JPS61205900A - Microfocus x rays generator - 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 relates to microfocus X-rays. Conventionally, this type of X-ray generator uses a filament-only cathode and thermoelectrons emitted from this cathode. It is a vacuum diode structure consisting of an anode that collides with the anode and emits X-rays. In particular, in microfocus X-ray tubes, the shape of the filament is made smaller to increase the amount of X411 generated, and the electric field distribution inside the X-ray tube is adjusted to reduce the area of the thermionic beam that collides with the anode target. We are working on ways to do this. Furthermore, the area (actual focal point) seen from the X-ray emission port is also reduced by reducing the angle of the target with respect to the X-ray tube axis.

However, the input energy per unit area of thermionic electrons colliding with the target is almost constant for any X-ray tube, not just a microfocus X-ray tube, due to the thermal characteristics determined by the material used for the anode and the cooling efficiency. be. Therefore, in a microfocus X-ray tube, the X-ray tube current flows only on the order of several 10 μ8 to several 100 μ8. Note that when the X-ray emission aperture is 50 μm, the X-ray tube current is about 100 μA.

For this reason, the X-ray tube is designed to have a structure in which a large amount of current flows through it, but this shortens the life of the target and filament and limits its use to several hundred hours.

(Object of the Invention) The present invention has been made based on the above-mentioned circumstances, and its purpose is to provide microfocus X-rays that can increase the X-ray dose by allowing a large amount of X-ray tube current to flow even in microfocus. The objective is to provide a generator.

(Summary of the Invention) The present invention provides a micro focus It is a device.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a microfocus X-ray generator. In the figure, reference numeral 1 denotes an X-ray generator having an indirectly heated cathode, and a vacuum container 3 is housed inside an outer container 2. This vacuum vessel 3 is provided with a cathode 5 heated by a filament 4 and an anode 6 at a position opposite to the cathode 5, and a target 7 with which thermoelectrons collide is fixed to the anode 6. Note that 8 is an X-ray emission port.

On the other hand, 10 is a pinhole moving unit that moves an X-ray hole holder in which a minute X-ray passage hole (hereinafter referred to as a pinhole) is formed to increase the X-ray tube current of the X-ray generator 1. be. 11 is made of a heavy metal such as tungsten or platinum and is made relatively thin so that X-rays cannot pass through.
This is a wire hole holder in which a pinhole 12 is formed.

A groove 13 is formed on the X-ray hole holder 11, and an arrow (
b) It is designed to move in the direction. The unit movement control section 16 also includes a mechanism for issuing a drive command to the drive motor 14 and for moving the pinhole movement unit 10 itself in the direction of the arrow (b). With the above configuration, the X-ray Ry passes through the pinhole 12 and is irradiated onto the X-ray irradiated object 20.

Here, the X-ray tube current will be explained with reference to FIG. In FIG. 2, F is the focus size of the target 7 seen from the X-ray irradiation object 20, P is the pinhole size, and FP is the required X-ray irradiation field. Also,
21 is the distance between the target 7 and the X-ray irradiated object 20, 22 is the distance from the target 7 to the pinhole 12, and f13 is the distance from the pinhole 1.2 to the X-ray irradiated object 20. . If the positional relationship is as above,
The radiation field FP is obtained as FP-(λ1/i)・(F-(P/2>)...(1), and the effective X as seen from the X-ray irradiated object 20
The tube current SmA is SmA-(11#!2>-P-(1/F)Ip...(
2) It becomes. Here, Ip is xm tube inflow current (X-ray tube current)
[IllAl.

Therefore, the X-ray irradiation field FP is set to 20 m or more, the focus size P is 2.5 m, the pinhole size (actual focus size) P is set to 50 μm, and the distance J23 from the pinhole 12 to the X-ray irradiated object 20 is set to 100 m. Then, the effective X-ray tube current SmA is SmA= (1000/900
) x 50
It becomes 0μA. This value is about twice as high as the conventional one, which is about 100 μ8, and the amount of X-rays is also doubled.

Furthermore, since the X-ray passage path as shown in FIG. 2 is formed, the best shape of the pinhole 12 can be obtained to optimize the X-ray intensity distribution and blur.

An example of the shape of the pinhole 12 is shown in FIG.

That is, X-rays f1, f from both ends of focus size F
2 and the X-ray f3 from the focus size center position Q1,
The shape is determined along the passage path of f4.

In this way, the above embodiment includes the X-ray passing body 11 in which the pinhole 12 for increasing the X-ray tube current p is formed in the radiation path of the X-ray RV generated from the X-ray generator 1. Therefore, the input energy per unit area to the target 7 is constant, and the X-ray tube current can be increased and the X-ray dose can be reduced as a small X-ray source because it has a simple structure and does not require an unreasonable structure. Can be increased. The emitted X-rays have a uniform intensity distribution. Therefore, when an image is obtained using the X-ray irradiation field FP, the image will be of high quality without blur. Further, the X-ray tube used may be of an indirectly heated type, and there is no need to use a microfocus X-ray tube. Therefore, the life of the X-ray tube can be extended. Further X
The wire hole holder 11 is moved by the pinhole moving unit 10
Since the configuration is such that the beam is exposed to the radiation path, micro focus and wide field of view can be used depending on the object to be irradiated with X-rays 20 and its intended use. Since the distance between the pinhole 12 and the Spatial resolution can be improved by moving it to the generator side. Note that if the X-ray tube is of an indirectly heated type and has a filament-only cathode, the
This is because the filament-specific influence appears in the radiation field FP.

