JP2007010332A - Radiation detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation detector capable of detecting a radioactive material existing in a measured part based on a signal by a beta ray when the radioactive material releases the beta ray and other radiation. <P>SOLUTION: A detecting section 31 comprises: a first scintillator 1 for emitting light in response to incoming of the beta ray and other radiation (for example, gamma ray); and a second scintillator 2 that is shielded by a beta ray impermeant matter 9 and emits light in response to incoming of radiation other than the beta ray. An arithmetic section detects a radioactive material existing in the measured part with a calculation using a signal by the first scintillator and a signal by the second scintillator. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radiation detection apparatus suitably used for a nuclear medicine examination or the like for detecting a radioactive substance accumulated in a body tissue by inserting a detection unit into the body after administering a radiopharmaceutical into the body.

  Conventionally, in a nuclear medicine examination, for example, Patent Documents 1 to 5 describe radiation detection apparatuses that detect radioactive substances accumulated in tissues in the body by inserting a detection unit into digestive organs such as the esophagus, stomach, and intestines. There is a radiation detection endoscope. These radiation detection endoscopes are provided with a radiation detection unit in addition to an endoscope probe, find a site suspected of cancer by the endoscope, bring the probe close to the site, and detect the detection unit Thus, the radiation is detected to check whether or not the site is cancerous.

  In this case, in the above-described nuclear medicine examination, 18F-FDG, which is a typical drug that accumulates in cancer as a radiopharmaceutical, is often used. 18F-FDG emits both high energy gamma rays and low energy beta rays.

Japanese Patent No. 2680052 Japanese Patent No. 2682650 Japanese Patent No. 2731170 Japanese Patent No. 2731176 Japanese Patent No. 2793844

  Cancers that occur in the digestive organs of the esophagus, stomach, intestines, etc. (digestive system cancer) are generally thin, so there is little accumulation of radiopharmaceuticals, so radiation from radiopharmaceuticals accumulated in the lesion is detected from outside the body. It ’s difficult. Therefore, in nuclear medicine examination of digestive system cancer, it is appropriate to detect the radiation from the lesion part in a state where the detection part is inserted into the body and the detection part is brought close to the lesion part.

However, 18F-FDG that emits both gamma rays and beta rays is used as the radiopharmaceutical, and the radiation detection endoscope (probe) of Patent Documents 1 to 5 is inserted into the body to detect radiation from the lesion. When doing so, the following problems (a) and (b) occurred.
(A) Gamma rays have high transmittance due to their characteristics. Therefore, even if a collimator for allowing only radiation from a specific direction to enter the scintillator is provided in the detection unit, the gamma rays penetrate the collimator. Therefore, in the radiation detection endoscopes of Patent Documents 1 to 5, even if a collimator is provided in the detection unit, it is difficult to detect only gamma rays from a specific direction because gamma rays reaching from all directions penetrate the collimator. Therefore, in the radiation detection endoscopes of Patent Documents 1 to 5, gamma rays from the background and gamma rays from the lesion cannot be distinguished, and it is considered difficult to identify the lesion.
(B) On the other hand, since the beta ray has low transmittance due to its characteristics, when detecting the beta ray by bringing the detection unit close to the lesion, there is a high possibility that the lesion can be identified. However, in the radiation detection endoscopes of Patent Documents 1 to 5, it is difficult to detect only beta rays.

  The present invention has been made in view of the above-described circumstances. When a radioactive substance emits beta rays and other radiation, the radioactive substance present in the measurement site is detected based on a signal from the beta rays. An object of the present invention is to provide a radiation detection apparatus capable of performing the above.

In order to achieve the above object, the present invention provides a first scintillator that emits light by the incidence of beta rays and other radiation, and a second light that is shielded by a beta-opaque substance and emits light by the incidence of radiation other than beta rays. A detector having a scintillator,
There is provided a radiation detection apparatus comprising: a calculation unit that detects a radioactive substance present in a measurement site by a calculation using a signal from the first scintillator and a signal from the second scintillator.

  The radiation detection apparatus of the present invention acquires beta rays and other radiation signals (signals from the first scintillator) by the first scintillator, and beta rays by the second scintillator shielded by the beta-opaque substance. The signal by the radiation other than (signal by the second scintillator) is acquired. And the radioactive substance which exists in a to-be-measured site | part can be detected based on the signal by a beta ray by calculating using the signal by a 1st scintillator, and the signal by a 2nd scintillator.

