JPH08122443A - Radiation detector - Google Patents

Abstract

PURPOSE: To provide a high sensitivity radiation detector in which energy differ ence measurement can be carried out. CONSTITUTION: A plurality of sets of electrode plates 3 are disposed oppositely, substantially in parallel with an incident X-ray, and housed in an ionization chamber 12 filled with an ionization gas 11. Solid state detectors 4, 5, 6 for detecting X-rays passed through the ionization chamber 12 are arranged tightly on the rear surface of the ionization chamber 12. Signal currents from the ionization chamber 12 and the solid state detectors 4, 5, 6 are measured and converted into signal voltages which are then subjected to difference processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation detector for measuring the difference in X-ray energy.

[0002]

2. Description of the Related Art There are currently two types of X-ray detectors.
One is an ionization chamber filled with an inert gas, especially Xe gas, and the other is a solid-state detector.

FIG. 2 is a block diagram showing the configuration of the ionization chamber detector. In FIG. 2, the X-ray 1 is incident from the window of the detector housing container 2. In the detector, the pressure vessel 12 is filled with the ionized gas 11, and a plurality of sets of electrode plates 3 are arranged inside the pressure vessel 12 so as to face each other substantially parallel to the X-ray incidence direction. Although not shown, a pair of adjacent electrode plates form one element, and the ions generated by the ionization of the sandwiched gas are extracted to the outside as a current component. The signal current is measured by the measuring circuit 22 and sent to the processing device 10 to be stored, calculated, and displayed.

On the other hand, the structure of the solid-state detector is shown in FIG.
Is. In FIG. 3, the X-ray 1 that has entered through the window of the storage container 33 is transmitted from the near-ultraviolet to the scintillator (for example, a fluorescent plate)
Converted to visible light.

The output light of the scintillator 4 is the scintillator 4
It is converted into a current value by the photodiode 5 which is an optical sensor that is in close contact with the back surface of the, and is measured by the measurement circuit 31 via the signal board 6. The measured value is sent to the processing device 10 in the same manner as in the case of the ionization chamber, and is subjected to storage calculation display processing.

[0006]

The above-mentioned two types of X-ray detectors are both excellent in that they have uniform output characteristics, and in the ionization chamber detector (1) they are used most closely. , Stable production is possible. (2) There is an advantage that the removal rate of scattered X-rays is high. On the other hand, the solid-state detector has the advantages of (1) high X-ray collection efficiency and high sensitivity (2) small size, strong mechanical vibration, and long life. However, the ionization chamber detector has the following problems: (1) large loss due to electrodes and isolated parts, low X-ray collection efficiency and low sensitivity (2) small high-energy X-ray blocking capability, and solid-state detector However, since there is no scattered X-ray removal function, it is necessary to add a collimator to reduce the noise level.

Further, in recent years, demands for improving the image quality of X-ray CT have increased, and performances such as energy difference measurement have been demanded, but the above-mentioned conventional two types of individual detectors have not been sufficient. An object of the present invention is to provide a radiation detection apparatus capable of measuring energy difference with high sensitivity.

[0008]

A first detector comprising an ionization chamber in which a plurality of sets of electrode plates, which are installed substantially parallel to and facing each other with respect to incident radiation, are installed together with an ionized gas, and the first detector. Is closely arranged on the rear surface of the detector of the
Second detector comprising a solid-state detector composed of a scintillator / photodiode / signal substrate for detecting the radiation passing through the detector, and each of the signal currents from the first and second detectors is detected. Radiation having a measuring circuit for measuring and converting into a signal voltage, a signal processing unit for performing a difference process between the signal output of the first detector and the signal output of the second detector, a control unit, and a display unit A detection device is disclosed.

[0009]

The first detector, which is an ionization chamber, captures incident radiation (X-rays) of relatively low energy and converts it into a signal current, and a plurality of sets of electrode plates remove scattered X-rays. The second detector, which is a scintillator-based solid-state detector, efficiently captures the high-energy radiation (X-rays) that has passed through the first detector and converts it into a signal current. When the signal output obtained by the first detector and the signal output obtained by the second detector are converted into voltages and the difference is obtained, the energy distribution of the radiation (X-rays) incident on the detector is obtained. be able to.

[0010]

EXAMPLES The present invention will be described in more detail based on the following examples. FIG. 1 is a configuration block diagram of a radiation detection apparatus according to an embodiment. Although the radiation is also applicable to α, β, γ rays, etc., the X-ray signal for X-ray CT (X-ray transmitted through the subject) is mainly taken into consideration.

Further, the reference numerals representing the same parts are the same as those in FIGS. That is, 1 is an incident X-ray (radiation), 2 is a storage container for a detector, 3 is a plurality of sets of electrode plates of an ionization chamber, 4 is a scintillator, 5 is a photodiode, 6 is a signal substrate, 10 is processing of detection signals. An apparatus, 11 is an ionized gas, and 12 is a pressure vessel. In addition to this, 7 is an incident window to the X-ray detector, 8 is a measurement circuit for the outputs of the first and second detectors, and 9 is signal processing for differentially processing the outputs of the first and second detectors , 20 is the signal current from the first detector, and 21 is the signal current from the second detector.

The ionization chamber, which is the first detector, includes a plurality of sets of electrode plates 3 and ionized gas 11 such as Xe, which are installed substantially parallel to the incident radiation and facing each other, together with the lead wires of the electrode plates. Although it is sealed in the pressure vessel 12, in the illustrated embodiment of the invention, behind the electrode plate in the same pressure vessel, there is a second X-ray receiving surface which is substantially perpendicular to the incident radiation. The detector is enclosed with its leads.

The electrode plate 3 is composed of a metal plate or a non-conductor plate such as ceramics on which both surfaces of a metal thin film are patterned. In either case, a plurality of plates are housed at regular intervals, and positive and negative voltages are applied from the outside between a pair of electrode plates facing each other with the ionized gas 11 in between.
Further, the second detection element is installed immediately behind the pair of electrode plates of positive and negative voltages described above with a pitch matched, and is electrically insulated from each other between adjacent solid detection elements. .

Next, the operation of the X-ray detection apparatus according to the embodiment will be described. X incident on the detector housing 2 of the device
The line 1 goes straight into the pressure vessel 12 through the entrance window 7. The pressure vessel 12 is filled with ionized gas 11 and X-ray 1
Pass through the electrode plates 3 substantially in parallel while colliding with gas molecules and ionizing them. In this process, particularly the low energy part is converted into gas ionization and disappears, and the high energy part is incident on the scintillator 4 located behind the electrode plate 3. The gas ionized in the low energy part of the X-ray is collected by the electrode plate by the electric field applied between the electrodes, flows out of the storage container 2 as a signal current 20 and enters the measurement circuit 8.

On the other hand, the high energy part of the X-ray is received by the scintillator 4. The output light of the scintillator 4 is applied to the photodiode 5 closely attached to the back surface of the scintillator 4.
Is detected as photocurrent by. The photocurrent generated is
The signal current 21 enters the measuring circuit 8 via the signal board 6.

Since the scintillator 4 is located behind the electrode plate 3, most of the scattered components other than the signal X-rays incident almost vertically are cut by the electrode plate 3, that is, the electrode plate 3.
Plays the role of the collimator of the second detector and is removed from the signal current 21.

The signal currents 20 and 21 are converted into corresponding signal voltages in the measuring circuit 8 and sent to the signal processing section 9.
The signal processing unit 9 performs signal processing such as selection of outputs of the first detector and the second detector and difference processing thereof. After that, it is sent to the signal processing device 10, where it is stored, operated,
Imaging processing such as composition, imaging, and display is performed.

The radiation detecting apparatus of this embodiment exhibits a spatial resolution corresponding to the element density (electrode plate pitch) of the first and second detectors. In the embodiment described above, the first and second detectors are enclosed in the same pressure vessel 12, but the second detector may be taken out of the pressure vessel.

[0019]

As described above, according to the present invention, high energy X-rays can be detected with high sensitivity while avoiding the influence of scattered radiation, and the low energy side and the high energy side of the signal X-ray spectrum can be detected. It is possible to configure a radiation detection device that can detect the difference on the side.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a radiation detection apparatus according to an embodiment.

FIG. 2 is a block diagram showing a configuration of an ionization box type radiation detection device according to a conventional example.

FIG. 3 is a block diagram showing a configuration of a conventional solid-state radiation detection device using a phosphor.

[Explanation of symbols]

 1 Incident Radiation (X-ray) 2 Storage Container 3 Electrode Plate 4 Fluorescent Plate 5 Photodiode 6 Signal Board 7 Incident Window 8 Measuring Circuit 9 Signal Processing Unit 10 Processing Device 11 Ionizing Gas 12 Pressure Vessel 20 Signal Current 21 Signal Current 22 Measuring Circuit 23 Measuring circuit 33 Storage container

Claims (1)

[Claims] 1. A first detector comprising an ionization chamber in which a plurality of sets of electrode plates, which are installed substantially parallel to incident radiation and are opposed to each other, together with an ionizing gas, and a first detector of the first detector. A second detector which is closely arranged on the rear surface and which is a solid-state detector composed of a scintillator / photodiode / signal substrate for detecting the radiation passing through the first detector, and the first and second A measuring circuit for measuring a signal current from each of the detectors and converting the signal current into a signal voltage, and a signal processing section for performing a difference process between the signal output of the first detector and the signal output of the second detector, A radiation detection apparatus having.