JPH0690289B2 - Method of manufacturing multi-channel ionization chamber type radiation detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a multi-channel ionization chamber type radiation detector used in a third generation X-ray CT apparatus, computer radiography and the like.

[Prior art]

A multi-channel ionization chamber type radiation detector (hereinafter simply referred to as a radiation detector) is composed of a large number of high voltage electrode plates between insulating plates opposite to each other in a metal or glass container filled with _Xe gas having a large radiation absorption coefficient. A large number of signal electrode plates are held alternately.

In particular, in the radiation detector for the CT device, the container and the insulating plate are formed in an arc shape, and the electrode plate is X-shaped between the opposing insulating plates.
Lined up toward the focal point of the tube.

FIGS. 5 and 6 are schematic views showing the structure of this type of radiation detector, and (1) is an insulating plate that supports electrodes, and generally secures an effective field of view sufficient for photographing a human body. For about 80
It has an arc length of 0 mm.

On each facing surface of the insulating plate (1), a large number of electrode supporting grooves (1) 'with a constant angle intersecting at a point (X-ray focus) about 1 m ahead, for example, 0.05 ° equiangular pitch are radially cut. It is cut and a large number (for example, 1000) of electrode plates (2) are inserted and fixed in the groove (1) '.

In the radiation detector having the above structure, each electrode is 10 ¹⁴
It is necessary to insulate and hold more than about Ω, the pitch between adjacent electrodes is narrow at about 0.5 mm to 1.5 mm, and the electrodes are firmly fixed so that they are not vibrated and deformed by external force. Since it is necessary, materials such as ceramics, glass, engineering plastics, etc. that have insulating properties / rigidity / precision workability are used for the insulating plates that support the electrodes.

On the other hand, as a detector of an X-ray CT device, it is necessary to continuously arrange the electrode plates in a length of about 800 mm in order to secure a field of view sufficient for tomography of the human body. The holding insulating plate also has a similar long arc shape. However, it is technically or costly difficult to manufacture the above-mentioned materials such as ceramics, which have the above-mentioned length and have sufficient characteristics for use as an insulating plate.

Therefore, a detector unit (3) having an electrode plate mounted between a pair of small insulating plates having a circular arc length l in which a groove is cut is prepared, and the detector unit (3) is connected to each other as shown in FIG. In addition, a long arc-shaped radiation detector having a predetermined arc length L was obtained.

[Problems to be Solved by the Invention]

In this type of radiation detector, since the electrodes are inserted and held in the grooves of the insulating plate, the error in the processing position of the grooves directly leads to the error in the arrangement of the electrodes.

The electrode support groove of the insulating plate is generally processed by a processing machine such as a diamond saw or a wire saw, but the position where the groove is processed is mechanical backlash and bending of the processing machine, changes in the atmospheric temperature of the installation environment and processing heat. , The design value may slightly deviate due to the thermal expansion of the processing machine and the work piece due to reaction heat.

Therefore, in the conventional method in which a detector unit is formed by supporting electrodes between a pair of small insulating plates and several to ten or more units are connected to form a radiation detector of a predetermined size, each detector unit is The machining accuracy is slightly different for each small insulating plate that forms a groove, and when these are finally connected, a large error exceeding the permissible error in the position of the groove generated for each small insulating plate, especially at the connecting portion, is generated. Occurs.

As a detector for X-ray CT, it is necessary to continuously provide a detection cell (a space between high voltage electrodes facing each other across the signal electrode) even at a connecting portion of a small insulating plate, so that the detection cell in that portion is particularly The characteristics are significantly different from other parts, and ring artifacts are likely to occur.

The position and direction of the grooves of the small insulating plate with the grooves individually processed have their own deviations from the design values. If it is attempted to match the pitches of the grooves in the connecting portion, the directions of the grooves will not intersect at one point, or if they will intersect at one point, the pitch will not match.

It is a time-consuming and difficult task to connect several small insulating plates by aligning the positions and directions of the grooves and the outer shapes.

Also, even if the grooves are machined exactly on the small insulating plate of each detector unit according to the design value and the electrode plates are arranged at equal pitches, when connecting each detector unit, the best arrangement and position of each unit It is not always possible to place them in the same position, and there is a risk that even larger errors will occur if they are arranged and linked at the wrong position.

The present invention has been made to solve the problems of the conventional method. It is possible to arrange electrodes at equal pitches, and especially even at joints of small insulating plates, electrodes can be arranged at equal pitches, and multi-channel ionization with no variation in spatial resolution. It is an object of the present invention to provide a manufacturing method capable of easily manufacturing a box-shaped radiation detector.

[Means for Solving the Problems]

In the method for manufacturing a multi-channel ionization chamber type radiation detector according to the present invention, a plurality of small insulating plates are connected and integrated to form an insulating substrate of a predetermined size, and then an electrode supporting groove is formed on one surface of the insulating plate. The next feature is that the electrode plates are sequentially attached to and supported by the grooves of the grooved insulating plate.

