JPH0687853B2 - Digital tomography system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital tomography apparatus for irradiating a subject with radiation to photograph and display a tomographic image of an arbitrary tomographic plane in the subject, and particularly to one time. The present invention relates to a digital tomography apparatus capable of obtaining a three-dimensional tomographic image of a subject only by the tomography.

2. Description of the Related Art A conventional digital tomography apparatus for photographing and displaying a tomographic image of an arbitrary tomographic plane is, as shown in FIG. 5, a radiation source 1 such as an X-ray tube and a subject 2 sandwiched between the above radiations. Image that is placed facing the source 1 and converts the transmitted radiation image into visible light.
A radiation detector 3 such as an intensifier (hereinafter abbreviated as "II"), an image pickup tube 4 for converting the output optical image into an electric signal, and a positional relationship between the radiation source 1 and the radiation detector 3 are changed. A scanning device, an A / D converter 5 for converting the output signal of the image pickup tube 4 into a digital amount, a recording memory 6 for storing the digital projection data, and an arithmetic process for reading the projection data from the recording memory 6. And a display device 8 for converting the processed digital signal into an analog signal for display and transmitting or absorbing the two-dimensional radiation of the subject 2. Distribution of the radiation source 1 and the radiation detector 3
Are measured a plurality of times while changing their mutual positional relationship, and a linear operation is performed on a set of data that passes through one point in the subject 2 from the plurality of images to obtain an arbitrary slice in the subject 2. The tomographic image of the plane was calculated and displayed.

Problems to be Solved by the Invention However, in such a digital tomography apparatus, it was not possible to obtain a three-dimensional tomographic image having an arbitrary tomographic thickness with respect to the imaging region of the subject. On the other hand, in a conventional tomography apparatus using a film, there is an applied technique called stereoscopic tomography. This is because the X-ray tube is separated by an angle corresponding to the binocular parallax, tomographic images are taken from two directions with respect to the same imaging site of the subject, and a tomographic image on a film for the left eye image and a tomographic image for the right eye image are obtained. Some stereoscopic tomographic images are obtained by stereoscopically viewing a tomographic image on a film with a binocular parallax using a stereoscope or the like.

However, in this case, it is necessary to change the direction of the same region of the subject to be imaged twice, and if there is movement between the first and second images, the Sometimes a tomographic image could not be obtained. In addition, since the same imaged region is imaged twice, the total time required for imaging becomes long, the burden on the patient becomes large, and the X-ray exposure dose also becomes large.

Therefore, the present invention provides a digital tomography apparatus capable of obtaining a tomographic image of an arbitrary tomographic plane in a subject and also a stereoscopic tomographic image in a digital tomography apparatus by only one tomography. To aim.

Means for Solving the Problems Means of the present invention for solving the above problems include a radiation source,
A radiation detector, an image pickup tube, a scanning device, an A / D converter, a recording memory, a calculation device, and a display device, and calculates a tomographic image of an arbitrary tomographic plane in the subject. In the digital tomography apparatus for displaying, the arithmetic unit fetches two sets of continuous projection data having a shift of the addition range corresponding to the binocular parallax from the recording memory and performs shift addition processing within each range to the left eye. An operation command section for sending command information for forming a tomographic image for an image and a right eye image is connected, and the output side of the operation device displays the left eye image and the right eye image independently. The digital tomography apparatus is provided with a memory and a display device.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of a digital tomography apparatus according to the present invention. This digital tomography apparatus irradiates a subject with radiation and photographs and displays a tomographic image of an arbitrary tomographic plane in the subject. The radiation source 1, the radiation detector 3, and the image pickup tube 4 are provided. , Scanning device and A / D converter 5
And a recording memory 6 and an arithmetic unit 7. The radiation source 1 irradiates the subject 2 with radiation,
It is composed of, for example, an X-ray tube, and is moved on a radiation source scanning orbit 9b by a driving device 9a. The radiation detector 3 is for converting a transmitted radiation image of the subject 2 into visible light, and is made of, for example, II and has a spherical detection surface, and the radiation source is sandwiched with the subject 2 therebetween. It is arranged so as to face 1. The imaging tube 4 is the radiation detector 3 described above.
The output optical image of is incident and converted into an electric signal. The scanning device changes the positional relationship between the radiation source 1 and the radiation detector 3, and includes the drive device 9a and the radiation source scanning trajectory 9b, and the scanning trajectory of the radiation detector 3 (not shown). . The A / D converter 5 converts the output signal of the image pickup tube 4 into a digital amount. The recording memory 6 stores the projection data converted into a digital amount by the A / D converter 5, and the writing address is designated by the address register 10. The arithmetic unit 7 reads the projection data stored in the recording memory 6 and performs arithmetic processing.

