JPS6092741A - High speed x-ray ct 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] [Technical Field of the Invention] The present invention can be used not only for medical purposes but also for industrial measurements such as the distribution of the Dito ratio of two-phase fluids (vapor volume fraction distribution, defect detection of piping structural materials, etc.) High-speed X-ray CT (Compute
[Technical background of the invention and its problems] X-ray CT devices that take tomographic images of objects to be measured have made dramatic progress, and Xif tubes and detectors are paired to perform linear scanning. Starting with the first-generation CT system, which rotates in the same direction, the fifth-generation ultra-high-speed CT system, which aims for a temporal resolution of 10m5, has recently been developed.

An example of the configuration of a conventional device will be described with reference to FIGS. 1 to 3 of the accompanying drawings. In addition, in the explanation of the following figures, the same elements are indicated by the same reference numerals. Figure 1 shows DSR (Dynam
ic 5patial Reconstructor)
It is a perspective view of an X-ray CT apparatus called. Fourteen X-ray tubes 1 and an X-ray television image pickup tube 2 are combined in a semicircular configuration, and the voltage of the X-ray tubes 1 is switched at high speed by a high-voltage switch 3. This allows IWr without mechanical scanning.
It is possible to take 240 cross sections within 10 m5 at intervals of In, and this can be repeated 60 times per second.

However, this would require too large a device (from the X-ray tube 1 to the main bearing 4, the video signal slip ring 5, etc.).
, very large if you include the high-speed slip lintaro),
Not suitable for industrial measurement. Particularly in places like nuclear reactors where piping is complex and densely packed, traps cannot be used to inspect piping while it is in service. Furthermore, 14 X-ray tubes cannot sufficiently increase the resolution and are not suitable for precise measurements.

Figure 2 shows CV CT (Cardio Vascula).
This is a perspective view of an X-ray CT device called
The figure is a side view thereof. The electron beam 8 emitted from the electron gun 7 has its traveling direction changed by a deflection coil 9.
The semi-circular vacuum vessel 10b passes through the semi-conical vacuum vessel 10.
Irradiation to the semi-annular target ring 11 provided at (irradiation point 1
2) To be done. The X-rays 13 emitted from this 1L pass through a collimator system, pass through the human body, and then are detected by the semi-annular X-ray array sensor 4.

Note that the path of the electron beam 8 is provided by vacuum pumps 15a and 15b.
is kept in a vacuum by In this way, it is possible to take images within 1200 m5 of 8 cross sections. However, the disadvantage is that the deflection coil 9 becomes larger, the electromagnet becomes larger, and vacuum pumps 15a + 15b are required, making the device larger. There is.

[Purpose of the invention]

The present invention has been made in order to overcome the drawbacks of the above-mentioned prior art.It is an object of the present invention to provide a high-speed X-ray CT device that is compact and lightweight and can be used not only for medical purposes but also for industrial measurement. With the goal.

[Summary of the invention]

In order to achieve the above object, the present invention has a plurality of electron guns arranged in a semi-annular shape facing an IJ tongue, a deflection means for each electron gun, and a gold film for deflecting the electron beam of the electron gun. An X-ray array in which the electron beam is continuously scanned over a target ring by electronically switching the emission operation and the deflection operation of the deflection means, and the X-rays emitted from the target ring are placed across the object to be measured. Detected by a sensor,
The present invention provides a high-speed X-ray CT apparatus that obtains a tomographic image of an object to be measured.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 4 to 7 of the accompanying drawings. FIG. 4 is a perspective view of the main part of the same embodiment. n electron guns 7 to 7 are installed facing a semi-annular target ring 11 provided in a semi-annular vacuum vessel 10b. In addition, each of the electron guns 7a to 78 has deflection plates 16a to 1.
6 is installed. Then, a semi-annular X
A line array sensor 14 is provided, which can be moved by a moving rail 18 and a moving device 19.

FIG. 5 is a cross-sectional view of a portion of the semicircular X-ray array sensor 4 of FIG. Conventional array sensors use a pair of scintillators and a large number of photomultiplier tubes, but the resolution is limited by the arrangement of the photomultiplier tubes. Therefore, in this embodiment, as shown in the figure, each light receiving section 21 of the semiconductor CCD element is provided with an optical silicon glass 22f:
The thin plate scintillator 23 is closely attached through the film, and the black adhesive 2/! and store them in a light-shielding container.
A semi-annular X-ray array sensor 14 was used.

Although individual semiconductor COD elements are sensitive to nJ visible light, ultraviolet light, and even X-rays with energies below about 10 KeV, they are sensitive to high-energy (about 15
X-rays (more than KeV) are easily transmitted. Therefore, we used a scintillator that emits well against γ-rays and high-energy X-rays to convert X-rays into visible light and convert semiconductors into visible light.
Convert it into an electrical signal using a CD cable. The width of each light receiving part 21 of the semiconductor CCI) element can be as small as about 25 μm, and the resolution is very high. In addition, the driving clock pulse for signal reading is 5MHz to 10MHz.
This makes it possible to read OCT image data at high speed.

FIG. 6 is a circuit diagram of the embodiment shown in FIGS. 4 and 5. The electron gun 7 includes a cathode that is heated by a heater H (H,, H2) and generates thermoelectrons, a first hole-shaped grid I'01, and a cylindrical second grid G2 that constitutes an electron lens. , a first anode P1, and a second anode P2 that accelerates electrons, and emits a narrow electron beam 8. At this time, if the negative voltage applied to the first grid G1 is increased to below the cutoff voltage, the thermoelectrons are pushed back to the cathode K and the electron beam 8 is not emitted. Therefore, in order to operate only one electron gun 7, the voltage applied to the first grid G of the electron gun 7 can be appropriately reduced, and switching is easy.