Next, an application example of the apparatus shown in FIG. 1 will be described. Fourth
The figure is a configuration diagram when applied to an X-ray imaging device. The generation of X-rays in the X-ray generator 1 is controlled by an X-ray control section 31 which receives commands from the main control section 30 and outputs an X-ray generation signal, and the pinhole moving unit 10 is controlled by the main control section 30. It operates by receiving a signal. An X-ray camera 32 is installed at a position facing the X-ray generator 1.
The image signal output from the camera controller 33 is appropriately processed and sent to the image processing section 34. The image data obtained through the processing by the image processing section 34 is then displayed on the display. If applied to the above-mentioned apparatus, the X-ray intensity distribution is uniform and the radiation dose is large with a small X-ray source, so the displayed image will be of high quality without blurring, and the X-ray generator 1 and Depending on the subject (not shown) placed between the X-ray camera 32 and the X-ray camera 32, the size of the micro focus can be adjusted by moving the bin hold moving unit 10 in the direction of the arrow (c), or the size of the micro focus and the wide X Can be used by switching between line irradiation and ray irradiation.

Next, FIG. 5 shows a configuration diagram when applied to a second generation CT scanner. To briefly explain each part, numeral 36 is an X-ray control part, and numeral 37 is a table movement control part, each of which operates according to commands from a console 38. The table movement control unit 37 rotates the pedestal 39 on which the subject is placed to perform a rotation operation. A plurality of X-ray detection elements are arranged in a position opposite to the X-ray generator 1, for example, 8
An X-ray detector 40 having a channel configuration is installed. The X-ray generator 1 and the X-ray detector 40 move together to perform a traverse operation.

Detection signals for each detection element outputted from the X-ray generator 40 are sent to a data acquisition section 41, converted into digital signals, and sent to a preprocessing section 42 as radiation absorption data.

The preprocessing section 42 sequentially performs offset correction, reference correction, etc. on the received radiation absorption data, and sends the data to the convolution section 43.

The convolution unit 43 performs convolution with a filter function on the radiation data to obtain corrected projection data and sends it to the back projection unit 44 . Then, in this pack projection section 44, the projection data is back-projected from the projection direction of the X-ray generator 1.
This is to obtain reconstructed image data at each pixel position on a dimensional plane. This obtained reconstructed image data is stored in the memory 4.
5 and displayed on the display 46. Note that this device operates according to instructions from a CPU (central processing unit) 47. If applied to a CT scanner in this way, the X-ray intensity distribution will be uniform and the radiation dose will increase, so the displayed image will be free of blur and of high quality. Bin hold moving unit 1 according to the subject (not shown) placed between
0 in the direction of arrow (d) to adjust the size of the microfocus and improve the spatial resolution. In this case, the pinhole moving unit 10G moves toward the tX-ray detector. Although the above two examples have been described, the present invention can be applied to other devices that use X-rays.

Note that the present invention is not limited to the above embodiment. For example, the pinhole may be located at the radiation port 8 of the outer container 2 as shown in FIG. It may be formed. Note that 50 is a target, 51 is a filament, and 52 is a cathode. Even with the above configuration, the same effects as in the above embodiment can be achieved.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide a microfocus X-ray generator that can flow a large amount of X-ray tube current and increase the amount of X-rays even when the X-ray tube is microfocused.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the microfocus X-ray generator according to the present invention, FIG. 2 is a schematic diagram for determining the X-ray tube current of the device of the present invention, and FIG. 3 is a schematic diagram of the device of the present invention. FIG. 4 and FIG. 5 are diagrams showing an example of the shape of a pinhole, FIG. 4 and FIG. 5 are diagrams showing the overall configuration of a device to which the device of the present invention is applied, and FIG. 6 is a diagram showing a modification of the device of the present invention. DESCRIPTION OF SYMBOLS 1... X-ray generator, 3... Vacuum container, 5... Cathode, 6... 7 node, 7... Target, 10...
...Pinhole moving unit, 11...X-ray transparent body,
12... Pinhole, 20... X-ray irradiated object. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 3 C Tsuso

Claims (4)

[Claims] (1) Equipped with an X-ray tube and an X-ray hole holder in which a minute X-ray passage hole is formed in the radiation path of the X-rays generated from the X-ray tube to reduce the effective area of the target of the X-ray tube. A microfocus X-ray generator characterized by: (2) The X-ray tube has an indirectly heated cathode.
1) The microfocus X-ray generator described in section 1). (3) The X-ray passing body is defined in claim (1), in which a minute X-ray passing hole is formed in a shape along the X-ray passing path of the X-rays irradiated to the X-ray irradiated body. micro focus
Line generator. (4) The X-ray passing body has one or both of a mechanism for changing the distance from the X-ray tube and a mechanism for extending the body to the radiation path of the X-rays, as described in claim (1). Microfocus X-ray generator.