JPS63230152A - Digital televison tomographic imaging apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention involves relatively moving a radiation source and a radiation detector with a subject in between, and irradiating the subject with radiation. Regarding digital television tomography equipment that captures and displays tomographic images of arbitrary tomographic planes, in particular, it is possible to control radiation exposure and capture of projection data by detecting positional information during relative movement between a radiation source and a radiation detector. This invention relates to a digital television tomography device.

[Conventional technology]

Conventional digital television tomography equipment includes a radiation source and
a radiation detector arranged to face the radiation source with the subject in between and convert the transmitted radiation image into visible light; a television camera that converts the output optical image into a video signal; and the radiation source and radiation detector. a fault machine part that relatively moves the
An A/D converter that converts the video signal from the television camera into a digital quantity, a recording device that stores this digital projection data, an arithmetic device that reads the projection data from this recording device and processes it, and this calculation device. It consisted of a display device that converted a processed digital signal into an analog video signal and displayed it, and a controller that controlled each of these elements.

Then, a plurality of images are taken while changing the relative positions of the radiation source and the radiation detector, and tomographic images of arbitrary tomographic planes within the subject are calculated and displayed.

[Problem that the invention seeks to solve]

However, in such a conventional digital television tomography apparatus, the radiation source is moved in a predetermined direction with the subject as the center of movement to emit radiation, and the radiation detector is relatively moved in the opposite direction to emit radiation. From the beginning of the radiation exposure, the subject was photographed and the projected images were independently captured using a radiation detector and a television camera. In this case, the synchronization signal of the television camera and the radiation exposure from the radiation source and the capture of the projected image are not synchronized at all, and the captured image of the projection image into the recording device is at most one frame (1/1 frame).
30 seconds). In such a situation, if you try to reconstruct a tomographic image of an arbitrary tomographic plane a certain distance away from a certain loaded plane using the projection images captured as described above, each projected image is Although the images are shifted and added as appropriate depending on whether the image was captured at the projection position, it becomes uncertain to which projection position the projected image corresponds, and it may not be possible to shift with a highly accurate shift amount. Therefore, blurring occurs in the obtained tomographic image of an arbitrary tomographic plane. Furthermore, since the detection surface of the radiation detector is spherical and radiation is obliquely incident on the detection surface, large distortions occur in the obtained projected image.
At this time as well, if the correspondence between the projection positions of the radiation source at which each projection image was taken was not known, the angle of incidence could not be determined correctly, and distortion correction could not be performed with high precision. Therefore, the obtained tomographic images are difficult to understand, and good diagnostic information may not be obtained.

Therefore, one object of the present invention is to provide a digital television tomography apparatus that can solve such problems.

[Means for solving problems]

Means of the present invention for solving the above problems include a radiation source,
a radiation detector arranged to face the radiation source with the subject in between and convert the transmitted radiation image into visible light; a television camera that converts the output optical image into a video signal; and the radiation source and radiation detector. a fault machine part that relatively moves the
An A/D converter that converts the video signal from the television camera into a digital quantity, a recording device that stores this digital projection data, an arithmetic device that reads the projection data from this recording device and processes it, and this calculation device. It has a display device that converts the processed digital signal into an analog video signal and displays it, and a controller that controls each of these elements, and displays multiple images while changing the relative positions of the radiation source and the radiation detector. In the digital television tomography apparatus that takes images, calculates and displays tomographic images of arbitrary tomographic planes within the subject, the tomographic machine section includes position information for detecting position information between the relative movement of the radiation source and the radiation detector. A digital television that is provided with a detector, sends a detection signal from the position information detector to the controller, and controls the radiation of radiation from the radiation source and the capture of projection data to the recording device based on the position information. This is done using a tomography device.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of a digital television tomography apparatus according to the present invention. This digital television tomography apparatus irradiates a subject with radiation to photograph and display tomographic images of arbitrary tomographic planes within the subject, and includes a radiation source 1, a radiation detector 2, and a television camera 3. , a tomography machine section 4 , an A/D converter 5 , a recording device 6 , an arithmetic device 7 , a D/A converter 8 , a display device 9 , and a controller 10 .

The radiation source 1 irradiates the subject 11 with radiation, and is composed of, for example, an X-ray tube. The radiation detector 2 is
It converts the transmitted radiation image of the subject 11 into visible light, and is composed of, for example, an image intensifier, and is placed opposite the radiation source 1 with the subject 11 in between. The television camera 3 receives the optical image output from the radiation detector 2 and converts it into a video signal. The tomography machine section 4 moves the radiation source 1 and the radiation detector 2, which are attached to opposite ends of the connecting rod 12, relative to each other in the directions of arrows A and B, for example, about a point on the mounting surface 13. , has a drive unit 14 as a power source for the relative movement. The A/D converter 5 receives the video signal output from the television camera 3 and converts it into a digital quantity. The recording device 6 stores the digital projection data output from the A/D converter 5 for each projection position, and is composed of, for example, a frame memory. The arithmetic device 7 reads out the projection data stored in the recording device 6 and performs arithmetic processing, and performs image distortion correction and shift addition to reconstruct a tomographic image of an arbitrary tomographic plane. The D/A converter 8 converts the digital signal processed by the arithmetic unit 7 into an analog video signal. The display device 9 receives the analog video signal output from the D/A converter 8 and displays a tomographic image, and is composed of a television monitor. The controller 10 controls each of the above elements, and the radiation source 1
It is designed to control the radiation exposure, drive control of the tomography machine section 4, and capture of projection data into the recording device 6. In FIG. 1, reference numeral 15 is a high voltage generator for applying a high voltage to the radiation source 1, reference numeral 16 is a tomography controller for controlling the drive of the tomography machine section 4, and reference numeral 17 is a tomography controller for controlling the drive of the tomography machine section 4. This is an operation console that performs operations for setting the imaging mode and displaying tomographic images of arbitrary tomographic planes.

Then, a plurality of images are taken of the two-dimensional radiation transmission or absorption distribution of the subject 11 while changing the relative positional relationship between the radiation source 1 and the radiation detector 2. A linear calculation is performed on a set of projection data passing through one point within the subject 11, and a tomographic image of an arbitrary tomographic plane within the subject 11 is calculated and displayed.

Here, in the present invention, the tomographic machine section 4 is provided with a position information detector 18. This position information detector 1
Reference numeral 8 detects momentary positional information during the relative movement of the radiation source 1 and radiation detector 2 in the directions of arrows A and B, such as information on the imaging angle or imaging position of the radiation source 1. A connecting rod 1 connecting the and radiation detector 2
It consists of an angle detector installed at the center axis of two rotational movements.

The position information detector 18 is connected to the controller 10 via a signal line 19, and the angle detection signal S□ detected by the position information detector 18 is sent to the controller 10 via the signal line 19. It is now possible to do so.

Next, the operation of the digital television tomography apparatus configured as described above will be explained with reference to the timing diagram shown in FIG. First, a drive signal S2 is sent from the controller 1o to the tomography controller 16 in synchronization with a vertical synchronization signal, for example, v2 (see FIG. 2(a)) of the television camera 3 shown in FIG. Then, under the control of the tomography controller 16, the tomography machine section 4 starts scanning in synchronization with the vertical synchronization signal v2, as shown in FIG. 2(b).

At this time, the drive section 14 of the tomography machine section 4 operates,
By rotating the connecting rod 12 in a predetermined direction, the radiation source 1
and the radiation detector 2 start relative movement as shown by arrows A and B. At the same time, the position information detector 18 provided at the center of rotation of the connecting rod 12 also starts operating, and outputs, for example, an angle detection signal S□, as shown in FIG. Send to. The controller 10 is
The detection signal S1 is converted into a vertical synchronization signal V shown in FIG. 2(a).
1+ Vz t Va y...Vn is monitored, and when the value exceeds a preset constant value (threshold) t, this is judged, and in synchronization with the immediately following vertical synchronization signal, for example, v4, a high voltage Exposure signal S to the generator 15
, is sent. Then, this high voltage generator 15 applies a high voltage of a predetermined value to the radiation source 1, so that the radiation source 1 is synchronized with the vertical synchronization signal v4 as shown in FIG. 2(d). radiation exposure.

This radiation passes through the subject 11 and enters the radiation detector 2 placed opposite to it, where the radiation image is converted into visible light, and this output optical image enters the television camera 3 and is converted into a video signal. be done.

The video signal output from this television camera 3 is.

The digital projection data is input to the A/D converter 5 and converted into digital quantities, and the digital projection data output from the A/D converter 5 is sent to the recording device 6. At this time, immediately after the image pickup tube of the television camera 3 starts up, the recording device 6 does not capture projection data while the video signal is not yet stable. Then, as shown in FIG. 2 (8), at a timing when the video signal becomes stable after a while after the radiation starts to be irradiated, for example, the vertical synchronization signal V,
Each frame F11 is continuously displayed for each projection position from the point in time.
FIIF F39... Load projection data into Fn. At this time, at the same time, the controller 10 transmits the data of the detection signal S1 of the momentary position information 1, for example, the photographing angle, during the relative movement of the radiation source 1 detected by the position information detector 18.
, and is recorded in an area that does not affect image display in correspondence with the projection data of each frame F1 to Fn. Then, as shown in Fig. 2(e), when n frames of projection data have been captured, radiation exposure is stopped as shown in Fig. 2(d), and further as shown in Fig. 2(b). For example, scanning of the tomographic machine section 4 is stopped in synchronization with the vertical synchronization signal Vn.

After a tomographic image of the subject 11 is taken in this way, the projection data and position information are read out from the recording device 6 for each frame FL-Fn, and the arithmetic device 7 corrects image distortion and adds shift. is performed to reconstruct a tomographic image of an arbitrary tomographic plane.

The data of the tomographic image reconstructed by the arithmetic unit 7 is converted into an analog video signal by the D/A converter 8, and this analog video signal is input to the display device 9, and the subject 11 is displayed on the screen. A tomographic image of a desired arbitrary tomographic plane is displayed.

Here, the positional information, for example, the angle detection signal S, recorded in the recording device 6 together with each projection data as described above is used for image distortion correction and shift addition calculation processing as described below. First, regarding the correction of image distortion, since image distortion is complicated due to the use of an image intensifier as the radiation detector 2 and oblique incidence on the detection surface, the distortion vectors of the representative points of the five images are taken for each imaging angle. , it is usual to find the distortion vector for each pixel from this representative distortion vector. The representative distortion vector table used for this purpose is shown in Table 1.

Table 1 Here, Pt*pz+..., Pn are representative points on the image, θ□, θ2. ..., on is the representative angle of the photographing angle, and the numerical values a1 to an, b, to bn, -, Q1 to Qn
are respectively angles θ1. θ2. . . . The distortion vector at ON is measured. In the present invention, along with the projection data of each image, the angle θ11 Ll..., o
Since the positional information regarding n is recorded, by performing interpolation calculation in the angular direction, it is possible to accurately obtain the distortion vector for each photographing angle. Therefore, the distortion of one image can be corrected with high precision using this distortion vector.

Next, regarding shift addition, a shift amount table as shown in Table 2 is prepared for each mounting surface.