Therefore, in this embodiment, in addition to the electron gun power supply circuit for controlling these grids, etc., a first grid control circuit n is provided for switching the firing operation of the electron beam 480 from each child gun 7. Further, a step-like sawtooth wave generating circuit is provided to apply a step-like sawtooth wave to the deflecting plate 168 to 16° for changing the direction of the emitted electron beam 8. A high voltage power source 29 is supplied to the semi-annular target ring 11 .

FIG. 7 is a waveform diagram illustrating changes in signals at each part of the circuit shown in FIG. 6. Signals g1+g2+...gn are sent from the first grid control circuit τ to each electron gun 7a#7b+...78
With the cutoff switching voltage applied to each first grid G1, the electron gun 7a is applied to the electron gun 7a during the period T1, and the electron gun 7b is applied to the electron gun 7b during the period T2.
During the second period T3, the electron beam 8 is emitted from the electron gun 7c.

The signal a is transmitted from the stepped sawtooth wave generating circuit 4 to the electron gun 7a,
Each deflection plate 16a of 7b...7o, IG,...-16
, and the signal S is a sampling signal activation/e pulse with a period ΔT for starting data (signal charge) recording of the semi-annular X-ray array sensor 14. In this way, the electron guns 7a to 7e that emit the electron beam 8 are sequentially switched according to the signals g1 to g+1, and the sawtooth fall signal a is given to the deflection plates 16a to 16e, so that the irradiation point 12 of the electron beam 8 is semicircular. It will move sequentially on the target ring ll. Since the sampling signal starting pulse b is given in synchronization with the stepped saw voltage a, data is recorded from the X-ray array sensor 14 during the period ΔT when the irradiation point 12 of the electron beam 8 is stopped. Therefore, blurring between both CT images is eliminated and the image quality is improved.

In this embodiment, since a semiconductor CCDCD element with a thin plate scintillator is used as the semi-annular X-ray array sensor 14, a sampling clock pulse C with a period Δt is applied to it in synchronization with the sampling signal activation pulse b. . Set the frequency of sampling clock/eRus C to 1
If 0MHz, Δt = ioo psoseconds, ΔT =
100 microseconds, and even if the resolution is much higher than before, it will take 10 milliseconds (T = 10 milJ seconds) per screen.
can achieve high-speed recording.

All recorded data for one screen can be transferred to a plurality of semiconductor memory groups, and reconstruction of the CT image can be completed by the ultra-high-speed CT processor during the next measurement period T. The image data after reconstruction is saved to a disk file,
It will be played back later and the object to be measured will be examined in detail.

〔Effect of the invention〕

As described above, according to the present invention, a plurality of "dL sub-guns are disposed in a semi-annular shape facing a semi-annular target ring, and the electron beam emitting operation of the electron gun and the deflecting operation of the deflection means for each electron gun are performed. This eliminates complex mechanical moving parts and reduces the size of the device by reducing large electromagnets.
It is possible to obtain a high-speed X-string CT device that is lightweight and can be used not only for medical purposes but also for industrial measurement.

In addition, by using an X-ray array sensor with a thin plate-shaped scintillator tightly attached to each light-receiving part of a semiconductor COD element and housed in a light-shielding container, the resolution is improved and both high-quality CT images are sent online every 10 milliseconds. etc. can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view of one configuration example of the conventional device, FIG. 2 is a perspective view of another configuration example of the conventional device, FIG. 3 is a side view of the configuration example of FIG. 2, and FIG. 4 is a perspective view of another configuration example of the conventional device. Perspective view of main parts of one embodiment, No. 5
The figure is a cross-sectional view of a part of the semi-annular X-ray array sensor in Figure 4.
FIG. 6 is a circuit diagram of the embodiment shown in FIGS. 4 and 5, and FIG. 7 is a waveform diagram of signals at various parts of the circuit shown in FIG. 6. 1... X-ray tube, 2... X-ray television imaging tube, 3...
High voltage switch, 4... Main bearing, 5... Video signal slip ring, 6... High speed slip ring,
7゜7a, 7b... 78... Electron gun, 8... Electron beam, 9... Deflection coil, 10a, 105...
Vacuum container, 11... Semi-annular target ring, 12.
...Irradiation point, 13...X-ray, 14...Semi-annular X-ray array sensor, 15a, 15b...Vacuum pump, 16a
, 16b,...16. . . . Deflection plate, 17 . . . Object to be measured, 18 .
...Thin scintillator. Applicant's agent Kiyoshi Inomata Figure 1 Figure 5

Claims (1)

[Claims] 1. A semi-annular target ring, a plurality of electron guns arranged in a semi-annular shape corresponding to the target ring, and deflecting electron beams emitted from each of the electron guns. a plurality of deflection means for irradiating the target ring with the deflection means;
a switching means for sequentially switching the electron beam emitting operation of each of the electron guns; a semi-annular X-ray array sensor provided opposite to the target ring across the object to be measured; and an output of the X-ray array sensor. A high-speed X-ray CT apparatus that processes a tomographic image of the object to be measured, comprising a signal processing means that processes signals. 2. The high-speed X-ray CT apparatus according to claim 1, wherein the switching means switches the deflection operation by the deflection means and presses the electron beam to continuously scan the target ring. 3. The X-ray array sensor has a thin plate-shaped scintillator attached to each light-receiving part of the semiconductor CCD element to block light.