In FIG. 1, reference numeral 11 is an exposure control device,
The radiation command is sent to the radiation source 1 and the output signal of the driving device 9a is input to monitor the scanning position of the radiation source 1. Further, reference numeral 12 is a control device, which inputs a monitor signal of the scanning position of the radiation source 1 output from the exposure control device 11 to generate a signal necessary for scanning with respect to the image pickup tube 4, and at the same time, A control signal is sent to the A / D converter 5, and a write control signal is also sent to the address register 10. Further, reference numeral 13 is a distortion correction table memory connected to the arithmetic unit 7,
This is for correcting the distortion of the image generated by the spherical detection surface of the radiation detector 3 composed of II, and the distortion amount data obtained by previously measuring the distortion amount of the image by the radiation detector 3 is tabulated. A distortion correction table is stored. Then, each time the subject 2 is exposed to radiation and a tomographic image is taken, the image data is corrected by the arithmetic unit 7 using the distortion correction table stored in the distortion correction table memory 13. .

Then, the two-dimensional radiation transmission or absorption distribution of the subject 2 is measured a plurality of times while changing the mutual positional relationship between the radiation source 1 and the radiation detector 3, and from the plurality of images, the A linear operation is performed on a set of data passing through one point in the subject 2 to calculate and display a tomographic image of an arbitrary tomographic plane in the subject 2.

Here, in the present invention, the arithmetic command unit 14 is connected to the arithmetic device 7, and two series of display memories 15a, 15b and display devices 16a, 16b are provided on the output side of the arithmetic device 7. ing. The calculation command section 14 sends command information to the calculation device 7 when the projection data is read from the recording memory 6 and is subjected to a calculation process. From the memory 6, as shown in FIG. 3, two sets of continuous projection data 18a, 18b having a shift of the addition ranges 17a, 17b corresponding to the binocular parallax are taken out, and the shift addition processing is performed within the respective ranges 17a, 17b. Command information for performing a tomographic image for the left eye image and a right eye image is transmitted. Further, the two series of display memories 15a and 15b and the display devices 16a and 16b respectively display a left eye image tomographic image and a right eye image tomographic image created by the arithmetic processing of the arithmetic device 7. In order to do so, for example, with the first series of display memory 15a and the display device 16a for the left eye image,
The display memory 15b and the display device 16b of the second series are for the right eye image, and each series is provided independently. The display memories 15a and 15b are used to write the left-eye image data and the right-eye image data output from the arithmetic unit 7 for display. The display devices 16a and 16b are each a display memory 1
The digital signals read from 5a and 15b are converted into analog signals and displayed, and are composed of, for example, CRT monitors.

Next, the operation of the digital tomography apparatus configured as above will be described. First, the radiation source 1 shown in FIG.
1n and 3a, 3b, ... 3n in FIG. 2 depending on the scanning position, the mutual positional relationship between the radiation detector 3 and the radiation detector 3 is changed on the linear trajectory, and A plurality of projection images 19a, 19b, ... 19n are photographed by measuring a dimensional radiation transmission or absorption distribution a plurality of times. Next, such projection images 19a to 19n are converted into electric signals by the image pickup tube 4, the output signal of the image pickup tube 4 is converted into a digital amount by the A / D converter 5, and then this digital projection data is converted. It is stored in the recording memory 6. Next, by designating the address of the address register 10, the projection data is sequentially read from the recording memory 6 and input to the arithmetic unit 7. Then, the arithmetic unit 7 refers to the distortion correction table of each pixel stored in the distortion correction table memory 13 and refers to the distortion of the image generated by the spherical detection surface of the radiation detector 3 for each of the projected images 19a to 19n. Is corrected, and the corrected data of the projected images 19a to 19n are shifted by an appropriate amount and then added (shift addition). As a result, a tomographic image of an arbitrary tomographic plane of the subject 2 is obtained. The tomographic image is displayed as a normal tomographic image using one of the series shown in FIG. 1, for example, the first display memory 15a and the first display device 16a.

