JPH0134059B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a radiation tomography examination apparatus that is effective in obtaining a tomographic image of a subject using a high-energy radiation beam.

[Technical background of the invention and its problems]

This type of device is a CT (Computed
This device uses an X-ray beam and an image processing computer to accurately reproduce a two-dimensional tomographic image of a three-dimensional object, and is widely used particularly in the medical field.

By the way, when obtaining a two-dimensional tomographic image, there is an It is necessary to drive the motor with a certain correlation, and there have been several methods of controlling the motion.

One of them is called the pencil beam method, in which a single X-ray generator 1 and a single detector 2 are translated in the direction of the arrow shown in FIG. After sampling the X-ray transmission data of the specimen 3 at each predetermined pitch and then rotating it by a predetermined angle in the direction of the arrow B in the figure, this time a translation operation is performed in the direction of the arrow C in the figure, which is the opposite direction to the arrow A in the figure. In this method, the X-ray transmission data of the subject 3 is similarly sampled at each predetermined pitch, and the X-ray transmission data of the subject 3 is collected while repeating this translational-rotational motion until the rotation angle reaches at least 180°. .

The other one is called the fan beam method, which consists of an X-ray generator 1' and, for example, about 256 to 512 detectors 4-1, 4-1, arranged in an arc, as shown in FIG. 2, X-ray detector group 4 with...
The radiation of the fan-shaped X-ray beam 5 from the X-ray generator 1' causes each detector 4-1, 4-
2, sequentially sample the X-ray transmission data of the subject 3 obtained from... in a predetermined order, and then
The detectors 4-1, 4-2,
. . . X-ray transmission data of the subject 3 taken out from the object 3 is sequentially sampled in a predetermined order, and the X-ray transmission data of the subject 3 is collected while repeating this rotational movement until the rotation angle reaches at least 180°. be. FIG. 3 is a timing chart when data obtained by the two drive control means described above is collected. In other words, in FIG. 3, X-ray generators 1, 1' and X-ray detectors 2,
This shows that the ray detector group 4 is rotated by a predetermined angle, and then the X-ray transmission data is sampled based on timing S2.

However, the above two drive control means have the following problems.

(1) Difficulty in installing high-voltage cables, etc.

High-voltage cables are introduced into the X-ray generators 1 and 1' to control the acceleration of electrons, and cooling pipes are introduced to avoid functional deterioration due to heat. If the Very difficult to install,
Another disadvantage is that there are many accidents that damage high-voltage cables.

(2) X-ray beam deviation.

Industrial X-ray generators 1 and 1' often have to generate a higher-energy X-ray beam than those for medical use from the perspective of inspecting industrial products, and for this reason they are generally larger. A heavy weight is used, and it is held by a holding frame to minimize displacement. However, as mentioned above, the X-ray generators 1 and 1' are
Since vibration is generated each time rotation, reverse translation, and rotational motion is repeated, a vibration absorbing material such as rubber is interposed between the X-ray generators 1, 1' and the holding frame to absorb the vibrations. Therefore, the X-ray generators 1, 1' themselves cannot be firmly fixed by the holding frame. As a result, the X-ray generators 1 and 1' and the holding frame tilt each time they are rotated to the right or left, making it impossible to emit an X-ray beam more accurately than the X-ray generators 1 and 1'. There is.

(3) In addition to the above-mentioned drawbacks, the fan-beam method also has the following drawbacks. In general, medical equipment has weak X-ray energy, so
Gas detectors are used as the detectors 4-1, 4-2, . . . . However, the sensitivity of gas detectors decreases when a high-energy X-ray beam is used, such as when inspecting industrial products, and furthermore, the sensitivity becomes uneven. Therefore, when handling high-energy X-ray beams, the detector 4
As -1, 4-2, . . . , solid state detectors such as scintillation detectors and semiconductor detectors are used. However, since solid-state detectors have a larger external shape than gas detectors, it is difficult to mount a large number of detectors 4-1, 4-2, etc. as shown in Figure 2, and as a result, X-ray transmission data The disadvantage is that it cannot collect data with high precision.