Table 2 where θ1. θ2. ..., if it is on, it is the representative angle of the photographing angle, and the numerical values p1 to Pn* qi to qn, ... l
z1 to zn are respectively angles θ1. The required shift amount when θ is on is calculated. In the present invention, along with the projection data of each image, the angles θ1, θ2, .・
. . , since the position information related to ON is recorded, the shift amount for each photographing angle can be accurately determined by performing interpolation calculation in the angular direction. Therefore, using this shift amount, shift addition can be performed with high precision. Note that the shift amount is not limited to the one using the shift amount table shown in Table 2, but the shift amount can be expressed analytically once the geometrical system of the tomography device is determined, and the shift amount can be expressed directly using position information related to angle. It can also be calculated from.

In addition, in FIG. 1 and the above explanation, the 1 position information detector 18 is the connecting rod 1 that connects the radiation source 1 and the radiation detector 2.
The angle detector is provided at the central axis of the rotational movement of the radiation source 1, and the angle detection signal S□ is used as position information of the radiation source 11. However, the present invention is not limited to this, and the present invention is not limited to this. Any detector can be used as long as it can detect the angle and position information corresponding to 1=1.
It can be attached to any part of the throat. For example, a position detector that detects the position of the radiation source 1 on the track during relative movement may be attached to the track rail or the drive lever of the drive unit 14, and the detection signal of the position may be used as the position information of the radiation source 1.

〔Effect of the invention〕

Since the present invention is configured as described above, the position information detector 18 detects the position information during the relative movement of the radiation source 1 and the radiation detector 2, and the recording device detects the radiation of radiation from the radiation source 1. In addition to controlling the acquisition of projection data to the recording device 6, the recording device 6 can record positional information of the radiation source 1 in association with projection data at each projection position.

Therefore, it is possible to correctly associate each projection data with which projection position of the radiation source 1 the image was taken.

Therefore, in correcting image distortion, it is possible to accurately obtain a distortion vector for each projection position, and using this distortion vector, it is possible to perform correction of image distortion with high precision. Further, in the shift addition of each projection data, the shift amount for each projection position can be accurately determined, and the shift addition can be performed with high precision using this shift amount.

Therefore, it is possible to obtain a high-quality tomographic image with less image distortion and blurring, making it easy to observe and obtaining good diagnostic information. Furthermore, as described above, it is possible to correctly associate each projection data with which projection position of the radiation source 1 the image was taken.

Various photographing modes can be easily realized by changing the scanning speed or changing the capture angle of projection data.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the digital television tomography apparatus according to the present invention, and FIG. 2 is a timing diagram showing the imaging operation. 1... Radiation source, 2... Radiation detector, 3...
・TV camera, 4...Fault machine section, 5...A
/D converter, 6... Recording device, 7... Arithmetic device, 8... D/A converter, 9... Display device, 1
0... Controller, 11... Subject, 12.
...Connecting rod, 14...Drive unit, 18...Position information detector, 19...Signal line.

Claims (3)

[Claims] (1) a radiation source, a radiation detector placed opposite to the radiation source with the subject in between and converting a transmitted radiation image into visible light; and a television camera converting this output optical image into a video signal; a tomography machine section for relatively moving a radiation source and a radiation detector; an A/D converter for converting a video signal from the television camera into a digital quantity; a recording device for storing this digital projection data; a calculation device that reads projection data from the device and processes it;
It has a display device that converts this processed digital signal into an analog video signal and displays it, and a controller that controls each of these elements, and while changing the relative position of the radiation source and radiation detector. Take multiple images,
In the digital television tomography apparatus that calculates and displays tomographic images of arbitrary tomographic planes within the subject, the tomographic machine section includes a position information detector that detects position information during relative movement between the radiation source and the radiation detector. A detection signal from the position information detector is sent to the controller, and the radiation exposure from the radiation source and the capture of projection data to the recording device are controlled based on the position information. Digital television tomography device. (2) The digital television tomography apparatus according to claim 1, wherein the detection signal from the position information detector is captured and recorded at the same time as the projection data is captured. (3) The digital television tomography apparatus according to claim 1, wherein the tomographic machine section is driven in synchronization with a vertical synchronization signal of a television camera.