as to pass through the cervical spine and the mandibular corner, and the first fault plane and the second fault plane are set. It is characterized in that the distance to the surface is variable.

Further, according to the present invention, the first fault plane is set so as to pass through the dentition and the jawbone, the second fault plane is set so as to pass through the cervical vertebra and the mandibular corner, and the fault width of the second fault plane is set. It is variable.

According to the present invention, the first fault plane is set so as to pass through the dentition and the jawbone, the second fault plane is set so as to pass through the cervical vertebra and the corner of the mandible, and the first fault plane and the second fault plane are set. The distance to the plane is variable, and the fault width of the second fault plane is variable.

[0012]

According to the invention, the first tomographic image is stored in the first
A frame memory, a second frame memory for storing a second tomographic image, a third frame memory for storing a converted image obtained by converting the second tomographic image along the first tomographic plane, and a converted image subtracted from the first tomographic image. By preparing four frame memories, that is, a fourth frame memory for storing the obtained panorama image, the calculation result is stored in another frame memory while the image data as the source of calculation is stored in each frame memory. be able to. Therefore, it is not necessary to rewrite the data in the frame memory, and the next image calculation can be started immediately. The panoramic image calculated by the arithmetic processing is promptly displayed on the screen by an image output means such as a display, and is used for rapid image diagnosis.

By sharing the second frame memory and the fourth frame memory in the same frame memory, the number of frame memories to be used can be reduced without lowering the calculation speed. That is, if the second tomographic image is converted into a converted image and stored in the third frame memory, the second tomographic image stored in the second frame memory is no longer necessary. It can be utilized as the fourth frame memory.

The first tomographic plane is set so as to pass through the dentition and the jawbone, so that a tomographic image along the dental arch can be obtained. Further, the second tomographic plane is set so as to pass through the cervical vertebra and the corner of the mandible, so that a tomographic image that is an obstacle shadow for dental diagnosis can be obtained. Therefore, a clear panoramic tomographic image can be obtained by removing the obstacle shadow component from the tomographic image of the dental arch.

On the other hand, even if the shape and position of the cervical spine, dental arch, etc. change depending on the body type, sex, age, race, etc. of the patient, the faulty tomographic image can be removed properly so that the faulty shadow image can be properly removed. It is preferable to set the fault width of the plane relatively wide. In other words, if the cervical vertebrae and mandibular corners of the majority of patients are within the set range of the fault width of the fault plane that becomes the obstruction shadow, it is not necessary to readjust the fault width. However, when the patient's cervical vertebra and the corners of the lower jaw extend beyond this set range, the obstructed shadow image cannot be accurately removed. Therefore, since the distance between the first tomographic plane and the second tomographic plane is variable, the position of the second tomographic plane is reset even if the distance between the anterior tooth and the cervical vertebra changes depending on the patient. This makes it possible to always obtain an accurate panoramic image with the obstructed shadow image removed.

The first fault plane is set so as to pass through the dentition and the jawbone, the second fault plane is set so as to pass through the cervical vertebra and the mandibular corner, and the fault width of the second fault plane is variable. As a result, even if the patient's cervical vertebra and mandibular corner do not fit within the initially set tomographic width, the tomographic width can be reset, and an accurate panoramic image from which the obstructed shadow image is removed can always be obtained. .

The first fault plane is set so as to pass through the dentition and the jawbone, the second fault plane is set so as to pass through the cervical vertebra and the mandibular corner, and the first and second fault planes are formed. Since the distance between them is variable and the tomographic width of the second tomographic plane is variable, the range that is the obstruction shadow, that is, the position or range of the second tomographic plane can be reset according to the patient, so that the obstruction shadow is always An accurate panoramic image with the image removed can be obtained.

