JPH0838466A - Computer tomography apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the quality of an image by increasing the number of locations of each focus, under the condition wherein the power consumption for heating of cathodes is kept in small quantities, by providing a means used for relative motion with the cathode, anode and a detector ring. SOLUTION: A ring anode 6, a detector ring 15 which is surrounded by the ring anode 6 and is also coaxially arranged with the ring anode 6, and a ring cathode 42 which is coaxially arranged with the anode 6 are equipped on this device. The ring cathode 42 has a series of cathodes 7, 8, 9, 10,..., and electron beams of cathodes 7, 8, 9, 10,... are triggered stepwise towards the anode 6. The means 40-43 for the relative motion between cathodes 7, 8, 9, 10,..., the detector ring 15 and the anode 6 are also equipped. In addition, the ring cathode 42 is allowed to rotate by a motor. Thus, during the detection of measuring data, the relative motion with each cathode on one side, and that with the anode 6 and the detector ring 15 on the other side are performed at a small rotational speed, which makes it possible to reduce the number of cathodes and the electric power to heat every cathode.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an annular anode, a detector ring which is surrounded by the annular anode and is arranged coaxially with respect to the annular anode, and also coaxially with respect to the anode. Having a cathode ring disposed on, the cathode ring having a series of cathodes, the electron beam of the cathode being
It relates to a computed tomography device (according to the preamble of claim 1) adapted to be triggered in steps towards the anode.

[0002]

2. Description of the Related Art In the case of a computer tomography apparatus of this type, both the anode and the detector ring and the cathode ring are fixed during scanning while irradiating an inspection object at various angles with a fan-shaped X-ray beam bundle. There is. Therefore, the inspection object can be illuminated very quickly over the entire 360 ° angle. Therefore, the image capturing time can be made extremely short.

However, since each individual cathode device of the cathode ring has the same width, the number of each cathode device that can be mounted in the cathode ring, and thus the number of focal positions that can be irradiated, is limited. Is limited. Moreover, the power consumption for heating each cathode is rather high.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a computer tomography apparatus of the type described at the beginning (claim 1).
(By the superordinate concept), while increasing the number of each focus position while keeping the power consumption for heating each cathode small, the image quality can be improved by doing so. is there.

[0005]

This object is achieved according to the invention by means of a computer tomography apparatus of the type described at the outset for relative movement between the cathode on the one hand and the anode and the detector ring on the other hand. Will be solved.

[0006]

1 shows a schematic cross-sectional view and a block connection diagram of an embodiment of a computer tomography apparatus for explaining the technical idea of the present invention, and FIG. 1a shows a computer tomography apparatus of FIG. FIG. 2 shows a part of the computer tomography apparatus taken along the alternate long and short dash line II-II in FIG.

The computer tomography apparatus shown in FIGS. 1, 1a and 2 has a casing 1.
Are supported on two bearings 2 so that they can rotate about a horizontal axis 3. By rotating the casing 1 around the axis 3, it is possible to select the desired position of the transverse layer of the object to be imaged. An X-ray source 4 is provided in the casing 1, and the X-ray source 4 has a vacuumed glass ring 5, and the glass ring 5 is similarly configured as a ring. An anode 6 is provided. The cathode 6 is provided with a large number of cathodes 7, 8, 9, 10 and the like assigned thereto. Each cathode 7 etc. is connected to the switching device 11, and the switching device 11 connects the negative electrode of the high voltage rectifier 12 (powered by the high voltage transformer 13) to each cathode 7 etc. stepwise. The positive electrode of the high frequency voltage rectifier 12 is connected to the positive electrode 6. The primary winding of the high voltage transformer 13 can be connected to the power supply via the main switch 14.

The X-ray source 4 concentrically surrounds a beam receiver 15, which is likewise configured as an annulus, the beam receiver 15 being composed of a series of individual detectors, each individual detector. The number of detectors depends on the number of desired measurements.
In order to adjust the focus of the fan-shaped X-ray beam bundles 16a, 16b, 16c,
A diaphragm device 28 is provided.

In the case of the embodiment of FIG.
Two X-ray beam bundles 16a, 16b, 16c are provided so that a very fast scanning of the object to be imaged is possible. That is, one X-ray beam bundle needs to move while irradiating only an angular portion of about 120 °. Within the scope of the invention,
Depending on the scattered beam correction, it is also possible to use only two or one X-ray beam bundle. In this case, X
The line beam bundle must move while illuminating the 180 ° to 360 ° angular portion. Even in that case, a very high-speed scanning can be performed because the focal point is continuously switched electronically.

The configuration of the switching device 11 is such that a plurality of (three in the embodiment) X-ray beam bundles 16a, 16b, 16c are simultaneously transmitted through the patient from various directions and synchronized with each other at the same step. It is supposed to move. At this time, the central beams of the X-ray beam bundles 16a, 16b, 16c are displaced from each other by 120 °.

The beam receiver 15 is provided on the side of the annular slit diaphragm 37, which restricts the X-ray beam bundles 16a, 16b, 16c in the direction perpendicular to the layer plane. The projections 38 and 39 are provided to shield the X-ray beam directed toward the object to be imaged.

The casing 1 has a central opening 17, into which a bed on which a patient is placed is inserted.