[Purpose of the invention]

The present invention has a structure that allows easy introduction of high-voltage cables and cooling pipes and prevents accidents such as damage.
Moreover, it is an object of the present invention to provide a radiation tomography inspection apparatus that does not cause deviation of the X-ray beam during scanning control, maintains high sensitivity and constant sensitivity, and reliably collects data even in the case of high-energy radiation beams. be.

[Summary of the invention]

The present invention provides a rotary turntable on which a subject is placed between a radiation generator that emits a fan-shaped radiation beam and a group of radiation detectors having a plurality of detectors. Each time the radiation detector group is rotated by a predetermined angle, the radiation detector group is moved at least α/
This is a radiation tomography examination apparatus that collects radiation transmission data from the group of radiation detectors while rotating within an angular range of n (α is the fan angle of the radiation beam, n is the number of detectors).

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to FIGS. 4 to 8. First, FIG. 4 shows the arrangement relationship among the radiation generator 11, the subject 12, and the radiation detector group 13. This radiation generator 11 emits a fan-shaped X-ray beam 14 with a fan angle α, and is fixedly installed at a predetermined position and direction. This fan-shaped X-ray beam 14 is irradiated onto the subject 12 through a slit 15. Note that the radiation generator 11 may be one that emits radiation beams 14 other than X-rays depending on the properties of the subject 12.
The subject 12 is placed on a turntable 16, and is rotated by the rotation of the turntable 16. Radiation detector group 13
The method detects the radiation energy transmitted by the subject 12 to obtain radiation transmission data, and this is done by using n detectors 13-1 so as to receive the radiation energy equally within at least the fan angle α and on the same plane. , 13-2, . . . and these detectors 13-1, 13-2, . . . are arranged in an arc shape. Each biopsy device 13-1, 13-2,
... uses a solid-state scintillation detector as shown in Figure 5. This scintillation detector is made up of a scintillator 13a that converts incident radiation into light, a photomultiplier 13b that receives an optical signal and converts it into an electrical signal, and a preamplifier 13c. It is also possible to obtain radiographic data with high sensitivity and constant sensitivity.

Next, FIG. 6 is a diagram showing a drive system for the turntable 16 and the radiation detector group 13. The turntable 16 is controlled by a table drive control section 21. The table control unit 21 includes, for example, a table drive motor that rotates each time an external signal is input, a gear that transmits the rotation of this motor to rotate the turntable 16 by a predetermined angle, and the like. Further, the radiation detector group 13 is controlled by a detector group drive control section 22. The detector group drive control unit 22 rotates the radiation detector group 13 continuously within an angular range of at least α/n or intermittently at every predetermined angle, and includes, for example, a detector group drive motor, a It includes gears and the like that transmit the rotation of the motor to the detector group 13.

Next, FIG. 7 is a block diagram showing the overall configuration of the apparatus. In the figure, 23 is the radiation generator 11
24 is a data acquisition section, 25 is an image reconstruction device such as a computer, and 26 is a CRT display console.

Next, the operation of the device configured as above will be explained. First, when an operation command signal is output from the CRT display console 26, the radiation generation control unit 23 receives the signal and starts the radiation generator 11.
The fan-shaped radiation beam 14 is emitted from the generator 11. On the other hand, the table drive control section 21 similarly uses a signal from the console 26 to rotate the turntable 16 by a predetermined angle using a motor. When the object 12 on the turntable has been rotated by a predetermined angle by the table drive control unit 21, the detector group drive unit 22 is activated by a signal from the console 26 to a predetermined angle Δα=α/ as shown in FIG. The radiation detector group 13 is rotated intermittently or continuously within a range of n in the direction of the arrow shown in the figure. On the other hand, a data collection operation is performed in synchronization with the rotation of this radiation detector group 13. That is, the data collection unit 24 sequentially samples the radiation transmission data obtained by each of the detectors 13-1 to 13-7 in a predetermined order. Therefore, radiation detector group 1
3 is rotated by Δα, data shown by diagonal lines in FIG. 8 will be collected.