[0018]

FIG. 1 shows the principle of digital panoramic tomography according to the present invention. Here, the slit image in which the subject 1 is projected is considered in one dimension, and the number of slit images is S1 to S3.
The mathematical verification is performed on the assumption that the discrete data of each of the three slit images is 3 pixels. Subject 1 has tissue A in the thickness direction,
Having B and C, the X-ray source turns around the center R1 of the subject 1 and moves in the order of positions X1, X2, and X3, for example.
When the X-ray source is located at the position X1, the slit image S1 of the subject 1 is configured such that the image a of the tissue A, the image b of the tissue B, and the image c of the tissue C are arranged from left to right in FIG. When the X-ray source is located at the position X2, the slit image S2 of the subject 1
Is configured such that the image a, the image b, and the image c overlap. Further, when the X-ray source is located at the position X3, the slit image S3 of the subject 1 is configured such that the images a, b, and c are arranged from right to left in FIG. 1 opposite to the slit image S1. Therefore, the data of each slit image S1 to S3 is expressed by the following equation.

S1 = (a, b, c) (1) S2 = (0, a + b + c, 0) (2) S3 = (c, b, a) (3) Next, the shift function is To be defined as Data string S
When (a, b, c) is shifted to the left n times (n is a natural number), S (a, b, c) >> (n) = d (0,
0, 0, ..., 0, a, b, c). Where d
Means image data.

When shifting to the right n times as an inverse function, d (0, 0, 0, ..., 0, a, b, c) <<
Define (n) = S (a, b, c). Here, in the image data d on the left side, n 0s are arranged from the left.

1) Calculation of Original Image Using the slit images S1 to S3 of FIG. 1, the data of the tissue A is moved by the shift function F1 so as to obtain the arithmetic mean. That is, when the slit image S1 is shifted to the left by two digits and the slit image S2 is shifted to the left by one digit along the row direction,

[0022]

[Equation 1]

It becomes Therefore, when the arithmetic mean is applied in the column direction, the original image D1 is obtained as D1 = 1/3 × (c, b, 3a + b + c, b, c) (5). Here, the images b and c are superimposed on the image a by one-third each, and when the tissue A is a tomographic plane, the tissues B and C are superimposed as obstacle shadow images. Indicates that. Further, the signal intensity of the obstacle shadow image is reduced to one third of the original.

2) Calculation of Image Underlying Obstruction Shadow Next, slit images S1 to S3 are performed in the same manner as in 1) above.
By using the shift function F2 so that the data of the tissue C becomes maximum, and the addition calculation is performed. That is,
When the slit image S3 is shifted to the left by two digits along the row direction and the slit image S2 is shifted to the left by one digit respectively, and the arithmetic mean is taken in the column direction, the original image D2 of the obstacle shadow is

[0025]

[Equation 2]

D2 = 1/3 × (a, b, a + b + 3c, b, a) (7) Here, the images a and b are superimposed on the image c by one-third each, and when the tissue C is a tomographic plane, the tissues A and B are superimposed as obstacle shadow images. Indicates that. Further, the signal intensity of the obstacle shadow image is reduced to one third of the original.

3) Back projection onto virtual slit Next, from the original image D2 of the obstacle shadow, the virtual slit image S is obtained.
When the inverse function of the shift function F2 is mapped to 1'to S3 ', the data of the virtual slit images S1' to S3 'are obtained as follows.

D2 = 1/3 × (a, b, a + b + 3c, b, a) (7)

[0029]

[Equation 3]

S1 ′ = 1/3 × (a, b, a + b + 3c) (9) S2 ′ = 1/3 × (b, a + b + 3c, b) (10) S3 ′ = 1/3 × (a + b + 3c, b , A) (11) 4) Calculation of obstruction shadow image The virtual slit images S1 ′ to S3 ′ thus obtained are moved by the shift function F1 in the same manner as in 1) above, and the arithmetic mean is taken in the column direction. Then, the obstacle shadow image D1 ′ is obtained as follows.

[0031]

[Equation 4]

D1 ′ = 1/9 × (a + b + 3c, 2b, 3a + b + 3c, 2b, 2b, a + b + 3c) (13) 5) Removal of obstructive shadow image from original image Next, from original images D1 to 4 obtained in 1) ), The shadow image D1 'of the obstacle obtained in () is subtracted to obtain an image D1 ".