In this case, the calculation method using the signal from the first scintillator and the signal from the second scintillator is not particularly limited. For example, the following methods (1) to (3) can be employed.
(1) A method of detecting a radioactive substance present in a measurement site based on a difference between a signal from a first scintillator and a signal from a second scintillator.
(2) A method of detecting a radioactive substance present in a measurement site based on a ratio between a signal from the first scintillator and a signal from the second scintillator.
(3) Detecting radioactive substances present in the measurement site based on the difference between the signal from the first scintillator and the signal from the second scintillator and the ratio between the signal from the first scintillator and the signal from the second scintillator how to.

  In the present invention, examples of the material of the first scintillator and the second scintillator include plastic scintillator, cesium iodide, BGO, and YAP (Ce). Moreover, as a material of a beta ray impermeability substance, stainless steel, tungsten, a tantalum, gold | metal | money, silver etc. can be mentioned, for example.

In the present invention, examples of the arrangement of the first scintillator, the second scintillator, and the beta-opaque substance in the detection unit include the following (A) and (B). It is not limited.
(A) The first scintillator with the radiation incident surface facing forward and the second scintillator with the rear radiation incident surface facing forward are disposed between the first scintillator and the second scintillator. A mode in which a beta-ray-impermeable substance is interposed in
(B) A first scintillator having a radiation incident surface facing outward and a second scintillator having an inner radiation incident surface facing outward, and a first scintillator and a second scintillator A mode in which a beta-opaque substance is interposed between the two.

  In the present invention, in performing the above-described calculation, the light emission of the first scintillator and the light emission of the second scintillator are each transmitted to the photomultiplier tube and converted into an electric signal. The radioactive substance present in the measurement site can be detected by calculation using the electrical signal from the scintillator and the electrical signal from the second scintillator.

  Further, in the present invention, a positioning member capable of positioning in the computed tomography apparatus can be disposed in the detection unit, whereby the position of the detection unit can be displayed on the screen obtained by the computed tomography apparatus. . In this case, examples of the computed tomography apparatus include CT, PET, and MRI. Examples of the positioning member include those using heavy metals, water, Gd aqueous solution, and the like.

  The radiation detection apparatus according to the present invention can be applied to, for example, detection of radioactive substances accumulated in internal tissues in nuclear medicine examinations, for example, exploration of piping contamination in nuclear power plants, nondestructive inspection of structural defects, etc. It is.

  According to the radiation detection apparatus according to the present invention, when a radioactive substance emits beta rays and other radiation, the radioactive substance existing in the measurement site can be detected based on a signal from the beta rays.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples. In the following, the present invention will be described focusing on a case where a nuclear medicine examination is performed using 18F-FDG that emits gamma rays and beta rays as a radiopharmaceutical.

(First embodiment)
1 is an overall perspective view showing a first embodiment of a radiation detection apparatus according to the present invention, FIG. 2 is a longitudinal sectional view of a detection section of the apparatus, FIG. 3 is a transverse sectional view of the detection section of the apparatus, and FIG. It is a circuit block diagram of the same apparatus.

  As shown in FIG. 1, the radiation detection apparatus of this example includes an apparatus main body 40 and a personal computer 41 connected to the apparatus main body 40. The apparatus main body 40 includes an instrumentation casing 29, a guide tube 32 connected to the instrumentation casing 29, a detection probe (detection unit) 31 provided at the tip of the guide tube 32, and an auto pull back that moves the guide tube 32. It has a device 28. The personal computer 41 has a PC main body 33 and a display 34. The automatic pullback device 28 is controlled by the personal computer 41 and can arbitrarily advance, retract, bend and rotate the detection unit 31.

  As shown in FIGS. 2 and 3, the front end of the detection probe 31 has a first scintillator 1 with the front (radiation detection surface) facing forward, and a front (radiation detection surface) behind the front. And the second scintillator 2 facing each other are arranged so as to face each other, and a disk-like beta-ray impermeable substance 9 is arranged therebetween.

  A distal end portion of a cylindrical first light guide 3 is fixed to the outer periphery of the first scintillator 1, and a first scintillator optical fiber group (single wire) 5 is connected to the rear end portion of the first light guide 3. ing. A disc-shaped second light guide 4 is fixed to the back surface of the second scintillator 2, and a second scintillator optical fiber group (single wire) 6 is connected to the back surface of the second light guide 4.

  The structure composed of the above-described members is covered with a substantially disc-shaped tip cap 7 and a light-shielding cover tube 8. A molding material 33 is disposed between the outer periphery of the second scintillator 2, the second light guide 4, and the second scintillator optical fiber group (single wire) 6 and the inner periphery of the first light guide 3.

  The first scintillator optical fiber group (single wire) 5 and the second scintillator optical fiber group (single wire) 6 passing through the guide tube 32 are connected to the distribution device 10 as shown in FIG. 29. In FIG. 4, 11 is a first scintillator optical fiber group (bundle), 12 is a second scintillator optical fiber group (bundle), 13, 14 are distribution devices, and 15 and 16 are random distribution lights for the first scintillator. Fiber group, 17 and 18 are random distribution optical fiber groups for the second scintillator, 19 is a photomultiplier tube, 20 is a divider circuit, 21 is an amplifier, 22 is a pulse height discriminator, 23 is a coincidence circuit, 24 is a controller, 25 Is a high-voltage power supply, 26 is a power supply, 27 is a personal computer, 28 is an automatic pullback device, and 30 is an external power supply.

  In the radiation detection apparatus of the present example, the light emitted from the first scintillator 1 and the light emitted from the second scintillator 2 are transmitted to the photomultiplier tube 19 through optical fibers 5 and 6 and converted into electric signals, and the amplifier 21 and the wave height discriminator. 22. Radioactive substance present in the measurement site by calculation using the electrical signal from the first scintillator 1 and the electrical signal from the second scintillator 2 converted by the photomultiplier tube 19 using the coincidence circuit 23 and the controller 24 Is detected.

(Second Embodiment)
FIG. 5 is an overall perspective view showing a second embodiment of the radiation detection apparatus according to the present invention, FIG. 6 is a longitudinal sectional view of the detection section of the apparatus, FIG. 7 is a transverse sectional view of the detection section of the apparatus, and FIG. It is a circuit block diagram of the same apparatus.

  As shown in FIG. 5, the radiation detection apparatus of this example includes an apparatus main body 140 and a personal computer 141 connected to the apparatus main body 140. The apparatus main body 140 includes an instrumentation casing 139, a guide tube 143 connected to the instrumentation casing 139, a detection probe (detection unit) 142 provided at the tip of the guide tube 143, and an auto pull back for moving the guide tube 143. Device 138. The personal computer 141 has a PC main body 146 and a display 145. The automatic pull back device 138 is controlled by the personal computer 141, and can arbitrarily advance, retract, bend and rotate the detection unit 142.

  As shown in FIGS. 6 and 7, a pair of first scintillators 103 and 104 having a plate-like shape having a circular arc cross section with the front surface (radiation detection surface) facing outward, as shown in FIGS. Are arranged facing each other. In addition, a pair of second scintillators 101 and 102 having a substantially semicircular cross section with the front surface (radiation detection surface) facing outward are disposed inside the first scintillators 103 and 104 so as to face each other. ing. A beta-ray impermeable substance 109 is disposed between the first scintillators 103 and 104 and the second scintillators 101 and 102 and between the second scintillators 101 and 102.

  First scintillator optical fiber groups (single wires) 106 and 108 are connected to the rear ends of the first scintillators 103 and 104. Further, second scintillator optical fiber groups (single wires) 105 and 107 are connected to rear end portions of the second scintillators 101 and 102.

  The structure including the above-described members is covered with a substantially hemispherical tip cap 110 and a light-shielding cover tube 111. A molding material 112 is disposed in a portion where the first scintillators 103 and 104 are not present between the beta-ray impermeable substance 109 and the cover tube 111.

  The first scintillator optical fiber groups (single wires) 106 and 108 and the second scintillator optical fiber groups (single wires) 105 and 107 passing through the guide tube 143 are connected to a distribution device 113 as shown in FIG. It is connected to the instrumentation casing 139. In FIG. 8, 114 and 115 are first scintillator optical fiber groups (bundles), 116 and 117 are second scintillator optical fiber groups (bundles), 118, 119, 120, and 121 are distribution devices, and 122 and 123. , 124, 125 are random distribution optical fiber groups for the first scintillator, 126, 127, 128, 129 are random distribution optical fiber groups for the second scintillator, 130 is a photomultiplier tube, 131 is a divider circuit, 132 is an amplifier, 133 Is a wave height discriminator, 134 is a coincidence circuit, 135 is a controller, 136 is a high voltage power source, 137 is a power source, 141 is a personal computer, 138 is an auto pull back device, and 144 is an external power source.

  In the radiation detection apparatus of this example, the light emission of the first scintillators 103 and 104 and the light emission of the second scintillators 101 and 102 are transmitted to the photomultiplier tube 130 through the optical fibers 106, 108, 105 and 107, respectively, and converted into electrical signals. Then, using the amplifier 132, the wave height discriminator 133, the coincidence counting circuit 134, and the controller 135, the electric signals by the first scintillators 103 and 104 and the electric signals by the second scintillators 101 and 102 converted by the photomultiplier tube 130 are used. The radioactive substance present in the measurement site is detected by the calculation used.

  In the case of performing a nuclear medicine examination using the radiation detection apparatus of the first embodiment and the second embodiment described above, after the radiopharmaceutical (18F-FDG) is administered into the body, the detection unit is placed in the body, for example, the esophagus, stomach, intestine. To obtain a signal by the first scintillator (signal by gamma rays and beta rays) and a signal by the second scintillator (signal by gamma rays alone). In this case, advancement / retraction, bending, and rotation of the detection unit are appropriately performed. The gamma dose incident on the first scintillator and the gamma dose incident on the second scintillator are adjusted to be equal. And the radioactive substance which exists in a to-be-measured site | part is detected by the calculation using the electric signal by the 1st scintillator converted by the photomultiplier tube, and the electric signal by the 2nd scintillator.

  In this case, as described above, as described above, the method is based on one or both of the difference between the signal from the first scintillator and the signal from the second scintillator and the ratio of the signal from the second scintillator to the signal from the first scintillator. Can be adopted.

  In this case, the display includes, for example, a total measured value of gamma rays and beta rays based on a signal from the first scintillator, a measured value of only gamma rays based on a signal from the second scintillator, a signal from the first scintillator and a signal from the second scintillator. It is possible to display the measured value of only the beta ray based on the difference between the two. Further, it is possible to display position information such as a part having a high measurement value or a part having a low measurement value by scanning of the detection unit.

  According to the radiation detection apparatus of 1st Embodiment and 2nd Embodiment, when 18F-FDG which discharge | releases a gamma ray and a beta ray is used as a radiopharmaceutical, the radioactivity which exists in a lesion part based on the signal by a beta ray By detecting the substance, the lesion can be identified. In other words, since beta rays have low energy and low permeability, the beta ray count value at a place other than the lesion is low, and the beta ray count value from the vicinity of the lesion is high, so that the two can be distinguished. The part can be specified.

  In this case, since the radiation incident surfaces of the first scintillator and the second scintillator are facing forward, the radiation detection apparatus of the first embodiment can detect the radiation from the front of the detection unit, and thus, like a stomach It is effective for detecting a lesion in a wide organ. In addition, since the radiation incident surfaces of the first scintillator and the second scintillator are directed outward from the radiation detection apparatus of the second embodiment, radiation from the outside of the detection unit can be detected, and therefore the esophagus, It is effective for detecting a lesion in a narrow tubular organ such as the intestine.

[Experiment 1: Evaluation of detector performance]
In order to verify the effect of the present invention, the following phantom (model) was created, and simulation calculation was performed under the following conditions.

(Phantom)
A plastic scintillator (diameter: 6 mm, thickness: 1 mm) corresponding to the scintillator of the radiation detection apparatus of the first embodiment is located in the center of a sphere filled with a body tissue having a diameter of 30 cm and a specific gravity of 1 and is 2 mm facing this. There is a cancer with a diameter of 10 mm and a thickness of 3 mm. Like the sphere, the specific gravity of the cancer is also 1. The measurement problem is background radioactivity from other than the detection target site, but the radiation detection device of the present invention mainly assumes use in the upper digestive tract, so the head, upper limb, lower limb, etc. The remote part of was considered negligible, and a sphere with a diameter of 30 cm was placed as a background.

(conditions)
185 MBq of 18F-FDG is administered as a radiopharmaceutical to a patient weighing 60 kg, and the drug is uniformly distributed throughout the body. That is, the radioactivity is distributed to a sphere having a diameter of 30 cm in accordance with the weight ratio in the total dose. However, since 18F-FDG is known to accumulate 3 to 8 times as much as normal tissues in cancer, it is assumed here that it accumulates 5 times as much in cancer. In addition, the plastic scintillator used in this experiment has a counting efficiency of approximately 20% when the 18F-FDG beta ray is vertically incident and approximately 1% when a gamma ray is incident. Simulate as 20% and 1% respectively.

(Simulation calculation)
The scintillator measurement (here, calculation) is performed 2 hours after 18F-FDG administration, and the radioactivity is corrected with the half-life of 18F-FDG.
1. Background count rate Radioactivity incident on the scintillator from 18F-FDG uniformly distributed in a sphere having a diameter of 30 cm is measured for both beta rays and gamma rays. The solid angle of the incident radioactivity on the scintillator is calculated, and these values are multiplied by 20% and 1%, respectively, for the scintillator beta ray and gamma ray, and the count rate, that is, the beta ray count and the gamma ray count are obtained.
2. Counting rate from cancer A beta ray and a gamma ray count from a cancer having a diameter of 10 mm and a thickness of 3 mm to a scintillator are obtained by the same method as described above.

(result)
1. Background count rate Beta ray count rate: 61.41 c / s (β2)
Gamma ray counting rate: 49.50 c / s (γ2)
Total: 110.91c / s
2. Count rate from cancer Beta ray count rate: 10.67 c / s (β1)
Gamma ray counting rate: 4.53 c / s (γ1)

(Detection limit value for 18F-FDG beta ray and time required for measurement)
The detection limit of the present detector for beta rays detected from cancer can be viewed as the upper limit of the fluctuation range of the background count value. The upper limit of the fluctuation range of the background count value is a function of the measurement time based on the total count rate of the background, and is obtained by the following formula (X) by Kaiser's 3σ method.
(3/2) × {(3 / T) + [(3 / T) ² + 8Nb / T] ^1/2 } (X)
Nb: Total of background counting rates of gamma rays and beta rays T: Measurement time

In the case of this detector, the count rate of beta rays detected from cancer is 10.67 c / s, so 10.67 c / s = (3/2) × {(3 / T) + [(3 / T ) ² + 8 × 110.91 / T] ^1/2 }, and when this is solved, T = 18.34. In other words, this detector can detect cancer with high reliability because the count value of the beta ray exceeds the count value of the background fluctuation range if it takes 18.34 seconds to measure at one place. it can.

(Measurement of beta ray count value)
With this detector, the measurement when 19 seconds is taken per measurement is as follows.
Total count rate of beta rays and gamma rays = (β1 + β2 + γ1 + γ2) × 19 = 2396.09 c / s
Sum of count rates of gamma rays only = (γ1 + γ2) × 19 = 1026.09 c / s
The difference 1369.52 c / s is the beta ray count value.

[Experiment 2: Evaluation of detector performance]
In order to verify the effect of the present invention, the following phantom (model) was created, and simulation calculation was performed under the following conditions.

(Phantom)
The scintillator was the same as the phantom of Experiment 1 except that a plastic scintillator (vertical and horizontal 6 × 8 mm, thickness 1 mm) corresponding to the scintillator of the radiation detection apparatus of the second embodiment was used.

(conditions)
The conditions were the same as those in Experiment 1.

(Simulation calculation)
The calculation was the same as in Experiment 1.

(result)
1. Background count rate Beta ray count rate: 162.56c / s (β2)
Gamma ray count rate: 87.89 c / s (γ2)
Total: 250.45c / s
2. Counting rate from cancer Beta ray counting rate: 14.86 c / s (β1)
Gamma ray count rate: 6.30 c / s (γ1)

(Detection limit value for 18F-FDG beta ray and time required for measurement)
As in Example 1, the detection limit value for the beta ray of 18F-FDG and the time required for measurement are obtained. The upper limit of the fluctuation range of the background count value is a function of the measurement time based on the total count rate of the background, and is obtained by the above formula (X) by Kaiser's 3σ method. In the case of this detector, Nb (sum of background count rates of gamma rays and beta rays) = 250.45 c / s.
T: Measurement time

In the case of this detector, the count rate of beta rays detected from cancer is 14.86 c / s, so 14.86 c / s = (3/2) × {(3 / T) + [(3 / T ) ² + 8 × 250.45 / T] ^1/2 }, and when this is solved, T = 22.23. That is, this detector can detect cancer with high reliability because the count value of the beta ray exceeds the count value of the background fluctuation range if it takes 22.23 seconds to measure at one place. it can.

(Measurement of beta ray count value)
With this detector, the measurement when 23 seconds are taken per measurement is as follows.
Total count rate of beta rays and gamma rays = (β1 + β2 + γ1 + γ2) × 23 = 6247.03 c / s
Total of counting rate of only gamma rays = (γ1 + γ2) × 23 = 2164.53 c / s
The difference 4082.5 c / s is the beta ray count value.

  As described above, the difference and ratio between the counting rate of beta rays and gamma rays and the counting rate of only gamma rays is greater when the cancer is present (under a uniform background) than when it is absent. When the probe is actually scanned in the gastrointestinal tract, the background count value may fluctuate, but as described above, whether the change in the beta ray count value is within the fluctuation range or exceeds the fluctuation range. Cancer can be detected by sequential calculation.

  From the above-described experiment, it was confirmed that the radiation detection apparatus according to the present invention can be detected with high accuracy in detecting the radioactive substance existing in the measurement site even in the background that is most problematic in actual measurement.

1 is an overall perspective view showing a first embodiment of a radiation detection apparatus according to the present invention. It is a longitudinal cross-sectional view of the detection part of the same apparatus. It is a cross-sectional view of the detection part of the same apparatus. It is a circuit block diagram of the same apparatus. It is a whole perspective view which shows 2nd Embodiment of the radiation detection apparatus which concerns on this invention. It is a longitudinal cross-sectional view of the detection part of the same apparatus. It is a cross-sectional view of the detection part of the same apparatus. It is a circuit block diagram of the same apparatus.

Explanation of symbols

31 detector 1 first scintillator 2 second scintillator 9 beta ray opaque material 5 first scintillator optical fiber group (single wire)
6 Optical fiber group for second scintillator (single wire)
DESCRIPTION OF SYMBOLS 19 Photomultiplier tube 22 Wave height discriminator 23 Simultaneous counting circuit 24 Controller 142 Detection part 103 1st scintillator 104 1st scintillator 101 2nd scintillator 102 2nd scintillator 109 Beta ray impermeable substance 106 1st scintillator optical fiber group (single line) )
108 First scintillator optical fiber group (single wire)
105 Second scintillator optical fiber group (single wire)
107 Optical fiber group for second scintillator (single wire)
130 Photomultiplier tube 132 Amplifier 133 Wave height discriminator 134 Simultaneous counting circuit 135 Controller

Claims (6)

A detection unit comprising: a first scintillator that emits light by incidence of beta rays and other radiation; and a second scintillator that is shielded by a beta-ray-impermeable material and emits light by incidence of radiation other than beta rays;
A radiation detection apparatus comprising: a calculation unit that detects a radioactive substance present in a measurement site by calculation using a signal from the first scintillator and a signal from the second scintillator.   In the detection unit, a first scintillator having a radiation incident surface facing forward and a second scintillator having a radiation incident surface behind the first scintillator are disposed, and the first scintillator and the second scintillator The radiation detection apparatus according to claim 1, wherein a beta-opaque substance is interposed between the radiation detection apparatus and the radiation detection apparatus.   In the detection unit, a first scintillator having a radiation incident surface facing outward and a second scintillator having an inner radiation incident surface facing outward are disposed, and the first scintillator and the first scintillator are arranged. The radiation detection apparatus according to claim 1, wherein a beta-ray opaque material is interposed between the two scintillators.   The light emitted from the first scintillator and the light emitted from the second scintillator are each transmitted to a photomultiplier tube and converted into an electric signal. In the arithmetic unit, the electric signal from the first scintillator after conversion and the first 4. The radiation detection apparatus according to claim 1, wherein a radioactive substance existing in a measurement site is detected by a calculation using an electrical signal from the scintillator.   The radiation detection apparatus according to claim 1, wherein the radiation other than the beta rays is gamma rays. The radiation detecting apparatus according to claim 1, wherein a positioning member capable of positioning in a computed tomography apparatus is disposed in the detection unit.

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