JPS6114815B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus capable of obtaining an X-ray body axial tomogram at ultra-high speed.

Recently, an apparatus for acquiring body axial tomographic images using X-rays has been developed and is attracting attention as an innovative medical diagnostic apparatus. Such a device irradiates and scans an object with an X-ray microbeam from various directions, detects the X-rays transmitted through the object in each scanning line, and sends this to a computer to calculate the relative value of the X-ray absorption rate at each point in a virtual matrix. It calculates and displays it as a body axial tomographic image, which is extremely useful for diagnosing tumors inside the body.

However, the currently developed apparatus has a structure in which an X-ray tube with a collimator is mechanically moved and scanned, and is also mechanically rotated around the subject. For this reason, it takes several seconds to several tens of seconds to obtain a series of information on an arbitrary cross section, and therefore it is impossible to obtain a tomographic image of an organ that changes over time, such as the heart.

Of course, strong research is currently underway to speed up imaging, but the mainstream is to arrange a large number of conventional X-ray tubes around the subject and capture a large number of X-rays generated from these tubes and transmitted through the subject. The structure is such that it can be detected simultaneously by two detectors. However, such a device is complicated in structure, large in size, and expensive, which poses a major obstacle in practical use.

The present invention solves the above-mentioned problems and provides an apparatus for obtaining X-ray tomographic images that enables high-speed imaging at several tenths of a second to several hundredths of a second.

Embodiments will be described in detail below according to embodiments shown in the drawings. 1st
In the figures and FIG. 2, 1 is a column supported by a base 2, and is shaped like a bell.
An electron gun 6 consisting of a filament 3, Wehnelt 4, and an anode 5 is installed at the end of the small diameter portion of the lens barrel. Following this electron gun, a focusing lens 7,
A first deflection coil 8 is installed, and after appropriately focusing the electron beam 9 generated from the electron gun, it is largely deflected by the first deflection coil 8 . This deflected electron beam is deflected in the opposite direction by a second deflection coil 10 placed at the large diameter portion of the lens barrel, and the It is projected onto the generation target 11. Reference numeral 12 denotes a coach on which a subject (human being) 14 supported on the base 1 lies, one end of which is inserted into the hollow portion 13 of the large diameter portion of the bell-shaped lens barrel.
Further, it is preferable that the coach is configured to be able to move in the direction of the body axis, in a direction perpendicular to the body axis, and in the vertical direction in order to set the position of the subject. 15 is an X-ray beam guide placed between the target 11 and the subject 14, and as can be seen from FIG.
It has a hole (guide hole) 16 for extracting a fan-shaped X-ray beam X that can cover a desired area of the subject 14 among the X-rays generated from the point P. Of course X
The thickness of the line beam in the body axis direction is made as thin as possible. A rotating body 17 is arranged coaxially with the lens barrel 1 and connected to a motor 19 on the base 2 via a transmission mechanism such as a gear mechanism 18. The beam guide is fixed on this rotating body. Reference numeral 20 denotes an X-ray detector, and a large number (several tens to hundreds) of independent microscopic detection elements are arranged and fixed inside the beam guide 15 so as to form a ring shape or a part thereof. The detection surface is placed on the target 1 so as not to prevent the X-ray beam from the X-ray extraction hole 16 from irradiating the object.
The beam guide 15 is slightly offset from the virtual plane (indicated by line A in the figure) containing the circular electron beam irradiation point (X-ray generation point) on X-rays taken out in an inclined direction are detected by the X-ray detector 20. Reference numeral 21 denotes a position detection device for the beam guide 15, which uses, for example, optical detection means and generates a signal when the X-ray extraction hole 16 of the beam guide reaches a predetermined position. This signal is sent to the deflection power supply 22 and the Wehnelt voltage control circuit 23, and at the same time as the electron beam is emitted, the X-direction and Y-direction deflection coils 8 and 10 are sent to the deflection coils 8 and 10, respectively, to generate a sine wave of a frequency corresponding to the rotational speed of the beam guide. Waves and cosine waves are provided. Thereby, the electron beam 9 can be deflected and moved over the target along the circle C (FIG. 2) following the X-ray extraction hole of the beam guide. This situation is shown in FIG. As can be seen from the figure, the X-ray extraction holes 16 of the beam guide 15 are 16a, 16b,
16c, the electron beam irradiation point moves to P ₁ , P ₂ , P ₃ following this, and the X-ray beam
The object 14 is irradiated from different directions such as X ₁ , X ₂ , and X ₃ . In Figure 3, when point P ₁ is irradiated with the electron beam, the range of the detector is , when point P ₂ is irradiated, the range is , and when point P ₃ is irradiated, the range of is . is used, and the signals from the sensing elements in that range are introduced into the computer.