When the radiation detector group 13 has finished rotating Δα in this manner, the console 26 is again operated by the table drive control unit 21 in response to a signal from the detector group drive control unit 22.
Give a rotation command signal to. When this signal is received, the table drive control section 21 rotates the turntable 16 by a predetermined angle as described above. After the turntable 16 is rotated, data is collected while similarly rotating the radiation detector group 13 intermittently or continuously within the range of Δα. Note that the rotation of the radiation detector group 13 is as follows:
As shown in FIG. 4, it may be rotated alternately in the direction shown by the arrow H and in the direction shown by the arrow H, or it may be rotated Δα and then returned to its original position and the rotation in the direction shown by the arrow H may be repeated again. As described above, data collection section 2
After collecting the data in step 4, the image reconstruction device 25
reads the data, reconstructs the image, and displays it on the CRT.
It is displayed on the display console 26. This image reconstruction can be realized using almost the same software as the conventional fan beam method.

Note that the present invention is not limited to the above embodiments. Although the detector group drive control unit 22 receives the end timing of rotation of the turntable 16 by a predetermined angle from the console 26, it may receive the timing directly from the table drive control unit 21. The data collection unit 24 also connects the image reconstruction device 2 to the console 26.
Although the data collection timing is determined through step 5, the data collection timing signal may be directly received from the detector group drive control section 22. Further, although scintillation detectors are used as an example of the detectors 13-1 to 13-7, it goes without saying that other detectors can be similarly applied.

〔Effect of the invention〕

Since the present invention is configured as described above, it has the following effects.

(1) Since the radiation generator is fixed, it is particularly effective for those that are unsuitable for movement or have high energy.

(2) By making the radiation generator a fixed type,
The high-voltage cable and cooling system can be drawn in very easily to the line generator, and since the high-voltage cable does not move even during scan control, there is no chance of damage and accidents, and of course the high-voltage cable can be easily insulated. Furthermore, since the X-ray generator can be firmly fixed, it will not be displaced or tilted, and a fan-shaped radiation beam can be emitted accurately.

(3) Furthermore, when using high-energy radiation beams, such as in the inspection of industrial products, solid-state detectors are more advantageous than gas detectors due to the problems of decreased sensitivity and non-uniformity of sensitivity; With conventional methods, it is not possible to mount a solid-state detector with a relatively large external size. In this regard, this device moves a small number of detectors continuously or intermittently by α/n angle each time the subject rotates by a predetermined angle, so even large detectors can be installed and data can be collected reliably. Moreover, even with a high-energy radiation beam, high sensitivity and uniform sensitivity can be achieved.

(4) Furthermore, not only can the number of detectors be reduced, but the rotation angle range is smaller than in conventional systems, which has the advantage of eliminating troubles such as breakdowns.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams explaining the conventional method;
FIG. 3 is a diagram showing the data collection timing in the conventional method, and FIGS. 4 to 8 are shown to explain an embodiment of the radiation tomography examination apparatus according to the present invention. 5 is a configuration diagram of the scintillation detector, FIG. 6 is a schematic configuration diagram showing the drive system of the subject and radiation detector group, and FIG.
The figure is a block diagram showing the overall configuration of the apparatus, and FIG. 8 is a diagram explaining the data collection order. 11... Radiation generator, 12... Subject, 13
... Radiation detector group, 13-1 to 13-7 ... Detector, 16 ... Turntable, 21 ... Table drive control section, 22 ... Detector group drive control section, 2
4...Data collection unit, 25...Image reconstruction device,
26...CRT display console.

Claims (1)

[Claims] 1 A fixedly installed radiation detector that emits a fan-shaped radiation beam, and n detectors arranged equally within at least the fan angle α of the radiation beam emitted from this radiation generator and on the same plane. A group of radiation detectors arranged opposite to each other in an arc shape, a turntable provided between the group of radiation detectors and the radiation generator and rotated with a subject placed thereon, and the turntable rotated by a predetermined angle. a detector driving means for rotating the radiation detector group intermittently or continuously within an angular range of at least α/n each time the turntable rotates by a predetermined angle; A radiation tomography examination apparatus comprising: data collection means for collecting radiation transmission data obtained from a group of radiation detectors rotating within the radiation tomography examination apparatus.