JPS60216433A - Ionization chamber type radioactive ray detector - Google Patents

Abstract

PURPOSE:To realize fine sampling and improve resolution by providing two stages of integrated detection elements where the cathode electrode plate and anode electrode plate are arranged alternately and the detection elements are arranged with deviation of 1/2 in size of respective elements. CONSTITUTION:Two stages of integrated detection elements 15, 16 where the anode electrode plate 21 and the cathode electrode plate 22 are arranged with a constant interval are accommodated with a pressure vessel consisting of a body 11 and a cover 12 for the radioactive ray beam direction 26 and these are fixed by the electrode supporting bodies 23, 24, thus forming the ionization chamber type radioactive ray detector for CT scanner. When the width of detection element is W, the integrated body 16 is arranged with deviation in distance W/2 for the integrated body 15 in the arranging direction of electrode plate and the length L16 is set longer than the length L15 of integrated body 15. Therefore, fine sampling can be realized even if the electrode interval is not small and the CT image having high resolution can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an ionization chamber radiation detector, and particularly to an ionization chamber radiation detector suitable as an X-ray detector in a CT scanner.

[Background of the invention]

As an ionization chamber radiation detector for a CT scanner, in an electrode assembly in which cathode electrode plates and anode electrode plates are arranged alternately at a predetermined interval, the seven-node electrode plate is divided into two stages in the direction of the X-ray beam, and the front and rear stages are divided into two stages. It is known that different X-ray energies can be detected from the anode of the X-ray. This is disclosed, for example, in the Journal of Computer-Assisted Tomography, July 1978 issue.

[Purpose of the invention]

The object of the present invention is to provide such an ionization chamber type detector,
The goal is to be able to obtain higher resolution.

[Summary of the invention]

The radiation detector of the present invention includes a detection element assembly in which cathode electrode plates and anode electrode plates are alternately arranged at predetermined intervals and fixed to an electrode support made of an insulating material, and a detection element assembly in which cathode electrode plates and anode electrode plates are arranged alternately at predetermined intervals and fixed to an electrode support made of an insulating material. A pressure vessel is also included.

3. Lamp In the present invention, the detection element assembly has two stages in front and behind in the direction of the radiation beam, and each stage is formed by one anode electrode plate and two cathode electrode plates on both sides thereof. It is characterized in that it is arranged with a shift of 1/2 the width of one detecting element, and this arrangement is fixed. The two assemblies measure radiation beams that are offset by 1/2 the width of the detector element, thereby providing projection data with a conventional 1/2 pitch. Moreover, the arrangement pitch of the electrode plates in each stage of the assembly can be the same as that of the conventional one, and manufacturing and assembly costs can also be reduced. In this regard, in conventional detectors, since the arrangement pitch of the electrode plates must be reduced, the associated processing and assembly must be performed with extremely high precision, resulting in a significant increase in cost. However, according to the present invention, high resolution CT can be performed without such problems.
It gives you an image.

In this radiation detector, the level of the output signal of the downstream assembly is reduced compared to that of the preceding stage. However, by making the electrode plates of the front and rear assemblies have different lengths in the direction of the radiation beam, that is, by making the electrode plates of the latter assembly much longer than those of the front stage, The level of the output signal of each stage assembly can be made equal.

Embodiments of the radiation detector of the present invention will be described below with reference to the accompanying drawings.

[Embodiments of the invention]

In FIGS. 1 and 2, reference numeral 10 indicates a pressure vessel. The pressure vessel has a body 11 and a lid 12. The main body is in the shape of a hollow box, a lid is placed over the main body with a gasket 13 interposed therebetween so as to close the opening in the main body, and is fixed to the main body with bolts 14.