FIG. 4 is a block diagram showing the outline from the detector to the computer. 24a, 24b, 2 in the figure
4c...24n is a detection circuit, which detects signals from each detection element 20a, 20b, 20c...20n, and amplifiers 25a, 25b, 25c...2
Integrating circuits 26a, 26b, 26c... via 5n.
...26n, and the signal over a certain period of time is integrated. This integral signal is transferred to the next hold circuits 27a, 2.
7b, 27c...27n to the multiplexer 28. The multiplexer is for sending a signal from a desired circuit out of the hold circuits 27a, 27b, 27c, . . . , 27n to the computer 30 via the AD converter 29, and is controlled by the computer. A reset signal is sent from the computer 30 to the integrating circuits 26a, 26b, 26c, . Based on the series of information introduced in this way, the computer 30 calculates the X-ray absorption rate at each point in the virtual matrix and displays it as a tomographic image on the display device 31.

With such a configuration, when the beam guide 15 is rotated at, for example, 1800 rpm, a series of image information is transmitted.
It is not impossible to obtain it in a short time of about 1/30 seconds.

However, in reality, one scan is insufficient due to the problem of signal amount, and it is preferable for accurate analysis to increase the amount of data by measuring angles of view from multiple directions. In this case, it is necessary to accurately synchronize organs that change periodically, such as the heart. FIG. 5 shows an embodiment suitable for achieving such precise synchronization. In this embodiment, a large number (plurality) of X-ray extraction holes 32a, 32b,...32
A beam guide 15 with n is used. In this embodiment as well, the beam guide is rotated at a constant speed, and its X-ray extraction hole is connected to the position detection device 21.
It is always detected by Now, if you want to obtain a tomographic image at the peak of a heart sound, and there is only one X-ray extraction hole, the mechanical rotation speed of the beam guide will be the controlling factor for the time required to acquire a series of data, and even faster It is difficult to hope for a change. In this embodiment, by providing a large number of extraction holes, if a heart sound is detected, even if the beam guide remains fixed, scanning for data acquisition at a large number of viewing angles can be performed using only the electron beam. sell. This makes the accuracy of synchronization detection extremely high. FIG. 6 is a diagram explaining the operation of the embodiment shown in FIG.
indicates, for example, a heart sound peak detection signal. b is a position detection signal of the X-ray extraction hole, which is expressed at equal intervals. The X-ray extraction hole position immediately after the heart sound peak signal is detected is used as the scanning start point, and the electron beam deflection power source 22 and Wehnelt voltage control circuit 23 are controlled by the signal b' in figure b, as shown in c and d. Deflection currents having a sine and cosine relationship are supplied to the X-direction and Y-direction coils in correspondence with the guide hole positions of the beam guide. Further, the Wehnelt voltage shown at e or f is applied to the Wehnelt electrode 4, and the electron beam can be irradiated onto the target for any desired time.
In the case of figure e, the electron beam is projected onto the target during scanning, but in the case of figure f, the electron beam is emitted only during the time when the extraction hole is at the measurement angle position. By irradiating the target with the electron beam only when necessary in this way, the target is not heated unnecessarily, which contributes to preventing damage to the target and increasing power. In order to intermittently irradiate a target with an electron beam, in addition to controlling the electron gun, a shutter device consisting of an electron beam deflector and a slit may be placed in the beam path, thereby allowing the beam to pass intermittently. . It goes without saying that the intermittent irradiation of the beam can also be applied to the embodiment of FIG.

