JPH02156930A - Tomography device - Google Patents

Abstract

PURPOSE:To obtain a clear tomogram responding to a selective exposure, and the speed variation and the inclination angle of an X-ray source holder, and at the same time, to improve the X-ray exposure accuracy and to simplify the circuit, by computing the preset rotation angular position on a curved passage of an X-ray source, and adding a correction value which can be set as desired to the resultant computation to correct the X-ray signal. CONSTITUTION:An encoder 1 divides one rotation of an X-ray tube holder into 1,024 pulses, and the rotation angular position of the X-ray tube holder from the standard exposure starting position is detected in the number of pulses. A counter 2 computes the pulse number from the encoder 1. An exposure starting correcting device 3 is to correct the lag of the actual exposure starting point from the standard exposure starting point, and an adder 33 inputs counter signals f1-f4 being the holder rotation angular position data from responding counters 2, and at the same time, inputs correction signals s7 and s8 from bit shift circuits 32a and 32b to adders 33a and 33b to add these signals to the adders. An exposure position detector 34 receives the outputs from the adder 33 and detects the exposure positions.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to the
The present invention relates to a tomography apparatus that obtains tomographic images on an X-ray film that moves in synchronization with a ray tube.

(Prior Art) A tomography apparatus is a device that photographs the layers of a target part of a subject as an X-ray image, and X-rays that have passed through the subject from an X-ray tube are synchronized with the X-ray tube. A tomographic image is obtained on a moving X-ray film. Conventionally, this type of tomography apparatus generally uses a linear tomography apparatus, and this apparatus obtains tomographic images by moving the X-ray tube and the X-ray film in a straight line while facing each other. On the other hand, recently,
2. Description of the Related Art Tomography apparatuses employing a multi-orbit system in which an X-ray tube and an X-ray film move in a curved orbit around a rotation center have been used, and clearer tomographic images have come to be obtained. In a tomography apparatus employing this type of multi-orbit system, for example, circular orbit imaging is used.

FIG. 4 is a diagram showing X-ray exposure when performing conventional circular orbit imaging. As shown in FIG. 4(a), an X-ray signal s1 for irradiating X-rays is sent from a tomography apparatus (not shown) to an X-ray controller from a reference irradiation start point a1 to a reference irradiation end point b1.

That is, the X-ray signal sl is at point a as shown in FIG. 4(b).
After going around a circular orbit in the counterclockwise direction from 1, it is sent to a point bl, which overlaps the point a1. Then, the X-ray signal s1 is input to the xl controller (not shown), and the actual X-ray exposure s2 is controlled by the X-ray controller as shown in FIG. 4(C).
As shown in the figure, the reference exposure start point al and the reference exposure end point b1 of the X-ray signal s1 are delayed by time tl and t2, respectively, and the actual exposure start point a2 is delayed from the actual exposure end point b.
This will be done up to 2. That is, as shown in FIG. 4(d), it is rotated counterclockwise from the actual irradiation start point a2, and X-ray irradiation is performed to the subject (not shown) until the actual irradiation end point b2. Therefore, only the period from point b2 to point a2 is
The line is not exposed, that is, only the circular trajectory from point a2 to point b2 is photographed on the XGT film (not shown).
There was a problem that clear tomographic images could not be obtained.

Therefore, as a solution, a method as shown in FIG. 5 has conventionally been used. That is, the actual exposure start point a2 and exposure end point b2 are the reference exposure start point a of the X-ray signal s1.
1 and the reference irradiation end point b1, the actual irradiation end point b2 is delayed in advance. The actual irradiation end point b2 is controlled to overlap the actual irradiation start point a2, and the irradiation is performed by a circular movement from point a2 to the same point a2 by going around counterclockwise.

(Problem to be Solved by the Invention) However, in the conventional X-ray irradiation by circular motion, the actual irradiation start point and end point a2 are different from the reference irradiation start point al, M of the X-ray signal s1. This results in a circular orbit whose phase is delayed with respect to the quasi-exposure end point b1. The actual irradiation start point and end point a2 are the reference irradiation start point a1 and end point bi
In order to correct it, it is sufficient to correct it to an angle that is more advanced than the points al and bl.

However, when correcting this X-ray exposure using a conventional device, due to the limitations of the detection mechanism, the rotational speed of the X-ray tube, the oblique angle of the X-ray tube support, and the device 1 that corrects the actual exposure starting point. There is a problem in that the device for correcting the actual exposure end point needs to be corrected individually, making the circuit complicated.

Therefore, an object of the present invention is to obtain a clear tomographic image corresponding to selective irradiation, speed changes of the X-ray source column, and oblique angle when X-rays are irradiated to a subject by circular motion, and It is an object of the present invention to provide a tomography apparatus that can improve the accuracy of X-ray exposure and simplify the circuit.