Here, in FIG. 2, θ max is the maximum exposure angle when capturing the projected images 19a to 19n. This maximum exposure angle θ max
Is a quantity related to the layer thickness of the tomographic image. The larger the θ max, the smaller the layer thickness, and the smaller the θ max, the larger the layer thickness. To obtain a three-dimensional tomographic image of the subject 2,
The thickness of the tomographic image within a certain range is required, and θ max needs to be reduced. Regarding this, in digital tomography, θ max is reduced by reducing the addition range of the data of the projected images 19a to 19n shown in FIG. 2, and it is easy to increase the layer thickness of the tomographic image. it can.
Further, as shown in FIG. 3, the range in which projection data is added
The data 18a and 18b of two tomographic images having binocular parallax can be created by shifting 17a and 17b to the left and right around a certain position by an appropriate amount.

Next, in this state, in order to obtain a three-dimensional tomographic image of an arbitrary tomographic plane of the subject 2, the operation command unit 14 shown in FIG.
With respect to the arithmetic unit 7, two sets of continuous projection data having a shift of the addition range corresponding to the binocular parallax are taken out from the recording memory 6 and shift addition processing is performed within each range, and the left eye image and the right eye image are processed. Command information for creating a tomographic image for the eye image may be sent. That is, as shown in FIG. 4, the left eye image addition range 17a is located at a position shifted by an angle θ to the left and right with a line of θ = 0 ° standing upright on the subject 2 as the center.
Assuming the center of the center of the right eye image and the center of the addition range 17b of the right eye image, 2θ
Is the binocular parallax. Therefore, in order to obtain the binocular parallax, the angle θ is sent from the calculation command unit 14 to the calculation device 7 as information on the center of each addition range 17a, 17b. The angle θ is determined by the system of the device, but has a certain width that allows stereoscopic viewing. In addition, the layer thickness of the tomographic image is determined by adding the projection data within the range of a certain angle α around the position of the angle θ. Therefore, in order to set the layer thickness of the tomographic image within a certain range, the calculation command section 14 sends the angle α as information of the range to which the projection data is added to the calculation device 7. Note that the larger the angle α, the thinner the layer thickness of the tomographic image and the narrower the stereoscopic region.
Conversely, when the angle α becomes smaller, the layer thickness of the tomographic image becomes larger,
The stereoscopic area becomes wider. Therefore, the angle α may be freely selected depending on the structure of the target imaging region.

In this way, when the angles θ, α, etc. are input as necessary command information for creating tomographic images for the left-eye image and the right-eye image,
The arithmetic unit 7 adds the projection data within the range of the angle α, centering on the position shifted by the angle θ to the left and right with the position of θ = 0 ° as the symmetry. As a result, as shown in FIG. 3, two sets of continuous projection data 18a, 18b having a shift of the addition ranges 17a, 17b corresponding to the binocular parallax are extracted, and the projection data for the left eye image and the projection data for the right eye image are extracted. Each tomographic image is created.
Then, the tomographic image for the left eye image is the first display memory 15a.
Is displayed on the first display device 16a via the, and the tomographic image for the right eye image is displayed on the second display device 16b via the second display memory 15b. By stereoscopically viewing the screens of these two display devices 16a, 16b with the naked eye or with a binocular parallax using a stereoscope or the like, the layer thicknesses above and below the cross section 20 (see FIG. 4) are centered. It is possible to observe the stereoscopic tomographic image that it has.