As best shown in FIG. 3, sensing element assemblies 15, 16 are enclosed within the interior space of the pressure vessel along with an ionized gas such as xenon gas. Each detection element assembly is supported by a bottom plate 17 fixed to the main body 11. Gasket 13 consists of a printed wiring board, the conductors of which extend into and out of the pressure vessel. The six-page detection elements of each detection element assembly are connected to the conductor of the printed wiring board by lead wires 18 and 19, so that the output signal of each detection element is extracted to the outside via the printed wiring board.

In each of the detection element assemblies, an anode electrode plate 21 and a cathode electrode plate 22 are arranged in one direction at regular intervals.

The electrode supports 23, 24 are made of electrically insulating material and have grooves on their mutually facing sides.

The electrode plates 21.22 are inserted into facing grooves of the supports 23.24 and fixed with adhesive or the like. One detection element is formed by one anode electrode plate and two cathode electrode plates on both sides thereof. Each anode electrode plate has an outwardly extending portion 25 of insulating material 23 . The anode electrode plate of each detection element is this extension part 25.
are connected to the conductor groups of the printed wiring board 13 by lead wires 18 and 19, respectively.

The detection element assemblies 15, 16 are arranged parallel to each other in the main body 11, and the detection element assemblies 16 have a width of 1 to 1, where the width of the detection elements is W. They are arranged offset by a distance W/2 in the direction in which the electrode plates are arranged.

Radiation 26 enters the pressure vessel through window 27. In FIG. 4, electrode plates 21 and 22 of the assembly 15 are shown.
A part of the radiation incident between the electrode plates 21 and 22. ionizes the ionized gas between them. A current corresponding to the amount of incident radiation is generated between ゛ and . at the same time,
The residual radiation ionizes the ionized gas between the electrode plates 21 and 22 of the assembly 16, and a current is generated between the electrode plates 21 and 22 depending on the amount of radiation incident thereon. These occur for each detection element, and the radiation is detected as a beam with a pitch of 1/2 the spacing of the detection elements of the assembly 15.

In this respect, the conventional radiation detector is the assembly 1 in the present invention.
5, the radiation detector according to the present invention can perform sampling with a pitch that is 1/2 compared to this. Therefore, by using the sample obtained with the radiation detector according to the present invention as data for CT image reconstruction, a CT image with better resolution than the conventional radiation detector can be obtained. can be obtained.

The output obtained by the sensing elements of assembly 16 is
The level is smaller compared to the output obtained from that of 5. However, in this radiation detector, as shown in FIG. It is longer than ts,
This is done so that the signals output from the detection elements of both assemblies are at the same level.

〔Effect of the invention〕

As described above, the radiation detector of the present invention can obtain a large nozzle with a finer sampling interval than the conventional one, and there is no need to reduce the electrode plate interval, so processing and Assembly can also be done easily and at low cost.

[Brief explanation of drawings]

The drawing shows an embodiment of the radiation detector of the present invention,
Figure 1 is a plan view, Figure 2 is a front view, Figure 3 is Figure 2 m-
An enlarged cross-sectional view on the m-line, Figure 4 is JP-A-Sho GO-2164.
33(3) FIG. 3 is a sectional view of only the electrode plate taken along the line IV-IV. DESCRIPTION OF SYMBOLS 10... Pressure vessel, 15.16... Detection element assembly, 21... Anode electrode plate, 22... Cathode electrode plate, 23.24... Electrode support body. Agent Patent Attorney Tadashi Akimoto Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A detection element assembly in which cathode electrode plates and anode electrode plates are arranged alternately at predetermined intervals and fixed to an electrode support made of an insulating material, and the detection element assembly is arranged in an ionized gas. It includes a pressure vessel sealed together with a pressure vessel, and has two stages of detection element assemblies, front and rear in the direction of the radiation beam, each stage consisting of one anode electrode plate and two cathode electrode plates on both sides thereof. An ionization box-shaped radiation detector characterized in that the radiation detector is arranged with a width shifted by 1/2 of the width of one detection element formed, and this arrangement is fixed. 2. The radiation detector according to claim 1, wherein the electrode plates at each stage have different lengths in the radiation beam direction.