[Structure of the Invention] (Means for Solving the Problems) The present invention has taken the following measures to solve the above problems. The present invention provides a method for starting reference exposure on the curved trajectory when the X-ray source and the imaging system are moved in a curved orbit around the subject and the X-ray source is irradiating the subject with X-rays. The X-ray control means inputs an X-ray signal that instructs X-ray irradiation to the reference irradiation end point after going around this curved trajectory from the point to the reference irradiation start point and the reference irradiation end point. In a tomography apparatus that irradiates X-rays from the X-ray source at different actual irradiation start points and actual irradiation end points, and uses the imaging system to image the X-rays that have passed through the subject, a detection means for detecting the rotational angular position on the curved trajectory of the X-ray source, a counting means for counting the rotational angular position from the detection means, and a correction value that can be set arbitrarily to the count from the counting means. correction means for advancing or delaying the actual irradiation start point and the actual irradiation end point to match the reference irradiation start point and the reference irradiation end point by adding and correcting the X-ray signal; ,
It is equipped with the following.

(Effects) By taking such measures, the following effects are achieved. The X-ray signal is corrected by adding the preset X-ray source position data and the settable correction value by the correction means, and the corrected X-ray signal allows the actual X-ray irradiation start point and end point to advance or Since the angle θ0 can be corrected from the reference irradiation start point and end point with a delay, there is no gap between X-ray irradiation on the curved trajectory, and a clear tomographic image can be obtained. Therefore, for example, even in the selective exposure 1 circle mode,
X-ray irradiation can be performed accurately even with n rotations, and the accuracy of irradiation can be improved. In addition, it is not affected by changes in the oblique angle, and the WJ
The adjustment time is shortened and the circuit can be simplified.

(Embodiment) FIG. 1 is a block diagram showing the configuration of essential parts of an embodiment of a tomography apparatus according to the present invention. In FIG. 1, the tomography apparatus includes an encoder 1. Counter 2 (2a to 2d), exposure start correction device 3. Flip flop, b4. An irradiation end correction device 5 is provided.

The encoder 1 detects a preset rotation angle position of an X-ray tube support (not shown). Further, the encoder 1 divides one revolution of the X-ray tube support into 1024 pulses, and detects the rotational angular position of the X-ray tube support from the reference exposure start position based on the number of pulses. counter 2
is composed of four counters 2a to 2d each consisting of 4 bits, and counts the number of pulses from the encoder (2). The irradiation start correction device 3 corrects the delay of the actual irradiation start point with respect to the reference irradiation start point, and is configured as follows. Correction switches 81a, 31b
is a binary rotary switch that is provided corresponding to the counters 2a and 2b and performs correction.

The bit shift circuits 32a, 32b receive arbitrarily settable correction signals s5. from the corresponding correction switches 31a, 31b. s8 and the high speed signal H or low speed signal as X-ray tube column rotational speed information, the correction value is adjusted and correction signals s7 to s8 are output. The adder 33 consists of four adders 33a to 33d each consisting of 4 bits, and receives the counter signal fl-f4, which is the X-ray tube column rotation angle position data, from the corresponding counter 2 (2a to 2d). At the same time,
Correction signal s from bit shift circuits 32a and 32b
7. s8 is input to adders 33a and 33b, and these signals are added. The exposure position detector 34 receives the output from the adder 33 (33a to 33d) and detects the exposure position. Therefore, the X-ray exposure timing is corrected to be advanced or delayed.

Flip-flops F and F (hereinafter referred to as F and F) 4 are set based on the output from the exposure position detector 34 and output corrected X-ray signals at the start of exposure, and an exposure end correction device 5 The X-ray signal that has been reset and corrected is output at the end of exposure.

Next, the effects of the embodiment configured as described above will be explained in the first to fourth sections.
This will be explained with reference to the figures. First, an X-ray tube (not shown) is set in advance at a position delayed by 22.5' (-22.5@) from the reference exposure start point a3 (180'). In addition, as shown in FIG. 2(a), the correction switches 31a and 31b adjust the actual X-ray irradiation start point a4 to 180'+22.
．． 5' (57B pulse), and set the actual X-ray irradiation end point b4 to 180°+36 as shown in Figure 2(b).
0° + 22.5" (1800 pulses). Then, when the circular orbit of the tomography device is selected and the hand switch of the X-ray controller 2 (not shown) is pressed, the X-ray tube will move in a circular motion. Start.

Then, the encoder l determines the X-ray tube support position 18.
0'-22,5' is detected as a pulse number of 64 pulses in 1 pulse 0.35'' steps with respect to the reference exposure start position iao''. The number of pulses from encoder 1 is counted by counter 2 (2a to 2d), and a counter signal f
1 to f4 are output to the adder 33.