D1 ″ = D1-D1 ′ = 1/9 × (−a−b, b, 6a + 2b, b, −a−b) (14) From the above, the image D1 ″ is the tissue C from the original image D1. Is a noise component, that is, the image in which the obstacle shadow image D1 ′ is removed. Here, although the components of the images a and b are superimposed as new noise, if (a + b) / 9 << a and b
If / 9 << a is satisfied, the degree of separation of the tissue A is improved in the image D1 ”compared to the original image D1. Here, the number of additions is three and the noise component is 1/9. In general, when the number of additions is m, noise is attenuated by a factor of m. In actual digital panoramic photography, since addition averaging is performed 30 to 100 times, newly superimposed noise is 1/900 to 1/100 of the signal strength of
It becomes 00, and it will be attenuated sufficiently.

FIG. 2 is a block diagram showing an embodiment of the present invention. An X-ray source 2 and an X-ray image detector 3 are arranged so as to face each other with the subject 1 interposed therebetween, and are attached to both ends of a swivel arm 4. The X-ray source 2 is provided with a primary slit to generate a vertically long X-ray beam parallel to the turning axis and irradiate the subject 1.

The X-ray image detector 3 detects the X-ray passing through the subject 1.
The intensity distribution of the line is two-dimensionally detected as a vertically long slit image and converted into an electric signal. A well-known X-ray image sensor can be used as the X-ray image detector 3.
For example, a fluorescent plate that converts X-rays into visible light and an SIT (Silicon Inten) that converts an image on the fluorescent plate into an electric signal with high sensitivity.
X-ray CCD (Charge Coupled Devic) that uses semiconductor elements instead of SIT
e) A sensor or an X-ray fluorescence multiplier tube is used.

The revolving arm 4 is rotatably supported by the revolving device 5, and is rotated at a constant angular velocity in response to a drive signal from the image processing section 5, so that the revolving arm 4 moves around the subject 1 in an X direction.
The radiation source 2 and the X-ray image detector 3 are integrally rotated, and the X-ray beam from the X-ray source 2 is controlled so as to irradiate a predetermined position of the subject 1.

The image storage unit 6 continuously stores the image information of the subject 1 output from the X-ray image detector 3 while the revolving arm 4 is revolving. For example, a VTR (Vide)
o Tape signal recorders, optical discs, magneto-optical discs, and other video signal recording devices and large-capacity DRAMs (Dynamic Rands)
Semiconductor memory devices such as om access memory) are used.

The image processing unit 7 is realized by a computer or the like, performs arithmetic processing based on the image information stored in the image storage unit 6, and controls the operation of the entire apparatus. The shift amount storage unit 8 stores the shift amount of the slit image necessary to reproduce the first tomographic image along the first tomographic plane of the subject 1, as will be described later, and the shift amount storage unit 9
Is for storing the shift amount of the slit image necessary for reproducing the second tomographic image along the second tomographic plane of the subject 1. The keyboard 10 is used for inputting numerical data and character data necessary for arithmetic processing to the image processing unit 7, for example, position information of a tomographic plane and giving an operation instruction, and further, the physical constitution information of the subject 1 can be simplified. A patient physique switch 11 for selective input is connected to.

The frame memory M1 stores the first tomographic image along the first tomographic plane calculated by the image processing section 7. The frame memory M2 stores the second tomographic image along the second tomographic plane calculated by the image processing unit 7. The frame memory M3 stores a converted image obtained by the image processing unit 7 converting the second tomographic image stored in the frame memory M2 along the first tomographic plane. The frame memory M4 stores a panoramic image obtained by the image processing unit 7 subtracting the converted image stored in the frame memory M3 from the first tomographic image stored in the frame memory M1.

The output unit 20 includes the frame memories M1 to M.
The image stored in 4 is selectively displayed, and in many cases, the panoramic image stored in the frame memory M4 is displayed. The output unit 20 visualizes image data stored as an electric signal, and is a CRT (cathode ray tube).
An image display such as a liquid crystal panel or an image printer that forms an image on recording paper is used.

FIG. 3 is a flow chart showing the operation of the embodiment shown in FIG. First, in step a1, the turning device 5 is driven to start the rotating operation of the turning arm 4. Next, in step a2, the X-ray source 2 irradiates X-rays while the swivel arm 4 swivels, and the X-rays passing through the subject 1
The line is detected by the X-ray image detector 3, and the obtained X-ray image is converted into an electric signal. As this electric signal, for example, the same signal format as that of a video signal of a television is adopted, and in step a3, it is continuously stored in the image storage section 6 at a rate of 30 sheets per second. The X-ray image detected by the X-ray image detector 3 is a vertically long slit image corresponding to the vertically long X-ray beam. For example, when the X-ray image detector 3 is rotated halfway around the subject 1 in 30 seconds. , 30 × 30 = 900 sheets, a series of slit images are continuously obtained. Note that the slit image does not have to be a continuous signal such as the above-described video signal, and may be captured intermittently at a short cycle and sequentially converted into an electrical signal.

Next, in step a4, the parameters necessary for reconstructing the first tomographic image along the first tomographic plane are set. Here, a take-out interval P1 for selectively taking out slit images arranged at a predetermined time interval from a series of slit images stored in the image storage unit 6 is set. Further, a distance for adding the extracted slit images while shifting the positions by a predetermined distance in the width direction (turning direction), that is, a shift amount Q1 is set. The take-out interval P1 and the shift amount Q1 can be arbitrarily selected, whereby a desired tomographic plane can be arbitrarily set. The first tomographic plane is set so that the final image to be diagnosed is obtained, and in many cases of panoramic photography,
Set along the dental arch that passes through the dentition and jawbone. Further, the selected shift amount Q1 is stored in the shift amount storage unit 8.

Next, in step a5, the parameters necessary for reconstructing the second tomographic image along the second tomographic plane are set. Here, a take-out interval P2 for selectively taking out slit images arranged at a predetermined time interval from a series of slit images stored in the image storage unit 6 is set. Further, a distance for adding each taken-out slit image while shifting the position by a predetermined distance in the width direction (turning direction), that is, a shift amount Q2 is set. The take-out interval P2 and the shift amount Q2 can be arbitrarily selected, whereby a desired tomographic plane can be arbitrarily set. The second tomographic plane is set so as to pass through the tissue that causes the obstruction shadow in the final image, and in many cases of panoramic radiography, is set so as to pass through the cervical vertebra and the corner of the lower jaw. Further, the selected shift amount Q2 is stored in the shift amount storage unit 9.

Next, at step a6, the take-out interval P
Based on 1, the corresponding slit image is sequentially extracted in the form of a quantized digital signal for each pixel, and addition processing is performed while shifting the pixel data of the slit image as described above according to the set shift amount Q1. Then, the first tomographic image along the first tomographic plane such as the dental arch is reconstructed and stored in the frame memory M1.

Next, in step a7, the take-out interval P
Based on 2, the corresponding slit image is sequentially extracted in the form of a quantized digital signal for each pixel, and addition processing is performed while shifting the pixel data of the slit image as described above according to the set shift amount Q2. Then, the second tomographic image along the second tomographic plane passing through the cervical spine and the corners of the lower jaw is reconstructed and stored in the frame memory M2.

Next, at step a8, as described above, based on the second tomographic image of the cervical spine stored in the frame memory M2, the virtual slit is formed in accordance with the same shift amount Q2 as when the second tomographic plane is reconstructed. Backproject to the image.
Next, using the same shift amount Q1 as when the first tomographic image is reconstructed, the back-projected virtual slit image is reconstructed into an obstruction shadow image along the first tomographic plane, and this obstruction shadow image is reconstructed. Are stored in the frame memory M3.

Next, at step a9, as described above, the obstacle shadow component stored in the frame memory M3 is subtracted from the first tomographic image of the dentition stored in the frame memory M1 to obtain the obstacle shadow component. A panoramic image from which is removed is obtained and stored in the frame memory M4.

Next, in step a10, the output unit 20
By displaying the panoramic image stored in the frame memory M4, the panoramic image having no obstacle shadow is used for diagnosis. In this way, since the image data required for the arithmetic processing is stored in each corresponding frame memory in advance, unnecessary data transfer is unnecessary, and the arithmetic processing can be speeded up.

When calculating the final panoramic image,
If the second tomographic image stored in the frame memory M2 is unnecessary, the final panoramic image may be stored in the frame memory M2 instead of the frame memory M4, and thus the calculation speed is not reduced. The number of frame memories used can be reduced.

If the frame memory M1 is selected as the image displayed by the output unit 20, the first tomographic image before the subtraction processing is displayed, and if the frame memory M2 is selected, the first tomographic image such as the cervical spine which becomes the shadow of the obstacle is displayed. 2 tomographic images are displayed,
Further, if the frame memory M3 is selected, the obstruction shadow image of the second tomographic image on the first tomographic plane is displayed. Therefore, the effect of the image processing and the accuracy of the tomographic plane setting can be visually confirmed by appropriately selecting and displaying on the output unit 20.

FIG. 4 is an explanatory diagram showing the relationship between the take-out interval and the shift amount and the tomographic plane. Assuming that the X-ray beam XB is rotating clockwise around the rotation center R1, the image of the object on a certain tomographic plane Z1 is the X-ray of the X-ray image detector 3 that is rotating together with the X-ray beam XB. The image is projected on the detection surface 3a and crosses the X-ray detection surface 3a from left to right when viewed from the imaging device 3b side. Similarly, the image of the object on another tomographic plane Z2 is also X
Although it is projected on the line detection surface 3a and crosses in the same direction, the moving speed at the time of crossing is faster than the image of the tomographic plane Z1 because the distance from the turning center R1 is long. Therefore, if the extraction interval and shift amount are selected according to the moving speed of these images,
A panoramic image of the object on the tomographic planes Z1 and Z2 synchronized with this is formed.

Here, if the take-out interval and the shift amount are constant, it becomes arcuate like the tomographic planes Z1 and Z2 shown in FIG. 4, but the take-out interval and the shift amount need not be constant for one process. Instead, if the change is made in association with the movement of the center of rotation of the X-ray beam, the slice plane Z in FIG.
As shown in 4, it is possible to select a tomographic plane composed of a plurality of planes having different curvatures.

As described above, in this apparatus, the X-ray photography is 1
The panorama image obtained can be formed anytime after imaging without waste of the image information including all the information of the objects existing in the X-ray path. Even if the image deviates from the desired tomographic plane, the image processing may be redone and the X-ray re-imaging is not necessary.

The above-mentioned take-out interval and shift amount are such that a series of slit images continuously stored in the image storage section 6 are reproduced, and the speed at which the target image moves in the reproduced image is detected. However, it is possible to set according to the result. That is, although it is unclear, an image of an object through which X-rays are transmitted appears in the reproduced image, and it is possible to know the moving speed of the target image. It is possible to easily calculate how much the extraction interval and the shift amount should be set to obtain the panoramic image of the tomographic plane.

The take-out interval and the shift amount can be set by a data input device such as the keyboard 10, and the set shift amount is stored in the shift amount storage sections 8 and 9. Further, the patient physique switch 11 connected to the keyboard 10 is provided with three selection switches 11a, 11b, 11c corresponding to large, medium, and small physiques. For example, a dental arch that changes depending on the physique of the patient. A plurality of tomographic planes corresponding to the shapes and positions of the tomographic planes are preset, and the take-out intervals and shift amounts corresponding to the respective tomographic planes are selected by the selection switches 11a to
It is possible to collectively select by 11c.

The tomographic plane thus set is not limited to the tomographic planes Z1 and Z2 on the X-ray detection plane 3a side of the turning center R1 as shown in FIG. Those on the X-ray source side are also included. In this case, the image of the tomographic plane Z3 or the like is in the opposite direction to that of the tomographic plane Z1 or the like.
That is, since the X-ray detection surface 3a is crossed from right to left when viewed from the imaging device 3b side, the direction of shifting the position when adding the extracted slit images is reversed, that is, the shift amount is made negative. Become.

FIG. 5 is a schematic view showing the positional relationship between the subject and the tomographic plane. The dentition is lined up on the jawbone 30, the dental arch is set so as to pass through substantially the center of the dentition and the lower jaw corner portion 31, and the tomographic plane Z4a substantially coincides with this dental arch. In general, a dental arch consists of curves with multiple curvatures,
In order to obtain a clear panoramic image, it is preferable that the turning center R1 of the X-ray beam moves along the trajectory R2 in accordance with the turning operation.

In order to obtain the panoramic image from which the obstacle shadows as described above are removed, the first slice plane is set to the slice plane Z4a along the dental arch, and the region sandwiched between the boundary plane Z4b and the boundary plane Z4c. Is the tomographic width configured as a panoramic image. The second tomographic plane is the cervical vertebra 32 and the mandibular corner 31.
It is set on the fault plane Z5 passing through. The boundary surface Z6 is
It is a curve that passes slightly in front of the cervical vertebra 32, and the boundary surface Z
Reference numeral 7 is a curve that passes slightly rearward from the cervical vertebra 32, and the interval between these boundary surfaces is the slice width W. The center distance from the center of the front tooth to the tomographic plane Z5 is L.

In this case, even if the shape and position of the cervical spine or dental arch changes depending on the body type, sex, age, race, etc. of the patient,
It is preferable to set the tomographic width W of the second tomographic plane, which is the obstruction shadow, to be relatively wide so that the obstruction shadow image can be properly removed. That is, if the cervical vertebrae 32 and the mandibular corners 31 of the majority of patients are within the set range of the tomographic width W of the second tomographic plane that becomes the obstacle shadow, it is not necessary to readjust the tomographic width W. However, if the patient's cervical vertebra 32 and mandibular corner 31 extend beyond this set range, the obstructed shadow image cannot be accurately removed. Therefore, since the distance L between the first tomographic plane and the second tomographic plane is variable, even if the distance between the anterior tooth and the cervical vertebra 32 changes depending on the patient, the position of the second tomographic plane is re-established. It becomes possible to set, and it is possible to always obtain an accurate panoramic image with the obstructed shadow image removed.

The first tomographic plane is set to pass through the dentition and the jawbone 30, the second tomographic plane is set to pass through the cervical vertebra 32 and the mandibular corner 31, and the tomographic width W of the second tomographic plane is set. Is variable, it becomes possible to reset the tomographic width W even if the patient's cervical vertebra 32 and the mandibular corner 31 do not fit within the initially set tomographic width, and it is possible to accurately remove the obstructed shadow image. A panoramic image can be obtained.

The first tomographic plane is set to pass through the dentition and the jawbone 30, the second tomographic plane is set to pass through the cervical vertebra 32 and the mandibular corner 31, and the first tomographic plane and the second tomographic plane are set.
Since the distance to the tomographic plane is variable and the tomographic width W of the second tomographic plane is variable, the range that becomes an obstacle shadow, that is, the position or range of the second tomographic plane can be reset according to the patient. Therefore, it is possible to always obtain an accurate panoramic image from which the obstacle shadow image is removed.

FIG. 6 is a schematic view of a panoramic image of a dentition and a jawbone. By correctly aligning the plane of the patient's eye and ear and the midsagittal plane and positioning the anterior tooth accurately, the fault trajectory runs accurately from the temporomandibular joint to the molar, premolar, canine and anterior teeth. A panoramic X-ray image in which the chin and the facial area can be read is obtained. In FIG. 6, the shadow V1 located at the center is the X-ray passing through the cervical spine,
The amount of X-ray exposure was reduced, and it appeared as a blank defect. The fan-shaped shadows V2 and V3 on the left and right are white spot defects due to X-rays passing through the left and right lower jaw corners.