The beam receiver 15 is connected to a measurement value converter 20, which calculates an image of the patient's X-ray transmissive transverse layer from each measurement value and reproduces it by a video device 21. Done in.

The mutual orientation of the X-ray beam bundles 16a, b, c and the beam receiver 15 is such that the X-ray beam bundle first passes by a side position 22 lateral to the beam receiver 15 in the beam direction, When the X-ray beam bundle is transmitted to the patient, the X-ray beam bundle is made to irradiate (impact) the beam receiver 15.

For the examination of the patient, that is to say for the acquisition of layer images, the switch of the switching device 11 is first connected. Thereby, a high voltage is applied between the anode and the three cathodes, and the X-ray beam bundles 16a, 16b, 16c are irradiated, for example, in the directions shown in FIG. After the measured value converter 20 has processed each measured value of the beam receiver 15, the measured value converter sends a signal to the switching device 11 for opening this switch and closing the next switch. Therefore, the axis of symmetry of the X-ray beam bundle is displaced in the direction of the clock hands, for example by 0.1 °. After the measured value converter 20 again detects each measured value of the beam receiver 15, the measured value converter sends a signal to the switching device 11 for opening this switch and closing the next switch. In this way, the axis of symmetry of the X-ray beam bundle is repeatedly displaced by 0.1 °. The stepwise rotation of the X-ray beam bundle is
This is repeated until the line beam bundle illuminates a predetermined angular region (eg 120 °). Then, the shooting of the image is completed, and the calculated cross-sectional image is reproduced by the video device 21.

As can be seen from FIG. 1, the X-ray beam bundle 16
Each of a, b, and c is fan-shaped and has a size such that the entire patient is simultaneously transmitted in the layer plane. The spread of the X-ray beam bundle perpendicular to the layer plane is approximately equal to the layer intensity.

As shown in FIG. 3, teeth 43 are provided on the outer side of the cathode ring 42 (to which the cathode 7 and the like not shown are attached). A worm 41 meshes with the teeth, and the worm is rotated by the motor 40. Thereby, the cathode ring 42
Can be rotated by a motor with respect to the anode 6 and the detector ring 15.

Examples of fixed cathode rings: circumference 3,000 mm Number of cathodes: 3,000 (spacing 1 mm
For a heating power of 10 W per cathode, a fixed cathode ring 42 requires a total of 30 kW just for heating.

On the other hand, in the case of the embodiment of the present invention, the number of cathodes can be reduced to 300 evenly arranged cathodes at intervals of 10 mm, and the cathode ring 42 forms a corresponding number of measured values. To rotate. Heating power is only 3kW
There is nothing. In order to achieve an image capturing time of 100 ms, it is necessary to use a slow rotary motion to achieve 10 mm.
It is necessary to irradiate the cathode for 100 ms. The required rotation speed is 100 mm / s. Therefore, in the case of continuous rotation, the cathode ring 42 is 360 times once in 30 seconds.
Rotate °. Here, the cathodes are controlled according to a time pattern, advantageously simply in a geometrically continuous sequence of cathodes. After 300 triggered irradiations, the first cathode is newly controlled. However, during this period, the cathode slightly changed, namely, 10 ms × 100 mm /
It has moved only = 1 mm.

If a relatively short shooting time has to be realized, the cathode ring 42 has to be rotated at a relatively high speed. In the case of the preferred embodiment of 300 cathodes,
3.000 focus positions can be achieved in 50 ms, with the cathode ring 42 rotating once during 15 s. The number of cathodes can be easily changed in inverse proportion to the rotation time. That is, the smaller the number of cathodes, the faster the cathode ring 42 must rotate.

[0021]

According to the computer tomography apparatus of the present invention, during the detection of the measurement data, the relative movement of each cathode on the one hand and the anode and the detector ring on the other hand is carried out at a small rotational speed so that each cathode is moved. The number and heating power for each cathode can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic sectional view and block connection diagram of an embodiment of a computer tomography apparatus for explaining the technical idea of the present invention.

FIG. 2 is a view of the computer tomography apparatus taken along the alternate long and short dash line II-II in FIG. 1 and viewed in the direction of the arrow.

FIG. 3 is a view showing means for relative movement of the computer tomography apparatus of FIGS. 1 and 2.

[Explanation of symbols]

1 casing, 2 bearings, 4 X-ray source, 5
Glass ring, 6 ring anode, 7, 8, 9, 10 cathode, 11 switching device, 15 beam receiver, 20 measurement value converter, 21 imaging device, 28 diaphragm device

Claims (2)

[Claims] 1. An annular anode (6), a detector ring (15) surrounded by said annular anode and arranged coaxially to said annular anode and also to said anode (6). It has a cathode ring (42) arranged coaxially, the cathode ring has a series of cathodes (7, 8, 9, 10, ...) And the electron beam of the cathode is In a computed tomography apparatus adapted to be triggered stepwise towards the anode (6), on the one hand the cathode (7,8,
, 10) on the one hand and detector means (40 to 43) on the other hand for relative movement between the detector ring (15) and the anode (6). 2. The computed tomography apparatus according to claim 1, wherein the cathode ring (42) is rotatable by a motor.