[Action]

 After the small insulating plates are connected and integrated, the electrode supporting groove is processed.

Many of the factors of error in groove processing do not change in a short time when processing one groove, but slowly change in a long time period while processing a large number of grooves. Further, the small insulating plates are already connected before the groove is processed, and the groove provided in the connection portion is also processed at the same time. Therefore, there is no local and discontinuous groove position and direction error in the connecting portion that occurs when the conventional method is used.

Further, since it is not necessary to connect the grooves by aligning the positions and the directions, no error occurs in the process. Therefore,
The electrode plates can be arranged at equal pitch, and a multichannel ionization chamber type radiation detector with uniform spatial resolution can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1 to 3 are perspective views showing steps of manufacturing an insulating substrate of a radiation detector according to the present invention.

Fig. 1 shows a small insulating plate (1
In 1) ′, it is generally a ceramic plate having a large diameter (for example, a radius of 1 m) processed into an arc shape and having an arc length l, width W, and thickness t.

As a first step, the small insulating plate (11) 'is fixedly integrated by connecting the end faces of a plurality of (three in the drawing) so as to have a predetermined arc length (size) to form an insulating substrate (11). . Figure 2 shows the insulating substrate (1
1) is shown.

The fixing method of each small insulating plate (11) 'is to connect the end faces to be joined of each small insulating plate with an adhesive agent or to use a metal plate such as stainless steel as a pedestal to adhere, braze or screw it. You may. A plurality of grooves (12) for supporting the electrode plate are cut and cut on one surface of the insulating substrate (11) formed in the first step. (Second step) The groove may be machined by cutting a small insulator with a dicing saw.
The groove may be formed by etching with a photomask or by adding another insulator on the small insulating plate.

FIG. 3 shows the insulating substrate (11) produced in the second step.
In the next step, the two insulating substrates prepared in the second step are made to face each other in parallel with a distance corresponding to the length of one side of the electrode plate so that the groove surfaces face each other. Insert the plates in sequence and hold them in place. (Third step) In the embodiment, the end face of the small insulating plate (11) 'is cut in the same radial shape as the groove, but as shown in JP-A-57-203982, it obliquely intersects with the groove. Alternatively, a small insulating plate having a cut end face may be used.

FIG. 4 shows an insulating substrate (11) in which the small insulating plates (11) 'thus formed are connected and integrated, and the grooves are cut and processed. Further, in the embodiment, an arc-shaped small insulating plate is prepared and a plurality of arc-shaped insulating plates are connected to form an arc-shaped insulating substrate having a predetermined arc length.
A plurality of small insulating plates may be connected and integrated, and then processed into an arc shape, or a groove may be cut and processed, and then processed into a predetermined shape and size such as an arc shape. Further, although the insulating substrate is formed in an arc shape in the embodiment, it may be formed in a rectangular shape and the grooves parallel to each other on one surface thereof or the radial grooves converged at one point may be cut.

Furthermore, when a plurality of small insulating plates are connected and integrated with a pedestal, especially by screwing, after fixing the fixed small insulating plates after the groove processing in the second step, Disassemble into small insulating plates, and make two small insulating plates with grooves facing each other to hold the electrode plate to make a detector unit. Connect a plurality of detector units and fix them to the pedestal for detection. You may make a container.

〔effect〕

According to the present invention, the position accuracy of the groove is improved, and a highly accurate multi-channel ionization chamber type radiation detector having a uniform pitch pitch between adjacent electrode plates and its direction accuracy and uniform sensitivity can be manufactured easily and inexpensively.

If the multi-channel ionization chamber type radiation detector manufactured according to the present invention is used in an X-ray CT apparatus, a good quality reconstructed image without ring artifacts can be obtained.

[Brief description of drawings]

1 to 3 are processed views of an insulating substrate (perspective view) for explaining a part of a manufacturing method according to an embodiment of the present invention, and FIG. 4 is a processed view of an insulating substrate of another embodiment. (Perspective view), FIG. 5 is a perspective view showing a schematic configuration of a conventional radiation detector, and FIG. 6 is a partially enlarged view of FIG. 11: Insulation board, 11 ': Small insulation board, 12: Groove

Claims (1)

[Claims] 1. A radiation detector comprising a plurality of electrode plates mounted on a pair of insulating plates arranged in parallel, wherein a step of connecting and integrating a plurality of small insulating plates to form an insulating substrate; Method for manufacturing a multi-channel ionization chamber type radiation detector comprising: forming a groove for supporting the electrode plate on one surface; and inserting an end portion of the electrode plate into the groove sequentially and mounting the electrode plate on an insulating substrate .