In addition, the low speed signal which is the pillar rotation speed information and the correction value set by the correction switches 31a and Blb + 22
．． Correction signal s5 as 5@. s8 are input to the bit shift circuits 32a, 32b, thereby correcting signals s7. s8 is output to the adder 33. Suna adder 3
3, the counter signal from the counter 2 and the correction signal from the bit shift circuit 32 are added together and output to F and F4 via the exposure position detector 34. And this F
, F4, and the corrected X-ray signal of the actual exposure start point is output to an X-ray controller (not shown). Therefore, even if the actual irradiation start point is delayed by this X-ray controller, the corrected X-ray signal can easily be used to set the reference irradiation start point 180'+360'' as shown in FIG. 2(a). As shown in FIG.
Exposure can be performed in the range of 0'+380''.The exposure end correction device 5 is also operated in the same manner as the exposure start correction device 3 described above, and is reset by the FF 4 to adjust the X-ray signal to the radiation level. At this exposure end position, as shown in FIG. 2(b), point b5 (-22,5
0 to 4 from point b 4 (+22.5°)
5" correction is possible.

Next, a case will be described in which tomography is performed by moving the column at a HIGH speed. High speed signal H is transmitted to bit shift circuit 32
a, 32b, the correction switch 31
a, 31b correction signal s5. s8 is bit-shifted by the bit shift circuits 32a and 32b, and as shown in FIG. 3(a), the exposure start point aft (-67,5') to the point a4 (+22.
5"), the correction ffi will be twice that of 90". Similarly, the end point of X-ray irradiation is also at the LO as shown in FIG. 3(b).
Exposure end point b6 (-!37.5”) for W speed
- Double correction up to point b4 (+22.5') [
90". Therefore, when the rotational speed of the support column changes, it is possible to switch between the high speed signal H and the low speed signal using the switching signal, adjust the correction value, and prevent a shift in the X-ray exposure timing with respect to the speed.

As described above, according to this embodiment, the exposure start correction device 3. The exposure end correction device 5 sets the reference X-ray exposure position a'3. b3
Since the angle ±θ0 can be corrected from
There are no gaps in radiation exposure, and clear tomographic images can be obtained.

Therefore, for example, even if the selective exposure mode is 1 circle, n
X-ray irradiation can be performed accurately even when rotated, and the accuracy of irradiation can be improved. Furthermore, since it is not affected by changes in the oblique angle, the adjustment time is shortened, and the circuit can be simplified.

Note that the present invention is not limited to the embodiments described above. In the embodiment described above, the HIGH speed is doubled, but other speeds may be used. Furthermore, in the above-described embodiments, circular motion has been described as the motion of the support of the X-ray tube, but for example, an elliptical orbit may also be used. In short, it goes without saying that various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the present invention, there is provided a detection means for detecting a rotational angular position on a preset curved trajectory of an X-ray source, a counting means for counting the rotational angular position from the detection means, and a counting means for counting the rotational angular position from the detection means. By adding an arbitrarily settable correction value to the count value from the means and correcting the X-ray signal, the actual irradiation start point and actual irradiation end point are advanced or delayed, and the reference irradiation start point and standard are set. Since it is equipped with a correction means to match the exposure end point, the reference
The angle ±θ0 can be corrected from the radiation exposure position, eliminating gaps in X-ray radiation on a curved trajectory, and providing a clear tomographic image. Therefore, for example, even in the selective exposure 1-circle mode, X-ray exposure can be performed accurately even with n rotations, and the accuracy of exposure can be improved.

Further, it is possible to provide a tomography apparatus that is not affected by changes in the oblique angle, has a short adjustment time, and can have a simplified circuit.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of the main parts of an embodiment of the tomography apparatus according to the present invention, and Fig. 2 shows the case where the actual X-ray irradiation start and end points are corrected by a maximum of 45''. Figure 3 shows the case where the actual X-ray exposure start and end points are corrected by a maximum of 90'' when the X-ray tube prop is at high speed, and Figure 4 shows the case where the actual FIG. 5 is a diagram showing an irradiation start point and an irradiation end point, and is a diagram showing an improved method of the irradiation method shown in FIG. 4. ■... Encoder, 2... Counter, 3... Exposure start correction device, 4... Flip-flop (F, F),
5... Exposure end correction device, 31... Correction switch,
32... Bit shift circuit, 33... Adder, 34
...Exposure position detector. Applicant's representative Patent attorney Takehiko Suzue Figure 71 Figure 7; Symbol Figure 5: Figure 5

Claims (1)

[Claims] When the X-ray source and the imaging system are moved in a curved orbit around the subject and the X-ray source irradiates the subject with X-rays, this curve starts from the reference irradiation start point on the curved trajectory. The X-ray control means inputs an X-ray signal that instructs X-ray exposure up to the reference exposure end point after completing one revolution on the orbit, and performs different actual exposures with respect to the reference exposure start point and reference exposure end point. In a tomography apparatus that irradiates X-rays from the X-ray source at an irradiation start point and an actual irradiation end point, and uses the imaging system to image the X-rays that have passed through the subject, the X-rays are set in advance. a detection means for detecting the rotational angular position on the curved trajectory of the source; a counting means for counting the rotational angular position from the detection means; A correction means for advancing or delaying the actual exposure start point and the actual exposure end point by correcting the X-ray signal to match the reference exposure start point and reference exposure end point. A tomography device characterized by: