JP2002341040A - Radiation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized radiation detector with high precision used in a place limited in setting space or weight such as a portable radioactive chemical automatic administration device or the like. SOLUTION: This detector comprises molded tubes 10-13 fixed in shape for passing a measuring object, and a radiation detecting means for detecting the radiation emitted from the measuring object passing in the molded tubes 10-13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation detector and, more particularly, to a small and highly accurate radiation suitable for use in places where installation space and weight are limited, such as a movable radiopharmaceutical automatic administration device. Related to the detector.

[0002]

The short-lived nuclides to be administered to a subject BACKGROUND OF THE INVENTION Hospital, single photon nuclide such as ²⁰¹ T1 and ¹³¹ I, or positron nuclide such as ¹⁸ F and ¹⁵ O is used. These nuclides generally emit gamma rays having a specific energy evenly in the entire space as they decay. The radiation detector measures this energy using a counting device and an amplifier, and gives information such as the type of radiation and energy to measure the amount of radioactivity according to the nuclide. At this time, the measured value is affected by the positional relationship of the nuclide with respect to the detector, and when the nuclide is in a liquid, the material and thickness of the container.

As a detector for measuring a liquid, a method is generally adopted in which a well type detector comprising an ionization chamber or a scintillator (NaI or the like) is arranged, a container is placed inside the detector, and radiation from the container is detected. . In this method, the detector itself has a considerable thickness to prevent external shielding and noise, and requires a considerable thickness of shielding around its periphery.

The radioactive liquid measured by this device exists in a tube or a syringe (syringe), and the following method is generally used to measure the amount of radioactivity.

(1) A syringe is inserted into the well-type detector and measurement is performed.

(2) The movement of the radioactive liquid in the tube is stopped, and the liquid is inserted into the well type detector together with the tube for measurement.

(3) A radiation detector is attached to a part of the tube flow path, and by making the velocity of the radioactive liquid passing through the tube constant, the count value is integrated to obtain the radioactivity.

[0008]

However, in the case of a well-type detector, when a device having a predetermined shape is measured as in (1), accurate measurement can be performed.
When measuring the amount of radioactivity in a tube whose shape changes every time as shown in (2), it is difficult to measure accurately because the position and state of the tube inside the detector are not the same. In addition, the method (3) has a problem that the measurement cannot be performed in a state where the liquid is stopped, and the measured value differs depending on the transfer speed of the liquid.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and maintains the same level of accuracy as a well-type detector when measuring the radioactivity of a radioactive liquid in a tube. Moreover, it is an object to provide a lightweight, simple, and inexpensive radiation detector.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a radiation detector for detecting a radiation emitted from a measurement tube flowing in the molding tube, the molding tube having a fixed shape through which the measurement object flows. This problem has been solved by providing a radiation detecting unit that performs the above.

Further, the molded tube is molded into a coil shape, and the radiation detecting means detects radiation emitted inside the coil.

Alternatively, the tube is formed into a spiral shape, and the radiation detecting means detects radiation emitted to one or both sides of the spiral.

Alternatively, the molded tube is formed into a cone shape, and the radiation detecting means detects radiation emitted inside the cone.

Further, the radiation detecting means includes a scintillator provided near the molded tube, and a photomultiplier tube for multiplying light generated by the scintillator by the radiation.

Further, a light guide is arranged between the scintillator and the photomultiplier tube to improve the efficiency of detecting the fluorescence generated by the scintillator.

Further, a shielding means for shielding the tube from the outside is provided to prevent radiation exposure.

According to the present invention, the shielding means also performs positioning of the tube so that accurate measurement can be repeatedly performed with a simple configuration.

Further, the present invention provides an automatic radiation measuring apparatus including the radiation detector, wherein the object to be measured always stops at the same position in the molded tube when detecting radiation.

Another object of the present invention is to provide a radiopharmaceutical automatic administration apparatus including the automatic radiation measurement apparatus.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Here, a radiation detector for measuring the energy of 511 KeV will be described mainly for use in quantifying positron nuclides. However, it goes without saying that the present invention can be similarly applied to single photon nuclides having different energies.

The radiation detector usually includes a radiation sensor for measuring a target γ-ray, and a shielding container for blocking a peripheral source (noise) which is not intended by the sensor.

The first embodiment of the present invention is shown in FIGS. 1 (perspective view when the molded tube is at the measurement position), FIG. 2 (longitudinal cross-sectional view in a state of being attached to the apparatus), FIG. FIG.
As shown in (exploded perspective view), a molded tube 1 through which a measurement object is distributed and whose shape is fixed in a coil shape by adhesion or the like
0 and a radiation sensor 20 that detects radiation emitted from a measurement object flowing through the molded tube 10.

The molded tube 10 is previously molded and fixed in a coil shape by, for example, an adhesive.

As shown in detail in FIG. 5, the radiation sensor 20 includes a light-shielding case 24 disposed inside the molded tube 10 for protecting the scintillator.
Radiation detection including a cylindrical plastic scintillator 26 that emits fluorescence by radiation provided therein and a light guide 28 made of, for example, a rod-shaped transparent plastic disposed inside the plastic scintillator 26. A photomultiplier tube 32 for detecting light guided by the light guide 28; a signal amplifier / high voltage power supply 34 for applying a high voltage to the photomultiplier tube 32 and amplifying an output signal thereof; And an amplifier unit 30 including a cable 36 and
A sensor case 38 accommodating them, and a radiation sensor 2
0 to the mounting housing 12 (see FIG. 2). In FIG. 5, a shaded portion in the molded tube 10 indicates a portion into which a radioactive liquid enters during measurement, and a blank portion indicates a portion into which water (saline) enters.

The radiation detector 22 of the radiation sensor 20
2 and 4, is passed through the inside of an inner shield 42 made of, for example, lead, and has a cylindrical shape.
The outside of the molding tube 10 is disposed outside the molding tube 10, and a tubular outside shielding body 44 made of, for example, lead is disposed outside the molding tube 10.

The outer shield 44 has a molded tube 1
A slit 44A for defining an insertion depth of 0 is formed.

The molded tube 10 includes the radiation detecting section 2
2 is inserted like a quoit, and its slit 44A is
Used as a tube entrance.

In the radiation sensor 20, as shown in FIG. 6, a part of radiation generated in all directions from the radiopharmaceutical (referred to as a test solution) 8 in the molded tube 10 is converted into fluorescent light by a plastic scintillator 26. Further, the light is guided to the photomultiplier tube 32 by the light guide 28. Here, the light guide 28 is a transparent material close to the light refraction of both the photoelectric conversion part (scintillator surface) 32A of the photomultiplier tube 32 and the plastic scintillator 26 (particularly, the photomultiplier tube 32).
The plastic scintillator 26 and the photomultiplier tube 32 are connected. That is, when the light guide 28 is not provided, the light use efficiency is extremely reduced due to both surface reflections. Therefore, the light and the wavelength are integrated by the light guide 28 to prevent this.

As shown in FIG. 6, light emitted on the plastic scintillator 26 jumps at an angle (a transmission critical angle) at which the light can pass through the scintillator surface 32A of the photomultiplier tube 32, and is almost a part. , And photoelectrically converts light that has been repeatedly reflected and diffused. Therefore, without the light guide 28, reflection occurs on the scintillator surface 32A of the photomultiplier tube 32, and the number of times of reflection and diffusion increases, resulting in extremely low detection efficiency (for example, 1/100 or less).

As the material of the light guide 28, any of glass, plastic, and crystal can be used as long as it is a transparent material having a matching refractive index. In the present embodiment, plastic (acryl) having good workability is used.

The shape of the light guide 28 may be any shape as long as there is no loss in the shape of the coupling surface between the scintillator surface 32A of the photomultiplier tube 32 and the plastic scintillator 26. When measuring the molded tube 10 wound in a coil shape as in the present embodiment, the plastic scintillator 26 can be made a cylinder, and the distance between both can be made uniform to increase the conversion efficiency. Along with this, the shape of the light guide 28 can also be cylindrical.

The photomultiplier tube 32 to which the light is guided by the light guide 28 converts the light into electrons on the scintillator surface 32A which is the light incident surface, amplifies the light by the multiplier, and jumps into an electric signal. Output to a circuit that measures the number and energy of light.

When measuring the radioactive liquid in the tube 10 using a radioactivity detector, it is necessary to consider the change in the counting rate depending on the distance from the tube to the detector or the position of the radioactive liquid. Therefore, in order to measure the radioactivity accurately, it is desired to satisfy the following conditions.

(1) The shape of the tube to be measured in the detector takes the same shape each time measurement is performed.

(2) When the shape of the tube is fixed, the position of the radioactive liquid is always in the same position in the tube.

When the tube is not formed as in the present embodiment, for example, a method is generally used in which a core for winding the tube is made of a resin such as acrylic or hard paper, and the core is wound around the core without any gap. This is time-consuming and time-consuming, and it is not practical to force such an operation for tubes that are replaced each time they are used.

Further, in the present embodiment, the outer shield 44 of the detector is provided so that both ends of the coil are at the same position each time.
As shown in FIG. 4, a slit 44A small enough to allow the tube to pass through is provided so that the inlet and outlet of the molded tube containing no radioactive liquid are always at the same position. This prevents the molded tube 10 from wobbling in the detector, and enables accurate measurement. Furthermore, it is possible to make the length of the molded tube the shortest and contact the external mechanism at the shortest distance. Note that the positioning means is not limited to the slit.

For example, the applicant has disclosed Japanese Patent Application Laid-Open No. 2000-35078.
The automatic radiopharmaceutical dispenser as proposed in 3 has a mechanism for automatically introducing a radiopharmaceutical into a tube in the detector. Therefore, by setting the transfer speed and the transfer time of the radioactive liquid to be transferred by the controller, it is possible to keep the radioactive liquid at the same position in the forming tube 10 every time, thereby reducing the repetition error due to the location of the radioactive liquid. It is possible to do.

In this embodiment, the radiation sensor 20
Is arranged inside the molded tube 10, so that the shield can be downsized. Further, since the measurement target surrounds the detection unit, it is hardly affected by noise such as environmental radiation.

In particular, when measuring radiation by using the apparatus proposed in JP-A-2000-350783, the detector can be easily mounted on the apparatus because the detector is small and lightweight.

FIG. 7 shows an example in which the radiation sensor 20 of this embodiment is arranged in an automatic radiopharmaceutical administration device proposed by the applicant in Japanese Patent Application Laid-Open No. 2000-350783. In the figure, 5
Numeral 0 indicates a saline bag (or a distilled water for injection), and numeral 54 indicates a sterilized saline bag for extracting a saline solution for dilution from the saline bag 50, and an injection needle at the tip. An extension tube (simply referred to as a tube) provided with 52 and 56 for injecting physiological saline or the like in the tube 54 into the tube 60 via a valve with a three-way cock (hereinafter simply referred to as a three-way cock) 58. For example, a syringe driving device using a pulse motor (not shown)
Disposable syringe for pushing with
A syringe 62 for a drug solution for injecting a radiopharmaceutical (test solution 8) into a tube 66 connected to the three-way cock 58 via the tube 60, and a syringe 63 for the syringe 62 For shielding from the outside, for example, a radiation shield made of tungsten, 70 is a three-way cock for switching between injecting or discarding the drug after the radioactivity is measured by the radiation sensor 20, and 72, An air vent filter 74 and a winged needle 7 that can exchange the medicine branched by the three-way cock 70 for each patient.
Tube for injection into the patient's body via 6, 80
Are radiation passage sensors for detecting radiation of the medicine passing through the tube 72 and detecting the discharge of the medicine;
Reference numeral 4 denotes a waste liquid bottle which is switched by the three-way cock and accommodates a waste liquid supplied by the tube 82;
Reference numeral 6 denotes a radiation shield made of, for example, lead for shielding a main part from the outside.

The specific operation when mounted on this device is as follows.

(1) The molded tube 10 is set at a predetermined position including the radiation sensor 20 by a predetermined method.

(2) Take a radiopharmaceutical into a predetermined syringe 62 and set it at a predetermined position.

(3) The other amount of the radiopharmaceutical is sent to a predetermined position of the molded tube 10 by another syringe 56.

(4) The radiation sensor 20 measures the amount of radioactivity of the drug in the molded tube 10. In the measurement, γ-rays are measured for a certain period of time, and the measured amount is compared with a calibration curve prepared in advance with a solution having a known amount of radioactivity to display an accurate radioactivity.

(5) The winged needle 76 at the tip of the tube 72 is inserted into the subject, and the whole amount of the drug is automatically administered to the subject.

(6) Returning to (1), the same operation is performed by exchanging the molding tube 10.

In this embodiment, the molded tube 10
Is shaped like a coil, and by arranging the radiation detection unit 22 of the radiation sensor 20 inside the coil, the radiation sensor can be particularly downsized.

The shape of the formed tube 10 is not limited to a coil shape, but may be a spiral formed tube 11 as shown in FIG. 8 (longitudinal sectional view) and FIG. 9 (side view).
On one or both sides (one side in the figure), a flat plastic scintillator 26 ′, the tip side is the outer diameter of the spiral tube 11, and the photomultiplier tube 32 is a funnel-shaped light guide adapted to the size of the scintillator. It is also possible to use a combination of the bodies 28 '. In FIG. 9, a shaded portion in the molded tube 11 indicates a portion into which a radioactive liquid enters during measurement, and a blank portion indicates a portion into which water (saline) enters.

Further, if the counting detection efficiency is high and the scintillator size of the photomultiplier tube 32 is large enough for the molded tube, the light guide is omitted as in the third embodiment shown in FIG. It can be downsized.

11 (longitudinal sectional view) and FIG.
As in the fourth embodiment shown in (side view), it is also possible to use a serpentine-shaped formed tube 12. In FIG. 12, a shaded portion in the molded tube 12 indicates a portion into which a radioactive liquid enters during measurement, and a blank portion indicates a portion into which water (saline) enters.

Alternatively, as in the fifth embodiment shown in FIG. 13, the molded tube 13 itself may be formed in a cone shape, and the plastic scintillator 26 "and the light guide 28" may be formed in a cone shape corresponding thereto. is there.

According to the present embodiment, the fluorescent light generated by the plastic scintillator 26 "can be taken into the photomultiplier tube 32 very efficiently.

In the above embodiment, a plastic scintillator is used. However, the type of the scintillator is not limited to this, and a crystal scintillator such as NaI can be used depending on the application.

In the above description, the positron nuclide has been described when applied to the administration device. However, the present invention can be easily applied to single photon nuclides having different energies by changing the detected energy. Applicable. Also, the dosing device need not be automatic, and need not be a dosing device. The present invention can be generally applied to a device for accurately measuring the amount of radioactivity contained in a tube and transferring the entire amount to the next step while preventing exposure of an operator.

[0058]

According to the present invention, it is possible to reduce the size and weight of the detector while maintaining the accuracy of the repeated measurement for measuring the radioactivity every time the tube is replaced.

[Brief description of the drawings]

FIG. 1 is a first embodiment of a radiation detector according to the present invention,
Perspective view when the molded tube is at the measurement position

FIG. 2 is a longitudinal sectional view showing a state where the apparatus is attached to the apparatus.

FIG. 3 is a side view of the same.

FIG. 4 is an exploded perspective view of the same.

FIG. 5 is a longitudinal sectional view showing a configuration of a main part of the radiation sensor.

FIG. 6 is a conceptual diagram for explaining the detection principle.

FIG. 7 is a skeletal view showing the entire configuration of the automatic radiopharmaceutical administration device on which the first embodiment is mounted.

FIG. 8 is a longitudinal sectional view showing a second embodiment of the present invention.

FIG. 9 is a side view of the same.

FIG. 10 is a perspective view showing a third embodiment of the present invention.

FIG. 11 is a longitudinal sectional view showing a fourth embodiment of the present invention.

FIG. 12 is a side view of the same.

FIG. 13 is a longitudinal sectional view showing a fifth embodiment of the present invention.

[Explanation of symbols]

 10-13 Molded tube 12 Mounting housing 20 Radiation sensor 22 Radiation detector 24 Light-shielding case 26, 26 ', 26 "Plastic scintillator 28, 28', 28" Light guide 30 Amplifier unit 32 ... Photomultiplier tube 32A ... Scintillator surface 34 ... Signal amplifier / high voltage power supply 38 ... Sensor case 42,44 ... Shield 44A ... Slit

Continued on the front page (72) Inventor Motohito Sasaki 5-11-11 Kita-Shinagawa, Shinagawa-ku, Tokyo Sumitomo Heavy Industries, Ltd. (72) Inventor Toru Kanai 66-4 Maekawa, Odawara-shi, Kanagawa Pref. (72) Inventor Hidehiro Shinshu 66-4, Maekawa, Odawara-shi, Kanagawa F-term (reference) 2G088 EE25 FF04 GG18 JJ09 JJ29 4C066 AA09 BB01 CC01 DD08 EE14 FF04 GG06 GG08 GG11 GG20 H12 JJ10 KK09 LL07 LL19 QQ15 QQ41 4C082 AA05 AC03 AC05 AE05 AG04 AP02 AR01 AR12

Claims (10)

[Claims] 1. A molded tube having a fixed shape through which a measurement object flows, and radiation detection means for detecting radiation emitted from the measurement object flowing through the molding tube. Radiation detector. 2. The molding tube is formed into a coil shape,
The radiation detector according to claim 1, wherein the radiation detection unit is configured to detect radiation emitted inside the coil. 3. The method according to claim 1, wherein the forming tube is formed in a spiral shape, and the radiation detecting means detects radiation emitted to one or both sides of the spiral. Radiation detector. 4. The molding tube is molded in a cone shape,
The radiation detector according to claim 1, wherein the radiation detection means detects radiation emitted inside the cone. 5. The radiation detecting means according to claim 1, wherein said radiation detecting means includes a scintillator disposed near said forming tube, and a photomultiplier tube for multiplying light generated by said scintillator by radiation. The radiation detector according to any one of claims 1 to 4. 6. The radiation detector according to claim 5, wherein a light guide is provided between the scintillator and the photomultiplier. 7. A shielding means for shielding the molded tube from the outside is provided.
7. The radiation detector according to any one of claims 1 to 6. 8. The apparatus according to claim 7, wherein said shielding means also performs positioning of said forming tube.
3. A radiation detector according to claim 1. 9. The radiation detector according to claim 1, wherein an object to be measured always stops at the same position in the molded tube when radiation is detected. Automatic radiation measurement device. 10. An automatic radiopharmaceutical administration device comprising the automatic radiation measurement device according to claim 9.