At this time, in digital tomography, by shifting each continuous projection data by an appropriate amount and performing shift addition, tomographic images substantially equivalent to those of the subject 2 taken at different positions on the cross section 20 are obtained. be able to. Therefore, when the three-dimensional tomographic image of the subject 2 is obtained, the cross section 20 is set at an arbitrary position of the subject 2 by performing shift addition instead of simple addition on the projection data of the respective addition ranges 17a and 17b. It is possible to obtain a three-dimensional tomographic image having a certain layer thickness centering on the cross section 20.

Note that in FIG. 4, the positions shifted leftward and rightward by an angle θ around the line of θ = 0 ° are the center of the addition range 17a of the left eye image and the center of the addition range 17b of the right eye image, respectively.
The present invention is not limited to this. For example, the addition ranges 17a and 17b may be shifted leftward and rightward by an angle θ with respect to a line that is tilted slightly leftward from the line of θ = 0 ° by an angle θ ₁ . in this case,
It is possible to observe a three-dimensional tomographic image corresponding to a state in which the subject 2 is viewed from a direction inclined by an angle θ _{1 with} respect to the front surface of the subject 2, and it is also possible to see a hidden portion diagonally below an object.

Moreover, in FIG. 2, the radiation source 1 and the radiation detector 3 are shown.
And are shown as being scanned and moved on a linear trajectory,
The present invention is not limited to this, and the same can be applied to the case where both of the above are moved by scanning along another locus such as a circular orbit by regarding the curved portion as a straight line.

EFFECTS OF THE INVENTION Since the present invention is configured as described above, a tomographic image of an arbitrary tomographic plane in the subject 2 can be obtained with only one tomographic image, and
It is also possible to obtain a three-dimensional tomographic image having an arbitrary layer thickness.
Therefore, unlike the three-dimensional tomography method in the conventional tomography apparatus using the film, it is not necessary to perform the imaging twice on the same imaging site of the subject 2. As a result, an accurate three-dimensional tomographic image can be obtained with little influence of the body movement of the subject 2, and accurate diagnostic information can be obtained for the target site. In addition, the total time required for imaging is shortened, the burden on the patient can be reduced, and the radiation dose can be reduced. Further, it is possible to facilitate the three-dimensional grasp of the cross-sectional structure of the subject 2 which is the original purpose of tomography and increase the added value of the digital tomography apparatus.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a digital tomography apparatus according to the present invention, and FIG. 2 is an explanatory view showing a state in which a radiation source and a radiation detector are moved on a scanning orbit to capture a plurality of projection images. FIG. 3 is an explanatory diagram showing a shift of an addition range of projection data corresponding to binocular parallax for creating a stereoscopic tomographic image, and FIG. 4 is for creating tomographic images for left eye image and right eye image. 5 is a block diagram showing a conventional digital tomography apparatus. 1 ... Radiation source, 2 ... Subject, 3 ... Radiation detector,
4 ... Image pickup tube, 5 ... A / D converter, 6 ... Recording memory,
7 ... Arithmetic unit, 14 ... Arithmetic command unit, 15a, 15b ... Display memory, 16a, 16b ... Display unit, 17a ... Addition range for left eye image, 17b ... Addition for right eye image Range, 18a ... Projection data for left eye image, 18b ... Projection data for right eye image.

Claims (1)

[Claims] 1. A radiation source, a radiation detector which is arranged to face the radiation source with a subject interposed therebetween and which converts a transmitted radiation image into visible light, and an image pickup tube which converts the output optical image into an electric signal. A scanning device for changing the positional relationship between the radiation source and the radiation detector, an A / D converter for converting the output signal of the image pickup tube into a digital amount, a recording memory for storing the digital projection data, A tomographic image of an arbitrary tomographic plane in the subject, which has an arithmetic unit for reading projection data from a recording memory and arithmetically processing it, and a display unit for converting the arithmetically processed digital signal into an analog signal for display. In the digital tomography apparatus for computing and displaying the above, the computing apparatus fetches two sets of continuous projection data having a deviation of the addition range corresponding to the binocular parallax from the recording memory. A calculation command unit that sends command information for performing a shift addition process within the range to create tomographic images for the left eye image and the right eye image is connected, and the left eye image is connected to the output side of the calculation device. A digital tomography apparatus, characterized in that a display memory and a display device are separately provided for the right eye image and the right eye image, respectively.