[0063]

As described in detail above, according to the present invention, since the frame memories required for each image processing are individually provided, the calculation processing can be speeded up by omitting extra calculation time such as data transfer. This makes it possible to display the final panoramic image quickly. Therefore, the time from X-ray imaging to image diagnosis can be shortened.

By sharing the frame memory, the number of frame memories to be used can be reduced without lowering the calculation speed.

Further, the distance between the first tomographic plane and the second tomographic plane and the tomographic width of the second tomographic plane are variable, so that the cervical vertebrae and teeth may be changed depending on the patient's body type, sex, age and race. Even if the shape and position of the arches change, the obstruction shadow image is accurately removed. Therefore, it is possible to obtain a panoramic image that is free from the shadow of obstruction and is easy to diagnose.

[Brief description of drawings]

FIG. 1 is a principle diagram of digital panoramic tomography according to the present invention.

FIG. 2 is a block diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of the embodiment of FIG.

FIG. 4 is an explanatory diagram showing a relationship between a take-out interval and a shift amount and a tomographic plane.

FIG. 5 is a schematic diagram showing a positional relationship between a subject and a tomographic plane.

FIG. 6 is a schematic view of a panoramic image of a dentition and a jawbone.

[Explanation of symbols]

 1 subject 2 X-ray source 3 X-ray image detector 4 swivel arm 5 swivel device 6 image storage unit 7 image processing unit 8, 9 shift amount storage unit 10 keyboard 11 patient build switch 20 output unit 30 jawbone 31 lower jaw angle 32 cervical spine M1 to M4 frame memory

Claims (5)

[Claims] 1. An X-ray source for irradiating an object with X-rays, an X-ray image detecting means for detecting an X-ray image transmitted through the object, and the X-ray source and the X-ray image detecting means around the object. The turning means for turning integrally, the image storing means for storing the image information output from the X-ray image detecting means during the operation of the turning means, and the image information stored in the image storing means are used. An image processing means for forming a tomographic image along a desired tomographic plane and performing arithmetic processing on the tomographic image; and a first for storing the first tomographic image along the first tomographic plane.
A frame memory and a second for storing a second tomographic image along the second tomographic plane
A frame memory; a third frame memory for the image processing means to convert the second tomographic image into a converted image along the first tomographic plane; and for storing the converted image; and the image processing means for the first frame memory The converted image stored in the third frame memory is subtracted from the first tomographic image stored in to form a panoramic image, and the panoramic image is stored in the fourth frame memory and the fourth frame memory. And an image output unit for displaying a panorama image. 2. The digital panoramic X-ray imaging apparatus according to claim 1, wherein the second frame memory and the fourth frame memory are the same frame memory. 3. The first fault plane is set so as to pass through the dentition and the jawbone, the second fault plane is set so as to pass through the cervical vertebra and the corner of the mandible, and the first fault plane and the second fault plane are defined. The digital panoramic X-ray imaging apparatus according to claim 1 or 2, wherein the distance between them is variable. 4. The first tomographic plane is set so as to pass through the dentition and the jawbone, the second tomographic plane is set so as to pass through the cervical vertebra and the corner of the mandible, and the tomographic width of the second tomographic plane is variable. The digital panoramic X-ray imaging apparatus according to claim 1 or 2, characterized in that. 5. The first tomographic plane is set to pass through the dentition and the jawbone, the second tomographic plane is set to pass through the cervical vertebra and the corner of the mandible, and the first tomographic plane and the second tomographic plane are formed. The digital panoramic X-ray imaging apparatus according to claim 1 or 2, wherein the distance between them is variable, and the tomographic width of the second tomographic plane is variable.