JPH02147883A - Multichannel radiation detecting device - Google Patents

Abstract

PURPOSE:To improve the accuracy of measurement data and to prevent the measurement data from having an omission by providing a correcting means which removes a crosstalk quantity between detectors from the measured values of the detectors. CONSTITUTION:A unit-channel radiation detector consists of a scindillator 1, a light shield material 2, a collimator 3, a photoelectric converting element 4, and an amplifier 5 and many radiation detectors are arrayed to constitute the detection part of the multichannel radiation detecting device. Then the outputs of amplifiers 5 of respective channels are inputted to a crosstalk correcting computing element 6. The output of the computing element 6 is inputted to a calculator memory 7 and a measurement data display device 8. The computing element 6 is stored with correction data regarding the crosstalk quantity between detectors which is measured previously and the outputs of the amplifiers 5 are corrected according to the correction data to find the real quantity of incident radiation.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a multichannel radiation detection device, and in particular,
A multichannel radiation detection device and detection method suitable for removing the effects of crosstalk between detectors due to radiation scattering,
The present invention also relates to a communication rad tomography device using a channel radiation detection device.

[Conventional technology]

Combuti rad tomography device (hereinafter simply C'r
The device is equipped with a multi-channel radiation detection device in which a plurality of radiation detectors are arranged in a row, collects and processes measurement data of this multi-channel radiation detection device, and synthesizes a two-dimensional image. It is used to obtain tomographic images.

Multi-channel radiation detection devices used in conventional CT devices do not have heavy metals such as tungsten between the detectors, as described in Electronic Engineering Progress Series 9, CT Scanners, edited by Yoshinori Iwai, Coronasha (1979) Pi10-P112. A shielding material was used to reduce the effects of crosstalk between detectors.

That is, the conventional C'F device uses 120 keV as radiation.
The radiation multi-channel detection device used a relatively low-energy X-ray, as shown in FIG. As shown in FIG. 12, the electrode plate 21 has bias application loads &21A and signal electrodes 21 arranged alternately.
It consists of B.

Two adjacent bias application electrodes 21A and a signal type [21
When an X-ray enters the section sandwiched by B, the incident X-ray becomes xe
It is absorbed by the gas and ionizes the xe gas. Due to this ionization effect, bias application = fl! A current flows between the signal electrode 21A and the signal electrode 21B. Therefore, by measuring the current flowing through the signal electrode 21B, it is possible to measure the X-rays incident between the adjacent bias application electrode and the signal electrode. Here, the adjacent bias applied voltage fli21A and the signal 'a
The area between the poles 2 i 8 constitutes a unit channel of the radiation detector, and X-ray measurement is performed in each channel.

By the way, when X-rays are absorbed by xe dregs, KX-rays are generated. A portion of the KX-rays generated in each channel enters the adjacent channel and is detected. In this manner, in each channel of the detector, a signal exceeding that corresponding to the actually incident X-ray is detected due to crosstalk between the detectors, causing an error in the measured value. Therefore, in order to reduce the amount of KX rays incident on the adjacent channel, a heavy metal shielding material such as tungsten or tantalum is used as the electrode plate material to shield the KX rays. That is, a heavy metal shielding material such as tungsten is placed between the detectors. When a 0.1-thick tungsten plate is used as this shielding material, the KX-rays of Xe gas (
It absorbs more than 98% of the energy (approximately 30 keV). This shielding material made it possible to minimize crosstalk between the detectors.

[Problem to be solved by the invention]

In the conventional apparatus described above, X-rays incident on each channel are scattered to the adjacent channel, and it is impossible to completely prevent the influence of crosstalk detected in the adjacent channel.

Furthermore, when gamma rays such as cobalt-60 and cesium-137 or high-energy X-rays are used as a radiation source, a solid scintillator with high radiation absorption efficiency is used for the detector instead of Xe gas.

In this case, high-energy X-rays and γ-rays incident on the solid scintillator are Compton-scattered by the solid-state scintillator, and in order to prevent the scattered radiation after Compton scattering from being detected in adjacent channels, the solid-state scintillator of each channel is It is necessary to insert a fairly thick shielding material in between. When the shielding material between each channel is made thicker, there is a problem that not only does the distance between each channel of the detector become longer, but also there is an increase in the area where data is missing where radiation is not measured between each channel. Also in this case, there was a problem in that it was impossible to completely remove the scattered radiation due to Compton scattering with a shielding material, and it was impossible to completely prevent the scattered radiation from being detected in the adjacent channel. .

An object of the present invention is to provide a multi-channel radiation detection device that can almost completely eliminate the effects of crosstalk caused by radiation incident on each channel being scattered and detected in adjacent channels, and that can minimize omissions in measurement data. The present invention also provides a detection method and a CT wave device.

[Means to solve the problem]

The above object is to provide a multi-channel radiation detection device in which a plurality of radiation detectors are arranged in a row, and to perform correction on the output signal 1 of the detector to remove the amount of crosstalk between the detectors from the measured value of the detector. This is achieved by providing means.

Further, the above object is achieved by providing the above multi-channel radiation detection device in the radiation detection section of the CT wave device.

The above object is further achieved by measuring and obtaining correction data related to the amount of crosstalk between the detectors in advance in a radiation detection method using a plurality of radiation detectors arranged in a row, This is achieved by correcting the measured value of the detector using this crosstalk amount correction data to determine the true incident radiation dose.

[Effect]

In the present invention configured as described above, preferably, the amount of crosstalk between the detectors for any radiation source is measured in advance, correction data related to this amount of crosstalk is obtained, and this is stored in the correction means. Then, during actual measurement, the correction means uses this stored correction data for the amount of crosstalk and calculates the true incident radiation dose by discounting the tarost difference between the detectors from the measured value of each detector. Perform calculations.

To measure the amount of crosstalk between detectors in advance, all but one of the entrance slit rows of the detectors are closed.
This is done by looking at the output signal of each detector.

As described above, in the present invention, an incident radiation dose without the influence of crosstalk between detectors is determined.

Furthermore, since there is no need to place a shielding material between the detectors, missing measurement data can be minimized.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

In FIG. 1, the multichannel radiation detection apparatus of this embodiment includes a large number of scintillators 1 arranged in an array with a light shielding material 2 in between. A radiation collimator 3 is installed in the front of each scintillator 1, and a photoelectric conversion element 4 such as a photomultiplier tube or a photodiode that converts the light from the scintillator 1 into an electric current is bonded to the rear of the scintillator 1. An amplifier 5 is connected to each photoelectric conversion element 4,
A current, which is an output signal of the photoelectric conversion element 4, is converted into a voltage by an amplifier 5 and amplified. In this way, scintillator 1
, the photoelectric conversion element 4, and the amplifier 5 constitute a unit channel radiation detector, and a large number of these radiation detectors are arranged in rows to constitute a detection section of a multichannel radiation detection apparatus. Here, the distance between adjacent collimators 3 defines the unit channel width of each radiation detector.

A crosstalk correction calculator 6 is connected to the output side of the amplifier 5, and the output from the amplifier 5 of each channel is crosstalk corrected.
and is input to the correction calculator 6. The output from the crosstalk correction calculator 6 is input to a calculator memory 7 and a measured data display device 8.

The crosstalk correction calculator 6 stores correction data related to the amount of crosstalk between the detectors, which will be described below, and has been determined in advance by measurement. Based on this correction data, the output of the amplifier 5 is corrected to obtain the true value. Find the incident radiation dose.

The correction data stored in the crosstalk correction/correction calculator 6 will be explained below. First, the measurement during the initial setting work of the correction data will be described.

First, as a first step, for a known radiation source, as shown in Figure 2, all but one of the slits of the collimator 3 are closed. All slits except for the slit are blocked. Here, if the weight of radiation incident on the fifth scintillator 1 from the radiation source is ■, then from the amplifier 5 at the rear of this fifth scintillator, the incident radiation &! An output corresponding to μ, ■ is obtained by multiplying ■ by the detection efficiency μ of the scintillator. By the way, from the amplifier 5 at the rear of the fourth scintillator adjacent to the fifth scintillator 1, the light incident on the fifth scintillator An output corresponding to X541 is obtained by multiplying the radiation I by the proportion of the radiation incident on the fifth scintillator that is scattered by the fourth scintillator and detected by the fourth scintillator, that is, the crosstalk rate Xs<. Also, in the third detector separated by one channel,
An output corresponding to 531 is obtained. Similarly, the i-th detector output corresponds to Xs+I. Here, the radiation dose ■ entering from the slit is the intensity of the radiation source,
Determined from the slit shape and the distance between the source and detector. Therefore, μ and XSI are found.

The above operations are performed for each channel, and the detection efficiency μ and crosstalk rate X are similarly determined.

The above results are summarized in a general form in Figure 3.

In FIG. 3, each channel of the detector is designated as 1 to 1. Then, the radiation dose incident on the n-channel detector is I
s, the detection efficiency of the n channel is μ1, the output of the n channel is O, and the ratio of scattering from the n channel scintillator to the m channel scintillator (where m≠n) and being detected by the m channel detector is (Crosstalk rate) is assumed to be Xpm. Then, the n-channel detector output o1 is μm I n from x, ,■, to x+*I+
It is the summation of

If the relationship between the input and output of each channel is organized and represented in a matrix, it will be as shown in FIG. Here, the elements μ of the large matrix. and X- are the values determined by the procedure described above.

On the other hand, the relationship between the input and output shown in Figure 4 is a relationship that also holds true in actual measurements, and the radiation dose emitted to each channel of the detector can be expressed as shown in Figure 5 using the inverse 7-trix A-1 of A. Ru. Therefore, the matrix A is the value μ obtained above.
. If set in advance from and The incident radiation dose can be determined.

This embodiment removes the amount of crosstalk between the detectors from the measured value of the detector based on the above idea, and the fourth
An inverse matrix A-1 of matrix A shown in the figure is stored in the crosstalk correction calculator 6 as correction data related to the amount of crosstalk between detectors. Note that if the detection efficiency μ and crosstalk rate Xsm are determined only once when assembling the detection device, they will not change permanently. Therefore, the initial setting work up to memorizing the above-mentioned inverse matrix A-1 is as follows. It is preferable to carry out this process during the manufacturing process of the detection device.

In actual measurement, the crosstalk correction calculator 6
Using the previously stored inverse matrix A-', crosstalk correction calculations are performed according to the procedure shown in the flowchart of FIG.

That is, each detector output 0, ~0. (Step S1)
, perform the calculation shown in FIG. 5 from the previously stored inverse matrix A''' and the detector outputs 0. to 0. to determine the true incident radiation dose ■1 to I+ for each detector output part ( Step S2), the obtained results I, .

As described above, according to this embodiment, it is possible to obtain the true incident radiation iH+~■, which completely removes the amount of 1 costtalk between detectors, without using a shielding material, and provides highly accurate data. can be obtained.

Furthermore, since there is no shielding material between the detectors, the detectors can be arranged closely, which also has the effect of preventing missing measurement data that conventionally occurs at the shielding material.

A second embodiment of the present invention will be described with reference to FIGS. 7 and 8.

When the properties and shapes of scintillator 1 are all the same, the fourth scintillator
μ, not shown in the figure, are all the same value μ.

In addition, the ratio of scattering to the adjacent scintillator and being detected by the adjacent scintillator, that is, the crosstalk rate X'S, and
. -1 also all have the same value X. Then, taking into account that the proportion of scattering farther away than adjacent scintillators is extremely small, measurements are performed during the initial setting work as follows.

That is, as shown in FIG. 7, one arbitrary scintillator is selected, all other scintillators except the selected scintillator are shielded from the radiation source, and a slit is opened in the entire surface of the selected scintillator. An output μI is obtained from the scintillator with the slits, and outputs xl are obtained from the scintillators adjacent on both sides of the scintillator with the slits. Here, xl is the average of the outputs of the scintillators adjacent on both sides. Since the radiation Jitl incident from the slit is determined from the intensity of the radiation source, the slit shape, and the distance between the radiation source and the detector, μ and X can be determined. If μ and X are determined only once when assembling the detection device, they will remain unchanged almost permanently.

71 Helix A is set as shown in FIG. 8 from the obtained μ and

Then, as in the first embodiment, the obtained inverse matrix A -1 is sent to the crosstalk correction calculator 6 (see FIG. 1).
be stored in advance. Further, the process of storing this A-1 is included in the manufacturing process of the detection device, and in actual measurement, crosstalk correction is performed using the previously determined A-' according to the flowchart shown in FIG.

According to this embodiment, when initializing the correction data, it is only necessary to select one arbitrary scintillator and measure it, so the initial setting can be done in a short time, and the actual measurement can be performed as shown in FIG. Since the matrix A is set using only μ and X, the crosstalk correction calculation time can be further shortened.

A third embodiment of the present invention will be explained with reference to FIG.

This embodiment attempts to perform the same calculation as the first or second embodiment without using a special losstalk correction calculator.

That is, in FIG. 9, the inverse matrix A''' of the matrix A shown in FIG. 4 or FIG. 8 is stored in the total X machine memory 15.
1 is stored in advance, and the crosstalk correction calculation function shown in the flowchart in FIG. 6 is added.
According to this method, the device configuration can be simplified.

An embodiment in which the multi-channel detection device of the present invention is applied to a CT device will be described with reference to FIG. 10.

In FIG. 10, the C'F apparatus includes a radiation source 21, a CT
It consists of a scanner 22, a multi-channel detector 23, a data acquisition and arithmetic processing device 24 including the above-mentioned crosstalk correction arithmetic function of the present invention, and an image display device 25. The multi-channel detector 23 includes a C'F scanner 2.
A radiation beam 26 from a radiation source 21 that has passed through the object to be imaged on the object 1 is incident, and its output is sent to a data collection and arithmetic processing device 24, which collects and collects true incident radiation dose data with crosstalk correction. After the arithmetic processing, a two-dimensional image is synthesized on the image display device 25 to obtain a tomographic image.
Since a crosstalk correction function is added to the system, highly accurate data can be obtained, and the image quality of CT can be improved.

Note that if a solid scintillator with an extremely high radiation absorption coefficient is developed, extremely small detectors can be arranged closely, which can contribute to improving the resolution of -layer CT.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a1 constant data from which the amount of crosstalk between detectors has been removed, so the accuracy of the measurement data can be improved, and since the shielding material between the detectors can be omitted, the measurement data It has the effect of preventing it from coming off. Furthermore, when applied to a C'r device, the image quality of C'r can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of a multi-channel radiation detection device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the initial setting work of the multi-channel radiation detection device, and FIG. The figure shows the relationship between the input and output of the same multi-channel radiation detection device, Figure 4 is a diagram showing the relationship between the input and output in a matrix, and Figure 5 shows the true value from the output of the detector. FIG. 6 is a flowchart showing the calculation procedure performed by the crosstalk correction calculator, and FIG. 7 is a diagram showing a formula for calculating the incident radiation dose; FIG. FIG. 8 is a diagram showing the relationship between input and output of the multi-channel radiation detection device, and FIG. 9 is a diagram for explaining the initial setting work of the device, and FIG. FIG. 2 is a schematic diagram showing the configuration of a channel radiation detection device;
FIG. 0 is a schematic diagram showing the configuration of a CT device to which the multi-channel radiation detection device of the present invention is applied, FIG. 11 is a partially cutaway perspective view of a conventional X-ray detector, and FIG. Xl
& FIG. 3 is a detailed diagram of the electrode section of the detector. Explanation of symbols 1...Scintillator (radiation detector) 2...Light shielding material (same) 3...Collimator (same) 4...Photoelectric conversion element (same) 5...Amplifier (same) 6. ...Crosstalk correction calculator (correction means) 5...
computer memory

Claims (7)

[Claims] (1) In a multi-channel radiation detection device in which a plurality of radiation detectors are arranged in a row, a correction means is provided on the output side of the detector to remove the amount of crosstalk between the detectors from the measured value of the detector. A multi-channel radiation detection device characterized by: (2) The correction means stores correction data related to the amount of crosstalk between the detectors determined in advance by measurement, and the correction means calculates the measured value of each detector based on this correction data. 2. The multi-channel radiation detection device according to claim 1, wherein the true incident radiation dose is determined by correcting the amount of radiation. (3) The correction data stored in advance in the correction means is an inverse matrix A^-^1 consisting of the detection efficiency μ of each detector and the crosstalk rate x between the detectors, and the correction means uses this inverse matrix 3. The multi-channel radiation detection apparatus according to claim 2, wherein the measured value is corrected by performing matrix calculation from A^-^1 and the measured value of the detector. (4) The multi-channel radiation detection device according to claim 1, wherein the correction means is configured as a part of a computer that collects and processes the measured values of the radiation detector. (5) Claim 1, wherein the radiation detectors are arranged in a row without providing a radiation shielding material between the detectors.
The multichannel radiation detection device described. (6) A CT apparatus, characterized in that the multi-channel radiation detection apparatus according to claim 1 is provided in a radiation detection section. (7) In a radiation detection method using a plurality of radiation detectors arranged in a row, correction data related to the amount of crosstalk between the detectors is measured and obtained in advance, and this crosstalk is calculated in advance during actual measurement. A radiation detection method, characterized in that the measured value of the detector is corrected using talk amount correction data to determine the true incident radiation dose.