With the configuration described in detail above, the only mechanical drive is the beam guide, and this guide has a very small capacity, and if there is some margin in the guide hole, it is sufficient to rotate at approximately constant speed. and
The exactness of the original data collection location is determined solely by electrical control. Therefore, extremely high-speed synchronization can be achieved and ultra-short-term imaging of several hundredths of a second is possible. Therefore, a device capable of synchronous measurement with internal organs is realized. In addition, since the electron beam is moved at high speed over the target following the rotation of the multi-beam guide, the same effect as a rotating anode cathode type X-ray source can be obtained, and compared to a static X-ray source, the electron beam is moved at high speed over the target. X-rays that are more than twice as strong can be obtained, making highly sensitive measurements possible.

Note that the above embodiment can be modified in various ways. For example, in the figure, the target 11 and the detector 20 are
Although the case of 360 degrees is shown, it may be 120 degrees or 180 degrees depending on the purpose of the device.
In addition, the detector may have a narrow angle range of about 60 degrees, for example, and the rotating body 1 on the opposite side of the X-ray extraction hole in Fig. 1 may be used.
7, and the beam guide may be rotated integrally.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing an embodiment of the present invention, Fig. 2 is a sectional view on plane A thereof, Fig. 3 is a diagram for explaining the scanning situation, and Fig. 4 is a block diagram of the electric circuit. , FIG. 5 is a diagram partially corresponding to FIG. 2 showing another embodiment, and FIG. 6 is an explanatory diagram of its operation. 1 is a bell-shaped lens barrel, 2 is a base, 6 is an electron gun, 7 is a focusing lens, 8 is a first deflection coil, 10 is a second deflection coil, 11 is a target, 12 is a bed, 1
4 is a subject, 15 is a beam guide, 16 is an X-ray extraction hole, 17 is a rotating body, 18 is a gear mechanism, 19
20 is a motor, 20 is an X-ray detector, 21 is an X-ray extraction hole detection device, 22 is a deflection power source, and 23 is a Wehnelt voltage control circuit.

Claims (1)

[Scope of Claims] 1. An X-ray generating target arranged around a subject and forming a ring or a part thereof, means for irradiating a focused electron beam onto the target, and a space between the target and the subject. a beam guide having an X-ray extraction hole for extracting a fan-shaped X-ray beam capable of covering a desired area of a subject; a means for rotating the beam guide around the subject at a substantially constant speed; means for deflecting and moving the electron beam on the target in accordance with the rotation of the X-ray extraction hole, and irradiating the electron beam on the target in a substantially circular shape; In order to detect the electron beam, the detector consists of a large number of detection elements arranged in parallel at positions facing the X-ray extraction hole, and the X-rays generated by irradiating the target with the electron beam are directed to the beam guide. Therefore, the beam guide and the X-ray detector are positioned so that the beam is taken out in a direction tilted at a slight angle with respect to the virtual plane containing the circular electron beam irradiation point on the target and detected by the detector. An apparatus for obtaining an X-ray tomographic image. 2. The apparatus according to claim 1, wherein the X-ray detector has a relatively narrow angular range and rotates integrally with the beam guide. 3. An apparatus for obtaining an X-ray tomographic image according to claim 1, wherein the electron beam irradiated onto the target is blocked at positions other than the measurement angle position. 4. The apparatus according to claim 1, wherein the beam guide is provided with a plurality of X-ray extraction holes,
An apparatus for obtaining an X-ray tomographic image in which an electron beam is deflected and moved to follow one of the holes.